{"parietal-bone":"The parietal bones are two bones in the skull which, when joined together at a fibrous joint, form the sides and roof of the cranium.\n\nIn humans, each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles.\n\nIt is named from the Latin paries (-ietis), wall.\n\n EXTERNAL SURFACE:\n\nThe external surface [Fig. 1] is convex, smooth, and marked near the center by an eminence, the parietal eminence (tuber parietale), which indicates the point where ossification commenced.\n\nCrossing the middle of the bone in an arched direction are two curved lines, the superior and inferior temporal lines; the former gives attachment to the temporal fascia, and the latter indicates the upper limit of the muscular origin of the temporal muscle.\n\nAbove these lines the bone is covered by a tough layer of fibrous tissue – the epicranial aponeurosis; below them it forms part of the temporal fossa, and affords attachment to the temporal muscle.\n\nAt the back part and close to the upper or sagittal border is the parietal foramen which transmits a vein to the superior sagittal sinus, and sometimes a small branch of the occipital artery; it is not constantly present, and its size varies considerably.\n\n INTERNAL SURFACE:\n\nThe internal surface is concave; it presents depressions corresponding to the cerebral convolutions, and numerous furrows (grooves) for the ramifications of the middle meningeal artery; the latter run upward and backward from the sphenoidal angle, and from the central and posterior part of the squamous border.\n\nAlong the upper margin is a shallow groove, which, together with that on the opposite parietal, forms a channel, the sagittal sulcus, for the superior sagittal sinus; the edges of the sulcus afford attachment to the falx cerebri.\n\nNear the groove are several depressions, best marked in the skulls of old persons, for the arachnoid granulations (Pacchionian bodies).\n\nIn the groove is the internal opening of the parietal foramen when that aperture exists.\n\n BORDERS:\n\n -The sagittal border, the longest and thickest, is dentated (has toothlike projections) and articulates with its fellow of the opposite side, forming the sagittal suture.\n\n -The frontal border is deeply serrated, and bevelled at the expense of the outer surface above and of the inner below; it articulates with the frontal bone, forming half of the coronal suture. The point where the coronal suture intersects with the sagittal suture forms a T-shape and is called the bregma.\n\n -The squamous border is divided into three parts: of these:\n -the anterior is thin and pointed, bevelled at the expense of the outer surface, and overlapped by the tip of the great wing of the sphenoid;\n -the middle portion is arched, bevelled at the expense of the outer surface, and overlapped by the squama of the temporal;\n -the posterior part is thick and serrated for articulation with the mastoid portion of the temporal.\n\n -The occipital border, deeply denticulated (finely toothed), articulates with the occipital bone, forming half of the lambdoid suture.\n\n That point where the sagittal suture intersects the lambdoid suture is called the lambda, because of its resemblance to the Greek letter.\n\nhttps://en.wikipedia.org/wiki/Parietal_bone","sinus-of-frontal-bone":"SINUS OF FRONTAL BONE\n\nThe frontal sinuses are one of the four pairs of paranasal sinuses that are situated behind the brow ridges.\n\nSinuses are mucosa-lined airspaces within the bones of the face and skull.\n\nEach opens into the anterior part of the corresponding middle nasal meatus of the nose through the frontonasal duct which traverses the anterior part of the labyrinth of the ethmoid.\n\nThese structures then open into the semilunar hiatus in the middle meatus.\n\n== Structure ==\n\nFrontal sinuses are rarely symmetrical and the septum between them frequently deviates to one or other side of the middle line.\n\nTheir average measurements are as follows: height 28 mm, breadth 24 mm, depth 20 mm, creating a space of 6-7 ml.\n\nThe mucous membrane in this sinus is innervated by the supraorbital nerve, which carries the postganglionic parasympathetic nerve fibers for mucous secretion from the ophthalmic nerve and supplied by the supraorbital artery and anterior ethmoidal artery.\n\n=== Development ===\n\nThe frontal sinuses are absent at birth, but are generally well developed, and functional between the sixth and eighth years, though they continue to grow slower until reaching their maximum size after puberty.\n\nThis is why many children experience suddenly increased mucus production at this age and learn to react accordingly.\n\nThe frontal bone is membranous at birth and the sinus region is occupied by a developing recess until bodily development hastens and bones begin to ossify at age two.\n\nConsequently, this structure does not show on radiographs before that time. Sinus development begins in the womb, the maxillary and ethmoid sinuses are present at birth.\n\nSphenoidal sinuses are present at birth as well but are very small.\n\nApproximately 5% of people have absent frontal sinuses.\n\n== Function ==\n\nThrough its copious mucus production, the sinus is an essential part of the immune defense/air filtration carried out by the nose.\n\nNasal and sinal mucosae are ciliated and move mucus to the choanae and finally to the stomach.\n\nThe thick upper layers of nasal mucus trap bacteria and small particles in tissue abundantly provided with immune cells, antibodies, and antibacterial proteins.\n\nThe layers beneath are thinner and provide a substrate in which the cilia are able to beat and move the upper layer with its debris through the ostia toward the choanae.\n\n== Clinical significance ==\n\nInfection of the frontal sinus causing sinusitis can give rise to serious complications, as it is in close proximity to the orbit and cranial cavity (orbital cellulitis, epidural and subdural abscess, meningitis).\n\nEndonasal approach into the frontal sinus in children with acute and chronic frontal sinusitis without the usage of surgical optics is not successful, because in this case the operation is performed almost blindly and technically difficult even in adults.\n\n=== Fractures ===\n\nFrontal sinus fractures occur from trauma to the part of the frontal bone that overlies the sinus, often from motor vehicle accidents and falls.\n\nThe hallmarks of a frontal sinus fracture is a frontal depression in the anterior table of the bone.\n\nAdditionally, clear fluid leaking from the nose may indicate that fractures to the posterior table have torn into the dura mater, creating a cerebrospinal fluid leak.\n\nGoals in management are to protect the intracranial structure, control any existing CSF leakage, prevent late complications, and aesthetically correct the deformity caused, if any.\n\nIn anterior table fractures, if the table is minimally displaced, there will be no treatment necessary, only observation.\n\nIf largely displaced, the correction is open reduction and internal fixation.\n\nIf inhibiting the nasofrontal outflow tract, procedure is to undergo open reduction and internal fixation of the anterior table and osteoplastic flap with obliteration.\n\nIn posterior table fractures, a nondiplaced fracture with no CSF leak will only be observed.\n\nThose with a CSF leak will undergo sinus exploration if the CSF leak is not internally resolved within 4 to 7 days.\n\nWith more dramatic displacements, sinus exploration will be required to determine the required level of cranialization, obliteration, and reparation to the dura.\n\n=== Aesthetic reconstruction ===\n\nIn the case of facial feminization surgery, modifications to the frontal sinus can be made to make the face more feminine, alongside softening the orbital rims.\n\nThe forehead operations for feminization were first described by Dr.\n\nDouglas Ousterhout in the 1980s.\n\nThose operations consisted of four different techniques based on the anatomy of the patient.\n\nThey were named arbitrarily by number (Type 1, Type 2, Type 3 and Type 4), with no particular relevance to their level of difficulty or frequency.\n\nType 1The Type I forehead describes a forehead with an absent frontal sinus or alternatively with sufficiently thick bone overlaying the frontal sinus so that burring alone is enough to correct the forehead.\n\nThis type of forehead tends to occur in approximately 3% to 5% of the population.\n\nIn these situations, the operation consists of using rotary instruments to shape and contour the bone to the desired level, while observing the thickness of the bone to avoid penetrating the intracranial space.\n\nThe main risks associated with this operation tend to be bleeding.\n\nThere are often venous lakes present throughout the frontal bone.\n\nType 2The Type II forehead describes another uncommon situation.\n\nThis describes a patient with brow bossing; however, the bossing is at the correction position in terms of prominence.\n\nTherefore, the problem lies primarily above the bossing.\n\nWe see this forehead type at about the same frequency as we see the Type I forehead.\n\nThe Type II forehead is corrected by using a filling material such as methyl methacrylate.7 Other materials may be more ideal at this point; however, none are superior in terms of cost to methyl methacrylate.\n\nAlthough many surgeons do not consider the cost of the materials they are using, hydroxyapatite and calcium phos-phate bone cements cost approximately 1000 times that of methyl methacrylate.\n\nThe advantage of bone cement is its adherence to the underlying bone, and the more analogous nature to native bone substrate.\n\nThe material is applied to fill in the area above the bossing, and then gently contoured to blend with the transverse forehead bossing thereby-creating a uniformly round forehead\n\nType 3The Type III forehead is the most common situation and occurs in more than 90% of patients.\n\nThe forehead, in this situation, has a prominent bossing across the top of the brows, and that bossing is overly projected.\n\nA frontal sinus is present.\n\nThe thinness of the sinus precludes using exclusively rotary instruments to thin the bone.\n\nAn osteotomy and reconstruction are the only operations to provide the proper round shape to the forehead with the decreased prominence that is necessary for a soft forehead, which involves a setback of the anterior table of the frontal sinus.\n\nThis procedure is described as Type 3 Forehead Cranioplasty.\n\nType 4This operation can be described as an extended Type II operation.\n\nIn this situation, the entire forehead is diminutive, including the area underlying the brows, and the entire forehead requires augmentation.\n\nRegardless of the material type, care should be taken to avoid having the implant sit directly underneath the incision as this leads to a higher rate of infection and removal.\n\nTreatment of the orbital rim is almost always necessary in all these various forehead operations, regardless of what is done with the frontal bossing.\n\nhttps://en.wikipedia.org/wiki/Frontal_sinus","frontal-bone":"The frontal bone is a bone in the human skull.\n\nThe bone consists of two portions.\n\nThese are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bony part of the forehead, part of the bony orbital cavity holding the eye, and part of the bony part of the nose respectively.\n\nThe name comes from the Latin word frons (meaning \"forehead\").\n\n== Structure of the frontal bone ==\n\nThe frontal bone is made up of two main parts.\n\nThese are the squamous part, and the orbital part.\n\nThe squamous part marks the vertical, flat, and also the biggest part, and the main region of the forehead.\n\nThe orbital part is the horizontal and second biggest region of the frontal bone.\n\nIt enters into the formation of the roofs of the orbital and nasal cavities.\n\nSometimes a third part is included as the nasal part of the frontal bone, and sometimes this is included with the squamous part.\n\nThe nasal part is between the brow ridges, and ends in a serrated nasal notch that articulates with the nasal bones inferiorly, and with the lacrimal and maxilla bones laterally.\n\n== Borders ==\n\nThe border of the squamous part is thick, strongly serrated, bevelled at the expense of the inner table above, where it rests upon the parietal bones, and at the expense of the outer table on either side, where it receives the lateral pressure of those bones; this border is continued below into a triangular, rough surface, which articulates with the great wing of the sphenoid.\n\nThe posterior borders of the orbital plates are thin and serrated, and articulate with the small wings of the sphenoid.\n\n== Development ==\n\nThe frontal bone is presumed to be derived from neural crest cells.The frontal bone is ossified in membrane from two primary centers, one for each half, which appear toward the end of the second month of fetal life, one above each supraorbital margin.\n\nFrom each of these centers, ossification extends upward to form the corresponding half of the squama, and backwards to form the orbital plate.\n\nThe spine is ossified from a pair of secondary centers, on either side of the middle line; similar centers appear in the nasal part and zygomatic processes.\nAt birth the bone consists of two pieces, separated by the frontal suture, which is usually obliterated by Intramembranous ossification, except at its lower part, by the eighth year, but occasionally persists throughout life.\n\nIt is generally maintained that the development of the frontal sinuses begins at the end of the first or beginning of the second year, but may begin at birth.\n\nThe sinuses are of considerable size by the seventh or eighth year, but do not attain their full proportions until after puberty.\n\n== Other animals ==\n\nIn most vertebrates, the frontal bone is paired, rather than presenting the single, fused structure found in humans (see frontal suture).\n\nIt typically lies on the upper part of the head, between the eyes, but in many non-mammalian animals it does not form part of the orbital cavity.\n\nInstead, in reptiles, bony fish and amphibians it is often separated from the orbits by one or two additional bones not found in mammals.\n\nThese bones, the prefrontals and postfrontals, together form the upper margin of the eye sockets, and lie to either side of the frontal bones.\n\n=== Dinosaurs ===\n\nThe frontal bone is one of the principal paired mid-line bones in dinosaur skulls.\n\nThis bone is part of the skull roof, which is a set of bones that cover the brain, eyes and nostrils.\n\nThe frontal makes contact with several other bones in the skull.\n\nThe anterior part of the bone articulates with the nasal bone and the prefrontal bone.\n\nThe posterior part of the bone articulates with the postorbital bone and the parietal bone.\n\nThis bone defines all of part of the upper margin of the orbit.\n\nhttps://en.wikipedia.org/wiki/Frontal_bone","occipital-bone":"The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull).\n\nIt is trapezoidal in shape and curved on itself like a shallow dish.\n\nThe occipital bone overlies the occipital lobes of the cerebrum.\n\nAt the base of skull in the occipital bone, there is a large oval opening called the foramen magnum, which allows the passage of the spinal cord.\nLike the other cranial bones, it is classed as a flat bone.\n\nDue to its many attachments and features, the occipital bone is described in terms of separate parts.\n\nFrom its front to the back is the basilar part, also called the basioccipital, at the sides of the foramen magnum are the lateral parts, also called the exoccipitals, and the back is named as the squamous part.\n\nThe basilar part is a thick, somewhat quadrilateral piece in front of the foramen magnum and directed towards the pharynx.\n\nThe squamous part is the curved, expanded plate behind the foramen magnum and is the largest part of the occipital bone.\nDue to its embryonic derivation from paraxial mesoderm (as opposed to neural crest, from which many other craniofacial bones are derived), it has been posited that \"the occipital bone as a whole could be considered as a giant vertebra enlarged to support the brain.\"\n\n== Structure ==\n\nThe occipital bone, like the other seven cranial bones, has outer and inner layers (also called plates or tables) of cortical bone tissue between which is the cancellous bone tissue known in the cranial bones as diploë.\n\nThe bone is especially thick at the ridges, protuberances, condyles, and anterior part of the basilar part; in the inferior cerebellar fossae it is thin, semitransparent, and without diploë.\n\n=== Outer surface ===\n\nNear the middle of the outer surface of the squamous part of the occipital (the largest part) there is a prominence – the external occipital protuberance.\n\nThe highest point of this is called the inion.\nFrom the inion, along the midline of the squamous part until the foramen magnum, runs a ridge – the external occipital crest (also called the medial nuchal line) and this gives attachment to the nuchal ligament.\nRunning across the outside of the occipital bone are three curved lines and one line (the medial line) that runs down to the foramen magnum.\n\nThese are known as the nuchal lines which give attachment to various ligaments and muscles.\n\nThey are named as the highest, superior and inferior nuchal lines.\n\nThe inferior nuchal line runs across the midpoint of the median nuchal line.\n\nThe area above the highest nuchal line is termed the occipital plane and the area below this line is termed the nuchal plane.\n\n=== Inner surface ===\n\nThe inner surface of the occipital bone forms the base of the posterior cranial fossa.\n\nThe foramen magnum is a large hole situated in the middle, with the clivus, a smooth part of the occipital bone travelling upwards in front of it.\n\nThe median internal occipital crest travels behind it to the internal occipital protuberance, and serves as a point of attachment to the falx cerebri.\nTo the sides of the foramen sitting at the junction between the lateral and base of the occipital bone are the hypoglossal canals.\n\nFurther out, at each junction between the occipital and petrous portion of the temporal bone lies a jugular foramen.The inner surface of the occipital bone is marked by dividing lines as shallow ridges, that form four fossae or depressions.\n\nThe lines are called the cruciform (cross-shaped) eminence.\nAt the midpoint where the lines intersect a raised part is formed called the internal occipital protuberance.\n\nFrom each side of this eminence runs a groove for the transverse sinuses.\nThere are two midline skull landmarks at the foramen magnum.\n\nThe basion is the most anterior point of the opening and the opisthion is the point on the opposite posterior part.\n\nThe basion lines up with the dens.\n\n=== Foramen magnum ===\n\nThe foramen magnum (Latin: large hole) is a large oval foramen longest front to back; it is wider behind than in front where it is encroached upon by the occipital condyles.\n\nThe clivus, a smooth bony section, travels upwards on the front surface of the foramen, and the median internal occipital crest travels behind it.Through the foramen passes the medulla oblongata and its membranes, the accessory nerves, the vertebral arteries, the anterior and posterior spinal arteries, and the tectorial membrane and alar ligaments.\n\n=== Angles ===\n\nThe superior angle of the occipital bone articulates with the occipital angles of the parietal bones and, in the fetal skull, corresponds in position with the posterior fontanelle.\nThe lateral angles are situated at the extremities of the groove for the transverse sinuses: each is received into the interval between the mastoid angle of the parietal bone, and the mastoid portion of the temporal bone.\nThe inferior angle is fused with the body of the sphenoid bone.\n\n=== Borders ===\n\nThe superior borders extend from the superior to the lateral angles: they are deeply serrated for articulation with the occipital borders of the parietals, and form by this union the lambdoidal suture.\nThe inferior borders extend from the lateral angles to the inferior angle; the upper half of each articulates with the mastoid portion of the corresponding temporal, the lower half with the petrous part of the same bone.\nThese two portions of the inferior border are separated from one another by the jugular process, the notch on the anterior surface of which forms the posterior part of the jugular foramen.\n\n=== Sutures ===\n\nThe lambdoid suture joins the occipital bone to the parietal bones.\nThe occipitomastoid suture joins the occipital bone and mastoid portion of the temporal bone.\n\nThe sphenobasilar suture joins the basilar part of the occipital bone and the back of the sphenoid bone body .\nThe petrous-basilar suture joins the side edge of the basilar part of the occipital bone to the petrous-part of the temporal bone .\n\n== Development ==\n\nThe occipital plane of the squamous part of the occipital bone is developed in membrane, and may remain separate throughout life when it constitutes the interparietal bone; the rest of the bone is developed in cartilage.\nThe number of nuclei for the occipital plane is usually given as four, two appearing near the middle line about the second month, and two some little distance from the middle line about the third month of fetal life.\nThe nuchal plane of the squamous part is ossified from two centers, which appear about the seventh week of fetal life and soon unite to form a single piece.\nUnion of the upper and lower portions of the squamous part takes place in the third month of fetal life.\nAn occasional centre (Kerckring) appears in the posterior margin of the foramen magnum during the fifth month; this forms a separate ossicle (sometimes double) which unites with the rest of the squamous part before birth.\nEach of the lateral parts begins to ossify from a single center during the eighth week of fetal life.\n\nThe basilar portion is ossified from two centers, one in front of the other; these appear about the sixth week of fetal life and rapidly coalesce.\nThe occipital plane is said to be ossified from two centers and the basilar portion from one.\nAbout the fourth year the squamous part and the two lateral parts unite, and by about the sixth year the bone consists of a single piece.\n\nBetween the 18th and 25th years the occipital and sphenoid bone become united, forming a single bone.\n\n== Clinical significance ==\n\nTrauma to the occiput can cause a fracture of the base of the skull, called a basilar skull fracture.\n\nThe basion-dens line as seen on a radiograph is the distance between the basion and the top of the dens, used in the diagnosis of dissociation injuries.Genetic disorders can cause a prominent occiput as found in Edwards syndrome, and Beckwith–Wiedemann syndrome.\nThe identification of the location of the fetal occiput is important in delivery.\n\n== Etymology ==\n\nOccipital stems from Latin occiput \"back of the skull\", from ob \"against, behind\" + caput \"head\".\n\nDistinguished from sinciput (anterior part of the skull).\n\n== Other animals ==\n\nIn many animals these parts stay separate throughout life; for example, in the dog as four parts: squamous part (supraoccipital); lateral parts–left and right parts (exoccipital); basilar part (basioccipital).\nThe occipital bone is part of the endocranium, the most basal portion of the skull.\n\nIn Chondrichthyes and Agnatha, the occipital does not form as a separate element, but remains part of the chondrocranium throughout life.\n\nIn most higher vertebrates, the foramen magnum is surrounded by a ring of four bones.\nThe basioccipital lies in front of the opening, the two exoccipital condyles lie to either side, and the larger supraoccipital lies to the posterior, and forms at least part of the rear of the cranium.\n\nIn many bony fish and amphibians, the supraoccipital is never ossified, and remains as cartilage throughout life.\n\nIn primitive forms the basioccipital and exoccipitals somewhat resemble the centrum and neural arches of a vertebra, and form in a similar manner in the embryo.\n\nTogether, these latter bones usually form a single concave circular condyle for the articulation of the first vertebra.In mammals, however, the condyle has divided in two, a pattern otherwise seen only in a few amphibians.\nMost mammals also have a single fused occipital bone, formed from the four separate elements around the foramen magnum, along with the paired postparietal bones that form the rear of the cranial roof in other vertebrates.\n\n=== Citations ===\n\nhttps://en.wikipedia.org/wiki/Occipital_bone","sinus-of-sphenoid-bone":"The sphenoid sinus is one of the four paired paranasal sinuses that is contained within the body of the sphenoid bone. The sphenoid sinuses vary in size and shape, and owing to the lateral displacement of the intervening septum, which may insert on the carotid canal, they are rarely symmetrical. They cannot be palpated during an extraoral examination.\n\nThe following are their average measurements: vertical height, 2.2 cm; transverse breadth, 2 cm; antero-posterior depth, 2.2 cm.\n\n STRUCTURE\n\nWhen exceptionally large the sphenoid sinuses may extend into the roots of the pterygoid processes or great wings, and may invade the basilar part of the occipital bone.\n\nEach sinus opens into the roof of the nasal cavity via apertures on the posterior wall of the sphenoethmoidal recess directly above the choana. The apertures are located high on the anterior walls of the sinuses themselves.\n\n DEVELOPMENT\n\nThey are not present at birth, they slowly develop with the growth of the skull. Just after puberty the sinuses finish development.\n\n NERVE SUPPLY\n\nThe mucous membrane receives sensory innervation by the posterior ethmoidal nerves (branch of the ophthalmic nerve), and postganglionic parasympathetic fibers of the facial nerve that synapsed at the pterygopalatine ganglion which controls secretion of mucus.\n\nhttps://en.wikipedia.org/wiki/Sphenoid_sinus","sphenoid-bone":"The sphenoid bone is an unpaired bone of the neurocranium.\n\nIt is situated in the middle of the skull towards the front, in front of the basilar part of the occipital bone.\n\nThe sphenoid bone is one of the seven bones that articulate to form the orbit. Its shape somewhat resembles that of a butterfly or bat with its wings extended.\n\n== Structure ==\n\nIt is divided into the following parts:\n\n-A median portion, known as the body of sphenoid bone, containing the sella turcica, which houses the pituitary gland as well as the paired paranasal sinuses, the sphenoidal sinuses.\n-Two greater wings on the lateral side of the body and two lesser wings from the anterior side.\n-Pterygoid processes of the sphenoides, directed downwards from the junction of the body and the greater wings.\n-Two sphenoidal conchae are situated at the anterior and inferior part of the body.\n\n=== Intrinsic ligaments of the sphenoid ===\n\nThe more important of these are:\n\n-The pterygospinous, stretching between the spina angularis and the lateral pterygoid plate see (cervical fascia);\n-The interclinoid, a fibrous process joining the anterior to the posterior clinoid process;\n-And the caroticoclinoid, connecting the anterior to the middle clinoid process.\n\nThese ligaments occasionally ossify.\n\n=== Features ===\n\n-pterygoid notch\n-pterygoid fossa\n-scaphoid fossa\n-pterygoid hamulus\n-pterygoid canal\n-pterygospinous process\n-sella turcica\n\n=== Articulations ===\n\nThe sphenoid articulates with the frontal, parietal, ethmoid, temporal, zygomatic, palatine, vomer, and occipital bones and helps to connect the neurocranium to the facial skeleton.\n\n== Body of sphenoid ==\n\n=== Superior or cerebral surface ===\n\nArticulates with ethmoid bone anteriorly and basilar part of occipital bone posteriorly.\n\nIt shows:\n\nJugum sphenoidale\nSulcus chiasmaticus\nTuberculum sellae\nSella turcica\nDorsum sellae\nClivus\n\n=== Inferior surface ===\n\nRostrum of sphenoid\nSphenoidal conchae\nVaginal processes of medial pterygoid plate\n\n=== Anterior surface ===\n\nSphenoidal crest articulates with the perpendicular plate of ethmoid leading to formation of a part of the septum of nose.\n\n=== Posterior surface ===\nBasilar part of occipital bone\n\n=== Lateral surface ===\n\nCarotid sulcus lodging cavernous sinus and internal carotid artery\n\n== Sphenoidal sinuses ==\n\nThese are asymmetrical air sinuses in the body of the sphenoid, closed by Sphenoidal conchae\n\n== Greater wings ==\n\n=== Superior or cerebral surface ===\n\nThis forms the floor of the middle cranial fossa. It presents (starting from the front):\n\n-Foramen rotundum\n-Foramen ovale\n-Sphenoidal emissary foramen\n-Foramen spinosum\n\n=== Lateral surface ===\n\nThis is divided into (by infratemporal crest):\n\nUpper or temporal surface\nLower or infratemporal surfaceForamen pierce it:\n\nForamen ovale\nForamen spinosum\n\n=== Orbital surface ===\n\nThis forms the posterior wall of the orbit\n\n== Lesser wings ==\n\nThese are two triangular wings projecting laterally from anterosuperior part of the body. Each consists of:\n\n-A base forming medial end of the wing.\n-Tip forming the lateral end of the wing.\n-Superior surface forming floor of anterior cranial fossa.\n-Inferior surface forming upper boundary of superior orbital fissure.\n-Posterior surface projects into the Sylvian point.\n-Medially, terminates in the anterior clinoid process.\n\n=== Development ===\n\nUntil the seventh or eighth month of fetal development, the body of the sphenoid consists of two parts:\n\n-One in front of the tuberculum sellæ, the presphenoid, with which the small wings are continuous;\n-The other, consisting of the sella turcica and dorsum sellae, the postsphenoid, with which are associated the great wings, and pterygoid processes.\n\nThe greater part of the bone is ossified in cartilage. There are fourteen centers in all, six for the presphenoid and eight for the postsphenoid.\n\n==== Presphenoid ====\n\nBy about the ninth week of fetal development an ossific center appears for each of the small wings (orbito-sphenoids) just lateral to the optic foramen; this is followed by the appearance of two nuclei in the presphenoid part of the body.\n\nThe sphenoidal conchae are each developed from a center that makes its appearance about the fifth month; at birth they consist of small triangular laminae, and it is not until the third year that they become hollowed out and coneshaped; about the fourth year they fuse with the labyrinths of the ethmoid bone, and between the ninth and twelfth years they unite with the sphenoid bone.\n\n==== Postsphenoid ====\n\nThe first ossific nuclei are those for the great wings (alisphenoids).\n\nOne makes its appearance in each wing between the foramen rotundum and foramen ovale about the eighth week.\n\nThe orbital plate and that part of the sphenoid, which is found in the temporal fossa, as well as the lateral pterygoid plate, are ossified in membrane (Fawcett).\n\nSoon after, the centers for the postsphenoid part of the body appear, one on either side of the sella turcica, and become blended together about the middle of fetal life.\n\nEach medial pterygoid plate (except its hamulus) is ossified in membrane, and its center probably appears about the ninth or tenth week; the hamulus becomes chondrified during the third month, and almost at once ossifies (Fawcett).\n\nThe medial joins the lateral pterygoid plate about the sixth month.\nAbout the fourth month, a center appears for each lingula and speedily joins the rest of the bone.\n\nThe presphenoid is united to the postsphenoid about the eighth month, and at birth the sphenoid is in three pieces :\n a central, consisting of the body and small wings, and two lateral, each comprising a great wing and pterygoid process.\n\nIn the first year after birth the great wings and body unite, and the small wings extend inward above the anterior part of the body, and, meeting with each other in the middle line, form an elevated smooth surface, termed the jugum sphenoidale.\n\nBy the twenty-fifth year the sphenoid and occipital are completely fused.\nBetween the pre- and postsphenoid there are occasionally seen the remains of a canal, the canalis cranio-pharyngeus, through which, in early fetal life, the hypophyseal diverticulum of the buccal ectoderm is transmitted.\n\nThe sphenoidal sinuses are present as minute cavities at the time of birth (Onodi), but do not attain their full size until after puberty.\n\n== Function ==\n\nThis bone assists with the formation of the base and the sides of the skull, and the floors and walls of the orbits.\n\nIt is the site of attachment for most of the muscles of mastication. Many foramina and fissures are located in the sphenoid that carry nerves and blood vessels of the head and neck, such as the superior orbital fissure (with ophthalmic nerve), foramen rotundum (with maxillary nerve) and foramen ovale (with mandibular nerve).\n\n== Other animals ==\n\nThe sphenoid bone of humans is homologous with a number of bones that are often separate in other animals, and have a somewhat complex arrangement.\n\nIn the early lobe-finned fishes and tetrapods, the pterygoid bones were flat, wing-like bones forming the major part of the roof of the mouth.\n\nAbove the pterygoids were the epipterygoid bones, which formed part of a flexible joint between the braincase and the palatal region, as well as extending a vertical bar of bone towards the roof of the skull.\n\nBetween the pterygoids lay an elongated, narrow parasphenoid bone, which also spread over some of the lower surface of the braincase, and connected, at its forward end, with a sphenethmoid bone helping to protect the olfactory nerves.\n\nFinally, the basisphenoid bone formed part of the floor of the braincase and lay immediately above the parasphenoid.Aside from the loss of the flexible joint at the rear of the palate, this primitive pattern is broadly retained in reptiles, albeit with some individual modifications.\n\nIn birds, the epipterygoids are absent and the pterygoids considerably reduced.\n\nLiving amphibians have a relatively simplified skull in this region; a broad parasphenoid forms the floor of the braincase, the pterygoids are relatively small, and all other related bones except the sphenethmoid are absent.\n\nIn mammals, these various bones are often (though not always) fused into a single structure; the sphenoid. The basisphenoid forms the posterior part of the base, while the pterygoid processes represent the pterygoid bones.\n\nThe epipterygoids have extended into the wall of the cranium; they are referred to as alisphenoids when separate in mammals, and form the greater wings of the sphenoid when fused into a larger structure.\n\nThe sphenethmoid bone forms as three bones: the lesser wings and the anterior part of the base.\n\nThese two parts of the sphenethmoid may be distinguished as orbitosphenoids and presphenoid, respectively, although there is often some degree of fusion.\n\nOnly the parasphenoid appears to be entirely absent in mammals.In the dog the sphenoid is represented by 8 bones:\n -basisphenoid, alisphenoids, presphenoid, orbitosphenoids, pterygoids.\n\n These bones remain separate and are the:\n\n2 Alisphenoids: each greater wing\n2 Orbitosphenoids: each lesser wing\nBasisphenoid: back part of body\nPresphenoid: front part of body\n2 Pterygoids: medial pterygoid plate\n\n== See also ==\n\nSphenoidal sinus\nPterygospinal ligament\nBasilar skull fracture\n\n== References ==\n\n This article incorporates text in the public domain from page 147 of the 20th edition of Gray's Anatomy (1918)\n\nhttps://en.wikipedia.org/wiki/Sphenoid_bone","temporal-bone":"The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex.\n\nThe temporal bones are overlaid by the sides of the head known as the temples, and house the structures of the ears.\n\nThe lower seven cranial nerves and the major vessels to and from the brain traverse the temporal bone.\n\n STRUCTURE\n\nThe temporal bone consists of four parts— the squamous, mastoid, petrous and tympanic parts.\n\nThe squamous part is the largest and most superiorly positioned relative to the rest of the bone.\n\nThe zygomatic process is a long, arched process projecting from the lower region of the squamous part and it articulates with the zygomatic bone.\n\nPosteroinferior to the squamous is the mastoid part.\n\nFused with the squamous and mastoid parts and between the sphenoid and occipital bones lies the petrous part, which is shaped like a pyramid.\n\nThe tympanic part is relatively small and lies inferior to the squamous part, anterior to the mastoid part, and superior to the styloid process.\n\nThe styloid, from the Greek stylos, is a phallic shaped pillar directed inferiorly and anteromedially between the parotid gland and internal jugular vein.\n\nAn elongated or deviated styloid process can result from calcification of the stylohyoid ligament in a condition known as Eagle syndrome.\n\n BORDERS\n\n-Occipitomastoid suture. It separates occipital bone and mastoid portion of temporal bone.\n\n-Squamosal suture. It separates parietal bone and squama portion of temporal bone.\n\n-Sphenosquamosal suture. It separates sphenoid bone and squama portion of temporal bone.\n\n-Zygomaticotemporal suture. It separates zygomatic bone and zygomatic process of temporal bone.\n\n DEVELOPMENT\n\nThe temporal bone is ossified from eight centers, exclusive of those for the internal ear and the tympanic ossicles:\n\n -one for the squama including the zygomatic process,\n -one for the tympanic part,\n -four for the petrous and mastoid parts,\n -and two for the styloid process.\n\nhttps://en.wikipedia.org/wiki/Temporal_bone","ethmoid-bone":"The ethmoid bone (from Greek ethmos, \"sieve\") is an unpaired bone in the skull that separates the nasal cavity from the brain.\n\nIt is located at the roof of the nose, between the two orbits.\n\nThe cubical bone is lightweight due to a spongy construction.\n\nThe ethmoid bone is one of the bones that make up the orbit of the eye.\n\n== Structure ==\n\nThe ethmoid bone is an anterior cranial bone located between the eyes.\n\nIt contributes to the medial wall of the orbit, the nasal cavity, and the nasal septum.\n\nThe ethmoid has three parts: cribriform plate, ethmoidal labyrinth, and perpendicular plate.\n\nThe cribriform plate forms the roof of the nasal cavity and also contributes to formation of the anterior cranial fossa, the ethmoidal labyrinth consists of a large mass on either side of the perpendicular plate, and the perpendicular plate forms the superior two-thirds of the nasal septum.\n\nBetween the orbital plate and the nasal conchae are the ethmoidal sinuses or ethmoidal air cells, which are a variable number of small cavities in the lateral mass of the ethmoid.\n\n=== Articulations ===\n\nThe ethmoid articulates with thirteen bones:\n\ntwo bones of the neurocranium—the frontal, and the sphenoid (at the sphenoidal body and at the sphenoidal conchae).\neleven bones of the viscerocranium—, two nasal bones, two maxillae, two lacrimals, two palatines, two inferior nasal conchae, and the vomer.\n\n=== Development ===\n\nThe ethmoid is ossified in the cartilage of the nasal capsule by three centers: one for the perpendicular plate, and one for each labyrinth.\nThe labyrinths are first developed, ossific granules making their appearance in the region of the lamina papyracea between the fourth and fifth months of fetal life, and extending into the conchæ.\nAt birth, the bone consists of the two labyrinths, which are small and ill-developed.\n\nDuring the first year after birth, the perpendicular plate and crista galli begin to ossify from a single center, and are joined to the labyrinths about the beginning of the second year.\nThe cribriform plate is ossified partly from the perpendicular plate and partly from the labyrinths.\nThe development of the ethmoidal cells begins during fetal life.\n\n== Function ==\n\n=== Role in magnetoception ===\n\nSome birds and other migratory animals have deposits of biological magnetite in their ethmoid bones which allow them to sense the direction of the Earth's magnetic field.\n\nHumans have a similar magnetite deposit (ferric iron), but it is believed to be vestigial.\n\n== Clinical significance ==\n\nFracture of the lamina papyracea, the lateral plate of the ethmoid labyrinth bone, permits communication between the nasal cavity and the orbit on the same side of the body through the inferomedial orbital wall, resulting in orbital emphysema.\n\nIncreased pressure within the nasal cavity, as seen during sneezing, for example, leads to temporary exophthalmos.\nThe porous fragile nature of the ethmoid bone makes it particularly susceptible to fractures.\n\nThe ethmoid is usually fractured from an upward force to the nose.\n\nThis could occur by hitting the dashboard in a car crash or landing on the ground after a fall.\n\nThe ethmoid fracture can produce bone fragments that penetrate the cribriform plate.\n\nThis trauma can lead to a leak of cerebrospinal fluid into the nasal cavity.\n\nThese openings let opportunistic bacteria in the nasal cavity enter the sterile environment of the central nervous system (CNS).\n\nThe CNS is usually protected by the blood-brain barrier, but holes in the cribriform plate let bacteria get through the barrier.\n\nThe blood-brain barrier makes it extremely difficult to treat such infections, because only certain drugs can cross into the CNS.\nAn ethmoid fracture can also sever the olfactory nerve.\n\nThis injury results in anosmia (loss of smell).\n\nA reduction in the ability to taste is also a side effect because it is based so heavily on smell.\n\nThis injury is not fatal, but can be dangerous, as when a person fails to smell smoke, gas, or spoiled food.\n\nIn fact, people with anosmia were more than four times as likely to die in five years compared to those with a healthy sense of smell.\n\nhttps://en.wikipedia.org/wiki/Ethmoid_bone","inferior-nasal-concha-bone":"The inferior nasal concha (inferior turbinated bone or inferior turbinal/turbinate) is one of the three paired nasal conchae in the nose.\n\nIt extends horizontally along the lateral wall of the nasal cavity and consists of a lamina of spongy bone, curled upon itself like a scroll, (turbinate meaning inverted cone).\n\nThe inferior nasal conchae are considered a pair of facial bones.\n\nAs the air passes through the turbinates, the air is churned against these mucosa-lined bones in order to receive warmth, moisture and cleansing.\n\nSuperior to inferior nasal concha are the middle nasal concha and superior nasal concha which both arise from the ethmoid bone, of the cranial portion of the skull.\n\nHence, these two are considered as a part of the cranial bones.\nIt has two surfaces, two borders, and two extremities.\n\n== Structure ==\n\n=== Surfaces ===\n\nThe medial surface is convex, perforated by numerous apertures, and traversed by longitudinal grooves for the lodgement of vessels.\n\nThe lateral surface is concave, and forms part of the inferior meatus.\n\n=== Borders ===\n\nIts upper border is thin, irregular, and connected to various bones along the lateral wall of the nasal cavity.\nIt may be divided into three portions: of these,\n\nthe anterior articulates with the conchal crest of the maxilla;\nthe posterior with the conchal crest of the palatine;\nthe middle portion presents three well-marked processes, which vary much in their size and form.\n\nOf these, the anterior or lacrimal process is small and pointed and is situated at the junction of the anterior fourth with the posterior three-fourths of the bone: it articulates, by its apex, with the descending process of the lacrimal bone, and, by its margins, with the groove on the back of the frontal process of the maxilla, and thus assists in forming the canal for the nasolacrimal duct.\n\nBehind this process a broad, thin plate, the ethmoidal process, ascends to join the uncinate process of the ethmoid; from its lower border a thin lamina, the maxillary process, curves downward and lateralward; it articulates with the maxilla and forms a part of the medial wall of the maxillary sinus.\n\nThe inferior border is free, thick, and cellular in structure, more especially in the middle of the bone.\n\n=== Extremities ===\n\nBoth extremities are more or less pointed, the posterior being the more tapering.\n\n=== Development ===\n\nThe inferior nasal concha is ossified from a single center, which appears about the fifth month of fetal life in the lateral wall of the cartilaginous nasal capsule.\n\nhttps://en.wikipedia.org/wiki/Inferior_nasal_concha","lacrimal-bone":"The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail.\n\nIt is situated at the front part of the medial wall of the orbit.\n\nIt has two surfaces and four borders.\n\nSeveral bony landmarks of the lacrimal bone function in the process of lacrimation or crying.\n\nSpecifically, the lacrimal bone helps form the nasolacrimal canal necessary for tear translocation.\n\nA depression on the anterior inferior portion of the bone, the lacrimal fossa, houses the membranous lacrimal sac.\n\nTears or lacrimal fluid, from the lacrimal glands, collect in this sac during excessive lacrimation.\n\nThe fluid then flows through the nasolacrimal duct and into the nasopharynx.\n\nThis drainage results in what is commonly referred to a runny nose during excessive crying or tear production.\n\nInjury or fracture of the lacrimal bone can result in posttraumatic obstruction of the lacrimal pathways.\n\n== Structure ==\n\n=== Lateral or orbital surface ===\n\nThe lateral or orbital surface is divided by a vertical ridge, the posterior lacrimal crest, into two parts.\nIn front of this crest is a longitudinal groove, the lacrimal sulcus (sulcus lacrimalis), the inner margin of which unites with the frontal process of the maxilla, and the lacrimal fossa is thus completed.\n\nThe upper part of this fossa lodges the lacrimal sac, the lower part, the nasolacrimal duct.\nThe portion behind the crest is smooth, and forms part of the medial wall of the orbit.\nThe crest, with a part of the orbital surface immediately behind it, gives origin to the lacrimal part of the orbicularis oculi and ends below in a small, hook-like projection, the lacrimal hamulus, which articulates with the lacrimal tubercle of the maxilla, and completes the upper orifice of the nasolacrimal canal; the hamulus sometimes exists as a separate piece, and is then called the lesser lacrimal bone.\n\n=== Medial or nasal surface ===\n\nThe medial or nasal surface presents a longitudinal furrow, corresponding to the crest on the lateral surface.\nThe area in front of this furrow forms part of the middle meatus of the nose.\n\nThe area behind it articulates with the ethmoid, and completes some of the anterior ethmoidal cells.\n\n=== Borders ===\n\nOf the four borders:\n\nthe anterior articulates with the frontal process of the maxilla;\nthe posterior with the lamina papyracea of the ethmoid;\nthe superior with the frontal bone.\nThe inferior is divided by the lower edge of the posterior lacrimal crest into two parts:\nthe posterior part articulates with the orbital plate of the maxilla;\nthe anterior is prolonged downward as the descending process, which articulates with the lacrimal process of the inferior nasal concha, and assists in forming the canal for the nasolacrimal duct.\n\n=== Development ===\n\nThe lacrimal is ossified from a single center, which appears about the twelfth week in the membrane covering the cartilaginous nasal capsule.\n\n=== Articulations ===\n\nThe lacrimal articulates with four bones: two of the cranium, the frontal and ethmoid, and two of the face, the maxilla and the inferior nasal concha.\n\n== Other animals ==\n\nIn early lobe-finned fishes and ancestral tetrapods, the lacrimal bone is a relatively large and robust bone, running from the orbit to the nostrils.\n\nIt forms part of the side of the face, between the nasal bones and the maxilla.\n\nIn primitive forms, it is often accompanied by a much smaller septomaxilla bone, lying immediately behind the nasal opening, but this is lost in most modern species.\n\nThe lacrimal bone is often smaller in living vertebrates, and is no longer always directly associated with the nasal opening, although it retains its connection with the orbit.\n\nThe bone is entirely absent in living amphibians, as well as some reptilian species.\n\n=== Dinosaurs ===\n\nIn dinosaurs, the lacrimal bone usually defines the anterior rim of the orbit (eye socket), and the posterior rim of the antorbital fenestra.\n\nIn some theropods (e.g.\n\nAllosaurus, Ceratosaurus, Albertosaurus) the upper part of the lacrimal bone grew in such a manner as to form a horn on the top of the dinosaur's head, usually situated above, and anterior to the eye.\n\nIn many dinosaurs, the lacrimal bone comes into contact with the nasal bone, the jugal bone, the prefrontal bone, and the maxillary and premaxillary bones.\n\nThe boundaries where some of these bones meet with the others are called sutures.\n\nRarely, the lacrimal bones fused with the nasal bones to form a pair of \"nasolacrimal\" crests, which are present in dinosaurs such as Dilophosaurus, Megapnosaurus and Sinosaurus.\n\nhttps://en.wikipedia.org/wiki/Lacrimal_bone","nasal-bone":"The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face and by their junction, form the bridge of the upper one third of the nose.\n\nEach has two surfaces and four borders.\n\n== Structure ==\n\nThe two nasal bones are joined at the midline internasal suture and make up the bridge of the nose.\n\n=== Surfaces ===\n\nThe outer surface is concavo-convex from above downward, convex from side to side; it is covered by the procerus and nasalis muscles, and perforated about its center by a foramen, for the transmission of a small vein.\nThe inner surface is concave from side to side, and is traversed from above downward, by a groove for the passage of a branch of the nasociliary nerve.\n\n=== Articulations ===\n\nThe nasal articulates with four bones: two of the cranium, the frontal and ethmoid, and two of the face, the opposite nasal and the maxilla.\n\n== Other animals ==\n\nIn primitive bony fish and tetrapods, the nasal bones are the most anterior of a set of four paired bones forming the roof of the skull, being followed in sequence by the frontals, the parietals, and the postparietals.\n\nTheir form in living species is highly variable, depending on the shape of the head, but they generally form the roof of the snout or beak, running from the nostrils to a position short of the orbits.\n\nIn most animals, they are generally therefore proportionally larger than in humans or great apes, because of the shortened faces of the latter.\n\nTurtles, unusually, lack nasal bones, with the prefrontal bones of the orbit reaching all the way to the nostrils.\n\nhttps://en.wikipedia.org/wiki/Nasal_bone","maxilla":"The maxilla (plural: maxillae) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones.\n\nIn humans, the upper jaw includes the hard palate in the front of the mouth.\n\nThe two maxillary bones are fused at the intermaxillary suture, forming the anterior nasal spine.\n\nThis is similar to the mandible (lower jaw), which is also a fusion of two mandibular bones at the mandibular symphysis.\n\nThe mandible is the movable part of the jaw.\n\nhttps://en.wikipedia.org/wiki/Maxilla","palatine-bone":"In anatomy, the palatine bones () are two irregular bones of the facial skeleton in many animal species, located above the uvula in the throat.\n\nTogether with the maxillae, they comprise the hard palate. (Palate is derived from the Latin palatum.)\n\n== Structure ==\n\nThe palatine bones are situated at the back of the nasal cavity between the maxilla and the pterygoid process of the sphenoid bone.\nThey contribute to the walls of three cavities: the floor and lateral walls of the nasal cavity, the roof of the mouth, and the floor of the orbits.\n\nThey help to form the pterygopalatine and pterygoid fossae, and the inferior orbital fissures.\nEach palatine bone somewhat resembles the letter L, and consists of a horizontal plate, a perpendicular plate, and three projecting processes — the pyramidal process, which is directed backward and lateral from the junction of the two parts, and the orbital and sphenoidal processes, which surmount the vertical part, and are separated by a deep notch, the sphenopalatine notch.\n\nThe two plates form the posterior part of the hard palate and the floor of the nasal cavity; anteriorly, they join with the maxillae.\n\nThe two horizontal plates articulate with each other at the posterior part of the median palatine suture and more anteriorly with the maxillae at the transverse palatine suture.The human palatine articulates with six bones: the sphenoid, ethmoid, maxilla, inferior nasal concha, vomer and opposite palatine.\nThere are two important foramina in the palatine bones that transmit nerves and blood vessels to this region: the greater and lesser palatine.\n\nThe larger greater palatine foramen is located in the posterolateral region of each of the palatine bones, usually at the apex of the maxillary third molar.\n\nThe greater palatine foramen transmits the greater palatine nerve and blood vessels.\n\nA smaller opening nearby, the lesser palatine foramen, transmits the lesser palatine nerve and blood vessels to the soft palate and tonsils.\n\nBoth foramina are openings of the pterygopalatine canal that carries the descending palatine nerves and blood vessels from the pterygopalatine fossa to the palate.\n\n== Function ==\n\nThe sphenopalatine foramen is the opening between the sphenoid bone and orbital processes of the palatine bone; it opens into the nasal cavity and gives passage to branches from the pterygopalatine ganglion and the sphenopalatine artery from the maxillary artery.\n\n== Other animals ==\n\nIn bony fish the palatine bone consists of the perpendicular plate only, lying on the inner edge of the maxilla.\n\nThe lower surface of the bone may bear several teeth, forming a second row behind those of the maxilla; in many cases, these are actually larger than the maxillary teeth.\n\nAlthough a similar pattern was present in primitive tetrapods, the palatine bone is reduced in most living amphibians, forming, in frogs and salamanders, only a narrow bar between the vomer and maxilla.Early fossil reptiles retained the arrangement seen in more primitive vertebrates, but in mammals, the lower surface of the palatine became folded over during evolution, forming the horizontal plate, and meeting in the midline of the mouth.\n\nThis forms the rear of the hard palate, separating the oral and nasal cavities, and making it easier to breathe while eating.\n\nA parallel development has occurred to varying degrees in many living reptiles, reaching its greatest extent in crocodilians.\n\nIn birds, the palatine bones remain separate, long the sides of the rear part of the upper jaw, and typically have a mobile articulation with the cranium.There are numerous variations amongst mammals, amphibians and other species.\n\nFor example, the palatine bone in many amphibians such as the rough-skinned newt manifests as a distinct V-shaped structure.\n\nIn the case of cat species, the horizontal and a vertical elements join at a forty five degree angle.\n\n== External links ==\n\nhttps://en.wikipedia.org/wiki/Palatine_bone","zygomatic-bone":"In the human skull, the zygomatic bone (cheekbone or malar bone) is a paired irregular bone which articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone.\n\nIt is situated at the upper and lateral part of the face and forms the prominence of the cheek, part of the lateral wall and floor of the orbit, and parts of the temporal fossa and the infratemporal fossa.\n\nIt presents a malar and a temporal surface; four processes (the frontosphenoidal, orbital, maxillary, and temporal), and four borders.\n\n== Etymology ==\n\nThe term zygomatic derives from the Greek Ζυγόμα zygoma meaning \"yoke\".\n\nThe zygomatic bone is occasionally referred to as the zygoma, but this term may also refer to the zygomatic arch.\n\n== Structure ==\n\n=== Surfaces ===\n\nThe malar surface is convex and perforated near its center by a small aperture, the zygomaticofacial foramen, for the passage of the zygomaticofacial nerve and vessels; below this foramen is a slight elevation, which gives origin to the zygomaticus muscle.\nThe temporal surface, directed posteriorly and medially, is concave, presenting medially a rough, triangular area, for articulation with the maxilla (articular surface), and laterally a smooth, concave surface, the upper part of which forms the anterior boundary of the temporal fossa, the lower a part of the infratemporal fossa.\n\nNear the center of this surface is the zygomaticotemporal foramen for the transmission of the zygomaticotemporal nerve.\nThe orbital surface forms the lateral part and some of the inferior part of the bony orbit.\n\nThe zygomatic nerve passes through the zygomatic-orbital foramen on this surface.\n\nThe lateral palpebral ligament attaches to a small protuberance called the orbital tubercle.\n\n=== Processes ===\n\nEach zygomatic bone is diamond-shaped and composed of three processes with similarly named associated bony articulations: frontal, temporal, and maxillary.\n\nEach process of the zygomatic bone forms important structures of the skull.\nThe orbital surface of the frontal process of the zygomatic bone forms the anterior lateral orbital wall, with usually a small paired foramen, the zygomaticofacial foramen opening on its lateral surface.\n\nThe temporal process of the zygomatic bone forms the zygomatic arch along with the zygomatic process of the temporal bone, with a paired zygomaticotemporal foramen present on the medial deep surface of the bone.\n\nThe orbital surface of the maxillary process of the zygomatic bone forms a part of the infraorbital rim and a small part of the anterior part of the lateral orbital wall.\n\n=== Orbital process ===\n\nThe orbital process is a thick, strong plate, projecting backward and medialward from the orbital margin.\n\nIts antero-medial surface forms, by its junction with the orbital surface of the maxilla and with the great wing of the sphenoid, part of the floor and lateral wall of the orbit.\n\nOn it are seen the orifices of two canals, the zygomatico-orbital foramina; one of these canals opens into the temporal fossa, the other on the malar surface of the bone; the former transmits the zygomaticotemporal, the latter the zygomaticofacial nerve.\n\nIts postero-lateral surface, smooth and convex, forms parts of the temporal and infratemporal fossae.\nIts anterior margin, smooth and rounded, is part of the circumference of the orbit.\nIts superior margin, rough, and directed horizontally, articulates with the frontal bone behind the zygomatic process.\nIts posterior margin is serrated for articulation, with the great wing of the sphenoid and the orbital surface of the maxilla.At the angle of junction of the sphenoidal and maxillary portions, a short, concave, non-articular part is generally seen; this forms the anterior boundary of the inferior orbital fissure: occasionally, this non-articular part is absent, the fissure then being completed by the junction of the maxilla and sphenoid, or by the interposition of a small sutural bone in the angular interval between them.\n\n=== Borders ===\n\nThe antero-superior or orbital border is smooth, concave, and forms a considerable part of the circumference of the orbit.\nThe antero-inferior or maxillary border is rough, and bevelled at the expense of its inner table, to articulate with the maxilla; near the orbital margin it gives origin to the quadratus labii superioris.\nThe postero-superior or temporal border, curved like an italic letter f, is continuous above with the commencement of the temporal line, and below with the upper border of the zygomatic arch; the temporal fascia is attached to it.\nThe postero-inferior or zygomatic border affords attachment by its rough edge to the masseter.\n\n=== Articulations ===\n\nThe zygomatic bone articulates with the frontal bone, sphenoid bone, and paired temporal bones, and maxillary bones.\n\n=== Development ===\n\nThe zygomatic bone is generally described as ossifying from three centers—one for the malar and two for the orbital portion; these appear about the eighth week and fuse about the fifth month of fetal life.\nMall describes it as being ossified from one center which appears just beneath and to the lateral side of the orbit.\nAfter birth, the bone is sometimes divided by a horizontal suture into an upper larger, and a lower smaller division.\nIn some quadrumana the zygomatic bone consisted of two parts, an orbital and a malar.\n\n== Society and culture ==\n\nPronounced zygomatic arches, commonly called \"high cheekbones\", are considered a beauty trait in some cultures, in both males and females.Ancient Chinese sculptures of goddesses typically have a \"broad forehead, raised eyebrows, high cheekbones, and large, sensuous mouth\".\n\nSimilarly, many depictions of Qin warriors in the Terracotta Army are depicted with \"broad foreheads, high cheekbones, large eyes, thick eyebrows, and stiff beards.\"For this reason some individuals undergo cheek augmentation, a form of cosmetic surgery.\n\n== Other animals ==\n\nThe zygomatic is homologous to the jugal bone of other tetrapods.\n\n=== Non-mammalian vertebrates ===\n\nIn non-mammalian vertebrates, the zygomatic bone is referred to as the jugal bone, since these animals have no zygomatic arch.\n\nIt is found in most reptiles, amphibians, and birds.\n\nIt is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species.\nThis bone is considered key in the determination of general traits of the skull, as in the case of creatures, such as dinosaurs in paleontology, whose entire skull has not been found.\n\nIn coelacanths and early tetrapods the bone is relatively large.\n\nHere, it is a plate-like bone forming the lower margin of the orbit and much of the side of the face.\n\nIn ray-finned fishes it is reduced or absent, and the entire cheek region is generally small.\n\nThe bone is also absent in living amphibians.With the exception of turtles, the jugal bone in reptiles forms a relatively narrow bar separating the orbit from the inferior temporal fenestra, of which it may also form the lower boundary.\n\nThe bone is similarly reduced in birds.\n\nIn mammals, it takes on broadly the form seen in humans, with the bar between the orbit and fenestra vanishing entirely, and only the lower boundary of the fenestra remaining, as the zygomatic arch.\n\nhttps://en.wikipedia.org/wiki/Zygomatic_bone","mandible":"In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton.\n\nIt forms the lower jaw and holds the lower teeth in place.\n\nThe mandible sits beneath the maxilla.\n\nIt is the only movable bone of the skull (discounting the ossicles of the middle ear).\n\nIt is connected to the temporal bones by the temporomandibular joints.\n\nThe bone is formed in the fetus from a fusion of the left and right mandibular prominences, and the point where these sides join, the mandibular symphysis, is still visible as a faint ridge in the midline.\n\nLike other symphyses in the body, this is a midline articulation where the bones are joined by fibrocartilage, but this articulation fuses together in early childhood.\n\nThe word \"mandible\" derives from the Latin word mandibula, \"jawbone\" (literally \"one used for chewing\"), from mandere \"to chew\" and -bula (instrumental suffix).\n\n== Structure ==\n\n=== Components ===\n\nThe mandible consists of:\n\nThe body, found at the front\nA ramus on the left and the right, the rami rise up from the body of the mandible and meet with the body at the angle of the mandible or the gonial angle.\n\n==== Body ====\n\nThe body of the mandible is curved, and the front part gives structure to the chin.\n\nIt has two surfaces and two borders.\n\nFrom the outside, the mandible is marked in the midline by a faint ridge, indicating the mandibular symphysis, the line of junction of the two halves of the mandible, which fuse at about one year of age.\n\nThis ridge divides below and encloses a triangular eminence, the mental protuberance (the chin), the base of which is depressed in the center but raised on both sides to form the mental tubercle.\n\nJust above this, on both sides, the mentalis muscles attach to a depression called the incisive fossa.\n\nBelow the second premolar tooth, on both sides, midway between the upper and lower borders of the body, are the mental foramen, for the passage of the mental vessels and nerve.\n\nRunning backward and upward from each mental tubercle is a faint ridge, the oblique line, which is continuous with the anterior border of the ramus.\n\nAttached to this is the masseter muscle, the depressor labii inferioris and depressor anguli oris, and the platysma (from below).From the inside, the mandible appears concave.\n\nNear the lower part of the symphysis is a pair of laterally placed spines, termed the mental spines, which give origin to the genioglossus.\n\nImmediately below these is a second pair of spines, or more frequently a median ridge or impression, for the origin of the geniohyoid.\n\nIn some cases, the mental spines are fused to form a single eminence, in others they are absent and their position is indicated merely by an irregularity of the surface.\n\nAbove the mental spines, a median foramen and furrow are sometimes seen; they mark the line of union of the halves of the bone.\n\nBelow the mental spines, on either side of the middle line, is an oval depression for the attachment of the anterior belly of the digastric.\n\nExtending upward and backward on either side from the lower part of the symphysis is the mylohyoid line, which gives origin to the mylohyoid muscle; the posterior part of this line, near the alveolar margin, gives attachment to a small part of the constrictor pharyngis superior, and to the pterygomandibular raphe.\n\nAbove the anterior part of this line is a smooth triangular area against which the sublingual gland rests, and below the hinder part, an oval fossa for the submandibular gland.\nBorders\n\nThe superior or alveolar border, wider behind than in front, is hollowed into cavities, for the reception of the teeth; these cavities are sixteen in number and vary in depth and size according to the teeth which they contain.\n\nTo the outer lip of the superior border, on either side, the buccinator is attached as far forward as the first molar tooth.\nThe inferior border is rounded, longer than the superior, and thicker in front than behind; at the point where it joins the lower border of the ramus a shallow groove; for the facial artery, may be present.\n\n==== Ramus ====\n\nThe ramus (Latin: branch) of the human mandible has four sides, two surfaces, four borders, and two processes.\nOn the outside, the ramus is flat and marked by oblique ridges at its lower part.\n\nIt gives attachment throughout nearly the whole of its extent to the masseter muscle.On the inside at the center there is an oblique mandibular foramen, for the entrance of the inferior alveolar vessels and nerve.\n\nThe margin of this opening is irregular; it presents in front a prominent ridge, surmounted by a sharp spine, the lingula of the mandible, which gives attachment to the sphenomandibular ligament; at its lower and back part is a notch from which the mylohyoid groove runs obliquely downward and forward, and lodges the mylohyoid vessels and nerve.\n\nBehind this groove is a rough surface, for the insertion of the medial pterygoid muscle.\n\nThe mandibular canal runs obliquely downward and forward in the ramus, and then horizontally forward in the body, where it is placed under the alveoli and communicates with them by small openings.\n\nOn arriving at the incisor teeth, it turns back to communicate with the mental foramen, giving off two small canals which run to the cavities containing the incisor teeth.\n\nIn the posterior two-thirds of the bone the canal is situated nearer the internal surface of the mandible; and in the anterior third, nearer its external surface.\n\nIt contains the inferior alveolar vessels and nerve, from which branches are distributed to the teeth.\nBorders\n\nThe lower border of the ramus is thick, straight, and continuous with the inferior border of the body of the bone.\n\nAt its junction with the posterior border is the angle of the mandible, which may be either inverted or everted and is marked by rough, oblique ridges on each side, for the attachment of the masseter laterally, and the medial pterygoid muscle medially; the stylomandibular ligament is attached to the angle between these muscles.\n\nThe anterior border is thin above, thicker below, and continuous with the oblique line.\nThe region where the lower border meets the posterior border is the angle of the mandible, often called the gonial angle.\nThe posterior border is thick, smooth, rounded, and covered by the parotid gland.\n\nThe upper border is thin, and is surmounted by two processes, the coronoid in front and the condyloid behind, separated by a deep concavity, the mandibular notch.Processes\n\nThe coronoid process is a thin, triangular eminence, which is flattened from side to side and varies in shape and size.\nThe condyloid process is thicker than the coronoid, and consists of two portions: the mandibular condyle, and the constricted portion which supports it, the neck.\n\nThe condyle is the most superior part of the mandible and is part of the temporomandibular joint.\nThe mandibular notch, separating the two processes, is a deep semilunar depression and is crossed by the masseteric vessels and nerve.\n\n=== Foramina ===\n\nThe mandible has two main holes (foramina), found on both its right and left sides:\n\nThe mandibular foramen, is above the mandibular angle in the middle of each ramus.\nThe mental foramen sits on either side of the mental protuberance (chin) on the body of mandible, usually inferior to the apices of the mandibular first and second premolars.\n\nAs mandibular growth proceeds in young children, the mental foramen alters in direction of its opening from anterior to posterosuperior.\n\nThe mental foramen allows the entrance of the mental nerve and blood vessels into the mandibular canal.\n\n=== Nerves ===\n\nThe inferior alveolar nerve, a branch of the mandibular nerve, (a major division of the trigeminal nerve), enters the mandibular foramen and runs forward in the mandibular canal, supplying sensation to the teeth.\n\nAt the mental foramen, the nerve divides into two terminal branches: incisive and mental nerves.\n\nThe incisive nerve runs forward in the mandible and supplies the anterior teeth.\n\nThe mental nerve exits the mental foramen and supplies sensation to the lower lip.\n\n=== Variation ===\n\nMales generally have squarer, stronger, and larger mandibles than females.\n\nThe mental protuberance is more pronounced in males but can be visualized and palpated in females.Rarely, a bifid inferior alveolar nerve may be present, in which case a second mandibular foramen, more inferiorly placed, exists and can be detected by noting a doubled mandibular canal on a radiograph.\n\n== Development ==\n\nThe mandible forms as a bone (ossifies) over time from a left and right piece of cartilage, called Meckel's cartilage.\nThese cartilages form the cartilaginous bar of the mandibular arch.\n\nNear the head, they are connected with the ear capsules, and they meet at the lower end at the mandibular symphysis, a fusion point between the two bones, by mesodermal tissue.\n\nThey run forward immediately below the condyles and then, bending downward, lie in a groove near the lower border of the bone; in front of the canine tooth they incline upward to the symphysis.\n\nFrom the proximal end of each cartilage the malleus and incus, two of the bones of the middle ear, are developed; the next succeeding portion, as far as the lingula, is replaced by fibrous tissue, which persists to form the sphenomandibular ligament.\n\nBetween the lingula and the canine tooth the cartilage disappears, while the portion of it below and behind the incisor teeth becomes ossified and incorporated with this part of the mandible.\n\nAbout the sixth week of fetal life, intramembranous ossification takes place in the membrane covering the outer surface of the ventral end of Meckel's cartilage, and each half of the bone is formed from a single center which appears, near the mental foramen.\n\nBy the tenth week, the portion of Meckel's cartilage which lies below and behind the incisor teeth is surrounded and invaded by the dermal bone (also known as the membrane bone).\n\nSomewhat later, accessory nuclei of cartilage make their appearance:\n\n-a wedge-shaped nucleus in the condyloid process and extending downward through the ramus;\n-a small strip along the anterior border of the coronoid process;\n-smaller nuclei in the front part of both alveolar walls and along the front of the lower border of the bone.These accessory nuclei possess no separate ossific centers but are invaded by the surrounding dermal bone and undergo absorption.\n\nThe inner alveolar border, usually described as arising from a separate ossific center (splenial center), is formed in the human mandible by an ingrowth from the main mass of the bone.\n\nAt birth the bone consists of two parts, united by a fibrous symphysis, in which ossification takes place during the first year.\n\n=== Aging ===\n\nAt birth, the body of the bone is a mere shell, containing the sockets of the two incisor, the canine, and the two deciduous molar teeth, imperfectly partitioned off from one another.\n\nThe mandibular canal is of large size and runs near the lower border of the bone; the mental foramen opens beneath the socket of the first deciduous molar tooth.\n\nThe angle is obtuse (175°), and the condyloid portion is nearly in line with the body.\n\nThe coronoid process is of comparatively large size, and projects above the level of the condyle.\n\nAfter birth, the two segments of the bone become joined at the symphysis, from below upward, in the first year; but a trace of separation may be visible in the beginning of the second year, near the alveolar margin.\n\nThe body becomes elongated in its whole length, but more especially behind the mental foramen, to provide space for the three additional teeth developed in this part.\n\nThe depth of the body increases owing to increased growth of the alveolar part, to afford room for the roots of the teeth, and by thickening of the subdental portion which enables the jaw to withstand the powerful action of the masticatory muscles; but, the alveolar portion is the deeper of the two, and, consequently, the chief part of the body lies above the oblique line.\n\nThe mandibular canal, after the second dentition, is situated just above the level of the mylohyoid line; and the mental foramen occupies the position usual to it in the adult.\n\nThe angle becomes less obtuse, owing to the separation of the jaws by the teeth; about the fourth year it is 140°.\n\nIn the adult, the alveolar and subdental portions of the body are usually of equal depth.\n\nThe mental foramen opens midway between the upper and lower borders of the bone, and the mandibular canal runs nearly parallel with the mylohyoid line.\n\nThe ramus is almost vertical in direction, the angle measuring from 110° to 120°, also the adult condyle is higher than the coronoid process and the sigmoid notch becomes deeper.\n\nIn old age, the bone can become greatly reduced in volume where there is a loss of teeth, and consequent resorption of the alveolar process and interalveolar septa.\n\nConsequently, the chief part of the bone is below the oblique line.\n\nThe mandibular canal, with the mental foramen opening from it, is closer to the alveolar border.\n\nThe ramus is oblique in direction, the angle measures about 140°, and the neck of the condyle is more or less bent backward.\n\nChanges in the mandible with age\n\n== Function ==\n\nThe mandible forms the lower jaw and holds the lower teeth in place.\n\nIt articulates with the left and right temporal bones at the temporomandibular joints.\n\nCondyloid process, superior (upper) and posterior projection from the ramus, which makes the temporomandibular joint with the temporal bone\nCoronoid process, superior and anterior projection from the ramus.\n\nThis provides attachment to the temporal muscle.Teeth sit in the upper part of the body of the mandible.\n\nThe frontmost part of teeth is more narrow and holds front teeth.\nThe back part holds wider and flatter teeth primarily for chewing food.\n\nThese teeth also often have wide and sometimes deep grooves on the surfaces.\n\n== Clinical significance ==\n\n=== Fracture ===\n\nOne fifth of facial injuries involve a mandibular fracture.\n\nMandibular fractures are often accompanied by a 'twin fracture' on the opposite side.\n\nThere is no universally accepted treatment protocol, as there is no consensus on the choice of techniques in a particular anatomical shape of mandibular fracture clinic.\n\nA common treatment involves attachment of metal plates to the fracture to assist in healing.\nThe mandible may be dislocated anteriorly (to the front) and inferiorly (downwards) but very rarely posteriorly (backwards).\n\nThe articular disk of the temporomandibular joint prevents the mandible from moving posteriorly, making the condylar neck particularly vulnerable to fractures.\n\nThe mandibular alveolar process can become resorbed when completely edentulous in the mandibular arch (occasionally noted also in partially edentulous cases).\n\nThis resorption can occur to such an extent that the mental foramen is virtually on the superior border of the mandible, instead of opening on the anterior surface, changing its relative position.\n\nHowever, the more inferior body of the mandible is not affected and remains thick and rounded.\n\nWith age and tooth loss, the alveolar process is absorbed so that the mandibular canal becomes nearer the superior border.\n\nSometimes with excessive alveolar process absorption, the mandibular canal disappears entirely and leaves the inferior alveolar nerve without its bony protection, although it is still covered by soft tissue.\n\n=== Forensic medicine ===\n\nWhen remains of humans are found, the mandible is one of the common findings, sometimes the only bone found.\n\nSkilled experts can estimate the age of the human upon death because the mandible changes over a person's life.\n\n== Other vertebrates ==\n\nIn lobe-finned fishes and the early fossil tetrapods, the bone homologous to the mandible of mammals is merely the largest of several bones in the lower jaw.\n\nIn such animals, it is referred to as the dentary bone or os dentale, and forms the body of the outer surface of the jaw.\n\nIt is bordered below by a number of splenial bones, while the angle of the jaw is formed by a lower angular bone and a suprangular bone just above it.\n\nThe inner surface of the jaw is lined by a prearticular bone, while the articular bone forms the articulation with the skull proper.\n\nFinally a set of three narrow coronoid bones lie above the prearticular bone.\n\nAs the name implies, the majority of the teeth are attached to the dentary, but there are commonly also teeth on the coronoid bones, and sometimes on the prearticular as well.This complex primitive pattern has, however, been simplified to various degrees in the great majority of vertebrates, as bones have either fused or vanished entirely.\n\nIn teleosts, only the dentary, articular, and angular bones remain, while in living amphibians, the dentary is accompanied only by the prearticular, and, in salamanders, one of the coronoids.\n\nThe lower jaw of reptiles has only a single coronoid and splenial, but retains all the other primitive bones except the prearticular and the periosteum.While, in birds, these various bones have fused into a single structure, in mammals most of them have disappeared, leaving an enlarged dentary as the only remaining bone in the lower jaw – the mandible.\n\nAs a result of this, the primitive jaw articulation, between the articular and quadrate bones, has been lost, and replaced with an entirely new articulation between the mandible and the temporal bone.\n\nAn intermediate stage can be seen in some therapsids, in which both points of articulation are present.\n\nAside from the dentary, only few other bones of the primitive lower jaw remain in mammals; the former articular and quadrate bones survive as the malleus and the incus of the middle ear.\n\nFinally, the cartilaginous fish, such as sharks, do not have any of the bones found in the lower jaw of other vertebrates.\n\nInstead, their lower jaw is composed of a cartilagenous structure homologous with the Meckel's cartilage of other groups.\n\nThis also remains a significant element of the jaw in some primitive bony fish, such as sturgeons.\n\n== Society and culture ==\n\nIn the Book of Judges, Samson used a donkey's jawbone to kill a thousand Philistines.\n\nDental remains of Adolf Hitler including part of a mandible with teeth were the solitary physical evidence used to confirm his death in 1945.\n\nThe Soviet account published in 1968 describes and photographically depicts the jawbone as being broken off at the alveolar process.\n\nhttps://en.wikipedia.org/wiki/Mandible","hyoid-bone":"The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage.\n\nAt rest, it lies at the level of the base of the mandible in the front and the third cervical vertebra (C3) behind.\n\nUnlike other bones, the hyoid is only distantly articulated to other bones by muscles or ligaments.\n\nThe hyoid is anchored by muscles from the anterior, posterior and inferior directions, and aids in tongue movement and swallowing.\n\nThe hyoid bone provides attachment to the muscles of the floor of the mouth and the tongue above, the larynx below, and the epiglottis and pharynx behind.\n\nIts name is derived from Greek hyoeides 'shaped like the letter upsilon (υ)'.\n\n== Structure ==\n\nThe hyoid bone is classed as an irregular bone and consists of a central part called the body, and two pairs of horns, the greater and lesser horns.\n\n=== Body ===\n\nThe body of the hyoid bone is the central part of the hyoid bone.\n\nAt the front, the body is convex and directed forward and upward.\n\nIt is crossed in its upper half by a well-marked transverse ridge with a slight downward convexity, and in many cases a vertical median ridge divides it into two lateral halves.\n\nThe portion of the vertical ridge above the transverse line is present in a majority of specimens, but the lower portion is evident only in rare cases.\n\nThe anterior surface gives insertion to the geniohyoid muscle in the greater part of its extent both above and below the transverse ridge; a portion of the origin of the hyoglossus notches the lateral margin of the geniohyoid attachment.\n\nBelow the transverse ridge the mylohyoid, sternohyoid, and omohyoid are inserted.\n\nAt the back, the smooth, concave, directed backward and downward, and separated from the epiglottis by the hyothyroid membrane and a quantity of loose areolar tissue; a bursa intervenes between it and the hyothyroid membrane.\n\nAbove, the body is rounded, and gives attachment to the hyothyroid membrane and some aponeurotic fibers of the genioglossus.\n\nBelow, the body affords insertion medially to the sternohyoid and laterally to the omohyoid and occasionally a portion of the thyrohyoid.\n\nIt also gives attachment to the Levator glandulae thyreoideae, when this muscle is present.\n\n=== Horns ===\n\nThe greater and lesser horns (Latin: cornua) are two sections of bone that project from each side of the hyoid.\n\nThe greater horns project backward from the outer borders of the body; they are flattened from above downward and taper to their end, which is a bony tubercle connecting to the lateral thyrohyoid ligament.\n\nThe upper surface of the greater horns are rough and close to its lateral border, and facilitates muscular attachment.\n\nThe largest of muscles that attach to the upper surface of the greater horns are the hyoglossus and the middle pharyngeal constrictor, which extend along the whole length of the horns; the digastric muscle and stylohyoid muscle have small insertions in front of these near the junction of the body with the horns.\n\nTo the medial border the thyrohyoid membrane is attached, while the anterior half of the lateral border gives insertion to the thyrohyoid muscle.\n\nThe lesser horns are two small, conical eminences, attached by their bases to the angles of junction between the body and greater horns of the hyoid bone.\n\nThey are connected to the body of the bone by fibrous tissue, and occasionally to the greater horns by distinct diarthrodial joints, which usually persist throughout life, but occasionally become ankylosed.\n\nThe lesser horns are situated in the line of the transverse ridge on the body and appear to be continuations of it.\n\nThe apex of each horn gives attachment to the stylohyoid ligament; the chondroglossus rises from the medial side of the base.\n\n=== Development ===\n\nThe second pharyngeal arch, also called the hyoid arch, gives rise to the lesser cornu of the hyoid and the upper part of the body of the hyoid.\n\nThe cartilage of the third pharyngeal arch forms the greater cornu of the hyoid and the lower portion of the body of the hyoid.\nThe greater horns derive from the third pharyngeal arch.\n\nThe lesser horns are derived from the second pharyngeal arch also called the hyoid arch.The hyoid is ossified from six centers: two for the body, and one for each cornu.\n\nOssification commences in the greater cornua toward the end of fetal development, in the hyoid body shortly afterward, and in the lesser cornua during the first or second year after birth.\n\nUntil middle age the connection between the body and greater cornu is fibrous.\n\nIn early life the outer borders of the body are connected to the greater horns by synchondroses; after middle life usually by bony union.\n\n=== Blood supply ===\n\nBlood is supplied to the hyoid bone via the lingual artery, which runs down from the tongue to the greater horns of the bone.\n\nThe suprahyoid branch of the lingual artery runs along the upper border of the hyoid bone and supplies blood to the attached muscles.\n\n== Function ==\n\nThe hyoid bone is present in many mammals.\n\nIt allows a wider range of tongue, pharyngeal and laryngeal movements by bracing these structures alongside each other in order to produce variation.\n\nIts descent in living creatures is not unique to Homo sapiens, and does not allow the production of a wide range of sounds: with a lower larynx, men do not produce a wider range of sounds than women and 2-year-old babies.\n\nMoreover, the larynx position of Neanderthals was not a handicap to producing speech sounds.\n\nThe discovery of a modern-looking hyoid bone of a Neanderthal man in the Kebara Cave in Israel led its discoverers to argue that the Neanderthals had a descended larynx, and thus human-like speech capabilities.\n\nHowever, other researchers have claimed that the morphology of the hyoid is not indicative of the larynx's position.\n\nIt is necessary to take into consideration the skull base, the mandible and the cervical vertebrae and a cranial reference plane.\n\n=== Muscle attachments ===\n\nA large number of muscles attach to the hyoid:\n\n== Clinical significance ==\n\nThe hyoid bone is important to a number of physiological functions, including breathing, swallowing and speech.\n\nIt is also thought to play a key role in keeping the upper airway open during sleep, and as such, the development and treatment of obstructive sleep apnea (OSA; characterized by repetitive collapse of the upper airway during sleep).\n\nA mechanistic involvement of the hyoid bone in OSA is supported by numerous studies demonstrating that a more inferiorly positioned hyoid bone is strongly associated with the presence and severity of the disorder.\n\nMovement of the hyoid bone is also thought to be important in modifying upper airway properties, which was recently demonstrated in computer model simulations.\n\nA surgical procedure that aims to potentially increase and improve the airway is called hyoid suspension.\nDue to its position, the hyoid bone is not easily susceptible to fracture.\n\nIn a suspected case of murder or physical abuse, a fractured hyoid strongly indicates throttling or strangulation in an adult.\n\nHowever, that is not necessarily the case in children and adolescents, in whom the hyoid bone is still flexible, because ossification is yet to be completed.\n\n== Other animals ==\n\nThe hyoid bone is derived from the lower half of the second gill arch in fish, which separates the first gill slit from the spiracle, and is often called the hyoid arch.\n\nIn many animals, it also incorporates elements of other gill arches, and has a correspondingly greater number of cornua.\n\nAmphibians and reptiles may have many cornua, while mammals (including humans) have two pairs, and birds only one.\n\nIn birds, and some reptiles, the body of the hyoid is greatly extended forward, creating a solid bony support for the tongue.\n\nThe howler monkey Alouatta has a pneumatized hyoid bone, one of the few cases of postcranial pneumatization of bones outside Saurischia.\n\nIn veterinary anatomy, the term hyoid apparatus is the collective term used to refer to the bones of the tongue — a pair of stylohyoidea, a pair of thyrohyoidea, and unpaired basihyoideum — and associated, upper-gular connective tissues.\n\nIn humans, the single hyoid bone is an equivalent of the hyoid apparatus.\n\nhttps://en.wikipedia.org/wiki/Hyoid_bone","malleus":"The malleus, or hammer, is a hammer-shaped small bone or ossicle of the middle ear.\n\nIt connects with the incus, and is attached to the inner surface of the eardrum. The word is Latin for 'hammer' or 'mallet'.\n\nIt transmits the sound vibrations from the eardrum to the incus (anvil).\n\n===Structure===\n\nSee also: Ossicles\n\nThe malleus is a bone situated in the middle ear.\n\nIt is the first of the three ossicles, and attached to the tympanic membrane.\n\nThe head of the malleus is the large protruding section, which attaches to the incus.\n\nThe head connects to the neck of malleus.\n\nThe bone continues as the handle (or manubrium) of malleus, which connects to the tympanic membrane.\n\nBetween the neck and handle of the malleus, lateral and anterior processes emerge from the bone.\n\nThe bone is oriented so that the head is superior and the handle is inferior.\n\n===Development===\n\nEmbryologically, the malleus is derived from the first pharyngeal arch along with the incus.\n\nIt grows from Meckel's cartilage.\n\n===Function===\n\nMain article: Hearing\n\nThe malleus is one of three ossicles in the middle ear which transmit sound from the tympanic membrane (ear drum) to the inner ear.\n\nThe malleus receives vibrations from the tympanic membrane and transmits this to the incus.\n\n===Clinical significance===\n\nThe malleus may be palpated by surgeons during ear surgery. It may become fixed in place due to surgical complications, causing hearing loss.\n\nThis may be corrected with further surgery.\n\n===History===\n\nSeveral sources attribute the discovery of the malleus to the anatomist and philosopher Alessandro Achillini.\n\nThe first brief written description of the malleus was by Berengario da Carpi in his Commentaria super anatomia Mundini (1521).\n\nNiccolo Massa's Liber introductorius anatomiae described the malleus in slightly more detail and likened both it and the incus to little hammers terming them malleoli.\n\n===Other animals===\n\nThe malleus is unique to mammals, and evolved from a lower jaw bone in basal amniotes called the articular, which still forms part of the jaw joint in reptiles and birds.\n\nhttps://en.wikipedia.org/wiki/Malleus","incus":"The incus or anvil is a bone in the middle ear.\n\nThe anvil-shaped small bone is one of three ossicles in the middle ear.\n\nThe incus receives vibrations from the malleus, to which it is connected laterally, and transmits these to the stapes medially.\n\nThe incus is so-called because of its resemblance to an anvil (Latin: Incus).\n\n== Structure ==\n\nThe incus is the second of the ossicles, three bones in the middle ear which act to transmit sound.\n\nIt is shaped like an anvil, and has a long and short crus extending from the body, which articulates with the malleus.: 862  The short crus attaches to the posterior ligament of the incus.\n\nThe long crus articulates with the stirrup at the lenticular process.\nThe superior ligament of the incus attaches at the body of the incus to the roof of the tympanic cavity.\n\n== Function ==\n\nVibrations in the middle ear are received via the tympanic membrane.\n\nThe malleus, resting on the membrane, conveys vibrations to the incus.\n\nThis in turn conveys vibrations to the stapes.\n\n== History ==\n\n\"Incus\" means \"anvil\" in Latin.\n\nSeveral sources attribute the discovery of the incus to the anatomist and philosopher Alessandro Achillini.\n\nThe first brief written description of the incus was by Berengario da Carpi in his Commentaria super anatomia Mundini (1521).\n\nAndreas Vesalius, in his De humani corporis fabrica, was the first to compare the second element of the ossicles to an anvil, thereby giving it the name incus.\n\nThe final part of the long limb was once described as a \"fourth ossicle\" by Pieter Paaw in 1615.\n\nhttps://en.wikipedia.org/wiki/Incus","stapes":"The stapes or stirrup is a bone in the middle ear of humans and other animals which is involved in the conduction of sound vibrations to the inner ear.\n\nThis bone is connected to the oval window by its annular ligament, which allows the footplate to transmit sound energy through the oval window into the inner ear.\n\nThe stapes is the smallest and lightest bone in the human body, and is so-called because of its resemblance to a stirrup (Latin: Stapes).\n\n== Structure ==\n\nThe stapes is the third bone of the three ossicles in the middle ear and the smallest in the human body.\n\nIt measures roughly 2 to 3 mm, greater along the head-base span.\n\nIt rests on the oval window, to which it is connected by an annular ligament and articulates with the incus, or anvil through the incudostapedial joint.\n\nThey are connected by anterior and posterior limbs (Latin: crura).: 862\n\n=== Development ===\n\nThe stapes develops from the second pharyngeal arch during the sixth to eighth week of embryological life.\n\nThe central cavity of the stapes, the obturator foramen, is due to the presence embryologically of the stapedial artery, which usually regresses in humans during normal development.\n\n=== Animals ===\n\nThe stapes is one of three ossicles in mammals.\n\nIn non-mammalian four-legged animals, the bone homologous to the stapes is usually called the columella; however, in reptiles, either term may be used.\n\nIn fish, the homologous bone is called the hyomandibular, and is part of the gill arch supporting either the spiracle or the jaw, depending on the species.\n\nThe equivalent term in amphibians is the pars media plectra.: 481–482\n\n=== Variation ===\n\nThe stapes appears to be relatively constant in size in different ethnic groups.\n\nIn 0.01–0.02% of people, the stapedial artery does not regress, and persists in the central foramen.\n\nIn this case, a pulsatile sound may be heard in the affected ear, or there may be no symptoms at all.\n\nRarely, the stapes may be completely absent.\n\n== Function ==\n\nSituated between the incus and the inner ear, the stapes transmits sound vibrations from the incus to the oval window, a membrane-covered opening to the inner ear.\n\nThe stapes is also stabilized by the stapedius muscle, which is innervated by the facial nerve.: 861–863\n\n== Clinical relevance ==\n\nOtosclerosis is a congenital or spontaneous-onset disease characterized by abnormal bone remodeling in the inner ear.\n\nOften this causes the stapes to adhere to the oval window, which impedes its ability to conduct sound, and is a cause of conductive hearing loss.\n\nClinical otosclerosis is found in about 1% of people, although it is more common in forms that do not cause noticeable hearing loss.\n\nOtosclerosis is more likely in young age groups, and females.\n\nTwo common treatments are stapedectomy, the surgical removal of the stapes and replacement with an artificial prosthesis, and stapedotomy, the creation of a small hole in the base of the stapes followed by the insertion of an artificial prosthesis into that hole.\n\nSurgery may be complicated by a persistent stapedial artery, fibrosis-related damage to the base of the bone, or obliterative otosclerosis, resulting in obliteration of the base. : 254–262\n\n== History ==\n\nThe stapes is commonly described as having been discovered by the professor Giovanni Filippo Ingrassia in 1546 at the University of Naples, although this remains the nature of some controversy, as Ingrassia's description was published posthumously in his 1603 anatomical commentary In Galeni librum de ossibus doctissima et expectatissima commentaria.\n\nSpanish anatomist Pedro Jimeno is first to have been credited with a published description, in Dialogus de re medica (1549).\n\nThe bone is so-named because of its resemblance to a stirrup (Latin: stapes), an example of a late Latin word, probably created in mediaeval times from \"to stand\" (Latin: stapia), as stirrups did not exist in the early Latin-speaking world.\n\nhttps://en.wikipedia.org/wiki/Stapes","upper-medial-incisor":"Incisors (from Latin incidere, \"to cut\") are the front teeth present in most mammals.\n\nThey are located in the premaxilla above and on the mandible below.\n\nHumans have a total of eight (two on each side, top and bottom).\n\nOpossums have 18, whereas armadillos have none.\n\n== Structure ==\n\nAdult humans normally have eight incisors, two of each type.\n\nThe types of incisor are:\n\nmaxillary central incisor (upper jaw, closest to the center of the lips)\nmaxillary lateral incisor (upper jaw, beside the maxillary central incisor)\nmandibular central incisor (lower jaw, closest to the center of the lips)\nmandibular lateral incisor (lower jaw, beside the mandibular central incisor)Children with a full set of deciduous teeth (primary teeth) also have eight incisors, named the same way as in permanent teeth.\n\nYoung children may have from zero to eight incisors depending on the stage of their tooth eruption and tooth development.\n\nTypically, the mandibular central incisors erupt first, followed by the maxillary central incisors, the mandibular lateral incisors and finally the maxillary laterals.\n\nThe rest of the primary dentition erupts after the incisors.Apart from the first molars, the incisors are also the first permanent teeth to erupt, following the same order as the primary teeth, among themselves.\n\n=== Other animals ===\n\nAmong other animals, the number varies from species to species.\n\nOpossums have 18, whereas armadillos have none.\n\nCats, dogs, foxes, pigs, and horses have twelve.\n\nRodents have four.\n\nRabbits and hares (lagomorphs) were once considered rodents, but are distinguished by having six—one small pair, called \"peg teeth\", is located directly behind the most anterior pair.\n\nIncisors are used to bite off tough foods, such as red meat.\nCattle (cows, bulls, etc.) have none on top but a total of six on the bottom.\n\n== Function ==\n\nIn cats, the incisors are small; biting off meat is done with the canines and the carnassials.\n\nIn elephants, the upper incisors are modified into curved tusks (unlike with Narwhals, where it is a canine that develops into a straight and twisted tusk).\n\nThe incisors of rodents grow throughout life and are worn by gnawing.\n\nIn humans, the incisors serve to cut off pieces of food, as well as in the grip of other food items.\n\nhttps://en.wikipedia.org/wiki/Incisor","upper-lateral-incisor":"Incisors (from Latin incidere, \"to cut\") are the front teeth present in most mammals.\n\nThey are located in the premaxilla above and on the mandible below.\n\nHumans have a total of eight (two on each side, top and bottom).\n\nOpossums have 18, whereas armadillos have none.\n\n== Structure ==\n\nAdult humans normally have eight incisors, two of each type.\n\nThe types of incisor are:\n\nmaxillary central incisor (upper jaw, closest to the center of the lips)\nmaxillary lateral incisor (upper jaw, beside the maxillary central incisor)\nmandibular central incisor (lower jaw, closest to the center of the lips)\nmandibular lateral incisor (lower jaw, beside the mandibular central incisor)Children with a full set of deciduous teeth (primary teeth) also have eight incisors, named the same way as in permanent teeth.\n\nYoung children may have from zero to eight incisors depending on the stage of their tooth eruption and tooth development.\n\nTypically, the mandibular central incisors erupt first, followed by the maxillary central incisors, the mandibular lateral incisors and finally the maxillary laterals.\n\nThe rest of the primary dentition erupts after the incisors.Apart from the first molars, the incisors are also the first permanent teeth to erupt, following the same order as the primary teeth, among themselves.\n\n=== Other animals ===\n\nAmong other animals, the number varies from species to species.\n\nOpossums have 18, whereas armadillos have none.\n\nCats, dogs, foxes, pigs, and horses have twelve.\n\nRodents have four.\n\nRabbits and hares (lagomorphs) were once considered rodents, but are distinguished by having six—one small pair, called \"peg teeth\", is located directly behind the most anterior pair.\n\nIncisors are used to bite off tough foods, such as red meat.\nCattle (cows, bulls, etc.) have none on top but a total of six on the bottom.\n\n== Function ==\n\nIn cats, the incisors are small; biting off meat is done with the canines and the carnassials.\n\nIn elephants, the upper incisors are modified into curved tusks (unlike with Narwhals, where it is a canine that develops into a straight and twisted tusk).\n\nThe incisors of rodents grow throughout life and are worn by gnawing.\n\nIn humans, the incisors serve to cut off pieces of food, as well as in the grip of other food items.\n\nhttps://en.wikipedia.org/wiki/Incisor","upper-canine":"In mammalian oral anatomy, the canine teeth, also called cuspids, dog teeth, or (in the context of the upper jaw) fangs, eye teeth, vampire teeth, or vampire fangs, are the relatively long, pointed teeth.\n\nThey can appear more flattened however, causing them to resemble incisors and leading them to be called incisiform.\n\nThey developed and are used primarily for firmly holding food in order to tear it apart, and occasionally as weapons.\n\nThey are often the largest teeth in a mammal's mouth.\n\nIndividuals of most species that develop them normally have four, two in the upper jaw and two in the lower, separated within each jaw by incisors; humans and dogs are examples.\n\nIn most species, canines are the anterior-most teeth in the maxillary bone.\nThe four canines in humans are the two maxillary canines and the two mandibular canines.\n\n== Details ==\n\nThere are four canine teeth: two in the upper (maxillary) and two in the lower (mandibular) arch.\n\nA canine is placed laterally to each lateral incisor and mesial to the premolars.\n\nThey are larger and stronger than the incisors, and their roots sink deeply into the bones, and cause well-marked prominences upon the surface.\n\nThey are the only teeth in dentition with a single cusp, their crowns are roughly triangular from mesial view and trapezoidal in buccal view.\n\nThe crown is large and conical, very convex on its labial surface, a little hollowed and uneven on its lingual surface, and tapering to a blunted point or cusp, which projects beyond the level of the other teeth.\n\nThe root is single, but longer and thicker than that of the incisors, conical in form, compressed laterally, and marked by a slight groove on each side.\n\nThe lingual surface also presents two depressions on either side of the surface separated by a ridge in between; these depressions are known as mesial and distal lingual fossae.\n\n=== Eruption ===\n\nIn humans, the upper canine teeth (popularly called eye teeth, from their position under the eyes) are larger and longer than the lower, and usually present a distinct basal ridge.\n\nEruption typically occurs between the ages of eleven and twelve years for upper canines and between nine and ten years for lower canines.\n\nUpper deciduous canines also known as the baby tooth, typically erupt between ages of sixteen and twenty-two months and sheds between ten and twelve years.\n\nLower deciduous canines typically erupt between ages of seventeen and twenty-two months and sheds between nine to twelve years\n\n=== Developmental defects ===\n\nTransposition (positional interchange of two adjacent teeth) is a development defect that most commonly found in the permanent canine, with the maxillary being more commonly seen than mandibular.\n\nThe upper canine frequently transposed with the first premolar whilst the lower canine transposed with the lateral incisor.\n\nOccasionally canines are congenitally missing.\n\n=== Maxillary canine morphology ===\n\nFrom a facial aspect, maxillary canines are approximately one millimetre narrower than the central incisor.\n\nTheir mesial aspects resemble the adjacent lateral incisors, while their distal aspects anticipate the first premolars.\n\nThey are slightly darker and more yellow in color than the other anterior teeth.\n\nFrom a lingual aspect, they have well developed mesial and distal marginal ridges and a well-developed cingulum.\n\nA prominent lingual ridge divides the lingual aspect in half and creates the mesial and distal lingual fossae between the lingual ridge and the marginal ridges.\n\nFrom a proximal aspect, they resemble the incisors, but are more robust, especially in the cingulum region.\n\nIncisally, they are visibly asymmetrical, as the mesial incisal edge is slightly shorter than the distal incisal edge, which places the cusp slightly mesial to the long axis of the tooth.\n\nThey are also thicker labiolingually than mesiodistally.\n\nBecause of the disproportionate incisal edges, the contacts are also asymmetrical.\n\nMesially, the contact sits at the junction of the incisal and middle third of the crown, while distally, the contact as more cervical, in the middle of the middle third of the crown.The root of the maxillary canines are the longest root of any tooth and conical in shape.\n\n=== Mandibular canine morphology ===\n\nThe lower canine teeth are placed nearer the middle line than the upper, so that their summits correspond to the intervals between the upper canines and the lateral incisors.\n\nFrom a facial aspect, the mandibular canine is notably narrower mesiodistally than the maxillary one, the root is compressed mesiodistally with well-marked grooves on both sides and may be just as long as the maxillary (and at times bifurcated).\n\nA distinctive feature is the nearly straight outline this tooth has compared to the maxillary canine which is slightly more bowed.\n\nAs in the maxillary canine, the mesial incisal edge (or cusp ridge) is shorter than the distal side, however, the cusp is displaced slightly lingual relative to the cusp of the maxillary canine.\n\nLingually, the surface of the tooth is much smoother compared to the very pronounced surface of the maxillary canine, and the cingulum is noted as less developed.\n\nThe cusp may be lost with attrition over time and may resemble an upper second permanent incisor.\n\n== Sexual dimorphism ==\n\nWith many species, the canine teeth in the upper or lower jaw, or in both, are much larger in the males than in the females, or are absent in females, except sometimes a hidden rudiment.\n\nCertain antelopes, the musk-deer, camel, horse, boar, various apes, seals, and the walrus, offer instances.\n\n== In non-synapsids ==\n\nIn non-synapsids (\"mammal-like reptiles\"), teeth similar to canines may be termed \"caniniform\" (\"canine-shaped\") teeth.\n\nhttps://en.wikipedia.org/wiki/Canine_tooth","lower-medial-incisor":"Incisors (from Latin incidere, \"to cut\") are the front teeth present in most mammals.\n\nThey are located in the premaxilla above and on the mandible below.\n\nHumans have a total of eight (two on each side, top and bottom).\n\nOpossums have 18, whereas armadillos have none.\n\n== Structure ==\n\nAdult humans normally have eight incisors, two of each type.\n\nThe types of incisor are:\n\nmaxillary central incisor (upper jaw, closest to the center of the lips)\nmaxillary lateral incisor (upper jaw, beside the maxillary central incisor)\nmandibular central incisor (lower jaw, closest to the center of the lips)\nmandibular lateral incisor (lower jaw, beside the mandibular central incisor)Children with a full set of deciduous teeth (primary teeth) also have eight incisors, named the same way as in permanent teeth.\n\nYoung children may have from zero to eight incisors depending on the stage of their tooth eruption and tooth development.\n\nTypically, the mandibular central incisors erupt first, followed by the maxillary central incisors, the mandibular lateral incisors and finally the maxillary laterals.\n\nThe rest of the primary dentition erupts after the incisors.Apart from the first molars, the incisors are also the first permanent teeth to erupt, following the same order as the primary teeth, among themselves.\n\n=== Other animals ===\n\nAmong other animals, the number varies from species to species.\n\nOpossums have 18, whereas armadillos have none.\n\nCats, dogs, foxes, pigs, and horses have twelve.\n\nRodents have four.\n\nRabbits and hares (lagomorphs) were once considered rodents, but are distinguished by having six—one small pair, called \"peg teeth\", is located directly behind the most anterior pair.\n\nIncisors are used to bite off tough foods, such as red meat.\nCattle (cows, bulls, etc.) have none on top but a total of six on the bottom.\n\n== Function ==\n\nIn cats, the incisors are small; biting off meat is done with the canines and the carnassials.\n\nIn elephants, the upper incisors are modified into curved tusks (unlike with Narwhals, where it is a canine that develops into a straight and twisted tusk).\n\nThe incisors of rodents grow throughout life and are worn by gnawing.\n\nIn humans, the incisors serve to cut off pieces of food, as well as in the grip of other food items.\n\nhttps://en.wikipedia.org/wiki/Incisor","lower-lateral-incisor":"Incisors (from Latin incidere, \"to cut\") are the front teeth present in most mammals.\n\nThey are located in the premaxilla above and on the mandible below.\n\nHumans have a total of eight (two on each side, top and bottom).\n\nOpossums have 18, whereas armadillos have none.\n\n== Structure ==\n\nAdult humans normally have eight incisors, two of each type.\n\nThe types of incisor are:\n\nmaxillary central incisor (upper jaw, closest to the center of the lips)\nmaxillary lateral incisor (upper jaw, beside the maxillary central incisor)\nmandibular central incisor (lower jaw, closest to the center of the lips)\nmandibular lateral incisor (lower jaw, beside the mandibular central incisor)Children with a full set of deciduous teeth (primary teeth) also have eight incisors, named the same way as in permanent teeth.\n\nYoung children may have from zero to eight incisors depending on the stage of their tooth eruption and tooth development.\n\nTypically, the mandibular central incisors erupt first, followed by the maxillary central incisors, the mandibular lateral incisors and finally the maxillary laterals.\n\nThe rest of the primary dentition erupts after the incisors.Apart from the first molars, the incisors are also the first permanent teeth to erupt, following the same order as the primary teeth, among themselves.\n\n=== Other animals ===\n\nAmong other animals, the number varies from species to species.\n\nOpossums have 18, whereas armadillos have none.\n\nCats, dogs, foxes, pigs, and horses have twelve.\n\nRodents have four.\n\nRabbits and hares (lagomorphs) were once considered rodents, but are distinguished by having six—one small pair, called \"peg teeth\", is located directly behind the most anterior pair.\n\nIncisors are used to bite off tough foods, such as red meat.\nCattle (cows, bulls, etc.) have none on top but a total of six on the bottom.\n\n== Function ==\n\nIn cats, the incisors are small; biting off meat is done with the canines and the carnassials.\n\nIn elephants, the upper incisors are modified into curved tusks (unlike with Narwhals, where it is a canine that develops into a straight and twisted tusk).\n\nThe incisors of rodents grow throughout life and are worn by gnawing.\n\nIn humans, the incisors serve to cut off pieces of food, as well as in the grip of other food items.\n\nhttps://en.wikipedia.org/wiki/Incisor","lower-canine":"In mammalian oral anatomy, the canine teeth, also called cuspids, dog teeth, or (in the context of the upper jaw) fangs, eye teeth, vampire teeth, or vampire fangs, are the relatively long, pointed teeth.\n\nThey can appear more flattened however, causing them to resemble incisors and leading them to be called incisiform.\n\nThey developed and are used primarily for firmly holding food in order to tear it apart, and occasionally as weapons.\n\nThey are often the largest teeth in a mammal's mouth.\n\nIndividuals of most species that develop them normally have four, two in the upper jaw and two in the lower, separated within each jaw by incisors; humans and dogs are examples.\n\nIn most species, canines are the anterior-most teeth in the maxillary bone.\nThe four canines in humans are the two maxillary canines and the two mandibular canines.\n\n== Details ==\n\nThere are four canine teeth: two in the upper (maxillary) and two in the lower (mandibular) arch.\n\nA canine is placed laterally to each lateral incisor and mesial to the premolars.\n\nThey are larger and stronger than the incisors, and their roots sink deeply into the bones, and cause well-marked prominences upon the surface.\n\nThey are the only teeth in dentition with a single cusp, their crowns are roughly triangular from mesial view and trapezoidal in buccal view.\n\nThe crown is large and conical, very convex on its labial surface, a little hollowed and uneven on its lingual surface, and tapering to a blunted point or cusp, which projects beyond the level of the other teeth.\n\nThe root is single, but longer and thicker than that of the incisors, conical in form, compressed laterally, and marked by a slight groove on each side.\n\nThe lingual surface also presents two depressions on either side of the surface separated by a ridge in between; these depressions are known as mesial and distal lingual fossae.\n\n=== Eruption ===\n\nIn humans, the upper canine teeth (popularly called eye teeth, from their position under the eyes) are larger and longer than the lower, and usually present a distinct basal ridge.\n\nEruption typically occurs between the ages of eleven and twelve years for upper canines and between nine and ten years for lower canines.\n\nUpper deciduous canines also known as the baby tooth, typically erupt between ages of sixteen and twenty-two months and sheds between ten and twelve years.\n\nLower deciduous canines typically erupt between ages of seventeen and twenty-two months and sheds between nine to twelve years\n\n=== Developmental defects ===\n\nTransposition (positional interchange of two adjacent teeth) is a development defect that most commonly found in the permanent canine, with the maxillary being more commonly seen than mandibular.\n\nThe upper canine frequently transposed with the first premolar whilst the lower canine transposed with the lateral incisor.\n\nOccasionally canines are congenitally missing.\n\n=== Maxillary canine morphology ===\n\nFrom a facial aspect, maxillary canines are approximately one millimetre narrower than the central incisor.\n\nTheir mesial aspects resemble the adjacent lateral incisors, while their distal aspects anticipate the first premolars.\n\nThey are slightly darker and more yellow in color than the other anterior teeth.\n\nFrom a lingual aspect, they have well developed mesial and distal marginal ridges and a well-developed cingulum.\n\nA prominent lingual ridge divides the lingual aspect in half and creates the mesial and distal lingual fossae between the lingual ridge and the marginal ridges.\n\nFrom a proximal aspect, they resemble the incisors, but are more robust, especially in the cingulum region.\n\nIncisally, they are visibly asymmetrical, as the mesial incisal edge is slightly shorter than the distal incisal edge, which places the cusp slightly mesial to the long axis of the tooth.\n\nThey are also thicker labiolingually than mesiodistally.\n\nBecause of the disproportionate incisal edges, the contacts are also asymmetrical.\n\nMesially, the contact sits at the junction of the incisal and middle third of the crown, while distally, the contact as more cervical, in the middle of the middle third of the crown.The root of the maxillary canines are the longest root of any tooth and conical in shape.\n\n=== Mandibular canine morphology ===\n\nThe lower canine teeth are placed nearer the middle line than the upper, so that their summits correspond to the intervals between the upper canines and the lateral incisors.\n\nFrom a facial aspect, the mandibular canine is notably narrower mesiodistally than the maxillary one, the root is compressed mesiodistally with well-marked grooves on both sides and may be just as long as the maxillary (and at times bifurcated).\n\nA distinctive feature is the nearly straight outline this tooth has compared to the maxillary canine which is slightly more bowed.\n\nAs in the maxillary canine, the mesial incisal edge (or cusp ridge) is shorter than the distal side, however, the cusp is displaced slightly lingual relative to the cusp of the maxillary canine.\n\nLingually, the surface of the tooth is much smoother compared to the very pronounced surface of the maxillary canine, and the cingulum is noted as less developed.\n\nThe cusp may be lost with attrition over time and may resemble an upper second permanent incisor.\n\n== Sexual dimorphism ==\n\nWith many species, the canine teeth in the upper or lower jaw, or in both, are much larger in the males than in the females, or are absent in females, except sometimes a hidden rudiment.\n\nCertain antelopes, the musk-deer, camel, horse, boar, various apes, seals, and the walrus, offer instances.\n\n== In non-synapsids ==\n\nIn non-synapsids (\"mammal-like reptiles\"), teeth similar to canines may be termed \"caniniform\" (\"canine-shaped\") teeth.\n\nhttps://en.wikipedia.org/wiki/Canine_tooth","upper-first-premolar":"The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth.\n\nIn humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth.\n\nThey have at least two cusps.\n\nPremolars can be considered transitional teeth during chewing, or mastication.\n\nThey have properties of both the canines, that lay anterior and molars that lay posterior, and so food can be transferred from the canines to the premolars and finally to the molars for grinding, instead of directly from the canines to the molars.\n\n== Human anatomy ==\n\nThe premolars in humans are the maxillary first premolar, maxillary second premolar, mandibular first premolar, and the mandibular second premolar.\n\nPremolar teeth by definition are permanent teeth distal to the canines, preceded by deciduous molars.\n\n=== Morphology ===\n\nThere is always one large buccal cusp, especially so in the mandibular first premolar.\n\nThe lower second premolar almost always presents with two lingual cusps.The lower premolars and the upper second premolar usually have one root.\n\nThe upper first usually has two roots, but can have just one root, notably in Sinodonts, and can sometimes have three roots.Premolars are unique to the permanent dentition.\n\nPremolars are referred to as bicuspid (has two main cusps), a buccal and a palatal/lingual cusp which are separated by a mesiodistal occlusal fissure.\nThe maxillary premolars are trapezoidal in shape.\n\nWhilst the mandibular premolars are rhomboidal in shape.\n\n==== Maxillary first premolar ====\nThe crown of the tooth appears ovoid, wider buccally than palatally\nFrom a buccal view, the first premolar is similar to the adjacent canine\nRoots: Two roots buccal and palatal.\n\nSometimes (40%) there is only one root.\n\n==== Maxillary second premolar ====\nSimilar to maxillary first premolar but the mesio-buccal and disto-buccal corners are rounder\nThe two cusps are smaller and more equal in size\nShorter occlusal fissure\nUsually one root\n\n==== Mandibular first premolar ====\n\n-The smallest premolar out of all four\n-Dominant buccal cusp and a very small lingual cusp\n-The buccal cusp is broad and the lingual cusp is less than half the size of the buccal cusp.\n-Two-thirds of the buccal surface can be seen from the occlusal aspect\n-A single conical root with an oval/round cross section.\n-The root is grooved longitudinally both mesially and distally.\n\n==== Mandibular second premolar ====\n\nThe crown is larger than the mandibular first premolar\nLingual cusp is smaller than the buccal cusp but better developed.\n\nThe lingual and buccal cusp is separated by a well defined mesiodistal occlusal fissure\n\nThe lingual cusp is divided into two; the mesiolingual and distolingual cusps with the mesiolingual cusp being higher and wider than the distolingual.\n\nRoot: Single conical root, oval/round in cross section.\n\n== Orthodontics ==\n\nThe four first premolars are the most commonly removed teeth, in 48.8% of cases, when teeth are removed for orthodontic treatment (which is in 45.8% of orthodontic patients).\n\nThe removal of only the maxillary first premolars is the second likeliest option, in 14.5% of cases.\n\n== Other mammals ==\n\nIn primitive placental mammals there are four premolars per quadrant, but the most mesial two (closer to the front of the mouth) have been lost in catarrhines (Old World monkeys and apes, including humans).\n\nPaleontologists therefore refer to human premolars as Pm3 and Pm4.\n\nhttps://en.wikipedia.org/wiki/Premolar","upper-second-premolar":"The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth.\n\nIn humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth.\n\nThey have at least two cusps.\n\nPremolars can be considered transitional teeth during chewing, or mastication.\n\nThey have properties of both the canines, that lay anterior and molars that lay posterior, and so food can be transferred from the canines to the premolars and finally to the molars for grinding, instead of directly from the canines to the molars.\n\n== Human anatomy ==\n\nThe premolars in humans are the maxillary first premolar, maxillary second premolar, mandibular first premolar, and the mandibular second premolar.\n\nPremolar teeth by definition are permanent teeth distal to the canines, preceded by deciduous molars.\n\n=== Morphology ===\n\nThere is always one large buccal cusp, especially so in the mandibular first premolar.\n\nThe lower second premolar almost always presents with two lingual cusps.The lower premolars and the upper second premolar usually have one root.\n\nThe upper first usually has two roots, but can have just one root, notably in Sinodonts, and can sometimes have three roots.Premolars are unique to the permanent dentition.\n\nPremolars are referred to as bicuspid (has two main cusps), a buccal and a palatal/lingual cusp which are separated by a mesiodistal occlusal fissure.\nThe maxillary premolars are trapezoidal in shape.\n\nWhilst the mandibular premolars are rhomboidal in shape.\n\n==== Maxillary first premolar ====\nThe crown of the tooth appears ovoid, wider buccally than palatally\nFrom a buccal view, the first premolar is similar to the adjacent canine\nRoots: Two roots buccal and palatal.\n\nSometimes (40%) there is only one root.\n\n==== Maxillary second premolar ====\nSimilar to maxillary first premolar but the mesio-buccal and disto-buccal corners are rounder\nThe two cusps are smaller and more equal in size\nShorter occlusal fissure\nUsually one root\n\n==== Mandibular first premolar ====\n\n-The smallest premolar out of all four\n-Dominant buccal cusp and a very small lingual cusp\n-The buccal cusp is broad and the lingual cusp is less than half the size of the buccal cusp.\n-Two-thirds of the buccal surface can be seen from the occlusal aspect\n-A single conical root with an oval/round cross section.\n-The root is grooved longitudinally both mesially and distally.\n\n==== Mandibular second premolar ====\n\nThe crown is larger than the mandibular first premolar\nLingual cusp is smaller than the buccal cusp but better developed.\n\nThe lingual and buccal cusp is separated by a well defined mesiodistal occlusal fissure\n\nThe lingual cusp is divided into two; the mesiolingual and distolingual cusps with the mesiolingual cusp being higher and wider than the distolingual.\n\nRoot: Single conical root, oval/round in cross section.\n\n== Orthodontics ==\n\nThe four first premolars are the most commonly removed teeth, in 48.8% of cases, when teeth are removed for orthodontic treatment (which is in 45.8% of orthodontic patients).\n\nThe removal of only the maxillary first premolars is the second likeliest option, in 14.5% of cases.\n\n== Other mammals ==\n\nIn primitive placental mammals there are four premolars per quadrant, but the most mesial two (closer to the front of the mouth) have been lost in catarrhines (Old World monkeys and apes, including humans).\n\nPaleontologists therefore refer to human premolars as Pm3 and Pm4.\n\nhttps://en.wikipedia.org/wiki/Premolar","upper-first-molar-tooth":"The molars or molar teeth are large, flat teeth at the back of the mouth.\n\nThey are more developed in mammals.\n\nThey are used primarily to grind food during chewing.\n\nThe name molar derives from Latin, molaris dens, meaning \"millstone tooth\", from mola, millstone and dens, tooth.\n\nMolars show a great deal of diversity in size and shape across mammal groups.\n\nThe third molar of humans is sometimes vestigial.\n\n== Human anatomy ==\n\nIn humans, the molar teeth have either four or five cusps.\n\nAdult humans have 12 molars, in four groups of three at the back of the mouth.\n\nThe third, rearmost molar in each group is called a wisdom tooth.\n\nIt is the last tooth to appear, breaking through the front of the gum at about the age of 20, although this varies from individual to individual.\n\nRace can also affect the age at which this occurs, with statistical variations between groups.\n\nIn some cases, it may not even erupt at all.\nThe human mouth contains upper (maxillary) and lower (mandibular) molars.\n\nThey are: maxillary first molar, maxillary second molar, maxillary third molar, mandibular first molar, mandibular second molar, and mandibular third molar.\n\n== Mammal evolution ==\n\nIn mammals, the crown of the molars and premolars is folded into a wide range of complex shapes.\n\nThe basic elements of the crown are the more or less conical projections called cusps and the valleys that separate them.\n\nThe cusps contain both dentine and enamel, whereas minor projections on the crown, called crenulations, are the result of different enamel thickness.\n\nCusps are occasionally joined to form ridges and expanded to form crests.\n\nCingula are often incomplete ridges that pass around the base of the crown.Mammalian, multicusped cheek teeth probably evolved from single-cusped teeth in synapsids, although the diversity of therapsid molar patterns and the complexity in the molars of the earliest mammals make determining how this happened impossible.\n\nAccording to the widely accepted \"differentiation theory\", additional cusps have arisen by budding or outgrowth from the crown, while the rivalling \"concrescence theory\" instead proposes that complex teeth evolved by the clustering of originally separate conical teeth.\n\nTherian mammals (placentals and marsupials) are generally agreed to have evolved from an ancestor with tribosphenic cheek teeth, with three main cusps arranged in a triangle.\n\n== Morphology ==\n\nEach major cusp on an upper molar is called a cone and is identified by a prefix dependent on its relative location on the tooth: proto-, para-, meta-, hypo-, and ento-.\n\nSuffixes are added to these names: -id is added to cusps on a lower molar (e.g., protoconid); -ule to a minor cusp (e.g., protoconulid).\n\nA shelf-like ridge on the lower part of the crown (on an upper molar) is called a cingulum; the same feature on the lower molar a cingulid, and a minor cusp on these, for example, a cingular cuspule or conulid.\n\n=== Tribosphenic ===\n\nThe design that is considered one of the most important characteristics of mammals is a three-cusped shape called a tribosphenic molar.\n\nThis molar design has two important features: the trigonid, or shearing end, and the talonid, or crushing heel.\n\nIn modern tribosphenic molars, the trigonid is towards the front of the jaw and the talonid is towards the rear.\n\nThe tribosphenic tooth is found in insectivores and young platypuses (adults have no teeth).\n\nUpper molars look like three-pointed mountain ranges; lowers look like two peaks and a third off to the side.\nThe tribosphenic design appears primitively in all groups of mammals.\n\nSome paleontologists believe that it developed independently in monotremes (or australosphenidans), rather than being inherited from an ancestor that they share with marsupials and placentals (or boreosphenidans); but this idea has critics and the debate is still going on.\n\nFor example, the dentition of the Early Cretaceous monotreme Steropodon is similar to those of Peramus and dryolestoids, which suggests that monotremes are related to some pre-tribosphenic therian mammals, but, on the other hand, the status of neither of these two groups is well-established.\n\nSome Jurassic mammals, such as Shuotherium and Pseudotribos, have \"reversed tribosphenic\" molars, in which the talonid is towards the front.\n\nThis variant is regarded as an example of convergent evolution.From the primitive tribosphenic tooth, molars have diversified into several unique morphologies.\n\nIn many groups, a fourth cusp, the hypocone (hypoconid), subsequently evolved (see below).\n\n=== Quadrate ===\n\nQuadrate (also called quadritubercular or euthemorphic) molars have an additional fourth cusp on the lingual (tongue) side called the hypocone, located posterior to the protocone.\n\nQuadrate molars appeared early in mammal evolution and are present in many species, including hedgehogs, raccoons, and many primates, including humans.\n\nThere may be a fifth cusp.\n\nIn many mammals, additional smaller cusps called conules appear between the larger cusps.\n\nThey are named after their locations, e.g. a paraconule is located between a paracone and a metacone, a hypoconulid is located between a hypoconid and an entoconid.\n\n=== Bunodont ===\n\nIn bunodont molars, the cusps are low and rounded hills rather than sharp peaks.\n\nThey are most common among omnivores such as pigs, bears, and humans.\n\nBunodont molars are effective crushing devices and often basically quadrate in shape.\n\n=== Hypsodont ===\n\nHypsodont dentition is characterized by high-crowned teeth and enamel that extends far past the gum line, which provides extra material for wear and tear.\n\nSome examples of animals with hypsodont dentition are cattle and horses, all animals that feed on gritty, fibrous material.\n\nHypsodont molars can continue to grow throughout life, for example in some species of Arvicolinae (herbivorous rodents).Hypsodont molars lack both a crown and a neck.\n\nThe occlusal surface is rough and mostly flat, adapted for crushing and grinding plant material.\n\nThe body is covered with cementum both above and below the gingival line, below which is a layer of enamel covering the entire length of the body.\n\nThe cementum and the enamel invaginate into the thick layer of dentin.\n\n=== Brachydont ===\n\nThe opposite condition to hypsodont is called brachydont or brachyodont (from brachys 'short').\n\nIt is a type of dentition characterized by low-crowned teeth.\n\nHuman teeth are brachydont.A brachydont tooth has a crown above the gingival line and a neck just below it, and at least one root.\n\nA cap of enamel covers the crown and extends down to the neck.\n\nCementum is only found below the gingival line.\n\nThe occlusal surfaces tend to be pointed, well-suited for holding prey and tearing and shredding.\n\n=== Zalambdodont ===\n\nZalambdodont molars have three cusps, one larger on the lingual side and two smaller on the labial side, joined by two crests that form a V- or λ-shape.\n\nThe larger inner cusp might be homologous with the paracone in a tribosphenic molar, but can also be fused with the metacone.\n\nThe protocone is typically missing.\n\nThe two smaller labial cusps are located on an expanded shelf called the stylar shelf.\n\nZalambdodont molars are found in, for example, golden moles and solenodons.\n\n=== Dilambdodont ===\n\nLike zalambdodont molars, dilambdodont molars have a distinct ectoloph, but are shaped like two lambdas or a W.\n\nOn the lingual side, at the bottom of the W, are the metacone and paracone, and the stylar shelf is on the labial side.\n\nA protocone is present lingual to the ectoloph.\n\nDilambdodont molars are present in shrews, moles, and some insectivorous bats.\n\n=== Lophodont ===\n\nLophodont teeth are easily identified by the differentiating patterns of ridges or lophs of enamel interconnecting the cusps on the crowns.\n\nPresent in most herbivores, these patterns of lophs can be a simple, ring-like edge, as in mole rats, or a complex arrangement of series of ridges and cross-ridges, as those in odd-toed ungulates, such as equids.Lophodont molars have hard and elongated enamel ridges called lophs oriented either along or perpendicular to the dental row.\n\nLophodont molars are common in herbivores that grind their food thoroughly.\n\nExamples include tapirs, manatees, and many rodents.When two lophs form transverse, often ring-shaped, ridges on a tooth, the arrangement is called bilophodont.\n\nThis pattern is common in primates, but can also be found in lagomorphs (hares, rabbits, and pikas) and some rodents.\n\nExtreme forms of lophodonty in elephants and some rodents (such as Otomys) is known as loxodonty.\n\nThe African elephant belongs to a genus called Loxodonta because of this feature.\n\n=== Selenodont ===\n\nIn selenodont molars (so-named after moon goddess Selene), the major cusp is elongated into crescent-shaped ridge.\n\nExamples include most even-toed ungulates, such as cattle and deer.\n\n=== Secodont ===\n\nMany carnivorous mammals have enlarged and blade-like teeth especially adapted for slicing and chopping called carnassials.\n\nA general term for such blade-like teeth is secodont or plagiaulacoid.\n\nhttps://en.wikipedia.org/wiki/Molar_(tooth)","upper-second-molar-tooth":"The molars or molar teeth are large, flat teeth at the back of the mouth.\n\nThey are more developed in mammals.\n\nThey are used primarily to grind food during chewing.\n\nThe name molar derives from Latin, molaris dens, meaning \"millstone tooth\", from mola, millstone and dens, tooth.\n\nMolars show a great deal of diversity in size and shape across mammal groups.\n\nThe third molar of humans is sometimes vestigial.\n\n== Human anatomy ==\n\nIn humans, the molar teeth have either four or five cusps.\n\nAdult humans have 12 molars, in four groups of three at the back of the mouth.\n\nThe third, rearmost molar in each group is called a wisdom tooth.\n\nIt is the last tooth to appear, breaking through the front of the gum at about the age of 20, although this varies from individual to individual.\n\nRace can also affect the age at which this occurs, with statistical variations between groups.\n\nIn some cases, it may not even erupt at all.\nThe human mouth contains upper (maxillary) and lower (mandibular) molars.\n\nThey are: maxillary first molar, maxillary second molar, maxillary third molar, mandibular first molar, mandibular second molar, and mandibular third molar.\n\n== Mammal evolution ==\n\nIn mammals, the crown of the molars and premolars is folded into a wide range of complex shapes.\n\nThe basic elements of the crown are the more or less conical projections called cusps and the valleys that separate them.\n\nThe cusps contain both dentine and enamel, whereas minor projections on the crown, called crenulations, are the result of different enamel thickness.\n\nCusps are occasionally joined to form ridges and expanded to form crests.\n\nCingula are often incomplete ridges that pass around the base of the crown.Mammalian, multicusped cheek teeth probably evolved from single-cusped teeth in synapsids, although the diversity of therapsid molar patterns and the complexity in the molars of the earliest mammals make determining how this happened impossible.\n\nAccording to the widely accepted \"differentiation theory\", additional cusps have arisen by budding or outgrowth from the crown, while the rivalling \"concrescence theory\" instead proposes that complex teeth evolved by the clustering of originally separate conical teeth.\n\nTherian mammals (placentals and marsupials) are generally agreed to have evolved from an ancestor with tribosphenic cheek teeth, with three main cusps arranged in a triangle.\n\n== Morphology ==\n\nEach major cusp on an upper molar is called a cone and is identified by a prefix dependent on its relative location on the tooth: proto-, para-, meta-, hypo-, and ento-.\n\nSuffixes are added to these names: -id is added to cusps on a lower molar (e.g., protoconid); -ule to a minor cusp (e.g., protoconulid).\n\nA shelf-like ridge on the lower part of the crown (on an upper molar) is called a cingulum; the same feature on the lower molar a cingulid, and a minor cusp on these, for example, a cingular cuspule or conulid.\n\n=== Tribosphenic ===\n\nThe design that is considered one of the most important characteristics of mammals is a three-cusped shape called a tribosphenic molar.\n\nThis molar design has two important features: the trigonid, or shearing end, and the talonid, or crushing heel.\n\nIn modern tribosphenic molars, the trigonid is towards the front of the jaw and the talonid is towards the rear.\n\nThe tribosphenic tooth is found in insectivores and young platypuses (adults have no teeth).\n\nUpper molars look like three-pointed mountain ranges; lowers look like two peaks and a third off to the side.\nThe tribosphenic design appears primitively in all groups of mammals.\n\nSome paleontologists believe that it developed independently in monotremes (or australosphenidans), rather than being inherited from an ancestor that they share with marsupials and placentals (or boreosphenidans); but this idea has critics and the debate is still going on.\n\nFor example, the dentition of the Early Cretaceous monotreme Steropodon is similar to those of Peramus and dryolestoids, which suggests that monotremes are related to some pre-tribosphenic therian mammals, but, on the other hand, the status of neither of these two groups is well-established.\n\nSome Jurassic mammals, such as Shuotherium and Pseudotribos, have \"reversed tribosphenic\" molars, in which the talonid is towards the front.\n\nThis variant is regarded as an example of convergent evolution.From the primitive tribosphenic tooth, molars have diversified into several unique morphologies.\n\nIn many groups, a fourth cusp, the hypocone (hypoconid), subsequently evolved (see below).\n\n=== Quadrate ===\n\nQuadrate (also called quadritubercular or euthemorphic) molars have an additional fourth cusp on the lingual (tongue) side called the hypocone, located posterior to the protocone.\n\nQuadrate molars appeared early in mammal evolution and are present in many species, including hedgehogs, raccoons, and many primates, including humans.\n\nThere may be a fifth cusp.\n\nIn many mammals, additional smaller cusps called conules appear between the larger cusps.\n\nThey are named after their locations, e.g. a paraconule is located between a paracone and a metacone, a hypoconulid is located between a hypoconid and an entoconid.\n\n=== Bunodont ===\n\nIn bunodont molars, the cusps are low and rounded hills rather than sharp peaks.\n\nThey are most common among omnivores such as pigs, bears, and humans.\n\nBunodont molars are effective crushing devices and often basically quadrate in shape.\n\n=== Hypsodont ===\n\nHypsodont dentition is characterized by high-crowned teeth and enamel that extends far past the gum line, which provides extra material for wear and tear.\n\nSome examples of animals with hypsodont dentition are cattle and horses, all animals that feed on gritty, fibrous material.\n\nHypsodont molars can continue to grow throughout life, for example in some species of Arvicolinae (herbivorous rodents).Hypsodont molars lack both a crown and a neck.\n\nThe occlusal surface is rough and mostly flat, adapted for crushing and grinding plant material.\n\nThe body is covered with cementum both above and below the gingival line, below which is a layer of enamel covering the entire length of the body.\n\nThe cementum and the enamel invaginate into the thick layer of dentin.\n\n=== Brachydont ===\n\nThe opposite condition to hypsodont is called brachydont or brachyodont (from brachys 'short').\n\nIt is a type of dentition characterized by low-crowned teeth.\n\nHuman teeth are brachydont.A brachydont tooth has a crown above the gingival line and a neck just below it, and at least one root.\n\nA cap of enamel covers the crown and extends down to the neck.\n\nCementum is only found below the gingival line.\n\nThe occlusal surfaces tend to be pointed, well-suited for holding prey and tearing and shredding.\n\n=== Zalambdodont ===\n\nZalambdodont molars have three cusps, one larger on the lingual side and two smaller on the labial side, joined by two crests that form a V- or λ-shape.\n\nThe larger inner cusp might be homologous with the paracone in a tribosphenic molar, but can also be fused with the metacone.\n\nThe protocone is typically missing.\n\nThe two smaller labial cusps are located on an expanded shelf called the stylar shelf.\n\nZalambdodont molars are found in, for example, golden moles and solenodons.\n\n=== Dilambdodont ===\n\nLike zalambdodont molars, dilambdodont molars have a distinct ectoloph, but are shaped like two lambdas or a W.\n\nOn the lingual side, at the bottom of the W, are the metacone and paracone, and the stylar shelf is on the labial side.\n\nA protocone is present lingual to the ectoloph.\n\nDilambdodont molars are present in shrews, moles, and some insectivorous bats.\n\n=== Lophodont ===\n\nLophodont teeth are easily identified by the differentiating patterns of ridges or lophs of enamel interconnecting the cusps on the crowns.\n\nPresent in most herbivores, these patterns of lophs can be a simple, ring-like edge, as in mole rats, or a complex arrangement of series of ridges and cross-ridges, as those in odd-toed ungulates, such as equids.Lophodont molars have hard and elongated enamel ridges called lophs oriented either along or perpendicular to the dental row.\n\nLophodont molars are common in herbivores that grind their food thoroughly.\n\nExamples include tapirs, manatees, and many rodents.When two lophs form transverse, often ring-shaped, ridges on a tooth, the arrangement is called bilophodont.\n\nThis pattern is common in primates, but can also be found in lagomorphs (hares, rabbits, and pikas) and some rodents.\n\nExtreme forms of lophodonty in elephants and some rodents (such as Otomys) is known as loxodonty.\n\nThe African elephant belongs to a genus called Loxodonta because of this feature.\n\n=== Selenodont ===\n\nIn selenodont molars (so-named after moon goddess Selene), the major cusp is elongated into crescent-shaped ridge.\n\nExamples include most even-toed ungulates, such as cattle and deer.\n\n=== Secodont ===\n\nMany carnivorous mammals have enlarged and blade-like teeth especially adapted for slicing and chopping called carnassials.\n\nA general term for such blade-like teeth is secodont or plagiaulacoid.\n\nhttps://en.wikipedia.org/wiki/Molar_(tooth)","lower-first-premolar":"The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth.\n\nIn humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth.\n\nThey have at least two cusps.\n\nPremolars can be considered transitional teeth during chewing, or mastication.\n\nThey have properties of both the canines, that lay anterior and molars that lay posterior, and so food can be transferred from the canines to the premolars and finally to the molars for grinding, instead of directly from the canines to the molars.\n\n== Human anatomy ==\n\nThe premolars in humans are the maxillary first premolar, maxillary second premolar, mandibular first premolar, and the mandibular second premolar.\n\nPremolar teeth by definition are permanent teeth distal to the canines, preceded by deciduous molars.\n\n=== Morphology ===\n\nThere is always one large buccal cusp, especially so in the mandibular first premolar.\n\nThe lower second premolar almost always presents with two lingual cusps.The lower premolars and the upper second premolar usually have one root.\n\nThe upper first usually has two roots, but can have just one root, notably in Sinodonts, and can sometimes have three roots.Premolars are unique to the permanent dentition.\n\nPremolars are referred to as bicuspid (has two main cusps), a buccal and a palatal/lingual cusp which are separated by a mesiodistal occlusal fissure.\nThe maxillary premolars are trapezoidal in shape.\n\nWhilst the mandibular premolars are rhomboidal in shape.\n\n==== Maxillary first premolar ====\nThe crown of the tooth appears ovoid, wider buccally than palatally\nFrom a buccal view, the first premolar is similar to the adjacent canine\nRoots: Two roots buccal and palatal.\n\nSometimes (40%) there is only one root.\n\n==== Maxillary second premolar ====\nSimilar to maxillary first premolar but the mesio-buccal and disto-buccal corners are rounder\nThe two cusps are smaller and more equal in size\nShorter occlusal fissure\nUsually one root\n\n==== Mandibular first premolar ====\n\n-The smallest premolar out of all four\n-Dominant buccal cusp and a very small lingual cusp\n-The buccal cusp is broad and the lingual cusp is less than half the size of the buccal cusp.\n-Two-thirds of the buccal surface can be seen from the occlusal aspect\n-A single conical root with an oval/round cross section.\n-The root is grooved longitudinally both mesially and distally.\n\n==== Mandibular second premolar ====\n\nThe crown is larger than the mandibular first premolar\nLingual cusp is smaller than the buccal cusp but better developed.\n\nThe lingual and buccal cusp is separated by a well defined mesiodistal occlusal fissure\n\nThe lingual cusp is divided into two; the mesiolingual and distolingual cusps with the mesiolingual cusp being higher and wider than the distolingual.\n\nRoot: Single conical root, oval/round in cross section.\n\n== Orthodontics ==\n\nThe four first premolars are the most commonly removed teeth, in 48.8% of cases, when teeth are removed for orthodontic treatment (which is in 45.8% of orthodontic patients).\n\nThe removal of only the maxillary first premolars is the second likeliest option, in 14.5% of cases.\n\n== Other mammals ==\n\nIn primitive placental mammals there are four premolars per quadrant, but the most mesial two (closer to the front of the mouth) have been lost in catarrhines (Old World monkeys and apes, including humans).\n\nPaleontologists therefore refer to human premolars as Pm3 and Pm4.\n\nhttps://en.wikipedia.org/wiki/Premolar","lower-second-premolar":"The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth.\n\nIn humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth.\n\nThey have at least two cusps.\n\nPremolars can be considered transitional teeth during chewing, or mastication.\n\nThey have properties of both the canines, that lay anterior and molars that lay posterior, and so food can be transferred from the canines to the premolars and finally to the molars for grinding, instead of directly from the canines to the molars.\n\n== Human anatomy ==\n\nThe premolars in humans are the maxillary first premolar, maxillary second premolar, mandibular first premolar, and the mandibular second premolar.\n\nPremolar teeth by definition are permanent teeth distal to the canines, preceded by deciduous molars.\n\n=== Morphology ===\n\nThere is always one large buccal cusp, especially so in the mandibular first premolar.\n\nThe lower second premolar almost always presents with two lingual cusps.The lower premolars and the upper second premolar usually have one root.\n\nThe upper first usually has two roots, but can have just one root, notably in Sinodonts, and can sometimes have three roots.Premolars are unique to the permanent dentition.\n\nPremolars are referred to as bicuspid (has two main cusps), a buccal and a palatal/lingual cusp which are separated by a mesiodistal occlusal fissure.\nThe maxillary premolars are trapezoidal in shape.\n\nWhilst the mandibular premolars are rhomboidal in shape.\n\n==== Maxillary first premolar ====\nThe crown of the tooth appears ovoid, wider buccally than palatally\nFrom a buccal view, the first premolar is similar to the adjacent canine\nRoots: Two roots buccal and palatal.\n\nSometimes (40%) there is only one root.\n\n==== Maxillary second premolar ====\nSimilar to maxillary first premolar but the mesio-buccal and disto-buccal corners are rounder\nThe two cusps are smaller and more equal in size\nShorter occlusal fissure\nUsually one root\n\n==== Mandibular first premolar ====\n\n-The smallest premolar out of all four\n-Dominant buccal cusp and a very small lingual cusp\n-The buccal cusp is broad and the lingual cusp is less than half the size of the buccal cusp.\n-Two-thirds of the buccal surface can be seen from the occlusal aspect\n-A single conical root with an oval/round cross section.\n-The root is grooved longitudinally both mesially and distally.\n\n==== Mandibular second premolar ====\n\nThe crown is larger than the mandibular first premolar\nLingual cusp is smaller than the buccal cusp but better developed.\n\nThe lingual and buccal cusp is separated by a well defined mesiodistal occlusal fissure\n\nThe lingual cusp is divided into two; the mesiolingual and distolingual cusps with the mesiolingual cusp being higher and wider than the distolingual.\n\nRoot: Single conical root, oval/round in cross section.\n\n== Orthodontics ==\n\nThe four first premolars are the most commonly removed teeth, in 48.8% of cases, when teeth are removed for orthodontic treatment (which is in 45.8% of orthodontic patients).\n\nThe removal of only the maxillary first premolars is the second likeliest option, in 14.5% of cases.\n\n== Other mammals ==\n\nIn primitive placental mammals there are four premolars per quadrant, but the most mesial two (closer to the front of the mouth) have been lost in catarrhines (Old World monkeys and apes, including humans).\n\nPaleontologists therefore refer to human premolars as Pm3 and Pm4.\n\nhttps://en.wikipedia.org/wiki/Premolar","lower-first-molar-tooth":"The molars or molar teeth are large, flat teeth at the back of the mouth.\n\nThey are more developed in mammals.\n\nThey are used primarily to grind food during chewing.\n\nThe name molar derives from Latin, molaris dens, meaning \"millstone tooth\", from mola, millstone and dens, tooth.\n\nMolars show a great deal of diversity in size and shape across mammal groups.\n\nThe third molar of humans is sometimes vestigial.\n\n== Human anatomy ==\n\nIn humans, the molar teeth have either four or five cusps.\n\nAdult humans have 12 molars, in four groups of three at the back of the mouth.\n\nThe third, rearmost molar in each group is called a wisdom tooth.\n\nIt is the last tooth to appear, breaking through the front of the gum at about the age of 20, although this varies from individual to individual.\n\nRace can also affect the age at which this occurs, with statistical variations between groups.\n\nIn some cases, it may not even erupt at all.\nThe human mouth contains upper (maxillary) and lower (mandibular) molars.\n\nThey are: maxillary first molar, maxillary second molar, maxillary third molar, mandibular first molar, mandibular second molar, and mandibular third molar.\n\n== Mammal evolution ==\n\nIn mammals, the crown of the molars and premolars is folded into a wide range of complex shapes.\n\nThe basic elements of the crown are the more or less conical projections called cusps and the valleys that separate them.\n\nThe cusps contain both dentine and enamel, whereas minor projections on the crown, called crenulations, are the result of different enamel thickness.\n\nCusps are occasionally joined to form ridges and expanded to form crests.\n\nCingula are often incomplete ridges that pass around the base of the crown.Mammalian, multicusped cheek teeth probably evolved from single-cusped teeth in synapsids, although the diversity of therapsid molar patterns and the complexity in the molars of the earliest mammals make determining how this happened impossible.\n\nAccording to the widely accepted \"differentiation theory\", additional cusps have arisen by budding or outgrowth from the crown, while the rivalling \"concrescence theory\" instead proposes that complex teeth evolved by the clustering of originally separate conical teeth.\n\nTherian mammals (placentals and marsupials) are generally agreed to have evolved from an ancestor with tribosphenic cheek teeth, with three main cusps arranged in a triangle.\n\n== Morphology ==\n\nEach major cusp on an upper molar is called a cone and is identified by a prefix dependent on its relative location on the tooth: proto-, para-, meta-, hypo-, and ento-.\n\nSuffixes are added to these names: -id is added to cusps on a lower molar (e.g., protoconid); -ule to a minor cusp (e.g., protoconulid).\n\nA shelf-like ridge on the lower part of the crown (on an upper molar) is called a cingulum; the same feature on the lower molar a cingulid, and a minor cusp on these, for example, a cingular cuspule or conulid.\n\n=== Tribosphenic ===\n\nThe design that is considered one of the most important characteristics of mammals is a three-cusped shape called a tribosphenic molar.\n\nThis molar design has two important features: the trigonid, or shearing end, and the talonid, or crushing heel.\n\nIn modern tribosphenic molars, the trigonid is towards the front of the jaw and the talonid is towards the rear.\n\nThe tribosphenic tooth is found in insectivores and young platypuses (adults have no teeth).\n\nUpper molars look like three-pointed mountain ranges; lowers look like two peaks and a third off to the side.\nThe tribosphenic design appears primitively in all groups of mammals.\n\nSome paleontologists believe that it developed independently in monotremes (or australosphenidans), rather than being inherited from an ancestor that they share with marsupials and placentals (or boreosphenidans); but this idea has critics and the debate is still going on.\n\nFor example, the dentition of the Early Cretaceous monotreme Steropodon is similar to those of Peramus and dryolestoids, which suggests that monotremes are related to some pre-tribosphenic therian mammals, but, on the other hand, the status of neither of these two groups is well-established.\n\nSome Jurassic mammals, such as Shuotherium and Pseudotribos, have \"reversed tribosphenic\" molars, in which the talonid is towards the front.\n\nThis variant is regarded as an example of convergent evolution.From the primitive tribosphenic tooth, molars have diversified into several unique morphologies.\n\nIn many groups, a fourth cusp, the hypocone (hypoconid), subsequently evolved (see below).\n\n=== Quadrate ===\n\nQuadrate (also called quadritubercular or euthemorphic) molars have an additional fourth cusp on the lingual (tongue) side called the hypocone, located posterior to the protocone.\n\nQuadrate molars appeared early in mammal evolution and are present in many species, including hedgehogs, raccoons, and many primates, including humans.\n\nThere may be a fifth cusp.\n\nIn many mammals, additional smaller cusps called conules appear between the larger cusps.\n\nThey are named after their locations, e.g. a paraconule is located between a paracone and a metacone, a hypoconulid is located between a hypoconid and an entoconid.\n\n=== Bunodont ===\n\nIn bunodont molars, the cusps are low and rounded hills rather than sharp peaks.\n\nThey are most common among omnivores such as pigs, bears, and humans.\n\nBunodont molars are effective crushing devices and often basically quadrate in shape.\n\n=== Hypsodont ===\n\nHypsodont dentition is characterized by high-crowned teeth and enamel that extends far past the gum line, which provides extra material for wear and tear.\n\nSome examples of animals with hypsodont dentition are cattle and horses, all animals that feed on gritty, fibrous material.\n\nHypsodont molars can continue to grow throughout life, for example in some species of Arvicolinae (herbivorous rodents).Hypsodont molars lack both a crown and a neck.\n\nThe occlusal surface is rough and mostly flat, adapted for crushing and grinding plant material.\n\nThe body is covered with cementum both above and below the gingival line, below which is a layer of enamel covering the entire length of the body.\n\nThe cementum and the enamel invaginate into the thick layer of dentin.\n\n=== Brachydont ===\n\nThe opposite condition to hypsodont is called brachydont or brachyodont (from brachys 'short').\n\nIt is a type of dentition characterized by low-crowned teeth.\n\nHuman teeth are brachydont.A brachydont tooth has a crown above the gingival line and a neck just below it, and at least one root.\n\nA cap of enamel covers the crown and extends down to the neck.\n\nCementum is only found below the gingival line.\n\nThe occlusal surfaces tend to be pointed, well-suited for holding prey and tearing and shredding.\n\n=== Zalambdodont ===\n\nZalambdodont molars have three cusps, one larger on the lingual side and two smaller on the labial side, joined by two crests that form a V- or λ-shape.\n\nThe larger inner cusp might be homologous with the paracone in a tribosphenic molar, but can also be fused with the metacone.\n\nThe protocone is typically missing.\n\nThe two smaller labial cusps are located on an expanded shelf called the stylar shelf.\n\nZalambdodont molars are found in, for example, golden moles and solenodons.\n\n=== Dilambdodont ===\n\nLike zalambdodont molars, dilambdodont molars have a distinct ectoloph, but are shaped like two lambdas or a W.\n\nOn the lingual side, at the bottom of the W, are the metacone and paracone, and the stylar shelf is on the labial side.\n\nA protocone is present lingual to the ectoloph.\n\nDilambdodont molars are present in shrews, moles, and some insectivorous bats.\n\n=== Lophodont ===\n\nLophodont teeth are easily identified by the differentiating patterns of ridges or lophs of enamel interconnecting the cusps on the crowns.\n\nPresent in most herbivores, these patterns of lophs can be a simple, ring-like edge, as in mole rats, or a complex arrangement of series of ridges and cross-ridges, as those in odd-toed ungulates, such as equids.Lophodont molars have hard and elongated enamel ridges called lophs oriented either along or perpendicular to the dental row.\n\nLophodont molars are common in herbivores that grind their food thoroughly.\n\nExamples include tapirs, manatees, and many rodents.When two lophs form transverse, often ring-shaped, ridges on a tooth, the arrangement is called bilophodont.\n\nThis pattern is common in primates, but can also be found in lagomorphs (hares, rabbits, and pikas) and some rodents.\n\nExtreme forms of lophodonty in elephants and some rodents (such as Otomys) is known as loxodonty.\n\nThe African elephant belongs to a genus called Loxodonta because of this feature.\n\n=== Selenodont ===\n\nIn selenodont molars (so-named after moon goddess Selene), the major cusp is elongated into crescent-shaped ridge.\n\nExamples include most even-toed ungulates, such as cattle and deer.\n\n=== Secodont ===\n\nMany carnivorous mammals have enlarged and blade-like teeth especially adapted for slicing and chopping called carnassials.\n\nA general term for such blade-like teeth is secodont or plagiaulacoid.\n\nhttps://en.wikipedia.org/wiki/Molar_(tooth)","lower-second-molar-tooth":"The molars or molar teeth are large, flat teeth at the back of the mouth.\n\nThey are more developed in mammals.\n\nThey are used primarily to grind food during chewing.\n\nThe name molar derives from Latin, molaris dens, meaning \"millstone tooth\", from mola, millstone and dens, tooth.\n\nMolars show a great deal of diversity in size and shape across mammal groups.\n\nThe third molar of humans is sometimes vestigial.\n\n== Human anatomy ==\n\nIn humans, the molar teeth have either four or five cusps.\n\nAdult humans have 12 molars, in four groups of three at the back of the mouth.\n\nThe third, rearmost molar in each group is called a wisdom tooth.\n\nIt is the last tooth to appear, breaking through the front of the gum at about the age of 20, although this varies from individual to individual.\n\nRace can also affect the age at which this occurs, with statistical variations between groups.\n\nIn some cases, it may not even erupt at all.\nThe human mouth contains upper (maxillary) and lower (mandibular) molars.\n\nThey are: maxillary first molar, maxillary second molar, maxillary third molar, mandibular first molar, mandibular second molar, and mandibular third molar.\n\n== Mammal evolution ==\n\nIn mammals, the crown of the molars and premolars is folded into a wide range of complex shapes.\n\nThe basic elements of the crown are the more or less conical projections called cusps and the valleys that separate them.\n\nThe cusps contain both dentine and enamel, whereas minor projections on the crown, called crenulations, are the result of different enamel thickness.\n\nCusps are occasionally joined to form ridges and expanded to form crests.\n\nCingula are often incomplete ridges that pass around the base of the crown.Mammalian, multicusped cheek teeth probably evolved from single-cusped teeth in synapsids, although the diversity of therapsid molar patterns and the complexity in the molars of the earliest mammals make determining how this happened impossible.\n\nAccording to the widely accepted \"differentiation theory\", additional cusps have arisen by budding or outgrowth from the crown, while the rivalling \"concrescence theory\" instead proposes that complex teeth evolved by the clustering of originally separate conical teeth.\n\nTherian mammals (placentals and marsupials) are generally agreed to have evolved from an ancestor with tribosphenic cheek teeth, with three main cusps arranged in a triangle.\n\n== Morphology ==\n\nEach major cusp on an upper molar is called a cone and is identified by a prefix dependent on its relative location on the tooth: proto-, para-, meta-, hypo-, and ento-.\n\nSuffixes are added to these names: -id is added to cusps on a lower molar (e.g., protoconid); -ule to a minor cusp (e.g., protoconulid).\n\nA shelf-like ridge on the lower part of the crown (on an upper molar) is called a cingulum; the same feature on the lower molar a cingulid, and a minor cusp on these, for example, a cingular cuspule or conulid.\n\n=== Tribosphenic ===\n\nThe design that is considered one of the most important characteristics of mammals is a three-cusped shape called a tribosphenic molar.\n\nThis molar design has two important features: the trigonid, or shearing end, and the talonid, or crushing heel.\n\nIn modern tribosphenic molars, the trigonid is towards the front of the jaw and the talonid is towards the rear.\n\nThe tribosphenic tooth is found in insectivores and young platypuses (adults have no teeth).\n\nUpper molars look like three-pointed mountain ranges; lowers look like two peaks and a third off to the side.\nThe tribosphenic design appears primitively in all groups of mammals.\n\nSome paleontologists believe that it developed independently in monotremes (or australosphenidans), rather than being inherited from an ancestor that they share with marsupials and placentals (or boreosphenidans); but this idea has critics and the debate is still going on.\n\nFor example, the dentition of the Early Cretaceous monotreme Steropodon is similar to those of Peramus and dryolestoids, which suggests that monotremes are related to some pre-tribosphenic therian mammals, but, on the other hand, the status of neither of these two groups is well-established.\n\nSome Jurassic mammals, such as Shuotherium and Pseudotribos, have \"reversed tribosphenic\" molars, in which the talonid is towards the front.\n\nThis variant is regarded as an example of convergent evolution.From the primitive tribosphenic tooth, molars have diversified into several unique morphologies.\n\nIn many groups, a fourth cusp, the hypocone (hypoconid), subsequently evolved (see below).\n\n=== Quadrate ===\n\nQuadrate (also called quadritubercular or euthemorphic) molars have an additional fourth cusp on the lingual (tongue) side called the hypocone, located posterior to the protocone.\n\nQuadrate molars appeared early in mammal evolution and are present in many species, including hedgehogs, raccoons, and many primates, including humans.\n\nThere may be a fifth cusp.\n\nIn many mammals, additional smaller cusps called conules appear between the larger cusps.\n\nThey are named after their locations, e.g. a paraconule is located between a paracone and a metacone, a hypoconulid is located between a hypoconid and an entoconid.\n\n=== Bunodont ===\n\nIn bunodont molars, the cusps are low and rounded hills rather than sharp peaks.\n\nThey are most common among omnivores such as pigs, bears, and humans.\n\nBunodont molars are effective crushing devices and often basically quadrate in shape.\n\n=== Hypsodont ===\n\nHypsodont dentition is characterized by high-crowned teeth and enamel that extends far past the gum line, which provides extra material for wear and tear.\n\nSome examples of animals with hypsodont dentition are cattle and horses, all animals that feed on gritty, fibrous material.\n\nHypsodont molars can continue to grow throughout life, for example in some species of Arvicolinae (herbivorous rodents).Hypsodont molars lack both a crown and a neck.\n\nThe occlusal surface is rough and mostly flat, adapted for crushing and grinding plant material.\n\nThe body is covered with cementum both above and below the gingival line, below which is a layer of enamel covering the entire length of the body.\n\nThe cementum and the enamel invaginate into the thick layer of dentin.\n\n=== Brachydont ===\n\nThe opposite condition to hypsodont is called brachydont or brachyodont (from brachys 'short').\n\nIt is a type of dentition characterized by low-crowned teeth.\n\nHuman teeth are brachydont.A brachydont tooth has a crown above the gingival line and a neck just below it, and at least one root.\n\nA cap of enamel covers the crown and extends down to the neck.\n\nCementum is only found below the gingival line.\n\nThe occlusal surfaces tend to be pointed, well-suited for holding prey and tearing and shredding.\n\n=== Zalambdodont ===\n\nZalambdodont molars have three cusps, one larger on the lingual side and two smaller on the labial side, joined by two crests that form a V- or λ-shape.\n\nThe larger inner cusp might be homologous with the paracone in a tribosphenic molar, but can also be fused with the metacone.\n\nThe protocone is typically missing.\n\nThe two smaller labial cusps are located on an expanded shelf called the stylar shelf.\n\nZalambdodont molars are found in, for example, golden moles and solenodons.\n\n=== Dilambdodont ===\n\nLike zalambdodont molars, dilambdodont molars have a distinct ectoloph, but are shaped like two lambdas or a W.\n\nOn the lingual side, at the bottom of the W, are the metacone and paracone, and the stylar shelf is on the labial side.\n\nA protocone is present lingual to the ectoloph.\n\nDilambdodont molars are present in shrews, moles, and some insectivorous bats.\n\n=== Lophodont ===\n\nLophodont teeth are easily identified by the differentiating patterns of ridges or lophs of enamel interconnecting the cusps on the crowns.\n\nPresent in most herbivores, these patterns of lophs can be a simple, ring-like edge, as in mole rats, or a complex arrangement of series of ridges and cross-ridges, as those in odd-toed ungulates, such as equids.Lophodont molars have hard and elongated enamel ridges called lophs oriented either along or perpendicular to the dental row.\n\nLophodont molars are common in herbivores that grind their food thoroughly.\n\nExamples include tapirs, manatees, and many rodents.When two lophs form transverse, often ring-shaped, ridges on a tooth, the arrangement is called bilophodont.\n\nThis pattern is common in primates, but can also be found in lagomorphs (hares, rabbits, and pikas) and some rodents.\n\nExtreme forms of lophodonty in elephants and some rodents (such as Otomys) is known as loxodonty.\n\nThe African elephant belongs to a genus called Loxodonta because of this feature.\n\n=== Selenodont ===\n\nIn selenodont molars (so-named after moon goddess Selene), the major cusp is elongated into crescent-shaped ridge.\n\nExamples include most even-toed ungulates, such as cattle and deer.\n\n=== Secodont ===\n\nMany carnivorous mammals have enlarged and blade-like teeth especially adapted for slicing and chopping called carnassials.\n\nA general term for such blade-like teeth is secodont or plagiaulacoid.\n\nhttps://en.wikipedia.org/wiki/Molar_(tooth)","major-alar-cartilage":"The major alar cartilages are positioned with one structure on each side of the nasal tip.\n\nSuperiorly, the major alar cartilages are connected to the lateral nasal cartilage via fibrous tissues.\n\nComposed of hyaline cartilage, these structures are very thin and folded to form the lateral and medial crus.\n\nThe medial crus is the inner portion of the major alar cartilages that are situated perpendicularly to the septal nasal cartilage.\n\nThe lateral crus is the outer portion of the major alar cartilages that associate with the ala of the nose.\n\nBoth crus come together to form an oval tip at each nostril.\n\nBoth sides of the major alar cartilages merge together to form a notch at the tip, which is referred to as the apex of the nose.\n\nWith the formation of the medial and lateral walls within the nares, the major alar cartilages function to hold open each naris.\n\nThis allows maximal airflow to reach the nasal valve, allowing optimal respiration.\n\nDue to weakness corresponding with the lateral crus in certain individuals, a technique called sliding alar cartilage (SAC) has been a procedure practiced to restructure and support the nasal tip.","lateral-process-of-nasal-septal-cartilage":"The lateral cartilage (upper lateral cartilage, lateral process of septal nasal cartilage) is situated below the inferior margin of the nasal bone, and is flattened, and triangular in shape.\n\nIts anterior margin is thicker than the posterior, and is continuous above with the septal nasal cartilage, but separated from it below by a narrow fissure; its superior margin is attached to the nasal bone and the frontal process of the maxilla; its inferior margin is connected by fibrous tissue with the greater alar cartilage.\n\nWhere the lateral cartilage meets the greater alar cartilage, the lateral cartilage often curls up, to join with an inward curl of the greater alar cartilage.\n\nThat curl of the inferior portion of the lateral cartilage is called its \"scroll.\"\n\nhttps://en.wikipedia.org/wiki/Lateral_nasal_cartilage","nasal-septal-cartilage":"The nasal cartilages are structures within the nose that provide form and support to the nasal cavity.\n\nThe nasal cartilages are made up of a flexible material called hyaline cartilage (packed collagen) in the distal portion of the nose.\n\nThere are five individual cartilages that make up the nasal cavity: septal nasal cartilage, lateral nasal cartilage, major alar cartilage (greater alar cartilage, or cartilage of the aperture), minor alar cartilage (lesser alar cartilage, sesamoid, or accessory cartilage), and vomeronasal cartilage (Jacobson's cartilage).\n\nThe nasal cartilages associate with other cartilage structures of the nose or with bones of the facial skeleton.\n\nThese associations create vent-like structures within the nose so that air can flow from the nasal cavity to the lungs or vice versa.\n\nTherefore, the nasal cartilages are structures that aid the body in respiratory functions to intake oxygen or expire carbon dioxide.\n\nAbnormalities or defects in the nasal cartilages affect airflow through the nasal cavity, resulting in respiratory issues.\n\nSurgical techniques have been produced to adjust the position or repair the nasal cartilages so that maximal airflow is once again accomplished.\n\n=== Septal Nasal Cartilage ===\n\nThe septal nasal cartilage is a flat, quadrilateral piece of hyaline cartilage that separates both nasal cavities from one another.\n\nThe septal nasal cartilage fits in a place between the perpendicular plate of the ethmoid and vomer bones while also being covered by an internal mucous membrane.\n\nThe superior portion of the septal nasal cartilage attaches to the nasal bones, while the inferior portion attaches to the alar cartilages via fibrous tissues.\n\nThe septal nasal cartilage separates both right and left nasal cavities, which allows air to pass through them.\n\nProviding two cavities generates turbulence within the tight spaces, allowing air to flow quicker bidirectionally.\n\nThe septal nasal cartilage is also the main structure that provides the orientation of the nose, being the midline structure of the organ.\n\nWith an offset septal nasal cartilage, the nose will appear crooked to the viewer.\n\nA crooked nose can block airflow coming from the nares to the lungs or vice versa.\n\nThis can lead to respiratory issues due to low oxygen but high carbon dioxide counts within the body.\n\nA surgical procedure to correct this issue is called septoplasty.\n\n=== Septoplasty ===\n\nSeptoplasty is a surgical procedure that straightens the septal nasal cartilage within the center of the nose.\n\nWith a crooked septum, it is more difficult for an individual to breathe and the risk for getting a sinus infection increases.\n\nAlso called a deviated septum, a crooked nose will block one or both sides of the nose, affecting the quality of life.\n\nHowever, a deviated septum is very common and does not always create respiratory issues.\n\nRespiratory issues usually occur in more severe cases, requiring surgery to repair.\n\nSurgery is also permitted to individuals that seek cosmetic changes due to moderate cases of a deviated septum.\n\nSurgery may require a surgeon to cut and remove parts of the septal nasal cartilages, replacing them later in a reconstructed format.\n\nThis will allow the individual to receive more airflow through the nostrils when the surgery fully heals after 3 to 6 months.\n\nHowever, there are some risks correlated with this surgical procedure.\n\nThese risks include a change in the shape of the nose, excessive bleeding, vacant space in the septum, trouble smelling, blood clots that need to be removed, and numbness by the facial region.\n\nSmoking can also cause further damage during the healing process of septoplastic surgery.\n\nhttps://en.wikipedia.org/wiki/Nasal_cartilages","thyroid-cartilage":"The thyroid cartilage is the largest of the nine cartilages that make up the laryngeal skeleton, the cartilage structure in and around the trachea that contains the larynx.\n\nIt does not completely encircle the larynx (only the cricoid cartilage encircles it).\n\n== Structure ==\n\nThe thyroid cartilage is a hyaline cartilage structure that sits in front of the larynx and above the thyroid gland.\n\nThe cartilage is composed of two halves, which meet in the middle at a peak called the laryngeal prominence, also called the Adam's apple.\n\nIn the midline above the prominence is the superior thyroid notch.\n\nA counterpart notch at the bottom of the cartilage is called the inferior thyroid notch.\n\nThe two halves of the cartilage that make out the outer surfaces extend obliquely to cover the sides of the trachea.\n\nThe posterior edge of each half articulates with the cricoid cartilage inferiorly at a joint called the cricothyroid joint.\n\nThe most posterior part of the cartilage also has two projections upwards and downwards.\n\nThe upper projection is called the superior horn (cornu), and the lower is called the inferior horn.\n\nThe superior horn is long and narrow, backward, and medialward, and ends in a conical extremity, which gives attachment to the lateral thyrohyoid ligament.\n\nThe inferior horn is short and thick; it is directed downward, with a slight inclination forward and medialward, and presents, on the medial side of its tip, a small oval articular facet for articulation with the side of the cricoid cartilage.\n\nThe entire superior edge of the thyroid cartilage is attached to the hyoid bone by the thyrohyoid membrane.\n\nThe thyroid cartilage is found between the levels of the C4 to C5 vertebrae.\nThe oblique line is a line on the thyroid cartilage.\n\nIt marks the upper lateral borders of the thyroid gland.\n\nTwo muscles originate along the line, the thyrohyoid muscle and inferior pharyngeal constrictor.\n\nThe sternothyroid inserts along the line.\n\nMovement of the cartilage at this joint produces a change in tension at the vocal folds, which in turn produces variation in voice.\n\n== Function ==\n\nThe thyroid cartilage forms the bulk of the front wall of the larynx.\n\nIt protects the vocal folds (\"vocal cords\"), which are located directly behind it.\n\nWhen the angle of the thyroid cartilage changes relative to the cricoid cartilage, this changes the pitch of voice.\n\nThe cartilage also serves as an attachment for several muscles.\n\n== Etymology ==\n\n=== Shield-like ===\n\nThe English term thyroid cartilage is derived from the Latin expression cartilago thyreoides.\n\nThe latter is a translation of Ancient Greek χόνδρος θυρεοειδής, attested in the writings of the Greek physician Galen.\n\nThe Latin word cartilago, as well as the Ancient Greek word χόνδρος, both mean cartilage, while the ancient Greek word θυρεοειδής means shield-like or shield-shaped.\n\nThe latter compound is composed of Ancient Greek θυρεός, shield and εἶδος, form/shape.\n\nThe Greeks used εἶδος in compounds to indicate a resemblance with the first part of the word.The ancient Greek word θυρεός can be found in the Odyssey of Homer, and represented a large square stone that was put against the door to keep it shut.\n\nThose θυρεοί were eventually used by the Greek army as shields to protect themselves.\n\nThis shield was adapted by Roman legions and referred to by them as a scutum.\n\nThe Roman scutum was an oblong shield with an oval shape.\n\nNumerous shields were used by the Roman soldiers, such as the pelta, parma and clypeus.\n\nIn contrast to the scutum, these shields were round.\n\nDespite these latter shields bearing a clear round shape, coinages like petalis cartilago, cartilago parmalis, and cartilago clypealis were coined for the thyroid cartilage.\n\nIn 16th-century Italian anatomist Realdo Colombo's De re anatomica, besides the aforementioned incorrect petalis cartilago, correct forms like scutalis cartilago and scutiformis cartilago can be found, as the scutum is the real Roman pendant of the Greek θυρεός.\n\nThe latter Latin expression can be found in its English form in medical dictionaries as scutiform cartilage, while the name of the shield itself, i.e. scutum, is still being mentioned as a synonym for the thyroid cartilage.\n\n=== Spelling ===\n\nIn the various editions of the official Latin nomenclature (Nomina Anatomica, in 1998 rebaptized as Terminologia Anatomica), three different spellings can be found, i.e. cartilago thyreoidea. cartilago thyroidea and the previously mentioned cartilago thyreoides.\n\nThe variant with the adjective thyreoidea (with the ending -ea) would be a faulty rendering of Ancient Greek θυρεοειδής in Latin.\n\nGreek compounds ending in -ειδής, when imported into Latin as a loanword, ended in -ides.\n\nIn the 17th-century the non-classical Latin form -ideus/-idea/ideum for Greek -ειδής/-ειδές came into use, mostly by French anatomist Jean Riolan the Younger.\n\nNo Greek loanwords (originally -ειδής/-ειδές) ending in -ideus/-idea/-ideum exist in classical Latin, thereby making the -ideus/-idea/-ideum form non-Latinate in character.\n\nThe first edition of the Jena Nomina Anatomica (JNA) contained the incorrect cartilago thyreoidea, but after a list of recommendations/corrections was made this was corrected in subsequent editions of the JNA.\n\nThe variant with thyroidea (omitting e after thyr) is a compromise for English-speaking anatomists, as they have difficulties pronouncing that specific combination of letters, forcing a greater resemblance between Latin and English orthography.\n\nDorland's medical dictionary from 1948 already adopted this incorrect spelling with an erroneous reference to the official Basle Nomina Anatomica even before the nomenclature committee of the Nomina Anatomica officially approved this orthographic revision in its edition of 1961.\n\nThe spelling without an e is commonly accepted in English but earlier works preferred the etymologically correct thyreoid cartilage.\n\nThe official Latin veterinary nomenclature, Nomina Anatomica Veterinaria has the form cartilago thyroidea, in common with the human Nomina Anatomica/Terminologia Anatomica, but allows (in contrast to the latter) cartilago thyreoidea as an alternative spelling.\n\n=== Shield versus door ===\n\nAn unfortunate mishap is the resemblance between Latin thyroidea and English thyroid on the one side and Ancient Greek θυροειδής on the other side, as the latter does not mean shield-like, but actually means like a door, derived from θύρα, door.\n\nΘυροειδής is however used in anatomic nomenclature in the expression θυροειδές τρῆμα (τρῆμα = hole, perforation, aperture), coined by the Greek physician Galen.\n\nAncient Greek θύρα can be translated, besides the aforementioned door, as gate, entrance and opening.\n\nThe Greek name θυροειδές τρῆμα for this opening between the os pubis and the os ischii, currently called obturator foramen, clearly originates from its being an opening (θύρα), while bearing no resemblance to a shield (θυρεός).\n\nThe Latin translation foramen thyreoideum for θυροειδές τρῆμα by the 18th–19th-century German physician and anatomist Samuel Thomas von Sömmerring is clearly mistaken.\n\nThe current foramen thyroideum of the Terminologia Anatomica is not a Latin translation of Galen's θυροειδές τρῆμα, but an orthographic revision of what was previously known in the Nomina Anatomica as foramen thyreoideum, an inconstantly present opening in the lamina of the thyroid cartilage.\n\nhttps://en.wikipedia.org/wiki/Thyroid_cartilage","cricoid-cartilage":"The cricoid cartilage , or simply cricoid (from the Greek krikoeides meaning \"ring-shaped\") or cricoid ring, is the only complete ring of cartilage around the trachea.\n\nIt forms the back part of the voice box and functions as an attachment site for muscles, cartilages, and ligaments involved in opening and closing the airway and in producing speech.\n\n== Structure ==\n\nThe cricoid cartilage sits just inferior to the thyroid cartilage in the neck, at the level of the C6 vertebra, and is joined to it medially by the median cricothyroid ligament and postero-laterally by the cricothyroid joints.\n\nInferior to it are the rings of cartilage around the trachea (which are not continuous – rather they are C-shaped with a gap posteriorly).\n\nThe cricoid is joined to the first tracheal ring by the cricotracheal ligament, and this can be felt as a more yielding area between the firm thyroid cartilage and firmer cricoid.\n\nIt is also anatomically related to the thyroid gland; although the thyroid isthmus is inferior to it, the two lobes of the thyroid extend superiorly on each side of the cricoid as far as the thyroid cartilage above it.\n\nThe posterior part of the cricoid is slightly broader than the anterior and lateral parts, and is called the lamina, while the anterior part is the band; this may be the reason for the common comparison made between the cricoid and a signet ring.\n\nThe slender ventral half, and the most caudal of the palpable laryngeal landmarks, is also referred to as the anterior cricoid arch.\n\n=== Composition ===\n\nIt is made of hyaline cartilage, and so can become calcified or even ossified, particularly in old age.\n\n== Function ==\n\nThe function of the cricoid cartilage is to provide attachments for the cricothyroid muscle, posterior cricoarytenoid muscle and lateral cricoarytenoid muscle muscles, cartilages, and ligaments involved in opening and closing the airway and in speech production.\n\n== Clinical significance ==\n\nWhen intubating a patient under general anesthesia prior to surgery, the anesthesiologist will press on the cricoid cartilage to compress the esophagus behind it so as to prevent gastric reflux from occurring: this is known as the Sellick manoeuvre.\n\nThe Sellick Manoeuvre is typically only applied during a Rapid Sequence Induction (RSI), an induction technique reserved for those at high risk of aspiration.\nThe Sellick maneuver was considered the standard of care during rapid sequence induction for many years.\n\nThe American Heart Association still advocates the use of cricoid pressure during resuscitation using a BVM, and during emergent oral endotracheal intubation.\n\nHowever, recent research increasingly suggests that cricoid pressure may not be as advantageous as once thought.\n\nThe initial article by Sellick was based on a small sample size at a time when high tidal volumes, head-down positioning, and barbiturate anesthesia were the rule.Cricoid pressure may frequently be applied incorrectly.\n\nCricoid pressure may frequently displace the esophagus laterally, instead of compressing it as described by Sellick.\n\nSeveral studies demonstrate some degree of glottic compression reduction in tidal volume and increase in peak pressures.\n\nBased on the current literature, the widespread recommendation that cricoid pressure be applied during every rapid sequence intubation is quickly falling out of favor.\n\nGastric reflux could cause aspiration if this is not done considering the general anesthesia can cause relaxation of the gastroesophageal sphincter allowing stomach contents to ascend through the esophagus into the trachea.\n\nA medical procedure known as a cricoidectomy can be performed in which part or all of the cricoid cartilage is removed.\n\nThis is commonly done to relieve blockages within the trachea.Fractures of the cricoid cartilage can be seen after manual strangulation also known as throttling.\n\nhttps://en.wikipedia.org/wiki/Cricoid_cartilage","arytenoid-cartilage":"The arytenoid cartilages () are a pair of small three-sided pyramids which form part of the larynx.\n\nThey are the site of attachment of the vocal cords.\n\nEach is pyramidal or ladle-shaped and has three surfaces, a base, and an apex.\n\nThe arytenoid cartilages allow for movement of the vocal cords by articulating with the cricoid cartilage.\n\nIt may be affected by arthritis, dislocations, or sclerosis.\n\n== Structure ==\n\nThe arytenoid cartilages are part of the posterior part of the larynx.\n\n=== Surfaces ===\n\nThe posterior surface is triangular, smooth, concave, and gives attachment to the arytenoid muscle and transversus.\n\nThe antero-lateral surface is somewhat convex and rough.\n\nOn it, near the apex of the cartilage, is a rounded elevation (colliculus) from which a ridge (crista arcuata) curves at first backward and then downward and forward to the vocal process.\n\nThe lower part of this crest intervenes between two depressions or foveæ, an upper, triangular, and a lower oblong in shape; the latter gives attachment to the thyroarytenoid muscle (vocal muscle).\n\nThe medial surface is narrow, smooth, and flattened, covered by mucous membrane.\n\nIt forms the lateral boundary of the intercartilaginous part of the rima glottidis.\n\n=== Base and apex ===\n\nThe base of each cartilage is broad, and on it is a concave smooth surface, for articulation with the cricoid cartilage.\n\nIts lateral angle is called the muscular process.\nIts anterior angle is called the vocal process.\n\nThe apex of each cartilage is pointed, curved backward and medialward, and surmounted by a small conical, cartilaginous nodule, the corniculate cartilage.\n\nIt articulates with the cricoid lamina with a ball-and-socket joint.\n\n== Function ==\n\nThe arytenoid cartilages allow the vocal folds to be tensed, relaxed, or approximated.\n\nThey articulate with the supero-lateral parts of the cricoid cartilage lamina, forming the cricoarytenoid joints at which they can come together, move apart, tilt anteriorly or posteriorly, and rotate.\n\n== Clinical significance ==\n\n=== Arthritis ===\n\nRheumatoid arthritis and osteoarthritis can affect the cricoarytenoid joint.\n\nThis can cause airway obstruction, which may be life-threatening.\n\n=== Dislocation ===\n\nRarely, the arytenoid cartilage may be dislocated.\n\nThis is most often caused by tracheal intubation, major trauma to the larynx, or more rarely a laryngeal mask airway.\n\nThis may cause symptoms with problems breathing, such as \"breathiness\" when breathing.\n\nElectromyography and CT scans of the larynx may be used to assess a dislocation in detail.\n\nDislocations may be reduced using an endoscope.\n\n=== Laryngeal cancer ===\n\nSome cases of laryngeal cancer cause the arytenoid cartilage to appear sclerotic.\n\nThis may be observed, and is highly predictive of laryngeal cancer.\n\n== History ==\n\n=== Etymology ===\n\nThe term \"arytenoid\" comes from Ancient Greek ἀρύταινα arytaina meaning \"ladle\" and εἶδος eidos, meaning \"form\".\n\nThey are also often described as \"pyramid\" shaped.\n\nThe word \"arytenoid\" is pronounced .\n\n== Other animals ==\n\nThe arytenoid cartilages are in the larynxes of many animals, including horses.\n\nhttps://en.wikipedia.org/wiki/Arytenoid_cartilage","corniculate-cartilage":"The corniculate cartilages are two small conical nodules consisting of elastic cartilage, which articulate with the summits of the arytenoid cartilages and serve to prolong them posteriorly and medially.\n\nThey are situated in the posterior parts of the aryepiglottic folds of mucous membrane, and are sometimes fused with the arytenoid cartilages.\n\nhttps://en.wikipedia.org/wiki/Corniculate_cartilages","atlas-c1":"In anatomy, the atlas (C1) is the most superior (first) cervical vertebra of the spine and is located in the neck.\n\nIt is named for Atlas of Greek mythology because, just as Atlas supported the globe, it supports the entire head.\n\nThe atlas is the topmost vertebra and, with the axis (the vertebra below it), forms the joint connecting the skull and spine.\n\nThe atlas and axis are specialized to allow a greater range of motion than normal vertebrae.\n\nThey are responsible for the nodding and rotation movements of the head.\n\nThe atlanto-occipital joint allows the head to nod up and down on the vertebral column.\n\nThe dens acts as a pivot that allows the atlas and attached head to rotate on the axis, side to side.\n\nThe atlas's chief peculiarity is that it has no body.\n\nIt is ring-like and consists of an anterior and a posterior arch and two lateral masses.\n\nThe atlas and axis are important neurologically because the brainstem extends down to the axis.\n\n==Structure==\n\nStructure of the atlas, the first cervical vertebra\nAnterior arch\n\nThe anterior arch forms about one-fifth of the ring:\n\n its anterior surface is convex, and presents at its center the anterior tubercle for the attachment of the Longus colli muscles and the anterior longitudinal ligament; posteriorly it is concave, and marked by a smooth, oval or circular facet (fovea dentis), for articulation with the odontoid process (dens) of the axis.\n\nThe upper and lower borders respectively give attachment to the anterior atlantooccipital membrane and the anterior atlantoaxial ligament; the former connects it with the occipital bone above, and the latter with the axis below.\n\nPosterior arch\n\nMedian sagittal section through the occipital bone and first three cervical vertebræ, showing ligamentous attachments\n\nThe posterior arch forms about two-fifths of the circumference of the ring:\n\n it ends behind in the posterior tubercle, which is the rudiment of a spinous process and gives origin to the Recti capitis posteriores minores and the ligamentum nuchae.\n\nThe diminutive size of this process prevents any interference with the movements between the atlas and the skull.\n\nThe posterior part of the arch presents above and behind a rounded edge for the attachment of the posterior atlantooccipital membrane, while immediately behind each superior articular process is the superior vertebral notch (sulcus arteriae vertebralis).\n\nThis is a groove that is sometimes converted into a foramen by ossification of the posterior atlantooccipital membrane to create a delicate bony spiculum which arches backward from the posterior end of the superior articular process.\n\nThis anatomical variant is known as an arcuate foramen.\n\nThis groove transmits the vertebral artery, which, after ascending through the foramen in the transverse process, winds around the lateral mass in a direction backward and medially to enter the vertebrobasilar circulation through the foramen magnum; it also transmits the suboccipital nerve (first spinal nerve)\n\nOn the under surface of the posterior arch, behind the inferior articular facets, are two shallow grooves, the inferior vertebral notches. The lower border gives attachment to the posterior atlantoaxial ligament, which connects it with the axis.\nLateral masses\n\nThe lateral masses are the most bulky and solid parts of the atlas, in order to support the weight of the head.\n\nEach carries two articular facets, a superior and an inferior.\n\n The superior facets are of large size, oval, concave, and approach each other in front, but diverge behind: they are directed upward, medially, and a little backward, each forming a cup for the corresponding condyle of the occipital bone, and are admirably adapted to the nodding movements of the head.\n\n Not infrequently they are partially subdivided by indentations which encroach upon their margins.\n\n The inferior articular facets are circular in form, flattened or slightly convex and directed downward and medially, articulating with the axis, and permitting the rotatory movements of the head.\n\nVertebral foramen\n\nJust below the medial margin of each superior facet is a small tubercle, for the attachment of the transverse atlantal ligament which stretches across the ring of the atlas and divides the vertebral foramen into two unequal parts:\n\n the anterior or smaller receiving the odontoid process of the axis\n the posterior transmitting the spinal cord (medulla spinalis) and its membranes\n\nThis part of the vertebral canal is of considerable size, much greater than is required for the accommodation of the spinal cord.\n\nTransverse processes\n\nThe transverse processes are large; they project laterally and downward from the lateral masses, and serve for the attachment of muscles which assist in rotating the head.\n\nThey are long, and their anterior and posterior tubercles are fused into one mass; the foramen transversarium is directed from below, upward and backward.\n\n==Development==\n\nThe atlas ossifies from three centers\n\nThe atlas is usually ossified from three centers.\n\nOf these, one appears in each lateral mass about the seventh week of fetal life, and extends backward; at birth, these portions of bone are separated from one another behind by a narrow interval filled with cartilage.\n\nBetween the third and fourth years they unite either directly or through the medium of a separate center developed in the cartilage.\n\nAt birth, the anterior arch consists of cartilage; in this a separate center appears about the end of the first year after birth, and joins the lateral masses from the sixth to the eighth year.\n\nThe lines of union extend across the anterior portions of the superior articular facets.\n\nOccasionally there is no separate center, the anterior arch being formed by the forward extension and ultimate junction of the two lateral masses; sometimes this arch is ossified from two centers, one on either side of the middle line.\n\n==Function==\n\nMuscular attachments\nTransverse processes\n\nUpper surface:\n\n rectus capitis anterior – occipital bone (inferior surface of the base)\n rectus capitis lateralis – occipital bone (beneath the jugular process)\n obliquus capitis superior – occipital bone (between the superior and inferior nuchal lines)\n\nInterior and dorsal part:\n\n obliquus capitis inferior – spinous process of the axis\n\nLower surface:\n\n splenius cervicis (part) – spinous processes of T02–T05\n levator scapulae (part) – superior part of medial border of the scapula\n intertransversarius posterior cervicis – transverse process of the axis (posterior tubercle)\n intertransversarius anterior cervicis – transverse process of the axis (anterior tubercle)\n\nPosterior tubercle\n\nUpper surface:\n\n rectus capitis posterior minor – occipital bone (medial part of the interior nuchal line, and the surface between it and the foramen magnum)\n\nLower surface:\n\n interspinalis cervicis – spinous process of the axis\n\nAnterior arch\n\n longus colli (superior oblique) – transverse processes of C03–C05.\n\n==Clinical significance==\n\nThis section needs expansion. You can help by adding to it. (April 2014)\n\nA break in the first vertebra is referred to as a Jefferson fracture.\n\nCraniocervical junction misalignment is also suspected as a factor in neurodegenerative diseases where altered CSF flow plays a part in the pathological process.\n\nHyperextension (Whiplash) Injury\n\nA rear-end traffic collision or a poorly performed rugby tackle can both result in the head being whipped back on the shoulders, causing whiplash.\n\nIn minor cases, the anterior longitudinal ligament of the spine is damaged which is acutely painful for the patient.\n\nIn more severe cases, fractures can occur to any of the cervical vertebrae as they are suddenly compressed by rapid deceleration.\n\nAgain, since the vertebral foramen is large there is less chance of spinal cord involvement.\n\nThe worst-case scenario for these injuries is that dislocation or subluxation of the cervical vertebrae occurs.\n\nThis often happens at the C2 level, where the body of C2 moves anteriorly with respect to C3.\n\nSuch an injury may well lead to spinal cord involvement, and as a consequence quadriplegia or death may occur.\n\nMore commonly, subluxation occurs at the C6/C7 level (50% of cases).\n\nhttps://en.wikipedia.org/wiki/Atlas_(anatomy)","vertebra-c6":"In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull.\n\nTruncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae.\n\nIn sauropsid species, the cervical vertebrae bear cervical ribs.\n\nIn lizards and saurischian dinosaurs, the cervical ribs are large; in birds, they are small and completely fused to the vertebrae.\n\nThe vertebral transverse processes of mammals are homologous to the cervical ribs of other amniotes.\n\nMost mammals have seven cervical vertebrae, with the only three known exceptions being the manatee with six, the two-toed sloth with five or six, and the three-toed sloth with nine.\n\nIn humans, cervical vertebrae are the smallest of the true vertebrae and can be readily distinguished from those of the thoracic or lumbar regions by the presence of a foramen (hole) in each transverse process, through which the vertebral artery, vertebral veins, and inferior cervical ganglion pass.\n\nThe remainder of this article focuses upon human anatomy.\n\n== Structure ==\n\nBy convention, the cervical vertebrae are numbered, with the first one (C1) closest to the skull and higher numbered vertebrae (C2–C7) proceeding away from the skull and down the spine.\n\nThe general characteristics of the third through sixth cervical vertebrae are described here.\n\nThe first, second, and seventh vertebrae are extraordinary, and are detailed later.\n\nThe bodies of these four vertebrae are small, and broader from side to side than from front to back.\n\nThe anterior and posterior surfaces are flattened and of equal depth; the former is placed on a lower level than the latter, and its inferior border is prolonged downward, so as to overlap the upper and forepart of the vertebra below.\n\nThe upper surface is concave transversely, and presents a projecting lip on either side.\n\nThe lower surface is concave from front to back, convex from side to side, and presents laterally shallow concavities that receive the corresponding projecting lips of the underlying vertebra.\n\nThe pedicles are directed laterally and backward, and attach to the body midway between its upper and lower borders, so that the superior vertebral notch is as deep as the inferior, but it is, at the same time, narrower.\n\nThe laminae are narrow and thinner above than below; the vertebral foramen is large and of a triangular form.\nThe spinous process is short and bifid, the two divisions being often of unequal size.\n\nBecause the spinous processes are so short, certain superficial muscles (the trapezius and splenius capitis) attach to the nuchal ligament rather than directly to the vertebrae; the nuchal ligament itself attaching to the spinous processes of C2–C7 and to the posterior tubercle of the atlas.\n\nThe superior and inferior articular processes of cervical vertebrae have fused on either or both sides to form articular pillars, columns of bone that project laterally from the junction of the pedicle and lamina.\n\nThe articular facets are flat and of an oval form:\nthe superior face backward, upward, and slightly medially.\nthe inferior face forward, downward, and slightly laterally.\n\nThe transverse processes are each pierced by the foramen transversarium, which, in the upper six vertebrae, gives passage to the vertebral artery and vein, as well as a plexus of sympathetic nerves.\n\nEach process consists of an anterior and a posterior part.\n\nThese two parts are joined, outside the foramen, by a bar of bone that exhibits a deep sulcus on its upper surface for the passage of the corresponding spinal nerve.\n\nThe anterior portion is the homologue of the rib in the thoracic region, and is therefore named the costal process or costal element.\n\nIt arises from the side of the body, is directed laterally in front of the foramen, and ends in a tubercle, the anterior tubercle.\n\nThe posterior part, the true transverse process, springs from the vertebral arch behind the foramen and is directed forward and laterally; it ends in a flattened vertical tubercle, the posterior tubercle.\n\nThe anterior tubercle of the sixth cervical vertebra is known as the carotid tubercle or Chassaignac tubercle (for Édouard Chassaignac).\n\nThis separates the carotid artery from the vertebral artery and the carotid artery can be massaged against this tubercle to relieve the symptoms of supraventricular tachycardia.\n\nThe carotid tubercle is also used as a landmark for anaesthesia of the brachial plexus and cervical plexus.\n\nThe cervical spinal nerves emerge from above the cervical vertebrae.\n\nFor example, the cervical spinal nerve 3 (C3) passes above C3.\n\n=== Atlas and axis ===\n\nThe atlas (C1) and axis (C2) are the two topmost vertebrae.\n\nThe atlas (C1) is the topmost vertebra, and along with the axis forms the joint connecting the skull and spine.\n\nIt lacks a vertebral body, spinous process, and discs either superior or inferior to it.\n\nIt is ring-like and consists of an anterior arch, posterior arch, and two lateral masses.\nThe axis (C2) forms the pivot on which the atlas rotates.\n\nThe most distinctive characteristic of this bone is the strong odontoid process (dens) that rises perpendicularly from the upper surface of the body and articulates with C1.\n\nThe body is deeper in front than behind, and prolonged downward anteriorly so as to overlap the upper and front part of the third vertebra.\n\n=== Vertebra prominens ===\n\nThe vertebra prominens, or C7, has a distinctive long and prominent spinous process, which is palpable from the skin surface.\n\nSometimes, the seventh cervical vertebra is associated with an abnormal extra rib, known as a cervical rib, which develops from the anterior root of the transverse process.\n\nThese ribs are usually small, but may occasionally compress blood vessels (such as the subclavian artery or subclavian vein) or nerves in the brachial plexus, causing pain, numbness, tingling, and weakness in the upper limb, a condition known as thoracic outlet syndrome.\n\nVery rarely, this rib occurs in a pair.\nThe long spinous process of C7 is thick and nearly horizontal in direction.\n\nIt is not bifurcated, and ends in a tubercle that the ligamentum nuchae attaches to.\n\nThis process is not always the most prominent of the spinous processes, being found only about 70% of the time, C6 or T1 can sometimes be the most prominent.\n\nThe transverse processes are of considerable size; their posterior roots are large and prominent, while the anterior are small and faintly marked.\n\nThe upper surface of each usually has a shallow sulcus for the eighth spinal nerve, and its extremity seldom presents more than a trace of bifurcation.\n\nThe transverse foramen may be as large as that in the other cervical vertebrae, but it is generally smaller on one or both sides; occasionally, it is double, and sometimes it is absent.\n\nOn the left side, it occasionally gives passage to the vertebral artery; more frequently, the vertebral vein traverses it on both sides, but the usual arrangement is for both artery and vein to pass in front of the transverse process, not through the foramen.\n\n== Function ==\n\nThe movement of nodding the head takes place predominantly through flexion and extension at the atlanto-occipital joint between the atlas and the occipital bone.\n\nHowever, the cervical spine is comparatively mobile, and some component of this movement is due to flexion and extension of the vertebral column itself.\n\nThis movement between the atlas and occipital bone is often referred to as the \"yes joint\", owing to its nature of being able to move the head in an up-and-down fashion.\n\nThe movement of shaking or rotating the head left and right happens almost entirely at the joint between the atlas and the axis, the atlanto-axial joint.\n\nA small amount of rotation of the vertebral column itself contributes to the movement.\n\nThis movement between the atlas and axis is often referred to as the \"no joint\", owing to its nature of being able to rotate the head in a side-to-side fashion.\n\n== Clinical significance ==\n\nCervical degenerative changes arise from conditions such as spondylosis, stenosis of intervertebral discs, and the formation of osteophytes.\n\nThe changes are seen on radiographs, which are used in a grading system from 0–4 ranging from no changes (0) to early with minimal development of osteophytes (1) to mild with definite osteophytes (2) to moderate with additional disc space stenosis or narrowing (3) to the stage of many large osteophytes, severe narrowing of the disc space, and more severe vertebral end plate sclerosis (4).Injuries to the cervical spine are common at the level of the second cervical vertebrae, but neurological injury is uncommon.\n\nC4 and C5 are the areas that see the highest amount of cervical spine trauma.If it does occur, however, it may cause death or profound disability, including paralysis of the arms, legs, and diaphragm, which leads to respiratory failure.\n\nCommon patterns of injury include the odontoid fracture and the hangman's fracture, both of which are often treated with immobilization in a cervical collar or Halo brace.\n\nA common practice is to immobilize a patient's cervical spine to prevent further damage during transport to hospital.\n\nThis practice has come under review recently as incidence rates of unstable spinal trauma can be as low as 2% in immobilized patients.\n\nIn clearing the cervical spine, Canadian studies have developed the Canadian C-Spine Rule (CCR) for physicians to decide who should receive radiological imaging.\n\n=== Landmarks ===\n\nThe vertebral column is often used as a marker of human anatomy.\n\nThis includes:\n\nAt C1, base of the nose and the hard palate\nAt C2, the teeth of a closed mouth\nAt C3, the mandible and hyoid bone\nAt C4, the common carotid artery bifurcates.\nFrom C4–5, the thyroid cartilage\nFrom C6–7, the cricoid cartilage\nAt C6, the oesophagus becomes continuous with the laryngopharynx and also where the larynx becomes continuous with the trachea.\n\nIt is also the level where the carotid pulse can be palpated against the transverse process of the C6 vertebrae.\n\nhttps://en.wikipedia.org/wiki/Cervical_vertebrae","vertebra-c3":"In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull.\n\nTruncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae.\n\nIn sauropsid species, the cervical vertebrae bear cervical ribs.\n\nIn lizards and saurischian dinosaurs, the cervical ribs are large; in birds, they are small and completely fused to the vertebrae.\n\nThe vertebral transverse processes of mammals are homologous to the cervical ribs of other amniotes.\n\nMost mammals have seven cervical vertebrae, with the only three known exceptions being the manatee with six, the two-toed sloth with five or six, and the three-toed sloth with nine.\n\nIn humans, cervical vertebrae are the smallest of the true vertebrae and can be readily distinguished from those of the thoracic or lumbar regions by the presence of a foramen (hole) in each transverse process, through which the vertebral artery, vertebral veins, and inferior cervical ganglion pass.\n\nThe remainder of this article focuses upon human anatomy.\n\n== Structure ==\n\nBy convention, the cervical vertebrae are numbered, with the first one (C1) closest to the skull and higher numbered vertebrae (C2–C7) proceeding away from the skull and down the spine.\n\nThe general characteristics of the third through sixth cervical vertebrae are described here.\n\nThe first, second, and seventh vertebrae are extraordinary, and are detailed later.\n\nThe bodies of these four vertebrae are small, and broader from side to side than from front to back.\n\nThe anterior and posterior surfaces are flattened and of equal depth; the former is placed on a lower level than the latter, and its inferior border is prolonged downward, so as to overlap the upper and forepart of the vertebra below.\n\nThe upper surface is concave transversely, and presents a projecting lip on either side.\n\nThe lower surface is concave from front to back, convex from side to side, and presents laterally shallow concavities that receive the corresponding projecting lips of the underlying vertebra.\n\nThe pedicles are directed laterally and backward, and attach to the body midway between its upper and lower borders, so that the superior vertebral notch is as deep as the inferior, but it is, at the same time, narrower.\n\nThe laminae are narrow and thinner above than below; the vertebral foramen is large and of a triangular form.\nThe spinous process is short and bifid, the two divisions being often of unequal size.\n\nBecause the spinous processes are so short, certain superficial muscles (the trapezius and splenius capitis) attach to the nuchal ligament rather than directly to the vertebrae; the nuchal ligament itself attaching to the spinous processes of C2–C7 and to the posterior tubercle of the atlas.\n\nThe superior and inferior articular processes of cervical vertebrae have fused on either or both sides to form articular pillars, columns of bone that project laterally from the junction of the pedicle and lamina.\n\nThe articular facets are flat and of an oval form:\nthe superior face backward, upward, and slightly medially.\nthe inferior face forward, downward, and slightly laterally.\n\nThe transverse processes are each pierced by the foramen transversarium, which, in the upper six vertebrae, gives passage to the vertebral artery and vein, as well as a plexus of sympathetic nerves.\n\nEach process consists of an anterior and a posterior part.\n\nThese two parts are joined, outside the foramen, by a bar of bone that exhibits a deep sulcus on its upper surface for the passage of the corresponding spinal nerve.\n\nThe anterior portion is the homologue of the rib in the thoracic region, and is therefore named the costal process or costal element.\n\nIt arises from the side of the body, is directed laterally in front of the foramen, and ends in a tubercle, the anterior tubercle.\n\nThe posterior part, the true transverse process, springs from the vertebral arch behind the foramen and is directed forward and laterally; it ends in a flattened vertical tubercle, the posterior tubercle.\n\nThe anterior tubercle of the sixth cervical vertebra is known as the carotid tubercle or Chassaignac tubercle (for Édouard Chassaignac).\n\nThis separates the carotid artery from the vertebral artery and the carotid artery can be massaged against this tubercle to relieve the symptoms of supraventricular tachycardia.\n\nThe carotid tubercle is also used as a landmark for anaesthesia of the brachial plexus and cervical plexus.\n\nThe cervical spinal nerves emerge from above the cervical vertebrae.\n\nFor example, the cervical spinal nerve 3 (C3) passes above C3.\n\n=== Atlas and axis ===\n\nThe atlas (C1) and axis (C2) are the two topmost vertebrae.\n\nThe atlas (C1) is the topmost vertebra, and along with the axis forms the joint connecting the skull and spine.\n\nIt lacks a vertebral body, spinous process, and discs either superior or inferior to it.\n\nIt is ring-like and consists of an anterior arch, posterior arch, and two lateral masses.\nThe axis (C2) forms the pivot on which the atlas rotates.\n\nThe most distinctive characteristic of this bone is the strong odontoid process (dens) that rises perpendicularly from the upper surface of the body and articulates with C1.\n\nThe body is deeper in front than behind, and prolonged downward anteriorly so as to overlap the upper and front part of the third vertebra.\n\n=== Vertebra prominens ===\n\nThe vertebra prominens, or C7, has a distinctive long and prominent spinous process, which is palpable from the skin surface.\n\nSometimes, the seventh cervical vertebra is associated with an abnormal extra rib, known as a cervical rib, which develops from the anterior root of the transverse process.\n\nThese ribs are usually small, but may occasionally compress blood vessels (such as the subclavian artery or subclavian vein) or nerves in the brachial plexus, causing pain, numbness, tingling, and weakness in the upper limb, a condition known as thoracic outlet syndrome.\n\nVery rarely, this rib occurs in a pair.\nThe long spinous process of C7 is thick and nearly horizontal in direction.\n\nIt is not bifurcated, and ends in a tubercle that the ligamentum nuchae attaches to.\n\nThis process is not always the most prominent of the spinous processes, being found only about 70% of the time, C6 or T1 can sometimes be the most prominent.\n\nThe transverse processes are of considerable size; their posterior roots are large and prominent, while the anterior are small and faintly marked.\n\nThe upper surface of each usually has a shallow sulcus for the eighth spinal nerve, and its extremity seldom presents more than a trace of bifurcation.\n\nThe transverse foramen may be as large as that in the other cervical vertebrae, but it is generally smaller on one or both sides; occasionally, it is double, and sometimes it is absent.\n\nOn the left side, it occasionally gives passage to the vertebral artery; more frequently, the vertebral vein traverses it on both sides, but the usual arrangement is for both artery and vein to pass in front of the transverse process, not through the foramen.\n\n== Function ==\n\nThe movement of nodding the head takes place predominantly through flexion and extension at the atlanto-occipital joint between the atlas and the occipital bone.\n\nHowever, the cervical spine is comparatively mobile, and some component of this movement is due to flexion and extension of the vertebral column itself.\n\nThis movement between the atlas and occipital bone is often referred to as the \"yes joint\", owing to its nature of being able to move the head in an up-and-down fashion.\n\nThe movement of shaking or rotating the head left and right happens almost entirely at the joint between the atlas and the axis, the atlanto-axial joint.\n\nA small amount of rotation of the vertebral column itself contributes to the movement.\n\nThis movement between the atlas and axis is often referred to as the \"no joint\", owing to its nature of being able to rotate the head in a side-to-side fashion.\n\n== Clinical significance ==\n\nCervical degenerative changes arise from conditions such as spondylosis, stenosis of intervertebral discs, and the formation of osteophytes.\n\nThe changes are seen on radiographs, which are used in a grading system from 0–4 ranging from no changes (0) to early with minimal development of osteophytes (1) to mild with definite osteophytes (2) to moderate with additional disc space stenosis or narrowing (3) to the stage of many large osteophytes, severe narrowing of the disc space, and more severe vertebral end plate sclerosis (4).Injuries to the cervical spine are common at the level of the second cervical vertebrae, but neurological injury is uncommon.\n\nC4 and C5 are the areas that see the highest amount of cervical spine trauma.If it does occur, however, it may cause death or profound disability, including paralysis of the arms, legs, and diaphragm, which leads to respiratory failure.\n\nCommon patterns of injury include the odontoid fracture and the hangman's fracture, both of which are often treated with immobilization in a cervical collar or Halo brace.\n\nA common practice is to immobilize a patient's cervical spine to prevent further damage during transport to hospital.\n\nThis practice has come under review recently as incidence rates of unstable spinal trauma can be as low as 2% in immobilized patients.\n\nIn clearing the cervical spine, Canadian studies have developed the Canadian C-Spine Rule (CCR) for physicians to decide who should receive radiological imaging.\n\n=== Landmarks ===\n\nThe vertebral column is often used as a marker of human anatomy.\n\nThis includes:\n\nAt C1, base of the nose and the hard palate\nAt C2, the teeth of a closed mouth\nAt C3, the mandible and hyoid bone\nAt C4, the common carotid artery bifurcates.\nFrom C4–5, the thyroid cartilage\nFrom C6–7, the cricoid cartilage\nAt C6, the oesophagus becomes continuous with the laryngopharynx and also where the larynx becomes continuous with the trachea.\n\nIt is also the level where the carotid pulse can be palpated against the transverse process of the C6 vertebrae.\n\nhttps://en.wikipedia.org/wiki/Cervical_vertebrae","vertebra-c5":"In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull.\n\nTruncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae.\n\nIn sauropsid species, the cervical vertebrae bear cervical ribs.\n\nIn lizards and saurischian dinosaurs, the cervical ribs are large; in birds, they are small and completely fused to the vertebrae.\n\nThe vertebral transverse processes of mammals are homologous to the cervical ribs of other amniotes.\n\nMost mammals have seven cervical vertebrae, with the only three known exceptions being the manatee with six, the two-toed sloth with five or six, and the three-toed sloth with nine.\n\nIn humans, cervical vertebrae are the smallest of the true vertebrae and can be readily distinguished from those of the thoracic or lumbar regions by the presence of a foramen (hole) in each transverse process, through which the vertebral artery, vertebral veins, and inferior cervical ganglion pass.\n\nThe remainder of this article focuses upon human anatomy.\n\n== Structure ==\n\nBy convention, the cervical vertebrae are numbered, with the first one (C1) closest to the skull and higher numbered vertebrae (C2–C7) proceeding away from the skull and down the spine.\n\nThe general characteristics of the third through sixth cervical vertebrae are described here.\n\nThe first, second, and seventh vertebrae are extraordinary, and are detailed later.\n\nThe bodies of these four vertebrae are small, and broader from side to side than from front to back.\n\nThe anterior and posterior surfaces are flattened and of equal depth; the former is placed on a lower level than the latter, and its inferior border is prolonged downward, so as to overlap the upper and forepart of the vertebra below.\n\nThe upper surface is concave transversely, and presents a projecting lip on either side.\n\nThe lower surface is concave from front to back, convex from side to side, and presents laterally shallow concavities that receive the corresponding projecting lips of the underlying vertebra.\n\nThe pedicles are directed laterally and backward, and attach to the body midway between its upper and lower borders, so that the superior vertebral notch is as deep as the inferior, but it is, at the same time, narrower.\n\nThe laminae are narrow and thinner above than below; the vertebral foramen is large and of a triangular form.\nThe spinous process is short and bifid, the two divisions being often of unequal size.\n\nBecause the spinous processes are so short, certain superficial muscles (the trapezius and splenius capitis) attach to the nuchal ligament rather than directly to the vertebrae; the nuchal ligament itself attaching to the spinous processes of C2–C7 and to the posterior tubercle of the atlas.\n\nThe superior and inferior articular processes of cervical vertebrae have fused on either or both sides to form articular pillars, columns of bone that project laterally from the junction of the pedicle and lamina.\n\nThe articular facets are flat and of an oval form:\nthe superior face backward, upward, and slightly medially.\nthe inferior face forward, downward, and slightly laterally.\n\nThe transverse processes are each pierced by the foramen transversarium, which, in the upper six vertebrae, gives passage to the vertebral artery and vein, as well as a plexus of sympathetic nerves.\n\nEach process consists of an anterior and a posterior part.\n\nThese two parts are joined, outside the foramen, by a bar of bone that exhibits a deep sulcus on its upper surface for the passage of the corresponding spinal nerve.\n\nThe anterior portion is the homologue of the rib in the thoracic region, and is therefore named the costal process or costal element.\n\nIt arises from the side of the body, is directed laterally in front of the foramen, and ends in a tubercle, the anterior tubercle.\n\nThe posterior part, the true transverse process, springs from the vertebral arch behind the foramen and is directed forward and laterally; it ends in a flattened vertical tubercle, the posterior tubercle.\n\nThe anterior tubercle of the sixth cervical vertebra is known as the carotid tubercle or Chassaignac tubercle (for Édouard Chassaignac).\n\nThis separates the carotid artery from the vertebral artery and the carotid artery can be massaged against this tubercle to relieve the symptoms of supraventricular tachycardia.\n\nThe carotid tubercle is also used as a landmark for anaesthesia of the brachial plexus and cervical plexus.\n\nThe cervical spinal nerves emerge from above the cervical vertebrae.\n\nFor example, the cervical spinal nerve 3 (C3) passes above C3.\n\n=== Atlas and axis ===\n\nThe atlas (C1) and axis (C2) are the two topmost vertebrae.\n\nThe atlas (C1) is the topmost vertebra, and along with the axis forms the joint connecting the skull and spine.\n\nIt lacks a vertebral body, spinous process, and discs either superior or inferior to it.\n\nIt is ring-like and consists of an anterior arch, posterior arch, and two lateral masses.\nThe axis (C2) forms the pivot on which the atlas rotates.\n\nThe most distinctive characteristic of this bone is the strong odontoid process (dens) that rises perpendicularly from the upper surface of the body and articulates with C1.\n\nThe body is deeper in front than behind, and prolonged downward anteriorly so as to overlap the upper and front part of the third vertebra.\n\n=== Vertebra prominens ===\n\nThe vertebra prominens, or C7, has a distinctive long and prominent spinous process, which is palpable from the skin surface.\n\nSometimes, the seventh cervical vertebra is associated with an abnormal extra rib, known as a cervical rib, which develops from the anterior root of the transverse process.\n\nThese ribs are usually small, but may occasionally compress blood vessels (such as the subclavian artery or subclavian vein) or nerves in the brachial plexus, causing pain, numbness, tingling, and weakness in the upper limb, a condition known as thoracic outlet syndrome.\n\nVery rarely, this rib occurs in a pair.\nThe long spinous process of C7 is thick and nearly horizontal in direction.\n\nIt is not bifurcated, and ends in a tubercle that the ligamentum nuchae attaches to.\n\nThis process is not always the most prominent of the spinous processes, being found only about 70% of the time, C6 or T1 can sometimes be the most prominent.\n\nThe transverse processes are of considerable size; their posterior roots are large and prominent, while the anterior are small and faintly marked.\n\nThe upper surface of each usually has a shallow sulcus for the eighth spinal nerve, and its extremity seldom presents more than a trace of bifurcation.\n\nThe transverse foramen may be as large as that in the other cervical vertebrae, but it is generally smaller on one or both sides; occasionally, it is double, and sometimes it is absent.\n\nOn the left side, it occasionally gives passage to the vertebral artery; more frequently, the vertebral vein traverses it on both sides, but the usual arrangement is for both artery and vein to pass in front of the transverse process, not through the foramen.\n\n== Function ==\n\nThe movement of nodding the head takes place predominantly through flexion and extension at the atlanto-occipital joint between the atlas and the occipital bone.\n\nHowever, the cervical spine is comparatively mobile, and some component of this movement is due to flexion and extension of the vertebral column itself.\n\nThis movement between the atlas and occipital bone is often referred to as the \"yes joint\", owing to its nature of being able to move the head in an up-and-down fashion.\n\nThe movement of shaking or rotating the head left and right happens almost entirely at the joint between the atlas and the axis, the atlanto-axial joint.\n\nA small amount of rotation of the vertebral column itself contributes to the movement.\n\nThis movement between the atlas and axis is often referred to as the \"no joint\", owing to its nature of being able to rotate the head in a side-to-side fashion.\n\n== Clinical significance ==\n\nCervical degenerative changes arise from conditions such as spondylosis, stenosis of intervertebral discs, and the formation of osteophytes.\n\nThe changes are seen on radiographs, which are used in a grading system from 0–4 ranging from no changes (0) to early with minimal development of osteophytes (1) to mild with definite osteophytes (2) to moderate with additional disc space stenosis or narrowing (3) to the stage of many large osteophytes, severe narrowing of the disc space, and more severe vertebral end plate sclerosis (4).Injuries to the cervical spine are common at the level of the second cervical vertebrae, but neurological injury is uncommon.\n\nC4 and C5 are the areas that see the highest amount of cervical spine trauma.If it does occur, however, it may cause death or profound disability, including paralysis of the arms, legs, and diaphragm, which leads to respiratory failure.\n\nCommon patterns of injury include the odontoid fracture and the hangman's fracture, both of which are often treated with immobilization in a cervical collar or Halo brace.\n\nA common practice is to immobilize a patient's cervical spine to prevent further damage during transport to hospital.\n\nThis practice has come under review recently as incidence rates of unstable spinal trauma can be as low as 2% in immobilized patients.\n\nIn clearing the cervical spine, Canadian studies have developed the Canadian C-Spine Rule (CCR) for physicians to decide who should receive radiological imaging.\n\n=== Landmarks ===\n\nThe vertebral column is often used as a marker of human anatomy.\n\nThis includes:\n\nAt C1, base of the nose and the hard palate\nAt C2, the teeth of a closed mouth\nAt C3, the mandible and hyoid bone\nAt C4, the common carotid artery bifurcates.\nFrom C4–5, the thyroid cartilage\nFrom C6–7, the cricoid cartilage\nAt C6, the oesophagus becomes continuous with the laryngopharynx and also where the larynx becomes continuous with the trachea.\n\nIt is also the level where the carotid pulse can be palpated against the transverse process of the C6 vertebrae.\n\nhttps://en.wikipedia.org/wiki/Cervical_vertebrae","vertebra-c7":"In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull.\n\nTruncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae.\n\nIn sauropsid species, the cervical vertebrae bear cervical ribs.\n\nIn lizards and saurischian dinosaurs, the cervical ribs are large; in birds, they are small and completely fused to the vertebrae.\n\nThe vertebral transverse processes of mammals are homologous to the cervical ribs of other amniotes.\n\nMost mammals have seven cervical vertebrae, with the only three known exceptions being the manatee with six, the two-toed sloth with five or six, and the three-toed sloth with nine.\n\nIn humans, cervical vertebrae are the smallest of the true vertebrae and can be readily distinguished from those of the thoracic or lumbar regions by the presence of a foramen (hole) in each transverse process, through which the vertebral artery, vertebral veins, and inferior cervical ganglion pass.\n\nThe remainder of this article focuses upon human anatomy.\n\n== Structure ==\n\nBy convention, the cervical vertebrae are numbered, with the first one (C1) closest to the skull and higher numbered vertebrae (C2–C7) proceeding away from the skull and down the spine.\n\nThe general characteristics of the third through sixth cervical vertebrae are described here.\n\nThe first, second, and seventh vertebrae are extraordinary, and are detailed later.\n\nThe bodies of these four vertebrae are small, and broader from side to side than from front to back.\n\nThe anterior and posterior surfaces are flattened and of equal depth; the former is placed on a lower level than the latter, and its inferior border is prolonged downward, so as to overlap the upper and forepart of the vertebra below.\n\nThe upper surface is concave transversely, and presents a projecting lip on either side.\n\nThe lower surface is concave from front to back, convex from side to side, and presents laterally shallow concavities that receive the corresponding projecting lips of the underlying vertebra.\n\nThe pedicles are directed laterally and backward, and attach to the body midway between its upper and lower borders, so that the superior vertebral notch is as deep as the inferior, but it is, at the same time, narrower.\n\nThe laminae are narrow and thinner above than below; the vertebral foramen is large and of a triangular form.\nThe spinous process is short and bifid, the two divisions being often of unequal size.\n\nBecause the spinous processes are so short, certain superficial muscles (the trapezius and splenius capitis) attach to the nuchal ligament rather than directly to the vertebrae; the nuchal ligament itself attaching to the spinous processes of C2–C7 and to the posterior tubercle of the atlas.\n\nThe superior and inferior articular processes of cervical vertebrae have fused on either or both sides to form articular pillars, columns of bone that project laterally from the junction of the pedicle and lamina.\n\nThe articular facets are flat and of an oval form:\nthe superior face backward, upward, and slightly medially.\nthe inferior face forward, downward, and slightly laterally.\n\nThe transverse processes are each pierced by the foramen transversarium, which, in the upper six vertebrae, gives passage to the vertebral artery and vein, as well as a plexus of sympathetic nerves.\n\nEach process consists of an anterior and a posterior part.\n\nThese two parts are joined, outside the foramen, by a bar of bone that exhibits a deep sulcus on its upper surface for the passage of the corresponding spinal nerve.\n\nThe anterior portion is the homologue of the rib in the thoracic region, and is therefore named the costal process or costal element.\n\nIt arises from the side of the body, is directed laterally in front of the foramen, and ends in a tubercle, the anterior tubercle.\n\nThe posterior part, the true transverse process, springs from the vertebral arch behind the foramen and is directed forward and laterally; it ends in a flattened vertical tubercle, the posterior tubercle.\n\nThe anterior tubercle of the sixth cervical vertebra is known as the carotid tubercle or Chassaignac tubercle (for Édouard Chassaignac).\n\nThis separates the carotid artery from the vertebral artery and the carotid artery can be massaged against this tubercle to relieve the symptoms of supraventricular tachycardia.\n\nThe carotid tubercle is also used as a landmark for anaesthesia of the brachial plexus and cervical plexus.\n\nThe cervical spinal nerves emerge from above the cervical vertebrae.\n\nFor example, the cervical spinal nerve 3 (C3) passes above C3.\n\n=== Atlas and axis ===\n\nThe atlas (C1) and axis (C2) are the two topmost vertebrae.\n\nThe atlas (C1) is the topmost vertebra, and along with the axis forms the joint connecting the skull and spine.\n\nIt lacks a vertebral body, spinous process, and discs either superior or inferior to it.\n\nIt is ring-like and consists of an anterior arch, posterior arch, and two lateral masses.\nThe axis (C2) forms the pivot on which the atlas rotates.\n\nThe most distinctive characteristic of this bone is the strong odontoid process (dens) that rises perpendicularly from the upper surface of the body and articulates with C1.\n\nThe body is deeper in front than behind, and prolonged downward anteriorly so as to overlap the upper and front part of the third vertebra.\n\n=== Vertebra prominens ===\n\nThe vertebra prominens, or C7, has a distinctive long and prominent spinous process, which is palpable from the skin surface.\n\nSometimes, the seventh cervical vertebra is associated with an abnormal extra rib, known as a cervical rib, which develops from the anterior root of the transverse process.\n\nThese ribs are usually small, but may occasionally compress blood vessels (such as the subclavian artery or subclavian vein) or nerves in the brachial plexus, causing pain, numbness, tingling, and weakness in the upper limb, a condition known as thoracic outlet syndrome.\n\nVery rarely, this rib occurs in a pair.\nThe long spinous process of C7 is thick and nearly horizontal in direction.\n\nIt is not bifurcated, and ends in a tubercle that the ligamentum nuchae attaches to.\n\nThis process is not always the most prominent of the spinous processes, being found only about 70% of the time, C6 or T1 can sometimes be the most prominent.\n\nThe transverse processes are of considerable size; their posterior roots are large and prominent, while the anterior are small and faintly marked.\n\nThe upper surface of each usually has a shallow sulcus for the eighth spinal nerve, and its extremity seldom presents more than a trace of bifurcation.\n\nThe transverse foramen may be as large as that in the other cervical vertebrae, but it is generally smaller on one or both sides; occasionally, it is double, and sometimes it is absent.\n\nOn the left side, it occasionally gives passage to the vertebral artery; more frequently, the vertebral vein traverses it on both sides, but the usual arrangement is for both artery and vein to pass in front of the transverse process, not through the foramen.\n\n== Function ==\n\nThe movement of nodding the head takes place predominantly through flexion and extension at the atlanto-occipital joint between the atlas and the occipital bone.\n\nHowever, the cervical spine is comparatively mobile, and some component of this movement is due to flexion and extension of the vertebral column itself.\n\nThis movement between the atlas and occipital bone is often referred to as the \"yes joint\", owing to its nature of being able to move the head in an up-and-down fashion.\n\nThe movement of shaking or rotating the head left and right happens almost entirely at the joint between the atlas and the axis, the atlanto-axial joint.\n\nA small amount of rotation of the vertebral column itself contributes to the movement.\n\nThis movement between the atlas and axis is often referred to as the \"no joint\", owing to its nature of being able to rotate the head in a side-to-side fashion.\n\n== Clinical significance ==\n\nCervical degenerative changes arise from conditions such as spondylosis, stenosis of intervertebral discs, and the formation of osteophytes.\n\nThe changes are seen on radiographs, which are used in a grading system from 0–4 ranging from no changes (0) to early with minimal development of osteophytes (1) to mild with definite osteophytes (2) to moderate with additional disc space stenosis or narrowing (3) to the stage of many large osteophytes, severe narrowing of the disc space, and more severe vertebral end plate sclerosis (4).Injuries to the cervical spine are common at the level of the second cervical vertebrae, but neurological injury is uncommon.\n\nC4 and C5 are the areas that see the highest amount of cervical spine trauma.If it does occur, however, it may cause death or profound disability, including paralysis of the arms, legs, and diaphragm, which leads to respiratory failure.\n\nCommon patterns of injury include the odontoid fracture and the hangman's fracture, both of which are often treated with immobilization in a cervical collar or Halo brace.\n\nA common practice is to immobilize a patient's cervical spine to prevent further damage during transport to hospital.\n\nThis practice has come under review recently as incidence rates of unstable spinal trauma can be as low as 2% in immobilized patients.\n\nIn clearing the cervical spine, Canadian studies have developed the Canadian C-Spine Rule (CCR) for physicians to decide who should receive radiological imaging.\n\n=== Landmarks ===\n\nThe vertebral column is often used as a marker of human anatomy.\n\nThis includes:\n\nAt C1, base of the nose and the hard palate\nAt C2, the teeth of a closed mouth\nAt C3, the mandible and hyoid bone\nAt C4, the common carotid artery bifurcates.\nFrom C4–5, the thyroid cartilage\nFrom C6–7, the cricoid cartilage\nAt C6, the oesophagus becomes continuous with the laryngopharynx and also where the larynx becomes continuous with the trachea.\n\nIt is also the level where the carotid pulse can be palpated against the transverse process of the C6 vertebrae.\n\nhttps://en.wikipedia.org/wiki/Cervical_vertebrae","vertebra-c4":"In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull.\n\nTruncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae.\n\nIn sauropsid species, the cervical vertebrae bear cervical ribs.\n\nIn lizards and saurischian dinosaurs, the cervical ribs are large; in birds, they are small and completely fused to the vertebrae.\n\nThe vertebral transverse processes of mammals are homologous to the cervical ribs of other amniotes.\n\nMost mammals have seven cervical vertebrae, with the only three known exceptions being the manatee with six, the two-toed sloth with five or six, and the three-toed sloth with nine.\n\nIn humans, cervical vertebrae are the smallest of the true vertebrae and can be readily distinguished from those of the thoracic or lumbar regions by the presence of a foramen (hole) in each transverse process, through which the vertebral artery, vertebral veins, and inferior cervical ganglion pass.\n\nThe remainder of this article focuses upon human anatomy.\n\n== Structure ==\n\nBy convention, the cervical vertebrae are numbered, with the first one (C1) closest to the skull and higher numbered vertebrae (C2–C7) proceeding away from the skull and down the spine.\n\nThe general characteristics of the third through sixth cervical vertebrae are described here.\n\nThe first, second, and seventh vertebrae are extraordinary, and are detailed later.\n\nThe bodies of these four vertebrae are small, and broader from side to side than from front to back.\n\nThe anterior and posterior surfaces are flattened and of equal depth; the former is placed on a lower level than the latter, and its inferior border is prolonged downward, so as to overlap the upper and forepart of the vertebra below.\n\nThe upper surface is concave transversely, and presents a projecting lip on either side.\n\nThe lower surface is concave from front to back, convex from side to side, and presents laterally shallow concavities that receive the corresponding projecting lips of the underlying vertebra.\n\nThe pedicles are directed laterally and backward, and attach to the body midway between its upper and lower borders, so that the superior vertebral notch is as deep as the inferior, but it is, at the same time, narrower.\n\nThe laminae are narrow and thinner above than below; the vertebral foramen is large and of a triangular form.\nThe spinous process is short and bifid, the two divisions being often of unequal size.\n\nBecause the spinous processes are so short, certain superficial muscles (the trapezius and splenius capitis) attach to the nuchal ligament rather than directly to the vertebrae; the nuchal ligament itself attaching to the spinous processes of C2–C7 and to the posterior tubercle of the atlas.\n\nThe superior and inferior articular processes of cervical vertebrae have fused on either or both sides to form articular pillars, columns of bone that project laterally from the junction of the pedicle and lamina.\n\nThe articular facets are flat and of an oval form:\nthe superior face backward, upward, and slightly medially.\nthe inferior face forward, downward, and slightly laterally.\n\nThe transverse processes are each pierced by the foramen transversarium, which, in the upper six vertebrae, gives passage to the vertebral artery and vein, as well as a plexus of sympathetic nerves.\n\nEach process consists of an anterior and a posterior part.\n\nThese two parts are joined, outside the foramen, by a bar of bone that exhibits a deep sulcus on its upper surface for the passage of the corresponding spinal nerve.\n\nThe anterior portion is the homologue of the rib in the thoracic region, and is therefore named the costal process or costal element.\n\nIt arises from the side of the body, is directed laterally in front of the foramen, and ends in a tubercle, the anterior tubercle.\n\nThe posterior part, the true transverse process, springs from the vertebral arch behind the foramen and is directed forward and laterally; it ends in a flattened vertical tubercle, the posterior tubercle.\n\nThe anterior tubercle of the sixth cervical vertebra is known as the carotid tubercle or Chassaignac tubercle (for Édouard Chassaignac).\n\nThis separates the carotid artery from the vertebral artery and the carotid artery can be massaged against this tubercle to relieve the symptoms of supraventricular tachycardia.\n\nThe carotid tubercle is also used as a landmark for anaesthesia of the brachial plexus and cervical plexus.\n\nThe cervical spinal nerves emerge from above the cervical vertebrae.\n\nFor example, the cervical spinal nerve 3 (C3) passes above C3.\n\n=== Atlas and axis ===\n\nThe atlas (C1) and axis (C2) are the two topmost vertebrae.\n\nThe atlas (C1) is the topmost vertebra, and along with the axis forms the joint connecting the skull and spine.\n\nIt lacks a vertebral body, spinous process, and discs either superior or inferior to it.\n\nIt is ring-like and consists of an anterior arch, posterior arch, and two lateral masses.\nThe axis (C2) forms the pivot on which the atlas rotates.\n\nThe most distinctive characteristic of this bone is the strong odontoid process (dens) that rises perpendicularly from the upper surface of the body and articulates with C1.\n\nThe body is deeper in front than behind, and prolonged downward anteriorly so as to overlap the upper and front part of the third vertebra.\n\n=== Vertebra prominens ===\n\nThe vertebra prominens, or C7, has a distinctive long and prominent spinous process, which is palpable from the skin surface.\n\nSometimes, the seventh cervical vertebra is associated with an abnormal extra rib, known as a cervical rib, which develops from the anterior root of the transverse process.\n\nThese ribs are usually small, but may occasionally compress blood vessels (such as the subclavian artery or subclavian vein) or nerves in the brachial plexus, causing pain, numbness, tingling, and weakness in the upper limb, a condition known as thoracic outlet syndrome.\n\nVery rarely, this rib occurs in a pair.\nThe long spinous process of C7 is thick and nearly horizontal in direction.\n\nIt is not bifurcated, and ends in a tubercle that the ligamentum nuchae attaches to.\n\nThis process is not always the most prominent of the spinous processes, being found only about 70% of the time, C6 or T1 can sometimes be the most prominent.\n\nThe transverse processes are of considerable size; their posterior roots are large and prominent, while the anterior are small and faintly marked.\n\nThe upper surface of each usually has a shallow sulcus for the eighth spinal nerve, and its extremity seldom presents more than a trace of bifurcation.\n\nThe transverse foramen may be as large as that in the other cervical vertebrae, but it is generally smaller on one or both sides; occasionally, it is double, and sometimes it is absent.\n\nOn the left side, it occasionally gives passage to the vertebral artery; more frequently, the vertebral vein traverses it on both sides, but the usual arrangement is for both artery and vein to pass in front of the transverse process, not through the foramen.\n\n== Function ==\n\nThe movement of nodding the head takes place predominantly through flexion and extension at the atlanto-occipital joint between the atlas and the occipital bone.\n\nHowever, the cervical spine is comparatively mobile, and some component of this movement is due to flexion and extension of the vertebral column itself.\n\nThis movement between the atlas and occipital bone is often referred to as the \"yes joint\", owing to its nature of being able to move the head in an up-and-down fashion.\n\nThe movement of shaking or rotating the head left and right happens almost entirely at the joint between the atlas and the axis, the atlanto-axial joint.\n\nA small amount of rotation of the vertebral column itself contributes to the movement.\n\nThis movement between the atlas and axis is often referred to as the \"no joint\", owing to its nature of being able to rotate the head in a side-to-side fashion.\n\n== Clinical significance ==\n\nCervical degenerative changes arise from conditions such as spondylosis, stenosis of intervertebral discs, and the formation of osteophytes.\n\nThe changes are seen on radiographs, which are used in a grading system from 0–4 ranging from no changes (0) to early with minimal development of osteophytes (1) to mild with definite osteophytes (2) to moderate with additional disc space stenosis or narrowing (3) to the stage of many large osteophytes, severe narrowing of the disc space, and more severe vertebral end plate sclerosis (4).Injuries to the cervical spine are common at the level of the second cervical vertebrae, but neurological injury is uncommon.\n\nC4 and C5 are the areas that see the highest amount of cervical spine trauma.If it does occur, however, it may cause death or profound disability, including paralysis of the arms, legs, and diaphragm, which leads to respiratory failure.\n\nCommon patterns of injury include the odontoid fracture and the hangman's fracture, both of which are often treated with immobilization in a cervical collar or Halo brace.\n\nA common practice is to immobilize a patient's cervical spine to prevent further damage during transport to hospital.\n\nThis practice has come under review recently as incidence rates of unstable spinal trauma can be as low as 2% in immobilized patients.\n\nIn clearing the cervical spine, Canadian studies have developed the Canadian C-Spine Rule (CCR) for physicians to decide who should receive radiological imaging.\n\n=== Landmarks ===\n\nThe vertebral column is often used as a marker of human anatomy.\n\nThis includes:\n\nAt C1, base of the nose and the hard palate\nAt C2, the teeth of a closed mouth\nAt C3, the mandible and hyoid bone\nAt C4, the common carotid artery bifurcates.\nFrom C4–5, the thyroid cartilage\nFrom C6–7, the cricoid cartilage\nAt C6, the oesophagus becomes continuous with the laryngopharynx and also where the larynx becomes continuous with the trachea.\n\nIt is also the level where the carotid pulse can be palpated against the transverse process of the C6 vertebrae.\n\nhttps://en.wikipedia.org/wiki/Cervical_vertebrae","vertebra-t2":"The thoracic spinal nerve 2 (T2) passes out underneath it.\n\nThe second thoracic vertebra is larger than the first thoracic vertebra.\n\nSee: thoracic vertebrae.\n\nhttps://en.wikipedia.org/wiki/Thoracic_vertebrae","vertebra-t3":"The thoracic spinal nerve 3 (T3) passes out underneath it.\n\nSee: thoracic vertebrae.\n\nhttps://en.wikipedia.org/wiki/Thoracic_vertebrae","vertebra-t4":"The fourth thoracic vertebra, together with the fifth, is at the same level as the sternal angle.\n\nThe thoracic spinal nerve 4 (T4) passes out underneath it.\n\nSee: thoracic vertebrae.\n\nhttps://en.wikipedia.org/wiki/Thoracic_vertebrae","vertebra-t5":"The fifth thoracic vertebra, together with the fourth, is at the same level as the sternal angle.\n\nThe human trachea divides into two main bronchi at the level of the 5th thoracic vertebra, but may also end higher or lower, depending on breathing.\n\nThe thoracic spinal nerve 5 (T5) passes out underneath it.\n\nSee: thoracic vertebrae.\n\nhttps://en.wikipedia.org/wiki/Thoracic_vertebrae","vertebra-t6":"The thoracic spinal nerve 6 (T6) passes out underneath it.\n\nSee: thoracic vertebrae.\n\nhttps://en.wikipedia.org/wiki/Thoracic_vertebrae","vertebra-t7":"The thoracic spinal nerve 7 (T7) passes out underneath it.\n\nSee: thoracic vertebrae.\n\nhttps://en.wikipedia.org/wiki/Thoracic_vertebrae","vertebra-t9":"The ninth thoracic vertebra may have no demi-facets below.\n\nIn some subjects however, it has two demi-facets on either side; when this occurs the tenth doesn't have facets but demi-facets at the upper part.\n\nThe thoracic spinal nerve 9 (T9) passes out underneath it.\n\nThe xiphisternum (or xiphoid process of the sternum) is at the same level in the axial plane.\n\nSee: thoracic vertebrae.\n\nhttps://en.wikipedia.org/wiki/Thoracic_vertebrae","vertebra-t10":"The tenth thoracic vertebra has an entire articular facet (not demi-facet) on either side, which is placed partly on the lateral surface of the pedicle.\n\nIt doesn't have any kind of facet below, because the following ribs only have one facet on their heads.\n\nThe thoracic spinal nerve 10 (T10) passes out underneath it.\n\nSee: thoracic vertebrae.\n\nhttps://en.wikipedia.org/wiki/Thoracic_vertebrae","vertebra-t11":"In the eleventh thoracic vertebra the body approaches in its form and size to that of the lumbar vertebrae.\n\nThe articular facets for the heads of the ribs are of medium size, and placed chiefly on the pedicles, which are thicker and stronger in this and the next vertebra than in any other part of the thoracic region.\n\nThe spinous process is short, and nearly horizontal in direction.\n\nThe transverse processes are very short, tuberculated at their extremities, and do not have articular facets.\n\nThe thoracic spinal nerve 11 (T11) passes out underneath it.\n\nSee: thoracic vertebrae.\n\nhttps://en.wikipedia.org/wiki/Thoracic_vertebrae","vertebra-t12":"The twelfth thoracic vertebra has the same general characteristics as the eleventh, but may be distinguished from it by its inferior articular surfaces being convex and directed lateralward, like those of the lumbar vertebrae; by the general form of the body, laminae, and spinous process, in which it resembles the lumbar vertebrae; and by each transverse process being subdivided into three elevations, the superior, inferior, and lateral tubercles:\n\nthe superior and inferior correspond to the mammillary and accessory processes of the lumbar vertebrae.\n\nTraces of similar elevations are found on the transverse processes of the tenth and eleventh thoracic vertebrae.\n\nThe thoracic spinal nerve 12 (T12) passes out underneath it.\n\nhttps://en.wikipedia.org/wiki/Thoracic_vertebrae","vertebra-t8":"The eighth thoracic vertebra is, together with the ninth thoracic vertebra, at the same level as the xiphisternum.\n\nThe thoracic spinal nerve 8 (T8) passes out underneath it.\n\nSee: thoracic vertebrae.\n\nhttps://en.wikipedia.org/wiki/Thoracic_vertebrae","vertebra-t1":"The first thoracic vertebra has, on either side of the body, an entire articular facet for the head of the first rib, and a demi-facet for the upper half of the head of the second rib.\n\nThe body is like that of a cervical vertebra, being broad, concave, and lipped on either side.\n\nThe superior articular surfaces are directed upward and backward; the spinous process is thick, long, and almost horizontal.\n\nThe transverse processes are long, and the upper vertebral notches are deeper than those of the other thoracic vertebrae.\n\nThe thoracic spinal nerve 1 (T1) passes out underneath it.\n\nSee: Thoracic vertebrae\n\nhttps://en.wikipedia.org/wiki/Thoracic_vertebrae","vertebra-l1":"The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis.\n\nThey are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse process (since it is only found in the cervical region) and by the absence of facets on the sides of the body (as found only in the thoracic region).\n\nThey are designated L1 to L5, starting at the top.\n\nThe lumbar vertebrae help support the weight of the body, and permit movement.\n\n== Human anatomy ==\n\n=== General characteristics ===\n\nThe figure on the left depicts the general characteristics of the first through fourth lumbar vertebrae.\n\nThe fifth vertebra contains certain peculiarities, which are detailed below.\n\nAs with other vertebrae, each lumbar vertebra consists of a vertebral body and a vertebral arch.\n\nThe vertebral arch, consisting of a pair of pedicles and a pair of laminae, encloses the vertebral foramen (opening) and supports seven processes.\n\n==== Body ====\n\nThe vertebral body of each lumbar vertebra is kidney shaped, wider from side to side than from front to back, and a little thicker in front than in back.\n\nIt is flattened or slightly concave above and below, concave behind, and deeply constricted in front and at the sides.\n\n==== Arch ====\n\nThe pedicles are very strong, directed backward from the upper part of the vertebral body; consequently, the inferior vertebral notches are of considerable depth.\n\nThe pedicles change in morphology from the upper lumbar to the lower lumbar.\n\nThey increase in sagittal width from 9 mm to up to 18 mm at L5.\n\nThey increase in angulation in the axial plane from 10 degrees to 20 degrees by L5.\n\nThe pedicle is sometimes used as a portal of entrance into the vertebral body for fixation with pedicle screws or for placement of bone cement as with kyphoplasty or vertebroplasty.\n\nThe laminae are broad, short, and strong.\n\nThey form the posterior portion of the vertebral arch.\n\nIn the upper lumbar region the lamina are taller than wide but in the lower lumbar vertebra the lamina are wider than tall.\n\nThe lamina connects the spinous process to the pedicles.\nThe vertebral foramen within the arch is triangular, larger than the thoracic vertebrae, but smaller than in the cervical vertebrae.\n\n==== Processes ====\n\nThe spinous process is thick, broad, and somewhat quadrilateral; it projects backward and ends in a rough, uneven border, thickest below where it is occasionally notched.The superior and inferior articular processes are well-defined, projecting respectively upward and downward from the junctions of pedicles and laminae.\n\nThe facets on the superior processes are concave, and look backward and medialward; those on the inferior are convex, and are directed forward and lateralward.\n\nThe former are wider apart than the latter since in the articulated column, the inferior articular processes are embraced by the superior processes of the subjacent vertebra.The transverse processes are long and slender.\n\nThey are horizontal in the upper three lumbar vertebrae and incline a little upward in the lower two.\n\nIn the upper three vertebrae they arise from the junctions of the pedicles and laminae, but in the lower two they are set farther forward and spring from the pedicles and posterior parts of the vertebral bodies.\n\nThey are situated in front of the articular processes instead of behind them as in the thoracic vertebrae, and are homologous with the ribs.\n\nThree portions or tubercles can be noticed in a transverse process of a lower lumbar vertebrae: the lateral or costiform process, the mammillary process, and the accessory process.\n\nThe costiform is lateral, the mammillary is superior (cranial), and the accessory is inferior (caudal).\n\nThe mammillary is connected in the lumbar region with the back part of the superior articular process.\n\nThe accessory process is situated at the back part of the base of the transverse process.\n\nThe tallest and thickest costiform process is usually that of L5.\n\n=== First and fifth lumbar vertebrae ===\n\nThe first lumbar vertebra is level with the anterior end of the ninth rib.\n\nThis level is also called the important transpyloric plane, since the pylorus of the stomach is at this level.\n\nOther important structures are also located at this level, they include; fundus of the gall bladder, celiac trunk, superior mesenteric artery, termination of spinal cord, beginning of filum terminalis, renal vessels, middle suprarenal arteries, and hila of kidneys.\n\nThe fifth lumbar vertebra is characterized by its body being much deeper in front than behind, which accords with the prominence of the sacrovertebral articulation; by the smaller size of its spinous process; by the wide interval between the inferior articular processes, and by the thickness of its transverse processes, which spring from the body as well as from the pedicles.\n\nThe fifth lumbar vertebra is by far the most common site of spondylolysis and spondylolisthesis.Most individuals have five lumbar vertebrae, while some have four or six.\n\nLumbar disorders that normally affect L5 will affect L4 or L6 in these latter individuals.\n\n=== Segmental movements ===\n\nThe range of segmental movements in a single segment is difficult to measure clinically, not only because of variations between individuals, but also because it is age and sex dependent.\n\nFurthermore, flexion and extension in the lumbal spine is the product of a combination of rotation and translation in the sagittal plane between each vertebra.Ranges of segmental movements in the lumbar spine (White and Punjabi, 1990) are (in degrees):\n\n=== Congenital anomalies ===\n\nCongenital vertebral anomalies can cause compression of the spinal cord by deforming the vertebral canal or causing instability.\n\n== Other animals ==\n\nAfrican apes have three and four lumbar vertebrae, (bonobos have longer spines with an additional vertebra) and humans normally five.\n\nThis difference, and because the lumbar spines of the extinct Nacholapithecus (a Miocene hominoid with six lumbar vertebrae and no tail) are similar to those of early Australopithecus and early Homo, it is assumed that the Chimpanzee-human last common ancestor also had a long vertebral column with a long lumbar region and that the reduction in the number of lumbar vertebrae evolved independently in each ape clade.\n\nThe limited number of lumbar vertebrae in chimpanzees and gorillas result in an inability to lordose (curve) their lumbar spines, in contrast to the spines of Old World monkeys and Nacholapithecus and Proconsul, which suggests that the last common ancestor was not \"short-backed\" as previously believed.\n\nhttps://en.wikipedia.org/wiki/Lumbar_vertebrae","vertebra-l2":"The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis.\n\nThey are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse process (since it is only found in the cervical region) and by the absence of facets on the sides of the body (as found only in the thoracic region).\n\nThey are designated L1 to L5, starting at the top.\n\nThe lumbar vertebrae help support the weight of the body, and permit movement.\n\n== Human anatomy ==\n\n=== General characteristics ===\n\nThe figure on the left depicts the general characteristics of the first through fourth lumbar vertebrae.\n\nThe fifth vertebra contains certain peculiarities, which are detailed below.\n\nAs with other vertebrae, each lumbar vertebra consists of a vertebral body and a vertebral arch.\n\nThe vertebral arch, consisting of a pair of pedicles and a pair of laminae, encloses the vertebral foramen (opening) and supports seven processes.\n\n==== Body ====\n\nThe vertebral body of each lumbar vertebra is kidney shaped, wider from side to side than from front to back, and a little thicker in front than in back.\n\nIt is flattened or slightly concave above and below, concave behind, and deeply constricted in front and at the sides.\n\n==== Arch ====\n\nThe pedicles are very strong, directed backward from the upper part of the vertebral body; consequently, the inferior vertebral notches are of considerable depth.\n\nThe pedicles change in morphology from the upper lumbar to the lower lumbar.\n\nThey increase in sagittal width from 9 mm to up to 18 mm at L5.\n\nThey increase in angulation in the axial plane from 10 degrees to 20 degrees by L5.\n\nThe pedicle is sometimes used as a portal of entrance into the vertebral body for fixation with pedicle screws or for placement of bone cement as with kyphoplasty or vertebroplasty.\n\nThe laminae are broad, short, and strong.\n\nThey form the posterior portion of the vertebral arch.\n\nIn the upper lumbar region the lamina are taller than wide but in the lower lumbar vertebra the lamina are wider than tall.\n\nThe lamina connects the spinous process to the pedicles.\nThe vertebral foramen within the arch is triangular, larger than the thoracic vertebrae, but smaller than in the cervical vertebrae.\n\n==== Processes ====\n\nThe spinous process is thick, broad, and somewhat quadrilateral; it projects backward and ends in a rough, uneven border, thickest below where it is occasionally notched.The superior and inferior articular processes are well-defined, projecting respectively upward and downward from the junctions of pedicles and laminae.\n\nThe facets on the superior processes are concave, and look backward and medialward; those on the inferior are convex, and are directed forward and lateralward.\n\nThe former are wider apart than the latter since in the articulated column, the inferior articular processes are embraced by the superior processes of the subjacent vertebra.The transverse processes are long and slender.\n\nThey are horizontal in the upper three lumbar vertebrae and incline a little upward in the lower two.\n\nIn the upper three vertebrae they arise from the junctions of the pedicles and laminae, but in the lower two they are set farther forward and spring from the pedicles and posterior parts of the vertebral bodies.\n\nThey are situated in front of the articular processes instead of behind them as in the thoracic vertebrae, and are homologous with the ribs.\n\nThree portions or tubercles can be noticed in a transverse process of a lower lumbar vertebrae: the lateral or costiform process, the mammillary process, and the accessory process.\n\nThe costiform is lateral, the mammillary is superior (cranial), and the accessory is inferior (caudal).\n\nThe mammillary is connected in the lumbar region with the back part of the superior articular process.\n\nThe accessory process is situated at the back part of the base of the transverse process.\n\nThe tallest and thickest costiform process is usually that of L5.\n\n=== First and fifth lumbar vertebrae ===\n\nThe first lumbar vertebra is level with the anterior end of the ninth rib.\n\nThis level is also called the important transpyloric plane, since the pylorus of the stomach is at this level.\n\nOther important structures are also located at this level, they include; fundus of the gall bladder, celiac trunk, superior mesenteric artery, termination of spinal cord, beginning of filum terminalis, renal vessels, middle suprarenal arteries, and hila of kidneys.\n\nThe fifth lumbar vertebra is characterized by its body being much deeper in front than behind, which accords with the prominence of the sacrovertebral articulation; by the smaller size of its spinous process; by the wide interval between the inferior articular processes, and by the thickness of its transverse processes, which spring from the body as well as from the pedicles.\n\nThe fifth lumbar vertebra is by far the most common site of spondylolysis and spondylolisthesis.Most individuals have five lumbar vertebrae, while some have four or six.\n\nLumbar disorders that normally affect L5 will affect L4 or L6 in these latter individuals.\n\n=== Segmental movements ===\n\nThe range of segmental movements in a single segment is difficult to measure clinically, not only because of variations between individuals, but also because it is age and sex dependent.\n\nFurthermore, flexion and extension in the lumbal spine is the product of a combination of rotation and translation in the sagittal plane between each vertebra.Ranges of segmental movements in the lumbar spine (White and Punjabi, 1990) are (in degrees):\n\n=== Congenital anomalies ===\n\nCongenital vertebral anomalies can cause compression of the spinal cord by deforming the vertebral canal or causing instability.\n\n== Other animals ==\n\nAfrican apes have three and four lumbar vertebrae, (bonobos have longer spines with an additional vertebra) and humans normally five.\n\nThis difference, and because the lumbar spines of the extinct Nacholapithecus (a Miocene hominoid with six lumbar vertebrae and no tail) are similar to those of early Australopithecus and early Homo, it is assumed that the Chimpanzee-human last common ancestor also had a long vertebral column with a long lumbar region and that the reduction in the number of lumbar vertebrae evolved independently in each ape clade.\n\nThe limited number of lumbar vertebrae in chimpanzees and gorillas result in an inability to lordose (curve) their lumbar spines, in contrast to the spines of Old World monkeys and Nacholapithecus and Proconsul, which suggests that the last common ancestor was not \"short-backed\" as previously believed.\n\nhttps://en.wikipedia.org/wiki/Lumbar_vertebrae","vertebra-l4":"The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis.\n\nThey are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse process (since it is only found in the cervical region) and by the absence of facets on the sides of the body (as found only in the thoracic region).\n\nThey are designated L1 to L5, starting at the top.\n\nThe lumbar vertebrae help support the weight of the body, and permit movement.\n\n== Human anatomy ==\n\n=== General characteristics ===\n\nThe figure on the left depicts the general characteristics of the first through fourth lumbar vertebrae.\n\nThe fifth vertebra contains certain peculiarities, which are detailed below.\n\nAs with other vertebrae, each lumbar vertebra consists of a vertebral body and a vertebral arch.\n\nThe vertebral arch, consisting of a pair of pedicles and a pair of laminae, encloses the vertebral foramen (opening) and supports seven processes.\n\n==== Body ====\n\nThe vertebral body of each lumbar vertebra is kidney shaped, wider from side to side than from front to back, and a little thicker in front than in back.\n\nIt is flattened or slightly concave above and below, concave behind, and deeply constricted in front and at the sides.\n\n==== Arch ====\n\nThe pedicles are very strong, directed backward from the upper part of the vertebral body; consequently, the inferior vertebral notches are of considerable depth.\n\nThe pedicles change in morphology from the upper lumbar to the lower lumbar.\n\nThey increase in sagittal width from 9 mm to up to 18 mm at L5.\n\nThey increase in angulation in the axial plane from 10 degrees to 20 degrees by L5.\n\nThe pedicle is sometimes used as a portal of entrance into the vertebral body for fixation with pedicle screws or for placement of bone cement as with kyphoplasty or vertebroplasty.\n\nThe laminae are broad, short, and strong.\n\nThey form the posterior portion of the vertebral arch.\n\nIn the upper lumbar region the lamina are taller than wide but in the lower lumbar vertebra the lamina are wider than tall.\n\nThe lamina connects the spinous process to the pedicles.\nThe vertebral foramen within the arch is triangular, larger than the thoracic vertebrae, but smaller than in the cervical vertebrae.\n\n==== Processes ====\n\nThe spinous process is thick, broad, and somewhat quadrilateral; it projects backward and ends in a rough, uneven border, thickest below where it is occasionally notched.The superior and inferior articular processes are well-defined, projecting respectively upward and downward from the junctions of pedicles and laminae.\n\nThe facets on the superior processes are concave, and look backward and medialward; those on the inferior are convex, and are directed forward and lateralward.\n\nThe former are wider apart than the latter since in the articulated column, the inferior articular processes are embraced by the superior processes of the subjacent vertebra.The transverse processes are long and slender.\n\nThey are horizontal in the upper three lumbar vertebrae and incline a little upward in the lower two.\n\nIn the upper three vertebrae they arise from the junctions of the pedicles and laminae, but in the lower two they are set farther forward and spring from the pedicles and posterior parts of the vertebral bodies.\n\nThey are situated in front of the articular processes instead of behind them as in the thoracic vertebrae, and are homologous with the ribs.\n\nThree portions or tubercles can be noticed in a transverse process of a lower lumbar vertebrae: the lateral or costiform process, the mammillary process, and the accessory process.\n\nThe costiform is lateral, the mammillary is superior (cranial), and the accessory is inferior (caudal).\n\nThe mammillary is connected in the lumbar region with the back part of the superior articular process.\n\nThe accessory process is situated at the back part of the base of the transverse process.\n\nThe tallest and thickest costiform process is usually that of L5.\n\n=== First and fifth lumbar vertebrae ===\n\nThe first lumbar vertebra is level with the anterior end of the ninth rib.\n\nThis level is also called the important transpyloric plane, since the pylorus of the stomach is at this level.\n\nOther important structures are also located at this level, they include; fundus of the gall bladder, celiac trunk, superior mesenteric artery, termination of spinal cord, beginning of filum terminalis, renal vessels, middle suprarenal arteries, and hila of kidneys.\n\nThe fifth lumbar vertebra is characterized by its body being much deeper in front than behind, which accords with the prominence of the sacrovertebral articulation; by the smaller size of its spinous process; by the wide interval between the inferior articular processes, and by the thickness of its transverse processes, which spring from the body as well as from the pedicles.\n\nThe fifth lumbar vertebra is by far the most common site of spondylolysis and spondylolisthesis.Most individuals have five lumbar vertebrae, while some have four or six.\n\nLumbar disorders that normally affect L5 will affect L4 or L6 in these latter individuals.\n\n=== Segmental movements ===\n\nThe range of segmental movements in a single segment is difficult to measure clinically, not only because of variations between individuals, but also because it is age and sex dependent.\n\nFurthermore, flexion and extension in the lumbal spine is the product of a combination of rotation and translation in the sagittal plane between each vertebra.Ranges of segmental movements in the lumbar spine (White and Punjabi, 1990) are (in degrees):\n\n=== Congenital anomalies ===\n\nCongenital vertebral anomalies can cause compression of the spinal cord by deforming the vertebral canal or causing instability.\n\n== Other animals ==\n\nAfrican apes have three and four lumbar vertebrae, (bonobos have longer spines with an additional vertebra) and humans normally five.\n\nThis difference, and because the lumbar spines of the extinct Nacholapithecus (a Miocene hominoid with six lumbar vertebrae and no tail) are similar to those of early Australopithecus and early Homo, it is assumed that the Chimpanzee-human last common ancestor also had a long vertebral column with a long lumbar region and that the reduction in the number of lumbar vertebrae evolved independently in each ape clade.\n\nThe limited number of lumbar vertebrae in chimpanzees and gorillas result in an inability to lordose (curve) their lumbar spines, in contrast to the spines of Old World monkeys and Nacholapithecus and Proconsul, which suggests that the last common ancestor was not \"short-backed\" as previously believed.\n\nhttps://en.wikipedia.org/wiki/Lumbar_vertebrae","vertebra-l5":"The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis.\n\nThey are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse process (since it is only found in the cervical region) and by the absence of facets on the sides of the body (as found only in the thoracic region).\n\nThey are designated L1 to L5, starting at the top.\n\nThe lumbar vertebrae help support the weight of the body, and permit movement.\n\n== Human anatomy ==\n\n=== General characteristics ===\n\nThe figure on the left depicts the general characteristics of the first through fourth lumbar vertebrae.\n\nThe fifth vertebra contains certain peculiarities, which are detailed below.\n\nAs with other vertebrae, each lumbar vertebra consists of a vertebral body and a vertebral arch.\n\nThe vertebral arch, consisting of a pair of pedicles and a pair of laminae, encloses the vertebral foramen (opening) and supports seven processes.\n\n==== Body ====\n\nThe vertebral body of each lumbar vertebra is kidney shaped, wider from side to side than from front to back, and a little thicker in front than in back.\n\nIt is flattened or slightly concave above and below, concave behind, and deeply constricted in front and at the sides.\n\n==== Arch ====\n\nThe pedicles are very strong, directed backward from the upper part of the vertebral body; consequently, the inferior vertebral notches are of considerable depth.\n\nThe pedicles change in morphology from the upper lumbar to the lower lumbar.\n\nThey increase in sagittal width from 9 mm to up to 18 mm at L5.\n\nThey increase in angulation in the axial plane from 10 degrees to 20 degrees by L5.\n\nThe pedicle is sometimes used as a portal of entrance into the vertebral body for fixation with pedicle screws or for placement of bone cement as with kyphoplasty or vertebroplasty.\n\nThe laminae are broad, short, and strong.\n\nThey form the posterior portion of the vertebral arch.\n\nIn the upper lumbar region the lamina are taller than wide but in the lower lumbar vertebra the lamina are wider than tall.\n\nThe lamina connects the spinous process to the pedicles.\nThe vertebral foramen within the arch is triangular, larger than the thoracic vertebrae, but smaller than in the cervical vertebrae.\n\n==== Processes ====\n\nThe spinous process is thick, broad, and somewhat quadrilateral; it projects backward and ends in a rough, uneven border, thickest below where it is occasionally notched.The superior and inferior articular processes are well-defined, projecting respectively upward and downward from the junctions of pedicles and laminae.\n\nThe facets on the superior processes are concave, and look backward and medialward; those on the inferior are convex, and are directed forward and lateralward.\n\nThe former are wider apart than the latter since in the articulated column, the inferior articular processes are embraced by the superior processes of the subjacent vertebra.The transverse processes are long and slender.\n\nThey are horizontal in the upper three lumbar vertebrae and incline a little upward in the lower two.\n\nIn the upper three vertebrae they arise from the junctions of the pedicles and laminae, but in the lower two they are set farther forward and spring from the pedicles and posterior parts of the vertebral bodies.\n\nThey are situated in front of the articular processes instead of behind them as in the thoracic vertebrae, and are homologous with the ribs.\n\nThree portions or tubercles can be noticed in a transverse process of a lower lumbar vertebrae: the lateral or costiform process, the mammillary process, and the accessory process.\n\nThe costiform is lateral, the mammillary is superior (cranial), and the accessory is inferior (caudal).\n\nThe mammillary is connected in the lumbar region with the back part of the superior articular process.\n\nThe accessory process is situated at the back part of the base of the transverse process.\n\nThe tallest and thickest costiform process is usually that of L5.\n\n=== First and fifth lumbar vertebrae ===\n\nThe first lumbar vertebra is level with the anterior end of the ninth rib.\n\nThis level is also called the important transpyloric plane, since the pylorus of the stomach is at this level.\n\nOther important structures are also located at this level, they include; fundus of the gall bladder, celiac trunk, superior mesenteric artery, termination of spinal cord, beginning of filum terminalis, renal vessels, middle suprarenal arteries, and hila of kidneys.\n\nThe fifth lumbar vertebra is characterized by its body being much deeper in front than behind, which accords with the prominence of the sacrovertebral articulation; by the smaller size of its spinous process; by the wide interval between the inferior articular processes, and by the thickness of its transverse processes, which spring from the body as well as from the pedicles.\n\nThe fifth lumbar vertebra is by far the most common site of spondylolysis and spondylolisthesis.Most individuals have five lumbar vertebrae, while some have four or six.\n\nLumbar disorders that normally affect L5 will affect L4 or L6 in these latter individuals.\n\n=== Segmental movements ===\n\nThe range of segmental movements in a single segment is difficult to measure clinically, not only because of variations between individuals, but also because it is age and sex dependent.\n\nFurthermore, flexion and extension in the lumbal spine is the product of a combination of rotation and translation in the sagittal plane between each vertebra.Ranges of segmental movements in the lumbar spine (White and Punjabi, 1990) are (in degrees):\n\n=== Congenital anomalies ===\n\nCongenital vertebral anomalies can cause compression of the spinal cord by deforming the vertebral canal or causing instability.\n\n== Other animals ==\n\nAfrican apes have three and four lumbar vertebrae, (bonobos have longer spines with an additional vertebra) and humans normally five.\n\nThis difference, and because the lumbar spines of the extinct Nacholapithecus (a Miocene hominoid with six lumbar vertebrae and no tail) are similar to those of early Australopithecus and early Homo, it is assumed that the Chimpanzee-human last common ancestor also had a long vertebral column with a long lumbar region and that the reduction in the number of lumbar vertebrae evolved independently in each ape clade.\n\nThe limited number of lumbar vertebrae in chimpanzees and gorillas result in an inability to lordose (curve) their lumbar spines, in contrast to the spines of Old World monkeys and Nacholapithecus and Proconsul, which suggests that the last common ancestor was not \"short-backed\" as previously believed.\n\nhttps://en.wikipedia.org/wiki/Lumbar_vertebrae","vertebra-l3":"The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis.\n\nThey are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse process (since it is only found in the cervical region) and by the absence of facets on the sides of the body (as found only in the thoracic region).\n\nThey are designated L1 to L5, starting at the top.\n\nThe lumbar vertebrae help support the weight of the body, and permit movement.\n\n== Human anatomy ==\n\n=== General characteristics ===\n\nThe figure on the left depicts the general characteristics of the first through fourth lumbar vertebrae.\n\nThe fifth vertebra contains certain peculiarities, which are detailed below.\n\nAs with other vertebrae, each lumbar vertebra consists of a vertebral body and a vertebral arch.\n\nThe vertebral arch, consisting of a pair of pedicles and a pair of laminae, encloses the vertebral foramen (opening) and supports seven processes.\n\n==== Body ====\n\nThe vertebral body of each lumbar vertebra is kidney shaped, wider from side to side than from front to back, and a little thicker in front than in back.\n\nIt is flattened or slightly concave above and below, concave behind, and deeply constricted in front and at the sides.\n\n==== Arch ====\n\nThe pedicles are very strong, directed backward from the upper part of the vertebral body; consequently, the inferior vertebral notches are of considerable depth.\n\nThe pedicles change in morphology from the upper lumbar to the lower lumbar.\n\nThey increase in sagittal width from 9 mm to up to 18 mm at L5.\n\nThey increase in angulation in the axial plane from 10 degrees to 20 degrees by L5.\n\nThe pedicle is sometimes used as a portal of entrance into the vertebral body for fixation with pedicle screws or for placement of bone cement as with kyphoplasty or vertebroplasty.\n\nThe laminae are broad, short, and strong.\n\nThey form the posterior portion of the vertebral arch.\n\nIn the upper lumbar region the lamina are taller than wide but in the lower lumbar vertebra the lamina are wider than tall.\n\nThe lamina connects the spinous process to the pedicles.\nThe vertebral foramen within the arch is triangular, larger than the thoracic vertebrae, but smaller than in the cervical vertebrae.\n\n==== Processes ====\n\nThe spinous process is thick, broad, and somewhat quadrilateral; it projects backward and ends in a rough, uneven border, thickest below where it is occasionally notched.The superior and inferior articular processes are well-defined, projecting respectively upward and downward from the junctions of pedicles and laminae.\n\nThe facets on the superior processes are concave, and look backward and medialward; those on the inferior are convex, and are directed forward and lateralward.\n\nThe former are wider apart than the latter since in the articulated column, the inferior articular processes are embraced by the superior processes of the subjacent vertebra.The transverse processes are long and slender.\n\nThey are horizontal in the upper three lumbar vertebrae and incline a little upward in the lower two.\n\nIn the upper three vertebrae they arise from the junctions of the pedicles and laminae, but in the lower two they are set farther forward and spring from the pedicles and posterior parts of the vertebral bodies.\n\nThey are situated in front of the articular processes instead of behind them as in the thoracic vertebrae, and are homologous with the ribs.\n\nThree portions or tubercles can be noticed in a transverse process of a lower lumbar vertebrae: the lateral or costiform process, the mammillary process, and the accessory process.\n\nThe costiform is lateral, the mammillary is superior (cranial), and the accessory is inferior (caudal).\n\nThe mammillary is connected in the lumbar region with the back part of the superior articular process.\n\nThe accessory process is situated at the back part of the base of the transverse process.\n\nThe tallest and thickest costiform process is usually that of L5.\n\n=== First and fifth lumbar vertebrae ===\n\nThe first lumbar vertebra is level with the anterior end of the ninth rib.\n\nThis level is also called the important transpyloric plane, since the pylorus of the stomach is at this level.\n\nOther important structures are also located at this level, they include; fundus of the gall bladder, celiac trunk, superior mesenteric artery, termination of spinal cord, beginning of filum terminalis, renal vessels, middle suprarenal arteries, and hila of kidneys.\n\nThe fifth lumbar vertebra is characterized by its body being much deeper in front than behind, which accords with the prominence of the sacrovertebral articulation; by the smaller size of its spinous process; by the wide interval between the inferior articular processes, and by the thickness of its transverse processes, which spring from the body as well as from the pedicles.\n\nThe fifth lumbar vertebra is by far the most common site of spondylolysis and spondylolisthesis.Most individuals have five lumbar vertebrae, while some have four or six.\n\nLumbar disorders that normally affect L5 will affect L4 or L6 in these latter individuals.\n\n=== Segmental movements ===\n\nThe range of segmental movements in a single segment is difficult to measure clinically, not only because of variations between individuals, but also because it is age and sex dependent.\n\nFurthermore, flexion and extension in the lumbal spine is the product of a combination of rotation and translation in the sagittal plane between each vertebra.Ranges of segmental movements in the lumbar spine (White and Punjabi, 1990) are (in degrees):\n\n=== Congenital anomalies ===\n\nCongenital vertebral anomalies can cause compression of the spinal cord by deforming the vertebral canal or causing instability.\n\n== Other animals ==\n\nAfrican apes have three and four lumbar vertebrae, (bonobos have longer spines with an additional vertebra) and humans normally five.\n\nThis difference, and because the lumbar spines of the extinct Nacholapithecus (a Miocene hominoid with six lumbar vertebrae and no tail) are similar to those of early Australopithecus and early Homo, it is assumed that the Chimpanzee-human last common ancestor also had a long vertebral column with a long lumbar region and that the reduction in the number of lumbar vertebrae evolved independently in each ape clade.\n\nThe limited number of lumbar vertebrae in chimpanzees and gorillas result in an inability to lordose (curve) their lumbar spines, in contrast to the spines of Old World monkeys and Nacholapithecus and Proconsul, which suggests that the last common ancestor was not \"short-backed\" as previously believed.\n\nhttps://en.wikipedia.org/wiki/Lumbar_vertebrae","coccyx":"The coccyx (plural: coccyges or coccyxes), commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horses.\n\nIn tailless primates (e.g. humans and other great apes) since Nacholapithecus (a Miocene hominoid), the coccyx is the remnant of a vestigial tail.\n\nIn animals with bony tails, it is known as tailhead or dock, in bird anatomy as tailfan.\n\nIt comprises three to five separate or fused coccygeal vertebrae below the sacrum, attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement between the sacrum and the coccyx.\n\n== Structure ==\n\nThe coccyx is formed of either three, four or five rudimentary vertebrae.\n\nIt articulates superiorly with the sacrum.\n\nIn each of the first three segments may be traced a rudimentary body and articular and transverse processes; the last piece (sometimes the third) is a mere nodule of bone.\n\nThe transverse processes are most prominent and noticeable on the first coccygeal segment.\n\nAll the segments lack pedicles, laminae and spinous processes.\n\nThe first is the largest; it resembles the lowest sacral vertebra, and often exists as a separate piece; the remaining ones diminish in size from above downward.\n\nMost anatomy books incorrectly state that the coccyx is normally fused in adults.\n\nIn fact it has been shown that the coccyx may consist of up to five separate bony segments, the most common configuration being two or three segments.\n\n=== Surfaces ===\n\nThe anterior surface is slightly concave and marked with three transverse grooves that indicate the junctions of the different segments.\n\nIt gives attachment to the anterior sacrococcygeal ligament and the levatores ani and supports part of the rectum.\n\nThe posterior surface is convex, marked by transverse grooves similar to those on the anterior surface, and presents on either side a linear row of tubercles–the rudimentary articular processes of the coccygeal vertebrae.\n\nOf these, the superior pair are the largest, and are called the coccygeal cornua they project upward, and articulate with the cornua of the sacrum, and on either side complete the foramen for the transmission of the posterior division of the fifth sacral nerve.\n\n=== Borders ===\n\nThe lateral borders are thin and exhibit a series of small eminences, which represent the transverse processes of the coccygeal vertebrae.\n\nOf these, the first is the largest; it is flattened from before backward, and often ascends to join the lower part of the thin lateral edge of the sacrum, thus completing the foramen for the transmission of the anterior division of the fifth sacral nerve; the others diminish in size from above downward, and are often wanting.\n\nThe borders of the coccyx are narrow, and give attachment on either side to the sacrotuberous and sacrospinous ligaments, to the coccygeus and levator ani in front of the ligaments, and to the gluteus maximus behind them.\n\n=== Apex ===\n\nThe apex is rounded, and has attached to it the tendon of the external anal sphincter.\n\nIt may be bifid (divided into two).\n\n=== Coccygeal fossa ===\n\nThe coccygeal fossa is a shallow depression (fossa) on the surface between the sacrum and the perineum, located in the intergluteal cleft that runs from just below the sacrum to the perineum.\n\nIt does not always appear.\n\nThe coccygeal fossa marks the deepest part of the pelvic floor, next to the coccyx.\n\nThe levator ani ascends from here.\n\n=== Extensor coccygis ===\n\nThe extensor coccygis is a slender muscle fascicle, which is not always present.\n\nIt extends over the lower part of the posterior surface of the sacrum and coccyx.\n\nIt arises by tendinous fibers from the last segment of the sacrum, or first piece of the coccyx, and passes downward to be inserted into the lower part of the coccyx.\n\nIt is a rudiment of the extensor muscle of the caudal vertebrae of other animals.\n\n=== Sacrococcygeal and intercoccygeal joints ===\n\nThe joints are variable and may be: (1) synovial joints; (2) thin discs of fibrocartilage; (3) intermediate between these two; (4) ossified.\n\n=== Attachments ===\n\nThe anterior side of the coccyx has attachments to the levator ani muscle, coccygeus, iliococcygeus, and pubococcygeus, anococcygeal raphe.\n\nAttached to the posterior side is the gluteus maximus, which extends the thigh at the hip joint.\n\nThe ligaments attached to the coccyx include the anterior and posterior sacrococcygeal ligaments which are the continuations of the anterior and posterior longitudinal ligaments that stretches along the entire spine.\n\nThe lateral sacrococcygeal ligaments complete the foramina for the last sacral nerve.\n\nSome fibers of the sacrospinous and sacrotuberous ligaments (arising from the spine of the ischium and the ischial tuberosity respectively) also attach to the coccyx.\n\nAn extension of the pia mater, the filum terminale, extends from the apex of the conus, and inserts on the coccyx.\n\n== Function ==\n\nThe coccyx is not entirely useless in humans, based on the fact that the coccyx has attachments to various muscles, tendons and ligaments.\n\nHowever, these muscles, tendons and ligaments are also attached at many other points, to stronger structures than the coccyx.\n\nIt is doubtful that the coccyx attachments are important to the well-being of humans, given the large number of cases of coccygectomy for coccydynia.\n\nReviews of studies covering more than 700 operations found the operation was successful in relieving pain in 84% of cases. 12% of the time, the only major complication faced was infection due to the proximity to the anus.\n\nHowever, one notable issue that arises from its removal is an increased risk of perineal hernia.\n\n== Clinical significance ==\n\nInjuring the coccyx can give rise to a painful condition called coccydynia and one or more of the bones or the connections thereof may be broken, fractured tailbone.\n\nA number of tumors are known to involve the coccyx; of these, the most common is sacrococcygeal teratoma.\n\nBoth coccydynia and coccygeal tumors may require surgical removal of the coccyx (coccygectomy).\n\nOne very rare complication of coccygectomy is a type of perineal hernia known as a coccygeal hernia.\n\n== History ==\n\n=== Etymology ===\n\nThe term coccyx is derived from the ancient Greek word κόκκυξ kokkyx \"cuckoo\"; the latter is attested in the writings of the Greek physician Herophilus to denote the end of the vertebral column.\n\nThis Greek name for the cuckoo was applied as the last three or four bones of the coccyx resemble the beak of this bird, when viewed from the side.This established etymological explanation can also be found in the writings of the 16th century anatomist Andreas Vesalius who wrote: os cuculi, a similitudine rostri cuculi avis (the cuckoo bone shows a likeness to the beak of the cuckoo bird).\n\nVesalius used the Latin expression os cuculi, with os, bone and cuculus, the Latin name for the cuckoo.\n\nThe 16th/17th century French anatomist Jean Riolan the Younger gives a rather hilarious etymological explanation, as he writes: quia crepitus, qui per sedimentum exeunt, ad is os allisi, cuculi vocis similitudinem effingunt (because the sound of the farts that leave the anus and dash against this bone, shows a likeness to the call of the cuckoo).\n\nThe latter is not considered as potential candidate.Besides os cuculi, os caudae, with caudae, of the tail is attested.\n\nThis Latin expression might be the source of the English, French language, German and Dutch terms tailbone, l'os de la queue, Schwanzbein and staartbeen.\n\nIn the current official anatomic Latin nomenclature, Terminologia Anatomica, coccyx and os coccygis is used.\n\nhttps://en.wikipedia.org/wiki/Coccyx","fifth-rib":"== Structure of the rib cage ==\n\nRibs are described based on their location and connection with the sternum.\n\nAll ribs are attached posteriorly to the thoracic vertebrae and are numbered accordingly one to twelve.\n\nRibs that articulate directly with the sternum are called true ribs, whereas those that do not articulate directly are termed false ribs.\n\n=== Attachment of the rib cage ===\n\nThe terms true ribs and false ribs describe rib pairs that are directly or indirectly attached to the sternum.\n\nThe first seven rib pairs known as the fixed or vertebrosternal ribs are the true ribs (Latin: costae verae) as they connect directly to the sternum; the next five pairs (eighth to twelfth) are the false ribs (Latin: costae spuriae).\n\n=== Parts of rib (general) ===\n\nEach rib consists of a head, neck, and a shaft.\n\nAll ribs are attached posteriorly to the thoracic vertebrae.\n\nThey are numbered to match the vertebrae they attach to – one to twelve, from top (T1) to bottom.\n\nThe head of the rib is the end part closest to the vertebra with which it articulates.\n\nIt is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two articulating regions.\n\nThe upper region articulates with the inferior costal facet on the vertebra above, and the larger region articulates with the superior costal facet on the vertebra with the same number.\n\nThe transverse process of a thoracic vertebra also articulates at the transverse costal facet with the tubercle of the rib of the same number.\n\nThe crest gives attachment to the intra-articular ligament.The neck of the rib is the flattened part that extends laterally from the head.\n\nThe neck is about 3 cm long.\n\nIts anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough, to give attachment to the ligament of the neck.\n\nIts upper border presents a rough crest (crista colli costae) for the attachment of the anterior costotransverse ligament; its lower border is rounded.\n\nOn the posterior surface at the neck, is an eminence—the tubercle that consists of an articular and a non-articular portion.\n\nThe articular portion is the lower and more medial of the two and presents a small, oval surface for articulation with the transverse costal facet on the end of the transverse process of the lower of the two vertebrae to which the head is connected.\n\nThe non-articular portion is a rough elevation and affords attachment to the ligament of the tubercle.\n\nThe tubercle is much more prominent in the upper ribs than in the lower ribs.\n\nThe angle of a rib (costal angle) may both refer to the bending part of it, and a prominent line in this area, a little in front of the tubercle.\n\nThis line is directed downward and laterally; this gives attachment to a tendon of the iliocostalis muscle.\n\nAt this point, the rib is bent in two directions, and at the same time twisted on its long axis.\n\nThe distance between the angle and the tubercle is progressively greater from the second to the tenth ribs.\n\nThe area between the angle and the tubercle is rounded, rough, and irregular, and serves for the attachment of the longissimus dorsi muscle.\n\nhttps://en.wikipedia.org/wiki/Rib_cage","first-rib":"== Structure of the rib cage ==\n\nRibs are described based on their location and connection with the sternum.\n\nAll ribs are attached posteriorly to the thoracic vertebrae and are numbered accordingly one to twelve.\n\nRibs that articulate directly with the sternum are called true ribs, whereas those that do not articulate directly are termed false ribs.\n\n=== Attachment of the rib cage ===\n\nThe terms true ribs and false ribs describe rib pairs that are directly or indirectly attached to the sternum.\n\nThe first seven rib pairs known as the fixed or vertebrosternal ribs are the true ribs (Latin: costae verae) as they connect directly to the sternum; the next five pairs (eighth to twelfth) are the false ribs (Latin: costae spuriae).\n\n=== Parts of rib (general) ===\n\nEach rib consists of a head, neck, and a shaft.\n\nAll ribs are attached posteriorly to the thoracic vertebrae.\n\nThey are numbered to match the vertebrae they attach to – one to twelve, from top (T1) to bottom.\n\nThe head of the rib is the end part closest to the vertebra with which it articulates.\n\nIt is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two articulating regions.\n\nThe upper region articulates with the inferior costal facet on the vertebra above, and the larger region articulates with the superior costal facet on the vertebra with the same number.\n\nThe transverse process of a thoracic vertebra also articulates at the transverse costal facet with the tubercle of the rib of the same number.\n\nThe crest gives attachment to the intra-articular ligament.The neck of the rib is the flattened part that extends laterally from the head.\n\nThe neck is about 3 cm long.\n\nIts anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough, to give attachment to the ligament of the neck.\n\nIts upper border presents a rough crest (crista colli costae) for the attachment of the anterior costotransverse ligament; its lower border is rounded.\n\nOn the posterior surface at the neck, is an eminence—the tubercle that consists of an articular and a non-articular portion.\n\nThe articular portion is the lower and more medial of the two and presents a small, oval surface for articulation with the transverse costal facet on the end of the transverse process of the lower of the two vertebrae to which the head is connected.\n\nThe non-articular portion is a rough elevation and affords attachment to the ligament of the tubercle.\n\nThe tubercle is much more prominent in the upper ribs than in the lower ribs.\n\nThe angle of a rib (costal angle) may both refer to the bending part of it, and a prominent line in this area, a little in front of the tubercle.\n\nThis line is directed downward and laterally; this gives attachment to a tendon of the iliocostalis muscle.\n\nAt this point, the rib is bent in two directions, and at the same time twisted on its long axis.\n\nThe distance between the angle and the tubercle is progressively greater from the second to the tenth ribs.\n\nThe area between the angle and the tubercle is rounded, rough, and irregular, and serves for the attachment of the longissimus dorsi muscle.\n\n==== Ribs and vertebrae ====\n\nThe first rib (the topmost one) is the most curved and usually the shortest of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward.\n\nThe head is small and rounded, and possesses only a single articular facet, for articulation with the body of the first thoracic vertebra.\n\nThe neck is narrow and rounded.\n\nThe tubercle, thick and prominent, is placed on the outer border.\n\nIt bears a small facet for articulation with the transverse costal facet on the transverse process of T1.\n\nThere is no angle, but at the tubercle, the rib is slightly bent, with the convexity upward, so that the head of the bone is directed downward.\n\nThe upper surface of the body is marked by two shallow grooves, separated from each other by a slight ridge prolonged internally into a tubercle, the scalene tubercle, for the attachment of the anterior scalene; the anterior groove transmits the subclavian vein, the posterior the subclavian artery and the lowest trunk of the brachial plexus.\n\nBehind the posterior groove is a rough area for the attachment of the medial scalene.\n\nThe under surface is smooth and without a costal groove.\n\nThe outer border is convex, thick, and rounded, and at its posterior part gives attachment to the first digitation of the serratus anterior.\n\nThe inner border is concave, thin, and sharp, and marked about its center by the scalene tubercle.\n\nThe anterior extremity is larger and thicker than that of any of the other ribs.\n\nhttps://en.wikipedia.org/wiki/Rib_cage","fourth-rib":"== Structure of the rib cage ==\n\nRibs are described based on their location and connection with the sternum.\n\nAll ribs are attached posteriorly to the thoracic vertebrae and are numbered accordingly one to twelve.\n\nRibs that articulate directly with the sternum are called true ribs, whereas those that do not articulate directly are termed false ribs.\n\n=== Attachment of the rib cage ===\n\nThe terms true ribs and false ribs describe rib pairs that are directly or indirectly attached to the sternum.\n\nThe first seven rib pairs known as the fixed or vertebrosternal ribs are the true ribs (Latin: costae verae) as they connect directly to the sternum; the next five pairs (eighth to twelfth) are the false ribs (Latin: costae spuriae).\n\n=== Parts of rib (general) ===\n\nEach rib consists of a head, neck, and a shaft.\n\nAll ribs are attached posteriorly to the thoracic vertebrae.\n\nThey are numbered to match the vertebrae they attach to – one to twelve, from top (T1) to bottom.\n\nThe head of the rib is the end part closest to the vertebra with which it articulates.\n\nIt is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two articulating regions.\n\nThe upper region articulates with the inferior costal facet on the vertebra above, and the larger region articulates with the superior costal facet on the vertebra with the same number.\n\nThe transverse process of a thoracic vertebra also articulates at the transverse costal facet with the tubercle of the rib of the same number.\n\nThe crest gives attachment to the intra-articular ligament.The neck of the rib is the flattened part that extends laterally from the head.\n\nThe neck is about 3 cm long.\n\nIts anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough, to give attachment to the ligament of the neck.\n\nIts upper border presents a rough crest (crista colli costae) for the attachment of the anterior costotransverse ligament; its lower border is rounded.\n\nOn the posterior surface at the neck, is an eminence—the tubercle that consists of an articular and a non-articular portion.\n\nThe articular portion is the lower and more medial of the two and presents a small, oval surface for articulation with the transverse costal facet on the end of the transverse process of the lower of the two vertebrae to which the head is connected.\n\nThe non-articular portion is a rough elevation and affords attachment to the ligament of the tubercle.\n\nThe tubercle is much more prominent in the upper ribs than in the lower ribs.\n\nThe angle of a rib (costal angle) may both refer to the bending part of it, and a prominent line in this area, a little in front of the tubercle.\n\nThis line is directed downward and laterally; this gives attachment to a tendon of the iliocostalis muscle.\n\nAt this point, the rib is bent in two directions, and at the same time twisted on its long axis.\n\nThe distance between the angle and the tubercle is progressively greater from the second to the tenth ribs.\n\nThe area between the angle and the tubercle is rounded, rough, and irregular, and serves for the attachment of the longissimus dorsi muscle.\n\nhttps://en.wikipedia.org/wiki/Rib_cage","second-rib":"The second rib is the second uppermost rib in humans or second most frontal in animals that walk on four limbs.\n\nIn humans, the second rib is defined as a true rib since it connects with the sternum through the intervention of the costal cartilage anteriorly (at the front).\n\nPosteriorly, the second rib is connected with the vertebral column by the second thoracic vertebra.\n\nThe second rib is much longer than the first rib, but has a very similar curvature.\n\nThe non-articular portion of the tubercle is occasionally only feebly marked.\n\nThe angle is slight and situated close to the tubercle.\n\nThe body is not twisted so that both ends touch any plane surface upon which it may be laid; but there is a bend, with its convexity upward, similar to, though smaller than that found in the first rib.\n\nThe body is not flattened horizontally like that of the first rib.\n\nIts external surface is convex, and looks upward and a little outward; near the middle of it is a rough eminence for the origin of the lower part of the first and the whole of the second digitation of the serratus anterior; behind and above this is attached the posterior scalene.\n\nThe internal surface, smooth, and concave, is directed downward and a little inward: on its posterior part there is a short costal groove between the ridge of the internal surface of the rib and the inferior border.\n\nIt protects the intercostal space containing the intercostal veins, intercostal arteries, and intercostal nerves.","seventh-rib":"== Structure of the rib cage ==\n\nRibs are described based on their location and connection with the sternum.\n\nAll ribs are attached posteriorly to the thoracic vertebrae and are numbered accordingly one to twelve.\n\nRibs that articulate directly with the sternum are called true ribs, whereas those that do not articulate directly are termed false ribs.\n\n=== Attachment of the rib cage ===\n\nThe terms true ribs and false ribs describe rib pairs that are directly or indirectly attached to the sternum.\n\nThe first seven rib pairs known as the fixed or vertebrosternal ribs are the true ribs (Latin: costae verae) as they connect directly to the sternum; the next five pairs (eighth to twelfth) are the false ribs (Latin: costae spuriae).\n\n=== Parts of rib (general) ===\n\nEach rib consists of a head, neck, and a shaft.\n\nAll ribs are attached posteriorly to the thoracic vertebrae.\n\nThey are numbered to match the vertebrae they attach to – one to twelve, from top (T1) to bottom.\n\nThe head of the rib is the end part closest to the vertebra with which it articulates.\n\nIt is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two articulating regions.\n\nThe upper region articulates with the inferior costal facet on the vertebra above, and the larger region articulates with the superior costal facet on the vertebra with the same number.\n\nThe transverse process of a thoracic vertebra also articulates at the transverse costal facet with the tubercle of the rib of the same number.\n\nThe crest gives attachment to the intra-articular ligament.The neck of the rib is the flattened part that extends laterally from the head.\n\nThe neck is about 3 cm long.\n\nIts anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough, to give attachment to the ligament of the neck.\n\nIts upper border presents a rough crest (crista colli costae) for the attachment of the anterior costotransverse ligament; its lower border is rounded.\n\nOn the posterior surface at the neck, is an eminence—the tubercle that consists of an articular and a non-articular portion.\n\nThe articular portion is the lower and more medial of the two and presents a small, oval surface for articulation with the transverse costal facet on the end of the transverse process of the lower of the two vertebrae to which the head is connected.\n\nThe non-articular portion is a rough elevation and affords attachment to the ligament of the tubercle.\n\nThe tubercle is much more prominent in the upper ribs than in the lower ribs.\n\nThe angle of a rib (costal angle) may both refer to the bending part of it, and a prominent line in this area, a little in front of the tubercle.\n\nThis line is directed downward and laterally; this gives attachment to a tendon of the iliocostalis muscle.\n\nAt this point, the rib is bent in two directions, and at the same time twisted on its long axis.\n\nThe distance between the angle and the tubercle is progressively greater from the second to the tenth ribs.\n\nThe area between the angle and the tubercle is rounded, rough, and irregular, and serves for the attachment of the longissimus dorsi muscle.\n\nhttps://en.wikipedia.org/wiki/Rib_cage","sixth-rib":"== Structure of the rib cage ==\n\nRibs are described based on their location and connection with the sternum.\n\nAll ribs are attached posteriorly to the thoracic vertebrae and are numbered accordingly one to twelve.\n\nRibs that articulate directly with the sternum are called true ribs, whereas those that do not articulate directly are termed false ribs.\n\n=== Attachment of the rib cage ===\n\nThe terms true ribs and false ribs describe rib pairs that are directly or indirectly attached to the sternum.\n\nThe first seven rib pairs known as the fixed or vertebrosternal ribs are the true ribs (Latin: costae verae) as they connect directly to the sternum; the next five pairs (eighth to twelfth) are the false ribs (Latin: costae spuriae).\n\n=== Parts of rib (general) ===\n\nEach rib consists of a head, neck, and a shaft.\n\nAll ribs are attached posteriorly to the thoracic vertebrae.\n\nThey are numbered to match the vertebrae they attach to – one to twelve, from top (T1) to bottom.\n\nThe head of the rib is the end part closest to the vertebra with which it articulates.\n\nIt is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two articulating regions.\n\nThe upper region articulates with the inferior costal facet on the vertebra above, and the larger region articulates with the superior costal facet on the vertebra with the same number.\n\nThe transverse process of a thoracic vertebra also articulates at the transverse costal facet with the tubercle of the rib of the same number.\n\nThe crest gives attachment to the intra-articular ligament.The neck of the rib is the flattened part that extends laterally from the head.\n\nThe neck is about 3 cm long.\n\nIts anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough, to give attachment to the ligament of the neck.\n\nIts upper border presents a rough crest (crista colli costae) for the attachment of the anterior costotransverse ligament; its lower border is rounded.\n\nOn the posterior surface at the neck, is an eminence—the tubercle that consists of an articular and a non-articular portion.\n\nThe articular portion is the lower and more medial of the two and presents a small, oval surface for articulation with the transverse costal facet on the end of the transverse process of the lower of the two vertebrae to which the head is connected.\n\nThe non-articular portion is a rough elevation and affords attachment to the ligament of the tubercle.\n\nThe tubercle is much more prominent in the upper ribs than in the lower ribs.\n\nThe angle of a rib (costal angle) may both refer to the bending part of it, and a prominent line in this area, a little in front of the tubercle.\n\nThis line is directed downward and laterally; this gives attachment to a tendon of the iliocostalis muscle.\n\nAt this point, the rib is bent in two directions, and at the same time twisted on its long axis.\n\nThe distance between the angle and the tubercle is progressively greater from the second to the tenth ribs.\n\nThe area between the angle and the tubercle is rounded, rough, and irregular, and serves for the attachment of the longissimus dorsi muscle.\n\n==== Ribs and vertebrae ====\n\nThe first rib (the topmost one) is the most curved and usually the shortest of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward.\n\nThe head is small and rounded, and possesses only a single articular facet, for articulation with the body of the first thoracic vertebra.\n\nThe neck is narrow and rounded.\n\nThe tubercle, thick and prominent, is placed on the outer border.\n\nIt bears a small facet for articulation with the transverse costal facet on the transverse process of T1.\n\nThere is no angle, but at the tubercle, the rib is slightly bent, with the convexity upward, so that the head of the bone is directed downward.\n\nThe upper surface of the body is marked by two shallow grooves, separated from each other by a slight ridge prolonged internally into a tubercle, the scalene tubercle, for the attachment of the anterior scalene; the anterior groove transmits the subclavian vein, the posterior the subclavian artery and the lowest trunk of the brachial plexus.\n\nBehind the posterior groove is a rough area for the attachment of the medial scalene.\n\nThe under surface is smooth and without a costal groove.\n\nThe outer border is convex, thick, and rounded, and at its posterior part gives attachment to the first digitation of the serratus anterior.\n\nThe inner border is concave, thin, and sharp, and marked about its center by the scalene tubercle.\n\nThe anterior extremity is larger and thicker than that of any of the other ribs.\n\nhttps://en.wikipedia.org/wiki/Rib_cage","third-rib":"== Structure of the rib cage ==\n\nRibs are described based on their location and connection with the sternum.\n\nAll ribs are attached posteriorly to the thoracic vertebrae and are numbered accordingly one to twelve.\n\nRibs that articulate directly with the sternum are called true ribs, whereas those that do not articulate directly are termed false ribs.\n\n=== Attachment of the rib cage ===\n\nThe terms true ribs and false ribs describe rib pairs that are directly or indirectly attached to the sternum.\n\nThe first seven rib pairs known as the fixed or vertebrosternal ribs are the true ribs (Latin: costae verae) as they connect directly to the sternum; the next five pairs (eighth to twelfth) are the false ribs (Latin: costae spuriae).\n\n=== Parts of rib (general) ===\n\nEach rib consists of a head, neck, and a shaft.\n\nAll ribs are attached posteriorly to the thoracic vertebrae.\n\nThey are numbered to match the vertebrae they attach to – one to twelve, from top (T1) to bottom.\n\nThe head of the rib is the end part closest to the vertebra with which it articulates.\n\nIt is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two articulating regions.\n\nThe upper region articulates with the inferior costal facet on the vertebra above, and the larger region articulates with the superior costal facet on the vertebra with the same number.\n\nThe transverse process of a thoracic vertebra also articulates at the transverse costal facet with the tubercle of the rib of the same number.\n\nThe crest gives attachment to the intra-articular ligament.The neck of the rib is the flattened part that extends laterally from the head.\n\nThe neck is about 3 cm long.\n\nIts anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough, to give attachment to the ligament of the neck.\n\nIts upper border presents a rough crest (crista colli costae) for the attachment of the anterior costotransverse ligament; its lower border is rounded.\n\nOn the posterior surface at the neck, is an eminence—the tubercle that consists of an articular and a non-articular portion.\n\nThe articular portion is the lower and more medial of the two and presents a small, oval surface for articulation with the transverse costal facet on the end of the transverse process of the lower of the two vertebrae to which the head is connected.\n\nThe non-articular portion is a rough elevation and affords attachment to the ligament of the tubercle.\n\nThe tubercle is much more prominent in the upper ribs than in the lower ribs.\n\nThe angle of a rib (costal angle) may both refer to the bending part of it, and a prominent line in this area, a little in front of the tubercle.\n\nThis line is directed downward and laterally; this gives attachment to a tendon of the iliocostalis muscle.\n\nAt this point, the rib is bent in two directions, and at the same time twisted on its long axis.\n\nThe distance between the angle and the tubercle is progressively greater from the second to the tenth ribs.\n\nThe area between the angle and the tubercle is rounded, rough, and irregular, and serves for the attachment of the longissimus dorsi muscle.\n\nhttps://en.wikipedia.org/wiki/Rib_cage","eleventh-rib":"The phrase floating rib or vertebral rib (Latin: costae fluctuantes) refers to the two lowermost, the eleventh and twelfth rib pairs; so-called because they are attached only to the vertebrae–and not to the sternum or cartilage of the sternum.\n\nThese ribs are relatively small and delicate, and include a cartilaginous tip.","twelfth-rib":"The phrase floating rib or vertebral rib (Latin: costae fluctuantes) refers to the two lowermost, the eleventh and twelfth rib pairs; so-called because they are attached only to the vertebrae–and not to the sternum or cartilage of the sternum.\n\nThese ribs are relatively small and delicate, and include a cartilaginous tip.","eighth-rib":"== Structure of the rib cage ==\n\nRibs are described based on their location and connection with the sternum.\n\nAll ribs are attached posteriorly to the thoracic vertebrae and are numbered accordingly one to twelve.\n\nRibs that articulate directly with the sternum are called true ribs, whereas those that do not articulate directly are termed false ribs.\n\n=== Attachment of the rib cage ===\n\nThe terms true ribs and false ribs describe rib pairs that are directly or indirectly attached to the sternum.\n\nThe first seven rib pairs known as the fixed or vertebrosternal ribs are the true ribs (Latin: costae verae) as they connect directly to the sternum; the next five pairs (eighth to twelfth) are the false ribs (Latin: costae spuriae).\n\n=== Parts of rib (general) ===\n\nEach rib consists of a head, neck, and a shaft.\n\nAll ribs are attached posteriorly to the thoracic vertebrae.\n\nThey are numbered to match the vertebrae they attach to – one to twelve, from top (T1) to bottom.\n\nThe head of the rib is the end part closest to the vertebra with which it articulates.\n\nIt is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two articulating regions.\n\nThe upper region articulates with the inferior costal facet on the vertebra above, and the larger region articulates with the superior costal facet on the vertebra with the same number.\n\nThe transverse process of a thoracic vertebra also articulates at the transverse costal facet with the tubercle of the rib of the same number.\n\nThe crest gives attachment to the intra-articular ligament.The neck of the rib is the flattened part that extends laterally from the head.\n\nThe neck is about 3 cm long.\n\nIts anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough, to give attachment to the ligament of the neck.\n\nIts upper border presents a rough crest (crista colli costae) for the attachment of the anterior costotransverse ligament; its lower border is rounded.\n\nOn the posterior surface at the neck, is an eminence—the tubercle that consists of an articular and a non-articular portion.\n\nThe articular portion is the lower and more medial of the two and presents a small, oval surface for articulation with the transverse costal facet on the end of the transverse process of the lower of the two vertebrae to which the head is connected.\n\nThe non-articular portion is a rough elevation and affords attachment to the ligament of the tubercle.\n\nThe tubercle is much more prominent in the upper ribs than in the lower ribs.\n\nThe angle of a rib (costal angle) may both refer to the bending part of it, and a prominent line in this area, a little in front of the tubercle.\n\nThis line is directed downward and laterally; this gives attachment to a tendon of the iliocostalis muscle.\n\nAt this point, the rib is bent in two directions, and at the same time twisted on its long axis.\n\nThe distance between the angle and the tubercle is progressively greater from the second to the tenth ribs.\n\nThe area between the angle and the tubercle is rounded, rough, and irregular, and serves for the attachment of the longissimus dorsi muscle.\n\n==== Ribs and vertebrae ====\n\nThe first rib (the topmost one) is the most curved and usually the shortest of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward.\n\nThe head is small and rounded, and possesses only a single articular facet, for articulation with the body of the first thoracic vertebra.\n\nThe neck is narrow and rounded.\n\nThe tubercle, thick and prominent, is placed on the outer border.\n\nIt bears a small facet for articulation with the transverse costal facet on the transverse process of T1.\n\nThere is no angle, but at the tubercle, the rib is slightly bent, with the convexity upward, so that the head of the bone is directed downward.\n\nThe upper surface of the body is marked by two shallow grooves, separated from each other by a slight ridge prolonged internally into a tubercle, the scalene tubercle, for the attachment of the anterior scalene; the anterior groove transmits the subclavian vein, the posterior the subclavian artery and the lowest trunk of the brachial plexus.\n\nBehind the posterior groove is a rough area for the attachment of the medial scalene.\n\nThe under surface is smooth and without a costal groove.\n\nThe outer border is convex, thick, and rounded, and at its posterior part gives attachment to the first digitation of the serratus anterior.\n\nThe inner border is concave, thin, and sharp, and marked about its center by the scalene tubercle.\n\nThe anterior extremity is larger and thicker than that of any of the other ribs.\n\nhttps://en.wikipedia.org/wiki/Rib_cage","ninth-rib":"== Structure of the rib cage ==\n\nRibs are described based on their location and connection with the sternum.\n\nAll ribs are attached posteriorly to the thoracic vertebrae and are numbered accordingly one to twelve.\n\nRibs that articulate directly with the sternum are called true ribs, whereas those that do not articulate directly are termed false ribs.\n\n=== Attachment of the rib cage ===\n\nThe terms true ribs and false ribs describe rib pairs that are directly or indirectly attached to the sternum.\n\nThe first seven rib pairs known as the fixed or vertebrosternal ribs are the true ribs (Latin: costae verae) as they connect directly to the sternum; the next five pairs (eighth to twelfth) are the false ribs (Latin: costae spuriae).\n\n=== Parts of rib (general) ===\n\nEach rib consists of a head, neck, and a shaft.\n\nAll ribs are attached posteriorly to the thoracic vertebrae.\n\nThey are numbered to match the vertebrae they attach to – one to twelve, from top (T1) to bottom.\n\nThe head of the rib is the end part closest to the vertebra with which it articulates.\n\nIt is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two articulating regions.\n\nThe upper region articulates with the inferior costal facet on the vertebra above, and the larger region articulates with the superior costal facet on the vertebra with the same number.\n\nThe transverse process of a thoracic vertebra also articulates at the transverse costal facet with the tubercle of the rib of the same number.\n\nThe crest gives attachment to the intra-articular ligament.The neck of the rib is the flattened part that extends laterally from the head.\n\nThe neck is about 3 cm long.\n\nIts anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough, to give attachment to the ligament of the neck.\n\nIts upper border presents a rough crest (crista colli costae) for the attachment of the anterior costotransverse ligament; its lower border is rounded.\n\nOn the posterior surface at the neck, is an eminence—the tubercle that consists of an articular and a non-articular portion.\n\nThe articular portion is the lower and more medial of the two and presents a small, oval surface for articulation with the transverse costal facet on the end of the transverse process of the lower of the two vertebrae to which the head is connected.\n\nThe non-articular portion is a rough elevation and affords attachment to the ligament of the tubercle.\n\nThe tubercle is much more prominent in the upper ribs than in the lower ribs.\n\nThe angle of a rib (costal angle) may both refer to the bending part of it, and a prominent line in this area, a little in front of the tubercle.\n\nThis line is directed downward and laterally; this gives attachment to a tendon of the iliocostalis muscle.\n\nAt this point, the rib is bent in two directions, and at the same time twisted on its long axis.\n\nThe distance between the angle and the tubercle is progressively greater from the second to the tenth ribs.\n\nThe area between the angle and the tubercle is rounded, rough, and irregular, and serves for the attachment of the longissimus dorsi muscle.\n\n==== Ribs and vertebrae ====\n\nThe first rib (the topmost one) is the most curved and usually the shortest of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward.\n\nThe head is small and rounded, and possesses only a single articular facet, for articulation with the body of the first thoracic vertebra.\n\nThe neck is narrow and rounded.\n\nThe tubercle, thick and prominent, is placed on the outer border.\n\nIt bears a small facet for articulation with the transverse costal facet on the transverse process of T1.\n\nThere is no angle, but at the tubercle, the rib is slightly bent, with the convexity upward, so that the head of the bone is directed downward.\n\nThe upper surface of the body is marked by two shallow grooves, separated from each other by a slight ridge prolonged internally into a tubercle, the scalene tubercle, for the attachment of the anterior scalene; the anterior groove transmits the subclavian vein, the posterior the subclavian artery and the lowest trunk of the brachial plexus.\n\nBehind the posterior groove is a rough area for the attachment of the medial scalene.\n\nThe under surface is smooth and without a costal groove.\n\nThe outer border is convex, thick, and rounded, and at its posterior part gives attachment to the first digitation of the serratus anterior.\n\nThe inner border is concave, thin, and sharp, and marked about its center by the scalene tubercle.\n\nThe anterior extremity is larger and thicker than that of any of the other ribs.\n\nhttps://en.wikipedia.org/wiki/Rib_cage","tenth-rib":"== Structure of the rib cage ==\n\nRibs are described based on their location and connection with the sternum.\n\nAll ribs are attached posteriorly to the thoracic vertebrae and are numbered accordingly one to twelve.\n\nRibs that articulate directly with the sternum are called true ribs, whereas those that do not articulate directly are termed false ribs.\n\n=== Attachment of the rib cage ===\n\nThe terms true ribs and false ribs describe rib pairs that are directly or indirectly attached to the sternum.\n\nThe first seven rib pairs known as the fixed or vertebrosternal ribs are the true ribs (Latin: costae verae) as they connect directly to the sternum; the next five pairs (eighth to twelfth) are the false ribs (Latin: costae spuriae).\n\n=== Parts of rib (general) ===\n\nEach rib consists of a head, neck, and a shaft.\n\nAll ribs are attached posteriorly to the thoracic vertebrae.\n\nThey are numbered to match the vertebrae they attach to – one to twelve, from top (T1) to bottom.\n\nThe head of the rib is the end part closest to the vertebra with which it articulates.\n\nIt is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two articulating regions.\n\nThe upper region articulates with the inferior costal facet on the vertebra above, and the larger region articulates with the superior costal facet on the vertebra with the same number.\n\nThe transverse process of a thoracic vertebra also articulates at the transverse costal facet with the tubercle of the rib of the same number.\n\nThe crest gives attachment to the intra-articular ligament.The neck of the rib is the flattened part that extends laterally from the head.\n\nThe neck is about 3 cm long.\n\nIts anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough, to give attachment to the ligament of the neck.\n\nIts upper border presents a rough crest (crista colli costae) for the attachment of the anterior costotransverse ligament; its lower border is rounded.\n\nOn the posterior surface at the neck, is an eminence—the tubercle that consists of an articular and a non-articular portion.\n\nThe articular portion is the lower and more medial of the two and presents a small, oval surface for articulation with the transverse costal facet on the end of the transverse process of the lower of the two vertebrae to which the head is connected.\n\nThe non-articular portion is a rough elevation and affords attachment to the ligament of the tubercle.\n\nThe tubercle is much more prominent in the upper ribs than in the lower ribs.\n\nThe angle of a rib (costal angle) may both refer to the bending part of it, and a prominent line in this area, a little in front of the tubercle.\n\nThis line is directed downward and laterally; this gives attachment to a tendon of the iliocostalis muscle.\n\nAt this point, the rib is bent in two directions, and at the same time twisted on its long axis.\n\nThe distance between the angle and the tubercle is progressively greater from the second to the tenth ribs.\n\nThe area between the angle and the tubercle is rounded, rough, and irregular, and serves for the attachment of the longissimus dorsi muscle.\n\n==== Ribs and vertebrae ====\n\nThe first rib (the topmost one) is the most curved and usually the shortest of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward.\n\nThe head is small and rounded, and possesses only a single articular facet, for articulation with the body of the first thoracic vertebra.\n\nThe neck is narrow and rounded.\n\nThe tubercle, thick and prominent, is placed on the outer border.\n\nIt bears a small facet for articulation with the transverse costal facet on the transverse process of T1.\n\nThere is no angle, but at the tubercle, the rib is slightly bent, with the convexity upward, so that the head of the bone is directed downward.\n\nThe upper surface of the body is marked by two shallow grooves, separated from each other by a slight ridge prolonged internally into a tubercle, the scalene tubercle, for the attachment of the anterior scalene; the anterior groove transmits the subclavian vein, the posterior the subclavian artery and the lowest trunk of the brachial plexus.\n\nBehind the posterior groove is a rough area for the attachment of the medial scalene.\n\nThe under surface is smooth and without a costal groove.\n\nThe outer border is convex, thick, and rounded, and at its posterior part gives attachment to the first digitation of the serratus anterior.\n\nThe inner border is concave, thin, and sharp, and marked about its center by the scalene tubercle.\n\nThe anterior extremity is larger and thicker than that of any of the other ribs.\n\nhttps://en.wikipedia.org/wiki/Rib_cage","manubrium-of-sternum":"The manubrium (Latin for \"handle\") is the broad upper part of the sternum.\n\nIt has a quadrangular shape, narrowing from the top, which gives it four borders.\n\nThe suprasternal notch (jugular notch) is located in the middle at the upper broadest part of the manubrium.\n\nThis notch can be felt between the two clavicles.\n\nOn either side of this notch are the right and left clavicular notches.The manubrium joins with the body of the sternum, the clavicles and the cartilages of the first pair of ribs.\n\nThe inferior border, oval and rough, is covered with a thin layer of cartilage for articulation with the body.\n\nThe lateral borders are each marked above by a depression for the first costal cartilage, and below by a small facet, which, with a similar facet on the upper angle of the body, forms a notch for the reception of the costal cartilage of the second rib.\n\nBetween the depression for the first costal cartilage and the demi-facet for the second is a narrow, curved edge, which slopes from above downward towards the middle.\n\nAlso, the superior sternopericardial ligament attaches the pericardium to the posterior side of the manubrium.","xiphoid-process":"Located at the inferior end of the sternum is the pointed xiphoid process.\n\nImproperly performed chest compressions during cardiopulmonary resuscitation can cause the xiphoid process to snap off, driving it into the liver which can cause a fatal hemorrhage.\n\nThe sternum is composed of highly vascular tissue, covered by a thin layer of compact bone which is thickest in the manubrium between the articular facets for the clavicles.\n\nThe inferior sternopericardial ligament attaches the pericardium to the posterior xiphoid process.","body-of-sternum":"The body, or gladiolus, is the longest sternal part.\n\nIt is flat and considered to have only a front and back surface.\n\nIt is flat on the front, directed upward and forward, and marked by three transverse ridges which cross the bone opposite the third, fourth, and fifth articular depressions.\n\nThe pectoralis major attaches to it on either side.\n\nAt the junction of the third and fourth parts of the body is occasionally seen an orifice, the sternal foramen, of varying size and form.\n\nThe posterior surface, slightly concave, is also marked by three transverse lines, less distinct, however, than those in front; from its lower part, on either side, the transversus thoracis takes origin.\n\nThe sternal angle is located at the point where the body joins the manubrium.\n\nThe sternal angle can be felt at the point where the sternum projects farthest forward.\n\nHowever, in some people the sternal angle is concave or rounded.\n\nDuring physical examinations, the sternal angle is a useful landmark because the second rib attaches here.\n\nEach outer border, at its superior angle, has a small facet, which with a similar facet on the manubrium, forms a cavity for the cartilage of the second rib; below this are four angular depressions which receive the cartilages of the third, fourth, fifth, and sixth ribs.\n\nThe inferior angle has a small facet, which, with a corresponding one on the xiphoid process, forms a notch for the cartilage of the seventh rib.\n\nThese articular depressions are separated by a series of curved interarticular intervals, which diminish in length from above downward, and correspond to the intercostal spaces.\n\nMost of the cartilages belonging to the true ribs, articulate with the sternum at the lines of junction of its primitive component segments.\n\nThis is well seen in some other vertebrates, where the parts of the bone remain separated for longer.\n\nThe upper border is oval and articulates with the manubrium, at the sternal angle.\n\nThe lower border is narrow, and articulates with the xiphoid process.","clavicle":"The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone).\n\nThere are two clavicles, one on the left and one on the right.\n\nThe clavicle is the only long bone in the body that lies horizontally.\nTogether with the shoulder blade, it makes up the shoulder girdle.\n\nIt is a touchable bone, and in people who have less fat in this region, the location of the bone is clearly visible, as it creates a bulge in the skin.\n\nIt receives its name from the Latin clavicula (\"little key\"), because the bone rotates along its axis like a key when the shoulder is abducted.\n\nThe clavicle is the most commonly fractured bone.\n\nIt can easily be fractured by impacts to the shoulder from the force of falling on outstretched arms or by a direct hit.\n\n== Structure ==\n\nThe collarbone is a thin doubly curved long bone that connects the arm to the trunk of the body.\n\nLocated directly above the first rib, it acts as a strut to keep the scapula in place so that the arm can hang freely.\n\nAt its rounded medial end (sternal end), it articulates with the manubrium of the sternum (breastbone) at the sternoclavicular joint.\n\nAt its flattened lateral end (acromial end), it articulates with the acromion, a process of the scapula (shoulder blade), at the acromioclavicular joint.\n\nThe rounded medial region (sternal region) of the shaft has a long curve laterally and anteriorly along two-thirds of the entire shaft.\n\nThe flattened lateral region (acromial region) of the shaft has an even larger posterior curve to articulate with the acromion of the scapula.\n\nThe medial region is the longest clavicular region as it takes up two-thirds of the entire shaft.\n\nThe lateral region is both the widest clavicular region and thinnest clavicular region.\n\nThe lateral end has a rough inferior surface that bears a ridge, the trapezoid line, and a slight rounded projection, the conoid tubercle (above the coracoid process).\n\nThese surface features are attachment sites for muscles and ligaments of the shoulder.\n\nIt can be divided into three parts: medial end, lateral end, and shaft.\n\n=== Medial end ===\n\nThe medial end is also known as the sternal end.\n\nIt is quadrangular and articulates with the clavicular notch of the manubrium of the sternum to form the sternoclavicular joint.\n\nThe articular surface extends to the inferior aspect for articulation with the first costal cartilage.\n\n=== Lateral end ===\n\nThe lateral end is also known as the acromial end.\n\nIt is flat from above downward.\n\nIt bears a facet that articulates with the shoulder to form the acromioclavicular joint.\n\nThe area surrounding the joint gives an attachment to the joint capsule.\n\nThe anterior border is concave forward and the posterior border is convex backward.\n\n=== Shaft ===\n\nThe shaft is divided into two main regions, the medial region, and the lateral region.\n\nThe medial region is also known as the sternal region, it is the longest clavicular region as it takes up two-thirds of the entire shaft.\n\nThe lateral region is also known as the acromial region, it is both the widest clavicular region and thinnest clavicular region.\n\n==== Lateral region of the shaft ====\n\nThe lateral region of the shaft has two borders and two surfaces.\n\n-the anterior border is concave forward and gives origin to the deltoid muscle.\n-the posterior border is convex and gives attachment to the trapezius muscle.\n-the inferior surface has a ridge called the trapezoid line and a tubercle; the conoid tubercle for attachment with the trapezoid and the conoid ligament, part of the coracoclavicular ligament that serves to connect the collarbone with the coracoid process of the scapula.\n\n=== Development ===\n\nThe collarbone is the first bone to begin the process of ossification (laying down of minerals onto a preformed matrix) during development of the embryo, during the fifth and sixth weeks of gestation.\n\nHowever, it is one of the last bones to finish ossification at about 21–25 years of age.\n\nIts lateral end is formed by intramembranous ossification while medially it is formed by endochondral ossification.\n\nIt consists of a mass of cancellous bone surrounded by a compact bone shell.\n\nThe cancellous bone forms via two ossification centres, one medial and one lateral, which fuse later on.\n\nThe compact forms as the layer of fascia covering the bone stimulate the ossification of adjacent tissue.\n\nThe resulting compact bone is known as a periosteal collar.\n\nEven though it is classified as a long bone, the collarbone has no medullary cavity (marrow cavity) like other long bones, though this is not always true.\n\nIt is made up of spongy cancellous bone with a shell of compact bone.\n\nIt is a dermal bone derived from elements originally attached to the skull.\n\n=== Variation ===\n\nThe shape of the clavicle varies more than most other long bones.\n\nIt is occasionally pierced by a branch of the supraclavicular nerve.\n\nIn males the clavicle is usually longer and larger than in females.\n\nA study measuring 748 males and 252 females saw a difference in collarbone length between age groups 18–20 and 21–25 of about 6 and 5 mm (0.24 and 0.20 in) for males and females respectively.\n\nThe left clavicle is usually longer and weaker than the right clavicle.\n\nThe collarbones are sometimes partly or completely absent in cleidocranial dysostosis.\n\nThe levator claviculae muscle, present in 2–3% of people, originates on the transverse processes of the upper cervical vertebrae and is inserted in the lateral half of the clavicle.\n\n== Functions ==\n\nThe collarbone serves several functions:\n\nIt serves as a rigid support from which the scapula and free limb suspended; an arrangement that keeps the upper limb away from the thorax so that the arm has maximum range of movement.\n\nActing as a flexible, crane-like strut, it allows the scapula to move freely on the thoracic wall.\n\nCovering the cervicoaxillary canal, it protects the neurovascular bundle that supplies the upper limb.\n\nTransmits physical impacts from the upper limb to the axial skeleton.\n\n=== Muscle ===\n\nMuscles and ligaments that attach to the collarbone include:\n\n== Clinical significance ==\n\n-Acromioclavicular dislocation (\"AC Separation\")\n-Degeneration of the clavicle\n-Osteolysis\n-Sternoclavicular dislocationsA vertical line drawn from the mid-clavicle called the mid-clavicular line is used as a reference in describing cardiac apex beat during medical examination.\n-It is also useful for evaluating an enlarged liver, and for locating the gallbladder which is between the mid-clavicular line and the transpyloric plane.\n\n=== Collarbone fracture ===\n\nClavicle fractures (colloquially, a broken collarbone) occur as a result of injury or trauma.\n\nThe most common type of fractures occur when a person falls horizontally on the shoulder or with an outstretched hand.\n\nA direct hit to the collarbone will also cause a break.\n\nIn most cases, the direct hit occurs from the lateral side towards the medial side of the bone.\n\nThe most common site of fracture is the junction between the two curvatures of the bone, which is the weakest point.\n\nThis results in the sternocleidomastoid muscle lifting the medial aspect superiorly, which can result in perforation of the overlying skin.\n\n== Other animals ==\n\nThe clavicle first appears as part of the skeleton in primitive bony fish, where it is associated with the pectoral fin; they also have a bone called the cleithrum.\n\nIn such fish, the paired clavicles run behind and below the gills on each side, and are joined by a solid symphysis on the fish's underside.\n\nThey are, however, absent in cartilaginous fish and in the vast majority of living bony fish, including all of the teleosts.\n\nThe earliest tetrapods retained this arrangement, with the addition of a diamond-shaped interclavicle between the base of the clavicles, although this is not found in living amphibians.\n\nThe cleithrum disappeared early in the evolution of reptiles, and is not found in any living amniotes, but the interclavicle is present in most modern reptiles, and also in monotremes.\n\nIn modern forms, however, there are a number of variations from the primitive pattern.\n\nFor example, crocodilians and salamanders lack clavicles altogether (although crocodilians do retain the interclavicle), while in turtles, they form part of the armoured plastron.The interclavicle is absent in marsupials and placental mammals.\n\nIn many mammals, the clavicles are also reduced, or even absent, to allow the scapula greater freedom of motion, which may be useful in fast-running animals.\n\nThough a number of fossil hominin (humans and chimpanzees) clavicles have been found, most of these are mere segments offering limited information on the form and function of the pectoral girdle.\n\nOne exception is the clavicle of AL 333x6/9 attributed to Australopithecus afarensis which has a well-preserved sternal end.\n\nOne interpretation of this specimen, based on the orientation of its lateral end and the position of the deltoid attachment area, suggests that this clavicle is distinct from those found in extant apes (including humans), and thus that the shape of the human shoulder dates back to less than 3 to 4 million years ago.\n\nHowever, analyses of the clavicle in extant primates suggest that the low position of the scapula in humans is reflected mostly in the curvature of the medial portion of the clavicle rather than the lateral portion.\n\nThis part of the bone is similar in A.afarensis and it is thus possible that this species had a high shoulder position similar to that in modern humans.\n\n=== In dinosaurs ===\n\nIn dinosaurs the main bones of the pectoral girdle were the scapula (shoulder blade) and the coracoid, both of which directly articulated with the clavicle.\n\nThe clavicle was present in saurischian dinosaurs but largely absent in ornithischian dinosaurs.\n\nThe place on the scapula where it articulated with the humerus (upper bone of the forelimb) is the called the glenoid.\n\nThe clavicles fused in some theropod dinosaurs to form a furcula, which is the equivalent to a wishbone.In birds, the clavicles and interclavicle have fused to form a single Y-shaped bone, the furcula or \"wishbone\" which evolved from the clavicles found in coelurosaurian theropods.\n\nhttps://en.wikipedia.org/wiki/Clavicle","humerus":"The humerus (plural: humeri) is a long bone in the arm that runs from the shoulder to the elbow.\n\nIt connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections.\n\nThe humeral upper extremity consists of a rounded head, a narrow neck, and two short processes (tubercles, sometimes called tuberosities).\n\nThe body is cylindrical in its upper portion, and more prismatic below. The lower extremity consists of 2 epicondyles, 2 processes (trochlea & capitulum), and 3 fossae (radial fossa, coronoid fossa, and olecranon fossa).\n\nAs well as its true anatomical neck, the constriction below the greater and lesser tubercles of the humerus is referred to as its surgical neck due to its tendency to fracture, thus often becoming the focus of surgeons.\n\n=== Upper extremity ===\n\nThe upper or proximal extremity of the humerus consists of the bone's large rounded head joined to the body by a constricted portion called the neck, and two eminences, the greater and lesser tubercles.\n\n==== Head ====\n\nThe head (caput humeri), is nearly hemispherical in form. It is directed upward, medialward, and a little backward, and articulates with the glenoid cavity of the scapula to form the glenohumeral joint (shoulder joint).\n\nThe circumference of its articular surface is slightly constricted and is termed the anatomical neck, in contradistinction to a constriction below the tubercles called the surgical neck which is frequently the seat of fracture.\n\nFracture of the anatomical neck rarely occurs.\n\nThe diameter of the humeral head is generally larger in men than in women.\n\n==== Anatomical neck ====\n\nThe anatomical neck (collum anatomicum) is obliquely directed, forming an obtuse angle with the body.\n\nIt is best marked in the lower half of its circumference; in the upper half it is represented by a narrow groove separating the head from the tubercles.\n\nThe line separating the head from the rest of the upper end is called the anatomical neck.\n\nIt affords attachment to the articular capsule of the shoulder-joint, and is perforated by numerous vascular foramina. Fracture of the anatomical neck rarely occurs.\n\nThe anatomical neck of the humerus is an indentation distal to the head of the humerus on which the articular capsule attaches.\n\n==== Surgical neck ====\n\nThe surgical neck is a narrow area distal to the tubercles that is a common site of fracture.\n\nIt makes contact with the axillary nerve and the posterior humeral circumflex artery.\n\n==== Greater tubercle ====\n\nThe greater tubercle (tuberculum majus; greater tuberosity) is a large, posteriorly placed projection that is placed laterally.\n\nThe greater tubercle is where supraspinatus, infraspinatus and teres minor muscles are attached.\n\nThe crest of the greater tubercle forms the lateral lip of the bicipital groove and is the site for insertion of pectoralis major.\n\nThe greater tubercle is just lateral to the anatomical neck.\n\nIts upper surface is rounded and marked by three flat impressions: the highest of these gives insertion to the supraspinatus muscle; the middle to the infraspinatus muscle; the lowest one, and the body of the bone for about 2.5 cm. below it, to the teres minor muscle.\n\nThe lateral surface of the greater tubercle is convex, rough, and continuous with the lateral surface of the body.\n\n==== Lesser tubercle ====\n\nThe lesser tubercle (tuberculum minus; lesser tuberosity) is smaller, anterolaterally placed to the head of the humerus.\n\nThe lesser tubercle provides insertion to subscapularis muscle.\n\nBoth these tubercles are found in the proximal part of the shaft.\n\nThe crest of the lesser tubercle forms the medial lip of the bicipital groove and is the site for insertion of teres major and latissimus dorsi muscles.\n\nThe lesser tuberosity, is more prominent than the greater: it is situated in front, and is directed medialward and forward.\n\nAbove and in front it presents an impression for the insertion of the tendon of the subscapularis muscle.\n\n==== Bicipital groove ====\n\nThe tubercles are separated from each other by a deep groove, the bicipital groove (intertubercular groove; bicipital sulcus), which lodges the long tendon of the biceps brachii muscle and transmits a branch of the anterior humeral circumflex artery to the shoulder-joint.\n\nIt runs obliquely downward, and ends near the junction of the upper with the middle third of the bone.\n\nIn the fresh state its upper part is covered with a thin layer of cartilage, lined by a prolongation of the synovial membrane of the shoulder-joint; its lower portion gives insertion to the tendon of the latissimus dorsi muscle.\n\nIt is deep and narrow above, and becomes shallow and a little broader as it descends.\n\nIts lips are called, respectively, the crests of the greater and lesser tubercles (bicipital ridges), and form the upper parts of the anterior and medial borders of the body of the bone.\n\n=== Shaft ===\n\nThe body or shaft of the humerus is triangular to cylindrical in cut section and is compressed anteroposteriorly. It has 3 surfaces, namely:\n\nAnterolateral surface: the area between the lateral border of the humerus to the line drawn as a continuation of the crest of the greater tubercle.\n\nThe antero-lateral surface is directed lateralward above, where it is smooth, rounded, and covered by the deltoid muscle; forward and lateralward below, where it is slightly concave from above downward, and gives origin to part of the Brachialis.\n\nAbout the middle of this surface is a rough, rectangular elevation, the deltoid tuberosity for the insertion of the deltoid muscle; below this is the radial sulcus, directed obliquely from behind, forward, and downward, and transmitting the radial nerve and profunda artery.\n\nAnteromedial surface: the area between the medial border of the humerus to the line drawn as a continuation of the crest of the greater tubercle.\n\nThe antero-medial surface, less extensive than the antero-lateral, is directed medialward above, forward and medialward below; its upper part is narrow, and forms the floor of the intertubercular groove which gives insertion to the tendon of the latissimus dorsi muscle; its middle part is slightly rough for the attachment of some of the fibers of the tendon of insertion of the coracobrachialis muscle; its lower part is smooth, concave from above downward, and gives origin to the brachialis muscle.\n\nPosterior surface: the area between the medial and lateral borders.\n\nThe posterior surface appears somewhat twisted, so that its upper part is directed a little medialward, its lower part backward and a little lateralward.\n\nNearly the whole of this surface is covered by the lateral and medial heads of the Triceps brachii, the former arising above, the latter below the radial sulcus.\n\nIts three borders are:\n\nAnterior border of humerus:\n the anterior border runs from the front of the greater tubercle above to the coronoid fossa below, separating the antero-medial from the antero-lateral surface.\n\nIts upper part is a prominent ridge, the crest of the greater tubercle; it serves for the insertion of the tendon of the pectoralis major muscle.\n\nAbout its center it forms the anterior boundary of the deltoid tuberosity, on which the deltoid muscle attaches; below, it is smooth and rounded, affording attachment to the brachialis muscle.\n\nLateral border of humerus:\n the lateral border runs from the back part of the greater tubercle to the lateral epicondyle, and separates the anterolateral from the posterior surface.\n\nIts upper half is rounded and indistinctly marked, serving for the attachment of the lower part of the insertion of the teres minor muscle, and below this giving origin to the lateral head of the triceps brachii muscle; its center is traversed by a broad but shallow oblique depression, the spiral groove (musculospiral groove).\n\nThe radial nerve runs in the spiral groove.\n\nIts lower part forms a prominent, rough margin, a little curved from backward, forward the lateral supracondylar ridge, which presents an anterior lip for the origin of the brachioradialis muscle above, and extensor carpi radialis longus muscle above, a posterior lip for the triceps brachii muscle, and an intermediate ridge for the attachment of the lateral intermuscular septum.\n\nMedial border of humerus:\n the medial border extends from the lesser tubercle to the medial epicondyle.\n\nIts upper third consists of a prominent ridge, the crest of the lesser tubercle, which gives insertion to the tendon of the teres major muscle.\n\nAbout its center is a slight impression for the insertion of the coracobrachialis muscle, and just below this is the entrance of the nutrient canal, directed downward; sometimes there is a second nutrient canal at the commencement of the radial sulcus.\n\nThe inferior third of this border is raised into a slight ridge, the medial supracondylar ridge, which became very prominent below; it presents an anterior lip for the origins of the brachialis muscle and the pronator teres muscle, a posterior lip for the medial head of the triceps brachii muscle, and an intermediate ridge for the attachment of the medial intermuscular septum.\n\nThe Deltoid tuberosity is a roughened surface on the lateral surface of the shaft of the Humerus and acts as the site of insertion of deltoideus muscle.\n\nThe posteror superior part of the shaft has a crest, beginning just below the surgical neck of the humerus and extends till the superior tip of the deltoid tuberosity. This is where the lateral head of triceps brachii is attached.\n\nThe radial sulcus, also known as the spiral groove is found on the posterior surface of the shaft and is a shallow oblique groove through which the radial nerve passes along with deep vessels.\n\nThis is located posteroinferior to the deltoid tuberosity. The inferior boundary of the spiral groove is continuous distally with the lateral border of the shaft.\n\nThe nutrient foramen of the humerus is located in the anteromedial surface of the humerus. The nutrient arteries enter the humerus through this foramen.\n\n=== Distal humerus ===\n\nThe distal or lower extremity of the humerus is flattened from before backward, and curved slightly forward; it ends below in a broad, articular surface, which is divided into two parts by a slight ridge.\n\nProjecting on either side are the lateral and medial epicondyles.\n\n==== Articular surface ====\n\nThe articular surface extends a little lower than the epicondyles, and is curved slightly forward; its medial extremity occupies a lower level than the lateral.\n\nThe lateral portion of this surface consists of a smooth, rounded eminence, named the capitulum of the humerus; it articulates with the cup-shaped depression on the head of the radius, and is limited to the front and lower part of the bone.\n\n=== Fossae ===\n\nAbove the front part of the trochlea is a small depression, the coronoid fossa, which receives the coronoid process of the ulna during flexion of the forearm.\n\nAbove the back part of the trochlea is a deep triangular depression, the olecranon fossa, in which the summit of the olecranon is received in extension of the forearm.\n\nThe coronoid fossa is the medial hollow part on the anterior surface of the distal humerus.\n\nThe coronoid fossa is smaller than the olecranon fossa and receives the coronoid process of the ulna during maximum flexion of the elbow.\n\nAbove the front part of the capitulum is a slight depression, the radial fossa, which receives the anterior border of the head of the radius, when the forearm is flexed.\n\nThese fossæ are separated from one another by a thin, transparent lamina of bone, which is sometimes perforated by a supratrochlear foramen; they are lined in the fresh state by the synovial membrane of the elbow-joint, and their margins afford attachment to the anterior and posterior ligaments of this articulation.\n\nThe Capitulum is a rounded eminence forming the lateral part of the distal humerus. The head of the radius articulates with the capitulum.\n\nThe trochlea is spool-shaped medial portion of the distal humerus and articulates with the ulna.\n\n==== Epicondyles ====\n\nThe epicondyles are continuous above with the supracondylar ridges.\n\nThe lateral epicondyle is a small, tuberculated eminence, curved a little forward, and giving attachment to the radial collateral ligament of the elbow-joint, and to a tendon common to the origin of the Supinator and some of the Extensor muscles.\n\nThe medial epicondyle, larger and more prominent than the lateral, is directed a little backward; it gives attachment to the ulnar collateral ligament of the elbow-joint, to the Pronator teres, and to a common tendon of origin of some of the Flexor muscles of the forearm; the ulnar nerve runs in a groove on the back of this epicondyle.\n\nThe Medial supracondylar crest forms the sharp medial border of the distal humerus continuing superiorly from the medial epicondyle.\n\nThe Lateral Supracondylar crest forms the sharp lateral border of the distal humerus continuing superiorly from the lateral epicondyle.\n\n==== Borders ====\n\nThe medial portion of the articular surface is named the trochlea, and presents a deep depression between two well-marked borders; it is convex from before backward, concave from side to side, and occupies the anterior, lower, and posterior parts of the extremity.\n\nThe lateral border separates it from the groove which articulates with the margin of the head of the radius.\n\nThe medial border is thicker, of greater length, and consequently more prominent, than the lateral.\n\nThe grooved portion of the articular surface fits accurately within the semilunar notch of the ulna; it is broader and deeper on the posterior than on the anterior aspect of the bone, and is inclined obliquely downward and forward toward the medial side.\n\n=== Articulations ===\n\nAt the shoulder, the head of the humerus articulates with the glenoid fossa of the scapula.\n\nMore distally, at the elbow, the capitulum of the humerus articulates with the head of the radius, and the trochlea of the humerus articulates with the trochlear notch of the ulna.\n\n=== Nerves ===\n\nThe axillary nerve is located at the proximal end, against the shoulder girdle.\n\nDislocation of the humerus's glenohumeral joint has the potential to injure the axillary nerve or the axillary artery. Signs and symptoms of this dislocation include a loss of the normal shoulder contour and a palpable depression under the acromion.\n\nThe radial nerve follows the humerus closely.\n\nAt the midshaft of the humerus, the radial nerve travels from the posterior to the anterior aspect of the bone in the spiral groove. A fracture of the humerus in this region can result in radial nerve injury.\n\nThe ulnar nerve lies at the distal end of the humerus near the elbow.\n\nWhen struck, it can cause a distinct tingling sensation, and sometimes a significant amount of pain.\n\nIt is sometimes popularly referred to as 'the funny bone', possibly due to this sensation (a \"funny\" feeling), as well as the fact that the bone's name is a homophone of 'humorous'.\n\nIt lies posterior to the medial epicondyle, and is easily damaged in elbow injuries.\n\n=== Muscular attachment ===\n\nThe deltoid originates on the lateral third of the clavicle, acromion and the crest of the spine of the scapula.\n\nIt is inserted on the deltoid tuberosity of the humerus and has several actions including abduction, extension, and circumduction of the shoulder.\n\nThe supraspinatus also originates on the spine of the scapula. It inserts on the greater tubercle of the humerus, and assists in abduction of the shoulder.\n\nThe pectoralis major, teres major, and latissimus dorsi insert at the intertubercular groove of the humerus.\n\nThey work to adduct and medially, or internally, rotate the humerus.\n\nThe infraspinatus and teres minor insert on the greater tubercle, and work to laterally, or externally, rotate the humerus.\n\nIn contrast, the subscapularis muscle inserts onto the lesser tubercle and works to medially, or internally, rotate the humerus.\n\nThe biceps brachii, brachialis, and brachioradialis (which attaches distally) act to flex the elbow.\n\n(The biceps do not attach to the humerus.) The triceps brachii and anconeus extend the elbow, and attach to the posterior side of the humerus.\n\nThe four muscles of supraspinatus, infraspinatus, teres minor and subscapularis form a musculo-ligamentous girdle called the rotator cuff.\n\nThis cuff stabilizes the very mobile but inherently unstable glenohumeral joint.\n\nThe other muscles are used as counterbalances for the actions of lifting/pulling and pressing/pushing.\n\n== Other animals ==\n\nPrimitive fossils of amphibians had little, if any, shaft connecting the upper and lower extremities, making their limbs very short.\n\nIn most living tetrapods, however, the humerus has a similar form to that of humans.\n\nIn many reptiles and some primitive mammals, the lower extremity includes a large foramen, or opening, which allows nerves and blood vessels pass through.\n\nhttps://en.wikipedia.org/wiki/Humerus\n\n== Ossification ==\n\nDuring embryonic development, the humerus is one of the first structures to ossify, beginning with the first ossification center in the shaft of the bone. Ossification of the humerus occurs predictably in the embryo and fetus, and is therefore used as a fetal biometric measurement when determining gestational age of a fetus. At birth, the neonatal humerus is only ossified in the shaft. The epiphyses are cartilaginous at birth. The medial humeral head develops an ossification center around 4 months of age and the greater tuberosity around 10 months of age. These ossification centers begin to fuse at 3 years of age. The process of ossification is complete by 13 years of age, though the epiphyseal plate (growth plate) persists until skeletal maturity, usually around 17 years of age.\n\n== See also ==\nHumerus fracture\n\n== References ==\n\n This article incorporates text in the public domain from page 209 of the 20th edition of Gray's Anatomy (1918)\n\n== External links ==\n\"Humerus\" . New International Encyclopedia. 1905.\nHumerus - BlueLink Anatomy, University of Michigan Medical School\n\nhttps://en.wikipedia.org/wiki/Humerus","patella":"The patella, also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint.\n\nThe patella is found in many tetrapods, such as mice, cats, birds and dogs, but not in whales, or most reptiles.\nIn humans, the patella is the largest sesamoid bone in the body.\n\nBabies are born with a patella of soft cartilage which begins to ossify into bone at about four years of age.\n\n== Structure ==\n\nThe patella is a sesamoid bone roughly triangular in shape, with the apex of the patella facing downwards.\n\nThe apex is the most inferior (lowest) part of the patella.\n\nIt is pointed in shape, and gives attachment to the patellar ligament.\nThe front and back surfaces are joined by a thin margin and towards centre by a thicker margin.\n\nThe tendon of the quadriceps femoris muscle attaches to the base of the patella., with the vastus intermedius muscle attaching to the base itself, and the vastus lateralis and vastus medialis are attached to outer lateral and medial borders of patella respectively.\nThe upper third of the front of the patella is coarse, flattened, and rough, and serves for the attachment of the tendon of the quadriceps and often has exostoses.\n\nThe middle third has numerous vascular canaliculi.\n\nThe lower third culminates in the apex which serves as the origin of the patellar ligament.\n\nThe posterior surface is divided into two parts.\n\nThe upper three-quarters of the patella articulates with the femur and is subdivided into a medial and a lateral facet by a vertical ledge which varies in shape.\nIn the adult the articular surface is about 12 cm2 (1.9 sq in) and covered by cartilage, which can reach a maximal thickness of 6 mm (0.24 in) in the centre at about 30 years of age.\n\nOwing to the great stress on the patellofemoral joint during resisted knee flexion, the articular cartilage of the patella is among the thickest in the human body.\nThe lower part of the posterior surface has vascular canaliculi filled and is filled by fatty tissue, the infrapatellar fat pad.\n\n=== Variation ===\n\nEmarginations (i.e. patella emarginata, a \"missing piece\") are common laterally on the proximal edge.\n\nBipartite patellas are the result of an ossification of a second cartilaginous layer at the location of an emargination.\n\nPreviously, bipartite patellas were explained as the failure of several ossification centres to fuse, but this idea has been rejected.\n\nPartite patellas occur almost exclusively in men.\n\nTripartite and even multipartite patellas occur.\nThe upper three-quarters of the patella articulates with the femur and is subdivided into a medial and a lateral facet by a vertical ledge which varies in shape.\n\nFour main types of articular surface can be distinguished:\n\nMost commonly the medial articular surface is smaller than the lateral.\nSometimes both articular surfaces are virtually equal in size.\nOccasionally, the medial surface is hypoplastic or\nthe central ledge is only indicated.\n\n=== Development ===\n\nIn the patella an ossification centre develops at the age of 3–6 years.\n\nThe patella originates from two centres of ossification which unite when fully formed.\n\n== Function ==\n\nThe primary functional role of the patella is knee extension.\n\nThe patella increases the leverage that the quadriceps tendon can exert on the femur by increasing the angle at which it acts.\nThe patella is attached to the tendon of the quadriceps femoris muscle, which contracts to extend/straighten the knee.\n\nThe patella is stabilized by the insertion of the horizontal fibres of vastus medialis and by the prominence of the lateral femoral condyle, which discourages lateral dislocation during flexion.\n\nThe retinacular fibres of the patella also stabilize it during exercise.\n\n== Clinical significance ==\n\n=== Dislocation ===\n\nPatellar dislocations occur with significant regularity, particularly in young female athletes.\n\nIt involves the patella sliding out of its position on the knee, most often laterally, and may be associated with extremely intense pain and swelling.\n\nThe patella can be tracked back into the groove with an extension of the knee, and therefore sometimes returns into the proper position on its own.\n\n=== Vertical alignment ===\n\nA patella alta is a high-riding (superiorly aligned) patella.\n\nAn attenuated patella alta is an unusually small patella that develops out of and above the joint.\nA patella baja is a low-riding patella.\n\nA long-standing patella baja may result in extensor dysfunction.\n\nThe Insall-Salvati ratio helps to indicate patella baja on lateral X-rays, and is calculated as the patellar tendon length divided by the patellar bone length.\n\nAn Insall-Salvati ratio of < 0.8 indicates patella baja.\n\n=== Fracture ===\n\nThe kneecap is prone to injury because of its particularly exposed location, and fractures of the patella commonly occur as a consequence of direct trauma onto the knee.\n\nThese fractures usually cause swelling and pain in the region, bleeding into the joint (hemarthrosis), and an inability to extend the knee.\n\nPatella fractures are usually treated with surgery, unless the damage is minimal and the extensor mechanism is intact.\n\n=== Exostosis ===\n\nAn exostosis is the formation of new bone onto a bone, as a result of excess calcium formation.\n\nThis can be the cause of chronic pain when formed on the patella.\n\n== In animals ==\n\nThe patella is found in placental mammals and birds; most marsupials have only rudimentary, non-ossified patellae although a few species possess a bony patella.\n\nA patella is also present in the living monotremes, the platypus and the echidna.\n\nIn more primitive tetrapods, including living amphibians and most reptiles (except some Lepidosaurs), the muscle tendons from the upper leg are attached directly to the tibia, and a patella is not present.\n\nIn 2017 it was discovered that frogs have kneecaps, contrary to what was thought.\n\nThis raises the possibility that the kneecap arose 400 million years ago when tetrapods first appeared, but that it disappeared in some animals.\n\n== Etymology ==\n\nThe word patella originated in the late 17th century from the diminutive form of Latin patina or patena or paten, meaning shallow dish.\n\nhttps://en.wikipedia.org/wiki/Patella","talus":"The talus (Latin for ankle), talus bone, astragalus , or ankle bone is one of the group of foot bones known as the tarsus.\n\nThe tarsus forms the lower part of the ankle joint.\n\nIt transmits the entire weight of the body from the lower legs to the foot.\n\nThe talus has joints with the two bones of the lower leg, the tibia and thinner fibula.\n\nThese leg bones have two prominences (the lateral and medial malleoli) that articulate with the talus.\n\nAt the foot end, within the tarsus, the talus articulates with the calcaneus (heel bone) below, and with the curved navicular bone in front; together, these foot articulations form the ball-and-socket-shaped talocalcaneonavicular joint.\n\nThe talus is the second largest of the tarsal bones; it is also one of the bones in the human body with the highest percentage of its surface area covered by articular cartilage.\n\nIt is also unusual in that it has a retrograde blood supply, i.e. arterial blood enters the bone at the distal end.\n\nIn humans, no muscles attach to the talus, unlike most bones, and its position therefore depends on the position of the neighbouring bones.\n\n== Structure ==\n\nThough irregular in shape, the talus can be subdivided into three parts.\nFacing anteriorly, the head carries the articulate surface of the navicular bone, and the neck, the roughened area between the body and the head, has small vascular channels.\n\nThe body features several prominent articulate surfaces: On its superior side is the trochlea tali, which is semi-cylindrical, and it is flanked by the articulate facets for the two malleoli.\n\nThe ankle mortise, the fork-like structure of the malleoli, holds these three articulate surfaces in a steady grip, which guarantees the stability of the ankle joint.\n\nHowever, because the trochlea is wider in front than at the back (approximately 5–6 mm) the stability in the joint vary with the position of the foot: with the foot dorsiflexed (toes pulled upward) the ligaments of the joint are kept stretched, which guarantees the stability of the joint; but with the foot plantarflexed (as when standing on the toes) the narrower width of the trochlea causes the stability to decrease.\n\nBehind the trochlea is a posterior process with a medial and a lateral tubercle separated by a groove for the tendon of the flexor hallucis longus.\n\nExceptionally, the lateral of these tubercles forms an independent bone called os trigonum or accessory talus; it may represent the tarsale proximale intermedium.\n\nOn the bone's inferior side, three articular surfaces serve for the articulation with the calcaneus, and several variously developed articular surfaces exist for the articulation with ligaments.For descriptive purposes the talus bone is divided into three sections, neck, body, and head.\n\n=== Head ===\n\nThe talus bone of the ankle joint connects the leg to the foot.\nThe head of talus looks forward and medialward; its anterior articular or navicular surface is large, oval, and convex.\n\nIts inferior surface has two facets, which are best seen in the fresh condition.\n\nThe medial, situated in front of the middle calcaneal facet, is convex, triangular, or semi-oval in shape, and rests on the plantar calcaneonavicular ligament; the lateral, named the anterior calcaneal articular surface, is somewhat flattened, and articulates with the facet on the upper surface of the anterior part of the calcaneus.\n\n=== Neck ===\n\nThe neck of talus is directed anteromedially, and comprises the constricted portion of the bone between the body and the oval head.\n\nIts upper and medial surfaces are rough, for the attachment of ligaments; its lateral surface is concave and is continuous below with the deep groove for the interosseous talocalcaneal ligament.\n\n=== Body ===\n\nThe body of the talus comprises most of the volume of the talus bone (ankle bone).\n\nIt presents with five surfaces; a superior, inferior, medial, lateral and a posterior:\n\n-The superior surface of the body presents, behind, a smooth trochlear surface, the trochlea, for articulation with the tibia.\n\nThe trochlea is broader in front than behind, convex from before backward, slightly concave from side to side: in front it is continuous with the upper surface of the neck of the bone.\nthe inferior surface presents two articular areas, the posterior and middle calcaneal surfaces, separated from one another by a deep groove, the sulcus tali.\n\nThe groove runs obliquely forward and lateralward, becoming gradually broader and deeper in front: in the articulated foot it lies above a similar groove upon the upper surface of the calcaneus, and forms, with it, a canal (sinus tarsi) filled up in the fresh state by the interosseous talocalcaneal ligament.\n\nThe posterior calcaneal articular surface is large and of an oval or oblong form.\n\nIt articulates with the corresponding facet on the upper surface of the calcaneus, and is deeply concave in the direction of its long axis which runs forward and lateralward at an angle of about 45° with the median plane of the body.\n\nThe middle calcaneal articular surface is small, oval in form and slightly convex; it articulates with the upper surface of the sustentaculum tali of the calcaneus.\n\n-The medial surface presents at its upper part a pear-shaped articular facet for the medial malleolus, continuous above with the trochlea; below the articular surface is a rough depression for the attachment of the deep portion of the deltoid ligament of the ankle-joint.\n\n-The lateral surface carries a large triangular facet, concave from above downward, for articulation with the lateral malleolus; its anterior half is continuous above with the trochlea; and in front of it is a rough depression for the attachment of the anterior talofibular ligament.\n\nBetween the posterior half of the lateral border of the trochlea and the posterior part of the base of the fibular articular surface is a triangular facet which comes into contact with the transverse inferior tibiofibular ligament during flexion of the ankle-joint; below the base of this facet is a groove which affords attachment to the posterior talofibular ligament.\n\n-The posterior surface is narrow, and traversed by a groove running obliquely downward and medialward, and transmitting the tendon of the Flexor hallucis longus.\n\nLateral to the groove is a prominent tubercle, the posterior process, to which the posterior talofibular ligament is attached; this process is sometimes separated from the rest of the talus, and is then known as the os trigonum.\n\nMedial to the groove is a second smaller tubercle.\n\n== Development ==\n\nDuring the 7-8th intrauterine month an ossification center is formed in the anklebone.\n\n== Fracture ==\n\nThe talus bone lacks a good blood supply.\n\nBecause of this, healing a broken talus can take longer than most other bones.\n\nOne with a broken talus may not be able to walk for many months without crutches and will further wear a walking cast or boot of some kind after that.\n\nTalus injuries may be difficult to recognize, and lateral process fractures in particular may be radiographically occult.\n\nIf not recognized and managed appropriately, a talus fracture may result in complications and long-term morbidity.\n\nA 2015 review came to the conclusion that isolated talar body fractures may be more common than previously thought.\n\nA fractured talar body often has a displacement that is best visualised using CT imaging.\n\nIn case a talus fracture is accompanied by a dislocation, restoration of articular and axial alignment is necessary to optimize ankle and hindfoot function.\n\n== As dice ==\n\nDice were originally made from the talus of hoofed animals, leading to the nickname \"bones\" for dice.\n\nColloquially known as \"knucklebones\", these are approximately tetrahedral.\n\nModern Mongolians still use such bones as shagai for games and fortune-telling, with each piece relating to a symbolic meaning.\n\n== In other animals ==\n\nThe talus apparently derives from the fusion of three separate bones in the feet of primitive amphibians; the tibiale, articulating with tibia, the intermedium, between the bases of the tibia and fibula, and the fourth centrale, lying in the mid-part of the tarsus.\n\nThese bones are still partially separate in modern amphibians, which therefore do not have a true talus.\n\nThe talus forms a considerably more flexible joint in mammals than it does in reptiles.\n\nThis reaches its greatest extent in artiodactyls, where the distal surface of the bone has a smooth keel to allow greater freedom of movement of the foot, and thus increase running speed.\n\nhttps://en.wikipedia.org/wiki/Talus_bone","calcaneus":"In humans and many other primates, the calcaneus (from the Latin calcaneus or calcaneum, meaning heel) or heel bone is a bone of the tarsus of the foot which constitutes the heel.\n\nIn some other animals, it is the point of the hock.\n\n== Structure ==\n\nIn humans, the calcaneus is the largest of the tarsal bones and the largest bone of the foot.\n\nThe talus bone, calcaneus, and navicular bone are considered the proximal row of tarsal bones.\n\nIn the calcaneus, several important structures can be distinguished:The half of the bone closest to the heel is the calcaneal tuberosity.\n\nOn its lower edge on either side are its lateral and medial processes (serving as the origins of the abductor hallucis and abductor digiti minimi).\n\nThe Achilles tendon is inserted into a roughened area on its superior side, the cuboid bone articulates with its anterior side, and on its superior side are three articular surfaces for the articulation with the talus bone.\n\nBetween these superior articulations and the equivalents on the talus is the tarsal sinus (a canal occupied by the interosseous talocalcaneal ligament).\n\nAt the upper and forepart of the medial surface of the calcaneus, below the middle talar facet, there is a horizontal eminence, the talar shelf (also sustentaculum tali), which gives attachment to the plantar calcaneonavicular (spring) ligament, tibiocalcaneal ligament, and medial talocalcaneal ligament.\n\nThis eminence is concave above, and articulates with the middle calcaneal articular surface of the talus; below, it is grooved for the tendon of the flexor hallucis longus; its anterior margin gives attachment to the plantar calcaneonavicular ligament, and its medial margin to a part of the deltoid ligament of the ankle-joint.\n\nOn the lateral side is commonly a tubercle called the calcaneal tubercle (or trochlear process).\n\nThis is a raised projection located between the tendons of the peroneus longus and brevis.\n\nIt separates the two oblique grooves of the lateral surface of the calcaneus (for the tendons of the peroneal muscles).\n\nIts chief anatomical significance is as a point of divergence of the previously common pathway shared by the distal tendons of peroneus longus and peroneus brevis en route to their distinct respective attachment sites.\n\nThe calcaneus is part of two joints: the proximal intertarsal joint and the talocalcaneal joint.\n\nThe point of the calcaneus is covered by the calcanean bursa.\n\n=== Development ===\n\nIn the calcaneus, an ossification center, is developed during the 4th–7th week of fetal development.\n\n== Function ==\n\nThree muscles insert on the calcaneus: the gastrocnemius, soleus, and plantaris.\n\nThese muscles are part of the posterior compartment of the leg and aid in walking, running and jumping.\n\nTheir specific functions include plantarflexion of the foot, flexion of the knee, and steadying the leg on the ankle during standing.\n\nThe calcaneus also serves as origin for several short muscles that run along the sole of the foot and control the toes.\n\n== Clinical significance ==\n\nNormally the tibia sits vertically above the calcaneus (pes rectus).\n\nIf the calcaneal axis between these two bones is turned medially the foot is in an everted position (pes valgus), and if it is turned laterally the foot is in an inverted position (pes varus).\n\nCalcaneal fracture, also known as Lover's fracture and Don Juan fracture\n\n== Disease ==\n\nThe talar shelf is typically involved in subtalar or talocalcaneal tarsal coalition.\n\nhttps://en.wikipedia.org/wiki/Calcaneus","navicular-bone":"The navicular bone is a small bone found in the feet of most mammals.\n\n== Human anatomy ==\n\nThe navicular bone in humans is one of the tarsal bones, found in the foot.\n\nIts name derives from the human bone's resemblance to a small boat, caused by the strongly concave proximal articular surface.\n\nThe term navicular bone or hand navicular bone was formerly used for the scaphoid bone, one of the carpal bones of the wrist.\n\nThe navicular bone in humans is located on the medial side of the foot, and articulates proximally with the talus, distally with the three cuneiform bones, and laterally with the cuboid.\n\nIt is the last of the foot bones to start ossification and does not tend to do so until the end of the third year in girls and the beginning of the fourth year in boys, although a large range of variation has been reported.\n\nThe tibialis posterior is the only muscle that attaches to the navicular bone.\n\nThe main portion of the muscle inserts into the tuberosity of the navicular bone.\n\nAn accessory navicular bone may be present in 2–14% of the general population.\n\n=== Clinical significance ===\n\nThe human navicular is not a commonly broken bone but it breaks due two reasons.\n\nThe first mechanism is a stress fracture which happens commonly in athletes and the other mechanism is a high energy trauma.\n\nThe navicular bone is a keystone of the foot: it is part of the coxa pedis and articulates with the talus, first, second and third cuneiform, cuboid and calcaneus.\n\nIt plays an important role in the biomechanics of the foot helping in inversion, eversion and motion; it is a structural link between midfoot and forefoot and it is part of the longitudinal and transverse arch of the foot.\n\n== Horse anatomy ==\n\nThe horse has a sesamoid bone called the navicular bone, located within the hoof, that lies on the palmar aspect of the coffin joint between the second phalanx and third phalanx (coffin bone).\n\nThe navicular bone in the horse is supported by the distal sesamoidean impar ligament and two collateral sesamoidean ligaments.\n\nThe navicular bursa is located between the flexor surface of the navicular bone and the deep digital flexor tendon, which runs between the bursa and the distal phalanx.\n\nThe central tarsal bone in the hock of the horse is homologous and analogous to the navicular bone of the human foot, and thus the navicular bone in the horse is a different structure from the eponymously labeled bone in humans.\n\nThe navicular region is an important structure in relation to lameness, particularly in the front feet, and is involved with a significant disease process called navicular disease or navicular syndrome.\n\nRecently much of the original literature concerning navicular disease has been called into question, particularly the significance of radiographic changes as a sole diagnostic criterion.\n\nNavicular syndrome may be responsible for as much as 1/3 of all cases of lameness in horses, but radiographic changes in the navicular bone do not always provide a definitive diagnosis.\n\nNewer imaging techniques have shown that damage to the soft tissues in the region may be significant contributors to lameness and that multiple causes may result in visible lameness.\n\nhttps://en.wikipedia.org/wiki/Navicular_bone","cuboid-bone":"In the human body, the cuboid bone is one of the seven tarsal bones of the foot.\n\n== Structure ==\n\nThe cuboid bone is the most lateral of the bones in the distal row of the tarsus.\n\nIt is roughly cubical in shape, and presents a prominence in its inferior (or plantar) surface, the tuberosity of the cuboid.\n\nThe bone provides a groove where the tendon of the peroneus longus muscle passes to reach its insertion in the first metatarsal and medial cuneiform bones.\n\n=== Surfaces ===\n\nThe dorsal surface, directed upward and lateralward, is rough, for the attachment of ligaments.\n\nThe plantar surface presents in front a deep groove, the peroneal sulcus, which runs obliquely forward and medialward; it lodges the tendon of the peroneus longus, and is bounded behind by a prominent ridge, to which the long plantar ligament is attached.\n\nThe ridge ends laterally in an eminence, the tuberosity, the surface of which presents an oval facet; on this facet glides the sesamoid bone or cartilage frequently found in the tendon of the peroneus longus.\n\nThe surface of bone behind the groove is rough, for the attachment of the plantar calcaneocuboid ligament, a few fibers of the flexor hallucis brevis, and a fasciculus from the tendon of the tibialis posterior.\n\nThe lateral surface presents a deep notch formed by the commencement of the peroneal sulcus.\n\nThe posterior surface is smooth, triangular, and concavo-convex, for articulation with the anterior surface of the calcaneus (the calcaneocuboid joint); its infero-medial angle projects backward as a process which underlies and supports the anterior end of the calcaneus.\n\nThe anterior surface, of smaller size, but also irregularly triangular, is divided by a vertical ridge into two facets, forming the fourth and fifth tarsometatarsal joints: the medial facet, quadrilateral in form, articulates with the fourth metatarsal; the lateral, larger and more triangular, articulates with the fifth.\n\nThe medial surface is broad, irregularly quadrilateral, and presents at its middle and upper part a smooth oval facet, for articulation with the third cuneiform; and behind this (occasionally) a smaller facet, for articulation with the navicular bone; it is rough in the rest of its extent, for the attachment of strong interosseous ligaments.\n\n=== Muscle attachments ===\n\nOnly one muscle is attached to the cuboid bone; the tibialis posterior.\n\nThe tibialis posterior inserts to the under surface of the cuboid bone.\n\nWhile the flexor hallucis brevis arises, by a pointed tendinous process, from the medial part of the under surface of the cuboid bone, from the contiguous portion of the lateral cuneiform bone, and from the prolongation of the tendon of the tibialis posterior.\n\n== Clinical significance ==\n\nIn a condition known as cuboid syndrome, the cuboid can be subluxated downward causing a swollen kind of ache along the central portion of the lateral border of the foot.\n\nhttps://en.wikipedia.org/wiki/Cuboid_bone","intermediate-cuneiform-bone":"There are three cuneiform (\"wedge-shaped\") bones in the human foot:\n\n-the first or medial cuneiform\n-the second or intermediate cuneiform, also known as the middle cuneiform\n-the third or lateral cuneiformThey are located between the navicular bone and the first, second and third metatarsal bones and are medial to the cuboid bone.\n\n== Structure ==\n\nThe intermediate cuneiform is situated between the other two cuneiform bones (the medial and lateral cuneiforms), and articulates with the navicular posteriorly, the second metatarsal anteriorly and with the other cuneiforms on either side.\n\nhttps://en.wikipedia.org/wiki/Cuneiform_bones","lateral-cuneiform-bone":"There are three cuneiform (\"wedge-shaped\") bones in the human foot:\n\n-the first or medial cuneiform\n-the second or intermediate cuneiform, also known as the middle cuneiform\n-the third or lateral cuneiform.\n\nThey are located between the navicular bone and the first, second and third metatarsal bones and are medial to the cuboid bone.\n\n== Structure ==\n\nThe lateral cuneiform (also known as third cuneiform or external cuneiform) intermediate in size between the other two cuneiform bones, is also wedge-shaped, the base being uppermost.\n\nIt occupies the center of the front row of the tarsal bones, between the intermediate cuneiform medially, the cuboid laterally, the navicular posteriorly and the third metatarsal in front.\n\nThe tibialis posterior inserts at the medial cuneiform, while the flexor hallucis brevis originates from it.\n\nhttps://en.wikipedia.org/wiki/Cuneiform_bones","medial-cuneiform-bone":"There are three cuneiform (\"wedge-shaped\") bones in the human foot:\n\nthe first or medial cuneiform\nthe second or intermediate cuneiform, also known as the middle cuneiform\nthe third or lateral cuneiformThey are located between the navicular bone and the first, second and third metatarsal bones and are medial to the cuboid bone.\n\n== Structure ==\n\nThere are three cuneiform bones:\n\nThe medial cuneiform (also known as first cuneiform) is the largest of the cuneiforms.\n\nIt is situated at the medial side of the foot, anterior to the navicular bone and posterior to the base of the first metatarsal.\n\nIt articulates with four bones: the navicular, second cuneiform, and first and second metatarsals.\n\nThe tibialis anterior and fibularis longus muscle inserts at the medial cuneiform bone.\n\nThe tibialis posterior inserts at the medial cuneiform, while the flexor hallucis brevis originates from it.\n\nLateral to it is the intermediate cuneiform.\n\nhttps://en.wikipedia.org/wiki/Cuneiform_bones","first-metatarsal-bone":"The metatarsal bones, or metatarsus are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes.\n\nLacking individual names, the metatarsal bones are numbered from the medial side (the side of the great toe): the first, second, third, fourth, and fifth metatarsal (often depicted with Roman numerals).\n\nThe metatarsals are analogous to the metacarpal bones of the hand.\n\nThe lengths of the metatarsal bones in humans are, in descending order: second, third, fourth, fifth and first.\n\n== Structure ==\n\nThe five metatarsals are dorsally convex long bones consisting of a shaft or body, a base (proximally), and a head (distally).\n\nThe body is prismoid in form, tapers gradually from the tarsal to the phalangeal extremity, and is curved longitudinally, so as to be concave below, slightly convex above.\n\nThe base or posterior extremity is wedge-shaped, articulating proximally with the tarsal bones, and by its sides with the contiguous metatarsal bones: its dorsal and plantar surfaces are rough for the attachment of ligaments.\n\nThe head or distal extremity presents a convex articular surface, oblong from above downward, and extending farther backward below than above.\n\nIts sides are flattened, and on each is a depression, surmounted by a tubercle, for ligamentous attachment.\n\nIts plantar surface is grooved antero-posteriorly for the passage of the flexor tendons, and marked on either side by an articular eminence continuous with the terminal articular surface.\n\nDuring growth, the growth plates are located distally on the metatarsals, except on the first metatarsal where it is located proximally.\n\nYet it is quite common to have an accessory growth plate on the distal first metatarsal.\n\n=== Articulations ===\n\nThe base of each metatarsal bone articulates with one or more of the tarsal bones at the tarsometatarsal joints, and the head with one of the first row of phalanges at the metatarsophalangeal joints.\n\nTheir bases also articulate with each other at the intermetatarsal joints\n\n-The first metatarsal articulates with the medial cuneiform, and to a small extent to the intermediate cuneiform.\n-the second with all three cuneiforms.\n-the third with the lateral cuneiform.\n-the fourth with the lateral cuneiform and the cuboid.\n-The fifth with the cuboid.\n\n== Clinical significance ==\n\n=== Injuries ===\n\nThe metatarsal bones are often broken by association football players.\n\nThese and other recent cases have been attributed to the lightweight design of modern football boots, which provide less protection to the foot.\n\nIn 2010 some soccer players began testing a new sock that incorporated a rubber silicone pad over the foot to provide protection to the top of the foot.\n\nStress fractures are thought to account for 16% of injuries related to sports participation, and the metatarsals are the bones most often involved.\n\nThese fractures are sometimes called march fractures, based on their traditional association with military recruits after long marches.\n\nThe second and third metatarsals are fixed while walking, thus these metatarsals are common sites of injury.\n\nThe fifth metatarsal may be fractured if the foot is oversupinated during locomotion.Protection from injuries can be given by the use of safety footwear which can use built-in or removable metatarsal guards.\n\nhttps://en.wikipedia.org/wiki/Metatarsal_bones","fifth-metatarsal-bone":"The metatarsal bones, or metatarsus are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes.\n\nLacking individual names, the metatarsal bones are numbered from the medial side (the side of the great toe): the first, second, third, fourth, and fifth metatarsal (often depicted with Roman numerals).\n\nThe metatarsals are analogous to the metacarpal bones of the hand.\n\nThe lengths of the metatarsal bones in humans are, in descending order: second, third, fourth, fifth and first.\n\n== Structure ==\n\nThe five metatarsals are dorsally convex long bones consisting of a shaft or body, a base (proximally), and a head (distally).\n\nThe body is prismoid in form, tapers gradually from the tarsal to the phalangeal extremity, and is curved longitudinally, so as to be concave below, slightly convex above.\n\nThe base or posterior extremity is wedge-shaped, articulating proximally with the tarsal bones, and by its sides with the contiguous metatarsal bones: its dorsal and plantar surfaces are rough for the attachment of ligaments.\n\nThe head or distal extremity presents a convex articular surface, oblong from above downward, and extending farther backward below than above.\n\nIts sides are flattened, and on each is a depression, surmounted by a tubercle, for ligamentous attachment.\n\nIts plantar surface is grooved antero-posteriorly for the passage of the flexor tendons, and marked on either side by an articular eminence continuous with the terminal articular surface.\n\nDuring growth, the growth plates are located distally on the metatarsals, except on the first metatarsal where it is located proximally.\n\nYet it is quite common to have an accessory growth plate on the distal first metatarsal.\n\n=== Articulations ===\n\nThe base of each metatarsal bone articulates with one or more of the tarsal bones at the tarsometatarsal joints, and the head with one of the first row of phalanges at the metatarsophalangeal joints.\n\nTheir bases also articulate with each other at the intermetatarsal joints\n\n-The first metatarsal articulates with the medial cuneiform, and to a small extent to the intermediate cuneiform.\n-the second with all three cuneiforms.\n-the third with the lateral cuneiform.\n-the fourth with the lateral cuneiform and the cuboid.\n-The fifth with the cuboid.\n\n== Clinical significance ==\n\n=== Injuries ===\n\nThe metatarsal bones are often broken by association football players.\n\nThese and other recent cases have been attributed to the lightweight design of modern football boots, which provide less protection to the foot.\n\nIn 2010 some soccer players began testing a new sock that incorporated a rubber silicone pad over the foot to provide protection to the top of the foot.\n\nStress fractures are thought to account for 16% of injuries related to sports participation, and the metatarsals are the bones most often involved.\n\nThese fractures are sometimes called march fractures, based on their traditional association with military recruits after long marches.\n\nThe second and third metatarsals are fixed while walking, thus these metatarsals are common sites of injury.\n\nThe fifth metatarsal may be fractured if the foot is oversupinated during locomotion.Protection from injuries can be given by the use of safety footwear which can use built-in or removable metatarsal guards.\n\nhttps://en.wikipedia.org/wiki/Metatarsal_bones","second-metatarsal-bone":"The metatarsal bones, or metatarsus are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes.\n\nLacking individual names, the metatarsal bones are numbered from the medial side (the side of the great toe): the first, second, third, fourth, and fifth metatarsal (often depicted with Roman numerals).\n\nThe metatarsals are analogous to the metacarpal bones of the hand.\n\nThe lengths of the metatarsal bones in humans are, in descending order: second, third, fourth, fifth and first.\n\n== Structure ==\n\nThe five metatarsals are dorsally convex long bones consisting of a shaft or body, a base (proximally), and a head (distally).\n\nThe body is prismoid in form, tapers gradually from the tarsal to the phalangeal extremity, and is curved longitudinally, so as to be concave below, slightly convex above.\n\nThe base or posterior extremity is wedge-shaped, articulating proximally with the tarsal bones, and by its sides with the contiguous metatarsal bones: its dorsal and plantar surfaces are rough for the attachment of ligaments.\n\nThe head or distal extremity presents a convex articular surface, oblong from above downward, and extending farther backward below than above.\n\nIts sides are flattened, and on each is a depression, surmounted by a tubercle, for ligamentous attachment.\n\nIts plantar surface is grooved antero-posteriorly for the passage of the flexor tendons, and marked on either side by an articular eminence continuous with the terminal articular surface.\n\nDuring growth, the growth plates are located distally on the metatarsals, except on the first metatarsal where it is located proximally.\n\nYet it is quite common to have an accessory growth plate on the distal first metatarsal.\n\n=== Articulations ===\n\nThe base of each metatarsal bone articulates with one or more of the tarsal bones at the tarsometatarsal joints, and the head with one of the first row of phalanges at the metatarsophalangeal joints.\n\nTheir bases also articulate with each other at the intermetatarsal joints\n\n-The first metatarsal articulates with the medial cuneiform, and to a small extent to the intermediate cuneiform.\n-the second with all three cuneiforms.\n-the third with the lateral cuneiform.\n-the fourth with the lateral cuneiform and the cuboid.\n-The fifth with the cuboid.\n\n== Clinical significance ==\n\n=== Injuries ===\n\nThe metatarsal bones are often broken by association football players.\n\nThese and other recent cases have been attributed to the lightweight design of modern football boots, which provide less protection to the foot.\n\nIn 2010 some soccer players began testing a new sock that incorporated a rubber silicone pad over the foot to provide protection to the top of the foot.\n\nStress fractures are thought to account for 16% of injuries related to sports participation, and the metatarsals are the bones most often involved.\n\nThese fractures are sometimes called march fractures, based on their traditional association with military recruits after long marches.\n\nThe second and third metatarsals are fixed while walking, thus these metatarsals are common sites of injury.\n\nThe fifth metatarsal may be fractured if the foot is oversupinated during locomotion.\n\nProtection from injuries can be given by the use of safety footwear which can use built-in or removable metatarsal guards.\n\nhttps://en.wikipedia.org/wiki/Metatarsal_bones","third-metatarsal-bone":"The metatarsal bones, or metatarsus are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes.\n\nLacking individual names, the metatarsal bones are numbered from the medial side (the side of the great toe): the first, second, third, fourth, and fifth metatarsal (often depicted with Roman numerals).\n\nThe metatarsals are analogous to the metacarpal bones of the hand.\n\nThe lengths of the metatarsal bones in humans are, in descending order: second, third, fourth, fifth and first.\n\n== Structure ==\n\nThe five metatarsals are dorsally convex long bones consisting of a shaft or body, a base (proximally), and a head (distally).\n\nThe body is prismoid in form, tapers gradually from the tarsal to the phalangeal extremity, and is curved longitudinally, so as to be concave below, slightly convex above.\n\nThe base or posterior extremity is wedge-shaped, articulating proximally with the tarsal bones, and by its sides with the contiguous metatarsal bones: its dorsal and plantar surfaces are rough for the attachment of ligaments.\n\nThe head or distal extremity presents a convex articular surface, oblong from above downward, and extending farther backward below than above.\n\nIts sides are flattened, and on each is a depression, surmounted by a tubercle, for ligamentous attachment.\n\nIts plantar surface is grooved antero-posteriorly for the passage of the flexor tendons, and marked on either side by an articular eminence continuous with the terminal articular surface.\n\nDuring growth, the growth plates are located distally on the metatarsals, except on the first metatarsal where it is located proximally.\n\nYet it is quite common to have an accessory growth plate on the distal first metatarsal.\n\n=== Articulations ===\n\nThe base of each metatarsal bone articulates with one or more of the tarsal bones at the tarsometatarsal joints, and the head with one of the first row of phalanges at the metatarsophalangeal joints.\n\nTheir bases also articulate with each other at the intermetatarsal joints\n\n-The first metatarsal articulates with the medial cuneiform, and to a small extent to the intermediate cuneiform.\n-the second with all three cuneiforms.\n-the third with the lateral cuneiform.\n-the fourth with the lateral cuneiform and the cuboid.\n-The fifth with the cuboid.\n\n== Clinical significance ==\n\n=== Injuries ===\n\nThe metatarsal bones are often broken by association football players.\n\nThese and other recent cases have been attributed to the lightweight design of modern football boots, which provide less protection to the foot.\n\nIn 2010 some soccer players began testing a new sock that incorporated a rubber silicone pad over the foot to provide protection to the top of the foot.\n\nStress fractures are thought to account for 16% of injuries related to sports participation, and the metatarsals are the bones most often involved.\n\nThese fractures are sometimes called march fractures, based on their traditional association with military recruits after long marches.\n\nThe second and third metatarsals are fixed while walking, thus these metatarsals are common sites of injury.\n\nThe fifth metatarsal may be fractured if the foot is oversupinated during locomotion.Protection from injuries can be given by the use of safety footwear which can use built-in or removable metatarsal guards.\n\nhttps://en.wikipedia.org/wiki/Metatarsal_bones","fourth-metatarsal-bone":"The metatarsal bones, or metatarsus are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes.\n\nLacking individual names, the metatarsal bones are numbered from the medial side (the side of the great toe): the first, second, third, fourth, and fifth metatarsal (often depicted with Roman numerals).\n\nThe metatarsals are analogous to the metacarpal bones of the hand.\n\nThe lengths of the metatarsal bones in humans are, in descending order: second, third, fourth, fifth and first.\n\n== Structure ==\n\nThe five metatarsals are dorsally convex long bones consisting of a shaft or body, a base (proximally), and a head (distally).\n\nThe body is prismoid in form, tapers gradually from the tarsal to the phalangeal extremity, and is curved longitudinally, so as to be concave below, slightly convex above.\n\nThe base or posterior extremity is wedge-shaped, articulating proximally with the tarsal bones, and by its sides with the contiguous metatarsal bones: its dorsal and plantar surfaces are rough for the attachment of ligaments.\n\nThe head or distal extremity presents a convex articular surface, oblong from above downward, and extending farther backward below than above.\n\nIts sides are flattened, and on each is a depression, surmounted by a tubercle, for ligamentous attachment.\n\nIts plantar surface is grooved antero-posteriorly for the passage of the flexor tendons, and marked on either side by an articular eminence continuous with the terminal articular surface.\n\nDuring growth, the growth plates are located distally on the metatarsals, except on the first metatarsal where it is located proximally.\n\nYet it is quite common to have an accessory growth plate on the distal first metatarsal.\n\n=== Articulations ===\n\nThe base of each metatarsal bone articulates with one or more of the tarsal bones at the tarsometatarsal joints, and the head with one of the first row of phalanges at the metatarsophalangeal joints.\n\nTheir bases also articulate with each other at the intermetatarsal joints\n\n-The first metatarsal articulates with the medial cuneiform, and to a small extent to the intermediate cuneiform.\n-the second with all three cuneiforms.\n-the third with the lateral cuneiform.\n-the fourth with the lateral cuneiform and the cuboid.\n-The fifth with the cuboid.\n\n== Clinical significance ==\n\n=== Injuries ===\n\nThe metatarsal bones are often broken by association football players.\n\nThese and other recent cases have been attributed to the lightweight design of modern football boots, which provide less protection to the foot.\n\nIn 2010 some soccer players began testing a new sock that incorporated a rubber silicone pad over the foot to provide protection to the top of the foot.\n\nStress fractures are thought to account for 16% of injuries related to sports participation, and the metatarsals are the bones most often involved.\n\nThese fractures are sometimes called march fractures, based on their traditional association with military recruits after long marches.\n\nThe second and third metatarsals are fixed while walking, thus these metatarsals are common sites of injury.\n\nThe fifth metatarsal may be fractured if the foot is oversupinated during locomotion.Protection from injuries can be given by the use of safety footwear which can use built-in or removable metatarsal guards.\n\nhttps://en.wikipedia.org/wiki/Metatarsal_bones","distal-phalanx-of-fifth-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","distal-phalanx-of-first-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","distal-phalanx-of-fourth-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","distal-phalanx-of-second-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","distal-phalanx-of-third-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","middle-phalanx-of-second-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","middle-phalanx-of-third-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","middle-phalanx-of-fourth-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","middle-phalanx-of-fifth-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","proximal-phalanx-of-first-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","proximal-phalanx-of-second-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","proximal-phalanx-of-third-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","proximal-phalanx-of-fourth-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","proximal-phalanx-of-fifth-finger-of-foot":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","sesamoid-bones-of-foot":"In the foot—the first metatarsal bone usually has two sesamoid bones at its connection to the big toe (both within the tendon of flexor hallucis brevis).\n\nOne is found on the lateral side of the first metatarsal while the other is found on the medial side.\n\nIn some people, only a single sesamoid is found on the first metatarsal bone.\n\nhttps://en.wikipedia.org/wiki/Sesamoid_bone","distal-phalanx-of-first-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","distal-phalanx-of-second-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","distal-phalanx-of-third-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","distal-phalanx-of-fourth-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","distal-phalanx-of-fifth-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","middle-phalanx-of-second-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","middle-phalanx-of-third-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","middle-phalanx-of-fourth-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","middle-phalanx-of-fifth-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","proximal-phalanx-of-first-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","proximal-phalanx-of-second-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","proximal-phalanx-of-third-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","proximal-phalanx-of-fourth-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","proximal-phalanx-of-fifth-finger-of-hand":"The phalanx (Ancient Greek: φάλαγξ; plural phalanxes or phalanges, φάλαγγες, phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons.\n\nThe term is particularly used to describe the use of this formation in Ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment.\n\nArrian uses the term in his Array against the Alans when he refers to his legions.\n\nIn Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle.\n\nThey marched forward as one entity.\nThe term itself, as used today, does not refer to a distinctive military unit or division (e.g., the Roman legion or the contemporary Western-type battalion), but to the type of formation of an army's troops.\n\nTherefore, this term does not indicate a standard combat strength or composition but includes the total number of infantry, which is deployed in a single formation known as a \"phalanx\".\nMany spear-armed troops historically fought in what might be termed phalanx-like formations.\n\nThis article focuses on the use of the military phalanx formation in Ancient Greece, the Hellenistic world, and other ancient states heavily influenced by Greek civilization.\n\n== History ==\n\nThe earliest known depiction of a phalanx-like formation occurs in a Sumerian stele from the 25th century BC.\n\nHere the troops seem to have been equipped with spears, helmets, and large shields covering the whole body.\n\nAncient Egyptian infantry were known to have employed similar formations.\n\nThe first usage of the term phalanx comes from Homer's \"φαλαγξ\", used to describe hoplites fighting in an organized battle line.\n\nHomer used the term to differentiate the formation-based combat from the individual duels so often found in his poems.Historians have not arrived at a consensus about the relationship between the Greek formation and these predecessors of the hoplites.\n\nThe principles of shield wall and spear hedge were almost universally known among the armies of major civilizations throughout history, and so the similarities may be related to convergent evolution instead of diffusion.\nTraditionally, historians date the origin of the hoplite phalanx of ancient Greece to the 8th century BC in Sparta, but this is under revision.\n\nIt is perhaps more likely that the formation was devised in the 7th century BC after the introduction of the aspis by the city of Argos, which would have made the formation possible.\n\nThis is further evidenced by the Chigi vase, dated to 650 BC, identifying hoplites armed with aspis, spear and panoply.Another possible theory as to the birth of Greek phalanx warfare stems from the idea that some of the basic aspects of the phalanx were present in earlier times yet were not fully developed due to the lack of appropriate technology.\n\nTwo of the basic tactics seen in earlier warfare include the principle of cohesion and the use of large groups of soldiers.\n\nThis would suggest that the Greek phalanx was rather the culmination and perfection of a slowly developed idea that originated many years earlier.\n\nAs weaponry and armour advanced through the years in different city-states, the phalanx became complex and effective.\n\n== Overview ==\n\nThe hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order.\n\nThe hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields.\n\nThe phalanx therefore presented a shield wall and a mass of spear points to the enemy, making frontal assaults against it very difficult.\n\nIt also allowed a higher proportion of the soldiers to be actively engaged in combat at a given time (rather than just those in the front rank).\nBattles between two phalanxes usually took place in open, flat plains where it was easier to advance and stay in formation.\n\nRough terrain or hilly regions would have made it difficult to maintain a steady line and would have defeated the purpose of a phalanx.\n\nAs a result, battles between Greek city-states would not take place in just any location, nor would they be limited to sometimes obvious strategic points.\n\nRather, many times, the two opposing sides would find the most suitable piece of land where the conflict could be settled.\n\nTypically, the battle ended with one of the two fighting forces fleeing to safety.The phalanx usually advanced at a walking pace, although it is possible that they picked up speed during the last several yards.\n\nOne of the main reasons for this slow approach was to maintain formation.\n\nThe formation would be rendered useless if the phalanx was lost as the unit approached the enemy and could even become detrimental to the advancing unit, resulting in a weaker formation that was easier for an enemy force to break through.\n\nIf the hoplites of the phalanx were to pick up speed toward the latter part of the advance, it would have been for the purpose of gaining momentum against the enemy in the initial collision.\n\nHerodotus states of the Greeks at the Battle of Marathon, that \"They were the first Greeks we know of to charge their enemy at a run\".\n\nMany historians believe that this innovation was precipitated by their desire to minimize their losses from Persian archery.\n\nThe opposing sides would collide, possibly severing many of the spears of the row in front and killing the front part of the enemy army due to the bone-breaking collision.\nThe spears of a phalanx had spiked butts.\n\nIn battle, the back ranks used the spikes to finish fallen enemy soldiers.\n\n=== Pushing ===\n\nThe \"physical pushing match\" theory is one where the battle would rely on the valour of the men in the front line, whilst those in the rear maintained forward pressure on the front ranks with their shields, and the whole formation would consistently press forward trying to break the enemy formation.\n\nThis is the most widely accepted interpretation of the ancient sources thus when two phalanx formations engaged, the struggle essentially became a pushing match.\n\nHistorians such as Victor Davis Hanson point out that it is difficult to account for exceptionally deep phalanx formations unless they were necessary to facilitate the physical pushing depicted by this theory, as those behind the first two ranks could not take part in the actual spear thrusting.No Greek art ever depicts anything like a phalanx pushing match, so this hypothesis is a product of educated speculation rather than explicit testimony from contemporary sources and is far from being academically resolved.\n\nThe Greek term for \"push\" was used in the same metaphorical manner as the English word is (for example it was also used to describe the process of rhetorical arguments) and so does not necessarily describe a literal physical push, although it is possible that it did.\nFor instance, if Othismos were to accurately describe a physical pushing match, it would be logical to state that the deeper phalanx would always win an engagement since the physical strength of individuals would not compensate for even one additional rank on the enemy side.\n\nHowever, there are numerous examples of shallow phalanxes holding off an opponent.\n\nFor instance, at Delium in 424 BC, the Athenian left flank, a formation eight men deep, held off a formation of Thebans 25 deep without immediate collapse.\n\nIt is difficult with the physical pushing model to imagine eight men withstanding the pushing force of 25 opponents for a matter of seconds, let alone half the battle.\nSuch arguments have led to a wave of counter-criticism to physical shoving theorists.\n\nAdrian Goldsworthy, in his article \"The Othismos, Myths and Heresies: The nature of Hoplite Battle\", argues that the physical pushing match model does not fit with the average casualty figures of hoplite warfare nor the practical realities of moving large formations of men in battle.\n\nThis debate has yet to be resolved amongst scholars.\nPractical difficulties with this theory also include the fact that, in a shoving match, an eight-foot spear is too long to fight effectively or even parry attacks.\n\nSpears enable a formation of men to keep their enemies at a distance, parry attacks aimed at them and their comrades, and give the necessary reach to strike multiple men in the opposite formation.\n\nA pushing match would put enemies so close together that a quick stabbing with a knife would kill the front row almost instantly.\n\nThe crush of men would also prevent the formation from withdrawing or retreating, which would result in much higher casualties than is recorded.\n\nThe speed at which this would occur would also end the battle very quickly, instead of prolonging it for hours.\n\n=== Shields ===\n\nEach individual hoplite carried his shield on his left arm, protecting not only himself but also the soldier to the left.\n\nThis meant that the men at the extreme right of the phalanx were only half-protected.\n\nIn battle, opposing phalanxes would try to exploit this weakness by attempting to overlap the enemy's right flank.\n\nIt also meant that, in battle, a phalanx would tend to drift to the right (as hoplites sought to remain behind the shield of their neighbor).\n\nSome groups, such as the Spartans at Nemea, tried to use this phenomenon to their advantage.\n\nIn this case, the phalanx would sacrifice its left side, which typically consisted of allied troops, in an effort to overtake the enemy from the flank.\n\nIt is unlikely that this strategy worked very often, as it is not mentioned frequently in ancient Greek literature.There was a leader in each row of a phalanx, and a rear rank officer, the ouragos (meaning tail-leader), who kept order in the rear.\n\nThe hoplites had to trust their neighbors to protect them and in turn be willing to protect their neighbors; a phalanx was thus only as strong as its weakest elements.\n\nThe effectiveness of the phalanx therefore depended on how well the hoplites could maintain this formation in combat and how well they could stand their ground, especially when engaged against another phalanx.\n\nFor this reason, the formation was deliberately organized to group friends and family close together, thus providing a psychological incentive to support one's fellows, and a disincentive, through shame, to panic or attempt to flee.\n\nThe more disciplined and courageous the army, the more likely it was to win – often engagements between the various city-states of Greece would be resolved by one side fleeing before the battle.\n\nThe Greek word dynamis, the 'will to fight', expresses the drive that kept hoplites in formation.\n\nNow of those, who dare, abiding one beside another, to advance to the close fray, and the foremost champions, fewer die, and they save the people in the rear; but in men that fear, all excellence is lost.\n\nNo one could ever in words go through those several ills, which befall a man, if he has been actuated by cowardice.\n\nFor 'tis grievous to wound in the rear the back of a flying man in hostile war.\n\nShameful too is a corpse lying low in the dust, wounded behind in the back by the point of a spear.\n\n=== Hoplite armament ===\n\nEach hoplite provided his own equipment.\n\nThe primary hoplite weapon was a spear around 2.4 metres (7.9 ft) in length called a dory.\n\nAlthough accounts of its length vary, it is usually now believed to have been seven to nine feet long (~2.1–2.7 m).\n\nIt was held one-handed, with the other hand holding the hoplite's shield (aspis).\n\nThe spearhead was usually a curved leaf shape, while the rear of the spear had a spike called a sauroter ('lizard-killer') which was used to stand the spear in the ground (hence the name).\n\nIt was also used as a secondary weapon if the main shaft snapped or to kill enemies lying on the ground.\n\nThis was a common problem, especially for soldiers who were involved in the initial clash with the enemy.\n\nDespite the snapping of the spear, hoplites could easily switch to the sauroter without great consequence.\n\nThe rear ranks used the secondary end to finish off fallen opponents as the phalanx advanced over them.\nThroughout the hoplite era, the standard hoplite armour went through many cyclical changes.\n\nAn Archaic hoplite typically wore a bronze breastplate, a bronze helmet with cheekplates, as well as greaves and other armour.\n\nLater, in the classical period, the breastplate became less common, replaced instead with a corselet that some claim was made of linothorax (layers of linen glued together), or perhaps of leather, sometimes covered in whole or in part with overlapping metal scales.\n\nEventually, even greaves became less commonly used, although degrees of heavier armour remained, as attested by Xenophon as late as 401 BC.These changes reflected the balancing of mobility with protection, especially as cavalry became more prominent in the Peloponnesian War and the need to combat light troops, which were increasingly used to negate the hoplite's role as the primary force in battle.\n\nYet bronze armour remained in some form until the end of the hoplite era.\n\nSome archaeologists have pointed out that bronze armour does not actually provide as much protection from direct blows as more extensive corselet padding, and have suggested its continued use was a matter of status for those who could afford it.\n\nIn the classical Greek dialect, there is no word for swordsmen; yet hoplites also carried a short sword called the xiphos, used as a secondary weapon if the dory was broken or lost.\n\nSamples of the xiphos recovered at excavation sites were typically around 60 cm (24 in) in length.\n\nThese swords were double-edged and could therefore be used as a cutting and thrusting weapon.\n\nThese short swords were often used to stab or cut at the enemy's neck during close combat.Hoplites carried a circular shield called a hoplon (often referred to as an aspis) made from wood and covered in bronze, measuring roughly 1 metre (3.3 ft) in diameter.\n\nIt spanned from chin to knee and was very heavy (8–15 kg (18–33 lb)).\n\nThis medium-sized shield (fairly large for the period considering the average male height) was made possible partly by its dish-like shape, which allowed it to be supported with the rim on the shoulder.\n\nThis was quite an important feature of the shield, especially for the hoplites that remained in the latter ranks.\n\nWhile these soldiers continued to help press forward, they did not have the added burden of holding up their shield.\n\nBut the circular shield was not without its disadvantages.\n\nDespite its mobility, protective curve, and double straps the circular shape created gaps in the shield wall at both its top and bottom. (Top gaps were somewhat reduced by the one or two spears jutting out of the gap.\n\nIn order to minimize the bottom gaps, thick leather 'curtains' were used but only by an [unknown] percentage of the hoplites, possibly mostly in the first row only since there were disadvantages as well: considerable added weight on an already heavy shield and a certain additional cost.) These gaps left parts of the hoplite exposed to potentially lethal spear thrusts and were a persistent vulnerability for hoplites controlling the front lines.\n\n=== Phalangite armament ===\n\nThe phalanx of the Ancient Macedonian kingdom and the later Hellenistic successor states was a development of the hoplite phalanx.\n\nThe 'phalangites' were armed with a much longer spear, the sarissa, and less heavily armoured.\n\nThe sarissa was the pike used by the ancient Macedonian army.\n\nIts actual length is unknown, but apparently it was twice as long as the dory.\n\nThis makes it at least 14 feet (4.3 m), but 18 feet (5.5 m) appears more likely. (The cavalry xyston was 12.5 feet (3.8 m) by comparison.) The great length of the pike was balanced by a counterweight at the rear end, which also functioned as a butt-spike, allowing the sarissa to be planted into the ground.\n\nBecause of its great length, weight and different balance, a sarissa was wielded two-handed.\n\nThis meant that the aspis was no longer a practical defence.\n\nInstead, the phalangites strapped a smaller pelte shield (usually reserved for peltasts, light skirmishers) to their left forearm.\n\nRecent theories, including examination of ancient frescoes depicting full sets of weapons and armor, claim that the shields used were actually larger than the pelte but smaller than the aspis, hanging by leather strap(s) from the left shoulder or from both shoulders.\n\nThe shield would retain handling straps in the inner curve, to be handled like a (smaller) aspis if the fight progressed to sword-wielding.\n\nAlthough in both shield size assumptions this reduced the shield wall, the extreme length of the spear kept the enemy at a greater distance, as the pikes of the first three to five ranks could all be brought to bear in front of the front row.\n\nThis pike had to be held underhand, as the shield would have obscured the soldier's vision had it been held overhead.\n\nIt would also be very hard to remove a sarissa from anything it stuck in (the earth, shields, and soldiers of the opposition) if it were thrust downwards, due to its length.\n\nThe Macedonian phalanx was much less able to form a shield wall, but the lengthened spears would have compensated for this.\n\nSuch a phalanx formation also reduced the likelihood that battles would degenerate into a pushing match.\n\n== Deployment and combat ==\n\n=== Phalanx composition and strength ===\n\nThe basic combat element of the Greek armies was either the stichos (meaning 'file'; usually 8–16 men strong) or the enomotia (meaning 'sworn' and made up by 2–4 stichœ, totaling up to 32 men), both led by a dimœrites who was assisted by a decadarchos and two decasterœ (sing. decasteros).\n\nFour to a maximum of 32 enomotiæ (depending on the era in question or the city) were forming a lochos led by a lochagos, who in this way was in command of initially 100 hoplites to a maximum of c. 500 in the late Hellenistic armies.\n\nHere, it has to be noted that the military manuals of Asclepiodotus and Aelian use the term lochos to denote a file in the phalanx.\n\nA taxis (mora for the Spartans) was the greatest standard hoplitic formation of 500 to 1500 men, led by a strategos (general).\n\nThe entire army, a total of several taxeis or moræ was led by a generals' council.\n\nThe commander-in-chief was usually called a polemarchos or a strategos autocrator.\n\n=== Phalanx front and depth ===\n\nHoplite phalanxes usually deployed in ranks of eight men or more deep; the Macedonian phalanxes were usually 16 men deep, sometimes reported to have been arrayed 32 men deep.\n\nThere are some notable extremes; at the battles of Leuctra and Mantinea, the Theban general Epaminondas arranged the left wing of the phalanx into a \"hammerhead\" of 50 ranks of elite hoplites deep (see below) and when depth was less important, phalanxes just four deep are recorded, as at the battle of Marathon.The phalanx depth could vary depending on the needs of the moment and plans of the general.\n\nWhile the phalanx was in march, an eis bathos formation (loose, meaning literally 'in depth') was adopted in order to move more freely and maintain order.\n\nThis was also the initial battle formation as, in addition, it permitted friendly units to pass through whether assaulting or retreating.\n\nIn this status, the phalanx had twice the normal depth and each hoplite had to occupy about 1.8–2 metres (5 ft 11 in–6 ft 7 in) in width.\n\nWhen enemy infantry was approaching, a rapid switch to the pycne (spelled also pucne) formation (dense or tight formation) was necessary.\n\nIn that case, each man's space was halved (0.9–1 metre or 2 feet 11 inches–3 feet 3 inches in width) and the formation depth returned to normal.\n\nAn even denser formation, the synaspismos or sunaspismos (ultra-tight or locked shields formation), was used when the phalanx was expected to experience extra pressure, intense missile volleys or frontal cavalry charges.\n\nIn synaspismos, the rank depth was half that of a normal phalanx and the width each man occupied was as small as 0.45 metres (1.5 ft).\n\n=== Stages of combat ===\n\nSeveral stages in hoplite combat can be defined:\nEphodos: The hoplites stop singing their pæanes (battle hymns) and move towards the enemy, gradually picking up pace and momentum.\n\nIn the instants before impact, war cries (alalagmœ, sing. alalagmos) would be made.\n\nNotable war cries were the Athenian (eleleleleu! eleleleleu!) and the Macedonian (alalalalai! alalalalai!) alalagmœ.\nKrousis: The opposing phalanxes meet each other almost simultaneously along their front.\nDoratismos: Repeated, rapid spear thrusts in order to disrupt the enemy formation.\n\nThe use of long spears would keep enemies apart as well as allow men in a row to assist their comrades next to them.\n\nThe prodding could also open up a man to allow a comrade to spear him.\n\nToo hard prodding could get a spear stuck in a shield, which would necessitate someone in the back to lend his to the now-disarmed man.\nOthismos: Literally 'pushing' after most spears have been broken, the hoplites begin to push with their spears and spear shafts against their opponents' shields.\n\nThis could be the longest phase.Pararrhexis: 'Breaching' the opposing phalanx, the enemy formation shatters and the battle ends.\n\nCavalry would be used at this point to mop up the scattered enemy.\n\n== Tactics ==\n\nThe early history of the phalanx is largely one of combat between hoplite armies from competing Greek city-states.\n\nThe usual result was rather identical, inflexible formations pushing against each other until one broke.\n\nThe potential of the phalanx to achieve something more was demonstrated at Battle of Marathon (490 BC).\n\nFacing the much larger army of Darius I, the Athenians thinned out their phalanx and consequently lengthened their front, to avoid being outflanked.\n\nHowever, even a reduced-depth phalanx proved unstoppable to the lightly armed Persian infantry.\n\nAfter routing the Persian wings, the hoplites on the Athenian wings wheeled inwards, destroying the elite troop at the Persian centre, resulting in a crushing victory for Athens.\n\nThroughout the Greco-Persian Wars the hoplite phalanx was to prove superior to the Persian infantry (e.g. the battles of Thermopylae and Plataea).\nPerhaps the most prominent example of the phalanx's evolution was the oblique order, made famous in the Battle of Leuctra.\n\nThere, the Theban general Epaminondas thinned out the right flank and centre of his phalanx, and deepened his left flank to an unheard-of 50 men deep.\n\nIn doing so, Epaminondas reversed the convention by which the right flank of the phalanx was strongest.\n\nThis allowed the Thebans to assault in strength the elite Spartan troops on the right flank of the opposing phalanx.\n\nMeanwhile, the centre and right flank of the Theban line were echeloned back, from the opposing phalanx, keeping the weakened parts of the formation from being engaged.\n\nOnce the Spartan right had been routed by the Theban left, the remainder of the Spartan line also broke.\n\nThus, by localising the attacking power of the hoplites, Epaminondas was able to defeat an enemy previously thought invincible.\nPhilip II of Macedon spent several years in Thebes as a hostage, and paid attention to Epaminondas' innovations.\n\nOn return to his homeland, he raised a revolutionary new infantry force, which was to change the face of the Greek world.\n\nPhilip's phalangites were the first force of professional soldiers seen in Ancient Greece apart from Sparta.\n\nThey were armed with longer spears (the sarissa) and were drilled more thoroughly in more evolved, complicated tactics and manoeuvres.\n\nMore importantly, though, Philip's phalanx was part of a multi-faceted, combined force that included a variety of skirmishers and cavalry, most notably the famous Companion cavalry.\n\nThe Macedonian phalanx now was used to pin the centre of the enemy line, while cavalry and more mobile infantry struck at the foe's flanks.\n\nIts supremacy over the more static armies fielded by the Greek city-states was shown at the Battle of Chaeronea, where Philip II's army crushed the allied Theban and Athenian phalanxes.\n\n== Weaknesses ==\n\nThe hoplite phalanx was weakest when facing an enemy fielding lighter and more flexible troops without its own such supporting troops.\n\nAn example of this would be the Battle of Lechaeum, where an Athenian contingent led by Iphicrates routed an entire Spartan mora (a unit of anywhere from 500 to 900 hoplites).\n\nThe Athenian force had a considerable proportion of light missile troops armed with javelins and bows that wore down the Spartans with repeated attacks, causing disarray in the Spartan ranks and an eventual rout when they spotted Athenian heavy infantry reinforcements trying to flank them by boat.\nThe Macedonian phalanx had weaknesses similar to its hoplitic predecessor.\n\nTheoretically indestructible from the front, its flanks and rear were very vulnerable, and once engaged it may not easily disengage or redeploy to face a threat from those directions.\n\nThus, a phalanx facing non-phalangite formations required some sort of protection on its flanks—lighter or at least more mobile infantry, cavalry, etc.\n\nThis was shown at the Battle of Magnesia, where, once the Seleucid supporting cavalry elements were driven off, the phalanx was static and unable to go on the offensive against its Roman opponents (although they continued to resist stoutly and attempted a fighting withdrawal under a hail of Roman missiles, until the elephants posted on their flanks panicked and disrupted their formation).\nThe Macedonian phalanx could also lose its cohesion without proper coordination or while moving through broken terrain; doing so could create gaps between individual blocks/syntagmata, or could prevent a solid front within those sub-units as well, causing other sections of the line to bunch up.\n\nIn this event, as in the battles of Cynoscephalae and Pydna, the phalanx became vulnerable to attacks by more flexible units—such as Roman legionary centuries, which were able to avoid the sarissae and engage in hand-to-hand combat with the phalangites.\nAnother important area that must be considered concerns the psychological tendencies of the hoplites.\n\nBecause the strength of a phalanx depended on the ability of the hoplites to maintain their frontline, it was crucial that a phalanx be able to quickly and efficiently replace fallen soldiers in the front ranks.\n\nIf a phalanx failed to do this in a structured manner, the opposing phalanx would have an opportunity to breach the line which, many times, would lead to a quick defeat.\n\nThis then implies that the hoplites ranks closer to the front must be mentally prepared to replace their fallen comrade and adapt to his new position without disrupting the structure of the frontline.Finally, most of the phalanx-centric armies tended to lack supporting echelons behind the main line of battle.\n\nThis meant that breaking through the line of battle or compromising one of its flanks often ensured victory.\n\n== Classical decline and post-classical use ==\n\nAfter reaching its zenith in the conquests of Alexander the Great, the phalanx began a slow decline, as Macedonian successor states declined.\n\nThe combined arms tactics used by Alexander and his father were gradually replaced by a return to the simpler frontal charge tactics of the hoplite phalanx.\n\nThe expense of the supporting arms and cavalry, and the widespread use of mercenaries, caused the Diadochi to rely on phalanx vs. phalanx tactics during the Wars of the Diadochi.\nThe decline of the Diadochi and the phalanx was linked with the rise of Rome and the Roman legions from the 3rd century BC.\n\nThe Battle of the Caudine Forks showed the clumsiness of the Roman phalanx against the Samnites.\n\nThe Romans had originally employed the phalanx themselves but gradually evolved more flexible tactics.\n\nThe result was the three-line Roman legion of the middle period of the Roman Republic, the Manipular System.\n\nRomans used a phalanx for their third military line, the triarii.\n\nThese were veteran reserve troops armed with the hastae or spear.\n\nRome conquered most of the Macedonian successor states.\n\nAlso the various Greek city-states and leagues.\n\nAs these states ceased to exist, so did the armies which used the traditional phalanx.\n\nSubsequently, troops from these regions were equipped, trained and fought using the Roman model.\nA phalanx formation called the phoulkon appeared in the late Roman army and Byzantine army.\n\nIt had characteristics of the classical Greek and Hellenistic phalanxes, but was more flexible.\n\nIt was used against cavalry more than infantry.\nHowever, the phalanx did not totally disappear.\n\nIn some battles between the Roman army and Hellenistic phalanxes, such as Pydna (168 BC), Cynoscephalae (197 BC) and Magnesia (190 BC), the phalanx performed well.\n\nIt even drove back the Roman infantry.\n\nHowever, at Cynoscephalae and Magnesia, failure to defend the flanks of the phalanx led to defeat.\n\nAt Pydna, the phalanx lost cohesion when pursuing retreating Roman soldiers.\n\nThis allowed the Romans to penetrate the formation.\n\nThen, Roman close combat skills proved decisive.\n\nThe historian Polybius details the effectiveness of the Roman legion against the phalanx.\n\nHe deduces that the Romans refused to fight the phalanx where the phalanx was effective, Romans offered battle only when a legion could exploit the clumsiness and immobility of a phalanx.\n\nSpear-armed troops continued to be important elements in many armies until reliable firearms became available.\n\nThese did not necessarily fight as a phalanx.\n\nFor example, compare the classical phalanx and late medieval pike formations.Military historians have suggested that the Scots under William Wallace and Robert the Bruce consciously imitated the Hellenistic phalanx to produce the Scots 'hedgehog' or schiltron.\n\nHowever, long spears might have been used by Picts and others in Scotlands' Early Middle Ages.\n\nPrior to 1066, long spear tactics (also found in North Wales) might have been part of irregular warfare in Britain.\n\nThe Scots used imported French pikes and dynamic tactics at the Battle of Flodden.\n\nHowever, Flodden found the Scots pitted against effective light artillery, while advancing over bad ground.\n\nThe combination disorganised the Scotts phalanxes and permitted effective attacks by English longbowmen, and soldiers wielding shorter, handier polearms called bills.\n\nSome contemporary sources might say that the bills cut off the heads of Scots pikes.\nThe pike was briefly reconsidered as a weapon by European armies in the late 18th and early 19th centuries.\n\nIt could protect riflemen, whose slower rate of fire made them vulnerable.\n\nA collapsible pike was invented but never issued.\n\nThe Confederate Army considered these for the American Civil War.\n\nSome were even manufactured but probably were never issued.\n\nPikes were manufactured during World War II as \"Croft's Pikes\".\nWhile obsolete in military practice, the phalanx remained in use as a metaphor of warriors moving forward as a single united block.\n\nThis metaphor inspired several 20th-century political movements, notably the Spanish Falange and its ideology of Falangism.\nThe Byzantines continued and improved the use of the classical Greek phalanx alongside the Macedonian-style phalanx.\n\nThe latter was based on a model that Alexander himself had created and had tried to give more importance to the skirmishers and cavalry, yet it never saw action until the Byzantines adopted the model that rely in a mixture of many units sometimes.\n\nMany writers of the age describe the spear as being a sarissa yet it was a meter short than the original sarissa and had being modified by the time, yet the term for the long spear remained alongside with its other names.\n\nhttps://en.wikipedia.org/wiki/Phalanx","first-metacarpal-bone":"In human anatomy, the metacarpal bones or metacarpus, form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist which forms the connection to the forearm.\n\nThe metacarpal bones are analogous to the metatarsal bones in the foot.\n\n== Structure ==\n\nThe metacarpals form a transverse arch to which the rigid row of distal carpal bones are fixed.\n\nThe peripheral metacarpals (those of the thumb and little finger) form the sides of the cup of the palmar gutter and as they are brought together they deepen this concavity.\n\nThe index metacarpal is the most firmly fixed, while the thumb metacarpal articulates with the trapezium and acts independently from the others.\n\nThe middle metacarpals are tightly united to the carpus by intrinsic interlocking bone elements at their bases.\n\nThe ring metacarpal is somewhat more mobile while the fifth metacarpal is semi-independent.Each metacarpal bone consists of a body or shaft, and two extremities: the head at the distal or digital end (near the fingers), and the base at the proximal or carpal end (close to the wrist).\n\n=== Body ===\n\nThe body (shaft) is prismoid in form, and curved, so as to be convex in the longitudinal direction behind, concave in front.\n\nIt presents three surfaces: medial, lateral, and dorsal.\n\nThe medial and lateral surfaces are concave, for the attachment of the interosseus muscles, and separated from one another by a prominent anterior ridge.\n\nThe dorsal surface presents in its distal two-thirds a smooth, triangular, flattened area which is covered in by the tendons of the extensor muscles.\n\nThis surface is bounded by two lines, which commence in small tubercles situated on either side of the digital extremity, and, passing upward, converge and meet some distance above the center of the bone and form a ridge which runs along the rest of the dorsal surface to the carpal extremity.\n\nThis ridge separates two sloping surfaces for the attachment of the interossei dorsales.\n\nTo the tubercles on the digital extremities are attached the collateral ligaments of the metacarpophalangeal joints.\n\n=== Base ===\n\nThe base (basis) or carpal extremity is of a cuboidal form, and broader behind than in front: it articulates with the carpal bones and with the adjoining metacarpal bones; its dorsal and volar surfaces are rough, for the attachment of ligaments.\n\n=== Head ===\n\nThe head (caput) or digital extremity presents an oblong surface markedly convex from before backward, less so transversely, and flattened from side to side; it articulates with the proximal phalanx.\n\nIt is broader, and extends farther upward, on the volar than on the dorsal aspect, and is longer in the antero-posterior than in the transverse diameter.\n\nOn either side of the head is a tubercle for the attachment of the collateral ligament of the metacarpophalangeal joint.\n\nThe dorsal surface, broad and flat, supports the tendons of the extensor muscles.\n\nThe volar surface is grooved in the middle line for the passage of the flexor tendons, and marked on either side by an articular eminence continuous with the terminal articular surface.\n\n=== Neck ===\n\nThe neck, or subcapital segment, is the transition zone between the body and the head.\n\n=== Articulations ===\n\nBesides the metacarpophalangeal joints, the metacarpal bones articulate by carpometacarpal joints as follows:\n\n-the first with the trapezium;\n-the second with the trapezium, trapezoid, capitate and third metacarpal;\n-the third with the capitate and second and fourth metacarpals;\n-the fourth with the capitate, hamate, and third and fifth metacarpals;\n-and the fifth with the hamate and fourth metacarpal;\n\n=== Insertions ===\n\n-Extensor Carpi Radialis Longus/Brevis: Both insert on the base of metacarpal II; Assist with wrist extension and radial flexion of the wrist\n-Extensor Carpi Ulnaris: Inserts on the base of metacarpal V; Extends and fixes wrist when digits are being flexed; assists with ulnar flexion of wrist\n-Abductor Pollicis Longus: Inserts on the trapezium and base of metacarpal I; Abducts thumb in frontal plane; extends thumb at carpometacarpal joint\n-Opponens Pollicis: Inserts on metacarpal I; flexes metacarpal I to oppose the thumb to the fingertips\n-Opponens digiti minimi: Inserts on the medial surface of metacarpal V; Flexes metacarpal V at carpometacarpal joint when little finger is moved into opposition with tip of thumb; deepens palm of hand.\n\n== Clinical significance ==\n\n=== Congenital disorders ===\n\nThe fourth and fifth metacarpal bones are commonly \"blunted\" or shortened, in pseudohypoparathyroidism and pseudopseudohypoparathyroidism.\n\nA blunted fourth metacarpal, with normal fifth metacarpal, can signify Turner syndrome.\n\nBlunted metacarpals (particularly the fourth metacarpal) are a symptom of Nevoid basal cell carcinoma syndrome.\n\n=== Fracture ===\n\nThe neck of a metacarpal is a common location for a boxer's fracture.\n\nHowever, all parts of the metacarpal bone (including head, body and base) are susceptible to fracture.\n\nFor these fractures several types of treatment exist ranging from non-operative techniques with or without immobilization to operative techniques using closed or open reduction and internal fixation (ORIF).\n\nGenerally speaking most fractures showing little or no displacement can be treated successfully without surgery.\n\nIntraarticular fracture-dislocations of the metacarpal head or base may require surgical fixation, as fragment displacement affecting the joint surface is rarely tolerated well.\n\n== Other animals ==\n\nIn four-legged animals, the metacarpals form part of the forefeet, and are frequently reduced in number, appropriate to the number of toes.\n\nIn digitigrade and unguligrade animals, the metacarpals are greatly extended and strengthened, forming an additional segment to the limb, a feature that typically enhances the animal's speed.\n\nIn both birds and bats, the metacarpals form part of the wing.\n\n== History ==\n\n=== Etymology ===\n\nThe Greek physician Galen used to refer to the metacarpus as μετακάρπιον.\n\nThe Latin form metacarpium more truly resembles its Ancient Greek predecessor μετακάρπιον than metacarpus.\n\nMeta– is Greek for beyond and carpal from Ancient Greek καρπός (karpós, “wrist”).\n\nIn anatomic Latin, adjectives like metacarpius, metacarpicus, metacarpiaeus, metacarpeus, metacarpianus and metacarpalis can be found.\n\nThe form metacarpius is more true to the later Greek form μετακάρπιος.\n\nMetacarpalis, as in ossa metacarpalia in the current official Latin nomenclature, Terminologia Anatomica is a compound consisting of Latin and Greek parts.\n\nThe usage of such hybrids in anatomic Latin is disapproved by some.\n\nhttps://en.wikipedia.org/wiki/Metacarpal_bones","second-metacarpal-bone":"In human anatomy, the metacarpal bones or metacarpus, form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist which forms the connection to the forearm.\n\nThe metacarpal bones are analogous to the metatarsal bones in the foot.\n\n== Structure ==\n\nThe metacarpals form a transverse arch to which the rigid row of distal carpal bones are fixed.\n\nThe peripheral metacarpals (those of the thumb and little finger) form the sides of the cup of the palmar gutter and as they are brought together they deepen this concavity.\n\nThe index metacarpal is the most firmly fixed, while the thumb metacarpal articulates with the trapezium and acts independently from the others.\n\nThe middle metacarpals are tightly united to the carpus by intrinsic interlocking bone elements at their bases.\n\nThe ring metacarpal is somewhat more mobile while the fifth metacarpal is semi-independent.Each metacarpal bone consists of a body or shaft, and two extremities: the head at the distal or digital end (near the fingers), and the base at the proximal or carpal end (close to the wrist).\n\n=== Body ===\n\nThe body (shaft) is prismoid in form, and curved, so as to be convex in the longitudinal direction behind, concave in front.\n\nIt presents three surfaces: medial, lateral, and dorsal.\n\nThe medial and lateral surfaces are concave, for the attachment of the interosseus muscles, and separated from one another by a prominent anterior ridge.\n\nThe dorsal surface presents in its distal two-thirds a smooth, triangular, flattened area which is covered in by the tendons of the extensor muscles.\n\nThis surface is bounded by two lines, which commence in small tubercles situated on either side of the digital extremity, and, passing upward, converge and meet some distance above the center of the bone and form a ridge which runs along the rest of the dorsal surface to the carpal extremity.\n\nThis ridge separates two sloping surfaces for the attachment of the interossei dorsales.\n\nTo the tubercles on the digital extremities are attached the collateral ligaments of the metacarpophalangeal joints.\n\n=== Base ===\n\nThe base (basis) or carpal extremity is of a cuboidal form, and broader behind than in front: it articulates with the carpal bones and with the adjoining metacarpal bones; its dorsal and volar surfaces are rough, for the attachment of ligaments.\n\n=== Head ===\n\nThe head (caput) or digital extremity presents an oblong surface markedly convex from before backward, less so transversely, and flattened from side to side; it articulates with the proximal phalanx.\n\nIt is broader, and extends farther upward, on the volar than on the dorsal aspect, and is longer in the antero-posterior than in the transverse diameter.\n\nOn either side of the head is a tubercle for the attachment of the collateral ligament of the metacarpophalangeal joint.\n\nThe dorsal surface, broad and flat, supports the tendons of the extensor muscles.\n\nThe volar surface is grooved in the middle line for the passage of the flexor tendons, and marked on either side by an articular eminence continuous with the terminal articular surface.\n\n=== Neck ===\n\nThe neck, or subcapital segment, is the transition zone between the body and the head.\n\n=== Articulations ===\n\nBesides the metacarpophalangeal joints, the metacarpal bones articulate by carpometacarpal joints as follows:\n\n-the first with the trapezium;\n-the second with the trapezium, trapezoid, capitate and third metacarpal;\n-the third with the capitate and second and fourth metacarpals;\n-the fourth with the capitate, hamate, and third and fifth metacarpals;\n-and the fifth with the hamate and fourth metacarpal;\n\n=== Insertions ===\n\n-Extensor Carpi Radialis Longus/Brevis: Both insert on the base of metacarpal II; Assist with wrist extension and radial flexion of the wrist\n-Extensor Carpi Ulnaris: Inserts on the base of metacarpal V; Extends and fixes wrist when digits are being flexed; assists with ulnar flexion of wrist\n-Abductor Pollicis Longus: Inserts on the trapezium and base of metacarpal I; Abducts thumb in frontal plane; extends thumb at carpometacarpal joint\n-Opponens Pollicis: Inserts on metacarpal I; flexes metacarpal I to oppose the thumb to the fingertips\n-Opponens digiti minimi: Inserts on the medial surface of metacarpal V; Flexes metacarpal V at carpometacarpal joint when little finger is moved into opposition with tip of thumb; deepens palm of hand.\n\n== Clinical significance ==\n\n=== Congenital disorders ===\n\nThe fourth and fifth metacarpal bones are commonly \"blunted\" or shortened, in pseudohypoparathyroidism and pseudopseudohypoparathyroidism.\n\nA blunted fourth metacarpal, with normal fifth metacarpal, can signify Turner syndrome.\n\nBlunted metacarpals (particularly the fourth metacarpal) are a symptom of Nevoid basal cell carcinoma syndrome.\n\n=== Fracture ===\n\nThe neck of a metacarpal is a common location for a boxer's fracture.\n\nHowever, all parts of the metacarpal bone (including head, body and base) are susceptible to fracture.\n\nFor these fractures several types of treatment exist ranging from non-operative techniques with or without immobilization to operative techniques using closed or open reduction and internal fixation (ORIF).\n\nGenerally speaking most fractures showing little or no displacement can be treated successfully without surgery.\n\nIntraarticular fracture-dislocations of the metacarpal head or base may require surgical fixation, as fragment displacement affecting the joint surface is rarely tolerated well.\n\n== Other animals ==\n\nIn four-legged animals, the metacarpals form part of the forefeet, and are frequently reduced in number, appropriate to the number of toes.\n\nIn digitigrade and unguligrade animals, the metacarpals are greatly extended and strengthened, forming an additional segment to the limb, a feature that typically enhances the animal's speed.\n\nIn both birds and bats, the metacarpals form part of the wing.\n\n== History ==\n\n=== Etymology ===\n\nThe Greek physician Galen used to refer to the metacarpus as μετακάρπιον.\n\nThe Latin form metacarpium more truly resembles its Ancient Greek predecessor μετακάρπιον than metacarpus.\n\nMeta– is Greek for beyond and carpal from Ancient Greek καρπός (karpós, “wrist”).\n\nIn anatomic Latin, adjectives like metacarpius, metacarpicus, metacarpiaeus, metacarpeus, metacarpianus and metacarpalis can be found.\n\nThe form metacarpius is more true to the later Greek form μετακάρπιος.\n\nMetacarpalis, as in ossa metacarpalia in the current official Latin nomenclature, Terminologia Anatomica is a compound consisting of Latin and Greek parts.\n\nThe usage of such hybrids in anatomic Latin is disapproved by some.\n\nhttps://en.wikipedia.org/wiki/Metacarpal_bones","third-metacarpal-bone":"In human anatomy, the metacarpal bones or metacarpus, form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist which forms the connection to the forearm.\n\nThe metacarpal bones are analogous to the metatarsal bones in the foot.\n\n== Structure ==\n\nThe metacarpals form a transverse arch to which the rigid row of distal carpal bones are fixed.\n\nThe peripheral metacarpals (those of the thumb and little finger) form the sides of the cup of the palmar gutter and as they are brought together they deepen this concavity.\n\nThe index metacarpal is the most firmly fixed, while the thumb metacarpal articulates with the trapezium and acts independently from the others.\n\nThe middle metacarpals are tightly united to the carpus by intrinsic interlocking bone elements at their bases.\n\nThe ring metacarpal is somewhat more mobile while the fifth metacarpal is semi-independent.Each metacarpal bone consists of a body or shaft, and two extremities: the head at the distal or digital end (near the fingers), and the base at the proximal or carpal end (close to the wrist).\n\n=== Body ===\n\nThe body (shaft) is prismoid in form, and curved, so as to be convex in the longitudinal direction behind, concave in front.\n\nIt presents three surfaces: medial, lateral, and dorsal.\n\nThe medial and lateral surfaces are concave, for the attachment of the interosseus muscles, and separated from one another by a prominent anterior ridge.\n\nThe dorsal surface presents in its distal two-thirds a smooth, triangular, flattened area which is covered in by the tendons of the extensor muscles.\n\nThis surface is bounded by two lines, which commence in small tubercles situated on either side of the digital extremity, and, passing upward, converge and meet some distance above the center of the bone and form a ridge which runs along the rest of the dorsal surface to the carpal extremity.\n\nThis ridge separates two sloping surfaces for the attachment of the interossei dorsales.\n\nTo the tubercles on the digital extremities are attached the collateral ligaments of the metacarpophalangeal joints.\n\n=== Base ===\n\nThe base (basis) or carpal extremity is of a cuboidal form, and broader behind than in front: it articulates with the carpal bones and with the adjoining metacarpal bones; its dorsal and volar surfaces are rough, for the attachment of ligaments.\n\n=== Head ===\n\nThe head (caput) or digital extremity presents an oblong surface markedly convex from before backward, less so transversely, and flattened from side to side; it articulates with the proximal phalanx.\n\nIt is broader, and extends farther upward, on the volar than on the dorsal aspect, and is longer in the antero-posterior than in the transverse diameter.\n\nOn either side of the head is a tubercle for the attachment of the collateral ligament of the metacarpophalangeal joint.\n\nThe dorsal surface, broad and flat, supports the tendons of the extensor muscles.\n\nThe volar surface is grooved in the middle line for the passage of the flexor tendons, and marked on either side by an articular eminence continuous with the terminal articular surface.\n\n=== Neck ===\n\nThe neck, or subcapital segment, is the transition zone between the body and the head.\n\n=== Articulations ===\n\nBesides the metacarpophalangeal joints, the metacarpal bones articulate by carpometacarpal joints as follows:\n\n-the first with the trapezium;\n-the second with the trapezium, trapezoid, capitate and third metacarpal;\n-the third with the capitate and second and fourth metacarpals;\n-the fourth with the capitate, hamate, and third and fifth metacarpals;\n-and the fifth with the hamate and fourth metacarpal;\n\n=== Insertions ===\n\n-Extensor Carpi Radialis Longus/Brevis: Both insert on the base of metacarpal II; Assist with wrist extension and radial flexion of the wrist\n-Extensor Carpi Ulnaris: Inserts on the base of metacarpal V; Extends and fixes wrist when digits are being flexed; assists with ulnar flexion of wrist\n-Abductor Pollicis Longus: Inserts on the trapezium and base of metacarpal I; Abducts thumb in frontal plane; extends thumb at carpometacarpal joint\n-Opponens Pollicis: Inserts on metacarpal I; flexes metacarpal I to oppose the thumb to the fingertips\n-Opponens digiti minimi: Inserts on the medial surface of metacarpal V; Flexes metacarpal V at carpometacarpal joint when little finger is moved into opposition with tip of thumb; deepens palm of hand.\n\n== Clinical significance ==\n\n=== Congenital disorders ===\n\nThe fourth and fifth metacarpal bones are commonly \"blunted\" or shortened, in pseudohypoparathyroidism and pseudopseudohypoparathyroidism.\n\nA blunted fourth metacarpal, with normal fifth metacarpal, can signify Turner syndrome.\n\nBlunted metacarpals (particularly the fourth metacarpal) are a symptom of Nevoid basal cell carcinoma syndrome.\n\n=== Fracture ===\n\nThe neck of a metacarpal is a common location for a boxer's fracture.\n\nHowever, all parts of the metacarpal bone (including head, body and base) are susceptible to fracture.\n\nFor these fractures several types of treatment exist ranging from non-operative techniques with or without immobilization to operative techniques using closed or open reduction and internal fixation (ORIF).\n\nGenerally speaking most fractures showing little or no displacement can be treated successfully without surgery.\n\nIntraarticular fracture-dislocations of the metacarpal head or base may require surgical fixation, as fragment displacement affecting the joint surface is rarely tolerated well.\n\n== Other animals ==\n\nIn four-legged animals, the metacarpals form part of the forefeet, and are frequently reduced in number, appropriate to the number of toes.\n\nIn digitigrade and unguligrade animals, the metacarpals are greatly extended and strengthened, forming an additional segment to the limb, a feature that typically enhances the animal's speed.\n\nIn both birds and bats, the metacarpals form part of the wing.\n\n== History ==\n\n=== Etymology ===\n\nThe Greek physician Galen used to refer to the metacarpus as μετακάρπιον.\n\nThe Latin form metacarpium more truly resembles its Ancient Greek predecessor μετακάρπιον than metacarpus.\n\nMeta– is Greek for beyond and carpal from Ancient Greek καρπός (karpós, “wrist”).\n\nIn anatomic Latin, adjectives like metacarpius, metacarpicus, metacarpiaeus, metacarpeus, metacarpianus and metacarpalis can be found.\n\nThe form metacarpius is more true to the later Greek form μετακάρπιος.\n\nMetacarpalis, as in ossa metacarpalia in the current official Latin nomenclature, Terminologia Anatomica is a compound consisting of Latin and Greek parts.\n\nThe usage of such hybrids in anatomic Latin is disapproved by some.\n\nhttps://en.wikipedia.org/wiki/Metacarpal_bones","fourth-metacarpal-bone":"In human anatomy, the metacarpal bones or metacarpus, form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist which forms the connection to the forearm.\n\nThe metacarpal bones are analogous to the metatarsal bones in the foot.\n\n== Structure ==\n\nThe metacarpals form a transverse arch to which the rigid row of distal carpal bones are fixed.\n\nThe peripheral metacarpals (those of the thumb and little finger) form the sides of the cup of the palmar gutter and as they are brought together they deepen this concavity.\n\nThe index metacarpal is the most firmly fixed, while the thumb metacarpal articulates with the trapezium and acts independently from the others.\n\nThe middle metacarpals are tightly united to the carpus by intrinsic interlocking bone elements at their bases.\n\nThe ring metacarpal is somewhat more mobile while the fifth metacarpal is semi-independent.Each metacarpal bone consists of a body or shaft, and two extremities: the head at the distal or digital end (near the fingers), and the base at the proximal or carpal end (close to the wrist).\n\n=== Body ===\n\nThe body (shaft) is prismoid in form, and curved, so as to be convex in the longitudinal direction behind, concave in front.\n\nIt presents three surfaces: medial, lateral, and dorsal.\n\nThe medial and lateral surfaces are concave, for the attachment of the interosseus muscles, and separated from one another by a prominent anterior ridge.\n\nThe dorsal surface presents in its distal two-thirds a smooth, triangular, flattened area which is covered in by the tendons of the extensor muscles.\n\nThis surface is bounded by two lines, which commence in small tubercles situated on either side of the digital extremity, and, passing upward, converge and meet some distance above the center of the bone and form a ridge which runs along the rest of the dorsal surface to the carpal extremity.\n\nThis ridge separates two sloping surfaces for the attachment of the interossei dorsales.\n\nTo the tubercles on the digital extremities are attached the collateral ligaments of the metacarpophalangeal joints.\n\n=== Base ===\n\nThe base (basis) or carpal extremity is of a cuboidal form, and broader behind than in front: it articulates with the carpal bones and with the adjoining metacarpal bones; its dorsal and volar surfaces are rough, for the attachment of ligaments.\n\n=== Head ===\n\nThe head (caput) or digital extremity presents an oblong surface markedly convex from before backward, less so transversely, and flattened from side to side; it articulates with the proximal phalanx.\n\nIt is broader, and extends farther upward, on the volar than on the dorsal aspect, and is longer in the antero-posterior than in the transverse diameter.\n\nOn either side of the head is a tubercle for the attachment of the collateral ligament of the metacarpophalangeal joint.\n\nThe dorsal surface, broad and flat, supports the tendons of the extensor muscles.\n\nThe volar surface is grooved in the middle line for the passage of the flexor tendons, and marked on either side by an articular eminence continuous with the terminal articular surface.\n\n=== Neck ===\n\nThe neck, or subcapital segment, is the transition zone between the body and the head.\n\n=== Articulations ===\n\nBesides the metacarpophalangeal joints, the metacarpal bones articulate by carpometacarpal joints as follows:\n\n-the first with the trapezium;\n-the second with the trapezium, trapezoid, capitate and third metacarpal;\n-the third with the capitate and second and fourth metacarpals;\n-the fourth with the capitate, hamate, and third and fifth metacarpals;\n-and the fifth with the hamate and fourth metacarpal;\n\n=== Insertions ===\n\n-Extensor Carpi Radialis Longus/Brevis: Both insert on the base of metacarpal II; Assist with wrist extension and radial flexion of the wrist\n-Extensor Carpi Ulnaris: Inserts on the base of metacarpal V; Extends and fixes wrist when digits are being flexed; assists with ulnar flexion of wrist\n-Abductor Pollicis Longus: Inserts on the trapezium and base of metacarpal I; Abducts thumb in frontal plane; extends thumb at carpometacarpal joint\n-Opponens Pollicis: Inserts on metacarpal I; flexes metacarpal I to oppose the thumb to the fingertips\n-Opponens digiti minimi: Inserts on the medial surface of metacarpal V; Flexes metacarpal V at carpometacarpal joint when little finger is moved into opposition with tip of thumb; deepens palm of hand.\n\n== Clinical significance ==\n\n=== Congenital disorders ===\n\nThe fourth and fifth metacarpal bones are commonly \"blunted\" or shortened, in pseudohypoparathyroidism and pseudopseudohypoparathyroidism.\n\nA blunted fourth metacarpal, with normal fifth metacarpal, can signify Turner syndrome.\n\nBlunted metacarpals (particularly the fourth metacarpal) are a symptom of Nevoid basal cell carcinoma syndrome.\n\n=== Fracture ===\n\nThe neck of a metacarpal is a common location for a boxer's fracture.\n\nHowever, all parts of the metacarpal bone (including head, body and base) are susceptible to fracture.\n\nFor these fractures several types of treatment exist ranging from non-operative techniques with or without immobilization to operative techniques using closed or open reduction and internal fixation (ORIF).\n\nGenerally speaking most fractures showing little or no displacement can be treated successfully without surgery.\n\nIntraarticular fracture-dislocations of the metacarpal head or base may require surgical fixation, as fragment displacement affecting the joint surface is rarely tolerated well.\n\n== Other animals ==\n\nIn four-legged animals, the metacarpals form part of the forefeet, and are frequently reduced in number, appropriate to the number of toes.\n\nIn digitigrade and unguligrade animals, the metacarpals are greatly extended and strengthened, forming an additional segment to the limb, a feature that typically enhances the animal's speed.\n\nIn both birds and bats, the metacarpals form part of the wing.\n\n== History ==\n\n=== Etymology ===\n\nThe Greek physician Galen used to refer to the metacarpus as μετακάρπιον.\n\nThe Latin form metacarpium more truly resembles its Ancient Greek predecessor μετακάρπιον than metacarpus.\n\nMeta– is Greek for beyond and carpal from Ancient Greek καρπός (karpós, “wrist”).\n\nIn anatomic Latin, adjectives like metacarpius, metacarpicus, metacarpiaeus, metacarpeus, metacarpianus and metacarpalis can be found.\n\nThe form metacarpius is more true to the later Greek form μετακάρπιος.\n\nMetacarpalis, as in ossa metacarpalia in the current official Latin nomenclature, Terminologia Anatomica is a compound consisting of Latin and Greek parts.\n\nThe usage of such hybrids in anatomic Latin is disapproved by some.\n\nhttps://en.wikipedia.org/wiki/Metacarpal_bones","fifth-metacarpal-bone":"In human anatomy, the metacarpal bones or metacarpus, form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist which forms the connection to the forearm.\n\nThe metacarpal bones are analogous to the metatarsal bones in the foot.\n\n== Structure ==\n\nThe metacarpals form a transverse arch to which the rigid row of distal carpal bones are fixed.\n\nThe peripheral metacarpals (those of the thumb and little finger) form the sides of the cup of the palmar gutter and as they are brought together they deepen this concavity.\n\nThe index metacarpal is the most firmly fixed, while the thumb metacarpal articulates with the trapezium and acts independently from the others.\n\nThe middle metacarpals are tightly united to the carpus by intrinsic interlocking bone elements at their bases.\n\nThe ring metacarpal is somewhat more mobile while the fifth metacarpal is semi-independent.Each metacarpal bone consists of a body or shaft, and two extremities: the head at the distal or digital end (near the fingers), and the base at the proximal or carpal end (close to the wrist).\n\n=== Body ===\n\nThe body (shaft) is prismoid in form, and curved, so as to be convex in the longitudinal direction behind, concave in front.\n\nIt presents three surfaces: medial, lateral, and dorsal.\n\nThe medial and lateral surfaces are concave, for the attachment of the interosseus muscles, and separated from one another by a prominent anterior ridge.\n\nThe dorsal surface presents in its distal two-thirds a smooth, triangular, flattened area which is covered in by the tendons of the extensor muscles.\n\nThis surface is bounded by two lines, which commence in small tubercles situated on either side of the digital extremity, and, passing upward, converge and meet some distance above the center of the bone and form a ridge which runs along the rest of the dorsal surface to the carpal extremity.\n\nThis ridge separates two sloping surfaces for the attachment of the interossei dorsales.\n\nTo the tubercles on the digital extremities are attached the collateral ligaments of the metacarpophalangeal joints.\n\n=== Base ===\n\nThe base (basis) or carpal extremity is of a cuboidal form, and broader behind than in front: it articulates with the carpal bones and with the adjoining metacarpal bones; its dorsal and volar surfaces are rough, for the attachment of ligaments.\n\n=== Head ===\n\nThe head (caput) or digital extremity presents an oblong surface markedly convex from before backward, less so transversely, and flattened from side to side; it articulates with the proximal phalanx.\n\nIt is broader, and extends farther upward, on the volar than on the dorsal aspect, and is longer in the antero-posterior than in the transverse diameter.\n\nOn either side of the head is a tubercle for the attachment of the collateral ligament of the metacarpophalangeal joint.\n\nThe dorsal surface, broad and flat, supports the tendons of the extensor muscles.\n\nThe volar surface is grooved in the middle line for the passage of the flexor tendons, and marked on either side by an articular eminence continuous with the terminal articular surface.\n\n=== Neck ===\n\nThe neck, or subcapital segment, is the transition zone between the body and the head.\n\n=== Articulations ===\n\nBesides the metacarpophalangeal joints, the metacarpal bones articulate by carpometacarpal joints as follows:\n\n-the first with the trapezium;\n-the second with the trapezium, trapezoid, capitate and third metacarpal;\n-the third with the capitate and second and fourth metacarpals;\n-the fourth with the capitate, hamate, and third and fifth metacarpals;\n-and the fifth with the hamate and fourth metacarpal;\n\n=== Insertions ===\n\n-Extensor Carpi Radialis Longus/Brevis: Both insert on the base of metacarpal II; Assist with wrist extension and radial flexion of the wrist\n-Extensor Carpi Ulnaris: Inserts on the base of metacarpal V; Extends and fixes wrist when digits are being flexed; assists with ulnar flexion of wrist\n-Abductor Pollicis Longus: Inserts on the trapezium and base of metacarpal I; Abducts thumb in frontal plane; extends thumb at carpometacarpal joint\n-Opponens Pollicis: Inserts on metacarpal I; flexes metacarpal I to oppose the thumb to the fingertips\n-Opponens digiti minimi: Inserts on the medial surface of metacarpal V; Flexes metacarpal V at carpometacarpal joint when little finger is moved into opposition with tip of thumb; deepens palm of hand.\n\n== Clinical significance ==\n\n=== Congenital disorders ===\n\nThe fourth and fifth metacarpal bones are commonly \"blunted\" or shortened, in pseudohypoparathyroidism and pseudopseudohypoparathyroidism.\n\nA blunted fourth metacarpal, with normal fifth metacarpal, can signify Turner syndrome.\n\nBlunted metacarpals (particularly the fourth metacarpal) are a symptom of Nevoid basal cell carcinoma syndrome.\n\n=== Fracture ===\n\nThe neck of a metacarpal is a common location for a boxer's fracture.\n\nHowever, all parts of the metacarpal bone (including head, body and base) are susceptible to fracture.\n\nFor these fractures several types of treatment exist ranging from non-operative techniques with or without immobilization to operative techniques using closed or open reduction and internal fixation (ORIF).\n\nGenerally speaking most fractures showing little or no displacement can be treated successfully without surgery.\n\nIntraarticular fracture-dislocations of the metacarpal head or base may require surgical fixation, as fragment displacement affecting the joint surface is rarely tolerated well.\n\n== Other animals ==\n\nIn four-legged animals, the metacarpals form part of the forefeet, and are frequently reduced in number, appropriate to the number of toes.\n\nIn digitigrade and unguligrade animals, the metacarpals are greatly extended and strengthened, forming an additional segment to the limb, a feature that typically enhances the animal's speed.\n\nIn both birds and bats, the metacarpals form part of the wing.\n\n== History ==\n\n=== Etymology ===\n\nThe Greek physician Galen used to refer to the metacarpus as μετακάρπιον.\n\nThe Latin form metacarpium more truly resembles its Ancient Greek predecessor μετακάρπιον than metacarpus.\n\nMeta– is Greek for beyond and carpal from Ancient Greek καρπός (karpós, “wrist”).\n\nIn anatomic Latin, adjectives like metacarpius, metacarpicus, metacarpiaeus, metacarpeus, metacarpianus and metacarpalis can be found.\n\nThe form metacarpius is more true to the later Greek form μετακάρπιος.\n\nMetacarpalis, as in ossa metacarpalia in the current official Latin nomenclature, Terminologia Anatomica is a compound consisting of Latin and Greek parts.\n\nThe usage of such hybrids in anatomic Latin is disapproved by some.\n\nhttps://en.wikipedia.org/wiki/Metacarpal_bones","capitate-bone":"The capitate bone is found in the center of the carpal bone region, colloquially known as the wrist, which is at the distal end of the radius and ulna bones.\n\nIt articulates with the third metacarpal bone (the middle finger) and forms the third carpometacarpal joint.\n\nThe capitate bone is the largest of the carpal bones in the human hand.\n\nIt presents, above, a rounded portion or head, which is received into the concavity formed by the scaphoid and lunate bones; a constricted portion or neck; and below this, the body.\n\nThe bone is also found in many other mammals, and is homologous with the \"third distal carpal\" of reptiles and amphibians.\n\n== Structure ==\n\nThe capitate is the largest carpal bone found within the hand.\n\nThe capitate is found within the distal row of carpal bones.\n\nThe capitate lies directly adjacent to the metacarpal of the ring finger on its distal surface, has the hamate on its ulnar surface and trapezoid on its radial surface, and abuts the lunate and scaphoid proximally.\n\n=== Surfaces ===\n\nThe superior surface is round, smooth, and articulates with the lunate bone.\n\nThe inferior surface is divided by two ridges into three facets, for articulation with the second, third, and fourth metacarpal bones, that for the third being the largest.\n\nThe dorsal surface is broad and rough.The palmar surface is narrow, rounded, and rough, for the attachment of ligaments and a part of the adductor pollicis muscle.\n\nThe lateral surface articulates with the lesser multangular by a small facet at its anterior inferior angle, behind which is a rough depression for the attachment of an interosseous ligament.\n\nAbove this is a deep, rough groove, forming part of the neck, and serving for the attachment of ligaments; it is bounded superiorly by a smooth, convex surface, for articulation with the scaphoid bone.\n\nThe medial surface articulates with the hamate bone by a smooth, concave, oblong facet, which occupies its posterior and superior parts; it is rough in front, for the attachment of an interosseous ligament.\n\n=== Variation ===\n\nThe capitate bone variably articulates with the metacarpal of the index finger.\n\nHowever, its normal articulation is with the middle finger.\n\n=== Development ===\n\nThe ossification of capitate starts at 1 – 5 months.\n\n== Function ==\n\nThe carpal bones function as a unit to provide a bony superstructure for the hand. : 708  They allow movements of the wrist from side to side (medial to lateral) as well as up and down (anterior to posterior).\n\nHarris wrote in the British Medical Journal in 1944 that \"the strength of construction of the hand in a man is concentrated in the radius, thumb, and index and middle fingers.\"\n\nTherefore, the capitate is larger to support the strength and stress that the middle finger undergoes.\n\n== Clinical significance ==\n\nA capitate fracture accounts for 1.3% of all wrist fractures.\n\nIsolated fractures of the capitate comprise only 0.3% and are often non-displace.\n\nThis is since the capitate is at the centre of the carpal region and is therefore quite well protected.\n\nCapitate fractures occur together with fractures of another carpal bone, the scaphoid.\n\nVarious mechanisms for fractures of the capitate have been postulated.\n\nAdler et al. described three mechanisms—the first is direct trauma to the dorsal surface of the bone, the second is fall on the palm with the wrist in forced extension and the third is fall on the forcefully flexed hand; the second being the most frequent and the third rarest.\n\nIn the case of an acute capitate fracture where there is x-ray evidence of excellent alignment of the fracture fragments, the attending doctor will immobilise the wrist in a plaster or lightweight wrist brace.\n\nOnce the cast has been removed the patient begins physiotherapy to regain the range of movement of the wrist joint and strength in the muscles involved.\n\nIf x-rays show that the capitate fracture fragments are out of alignment, surgery is indicated.\n\nA surgeon can use small compression screws or K-wires to unite the two pieces of bone.\n\nThe headless compression screw has advantage over the K-wire as it provides compression across the fracture site and allows early motion.\n\nIt may be the case that the ligament between the сapitate and the scaphoid bone is also injured; if so, this would be repaired at the same time.\n\nBecause the capitate has a poor blood supply there are sometimes complications with the healing process.\n\nThis may manifest itself as a diffuse ache in the wrist upon activity, and can persist for many months.\n\nThis is due to a breakdown of the capitate caused by the lack of blood supply and healing (avascular necrosis).\n\nNonunion has been reported as the most common complication; 19.6% to 56% in isolated capitate fractures.\n\nEarly diagnosis is key to preventing this.\n\n== Etymology ==\n\nThe etymology derives from the Latin Latin: capitātus, \"having a head,\" from Latin: capit-, meaning \"head.\"\n\nhttps://en.wikipedia.org/wiki/Capitate_bone","hamate-bone":"The hamate bone (from Latin hamatus, \"hooked\"), or unciform bone (from Latin uncus, \"hook\") is a bone in the human wrist readily distinguishable by its wedge shape and a hook-like process (\"hamulus\") projecting from its palmar surface.\n\n== Structure ==\n\nThe hamate is an irregularly shaped carpal bone found within the hand.\n\nThe hamate is found within the distal row of carpal bones, and abuts the metacarpals of the little finger and ring finger.\n\nAdjacent to the hamate on the ulnar side, and slightly above it, is the pisiform bone.\n\nAdjacent on the radial side is the capitate, and proximal is the lunate bone.\n\n=== Surfaces ===\n\nThe hamate bone has six surfaces:\n\nThe superior, the apex of the wedge, is narrow, convex, smooth, and articulates with the lunate.\n\nThe inferior articulates with the fourth and fifth metacarpal bones, by concave facets which are separated by a ridge.\n\nThe dorsal is triangular and rough for ligamentous attachment.\n\nThe palmar presents, at its lower and ulnar side, a curved, hook-like process, the hamulus, directed forward and laterally.\n\nThe medial articulates with the triangular bone by an oblong facet, cut obliquely from above, downward and medialward.\n\nThe lateral articulates with the capitate by its upper and posterior part, the remaining portion being rough, for the attachment of ligaments.\n\n=== Hook ===\n\nThe hook of hamate (Latin: hamulus) is found at the proximal, ulnar side of the hamate bone.\n\nThe hook is a curved, hook-like process that projects 1–2 mm distally and radially.\n\nThe ulnar nerve hooks around the hook of hamate as it crosses towards the medial side of hand.\n\nThe hook forms the ulnar border of the carpal tunnel, and the radial border for Guyon's canal.\n\nNumerous structures attach to it, including ligaments from the pisiform, the transverse carpal ligament, and the tendon of Flexor carpi ulnaris.\n\nIts medial surface to the flexor digiti minimi brevis and opponens digiti minimi; its lateral side is grooved for the passage of the flexor tendons into the palm of the hand.\n\n=== Development ===\n\nThe ossification of the hamate starts between 1 and 12 months.\n\nThe hamate does not fully ossify until about the 15th year of life.\n\n=== In animals ===\n\nThe bone is also found in many other mammals, and is homologous with the \"fourth distal carpal\" of reptiles and amphibians.\n\n== Function ==\n\nThe carpal bones function as a unit to provide a bony superstructure for the hand.: 708\n\n== Clinical significance ==\n\nThe hamate bone is the bone most commonly fractured when a golfer hits the ground hard with a golf club on the downswing or a hockey player hits the ice with a slap shot.\n\nThe fracture is usually a hairline fracture, commonly missed on normal X-rays.\n\nSymptoms are pain aggravated by gripping, tenderness over the hamate and symptoms of irritation of the ulnar nerve.\n\nThis is characterized by numbness and weakness of the pinkie finger with partial involvement of the ring finger as well, the \"ulnar 1½ fingers\".\n\nThe hook of hamate is particularly prone to fracture-related complications such as non-union due to its tenuous blood supply.\n\nIt is also a common injury in baseball players.\n\nSeveral professional baseball players have had the bone removed during the course of their careers.\n\nThis condition has been called \"Wilson's Wrist\".\n\nThe calcification of the unciform bone is seen on X-rays during puberty and is sometimes used in orthodontics to determine if an adolescent patient is suitable for orthognathic intervention (i.e. before or at their growth spurt).\n\n== Etymology ==\n\nThe etymology derives from the Latin hamatus \"hooked,\" from hamus which means \"hook\".\n\nhttps://en.wikipedia.org/wiki/Hamate_bone","lunate-bone":"The lunate bone (semilunar bone) is a carpal bone in the human hand.\n\nIt is distinguished by its deep concavity and crescentic outline.\n\nIt is situated in the center of the proximal row carpal bones, which lie between the ulna and radius and the hand.\n\nThe lunate carpal bone is situated between the lateral scaphoid bone and medial triquetral bone.\n\n== Structure ==\n\nThe lunate is a crescent-shaped carpal bone found within the hand.\n\nThe lunate is found within the proximal row of carpal bones.\n\nProximally, it abuts the radius.\n\nLaterally, it articulates with the scaphoid, medially with the triquetral, and distally with the capitate.\n\nThe lunate also articulates on its distal and medial surface with the hamate bone.: 708 The lunate is stabilised by a medial ligament to the scaphoid and a lateral ligament to the triquetrum.\n\nLigaments between the radius and carpal bone also stabilise the position of the lunate, as does its position in the lunate fossa of the radius.\n\n=== Bone ===\n\nThe proximal surface of the lunate bone is smooth and convex, articulating with the radius.\n\nThe lateral surface is flat and narrow, with a crescentic facet for articulation with the scaphoid.\n\nThe medial surface possesses a smooth and quadrilateral facet for articulation with the triquetral.\n\nThe palmar surface is rough, as is the dorsal surface.\n\nThe dorsal surface is broad and rounded.\n\nThe distal surface of the bone is deep and concave.\n\n=== Blood supply ===\n\nThe lunate receives its blood supply from dorsal and palmar branches.\n\n=== Variation ===\n\nThe lunate has a variable shape.\n\nAbout one-third of lunate bones do not possess a medial facet, meaning they do not articulate with the hamate bone.\n\nAdditionally, in about 20% of people, blood supply may arise from palmar vessels alone.\n\n=== Ossification ===\n\nThe ossification of the lunate bone commences between 18 months and 4 years and 3 months.\n\n== Function ==\n\nThe carpal bones function as a unit to provide a bony superstructure for the hand.: 708  As a proximal carpal bone, the lunate is also involved in movement of the wrist.\n\n== Clinical relevance ==\n\nThe lunate bone is the most frequently dislocated carpal bone.\n\nCarpal coalition\nKienbock's disease\nTeisen classification\n\n== Etymology ==\n\nThe name of the lunate bone derives from the \"crescent-shaped\" (Latin: lunatus), from Latin luna (\"moon\"), from the bone's resemblance to a crescent moon.\n\nIn amphibians and reptiles, the bone is instead referred to as the intermedium, because of its position between the other two proximal carpals.\n\nhttps://en.wikipedia.org/wiki/Lunate_bone","pisiform-bone":"The pisiform bone ( or ), also spelled pisiforme (from the Latin pisifomis, pea-shaped), is a small knobbly, sesamoid bone that is found in the wrist.\n\nIt forms the ulnar border of the carpal tunnel.\n\n== Structure ==\n\nThe pisiform is a sesamoid bone, with no covering membrane of periosteum.\n\nIt is the last carpal bone to ossify.\n\nThe pisiform bone is a small bone found in the proximal row of the wrist (carpus).\n\nIt is situated where the ulna joins the wrist, within the tendon of the flexor carpi ulnaris muscle.\n\nIt only has one side that acts as a joint, articulating with the triquetral bone.\n\nIt is on a plane anterior to the other carpal bones and is spheroidal in form.\nThe pisiform bone has four surfaces:\n\nThe dorsal surface is smooth and oval, and articulates with the triquetral: this facet approaches the superior, but not the inferior border of the bone.\n\nThe palmar surface is rounded and rough, and gives attachment to the transverse carpal ligament, the flexor carpi ulnaris and the abductor digiti quinti.\n\nThe lateral surface is rough, and concave.\n\nThe medial surface' is rough and usually convex.\n\n== Etymology ==\n\nThe etymology derives from the Latin pīsum which means \"pea\" ultimately derived from the Greek \"pison\" (pea).\n\n== Function ==\n\nThe pisiform bone is most recognizable as an unassuming palmar projection forming the heel of your hand.\n\nThe pisiform bone, along with the hamulus of the hamate, defines the medial boundary of the carpal tunnel because the pisiform body acts as one of the four attachments points of the flexor retinaculum.\n\nIt also acts as an attachment site for tendons of the abductor digiti minimi and for the flexor carpi ulnaris - the tendon in which it develops.\n\nThe pisiform is the only carpal bone with insertions and attachments for the abductor digiti minimi and the flexor carpi ulnaris.\n\nIt is suggested that due to the pisiform's surprisingly large range of movement along its articulation surface with the triquetral bone (about 1 cm of movement is allowed), contraction of the flexor carpi ulnaris is necessary for the pisiform to remain stable enough for the abductor digiti minimi to function effectively.\n\nIn clinical studies, the pisiform has been removed as treatment for osteoarthritis in the pisotriquetral joint.\n\nWhile some studies came to the conclusion that the pisiform \"contributes to the stability of the ulnar column of the wrist\", others suggested that while excision slightly impairs the range of motion of the wrist (especially wrist extension), the forces generated within the wrist are not significantly impacted.\n\nSubjects in the latter study did report impaired function after excision when performing heavy lifting and weightbearing activities, but this is suggested to be subjective considering that they did not have to change occupation or their level of activity as a result of the excision.\n\n== Development ==\n\nCompared with other non-human primates, humans have a short pisiform bone.\n\nThis dramatic size difference is suggested to be the outcome of a lost growth plate in hominins some time between Australopithecus afarensis, who has been shown to have an elongated and ape-like pisiform, and Homo neanderthalensis, who is suggested to have a pisiform resembling the modern human condition.\n\nIt is suggested that the first signs of human pisiform ossification, observed between the ages of 7 and 12, corresponds to the period of secondary pisiform ossification in apes.\n\nThis can point to a couple different changes in development: either this growth plate loss in humans is also accompanied by a developmental shift in the timing of pisiform formation, or it is the primary center that fails to form in humans and as a result our pisiform is homologous to the epiphysis of other mammalian pisiforms.\n\nStudies looking at the effect of Hox gene knockouts on the formation of the pisiform in mice have suggested that the modification of Hoxa11 or Hoxd11 genes, or the downstream targets they affect, could have acted as the mechanism for the reduction we see in the human pisiform condition.\n\n== Evolution ==\n\nThere are several hypotheses that seek to explain why we see pisiform reduction during the course of hominin evolution.\n\nSome suggest that the reduction of the pisiform allowed for ulnar deviation and that allowed for greater extension in the human wrist which increased our capacity for throwing.\n\nScholars with this point of view would believe that these anatomical changes would improve the action of clubbing in our hominin ancestors.\nOthers suggest that the pisiform's link with Hoxa11 and Hoxd11 could tie its developmental history to that of the forearm, whose length is determined by Hox gene expression.\n\nWithin the context of this hypothesis, because modern forearm proportions are not seen until Homo erectus at 1.5 million years ago, it is possible that pisiform reduction would have also occurred around this time.\n\nAlternatively, the same group suggests that the reduction could be a reflection of independent selection associated with the production and use of stone tools, but changes in pisiform morphology have yet to be studied in relation to their effect on wrist function.\n\n== Other animals ==\n\nAll other tetrapods have a pisiform, being the most common sesamoid.\n\nIn mammals and non-human primates, the pisiform is an enlarged and elongated bone that articulates with the distal ulna.\n\nIn some taxa, the pisiform even articulates with the hammate or radius.\n\nIn these non-human taxa, the pisiform develops from two ossification centers that are divided by a palmar epiphyseal plate.\n\nBecause in other mammals, the bone does not follow a typical sesamoid development pattern and can be seen articulating with more than one bone, the pisiform is not a true sesamoid bone.\n\nhttps://en.wikipedia.org/wiki/Pisiform_bone","scaphoid-bone":"The scaphoid bone is one of the carpal bones of the wrist.\n\nIt is situated between the hand and forearm on the thumb side of the wrist (also called the lateral or radial side).\n\nIt forms the radial border of the carpal tunnel.\n\nThe scaphoid bone is the largest bone of the proximal row of wrist bones, its long axis being from above downward, lateralward, and forward.\n\nIt is approximately the size and shape of a medium cashew.\n\n== Structure ==\n\nThe scaphoid is situated between the proximal and distal rows of carpal bones.\n\nIt is located on the radial side of the wrist, and articulates with the radius, lunate, trapezoid, trapezium and capitate.: 176  Over 80% of the bone is covered in articular cartilage.\n\n=== Bone ===\n\nThe palmar surface of the scaphoid is concave, and forming a tubercle, giving attachment to the transverse carpal ligament.\n\nThe proximal surface is triangular, smooth and convex, and articulates with the radius and adjacent carpal bones, namely the lunate, capitate, trapezium and trapezoid.\n\nThe lateral surface is narrow and gives attachment to the radial collateral ligament.\n\nThe medial surface has two facets, a flattened semi-lunar facet articulating with the lunate bone, and an inferior concave facet, articulating alongside the lunate with the head of the capitate bone.The dorsal surface of the bone is narrow, with a groove running the length of the bone and allowing ligaments to attach, and the surface facing the fingers (anatomically inferior) is smooth and convex, also triangular, and divided into two parts by a slight ridge.\n\n=== Blood supply ===\n\nIt receives its blood supply primarily from lateral and distal branches of the radial artery, via palmar and dorsal branches.\n\nThese provide an \"abundant\" supply to middle and distal portions of the bone, but neglect the proximal portion, which relies on retrograde flow.: 189  The dorsal branch supplies the majority of the middle and distal portions, with the palmar branch supplying only the distal third of the bone.\n\n=== Variation ===\n\nThe dorsal blood supply, particularly of the proximal portion, is highly variable.: 189  Sometimes the fibers of the abductor pollicis brevis emerge from the tubercle.\n\n=== In animals ===\n\nIn reptiles, birds, and amphibians, this bone is instead commonly referred to as the radiale because of its articulation with the radius.\n\n== Function ==\n\nThe carpal bones function as a unit to provide a bony superstructure for the hand.: 708  The scaphoid is also involved in movement of the wrist.: 6  It, along with the lunate, articulates with the radius and ulna to form the major bones involved in movement of the wrist.\n\nThe scaphoid serves as a link between the two rows of carpal bones.\n\nWith wrist movement, the scaphoid may flex from its position in the same plane as the forearm to perpendicular.: 176–177\n\n== Clinical significance ==\n\n=== Fracture ===\n\nFractures of the scaphoid are the most common of the carpal bone injuries, because of its connections with the two rows of carpal bones.: 177 The scaphoid can be slow to heal because of the limited circulation to the bone.\n\nFractures of the scaphoid must be recognized and treated quickly, as prompt treatment by immobilization or surgical fixation increases the likelihood of the bone healing in anatomic alignment, thus avoiding mal-union or non-union.\n\nDelays may compromise healing.\n\nFailure of the fracture to heal (\"non-union\") will lead to post-traumatic osteoarthritis of the carpus.: 189  One reason for this is because of the \"tenuous\" blood supply to the proximal segment.\n\nEven rapidly immobilized fractures may require surgical treatment, including use of a headless compression screw such as the Herbert screw to bind the two halves together.\nHealing of the fracture with a non-anatomic deformity (frequently, a volar flexed \"humpback\") can also lead to post-traumatic arthritis.\n\nNon-unions can result in loss of blood supply to the proximal pole, which can result in avascular necrosis of the proximal segment.\nScaphoid fractures may be difficult to diagnose via plain x-ray, so repeat x-ray may be used at a later date, or cross-sectional imaging via MRI or CT scan.\n\n=== Other diseases ===\n\nA condition called scapholunate instability can occur when the scapholunate ligament (connecting the scaphoid to the lunate bone) and other surrounding ligaments are disrupted.\n\nIn this state, the distance between the scaphoid and lunate bones is increased.: 180 There is a rare disease of this bone called Preiser's Disease.\n\n=== Palpation ===\n\nThe scaphoid can be palpated at the base of the anatomical snuff box.\n\nIt can also be palpated in the volar (palmar) hand/wrist.\n\nIts position is the intersections of the long axes of the four fingers while in a fist, or the base of the thenar eminence.\n\nWhen palpated in this position, the bone will be felt to slide forward during radial deviation (wrist abduction) and flexion.\nClicking of the scaphoid or no anterior translation can indicate scapholunate instability.\n\n== Etymology ==\n\nThe etymology of the scaphoid bone (Greek: σκαφοειδές) is derived from the Greek skaphos, which means \"a boat,\" and the Greek eidos, which means \"kind\".\n\nThe name refers to the shape of the bone, supposedly reminiscent of a boat.\n\nIn older literature about human anatomy, the scaphoid is referred to as the navicular bone of the hand (this time from the Latin word “navis” = boat), since there is also a bone in a similar position in the foot which is called the navicular.\n\nThe medical term for the bone is the scaphoid, as the term \"navicular\" is solely reserved for the bone located in the tarsals of the human body.\n\n== References ==\n\nhttps://en.wikipedia.org/wiki/Scaphoid_bone","trapezium-bone":"== Structure ==\n\nThe trapezium is distinguished by a deep groove on its anterior surface.\n\nIt is situated at the radial side of the carpus, between the scaphoid and the first metacarpal bone (the metacarpal bone of the thumb).\n\nIt is homologous with the first distal carpal of reptiles and amphibians.\n\n=== Surfaces ===\n\nThe trapezium is an irregular-shaped carpal bone found within the hand.\n\nThe trapezium is found within the distal row of carpal bones, and is directly adjacent to the metacarpal bone of the thumb.\n\nOn its ulnar surface are found the trapezoid and scaphoid bones.\n\nThe superior surface is directed upward and medialward; medially it is smooth, and articulates with the scaphoid; laterally it is rough and continuous with the lateral surface.\n\nThe inferior surface is oval, concave from side to side, convex from before backward, so as to form a saddle-shaped surface for articulation with the base of the first metacarpal bone.\n\nThis saddle-shaped articulation is partially responsible for the thumb's opposable motion.\n\nThe dorsal surface is smooth.\nThe palmar surface is narrow and rough.\n\nAt its upper part is a deep groove, running from above obliquely downward and medialward; it transmits the tendon of the Flexor carpi radialis, and is bounded laterally by an oblique ridge.\n\nThis surface gives origin to the Opponens pollicis and to the Abductor and Flexor pollicis brevis; it also affords attachment to the transverse carpal ligament.\n\nThe lateral surface is broad and rough, for the attachment of ligaments.\n\nThe medial surface presents two facets; the upper, large and concave, articulates with the trapezoid bone; the lower, small and oval, with the base of the second metacarpal.\n\n=== Tubercle of trapezium ===\n\nThe tubercle of trapezium is a tubercle found on the anterior surface of the bone.\n\nIt is where sometimes abductor pollicis brevis muscle attaches.\n\n== Function ==\n\nThe carpal bones function as a unit to provide a bony superstructure for the hand.\n\nThe trapezium is the most radial of the bones surrounding the carpal tunnel.\n\nIt is important in thumb movement.\n\n== Clinical relevance ==\n\nThe trapezium is susceptible to arthritis at the joint with the metacarpal bone of the thumb, due to overuse.\n\n== History ==\n\nThe etymology derives from the Greek trapezion which means \"a little table\", from trapeza meaning \"table\", itself from (te)tra- \"four\" and pod- \"foot\".\n\nThe bone was first documented in 1840.\n\nhttps://en.wikipedia.org/wiki/Trapezium_(bone)","trapezoid-bone":"The trapezoid bone (lesser multangular bone) is a carpal bone in tetrapods, including humans.\n\nIt is the smallest bone in the distal row of carpal bones that give structure to the palm of the hand.\n\nIt may be known by its wedge-shaped form, the broad end of the wedge constituting the dorsal, the narrow end the palmar surface; and by its having four articular facets touching each other, and separated by sharp edges.\n\nIt is homologous with the \"second distal carpal\" of reptiles and amphibians.\n\n== Structure ==\n\nThe trapezoid is a four-sided carpal bone found within the hand.\n\nThe trapezoid is found within the distal row of carpal bones.\n\n=== Surfaces ===\n\nThe superior surface, quadrilateral, smooth, and slightly concave, articulates with the scaphoid.\n\nThe inferior surface articulates with the proximal end of the second metacarpal bone; it is convex from side to side, concave from before backward and subdivided by an elevated ridge into two unequal facets.\n\nThe dorsal and palmar surfaces are rough for the attachment of ligaments, the former being the larger of the two.\n\nThe lateral surface, convex and smooth, articulates with the trapezium.\n\nThe medial surface is concave and smooth in front, for articulation with the capitate; rough behind, for the attachment of an interosseous ligament.\n\n== Function ==\n\nThe carpal bones function as a unit to provide a bony superstructure for the hand.\n\n== Clinical Significance ==\n\nIsolated fractures of the trapezoid are rare, representing 0.4% of the total, thus being the least common of all carpal fractures.\n\nThis is due to the bone being in a fairly protected position.\n\nDistally, it forms a stable, relatively immobile joint with the second metacarpal, radially and proximally it forms strong ligaments with the trapezium and the capitate ulnarly, scaphoid respectively.\n\nHowever, injury can occur through axial force applied to the second metacarpal base.\n\nSubluxations, such as ones caused by delivering a blow, are not uncommon.\n\nDirect trauma to the bone can also cause fracture.\nDue to its rarity, standard treatment has not been established.\n\nA wide range of treatments are possible, including rest, surgery and casting.\n\n== History ==\n\nThe etymology derives from the Greek trapezion which means \"irregular quadrilateral,\" from tra- \"four\" and peza \"foot\" or \"edge.\" Literally, \"a little table\" from trapeza meaning \"table\" and -oeides \"shaped.\"\n\nhttps://en.wikipedia.org/wiki/Trapezoid_bone","triquetrum-bone":"The triquetral bone also called triquetrum, pyramidal, three-faced, and formerly cuneiform bone) is located in the wrist on the medial side of the proximal row of the carpus between the lunate and pisiform bones.\n\nIt is on the ulnar side of the hand, but does not articulate with the ulna.\n\nIt connects with the pisiform, hamate, and lunate bones.\n\nIt is the 3rd most commonly fractured carpal bone.\n\n== Structure ==\n\nThe triquetral is one of the eight carpal bones of the hand.\n\nIt is a three-faced bone found within the proximal row of carpal bones.\n\nSituated beneath the pisiform, it is one of the carpal bones that form the carpal arch, within which lies the carpal tunnel.\n\nThe triquetral bone may be distinguished by its pyramidal shape, and by an oval isolated facet for articulation with the pisiform bone.\n\nIt is situated at the upper and ulnar side of the carpus.\n\nTo facilitate its palpation in an exam, the hand must be radially deviated so that the triquetrium moves out from under the ulnar styloid process.\n\nThe triquetrum may be difficult to find, since it also lies under the pisiform.\n\n== Ossification ==\n\nThe triquetral bone ossifies between 9 months and 50 months (4 years and 2 months).\n\n=== Surfaces ===\n\nThe superior surface presents a medial, rough, non-articular portion, and a lateral convex articular portion which articulates with the triangular articular disk of the wrist.\n\nThe inferior surface, directed lateralward, is concave, sinuously curved, and smooth for articulation with the hamate.\n\nThe dorsal surface is rough for the attachment of ligaments.\nThe volar surface presents, on its medial part, an oval facet, for articulation with the pisiform; its lateral part is rough for ligamentous attachment.\n\nThe lateral surface, the base of the pyramid, is marked by a flat, quadrilateral facet, for articulation with the lunate.\n\nThe medial surface, the summit of the pyramid, is pointed and roughened, for the attachment of the ulnar collateral ligament of the wrist.\n\n=== In animals ===\n\nIn reptiles and amphibians, the bone is instead referred to as the ulnare, since (at least in the most primitive fossils) it articulates with the ulna.\n\n== Function ==\n\nThe carpal bones function as a unit to provide a bony superstructure for the hand.\n\n== Fracture ==\n\nTriquetral fractures can occur due to forceful flexion of the wrist, causing an avulsion of the dorsal aspect of the bone that is often hidden on anterior radiographs, but can be seen as a tiny bone fragment on lateral views.\n\n== Etymology ==\n\nThe etymology derives from the Latin triquetrus which means \"three-cornered.\"\n\nTherefore, it is sometimes also called the triangular bone or os triangulare.\n\nHowever, os triangulare may also refer to a nearby accessory bone.\n\nhttps://en.wikipedia.org/wiki/Triquetral_bone","axis-c2":"In anatomy, the axis (from Latin axis, \"axle\") or epistropheus, is the second cervical vertebra (C2) of the spine, immediately posterior to the atlas, upon which the head rests.\n\nThe axis' defining feature is its strong odontoid process (bony protrusion) known as the dens, which rises dorsally from the rest of the bone.\n\n== Structure ==\n\nThe body is deeper in front or in the back and is prolonged downward anteriorly to overlap the upper and front part of the third vertebra.\n\nIt presents a median longitudinal ridge in front, separating two lateral depressions for the attachment of the longus colli muscles.\n\n=== Dens ===\n\nThe dens, also called the odontoid process or the peg, are the most pronounced projecting feature of the axis.\n\nThe dens exhibit a slight constriction where it joins the main body of the vertebra.\n\nThe condition where the dens are separated from the body of the axis is called os odontoideum and may cause nerve and circulation compression syndrome.\n\nOn its anterior surface is an oval or nearly circular facet for articulation with that on the anterior arch of the atlas.\n\nOn the back of the neck, and frequently extending on to its lateral surfaces, is a shallow groove for the transverse atlantal ligament which retains the process in position.\n\nThe apex is pointed and gives attachment to the apical odontoid ligament.\n\nBelow the apex, the process is somewhat enlarged and presents on either side a rough impression for the attachment of the alar ligament; these ligaments connect the process to the occipital bone.\n\nThe internal structure of the odontoid process is more compact than that of the body.\n\nThe odontoid peg is the ascension of the atlas fused to the ascension of the axis.\n\nThe peg has an articular facet at its front and forms part of a joint with the anterior arch of the atlas.\n\nIt is a non-weight bearing joint.\n\nThe alar ligaments, together with the apical ligaments, are attached from the sloping upper edge of the odontoid peg to the margins of the foramen magnum.\n\nThe inner ligaments limit rotation of the head and are very strong.\n\nThe weak apical ligament lies in front of the upper longitudinal bone of the cruciform ligament and joins the apex of the deltoid peg to the anterior margin of the foramen magnum.\n\nIt is the fibrous remnant of the notochord.\n\n=== Other features ===\n\nThe pedicles are broad and strong, especially in the front, where they coalesce with the sides of the body and the root of the odontoid process.\n\nThey are covered above by the superior articular surfaces.\nThe laminae are thick and strong.\n\nThey play a large role in the stability of the cervical spine alongside the laminae of C7.\n\nThe vertebral foramen is large, but smaller than the atlas.\nThe transverse processes are very small, and each ends in a single tubercle.\n\nEach process is perforated by the transverse foramen, which is directed obliquely upward and laterally.\n\nThe superior articular surfaces are round, slightly convex, directed upward and laterally, and are supported on the body, pedicles, and transverse processes.\n\nThe inferior articular surfaces have the same direction as those of the other cervical vertebrae.\n\nThe superior vertebral notches are very shallow, and lie behind the articular processes.\n\nThe inferior vertebral notches lie in front of the articular processes, as in the other cervical vertebrae.\n\nThe spinous process is large, very strong, deeply channelled on its under surface, and presents a bifurcated extremity.\n\n=== Variation ===\n\nContact sports are contraindicated for individuals with anomalous dens, as any violent impact may result in a catastrophic injury.\n\nThis is because a malformed odontoid process may lead to instability between the atlas and axis (the C1 and C2 cervical vertebrae).\n\n=== Development ===\n\nThe axis is ossified from five primary and two secondary centres.\n\nThe body and vertebral arch are ossified in the same manner as the corresponding parts in the other vertebrae, viz., one centre for the body, and two for the vertebral arch.\n\nThe centres for the arch appear about the seventh or eighth week of fetal life, while the centres for the body appear in about the fourth or fifth month.\n\nThe dens, or odontoid process, consist originally of a continuation upward of the cartilaginous mass, in which the lower part of the body is formed.\n\nDuring about the sixth month of fetal life, two centres make their appearance in the base of this process: they are placed laterally, and join before birth to form a conical bilobed mass deeply cleft above; the interval between the sides of the cleft and the summit of the process is formed by a wedge-shaped piece of cartilage.\n\nThe base of the process is separated from the body by a cartilaginous disk, which gradually becomes ossified at its circumference, but remains cartilaginous in its center until advanced age.\n\nIn this cartilage, rudiments of the lower epiphyseal lamella of the atlas and the upper epiphyseal lamella of the axis may sometimes be found.\n\nThe apex of the odontoid process has a separate centre that appears in the second and joins about the twelfth year; this is the upper epiphyseal lamella of the atlas.\n\nIn addition to these, there is a secondary centre for a thin epiphyseal plate on the undersurface of the body of the bone.\n\n== Clinical significance ==\n\n=== Fracture of dens ===\n\nFractures of the dens, not to be confused with Hangman's fractures, are classified into three categories according to the Anderson Alonso system:\n\nType I Fracture - Extends through the tip of the dens.\n\nThis type is usually stable.\nType II Fracture - Extends through the base of the dens.\n\nIt is the most commonly encountered fracture for this region of the axis.\n\nThis type is unstable and has a high rate of non-union.\nType III Fracture - Extends through the vertebral body of the axis.\n\nThis type can be stable or unstable and may require surgery.\n\nhttps://en.wikipedia.org/wiki/Axis_(anatomy)","scapula":"In anatomy, the scapula (plural scapulae or scapulas), also known as the shoulder bone, shoulder blade, wing bone, speal bone or blade bone, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone).\n\nLike their connected bones, the scapulae are paired, with each scapula on either side of the body being roughly a mirror image of the other.\n\nThe name derives from the Classical Latin word for trowel or small shovel, which it was thought to resemble.\n\nIn compound terms, the prefix omo- is used for the shoulder blade in medical terminology.\n\nThis prefix is derived from ὦμος (ōmos), the Ancient Greek word for shoulder, and is cognate with the Latin (h)umerus, which in Latin signifies either the shoulder or the upper arm bone.\n\nThe scapula forms the back of the shoulder girdle. In humans, it is a flat bone, roughly triangular in shape, placed on a posterolateral aspect of the thoracic cage.\n\n== Structure ==\n\nThe scapula is a wide, flat bone lying on the thoracic wall that provides an attachment for three groups of muscles: intrinsic, extrinsic, and stabilising and rotating muscles.\n\nThe intrinsic muscles of the scapula include the muscles of the rotator cuff—the subscapularis, teres minor, supraspinatus, and infraspinatus.\n\nThese muscles attach to the surface of the scapula and are responsible for the internal and external rotation of the shoulder joint, along with humeral abduction.\n\nThe extrinsic muscles include the biceps, triceps, and deltoid muscles and attach to the coracoid process and supraglenoid tubercle of the scapula, infraglenoid tubercle of the scapula, and spine of the scapula.\n\nThese muscles are responsible for several actions of the glenohumeral joint.\n\nThe third group, which is mainly responsible for stabilization and rotation of the scapula, consists of the trapezius, serratus anterior, levator scapulae, and rhomboid muscles.\n\nThese attach to the medial, superior, and inferior borders of the scapula.\n\nThe head, processes, and the thickened parts of the bone contain cancellous tissue; the rest consists of a thin layer of compact tissue.\n\nThe central part of the supraspinatus fossa and the upper part of the infraspinatous fossa, but especially the former, are usually so thin in humans as to be semitransparent; occasionally the bone is found wanting in this situation, and the adjacent muscles are separated only by fibrous tissue.\n\nThe scapula has two surfaces, three borders, three angles, and three processes.\n\n=== Surfaces ===\n\n===Front or subscapular fossa===\n\nThe front of the scapula (also known as the costal or ventral surface) has a broad concavity called the subscapular fossa, to which the subscapularis muscle attaches.\n\nThe medial two-thirds of the fossa have 3 longitudinal oblique ridges, and another thick ridge adjoins the lateral border; they run outward and upward.\n\nThe ridges give attachment to the tendinous insertions, and the surfaces between them to the fleshy fibers, of the subscapularis muscle.\n\nThe lateral third of the fossa is smooth and covered by the fibers of this muscle.\n\nAt the upper part of the fossa is a transverse depression, where the bone appears to be bent on itself along a line at right angles to and passing through the center of the glenoid cavity, forming a considerable angle, called the subscapular angle; this gives greater strength to the body of the bone by its arched form, while the summit of the arch serves to support the spine and acromion.\n\nThe costal surface superior of the scapula is the origin of 1st digitation for the serratus anterior origin.\n\n===Back===\n\nThe back of the scapula (also called the dorsal or posterior surface) is arched from above downward, and is subdivided into two unequal parts by the spine of the scapula.\n\nThe portion above the spine is called the supraspinous fossa, and that below it the infraspinous fossa.\n\nThe two fossae are connected by the spinoglenoid notch, situated lateral to the root of the spine.\n\nThe supraspinous fossa, above the spine of scapula, is concave, smooth, and broader at its vertebral than at its humeral end; its medial two-thirds give origin to the Supraspinatus.\n\nAt its lateral surface resides the spinoglenoid fossa which is situated by the medial margin of the glenoid.\n\nThe spinoglenoid fossa houses the suprascpular canal which forms a connecting passage between the suprascapular notch and the spinoglenoid notch conveying the suprascapular nerve and vessels.\n\nThe infraspinous fossa is much larger than the preceding; toward its vertebral margin a shallow concavity is seen at its upper part; its center presents a prominent convexity, while near the axillary border is a deep groove which runs from the upper toward the lower part.\n\nThe medial two-thirds of the fossa give origin to the Infraspinatus; the lateral third is covered by this muscle.\n\nThere is a ridge on the outer part of the back of the scapula. This runs from the lower part of the glenoid cavity, downward and backward to the vertebral border, about 2.5 cm above the inferior angle.\n\nAttached to the ridge is a fibrous septum, which separates the infraspinatus muscle from the Teres major and Teres minor muscles.\n\nThe upper two-thirds of the surface between the ridge and the axillary border is narrow, and is crossed near its center by a groove for the scapular circumflex vessels; the Teres minor attaches here.\n\nThe broad and narrow portions above alluded to are separated by an oblique line, which runs from the axillary border, downward and backward, to meet the elevated ridge:\n to it is attached a fibrous septum which separates the Teres muscles from each other.\n\nIts lower third presents a broader, somewhat triangular surface, the inferior angle of the scapula, which gives origin to the Teres major, and over which the Latissimus dorsi glides; frequently the latter muscle takes origin by a few fibers from this part.\n\n===Side===\n\nThe acromion forms the summit of the shoulder, and is a large, somewhat triangular or oblong process, flattened from behind forward, projecting at first laterally, and then curving forward and upward, so as to overhang the glenoid cavity.\n\n=== Angles ===\n\nThere are 3 angles:\n\n -The superior angle of the scapula or medial angle, is covered by the trapezius muscle.\n\nThis angle is formed by the junction of the superior and medial borders of the scapula.\n\nThe superior angle is located at the approximate level of the second thoracic vertebra.\n\nThe superior angle of the scapula is thin, smooth, rounded, and inclined somewhat lateralward, and gives attachment to a few fibers of the levator scapulae muscle.\n\n -The inferior angle of the scapula is the lowest part of the scapula and is covered by the latissimus dorsi muscle.\n\nIt moves forwards round the chest when the arm is abducted.\n\nThe inferior angle is formed by the union of the medial and lateral borders of the scapula.\n\nIt is thick and rough and its posterior or back surface affords attachment to the teres major and often to a few fibers of the latissimus dorsi.\n\nThe anatomical plane that passes vertically through the inferior angle is named the scapular line.\n\n -The lateral angle of the scapula or glenoid angle also known as the head of the scapula is the thickest part of the scapula.\n\nIt is broad and bears the glenoid cavity on its articular surface which is directed forward, laterally and slightly upwards, and articulates with the head of the humerus.\n\nThe inferior angle is broader below than above and its vertical diameter is the longest.\n\nThe surface is covered with cartilage in the fresh state; and its margins, slightly raised, give attachment to a fibrocartilaginous structure, the glenoidal labrum, which deepens the cavity.\n\nAt its apex is a slight elevation, the supraglenoid tuberosity, to which the long head of the biceps brachii is attached.\n\nThe anatomic neck of the scapula is the slightly constricted portion which surrounds the head and is more distinct below and behind than above and in front.\n\nThe surgical neck of the scapula passes directly medial to the base of the coracoid process.\n\n=== Borders ===\n\nThere are three borders of the scapula:\n\n -The superior border is the shortest and thinnest; it is concave, and extends from the superior angle to the base of the coracoid process.\n\nIt is referred to as the cranial border in animals.\n\nAt its lateral part is a deep, semicircular notch, the scapular notch, formed partly by the base of the coracoid process.\n\nThis notch is converted into a foramen by the superior transverse scapular ligament, and serves for the passage of the suprascapular nerve; sometimes the ligament is ossified.\n\nThe adjacent part of the superior border affords attachment to the omohyoideus.\n\n -The axillary border (or \"lateral border\") is the thickest of the three.\n\nIt begins above at the lower margin of the glenoid cavity, and inclines obliquely downward and backward to the inferior angle.\n\nIt is referred to as the caudal border in animals.\n\nIt begins above at the lower margin of the glenoid cavity, and inclines obliquely downward and backward to the inferior angle.\n\nImmediately below the glenoid cavity is a rough impression, the infraglenoid tuberosity, about 2.5 cm (1 in). in length, which gives origin to the long head of the triceps brachii; in front of this is a longitudinal groove, which extends as far as the lower third of this border, and affords origin to part of the subscapularis.\n\nThe inferior third is thin and sharp, and serves for the attachment of a few fibers of the teres major behind, and of the subscapularis in front.\n\n -The medial border (also called the vertebral border or medial margin) is the longest of the three borders, and extends from the superior angle to the inferior angle.\n\nIn animals it is referred to as the dorsal border.Four muscles attach to the medial border. Serratus anterior has a long attachment on the anterior lip.\n\nThree muscles insert along the posterior lip:\n the levator scapulae (uppermost), rhomboid minor (middle), and to the rhomboid major (lower middle).\n\n=== Development ===\n\nThe scapula is ossified from 7 or more centers: one for the body, two for the coracoid process, two for the acromion, one for the vertebral border, and one for the inferior angle.\n\nOssification of the body begins about the second month of fetal life, by an irregular quadrilateral plate of bone forming, immediately behind the glenoid cavity.\n\nThis plate extends to form the chief part of the bone, the scapular spine growing up from its dorsal surface about the third month.\n\nOssification starts as membranous ossification before birth. After birth, the cartilaginous components would undergo endochondral ossification.\n\nThe larger part of the scapula undergoes membranous ossification. Some of the outer parts of the scapula are cartilaginous at birth, and would therefore undergo endochondral ossification.\n\nAt birth, a large part of the scapula is osseous, but the glenoid cavity, the coracoid process, the acromion, the vertebral border and the inferior angle are cartilaginous.\n\nFrom the 15th to the 18th month after birth, ossification takes place in the middle of the coracoid process, which as a rule becomes joined with the rest of the bone about the 15th year.\n\nBetween the 14th and 20th years, the remaining parts ossify in quick succession, and usually in the following order: first, in the root of the coracoid process, in the form of a broad scale; secondly, near the base of the acromion; thirdly, in the inferior angle and contiguous part of the vertebral border; fourthly, near the outer end of the acromion; fifthly, in the vertebral border.\n\nThe base of the acromion is formed by an extension from the spine; the two nuclei of the acromion unite, and then join with the extension from the spine.\n\nThe upper third of the glenoid cavity is ossified from a separate center (sub coracoid), which appears between the 10th and 11th years and joins between the 16th and the 18th years.\n\nFurther, an epiphysial plate appears for the lower part of the glenoid cavity, and the tip of the coracoid process frequently has a separate nucleus.\n\nThese various epiphyses are joined to the bone by the 25th year.\n\nFailure of bony union between the acromion and spine sometimes occurs (see os acromiale), the junction being effected by fibrous tissue, or by an imperfect articulation; in some cases of supposed fracture of the acromion with ligamentous union, it is probable that the detached segment was never united to the rest of the bone.\n\n\"In terms of comparative anatomy the human scapula represents two bones that have become fused together; the (dorsal) scapula proper and the (ventral) coracoid.\n\nThe epiphyseal line across the glenoid cavity is the line of fusion. They are the counterparts of the ilium and ischium of the pelvic girdle.\"\n\n== Function ==\n\nThe following muscles attach to the scapula:\n\n=== Movements ===\n\nMovements of the scapula are brought about by the scapular muscles.\n\nThe scapula can perform six actions:\n\nElevation: upper trapezius and levator scapulae\nDepression: lower trapezius\nRetraction (adduction): rhomboids and middle trapezius\nProtraction (abduction): serratus anterior\nUpward rotation: upper and lower trapezius, serratus anterior\nDownward rotation: rhomboids, Levator Scapulae, and Pec Minor\n\n== Clinical significance ==\n\n=== Scapular fractures ===\n\nBecause of its sturdy structure and protected location, fractures of the scapula are uncommon. When they do occur, they are an indication that severe chest trauma has occurred.\nScapular fractures involving the neck of the scapula have two patterns.\n\nOne (rare) type of fracture is through the anatomical neck of the scapula. The other more common type of fracture is through the surgical neck of the scapula.\n\nThe surgical neck exits medial to the coracoid process.An abnormally protruding inferior angle of the scapula is known as a winged scapula and can be caused by paralysis of the serratus anterior muscle.\n\nIn this condition the sides of the scapula nearest the spine are positioned outward and backward.\n\nThe appearance of the upper back is said to be wing-like.\n\nIn addition, any condition causing weakness of the serratus anterior muscle may cause scapular \"winging\".\n\n=== Impingement syndrome ===\n\nThe scapula plays an important role in shoulder impingement syndrome.Abnormal scapular function is called scapular dyskinesis.\n\nOne action the scapula performs during a throwing or serving motion is elevation of the acromion process in order to avoid impingement of the rotator cuff tendons.\n\nIf the scapula fails to properly elevate the acromion, impingement may occur during the cocking and acceleration phase of an overhead activity.\n\nThe two muscles most commonly inhibited during this first part of an overhead motion are the serratus anterior and the lower trapezius.\n\nThese two muscles act as a force couple within the glenohumeral joint to properly elevate the acromion process, and if a muscle imbalance exists, shoulder impingement may develop.\n\n=== Etymology ===\n\n==== Scapula/Scapulae ====\n\nThe name scapula as synonym of shoulder blade is of Latin origin.\n\nIt is commonly used in medical English and is part of the current official Latin nomenclature, Terminologia Anatomica.\n\nIn classical Latin scapula is only used in its plural scapulae.\n\nAlthough some sources mention that scapulae is used to refer during Roman antiquity to the shoulders or to the shoulder blades, others persist in that the Romans used scapulae only to refer to the back, in contrast to the pectus, the Latin name for breast or chest.\n\n==== Os latum scapularum and related ====\n\nThe Roman encyclopedist Aulus Cornelius Celsus who lived during the beginning of the era, also used scapulae to refer to the back. He used os latum scapularum to refer to the shoulder blade.\n\nThis expressions can be translated as broad (Latin: latum) bone (Latin: os) of the back (Latin: scapularum).\n\nA similar expression in ancient Greek can be seen in the writings of the Greek philosopher Aristoteles and in the writings of the Greek physician Galen.\n\nThey both use the name ὠμοπλάτη to refer to the shoulder blade.\n\nThis compound consists of ancient Greek ὦμος, shoulder and πλάτη, blade or flat or broad object. Πλάτη in its plural πλάται without ὦμο- was also used in ancient Greek to refer to the shoulder blades.\n\nIn anatomic Latin, ὠμοπλάτη is Latinized as omoplata.The Latin word umerus is related to ὦμος.\n\nThe Romans referred with umerus to what is now commonly known in English as the following 3 bones: humerus or the upper bone of the arm, the clavicle or the collarbone and the scapula or the shoulder blade.\n\nThe spelling humerus is actually incorrect in classical Latin.Those three bones were referred to as the ossa (Latin: bones) umeri (Latin: of the umerus).\n\nUmerus was also used to refer specifically to the shoulder.\n\nThis mirrors the use of ὦμος in ancient Greek as that could refer to the shoulder with the upper arm or to the shoulder alone.\nSince Celsus, the os umeri could refer specifically to the upper bone of the arm.\n\nThe 16th century anatomist Andreas Vesalius used humerus to refer to the clavicle.\n\nBesides the aforementioned os latum scapularum, Celsus used os latum umeri to refer to the shoulder blade. Similarly, Laurentius used the expression latitudo umeri (Latitudo = breadth, width ) to refer to the shoulder blade.\n\n==== Pala ====\n\nThe Roman physician Caelius Aurelianus (5th century) used pala to refer to the shoulder blade.\n\nThe name pala is normally used to refer to a spade in Latin and was therefore probably used by Caelius Aurelianus to describe the shoulder blade, as both exhibit a flat curvature.\n\n==== Spathula/Σπάθη ====\n\nDuring the Middle Ages spathula was used to refer to the shoulder blade.\n\nSpathula is a diminutive of spatha, with the latter originally meaning broad, two-edged sword without a point, broad, flat, wooden instrument for stirring any liquid, a spattle, spatula or spathe of the palm tree and its diminutive used in classical and late Latin for referring to a leg of pork or a little palmbranch.\n\nThe English word spatula is actually derived from Latin spatula, an orthographic variant of spathula. Oddly enough, classical Latin non-diminutive spatha can be translated as English spatula, while its Latin diminutive spatula is not translated as English spatula.\n\nLatin spatha is derived from ancient Greek σπάθη. Therefore, the form spathula is more akin to its origin than spatula.\n\nAncient Greek σπάθη has a similar meaning as Latin spatha, as any broad blade, and can also refer to a spatula or to the broad blade of a sword., but also to the blade of an oar.\n\nThe aforementioned πλάται for shoulder blades was also used for blades of an oar. Concordantly σπάθη was also used to refer to the shoulder blade.\n\nThe English word spade, as well as the Dutch equivalent spade is cognate with σπάθη. Please notice, that the aforementioned term pala as applied by Roman physician Caelius Aurelianus, also means spade.\n\nPala is probably related to the Latin verb pandere, to spread out, and to extend.\n\nThis verb is thought to be derived from an earlier form spandere, with the root spa-. Σπάθη is actually derived from the similar root spē(i), that means to extend.\n\nIt seems that os latum scapularum, ὠμοπλάτη, πλάται, pala, spathula and σπάθη all refer to the same aspect of the shoulder blade, i.e. being a flat, broad blade, with the latter three words etymological related to each other.\n\n==== Scapula after the Middle Ages ====\n\nAfter the Middle Ages, the name scapula for shoulder blade became dominant.\n\nThe word scapula can etymologically be explained by its relatedness to the ancient Greek verb σκάπτειν, to dig.\n\nThis relatedness gives rise to several possible explanations.\nFirst, the noun σκάπετος, trench, and the scapula related noun σκαφη, are both derived from this verb and might connect scapula to the notion of concavity. The name scapula then may be related to the concavity of the bone that exists due to its spine. The designation scapulae is additionally seen as synonym of ancient Greek συνωμία, the space between the shoulder blades, that is obviously concave. Συνωμία consists of σύν, together with, and ὦμος, shoulder.Second, scapula, due to its relatedness to σκάπτειν might have originally meant shovel. Similarly to the Latin use of pala (spade), a resemblance might be felt between the shape of a shovel and the shoulder blade. Alternatively, the shoulder blade might have been used originally for digging and shoveling.\n\n==== Shoulder blade ====\nShoulder blade is colloquial name for this bone. Shoulder is cognate to German and Dutch equivalents Schulter and schouder. There are a few etymological explanations for shoulder. The first supposes that shoulder can be literally translated as that which shields or protects, as its possibly related to Icelandic skioldr, shield and skyla, to cover, to defend. The second explanation relates shoulder to ancient Greek σκέλος, leg. The latter spots the possible root skel-, meaning to bend, to curve. The third explanation links the root skel- to to cleave. This meaning could refer to the shape of the shoulder blade.\n\n== In other animals ==\n\nIn fish, the scapular blade is a structure attached to the upper surface of the articulation of the pectoral fin, and is accompanied by a similar coracoid plate on the lower surface.\n\nAlthough sturdy in cartilagenous fish, both plates are generally small in most other fish, and may be partially cartilagenous, or consist of multiple bony elements.\n\nIn the early tetrapods, these two structures respectively became the scapula and a bone referred to as the procoracoid (commonly called simply the \"coracoid\", but not homologous with the mammalian structure of that name).\n\nIn amphibians and reptiles (birds included), these two bones are distinct, but together form a single structure bearing many of the muscle attachments for the forelimb.\n\nIn such animals, the scapula is usually a relatively simple plate, lacking the projections and spine that it possesses in mammals.\n\nHowever, the detailed structure of these bones varies considerably in living groups.\n\nFor example, in frogs, the procoracoid bones may be braced together at the animal's underside to absorb the shock of landing, while in turtles, the combined structure forms a Y-shape in order to allow the scapula to retain a connection to the clavicle (which is part of the shell).\n\nIn birds, the procoracoids help to brace the wing against the top of the sternum.In the fossil therapsids, a third bone, the true coracoid, formed just behind the procoracoid.\n\nThe resulting three-boned structure is still seen in modern monotremes, but in all other living mammals, the procoracoid has disappeared, and the coracoid bone has fused with the scapula, to become the coracoid process.\n\nThese changes are associated with the upright gait of mammals, compared with the more sprawling limb arrangement of reptiles and amphibians; the muscles formerly attached to the procoracoid are no longer required.\n\nThe altered musculature is also responsible for the alteration in the shape of the rest of the scapula; the forward margin of the original bone became the spine and acromion, from which the main shelf of the shoulder blade arises as a new structure.\n\n=== In dinosaurs ===\n\nIn dinosaurs the main bones of the pectoral girdle were the scapula (shoulder blade) and the coracoid, both of which directly articulated with the clavicle.\n\nThe clavicle was present in saurischian dinosaurs but largely absent in ornithischian dinosaurs.\n\nThe place on the scapula where it articulated with the humerus (upper bone of the forelimb) is called the glenoid.\n\nThe scapula serves as the attachment site for a dinosaur's back and forelimb muscles.\n\nhttps://en.wikipedia.org/wiki/Scapula","radius":"The radius or radial bone is one of the two large bones of the forearm, the other being the ulna.\n\nIt extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna.\n\nThe ulna is usually slightly longer than the radius, but the radius is thicker.\n\nTherefore the radius is considered to be the larger of the two.\n\nIt is a long bone, prism-shaped and slightly curved longitudinally.\n\nThe radius is part of two joints: the elbow and the wrist.\n\nAt the elbow, it joins with the capitulum of the humerus, and in a separate region, with the ulna at the radial notch. At the wrist, the radius forms a joint with the ulna bone.\n\nThe corresponding bone in the lower leg is the fibula.\n\n== Structure ==\n\nThe long narrow medullary cavity is enclosed in a strong wall of compact bone.\n\nIt is thickest along the interosseous border and thinnest at the extremities, same over the cup-shaped articular surface (fovea) of the head.\n\nThe trabeculae of the spongy tissue are somewhat arched at the upper end and pass upward from the compact layer of the shaft to the fovea capituli (the humerus's cup-shaped articulatory notch); they are crossed by others parallel to the surface of the fovea.\n\nThe arrangement at the lower end is somewhat similar.\n\nIt is missing in radial aplasia.\nThe radius has a body and two extremities.\n\nThe upper extremity of the radius consists of a somewhat cylindrical head articulating with the ulna and the humerus, a neck, and a radial tuberosity.\n\nThe body of the radius is self-explanatory, and the lower extremity of the radius is roughly quadrilateral in shape, with articular surfaces for the ulna, scaphoid and lunate bones.\n\nThe distal end of the radius forms two palpable points, radially the styloid process and Lister's tubercle on the ulnar side.\n\nAlong with the proximal and distal radioulnar articulations, an interosseous membrane originates medially along the length of the body of the radius to attach the radius to the ulna.\n\n=== Near the wrist ===\n\nThe distal end of the radius is large and of quadrilateral form.\n\n===Joint surfaces===\n\nIt is provided with two articular surfaces – one below, for the carpus, and another at the medial side, for the ulna.\n\nThe carpal articular surface is triangular, concave, smooth, and divided by a slight antero-posterior ridge into two parts.\n\nOf these, the lateral, triangular, articulates with the scaphoid bone; the medial, quadrilateral, with the lunate bone.\n\nThe articular surface for the ulna is called the ulnar notch (sigmoid cavity) of the radius; it is narrow, concave, smooth, and articulates with the head of the ulna.\n\nThese two articular surfaces are separated by a prominent ridge, to which the base of the triangular articular disk is attached; this disk separates the wrist-joint from the distal radioulnar articulation.\n\nOther surfacesThis end of the bone has three non-articular surfaces – volar, dorsal, and lateral.\n\nThe volar surface, rough and irregular, affords attachment to the volar radiocarpal ligament.\nThe dorsal surface is convex, affords attachment to the dorsal radiocarpal ligament, and is marked by three grooves. Enumerated from the lateral side:\n\nThe first groove is broad, but shallow, and subdivided into two by a slight ridge: the lateral of these two, transmits the tendon of the extensor carpi radialis longus muscle; the medial, the tendon of the extensor carpi radialis brevis muscle.\n\nThe second is deep but narrow, and bounded laterally by a sharply defined ridge; it is directed obliquely from above downward and lateralward, and transmits the tendon of the extensor pollicis longus muscle.\n\nThe third is broad, for the passage of the tendons of the extensor indicis proprius and extensor digitorum communis.\n\nThe lateral surface is prolonged obliquely downward into a strong, conical projection, the styloid process, which gives attachment by its base to the tendon of the brachioradialis, and by its apex to the radial collateral ligament of wrist joint.\n\nThe lateral surface of this process is marked by a flat groove, for the tendons of the abductor pollicis longus muscle and extensor pollicis brevis muscle.\n\n=== Body ===\n\nThe body of the radius (or shaft of radius) is prismoid in form, narrower above than below, and slightly curved, so as to be convex lateralward.\n\nIt presents three borders and three surfaces.\n\n===Borders===\n\nThe volar border (margo volaris; anterior border; palmar;) extends from the lower part of the tuberosity above to the anterior part of the base of the styloid process below, and separates the volar from the lateral surface.\n\nIts upper third is prominent, and from its oblique direction has received the name of the oblique line of the radius; it gives origin to the flexor digitorum superficialis muscle (also flexor digitorum sublimis) and flexor pollicis longus muscle; the surface above the line gives insertion to part of the supinator muscle.\n\nThe middle third of the volar border is indistinct and rounded.\n\nThe lower fourth is prominent, and gives insertion to the pronator quadratus muscle, and attachment to the dorsal carpal ligament; it ends in a small tubercle, into which the tendon of the brachioradialis muscle is inserted.\n\nThe dorsal border (margo dorsalis; posterior border) begins above at the back of the neck, and ends below at the posterior part of the base of the styloid process; it separates the posterior from the lateral surface. is indistinct above and below, but well-marked in the middle third of the bone.\n\nThe interosseous border (internal border; crista interossea; interosseous crest;) begins above, at the back part of the tuberosity, and its upper part is rounded and indistinct; it becomes sharp and prominent as it descends, and at its lower part divides into two ridges which are continued to the anterior and posterior margins of the ulnar notch.\n\nTo the posterior of the two ridges the lower part of the interosseous membrane is attached, while the triangular surface between the ridges gives insertion to part of the pronator quadratus muscle.\n\nThis crest separates the volar from the dorsal surface, and gives attachment to the interosseous membrane.\n\nThe connection between the two bones is actually a joint referred to as a syndesmosis joint.\n\n===Surfaces===\n\nThe volar surface (facies volaris; anterior surface) is concave in its upper three-fourths, and gives origin to the flexor pollicis longus muscle; it is broad and flat in its lower fourth, and affords insertion to the Pronator quadratus.\n\nA prominent ridge limits the insertion of the Pronator quadratus below, and between this and the inferior border is a triangular rough surface for the attachment of the volar radiocarpal ligament.\n\nAt the junction of the upper and middle thirds of the volar surface is the nutrient foramen, which is directed obliquely upward.\n\nThe dorsal surface (facies dorsalis; posterior surface) is convex, and smooth in the upper third of its extent, and covered by the Supinator.\n\nIts middle third is broad, slightly concave, and gives origin to the Abductor pollicis longus above, and the extensor pollicis brevis muscle below.\n\nIts lower third is broad, convex, and covered by the tendons of the muscles which subsequently run in the grooves on the lower end of the bone.\n\nThe lateral surface (facies lateralis; external surface) is convex throughout its entire extent and is known as the convexity of the radius, curving outwards to be convex at the side.\n\nIts upper third gives insertion to the supinator muscle. About its center is a rough ridge, for the insertion of the pronator teres muscle.\n\nIts lower part is narrow, and covered by the tendons of the abductor pollicis longus muscle and extensor pollicis brevis muscle.\n\n=== Near the elbow ===\n\nThe upper extremity of the radius (or proximal extremity) presents a head, neck, and tuberosity.\n\nThe radial head has a cylindrical form, and on its upper surface is a shallow cup or fovea for articulation with the capitulum (or capitellum) of the humerus.\n\nThe circumference of the head is smooth; it is broad medially where it articulates with the radial notch of the ulna, narrow in the rest of its extent, which is embraced by the annular ligament.\n\nThe deepest point in the fovea is not axi-symmetric with the long axis of the radius, creating a cam effect during pronation and supination.\n\nThe head is supported on a round, smooth, and constricted portion called the neck, on the back of which is a slight ridge for the insertion of part of the supinator muscle.\n\nBeneath the neck, on the medial side, is an eminence, the radial tuberosity; its surface is divided into a posterior, rough portion, for the insertion of the tendon of the biceps brachii muscle, and an anterior, smooth portion, on which a bursa is interposed between the tendon and the bone.\n\n=== Development ===\n\nThe radius is ossified from three centers: one for the body, and one for each extremity.\n\nThat for the body makes its appearance near the center of the bone, during the eighth week of fetal life.\n\nOssification commences in the lower end between 9 and 26 months of age.\n\nThe ossification center for the upper end appears by the fifth year.\n\nThe upper epiphysis fuses with the body at the age of seventeen or eighteen years, the lower about the age of twenty.\n\nAn additional center sometimes found in the radial tuberosity, appears about the fourteenth or fifteenth year.\n\n== Function ==\n\n=== Muscle attachments ===\n\nThe biceps muscle inserts on the radial tuberosity of the upper extremity of the bone.\n\nThe upper third of the body of the bone attaches to the supinator, the flexor digitorum superficialis, and the flexor pollicis longus muscles.\n\nThe middle third of the body attaches to the extensor ossis metacarpi pollicis, extensor primi internodii pollicis, and the pronator teres muscles.\n\nThe lower quarter of the body attaches to the pronator quadratus muscle and the tendon of the supinator longus.\n\n== Clinical significance ==\n\nRadial aplasia refers to the congenital absence or shortness of the radius.\n\n=== Fracture ===\n\nSpecific fracture types of the radius include:\n\n-Proximal radius fracture.\n\n-A fracture within the capsule of the elbow joint results in the fat pad sign or \"sail sign\" which is a displacement of the fat pad at the elbow.\n\n-Essex-Lopresti fracture – a fracture of the radial head with concomitant dislocation of the distal radio-ulnar joint with disruption of the interosseous membrane.\n\n-Radial shaft fracture\n\n-Distal radius fracture\n\n-Galeazzi fracture – a fracture of the radius with dislocation of the distal radioulnar joint\n\n-Colles' fracture – a distal fracture of the radius with dorsal (posterior) displacement of the wrist and hand\n\n-Smith's fracture – a distal fracture of the radius with volar (ventral) displacement of the wrist and hand\n\n-Barton's fracture – an intra-articular fracture of the distal radius with dislocation of the radiocarpal joint.\n\n== History ==\n\nThe word radius is Latin for \"ray\".\n\nIn the context of the radius bone, a ray can be thought of rotating around an axis line extending diagonally from center of capitulum to the center of distal ulna.\n\nWhile the ulna is the major contributor to the elbow joint, the radius primarily contributes to the wrist joint.\n\nThe radius is named so because the radius (bone) acts like the radius (of a circle).\n\nIt rotates around the ulna and the far end (where it joins to the bones of the hand), known as the styloid process of the radius, is the distance from the ulna (center of the circle) to the edge of the radius (the circle).\n\nThe ulna acts as the center point to the circle because when the arm is rotated the ulna does not move.\n\n== Animals ==\n\nIn four-legged animals, the radius is the main load-bearing bone of the lower forelimb.\n\nIts structure is similar in most terrestrial tetrapods, but it may be fused with the ulna in some mammals (such as horses) and reduced or modified in animals with flippers or vestigial forelimbs.\n\nhttps://en.wikipedia.org/wiki/Radius_(bone)","ulna":"The ulna (pl. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm.\n\nIt runs parallel to the radius, the other long bone in the forearm.\n\nThe ulna is usually slightly longer than the radius, but the radius is thicker.\n\nTherefore, the radius is considered to be the larger of the two.\n\n== Structure ==\n\nThe ulna is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. It is broader close to the elbow, and narrows as it approaches the wrist.\n\nClose to the elbow, the ulna has a bony process, the olecranon process, a hook-like structure that fits into the olecranon fossa of the humerus.\n\nThis prevents hyperextension and forms a hinge joint with the trochlea of the humerus.\n\nThere is also a radial notch for the head of the radius, and the ulnar tuberosity to which muscles attach.\n\nClose to the wrist, the ulna has a styloid process.\n\n=== Near the elbow ===\n\nNear the elbow, the ulna has two curved processes, the olecranon and the coronoid process; and two concave, articular cavities, the semilunar and radial notches.\n\nThe olecranon is a large, thick, curved eminence, situated at the upper and back part of the ulna.\n\nIt is bent forward at the summit so as to present a prominent lip which is received into the olecranon fossa of the humerus in extension of the forearm.\n\nIts base is contracted where it joins the body and the narrowest part of the upper end of the ulna.\n\nIts posterior surface, directed backward, is triangular, smooth, subcutaneous, and covered by a bursa.\n\nIts superior surface is of quadrilateral form, marked behind by a rough impression for the insertion of the triceps brachii; and in front, near the margin, by a slight transverse groove for the attachment of part of the posterior ligament of the elbow joint.\n\nIts anterior surface is smooth, concave, and forms the upper part of the semilunar notch.\n\nIts borders present continuations of the groove on the margin of the superior surface; they serve for the attachment of ligaments: the back part of the ulnar collateral ligament medially, and the posterior ligament laterally.\n\nFrom the medial border a part of the flexor carpi ulnaris arises; while to the lateral border the anconeus is attached.\n\nThe coronoid process is a triangular eminence projecting forward from the upper and front part of the ulna.\n\nIts base is continuous with the body of the bone, and of considerable strength.\n\nIts apex is pointed, slightly curved upward, and in flexion of the forearm is received into the coronoid fossa of the humerus.\n\nIts upper surface is smooth, concave, and forms the lower part of the semilunar notch.\n\nIts antero-inferior surface is concave, and marked by a rough impression for the insertion of the brachialis.\n\nAt the junction of this surface with the front of the body is a rough eminence, the tuberosity of the ulna, which gives insertion to a part of the brachialis; to the lateral border of this tuberosity the oblique cord is attached.\n\nIts lateral surface presents a narrow, oblong, articular depression, the radial notch.\n\nIts medial surface, by its prominent, free margin, serves for the attachment of part of the ulnar collateral ligament.\n\nAt the front part of this surface is a small rounded eminence for the origin of one head of the flexor digitorum superficialis; behind the eminence is a depression for part of the origin of the flexor digitorum profundus; descending from the eminence is a ridge which gives origin to one head of the pronator teres.\n\nFrequently, the flexor pollicis longus arises from the lower part of the coronoid process by a rounded bundle of muscular fibers.\n\nThe semilunar notch is a large depression, formed by the olecranon and the coronoid process, and serving as articulation with the trochlea of the humerus.\n\nAbout the middle of either side of this notch is an indentation, which contracts it somewhat, and indicates the junction of the olecranon and the coronoid process.\n\nThe notch is concave from above downward, and divided into a medial and a lateral portion by a smooth ridge running from the summit of the olecranon to the tip of the coronoid process. The medial portion is the larger, and is slightly concave transversely; the lateral is convex above, slightly concave below.\n\nThe radial notch is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the radius.\n\nIt is concave from before backward, and its prominent extremities serve for the attachment of the annular ligament.\n\n=== Body ===\n\nThe body of the ulna at its upper part is prismatic in form, and curved so as to be convex behind and lateralward; its central part is straight; its lower part is rounded, smooth, and bent a little lateralward.\n\nIt tapers gradually from above downward, and has three borders and three surfaces.\n\n===Borders===\n\nThe volar border (margo volaris; anterior border) begins above at the prominent medial angle of the coronoid process, and ends below in front of the styloid process.\n\nIts upper part, well-defined, and its middle portion, smooth and rounded, give origin to the flexor digitorum profundus; its lower fourth serves for the origin of the pronator quadratus.\n\nThis border separates the volar from the medial surface.\n\nThe dorsal border (margo dorsalis; posterior border) begins above at the apex of the triangular subcutaneous surface at the back part of the olecranon, and ends below at the back of the styloid process; it is well-marked in the upper three-fourths, and gives attachment to an aponeurosis which affords a common origin to the flexor carpi ulnaris, the extensor carpi ulnaris, and the flexor digitorum profundus; its lower fourth is smooth and rounded.\n\nThis border separates the medial from the dorsal surface.\n\nThe interosseous crest (crista interossea; external or interosseous border) begins above by the union of two lines, which converge from the extremities of the radial notch and enclose between them a triangular space for the origin of part of the Supinator; it ends below at the head of the ulna.\n\nIts upper part is sharp, its lower fourth smooth and rounded.\n\nThis crest gives attachment to the interosseous membrane, and separates the volar from the dorsal surface.\n\n===Surfaces===\n\nThe volar surface (facies volaris; anterior surface), much broader above than below, is concave in its upper three-fourths, and gives origin to the flexor digitorum profundus; its lower fourth, also concave, is covered by the pronator quadratus. The lower fourth is separated from the remaining portion by a ridge, directed obliquely downward and medialward, which marks the extent of origin of the pronator quadratus.\n\nAt the junction of the upper with the middle third of the bone is the nutrient canal, directed obliquely upward.\n\nThe dorsal surface (facies dorsalis; posterior surface) directed backward and lateralward, is broad and concave above; convex and somewhat narrower in the middle; narrow, smooth, and rounded below.\n\nOn its upper part is an oblique ridge, which runs from the dorsal end of the radial notch, downward to the dorsal border; the triangular surface above this ridge receives the insertion of the Anconæus, while the upper part of the ridge affords attachment to the supinator.\n\nBelow this the surface is subdivided by a longitudinal ridge, sometimes called the perpendicular line, into two parts: the medial part is smooth, and covered by the extensor carpi ulnaris; the lateral portion, wider and rougher, gives origin from above downward to the Supinator, the abductor pollicis longus, the extensor pollicis longus, and the extensor indicis proprius.\n\nThe medial surface (facies medialis; internal surface) is broad and concave above, narrow and convex below.\n\nIts upper three-fourths give origin to the Flexor digitorum profundus; its lower fourth is subcutaneous.\n\n=== Near the wrist ===\n\nThe head of ulna presents an articular surface, part of which, of an oval or semilunar form, is directed downward, and articulates with the upper surface of the triangular articular disc which separates it from the wrist-joint; the remaining portion, directed lateralward, is narrow, convex, and received into the ulnar notch of the radius.\n\nNear the wrist, the ulnar, with two eminences; the lateral and larger is a rounded, articular eminence, termed the head of the ulna; the medial, narrower and more projecting, is a non-articular eminence, the styloid process.\n\nThe head presents an articular surface, part of which, of an oval or semilunar form, is directed downward, and articulates with the upper surface of the triangular articular disk which separates it from the wrist-joint; the remaining portion, directed lateralward, is narrow, convex, and received into the ulnar notch of the radius.\n\nThe styloid process projects from the medial and back part of the bone; it descends a little lower than the head, and its rounded end affords attachment to the ulnar collateral ligament of the wrist-joint.\n\nThe head is separated from the styloid process by a depression for the attachment of the apex of the triangular articular disk, and behind, by a shallow groove for the tendon of the extensor carpi ulnaris.\n\n=== Microanatomy ===\n\nThe ulna is a long bone.\n\nThe long, narrow medullary cavity of the ulna is enclosed in a strong wall of cortical tissue which is thickest along the interosseous border and dorsal surface. At the extremities the compact layer thins.\n\nThe compact layer is continued onto the back of the olecranon as a plate of close spongy bone with lamellæ parallel.\n\nFrom the inner surface of this plate and the compact layer below it trabeculæ arch forward toward the olecranon and coronoid and cross other trabeculæ, passing backward over the medullary cavity from the upper part of the shaft below the coronoid. Below the coronoid process there is a small area of compact bone from which trabeculæ curve upward to end obliquely to the surface of the semilunar notch which is coated with a thin layer of compact bone.\n\nThe trabeculæ at the lower end have a more longitudinal direction.\n\n=== Development ===\n\nThe ulna is ossified from three centers: one each for the body, the wrist end, and the elbow end, near the top of the olecranon.\n\nOssification begins near the middle of the body of the ulna, about the eighth week of fetal life, and soon extends through the greater part of the bone.\n\nAt birth, the ends are cartilaginous.\n\nAbout the fourth year or so, a center appears in the middle of the head, and soon extends into the ulnar styloid process.\n\nAbout the tenth year, a center appears in the olecranon near its extremity, the chief part of this process being formed by an upward extension of the body.\n\nThe upper epiphysis joins the body about the sixteenth, the lower about the twentieth year.\n\n== Function ==\n\n=== Joints ===\n\nThe ulna forms part of the wrist joint and elbow joints.\n\nSpecifically, the ulna joins (articulates) with:\n\n-trochlea of the humerus, at the right side elbow as a hinge joint with semilunar trochlear notch of the ulna.\n-the radius, near the elbow as a pivot joint, this allows the radius to cross over the ulna in pronation.\n-the distal radius, where it fits into the ulnar notch.\n-the radius along its length via the interosseous membrane that forms a syndesmosis joint\n\n=== Muscle attachments ===\n\n== Clinical significance ==\n\n=== Fractures ===\n\nSpecific types of ulna fracture include:\n\n-Monteggia fracture - a fracture of the proximal third of the ulna with the dislocation of the head of the radius\n-Hume fracture - a fracture of the olecranon with an associated anterior dislocation of the radial headConservative management is possible for ulnar fractures when they are located in the distal two-thirds, only involve the shaft, with no shortening, less than 10° angulation and less than 50% displacement.\n\nIn such cases, a cast should be applied that goes above the elbow.\n\n== Other animals ==\n\nIn four-legged animals, the radius is the main load-bearing bone of the lower forelimb, and the ulna is important primarily for muscular attachment.\n\nIn many mammals, the ulna is partially or wholly fused with the radius, and may therefore not exist as a separate bone.\n\nHowever, even in extreme cases of fusion, such as in horses, the olecranon process is still present, albeit as a projection from the upper radius.\n\nhttps://en.wikipedia.org/wiki/Ulna","femur":"The femur (, pl. femurs or femora ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates.\n\nThe head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with the tibia (shinbone) and patella (kneecap), forming the knee joint.\n\nBy most measures the two (left and right) femurs are the strongest bones of the body, and in humans, the largest and thickest.\n\n== Structure ==\n\nThe femur is the only bone in the upper leg. The two femurs converge medially toward the knees, where they articulate with the proximal ends of the tibiae.\n\nThe angle of convergence of the femora is a major factor in determining the femoral-tibial angle.\n\nHuman females have thicker pelvic bones, causing their femora to converge more than in males.\n\nIn the condition genu valgum (knock knee) the femurs converge so much that the knees touch one another.\n\nThe opposite extreme is genu varum (bow-leggedness).\n\nIn the general population of people without either genu valgum or genu varum, the femoral-tibial angle is about 175 degrees.\n\nThe femur is the largest and thickest bone in the human body.\n\nBy some measures, it is also the strongest bone in the human body.\n\nThis depends on the type of measurement taken to calculate strength.\n\nSome strength tests show the temporal bone in the skull to be the strongest bone.\n\nThe femur length on average is 26.74% of a person's height, a ratio found in both men and women and most ethnic groups with only restricted variation, and is useful in anthropology because it offers a basis for a reasonable estimate of a subject's height from an incomplete skeleton.\n\nThe femur is categorised as a long bone and comprises a diaphysis (shaft or body) and two epiphyses (extremities) that articulate with adjacent bones in the hip and knee.\n\n=== Upper part ===\n\nThe upper or proximal extremity (close to the torso) contains the head, neck, the two trochanters and adjacent structures.\n\nThe upper extremity is the shortest femoral extremity, the lower extremity is the thickest femoral extremity.\n\nThe head of the femur, which articulates with the acetabulum of the pelvic bone, comprises two-thirds of a sphere.\n\nIt has a small groove, or fovea, connected through the round ligament to the sides of the acetabular notch.\n\nThe head of the femur is connected to the shaft through the neck or collum.\n\nThe neck is 4–5 cm. long and the diameter is smallest front to back and compressed at its middle.\n\nThe collum forms an angle with the shaft in about 130 degrees. This angle is highly variant.\n\nIn the infant it is about 150 degrees and in old age reduced to 120 degrees on average. An abnormal increase in the angle is known as coxa valga and an abnormal reduction is called coxa vara.\n\nBoth the head and neck of the femur is vastly embedded in the hip musculature and can not be directly palpated.\n\nIn skinny people with the thigh laterally rotated, the head of the femur can be felt deep as a resistance profound (deep) for the femoral artery.\n\nThe transition area between the head and neck is quite rough due to attachment of muscles and the hip joint capsule.\n\nHere the two trochanters, greater and lesser trochanter, are found.\n\nThe greater trochanter is almost box-shaped and is the most lateral prominent of the femur.\n\nThe highest point of the greater trochanter is located higher than the collum and reaches the midpoint of the hip joint. The greater trochanter can easily be felt.\n\nThe trochanteric fossa is a deep depression bounded posteriorly by the intertrochanteric crest on the medial surface of the greater trochanter.\n\nThe lesser trochanter is a cone-shaped extension of the lowest part of the femur neck.\n\nThe two trochanters are joined by the intertrochanteric crest on the back side and by the intertrochanteric line on the front.\n\nA slight ridge is sometimes seen commencing about the middle of the intertrochanteric crest, and reaching vertically downward for about 5 cm. along the back part of the body: it is called the linea quadrata (or quadrate line).\n\nAbout the junction of the upper one-third and lower two-thirds on the intertrochanteric crest is the quadrate tubercle located.\n\nThe size of the tubercle varies and it is not always located on the intertrochanteric crest and that also adjacent areas can be part of the quadrate tubercle, such as the posterior surface of the greater trochanter or the neck of the femur.\n\nIn a small anatomical study it was shown that the epiphyseal line passes directly through the quadrate tubercle.\n\n=== Body ===\n\nThe body of the femur (or shaft) is large, thick and almost cylindrical in form.\n\nIt is a little broader above than in the center, broadest and somewhat flattened from before backward below.\n\nIt is slightly arched, so as to be convex in front, and concave behind, where it is strengthened by a prominent longitudinal ridge, the linea aspera which diverges proximally and distal as the medial and lateral ridge.\n\nProximally the lateral ridge of the linea aspera becomes the gluteal tuberosity while the medial ridge continues as the pectineal line.\n\nBesides the linea aspera the shaft has two other bordes; a lateral and medial border.\n\nThese three bordes separates the shaft into three surfaces: One anterior, one medial and one lateral.\n\nDue to the vast musculature of the thigh the shaft can not be palpated.\n\nThe third trochanter is a bony projection occasionally present on the proximal femur near the superior border of the gluteal tuberosity.\n\nWhen present, it is oblong, rounded, or conical in shape and sometimes continuous with the gluteal ridge.\n\nA structure of minor importance in humans, the incidence of the third trochanter varies from 17–72% between ethnic groups and it is frequently reported as more common in females than in males.\n\n=== Lower part ===\n\nThe lower extremity of the femur (or distal extremity) is the thickest femoral extremity, the upper extremity is the shortest femoral extremity.\n\nIt is somewhat cuboid in form, but its transverse diameter is greater than its antero-posterior (front to back).\n\nIt consists of two oblong eminences known as the condyles.\n\nAnteriorly, the condyles are slightly prominent and are separated by a smooth shallow articular depression called the patellar surface.\n\nPosteriorly, they project considerably and a deep notch, the Intercondylar fossa of femur, is present between them.\n\nThe lateral condyle is the more prominent and is the broader both in its antero-posterior and transverse diameters.\n\nThe medial condyle is the longer and, when the femur is held with its body perpendicular, projects to a lower level.\n\nWhen, however, the femur is in its natural oblique position the lower surfaces of the two condyles lie practically in the same horizontal plane.\n\nThe condyles are not quite parallel with one another; the long axis of the lateral is almost directly antero-posterior, but that of the medial runs backward and medialward.\n\nTheir opposed surfaces are small, rough, and concave, and form the walls of the intercondyloid fossa.\n\nThis fossa is limited above by a ridge, the intercondyloid line, and below by the central part of the posterior margin of the patellar surface.\n\nThe posterior cruciate ligament of the knee joint is attached to the lower and front part of the medial wall of the fossa and the anterior cruciate ligament to an impression on the upper and back part of its lateral wall.\n\nThe articular surface of the lower end of the femur occupies the anterior, inferior, and posterior surfaces of the condyles.\n\nIts front part is named the patellar surface and articulates with the patella; it presents a median groove which extends downward to the intercondyloid fossa and two convexities, the lateral of which is broader, more prominent, and extends farther upward than the medial.\n\nEach condyle is surmounted by an elevation, the epicondyle. The medial epicondyle is a large convex eminence to which the tibial collateral ligament of the knee-joint is attached.\n\nAt its upper part is the adductor tubercle and behind it is a rough impression which gives origin to the medial head of the gastrocnemius.\n\nThe lateral epicondyle which is smaller and less prominent than the medial, gives attachment to the fibular collateral ligament of the knee-joint.\n\n=== Development ===\n\nThe femur develops from the limb buds as a result of interactions between the ectoderm and the underlying mesoderm, formation occurs roughly around the fourth week of development.\n\nBy the sixth week of development, the first hyaline cartilage model of the femur is formed by chondrocytes.\n\nEndochondral ossification begins by the end of the embryonic period and primary ossification centers are present in all long bones of the limbs, including the femur, by the 12th week of development.\n\nThe hindlimb development lags behind forelimb development by 1–2 days.\n\n== Function ==\n\nAs the femur is the only bone in the thigh, it serves as an attachment point for all the muscles that exert their force over the hip and knee joints.\n\nSome biarticular muscles – which cross two joints, like the gastrocnemius and plantaris muscles – also originate from the femur.\n\nIn all, 23 individual muscles either originate from or insert onto the femur.\n\nIn cross-section, the thigh is divided up into three separate fascial compartments divided by fascia, each containing muscles.\n\nThese compartments use the femur as an axis, and are separated by tough connective tissue membranes (or septa).\n\nEach of these compartments has its own blood and nerve supply, and contains a different group of muscles.\n\nThese compartments are named the anterior, medial and posterior fascial compartments.\n\n=== Fractures ===\n\nA femoral fracture that involves the femoral head, femoral neck or the shaft of the femur immediately below the lesser trochanter may be classified as a hip fracture, especially when associated with osteoporosis.\n\nFemur fractures can be managed in a pre-hospital setting with the use of a traction splint.\n\n== Diversity among animals ==\n\nIn primitive tetrapods, the main points of muscle attachment along the femur are the internal trochanter and third trochanter, and a ridge along the ventral surface of the femoral shaft referred to as the adductor crest.\n\nThe neck of the femur is generally minimal or absent in the most primitive forms, reflecting a simple attachment to the acetabulum.\n\nThe greater trochanter was present in the extinct archosaurs, as well as in modern birds and mammals, being associated with the loss of the primitive sprawling gait.\n\nThe lesser trochanter is a unique development of mammals, which lack both the internal and fourth trochanters.\n\nThe adductor crest is also often absent in mammals or alternatively reduced to a series of creases along the surface of the bone.\n\nStructures analogous to the third trochanter are present in mammals, including some primates.\n\nSome species of whales, snakes, and other non-walking vertebrates have vestigial femurs.\n\nIn some snakes the protruding end of a pelvic spur, a vestigial pelvis and femur remnant which is not connected to the rest of the skeleton, plays a role in mating.\n\nThis role in mating is hypothesized to have possibly occurred in Basilosauridae, an extinct family of whales with well-defined femurs, lower legs and feet.\n\nOccasionally, the genes that code for longer extremities cause a modern whale to develop miniature legs (atavism).\n\nOne of the earliest known vertebrates to have a femur is the eusthenopteron, a prehistoric lobe-finned fish from the Late Devonian period.\n\n=== Invertebrates ===\n\nIn invertebrate zoology the name femur appears in arthropodology.\n\nThe usage is not homologous with that of vertebrate anatomy; the term \"femur\" simply has been adopted by analogy and refers, where applicable, to the most proximal of (usually) the two longest jointed segments of the legs of the arthropoda.\n\nThe two basal segments preceding the femur are the coxa and trochanter.\n\nThis convention is not followed in carcinology but it applies in arachnology and entomology.\n\nIn myriapodology another segment, the prefemur, connects the trochanter and femur.\n\nhttps://en.wikipedia.org/wiki/Femur","hip-bone":"The hip bone (os coxae, innominate bone, pelvic bone or coxal bone) is a large flat bone, constricted in the center and expanded above and below.\n\nIn some vertebrates (including humans before puberty) it is composed of three parts: the ilium, ischium, and the pubis.\n\nThe two hip bones join at the pubic symphysis and together with the sacrum and coccyx (the pelvic part of the spine) comprise the skeletal component of the pelvis – the pelvic girdle which surrounds the pelvic cavity.\n\nThey are connected to the sacrum, which is part of the axial skeleton, at the sacroiliac joint. Each hip bone is connected to the corresponding femur (thigh bone) (forming the primary connection between the bones of the lower limb and the axial skeleton) through the large ball and socket joint of the hip.\n\n== Structure ==\n\nThe hip bone is formed by three parts: the ilium, ischium, and pubis.\n\nAt birth, these three components are separated by hyaline cartilage.\n\nThey join each other in a Y-shaped portion of cartilage in the acetabulum.\n\nBy the end of puberty the three regions will have fused together, and by the age 25 they will have ossified.\n\nThe two hip bones join each other at the pubic symphysis. Together with the sacrum and coccyx, the hip bones form the pelvis.\n\n=== Ilium ===\n\nIlium (plural ilia) is the uppermost and largest region. It makes up two fifths of the acetabulum.\n\nIt is divisible into two parts: the body and the ala or wing of ilium; the separation is indicated on the top surface by a curved line, the arcuate line, and on the external surface by the margin of the acetabulum.\n\nThe body of ilium forms the sacroiliac joint with the sacrum.\n\nThe edge of the wing of ilium forms the S-shaped iliac crest which is easily located through the skin.\n\nThe iliac crest shows clear marks of the attachment of the three abdominal wall muscles.\n\n=== Ischium ===\n\nThe ischium forms the lower and back part of the hip bone and is located below the ilium and behind the pubis.\n\nThe ischium is the strongest of the three regions that form the hip bone.\n\nIt is divisible into three portions: the body, the superior ramus, and the inferior ramus.\n\nThe body forms approximately one-third of the acetabulum.\n\nThe ischium forms a large swelling, the tuberosity of the ischium, also referred to colloquially as the \"sit bone\".\n\nWhen sitting, the weight is frequently placed upon the ischial tuberosity.\n\nThe gluteus maximus covers it in the upright posture, but leaves it free in the seated position.\n\n=== Pubis ===\n\nThe pubic region or pubis is the ventral and anterior of the three parts forming the hip bone.\n\nIt is divisible into a body, a superior ramus, and an inferior ramus.\n\nThe body forms one-fifth of the acetabulum.\n\nThe body forms the wide, strong, medial and flat portion of the pubic bone which unites with the other pubic bone in the pubic symphysis.\n\nThe fibrocartilaginous pad which lies between the symphysial surfaces of the coxal bones, that secures the pubic symphysis, is called the interpubic disc.\n\n=== Pelvic brim ===\n\nThe pelvic brim is a continuous oval ridge of bone that runs along the pubic symphysis, pubic crests, arcuate lines, sacral alae, and sacral promontory.\n\n=== False pelvis, pelvic inlet, and ramus ===\n\nThe false pelvis is that portion superior to the pelvic brim; it is bounded by the alae of the ilia laterally and the sacral promontory and lumbar vertebrae posteriorly.\n\nThe true pelvis is the region inferior to the pelvic brim that is almost entirely surrounded by bone.\n\nThe pelvic inlet is the opening delineated by the pelvic brim.\n\nThe widest dimension of the pelvic inlet is from left to right, that is, along the frontal plane.\n\nThe pelvic outlet is the margin of the true pelvis.\n\nIt is bounded anteriorly by the pubic arch, laterally by the ischia, and posteriorly by the sacrum and coccyx.\n\nThe superior pubic ramus is a part of the pubic bone which forms a portion of the obturator foramen.\n\nIt extends from the body to the median plane where it articulates with its fellow of the opposite side.\n\nIt is conveniently described in two portions: a medial flattened part and a narrow lateral prismoid portion.\n\nThe inferior pubic ramus is thin and flat.\n\nIt passes laterally and downward from the medial end of the superior ramus.\n\nIt becomes narrower as it descends and joins with the inferior ramus of the ischium below the obturator foramen.\n\n== Development and sexual dimorphism ==\n\nThe hip bone is ossified from eight centers: three primary, one each for the ilium, ischium, and pubis, and five secondary, one each for the iliac crest, the anterior inferior spine (said to occur more frequently in the male than in the female), the tuberosity of the ischium, the pubic symphysis (more frequent in the female than in the male), and one or more for the Y-shaped piece at the bottom of the acetabulum.\n\nThe centers appear in the following order: in the lower part of the ilium, immediately above the greater sciatic notch, about the eighth or ninth week of fetal life; in the superior ramus of the ischium, about the third month; in the superior ramus of the pubis, between the fourth and fifth months.\n\nAt birth, the three primary centers are quite separate, the crest, the bottom of the acetabulum, the ischial tuberosity, and the inferior rami of the ischium and pubis being still cartilaginous.\n\nBy the seventh or eighth year, the inferior rami of the pubis and ischium are almost completely united by bone.\n\nAbout the thirteenth or fourteenth year, the three primary centers have extended their growth into the bottom of the acetabulum, and are there separated from each other by a Y-shaped portion of cartilage, which now presents traces of ossification, often by two or more centers.\n\nOne of these, the os acetabuli, appears about the age of twelve, between the ilium and pubis, and fuses with them about the age of eighteen; it forms the pubic part of the acetabulum.\n\nThe ilium and ischium then become joined, and lastly the pubis and ischium, through the intervention of this Y-shaped portion.\n\nAt about the age of puberty, ossification takes place in each of the remaining portions, and they join with the rest of the bone between the twentieth and twenty-fifth years.\n\nSeparate centers are frequently found for the pubic tubercle and the ischial spine, and for the crest and angle of the pubis.\n\nThe proportions of the female hip bone may affect the ease of passage of the baby during childbirth.\n\n== Muscle attachments ==\n\nSeveral muscles attach to the hip bone including the internal muscles of the pelvic, abdominal muscles, back muscles, all the gluteal muscles, muscles of the lateral rotator group, hamstring muscles, two muscles from the anterior compartment of the thigh.\n\n=== Abdominal muscles ===\n\nThe abdominal external oblique muscle attaches to the iliac crest.\n\nThe abdominal internal oblique muscle attaches to pecten pubis.\n\nThe transversus abdominis muscle attaches to the pubic crest and pecten pubis via a conjoint tendon\n\n=== Back muscles ===\n\nThe multifidus muscle in the sacral region attaches to the medial surface of posterior superior iliac spine, the posterior sacroiliac ligaments and several places to the sacrum.\n\n=== Gluteal muscles ===\n\nThe gluteus maximus muscle arises from the posterior gluteal line of the inner upper ilium, and the rough portion of bone including the iliac crest, the fascia covering the gluteus medius (gluteal aponeurosis), as well as the sacrum, coccyx, the erector spinae (lumbodorsal fascia), the sacrotuberous ligament.\n\nThe gluteus medius muscle: originates on the outer surface of the ilium between the iliac crest and the posterior gluteal line above, and the anterior gluteal line below.\n\nThe gluteus medius also originates from the gluteal aponeurosis that covers its outer surface.\n\nGluteus minimus muscle originates between the anterior and inferior gluteal lines, and from the margin of the greater sciatic notch.\n\n=== Lateral rotator group ===\n\nThe piriformis muscle originates from the superior margin of the greater sciatic notch (as well as the sacroiliac joint capsule and the sacrotuberous ligament and part of the spine and sacrum.\n\nThe superior gemellus muscle arises from the outer surface of the ischial spine.\n\nThe obturator internus muscle arises from the inner surface of the antero-lateral wall of the hip bone, where it surrounds the greater part of the obturator foramen, being attached to the inferior rami of the pubis and ischium, and at the side to the inner surface of the hip bone below and behind the pelvic brim, reaching from the upper part of the greater sciatic foramen above and behind to the obturator foramen below and in front.\n\nIt also arises from the pelvic surface of the obturator membrane except in the posterior part, from the tendinous arch, and to a slight extent from the obturator fascia, which covers the muscle.\n\nThe inferior gemellus muscle arises from the upper part of the tuberosity of the ischium, immediately below the groove for the obturator internus tendon.\n\nThe obturator externus muscle arises from the margin of bone immediately around the medial side of the obturator foramen, from the rami of the pubis, and the inferior ramus of the ischium; it also arises from the medial two-thirds of the outer surface of the obturator membrane, and from the tendinous arch.\n\n=== Hamstrings ===\n\n-The long head biceps femoris arises from the lower and inner impression on the back part of the tuberosity of the ischium, by a tendon common to it and the semitendinosus, and from the lower part of the sacrotuberous ligament;\n\n-The semitendinosus arises from the lower and medial impression on the tuberosity of the ischium, by a tendon common to it and the long head of the biceps femoris; it also arises from an aponeurosis which connects the adjacent surfaces of the two muscles to the extent of about 7.5 cm. from their origin.\n\n-The semimembranosus arises from the lower and medial impression on the tuberosity of the ischium\n\n=== Anterior compartment of thigh ===\n\n-The rectus femoris muscle arises by two tendons: one, the anterior or straight, from the anterior inferior iliac spine; the other, the posterior or reflected, from a groove above the rim of the acetabulum.\n\n-The sartorius muscle arises by tendinous fibres from the anterior superior iliac spine,\n\n=== Shoulder muscles ===\n\nThe latissimus dorsi muscle attaches to the iliac crest and several places on the spine and ribs.\n\n== Clinical significance ==\n\n=== Fractures ===\n\nFractures of the hip bone are termed pelvic fractures, and should not be confused with hip fractures, which are actually femoral fractures that occur in the proximal end of the femur.\n\n=== Preparation for childbirth ===\n\nPelvimetry is the assessment of the female pelvis in relation to the birth of a baby in order to detect an increased risk for obstructed labor.\n\n== Evolution of the pelvis in animals ==\n\nThe hip bone first appears in fishes, where it consists of a simple, usually triangular bone, to which the pelvic fin articulates.\n\nThe hip bones on each side usually connect with each other at the forward end, and are even solidly fused in lungfishes and sharks, but they never attach to the vertebral column.\n\nIn the early tetrapods, this early hip bone evolved to become the ischium and pubis, while the ilium formed as a new structure, initially somewhat rod-like in form, but soon adding a larger bony blade. The acetabulum is already present at the point where the three bones meet.\n\nIn these early forms, the connection with the vertebral column is not complete, with a small pair of ribs connecting the two structures; nonetheless the pelvis already forms the complete ring found in most subsequent forms.\n\nIn practice, modern amphibians and reptiles have substantially modified this ancestral structure, based on their varied forms and lifestyles.\n\nThe obturator foramen is generally very small in such animals, although most reptiles do possess a large gap between the pubis and ischium, referred to as the thyroid fenestra, which presents a similar appearance to the obturator foramen in mammals.\n\nIn birds, the pubic symphysis is present only in the ostrich, and the two hip bones are usually widely separated, making it easier to lay large eggs.In therapsids, the hip bone came to rotate counter-clockwise, relative to its position in reptiles, so that the ilium moved forward, and the pubis and ischium moved to the rear.\n\nThe same pattern is seen in all modern mammals, and the thyroid fenestra and obturator foramen have merged to form a single space.\n\nThe ilium is typically narrow and triangular in mammals, but is much larger in ungulates and humans, in which it anchors powerful gluteal muscles.\n\nMonotremes and marsupials also possess a fourth pair of bones, the prepubes or \"marsupial bones\", which extend forward from the pubes, and help to support the abdominal muscles and, in marsupials, the pouch.\n\nIn placental mammals, the pelvis as a whole is generally wider in females than in males, to allow for the birth of the young.\n\nThe pelvic bones of cetaceans were formerly considered to be vestigial, but they are now known to play a role in sexual selection.\n\nhttps://en.wikipedia.org/wiki/Hip_bone","tibia":"The tibia (plural tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia), and it connects the knee with the ankle bones.\n\nThe tibia is found on the medial side of the leg next to the fibula and closer to the median plane or centre-line.\n\nThe tibia is connected to the fibula by the interosseous membrane of leg, forming a type of fibrous joint called a syndesmosis with very little movement.\n\nThe tibia is named for the flute tibia.\n\nIt is the second largest bone in the human body next to the femur.\n\nThe leg bones are the strongest long bones as they support the rest of the body.\n\n== Structure ==\n\nIn human anatomy, the tibia is the second largest bone next to the femur.\n\nAs in other vertebrates the tibia is one of two bones in the lower leg, the other being the fibula, and is a component of the knee and ankle joints.\n\nThe ossification or formation of the bone starts from three centers; one in the shaft and one in each extremity.\n\nThe tibia is categorized as a long bone and is as such composed of a diaphysis and two epiphyses.\n\nThe diaphysis is the midsection of the tibia, also known as the shaft or body.\n\nWhile the epiphyses are the two rounded extremities of the bone; an upper (also known as superior or proximal) closest to the thigh and a lower (also known as inferior or distal) closest to the foot.\n\nThe tibia is most contracted in the lower third and the distal extremity is smaller than the proximal.\n\n=== Upper extremity ===\n\n==== Condyles of tibia ====\n\nThe proximal or upper extremity of the tibia is expanded in the transverse plane with a medial and lateral condyle, which are both flattened in the horizontal plane.\n\nThe medial condyle is the larger of the two and is better supported over the shaft.\n\nThe upper surfaces of the condyles articulate with the femur to form the tibiofemoral joint, the weightbearing part of the kneejoint.\n\nThe medial and lateral condyle are separated by the intercondylar area, where the cruciate ligaments and the menisci attach.\n\nHere the medial and lateral intercondylar tubercle forms the intercondylar eminence.\n\nTogether with the medial and lateral condyle the intercondylar region forms the tibial plateau, which both articulates with and is anchored to the lower extremity of the femur.\n\nThe intercondylar eminence divides the intercondylar area into an anterior and posterior part.\n\nThe anterolateral region of the anterior intercondylar area are perforated by numerous small openings for nutrient arteries.\n\nThe articular surfaces of both condyles are concave, particularly centrally.\n\nThe flatter outer margins are in contact with the menisci.\n\nThe medial condyles superior surface is oval in form and extends laterally onto the side of medial intercondylar tubercle.\n\nThe lateral condyles superior surface is more circular in form and its medial edge extends onto the side of the lateral intercondylar tubercle.\n\nThe posterior surface of the medial condyle bears a horizontal groove for part of the attachment of the semimembranosus muscle, whereas the lateral condyle has a circular facet for articulation with the head of the fibula.\n\nBeneath the condyles is the tibial tuberosity which serves for attachment of the patellar ligament, a continuation of the quadriceps femoris muscle.\n\n==== Facets ====\n\nThe superior articular surface presents two smooth articular facets.\n\nThe medial facet, oval in shape, is slightly concave from side to side, and from before backward.\n\nThe lateral, nearly circular, is concave from side to side, but slightly convex from before backward, especially at its posterior part, where it is prolonged on to the posterior surface for a short distance.\n\nThe central portions of these facets articulate with the condyles of the femur, while their peripheral portions support the menisci of the knee joint, which here intervene between the two bones.\n\n==== Intercondyloid eminence ====\n\nBetween the articular facets in the intercondylar area, but nearer the posterior than the anterior aspect of the bone, is the intercondyloid eminence (spine of tibia), surmounted on either side by a prominent tubercle, on to the sides of which the articular facets are prolonged; in front of and behind the intercondyloid eminence are rough depressions for the attachment of the anterior and posterior cruciate ligaments and the menisci.\n\n==== Surfaces ====\n\nThe anterior surfaces of the condyles are continuous with one another, forming a large somewhat flattened area; this area is triangular, broad above, and perforated by large vascular foramina; narrow below where it ends in a large oblong elevation, the tuberosity of the tibia, which gives attachment to the patellar ligament; a bursa intervenes between the deep surface of the ligament and the part of the bone immediately above the tuberosity.\n\nPosteriorly, the condyles are separated from each other by a shallow depression, the posterior intercondyloid fossa, which gives attachment to part of the posterior cruciate ligament of the knee-joint. The medial condyle presents posteriorly a deep transverse groove, for the insertion of the tendon of the semimembranosus.\n\nIts medial surface is convex, rough, and prominent; it gives attachment to the medial collateral ligament.\nThe lateral condyle presents posteriorly a flat articular facet, nearly circular in form, directed downward, backward, and lateralward, for articulation with the head of the fibula.\n\nIts lateral surface is convex, rough, and prominent in front: on it is an eminence, situated on a level with the upper border of the tuberosity and at the junction of its anterior and lateral surfaces, for the attachment of the iliotibial band.\n\nJust below this a part of the extensor digitorum longus takes origin and a slip from the tendon of the biceps femoris is inserted.\n\n=== Shaft ===\n\nThe shaft or body of the tibia is triangular in cross-section and forms three borders: An anterior, medial and lateral or interosseous border.\n\nThese three borders form three surfaces; the medial, lateral and posterior.\n\nThe forward flat part of the tibia is called the fibia, often confused with the fibula.\n\n==== Borders ====\n\nThe anterior crest or border, the most prominent of the three, commences above at the tuberosity, and ends below at the anterior margin of the medial malleolus.\n\nIt is sinuous and prominent in the upper two-thirds of its extent, but smooth and rounded below; it gives attachment to the deep fascia of the leg.\n\nThe medial border is smooth and rounded above and below, but more prominent in the center; it begins at the back part of the medial condyle, and ends at the posterior border of the medial malleolus; its upper part gives attachment to the tibial collateral ligament of the knee-joint to the extent of about 5 cm., and insertion to some fibers of the popliteus muscle; from its middle third some fibers of the soleus and flexor digitorum longus muscles take origin.\n\nThe interosseous crest or lateral border is thin and prominent, especially its central part, and gives attachment to the interosseous membrane; it commences above in front of the fibular articular facet, and bifurcates below, to form the boundaries of a triangular rough surface, for the attachment of the interosseous ligament connecting the tibia and fibula.\n\n==== Surfaces ====\n\nThe medial surface is smooth, convex, and broader above than below; its upper third, directed forward and medialward, is covered by the aponeurosis derived from the tendon of the sartorius, and by the tendons of the Gracilis and Semitendinosus, all of which are inserted nearly as far forward as the anterior crest; in the rest of its extent it is subcutaneous.\n\nThe lateral surface is narrower than the medial; its upper two-thirds present a shallow groove for the origin of the Tibialis anterior; its lower third is smooth, convex, curves gradually forward to the anterior aspect of the bone, and is covered by the tendons of the Tibialis anterior, Extensor hallucis longus, and Extensor digitorum longus, arranged in this order from the medial side.\n\nThe posterior surface presents, at its upper part, a prominent ridge, the popliteal line, which extends obliquely downward from the back part of the articular facet for the fibula to the medial border, at the junction of its upper and middle thirds; it marks the lower limit of the insertion of the Popliteus, serves for the attachment of the fascia covering this muscle, and gives origin to part of the Soleus, Flexor digitorum longus, and Tibialis posterior.\n\nThe triangular area, above this line, gives insertion to the Popliteus.\n\nThe middle third of the posterior surface is divided by a vertical ridge into two parts; the ridge begins at the popliteal line and is well-marked above, but indistinct below; the medial and broader portion gives origin to the Flexor digitorum longus, the lateral and narrower to part of the Tibialis posterior.\n\nThe remaining part of the posterior surface is smooth and covered by the Tibialis posterior, Flexor digitorum longus, and Flexor hallucis longus. Immediately below the popliteal line is the nutrient foramen, which is large and directed obliquely downward.\n\n=== Lower extremity ===\n\nThe distal end of the tibia is much smaller than the proximal end and presents five surfaces; it is prolonged downward on its medial side as a strong pyramidal process, the medial malleolus.\n\nThe lower extremity of the tibia together with the fibula and talus forms the ankle joint.\n\n==== Surfaces ====\n\nThe inferior articular surface is quadrilateral, and smooth for articulation with the talus.\n\nIt is concave from before backward, broader in front than behind, and traversed from before backward by a slight elevation, separating two depressions.\n\nIt is continuous with that on the medial malleolus.\n\nThe anterior surface of the lower extremity is smooth and rounded above, and covered by the tendons of the Extensor muscles; its lower margin presents a rough transverse depression for the attachment of the articular capsule of the ankle-joint.\n\nThe posterior surface is traversed by a shallow groove directed obliquely downward and medialward, continuous with a similar groove on the posterior surface of the talus and serving for the passage of the tendon of the Flexor hallucis longus.\n\nThe lateral surface presents a triangular rough depression for the attachment of the inferior interosseous ligament connecting it with the fibula; the lower part of this depression is smooth, covered with cartilage in the fresh state, and articulates with the fibula.\n\nThe surface is bounded by two prominent borders (the anterior and posterior colliculi), continuous above with the interosseous crest; they afford attachment to the anterior and posterior ligaments of the lateral malleolus.\n\nThe medial surface -- see medial malleolus for details.\n\n==== Fractures ====\n\nAnkle fractures of the tibia have several classification systems based on location or mechanism:\n\nMedial malleolus - Herscovici classification\nPosterior malleolus - Haruguchi classification\nMechanism - Lauge-Hansen classification\n\n=== Blood supply ===\n\nThe tibia is supplied with blood from two sources: A nutrient artery, as the main source, and periosteal vessels derived from the anterior tibial artery.\n\n=== Joints ===\n\nThe tibia is a part of four joints; the knee, ankle, superior and inferior tibiofibular joint.\n\nIn the knee the tibia forms one of the two articulations with the femur, often referred to as the tibiofemoral components of the knee joint.\n\nThis is the weightbearing part of the knee joint.\n\nThe tibiofibular joints are the articulations between the tibia and fibula which allows very little movement.\n\nThe proximal tibiofibular joint is a small plane joint.\n\nThe joint is formed between the undersurface of the lateral tibial condyle and the head of fibula.\n\nThe joint capsule is reinforced by anterior and posterior ligament of the head of the fibula.\n\nThe distal tibiofibular joint (tibiofibular syndesmosis) is formed by the rough, convex surface of the medial side of the distal end of the fibula, and a rough concave surface on the lateral side of the tibia.\n\nThe part of the ankle joint known as the talocrural joint, is a synovial hinge joint that connects the distal ends of the tibia and fibula in the lower limb with the proximal end of the talus.\n\nThe articulation between the tibia and the talus bears more weight than between the smaller fibula and the talus.\n\n=== Development ===\n\nThe tibia is ossified from three centers; a primary center for the diaphysis (shaft) and a secondary center for each epiphysis (extremity). Ossification begins in the center of the body, about the seventh week of fetal life, and gradually extends toward the extremities.\n\nThe center for the upper epiphysis appears before or shortly after birth at close to 34 weeks gestation; it is flattened in form, and has a thin tongue-shaped process in front, which forms the tuberosity; that for the lower epiphysis appears in the second year.\n\nThe lower epiphysis fuses with the tibial shaft at about the eighteenth, and the upper one fuses about the twentieth year.\n\nTwo additional centers occasionally exist, one for the tongue-shaped process of the upper epiphysis, which forms the tuberosity, and one for the medial malleolus.\n\n== Function ==\n\n=== Muscle attachments ===\n\n=== Strength ===\n\nThe tibia has been modeled as taking an axial force during walking that is up to 4.7 bodyweight.\n\nIts bending moment in the sagittal plane in the late stance phase is up to 71.6 bodyweight times millimetre.\n\n== Clinical significance ==\n\n=== Fracture ===\n\nFractures of the tibia can be divided into those that only involve the tibia; bumper fracture, Segond fracture, Gosselin fracture, toddler's fracture, and those including both the tibia and fibula; trimalleolar fracture, bimalleolar fracture, Pott's fracture.\n\n== Society and culture ==\n\nIn Judaism, the tibia, or shankbone, of a goat is used in the Passover Seder plate.\n\n== Other animals ==\n\nThe structure of the tibia in most other tetrapods is essentially similar to that in humans.\n\nThe tuberosity of the tibia, a crest to which the patellar ligament attaches in mammals, is instead the point for the tendon of the quadriceps muscle in reptiles, birds, and amphibians, which have no patella.\n\nhttps://en.wikipedia.org/wiki/Tibia","fibula":"The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below.\n\nIt is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones.\n\nIts upper extremity is small, placed toward the back of the head of the tibia, below the knee joint and excluded from the formation of this joint.\n\nIts lower extremity inclines a little forward, so as to be on a plane anterior to that of the upper end; it projects below the tibia and forms the lateral part of the ankle joint.\n\n== Structure ==\n\nThe bone has the following components:\n\n-Lateral malleolus\n-Interosseous membrane connecting the fibula to the tibia, forming a syndesmosis joint\n-The superior tibiofibular articulation is an arthrodial joint between the lateral condyle of the tibia and the head of the fibula.\n-The inferior tibiofibular articulation (tibiofibular syndesmosis) is formed by the rough, convex surface of the medial side of the lower end of the fibula, and a rough concave surface on the lateral side of the tibia.\n\n=== Blood supply ===\n\nThe blood supply is important for planning free tissue transfer because the fibula is commonly used to reconstruct the mandible.\n\nThe shaft is supplied in its middle third by a large nutrient vessel from the fibular artery.\n\nIt is also perfused from its periosteum which receives many small branches from the fibular artery.\n\nThe proximal head and the epiphysis are supplied by a branch of the anterior tibial artery.\n\nIn harvesting the bone the middle third is always taken and the ends preserved (4 cm proximally and 6 cm distally)\n\n=== Development ===\n\nThe fibula is ossified from three centers, one for the shaft, and one for either end.\n\nOssification begins in the body about the eighth week of fetal life, and extends toward the extremities. At birth the ends are cartilaginous.\n\nOssification commences in the lower end in the second year, and in the upper about the fourth year. The lower epiphysis, the first to ossify, unites with the body about the twentieth year; the upper epiphysis joins about the twenty-fifth year.\n\n=== Head ===\n\nThe upper extremity or head of the fibula is of an irregular quadrate form, presenting above a flattened articular surface, directed upward, forward, and medialward, for articulation with a corresponding surface on the lateral condyle of the tibia.\n\nOn the lateral side is a thick and rough prominence continued behind into a pointed eminence, the apex (styloid process), which projects upward from the posterior part of the head.\n\nThe prominence, at its upper and lateral part, gives attachment to the tendon of the biceps femoris and to the fibular collateral ligament of the knee-joint, the ligament dividing the tendon into two parts.\n\nThe remaining part of the circumference of the head is rough, for the attachment of muscles and ligaments.\n\nIt presents in front a tubercle for the origin of the upper and anterior fibers of the peroneus longus, and a surface for the attachment of the anterior ligament of the head; and behind, another tubercle, for the attachment of the posterior ligament of the head and the origin of the upper fibers of the soleus.\n\n=== Body ===\n\nThe body of the fibula presents four borders - the antero-lateral, the antero-medial, the postero-lateral, and the postero-medial; and four surfaces - anterior, posterior, medial, and lateral.\n\n==Borders==\n\nThe antero-lateral border begins above in front of the head, runs vertically downward to a little below the middle of the bone, and then curving somewhat lateralward, bifurcates so as to embrace a triangular subcutaneous surface immediately above the lateral malleolus.\n\nThis border gives attachment to an intermuscular septum, which separates the extensor muscles on the anterior surface of the leg from the peronaei longus and brevis on the lateral surface.\n\nThe antero-medial border, or interosseous crest, is situated close to the medial side of the preceding, and runs nearly parallel with it in the upper third of its extent, but diverges from it in the lower two-thirds.\n\nIt begins above just beneath the head of the bone (sometimes it is quite indistinct for about 2.5 cm. below the head), and ends at the apex of a rough triangular surface immediately above the articular facet of the lateral malleolus.\n\nIt serves for the attachment of the interosseous membrane, which separates the extensor muscles in front from the flexor muscles behind.\n\nThe postero-lateral border is prominent; it begins above at the apex, and ends below in the posterior border of the lateral malleolus.\n\nIt is directed lateralward above, backward in the middle of its course, backward, and a little medialward below, and gives attachment to an aponeurosis which separates the peronaei on the lateral surface from the flexor muscles on the posterior surface.\n\nThe postero-medial border, sometimes called the oblique line, begins above at the medial side of the head, and ends by becoming continuous with the interosseous crest at the lower fourth of the bone.\n\nIt is well-marked and prominent at the upper and middle parts of the bone.\n\nIt gives attachment to an aponeurosis which separates the tibialis posterior from the soleus and flexor hallucis longus.\n\n===Surfaces===\n\nThe anterior surface is the interval between the antero-lateral and antero-medial borders.\n\nIt is extremely narrow and flat in the upper third of its extent; broader and grooved longitudinally in its lower third; it serves for the origin of three muscles: the extensor digitorum longus, extensor hallucis longus, and peroneus tertius.\n\nThe posterior surface is the space included between the postero-lateral and the postero-medial borders; it is continuous below with the triangular area above the articular surface of the lateral malleolus; it is directed backward above, backward and medialward at its middle, directly medialward below.\n\nIts upper third is rough, for the origin of the soleus; its lower part presents a triangular surface, connected to the tibia by a strong interosseous ligament; the intervening part of the surface is covered by the fibers of origin of the flexor hallucis longus.\n\nNear the middle of this surface is the nutrient foramen, which is directed downward.\n\nThe medial surface is the interval included between the antero-medial and the postero-medial borders.\n\nIt is grooved for the origin of the tibialis posterior.\n\nThe lateral surface is the space between the antero-lateral and postero-lateral borders.\n\nIt is broad, and often deeply grooved; it is directed lateralward in the upper two-thirds of its course, backward in the lower third, where it is continuous with the posterior border of the lateral malleolus.\n\nThis surface gives origin to the peronaei longus and brevis.\n\n== Function ==\n\nThe fibula does not carry any significant load (weight) of the body.\n\nIt extends past the lower end of the tibia and forms the outer part of the ankle providing stability to this joint.\n\nIt has grooves for certain ligaments which gives them leverage and multiplies the muscle force.\n\nIt provides attachment points for the following muscles:\n\n== Clinical significance ==\n\n=== Fractures ===\n\nThe most common type of fibula fracture is located at the distal end of the bone, and is classified as ankle fracture. In the Danis–Weber classification it has three categories:\n\n-Type A: Fracture of the lateral malleolus, distal to the syndesmosis (the connection between the distal ends of the tibia and fibula).\n-Type B: Fracture of the fibula at the level of the syndesmosis\n-Type C: Fracture of the fibula proximal to the syndesmosis.\n\nA Maisonneuve fracture is a spiral fracture of the proximal third of the fibula associated with a tear of the distal tibiofibular syndesmosis and the interosseous membrane. There is an associated fracture of the medial malleolus or rupture of the deep deltoid ligament.\n\nAn avulsion fracture of the head of the fibula refers to the fracture of the fibular head because of a sudden contraction of the biceps femoris muscle that pulls its site of attachment on the bone.\n\nThe attachment of the biceps femoris tendon on the fibular head is closely related to the lateral collateral ligament of the knee.\n\nTherefore, this ligament is prone to injury in this type of avulsion fracture.\n\n== History ==\n\n=== Etymology ===\n\nThe word fibula can be dated back to c. 1670 to describe a clasp or brooch – see fibula (brooch) – and was first used in English for the smaller bone in the lower leg c. 1706. It derives from Latin fībula, also meaning a clasp or brooch.\n\nThe bone was so called because it resembles a clasp like a modern safety pin.The adjective peroneal referring to the fibula bone or its surrounding structures derives from περόνη : perónē, the Ancient Greek word for a clasp.\n\n== Other animals ==\n\nBecause the fibula bears relatively little weight in comparison with the tibia, it is typically narrower in all but the most primitive tetrapods.\n\nIn many animals, it still articulates with the posterior part of the lower extremity of the femur, but this feature is frequently lost (as it is in humans).\n\nIn some animals, the reduction of the fibula has proceeded even further than it has in humans, with the loss of the tarsal articulation, and, in extreme cases (such as the horse), partial fusion with the tibia.\n\nhttps://en.wikipedia.org/wiki/Fibula","sacrum":"The sacrum (plural: sacra or sacrums), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1–S5) between ages 18 and 30.The sacrum situates at the upper, back part of the pelvic cavity, between the two wings of the pelvis.\n\nIt forms joints with four other bones.\n\nThe two projections at the sides of the sacrum are called the alae (wings), and articulate with the ilium at the L-shaped sacroiliac joints.\n\nThe upper part of the sacrum connects with the last lumbar vertebra (L5), and its lower part with the coccyx (tailbone) via the sacral and coccygeal cornua.\n\nThe sacrum has three different surfaces which are shaped to accommodate surrounding pelvic structures.\n\nOverall it is concave (curved upon itself).\n\nThe base of the sacrum, the broadest and uppermost part, is tilted forward as the sacral promontory internally.\n\nThe central part is curved outward toward the posterior, allowing greater room for the pelvic cavity.\n\nIn all other quadrupedal vertebrates, the pelvic vertebrae undergo a similar developmental process to form a sacrum in the adult, even while the bony tail (caudal) vertebrae remain unfused.\n\nThe number of sacral vertebrae varies slightly.\n\nFor instance, the S1–S5 vertebrae of a horse will fuse, the S1–S3 of a dog will fuse, and four pelvic vertebrae of a rat will fuse between the lumbar and the caudal vertebrae of its tail.\n\nThe Stegosaurus dinosaur had a greatly enlarged neural canal in the sacrum, characterized as a \"posterior brain case”.\n\n== Structure ==\n\nThe sacrum is a complex structure providing support for the spine and accommodation for the spinal nerves.\n\nIt also articulates with the hip bones.\n\nThe sacrum has a base, an apex, and three surfaces – a pelvic, dorsal and a lateral surface.\n\nThe base of the sacrum, which is broad and expanded, is directed upward and forward.\n\nOn either side of the base is a large projection known as an ala of sacrum and these alae (wings) articulate with the sacroiliac joints.\n\nThe alae support the psoas major muscles and the lumbosacral trunk which connects the lumbar plexus with the sacral plexus.\n\nIn the articulated pelvis the alae are continuous with the iliac fossa.\n\nEach ala is slightly concave from side to side, and convex from the back and gives attachment to a few of the fibers of the iliacus muscle.\n\nThe posterior quarter of the ala represents the transverse process, and its anterior three-quarters the costal process of the first sacral segment.\n\nEach ala also serves as part of the border of the pelvic brim.\n\nThe alae also form the base of the lumbosacral triangle.\n\nThe iliolumbar ligament and lumbosacral ligaments are attached to the ala.\n\nIn the middle of the base is a large oval articular surface, the upper surface of the body of the first sacral vertebra, which is connected with the under surface of the body of the last lumbar vertebra by an intervertebral fibrocartilage.\n\nBehind this is the large triangular orifice of the sacral canal, which is completed by the lamina and spinous process of the first sacral vertebra.\n\nThe superior articular processes project from it on either side; they are oval, concave, directed backward and medialward, like the superior articular processes of a lumbar vertebra.\n\nThey are attached to the body of the first sacral vertebra and to each ala, by short thick pedicles; on the upper surface of each pedicle is a vertebral notch, which forms the lower part of the foramen between the last lumbar and first sacral vertebrae.\n\nThe apex is directed downward and presents an oval facet for articulation with the coccyx.\n\nThe sacral canal as a continuation of the vertebral canal runs throughout the greater part of the sacrum.\n\nThe sacral angle is the angle formed by the true conjugate with the two pieces of sacrum.\n\nNormally it is greater than 60 degrees.\n\nA sacral angle of lesser degree suggests funneling of the pelvis.\n\n=== Promontory ===\n\nThe sacral promontory marks part of the border of the pelvic inlet, and comprises the iliopectineal line and the linea terminalis.\n\nThe sacral promontory articulates with the last lumbar vertebra to form the sacrovertebral angle, an angle of 30 degrees from the horizontal plane that provides a useful marker for a sling implant procedure.\n\n=== Surfaces ===\n\nThe pelvic surface of the sacrum is concave from the top, and curved slightly from side to side.\n\nIts middle part is crossed by four transverse ridges, which correspond to the original planes of separation between the five sacral vertebrae.\n\nThe body of the first segment is large and has the form of a lumbar vertebra; the bodies of the next bones get progressively smaller, are flattened from the back, and curved to shape themselves to the sacrum, being concave in front and convex behind.\n\nAt each end of the transverse ridges, are the four anterior sacral foramina, diminishing in size in line with the smaller vertebral bodies.\n\nThe foramina give exit to the anterior divisions of the sacral nerves and entrance to the lateral sacral arteries.\n\nEach part at the sides of the foramina is traversed by four broad, shallow grooves, which lodge the anterior divisions of the sacral nerves.\n\nThey are separated by prominent ridges of bone which give origin to the piriformis muscle.\n\nIf a sagittal section be made through the center of the sacrum, the bodies are seen to be united at their circumferences by bone, wide intervals being left centrally, which, in the fresh state, are filled by the intervertebral discs.\n\nThe dorsal surface of the sacrum is convex and narrower than the pelvic surface.\n\nIn the middle line is the median sacral crest, surmounted by three or four tubercles—the rudimentary spinous processes of the upper three or four sacral vertebrae.\n\nOn either side of the median sacral crest is a shallow sacral groove, which gives origin to the multifidus muscle.\n\nThe floor of the groove is formed by the united laminae of the corresponding vertebrae.\n\nThe laminae of the fifth sacral vertebra, and sometimes those of the fourth, do not meet at the back, resulting in a fissure known as the sacral hiatus in the posterior wall of the sacral canal.\n\nThe sacral canal is a continuation of the spinal canal and runs throughout the greater part of the sacrum.\n\nAbove the sacral hiatus, it is triangular in form.\n\nThe canal lodges the sacral nerves, via the anterior and posterior sacral foramina.\nOn the lateral aspect of the sacral groove is a linear series of tubercles produced by the fusion of the articular processes which together form the indistinct medial sacral crest.\n\nThe articular processes of the first sacral vertebra are large and oval-shaped.\n\nTheir facets are concave from side to side, face to the back and middle, and articulate with the facets on the inferior processes of the fifth lumbar vertebra.\n\nThe tubercles of the inferior articular processes of the fifth sacral vertebra, known as the sacral cornua, are projected downward and are connected to the cornua of the coccyx.\n\nAt the side of the articular processes are the four posterior sacral foramina; they are smaller in size and less regular in form than those at the front, and transmit the posterior divisions of the sacral nerves.\n\nOn the side of the posterior sacral foramina is a series of tubercles, the transverse processes of the sacral vertebrae, and these form the lateral sacral crest.\n\nThe transverse tubercles of the first sacral vertebra are large and very distinct; they, together with the transverse tubercles of the second vertebra, give attachment to the horizontal parts of the posterior sacroiliac ligaments; those of the third vertebra give attachment to the oblique fasciculi of the posterior sacroiliac ligaments; and those of the fourth and fifth to the sacrotuberous ligaments.\n\nThe lateral surface of the sacrum is broad above, but narrows into a thin edge below.\n\nThe upper half presents in front an ear-shaped surface, the auricular surface, covered with cartilage in the immature state, for articulation with the ilium.\n\nBehind it is a rough surface, the sacral tuberosity, on which are three deep and uneven impressions, for the attachment of the posterior sacroiliac ligament.\n\nThe lower half is thin, and ends in a projection called the inferior lateral angle.\n\nMedial to this angle is a notch, which is converted into a foramen by the transverse process of the first piece of the coccyx, and this transmits the anterior division of the fifth sacral nerve.\n\nThe thin lower half of the lateral surface gives attachment to the sacrotuberous and sacrospinous ligaments, to some fibers of the gluteus maximus at the back and to the coccygeus in the front.\n\n=== Articulations ===\n\nThe sacrum articulates with four bones:\n\n-the last lumbar vertebra above\n-the coccyx (tailbone) below\n-the illium portion of the hip bone on either side\n\nRotation of the sacrum superiorly and anteriorly whilst the coccyx moves posteriorly relative to the ilium is sometimes called \"nutation\" (from the Latin term nutatio which means \"nodding\") and the reverse, postero-inferior motion of the sacrum relative to the ilium whilst the coccyx moves anteriorly, \"counter-nutation\".\n\nIn upright vertebrates, the sacrum is capable of slight independent movement along the sagittal plane.\n\nOn bending backward the top (base) of the sacrum moves forward relative to the ilium; on bending forward the top moves back.\n\nThe sacrum refers to all of the parts combined.\n\nIts parts are called sacral vertebrae when referred individually.\n\n=== Variations ===\n\nIn some cases the sacrum will consist of six pieces or be reduced in number to four.\n\nThe bodies of the first and second vertebrae may fail to unite.\n\n=== Development ===\n\nThe somites that give rise to the vertebral column begin to develop from head to tail along the length of the notochord.\n\nAt day 20 of embryogenesis the first four pairs of somites appear in the future occipital bone region.\n\nDeveloping at the rate of three or four a day, the next eight pairs form in the cervical region to develop into the cervical vertebrae; the next twelve pairs will form the thoracic vertebrae; the next five pairs the lumbar vertebrae and by about day 29 the sacral somites will appear to develop into the sacral vertebrae; finally on day 30 the last three pairs will form the coccyx.\n\n== Clinical significance ==\n\n=== Congenital disorders ===\n\nThe congenital disorder, spina bifida, occurs as a result of a defective embryonic neural tube, characterised by the incomplete closure of vertebral arch or of the incomplete closure of the surface of the vertebral canal.\n\nThe most common sites for spina bifida malformations are the lumbar and sacral areas.\n\nAnother congenital disorder is that of caudal regression syndrome also known as sacral agenesis.\n\nThis is characterised by an abnormal underdevelopment in the embryo (occurring by the seventh week) of the lower spine.\n\nSometimes part of the coccyx is absent, or the lower vertebrae can be absent, or on occasion a small part of the spine is missing with no outward sign.\n\n=== Fracture ===\n\nSacral fractures are relatively uncommon; however, they are often associated with neurological deficits.\n\nIn the presence of neurological signs, most of the times they are treated with surgical fixation.\n\n=== Cancer ===\n\nThe sacrum is one of the main sites for the development of the sarcomas known as chordomas that are derived from the remnants of the embryonic notochord.\n\n== Other animals ==\n\nIn dogs the sacrum is formed by three fused vertebrae.\n\nThe sacrum in the horse is made up of five fused vertebrae.\n\nIn birds the sacral vertebrae are fused with the lumbar and some caudal and thoracic vertebrae to form a single structure called the synsacrum.\n\nIn the frog the ilium is elongated and forms a mobile joint with the sacrum that acts as an additional limb to give more power to its leaps.\n\n== History ==\n\nEnglish sacrum was introduced as a technical term in anatomy in the mid-18th century, as a shortening of the Late Latin name os sacrum \"sacred bone\", itself a translation of Greek ἱερόν ὀστέον, the term found in the writings of Galen.\n\nPrior to the adoption of sacrum, the bone was also called holy bone in English, paralleling German heiliges Bein or Heiligenbein (alongside Kreuzbein) and Dutch heiligbeen.\n\nThe origin of Galen's term is unclear.\n\nSupposedly the sacrum was the part of an animal offered in sacrifice (since the sacrum is the seat of the organs of procreation).\n\nOthers attribute the adjective ἱερόν to the ancient belief that this specific bone would be indestructible.\n\nAs the Greek adjective ἱερός may also mean \"strong\", it has also been suggested that os sacrum is a mistranslation of a term intended to mean \"the strong bone\".\n\nThis is supported by the alternative Greek name μέγας σπόνδυλος by the Greeks, translating to \"large vertebra\", translated into Latin as vertebra magna.\n\nIn Classical Greek the bone was known as κλόνις (Latinized clonis); this term is cognate to Latin clunis \"buttock\", Sanskrit śróṇis \"haunch\" and Lithuanian šlaunis \"hip, thigh\".\n\nThe Latin word is found in the alternative Latin name of the sacrum, ossa clunium, as it were \"bones of the buttocks\".\n\nDue to the fact that the os sacrum is broad and thick at its upper end, the sacrum is alternatively called os latum, \"broad bone\".\n\nhttps://en.wikipedia.org/wiki/Sacrum","vomer":"The vomer is one of the unpaired facial bones of the skull.\n\nIt is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones.\n\nThe vomer forms the inferior part of the nasal septum, with the superior part formed by the perpendicular plate of the ethmoid bone.\n\nThe name is derived from the Latin word for a ploughshare and the shape of the bone.\n\n== Structure ==\n\nThe vomer is situated in the median plane, but its anterior portion is frequently bent to one side.\n\nIt is thin, somewhat quadrilateral in shape, and forms the hinder and lower part of the nasal septum; it has two surfaces and four borders.\n\nThe surfaces are marked by small furrows for blood vessels, and on each is the nasopalatine groove, which runs obliquely downward and forward, and lodges the nasopalatine nerve and vessels.\n\n=== Borders ===\n\nThe superior border, the thickest, presents a deep furrow, bounded on either side by a horizontal projecting expansion of bone – called the wing of vomer; the furrow receives the rostrum of the sphenoid, while the margins of the alae articulate with the vaginal processes of the medial pterygoid plates of the sphenoid behind, and with the sphenoidal processes of the palatine bones in front.\n\nThe inferior border articulates with the crest formed by the maxillæ and palatine bones.\n\nThe anterior border is the longest and slopes downward and forward.\n\nIts upper half is fused with the perpendicular plate of the ethmoid; its lower half is grooved for the inferior margin of the septal cartilage of the nose.\nThe posterior border is free of bony articulation, having no muscle attachments.\n\nIt is concave, separates the choanae, and is thick and bifid above, thin below.\n\n=== Articulations ===\n\nThe vomer articulates with six bones:\n\ntwo of the cranium, the sphenoid and ethmoid.\nfour of the face, two maxillae; and two palatine bones.\n\nIt also articulates with the septal cartilage of the nose.\n\n== Function ==\n\nThe vomeronasal organ, also called Jacobson's organ, is a chemoreceptor organ named for its closeness to the vomer and nasal bones, and is particularly developed in animals such as cats (who adopt a characteristic pose called the Flehmen reaction or flehming when making use of it), and is thought to have to do with the perception of certain pheromones.\n\n== In other animals ==\n\nIn bony fish, the vomers are flattened, paired, bones forming the anterior part of the roof of the mouth, just behind the premaxillary bones.\n\nIn many species, they have teeth, supplementing those in the jaw proper; in some labyrinthodonts (extinct amphibians) the teeth on the vomers were actually larger than the primary set.\n\nIn amphibians and reptiles, the vomers become narrower, due to the presence of the enlarged choanae (the inner part of the nostrils) on either side, and they may extend further back in the jaw.\n\nThey are typically small in birds, where they form the upper hind part of the beak, again being located between the choanae.In mammals, the vomers have become narrower still, and are fused into a single, vertically oriented bone.\n\nThe development of the hard palate beneath the vomer means that the bone is now located in a nasal chamber, separate from the mouth.\n\nhttps://en.wikipedia.org/wiki/Vomer","lateral-rectus-muscle":"The lateral rectus muscle is a muscle on the lateral side of the eye in the orbit.\n\nIt is one of six extraocular muscles that control the movements of the eye.\n\nThe lateral rectus muscle is responsible for lateral movement of the eyeball, specifically abduction.\n\nAbduction describes the movement of the eye away from the midline (i.a. nose), allowing the eyeball to move horizontally in the lateral direction, bringing the pupil away from the midline of the body.\n\n== Structure ==\n\nThe lateral rectus muscle originates at the lateral part of the common tendinous ring, also known as the annular tendon.\n\nThe common tendinous ring is a tendinous ring that surrounds the optic nerve and serves as the origin for five of the seven extraocular muscles, excluding the inferior oblique muscle.\n\nThe lateral rectus muscle inserts into the temporal side of the eyeball.\n\nThis insertion is around 7 mm from the corneal limbus.\n\nIt has a width of around 10 mm.\n\n=== Nerve supply ===\n\nThe lateral rectus is the only muscle supplied by the abducens nerve (CN VI).\n\nThe neuron cell bodies are located in the abducens nucleus in the pons.\n\nThese neurons project axons as the abducens nerve which exit from the pontomedullary junction of the brainstem, travels through the cavernous sinus and enter the orbit through the superior orbital fissure.\n\nIt then enters the medial surface of the lateral rectus to innervate it.\n\n=== Relations ===\n\nThe insertion of the lateral rectus muscle is around 8 mm from the insertion of the inferior rectus muscle, around 7 mm from the insertion of the superior rectus muscle, and around 10 mm from the corneal limbus.\n\n== Function ==\n\nThe lateral rectus muscle abducts the eye, turning the eye laterally in the orbit.\n\n== Clinical significance ==\n\nA sixth nerve palsy, also known as abducens nerve palsy, is a neurological defect that results from a damaged or impaired abducens nerve.\n\nThis damage can stem from stroke, trauma, tumor, inflammation, and infection.\n\nDamage to the abducens nerve by trauma can be caused by any type of trauma that causes elevated intracranial pressure; including hydrocephalus, traumatic brain injury with intracranial bleeding, tumors, and lesions along the nerve at any point between the pons and lateral rectus muscle in orbit.\n\nThis defect can result in horizontal double vision and reduced lateral movement.\n\nThe lateral rectus muscle will be denervated and paralyzed and the patient will be unable to abduct the eye.\n\nFor example, if the left abducens nerve is damaged, the left eye will not abduct fully.\n\nWhile attempting to look straight ahead, the left eye will be deviated medially towards the nose due to the unopposed action of the medial rectus of the eye.\n\nProper function of the lateral rectus is tested clinically by asking the patient to look laterally.\n\nDepending on the underlying cause of the lateral rectus palsy, some improvement may occur naturally over time.\n\nWhile the prognosis for a lateral rectus palsy onset by a viral illness is generally positive, the prognosis for an onset of trauma or tumor is quite poor.\n\nUltimately, nerves are not very good at regenerating or healing themselves, so if the damage is severe there will be permanent damage.\n\nIn addition, another disorder associated with the lateral rectus muscle is Duane Syndrome.\n\nThis syndrome occurs when the sixth cranial nerve which controls the lateral rectus muscle does not develop properly.\n\nIt is believed that Duane Syndrome is a result of a disturbance of normal embryonic development due to a genetic or an environmental factor.\n\nhttps://en.wikipedia.org/wiki/Lateral_rectus_muscle","superior-oblique-muscle":"The superior oblique muscle, or obliquus oculi superior, is a fusiform muscle originating in the upper, medial side of the orbit (i.e. from beside the nose) which abducts, depresses and internally rotates the eye.\n\nIt is the only extraocular muscle innervated by the trochlear nerve (the fourth cranial nerve).\n\n== Structure ==\n\nThe superior oblique muscle loops through a pulley-like structure (the trochlea of superior oblique) and inserts into the sclera on the posterotemporal surface of the eyeball.\n\nIt is the pulley system that gives superior oblique its actions, causing depression of the eyeball despite being inserted on the superior surface.\n\nThe superior oblique arises immediately above the margin of the optic foramen, superior and medial to the origin of the superior rectus, and, passing forward, ends in a rounded tendon, which plays in a fibrocartilaginous ring or pulley attached to the trochlear fossa of the frontal bone.\n\nThe contiguous surfaces of the tendon and ring are lined by a delicate mucous sheath, and enclosed in a thin fibrous investment.\n\nThe tendon is reflected caudally, laterally, and inferiorly beneath the superior rectus to the lateral part of the bulb of the eye, and is inserted onto the scleral surface, behind the equator of the eyeball, the insertion of the muscle lying between the superior rectus and lateral rectus.\n\n== Function ==\n\nThe primary (main) action of the superior oblique muscle is intorsion (internal rotation), the secondary action is depression (primarily in the adducted position) and the tertiary action is abduction (lateral rotation).\n\nThe extraocular muscles rotate the eyeball around vertical, horizontal and antero-posterior axes.\n\nExtraocular muscles other than the medial rectus and lateral rectus have more than one action due to the angle they make with the optical axis of the eye while inserting into the eyeball.\n\nThe superior and inferior oblique muscles make an angle of 51 degrees with the optical axis.The depressing action of superior oblique (making the eye look down towards the mouth) is most effective when the eye is in an adducted position.\n\nThis is because as the eye is abducted (looks laterally), the contribution made by superior oblique to depression of the eye decreases, as the inferior rectus muscle causes this movement more directly and powerfully.\n\nThe main muscle for abduction is the lateral rectus, so although superior oblique contributes to a downwards and lateral eye movement, testing this motion would not be specific enough as inferior and lateral recti muscles would also be tested.\n\nTherefore, during neurological examinations, the superior oblique is tested by having the patient look inwards and downwards, testing only the depressing action of the muscle.\n\nThis is a source of confusion on the subject as although clinical testing asks the patient to adduct and depress the eye, anatomically the muscle depresses and abducts it.\n\nThe great importance of intorsion and extorsion produced by the two oblique muscles can only be understood when it is considered with regards to the other muscle actions present.\n\nThe two obliques prevent the eye from rotating about its long axis (retina to pupil) when the superior and inferior rectus muscles contract.\n\nThis is because the orbit does not face directly forwards- the centre-line of the orbit is a little over 20 degrees out from the mid-line.\n\nBut because the eyes do face forwards, when acting alone, as well as making the eye look up, superior rectus causes it to rotate slightly about the long axis, so the top of the eye moves medially (intorsion).\n\nSimilarly, in addition to making the eye look down, inferior rectus would cause the eye to rotate about the long axis so the top of the eye moves slightly laterally (extorsion), if acting alone.\n\nClearly this is undesirable as our vision would rotate when we looked up and down.\n\nFor this reason, these two rectus muscles work in conjunction with the two obliques.\n\nWhen acting alone, superior oblique causes intorsion, inferior oblique, extorsion.\n\nHence, when inferior rectus contracts so we look down, superior oblique also contracts to prevent extorsion of the eye, and when superior rectus contracts so we look up, inferior oblique contracts to prevent intorsion, thus the undesired rotatory actions of the inferior and superior recti about the long axis of the eye are cancelled out.\n\nThis keeps our vision horizontally level, irrespective of eye position in the orbit.\n\n== Clinical significance ==\n\nSuperior oblique palsy is a common complication of closed head trauma.\n\nRestriction of superior oblique movement due to an inelastic tendon is found in Brown syndrome, leading to difficulty elevating the eye in the adducted position.\n\nSuperior oblique myokymia is an uncommon neurological condition caused by vascular compression of the trochlear nerve resulting in repeated, brief, involuntary episodes of movement of the eye.\n\nSurgical operations of the superior oblique include tenotomy, recession, silicone expander lengthening, split tendon lengthening, tucking, and the Harada-Ito procedure.\n\nhttps://en.wikipedia.org/wiki/Superior_oblique_muscle","common-tendinous-ring":"The common tendinous ring, also known as the annulus of Zinn, or annular tendon, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit.\n\nIt is the common origin of the four recti muscles of the group of extraocular muscles.\n\nIt can be used to divide the regions of the superior orbital fissure.\n\nThe arteries surrounding the optic nerve form a vascular structure known as the circle of Zinn-Haller, or sometimes as the circle of Zinn.\n\nThe following structures pass through the tendinous ring (superior to inferior):\n\n -Superior division of the oculomotor nerve (CNIII)\n -Nasociliary nerve (branch of ophthalmic nerve)\n -Inferior division of the oculomotor nerve (CNIII)\n -Abducens nerve (CNVI)\n -Optic nerve\n\n== Parts ==\n\nThe common tendinous ring spans the superior orbital fissure and can be described as having two parts – an inferior tendon which gives origin to the inferior rectus muscle, and to part of the lateral rectus muscle; and a superior tendon which gives origin to the superior rectus muscle, and to part of the medial and lateral recti muscles.\n\n== Eponym ==\n\nIt is named for Johann Gottfried Zinn.\n\nIt should not be confused with the zonule of Zinn, though it is named after the same person.\n\nhttps://en.wikipedia.org/wiki/Common_tendinous_ring","inferior-oblique-muscle":"The inferior oblique muscle or obliquus oculi inferior is a thin, narrow muscle placed near the anterior margin of the floor of the orbit.\n\nThe inferior oblique is one of the extraocular muscles, and is attached to the maxillary bone (origin) and the posterior, inferior, lateral surface of the eye (insertion).\n\nThe inferior oblique is innervated by the inferior branch of the oculomotor nerve.\n\n== Structure ==\n\nThe inferior oblique arises from the orbital surface of the maxilla, lateral to the lacrimal groove.\n\nUnlike the other extraocular muscles (recti and superior oblique), the inferior oblique muscle does not originate from the common tendinous ring (annulus of Zinn).\n\nPassing lateralward, backward, and upward, between the inferior rectus and the floor of the orbit, and just underneath the lateral rectus muscle, the inferior oblique inserts onto the scleral surface between the inferior rectus and lateral rectus.\n\nIn humans, the muscle is about 35 mm long.\n\n=== Innervation ===\n\nThe inferior oblique is innervated by the inferior division of the oculomotor nerve (cranial nerve III).\n\n== Function ==\n\nIts actions are extorsion, elevation and abduction of the eye.\n\nPrimary action is extorsion (external rotation); secondary action is elevation; tertiary action is abduction (i.e. it extorts the eye and moves it upward and outwards).\n\nThe field of maximal inferior oblique elevation is in the adducted position.\n\nThe inferior oblique muscle is the only muscle that is capable of elevating the eye when it is in a fully adducted position.\n\n== Clinical significance ==\n\nWhile commonly affected by palsies of the inferior division of the oculomotor nerve, isolated palsies of the inferior oblique (without affecting other functions of the oculomotor nerve) are quite rare.\n\n\"Overaction\" of the inferior oblique muscle is a commonly observed component of childhood strabismus, particularly infantile esotropia and exotropia.\n\nBecause true hyperinnervation is not usually present, this phenomenon is better termed \"elevation in adduction\".\n\nSurgical procedures of the inferior oblique include: loosening (also known as recession see Strabismus surgery), myectomy, marginal myotomy, and denervation and extirpation.\n\nIt is also encountered and identified in lower lid blepharoplasty surgeries.\n\nhttps://en.wikipedia.org/wiki/Inferior_oblique_muscle","inferior-rectus-muscle":"The inferior rectus muscle is a muscle in the orbit near the eye.\n\nIt is one of the four recti muscles in the group of extraocular muscles.\n\nIt originates from the common tendinous ring, and inserts into the anteroinferior surface of the eye.\n\nIt depresses the eye (downwards).\n\n== Structure ==\n\nThe inferior rectus muscle originates from the common tendinous ring (annulus of Zinn).\n\nIt inserts into the anteroinferior surface of the eye.\n\nThis insertion has a width of around 10.5 mm.\n\nIt is around 7 mm from the corneal limbus.\n\n=== Blood supply ===\n\nThe inferior rectus muscle is supplied by an inferior muscular branch of the ophthalmic artery.\n\nIt may also be supplied by a branch of the infraorbital artery.\n\nIt is drained by the corresponding veins: the inferior muscular branch of the ophthalmic vein, and sometimes a branch of the infraorbital vein.\n\n=== Nerve supply ===\n\nThe inferior rectus muscle is supplied by the inferior division of the oculomotor nerve (III).\n\n=== Development ===\n\nThe inferior rectus muscle develops from the embryonic mesoderm in the orbit of the skull.\n\nThis is similar to the other extraocular muscles.\n\n=== Relations ===\n\nThe insertion of the inferior rectus muscle is around 6 mm from the insertion of the medial rectus muscle, and around 8 mm from the insertion of the lateral rectus muscle.\n\nA parasympathetic branch that supplies the ciliary muscles of the pupil passes close to the inferior rectus muscle.\n\n=== Variation ===\n\nVery rarely, the inferior rectus muscle may be congenitally absent.\n\nThis may cause inferior rectus palsy, where the eye cannot be depressed.\n\n== Function ==\n\nThe inferior rectus muscle depresses, adducts, and helps extort the eye.\n\nIt is the only muscle that is capable of depressing the pupil when it is in a fully abducted position.\n\n== Clinical significance ==\n\n=== Strabismus ===\n\nIf the inferior rectus muscle is damaged, weak, or paralysed, this can cause strabismus.\n\nThis can lead to elevation of the eye, as the superior rectus muscle remains stronger.\n\nFor minor cases, prism glasses can be used to gradually realign the eye.\n\nAlternatively for serious cases, it may be surgically corrected by slightly weakening the superior rectus muscle (opposite) - this reduces the elevation of the eye, and corrects the strabismus.\n\nThis procedure may lead to overcorrection of the strabismus, but is otherwise generally successful.\n\n=== Surgery ===\n\nAny surgery on the inferior rectus muscle may damage the parasympathetic branches to the ciliary muscles of the pupil.\n\nThis may cause problems with control of the pupil.\n\nNearby blood vessels and nerves may also be damaged.\n\nhttps://en.wikipedia.org/wiki/Inferior_rectus_muscle","inferior-tarsus":"The tarsi (tarsal plates) are two comparatively thick, elongated plates of dense connective tissue, about 10 mm (0.39 in) in length for the upper eyelid and 5 mm for the lower eyelid; one is found in each eyelid, and contributes to its form and support.\n\nThey are located directly above the lid margins.\n\nThe tarsus has a lower and upper part making up the palpebrae.\n\n== Inferior ==\n\nThe inferior tarsus (tarsus inferior; inferior tarsal plate) is smaller, is thin, is elliptical in form, and has a vertical diameter of about 5 mm (0.2 in).\n\nThe free or ciliary margins of these plates are thick and straight.\n\n== Relations ==\n\nThe attached or orbital margins are connected to the circumference of the orbit by the orbital septum.\n\nThe lateral angles are attached to the zygomatic bone by the lateral palpebral raphe.\n\nThe medial angles of the two plates end at the lacrimal lake, and are attached to the frontal process of the maxilla by the medial palpebral ligament).\n\nThe sulcus subtarsalis is a groove in the inner surface of each eyelid.\n\nAlong the inner margin of the tarsus are modified sebaceous glands known as tarsal glands (or meibomian glands), aligned vertically within the tarsi: 30 to 40 glands in the upper lid, and 20 to 30 in the lower lid, which secrete a lipid-rich product which helps keep the lacrimal secretions or tears from evaporating too quickly, thus keeping the eye moist.\n\nhttps://en.wikipedia.org/wiki/Tarsus_(eyelids)","levator-palpebrae-superioris":"The levator palpebrae superioris (Latin: elevating muscle of upper eyelid) is the muscle in the orbit that elevates the upper eyelid.\n\n== Structure ==\n\nThe levator palpebrae superioris originates from inferior surface of the lesser wing of the sphenoid bone, just above the optic foramen.\n\nIt broadens and decreases in thickness (becomes thinner) and becomes the levator aponeurosis.\n\nThis portion inserts on the skin of the upper eyelid, as well as the superior tarsal plate.\n\nIt is a skeletal muscle.\n\nThe superior tarsal muscle, a smooth muscle, is attached to the levator palpebrae superioris, and inserts on the superior tarsal plate as well.\n\n=== Blood supply ===\n\nThe levator palebrae superioris receives its blood supply from branches of the ophthalmic artery, specifically, muscular branches and the supraorbital artery.\n\nBlood is drained into the superior ophthalmic vein.\n\n=== Nerve supply ===\n\nThe levator palpebrae superioris receives motor innervation from the superior division of the oculomotor nerve.\n\nThe smooth muscle that originates from its undersurface, called the superior tarsal muscle is innervated by postganglionic sympathetic axons from the superior cervical ganglion.\n\n== Function ==\n\nThe levator palpebrae superioris elevates the upper eyelid.\n\n== Clinical significance ==\n\nDamage to this muscle or its innervation can cause ptosis, which is drooping of the eyelid.\n\nLesions in CN III can cause ptosis, because without stimulation from the oculomotor nerve the levator palpebrae cannot oppose the force of gravity, and the eyelid droops.\n\nPtosis can also result from damage to the adjoining superior tarsal muscle or its sympathetic innervation.\n\nSuch damage to the sympathetic supply occurs in Horner's syndrome and presents as a partial ptosis.\n\nIt is important to distinguish between these two very different causes of ptosis.\n\nThis can usually be done clinically without issue, as each type of ptosis is accompanied by other distinct clinical findings.\n\nThe ptosis seen in paralysis of the levator palpebrae superioris is usually more pronounced than that seen due to paralysis of the superior tarsal muscle.\n\nhttps://en.wikipedia.org/wiki/Levator_palpebrae_superioris_muscle","medial-rectus-muscle":"The medial rectus muscle is a muscle in the orbit near the eye.\n\nIt is one of the extraocular muscles.\n\nIt originates from the common tendinous ring, and inserts into the anteromedial surface of the eye.\n\nIt is supplied by the inferior division of the oculomotor nerve (III).\n\nIt rotates the eye medially (adduction).\n\n== Structure ==\n\nThe medial rectus muscle shares an origin with several other extrinsic eye muscles, the common tendinous ring.\n\nIt inserts into the anteromedial surface of the eye.\n\nThis insertion has a width of around 11 mm.\n\n=== Nerve supply ===\n\nThe medial rectus muscle is supplied by the inferior division of the oculomotor nerve (III).\n\nA branch of it enters the muscle around two fifths along its length.\n\nIt usually divides into 2 smaller branches, occasionally 3.\n\nThese further subdivide, becoming smaller down the length of the muscle until they become imperceptible to standard staining around 17 mm from the insertion of the muscle.\n\n=== Relations ===\n\nThe insertion of the medial rectus muscle is around 7.5 mm from the insertion of the superior rectus muscle, and around 6 mm from the inferior rectus muscle.\n\nIt is shorter but stronger than the other orbital recti muscles.\n\nIt rarely changes position significantly when it contracts, unlike the other extraocular muscles.\n\n== Function ==\n\nThe medial rectus muscle rotates the eye medially (adduction).\n\nIt works using a pulley system as it curves around the anterior surface of the eye.\n\n== Clinical significance ==\n\n=== Strabismus ===\n\nStrabismus (lazy eye) may be caused by a medial rectus muscle that is located too high in the orbit of the skull.\n\nEsotropia (convergent strabismus) may also be caused by sixth nerve palsy, which causes weakness or paralysis of the lateral rectus muscle.\n\nSometimes, botulinum toxin may be injected into the medial rectus muscle.\n\nWhilst this reduces the ability to abduct and adduct the eye for tracking, it corrects the esotropia and so generally improves vision.\n\n=== Compression ===\n\nThe medial rectus muscle lies directly adjacent to the orbit of the skull.\n\nThis leaves it vulnerable to being compressed (incarcerated) during skull fractures, which can prevent movement of the eye.\n\nThis usually resolves when skull fractures are fixed.\n\n=== Surgical damage ===\n\nThe medial rectus muscle may be damaged during eye surgery or skull surgery, such as functional endoscopic sinus surgery.\n\nThe damage can be minor, such as bruising, or sever, such as cutting through the muscle partially or completely, and nerve injury.\n\nhttps://en.wikipedia.org/wiki/Medial_rectus_muscle","superior-rectus-muscle":"The superior rectus muscle is a muscle in the orbit.\n\nIt is one of the extraocular muscles.\n\nIt is innervated by the superior division of the oculomotor nerve (III).\n\nIn the primary position (looking straight ahead), its primary function is elevation, although it also contributes to intorsion and adduction.\n\nIt is associated with a number of medical conditions, and may be weak, paralysed, overreactive, or even congenitally absent in some people.\n\n== Structure ==\n\nThe superior rectus muscle originates from the annulus of Zinn.\n\nIt inserts into the anterosuperior surface of the eye.\n\nThis insertion has a width of around 11 mm.\n\nIt is around 8 mm from the corneal limbus.\n\n=== Nerve supply ===\n\nThe superior rectus muscle is supplied by the superior division of the oculomotor nerve (III).\n\n=== Relations ===\n\nThe superior rectus muscle is related to the other extraocular muscles, particularly to the medial rectus muscle and the lateral rectus muscle.\n\nThe insertion of the superior rectus muscle is around 7.5 mm from the insertion of the medial rectus muscle, around 7.1 mm from the insertion of the lateral rectus muscle, and around 7.9 from the corneal limbus.\n\nThere is an intermuscular septum between it and the lateral rectus muscle.\n\n=== Variation ===\n\nVariations of the superior rectus muscle is rare.\n\nIt may rarely have two muscle bellies parallel to each other.\n\nMore rarely, it may be congenitally absent.\n\n== Function ==\n\nThe superior rectus muscle elevates, adducts, and helps intort (rotate medially) the eye.\n\n== Clinical significance ==\n\n=== Testing ===\n\nThe superior rectus muscle is the only muscle that is capable of elevating the eye when it is in a fully abducted position.\n\n=== Exophthalmos ===\n\nMuch of the venous drainage of the orbit and the extraocular muscles passes close to the superior rectus muscle.\n\nObstruction to this venous drainage can cause venous congestion in the eye, which may cause exophthalmos (bulging eye ball).\n\nThis may be shown with CT scans.\n\n=== Weakness and paralysis ===\n\nThe superior rectus muscle may be weakened or paralysed by problems with nerve conduction of the oculomotor nerve (III).\n\nThis may be congenital, often with a familial genetic link, or acquired, most often caused by head injuries.\n\n=== Overreaction ===\n\nLocal anaesthetics used in cataract surgery may weaken the inferior rectus muscle, despite efforts to use minimal anaesthetic and to avoid placing the needle into the muscle.\n\nWeakness of the inferior rectus muscle may strengthen the superior rectus muscle, causing it to be overreactive.\n\nThis may elevate the eye, and prevent its use in normal vision.\n\nTreatment may involve eye surgery that weakens or repositions the superior rectus muscle, which generally has good outcomes.\n\n=== Absence ===\n\nVery rarely, the superior rectus muscle may be congenitally absent.\n\nThis may be caused by Apert syndrome.\n\nThis causes a reduced ability to elevate the eye.\n\nIt may be treated with eye surgery that uses parts of the medial rectus muscle and the lateral rectus muscle to restore the functions normally performed by the superior rectus muscle.\n\nhttps://en.wikipedia.org/wiki/Superior_rectus_muscle","superior-tarsus":"The tarsi (tarsal plates) are two comparatively thick, elongated plates of dense connective tissue, about 10 mm (0.39 in) in length for the upper eyelid and 5 mm for the lower eyelid; one is found in each eyelid, and contributes to its form and support.\n\nThey are located directly above the lid margins.\n\nThe tarsus has a lower and upper part making up the palpebrae.\n\n== Superior ==\n\nThe superior tarsus (tarsus superior; superior tarsal plate), the larger, is of a semilunar form, about 10 mm (0.4 in) in breadth at the center, and gradually narrowing toward its extremities.\n\nIt is adjoined by the superior tarsal muscle.\n\nTo the anterior surface of this plate the aponeurosis of the levator palpebræ superioris is attached.\n\n== Relations ==\n\nThe attached or orbital margins are connected to the circumference of the orbit by the orbital septum.\n\nThe lateral angles are attached to the zygomatic bone by the lateral palpebral raphe.\n\nThe medial angles of the two plates end at the lacrimal lake, and are attached to the frontal process of the maxilla by the medial palpebral ligament).\n\nThe sulcus subtarsalis is a groove in the inner surface of each eyelid.\n\nAlong the inner margin of the tarsus are modified sebaceous glands known as tarsal glands (or meibomian glands), aligned vertically within the tarsi: 30 to 40 glands in the upper lid, and 20 to 30 in the lower lid, which secrete a lipid-rich product which helps keep the lacrimal secretions or tears from evaporating too quickly, thus keeping the eye moist.\n\nhttps://en.wikipedia.org/wiki/Tarsus_(eyelids)","trochlea-of-superior-oblique-muscle":"The superior oblique muscle loops through a pulley-like structure (the trochlea of superior oblique) and inserts into the sclera on the posterotemporal surface of the eyeball.\n\nIt is the pulley system that gives superior oblique its actions, causing depression of the eyeball despite being inserted on the superior surface.\n\nhttps://en.wikipedia.org/wiki/Superior_oblique_muscle","frontalis-muscle":"The frontalis muscle (from Latin 'frontal muscle') is a muscle which covers parts of the forehead of the skull.\n\nSome sources consider the frontalis muscle to be a distinct muscle.\n\nHowever, Terminologia Anatomica currently classifies it as part of the occipitofrontalis muscle along with the occipitalis muscle.\n\nIn humans, the frontalis muscle only serves for facial expressions.\n\nThe frontalis muscle is supplied by the facial nerve and receives blood from the supraorbital and supratrochlear arteries.\n\n== Structure ==\n\nThe frontalis muscle is thin, of a quadrilateral form, and intimately adherent to the superficial fascia.\n\nIt is broader than the occipitalis and its fibers are longer and paler in color.\n\nIt is located on the front of the head.\nThe muscle has no bony attachments.\n\nIts medial fibers are continuous with those of the procerus; its intermediate fibers blend with the corrugator and orbicularis oculi muscles, thus attached to the skin of the eyebrows; and its lateral fibers are also blended with the latter muscle over the zygomatic process of the frontal bone.\n\nFrom these attachments the fibers are directed upward, and join the galea aponeurotica below the coronal suture.\n\nThe medial margins of the frontalis muscles are joined together for some distance above the root of the nose; but between the occipitales there is a considerable, though variable, interval, occupied by the galea aponeurotica.\n\n== Function ==\n\nIn humans, the frontalis muscle only serves for facial expressions.\n\nIn the eyebrows, its primary function is to lift them (thus opposing the orbital portion of the orbicularis), especially when looking up.\n\nIt also acts when a view is too distant or dim.\n\nhttps://en.wikipedia.org/wiki/Frontalis_muscle","occipitalis-muscle":"The occipitalis muscle (occipital belly) is a muscle which covers parts of the skull.\n\nSome sources consider the occipital muscle to be a distinct muscle.\n\nHowever, Terminologia Anatomica currently classifies it as part of the occipitofrontalis muscle along with the frontalis muscle.\n\nThe occipitalis muscle is thin and quadrilateral in form.\n\nIt arises from tendinous fibers from the lateral two-thirds of the superior nuchal line of the occipital bone and from the mastoid process of the temporal and ends in the epicranial aponeurosis.\n\nThe occipitalis muscle is innervated by the facial nerve and its function is to move the scalp back.\n\nThe muscles receives blood from the occipital artery.\n\n== Additional image ==\n\nhttps://en.wikipedia.org/wiki/Occipitalis_muscle","epicranial-aponeurosis":"The epicranial aponeurosis (aponeurosis epicranialis, galea aponeurotica) is an aponeurosis (a tough layer of dense fibrous tissue).\n\nIt covers the upper part of the skull in humans and many other animals.\n\n== Structure ==\n\nIn humans, the epicranial aponeurosis originates from the external occipital protuberance and highest nuchal lines of the occipital bone.\n\nIt merges with the occipitofrontalis muscle.\n\nIn front, it forms a short and narrow prolongation between its union with the frontalis muscle (the frontal part of the occipitofrontalis muscle).\n\nOn either side, the epicranial aponeurosis attaches to the anterior auricular muscles and the superior auricular muscles.\n\nHere it is less aponeurotic, and is continued over the temporal fascia to the zygomatic arch as a layer of laminated areolar tissue.\n\nIt is closely connected to the integument by the firm, dense, fibro-fatty layer which forms the superficial fascia of the scalp.\n\nIt is attached to the pericranium by loose cellular tissue, which allows the aponeurosis, carrying with it the integument, to move through a considerable distance.\n\n== Clinical significance ==\n\nSubgaleal haemorrhage is defined as bleeding between the epicranial aponeurosis and the skull.\n\nConservative management is usually appropriate for these, as there is little risk of further damage to surrounding structures.\n\n== History ==\n\nThe epicranial aponeurosis is also known as the aponeurosis epicranialis (from Latin), and the galea aponeurotica.\n\nhttps://en.wikipedia.org/wiki/Epicranial_aponeurosis","temporoparietalis-muscle":"The temporoparietalis muscle is a distinct muscle of the head.\n\nIt lies above the auricularis superior muscle.\n\nIt lies just inferior to the epicranial aponeurosis of the occipitofrontalis muscle.\n\nThe temporoparietalis muscle may be used in reconstructive ear surgery.\n\nhttps://en.wikipedia.org/wiki/Temporoparietalis_muscle","nasalis-muscle":"The nasalis muscle is a sphincter-like muscle of the nose.\n\nIt has a transverse part and an alar part.\n\nIt compresses the nasal cartilages, and can \"flare\" the nostrils.\n\nSome people can use it to close the nostrils to prevent entry of water when underwater.\n\nIt can be used to test the facial nerve (VII), which supplies it.\n\n== Structure ==\n\nThe nasalis muscle covers the nasal cartilages of the lower surface of the nose.\n\nIt consists of two parts, transverse and alar:\n\n-The transverse part (compressor naris muscle) arises from the maxilla, above and lateral to the incisive fossa.\n\nIts fibers proceed upward and medially, expanding into a thin aponeurosis which is continuous on the bridge of the nose with that of the muscle of the opposite side, and with the aponeurosis of the procerus muscle. It compresses the nostrils and may completely close them.\n\nThe alar part (dilator naris muscle) arises from the maxilla over the lateral incisor and inserts into the greater alar cartilage.\n\nIts medial fibres tend to blend with the depressor septi nasi muscle, and has been described as part of that muscle.\n\n=== Nerve supply ===\n\nLike all the other muscles of facial expression, the nasalis muscle is supplied by the facial nerve (VII).\n\n== Function ==\n\nThe nasalis muscle compresses the nasal cartilages. It may also \"flare\" the nostrils.\n\nSome people can use it to close the nostrils to prevent entry of water when underwater.\n\n== Clinical significance ==\n\n=== Cleft lip and cleft palate ===\n\nThe nasalis muscle is one of the key muscles not formed or inserted correctly with cleft lip and cleft palate deformity.\n\nThe head of the transverse part needs to be identified during reconstructive surgery so that it can be surgically sutured (connected to) the nasal septum.\n\nThe origin at the maxilla may also be repositioned for better symmetry.\n\n=== Facial nerve testing ===\n\nDue to it being superficial, the nasalis muscle can be used to test the facial nerve. Specifically, it can be used to test the zygomatic branches.\n\nhttps://en.wikipedia.org/wiki/Nasalis_muscle","orbital-part-of-orbicularis-oculi":"The orbicularis oculi is a muscle in the face that closes the eyelids.\n\nIt arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short fibrous band, the medial palpebral ligament.\n\nFrom this origin, the fibers are directed laterally, forming a broad and thin layer, which occupies the eyelids or palpebræ, surrounds the circumference of the orbit, and spreads over the temple, and downward on the cheek.\n\n== Structure ==\n\nThere are at least 3 clearly defined sections of the orbicularis muscle.\n\nHowever, it is not clear whether the lacrimal section is a separate section, or whether it is just an extension of the preseptal and pretarsal sections.\n\n=== Orbital orbicularis ===\n\nThe orbital portion is thicker and of a reddish color; its fibers form a complete ellipse without interruption at the lateral palpebral commissure; the upper fibers of this portion blend with the frontalis and corrugator.\n\n=== Palpebral orbicularis ===\n\nThe palpebral portion of the muscle is thin and pale; it arises from the bifurcation of the medial palpebral ligament, forms a series of concentric curves, and is inserted into the lateral palpebral raphe at the outer canthus (corner) of the eye.\n\nThe palpebral portion contains the preseptal and pretarsal muscles. The pretarsal orbicularis is thought to be responsible for the spontaneous blink.\n\n=== Lacrimal orbicularis ===\n\nThe lacrimal part is a small, thin muscle, about 6 mm in breadth and 12 mm in length, situated behind the medial palpebral ligament and lacrimal sac.\n\nIt arises from the posterior crest and adjacent part of the orbital surface of the lacrimal bone, and passing behind the lacrimal sac, divides into two slips, upper and lower, which are inserted into the superior and inferior tarsi medial to the puncta lacrimalia; occasionally it is very indistinct.\n\nThe lacrimal orbicularis facilitates the tear pump into the lacrimal sac.\n\n== Function ==\n\nThe muscle acts to close the eye, and is the only muscle capable of doing so.\n\nLoss of function for any reason results in an inability to close the eye, necessitating eye drops at the minimum to surgical closure of the eye in extreme cases.\n\nThe palpebral portion acts involuntarily, closing the lids gently, as in sleep or in blinking; the orbital portion is subject to conscious control.\n\nWhen the entire muscle is brought into action, the skin of the forehead, temple, and cheek is drawn toward the medial angle of the orbit, and the eyelids are firmly closed, as in photophobia.\n\nThe skin thus drawn upon is thrown into folds, especially radiating from the lateral angle of the eyelids; these folds become permanent in senescence, and form the so-called \"crow's feet\".\n\nThe Levator palpebræ superioris is the direct antagonist of this muscle; it raises the upper eyelid and exposes the front of the bulb of the eye.\n\nIn addition, the orbital and palpebral portions can work independent of each other, as in the furrowing of the brows by contraction of the orbital to reduce glare while keeping the eyes open by virtue of the relaxation of the palpebral.\n\nEach time the eyelids are closed through the action of the orbicularis, the medial palpebral ligament is tightened, the wall of the lacrimal sac is thus drawn lateralward and forward, so that a vacuum is made in it and the tears are sucked along the lacrimal canals into it.\n\nThe lacrimal part of the orbicularis oculi draws the eyelids and the ends of the lacrimal canals medialward and compresses them against the surface of the globe of the eye, thus placing them in the most favorable situation for receiving the tears; it also compresses the lacrimal sac.\n\nThis part comprises two pieces: Horner's muscle and the muscle of Riolan, the latter helps hold the eyelids together to keep the lacrimal passage waterproof.\n\nAssociated pathology, such as a lesion of the facial nerve seen in Bell's palsy results in the inability to blink or close the ipsilateral eyelid.\n\nSubsequent lack of irrigation increases the risk of corneal inflammation and ulcers.A number of auxiliary muscles assist in cooperating with the eyelid muscles.\n\nFor example, the corrugator supercilii pulls the eyebrows to the bridge of the nose, making a roof over the middle of the forehead and forehead wrinkles, used mainly to protect the eyes from excess sunlight.\n\nThe procerus (pyramidalis) muscles, in the bridge of the nose, arise from the lower nasal bone to the lower forehead, on each side of the midline.\n\nThe procerus muscles pull the skin into horizontal wrinkles.\n\nThe frontalis muscle, which runs from the upper forehead, halfway between the coronal suture (which traverses the top of the skull) and the top edge of the orbit, attaches to the eyebrow skin.\n\nSince it pulls the eyebrows upward, it is the antagonist of the orbicularis oculi.\n\nIt is used in looking up, and increasing vision if there is insufficient light or when objects are far away.\n\n== Clinical significance ==\n\nIt is involved in the corneal reflex, part of the assessment of the function of the facial nerve.\n\nThis can be used to examine the facial nerve even in unconscious patients.\n\nhttps://en.wikipedia.org/wiki/Orbicularis_oculi_muscle","palpebral-part-of-orbicularis-oculi":"The orbicularis oculi is a muscle in the face that closes the eyelids.\n\nIt arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short fibrous band, the medial palpebral ligament.\n\nFrom this origin, the fibers are directed laterally, forming a broad and thin layer, which occupies the eyelids or palpebræ, surrounds the circumference of the orbit, and spreads over the temple, and downward on the cheek.\n\n== Structure ==\n\nThere are at least 3 clearly defined sections of the orbicularis muscle.\n\nHowever, it is not clear whether the lacrimal section is a separate section, or whether it is just an extension of the preseptal and pretarsal sections.\n\n=== Orbital orbicularis ===\n\nThe orbital portion is thicker and of a reddish color; its fibers form a complete ellipse without interruption at the lateral palpebral commissure; the upper fibers of this portion blend with the frontalis and corrugator.\n\n=== Palpebral orbicularis ===\n\nThe palpebral portion of the muscle is thin and pale; it arises from the bifurcation of the medial palpebral ligament, forms a series of concentric curves, and is inserted into the lateral palpebral raphe at the outer canthus (corner) of the eye.\n\nThe palpebral portion contains the preseptal and pretarsal muscles. The pretarsal orbicularis is thought to be responsible for the spontaneous blink.\n\n=== Lacrimal orbicularis ===\n\nThe lacrimal part is a small, thin muscle, about 6 mm in breadth and 12 mm in length, situated behind the medial palpebral ligament and lacrimal sac.\n\nIt arises from the posterior crest and adjacent part of the orbital surface of the lacrimal bone, and passing behind the lacrimal sac, divides into two slips, upper and lower, which are inserted into the superior and inferior tarsi medial to the puncta lacrimalia; occasionally it is very indistinct.\n\nThe lacrimal orbicularis facilitates the tear pump into the lacrimal sac.\n\n== Function ==\n\nThe muscle acts to close the eye, and is the only muscle capable of doing so.\n\nLoss of function for any reason results in an inability to close the eye, necessitating eye drops at the minimum to surgical closure of the eye in extreme cases.\n\nThe palpebral portion acts involuntarily, closing the lids gently, as in sleep or in blinking; the orbital portion is subject to conscious control.\n\nWhen the entire muscle is brought into action, the skin of the forehead, temple, and cheek is drawn toward the medial angle of the orbit, and the eyelids are firmly closed, as in photophobia.\n\nThe skin thus drawn upon is thrown into folds, especially radiating from the lateral angle of the eyelids; these folds become permanent in senescence, and form the so-called \"crow's feet\".\n\nThe Levator palpebræ superioris is the direct antagonist of this muscle; it raises the upper eyelid and exposes the front of the bulb of the eye.\n\nIn addition, the orbital and palpebral portions can work independent of each other, as in the furrowing of the brows by contraction of the orbital to reduce glare while keeping the eyes open by virtue of the relaxation of the palpebral.\n\nEach time the eyelids are closed through the action of the orbicularis, the medial palpebral ligament is tightened, the wall of the lacrimal sac is thus drawn lateralward and forward, so that a vacuum is made in it and the tears are sucked along the lacrimal canals into it.\n\nThe lacrimal part of the orbicularis oculi draws the eyelids and the ends of the lacrimal canals medialward and compresses them against the surface of the globe of the eye, thus placing them in the most favorable situation for receiving the tears; it also compresses the lacrimal sac.\n\nThis part comprises two pieces: Horner's muscle and the muscle of Riolan, the latter helps hold the eyelids together to keep the lacrimal passage waterproof.\n\nAssociated pathology, such as a lesion of the facial nerve seen in Bell's palsy results in the inability to blink or close the ipsilateral eyelid.\n\nSubsequent lack of irrigation increases the risk of corneal inflammation and ulcers.A number of auxiliary muscles assist in cooperating with the eyelid muscles.\n\nFor example, the corrugator supercilii pulls the eyebrows to the bridge of the nose, making a roof over the middle of the forehead and forehead wrinkles, used mainly to protect the eyes from excess sunlight.\n\nThe procerus (pyramidalis) muscles, in the bridge of the nose, arise from the lower nasal bone to the lower forehead, on each side of the midline.\n\nThe procerus muscles pull the skin into horizontal wrinkles.\n\nThe frontalis muscle, which runs from the upper forehead, halfway between the coronal suture (which traverses the top of the skull) and the top edge of the orbit, attaches to the eyebrow skin.\n\nSince it pulls the eyebrows upward, it is the antagonist of the orbicularis oculi.\n\nIt is used in looking up, and increasing vision if there is insufficient light or when objects are far away.\n\n== Clinical significance ==\n\nIt is involved in the corneal reflex, part of the assessment of the function of the facial nerve.\n\nThis can be used to examine the facial nerve even in unconscious patients.\n\nhttps://en.wikipedia.org/wiki/Orbicularis_oculi_muscle","orbicularis-oris-muscle":"In human anatomy, the orbicularis oris muscle is a complex of muscles in the lips that encircles the mouth.\n\nIt is a sphincter, or circular muscle, but it is actually composed of four independent quadrants that interlace and give only an appearance of circularity.\n\nIt is also one of the muscles used in the playing of all brass instruments and some woodwind instruments.\n\nThis muscle closes the mouth and puckers the lips when it contracts.\n\n== Anatomy ==\n\nThe orbicularis oris is not a simple sphincter muscle like the orbicularis oculi; it consists of numerous strata of muscular fibers surrounding the orifice of the mouth, but having different direction.\n\nIt consists partly of fibers derived from the other facial muscles which are inserted into the lips, and partly of fibers proper to the lips.\n\nOf the former, a considerable number are derived from the buccinator and form the deeper stratum of the orbicularis.\n\nSome of the buccinator fibers—namely, those near the middle of the muscle—decussate at the angle of the mouth, those arising from the maxilla passing to the lower lip, and those from the mandible to the upper lip.\n\nThe uppermost and lowermost fibers of the buccinator pass across the lips from side to side without decussation.\n\nSuperficial to this stratum is a second, formed on either side by the caninus and triangularis, which cross each other at the angle of the mouth; those from the caninus passing to the lower lip, and those from the triangularis to the upper lip, along which they run, to be inserted into the skin near the median line.\n\nIn addition to these, fibers from the quadratus labii superioris, the zygomaticus, and the quadratus labii inferioris intermingle with the transverse fibers above described, and have principally an oblique direction.\n\nThe proper fibers of the lips are oblique, and pass from the under surface of the skin to the mucous membrane, through the thickness of the lip.\n\nFinally, fibers occur by which the muscle is connected with the maxilla and the septum of the nose above and with the mandible below.\n\nIn the upper lip, these consist of two bands, lateral and medial, on either side of the middle line; the lateral band m. incisivus labii superioris arises from the alveolar border of the maxilla, opposite the lateral incisor tooth, and arching lateralward is continuous with the other muscles at the angle of the mouth; the medial band m. nasolabialis connects the upper lip to the back of the septum of the nose.\n\nThe interval between the two medial bands corresponds with the depression, called the philtrum, seen on the lip beneath the septum of the nose.\n\nThe additional fibers for the lower lip constitute a slip m. incisivus labii inferioris on either side of the middle line; this arises from the mandible, lateral to the Mentalis, and intermingles with the other muscles at the angle of the mouth.\n\n== Clinical significance ==\n\nBabies are occasionally born without one or both sides of this particular muscle, resulting in a slight droop to the affected side of the face.\n\nhttps://en.wikipedia.org/wiki/Orbicularis_oris_muscle","zygomaticus-major-muscle":"The zygomaticus major muscle is a muscle of the human body. It extends from each zygomatic arch (cheekbone) to the corners of the mouth.\n\nIt is a muscle of facial expression which draws the angle of the mouth superiorly and posteriorly to allow one to smile.\n\nBifid zygomaticus major muscle is a notable variant, and may cause cheek dimples.\n\n== Structure ==\n\nThe zygomaticus major muscle originates from the upper margin of the temporal process, part of the lateral surface of the zygomatic bone.\n\nIt inserts into tissue at the corner of the mouth.\n\n=== Nerve supply ===\n\nThe zygomaticus major muscle is supplied by a buccal branch and a zygomatic branch of the facial nerve (VII).\n\n=== Variation ===\n\nThe zygomaticus major muscle may occur in a bifid form, with two fascicles that are partially or completely separate from each other but adjacent.\n\nUsually a single unit, dimples are caused by variations in form. It is thought that cheek dimples are caused by bifid zygomaticus major muscle.\n\n== Function ==\n\nThe zygomaticus major muscle raises the corners of the mouth and draws them posteriorly when a person smiles.\n\nThe average muscle can contract with a force of 200 g.\n\n== Clinical significance ==\n\nThe zygomaticus major muscle may be used in reconstructive surgery to replace lost tissue, such as with injuries to the lips.\n\nhttps://en.wikipedia.org/wiki/Zygomaticus_major_muscle","corrugator-supercilii":"The corrugator supercilii muscle is a small, narrow, pyramidal muscle close to the eye.\n\nIt arises from the medial end of the superciliary arch, and inserts into the deep surface of the skin of the eyebrow.\n\nIt draws the eyebrow downward and medially, producing the vertical wrinkles of the forehead.\n\n== Structure ==\n\nThe corrugator supercilii muscle is located at the medial end of the eyebrow, beneath the frontalis muscle and just above the orbicularis oculi muscle.\n\nIt arises from the medial end of the superciliary arch.\n\nIts fibers pass upward and laterally, between the palpebral and orbital portions of the orbicularis oculi muscle.\n\nIt inserts into the deep surface of the skin of the eyebrow, above the middle of the orbital arch.\n\n=== Relations ===\n\nThe supratrochlear nerve passes by the corrugator supercilii muscle between it and the frontalis muscle.\n\n== Function ==\n\nThe corrugator supercilii muscle draws the eyebrow downward and medially, producing the vertical wrinkles of the forehead.\n\nIt is the \"frowning\" muscle, and may be regarded as the principal muscle in the expression of suffering.\n\nIt also contracts to prevent high sun glare, pulling the eyebrows toward the bridge of the nose, making a roof over the area above the middle corner of the eye and typical forehead furrows.\n\n== Clinical significance ==\n\nThe muscle is sometimes surgically severed or paralysed with botulinum toxin as a preventive treatment for some types of migraine or for aesthetic reasons.\n\n== Etymology ==\n\nThe name corrugator supercilii comes from Latin, and means wrinkler of the eyebrows.\n\nhttps://en.wikipedia.org/wiki/Corrugator_supercilii_muscle","depressor-anguli-oris":"The depressor anguli oris muscle (triangularis muscle) is a facial muscle.\n\nIt originates from the mandible and inserts into the angle of the mouth.\n\nIt is associated with frowning, as it depresses the corner of the mouth.\n\n== Structure ==\n\nThe depressor anguli oris arises from the lateral surface of the mandible.\n\nIts fibres then converge.\n\nIt is inserted by a narrow fasciculus into the angle of the mouth.\n\nAt its origin, it is continuous with the platysma muscle, and at its insertion with the orbicularis oris muscle and risorius muscle.\n\nSome of its fibers are directly continuous with those of the levator anguli oris muscle, and others are occasionally found crossing from the muscle of one side to that of the other; these latter fibers constitute the transverse muscle of the chin.\n\nThe depressor anguli oris muscle receives its blood supply from a branch of the facial artery.\n\n=== Nerve supply ===\n\nThe depressor anguli oris musclemuscle is supplied by the marginal mandibular branch of the facial nerve.\n\n== Function ==\n\nThe depressor anguli oris muscle is a muscle of facial expression.\n\nIt depresses the corner of the mouth, which is associated with frowning.\n\n== Clinical significance ==\n\n=== Paralysis ===\n\nDamage to the marginal mandibular branch of the facial nerve may cause paralysis of the depressor anguli oris muscle.\n\nThis may contribute to an asymmetrical smile.\n\nThis may be corrected by resecting (cutting and removing) the depressor labii inferioris muscle, which has a more significant impact on smiling.\n\nhttps://en.wikipedia.org/wiki/Depressor_anguli_oris_muscle","depressor-labii-inferioris":"The depressor labii inferioris (or quadratus labii inferioris) is a facial muscle.\n\nIt helps to lower the bottom lip.\n\n== Structure ==\n\nThe depressor labii inferioris muscle arises from the lateral surface of the mandible.\n\nThis is below the mental foramen, and the origin may be around 3 cm wide.\n\nIt inserts on the skin of the lower lip, blending in with the orbicularis oris muscle around 2 cm wide.\n\nAt its origin, depressor labii is continuous with the fibers of the platysma muscle. Some yellow fat is intermingled with the fibers.\n\n=== Nerve supply ===\n\nThe depressor labii inferioris muscle is supplied by the marginal mandibular branch of the facial nerve.\n\n== Function ==\n\nThe depressor labii inferioris muscle helps to depress and everts the lower lip.\n\nIt is the most important of the muscles of the lower lip for this function.\n\nIt is an antagonist of the orbicularis oris muscle. It is needed to expose the mandibular (lower) teeth during smiling.\n\n== Clinical significance ==\n\n=== Resection ===\n\nThe depressor labii inferioris muscle may be resected (cut and removed) using surgery to correct an asymmetry of the lower lip when smiling.\n\nThis asymmetry can be caused by paralysis of the marginal mandibular branch of the facial nerve on one side, so the healthy side may be cut to create symmetry.\n\nLocal anaesthesia may be used, such as by blocking the mental nerve. This operation tends to be successful.\n\n== History ==\n\nThe depressor labii inferioris muscle has also (mainly historically) been called the quadratus labii inferioris muscle.\n\nhttps://en.wikipedia.org/wiki/Depressor_labii_inferioris_muscle","levator-anguli-oris":"The levator anguli oris (caninus) is a facial muscle of the mouth arising from the canine fossa, immediately below the infraorbital foramen. It elevates angle of mouth medially. Its fibers are inserted into the angle of the mouth, intermingling with those of the zygomaticus, triangularis, and orbicularis oris. Specifically, the levator anguli oris is innervated by the buccal branches of the facial nerve.\n\n== Additional images ==\n\n== References ==\n This article incorporates text in the public domain from page 383 of the 20th edition of Gray's Anatomy (1918)\n\n== External links ==\nPTCentral\n\nhttps://en.wikipedia.org/wiki/Levator_anguli_oris","procerus-muscle":"The procerus muscle (or pyramidalis nasi) is a small pyramidal slip of muscle deep to the superior orbital nerve, artery and vein. Procerus is Latin, meaning tall or extended.\n\n== Structure ==\nThe procerus muscle arises by tendinous fibers from the fascia covering the lower part of the nasal bone and upper part of the lateral nasal cartilage. It is inserted into the skin over the lower part of the forehead between the two eyebrows on either side of the midline, its fibers merging with those of the frontalis muscle.\n\n=== Nerve supply ===\nThe procerus muscle is supplied by the temporal branch of the facial nerve (VII). It may also be supplied by other branches of the facial nerve, which can be varied.\n\n== Function ==\nThe procerus muscle helps to pull that part of the skin between the eyebrows downwards, which assists in flaring the nostrils. It can also contribute to an expression of anger.\nProcerus is supplied by temporal and lower zygomatic branches from the facial nerve. A supply from its buccal branch has also been described. Its contraction can produce transverse wrinkles.\n\n== Clinical significance ==\n\n=== Procerus sign ===\n\nDystonia of the procerus muscle is involved in the procerus sign, which is indicative of progressive supranuclear palsy (PSP).\n\n=== Denervation ===\nThe procerus muscle may be denervated to reduce furrow lines around the glabella caused by frowning. This may be for cosmetic purposes. Surgery can be used to transect the temporal branch of the facial nerve, although other branches of the facial nerve may also need to be cut.\n\n== References ==\n This article incorporates text in the public domain from page 382 of the 20th edition of Gray's Anatomy (1918)\n\n== Additional Images ==\n\nhttps://en.wikipedia.org/wiki/Procerus_muscle","risorius-muscle":"The risorius muscle is a muscle of facial expression.\n\nIt arises from the fascia over the parotid gland, and inserts into the angle of the mouth.\n\nIt is supplied by the facial nerve (CN VII).\n\nIt may be absent or asymmetrical in some people.\n\nIt retracts the angle of the mouth during smiling.\n\n== Structure ==\n\nThe risorius muscle arises in the fascia over the parotid gland.\n\nPassing horizontally forward, superficial to the platysma muscle, it inserts onto the skin at the angle of the mouth.\n\nIt is a narrow bundle of fibers, broadest at its origin, but varies much in its size and form.\n\nIt is superficial to the masseter muscle, partially covering it.\n\n=== Nerve supply ===\n\nLike all muscles of facial expression, the risorius is supplied by the facial nerve (CN VII).\n\nThe specific branch is debated, with some sources giving marginal mandibular branch of the facial nerve and others giving buccal branch of the facial nerve.\n\n=== Development ===\n\nIt has been suggested that the risorius muscle is only found in Homininae (African great apes and humans).\n\n=== Variation ===\n\nThe risorius muscle may be absent in a significant minority of people, and may be asymmetrical.\n\n== Function ==\n\nThe risorius muscle retracts the angle of the mouth to produce a smile, albeit an insincere-looking one that does not involve the skin around the eyes.\n\nCompare with a real smile, which raises the lips with the action of zygomaticus major and zygomaticus minor muscles and causes \"crow's feet\" around the eyes using the orbicularis oculi muscles.\n\nhttps://en.wikipedia.org/wiki/Risorius","zygomaticus-minor-muscle":"The zygomaticus minor muscle is a muscle of facial expression. It originates from the zygomatic bone, lateral to the rest of the levator labii superioris muscle, and inserts into the outer part of the upper lip.\n\nIt draws the upper lip backward, upward, and outward and is used in smiling. It is innervated by the facial nerve (VII).\n\n== Structure ==\n\nThe zygomaticus minor muscle originates from the zygomatic bone.\n\nIt inserts into the tissue around the upper lip, particularly blending its fibres with orbicularis oris muscle.\n\nIt lies lateral to the rest of levator labii superioris muscle, and medial to its stronger synergist zygomaticus major muscle.\n\nIt travels at an angle of approximately 30°.\n\nIt has a mean width of around 0.5 cm.\n\n=== Nerve supply ===\n\nThe zygomaticus minor muscle is supplied by the buccal branch of the facial nerve (VII).\n\n=== Variation ===\n\nThe zygomaticus minor muscle may have either a straight or a curved course along its length.\n\nIt may attach to both the upper lip and the lateral alar region.\n\nIt may be underdeveloped in some people, with its role taken over by nearby synergists.\n\nThese synergists rarely change shape or position, but any difference in smile is usually imperceptible.\n\n== Function ==\n\nThe zygomaticus minor muscle draws the upper lip up, back, and out, such as during smiling.\n\n== History ==\n\nThe zygomaticus minor muscle is sometimes referred to as the \"zygomatic head\" of the levator labii superioris muscle.\n\nhttps://en.wikipedia.org/wiki/Zygomaticus_minor_muscle","levator-labii-superioris":"The levator labii superioris (pl. levatores labii superioris, also called quadratus labii superioris, pl. quadrati labii superioris) is a muscle of the human body used in facial expression.\n\nIt is a broad sheet, the origin of which extends from the side of the nose to the zygomatic bone.\n\n== Structure ==\n\nIts medial fibers form the angular head (also known as the levator labii superioris alaeque nasi muscle,) which arises by a pointed extremity from the upper part of the frontal process of the maxilla and passing obliquely downward and lateralward divides into two slips.\n\nOne of these is inserted into the greater alar cartilage and skin of the nose; the other is prolonged into the lateral part of the upper lip, blending with the infraorbital head and with the orbicularis oris.\n\nThe intermediate portion or infraorbital head arises from the lower margin of the orbit immediately above the infraorbital foramen, some of its fibers being attached to the maxilla, others to the zygomatic bone.\n\nIts fibers converge, to be inserted into the muscular substance of the upper lip between the angular head and the levator anguli oris.\n\nThe lateral fibers, forming the zygomatic head (also known as the zygomaticus minor muscle) arise from the malar surface of the zygomatic bone immediately behind the zygomaticomaxillary suture and pass downward and medialward to the upper lip.\n\n== Function ==\n\nIts main function is to elevate the upper lip.\n\nhttps://en.wikipedia.org/wiki/Levator_labii_superioris","depressor-septi-nasi":"The depressor septi nasi muscle (or depressor alae nasi muscle) is a muscle of the face.\n\nIt connects the incisive fossa of the maxilla and the orbicularis oris muscle to the nasal septum of the nose.\n\nIt draws the ala of the nose downwards, reducing the size of the nostrils.\n\n== Structure ==\n\nThe depressor septi nasi muscle arises from the incisive foramen of the maxilla.\n\nIt may also partially originate from the orbicularis oris muscle.\n\nIts fibers ascend to be inserted into the nasal septum and back part of the alar part of nasalis muscle.\n\nIt lies between the mucous membrane and muscular structure of the lip.\n\n== Function ==\n\nThe depressor septi is a direct antagonist of the other muscles of the nose, drawing the ala of the nose downward, constricting the nostrils.\n\nIt works like the alar part of the nasalis muscle.\n\n== Clinical significance ==\n\nDuring rhinoplasty, repositioning of the head of the depressor septi nase muscle ensures normal nose position after surgery.\n\nVarious approaches may be used, with similar results.\n\nhttps://en.wikipedia.org/wiki/Depressor_septi_nasi_muscle","mentalis-muscle":"The mentalis muscle is a paired central muscle of the lower lip, situated at the tip of the chin.\n\nIt originates from the mentum of the mandible, and inserts into the soft tissue of the chin.\n\nIt is sometimes referred to as the \"pouting muscle\" due to it raising the lower lip and causing chin wrinkles.\n\n== Structure ==\n\nThe mentalis muscle originates from the mental protuberance of the mandible near the midline.\n\nIt inserts into the soft tissue and skin of the chin.\n\n== Function ==\n\nThe mentalis muscle causes a weak upward-inward movement of the soft tissue complex of the chin.\n\nThis raises the central portion of the lower lip.\n\nIn the setting of lip incompetence (the upper and lower lips do not touch each other at rest), the mentalis muscle contraction can bring temporary but strained oral competence.\n\nIn conjunction with the orbicularis oris muscle (for the upper lip), the mentalis muscle allows the lips to \"pout\".\n\nExternally, the mentalis muscle contraction causes wrinkling and dimpling of the skin on the chin, as used in expressions of doubt or displeasure.\n\n== Clinical significance ==\n\nThe mentalis muscle can be easily assessed using ultrasound.\n\n=== Geniospasm ===\n\nGeniospasm is a genetic movement disorder of the mentalis muscle.\n\nIt involves repetitive contraction of the muscle, with episodes lasting between seconds and hours.\n\nCertain medications may be used to treat it, such as haloperidol and benzodiazepines.\n\nInjection of botulinum toxin (permanently paralysing the muscle) may be more effective.\n\n=== Cosmetics ===\n\nThe mentalis muscle may be partially paralysed using botulinum toxin to reduce wrinkling of the skin of the chin.\n\nThis may be done for cosmetic purposes.\n\nhttps://en.wikipedia.org/wiki/Mentalis","levator-nasolabialis":"LEVATOR LABII SUPERIORIS ALAEQUE NASI MUSCLE\n\nThe levator labii superioris alaeque nasi muscle is, translated from Latin, the \"lifter of both the upper lip and of the wing of the nose\".\n\nIt has the longest name of any muscle in an animal.\n\nThe muscle is attached to the upper frontal process of the maxilla and inserts into the skin of the lateral part of the nostril and upper lip.\n\n== Overview ==\n\nHistorically known as Otto's muscle, it dilates the nostril and elevates the upper lip, enabling one to snarl.\n\nElvis Presley is famous for his use of this expression, earning the muscle's nickname \"The Elvis muscle\".\n\nA mnemonic to remember its name is, \"Little Ladies Snore All Night.\" Snore- because it is the labial elevator closest to the nose.\n\nThe levator labii superioris alaeque nasi is sometimes referred to as the \"angular head\" of the levator labii superioris muscle.\n\nhttps://en.wikipedia.org/wiki/Levator_labii_superioris_alaeque_nasi_muscle","bucinator":"BUCCINATOR MUSCLE\n\nThe bucinator is a thin quadrilateral muscle occupying the interval between the maxilla and the mandible at the side of the face.\n\nIt forms the anterior part of the cheek or the lateral wall of the oral cavity.\n\n== Structure ==\n\nIt arises from the outer surfaces of the alveolar processes of the maxilla and mandible, corresponding to the three pairs of molar teeth and in the mandible, it is attached upon the buccinator crest posterior to the third molar; and behind, from the anterior border of the pterygomandibular raphe which separates it from the constrictor pharyngis superior.\n\nThe fibers converge toward the angle of the mouth, where the central fibers intersect each other, those from below being continuous with the upper segment of the orbicularis oris, and those from above with the lower segment; the upper and lower fibers are continued forward into the corresponding lip without decussation.\n\n=== Innervation ===\n\nMotor innervation is from the buccal branch of the facial nerve (cranial nerve VII).\n\nSensory innervation is supplied by the buccal branch (one of the muscular branches) of the mandibular part of the trigeminal (cranial nerve V).\n\n== Function ==\n\nIts purpose is to pull back the angle of the mouth and to flatten the cheek area, which aids in holding the cheek to the teeth during chewing.\n\nThis action causes the muscle to keep food pushed back on the occlusal surface of the posterior teeth, as when a person chews.\n\nBy keeping the food in the correct position when chewing, the buccinator assists the muscles of mastication.\n\nIt aids whistling and smiling, and in neonates it is used to suckle.\n\n== Structures piercing the buccinator ==\n\n-Parotid duct (Stenson's duct)\n-Molar glands of cheeks\n-Buccal branch of mandibular nerve\n\n== Etymology ==\n\nIn the past the buccinator muscle was also written as bucinator muscle.\n\nA bucinator in classical Latin is a trumpeter, or more precisely, the person who blows the bucina.\n\nThe name bucina could refer in Roman antiquity to a crooked horn or trumpet, a shepherd's horn or a war-trumpet.\n\nDespite its similarity to the classical Latin name for cheek, i.e. bucca, the words bucinator, bucina, and bucinere (to blow the bucina) are not related to bucca, hence some disapproved the spelling buccinator.\n\nAlthough the name bucinator is not derived from bucca, this muscle is also called musculus buccae or musculus buccalis in Latin and muscle of the cheek in English.\n\nThe most recent official Latin anatomic nomenclature (Terminologia Anatomica), and preceding editions (Nomina Anatomica) dictate the spelling 'musculus buccinator' with double 'c', with the exception of the Jena Nomina Anatomica, authorized in 1935, which writes 'musculus bucinatorius' with a single 'c'.\n\nhttps://en.wikipedia.org/wiki/Buccinator_muscle","superficial-part-of-masseter":"In human anatomy, the masseter is one of the muscles of mastication.\n\nFound only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter.\n\nThe most obvious muscle of mastication is the masseter muscle, since it is the most superficial and one of the strongest.\n\n== Structure ==\n\nThe masseter is a thick, somewhat quadrilateral muscle, consisting of two heads, superficial and deep.\n\nThe fibers of the two heads are continuous at their insertion.\n\n=== Superficial head ===\n\nThe superficial head, the larger, arises by a thick, tendinous aponeurosis from the temporal process of the zygomatic bone, and from the anterior two-thirds of the inferior border of the zygomatic arch. Its fibers pass inferior and posterior, to be inserted into the angle of the mandible and inferior half of the lateral surface of the ramus of the mandible.\n\n=== Innervation ===\n\nAlong with the other three muscles of mastication (temporalis, medial pterygoid, and lateral pterygoid), the masseter is innervated by the anterior division of the mandibular division (V3) of the trigeminal nerve.\n\nThe innervation pathway is:\ngyrus precentralis > genu capsula interna > nucleus motorius nervi trigemini > nervus trigeminus > nervus mandibularis > musculus masseter.\n\n== Function ==\n\nThe action of the muscle during bilateral contraction of the entire muscle is to elevate the mandible, raising the lower jaw.\n\nElevation of the mandible occurs during the closing of the jaws.\n\nThe masseter parallels the medial pterygoid muscle, but it is stronger and superficial fibres can cause protrusion.\n\n== Clinical significance ==\n\n=== Examination ===\n\nTo perform an extraoral examination, stand near the patient and visually inspect and bilaterally palpate the muscle.\n\nPlace the fingers of each hand over the muscle and ask the patient to clench his or her teeth several times.\n\n=== Pathology ===\n\nThe masseter muscle can become enlarged in patients who habitually clench or grind (with bruxism) their teeth and even in those who constantly chew gum.\n\nThis masseteric hypertrophy is asymptomatic and soft; it is usually bilateral but can be unilateral.\n\nEven if the hypertrophy is bilateral, asymmetry of the face may still occur due to unequal enlargement of the muscles.\n\nThis extraoral enlargement may be confused with parotid salivary gland disease, dental infections, and maxillofacial neoplasms.\n\nHowever, no other signs are present except those involved in changes in occlusion intraorally such as pain, and the enlargement corresponds with the outline of the muscle.\n\nMost patients seek medical attention because of comments about facial appearance, and this situation may be associated with further pathology of the temporomandibular joint.\n\nFinally, the muscle undergoes spasm with malignant hyperthermia as do other skeletal muscles, but this one is easily noted, since it is on the face.\n\nhttps://en.wikipedia.org/wiki/Masseter_muscle","deep-part-of-masseter":"In human anatomy, the masseter is one of the muscles of mastication.\n\nFound only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter.\n\nThe most obvious muscle of mastication is the masseter muscle, since it is the most superficial and one of the strongest.\n\n== Structure ==\n\nThe masseter is a thick, somewhat quadrilateral muscle, consisting of two heads, superficial and deep.\n\nThe fibers of the two heads are continuous at their insertion.\n\n=== Deep head ===\n\nThe deep head is much smaller, and more muscular in texture. It arises from the posterior third of the lower border and from the whole of the medial surface of the zygomatic arch.\n\nIts fibers pass downward and forward, to be inserted into the upper half of the ramus as high as the coronoid process of the mandible.\n\nThe deep head of the muscle is partly concealed, anteriorly, by the superficial portion. Posteriorly, it is covered by the parotid gland.\n\n=== Innervation ===\n\nAlong with the other three muscles of mastication (temporalis, medial pterygoid, and lateral pterygoid), the masseter is innervated by the anterior division of the mandibular division (V3) of the trigeminal nerve.\n\nThe innervation pathway is:\ngyrus precentralis > genu capsula interna > nucleus motorius nervi trigemini > nervus trigeminus > nervus mandibularis > musculus masseter.\n\n== Function ==\n\nThe action of the muscle during bilateral contraction of the entire muscle is to elevate the mandible, raising the lower jaw.\n\nElevation of the mandible occurs during the closing of the jaws.\n\nThe masseter parallels the medial pterygoid muscle, but it is stronger and superficial fibres can cause protrusion.\n\n== Clinical significance ==\n\n=== Examination ===\n\nTo perform an extraoral examination, stand near the patient and visually inspect and bilaterally palpate the muscle.\n\nPlace the fingers of each hand over the muscle and ask the patient to clench his or her teeth several times.\n\n=== Pathology ===\n\nThe masseter muscle can become enlarged in patients who habitually clench or grind (with bruxism) their teeth and even in those who constantly chew gum.\n\nThis masseteric hypertrophy is asymptomatic and soft; it is usually bilateral but can be unilateral.\n\nEven if the hypertrophy is bilateral, asymmetry of the face may still occur due to unequal enlargement of the muscles.\n\nThis extraoral enlargement may be confused with parotid salivary gland disease, dental infections, and maxillofacial neoplasms.\n\nHowever, no other signs are present except those involved in changes in occlusion intraorally such as pain, and the enlargement corresponds with the outline of the muscle.\n\nMost patients seek medical attention because of comments about facial appearance, and this situation may be associated with further pathology of the temporomandibular joint.\n\nFinally, the muscle undergoes spasm with malignant hyperthermia as do other skeletal muscles, but this one is easily noted, since it is on the face.\n\nhttps://en.wikipedia.org/wiki/Masseter_muscle","medial-pterygoid-muscle":"The medial pterygoid muscle (or internal pterygoid muscle), is a thick, quadrilateral muscle of the face.\n\nIt is supplied by the mandibular branch of the trigeminal nerve (V).\n\nIt is important in mastication (chewing).\n\n== Structure ==\n\nThe medial pterygoid muscle consists of two heads.\n\nThe bulk of the muscle arises as a deep head from just above the medial surface of the lateral pterygoid plate.\n\nThe smaller, superficial head originates from the maxillary tuberosity and the pyramidal process of the palatine bone.\nIts fibers pass downward, lateral, and posterior, and are inserted, by a strong tendinous lamina, into the lower and back part of the medial surface of the ramus and angle of the mandible, as high as the mandibular foramen.\n\nThe insertion joins the masseter muscle to form a common tendinous sling which allows the medial pterygoid and masseter to be powerful elevators of the jaw.\n\n=== Nerve supply ===\n\nThe medial pterygoid muscle is supplied by the medial pterygoid nerve, a branch of the mandibular nerve, itself a branch of the trigeminal nerve (V).\n\nThis also supplies the tensor tympani muscle and the tensor veli palatini muscle.\n\nThe medial pterygoid nerve is a main trunk from the mandibular nerve, before the division of the trigeminal nerve - this is unlike the lateral pterygoid muscle, and all other muscles of mastication which are supplied by the anterior division of the mandibular nerve.\n\n== Function ==\n\nThe medial pterygoid muscle has functions including elevating the mandible (closing the mouth), protruding the mandible, mastication (especially for when the maxillary teeth and the mandibular teeth are close together), and excursing the mandible (contralateral excursion occurs with unilateral contraction).\n\nhttps://en.wikipedia.org/wiki/Medial_pterygoid_muscle","inferior-head-of-lateral-pterygoid-muscle":"The lateral pterygoid or external pterygoid is a muscle of mastication with two heads.\n\nIt lies superiorly to the medial pterygoid.\n\n== Origin and insertion ==\n\nThe upper/superior head originates on the infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone and inserts onto the articular disc and fibrous capsule of the temporomandibular joint.\n\nThe lower/inferior head originates on the lateral surface of the lateral pterygoid plate and inserts onto the neck of condyloid process of the mandible; upper/superior head\n\n== Innervation ==\n\nThe mandibular branch of the fifth cranial nerve, trigeminal nerve, specifically the lateral pterygoid nerve, innervates the lateral pterygoid muscle.\n\n== Function ==\n\nThe primary function of the lateral pterygoid muscle is to pull the head of the condyle out of the mandibular fossa along the articular eminence to protrude the mandible.\n\nA concerted effort of the lateral pterygoid muscles helps in lowering the mandible and opening the jaw, whereas unilateral action of a lateral pterygoid produces contralateral excursion (a form of mastication), usually performed in concert with the medial pterygoids.\n\nUnlike the other three muscles of mastication, the lateral pterygoid is the only muscle of mastication that assists in depressing the mandible (opening the jaw).\n\nAt the beginning of this action it is assisted by the digastric, mylohyoid and geniohyoid muscles.\n\nhttps://en.wikipedia.org/wiki/Lateral_pterygoid_muscle","superior-head-of-lateral-pterygoid-muscle":"The lateral pterygoid or external pterygoid is a muscle of mastication with two heads.\n\nIt lies superiorly to the medial pterygoid.\n\n== Origin and insertion ==\n\nThe upper/superior head originates on the infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone and inserts onto the articular disc and fibrous capsule of the temporomandibular joint.\n\nThe lower/inferior head originates on the lateral surface of the lateral pterygoid plate and inserts onto the neck of condyloid process of the mandible; upper/superior head\n\n== Innervation ==\n\nThe mandibular branch of the fifth cranial nerve, trigeminal nerve, specifically the lateral pterygoid nerve, innervates the lateral pterygoid muscle.\n\n== Function ==\n\nThe primary function of the lateral pterygoid muscle is to pull the head of the condyle out of the mandibular fossa along the articular eminence to protrude the mandible.\n\nA concerted effort of the lateral pterygoid muscles helps in lowering the mandible and opening the jaw, whereas unilateral action of a lateral pterygoid produces contralateral excursion (a form of mastication), usually performed in concert with the medial pterygoids.\n\nUnlike the other three muscles of mastication, the lateral pterygoid is the only muscle of mastication that assists in depressing the mandible (opening the jaw).\n\nAt the beginning of this action it is assisted by the digastric, mylohyoid and geniohyoid muscles.\n\nhttps://en.wikipedia.org/wiki/Lateral_pterygoid_muscle","temporalis-muscle":"In anatomy, the temporal muscle, also known as the temporalis, is one of the muscles of mastication.\n\nIt is a broad, fan-shaped convergent muscle on each side of the head that fills the temporal fossa, superior to the zygomatic arch so it covers much of the temporal bone.Temporal refers to the head's temples.\n\n== Structure ==\n\nIn humans, it arises from the temporal fossa and the deep part of temporal fascia.\n\nIt passes medial to the zygomatic arch and forms a tendon which inserts onto the coronoid process of the mandible, with its insertion extending into the retromolar fossa posterior to the most distal mandibular molar.\n\nIn other mammals, the muscle usually spans the dorsal part of the skull all the way up to the medial line.\n\nThere, it may be attached to a sagittal crest, as can be seen in early hominins such as Paranthropus aethiopicus.\n\nThe temporal muscle is covered by the temporal fascia, also known as the temporal aponeurosis.\n\nThis fascia is commonly used in tympanoplasty, or surgical reconstruction of the eardrum.\n\nThe muscle is accessible on the temples, and can be seen and felt contracting while the jaw is clenching and unclenching.\n\n=== Development ===\n\nThe temporalis is derived from the first pharyngeal arch in development.\n\n=== Innervation ===\n\nAs with the other muscles of mastication, control of the temporal muscle comes from the third (mandibular) branch of the trigeminal nerve.\n\nSpecifically, the muscle is innervated by the deep temporal nerves.\n\n=== Blood supply ===\n\nThe muscle receives its blood supply from the deep temporal arteries which anastomose with the middle temporal artery.\n\n== Function ==\n\nThe temporal muscle is the most powerful muscle of the temporomandibular joint.\n\nThe temporal muscle can be divided into two functional parts; anterior and posterior.\n\nThe anterior portion runs vertically and its contraction results in elevation of the mandible (closing the mouth).\n\nThe posterior portion has fibers which run horizontally and contraction of this portion results in retrusion of the mandible.\n\nThe middle portion which fibers run in an oblique direction towards inferior and anterior are used for both elevation and retraction of the mandible and in a unilateral contraction provoque lateral movement of the mandible.\n\nWhen lower dentures are fitted, they should not extend into the retromolar fossa to prevent trauma of the mucosa due to the contraction of the temporalis muscle.\n\n== Pathology ==\n\nThe temporalis is likely to be involved in jaw pain and headaches.\n\nBruxism, the habitual grinding of teeth typically while sleeping, and clenching of the jaw while stressed can lead to overwork of the temporalis and results in pain.\n\nA myotendinous rupture of the temporalis can occur during a seizure due to extreme clenching of the jaw.\n\nDuring a seizure the contralateral temporalis muscle can enter spastic paralysis, this clenching in extreme cases can lead to a rupture specifically on the myotendinous insertion at the coronoid process of the mandible.\n\nhttps://en.wikipedia.org/wiki/Temporal_muscle","hyoglossus-muscle":"The hyoglossus, thin and quadrilateral, arises from the side of the body and from the whole length of the greater cornu of the hyoid bone, and passes almost vertically upward to enter the side of the tongue, between the styloglossus and the inferior longitudinal muscle of the tongue.\n\nIt forms a part of the floor of submandibular triangle.\n\n== Structure ==\n\nThe fibers arising from the body of the hyoid bone overlap those from the greater cornu.\n\nStructures that are medial/deep to the hyoglossus are the glossopharyngeal nerve (cranial nerve 9), the stylohyoid ligament and the lingual artery and lingual vein.\n\nThe lingual vein passes medial to the hyoglossus, and the lingual artery passes deep to the hyoglossus.\n\nLaterally, in between the hyoglossus muscle and the mylohyoid muscle lay several important structures (from upper to lower): sublingual gland, submandibular duct, lingual nerve, vena comitans of hypoglossal nerve, and the hypoglossal nerve.\n\nNote, posteriorly, the lingual nerve is superior to the submandibular duct and a portion of the submandibular salivary gland protrudes into the space between the hyoglossus and mylohyoid muscles.\n\n== Function ==\n\nThe hyoglossus depresses and retracts the tongue and makes the dorsum more convex.\n\nhttps://en.wikipedia.org/wiki/Hyoglossus","genioglossus-muscle":"The genioglossus is one of the paired extrinsic muscles of the tongue. The genioglossus is the major muscle responsible for protruding (or sticking out) the tongue.\n\n== Structure ==\n\nGenioglossus is the fan-shaped extrinsic tongue muscle that forms the majority of the body of the tongue.\n\nIt arises from the mental spine of the mandible and its insertions are the hyoid bone and the bottom of the tongue.\n\nThe genioglossus is innervated by the hypoglossal nerve, as are all muscles of the tongue except for the palatoglossus.\n\nBlood is supplied to the sublingual branch of the lingual artery, a branch of the external carotid artery.\n\nThe canine genioglossus muscle has been divided into horizontal and oblique compartments.\n\n== Function ==\n\nThe left and right genioglossus muscles protrude the tongue and deviate it towards the opposite side.\n\nWhen acting together, the muscles depress the center of the tongue at its back.\n\n== Clinical significance ==\n\nContraction of the genioglossus stabilizes and enlarges the portion of the upper airway that is most vulnerable to collapse.\n\nRelaxation of the genioglossus and geniohyoideus muscles, especially during REM sleep, is implicated in obstructive sleep apnea.\n\nGiven this connection, the mandible can be pulled forward to maximise the airway space, and prevent the tongue from sinking backwards under anaesthesia and obstructing the airway.\n\nThe genioglossus is often used as a proxy to test the function of the hypoglossal nerve, by asking a patient to stick out their tongue.\n\nPeripheral damage to the hypoglossal nerve can result in deviation of the tongue to the damaged side.\n\nhttps://en.wikipedia.org/wiki/Genioglossus","palatopharyngeus-muscle":"The palatopharyngeus (palatopharyngeal or pharyngopalatinus) muscle is a small muscle in the roof of the mouth.\n\nIt is a long, fleshy fasciculus, narrower in the middle than at either end, forming, with the mucous membrane covering its surface, the palatopharyngeal arch.\n\n== Structure ==\n\nIt is separated from the palatoglossus muscle by an angular interval, in which the palatine tonsil is lodged.\n\nIt arises from the soft palate, where it is divided into two fasciculi by the levator veli palatini and musculus uvulae.\n\nThe posterior fasciculus lies in contact with the mucous membrane, and joins with that of the opposite muscle in the middle line.\n\nThe anterior fasciculus, the thicker, lies in the soft palate between the levator and tensor veli palatini muscles, and joins in the middle line the corresponding part of the opposite muscle.\n\nPassing laterally and downward behind the palatine tonsil, the palatopharyngeus joins the stylopharyngeus and is inserted with that muscle into the posterior border of the thyroid cartilage, some of its fibers being lost on the side of the pharynx and others passing across the middle line posteriorly to decussate with the muscle of the opposite side.\n\n=== Innervation ===\n\nMotor innervation of this muscle is provided through the pharyngeal plexus of the CN X (vagal nerve), SVE (special visceral efferent) fibers.\n\n== Function ==\n\nThe palatine velum is slightly raised by the levator veli palatini and made tense by the tensor veli palatini; the palatopharyngeus muscles, by their contraction, pull the pharynx upward over the bolus of food and nearly come together, the uvula filling up the slight interval between them.\n\nBy these means the bolus is prevented from passing into the nasopharynx; at the same time, the palatopharyngeus muscles form an inclined plane, directed obliquely downward and backward, along the under surface of which the bolus descends into the lower part of the pharynx.\n\nhttps://en.wikipedia.org/wiki/Palatopharyngeus_muscle","superficial-layer-of-temporal-fascia":"The temporal fascia covers the temporalis muscle.\nIt is a strong, fibrous investment, covered, laterally, by the auricularis anterior and superior, by the galea aponeurotica, and by part of the orbicularis oculi.\n\nThe superficial temporal vessels and the auriculotemporal nerve cross it from below upward.\n\nSuperiorly, it is a single layer, attached to the entire extent of the superior temporal line; but inferiorly, where it is fixed to the zygomatic arch, it consists of two layers, one of which is inserted into the lateral, and the other into the medial border of the arch.\n\nA small quantity of fat, the orbital branch of the superficial temporal artery, and a filament from the zygomatic branch of the maxillary nerve, are contained between these two layers.\n\nIt affords attachment by its deep surface to the superficial fibers of the temporalis.\n\nThe parotid fascia proceeds to the temporal fascia.\n\nhttps://en.wikipedia.org/wiki/Temporal_fascia","masseteric-fascia":"The masseteric fascia (parotideomasseteric fascia) is a strong layer of fascia derived from the deep cervical fascia on the human head and neck.\n\nIt covers the masseter, and is firmly connected to it.\n\nAbove, this fascia is attached to the lower border of the zygomatic arch, and behind, it invests the parotid gland proceeding into the parotid fascia.\n\nhttps://en.wikipedia.org/wiki/Masseteric_fascia","sternocleidomastoid-muscle":"The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles.\n\nThe primary actions of the muscle are rotation of the head to the opposite side and flexion of the neck.\n\nThe sternocleidomastoid is innervated by the accessory nerve.\nIt is given the name sternocleidomastoid because it originates at the manubrium of the sternum (sterno-) and the clavicle (cleido-) and has an insertion at the mastoid process of the temporal bone of the skull.\n\n== Structure ==\n\nThe sternocleidomastoid muscle originates from two locations: the manubrium of the sternum and the clavicle.\n\nIt travels obliquely across the side of the neck and inserts at the mastoid process of the temporal bone of the skull by a thin aponeurosis.\n\nThe sternocleidomastoid is thick and narrow at its centre, and broader and thinner at either end.\n\nThe sternal head is a round fasciculus, tendinous in front, fleshy behind, arising from the upper part of the front of the manubrium sterni.\n\nIt travels superiorly, laterally, and posteriorly.\n\nThe clavicular head is composed of fleshy and aponeurotic fibers, arises from the upper, frontal surface of the medial third of the clavicle; it is directed almost vertically upward.\n\nThe two heads are separated from one another at their origins by a triangular interval (lesser supraclavicular fossa) but gradually blend, below the middle of the neck, into a thick, rounded muscle which is inserted, by a strong tendon, into the lateral surface of the mastoid process, from its apex to its superior border, and by a thin aponeurosis into the lateral half of the superior nuchal line of the occipital bone.\n\n=== Nerve supply ===\n\nThe sternocleidomastoid is innervated by accessory nerve of the same side.\n\nIt supplies only motor fibres.\n\nThe cervical plexus supplies sensation, including proprioception, from the ventral primary rami of C2 and C3.\n\n=== Variation ===\n\nThe clavicular origin of the sternocleidomastoid varies greatly: in some cases the clavicular head may be as narrow as the sternal; in others it may be as much as 7.5 millimetres (0.30 in) in breadth.\n\nWhen the clavicular origin is broad, it is occasionally subdivided into several slips, separated by narrow intervals.\n\nMore rarely, the adjoining margins of the sternocleidomastoid and trapezius are in contact.\n\nThis would leave no posterior triangle.\n\nThe supraclavicularis muscle arises from the manubrium behind the sternocleidomastoid and passes behind the sternocleidomastoid to the upper surface of the clavicle.\n\n== Function ==\n\nThe function of this muscle is to rotate the head to the opposite side or obliquely rotate the head.\n\nIt also flexes the neck.\n\nWhen both sides of the muscle act together, it flexes the neck and extends the head.\n\nWhen one side acts alone, it causes the head to rotate to the opposite side and flexes laterally to the same side (ipsilaterally).\nIt also acts as an accessory muscle of respiration, along with the scalene muscles of the neck.\n\n=== Contraction ===\n\nThe signaling process to contract or relax the sternocleidomastoid begins in Cranial Nerve XI, the accessory nerve.\n\nThe accessory nerve nucleus is in the anterior horn of the spinal cord around C1-C3, where lower motor neuron fibers mark its origin.\n\nThe fibers from the accessory nerve nucleus travel upward to enter the cranium via the foramen magnum.\n\nThe internal carotid artery to reach both the sternocleidomastoid muscles and the trapezius.\n\nAfter a signal reaches the accessory nerve nucleus in the anterior horn of the spinal cord, the signal is conveyed to motor endplates on the muscle fibers located at the clavicle.\n\nAcetylcholine (ACH) is released from vesicles and is sent over the synaptic cleft to receptors on the postsynaptic bulb.\n\nThe ACH causes the resting potential to increase above -55mV, thus initiating an action potential which travels along the muscle fiber.\n\nAlong the muscle fibers are t-tubule openings which facilitate the spread of the action potential into the muscle fibers.\n\nThe t-tubule meets with the sarcoplasmic reticulum at locations throughout the muscle fiber, at these locations the sarcoplasmic reticulum releases calcium ions that results in the movement of troponin and tropomyosin on thin filaments.\n\nThe movement of troponin and tropomyosin is key in facilitating the myosin head to move along the thin filament, resulting in a contraction of the sternocleidomastoid muscle.\n\n=== Anatomical landmark ===\n\nThe sternocleidomastoid is within the investing fascia of the neck, along with the trapezius muscle, with which it shares its nerve supply (the accessory nerve).\n\nIt is thick and thus serves as a primary landmark of the neck, as it divides the neck into anterior and posterior cervical triangles (in front and behind the muscle, respectively) which helps define the location of structures, such as the lymph nodes for the head and neck.Many important structures relate to the sternocleidomastoid, including the common carotid artery, accessory nerve, and brachial plexus.\n\n== Clinical significance ==\n\nExamination of the sternocleidomastoid muscle forms part of the examination of the cranial nerves.\n\nIt can be felt on each side of the neck when a person moves their head to the opposite side.The triangle formed by the clavicle and the sternal and clavicular heads of the sternocleidomastoid muscle is used as a landmark in identifying the correct location for central venous catheterization.Contraction of the muscle gives rise to a condition called torticollis or wry neck, and this can have a number of causes.\n\nTorticollis gives the appearance of a tilted head on the side involved.\n\nTreatment involves physiotherapy exercises to stretch the involved muscle and strengthen the muscle on the opposite side of the neck.\n\nCongenital torticollis can have an unknown cause or result from birth trauma that gives rise to a mass or tumor that can be palpated within the muscle.\n\n== History ==\n\n=== Etymology ===\n\nIt is given the name sternocleidomastoid because it originates at the manubrium of the sternum (sterno-) and the clavicle (cleido-), and has an insertion at the mastoid process of the temporal bone of the skull.\n\nhttps://en.wikipedia.org/wiki/Sternocleidomastoid_muscle","intermediate-tendon-of-digastric-muscle":"The two bellies end in an intermediate tendon which perforates the stylohyoideus muscle, and is held in connection with the side of the body and the greater cornu of the hyoid bone by a fibrous loop, which is sometimes lined by a mucous sheath.\n\nhttps://en.wikipedia.org/wiki/Digastric_muscle#Intermediate_tendon","anterior-belly-of-digastric-muscle":"The digastric muscle (also digastricus) (named digastric as it has two 'bellies') is a small muscle located under the jaw.\n\nThe term \"digastric muscle\" refers to this specific muscle.\n\nHowever, other muscles that have two separate muscle bellies include the suspensory muscle of duodenum, omohyoid, occipitofrontalis.\n\nIt lies below the body of the mandible, and extends, in a curved form, from the mastoid notch to the mandibular symphysis.\n\nIt belongs to the suprahyoid muscles group.\n\nA broad aponeurotic layer is given off from the tendon of the digastric muscle on either side, to be attached to the body and greater cornu of the hyoid bone; this is termed the suprahyoid aponeurosis.\n\n== Structure ==\n\nThe digastricus (digastric muscle) consists of two muscular bellies united by an intermediate rounded tendon.\n\nThe two bellies of the digastric muscle have different embryological origins, and are supplied by different cranial nerves.\nEach person has a right and left digastric muscle.\n\nIn most anatomical discussions, the singular is used to refer to a muscle, even when each person actually has two of that muscle—one on the right side, and another on the left.\n\nFor example, we speak of the deltoid, even though there is one deltoid in each shoulder.\n\nLikewise, we speak of the digastric even though there is a right and left digastric muscle.\n\n=== Posterior belly ===\n\nThe posterior belly, longer than the anterior belly, arises from the mastoid notch which is on the inferior surface of the skull, medial to the mastoid process of the temporal bone.\n\nIt lies posterior to the parotid gland and the facial nerve.\n\nThe mastoid notch is a deep groove between the mastoid process and the styloid process.\n\nThe mastoid notch is also referred to as the digastric groove or the digastric fossa.\n\nThe posterior belly is supplied by the digastric branch of facial nerve.\n\nThe digastric muscle stretches between the mastoid process of the cranium to the mandible at the chin, and part-way between, it becomes a tendon which passes through a tendinous pulley attached to the hyoid bone.\n\nIt originates from the second pharyngeal arch.\n\n=== Anterior belly ===\n\nThe anterior belly arises from a depression on the inner side of the lower border of the mandible called the digastric fossa of mandible, close to the symphysis, and passes downward and backward.\n\nThe anterior body is supplied by the trigeminal via the mylohyoid nerve, a branch of the inferior alveolar nerve, itself a branch of the mandibular division of the trigeminal nerve.\n\nIt originates from the first pharyngeal arch.\n\n=== Intermediate tendon ===\n\nThe two bellies end in an intermediate tendon which perforates the stylohyoideus muscle, and is held in connection with the side of the body and the greater cornu of the hyoid bone by a fibrous loop, which is sometimes lined by a mucous sheath.\n\n=== Variations ===\n\nVariations are numerous.\nThe posterior belly may arise partly or entirely from the styloid process, or be connected by a muscle slip to the middle or inferior constrictor; the anterior belly may be double, or extra slips from this belly may pass to the jaw or mylohyoideus or decussate with a similar slip on opposite side; anterior belly may be absent and posterior belly inserted into the middle of the jaw or hyoid bone.\n\nThe tendon may pass in front, more rarely behind the stylohoideus.\n\nThe mentohyoideus muscle passes from the body of hyoid bone to chin.\n\n=== Triangles ===\n\nThe digastric muscle divides the anterior triangle of the neck into three smaller triangles.\n\n(1) the submandibular triangle (also called the digastric triangle), bounded above by the lower border of the body of the mandible, and a line drawn from its angle to the sternocleidomastoideus, below by the posterior belly of the digastricus and the stylohyoideus, in front by the anterior belly of the diagastricus;\n(2) the carotid triangle, bounded above by the posterior belly of the digastricus and stylohyoideus, behind by the sternocleidomastoideus, below by the omohyoideus;\n(3) the suprahyoid or submental triangle, bounded laterally by the anterior belly of the digastricus, medially by the middle line of the neck from the hyoid bone to the symphysis menti, and inferiorly by the body of the hyoid bone.\n(4) The inferior carotid triangle (or muscular triangle), is bounded, in front, by the median line of the neck from the hyoid bone to the sternum; behind, by the anterior margin of the sternocleidomastoideus; above, by the superior belly of the omohyoideus\n\n== Function ==\n\nThe digastric muscle is involved in any complex jaw action such as speaking, swallowing, chewing and breathing.\n\nWhen the digastric muscle contracts, it acts to elevate the hyoid bone.\n\nIf the hyoid is being held in place (by the infrahyoid muscles), it will tend to depress the mandible (open the mouth).\n\n== Other animals ==\n\nThe digastric muscles are present in a variety of animals, specific attachment sites may vary.\n\nFor example, in the orangutan, the posterior digastric attaches to the mandible rather than the hyoid.\n\nhttps://en.wikipedia.org/wiki/Digastric_muscle","posterior-belly-of-digastric-muscle":"The digastric muscle (also digastricus) (named digastric as it has two 'bellies') is a small muscle located under the jaw.\n\nThe term \"digastric muscle\" refers to this specific muscle.\n\nHowever, other muscles that have two separate muscle bellies include the suspensory muscle of duodenum, omohyoid, occipitofrontalis.\n\nIt lies below the body of the mandible, and extends, in a curved form, from the mastoid notch to the mandibular symphysis.\n\nIt belongs to the suprahyoid muscles group.\n\nA broad aponeurotic layer is given off from the tendon of the digastric muscle on either side, to be attached to the body and greater cornu of the hyoid bone; this is termed the suprahyoid aponeurosis.\n\n== Structure ==\n\nThe digastricus (digastric muscle) consists of two muscular bellies united by an intermediate rounded tendon.\n\nThe two bellies of the digastric muscle have different embryological origins, and are supplied by different cranial nerves.\nEach person has a right and left digastric muscle.\n\nIn most anatomical discussions, the singular is used to refer to a muscle, even when each person actually has two of that muscle—one on the right side, and another on the left.\n\nFor example, we speak of the deltoid, even though there is one deltoid in each shoulder.\n\nLikewise, we speak of the digastric even though there is a right and left digastric muscle.\n\n=== Posterior belly ===\n\nThe posterior belly, longer than the anterior belly, arises from the mastoid notch which is on the inferior surface of the skull, medial to the mastoid process of the temporal bone.\n\nIt lies posterior to the parotid gland and the facial nerve.\n\nThe mastoid notch is a deep groove between the mastoid process and the styloid process.\n\nThe mastoid notch is also referred to as the digastric groove or the digastric fossa.\n\nThe posterior belly is supplied by the digastric branch of facial nerve.\n\nThe digastric muscle stretches between the mastoid process of the cranium to the mandible at the chin, and part-way between, it becomes a tendon which passes through a tendinous pulley attached to the hyoid bone.\n\nIt originates from the second pharyngeal arch.\n\n=== Anterior belly ===\n\nThe anterior belly arises from a depression on the inner side of the lower border of the mandible called the digastric fossa of mandible, close to the symphysis, and passes downward and backward.\n\nThe anterior body is supplied by the trigeminal via the mylohyoid nerve, a branch of the inferior alveolar nerve, itself a branch of the mandibular division of the trigeminal nerve.\n\nIt originates from the first pharyngeal arch.\n\n=== Intermediate tendon ===\n\nThe two bellies end in an intermediate tendon which perforates the stylohyoideus muscle, and is held in connection with the side of the body and the greater cornu of the hyoid bone by a fibrous loop, which is sometimes lined by a mucous sheath.\n\n=== Variations ===\n\nVariations are numerous.\nThe posterior belly may arise partly or entirely from the styloid process, or be connected by a muscle slip to the middle or inferior constrictor; the anterior belly may be double, or extra slips from this belly may pass to the jaw or mylohyoideus or decussate with a similar slip on opposite side; anterior belly may be absent and posterior belly inserted into the middle of the jaw or hyoid bone.\n\nThe tendon may pass in front, more rarely behind the stylohoideus.\n\nThe mentohyoideus muscle passes from the body of hyoid bone to chin.\n\n=== Triangles ===\n\nThe digastric muscle divides the anterior triangle of the neck into three smaller triangles.\n\n(1) the submandibular triangle (also called the digastric triangle), bounded above by the lower border of the body of the mandible, and a line drawn from its angle to the sternocleidomastoideus, below by the posterior belly of the digastricus and the stylohyoideus, in front by the anterior belly of the diagastricus;\n(2) the carotid triangle, bounded above by the posterior belly of the digastricus and stylohyoideus, behind by the sternocleidomastoideus, below by the omohyoideus;\n(3) the suprahyoid or submental triangle, bounded laterally by the anterior belly of the digastricus, medially by the middle line of the neck from the hyoid bone to the symphysis menti, and inferiorly by the body of the hyoid bone.\n(4) The inferior carotid triangle (or muscular triangle), is bounded, in front, by the median line of the neck from the hyoid bone to the sternum; behind, by the anterior margin of the sternocleidomastoideus; above, by the superior belly of the omohyoideus\n\n== Function ==\n\nThe digastric muscle is involved in any complex jaw action such as speaking, swallowing, chewing and breathing.\n\nWhen the digastric muscle contracts, it acts to elevate the hyoid bone.\n\nIf the hyoid is being held in place (by the infrahyoid muscles), it will tend to depress the mandible (open the mouth).\n\n== Other animals ==\n\nThe digastric muscles are present in a variety of animals, specific attachment sites may vary.\n\nFor example, in the orangutan, the posterior digastric attaches to the mandible rather than the hyoid.\n\nhttps://en.wikipedia.org/wiki/Digastric_muscle","mylohyoid-muscle":"The mylohyoid muscle or diaphragma oris is a paired muscle of the neck.\n\nIt runs from the mandible to the hyoid bone, forming the floor of the oral cavity of the mouth.\n\nIt is named after its two attachments near the molar teeth.\n\nIt forms the floor of the submental triangle.\n\nIt elevates the hyoid bone and the tongue, important during swallowing and speaking.\n\n== Structure ==\n\nThe mylohyoid muscle is flat and triangular, and is situated immediately superior to the anterior belly of the digastric muscle.\n\nIt is a pharyngeal muscle (derived from the first pharyngeal arch) and classified as one of the suprahyoid muscles.\n\nTogether, the paired mylohyoid muscles form a muscular floor for the oral cavity of the mouth.\n\nThe two mylohyoid muscles arise from the mandible at the mylohyoid line, which extends from the mandibular symphysis in front to the last molar tooth behind.\n\nThe posterior fibers pass inferomedially and insert at anterior surface of the hyoid bone.\n\nThe medial fibres of the two mylohyoid muscles unite in a midline raphe (where the two muscles intermesh).\n\nThe mylohyoid muscle separates the sublingual space from the submandibular space, which communicate via a lateral gap between the mylohyoid and hyoglossus muscles at the posterior free margin of mylohyoid muscle.\n\nThe submandibular gland wraps around the edges of the mylohyoid, and is divided into superficial and deep lobes above and below the muscle.\n\n=== Nerve supply ===\n\nThe mylohyoid muscle is supplied by a branch of the mandibular nerve, the inferior alveolar nerve.\n\nThe mylohyoid nerve is a branch of the inferior alveolar nerve.\n\nThe mylohyoid nerve emerges to give motor supply to the mylohyoid muscle.\n\n=== Development ===\n\nThe mylohyoid muscles are derived from embryonic mesoderm, specifically the first pharyngeal arch.\n\n=== Variations ===\n\nThe mylohyoid muscle may be united to or replaced by the anterior belly of the digastric muscle; accessory slips to other hyoid muscles are frequent.\n\nThis median raphé is sometimes absent; the fibers of the two muscles are then continuous.\n\nVariations in the mylohyoid muscle itself are not common.\n\nAccessory mylohyoid muscles have been seen in some people, which have the same attachments, nerve supply, and function.\n\nThe mylohyoid muscle may also be split into an anterior portion and a posterior portion, with the sublingual gland occupying the space between these portions.\n\nAn area of herniation of the sublingual gland, blood vessels, or fat, may be present, with studies reporting this in 10-50% of people.\n\n== Function ==\n\nThe mylohyoid muscle elevates the hyoid bone and the tongue.\n\nThis is particularly important during swallowing and speaking.\n\nAlternatively, if other muscles are used to keep the position of the hyoid bone fixed, then the mylohyoid muscle depresses the mandible.\n\nIt also functions as reinforcing the floor of mouth.\n\n== Clinical significance ==\n\nThe mylohyoid muscle may be imaged by CT or MRI.\n\nThe mylohyoid separates the submandibular space below from the sublingual space above.\n\nAround the posterior border of the mylohoid muscle, these spaces communicate.\n\nInfections, especially odontogenic infections can spread from one space to the other via this communication, or alternatively penetrate the mylohyoid muscle, which is a poor barrier to the spread of infection.\n\nBecause the attachment of the mylohyoid muscle (the mylohoid line of the mandible) becomes more superior towards the posterior of the mandible, posterior infected teeth are more likely to drain into the submandibular space, and infected anterior teeth are more likely to drain into the sublingual space, since the apices of the teeth are more likely to be below and above the mylohoid line respectively (see diagram).\n\n== History ==\n\nThe myloyoid muscle may also be known as the diaphragma oris muscle.\n\nIt is named after its two attachments near the molar teeth (\"mylo\" comes from the Greek word for \"molar\").\n\nhttps://en.wikipedia.org/wiki/Mylohyoid_muscle","stylohyoid-muscle":"The stylohyoid muscle is a slender muscle, lying anterior and superior of the posterior belly of the digastric muscle.\n\nIt is one of the suprahyoid muscles.\n\nIt shares this muscle's innervation by the facial nerve, and functions to draw the hyoid bone backwards and elevate the tongue.\n\nIts origin is the styloid process of the temporal bone.\n\nIt inserts on the body of the hyoid.\n\n== Structure ==\n\nThe stylohyoid muscle originates from the posterior and lateral surface of the styloid process of the temporal bone, near the base.\n\nPassing inferior and anterior, it inserts into the body of the hyoid bone, at its junction with the greater cornu, and just superior to the omohyoid muscle.\n\nIt belongs to the group of suprahyoid muscles.It is perforated, near its insertion, by the intermediate tendon of the digastric muscle.\n\nThe stylohyoid muscle has vascular supply from the lingual artery, a branch of the external carotid artery.\n\n=== Nerve supply ===\n\nA branch of the facial nerve (CN VII) innervates the stylohyoid muscle.\n\n=== Variation ===\n\nIt may be absent or doubled, lie beneath the carotid artery, or be inserted into the omohyoid, or mylohyoid muscles.\n\n== Function ==\n\nThe stylohyoid muscle elevates and retracts hyoid bone.\n\nIt initiates a swallowing action by pulling the hyoid bone in a posterior and superior direction.\n\nhttps://en.wikipedia.org/wiki/Stylohyoid_muscle","geniohyoid-muscle":"The geniohyoid muscle is a narrow muscle situated superior to the medial border of the mylohyoid muscle.\n\nIt is named for its passage from the chin (\"genio-\" is a standard prefix for \"chin\") to the hyoid bone.\n\n== Structure ==\n\nIt arises from the inferior mental spine, on the back of the mandibular symphysis, and runs backward and slightly downward, to be inserted into the anterior surface of the body of the hyoid bone.\n\nIt lies in contact with its fellow of the opposite side.\n\nIt thus belongs to the suprahyoid muscles.\n\nThe muscle is supplied by branches of the lingual artery.\n\n=== Innervation ===\n\nThe geniohyoid muscle is innervated by fibres from the first cervical nerve travelling alongside the hypoglossal nerve.\n\nAlthough the first three cervical nerves give rise to the ansa cervicalis, the geniohyoid muscle is said to be innervated by the first cervical nerve, as some of its efferent fibers do not contribute to ansa cervicalis.\n\n=== Variations ===\n\nIt may be blended with the one on opposite side or double; slips to greater cornu of hyoid bone and genioglossus occur.\n\n== Function ==\n\nThe geniohyoid muscle brings the hyoid bone forward and upwards.\n\nThis dilates the upper airway, assisting respiration.\n\nDuring the first act of deglutition, when the mass of food is being driven from the mouth into the pharynx, the hyoid bone, and with it the tongue, is carried upward and forward by the anterior bellies of the Digastrici, the Mylohyoidei, and Geniohyoidei.\n\nIt also assists in depressing the mandible\n\n== History ==\n\nThe inclined position of the geniohyoid muscle has been contrasted to the horizontal position in neanderthals.\n\nhttps://en.wikipedia.org/wiki/Geniohyoid_muscle","omohyoid-muscle":"The omohyoid muscle is a muscle that depresses the hyoid.\n\nIt is located in the front of the neck, and consists of two bellies separated by an intermediate tendon.\n\nThe omohyoid muscle is proximally attached to the scapula and distally attached to the hyoid bone, stabilising it.\n\nIts superior belly serves as the most lateral member of the infrahyoid muscles, located lateral to both the sternothyroid muscles and the thyrohyoid muscles.\n\n== Structure ==\n\nThe omohyoid muscle arises from the upper border of the scapula, inserting into the lower border of the body of the hyoid bone.\n\nIt has two separate bellies, superior and inferior:\n-The inferior belly forms a flat, narrow fasciculus, which inclines forward and slightly upward across the lower part of the neck, being bound down to the clavicle by a fibrous expansion; it then passes behind the sternocleidomastoid, becomes tendinous and changes its direction, forming an obtuse angle.\n\n-The superior belly passes almost vertically upward, close to the lateral border of the sternohyoid, to be inserted into the lower border of the body of the hyoid bone, lateral to the insertion of the sternohyoid.\n\n-The central tendon of this muscle varies much in length and form, and is held in position by a process of the deep cervical fascia, which sheaths it, and is prolonged down to be attached to the clavicle and first rib; it is by this means that the angular form of the muscle is maintained.\n\nThe tendon overlies the internal jugular vein, and can be used as a landmark for this vein during surgery.\n\n=== Variation ===\n\nThe omohyoid muscle may be doubled or completely absent in some people.\n\nIt may originate from the clavicle rather than the scapula.It occasionally arises from the superior transverse scapular ligament, which crosses the scapular notch, its extent of attachment to the scapula varying from a few millimetres to 2.5 cm.\n\n=== Innervation ===\n\nThe omohyoid is innervated by a branch of the cervical plexus, the ansa cervicalis.\n\nThe inferior belly of the omohyoid is innervated by the three cervical branches (C1-C3) that make up the ansa cervicalis, while the superior belly is innervated by the superior root of ansa cervicalis which contains only fibers from the first cervical spinal nerves (C1).\n\n== Examination of the neck ==\n\nThe inferior belly of the omohyoid divides the posterior triangle of the neck into an upper or occipital triangle and a lower or subclavian triangle.\n\nIts superior belly divides the anterior triangle into an upper carotid triangle and a lower muscular triangle.\n\n== Name ==\n\nThe name \"omohyoid\" derives from the Greek \"omos\" meaning shoulder, giving one of its attachments, and \"hyoid\", giving the other attachment – the hyoid bone.\n\nhttps://en.wikipedia.org/wiki/Omohyoid_muscle","sternohyoid-muscle":"The sternohyoid muscle is a thin, narrow muscle attaching the hyoid bone to the sternum.\n\nIt is one of the paired strap muscles of the infrahyoid muscles.\n\nIt is supplied by the ansa cervicalis.\n\nIt depresses the hyoid bone.\n\n== Structure ==\n\nThe sternohyoid muscle is one of the paired strap muscles of the infrahyoid muscles.\n\nIt arises from the posterior border of the medial end of the clavicle, the posterior sternoclavicular ligament, and the upper and posterior part of the manubrium of the sternum.\n\nPassing upward and medially, it is inserted by short tendinous fibers into the lower border of the body of the hyoid bone.\n\nIt runs lateral to the trachea.\n\n=== Nerve supply ===\n\nThe sternohyoid muscle is supplied by a branch of the ansa cervicalis.\n\n=== Variations ===\n\nThe sternohyoid muscle may be doubled, have accessory slips (Cleidohyoideus) or be completely absent in some people.\n\nIt sometimes presents a transverse tendinous inscription immediately above its origin.\n\n== Function ==\n\nThe sternohyoid muscle performs a number of functions:\n\n-depresses the hyoid bone.\n-helps with speech, primarily to do with volume rather than intonation.\n-helps to move the head and neck.\n\nhttps://en.wikipedia.org/wiki/Sternohyoid_muscle","sternothyroid-muscle":"The sternothyroid muscle, or sternothyroideus, is an infrahyoid muscle in the neck.\n\nIt acts to depress the hyoid bone.\n\nIt is below the sternohyoid muscle.\n\nIt is shorter and wider than the sternohyoid.\n\n== Structure ==\n\nThe sternothyroid arises from the posterior surface of the manubrium of the sternum, below the origin of the sternohyoid.\n\nIt also arises from the edge of the cartilage of the first rib.\n\nIt is inserted into the oblique line on the lamina of the thyroid cartilage.\n\nIt is in close contact with its fellow at the lower part of the neck, but diverges somewhat as it ascends.\n\nIt is occasionally traversed by a transverse or oblique tendinous inscription.\n\n=== Innervation ===\n\nThe sternothyroid muscle is innervated by the ansa cervicalis.\n\n=== Variations ===\n\nDoubling; absence; accessory slips to the thyrohyoid, inferior pharyngeal constrictor, or to the carotid sheath.\n\n== Function ==\n\nThe sternothyroid muscle depresses the hyoid bone, along with the other infrahyoid muscle.\n\n== Clinical significance ==\n\nThe upward extension of a thyroid swelling (goitre) is prevented by the attachment of the sternothyroid to the thyroid cartilage.\n\nA goitre can therefore only grow to the front, back or middle but no higher.\n\nhttps://en.wikipedia.org/wiki/Sternothyroid_muscle","thyrohyoid-muscle":"The thyrohyoid muscle is a small skeletal muscle on the neck.\n\nIt originates from the lamina of the thyroid cartilage, and inserts into the greater cornu of the hyoid bone.\n\nIt is supplied by the hypoglossal nerve, and a branch of the ventral rami of the cervical plexus, spinal nerve C1, which travels with the hypoglossal nerve.\n\nThe thyrohyoid muscle depresses the hyoid bone and elevates the larynx.\n\nBy controlling the position and shape of the larynx, it aids in making sound.\n\n== Structure ==\n\nThe thyrohyoid muscle is a quadrilateral muscle in shape.\n\nIt appears like an upward continuation of the sternothyroid muscle.\n\nIt belongs to the infrahyoid muscles group.\n\nIt lies in the carotid triangle.\n\nIt arises from the oblique line on the lamina of the thyroid cartilage.\n\nIt is inserted into the lower border of the greater cornu of the hyoid bone.\n\n=== Nerve supply ===\n\nThe thyrohyoid muscle is supplied by the hypoglossal nerve (XII).\n\nIt is the only infrahyoid muscle that is not supplied by the ansa cervicalis.\n\nIt is also supplied by the thyrohyoid branch of cervical spinal nerve 1 (C1).\n\nThis is via the cervical plexus.\n\nThis nerve branches from the first cervical nerve as it joins the hypoglossal nerve for a short distance.\n\n== Function ==\n\nThe thyrohyoid muscle depresses the hyoid bone and elevates the larynx and the thyroid cartilage, drawing them together.\n\nBy controlling the position and shape of the larynx, it aids in making sound.\n\n== Other animals ==\n\nThe thyrohyoid muscle is found in many other animals, including horses.\n\nhttps://en.wikipedia.org/wiki/Thyrohyoid_muscle","superior-pharyngeal-constrictor":"The superior pharyngeal constrictor muscle is a muscle in the pharynx.\n\nIt is the highest located muscle of the three pharyngeal constrictors.\n\nThe muscle is a quadrilateral muscle, thinner and paler than the inferior pharyngeal constrictor muscle and middle pharyngeal constrictor muscle.\n\nThe muscle is divided into four parts: A pterygopharyngeal, buccopharyngeal, mylopharyngeal and a glossopharyngeal part.\n\n== Origin and insertion ==\n\nThe four parts of this muscle arise from:\n- the lower third of the posterior margin of the medial pterygoid plate and its hamulus (Pterygopharyngeal part)\n- from the pterygomandibular raphe (Buccopharyngeal part)\n- from the alveolar process of the mandible above the posterior end of the mylohyoid line (Mylopharyngeal part)\n- and by a few fibers from the side of the tongue (Glossopharyngeal part)\n\nThe fibers curve backward to be inserted into the median raphe, being also prolonged by means of an aponeurosis to the pharyngeal spine on the basilar part of the occipital bone.\n\nThe superior fibers arch beneath the levator veli palatini muscle and the Eustachian tube.\n\n== Relations ==\n\nThe interval between the upper border of the muscle and the base of the skull is closed by the pharyngeal aponeurosis, and is known as the sinus of Morgagni.\n\nThere is an interval between superior pharyngeal constrictor and middle pharyngeal constrictor, this space contains glossopharyngeal nerve and styloglossus muscle.\n\n== Action ==\n\nAs soon as the bolus of food is received in the pharynx, the elevator muscles relax, the pharynx descends, and the constrictors contract upon the bolus, and convey it downward into the esophagus.\n\n== Innervation ==\n\nThe superior pharyngeal constrictor muscle is innervated by the pharyngeal branch of the vagus nerve via the pharyngeal plexus.\n\nhttps://en.wikipedia.org/wiki/Superior_pharyngeal_constrictor_muscle","middle-pharyngeal-constrictor":"The middle pharyngeal constrictor is a fan-shaped muscle located in the neck.\n\nIt is one of three pharyngeal constrictors.\n\nSimilarly to the superior and inferior pharyngeal constrictor muscles, the middle pharyngeal constrictor is innervated by a branch of the vagus nerve through the pharyngeal plexus.\n\nThe middle pharyngeal constrictor is smaller than the inferior pharyngeal constrictor muscle.\n\n== Structure ==\n\nThe middle pharyngeal constrictor arises from the whole length of the upper border of the greater cornu of the hyoid bone, from the lesser cornu, and from the stylohyoid ligament.\n\nThe fibers diverge from their origin: the lower ones descend beneath the constrictor inferior, the middle fibers pass transversely, and the upper fibers ascend and overlap the constrictor superior.\n\nIt is inserted into the posterior median fibrous raphe, blending in the middle line with the muscle of the opposite side.\n\n== Function ==\n\nAs soon as the bolus of food is received in the pharynx, the elevator muscles relax, the pharynx descends, and the constrictors contract upon the bolus, and convey it downward into the esophagus.\n\nThey also have respiratory mechanical effects.\n\nhttps://en.wikipedia.org/wiki/Middle_pharyngeal_constrictor_muscle","inferior-pharyngeal-constrictor":"The Inferior pharyngeal constrictor, the thickest of the three constrictors, arises from the sides of the cricoid and thyroid cartilage.\n\nSimilarly to the superior and middle pharyngeal constrictor muscles, it is innervated by the vagus nerve (cranial nerve X), specifically, by branches from the pharyngeal plexus and by neuronal branches from the recurrent laryngeal nerve.\n\n== Origin and insertion ==\n\nThe muscle is composed of two parts.\n\nThe first (and more superior) arising from the thyroid cartilage (thyropharyngeal part) and the second arising from the cricoid cartilage (cricopharyngeal part).\n\nOn the thyroid cartilage it arises from the oblique line on the side of the lamina, from the surface behind this nearly as far as the posterior border and from the inferior cornu.\n\nFrom the cricoid cartilage it arises in the interval between the Cricothyreoideus in front, and the articular facet for the inferior cornu of the thyroid cartilage behind.\n\nFrom these origins the fibers spread backward and medialward to be inserted with the muscle of the opposite side into the fibrous pharyngeal raphe in the posterior median line of the pharynx.\n\nThe inferior fibers are horizontal and continuous with the circular fibers of the esophagus; the rest ascend, increasing in obliquity, and overlap the Constrictor medius.\n\nThe cricopharyngeal muscle is synonymous with the upper esophageal sphincter (UES), which controls the opening of the cervical esophagus, and is sometimes referred to as the cricopharyngeal inlet.\n\n== Action ==\n\nAs soon as the bolus of food is received in the pharynx, the elevator muscles relax, the pharynx descends, and the constrictors contract upon the bolus, and convey it downward into the esophagus.\n\nDuring deglutition, they contract and cause peristaltic movement in the pharynx.\n\n== Role in human disease ==\n\nUncoordinated contraction, and/or Cricopharyngeal Spasm and/or impaired relaxation of this muscle are currently considered the main factors in development of a Zenker's diverticulum.\n\nZenker's diverticulum develops between the two bellies of the inferior constrictor (Thyropharyngeal and Cricopharyngeal) in a small gap called Killian's dehiscence.\n\nA diverticulum can form where a balloon of mucosa becomes trapped outside the pharyngeal boundaries.\n\nFood or other materials may reside here, which may lead to infection.\n\nMotor incoordination of the cricopharyngeus can cause difficulty swallowing.\n\nIn extreme cases this can be related to Retrograde Cricopharyngeus Dysfunction (R-CPD) which causes the inability to burp, this is in part due to the muscle not being able to relax.\n\nBotox or a Cricopharyngeal myotomy are used to treat the condition.\n\nhttps://en.wikipedia.org/wiki/Inferior_pharyngeal_constrictor_muscle","stylopharyngeus-muscle":"The stylopharyngeus is a muscle in the head that stretches between the temporal styloid process and the pharynx.\n\n== Structure ==\n\nThe stylopharyngeus is a long, slender muscle, cylindrical above, flattened below.\n\nIt arises from the medial side of the base of the temporal styloid process, passes downward along the side of the pharynx between the superior pharyngeal constrictor and the middle pharyngeal constrictor, and spreads out beneath the mucous membrane.\nSome of its fibers are lost in the constrictor muscles while others, joining the palatopharyngeus muscle, are inserted into the posterior border of the thyroid cartilage.\nThe glossopharyngeal nerve runs on the lateral side of this muscle, and crosses over it to reach the tongue.\n\n=== Nerve supply ===\n\nThe stylopharyngeus is the only muscle in the pharynx innervated by the glossopharyngeal nerve (CN IX) via branchial motor neurons with their cell bodies in the rostral part of the nucleus ambiguus.\n\n=== Development ===\n\nEmbryological origin is the third pharyngeal arch.\n\n== Function ==\n\nThe stylopharyngeus:\n\nelevates the larynx\nelevates the pharynx\ndilates the pharynx to permit the passage of a large food bolus, thereby facilitating swallowing\n\nhttps://en.wikipedia.org/wiki/Stylopharyngeus_muscle","oblique-part-of-cricothyroid-muscle":"Posterior fibers of cricothyroid muscle, oriented more horizontally.","straight-part-of-cricothyroid-muscle":"Anterior fibers of the cricothyroid muscle, mostly vertically oriented.","external-part-of-thyro-arytenoid-muscle":"Main external part of the thyro-arytenoid muscle, by opposition to the thyro-epiglottic part of thyro-arytenoid muscle and the\nvocalis muscle.","ary-epiglottic-part-of-oblique-arytenoid-muscle":"Origin apex of arytenoid cartilage.\n\nInsertion: border of epiglottis.\n\nSupport of the ary-epiglottic fold.\n\nLower the epiglottis.","thyro-epiglottic-part-of-thyro-arytenoid-muscle":"Origin: In front, on the internal surface of the thyroid cartilage.\n\nInsertion: epiglottis and quadrangular membrane.\n\nInnervation: recurrent laryngeal nerve.","transverse-arytenoid-muscle":"The arytenoid muscle /ærɪˈtiːnɔɪd/ is a single muscle of the larynx.\n\nIt passes from one arytenoid cartilage to the opposite arytenoid cartilage.\n\nIt has oblique and transverse fibres.\n\nIt is supplied by the recurrent laryngeal nerve.\n\nIt approximates the arytenoid cartilages.\n\nContinuous electromyography may be used during neck surgeries such as thyroidectomy.\n\nStructure\n\nThe arytenoid muscle fills the posterior concave surface of the arytenoid cartilage.\n\nIt arises from the posterior surface and lateral border of one arytenoid cartilage.\n\nIt is inserted into the corresponding parts of the opposite arytenoid cartilage.\n\nIt consists of oblique and transverse fibres.\n\nNerve supply\n\nThe arytenoid muscle is supplied by the recurrent laryngeal nerve, a branch of the vagus nerve (CN X).\n\nThis is a bilateral supply.\n\nFunction\n\nThe arytenoid muscle approximates the arytenoid cartilages.\n\nThis closes the aperture of the glottis, especially at its back part to eliminate the posterior commissure of the vocal cords.\n\nClinical significance.\n\nElectromyography.\n\nFunction of the arytenoid muscle is a good method to determine function of the recurrent laryngeal nerve.\n\nContinuous electromyography of the arytenoid muscle can provide confidence to surgeons that the recurrent laryngeal nerve is not damaged during neck surgeries, such as thyroidectomy.\n\nOther animals\n\nThe arytenoid muscle is found in many animals, including dogs.","lateral-crico-arytenoid-muscle":"Origin: superior border and lateral external surface of the cricoid cartilage.\n\nInsertion: lateral border of muscular process of arytenoid cartilage and surrounding region.\n\nSynergic of the closing of the rima glottidis.\n\nInnervation: recurrent laryngeal nerve","posterior-crico-arytenoid-muscle":"The posterior cricoarytenoid muscles are small, paired intrinsic muscles of the larynx that extend between cricoid cartilage to the arytenoid cartilages in the larynx.\n\nStructure\n\nOrigin and insertion\n\nThe posterior cricoarytenoid originates from the posterior surface of the posterior quadrate lamina of the cricoid cartilage.\n\nIt inserts onto the muscular process of the arytenoid cartilage.\n\nIts distinct medial and lateral bellies insert onto opposite surfaces of the muscular process.\n\nNerve supply\n\nThe posterior cricoarytenoid muscles are supplied by the anterior division of the recurrent laryngeal nerve, a branch of the vagus nerve (CN X).\n\nSometimes, different parts of the muscle (such as the medial and lateral muscle bellies) are supplied by separate branches.\n\nThis may vary between 1 and 6 branches, usually 2 or 3.\n\nThese may connect within the muscle.\n\nFunction\n\nThe posterior cricoarytenoid muscles are the only muscles to open the vocal cords.\n\nBy rotating the arytenoid cartilages laterally, these muscles abduct the vocal cords.\n\nThis opens the rima glottidis.\n\nThis is important in breathing and speech.\n\nTheir action opposes the lateral cricoarytenoid muscles.\n\nClinical significance\n\nParalysis of the posterior cricoarytenoid muscles may lead to asphyxia, as they are the only laryngeal muscles to open the vocal cords (allowing breathing).\n\nDenervation leads to a slow fibrosis that worsens over many months","platysma":"The platysma muscle is a superficial muscle of the human neck that overlaps the sternocleidomastoid.\n\nIt covers the anterior surface of the neck superficially.\n\nWhen it contracts, it produces a slight wrinkling of the neck, and a \"bowstring\" effect on either side of the neck.\n\n== Structure ==\n\nThe platysma muscle is a broad sheet of muscle arising from the fascia covering the upper parts of the pectoralis major muscle and deltoid muscle.\n\nIts fibers cross the clavicle, and proceed obliquely upward and medially along the side of the neck.\n\nThis leaves the inferior part of the neck in the midline deficient of significant muscle cover.Fibres at the front of the muscle from the left and right sides intermingle together below and behind the mandibular symphysis, the junction where the two lateral halves of the mandible are fused at an early period of life (although not a true symphysis).\n\nFibres at the back of the muscle cross the mandible, some being inserted into the bone below the oblique line, others into the skin and subcutaneous tissue of the lower part of the face.\n\nMany of these fibers blend with the muscles about the angle and lower part of the mouth.Sometimes fibers can be traced to the zygomaticus major muscle, or to the margin of the orbicularis oris muscle.\n\nBeneath the platysma, the external jugular vein descends from the angle of the mandible to the clavicle.\n\n=== Nerve supply ===\n\nThe platysma muscle is supplied by the cervical branch of the facial nerve.\n\n=== Blood supply ===\n\nThe platysma muscle is supplied by branches of the submental artery and suprascapular artery.\n\n=== Relations ===\n\nThe platysma muscle lies just deep to the subcutaneous fascia and fat.\n\nIt covers many structures found deeper in the neck, such as the external carotid artery, the external jugular vein, the parotid gland, the lesser occipital nerve, the great auricular nerve, and the marginal mandibular branch of the facial nerve.\n\n=== Variation ===\n\nVariations occur in the extension over the face and over the clavicle and shoulder.\n\nThe platysma muscle may be absent or interdigitate with the muscle of the opposite side in front of the neck; attachment to clavicle, mastoid process or occipital bone occurs.\n\nA more or less independent fasciculus, the occipitalis minor muscle, may extend from the fascia over the trapezius muscle to fascia over the insertion of the sternocleidomastoid muscle.\n\n== Function ==\n\n=== Wrinkling ===\n\nWhen the entire platysma muscle is in action, it produces a slight wrinkling of the surface of the skin of the neck in an oblique direction (at an angle to the midline).\n\nIt creates a distinctive \"bowstring\" effect on either side of the neck, where fibres move away from the midline.\n\n=== Jaw and lip movement ===\n\nThe anterior portion of the platysma muscle, the thickest part of the muscle, depresses the lower jaw.\n\nIt also draws down the lower lip and angle of the mouth in a frown.\n\nHowever, the platysma muscle plays only a minor role in depressing the lower lip, which is primarily performed by the depressor anguli oris muscle and the depressor labii inferioris muscle.\n\n== Clinical significance ==\n\nIn a similar fashion to other muscles, the platysma muscle is vulnerable to tears, strains and muscle atrophy, among many other possible conditions.\nTurkey neck / Platysma synkinesis\nWrinkly skin of neck caused by decrease in muscle tone leading to thining and shortening of muscle,it is the secondary complication of facialy nerve plasy and can be associated with normal aging process\n\n=== Injury ===\n\nThe platysma muscle is vulnerable to neck injuries that may penetrate it, as it is both superficial and thin.\n\nPenetrating trauma in the neck injuries can be defined as any that completely penetrate the platysma muscle, making it an important landmark.\n\nCTA (computed tomography angiography) may be used to visualise arteries and veins, such as for complex injuries from gunshot wounds or stab wounds, and is useful to image any damage to the muscle.\n\nThis minimises the number of exploratory surgeries that need to be performed, thus improving the handling of the condition.\n\n=== Neck surgery ===\n\nWhen neck surgery is performed, the platysma muscle usually needs to be cut through to access deeper structures.\n\nFibres need to be sutured together accurately to prevent abnormal scar retraction, which may look unsightly.\n\n=== Plastic surgery ===\n\nNeck bands in the area above the platysma muscle become most noticeable with age.\n\nThese may be aggravated by weightlifting or facelift procedures.\n\nConservative management may be used.\n\nAlternatively, interventions include botulinum toxin injection and platysmaplasty.\n\nPlatysmaplasty is a surgery in this area, that can be open or closed, in the latter a specialised instrument called a plastymotome that allow the surgery to be done without incisions.\n\nIt takes approximately 2 weeks for the symptoms to be reduced.Adipose tissue is found above the platysma muscle, so liposuction of the neck may be performed fairly easily without the need to pierce it.\n\nIt is also important to not damage the platysma muscle to prevent bleeding.\n\nhttps://en.wikipedia.org/wiki/Platysma_muscle","scalenus-medius-muscle":"The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the anterior scalene, middle scalene, and posterior scalene.\n\nThey are innervated by the fourth, fifth, and sixth cervical spinal nerves (C4-C6).\nThe anterior and middle scalene muscles lift the first rib and bend the neck to the same side; the posterior scalene lifts the second rib and tilts the neck to the same side.\nThe muscles are named from Ancient Greek σκαληνός (skalenos) 'uneven'.\n\n== Structure ==\n\nThe scalene muscles originate from the transverse processes from the cervical vertebrae of C2 to C7 and insert onto the first and second ribs.\n\n=== Middle scalene ===\n\nThe middle scalene, (Latin: scalenus medius), is the largest and longest of the three scalene muscles.\n\nThe middle scalene arises from the posterior tubercles of the transverse processes of the lower six cervical vertebrae.\n\nIt descends along the side of the vertebral column to insert by a broad attachment into the upper surface of the first rib, posterior to the subclavian groove.\n\nThe brachial plexus and the subclavian artery pass anterior to it.\n\n=== Variation ===\n\nA fourth muscle, the scalenus minimus (Sibson's muscle), is sometimes present behind the lower portion of the anterior scalene.\n\n== Function ==\n\nThe anterior and middle scalene muscles lifts the first rib and bends the neck to the same side as the acting muscle; the posterior scalene lifts the second rib and tilts the neck to the same side.\nBecause they elevate the upper ribs they also act as accessory muscles of respiration, along with the sternocleidomastoids.\n\n=== Relations ===\n\nThe scalene muscles have an important relationship to other structures in the neck.\n\nThe brachial plexus and subclavian artery pass between the anterior and middle scalenes.\n\nThe subclavian vein and phrenic nerve pass anteriorly to the anterior scalene as the muscle crosses over the first rib.\n\nThe phrenic nerve is oriented vertically as it passes in front of the anterior scalene, while the subclavian vein is oriented horizontally as it passes in front of the anterior scalene muscle.The passing of the brachial plexus and the subclavian artery through the space of the anterior and middle scalene muscles constitute the scalene hiatus (the term \"scalene fissure\" is also used).\n\nThe region in which this lies is referred to as the scaleotracheal fossa.\n\nIt is bounded by the clavicle inferior anteriorly, the trachea medially, posteriorly by the trapezius, and anteriorly by the platysma muscle.\n\n== Clinical significance ==\n\nThe anterior and middle scalene muscles can be involved in certain forms of thoracic outlet syndrome as well as myofascial pain syndrome, the symptoms of which may mimic a spinal disc herniation of the cervical vertebrae.Since the nerves of the brachial plexus pass through the space between the anterior and middle scalene muscles, that area is sometimes targeted with the administration of regional anesthesia by an anesthesia provider.\n\nThe nerve block, called an interscalene block, may be performed prior to arm or shoulder surgery.According to the medical codes in the 2016 Procedural Coding Expert, published by the American Academy of Professional Coders, for Current Procedural Terminology (CPT) and other medical codes, the scalenus anticus muscle can be divided by reparative or reconstructive surgery, with (# 21705) or without (# 21700) resection of the cervical rib.\n\n== History ==\n\nThe scalenes used to be known as the lateral vertebral muscles.\n\n=== Etymology ===\n\nThe muscles are named from Greek σκαληνός, or skalenos, meaning uneven as the pairs are all of differing length\n\nhttps://en.wikipedia.org/wiki/Scalene_muscles","scalenus-posterior-muscle":"The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the anterior scalene, middle scalene, and posterior scalene.\n\nThey are innervated by the fourth, fifth, and sixth cervical spinal nerves (C4-C6).\nThe anterior and middle scalene muscles lift the first rib and bend the neck to the same side; the posterior scalene lifts the second rib and tilts the neck to the same side.\nThe muscles are named from Ancient Greek σκαληνός (skalenos) 'uneven'.\n\n== Structure ==\n\nThe scalene muscles originate from the transverse processes from the cervical vertebrae of C2 to C7 and insert onto the first and second ribs.\n\n=== Posterior scalene ===\n\nThe posterior scalene, (Latin: scalenus posterior) is the smallest and most deeply seated of the scalene muscles.\n\nIt arises, by two or three separate tendons, from the posterior tubercles of the transverse processes of the lower two or three cervical vertebrae, and is inserted by a thin tendon into the outer surface of the second rib, behind the attachment of the anterior scalene.\n\nIt is supplied by cervical nerves C5, C6 and C7.\n\nIt is occasionally blended with the middle scalene.\n\n=== Variation ===\n\nA fourth muscle, the scalenus minimus (Sibson's muscle), is sometimes present behind the lower portion of the anterior scalene.\n\n== Function ==\n\nThe anterior and middle scalene muscles lifts the first rib and bends the neck to the same side as the acting muscle; the posterior scalene lifts the second rib and tilts the neck to the same side.\nBecause they elevate the upper ribs they also act as accessory muscles of respiration, along with the sternocleidomastoids.\n\n=== Relations ===\n\nThe scalene muscles have an important relationship to other structures in the neck.\n\nThe brachial plexus and subclavian artery pass between the anterior and middle scalenes.\n\nThe subclavian vein and phrenic nerve pass anteriorly to the anterior scalene as the muscle crosses over the first rib.\n\nThe phrenic nerve is oriented vertically as it passes in front of the anterior scalene, while the subclavian vein is oriented horizontally as it passes in front of the anterior scalene muscle.The passing of the brachial plexus and the subclavian artery through the space of the anterior and middle scalene muscles constitute the scalene hiatus (the term \"scalene fissure\" is also used).\n\nThe region in which this lies is referred to as the scaleotracheal fossa.\n\nIt is bounded by the clavicle inferior anteriorly, the trachea medially, posteriorly by the trapezius, and anteriorly by the platysma muscle.\n\n== Clinical significance ==\n\nThe anterior and middle scalene muscles can be involved in certain forms of thoracic outlet syndrome as well as myofascial pain syndrome, the symptoms of which may mimic a spinal disc herniation of the cervical vertebrae.Since the nerves of the brachial plexus pass through the space between the anterior and middle scalene muscles, that area is sometimes targeted with the administration of regional anesthesia by an anesthesia provider.\n\nThe nerve block, called an interscalene block, may be performed prior to arm or shoulder surgery.According to the medical codes in the 2016 Procedural Coding Expert, published by the American Academy of Professional Coders, for Current Procedural Terminology (CPT) and other medical codes, the scalenus anticus muscle can be divided by reparative or reconstructive surgery, with (# 21705) or without (# 21700) resection of the cervical rib.\n\n== History ==\n\nThe scalenes used to be known as the lateral vertebral muscles.\n\n=== Etymology ===\n\nThe muscles are named from Greek σκαληνός, or skalenos, meaning uneven as the pairs are all of differing length\n\n== References ==\n\nhttps://en.wikipedia.org/wiki/Scalene_muscles","scalenus-anterior-muscle":"The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the anterior scalene, middle scalene, and posterior scalene.\n\nThey are innervated by the fourth, fifth, and sixth cervical spinal nerves (C4-C6).\nThe anterior and middle scalene muscles lift the first rib and bend the neck to the same side; the posterior scalene lifts the second rib and tilts the neck to the same side.\nThe muscles are named from Ancient Greek σκαληνός (skalenos) 'uneven'.\n\n== Structure ==\n\nThe scalene muscles originate from the transverse processes from the cervical vertebrae of C2 to C7 and insert onto the first and second ribs.\n\n=== Anterior scalene ===\n\nThe anterior scalene muscle (Latin: scalenus anterior), lies deeply at the side of the neck, behind the sternocleidomastoid muscle.\n\nIt arises from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and descending, almost vertically, is inserted by a narrow, flat tendon into the scalene tubercle on the inner border of the first rib, and into the ridge on the upper surface of the second rib in front of the subclavian groove.\n\nIt is supplied by the anterior ramus of cervical nerve 5 and 6.\n\n=== Variation ===\n\nA fourth muscle, the scalenus minimus (Sibson's muscle), is sometimes present behind the lower portion of the anterior scalene.\n\n== Function ==\n\nThe anterior and middle scalene muscles lifts the first rib and bends the neck to the same side as the acting muscle; the posterior scalene lifts the second rib and tilts the neck to the same side.\nBecause they elevate the upper ribs they also act as accessory muscles of respiration, along with the sternocleidomastoids.\n\n=== Relations ===\n\nThe scalene muscles have an important relationship to other structures in the neck.\n\nThe brachial plexus and subclavian artery pass between the anterior and middle scalenes.\n\nThe subclavian vein and phrenic nerve pass anteriorly to the anterior scalene as the muscle crosses over the first rib.\n\nThe phrenic nerve is oriented vertically as it passes in front of the anterior scalene, while the subclavian vein is oriented horizontally as it passes in front of the anterior scalene muscle.The passing of the brachial plexus and the subclavian artery through the space of the anterior and middle scalene muscles constitute the scalene hiatus (the term \"scalene fissure\" is also used).\n\nThe region in which this lies is referred to as the scaleotracheal fossa.\n\nIt is bounded by the clavicle inferior anteriorly, the trachea medially, posteriorly by the trapezius, and anteriorly by the platysma muscle.\n\n== Clinical significance ==\n\nThe anterior and middle scalene muscles can be involved in certain forms of thoracic outlet syndrome as well as myofascial pain syndrome, the symptoms of which may mimic a spinal disc herniation of the cervical vertebrae.Since the nerves of the brachial plexus pass through the space between the anterior and middle scalene muscles, that area is sometimes targeted with the administration of regional anesthesia by an anesthesia provider.\n\nThe nerve block, called an interscalene block, may be performed prior to arm or shoulder surgery.According to the medical codes in the 2016 Procedural Coding Expert, published by the American Academy of Professional Coders, for Current Procedural Terminology (CPT) and other medical codes, the scalenus anticus muscle can be divided by reparative or reconstructive surgery, with (# 21705) or without (# 21700) resection of the cervical rib.\n\n== History ==\n\nThe scalenes used to be known as the lateral vertebral muscles.\n\n=== Etymology ===\n\nThe muscles are named from Greek σκαληνός, or skalenos, meaning uneven as the pairs are all of differing length\n\nhttps://en.wikipedia.org/wiki/Scalene_muscles","longus-capitis-muscle":"The longus capitis muscle (Latin for long muscle of the head, alternatively rectus capitis anticus major), is broad and thick above, narrow below, and arises by four tendinous slips, from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebræ, and ascends, converging toward its fellow of the opposite side, to be inserted into the inferior surface of the basilar part of the occipital bone.\n\nIt is innervated by a branch of cervical plexus.\n\nLongus capitis has several actions:\nacting unilaterally, to:\n\n-flex the head and neck laterally\n-rotate the head ipsilaterallyacting bilaterally:\n-flex the head and neck\n\nhttps://en.wikipedia.org/wiki/Longus_capitis_muscle","longus-colli-muscle":"The longus colli muscle (Latin for long muscle of the neck) is a muscle of the human body.\n\nThe longus colli is situated on the anterior surface of the vertebral column, between the atlas and the third thoracic vertebra.\n\nIt is broad in the middle, narrow and pointed at either end, and consists of three portions, a superior oblique, an inferior oblique, and a vertical.\n\nThe superior oblique portion arises from the anterior tubercles of the transverse processes of the third, fourth, and fifth cervical vertebrae and, ascending obliquely with a medial inclination, is inserted by a narrow tendon into the tubercle on the anterior arch of the atlas.\n\nThe inferior oblique portion, the smallest part of the muscle, arises from the front of the bodies of the first two or three thoracic vertebrae; and, ascending obliquely in a lateral direction, is inserted into the anterior tubercles of the transverse processes of the fifth and sixth cervical vertebrae.\n\nThe vertical portion arises, below, from the front of the bodies of the upper three thoracic and lower three cervical vertebrae, and is inserted into the front of the bodies of the second, third, and fourth cervical vertebrae.\n\n== Clinical significance ==\n\nIt is commonly injured in rear end whiplash injuries, usually resulting from a car crash.\n\nThis muscle is in front of the spine and is thought by some scientists that it may cause some whiplash patients to have an unnatural lack of curvature in the patients' neck.\n\nAcute calcific tendinitis of the longus colli muscle can occur.\n\nThis presents with acute onset of neck pain, stiffness, dysphagia and odynophagia, and must be distinguished from retropharyngeal abscess and other sinister conditions.\n\nImaging diagnosis is by CT or MRI, demonstrating calcification in the muscle in addition to retropharyngeal oedema.\n\nTreatment is supportive, with non-steroidal anti-inflammatory drugs.\n\nhttps://en.wikipedia.org/wiki/Longus_colli_muscle","superficial-investing-cervical-fascia":"Superficial cervical fascia is a thin layer of subcutaneous connective tissue that lies between the dermis of the skin and the deep cervical fascia.\n\nIt contains the platysma, cutaneous nerves, blood, and lymphatic vessels. It also contains a varying amount of fat, which is its distinguishing characteristic.\n\nIt is considered by some to be a part of the panniculus adiposus, and not true fascia.","posterior-layer-of-thoracolumbar-fascia":"The thoracolumbar fascia (lumbodorsal fascia or thoracodorsal fascia) is a deep investing membrane throughout most of the posterior thorax and abdomen although it is a thin fibrous lamina in the thoracic region.\n\nAbove, it is continuous with a similar investing layer on the back of the neck—the nuchal fascia.\n\nIt is formed of longitudinal and transverse fibers that bridge the aponeuroses of internal oblique and transversus, costal angles and iliac crest laterally, to the vertebral column and sacrum medially.\n\nIn doing so, they cover the paravertebral muscles.\nIt is made up of three layers, anterior, middle, and posterior.\n\nThe anterior and middle layers insert onto the transverse processes of the vertebral column while the posterior layer inserts onto the tips of the spinous processes, hence it is indirectly continuous with the interspinous ligaments.\n\nThe anterior layer is the thinnest and the posterior layer is the thickest.\n\nTwo spaces are formed between these three layers of the fascia.\n\nPsoas major lies anterior to the anterior layer, with the anterior fascia of this muscle being continuous with the vertebral body and thus the anterior longitudinal ligament.\n\nBetween the anterior and middle layer lies the quadratus lumborum muscle.\n\nThe erector spinae muscles and the transversospinales muscles are then enclosed between the middle and posterior layers.\n\nVarious superficial muscle layers on the posterior thorax and abdomen then arise from the posterior layer.\n\nThese primarily include latissimus dorsi and serratus posterior inferior.\n\nhttps://en.wikipedia.org/wiki/Thoracolumbar_fascia","middle-layer-of-thoracolumbar-fascia":"The thoracolumbar fascia (lumbodorsal fascia or thoracodorsal fascia) is a deep investing membrane throughout most of the posterior thorax and abdomen although it is a thin fibrous lamina in the thoracic region.\n\nAbove, it is continuous with a similar investing layer on the back of the neck—the nuchal fascia.\n\nIt is formed of longitudinal and transverse fibers that bridge the aponeuroses of internal oblique and transversus, costal angles and iliac crest laterally, to the vertebral column and sacrum medially.\n\nIn doing so, they cover the paravertebral muscles.\nIt is made up of three layers, anterior, middle, and posterior.\n\nThe anterior and middle layers insert onto the transverse processes of the vertebral column while the posterior layer inserts onto the tips of the spinous processes, hence it is indirectly continuous with the interspinous ligaments.\n\nThe anterior layer is the thinnest and the posterior layer is the thickest.\n\nTwo spaces are formed between these three layers of the fascia.\n\nPsoas major lies anterior to the anterior layer, with the anterior fascia of this muscle being continuous with the vertebral body and thus the anterior longitudinal ligament.\n\nBetween the anterior and middle layer lies the quadratus lumborum muscle.\n\nThe erector spinae muscles and the transversospinales muscles are then enclosed between the middle and posterior layers.\n\nVarious superficial muscle layers on the posterior thorax and abdomen then arise from the posterior layer.\n\nThese primarily include latissimus dorsi and serratus posterior inferior.\n\nhttps://en.wikipedia.org/wiki/Thoracolumbar_fascia","anterior-layer-of-thoracolumbar-fascia":"The thoracolumbar fascia (lumbodorsal fascia or thoracodorsal fascia) is a deep investing membrane throughout most of the posterior thorax and abdomen although it is a thin fibrous lamina in the thoracic region.\n\nAbove, it is continuous with a similar investing layer on the back of the neck—the nuchal fascia.\n\nIt is formed of longitudinal and transverse fibers that bridge the aponeuroses of internal oblique and transversus, costal angles and iliac crest laterally, to the vertebral column and sacrum medially.\n\nIn doing so, they cover the paravertebral muscles.\nIt is made up of three layers, anterior, middle, and posterior.\n\nThe anterior and middle layers insert onto the transverse processes of the vertebral column while the posterior layer inserts onto the tips of the spinous processes, hence it is indirectly continuous with the interspinous ligaments.\n\nThe anterior layer is the thinnest and the posterior layer is the thickest.\n\nTwo spaces are formed between these three layers of the fascia.\n\nPsoas major lies anterior to the anterior layer, with the anterior fascia of this muscle being continuous with the vertebral body and thus the anterior longitudinal ligament.\n\nBetween the anterior and middle layer lies the quadratus lumborum muscle.\n\nThe erector spinae muscles and the transversospinales muscles are then enclosed between the middle and posterior layers.\n\nVarious superficial muscle layers on the posterior thorax and abdomen then arise from the posterior layer.\n\nThese primarily include latissimus dorsi and serratus posterior inferior.\n\nhttps://en.wikipedia.org/wiki/Thoracolumbar_fascia","obliquus-inferior-capitis-muscle":"The obliquus capitis inferior muscle (/əˈblaɪkwəs ˈkæpɪtɪs/) is the larger of the two oblique muscles of the neck.\n\nIt arises from the apex of the spinous process of the axis and passes laterally and slightly upward, to be inserted into the lower and back part of the transverse process of the atlas.\n\nIt lies deep to the semispinalis capitis and trapezius muscles.\n\nThe muscle is responsible for rotation of the head and first cervical vertebra (atlanto-axial joint).\n\nIt forms the lower boundary of the suboccipital triangle of the neck.\n\nThe naming of this muscle may be confusing, as it is the only capitis (L. \"head\") muscle that does NOT attach to the cranium.\n\nhttps://en.wikipedia.org/wiki/Obliquus_capitis_inferior_muscle","obliquus-superior-capitis-muscle":"The obliquus capitis superior muscle (/əˈblaɪkwəs ˈkæpɪtɪs/) is a small muscle in the upper back part of the neck and is one of the suboccipital muscles and part of the suboccipital triangle.\n\nIt arises from the lateral mass of the atlas bone.\n\nIt passes superiorly and posteriorly to insert into the lateral half of the inferior nuchal line on the external surface of the occipital bone.\n\nThe muscle is innervated by the suboccipital nerve, the dorsal ramus of the first spinal nerve.\n\nIt acts at the atlanto-occipital joint to extend the head and flex the head to the ipsilateral side.\n\nhttps://en.wikipedia.org/wiki/Obliquus_capitis_superior_muscle","rectus-posterior-major-capitis-muscle":"The rectus capitis posterior major (or rectus capitis posticus major, both being Latin for larger posterior straight muscle of the head) arises by a pointed tendon from the spinous process of the axis, and, becoming broader as it ascends, is inserted into the lateral part of the inferior nuchal line of the occipital bone and the surface of the bone immediately below the line.\n\nA soft tissue connection bridging from the rectus capitis posterior major to the cervical dura mater was described in 2011.\n\nVarious clinical manifestations may be linked to this anatomical relationship.\n\nIt has also been postulated that this connection serves as a monitor of dural tension along with the rectus capitis posterior minor and the obliquus capitis inferior.\n\nAs the muscles of the two sides pass upward and lateralward, they leave between them a triangular space, in which the rectus capitis posterior minor is seen.\n\nIts main actions are to extend and rotate the atlanto-occipital joint.\n\nhttps://en.wikipedia.org/wiki/Rectus_capitis_posterior_major_muscle","rectus-posterior-minor-capitis-muscle":"The rectus posterior minor capitis minor arises by a narrow pointed tendon from the tubercle on the posterior arch of the atlas, and, widening as it ascends, is inserted into the medial part of the inferior nuchal line of the occipital bone and the surface between it and the foramen magnum, and also takes some attachment to the spinal dura mater.\n\nThe synergists are the rectus capitis posterior major and obliquus capitis.\n\nConnective tissue bridges were noted at the atlanto-occipital joint between the rectus capitis posterior minor muscle and the dorsal spinal dura.\n\nSimilar connective tissue connections of the rectus capitis posterior major have been reported recently as well.\n\nThe perpendicular arrangement of these fibers appears to restrict dural movement toward the spinal cord.\n\nThe ligamentum nuchae was found to be continuous with the posterior cervical spinal dura and the lateral portion of the occipital bone.\n\nAnatomic structures innervated by cervical nerves C1-C3 have the potential to cause headache pain.\n\nIncluded are the joint complexes of the upper three cervical segments, the dura mater, and spinal cord.\n\nThe dura-muscular, dura-ligamentous connections in the upper cervical spine and occipital areas may provide anatomic and physiologic answers to the cause of the cervicogenic headache.\n\nThis proposal would further explain manipulation's efficacy in the treatment of cervicogenic headache.\n\nhttps://en.wikipedia.org/wiki/Rectus_capitis_posterior_minor_muscle","iliocostalis-lumborum-muscle":"Iliocostalis muscle is the muscle immediately lateral to the longissimus that is the nearest to the furrow that separates the epaxial muscles from the hypaxial.\n\nIt lies very deep to the fleshy portion of the serratus posterior muscle.\n\nIt laterally flexes the vertebral column to the same side.\n\n== Structure ==\n\nIliocostalis muscle has a common origin from the iliac crest, the sacrum, the thoracolumbar fascia, and the spinous processes of the vertebrae from T11 to L5.\n\nIliocostalis cervicis (cervicalis ascendens) arises from the angles of the third, fourth, fifth, and sixth ribs, and is inserted into the posterior tubercles of the transverse processes of the fourth, fifth, and sixth cervical vertebrae.\n\nIliocostalis thoracis (musculus accessorius; iliocostalis thoracis) arises by flattened tendons from the upper borders of the angles of the lower six ribs medial to the tendons of insertion of the iliocostalis lumborum; these become muscular, and are inserted into the upper borders of the angles of the upper six ribs and into the back of the transverse process of the seventh cervical vertebra.\n\nIliocostalis lumborum (iliocostalis muscle; sacrolumbalis muscle) is inserted, by flattened tendons, into the inferior borders of the angles of the lower six to nineribs.\n\n=== Nerve supply ===\n\nIliocostalis muscle is supplied by the dorsal rami of spinal nerves.\n\n== Function ==\n\nIliocostalis muscle laterally flexes the vertebral column to the same side.\n\nIt bilaterally extends the vertebral column.\n\nhttps://en.wikipedia.org/wiki/Iliocostalis","iliocostalis-thoracis-muscle":"Iliocostalis muscle is the muscle immediately lateral to the longissimus that is the nearest to the furrow that separates the epaxial muscles from the hypaxial.\n\nIt lies very deep to the fleshy portion of the serratus posterior muscle.\n\nIt laterally flexes the vertebral column to the same side.\n\n== Structure ==\n\nIliocostalis muscle has a common origin from the iliac crest, the sacrum, the thoracolumbar fascia, and the spinous processes of the vertebrae from T11 to L5.\n\nIliocostalis cervicis (cervicalis ascendens) arises from the angles of the third, fourth, fifth, and sixth ribs, and is inserted into the posterior tubercles of the transverse processes of the fourth, fifth, and sixth cervical vertebrae.\n\nIliocostalis thoracis (musculus accessorius; iliocostalis thoracis) arises by flattened tendons from the upper borders of the angles of the lower six ribs medial to the tendons of insertion of the iliocostalis lumborum; these become muscular, and are inserted into the upper borders of the angles of the upper six ribs and into the back of the transverse process of the seventh cervical vertebra.\n\nIliocostalis lumborum (iliocostalis muscle; sacrolumbalis muscle) is inserted, by flattened tendons, into the inferior borders of the angles of the lower six to nineribs.\n\n=== Nerve supply ===\n\nIliocostalis muscle is supplied by the dorsal rami of spinal nerves.\n\n== Function ==\n\nIliocostalis muscle laterally flexes the vertebral column to the same side.\n\nIt bilaterally extends the vertebral column.\n\nhttps://en.wikipedia.org/wiki/Iliocostalis","iliocostalis-colli-muscle":"Iliocostalis muscle is the muscle immediately lateral to the longissimus that is the nearest to the furrow that separates the epaxial muscles from the hypaxial.\n\nIt lies very deep to the fleshy portion of the serratus posterior muscle.\n\nIt laterally flexes the vertebral column to the same side.\n\n== Structure ==\n\nIliocostalis muscle has a common origin from the iliac crest, the sacrum, the thoracolumbar fascia, and the spinous processes of the vertebrae from T11 to L5.\n\nIliocostalis cervicis (cervicalis ascendens) arises from the angles of the third, fourth, fifth, and sixth ribs, and is inserted into the posterior tubercles of the transverse processes of the fourth, fifth, and sixth cervical vertebrae.\n\nIliocostalis thoracis (musculus accessorius; iliocostalis thoracis) arises by flattened tendons from the upper borders of the angles of the lower six ribs medial to the tendons of insertion of the iliocostalis lumborum; these become muscular, and are inserted into the upper borders of the angles of the upper six ribs and into the back of the transverse process of the seventh cervical vertebra.\n\nIliocostalis lumborum (iliocostalis muscle; sacrolumbalis muscle) is inserted, by flattened tendons, into the inferior borders of the angles of the lower six to nineribs.\n\n=== Nerve supply ===\n\nIliocostalis muscle is supplied by the dorsal rami of spinal nerves.\n\n== Function ==\n\nIliocostalis muscle laterally flexes the vertebral column to the same side.\n\nIt bilaterally extends the vertebral column.\n\nhttps://en.wikipedia.org/wiki/Iliocostalis","longissimus-thoracis-muscle":"The longissimus (Latin for 'the longest one') is the muscle lateral to the semispinalis muscles.\n\nIt is the longest subdivision of the erector spinae muscles that extends forward into the transverse processes of the posterior cervical vertebrae.\n\n== Structure ==\n\n=== Longissimus thoracis et lumborum ===\n\nThe longissimus thoracis et lumborum is the intermediate and largest of the continuations of the erector spinae.\n\nIn the lumbar region (longissimus lumborum), where it is as yet blended with the iliocostalis, some of its fibers are attached to the whole length of the posterior surfaces of the transverse processes and the accessory processes of the lumbar vertebrae, and to the anterior layer of the lumbodorsal fascia.\n\nIn the thoracic region (longissimus thoracis), it is inserted, by rounded tendons, into the tips of the transverse processes of all the thoracic vertebrae, and by fleshy processes into the lower nine or ten ribs between their tubercles and angles.\n\n=== Longissimus cervicis ===\n\nThe longissimus cervicis (transversalis cervicis), situated medial to the longissimus thoracis, arises by long, thin tendons from the summits of the transverse processes of thoracic vertebræ 1–5, and is inserted by similar tendons into the posterior tubercles of the transverse processes of cervical vertebrae 2–6.\n\n=== Longissimus capitis ===\n\nThe longissimus capitis (trachelomastoid muscle) lies medial to the longissimus cervicis, between it and the semispinalis capitis.\n\nIt arises by tendons from the transverse processes of the upper four or five thoracic vertebrae, and the articular processes of the lower three or four cervical vertebrae, and is inserted into the posterior margin of the mastoid process, beneath the splenius capitis and sternocleidomastoid.\n\nIt is almost always crossed by a tendinous intersection near its insertion.\n\nhttps://en.wikipedia.org/wiki/Longissimus","longissimus-capitis-muscle":"The longissimus capitis (trachelomastoid muscle) lies medial to the longissimus cervicis, between it and the semispinalis capitis.\n\nIt arises by tendons from the transverse processes of the upper four or five thoracic vertebrae, and the articular processes of the lower three or four cervical vertebrae, and is inserted into the posterior margin of the mastoid process, beneath the splenius capitis and sternocleidomastoid.\n\nIt is almost always crossed by a tendinous intersection near its insertion.\n\nhttps://en.wikipedia.org/wiki/Longissimus#Longissimus_capitis","longissimus-colli-muscle":"The longissimus colli, situated medial to the longissimus thoracis, arises by long, thin tendons from the summits of the transverse processes of thoracic vertebræ 1–5, and is inserted by similar tendons into the posterior tubercles of the transverse processes of cervical vertebrae 2–6.\n\nhttps://en.wikipedia.org/wiki/Longissimus","spinalis-capitis-muscle":"Spinalis capitis (biventer cervicis) is usually inseparably connected with the semispinalis capitis.\n\nSpinalis capitis is not well characterized in modern anatomy textbooks and atlases, and is often omitted from anatomical illustration.\n\nHowever, it can be identified as fibers that extend from the spinous processes of TV1 and CV7 to the cranium, often blending with semispinalis capitis.\n\nhttps://en.wikipedia.org/wiki/Spinalis","spinalis-colli-muscle":"Spinalis cervicis, or spinalis colli, is an inconstant muscle, which arises from the lower part of the nuchal ligament, the spinous process of the seventh cervical, and sometimes from the spinous processes of the first and second thoracic vertebrae, and is inserted into the spinous process of the axis, and occasionally into the spinous processes of the two cervical vertebrae below it.\n\nhttps://en.wikipedia.org/wiki/Spinalis","spinalis-thoracis-muscle":"/SPINALIS DORSI\n\nSpinalis dorsi, the medial continuation of the sacrospinalis, is scarcely separable as a distinct muscle.\n\nIt is situated at the medial side of the longissimus dorsi, and is intimately blended with it; it arises by three or four tendons from the spinous processes of the first two lumbar and the last two thoracic vertebrae:\n\n these, uniting, form a small muscle which is inserted by separate tendons into the spinous processes of the upper thoracic vertebrae, the number varying from four to eight.\n\nIt is intimately united with the semispinalis dorsi, situated beneath it.\n\nhttps://en.wikipedia.org/wiki/Spinalis","splenius-capitis-muscle":"The splenius capitis (from Greek spléníon 'bandage', and Latin caput 'head') is a broad, straplike muscle in the back of the neck.\n\nIt pulls on the base of the skull from the vertebrae in the neck and upper thorax.\n\nIt is involved in movements such as shaking the head.\n\n== Structure ==\n\nIt arises from the lower half of the nuchal ligament, from the spinous process of the seventh cervical vertebra, and from the spinous processes of the upper three or four thoracic vertebrae.\n\nThe fibers of the muscle are directed upward and laterally and are inserted, under cover of the sternocleidomastoideus, into the mastoid process of the temporal bone, and into the rough surface on the occipital bone just below the lateral third of the superior nuchal line.\n\nThe splenius capitis is deep to sternocleidomastoideus at the mastoid process, and to the trapezius for its lower portion.\n\nIt is one of the muscles that forms the floor of the posterior triangle of the neck.\n\nThe splenius capitis muscle is innervated by the posterior ramus of spinal nerves C3 and C4.\n\n== Function ==\n\nThe splenius capitis muscle is a prime mover for head extension.\n\nThe splenius capitis can also allow lateral flexion and rotation of the cervical spine.\n\nhttps://en.wikipedia.org/wiki/Splenius_capitis_muscle","splenius-colli-muscle":"The splenius cervicis (also known as the splenius colli) is a muscle in the back of the neck.\n\nIt arises by a narrow tendinous band from the spinous processes of the third to the sixth thoracic vertebrae; it is inserted, by tendinous fasciculi, into the posterior tubercles of the transverse processes of the upper two or three cervical vertebrae.\n\nIts name is based on the Greek word σπληνίον, splenion (meaning a bandage) and the Latin word cervix (meaning a neck).\n\nThe word collum also refers to the neck in Latin.The function of the splenius cervicis muscle is extension of the cervical spine, rotation to the ipsilateral side and lateral flexion to the ipsilateral side.\n\nhttps://en.wikipedia.org/wiki/Splenius_cervicis_muscle","multifidus-colli-muscle":"The multifidus (multifidus spinae : pl. multifidi ) muscle consists of a number of fleshy and tendinous fasciculi, which fill up the groove on either side of the spinous processes of the vertebrae, from the sacrum to the axis.\n\nWhile very thin, the multifidus muscle plays an important role in stabilizing the joints within the spine.\n\nThe multifidus is one of the transversospinales.\n\nLocated just superficially to the spine itself, the multifidus muscle spans three joint segments and works to stabilize these joints at each level.\n\nThe stiffness and stability makes each vertebra work more effectively, and reduces the degeneration of the joint structures caused by friction from normal physical activity.\n\nThese fasciculi arise:\n\nin the sacral region: from the back of the sacrum, as low as the fourth sacral foramen, from the aponeurosis of origin of the sacrospinalis, from the medial surface of the posterior superior iliac spine, and from the posterior sacroiliac ligaments.\n\nin the lumbar region: from all the mamillary processes.\n\nin the thoracic region: from all the transverse processes.\nin the cervical region: from the articular processes of the lower four vertebrae.Each fasciculus, passing obliquely upward and medially, is inserted into the whole length of the spinous process of one of the vertebræ above.\n\nThese fasciculi vary in length: the most superficial, the longest, pass from one vertebra to the third or fourth above; those next in order run from one vertebra to the second or third above; while the deepest connect two adjacent vertebrae.\n\nThe multifidus lies deep relative to the spinal erectors, transverse abdominis, abdominal internal oblique muscle and abdominal external oblique muscle.\n\n== Atrophy and association with low back pain ==\n\nDysfunction in the lumbar multifidus muscles is strongly associated with low back pain.\n\nThe dysfunction can be caused by inhibition of pain by the spine.\n\nThe dysfunction frequently persists even after the pain has disappeared.\n\nSuch persistence may help explain the high recurrence rates of low back pain.\n\nPersistent lumbar multifidus dysfunction is diagnosed by atrophic replacement of the multifidus with fat, as visualized by magnetic resonance imaging or ultrasound.\n\nOne way to help recruit and strengthen the lumbar multifidus muscles is by tensing the pelvic floor muscles for a few seconds \"as if stopping urination midstream\".\n\nhttps://en.wikipedia.org/wiki/Multifidus_muscle","multifidus-thoracis-muscle":"These fasciculi of the multifidus muscles arise from all the transverse processes of the thoracic vertebraes.","multifidus-lumborum-muscle":"These lumbar fasciculi of the multifidus muscles arise from all the mamillary processes of the lumbar vertebraes.","semispinalis-thoracis-muscle":"The semispinalis thoracis (or semispinalis dorsi) muscle consists of thin, narrow, fleshy fasciculi, interposed between tendons of considerable length.\n\nIt arises by a series of small tendons from the transverse processes of the sixth to the tenth thoracic vertebrae, and is inserted, by tendons, into the spinous processes of the upper four thoracic and lower two cervical vertebrae.\n\nhttps://en.wikipedia.org/wiki/Semispinalis_muscles","semispinalis-colli-muscle":"/SEMISPINALIS CERVICIS MUSCLES\n\nThe semispinalis cervicis (or semispinalis colli), arises by a series of tendinous and fleshy fibers from the transverse processes of the upper five or six thoracic vertebrae, and is inserted into the cervical spinous processes, from the axis to the fifth cervical vertebrae inclusive.\n\nThe semispinalis cervicis is thicker than the semispinalis thoracis. The fasciculus connected with the axis is the largest, and is chiefly muscular in structure.\n\nhttps://en.wikipedia.org/wiki/Semispinalis_muscles","rotatores":"The rotatores muscles (rotatores spinae muscles) lie beneath the multifidus and are present in all spinal regions but are most prominent in the thoracic region; they are eleven in number on either side.\n\nEach muscle is small and somewhat quadrilateral in form; it arises from the superior and posterior part of the transverse process, and is inserted into the lower border and lateral surface of the lamina of the vertebra above, the fibers extending as far as the root of the spinous process.\n\nThe first thoracic rotatores muscle is found between the first and second thoracic vertebrae; the last, between the eleventh and twelfth.\n\nSometimes the number of these muscles is diminished by the absence of one or more from the upper or lower end.\n\nThe Rotatores muscles have a high density of proprioceptors and have been implicated in postural control.\n\nhttps://en.wikipedia.org/wiki/Rotatores_muscles","interspinales-colli-muscles":"In the cervical region the cervical interspinales (interspinales colli muscles) are most distinct, and consist of six pairs, the first being situated between the axis and third vertebra, and the last between the seventh cervical and the first thoracic.\n\nhttps://en.wikipedia.org/wiki/Interspinales_muscles","interspinales-thoracis-muscles":"In the thoracic region the thoracic interspinales (Interspinales thoracis muscles) are found between the first and second vertebrae, and sometimes between the second and third, and between the eleventh and twelfth.\n\nhttps://en.wikipedia.org/wiki/Interspinales_muscles","interspinales-lumborum-muscles":"In the lumbar region there are four pairs of lumbar interspinales (Interspinales lumborum muscles) in the intervals between the five lumbar vertebrae.\n\nThere is also occasionally one between the last thoracic and first lumbar, and one between the fifth lumbar and the sacrum.\n\nhttps://en.wikipedia.org/wiki/Interspinales_muscles","ascending-part-of-trapezius-muscle":"The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula.\n\nIt moves the scapula and supports the arm.\n\nThe trapezius has three functional parts: an upper (descending) part which supports the weight of the arm; a middle region (transverse), which retracts the scapula; and a lower (ascending) part which medially rotates and depresses the scapula.\n\n== Name and history ==\n\nThe trapezius muscle resembles a trapezium (trapezoid in American English), or diamond-shaped quadrilateral.\n\nThe word \"spinotrapezius\" refers to the human trapezius, although it is not commonly used in modern texts.\n\nIn other mammals, it refers to a portion of the analogous muscle.\n\nSimilarly, the term \"tri-axle back plate\" was historically used to describe the trapezius muscle.\n\n== Structure ==\n\nThe superior or upper (or descending) fibers of the trapezius originate from the spinous process of C7, the external occipital protuberance, the medial third of the superior nuchal line of the occipital bone (both in the back of the head), and the ligamentum nuchae.\n\nFrom this origin they proceed downward and laterally to be inserted into the posterior border of the lateral third of the clavicle.\n\nThe middle fibers, or transverse of the trapezius arise from the spinous process of the seventh cervical (both in the back of the neck), and the spinous processes of the first, second, and third thoracic vertebrae.\n\nThey are inserted into the medial margin of the acromion, and into the superior lip of the posterior border of the spine of the scapula.\n\nThe inferior or lower (or ascending) fibers of the trapezius arise from the spinous processes of the remaining thoracic vertebrae (T4–T12).\n\nFrom this origin they proceed upward and laterally to converge near the scapula and end in an aponeurosis, which glides over the smooth triangular surface on the medial end of the spine, to be inserted into a tubercle at the apex of this smooth triangular surface.\n\nAt its occipital origin, the trapezius is connected to the bone by a thin fibrous lamina, firmly adherent to the skin.\n\nThe superficial and deep epimysia are continuous with an investing deep fascia that encircles the neck and also contains both sternocleidomastoid muscles.\n\nAt the middle, the muscle is connected to the spinous processes by a broad semi-elliptical aponeurosis, which reaches from the sixth cervical to the third thoracic vertebræ and forms, with that of the opposite muscle, a tendinous ellipse.\n\nThe rest of the muscle arises by numerous short tendinous fibers.\nIt is possible to feel the muscles of the superior trapezius become active by holding a weight in one hand in front of the body and, with the other hand, touching the area between the shoulder and the neck.\n\n=== Innervation ===\n\nMotor function is supplied by the accessory nerve.\n\nSensation, including pain and the sense of joint position (proprioception), travel via the ventral rami of the third (C3) and fourth (C4) cervical spinal nerves.\n\nSince it is a muscle of the upper limb, the trapezius is not innervated by dorsal rami, despite being placed superficially in the back.\n\n== Function ==\n\nContraction of the trapezius muscle can have two effects: movement of the scapulae when the spinal origins are stable, and movement of the spine when the scapulae are stable.\n\nIts main function is to stabilize and move the scapula.\n\n=== Scapular movements ===\n\nThe upper fibers elevate the scapulae, the middle fibers retract the scapulae, and the lower fibers depress the scapulae.\n\nIn addition to scapular translation, the trapezius induces scapular rotation.\n\nThe upper and lower fibers tend to rotate the scapula around the sternoclavicular articulation so that the acromion and inferior angles move up and the medial border moves down (upward rotation).\n\nThe upper and lower fibers work in tandem with serratus anterior to upwardly rotate the scapulae, and work in opposition to the levator scapulae and the rhomboids, which effect downward rotation.\nAn example of trapezius function is an overhead press.\n\nWhen activating together, the upper and lower fibers also assist the middle fibers (along with other muscles such as the rhomboids) with scapular retraction/adduction.\n\nThe trapezius also assists in abduction of the shoulder above 90 degrees by rotating the glenoid upward.\n\nInjury to cranial nerve XI will cause weakness in abducting the shoulder above 90 degrees.\n\n=== Spinal movements ===\n\nWhen the scapulae are stable, a co-contraction of both sides can extend the neck.\n\n== Clinical significance ==\n\nDysfunction of the trapezius can result in winged scapula, sometimes further specified as \"lateral winging\" and in an abnormal mobility or function of the scapula (scapular dyskinesia).\n\nThere are multiple causes of trapezius dysfunction.\n\n=== Palsy ===\n\nTrapezius palsy, due to damage of the spinal accessory nerve, is characterized by difficulty with arm adduction and abduction, and associated with a drooping shoulder, and shoulder and neck pain.\n\nIntractable trapezius palsy can be surgically managed with an Eden-Lange procedure.\n\n=== Facioscapulohumeral muscular dystrophy ===\n\nThe trapezius muscle is one of the commonly affected muscles in facioscapulohumeral muscular dystrophy (FSHD).\n\nThe lower and middle fibers are affected initially, and the upper fibers are commonly spared until late in the disease.\n\n=== Underdevelopment ===\n\nAlthough rare, underdevelopment or absence of the trapezius has been reported to correlate to neck pain and poor scapular control that are not responsive to physical therapy.\n\nAbsence of the trapezius has been reported in association with Poland syndrome.\n\n== Society and culture ==\n\n=== Exercises ===\n\nThe upper portion of the trapezius can be developed by elevating the shoulders.\n\nCommon exercises for this movement are any version of the clean, particularly the hang clean, and the shoulder shrug.\n\nMiddle fibers are developed by pulling shoulder blades together.\n\nThis adduction also uses the upper/lower fibers.\n\nThe uppermost area can be trained through neck extension.\n\nThe lower part can be developed by drawing the shoulder blades downward while keeping the arms almost straight and stiff.\n\nIt is mainly used in throwing, with the deltoid muscle and rotator cuff.\n\nhttps://en.wikipedia.org/wiki/Trapezius","descending-part-of-trapezius-muscle":"The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula.\n\nIt moves the scapula and supports the arm.\n\nThe trapezius has three functional parts: an upper (descending) part which supports the weight of the arm; a middle region (transverse), which retracts the scapula; and a lower (ascending) part which medially rotates and depresses the scapula.\n\n== Name and history ==\n\nThe trapezius muscle resembles a trapezium (trapezoid in American English), or diamond-shaped quadrilateral.\n\nThe word \"spinotrapezius\" refers to the human trapezius, although it is not commonly used in modern texts.\n\nIn other mammals, it refers to a portion of the analogous muscle.\n\nSimilarly, the term \"tri-axle back plate\" was historically used to describe the trapezius muscle.\n\n== Structure ==\n\nThe superior or upper (or descending) fibers of the trapezius originate from the spinous process of C7, the external occipital protuberance, the medial third of the superior nuchal line of the occipital bone (both in the back of the head), and the ligamentum nuchae.\n\nFrom this origin they proceed downward and laterally to be inserted into the posterior border of the lateral third of the clavicle.\n\nThe middle fibers, or transverse of the trapezius arise from the spinous process of the seventh cervical (both in the back of the neck), and the spinous processes of the first, second, and third thoracic vertebrae.\n\nThey are inserted into the medial margin of the acromion, and into the superior lip of the posterior border of the spine of the scapula.\n\nThe inferior or lower (or ascending) fibers of the trapezius arise from the spinous processes of the remaining thoracic vertebrae (T4–T12).\n\nFrom this origin they proceed upward and laterally to converge near the scapula and end in an aponeurosis, which glides over the smooth triangular surface on the medial end of the spine, to be inserted into a tubercle at the apex of this smooth triangular surface.\n\nAt its occipital origin, the trapezius is connected to the bone by a thin fibrous lamina, firmly adherent to the skin.\n\nThe superficial and deep epimysia are continuous with an investing deep fascia that encircles the neck and also contains both sternocleidomastoid muscles.\n\nAt the middle, the muscle is connected to the spinous processes by a broad semi-elliptical aponeurosis, which reaches from the sixth cervical to the third thoracic vertebræ and forms, with that of the opposite muscle, a tendinous ellipse.\n\nThe rest of the muscle arises by numerous short tendinous fibers.\nIt is possible to feel the muscles of the superior trapezius become active by holding a weight in one hand in front of the body and, with the other hand, touching the area between the shoulder and the neck.\n\n=== Innervation ===\n\nMotor function is supplied by the accessory nerve.\n\nSensation, including pain and the sense of joint position (proprioception), travel via the ventral rami of the third (C3) and fourth (C4) cervical spinal nerves.\n\nSince it is a muscle of the upper limb, the trapezius is not innervated by dorsal rami, despite being placed superficially in the back.\n\n== Function ==\n\nContraction of the trapezius muscle can have two effects: movement of the scapulae when the spinal origins are stable, and movement of the spine when the scapulae are stable.\n\nIts main function is to stabilize and move the scapula.\n\n=== Scapular movements ===\n\nThe upper fibers elevate the scapulae, the middle fibers retract the scapulae, and the lower fibers depress the scapulae.\n\nIn addition to scapular translation, the trapezius induces scapular rotation.\n\nThe upper and lower fibers tend to rotate the scapula around the sternoclavicular articulation so that the acromion and inferior angles move up and the medial border moves down (upward rotation).\n\nThe upper and lower fibers work in tandem with serratus anterior to upwardly rotate the scapulae, and work in opposition to the levator scapulae and the rhomboids, which effect downward rotation.\nAn example of trapezius function is an overhead press.\n\nWhen activating together, the upper and lower fibers also assist the middle fibers (along with other muscles such as the rhomboids) with scapular retraction/adduction.\n\nThe trapezius also assists in abduction of the shoulder above 90 degrees by rotating the glenoid upward.\n\nInjury to cranial nerve XI will cause weakness in abducting the shoulder above 90 degrees.\n\n=== Spinal movements ===\n\nWhen the scapulae are stable, a co-contraction of both sides can extend the neck.\n\n== Clinical significance ==\n\nDysfunction of the trapezius can result in winged scapula, sometimes further specified as \"lateral winging\" and in an abnormal mobility or function of the scapula (scapular dyskinesia).\n\nThere are multiple causes of trapezius dysfunction.\n\n=== Palsy ===\n\nTrapezius palsy, due to damage of the spinal accessory nerve, is characterized by difficulty with arm adduction and abduction, and associated with a drooping shoulder, and shoulder and neck pain.\n\nIntractable trapezius palsy can be surgically managed with an Eden-Lange procedure.\n\n=== Facioscapulohumeral muscular dystrophy ===\n\nThe trapezius muscle is one of the commonly affected muscles in facioscapulohumeral muscular dystrophy (FSHD).\n\nThe lower and middle fibers are affected initially, and the upper fibers are commonly spared until late in the disease.\n\n=== Underdevelopment ===\n\nAlthough rare, underdevelopment or absence of the trapezius has been reported to correlate to neck pain and poor scapular control that are not responsive to physical therapy.\n\nAbsence of the trapezius has been reported in association with Poland syndrome.\n\n== Society and culture ==\n\n=== Exercises ===\n\nThe upper portion of the trapezius can be developed by elevating the shoulders.\n\nCommon exercises for this movement are any version of the clean, particularly the hang clean, and the shoulder shrug.\n\nMiddle fibers are developed by pulling shoulder blades together.\n\nThis adduction also uses the upper/lower fibers.\n\nThe uppermost area can be trained through neck extension.\n\nThe lower part can be developed by drawing the shoulder blades downward while keeping the arms almost straight and stiff.\n\nIt is mainly used in throwing, with the deltoid muscle and rotator cuff.\n\nhttps://en.wikipedia.org/wiki/Trapezius","transverse-part-of-trapezius-muscle":"The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula.\n\nIt moves the scapula and supports the arm.\n\nThe trapezius has three functional parts: an upper (descending) part which supports the weight of the arm; a middle region (transverse), which retracts the scapula; and a lower (ascending) part which medially rotates and depresses the scapula.\n\n== Name and history ==\n\nThe trapezius muscle resembles a trapezium (trapezoid in American English), or diamond-shaped quadrilateral.\n\nThe word \"spinotrapezius\" refers to the human trapezius, although it is not commonly used in modern texts.\n\nIn other mammals, it refers to a portion of the analogous muscle.\n\nSimilarly, the term \"tri-axle back plate\" was historically used to describe the trapezius muscle.\n\n== Structure ==\n\nThe superior or upper (or descending) fibers of the trapezius originate from the spinous process of C7, the external occipital protuberance, the medial third of the superior nuchal line of the occipital bone (both in the back of the head), and the ligamentum nuchae.\n\nFrom this origin they proceed downward and laterally to be inserted into the posterior border of the lateral third of the clavicle.\n\nThe middle fibers, or transverse of the trapezius arise from the spinous process of the seventh cervical (both in the back of the neck), and the spinous processes of the first, second, and third thoracic vertebrae.\n\nThey are inserted into the medial margin of the acromion, and into the superior lip of the posterior border of the spine of the scapula.\n\nThe inferior or lower (or ascending) fibers of the trapezius arise from the spinous processes of the remaining thoracic vertebrae (T4–T12).\n\nFrom this origin they proceed upward and laterally to converge near the scapula and end in an aponeurosis, which glides over the smooth triangular surface on the medial end of the spine, to be inserted into a tubercle at the apex of this smooth triangular surface.\n\nAt its occipital origin, the trapezius is connected to the bone by a thin fibrous lamina, firmly adherent to the skin.\n\nThe superficial and deep epimysia are continuous with an investing deep fascia that encircles the neck and also contains both sternocleidomastoid muscles.\n\nAt the middle, the muscle is connected to the spinous processes by a broad semi-elliptical aponeurosis, which reaches from the sixth cervical to the third thoracic vertebræ and forms, with that of the opposite muscle, a tendinous ellipse.\n\nThe rest of the muscle arises by numerous short tendinous fibers.\nIt is possible to feel the muscles of the superior trapezius become active by holding a weight in one hand in front of the body and, with the other hand, touching the area between the shoulder and the neck.\n\n=== Innervation ===\n\nMotor function is supplied by the accessory nerve.\n\nSensation, including pain and the sense of joint position (proprioception), travel via the ventral rami of the third (C3) and fourth (C4) cervical spinal nerves.\n\nSince it is a muscle of the upper limb, the trapezius is not innervated by dorsal rami, despite being placed superficially in the back.\n\n== Function ==\n\nContraction of the trapezius muscle can have two effects: movement of the scapulae when the spinal origins are stable, and movement of the spine when the scapulae are stable.\n\nIts main function is to stabilize and move the scapula.\n\n=== Scapular movements ===\n\nThe upper fibers elevate the scapulae, the middle fibers retract the scapulae, and the lower fibers depress the scapulae.\n\nIn addition to scapular translation, the trapezius induces scapular rotation.\n\nThe upper and lower fibers tend to rotate the scapula around the sternoclavicular articulation so that the acromion and inferior angles move up and the medial border moves down (upward rotation).\n\nThe upper and lower fibers work in tandem with serratus anterior to upwardly rotate the scapulae, and work in opposition to the levator scapulae and the rhomboids, which effect downward rotation.\nAn example of trapezius function is an overhead press.\n\nWhen activating together, the upper and lower fibers also assist the middle fibers (along with other muscles such as the rhomboids) with scapular retraction/adduction.\n\nThe trapezius also assists in abduction of the shoulder above 90 degrees by rotating the glenoid upward.\n\nInjury to cranial nerve XI will cause weakness in abducting the shoulder above 90 degrees.\n\n=== Spinal movements ===\n\nWhen the scapulae are stable, a co-contraction of both sides can extend the neck.\n\n== Clinical significance ==\n\nDysfunction of the trapezius can result in winged scapula, sometimes further specified as \"lateral winging\" and in an abnormal mobility or function of the scapula (scapular dyskinesia).\n\nThere are multiple causes of trapezius dysfunction.\n\n=== Palsy ===\n\nTrapezius palsy, due to damage of the spinal accessory nerve, is characterized by difficulty with arm adduction and abduction, and associated with a drooping shoulder, and shoulder and neck pain.\n\nIntractable trapezius palsy can be surgically managed with an Eden-Lange procedure.\n\n=== Facioscapulohumeral muscular dystrophy ===\n\nThe trapezius muscle is one of the commonly affected muscles in facioscapulohumeral muscular dystrophy (FSHD).\n\nThe lower and middle fibers are affected initially, and the upper fibers are commonly spared until late in the disease.\n\n=== Underdevelopment ===\n\nAlthough rare, underdevelopment or absence of the trapezius has been reported to correlate to neck pain and poor scapular control that are not responsive to physical therapy.\n\nAbsence of the trapezius has been reported in association with Poland syndrome.\n\n== Society and culture ==\n\n=== Exercises ===\n\nThe upper portion of the trapezius can be developed by elevating the shoulders.\n\nCommon exercises for this movement are any version of the clean, particularly the hang clean, and the shoulder shrug.\n\nMiddle fibers are developed by pulling shoulder blades together.\n\nThis adduction also uses the upper/lower fibers.\n\nThe uppermost area can be trained through neck extension.\n\nThe lower part can be developed by drawing the shoulder blades downward while keeping the arms almost straight and stiff.\n\nIt is mainly used in throwing, with the deltoid muscle and rotator cuff.\n\nhttps://en.wikipedia.org/wiki/Trapezius","dorsal-parts-of-lateral-intertransversarii-lumborum-muscles":"In the lumbar region the intertransversarii lumborum muscles are arranged in pairs, on either side of the vertebral column.\n\nOne set occupying the entire interspace between the transverse processes of the lumbar vertebrae, are the Lateral intertransversarii lumborum muscles.\n\nEach lateral intertransversarius muscle in the lumbar region can be further subdivided into an anterior and posterior division.\n\nThe posterior division courses from the accessory process of the vertebra above to the transverse process of the vertebra below.\n\nBoth the anterior and posterior divisions of the lateral intertransversarii muscles are innervated by lumbar anterior primary divisions (ventral rami).","levator-scapulae":"The levator scapulae is a skeletal muscle situated at the back and side of the neck.\n\nAs the Latin name suggests, its main function is to lift the scapula.\n\n== Structure ==\n\nThe levator scapulae originates from the posterior tubercle of the transverse process of cervical vertebrae one to four.\n\nThe muscle is inserted into medial border of the scapula extending from superior angle to junction of spine and medial border of scapula.The levator scapulae may lie deep to the Sternocleidomastoid at its origin, deep or adjacent to the splenius capitis at its origin and mid-portion, and deep to the trapezius in its lower portion.\n\n=== Relations ===\n\nOne of the muscles within the floor of the posterior triangle of the neck, the superior part of levator scapulae is covered by sternocleidomastoid and its inferior part by the trapezius.\n\nIt is bounded in front by the scalenus medius and behind by splenius cervicis.\n\nThe spinal accessory nerve crosses laterally in the middle part of the muscle and the dorsal scapular nerve may lie deep to or pass through it.\n\n=== Variation ===\n\nThe number of attachments varies; a slip may extend to the occipital or mastoid, to the trapezius, scalene or serratus anterior, or to the first or second rib.\n\nThe muscle may be subdivided into several distinct parts from origin to insertion.\n\nLevator claviculæ from the transverse processes of one or two upper cervical vertebræ to the outer end of the clavicle corresponds to a muscle of lower animals.\n\nMore or less union with the serratus anterior muscle.\n\n=== Nerve supply ===\n\nThe levator scapulae is supplied by two or three branches of the third and fourth cervical nerves, and frequently by a branch from the dorsal scapular nerve.\n\n=== Blood supply ===\n\nThe levator scapulae is supplied by the dorsal scapular artery.\n\nNormally, this artery has a small branch which passes laterally to the supraspinatus fossa of the scapula, and in a third of cases, this branch supplies the muscle.\n\nIf the dorsal scapular artery comes off the transverse cervical artery, the parent transverse cervical artery splits, the dorsal scapular artery passes medially, while the transverse cervical artery passes laterally.\n\n== Function ==\n\nWhen the spine is fixed, levator scapulae elevates the scapula and rotates its inferior angle medially.\n\nIt often works in combination with other muscles like the rhomboids and pectoralis minor to produce downward rotation of the scapula.\n\nElevating or rotating one shoulder at a time would require muscles to stabilize the cervical spine and keep it immobile so it does not flex or rotate.\n\nElevating both at once with equal amounts of pull on both side of cervical spinal origins would counteract these forces.\n\nDownward rotation would be prevented by co-contraction of other muscles that elevate the spine, the upper fibers of the trapezius, which is an upward rotator.\n\nWhen the shoulder is fixed, levator scapulae rotates to the same side and flexes the cervical spine laterally.\n\nWhen both shoulders are fixed, a simultaneous co-contraction of both levator scapulae muscles in equal amounts would not produce lateral flexion or rotation, and may produce straight flexion or extension of the cervical spine.\n\n== Other animals ==\n\nThe muscles of the shoulder can be categorized into three topographic units: the scapulohumeral, axiohumeral, and axioscapular groups.\n\nLevator scapulae forms part of the latter group together with rhomboid major, rhomboid minor, serratus anterior, and trapezius. The trapezius evolved separately, but the other three muscles in this group evolved from the first eight or ten ribs and the transverse processes of the cervical vertebrae (homologous to the ribs).\n\nThe serratus anterior formed the basal unit for these three muscles.\n\nIn higher primates it has evolved into two separate muscles — serratus anterior and levator scapulae — by concentration of the proximal and distal fibers and progressive reduction of the intermediate fibers.\n\nThe fibers concerned with the cranial displacement of the scapula became the levator scapulae.\n\nhttps://en.wikipedia.org/wiki/Levator_scapulae_muscle","rhomboid-major-muscle":"The rhomboid major is a skeletal muscle on the back that connects the scapula with the vertebrae of the spinal column.\n\nIn human anatomy, it acts together with the rhomboid minor to keep the scapula pressed against thoracic wall and to retract the scapula toward the vertebral column.\n\n== Structure ==\n\nThe rhomboid major arises from the spinous processes of the thoracic vertebrae T2 to T5 as well as the supraspinous ligament.\n\nIt inserts on the medial border of the scapula, from about the level of the scapular spine to the scapula's inferior angle.\n\nThe rhomboid major is considered a superficial back muscle.\n\nIt is deep to the trapezius, and is located directly inferior to the rhomboid minor.\n\nAs the word rhomboid suggests, the rhomboid major is diamond-shaped.\n\nThe major in its name indicates that it is the larger of the two rhomboids.\n\n=== Variation ===\n\nThe two rhomboids are sometimes fused into a single muscle.\n\n== Nerve supply ==\n\nThe rhomboid major, like the rhomboid minor, is innervated by the ventral primary ramus via the dorsal scapular nerve (C5).\n\n=== Blood supply ===\n\nBoth rhomboid muscles also derive their arterial blood supply from the dorsal scapular artery.\n\n== Function ==\n\nThe rhomboid major helps to hold the scapula (and thus the upper limb) onto the ribcage.\n\nOther muscles that perform this function include the serratus anterior and pectoralis minor.\nBoth rhomboids (major and minor) also act to retract the scapula, pulling it towards the vertebral column.\nThe rhomboids work collectively with the levator scapulae muscles to elevate the medial border of the scapula, downwardly rotating the scapula with respect to the glenohumeral joint.\n\nAntagonists to this function (upward rotators of the scapulae) are the serratus anterior and lower fibers of the trapezius.\n\nIf the lower fibers are inactive, the serratus anterior and upper trapezius work in tandem with rhomboids and levators to elevate the entire scapula.\n\n== Clinical significance ==\n\nIf the rhomboid major is torn, wasted, or unable to contract, scapular instability may result.\n\nThe implications of scapular instability caused by the rhomboid major include scapular winging during scapular protraction, excessive lateral rotation and depression of the scapula, as the antagonistic action by the rhomboid major is absent.\n\nWith scapular instability, movement in the upper extremity is limited as the scapula cannot guide the desired movement of the arm and shoulders.\n\nPain, discomfort, and limited range of motion of the shoulder are possible implications of scapular instability.\nTreatment for scapular instability may include surgery followed by physical therapy or occupational therapy.\n\nPhysical therapy may consist of stretching and endurance exercises of the shoulder.\n\nPilates and yoga have been also suggested as potential treatment and prevention of scapular instability.\n\n== Other animals ==\n\nThe muscles of the shoulder can be categorized into three topographic units: the scapulohumeral, axiohumeral, and axioscapular groups.\n\nStretching from the spine to the scapula, rhomboid major forms part of the latter group together with rhomboid minor, serratus anterior, levator scapulae, and trapezius. The trapezius has evolved separately, but the other muscles in this group evolved from the first eight or ten ribs and the transverse processes of the cervical vertebrae (homologous to the ribs).\n\nFunctional demands have resulted in the evolution of individual muscles from the basal unit formed by the serratus anterior.\nIn primitive life forms, the main function of the axioscapular group is to control the movements of the vertebral border of the scapula: fibers concerned with the dorsal movement of scapula evolved into the rhomboids, those with ventral motion into serratus anterior, and those with cranial movements into levator scapulae.\n\nhttps://en.wikipedia.org/wiki/Rhomboid_major_muscle","rhomboid-minor-muscle":"In human anatomy, the rhomboid minor is a small skeletal muscle on the back that connects the scapula with the vertebrae of the spinal column.\n\nLocated inferior to levator scapulae and superior to rhomboid major, it acts together with the latter to keep the scapula pressed against the thoracic wall.\n\nIt lies deep to trapezius but superficial to the long spinal muscles.\n\n== Origin and insertion ==\n\nThe rhomboid minor arises from the inferior border of the nuchal ligament, from the spinous processes of the seventh cervical and first thoracic vertebrae, and from the intervening supraspinous ligaments.\n\nIt is inserted into a small area of the medial border of the scapula at the level of the scapular spine.\n\n== Action ==\n\nTogether with the rhomboid major, the rhomboid minor retracts the scapula when trapezius is contracted.\n\nActing as a synergist to the trapezius, the rhomboid major and minor elevate the medial border of the scapula medially and upward, working in tandem with the levator scapulae muscle to rotate the scapulae downward.\n\nWhile other shoulder muscles are active, the rhomboid major and minor stabilize the scapula.\n\n== Innervation and blood supply ==\n\nThe nerve supply comes from the dorsal scapular nerve, with most of its fibers derived from the C5 nerve root and only minor contribution from C4 or C6.\nThe rhomboid minor gets its arterial blood supply from the dorsal scapular artery.\n\n== Variation ==\n\nIt is usually separated from the rhomboid major by a slight interval, but the adjacent margins of the two muscles are occasionally united.\n\nhttps://en.wikipedia.org/wiki/Rhomboid_minor_muscle","latissimus-dorsi-muscle":"The latissimus dorsi is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline.\n\nThe word latissimus dorsi (plural: latissimi dorsi) comes from Latin and means \"broadest [muscle] of the back\", from \"latissimus\" (Latin: broadest)' and \"dorsum\" (Latin: back).\n\nThe pair of muscles are commonly known as \"lats\", especially among bodybuilders.\n\nThe latissimus dorsi is the largest muscle in the upper body.\n\nThe latissimus dorsi is responsible for extension, adduction, transverse extension also known as horizontal abduction (or horizontal extension), flexion from an extended position, and (medial) internal rotation of the shoulder joint.\n\nIt also has a synergistic role in extension and lateral flexion of the lumbar spine.\n\nDue to bypassing the scapulothoracic joints and attaching directly to the spine, the actions the latissimi dorsi have on moving the arms can also influence the movement of the scapulae, such as their downward rotation during a pull up.\n\n== Structure ==\n\n=== Variations ===\n\nThe number of dorsal vertebrae to which it is attached varies from four to eight; the number of costal attachments varies; muscle fibers may or may not reach the crest of the ilium.\n\nA muscle slip, the axillary arch, varying from 7 to 10 cm in length, and from 5 to 15 mm in breadth, occasionally springs from the upper edge of the latissimus dorsi about the middle of the posterior fold of the axilla, and crosses the axilla in front of the axillary vessels and nerves, to join the under surface of the tendon of the pectoralis major, the coracobrachialis, or the fascia over the biceps brachii.\n\nThis axillary arch crosses the axillary artery, just above the spot usually selected for the application of a ligature, and may mislead a surgeon.\n\nIt is present in about 7% of the population and may be easily recognized by the transverse direction of its fibers.\n\nGuy et al. extensively described this muscular variant using MRI data and positively correlated its presence with symptoms of neurological impingement.\n\nA fibrous slip usually passes from the upper border of the tendon of the Latissimus dorsi, near its insertion, to the long head of the triceps brachii.\n\nThis is occasionally muscular, and is the representative of the dorsoepitrochlearis brachii of apes.\n\nThis muscular form is found in ~5% of humans and is sometimes termed the latissimocondyloideus.The latissimus dorsi crosses the inferior angle of the scapula.\n\nA study found that, of 100 cadavers dissected:\n43% had \"a substantial amount\" of muscular fibers in the latissimus dorsi originating from the scapula.\n\n36% had few or no muscular fibers, but a \"soft fibrous link\" between the scapula and the latissimus dorsi\n21% had little or no connecting tissue between the two structures.\n\n=== Triangles ===\n\nThe lateral margin of the latissimus dorsi is separated below from the obliquus externus abdominis by a small triangular interval, the lumbar triangle of Petit, the base of which is formed by the iliac crest, and its floor by the obliquus internus abdominis.\n\nAnother triangle is situated behind the scapula.\n\nIt is bounded above by the trapezius, below by the latissimus dorsi, and laterally by the vertebral border of the scapula; the floor is partly formed by the rhomboideus major.\n\nIf the scapula is drawn forward by folding the arms across the chest, and the trunk bent forward, parts of the sixth and seventh ribs and the interspace between them become subcutaneous and available for auscultation.\n\nThe space is therefore known as the triangle of auscultation.\nThe latissimus dorsi can be remembered best for insertion as \"A Miss Between Two Majors\".\n\nAs the latissimus dorsi inserts into the floor of the intertubercular groove of the humerus it is surrounded by two major muscles.\n\nThe teres major inserts medially on the medial lip of the intertubercular groove and the pectoralis major inserts laterally onto the lateral lip.\n\n=== Nerve supply ===\n\nThe latissimus dorsi is innervated by the sixth, seventh, and eighth cervical nerves through the thoracodorsal (long subscapular) nerve.\n\nElectromyography suggests that it consists of six groups of muscle fibres that can be independently coordinated by the central nervous system.\n\n== Function ==\n\nThe latissimus dorsi assists in depression of the arm with the teres major and pectoralis major.\n\nIt adducts, extends, and internally rotates the shoulder.\n\nWhen the arms are in a fixed overhead position, the latissimus dorsi pulls the trunk upward and forward.\n\nIt has a synergistic role in extension (posterior fibers) and lateral flexion (anterior fibers) of the lumbar spine, and assists as a muscle of both forced expiration (anterior fibers) and an accessory muscle of inspiration (posterior fibers).Most latissimus dorsi exercises concurrently recruit the teres major, posterior fibres of the deltoid, long head of the triceps brachii, among numerous other stabilizing muscles.\n\nCompound exercises for the 'lats' typically involve elbow flexion and tend to recruit the biceps brachii, brachialis, and brachioradialis for this function.\n\nDepending on the line of pull, the trapezius muscles can be recruited as well; horizontal pulling motions such as rows recruit both latissimus dorsi and trapezius heavily.\n\n=== Training ===\n\nThe power/size/strength of this muscle can be trained with a variety of different exercises.\n\nSome of these include:\n\n-Vertical pulling movements such as pull-downs and pull-ups (including chin-ups)\n-Horizontal pulling movements such as bent-over row, T-bar row and other rowing exercises\n-Shoulder extension movements with straight arms such as straight-arm lat pulldowns and Pull-overs\n-Deadlift\n\n== Clinical significance ==\n\nTight latissimus dorsi has been shown to be a contributor to chronic shoulder pain and chronic back pain.\n\nBecause the latissimus dorsi connects the spine to the humerus, tightness in this muscle can manifest as either sub-optimal glenohumeral joint (shoulder) function which leads to chronic pain or tendinitis in the tendinous fasciae connecting the latissimus dorsi to the thoracic and lumbar spine.\n\nThe latissimus dorsi is a potential source of muscle for breast reconstruction surgery after mastectomy (e.g.\n\nMannu flap) or to correct pectoral hypoplastic defects such as Poland's syndrome.\n\nAn absent or hypoplastic latissimus dorsi can be one of the associated symptoms of Poland's syndrome.\n\n=== Cardiac support ===\n\nFor heart patients with low cardiac output and who are not candidates for cardiac transplantation, a procedure called cardiomyoplasty may support the failing heart.\n\nThis procedure involves wrapping the latissimus dorsi muscles around the heart and electrostimulating them in synchrony with ventricular systole.\n\n=== Injury ===\n\nInjuries to the latissimus dorsi are rare.\n\nThey occur disproportionately in baseball pitchers.\n\nDiagnosis can be achieved by visualization of the muscle and movement testing.\n\nMRI of the shoulder girdle will confirm the diagnosis.\n\nMuscle belly injuries are treated with rehabilitation while tendon avulsion injuries can be treated surgically, or with rehab.\n\nRegardless of treatment, patients tend to return to play without any functional losses.\n\nhttps://en.wikipedia.org/wiki/Latissimus_dorsi_muscle","serratus-posterior-inferior-muscle":"The serratus posterior inferior muscle, also known as the posterior serratus muscle, is a muscle of the human body.\n\n== Structure ==\n\nThe muscle is situated at the junction of the thoracic and lumbar regions.\n\nIt has an irregularly quadrilateral form, broader than the serratus posterior superior muscle, and separated from it by a wide interval.\n\nIt arises by a thin aponeurosis from the spinous processes of the lower two thoracic and upper two or three lumbar vertebrae.\n\nPassing obliquely upward and lateralward, it becomes fleshy, and divides into four flat digitations.\n\nThese are inserted into the inferior borders of the lower four ribs, a little beyond their angles.\n\nThe thin aponeurosis of origin is intimately blended with the thoracolumbar fascia, and aponeurosis of the latissimus dorsi muscle.\n\n== Function ==\n\nThe serratus posterior inferior draws the lower ribs backward and downward to assist in rotation and extension of the trunk.\n\nThis movement of the ribs may also contribute to inhalation and forced expiration of air from the lungs.\n\nhttps://en.wikipedia.org/wiki/Serratus_posterior_inferior_muscle","serratus-posterior-superior-muscle":"The serratus posterior superior muscle is a thin, quadrilateral muscle.\n\nIt is situated at the upper back part of the thorax, deep to the rhomboid muscles.\n\n== Structure ==\n\nThe serratus posterior superior muscle arises by an aponeurosis from the lower part of the nuchal ligament, from the spinous processes of C7, T1, T2, and sometimes T3, and from the supraspinal ligament.\n\nIt is inserted, by four fleshy digitations into the upper borders of the second, third, fourth, and fifth ribs past the angle of the rib.\n\n== Function ==\n\nThe serratus posterior superior muscle elevates the second to fifth ribs.\n\nThis aids deep respiration.\n\nhttps://en.wikipedia.org/wiki/Serratus_posterior_superior_muscle","clavicular-head-of-pectoralis-major-muscle":"The pectoralis major (from Latin pectus 'breast') is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body.\n\nIt makes up the bulk of the chest muscles and lies under the breast.\n\nBeneath the pectoralis major is the pectoralis minor, a thin, triangular muscle.\n\nThe pectoralis major's primary functions are flexion, adduction, and internal rotation of the humerus.\n\nThe pectoral major may colloquially be referred to as \"pecs\", \"pectoral muscle\" or \"chest muscle\" due to it being the largest and most superficial muscle in the chest area.\n\n== Structure ==\n\nIt arises from the anterior surface of the sternal half of the clavicle\nfrom breadth of the half of the anterior surface of the sternum, as low down as the attachment of the cartilage of the sixth or seventh rib; from the cartilages of all the true ribs, with the exception, frequently, of the first or seventh, and from the aponeurosis of the abdominal external oblique muscle.\n\nFrom this extensive origin the fibers converge toward their insertion; those arising from the clavicle pass obliquely downward and outwards (laterally), and are usually separated from the rest by a slight interval; those from the lower part of the sternum, and the cartilages of the lower true ribs, run upward and laterally, while the middle fibers pass horizontally.\n\nThey all end in a flat tendon, about 5 cm in breadth, which is inserted into the lateral lip of the bicipital groove (intertubercular sulcus) of the humerus.\n\nThis tendon consists of two laminae, placed one in front of the other, and usually blended together below:\n\nThe anterior lamina, which is thicker, receives the clavicular and the uppermost sternal fibers.\n\nThey are inserted in the same order as that in which they arise: the most lateral of the clavicular fibers are inserted at the upper part of the anterior lamina; the uppermost sternal fibers pass down to the lower part of the lamina which extends as low as the tendon of the Deltoid and joins with it.\n\nThe posterior lamina of the tendon receives the attachment of the greater part of the sternal portion and the deep fibers, i. e., those from the costal cartilages.These deep fibers, and particularly those from the lower costal cartilages, ascend the humerus insertion higher, turning backward successively behind the superficial and upper ones, so that the tendon appears to be twisted.\n\nThe posterior lamina reaches higher on the humerus than the anterior one, and from it an expansion is given off which covers the intertubercular groove of the humerus and blends with the capsule of the shoulder-joint.\n\nFrom the deepest fibers of this lamina at its insertion an expansion is given off which lines the intertubercular groove, while from the lower border of the tendon a third expansion passes downward to the fascia of the arm.\n\n=== Nerve supply ===\n\nThe pectoralis major receives dual motor innervation by the medial pectoral nerve and the lateral pectoral nerve, also known as the lateral anterior thoracic nerve.\n\nThe sternal head receives innervation from the C7, C8 and T1 nerve roots, via the lower trunk of the brachial plexus and the medial pectoral nerve.\n\nThe clavicular head receives innervation from the C5 and C6 nerve roots via the upper trunk and lateral cord of the brachial plexus, which gives off the lateral pectoral nerve.\n\nThe lateral pectoral nerve is distributed over the deep surface of the pectoralis major.\n\nThe sensory feedback from the pectoralis major follows the reverse path, returning via first-order neurons to the spinal nerves at C5, C6, C8, and T1 through the posterior rami.\n\nAfter the synapse in the posterior horn of the spinal cord, sensory information concerning movement of the muscle, proprioception, and pressure then travels through a second-order neuron in the dorsal column medial lemniscus tract to the medulla.\n\nThere, the fibers decussate to form the medial lemniscus which carries the sensory information the rest of the way to the thalamus, the \"gateway to the cortex\".\n\nThe thalamus diverts some sensory information to the cerebellum and the basal nuclei to complete the motor feedback loop while some sensory information ascends directly to the postcentral gyrus of the parietal lobe of the brain via third-order neurons.\n\nSensory information for the pectoralis major is processed in the superior portion of the sensory homunculus, adjacent to the longitudinal fissure which divides the two hemispheres of the brain.\n\nElectromyography suggests that it consists of at least six groups of muscle fibres that can be independently coordinated by the central nervous system.\n\n=== Variation ===\n\nThe more frequent variations include greater or less extent of attachment to the ribs and sternum, varying size of the abdominal part or its absence, greater or less extent of separation of sternocostal and clavicular parts, fusion of clavicular part with deltoid, and decussation in front of the sternum.\n\nDeficiency or absence of the sternocostal part is not uncommon and more frequent than absence of the clavicular part.\n\nPoland syndrome is a rare congenital condition in which the whole muscle is missing, most commonly on one side of the body.\n\nThis may accompany absence of the breast in females.\n\nThe sternalis muscle may be a variant form of the pectoralis major or the rectus abdominis. [Submuscular and intramuscular surgical implants (similar to breast augmentation implants) may be available from plastic surgeons to modify aesthetic contours, mass, and asymmetry or variation in both males and females.]\n\n== Function ==\n\nThe pectoralis major has four actions which are primarily responsible for movement of the shoulder joint.\n\nThe first action is flexion of the humerus, as in throwing a ball underhand, and in lifting a child.\n\nSecondly, it adducts the humerus, as when flapping the arms.\n\nThirdly, it rotates the humerus medially, as occurs when arm-wrestling.\n\nFourthly the pectoralis major is also responsible for keeping the arm attached to the trunk of the body.\n\nIt has two different parts which are responsible for different actions.\n\nThe clavicular part is close to the deltoid muscle and contributes to flexion, horizontal adduction, and inward rotation of the humerus.\n\nWhen at an approximately 110 degree angle, it contributes to adduction of the humerus.\n\nThe sternocostal part is antagonistic to the clavicular part contributing to downward and forward movement of the arm and inward rotation when accompanied by adduction.\n\nThe sternal fibers can also contribute to extension, but not beyond anatomical position.Hypertrophy of the pectoralis major increases functionality.\n\nMaximal activation of the pectoralis major occurs in the transverse plane through pressing motions.\n\nBoth multi-joint and single-joint exercises induce pectoralis major hypertrophy.\n\nA combination of both single-joint and multi-joint exercises will result in a maximum hypertrophic response. [Aesthetic contours of regions in the muscle may be specifically-addressed (“targeted”) by specific exercises; for instance, “plating” or “stitching” of the pectoralis major —towards the center of the sternum —-may be targeted by a wider hand position.\n\nThe pectoralis major can be targeted from numerous training angles along the sternum and clavicle.\n\nExercises that include horizontal adduction and elbow extensions such as the barbell bench press, dumbbell bench press, and machine bench press induce high activation of the pectoralis major in the sternocostal region.\n\nHeavy loads are strongly correlated with pectoralis major activation.\n\n== Clinical significance ==\n\n=== Injuries and imaging ===\n\nTears of the pectoralis major are rare and typically affect otherwise healthy individuals.\n\nThis type of injury is known to affect the athletic population, namely in high-impact contact sports such as powerlifting, and may result in pain, weakness, and disability.\n\nMost lesions are located at the musculotendinous junction and result from violent, eccentric contraction of the muscle, such as during bench press.\n\nA less frequent rupture site is the muscle belly, usually as a result of a direct blow.\n\nIn developed countries, most lesions occur in male athletes, especially those practicing contact sports and weight-lifting (particularly during a bench press maneuver).\n\nWomen are less susceptible to these tears because of larger tendon-to-muscle diameter, greater muscular elasticity, and less energetic injuries.\n\nThe injury is characterized by sudden and acute pain in the chest wall and shoulder area, bruising and loss of strength of the muscle.\n\nHigh grade partial or full thickness tears warrant surgical repair as the preferred treatment if function is to be preserved, particularly in the athletic population.\nActing fast, obtaining the correct diagnoses, and getting the surgical repair as soon as possible is a key to successful recovery.\n\nWaiting can cause the acute injury to become chronic and chances of success is greatly diminished as a result.\n\nAfter surgery, the impacted arm is then immobilized with a sling for about six to eight weeks to minimize and avoid movement of the arm and potentially re-rupturing the surgery site.\n\nAbout two months after the surgery, physical therapy is typically introduced for about six months, after which point strengthening of the muscle is needed to achieve good results.\n\nMost patients are able to return to activity after six months to a year following surgery with high patient satisfaction and slightly reduced strength compared to pre-injury.\n\nBoth US and MRI are useful to confirm the diagnosis, location and extent of a tear, though the first may be more cost-effective in experienced hands.\n\n=== Poland syndrome ===\n\nPoland syndrome is a congenital anomaly in which there is a malformation of the chest causing the pectoralis major on one side of the body to be absent.\n\nOther characteristics of this disease are \"unilateral shortening of the index, long, and ring fingers, syndactyly of the affected digits, hypoplasia of the hand, and the absence of the sternocostal portion of the ipsilateral pectoralis major muscle\".\n\nAlthough the absence of a pectoralis major is not life-threatening, it will have an effect on the person with Poland's syndrome.\n\nAdduction and medial rotation of the arm will be much harder to accomplish without the pectoralis major.\n\nThe latissimus dorsi and teres major also aid in adduction and medial rotation of the arm, so they may be able to compensate for the lack of extra muscle.\n\nHowever, some patients with Poland's syndrome may also be lacking these muscles, which make these actions nearly impossible.\nResearchers from the Department of Rehabilitation Medicine at the Yonsei University College of Medicine in Seoul, Korea reported a case of congenital absence of pectoralis major in 1990.\n\nAccording to Kakulas and Adams, pectoralis major is the most frequently congenitally absent muscle.\n\nThe case involved a 22-year-old marine who had asymmetrical configuration of chest wall who had never experienced difficulties performing daily activities, but who experienced difficulties in the military camp.\n\nHe had difficulty in some training activities especially those such as throwing a grenade or rope climbing.\n\nDuring a surgery performed to correct the sternal depression, it was found that the right pectoralis major was totally absent.\n\nHowever, previous physical exams did not show deficiencies in muscle strength as the right shoulder was good for flexion, adduction, horizontal adduction and internal rotation.\n\nMoreover, his pain and touch sensation were normal.\n\nX-rays were also performed and showed normal pictures of the chest's bones.\n\nThe fact that the absence of pectoralis major did not cause functional loss in ordinary activities in this case of congenital absence showed that other surrounding muscles played a compensatory role.\n\n=== Other diseases ===\n\nPectoralis major muscle in rare occasions may develop intramuscular lipomas.\n\nSuch rare tumors may mimic malignant breast tumors as they look like enlargements of the breasts.\n\nThey are well-encapsulated radiolucent tumours of fat density.\n\nTheir location can be accurately identified through computed tomography and magnetic resonance imaging (MRI).\n\nThe treatment in these cases involves complete surgical excision because of the risk of liposarcoma they post especially large intramuscular liposomas.\n\nPartial excision is risky because recurrence may occur.\n\nhttps://en.wikipedia.org/wiki/Pectoralis_major","sternocostal-head-of-pectoralis-major-muscle":"The pectoralis major (from Latin pectus 'breast') is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body.\n\nIt makes up the bulk of the chest muscles and lies under the breast.\n\nBeneath the pectoralis major is the pectoralis minor, a thin, triangular muscle.\n\nThe pectoralis major's primary functions are flexion, adduction, and internal rotation of the humerus.\n\nThe pectoral major may colloquially be referred to as \"pecs\", \"pectoral muscle\" or \"chest muscle\" due to it being the largest and most superficial muscle in the chest area.\n\n== Structure ==\n\nIt arises from the anterior surface of the sternal half of the clavicle\nfrom breadth of the half of the anterior surface of the sternum, as low down as the attachment of the cartilage of the sixth or seventh rib; from the cartilages of all the true ribs, with the exception, frequently, of the first or seventh, and from the aponeurosis of the abdominal external oblique muscle.\n\nFrom this extensive origin the fibers converge toward their insertion; those arising from the clavicle pass obliquely downward and outwards (laterally), and are usually separated from the rest by a slight interval; those from the lower part of the sternum, and the cartilages of the lower true ribs, run upward and laterally, while the middle fibers pass horizontally.\n\nThey all end in a flat tendon, about 5 cm in breadth, which is inserted into the lateral lip of the bicipital groove (intertubercular sulcus) of the humerus.\n\nThis tendon consists of two laminae, placed one in front of the other, and usually blended together below:\n\nThe anterior lamina, which is thicker, receives the clavicular and the uppermost sternal fibers.\n\nThey are inserted in the same order as that in which they arise: the most lateral of the clavicular fibers are inserted at the upper part of the anterior lamina; the uppermost sternal fibers pass down to the lower part of the lamina which extends as low as the tendon of the Deltoid and joins with it.\n\nThe posterior lamina of the tendon receives the attachment of the greater part of the sternal portion and the deep fibers, i. e., those from the costal cartilages.These deep fibers, and particularly those from the lower costal cartilages, ascend the humerus insertion higher, turning backward successively behind the superficial and upper ones, so that the tendon appears to be twisted.\n\nThe posterior lamina reaches higher on the humerus than the anterior one, and from it an expansion is given off which covers the intertubercular groove of the humerus and blends with the capsule of the shoulder-joint.\n\nFrom the deepest fibers of this lamina at its insertion an expansion is given off which lines the intertubercular groove, while from the lower border of the tendon a third expansion passes downward to the fascia of the arm.\n\n=== Nerve supply ===\n\nThe pectoralis major receives dual motor innervation by the medial pectoral nerve and the lateral pectoral nerve, also known as the lateral anterior thoracic nerve.\n\nThe sternal head receives innervation from the C7, C8 and T1 nerve roots, via the lower trunk of the brachial plexus and the medial pectoral nerve.\n\nThe clavicular head receives innervation from the C5 and C6 nerve roots via the upper trunk and lateral cord of the brachial plexus, which gives off the lateral pectoral nerve.\n\nThe lateral pectoral nerve is distributed over the deep surface of the pectoralis major.\n\nThe sensory feedback from the pectoralis major follows the reverse path, returning via first-order neurons to the spinal nerves at C5, C6, C8, and T1 through the posterior rami.\n\nAfter the synapse in the posterior horn of the spinal cord, sensory information concerning movement of the muscle, proprioception, and pressure then travels through a second-order neuron in the dorsal column medial lemniscus tract to the medulla.\n\nThere, the fibers decussate to form the medial lemniscus which carries the sensory information the rest of the way to the thalamus, the \"gateway to the cortex\".\n\nThe thalamus diverts some sensory information to the cerebellum and the basal nuclei to complete the motor feedback loop while some sensory information ascends directly to the postcentral gyrus of the parietal lobe of the brain via third-order neurons.\n\nSensory information for the pectoralis major is processed in the superior portion of the sensory homunculus, adjacent to the longitudinal fissure which divides the two hemispheres of the brain.\n\nElectromyography suggests that it consists of at least six groups of muscle fibres that can be independently coordinated by the central nervous system.\n\n=== Variation ===\n\nThe more frequent variations include greater or less extent of attachment to the ribs and sternum, varying size of the abdominal part or its absence, greater or less extent of separation of sternocostal and clavicular parts, fusion of clavicular part with deltoid, and decussation in front of the sternum.\n\nDeficiency or absence of the sternocostal part is not uncommon and more frequent than absence of the clavicular part.\n\nPoland syndrome is a rare congenital condition in which the whole muscle is missing, most commonly on one side of the body.\n\nThis may accompany absence of the breast in females.\n\nThe sternalis muscle may be a variant form of the pectoralis major or the rectus abdominis. [Submuscular and intramuscular surgical implants (similar to breast augmentation implants) may be available from plastic surgeons to modify aesthetic contours, mass, and asymmetry or variation in both males and females.]\n\n== Function ==\n\nThe pectoralis major has four actions which are primarily responsible for movement of the shoulder joint.\n\nThe first action is flexion of the humerus, as in throwing a ball underhand, and in lifting a child.\n\nSecondly, it adducts the humerus, as when flapping the arms.\n\nThirdly, it rotates the humerus medially, as occurs when arm-wrestling.\n\nFourthly the pectoralis major is also responsible for keeping the arm attached to the trunk of the body.\n\nIt has two different parts which are responsible for different actions.\n\nThe clavicular part is close to the deltoid muscle and contributes to flexion, horizontal adduction, and inward rotation of the humerus.\n\nWhen at an approximately 110 degree angle, it contributes to adduction of the humerus.\n\nThe sternocostal part is antagonistic to the clavicular part contributing to downward and forward movement of the arm and inward rotation when accompanied by adduction.\n\nThe sternal fibers can also contribute to extension, but not beyond anatomical position.Hypertrophy of the pectoralis major increases functionality.\n\nMaximal activation of the pectoralis major occurs in the transverse plane through pressing motions.\n\nBoth multi-joint and single-joint exercises induce pectoralis major hypertrophy.\n\nA combination of both single-joint and multi-joint exercises will result in a maximum hypertrophic response. [Aesthetic contours of regions in the muscle may be specifically-addressed (“targeted”) by specific exercises; for instance, “plating” or “stitching” of the pectoralis major —towards the center of the sternum —-may be targeted by a wider hand position.\n\nThe pectoralis major can be targeted from numerous training angles along the sternum and clavicle.\n\nExercises that include horizontal adduction and elbow extensions such as the barbell bench press, dumbbell bench press, and machine bench press induce high activation of the pectoralis major in the sternocostal region.\n\nHeavy loads are strongly correlated with pectoralis major activation.\n\n== Clinical significance ==\n\n=== Injuries and imaging ===\n\nTears of the pectoralis major are rare and typically affect otherwise healthy individuals.\n\nThis type of injury is known to affect the athletic population, namely in high-impact contact sports such as powerlifting, and may result in pain, weakness, and disability.\n\nMost lesions are located at the musculotendinous junction and result from violent, eccentric contraction of the muscle, such as during bench press.\n\nA less frequent rupture site is the muscle belly, usually as a result of a direct blow.\n\nIn developed countries, most lesions occur in male athletes, especially those practicing contact sports and weight-lifting (particularly during a bench press maneuver).\n\nWomen are less susceptible to these tears because of larger tendon-to-muscle diameter, greater muscular elasticity, and less energetic injuries.\n\nThe injury is characterized by sudden and acute pain in the chest wall and shoulder area, bruising and loss of strength of the muscle.\n\nHigh grade partial or full thickness tears warrant surgical repair as the preferred treatment if function is to be preserved, particularly in the athletic population.\nActing fast, obtaining the correct diagnoses, and getting the surgical repair as soon as possible is a key to successful recovery.\n\nWaiting can cause the acute injury to become chronic and chances of success is greatly diminished as a result.\n\nAfter surgery, the impacted arm is then immobilized with a sling for about six to eight weeks to minimize and avoid movement of the arm and potentially re-rupturing the surgery site.\n\nAbout two months after the surgery, physical therapy is typically introduced for about six months, after which point strengthening of the muscle is needed to achieve good results.\n\nMost patients are able to return to activity after six months to a year following surgery with high patient satisfaction and slightly reduced strength compared to pre-injury.\n\nBoth US and MRI are useful to confirm the diagnosis, location and extent of a tear, though the first may be more cost-effective in experienced hands.\n\n=== Poland syndrome ===\n\nPoland syndrome is a congenital anomaly in which there is a malformation of the chest causing the pectoralis major on one side of the body to be absent.\n\nOther characteristics of this disease are \"unilateral shortening of the index, long, and ring fingers, syndactyly of the affected digits, hypoplasia of the hand, and the absence of the sternocostal portion of the ipsilateral pectoralis major muscle\".\n\nAlthough the absence of a pectoralis major is not life-threatening, it will have an effect on the person with Poland's syndrome.\n\nAdduction and medial rotation of the arm will be much harder to accomplish without the pectoralis major.\n\nThe latissimus dorsi and teres major also aid in adduction and medial rotation of the arm, so they may be able to compensate for the lack of extra muscle.\n\nHowever, some patients with Poland's syndrome may also be lacking these muscles, which make these actions nearly impossible.\nResearchers from the Department of Rehabilitation Medicine at the Yonsei University College of Medicine in Seoul, Korea reported a case of congenital absence of pectoralis major in 1990.\n\nAccording to Kakulas and Adams, pectoralis major is the most frequently congenitally absent muscle.\n\nThe case involved a 22-year-old marine who had asymmetrical configuration of chest wall who had never experienced difficulties performing daily activities, but who experienced difficulties in the military camp.\n\nHe had difficulty in some training activities especially those such as throwing a grenade or rope climbing.\n\nDuring a surgery performed to correct the sternal depression, it was found that the right pectoralis major was totally absent.\n\nHowever, previous physical exams did not show deficiencies in muscle strength as the right shoulder was good for flexion, adduction, horizontal adduction and internal rotation.\n\nMoreover, his pain and touch sensation were normal.\n\nX-rays were also performed and showed normal pictures of the chest's bones.\n\nThe fact that the absence of pectoralis major did not cause functional loss in ordinary activities in this case of congenital absence showed that other surrounding muscles played a compensatory role.\n\n=== Other diseases ===\n\nPectoralis major muscle in rare occasions may develop intramuscular lipomas.\n\nSuch rare tumors may mimic malignant breast tumors as they look like enlargements of the breasts.\n\nThey are well-encapsulated radiolucent tumours of fat density.\n\nTheir location can be accurately identified through computed tomography and magnetic resonance imaging (MRI).\n\nThe treatment in these cases involves complete surgical excision because of the risk of liposarcoma they post especially large intramuscular liposomas.\n\nPartial excision is risky because recurrence may occur.\n\nhttps://en.wikipedia.org/wiki/Pectoralis_major","abdominal-part-of-pectoralis-major-muscle":"The more frequent variations include greater or less extent of attachment to the ribs and sternum, varying size of the abdominal part or its absence, greater or less extent of separation of sternocostal and clavicular parts, fusion of clavicular part with deltoid, and decussation in front of the sternum.\n\nhttps://en.wikipedia.org/wiki/Pectoralis_major","levatores-longi-costarum":"Each of the four lower muscles of the twelve pairs of levatores costarum divides into two fasciculi, adding the levatores longi costarum that passes down to the second rib below its origin, unlike the levatores breves costarum that only passes o the next rib.","levatores-breves-costarum":"Each of the four lower muscles of the twelve levatores costarum divides into two fasciculi, one of which pass obliquely downward and laterally, and is inserted into the outer surface of the rib immediately below the vertebra from which it takes origin, between the tubercle and the angle; it is called the levatores breves costarum.\n\nThe other passes down to the second rib below its origin and is called the levatores costarum longi.\n\nhttps://en.wikipedia.org/wiki/Levatores_costarum_muscles","pectoralis-minor-muscle":"Pectoralis minor muscle is a thin, triangular muscle, situated at the upper part of the chest, beneath the pectoralis major in the human body.\n\n== Structure ==\n\n=== Attachments ===\n\nPectoralis minor muscle arises from the upper margins and outer surfaces of the third, fourth, and fifth ribs, near their costal cartilages and from the aponeuroses covering the intercostalis.\n\nThe fibers pass superior and lateral and converge to form a flat tendon.\n\nThis tendon inserts onto the medial border and upper surface of the coracoid process of the scapula.\n\n=== Relations ===\n\nPectoralis minor muscle forms part of the anterior wall of the axilla.\n\nIt is covered anteriorly (superficially) by the clavipectoral fascia.\n\nThe medial pectoral nerve pierces the pectoralis minor and the clavipectoral fascia.\n\nIn attaching to the coracoid process, the pectoralis minor forms a 'bridge' - structures passing into the upper limb from the thorax will pass directly underneath.Axillary nodes are classified according to their positions relative to the pectoralis minor muscle.\n\nLevel 1 are lateral, Level 2 are deep, Level 3 are medial.\n\nThe pectoralis minor divides the axillary artery into three parts (in contrary sequence compared to the nodes) - first part medial, second part deep/posterior, third part lateral in relation to the pectoralis minor.\n\n=== Variations ===\n\nThe origin is from the second, third and fourth or fifth ribs.\n\nThe tendon of insertion may extend over the coracoid process to the greater tubercle.\n\nIt may be split into several parts.\n\nAbsence of this muscle is rare but happens with certain uncommon diseases, such as the Poland syndrome.\n\n== Function ==\n\nPectoralis minor muscle depresses the point of the shoulder, drawing the scapula superior, towards the thorax, and throwing its inferior angle posteriorly.\n\nhttps://en.wikipedia.org/wiki/Pectoralis_minor","external-intercostal-muscles":"The external intercostal muscles, or external intercostals (Intercostales externi) are eleven in number on both sides.\n\n== Structure ==\n\nThe muscles extend from the tubercles of the ribs behind, to the cartilages of the ribs in front, where they end in thin membranes, the external intercostal membranes, which are continued forward to the sternum.\n\nThese muscles work in unison when inhalation occurs.\n\nThe internal intercostal muscles relax while the external muscles contract causing the expansion of the chest cavity and an influx of air into the lungs.\n\nEach arises from the lower border of a rib, and is inserted into the upper border of the rib below.\n\nIn the two lower spaces they extend to the ends of the cartilages, and in the upper two or three spaces they do not quite reach the ends of the ribs.\n\nThey are thicker than the internal intercostals, and their fibers are directed obliquely downward and laterally on the back of the thorax, and downward, forward, and medially on the front.\n\n== Variations ==\n\nContinuation with the external oblique or serratus anterior: A supracostalis muscle, from the anterior end of the first rib down to the second, third or fourth ribs occasionally occurs.\n\nhttps://en.wikipedia.org/wiki/External_intercostal_muscles","internal-intercostal-muscles":"The internal intercostal muscles (intercostales interni) are a group of skeletal muscles located between the ribs.\n\nThey are eleven in number on either side.\n\nThey commence anteriorly at the sternum, in the intercostal spaces between the cartilages of the true ribs, and at the anterior extremities of the cartilages of the false ribs, and extend backward as far as the angles of the ribs, hence they are continued to the vertebral column by thin aponeuroses, the posterior intercostal membranes.They pull the sternum and ribs upward and inward.\n\n== Structure ==\n\nTheir fibers are also directed obliquely, but pass in a direction opposite to those of the external intercostal muscles.\n\nThe internal intercostal muscles originate from the costal groove of the rib and insert into the superior aspect of the rib below in a direction perpendicular to the external intercostal muscles.\n\nIt is this arrangement that allows these muscles to facilitate exhalation.For the most part, they are muscles of exhalation.\n\nIn exhalation the interosseous portions of the internal intercostal muscles, (the part of the muscle that is between the bone portion of the superior and inferior ribs), depresses and retracts the ribs, compressing the thoracic cavity and expelling air.\n\nThe internal intercostals, however, are only used in forceful exhalation such as coughing or during exercise and not in relaxed breathing.\n\nThe external intercostal muscles, and the intercartilaginous part of the internal intercostal muscles, (the part of the muscle that lies between the cartilage portion of the superior and inferior ribs), are used in inspiration, by aiding in elevating the ribs and expanding the thoracic cavity.\n\nhttps://en.wikipedia.org/wiki/Internal_intercostal_muscles","serratus-anterior-muscle":"The serratus anterior is a muscle that originates on the surface of the 1st to 8th ribs at the side of the chest and inserts along the entire anterior length of the medial border of the scapula.\n\nThe serratus anterior acts to pull the scapula forward around the thorax.\n\nThe muscle is named from Latin: serrare = to saw, referring to the shape, anterior = on the front side of the body.\n\n== Structure ==\n\nSerratus anterior normally originates by nine or ten muscle slips – branches from either the first to ninth ribs or the first to eighth ribs.\n\nBecause two slips usually arise from the second rib, the number of slips is greater than the number of ribs from which they originate.\n\nThe muscle is inserted along the medial border of the scapula between the superior and inferior angles along with being inserted along the thoracic vertebrae.\n\nThe muscle is divided into three named parts depending on their points of insertions:\n-the serratus anterior superior is inserted near the superior angle\n-the serratus anterior intermediate is inserted along the medial border\n-the serratus anterior inferior is inserted near the inferior angle.\n\n=== Relations ===\n\nThe serratus anterior lies deep to the subscapularis, from which it is separated by the subscapularis (supraserratus) bursa.\n\nIt is separated from the rib by the scapulothoracic (infraserratus) bursa.\n\n=== Innervation ===\n\nThe serratus anterior is innervated by the long thoracic nerve, a branch of the brachial plexus.\n\nThe long thoracic nerve travels inferiorly on the surface of the serratus anterior muscle.\n\n== Function ==\n\nAll three parts described above pull the scapula forward around the thorax, which is essential for anteversion of the arm.\n\nAs such, the muscle is an antagonist to the rhomboids.\n\nHowever, when the inferior and superior parts act together, they keep the scapula pressed against the thorax together with the rhomboids and therefore these parts also act as synergists to the rhomboids.\n\nThe inferior part can pull the lower end of the scapula laterally and forward and thus rotates the scapula to make elevation of the arm possible.\n\nAdditionally, all three parts can lift the ribs when the shoulder girdle is fixed, and thus assist in respiration.\n\nThe serratus anterior is occasionally called the \"big swing muscle\" or \"boxer's muscle\" because it is largely responsible for the protraction of the scapula — that is, the pulling of the scapula forward and around the rib cage that occurs when someone throws a punch.\n\nThe serratus anterior also plays an important role in the upward rotation of the scapula, such as when lifting a weight overhead.\n\nIt performs this in sync with the upper and lower fibers of the trapezius.\n\n== Clinical significance ==\n\nThe long thoracic nerve that supplies the serratus anterior muscle is vulnerable during certain types of surgery (for example, during lymph node clearance from the axilla for breast cancer).\n\nDamage to this nerve is the most common cause of winged scapula.\n\n== Other animals ==\n\nThe muscles of the shoulder can be categorized into three topographic units: the scapulohumeral, axiohumeral, and axioscapular groups.\n\nSerratus anterior forms part of the latter group together with rhomboid major, rhomboid minor, levator scapulae, and trapezius.\n\nThe trapezius evolved separately, but the other three muscles in this group evolved from the first eight or ten ribs and the transverse processes of the cervical vertebrae (homologous to the ribs).\n\nFunctional demands have resulted in the evolution of individual muscles from the basal unit formed by the serratus anterior.\n\nIn primitive life forms, the main function of the axioscapular group is to control the movements of the vertebral border of the scapula: fibers concerned with the dorsal movement of scapula evolved into the rhomboids, those with ventral motion into serratus anterior, and those with cranial movements into levator scapulae.\n\nThe evolution of the serratus anterior itself has resulted in (1) grouping of its distal and proximal fibers, (2) size reduction of its intermediate fibers, and (3) the insertion of its dominant superior and inferior parts onto the superior and inferior angles of the scapula.\n\nIn primates, the thoracic cage is wide and the scapula is rotated onto its posterior side to have the glenoid cavity face laterally.\n\nAdditionally, the clavicle takes care of medial forces.\n\nIn cursorial mammals (for example the horse and other quadrupeds), the scapula is hanging vertically on the side of the thorax and the clavicle is absent.\n\nTherefore, in climbing animals, the serratus anterior supports the scapula against the reaction forces of the free limb and exerts high bending forces on the ribs.\n\nTo sustain these forces, the ribs have a pronounced curvature and are supported by the clavicle.\n\nIn cursorial animals, the thorax is hanging between the scapulae at the serratus anterior and pectoralis muscles.\n\nhttps://en.wikipedia.org/wiki/Serratus_anterior_muscle","innermost-intercostal-muscles":"The innermost intercostal muscle is a layer of intercostal muscles.\n\nIt may also be called the intima of the internal intercostal muscles.\n\nIt is the deepest muscular layer of the thorax, with muscle fibres running vertically (in parallel with the internal intercostal muscles).\n\nIt is present only in the middle of each intercostal space, and often not present higher up the rib cage.\n\nIt lies deep to the plane that contains the intercostal nerves and intercostal vessels, and the internal intercostal muscles.\n\nThe diaphragm is continuous with the innermost intercostal muscle.\n\nhttps://en.wikipedia.org/wiki/Innermost_intercostal_muscle","subclavius-muscle":"The subclavius is a small triangular muscle, placed between the clavicle and the first rib.\n\nAlong with the pectoralis major and pectoralis minor muscles, the subclavius muscle makes up the anterior axioappendicular muscles, also known as anterior wall of the axilla.\n\n== Structure ==\n\nIt arises by a short, thick tendon from the first rib and its cartilage at their junction, in front of the costoclavicular ligament.\n\nThe fleshy fibers proceed obliquely superolaterally, to be inserted into the groove on the under surface of the clavicle.\n\n=== Innervation ===\n\nThe nerve to subclavius (or subclavian nerve) innervates the muscle.\n\nThis arises from the junction of the fifth and sixth cervical nerves, from the superior/upper trunk of the brachial plexus.\n\n=== Variation ===\n\nInsertion into coracoid process instead of clavicle or into both clavicle and coracoid process.\n\nSternoscapular fasciculus to the upper border of scapula.\n\nSternoclavicularis from manubrium to clavicle between pectoralis major and coracoclavicular fascia.\n\nRarely, the subclavius may be missing entirely.\n\n== Function ==\n\nIt depresses the lateral clavicle, acts to stabilize the clavicle while the shoulder moves the arm.\n\nIt also raises the first rib while lowering the clavicle during breathing.\n\nThe subclavius protects the underlying brachial plexus and subclavian vessels from a broken clavicle - the most frequently broken long bone\n\nhttps://en.wikipedia.org/wiki/Subclavius_muscle","transversus-thoracis-muscle":"The transversus thoracis muscle (), also known as triangularis sterni, lies internal to the thoracic cage, anteriorly.\n\nIt is usually a thin plane of muscular and tendinous fibers, however on athletic individuals it can be a thick 'slab of meat', situated upon the inner surface of the front wall of the chest.\n\nIt is in the same layer as the subcostal muscles and the innermost intercostal muscles.\n\nIt arises on either side from the lower third of the posterior surface of the body of the sternum, from the posterior surface of the xiphoid process, and from the sternal ends of the costal cartilages of the lower three or four true ribs.\n\nIts fibers diverge upward and lateralward, to be inserted by slips into the lower borders and inner surfaces of the costal cartilages of the second, third, fourth, fifth, and sixth ribs.\n\nThe lowest fibers of this muscle are horizontal in their direction, and are continuous with those of the transversus abdominis; the intermediate fibers are oblique, while the highest are almost vertical.\n\nThis muscle varies in its attachments, not only in different subjects, but on opposite sides of the same subject.\nThe muscle is supplied by the anterior rami of the thoracic spinal nerves (intercostal nerves).\n\n== Function ==\n\nIt is almost completely without function, but it separates the thoracic cage from the parietal pleura.\n\nIt depresses the ribs.\nContraction of this muscle aids in exertional expiration by decreasing the transverse diameter of the thoracic cage.\n\nhttps://en.wikipedia.org/wiki/Transversus_thoracis_muscle","pectoral-fascia":"The pectoral fascia is a thin lamina, covering the surface of the pectoralis major, and sending numerous prolongations between its fasciculi:\n\n it is attached, in the middle line, to the front of the sternum; above, to the clavicle; laterally and below it is continuous with the fascia of the shoulder, axilla, and thorax.\n\nIt is very thin over the upper part of the pectoralis major, but thicker in the interval between it and the latissimus dorsi, where it closes in the axillary space and forms the axillary fascia; it divides at the lateral margin of the latissimus dorsi into two layers, one of which passes in front of, and the other behind it; these proceed as far as the spinous processes of the thoracic vertebrae, to which they are attached.\n\nAs the fascia leaves the lower edge of the pectoralis major to cross the floor of the axilla it sends a layer upward under cover of the muscle; this lamina splits to envelop the pectoralis minor, at the upper edge of which it is continuous with the coracoclavicular fascia.\n\nThe hollow of the armpit, seen when the arm is abducted, is produced mainly by the traction of this fascia on the axillary floor, and hence the lamina is sometimes named the suspensory ligament of the axilla.\n\nAt the lower part of the thoracic region the deep fascia is well-developed, and is continuous with the fibrous sheaths of the rectus abdominis.\n\nhttps://en.wikipedia.org/wiki/Pectoral_fascia","diaphragm":"The thoracic diaphragm, or simply the diaphragm (Ancient Greek: διάφραγμα, romanized: diáphragma, lit. 'partition'), is a sheet of internal skeletal muscle in humans and other mammals that extends across the bottom of the thoracic cavity.\n\nThe diaphragm is the most important muscle of respiration, and separates the thoracic cavity, containing the heart and lungs, from the abdominal cavity:\n\n as the diaphragm contracts, the volume of the thoracic cavity increases, creating a negative pressure there, which draws air into the lungs.\n\nIts high oxygen consumption is noted by the many mitochondria and capillaries present; more than in any other skeletal muscle.\n\nThe term diaphragm in anatomy, created by Gerard of Cremona, can refer to other flat structures such as the urogenital diaphragm or pelvic diaphragm, but \"the diaphragm\" generally refers to the thoracic diaphragm.\n\nIn humans, the diaphragm is slightly asymmetric—its right half is higher up (superior) to the left half, since the large liver rests beneath the right half of the diaphragm.\n\nThere is also a theory that the diaphragm is lower on the other side due to the presence of the heart.\n\nOther mammals have diaphragms, and other vertebrates such as amphibians and reptiles have diaphragm-like structures, but important details of the anatomy may vary, such as the position of the lungs in the thoracic cavity.\n\n== Structure ==\n\nThe diaphragm is an upward curved, c-shaped structure of muscle and fibrous tissue that separates the thoracic cavity from the abdomen.\n\nThe superior surface of the dome forms the floor of the thoracic cavity, and the inferior surface the roof of the abdominal cavity.\n\nAs a dome, the diaphragm has peripheral attachments to structures that make up the abdominal and chest walls.\n\nThe muscle fibres from these attachments converge in a central tendon, which forms the crest of the dome.\n\nIts peripheral part consists of muscular fibers that take origin from the circumference of the inferior thoracic aperture and converge to be inserted into a central tendon.\n\nThe muscle fibres of the diaphragm emerge from many surrounding structures.\n\nAt the front, fibres insert into the xiphoid process and along the costal margin.\n\nLaterally, muscle fibers insert into ribs 6–12.\n\nIn the back, muscle fibres insert into the vertebra at T12, and two appendages, the right and left crus, descend and insert into the lumbar vertebrae.\n\nRight crus arises from L1-L3 their intervertebral discs.\n\nLeft crus from L1, L2 their intervertebral discs.\nThere are three associated arc-shaped (arcuate) ligaments: a medial, lateral, and median arcuate ligament.\n\n=== Crura and central tendon ===\n\nThe left and right crura are tendons that blend with\nthe anterior longitudinal ligament of the vertebral column.\n\nThe central tendon of the diaphragm is a thin but strong aponeurosis near the center of the vault formed by the muscle, closer to the front than to the back of the thorax, so that the posterior muscular fibers are the longer.\n\n=== Openings ===\n\nThere are a number of openings in the diaphragm through which structures pass between the thorax and abdomen.\n\nThere are three large openings — one for the aorta, one for the esophagus, and one for the inferior vena cava (the caval opening), plus a series of smaller ones.\n\nThe inferior vena cava passes through the caval opening, a quadrilateral opening at the junction of the right and middle leaflets of the central tendon, so that its margins are tendinous.\n\nSurrounded by tendons, the opening is stretched open every time inspiration occurs.\n\nHowever, there has been argument that the caval opening actually constricts during inspiration.\n\nSince thoracic pressure decreases upon inspiration and draws the caval blood upwards toward the right atrium, increasing the size of the opening allows more blood to return to the heart, maximizing the efficacy of lowered thoracic pressure returning blood to the heart.\n\nThe aorta does not pierce the diaphragm but rather passes behind it in between the left and right crus.\n\nThe thoracic spinal levels at which the three major structures pass through the diaphragm can be remembered by the number of letters contained in each structure:\n\nVena Cava (8 letters) – Passes through the diaphragm at T8.\n\nOesophagus (10 letters) – Passes through the diaphragm at T10.\n\nAortic Hiatus (12 letters) – Descending aorta passes through the diaphragm at T12.\n\n=== Nerve supply ===\n\nThe diaphragm is primarily innervated by the phrenic nerve which is formed from the cervical nerves C3, C4 and C5.\n\nWhile the central portion of the diaphragm sends sensory afferents via the phrenic nerve, the peripheral portions of the diaphragm send sensory afferents via the intercostal (T5–T11) and subcostal nerves (T12).\n\n=== Blood supply ===\n\nArteries and veins above and below the diaphragm supply and drain blood.\n\nFrom above, the diaphragm receives blood from branches of the internal thoracic arteries, namely the pericardiacophrenic artery and musculophrenic artery; from the superior phrenic arteries, which arise directly from the thoracic aorta; and from the lower internal intercostal arteries.\n\nFrom below, the inferior phrenic arteries supply the diaphragm.\n\nThe diaphragm drains blood into the brachiocephalic veins, azygos veins, and veins that drain into the inferior vena cava and left suprarenal vein.\n\n=== Variation ===\n\nThe sternal portion of the muscle is sometimes wanting and more rarely defects occur in the lateral part of the central tendon or adjoining muscle fibers.\n\n=== Development ===\n\nThe thoracic diaphragm develops during embryogenesis, beginning in the third week after fertilization with two processes known as transverse folding and longitudinal folding.\n\nThe septum transversum, the primitive central tendon of the diaphragm, originates at the rostral pole of the embryo and is relocated during longitudinal folding to the ventral thoracic region.\n\nTransverse folding brings the body wall anteriorly to enclose the gut and body cavities.\n\nThe pleuroperitoneal membrane and body wall myoblasts, from somatic lateral plate mesoderm, meet the septum transversum to close off the pericardio-peritoneal canals on either side of the presumptive esophagus, forming a barrier that separates the peritoneal and pleuropericardial cavities.\n\nFurthermore, dorsal mesenchyme surrounding the presumptive esophagus form the muscular crura of the diaphragm.\n\nBecause the earliest element of the embryological diaphragm, the septum transversum, forms in the cervical region, the phrenic nerve that innervates the diaphragm originates from the cervical spinal cord (C3,4, and 5).\n\nAs the septum transversum descends inferiorly, the phrenic nerve follows, accounting for its circuitous route from the upper cervical vertebrae, around the pericardium, finally to innervate the diaphragm.\n\n== Function ==\n\nThe diaphragm is the main muscle of respiration and functions in breathing.\n\nDuring inhalation, the diaphragm contracts and moves in the inferior direction, enlarging the volume of the thoracic cavity and reducing intra-thoracic pressure (the external intercostal muscles also participate in this enlargement), forcing the lungs to expand.\n\nIn other words, the diaphragm's movement downwards creates a partial vacuum in the thoracic cavity, which forces the lungs to expand to fill the void, drawing air in the process.\nCavity expansion happens in two extremes, along with intermediary forms.\n\nWhen the lower ribs are stabilized and the central tendon of the diaphragm is mobile, a contraction brings the insertion (central tendon) towards the origins and pushes the lower cavity towards the pelvis, allowing the thoracic cavity to expand downward.\n\nThis is often called belly breathing.\n\nWhen the central tendon is stabilized and the lower ribs are mobile, a contraction lifts the origins (ribs) up towards the insertion (central tendon) which works in conjunction with other muscles to allow the ribs to slide and the thoracic cavity to expand laterally and upwards.\n\nWhen the diaphragm relaxes (moves in the superior direction), air is exhaled by elastic recoil process of the lung and the tissues lining the thoracic cavity.\n\nAssisting this function with muscular effort (called forced exhalation) involves the internal intercostal muscles used in conjunction with the abdominal muscles, which act as an antagonist paired with the diaphragm's contraction.\n\nThe diaphragm is also involved in non-respiratory functions.\n\nIt helps to expel vomit, feces, and urine from the body by increasing intra-abdominal pressure, aids in childbirth, and prevents acid reflux by exerting pressure on the esophagus as it passes through the esophageal hiatus.\n\nIn some non-human animals, the diaphragm is not crucial for breathing; a cow, for instance, can survive fairly asymptomatically with diaphragmatic paralysis as long as no massive aerobic metabolic demands are made of it.\n\n== Clinical significance ==\n\n=== Paralysis ===\n\nIf either the phrenic nerve, cervical spine or brainstem is damaged, this will sever the nervous supply to the diaphragm.\n\nThe most common damage to the phrenic nerve is by bronchial cancer, which usually only affects one side of the diaphragm.\n\nOther causes include Guillain–Barré syndrome and systemic lupus erythematosus.\n\n=== Herniation ===\n\nA hiatus hernia is a hernia common in adults in which parts of the lower esophagus or stomach that are normally in the abdomen pass/bulge abnormally through the diaphragm and are present in the thorax.\n\nHernias are described as rolling, in which the hernia is beside the oesophagus, or sliding, in which the hernia directly involves the esophagus.\n\nThese hernias are implicated in the development of reflux, as the different pressures between the thorax and abdomen normally act to keep pressure on the esophageal hiatus.\n\nWith herniation, this pressure is no longer present, and the angle between the cardia of the stomach and the oesophagus disappear.\n\nNot all hiatus hernias cause symptoms however, although almost all people with Barrett's oesophagus or oesophagitis have a hiatus hernia.\n\nHernias may also occur as a result of congenital malformation, a congenital diaphragmatic hernia.\n\nWhen the pleuroperitoneal membranes fail to fuse, the diaphragm does not act as an effective barrier between the abdomen and thorax.\n\nHerniation is usually of the left, and commonly through the posterior lumbocostal triangle, although rarely through the anterior foramen of Morgagni.\n\nThe contents of the abdomen, including the intestines, may be present in the thorax, which may impact development of the growing lungs and lead to hypoplasia.\n\nThis condition is present in 0.8 - 5/10,000 births.\n\nA large herniation has high mortality rate, and requires immediate surgical repair.\n\n=== Imaging ===\n\nDue to its position separating the thorax and abdomen, fluid abnormally present in the thorax, or air abnormally present in the abdomen, may collect on one side of the diaphragm.\n\nAn X-ray may reveal this.\n\nPleural effusion, in which there is fluid abnormally present between the two pleurae of the lungs, is detected by an X-ray of the chest, showing fluid collecting in the angle between the ribs and diaphragm.\n\nAn X-ray may also be used to reveal a pneumoperitoneum, in which there is gas in the abdomen.\n\nAn X-ray may also be used to check for herniation.\n\n== Significance in strength training ==\n\nThe adoption of a deeper breathing pattern typically occurs during physical exercise in order to facilitate greater oxygen absorption.\n\nDuring this process the diaphragm more consistently adopts a lower position within the body's core.\n\nIn addition to its primary role in breathing, the diaphragm also plays a secondary role in strengthening the posture of the core.\n\nThis is especially evident during deep breathing where its generally lower position increases intra-abdominal pressure, which serves to strengthen the lumbar spine.\n\nThe key to real core stabilization is to maintain the increased IAP while going through normal breathing cycles. […]\n\nThe diaphragm then performs its breathing function at a lower position to facilitate a higher IAP.\n\nTherefore, if a person's diaphragm position is lower in general, through deep breathing, then this assists the strengthening of their core during that period.\n\nThis can be an aid in strength training and other forms of athletic endeavour.\n\nFor this reason, taking a deep breath or adopting a deeper breathing pattern is typically recommended when lifting heavy weights.\n\n== Other animals ==\n\nThe existence of a membrane separating the pharynx from the stomach can be traced widely among the chordates.\n\nThus the model organism, the marine chordate lancelet, possesses an atriopore by which water exits the pharynx, which has been claimed (and disputed) to be homologous to structures in ascidians and hagfishes.\n\nThe tunicate epicardium separates digestive organs from the pharynx and heart, but the anus returns to the upper compartment to discharge wastes through an outgoing siphon.\nThus the diaphragm emerges in the context of a body plan that separated an upper feeding compartment from a lower digestive tract, but the point at which it originates is a matter of definition.\n\nStructures in fish, amphibians, reptiles, and birds have been called diaphragms, but it has been argued that these structures are not homologous.\n\nFor instance, the alligator diaphragmaticus muscle does not insert on the esophagus and does not affect pressure of the lower esophageal sphincter.\n\nThe lungs are located in the abdominal compartment of amphibians and reptiles, so that contraction of the diaphragm expels air from the lungs rather than drawing it into them.\n\nIn birds and mammals, lungs are located above the diaphragm.\n\nThe presence of an exceptionally well-preserved fossil of Sinosauropteryx, with lungs located beneath the diaphragm as in crocodiles, has been used to argue that dinosaurs could not have sustained an active warm-blooded physiology, or that birds could not have evolved from dinosaurs.\n\nAn explanation for this (put forward in 1905), is that lungs originated beneath the diaphragm, but as the demands for respiration increased in warm-blooded birds and mammals, natural selection came to favor the parallel evolution of the herniation of the lungs from the abdominal cavity in both lineages.However, birds do not have diaphragms.\n\nThey do not breathe in the same way as mammals and do not rely on creating a negative pressure in the thoracic cavity, at least not to the same extent.\n\nThey rely on a rocking motion of the keel of the sternum to create local areas of reduced pressure to supply thin, membranous airsacs cranially and caudally to the fixed-volume, non-expansive lungs.\n\nA complicated system of valves and air sacs cycles air constantly over the absorption surfaces of the lungs so allowing maximal efficiency of gaseous exchange.\n\nThus, birds do not have the reciprocal tidal breathing flow of mammals.\n\nOn careful dissection, around eight air sacs can be clearly seen.\n\nThey extend quite far caudally into the abdomen.\n\nhttps://en.wikipedia.org/wiki/Thoracic_diaphragm","rectus-abdominis-muscle":"The rectus abdominis muscle, also known as the \"abdominal muscle\", is a paired muscle running vertically on each side of the anterior wall of the human abdomen, as well as that of some other mammals.\n\nThere are two parallel muscles, separated by a midline band of connective tissue called the linea alba.\n\nIt extends from the pubic symphysis, pubic crest and pubic tubercle inferiorly, to the xiphoid process and costal cartilages of ribs V to VII superiorly.\n\nThe proximal attachments are the pubic crest and the pubic symphysis.\n\nIt attaches distally at the costal cartilages of ribs 5-7 and the xiphoid process of the sternum.The rectus abdominis muscle is contained in the rectus sheath, which consists of the aponeuroses of the lateral abdominal muscles.\n\nThe outer, most lateral line, defining the rectus is the linea semilunaris.\n\nBands of connective tissue traverse the rectus abdominis, separating it into distinct muscle bellies.\n\nIn the abdomens of people with low body fat, these muscle bellies can be viewed externally.\n\nThey can appear in sets of as few as two to as many as twelve.\n\nAlthough, six is the most common.\n\n== Structure ==\n\nThe rectus abdominis is a very long flat muscle, which extends along the whole length of the front of the abdomen, and is separated from its fellow of the opposite side by the linea alba.\n\nTendinous intersections (intersectiones tendineae) further subdivide each rectus abdominis muscle into a series of smaller muscle bellies.\n\nTensing of the rectus abdominis causes the muscle to expand between each tendinous intersection.The upper portion, attached principally to the cartilage of the fifth rib, usually has some fibers of insertion into the anterior extremity of the rib itself.\n\n=== Size ===\n\nIt is typically around 10 mm thick.\n\nAlthough, some athletes can have a rectus up to 20 mm thick.\nTypical volume is around 300 cm³ in non-active individuals and 500 cm³ in athletes.\n\n=== Blood supply ===\n\nThe rectus abdominis has many sources of arterial blood supply.\n\nClassification of the vascular anatomy of muscles: First, the inferior epigastric artery and vein (or veins) run superiorly on the posterior surface of the rectus abdominis, enter the rectus fascia at the arcuate line, and serve the lower part of the muscle.\n\nSecond, the superior epigastric artery, a terminal branch of the internal thoracic artery, supplies blood to the upper portion.\n\nFinally, numerous small segmental contributions come from the lower six intercostal arteries as well.\n\n=== Nerve supply ===\n\nThe muscles are innervated by thoraco-abdominal nerves, these are continuations of the T7-T11 intercostal nerves and pierce the anterior layer of the rectus sheath.\n\nSensory supply is from the 7-12 thoracic nerves.\n\n=== Variation ===\n\nThe sternalis muscle may be a variant form of the pectoralis major or the rectus abdominis.\n\nSome fibers are occasionally connected with the costoxiphoid ligaments, and the side of the xiphoid process.\n\n== Function ==\n\nThe rectus abdominis is an important postural muscle.\n\nIt is responsible for flexing the lumbar spine, as when doing a crunch.\n\nThe rib cage is brought up to where the pelvis is when the pelvis is fixed, or the pelvis can be brought towards the rib cage (posterior pelvic tilt) when the rib cage is fixed, such as in a leg-hip raise.\n\nThe two can also be brought together simultaneously when neither is fixed in space.\n\nThe rectus abdominis assists with breathing and plays an important role in respiration when forcefully exhaling, as seen after exercise as well as in conditions where exhalation is difficult such as emphysema.\n\nIt also helps in keeping the internal organs intact and in creating intra-abdominal pressure, such as when exercising or lifting heavy weights, during forceful defecation or parturition (childbirth).\n\n== Clinical significance ==\n\nAn abdominal muscle strain, also called a pulled abdominal muscle, is an injury to one of the muscles of the abdominal wall.\n\nA muscle strain occurs when the muscle is stretched too far.\n\nWhen this occurs the muscle fibers are torn.\n\nMost commonly, a strain causes microscopic tears within the muscle, but occasionally, in severe injuries, the muscle can rupture from its attachment.\n\nA rectus sheath hematoma is an accumulation of blood in the sheath of the rectus abdominis muscle.\n\nIt causes abdominal pain with or without a mass.\n\nThe hematoma may be caused by either rupture of the epigastric artery or by a muscular tear.\n\nCauses of this include anticoagulation, coughing, pregnancy, abdominal surgery and trauma.\n\nWith an ageing population and the widespread use of anticoagulant medications, there is evidence that this historically benign condition is becoming more common and more serious.On abdominal examination, people may have a positive Carnett's sign.\n\nMost hematomas resolve without treatment, but they may take several months to resolve.\n\n== Other animals ==\n\nThe rectus abdominis is similar in most vertebrates.\n\nThe most obvious difference between animal and human abdominal musculature is that in animals, there are a different number of tendinous intersections.\n\nhttps://en.wikipedia.org/wiki/Rectus_abdominis_muscle","inguinal-ligament":"The inguinal ligament (), also known as Poupart's ligament or groin ligament, is a band running from the pubic tubercle to the anterior superior iliac spine.\n\nIt forms the base of the inguinal canal through which an indirect inguinal hernia may develop.\n\n== Structure ==\n\nThe inguinal ligament runs from the anterior superior iliac crest of the ilium to the pubic tubercle of the pubic bone.\n\nIt is formed by the external abdominal oblique aponeurosis and is continuous with the fascia lata of the thigh.\nThere is some dispute over the attachments.Structures that pass deep to the inguinal ligament include:\n\nPsoas major, iliacus, pectineus\nFemoral nerve, artery, and vein\nLateral cutaneous nerve of thigh\nLymphatics\n\n== Function ==\n\nThe ligament serves to contain soft tissues as they course anteriorly from the trunk to the lower extremity.\n\nThis structure demarcates the superior border of the femoral triangle.\n\nIt demarcates the inferior border of the inguinal triangle.\n\nThe midpoint of the inguinal ligament, halfway between the anterior superior iliac spine and pubic tubercle, is the landmark for the femoral nerve.\n\nThe mid-inguinal point, halfway between the anterior superior iliac spine and the pubic symphysis, is the landmark for the femoral artery.\n\nThe external iliac arteries pass the inguinal ligament posteriorly and inferiorly.\n\n== History ==\n\nIt is also referred to as Poupart's ligament, because François Poupart gave it relevance in relation to hernial repair, calling it \"the suspender of the abdomen\" (French: \"le suspenseur de l'abdomen\").\n\nIt is sometimes termed the Fallopian ligament.\n\nColles' ligament is the reflex ligament and not the inguinal ligament.\n\nhttps://en.wikipedia.org/wiki/Inguinal_ligament","external-abdominal-oblique-muscle":"The abdominal external oblique muscle (also external oblique muscle, or exterior oblique) is the largest and outermost of the three flat abdominal muscles of the lateral anterior abdomen.\n\n== Structure ==\n\nThe external oblique is situated on the lateral and anterior parts of the abdomen.\n\nIt is broad, thin, and irregularly quadrilateral, its muscular portion occupying the side, its aponeurosis the anterior wall of the abdomen.\n\nIn most humans (especially females), the oblique is not visible, due to subcutaneous fat deposits and the small size of the muscle.\n\nIt arises from eight fleshy digitations, each from the external surfaces and inferior borders of the fifth to twelfth ribs (lower eight ribs).\n\nThese digitations are arranged in an oblique line which runs inferiorly and anteriorly, with the upper digitations being attached close to the cartilages of the corresponding ribs, the lowest to the apex of the cartilage of the last rib, the intermediate ones to the ribs at some distance from their cartilages.\n\nThe five superior serrations increase in size from above downward, and are received between corresponding processes of the serratus anterior muscle; the three lower ones diminish in size from above downward and receive between them corresponding processes from the latissimus dorsi.\n\nFrom these attachments the fleshy fibers proceed in various directions.\n\nIts posterior fibers from the ribs to the iliac crest form a free posterior border.\n\nThose from the lowest ribs pass nearly vertically downward, and are inserted into the anterior half of the outer lip of the iliac crest; the middle and upper fibers, directed downward (inferiorly) and forward (anteriorly), become aponeurotic at approximately the midclavicular line and form the anterior layer of the rectus sheath.\n\nThis aponeurosis formed from fibres from either side of the external oblique decussates at the linea alba.\nThe aponeurosis of the external oblique muscle forms the inguinal ligament.\n\nThe muscle also contributes to the inguinal canal.\nThe internal oblique muscle is just deep to the external oblique muscle.\n\n=== Nerve supply ===\n\nThe external oblique muscle is supplied by ventral branches of the lower six thoracoabdominal nerves and the subcostal nerve on each side.\n\n=== Blood supply ===\n\nThe cranial portion of the muscle is supplied by the lower intercostal arteries, whereas the caudal portion is supplied by a branches of either the deep circumflex iliac artery or the iliolumbar artery.\n\n== Function ==\n\nThe external oblique functions to pull the chest downwards and compress the abdominal cavity, which increases the intra-abdominal pressure as in a valsalva maneuver.\n\nIt also performs ipsilateral (same side) side-bending and contralateral (opposite side) rotation.\n\nSo the right external oblique would side bend to the right and rotate to the left.\n\nThe internal oblique muscle functions similarly except it rotates ipsilaterally.\n\n== Society and culture ==\n\n=== Oblique strain ===\n\nThe oblique strain is a common baseball injury, particularly in pitchers.\n\nIn both batters and pitchers it can affect the contralateral (leading) side external oblique, or the trailing internal oblique.\n\n=== Training ===\n\nCrunch (exercise)\nSide plank\nSit-up (exercise)\n\nhttps://en.wikipedia.org/wiki/Abdominal_external_oblique_muscle","internal-abdominal-oblique-muscle":"The abdominal internal oblique muscle, also internal oblique muscle or interior oblique, is an abdominal muscle in the abdominal wall that lies below the external oblique muscle and just above the transverse abdominal muscle.\n\n== Structure ==\n\nIts fibers run perpendicular to the external oblique muscle, beginning in the thoracolumbar fascia of the lower back, the anterior 2/3 of the iliac crest (upper part of hip bone) and the lateral half of the inguinal ligament.\n\nThe muscle fibers run from these points superiomedially (up and towards midline) to the muscle's insertions on the inferior borders of the 10th through 12th ribs and the linea alba.\n\nIn males, the cremaster muscle is also attached to the internal oblique.\n\n=== Nerve supply ===\n\nThe internal oblique is supplied by the lower intercostal nerves, as well as the iliohypogastric nerve and the ilioinguinal nerve.\n\n== Function ==\n\nThe internal oblique performs two major functions.\n\nFirstly as an accessory muscle of respiration, it acts as an antagonist (opponent) to the diaphragm, helping to reduce the volume of the chest cavity during exhalation.\n\nWhen the diaphragm contracts, it pulls the lower wall of the chest cavity down, increasing the volume of the lungs which then fill with air.\n\nConversely, when the internal obliques contract they compress the organs of the abdomen, pushing them up into the diaphragm which intrudes back into the chest cavity reducing the volume of the air-filled lungs, producing an exhalation.\n\nSecondly, its contraction causes ipsilateral rotation and side-bending.\n\nIt acts with the external oblique muscle of the opposite side to achieve this torsional movement of the trunk.\n\nFor example, the right internal oblique and the left external oblique contract as the torso flexes and rotates to bring the left shoulder towards the right hip.\n\nFor this reason, the internal obliques are referred to as \"same-side rotators.\"\n\nhttps://en.wikipedia.org/wiki/Abdominal_internal_oblique_muscle","transversus-abdominis-muscle":"TRANSVERSE ABDOMINAL MUSCLE\n\nThe transverse abdominal muscle (TVA), also known as the transverse abdominis, transversalis muscle and transversus abdominis muscle, is a muscle layer of the anterior and lateral (front and side) abdominal wall which is deep to (layered below) the internal oblique muscle.\n\nIt is thought by most fitness instructors to be a significant component of the core.\n\n== Structure ==\n\nThe transverse abdominal, so called for the direction of its fibers, is the innermost of the flat muscles of the abdomen.\n\nIt is positioned immediately inside of the internal oblique muscle.\nThe transverse abdominal arises as fleshy fibers, from the lateral third of the inguinal ligament, from the anterior three-fourths of the inner lip of the iliac crest, from the inner surfaces of the cartilages of the lower six ribs, interdigitating with the diaphragm, and from the thoracolumbar fascia.\n\nIt ends anteriorly in a broad aponeurosis (the Spigelian fascia), the lower fibers of which curve inferomedially (medially and downward), and are inserted, together with those of the internal oblique muscle, into the crest of the pubis and pectineal line, forming the inguinal conjoint tendon also called the aponeurotic falx.\n\nIn layman's terms, the muscle ends in the middle line of a person's abdomen.: 248–250 Throughout the rest of its extent the aponeurosis passes horizontally to the middle line, and is inserted into the linea alba; its upper three-fourths lie behind the rectus muscle and blend with the posterior lamella of the aponeurosis of the internal oblique; its lower fourth is in front of the rectus abdominis.\n\n=== Innervation ===\n\nThe transverse abdominal is innervated by the lower intercostal nerves (thoracoabdominal, nerve roots T7-T11), as well as the iliohypogastric nerve and the ilioinguinal nerve.\n\n== Function ==\n\nThe transverse abdominal helps to compress the ribs and viscera, providing thoracic and pelvic stability.\n\nThis is explained further here.\n\nThe transverse abdominal also helps a pregnant woman to deliver her child.\nWithout a stable spine, one aided by proper contraction of the TVA, the nervous system fails to recruit the muscles in the extremities efficiently, and functional movements cannot be properly performed.\n\nThe transverse abdominal and the segmental stabilizers (e.g. the multifidi) of the spine have evolved to work in tandem.\n\nWhile it is true that the TVA is vital to back and core health, the muscle also has the effect of pulling in what would otherwise be a protruding abdomen (hence its nickname, the “corset muscle”).\n\nTraining the rectus abdominis muscles alone will not and can not give one a \"flat\" belly; this effect is achieved only through training the TVA.\n\nThus to the extent that traditional abdominal exercises (e.g. crunches) or more advanced abdominal exercises tend to \"flatten\" the belly, this is owed to the tangential training of the TVA inherent in such exercises.\n\nRecently the transverse abdominal has become the subject of debate between biokineticists, kinesiologists, strength trainers, and physical therapists.\n\nThe two positions on the muscle are that the muscle is effective and capable of bracing the human core during extremely heavy lifts and (2) that it is not.\n\nSpecifically, one recent systematic review has found that the baseline dysfunction of TVA cannot predict the clinical outcomes of low back pain.\n\nSimilarly, another systematic review has revealed that the changes in TVA function or morphology after different nonsurgical treatments are unrelated to the improvement of pain intensity or low back pain related-disability.\n\nThese findings have challenged the traditional emphasis of using TVA-targeted intervention to treat low back pain.\n\n=== Exercise ===\n\nThe most well known method of strengthening the TVA is the vacuum exercise.\n\nThe TVA also (involuntarily) contracts during many lifts; it is the body's natural weight-lifting belt, stabilizing the spine and pelvis during lifting movements.\n\nIt has been estimated that the contraction of the TVA and other muscles reduces the vertical pressure on the intervertebral discs by as much as 40%.\n\nFailure to engage the TVA during higher intensity lifts is dangerous and encourages injury to the spine.\n\nThe TVA acts as a girdle or corset by creating hoop tension around the midsection.\n\nhttps://en.wikipedia.org/wiki/Transverse_abdominal_muscle","linea-alba":"The linea alba (Latin: for white line) is a fibrous structure that runs down the midline of the abdomen in humans and other vertebrates.\n\n== Structure ==\n\nIn humans, the linea alba runs from the xiphoid process to the pubic symphysis down the midline of the abdomen.\n\nThe name means white line as it is composed mostly of collagen connective tissue, which has a white appearance.\n\nIt is formed by the fusion of the aponeuroses of the muscles of the anterior abdominal wall.\n\nIt separates the left and right rectus abdominis muscles.\n\nIn muscular individuals, its presence can be seen on the skin, forming the depression between the left and right halves of a \"six pack\".\n\n== Function ==\n\nThe linea alba stabilises the anterior abdominal wall, as it balances contractile forces from the muscles attached to it.\n\n== Clinical significance ==\n\nA median incision through the linea alba is a common surgical approach for abdominal surgery.\n\nThis is because it consists of mostly connective tissue, and does not contain any primary nerves or blood vessels.\n\nhttps://en.wikipedia.org/wiki/Linea_alba_(abdomen)","pyramidalis-muscle":"The pyramidalis muscle is a small triangular muscle, anterior to the rectus abdominis muscle, and contained in the rectus sheath.\n\n== Structure ==\n\nThe pyramidalis muscle is part of the anterior abdominal wall.\n\nInferiorly, the pyramidalis muscle attaches to the pelvis in two places: the pubic symphysis and pubic crest, arising by tendinous fibers from the anterior part of the pubis and the anterior pubic ligament.\n\nSuperiorly, the fleshy portion of the pyramidalis muscle passes upward, diminishing in size as it ascends, and ends by a pointed extremity which is inserted into the linea alba, midway between the umbilicus and pubis.\n\n=== Nerve supply ===\n\nThe pyramidalis muscle is innervated by the ventral portion of T12.\n\n=== Blood supply ===\n\nThe inferior and superior epigastric arteries supply blood to the pyramidalis muscle.\n\n=== Variation ===\n\nThe pyramidalis muscle is present in 80% of human population.\n\nIt may be absent on one or both sides; the lower end of the rectus then becomes proportionately increased in size.\n\nOccasionally, it is doubled on one side, and the muscles of the two sides are sometimes of unequal size.\n\nIt may also extend higher than the usual level.\n\n== Function ==\n\nThe pyramidalis muscle tenses the linea alba when contracting.\n\n== Clinical significance ==\n\nWhile making the longitudinal incision for a classical caesarean section, the pyramidalis muscle is used to determine midline and location of the linea alba.\n\nhttps://en.wikipedia.org/wiki/Pyramidalis_muscle","quadratus-lumborum-muscle":"The quadratus lumborum muscle, informally called the QL, is a paired muscle of the left and right posterior abdominal wall.\n\nIt is the deepest abdominal muscle, and commonly referred to as a back muscle.\n\nEach is irregular and quadrilateral in shape.\n\nThe quadratus lumborum muscles originate from the wings of the ilium; their insertions are on the transverse processes of the upper four lumbar vertebrae plus the lower posterior border of the twelfth rib.\n\nContraction of one of the pair of muscles causes lateral flexion of the lumbar spine, elevation of the pelvis, or both.\n\nContraction of both causes extension of the lumbar spine.\n\nA disorder of the quadratus lumborum muscles is pain due to muscle fatigue from constant contraction due to prolonged sitting, such as at a computer or in a car.\n\nKyphosis and weak gluteal muscles can also contribute to the likelihood of quadratus lumborum pain.\n\n== Structure ==\n\nThe quadratus lumborum muscle originates by aponeurotic fibers into the iliolumbar ligament and the internal lip of the iliac crest for about 5 centimetres (2.0 in).\n\nIt inserts from the lower border of the last rib for about half its length and by four small tendons from the apices of the transverse processes of the upper four lumbar vertebrae.\n\nThe number of attachments to the vertebræ, and the extent of its attachment to the last rib, may vary.\n\nAlso, occasionally, a second portion of this muscle is found in front of the preceding.\n\nIt arises from the upper borders of the transverse processes of the lower three or four lumbar vertebræ, and is inserted into the lower margin of the last rib.\n\n=== Relationships ===\n\nAnterior to the quadratus lumborum are the colon, the kidney, the psoas major muscle, (if present) the psoas minor muscle, and the diaphragm; between the fascia and the muscle are the twelfth thoracic, ilioinguinal, and iliohypogastric nerves.\n\nThe quadratus lumborum muscle is a continuation of transverse abdominal muscle.\n\n=== Nerve supply ===\n\nAnterior branches of the ventral rami of T12 to L4.\n\n== Functions ==\n\nThe quadratus lumborum can perform four actions:\n\n-Lateral flexion of vertebral column, with ipsilateral contraction\n\n-Extension of lumbar vertebral column, with bilateral contraction (based on line of force passing ~3.5 cm posterior L3 rotation axis)\n\n-Fixes the 12th rib during forced expiration.\n\n-The quadratus lumborum assists the diaphragm in inhalation\nElevates the Ilium (bone), with ipsilateral contraction (\"hip hiking\")Additional functions:\n\nVertical stabilization of pelvis, lumbar spine, and lumbosacral junction.\n\nPrevents collapse of the vertebral column in the frontal plane (i.e. scoliosis)\nReserve mover actions: Anterior pelvic tilt.\n\nContralateral lateral pelvic rotation.\n\n== Clinical significance ==\n\nThe quadratus lumborum muscles can be the source of back pain when overused, or in association with scoliosis or weak gluteal muscles.\n\n=== Mechanism ===\n\nThe quadratus lumborum is a common source of unilateral or bilateral lower back pain, including localized pain and tenderness over the wing of the ilium.\n\nBecause the QL connects the pelvis to the spine and is therefore capable of extending the lower back when contracting bilaterally, the two QLs pick up the slack, as it were, when the lower fibers of the erector spinae are weak or inhibited (as they often are in the case of habitual seated computer use and/or the use of a lower back support in a chair).\n\nGiven their comparable mechanical disadvantage, constant contraction while seated can overuse the QLs, resulting in muscle fatigue.\n\nA constantly contracted QL, like any other muscle, will experience decreased blood flow, and, in time, adhesions in the muscle and fascia may develop, the end point of which is muscle spasm.\n\n=== Association with kyphosis ===\n\nThis chain of events can be and often is accelerated by kyphosis, which is invariably accompanied by rounded shoulders, both of which place greater stress on the QLs by shifting body weight forward, forcing the erector spinae, QLs, multifidi, and especially the levator scapulae to work harder in both seated and standing positions to maintain an erect torso and neck.\n\nThe experience of \"productive pain\" or pleasure by a patient upon palpation of the QL is indicative of such a condition.\n\n=== Association with weak gluteal muscles ===\n\nHip abduction is performed primarily by the hip abductors (gluteus medius and minimus).\n\nWhen the gluteus medius/minimus are weak or inhibited, the TFL\n(tensor fasciae latae) or QL will compensate by becoming the prime mover.\n\nThe most impaired movement pattern of hip abduction is when the QL initiates the movement, which results in hip hiking during swing phase of gait.\n\nHip hiking places excessive side-bending compressive stresses on the lumbar segments.\n\nThus, a tight QL may be another hidden cause of low back pain (Janda 1987).\n\nWhen the hip adductors are tight or hypertonic, their antagonist (gluteus medius) may experience reciprocal inhibition.\n\nThe gluteus medius will become weak and inhibited.\n\nThis in turn may cause hypertonicity of ipsilateral QL.\n\nChronic hypertonicity of QL tends to cause low back pain due to its ability to create compressive stress on lumbar segment.\n\n=== Treatment ===\n\nWhile stretching and strengthening the QL are indicated for unilateral lower back pain, heat or ice applications as well as massage should be considered as part of any comprehensive rehabilitation regimen.\n\nCurrent studies show that application of heat or ice, massage, and estim will not leave long-term benefits.\n\nCareful assessment of muscular imbalances and movement impairments by a therapist is recommended in order to address the underlying issues mentioned.\n\nhttps://en.wikipedia.org/wiki/Quadratus_lumborum_muscle","investing-abdominal-fascia":"Abdominal fascia refers to the various types of fascia found in the abdominal region.\n\nFascia is a sheet of connective tissue that is found beneath the skin that attaches, stabilizes, encloses, and separates muscles and other internal organs.\n\nEveryone has fascia, as it is part of how the human body is composed.\n\nFascia is organized by layer, and can also be classified by location or function in the body.\n\nWhile abdominal fascia is quite a simple part of how the human body is made up, there are other implications and involvements that abdominal fascia is a part of.\n\n== Research ==\n\nIn a 2016 study, abdominal superficial fascia was collected from both male and female cadavers.\n\nThe elastic, collagen, and hydroxyproline components were sampled and then studied.\n\nIt was found that the elastic, collagen, and hydroxyproline components were higher in upper abdomen regions compared to lower abdomen regions.\n\nThis could be a reason as to why bulging of the abdomen and skin sagging occurs more in the lower regions of people, compared to the upper regions.\n\nThis study that was conducted could lead to further discussions and studies in finding ways to manage obesity.\n\nIn a study from January 2011, Mechanical properties of abdominal human fascia were studied according to the direction of loading and localization.\n\nHuman umbilical (UF) and transversalis fascia (FT) have been studied to understand the differences in mechanical properties of the human body.\n\nThe differences between the mechanical properties of both UF and FT were not significant according to localization; therefore, the mechanical properties of human abdominal fascia are not controlled by the localization.\n\nAnother study from 2018, showed differences in mechanical and structural properties of human fascia and their gender differences.\n\nWhile the study was done on fascia from the thighs, the results which were comparing the differences between males and females, can also be applied to understanding the abdominal area of males and females.\n\nUltimately, it was found that the fascia lata at the lateral site was thicker and longitudinally directed fibers had higher rates of distribution compared to other sites.\n\n== Further Findings ==\n\nIt can be involved in certain forms of breast reconstruction.\n\nhttps://en.wikipedia.org/wiki/Abdominal_fascia","coccygeus-muscle":"The coccygeus muscle or ischiococcygeus is a muscle of the pelvic floor, located posterior to levator ani and anterior to the sacrospinous ligament.\n\n== Structure ==\n\nThe coccygeus muscle is posterior to levator ani and anterior to the sacrospinous ligament in the pelvic floor.\n\nIt is a triangular plane of muscular and tendinous fibers.\n\nIt arises by its apex from the spine of the ischium and sacrospinous ligament.\n\nIt is inserted by its base into the margin of the coccyx and into the side of the lowest piece of the sacrum.\n\nIn combination with the levator ani, it forms the pelvic diaphragm.\n\nThe pudendal nerve runs between the coccygeus muscle and the piriformis muscle, superficial to the coccygeus muscle.\n\n=== Nerve supply ===\n\nThe coccygeus muscle is innervated by the pudendal nerve, which runs between it and the piriformis muscle.\n\n== Function ==\n\nThe coccygeus muscle assists the levator ani and piriformis muscle in closing in the back part of the outlet of the pelvis.\n\nThis helps to support the vagina in women, and the other pelvic organs.\n\nhttps://en.wikipedia.org/wiki/Coccygeus_muscle","iliococcygeus-muscle":"The levator ani is made up of 3 parts:\n\n -Iliococcygeus muscle\n -Pubococcygeus muscle\n -Puborectalis muscle\n\nThe iliococcygeus arises from the inner side of the ischium (the lower and back part of the hip bone) and from the posterior part of the tendinous arch of the obturator fascia, and is attached to the coccyx and anococcygeal body; it is usually thin, and may be absent, or be largely replaced by fibrous tissue.\n\nAn accessory slip at its posterior part is sometimes named the iliosacralis.\n\nhttps://en.wikipedia.org/wiki/Levator_ani","pubo-analis-muscle":"Muscular bundles going to the the external anal sphincter.","pubococcygeus-muscle":"The levator ani is made up of 3 parts:\n\n Iliococcygeus muscle\n Pubococcygeus muscle\n Puborectalis muscle\n\nThe pubococcygeus muscle has medial fibres forming the pubovaginalis in the female, and the puboprostaticus in the male.\n\nhttps://en.wikipedia.org/wiki/Levator_ani","piriformis-fascia":"The fascia of the Piriformis is very thin and is attached to the front of the sacrum and the sides of the greater sciatic foramen; it is prolonged on the muscle into the gluteal region.\n\nAt its sacral attachment around the margins of the anterior sacral foramina it comes into intimate association with and ensheathes the nerves emerging from these foramina.\n\nHence the sacral nerves are frequently described as lying behind the fascia.\n\nThe internal iliac artery, internal iliac vein, and their branches, on the other hand, lie in the subperitoneal tissue in front of the fascia, and the branches to the gluteal region emerge in special sheaths of this tissue, above and below the Piriformis muscle.\n\nhttps://en.wikipedia.org/wiki/Piriformis_fascia","acromial-part-of-deltoid-muscle":"The deltoid muscle is the muscle forming the rounded contour of the human shoulder.\n\nIt is also known as the 'common shoulder muscle', particularly in other animals such as the domestic cat.\n\nAnatomically, the deltoid muscle appears to be made up of three distinct sets of muscle fibers, namely the\n\n-anterior or clavicular part (pars clavicularis)\n-posterior or scapular part (pars scapularis)\n-intermediate or acromial part (pars acromialis)\n\nHowever, electromyography suggests that it consists of at least seven groups that can be independently coordinated by the nervous system.\n\nIt was previously called the deltoideus (plural deltoidei) and the name is still used by some anatomists.\n\nIt is called so because it is in the shape of the Greek capital letter delta (Δ).\n\nDeltoid is also further shortened in slang as \"delt\".\nA study of 30 shoulders revealed an average mass of 191.9 grams (6.77 oz) in humans, ranging from 84 grams (3.0 oz) to 366 grams (12.9 oz).\n\n== Structure ==\n\nPrevious studies showed that the insertions of the tendons of the deltoid muscle parts formed three discrete sets of muscle fibers, often referred to as \"heads\":\n\n-The anterior or clavicular fibers arise from most of the anterior border and upper surface of the lateral third of the clavicle.\n\nThe anterior origin lies adjacent to the lateral fibers of the pectoralis major muscle as do the end tendons of both muscles.\n\nThese muscle fibers are closely related and only a small chiasmatic space, through which the cephalic vein passes, prevents the two muscles from forming a continuous muscle mass.\n\nThe anterior deltoids are commonly called front delts for short.\n\n-Intermediate or acromial fibers arise from the superior surface of the acromion process of the scapula.\n\nThey are also commonly called lateral deltoid.\n\nThis muscle is also called middle delts, outer delts, or side delts for short.\n\nThey are also mistakenly called medial deltoid, which is wrong, as their origin is the least medial portion of the deltoid.\n\n-Posterior or spinal fibers arise from the lower lip of the posterior border of the spine of the scapula.\n\nThey are commonly called posterior deltoid or rear deltoid (rear delts for short).\n\nFick divided these three groups of fibers, often referred to as parts (Latin: pars) or bands, into seven functional components as did Kapandji and Sakoma Y et al. : the anterior part has two components (I and II); the lateral one (III); and the posterior four (IV, V, VI, and VII) components.\n\nIn standard anatomical position (with the upper limb hanging alongside the body), the central components (II, III, and IV) lie lateral to the axis of abduction and therefore contribute to abduction from the start of the movement while the other components (I, V, VI, and VII) then act as adductors.\n\nDuring abduction most of these latter components (except VI and VII which always act as adductors) are displaced laterally and progressively start to abduct.\n\n=== Insertion ===\n\nFrom this extensive origin the fibers converge toward their insertion on the deltoid tuberosity on the middle of the lateral aspect of the shaft of the humerus; the intermediate fibers passing vertically, the anterior obliquely backward and laterally, and the posterior obliquely forward and laterally.\n\nThough traditionally described as a single insertion, the deltoid insertion is divided into two or three discernible areas corresponding to the muscle's three areas of origin.\n\nThe insertion is an arch-like structure with strong anterior and posterior fascial connections flanking an intervening tissue bridge.\n\nIt additionally gives off extensions to the deep brachial fascia.\n\nFurthermore, the deltoid fascia contributes to the brachial fascia and is connected to the medial and lateral intermuscular septa.\n\n=== Blood supply ===\n\nThe deltoid is supplied by the thoracoacromial artery (acromial and deltoid branches), the circumflex humeral arteries, and the profunda brachii artery (deltoid branch). (Standring, 2005).\n\n=== Nerve supply ===\n\nThe deltoid is innervated by the axillary nerve.\n\nThe axillary nerve originates from the anterior rami of the cervical nerves C5 and C6, via the superior trunk, posterior division of the superior trunk, and the posterior cord of the brachial plexus.Studies have shown that there are seven neuromuscular segments to the deltoid muscle.\n\nThree of these lie in the anatomical anterior head of the deltoid, one in the anatomical middle head, and three in the anatomical posterior head of the deltoid.\n\nThese neuromuscular segments are supplied by smaller branches of the axillary nerve, and work in coordination with other muscles of the shoulder girdle include pectoralis major and supraspinatus.The axillary nerve is sometimes damaged during surgical procedures of the axilla, such as for breast cancer.\n\nIt may also be injured by anterior dislocation of the head of the humerus.\n\n== Function ==\n\nWhen all its fibers contract simultaneously, the deltoid is the prime mover of arm abduction along the frontal plane.\n\nThe arm must be medially rotated for the deltoid to have maximum effect.\n\nThis makes the deltoid an antagonist muscle of the pectoralis major and latissimus dorsi during arm adduction.\n\nThe anterior fibers assist the pectoralis major to flex the shoulder.\n\nThe anterior deltoid also works in tandem with the subscapularis, pecs and lats to internally (medially) rotate the humerus.\n\nThe intermediate fibers perform basic shoulder abduction when the shoulder is internally rotated, and perform shoulder transverse abduction when the shoulder is externally rotated.\n\nThey are not utilized significantly during strict transverse extension (shoulder internally rotated) such as in rowing movements, which use the posterior fibers.\n\nThe posterior fibers assist the latissimus dorsi to extend the shoulder.\n\nOther transverse extensors, the infraspinatus and teres minor, also work in tandem with the posterior deltoid as external (lateral) rotators, antagonists to strong internal rotators like the pecs and lats.\n\nAn important function of the deltoid in humans is preventing the dislocation of the humeral head when a person carries heavy loads.\n\nThe function of abduction also means that it would help keep carried objects a safer distance away from the thighs to avoid hitting them, as during a farmer's walk.\n\nIt also ensures a precise and rapid movement of the glenohumeral joint needed for hand and arm manipulation.\n\nThe intermediate fibers are in the most efficient position to perform this role, though like basic abduction movements (such as lateral raise) it is assisted by simultaneous co-contraction of anterior/posterior fibers.\n\nThe deltoid is responsible for elevating the arm in the scapular plane and its contraction in doing this also elevates the humeral head.\n\nTo stop this compressing against the undersurface of the acromion the humeral head and injuring the supraspinatus tendon, there is a simultaneous contraction of some of the muscles of the rotator cuff: the infraspinatus and subscapularis primarily perform this role.\n\nIn spite of this there may be still a 1–3 mm upward movement of the head of the humerus during the first 30° to 60° of arm elevation.\n\n== Clinical significance ==\n\nThe most common abnormalities affecting the deltoid are tears, fatty atrophy, and enthesopathy.\n\nDeltoid muscle tears are unusual and frequently related to traumatic shoulder dislocation or massive rotator cuff tears.\n\nMuscle atrophy is the result of various causes, including aging, disuse, denervation, muscular dystrophy, cachexia and iatrogenic injury.\n\nDeltoideal humeral enthesopathy is an exceedingly rare condition related to mechanical stress.\n\nConversely, deltoideal acromial enthesopathy is likely a hallmark of seronegative spondylarthropathies and its detection should probably be followed by pertinent clinical and serological investigation.\n\n== Other animals ==\n\nThe deltoid is also found in members of the great ape family other than humans.\n\nThe human deltoid is of similar proportionate size as the muscles of the rotator cuff in apes like the orangutan, which engage in brachiation and possess the muscle mass needed to support the body weight by the shoulders.\n\nIn other apes, like the common chimpanzee, the deltoid is much larger than in humans, weighing an average of 383.3 gram compared to 191.9 gram in humans.\n\nThis reflects the need to strengthen the shoulders, particularly the rotatory cuff, in knuckle walking apes for the purpose of supporting the entire body weight.\n\nThe deltoid muscle is a main component of both the bat and pterosaur wing musculature, but in crown-group birds it is strongly reduced, as they favour sternum attached muscles.\n\nSome Mesozoic flying theropods however had more developed deltoideus.\n\nhttps://en.wikipedia.org/wiki/Deltoid_muscle","clavicular-part-of-deltoid-muscle":"The deltoid muscle is the muscle forming the rounded contour of the human shoulder.\n\nIt is also known as the 'common shoulder muscle', particularly in other animals such as the domestic cat.\n\nAnatomically, the deltoid muscle appears to be made up of three distinct sets of muscle fibers, namely the\n\n-anterior or clavicular part (pars clavicularis)\n-posterior or scapular part (pars scapularis)\n-intermediate or acromial part (pars acromialis)\n\nHowever, electromyography suggests that it consists of at least seven groups that can be independently coordinated by the nervous system.\n\nIt was previously called the deltoideus (plural deltoidei) and the name is still used by some anatomists.\n\nIt is called so because it is in the shape of the Greek capital letter delta (Δ).\n\nDeltoid is also further shortened in slang as \"delt\".\nA study of 30 shoulders revealed an average mass of 191.9 grams (6.77 oz) in humans, ranging from 84 grams (3.0 oz) to 366 grams (12.9 oz).\n\n== Structure ==\n\nPrevious studies showed that the insertions of the tendons of the deltoid muscle parts formed three discrete sets of muscle fibers, often referred to as \"heads\":\n\n-The anterior or clavicular fibers arise from most of the anterior border and upper surface of the lateral third of the clavicle.\n\nThe anterior origin lies adjacent to the lateral fibers of the pectoralis major muscle as do the end tendons of both muscles.\n\nThese muscle fibers are closely related and only a small chiasmatic space, through which the cephalic vein passes, prevents the two muscles from forming a continuous muscle mass.\n\nThe anterior deltoids are commonly called front delts for short.\n\n-Intermediate or acromial fibers arise from the superior surface of the acromion process of the scapula.\n\nThey are also commonly called lateral deltoid.\n\nThis muscle is also called middle delts, outer delts, or side delts for short.\n\nThey are also mistakenly called medial deltoid, which is wrong, as their origin is the least medial portion of the deltoid.\n\n-Posterior or spinal fibers arise from the lower lip of the posterior border of the spine of the scapula.\n\nThey are commonly called posterior deltoid or rear deltoid (rear delts for short).\n\nFick divided these three groups of fibers, often referred to as parts (Latin: pars) or bands, into seven functional components as did Kapandji and Sakoma Y et al. : the anterior part has two components (I and II); the lateral one (III); and the posterior four (IV, V, VI, and VII) components.\n\nIn standard anatomical position (with the upper limb hanging alongside the body), the central components (II, III, and IV) lie lateral to the axis of abduction and therefore contribute to abduction from the start of the movement while the other components (I, V, VI, and VII) then act as adductors.\n\nDuring abduction most of these latter components (except VI and VII which always act as adductors) are displaced laterally and progressively start to abduct.\n\n=== Insertion ===\n\nFrom this extensive origin the fibers converge toward their insertion on the deltoid tuberosity on the middle of the lateral aspect of the shaft of the humerus; the intermediate fibers passing vertically, the anterior obliquely backward and laterally, and the posterior obliquely forward and laterally.\n\nThough traditionally described as a single insertion, the deltoid insertion is divided into two or three discernible areas corresponding to the muscle's three areas of origin.\n\nThe insertion is an arch-like structure with strong anterior and posterior fascial connections flanking an intervening tissue bridge.\n\nIt additionally gives off extensions to the deep brachial fascia.\n\nFurthermore, the deltoid fascia contributes to the brachial fascia and is connected to the medial and lateral intermuscular septa.\n\n=== Blood supply ===\n\nThe deltoid is supplied by the thoracoacromial artery (acromial and deltoid branches), the circumflex humeral arteries, and the profunda brachii artery (deltoid branch). (Standring, 2005).\n\n=== Nerve supply ===\n\nThe deltoid is innervated by the axillary nerve.\n\nThe axillary nerve originates from the anterior rami of the cervical nerves C5 and C6, via the superior trunk, posterior division of the superior trunk, and the posterior cord of the brachial plexus.Studies have shown that there are seven neuromuscular segments to the deltoid muscle.\n\nThree of these lie in the anatomical anterior head of the deltoid, one in the anatomical middle head, and three in the anatomical posterior head of the deltoid.\n\nThese neuromuscular segments are supplied by smaller branches of the axillary nerve, and work in coordination with other muscles of the shoulder girdle include pectoralis major and supraspinatus.The axillary nerve is sometimes damaged during surgical procedures of the axilla, such as for breast cancer.\n\nIt may also be injured by anterior dislocation of the head of the humerus.\n\n== Function ==\n\nWhen all its fibers contract simultaneously, the deltoid is the prime mover of arm abduction along the frontal plane.\n\nThe arm must be medially rotated for the deltoid to have maximum effect.\n\nThis makes the deltoid an antagonist muscle of the pectoralis major and latissimus dorsi during arm adduction.\n\nThe anterior fibers assist the pectoralis major to flex the shoulder.\n\nThe anterior deltoid also works in tandem with the subscapularis, pecs and lats to internally (medially) rotate the humerus.\n\nThe intermediate fibers perform basic shoulder abduction when the shoulder is internally rotated, and perform shoulder transverse abduction when the shoulder is externally rotated.\n\nThey are not utilized significantly during strict transverse extension (shoulder internally rotated) such as in rowing movements, which use the posterior fibers.\n\nThe posterior fibers assist the latissimus dorsi to extend the shoulder.\n\nOther transverse extensors, the infraspinatus and teres minor, also work in tandem with the posterior deltoid as external (lateral) rotators, antagonists to strong internal rotators like the pecs and lats.\n\nAn important function of the deltoid in humans is preventing the dislocation of the humeral head when a person carries heavy loads.\n\nThe function of abduction also means that it would help keep carried objects a safer distance away from the thighs to avoid hitting them, as during a farmer's walk.\n\nIt also ensures a precise and rapid movement of the glenohumeral joint needed for hand and arm manipulation.\n\nThe intermediate fibers are in the most efficient position to perform this role, though like basic abduction movements (such as lateral raise) it is assisted by simultaneous co-contraction of anterior/posterior fibers.\n\nThe deltoid is responsible for elevating the arm in the scapular plane and its contraction in doing this also elevates the humeral head.\n\nTo stop this compressing against the undersurface of the acromion the humeral head and injuring the supraspinatus tendon, there is a simultaneous contraction of some of the muscles of the rotator cuff: the infraspinatus and subscapularis primarily perform this role.\n\nIn spite of this there may be still a 1–3 mm upward movement of the head of the humerus during the first 30° to 60° of arm elevation.\n\n== Clinical significance ==\n\nThe most common abnormalities affecting the deltoid are tears, fatty atrophy, and enthesopathy.\n\nDeltoid muscle tears are unusual and frequently related to traumatic shoulder dislocation or massive rotator cuff tears.\n\nMuscle atrophy is the result of various causes, including aging, disuse, denervation, muscular dystrophy, cachexia and iatrogenic injury.\n\nDeltoideal humeral enthesopathy is an exceedingly rare condition related to mechanical stress.\n\nConversely, deltoideal acromial enthesopathy is likely a hallmark of seronegative spondylarthropathies and its detection should probably be followed by pertinent clinical and serological investigation.\n\n== Other animals ==\n\nThe deltoid is also found in members of the great ape family other than humans.\n\nThe human deltoid is of similar proportionate size as the muscles of the rotator cuff in apes like the orangutan, which engage in brachiation and possess the muscle mass needed to support the body weight by the shoulders.\n\nIn other apes, like the common chimpanzee, the deltoid is much larger than in humans, weighing an average of 383.3 gram compared to 191.9 gram in humans.\n\nThis reflects the need to strengthen the shoulders, particularly the rotatory cuff, in knuckle walking apes for the purpose of supporting the entire body weight.\n\nThe deltoid muscle is a main component of both the bat and pterosaur wing musculature, but in crown-group birds it is strongly reduced, as they favour sternum attached muscles.\n\nSome Mesozoic flying theropods however had more developed deltoideus.\n\nhttps://en.wikipedia.org/wiki/Deltoid_muscle","scapular-spinal-part-of-deltoid-muscle":"The deltoid muscle is the muscle forming the rounded contour of the human shoulder.\n\nIt is also known as the 'common shoulder muscle', particularly in other animals such as the domestic cat.\n\nAnatomically, the deltoid muscle appears to be made up of three distinct sets of muscle fibers, namely the\n\n-anterior or clavicular part (pars clavicularis)\n-posterior or scapular part (pars scapularis)\n-intermediate or acromial part (pars acromialis)\n\nHowever, electromyography suggests that it consists of at least seven groups that can be independently coordinated by the nervous system.\n\nIt was previously called the deltoideus (plural deltoidei) and the name is still used by some anatomists.\n\nIt is called so because it is in the shape of the Greek capital letter delta (Δ).\n\nDeltoid is also further shortened in slang as \"delt\".\nA study of 30 shoulders revealed an average mass of 191.9 grams (6.77 oz) in humans, ranging from 84 grams (3.0 oz) to 366 grams (12.9 oz).\n\n== Structure ==\n\nPrevious studies showed that the insertions of the tendons of the deltoid muscle parts formed three discrete sets of muscle fibers, often referred to as \"heads\":\n\n-The anterior or clavicular fibers arise from most of the anterior border and upper surface of the lateral third of the clavicle.\n\nThe anterior origin lies adjacent to the lateral fibers of the pectoralis major muscle as do the end tendons of both muscles.\n\nThese muscle fibers are closely related and only a small chiasmatic space, through which the cephalic vein passes, prevents the two muscles from forming a continuous muscle mass.\n\nThe anterior deltoids are commonly called front delts for short.\n\n-Intermediate or acromial fibers arise from the superior surface of the acromion process of the scapula.\n\nThey are also commonly called lateral deltoid.\n\nThis muscle is also called middle delts, outer delts, or side delts for short.\n\nThey are also mistakenly called medial deltoid, which is wrong, as their origin is the least medial portion of the deltoid.\n\n-Posterior or spinal fibers arise from the lower lip of the posterior border of the spine of the scapula.\n\nThey are commonly called posterior deltoid or rear deltoid (rear delts for short).\n\nFick divided these three groups of fibers, often referred to as parts (Latin: pars) or bands, into seven functional components as did Kapandji and Sakoma Y et al. : the anterior part has two components (I and II); the lateral one (III); and the posterior four (IV, V, VI, and VII) components.\n\nIn standard anatomical position (with the upper limb hanging alongside the body), the central components (II, III, and IV) lie lateral to the axis of abduction and therefore contribute to abduction from the start of the movement while the other components (I, V, VI, and VII) then act as adductors.\n\nDuring abduction most of these latter components (except VI and VII which always act as adductors) are displaced laterally and progressively start to abduct.\n\n=== Insertion ===\n\nFrom this extensive origin the fibers converge toward their insertion on the deltoid tuberosity on the middle of the lateral aspect of the shaft of the humerus; the intermediate fibers passing vertically, the anterior obliquely backward and laterally, and the posterior obliquely forward and laterally.\n\nThough traditionally described as a single insertion, the deltoid insertion is divided into two or three discernible areas corresponding to the muscle's three areas of origin.\n\nThe insertion is an arch-like structure with strong anterior and posterior fascial connections flanking an intervening tissue bridge.\n\nIt additionally gives off extensions to the deep brachial fascia.\n\nFurthermore, the deltoid fascia contributes to the brachial fascia and is connected to the medial and lateral intermuscular septa.\n\n=== Blood supply ===\n\nThe deltoid is supplied by the thoracoacromial artery (acromial and deltoid branches), the circumflex humeral arteries, and the profunda brachii artery (deltoid branch). (Standring, 2005).\n\n=== Nerve supply ===\n\nThe deltoid is innervated by the axillary nerve.\n\nThe axillary nerve originates from the anterior rami of the cervical nerves C5 and C6, via the superior trunk, posterior division of the superior trunk, and the posterior cord of the brachial plexus.Studies have shown that there are seven neuromuscular segments to the deltoid muscle.\n\nThree of these lie in the anatomical anterior head of the deltoid, one in the anatomical middle head, and three in the anatomical posterior head of the deltoid.\n\nThese neuromuscular segments are supplied by smaller branches of the axillary nerve, and work in coordination with other muscles of the shoulder girdle include pectoralis major and supraspinatus.The axillary nerve is sometimes damaged during surgical procedures of the axilla, such as for breast cancer.\n\nIt may also be injured by anterior dislocation of the head of the humerus.\n\n== Function ==\n\nWhen all its fibers contract simultaneously, the deltoid is the prime mover of arm abduction along the frontal plane.\n\nThe arm must be medially rotated for the deltoid to have maximum effect.\n\nThis makes the deltoid an antagonist muscle of the pectoralis major and latissimus dorsi during arm adduction.\n\nThe anterior fibers assist the pectoralis major to flex the shoulder.\n\nThe anterior deltoid also works in tandem with the subscapularis, pecs and lats to internally (medially) rotate the humerus.\n\nThe intermediate fibers perform basic shoulder abduction when the shoulder is internally rotated, and perform shoulder transverse abduction when the shoulder is externally rotated.\n\nThey are not utilized significantly during strict transverse extension (shoulder internally rotated) such as in rowing movements, which use the posterior fibers.\n\nThe posterior fibers assist the latissimus dorsi to extend the shoulder.\n\nOther transverse extensors, the infraspinatus and teres minor, also work in tandem with the posterior deltoid as external (lateral) rotators, antagonists to strong internal rotators like the pecs and lats.\n\nAn important function of the deltoid in humans is preventing the dislocation of the humeral head when a person carries heavy loads.\n\nThe function of abduction also means that it would help keep carried objects a safer distance away from the thighs to avoid hitting them, as during a farmer's walk.\n\nIt also ensures a precise and rapid movement of the glenohumeral joint needed for hand and arm manipulation.\n\nThe intermediate fibers are in the most efficient position to perform this role, though like basic abduction movements (such as lateral raise) it is assisted by simultaneous co-contraction of anterior/posterior fibers.\n\nThe deltoid is responsible for elevating the arm in the scapular plane and its contraction in doing this also elevates the humeral head.\n\nTo stop this compressing against the undersurface of the acromion the humeral head and injuring the supraspinatus tendon, there is a simultaneous contraction of some of the muscles of the rotator cuff: the infraspinatus and subscapularis primarily perform this role.\n\nIn spite of this there may be still a 1–3 mm upward movement of the head of the humerus during the first 30° to 60° of arm elevation.\n\n== Clinical significance ==\n\nThe most common abnormalities affecting the deltoid are tears, fatty atrophy, and enthesopathy.\n\nDeltoid muscle tears are unusual and frequently related to traumatic shoulder dislocation or massive rotator cuff tears.\n\nMuscle atrophy is the result of various causes, including aging, disuse, denervation, muscular dystrophy, cachexia and iatrogenic injury.\n\nDeltoideal humeral enthesopathy is an exceedingly rare condition related to mechanical stress.\n\nConversely, deltoideal acromial enthesopathy is likely a hallmark of seronegative spondylarthropathies and its detection should probably be followed by pertinent clinical and serological investigation.\n\n== Other animals ==\n\nThe deltoid is also found in members of the great ape family other than humans.\n\nThe human deltoid is of similar proportionate size as the muscles of the rotator cuff in apes like the orangutan, which engage in brachiation and possess the muscle mass needed to support the body weight by the shoulders.\n\nIn other apes, like the common chimpanzee, the deltoid is much larger than in humans, weighing an average of 383.3 gram compared to 191.9 gram in humans.\n\nThis reflects the need to strengthen the shoulders, particularly the rotatory cuff, in knuckle walking apes for the purpose of supporting the entire body weight.\n\nThe deltoid muscle is a main component of both the bat and pterosaur wing musculature, but in crown-group birds it is strongly reduced, as they favour sternum attached muscles.\n\nSome Mesozoic flying theropods however had more developed deltoideus.\n\nhttps://en.wikipedia.org/wiki/Deltoid_muscle","subscapularis-muscle":"The subscapularis is a large triangular muscle which fills the subscapular fossa and inserts into the lesser tubercle of the humerus and the front of the capsule of the shoulder-joint.\n\n== Structure ==\n\nIt arises from its medial two-thirds and from the lower two-thirds of the groove on the axillary border (subscapular fossa) of the scapula.\n\nSome fibers arise from tendinous laminae, which intersect the muscle and are attached to ridges on the bone; others from an aponeurosis, which separates the muscle from the teres major and the long head of the triceps brachii.\n\nThe fibers pass laterally and coalesce into a tendon that is inserted into the lesser tubercle of the humerus and the anterior part of the shoulder-joint capsule.\n\nTendinous fibers extend to the greater tubercle with insertions into the bicipital groove.\n\n=== Relations ===\n\nThe tendon of the muscle is separated from the neck of the scapula by a large bursa, which communicates with the cavity of the shoulder-joint through an aperture in the capsule.\n\nThe subscapularis is separated from the serratus anterior by the subscapularis (supraserratus) bursa.\n\n=== Nerve supply ===\n\nThe subscapularis is supplied by the upper and lower subscapular nerves, branches of the posterior cord of the brachial plexus. (C5-C6)\n\n== Function ==\n\nThe subscapularis rotates the head of the humerus medially (internal rotation) and adducts it; when the arm is raised, it draws the humerus forward and downward.\n\nIt is a powerful defense to the front of the shoulder-joint, preventing displacement of the head of the humerus.\n\n== Clinical significance ==\n\n=== Examination ===\n\nThe Gerber Lift-off test is the established clinical test for examination of the subscapularis.\n\nThe bear hug test (internal rotation while palm is held on opposite shoulder and elbow is held in a position of maximal anterior translation) for subscapularis muscle tears has high sensitivity.\n\nPositive bear-hug and belly press tests indicate significant tearing of subscapularis.\n\n=== Imaging ===\n\nThere is no singularly imaging device or technique for a satisfying and complete subscapularis examination, but rather the combination of the sagittal oblique MRI / short-axis US and axial MRI / long-axis US planes seems to generate useful results.\n\nAdditionally, lesser tuberosity bony changes have been associated with subscapularis tendon tears.\n\nFindings with cysts seem to be more specific and combined findings with cortical irregularities more sensitive.\n\nAnother fact typically for the subscapularis muscle is the fatty infiltration of the superior portions, while sparing the inferior portions.\n\nSince the long biceps tendon absents itself from the shoulder joint through the rotator cuff interval, it is easily possible to distinguish between the supraspinatus and the subscapularis tendon.\n\nThose two tendons build the interval sling.\n\n=== Ultrasonography ===\n\nMack et al. developed an ultrasonographic procedure with which it is possible to explore almost the complete rotator cuff within six steps.\n\nIt unveils clearly the whole area from the subedge of the subscapularis tendon until the intersection between the infraspinatus tendon and musculus teres minor.\n\nOne of six steps does focus on the subscapularis tendon.\n\nIn the first instance the examinator guides the applicator to the proximal humerus as perpendicularly as possible to the sulcus intertubercularis.\n\nGliding now medially shows the insertion of the subscapularis tendon.\n\n==== Longitudinal plane of the musculus subscapularis and its tendon ====\nThe subscapularis tendon lies approximately 3 to 5 cm under the surface.\n\nQuite deep for ultrasonography, and therefore displaying through a highly penetrative 5 MHz linear applicator is worth a try.\n\nAnd it really turned out to ease a detailed examination of the muscle which just abuts to the scapula.\n\nHowever, the tendon of primary interest does not get mapped as closely as desired.\n\nAs anatomical analysis showed, it is only by external rotation possible to see the ventral part of the joint socket and its labrum.\n\nWhile at the neutral position the tuberculum minus occludes the view.\n\nSumming up it is through an external arm rotation and a medially applied 5 MHz sector sonic head possible to display the ventral part of the joint socket and its labrum with notedly lower echogenicity.\n\nThe following sectional planes are defined for the sonographic examination of the different shoulder joint structures:\n\n==== Tissue harmonic imaging ====\n\nPrimarily in abdominal imaging, tissue harmonic imaging (THI) gets more and more valued and used additionally to conventional ultrasonography.\n\nTHI involves the use of harmonic frequencies that originate within the tissue as a result of nonlinear wave front propagation and are not present in the incident beam.\n\nThese harmonic signals may arise differently at anatomic sites with similar impedances and thus lead to higher contrast resolution.” Along with higher contrast resolution it has an elevated signal-to-noise ratio and significantly reduced inter- and intraobserver variability compared with conventional US.\n\nAdditionally it is possible to nearly eliminate ordinary US artifacts, i.e. side-lobe, near-field artifacts, reverberation artifacts.\n\nAs aforementioned THI has already led to enhanced abdominal, breast, vascular and cardiac sonography.\nFor musculo-skeletal aspects THI has not been used that much, although this method features some useful potential.\n\nFor example, for the still tricky discrimination between the presence of a hypoechoic defect and/or loss of the outer tendon convexity/non-visualization of the tendon, that is between partial- and full-thickness rotator cuff tears.\n\nIn comparison to a checking MR Arthrography Strobel K. et al. has arrived at the conclusion that through THI it is possible to achieve a generally improved visibility of joint and tendon surfaces, especially superior for subscapularis tendon abnormalities.\n\nhttps://en.wikipedia.org/wiki/Subscapularis_muscle","supraspinatus-muscle":"The supraspinatus (plural supraspinati) is a relatively small muscle of the upper back that runs from the supraspinous fossa superior portion of the scapula (shoulder blade) to the greater tubercle of the humerus.\n\nIt is one of the four rotator cuff muscles and also abducts the arm at the shoulder.\n\nThe spine of the scapula separates the supraspinatus muscle from the infraspinatus muscle, which originates below the spine.\n\n== Structure ==\n\nThe supraspinatus muscle arises from the supraspinous fossa, a shallow depression in the body of the scapula above its spine.\n\nThe supraspinatus muscle tendon passes laterally beneath the cover of the acromion.\n\nResearch in 1996 showed that the postero-lateral origin was more lateral than classically described.The supraspinatus tendon is inserted into the superior facet of the greater tubercle of the humerus.\n\nThe distal attachments of the three rotator cuff muscles that insert into the greater tubercle of the humerus can be abbreviated as SIT when viewed from superior to inferior (for supraspinatus, infraspinatus, and teres minor), or SITS when the subscapularis muscle, which attaches to the lesser tubercle of the humerus, is included.\n\n=== Nerve supply ===\n\nThe suprascapular nerve (C5) innervates the supraspinatus muscle as well as the infraspinatus muscle.\n\nIt comes from the upper trunk of the brachial plexus.\nThis nerve can be damaged along its course in fractures of the overlying clavicle, which can reduce the person's ability to initiate the abduction.\n\n== Function ==\n\nThe supraspinatus muscle performs abduction of the arm, and pulls the head of the humerus medially towards the glenoid cavity.\n\nIt independently prevents the head of the humerus to slip inferiorly.\n\nThe supraspinatus works in cooperation with the deltoid muscle to perform abduction, including when the arm is in adducted position.\n\nBeyond 15 degrees the deltoid muscle becomes increasingly more effective at abducting the arm and becomes the main propagator of this action.\n\n== Clinical significance ==\n\n=== Tear ===\n\n=Diagnosis=\n\nAntero-posterior projectional radiography of the shoulder may demonstrate a high-riding humeral head, with an acromiohumeral distance of less than 7 mm.\n\n=Repair=\n\nOne study has indicated that arthroscopic surgery for full-thickness supraspinatus tears is effective for improving shoulder functionality.\n\nA comparative effectiveness review of nonoperative and operative treatments for rotator cuff tears was performed at the University of Alberta Evidence-based Practice Center in 2010.\n\nThe review identified one study which reported that, \"Patients receiving early surgery had superior function compared with the delayed surgical group\".\n\nThe review noted that the level of significance of the study was not reported, and the review chose not to include it as one of their conclusions.\n\nInstead it concluded that \"The paucity of evidence related to early versus delayed surgery is of particular concern, as patients and providers must decide whether to attempt initial nonoperative management or proceed immediately with surgical repair\".\n\nIn terms of operative techniques, differences in neither cuff integrity nor shoulder function were reported in studies comparing single-row versus double-row suture anchor fixation and mattress locking versus absorbable sutures.\n\nPostoperatively, a slight advantage was evident in patients who performed continuous passive motion alongside physical therapy, as opposed to those who solely performed physical therapy.\n\nThere is insufficient evidence to adequately compare the effects of operative against nonoperative interventions.\n\nComplications were reported very seldom, or were not determined to be clinically significant.A 2016 study evaluating the effectiveness of arthroscopic treatment of rotator cuff calcification firmly supported surgical intervention.\n\nCalcification of the supraspinatus tendon is a major contributor to shoulder pain in the general population and is often worsened following a supraspinatus tear.\n\nThe results of the study included the return to sports and original functionality of 95.8% of the patients after a mean of 5.3 post-operative months.\n\nA significant decrease in pain was observed over time following removal of the calcification.\n\nThe study showed the overall effectiveness of arthroscopic procedures on shoulder repair, and the lack of risk experienced.\n\nBefore surgery, supraspinatus tendonitis should be ruled out as the cause of pain.\n\nhttps://en.wikipedia.org/wiki/Supraspinatus_muscle","teres-minor-muscle":"The teres minor (Latin teres meaning 'rounded') is a narrow, elongated muscle of the rotator cuff.\n\nThe muscle originates from the lateral border and adjacent posterior surface of the corresponding right or left scapula and inserts at both the greater tubercle of the humerus and the posterior surface of the joint capsule.\n\nThe primary function of the teres minor is to modulate the action of the deltoid, preventing the humeral head from sliding upward as the arm is abducted.\n\nIt also functions to rotate the humerus laterally.\n\nThe teres minor is innervated by the axillary nerve.\n\n== Structure ==\n\nIt arises from the dorsal surface of the axillary border of the scapula for the upper two-thirds of its extent, and from two aponeurotic laminae, one of which separates it from the infraspinatus muscle, the other from the teres major muscle.\n\nIts fibers run obliquely upwards and laterally; the upper ones end in a tendon which is inserted into the lowest of the three impressions on the greater tubercle of the humerus; the lowest fibers are inserted directly into the humerus immediately below this impression.\n\n=== Relations ===\n\nThe teres minor originates at the lateral border and adjacent posterior surface of the scapula.\n\nIt inserts at the greater tubercle of the humerus.\n\nThe tendon of this muscle passes across, and is united with, the posterior part of the capsule of the shoulder-joint.\n\n=== Innervation ===\n\nThe muscle is innervated by the posterior branch of axillary nerve where it forms a pseudoganglion.\n\nA pseudoganglion has no nerve cells but nerve fibres are present.\n\nDamage to the fibers innervating the teres minor is clinically significant.\n\n=== Variation ===\n\nSometimes a group of muscle fibres from teres minor may be fused with infraspinatus.\n\n== Function ==\n\nThe infraspinatus and teres minor attach to head of the humerus; as part of the rotator cuff they help hold the humeral head in the glenoid cavity of the scapula.\n\nThey work in tandem with the posterior deltoid to externally (laterally) rotate the humerus, as well as adduction.\n\nTeres Minor can produce only very small scapular plane adduction during maximal contraction (Hughes RE, An KN 1996) with adductor moment arm of approximately 0.2 cm at 45° of shoulder internal rotation and approximately 0.1 cm at 45° of shoulder external rotation.\n\n== Clinical significance ==\n\n=== Injury ===\n\nThere are two types of rotator cuff injuries: acute tears and chronic tears.\n\nAcute tears occur as a result of a sudden movement.\n\nThis might include throwing a powerful pitch, holding a fast moving rope during water sports, falling over onto an outstretched hand at speed, or making a sudden thrust with the paddle in kayaking.\n\nA chronic tear develops over a period of time.\n\nThey usually occur at or near the tendon, as a result of the tendon rubbing against the underlying bone.\n\nThe teres minor is typically normal following a rotator cuff tear.\n\n=== Imaging ===\n\nAtrophy of the teres minor muscle is often a consequence of a rotator cuff tear, but common isolated teres minor atrophies have also been found.\n\nA quadrangular space syndrome causes excessive and or chronically compression of the structures which pass through this anatomical tunnel.\n\nThe axillary nerve and the posterior humeral circumflex artery pass through the space.\n\nPeople affected note shoulder pain and paresthesia down the arm first and foremost in abduction, extension, external rotation and overhead activity.\n\nSelective atrophy of the teres minor muscle has been seen and pulled together directly with compression of the corresponding axillary nerve branch or posterior humeral circumflex artery.\n\nFibrous bands, cysts of the glenoid labrum, lipoma or dilated veins can occupy the quadrilateral space pathologically.\n\nSimilar symptoms are common with anterior shoulder dislocation, humeral neck fracture, brachial plexus injury and thoracic outlet and inlet syndrome.\n\nIt is important to include those pathologies for a complete as possible differential diagnosis.\n\nUltrasonography is a tool to detect a fatty degenerative atrophy of the teres minor and shows in affected muscles increased echogenicity and betimes a slight reduction in muscle bulk.\n\nMR imaging helps to consolidate the diagnosis of neurogenic muscle atrophy.\n\nExtracellular edema after traumatic events causing neural damage show an increased signal intensity on T2-weighted MRI sequences and normal intensity on T1-weighted sequences.\n\nPosterior humeral circumflex artery compression and reduced blood flow in stressful arm positions and or maneuvers can be diagnosed by a Doppler ultrasonography.\n\nThe nerve should be detected adjacent to the vessel.\n\nIn an elevated arm position the axillary neurovascular bundle can be seen at the posterior axillary fold just before it perforates the deltoideus, while the posterior course is well visible in the neutral position.\n\nFor a detailed assessment of the artery, a MR angiography is required.\n\nThe major task of an ultrasonographic examination is to rule out any space occupying mass.\n\nAdditional electromyography is helpful to reveal any decelerated nerve conduction velocity, and thus denervation of the concerned muscle.\n\nhttps://en.wikipedia.org/wiki/Teres_minor_muscle","infraspinatus-muscle":"In human anatomy, the infraspinatus muscle is a thick triangular muscle, which occupies the chief part of the infraspinatous fossa.\n\nAs one of the four muscles of the rotator cuff, the main function of the infraspinatus is to externally rotate the humerus and stabilize the shoulder joint.\n\n== Structure ==\n\nIt attaches medially to the infraspinous fossa of the scapula and laterally to the middle facet of the greater tubercle of the humerus.\n\nThe muscle arises by fleshy fibers from the medial two-thirds of the infraspinatous fossa, and by tendinous fibers from the ridges on its surface; it also arises from the infraspinatous fascia which covers it, and separates it from the teres major and teres minor.\n\nThe fibers converge to a tendon, which glides over the lateral border of the spine of the scapula and passing across the posterior part of the capsule of the shoulder-joint, is inserted into the middle impression on the greater tubercle of the humerus.\n\nThe trapezoidal insertion of the infraspinatus onto the humerus is much larger than the equivalent insertion of the supraspinatus, the reason why the infraspinatus is involved in rotator cuff tears about as frequently as the supraspinatus.\n\n=== Relations ===\n\nThe tendon of this muscle is sometimes separated from the capsule of the shoulder-joint by a bursa, which may communicate with the joint cavity.\n\n=== Innervation ===\n\nThe suprascapular nerve innervates the supraspinatus and infraspinatus muscles.\n\nThese muscles function to abduct and laterally rotate the arm, respectively.\n\n=== Variation ===\n\nThe infraspinatus is frequently fused with the teres minor.\n\n== Function ==\n\nThe infraspinatus is the main external rotator of the shoulder.\n\nWhen the arm is fixed, it adducts the inferior angle of the scapula.\n\nIts synergists are teres minor and the deltoid.\n\nThe infraspinatus and teres minor rotate the head of the humerus outward (external, or lateral, rotation); they also assist in carrying the arm backward.\n\nAdditionally, the infraspinatus reinforces the capsule of the shoulder joint.\n\n== In animals ==\n\nFrom an evolutionary prospective, the pectoral muscles – the pectoralis major and pectoralis minor – are thought to have evolved from a primitive muscle sheet that connected the coracoid to the humerus.\n\nIn late reptilians and early mammals, this muscle structure was displaced dorsally; while most of its components evolved into the pectoralis major, some fibers eventually attached to the scapula and evolved into the supraspinatus, the infraspinatus, and parts of the subscapularis.\n\nhttps://en.wikipedia.org/wiki/Infraspinatus_muscle","teres-major-muscle":"The teres major muscle is a muscle of the upper limb.\n\nIt attaches to the scapula and the humerus and is one of the seven scapulohumeral muscles.\n\nIt is a thick but somewhat flattened muscle.\n\nThe teres major muscle (from Latin teres, meaning \"rounded\") is positioned above the latissimus dorsi muscle and assists in the extension and medial rotation of the humerus.\n\nThis muscle is commonly confused as a rotator cuff muscle, but it is not because it does not attach to the capsule of the shoulder joint, unlike the teres minor muscle for example.\n\n== Structure ==\n\nThe teres major muscle originates on the dorsal surface of the inferior angle and the lower part of the lateral border of the scapula.\n\nThe fibers of teres major insert into the medial lip of the intertubercular sulcus of the humerus.\n\n=== Relations ===\n\nThe tendon, at its insertion, lies behind that of the latissimus dorsi, from which it is separated by a bursa, the two tendons being, however, united along their lower borders for a short distance.\n\nThe fibers of these two muscles run parallel to each other, and both muscles insert at the crest of the lesser tubercle of the humerus (also described as the medial lip of the intertubercular sulcus).\n\nTogether with teres minor muscle, teres major muscle forms the axillary space, through which several important arteries and veins pass.\n\n=== Innervation ===\n\nTeres major is supplied primarily by the lower subscapular nerve and additionally by the thoracodorsal nerve (middle subscapular nerve).\n\nThese are distal to the upper subscapular nerve.\n\nThese three nerves branch off the posterior cord of the brachial plexus.\n\nThe nerves that innervate teres major consist of fibers from spinal nerves C5-C8.\n\n== Function ==\n\nThe teres major is a medial rotator and adductor of the humerus and assists the latissimus dorsi in drawing the previously raised humerus downwards and backwards (extension, but not hyperextension).\n\nIt also helps stabilise the humeral head in the glenoid cavity.\n\n== Injury ==\n\nIsolated teres major injuries are rare.\n\nThey are almost exclusively encountered in professional and high-level recreational athletes— baseball pitchers in particular.\n\nThese injuries can be debilitating, requiring lengthy rehabilitation periods and missed seasons of athletics.\n\nNo clear indications for surgical treatment exist.\n\nOutcomes have been generally good after both nonoperative and operative treatment.\n\nhttps://en.wikipedia.org/wiki/Teres_major_muscle","long-head-of-biceps-brachii":"The biceps or biceps brachii (Latin: musculus biceps brachii, \"two-headed muscle of the arm\") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow.\n\nBoth heads of the muscle arise on the scapula and join to form a single muscle belly which is attached to the upper forearm.\n\nWhile the biceps crosses both the shoulder and elbow joints, its main function is at the elbow where it flexes the forearm and supinates the forearm.\n\nBoth these movements are used when opening a bottle with a corkscrew: first biceps screws in the cork (supination), then it pulls the cork out (flexion).\n\n== Structure ==\n\nThe biceps is one of three muscles in the anterior compartment of the upper arm, along with the brachialis muscle and the coracobrachialis muscle, with which the biceps shares a nerve supply.\n\nThe biceps muscle has two heads, the short head and the long head, distinguished according to their origin at the coracoid process and supraglenoid tubercle of the scapula, respectively.\n\nFrom its origin on the glenoid, the long head remains tendinous as it passes through the shoulder joint and through the intertubercular groove of the humerus.\n\nExtending from its origin on the coracoid, the tendon of the short head runs adjacent to the tendon of the coracobrachialis as the conjoint tendon.\n\nUnlike the other muscles in the anterior compartment of the arm, the biceps muscle crosses two joints, the shoulder joint and the elbow joint.\n\nBoth heads of the biceps join in the middle upper arm to form a single muscle mass usually near the insertion of the deltoid to form a common muscle belly, although several anatomic studies have demonstrated that the muscle bellies remain distinct structures without confluent fibers.\n\nAs the muscle extends distally, the two heads rotate 90 degrees externally before inserting onto the radial tuberosity.\n\nThe short head inserts distally on the tuberosity while the long head inserts proximally closer to the apex of the tuberosity.\n\nThe bicipital aponeurosis, also called the lacertus fibrosus, is a thick fascial band that organizes close to the musculotendinous junction of the biceps and radiates over and inserts onto the ulnar part of the antebrachial fascia.\n\nThe tendon that attaches to the radial tuberosity is partially or completely surrounded by a bursa, the bicipitoradial bursa, which ensures frictionless motion between the biceps tendon and the proximal radius during pronation and supination of the forearm.\n\nTwo muscles lie underneath the biceps brachii.\n\nThese are the coracobrachialis muscle, which like the biceps attaches to the coracoid process of the scapula, and the brachialis muscle which connects to the ulna and along the mid-shaft of the humerus.\n\nBesides those, the brachioradialis muscle is adjacent to the biceps and also inserts on the radius bone, though more distally.\n\n=== Variation ===\n\nTraditionally described as a two-headed muscle, biceps brachii is one of the most variable muscles of the human body and has a third head arising from the humerus in 10% of cases (normal variation)—most commonly originating near the insertion of the coracobrachialis and joining the short head—but four, five, and even seven supernumerary heads have been reported in rare cases.\n\nOne study found a higher than expected number of female cadavers with a third head of biceps brachii, equal incidence between sides of the body, and uniform innervation by musculocutaneous nerve.\n\nThe distal biceps tendons are completely separated in 40% and bifurcated in 25% of cases.\n\n=== Nerve supply ===\n\nThe biceps shares its nerve supply with the other two muscles of the anterior compartment.\n\nThe muscles are supplied by the musculocutaneous nerve.\n\nFibers of the fifth, sixth and seventh cervical nerves make up the components of the musculocutaneous nerve which supply the biceps.\n\n=== Blood supply ===\n\nThe blood supply of the biceps is the brachial artery.\n\nThe distal tendon of the biceps can be useful for palpating the brachial pulse, as the artery runs medial to the tendon in the cubital fossa.\n\n== Function ==\n\nThe biceps works across three joints.\n\nThe most important of these functions is to supinate the forearm and flex the elbow.\n\nBesides, the long head of biceps prevents the upward displacement of the head of the humerus.\n\nIn more detail, the actions are, by joint:\n\n- Proximal radioulnar joint of the elbow –\n\nThe biceps brachii functions as a powerful supinator of the forearm, i.e. it turns the palm upwards.\n\nThis action, which is aided by the supinator muscle, requires the humeroulnar joint of the elbow to be at least partially flexed.\n\nIf the humeroulnar joint, is fully extended, supination is then primarily carried out by the supinator muscle.\n\nThe biceps is a particularly powerful supinator of the forearm due to the distal attachment of the muscle at the radial tuberosity, on the opposite side of the bone from the supinator muscle.\n\nWhen flexed, the biceps effectively pulls the radius back into its neutral supinated position in concert with the supinator muscle.\n\n- Humeroulnar joint of the elbow –\n\nThe biceps brachii also functions as an important flexor of the forearm, particularly when the forearm is supinated.\n\nFunctionally, this action is performed when lifting an object, such as a bag of groceries or when performing a biceps curl.\n\nWhen the forearm is in pronation (the palm faces the ground), the brachialis, brachioradialis, and supinator function to flex the forearm, with minimal contribution from the biceps brachii.\n\nIt is also important to note that regardless of forearm position, (supinated, pronated, or neutral) the force exerted by the biceps brachii remains the same; however, the brachioradialis has a much greater change in exertion depending on position than the biceps during concentric contractions.\n\nThat is, the biceps can only exert so much force, and as forearm position changes, other muscles must compensate.\n\n- Glenohumeral joint (shoulder joint) –\n\nSeveral weaker functions occur at the glenohumeral joint.\n\nThe biceps brachii weakly assists in forward flexion of the shoulder joint (bringing the arm forward and upwards).\n\nIt may also contribute to abduction (bringing the arm out to the side) when the arm is externally (or laterally) rotated.\n\nThe short head of the biceps brachii also assists with horizontal adduction (bringing the arm across the body) when the arm is internally (or medially) rotated.\n\nFinally, the short head of the biceps brachii, due to its attachment to the scapula (or shoulder blade), assists with stabilization of the shoulder joint when a heavy weight is carried in the arm.\n\nThe tendon of the long head of the biceps also assists in holding the head of the humerus in the glenoid cavity.\n\nMotor units in the lateral portion of the long head of the biceps are preferentially activated during elbow flexion, while motor units in the medial portion are preferentially activated during forearm supination.\n\nThe biceps are usually attributed as representative of strength within a variety of worldwide cultures.\n\n== Clinical significance ==\n\nThe proximal tendons of the biceps brachii are commonly involved in pathological processes and are a frequent cause of anterior shoulder pain.\n\nDisorders of the distal biceps brachii tendon include insertional tendonitis and partial or complete tears of the tendon.\n\nPartial tears are usually characterized by pain and enlargement and abnormal contour of the tendon.\n\nComplete tears occur as avulsion of the tendinous portion of the biceps away from its insertion on the tuberosity of the radius, and is often accompanied by a palpable, audible \"pop\" and immediate pain and soft tissue swelling.\n\nA soft-tissue mass is sometimes encountered in the anterior aspect of the arm, the so-called Reverse Popeye deformity, which paradoxically leads to a decreased strength during flexion of the elbow and supination of the forearm.\n\n=== Tendon rupture ===\n\nTears of the biceps brachii may occur during athletic activities, however avulsion injuries of the distal biceps tendon are frequently occupational in nature and sustained during forceful, eccentric contraction of the biceps muscle while lifting.Treatment of a biceps tear depends on the severity of the injury.\n\nIn most cases, the muscle will heal over time with no corrective surgery.\n\nApplying cold pressure and using anti-inflammatory medications will ease pain and reduce swelling.\n\nMore severe injuries require surgery and post-op physical therapy to regain strength and functionality in the muscle.\n\nCorrective surgeries of this nature are typically reserved for elite athletes who rely on a complete recovery.\n\n=== Training ===\n\nThe biceps can be strengthened using weight and resistance training.\n\nExamples of well known biceps exercises are the chin-up and biceps curl.\n\n== Etymology and grammar ==\n\nThe biceps brachii muscle is the one that gave all muscles their name: it comes from the Latin musculus, \"little mouse\", because the appearance of the flexed biceps resembles the back of a mouse.\n\nThe same phenomenon occurred in Greek, in which μῦς, mȳs, means both \"mouse\" and \"muscle\".\n\nThe term biceps brachii is a Latin phrase meaning \"two-headed [muscle] of the arm\", in reference to the fact that the muscle consists of two bundles of muscle, each with its own origin, sharing a common insertion point near the elbow joint.\n\nThe proper plural form of the Latin adjective biceps is bicipites, a form not in general English use.\n\nInstead, biceps is used in both singular and plural (i.e., when referring to both arms).\n\nThe English form bicep [sic], attested from 1939, is a back formation derived from misinterpreting the s of biceps as the English plural marker -s.\n\n== History ==\n\nLeonardo da Vinci expressed the original idea of the biceps acting as a supinator in a series of annotated drawings made between 1505 and 1510; in which the principle of the biceps as a supinator, as well as its role as a flexor to the elbow were devised.\n\nHowever, this function remained undiscovered by the medical community as da Vinci was not regarded as a teacher of anatomy, nor were his results publicly released.\n\nIt was not until 1713 that this movement was re-discovered by William Cheselden and subsequently recorded for the medical community.\n\nIt was rewritten several times by different authors wishing to present information to different audiences.\n\nThe most notable recent expansion upon Cheselden's recordings was written by Guillaume Duchenne in 1867, in a journal named Physiology of Motion.\n\nTo this day it remains one of the major references on supination action of the biceps brachii.\n\n== Other species ==\n\n=== Neanderthals ===\n\nIn Neanderthals, the radial bicipital tuberosities were larger than in modern humans, which suggests they were probably able to use their biceps for supination over a wider range of pronation-supination.\n\nIt is possible that they relied more on their biceps for forceful supination without the assistance of the supinator muscle like in modern humans, and thus that they used a different movement when throwing.\n\n=== Horses ===\n\nIn the horse, the biceps' function is to extend the shoulder and flex the elbow.\n\nIt is composed of two short-fibred heads separated longitudinally by a thick internal tendon which stretches from the origin on the supraglenoid tubercle to the insertion on the medial radial tuberosity.\n\nThis tendon can withstand very large forces when the biceps is stretched.\n\nFrom this internal tendon a strip of tendon, the lacertus fibrosus, connects the muscle with the extensor carpi radialis -- an important feature in the horse's stay apparatus (through which the horse can rest and sleep whilst standing.)\n\nhttps://en.wikipedia.org/wiki/Biceps","short-head-of-biceps-brachii":"(...)\n\nThe short head inserts distally on the tuberosity while the long head inserts proximally closer to the apex of the tuberosity.\n\nThe bicipital aponeurosis, also called the lacertus fibrosus, is a thick fascial band that organizes close to the musculotendinous junction of the biceps and radiates over and inserts onto the ulnar part of the antebrachial fascia.\n\nThe tendon that attaches to the radial tuberosity is partially or completely surrounded by a bursa, the bicipitoradial bursa, which ensures frictionless motion between the biceps tendon and the proximal radius during pronation and supination of the forearm.\n\n(...)","brachialis-muscle":"The brachialis (brachialis anticus) Also known as the Teichmann muscle, is a muscle in the upper arm that flexes the elbow.\n\nIt lies deeper than the biceps brachii, and makes up part of the floor of the region known as the cubital fossa (elbow pit).\n\nThe brachialis is the prime mover of elbow flexion generating about 50% more power than the biceps.\n\n== Structure ==\n\nThe brachialis originates from the anterior surface of the distal half of the humerus, near the insertion of the deltoid muscle, which it embraces by two angular processes.\n\nIts origin extends below to within 2.5 cm of the margin of the articular surface of the humerus at the elbow joint.\n\nIts fibers converge to a thick tendon, which is inserted into the tuberosity of the ulna and the rough depression on the anterior surface of the coronoid process of the ulna.\n\n=== Blood supply ===\n\nThe brachialis is supplied by the Muscular branches of brachial artery and the recurrent radial artery.\n\n=== Nerve supply ===\n\nThe brachialis muscle is innervated by the musculocutaneous nerve, which runs on its superficial surface, between it and the biceps brachii.\n\nHowever, in 70-80% of people, the muscle has double innervation with the radial nerve (C5-T1).\n\nThe divide between the two innervations is at the insertion of the deltoid.\n\n=== Variation ===\n\nThe muscle is occasionally doubled; additional muscle slips to the supinator, pronator teres, biceps brachii, lacertus fibrosus, or radius are more rarely found.\n\n== Function ==\n\nThe brachialis flexes the arm at the elbow joint.\n\nUnlike the biceps, the brachialis does not insert on the radius, and does not participate in pronation and supination of the forearm.\n\n== History ==\n\n=== Etymology ===\n\nThe brachialis muscle In classical Latin bracchialis means of or belonging to the arm, and is derived from classical Latin bracchium,\"arm\".\n\nThe expression musculus brachialis is used in the current official anatomic nomenco Terminologia Anatomica.\n\nhttps://en.wikipedia.org/wiki/Brachialis_muscle","coracobrachialis-muscle":"The coracobrachialis muscle is the smallest of the three muscles that attach to the coracoid process of the scapula.\n\n(The other two muscles are pectoralis minor and the short head of the biceps brachii.)\n\nIt is situated at the upper and medial part of the arm.\n\n== Structure ==\n\nCoracobrachialis muscle arises from the apex of the coracoid process, in common with the short head of the biceps brachii, and from the intermuscular septum between the two muscles.\n\nIt is inserted by means of a flat tendon into an impression at the middle of the medial surface and border of the body of the humerus (shaft of the humerus) between the origins of the triceps brachii and brachialis.\n\n=== Innervation ===\n\nCoracobrachialis muscle is perforated by and innervated by the musculocutaneous nerve, which arises from the anterior division of the upper trunk (C5, C6) and middle trunk (C7) of the brachial plexus.\n\n=== Development ===\n\n=== Variation ===\n\n== Function ==\n\nThe action of the coracobrachialis is to flex and adduct the arm at the glenohumeral joint (shoulder joint).\n\nAlso, the coracobrachialis resists deviation of the arm from the frontal plane during abduction.\n\nTherefore, the contraction of the coracobrachialis leads to two distinct movements at the shoulder joint.\n\nIt both draws the humerus forward, causing flexion of the arm, and draws the humerus toward the torso, causing adduction of the arm.\n\nTo a smaller extent, it also turns the humerus inwards, causing internal rotation.\n\nAnother important function of the coracobrachialis is the stabilization of the humeral head within the shoulder joint, especially when the arm is hanging freely at a person's side.\n\n== Clinical significance ==\n\nThe overuse of the coracobrachialis can lead to stiffening of the muscle.\n\nCommon causes of injury include chest workouts or activities that require one to press the arm very tight towards the body, e.g. work on the rings in gymnastics.\n\nSymptoms of overuse or injury are pain in the arm and shoulder, radiating down to the back of the hand.\n\nIn more severe cases, the musculocutaneous nerve can get trapped, causing disturbances in sensation to the skin on the radial part of the forearm and weakened flexion of the elbow, as the nerve also supplies the biceps brachii and brachialis muscles.\n\nActual rupture to the coracobrachialis muscle is extremely rare.\n\nVery few case reports exist in the literature, and it is reported to be caused by direct trauma to the contracted muscle.\n\nAvulsion of the muscle's origin from the coracoid as a result of indirect forces is even more unusual.\n\nhttps://en.wikipedia.org/wiki/Coracobrachialis_muscle","medial-head-of-triceps-brachii":"The triceps, also triceps brachii (Latin for \"three-headed muscle of the arm\"), is a large muscle on the back of the upper limb of many vertebrates.\n\nIt consists of 3 parts: the medial, lateral, and long head.\n\nIt is the muscle principally responsible for extension of the elbow joint (straightening of the arm).\n\n== Structure ==\n\nThe long head arises from the infraglenoid tubercle of the scapula.\n\nIt extends distally anterior to the teres minor and posterior to the teres major.\n\nThe medial head arises proximally in the humerus, just inferior to the groove of the radial nerve; from the dorsal (back) surface of the humerus; from the medial intermuscular septum; and its distal part also arises from the lateral intermuscular septum.\n\nThe medial head is mostly covered by the lateral and long heads, and is only visible distally on the humerus.\n\nThe lateral head arises from the dorsal surface of the humerus, lateral and proximal to the groove of the radial nerve, from the greater tubercle down to the region of the lateral intermuscular septum.\n\nEach of the three fascicles has its own motorneuron subnucleus in the motor column in the spinal cord.\n\nThe medial head is formed predominantly by small type I fibers and motor units, the lateral head of large type IIb fibers and motor units and the long head of a mixture of fiber types and motor units.\n\nIt has been suggested that each fascicle \"may be considered an independent muscle with specific functional roles.\n\n\"The fibers converge to a single tendon to insert onto the olecranon process of the ulna (though some research indicates that there may be more than one tendon) and to the posterior wall of the capsule of the elbow joint where bursae (cushion sacks) are often found.\n\nParts of the common tendon radiates into the fascia of the forearm and can almost cover the anconeus muscle.\n\n=== Innervation ===\n\nAll three heads of the triceps brachii are classically believed to be innervated by the radial nerve.\n\nHowever, a study conducted in 2004 determined that, in 20 cadaveric specimens and 15 surgical dissections on participants, the long head was innervated by a branch of the axillary nerve in all cases.\n\n=== Variation ===\n\nA tendinous arch is frequently the origin of the long head and the tendon of latissimus dorsi.\n\nIn rare cases, the long head can originate from the lateral margin of the scapula and from the capsule of the shoulder joint.\n\n== Function ==\n\nThe triceps is an extensor muscle of the elbow joint and an antagonist of the biceps and brachialis muscles.\n\nIt can also fixate the elbow joint when the forearm and hand are used for fine movements, e.g., when writing.\n\nIt has been suggested that the long head fascicle is employed when sustained force generation is demanded, or when there is a need for a synergistic control of the shoulder and elbow or both.\n\nThe lateral head is used for movements requiring occasional high-intensity force, while the medial fascicle enables more precise, low-force movements.\n\nWith its origin on the scapula, the long head also acts on the shoulder joint and is also involved in retroversion and adduction of the arm.\n\nIt helps stabilise the shoulder joint at the top of the humerus.\n\n== Training ==\n\nThe triceps can be worked through either isolation or compound elbow extension movements and can contract statically to keep the arm straightened against resistance.\n\nIsolation movements include cable push-downs, lying triceps extensions and arm extensions behind the back.\n\nExamples of compound elbow extension include pressing movements like the push up, bench press, close grip bench press (flat, incline or decline), military press and dips.\n\nA closer grip targets the triceps more than wider grip movements.\n\nStatic contraction movements include pullovers, straight-arm pulldowns and bent-over lateral raises, which are also used to build the deltoids and latissimus dorsi.\n\nIt is important to work the triceps muscle through its full range of contraction.\n\nGiven that this is a two joint muscle (with attachments that cross both the elbow and shoulder) the most comprehensive training approach will have you train the triceps with exercises that fully straighten the elbow with the arm behind the body (to fully shorten the triceps long head).\n\nRuptures of the triceps muscle are rare, and typically only occur in anabolic steroid users.\n\n== Clinical significance ==\n\nThe triceps reflex, elicited by hitting the triceps, is often used to test the function of the nerves of the arm.\n\nThis tests spinal nerves C6 and C7, predominately C7.\n\n== History ==\n\n=== Etymology ===\n\nIt is sometimes called a three-headed muscle (Latin literally three-headed, tri - three, and ceps, from caput - head), because there are three bundles of muscles, each of different origins, joining together at the elbow.\n\nThough a similarly named muscle, the triceps surae, is found on the lower leg, the triceps brachii is commonly called the triceps.\n\nHistorically, the plural form of triceps was tricipites, a form not in general use today; instead, triceps is both singular and plural (i.e., when referring to both arms).\n\n== Animals ==\n\nIn the horse, 84%, 15%, and 3% of the total triceps muscle weight correspond to the long, lateral and medial heads, respectively.Many mammals, such as dogs, cattle, and pigs, have a fourth head, the accessory head.\n\nIt lies between the lateral and medial heads.\n\nIn humans, the anconeus is sometimes loosely called \"the fourth head of the triceps brachii\".\n\nhttps://en.wikipedia.org/wiki/Triceps","lateral-head-of-triceps-brachii":"The triceps, also triceps brachii (Latin for \"three-headed muscle of the arm\"), is a large muscle on the back of the upper limb of many vertebrates.\n\nIt consists of 3 parts: the medial, lateral, and long head.\n\nIt is the muscle principally responsible for extension of the elbow joint (straightening of the arm).\n\n== Structure ==\n\nThe long head arises from the infraglenoid tubercle of the scapula.\n\nIt extends distally anterior to the teres minor and posterior to the teres major.\n\nThe medial head arises proximally in the humerus, just inferior to the groove of the radial nerve; from the dorsal (back) surface of the humerus; from the medial intermuscular septum; and its distal part also arises from the lateral intermuscular septum.\n\nThe medial head is mostly covered by the lateral and long heads, and is only visible distally on the humerus.\n\nThe lateral head arises from the dorsal surface of the humerus, lateral and proximal to the groove of the radial nerve, from the greater tubercle down to the region of the lateral intermuscular septum.\n\nEach of the three fascicles has its own motorneuron subnucleus in the motor column in the spinal cord.\n\nThe medial head is formed predominantly by small type I fibers and motor units, the lateral head of large type IIb fibers and motor units and the long head of a mixture of fiber types and motor units.\n\nIt has been suggested that each fascicle \"may be considered an independent muscle with specific functional roles.\n\n\"The fibers converge to a single tendon to insert onto the olecranon process of the ulna (though some research indicates that there may be more than one tendon) and to the posterior wall of the capsule of the elbow joint where bursae (cushion sacks) are often found.\n\nParts of the common tendon radiates into the fascia of the forearm and can almost cover the anconeus muscle.\n\n=== Innervation ===\n\nAll three heads of the triceps brachii are classically believed to be innervated by the radial nerve.\n\nHowever, a study conducted in 2004 determined that, in 20 cadaveric specimens and 15 surgical dissections on participants, the long head was innervated by a branch of the axillary nerve in all cases.\n\n=== Variation ===\n\nA tendinous arch is frequently the origin of the long head and the tendon of latissimus dorsi.\n\nIn rare cases, the long head can originate from the lateral margin of the scapula and from the capsule of the shoulder joint.\n\n== Function ==\n\nThe triceps is an extensor muscle of the elbow joint and an antagonist of the biceps and brachialis muscles.\n\nIt can also fixate the elbow joint when the forearm and hand are used for fine movements, e.g., when writing.\n\nIt has been suggested that the long head fascicle is employed when sustained force generation is demanded, or when there is a need for a synergistic control of the shoulder and elbow or both.\n\nThe lateral head is used for movements requiring occasional high-intensity force, while the medial fascicle enables more precise, low-force movements.\n\nWith its origin on the scapula, the long head also acts on the shoulder joint and is also involved in retroversion and adduction of the arm.\n\nIt helps stabilise the shoulder joint at the top of the humerus.\n\n== Training ==\n\nThe triceps can be worked through either isolation or compound elbow extension movements and can contract statically to keep the arm straightened against resistance.\n\nIsolation movements include cable push-downs, lying triceps extensions and arm extensions behind the back.\n\nExamples of compound elbow extension include pressing movements like the push up, bench press, close grip bench press (flat, incline or decline), military press and dips.\n\nA closer grip targets the triceps more than wider grip movements.\n\nStatic contraction movements include pullovers, straight-arm pulldowns and bent-over lateral raises, which are also used to build the deltoids and latissimus dorsi.\n\nIt is important to work the triceps muscle through its full range of contraction.\n\nGiven that this is a two joint muscle (with attachments that cross both the elbow and shoulder) the most comprehensive training approach will have you train the triceps with exercises that fully straighten the elbow with the arm behind the body (to fully shorten the triceps long head).\n\nRuptures of the triceps muscle are rare, and typically only occur in anabolic steroid users.\n\n== Clinical significance ==\n\nThe triceps reflex, elicited by hitting the triceps, is often used to test the function of the nerves of the arm.\n\nThis tests spinal nerves C6 and C7, predominately C7.\n\n== History ==\n\n=== Etymology ===\n\nIt is sometimes called a three-headed muscle (Latin literally three-headed, tri - three, and ceps, from caput - head), because there are three bundles of muscles, each of different origins, joining together at the elbow.\n\nThough a similarly named muscle, the triceps surae, is found on the lower leg, the triceps brachii is commonly called the triceps.\n\nHistorically, the plural form of triceps was tricipites, a form not in general use today; instead, triceps is both singular and plural (i.e., when referring to both arms).\n\n== Animals ==\n\nIn the horse, 84%, 15%, and 3% of the total triceps muscle weight correspond to the long, lateral and medial heads, respectively.Many mammals, such as dogs, cattle, and pigs, have a fourth head, the accessory head.\n\nIt lies between the lateral and medial heads.\n\nIn humans, the anconeus is sometimes loosely called \"the fourth head of the triceps brachii\".\n\nhttps://en.wikipedia.org/wiki/Triceps","long-head-of-triceps-brachii":"The triceps, also triceps brachii (Latin for \"three-headed muscle of the arm\"), is a large muscle on the back of the upper limb of many vertebrates.\n\nIt consists of 3 parts: the medial, lateral, and long head.\n\nIt is the muscle principally responsible for extension of the elbow joint (straightening of the arm).\n\n== Structure ==\n\nThe long head arises from the infraglenoid tubercle of the scapula.\n\nIt extends distally anterior to the teres minor and posterior to the teres major.\n\nThe medial head arises proximally in the humerus, just inferior to the groove of the radial nerve; from the dorsal (back) surface of the humerus; from the medial intermuscular septum; and its distal part also arises from the lateral intermuscular septum.\n\nThe medial head is mostly covered by the lateral and long heads, and is only visible distally on the humerus.\n\nThe lateral head arises from the dorsal surface of the humerus, lateral and proximal to the groove of the radial nerve, from the greater tubercle down to the region of the lateral intermuscular septum.\n\nEach of the three fascicles has its own motorneuron subnucleus in the motor column in the spinal cord.\n\nThe medial head is formed predominantly by small type I fibers and motor units, the lateral head of large type IIb fibers and motor units and the long head of a mixture of fiber types and motor units.\n\nIt has been suggested that each fascicle \"may be considered an independent muscle with specific functional roles.\n\n\"The fibers converge to a single tendon to insert onto the olecranon process of the ulna (though some research indicates that there may be more than one tendon) and to the posterior wall of the capsule of the elbow joint where bursae (cushion sacks) are often found.\n\nParts of the common tendon radiates into the fascia of the forearm and can almost cover the anconeus muscle.\n\n=== Innervation ===\n\nAll three heads of the triceps brachii are classically believed to be innervated by the radial nerve.\n\nHowever, a study conducted in 2004 determined that, in 20 cadaveric specimens and 15 surgical dissections on participants, the long head was innervated by a branch of the axillary nerve in all cases.\n\n=== Variation ===\n\nA tendinous arch is frequently the origin of the long head and the tendon of latissimus dorsi.\n\nIn rare cases, the long head can originate from the lateral margin of the scapula and from the capsule of the shoulder joint.\n\n== Function ==\n\nThe triceps is an extensor muscle of the elbow joint and an antagonist of the biceps and brachialis muscles.\n\nIt can also fixate the elbow joint when the forearm and hand are used for fine movements, e.g., when writing.\n\nIt has been suggested that the long head fascicle is employed when sustained force generation is demanded, or when there is a need for a synergistic control of the shoulder and elbow or both.\n\nThe lateral head is used for movements requiring occasional high-intensity force, while the medial fascicle enables more precise, low-force movements.\n\nWith its origin on the scapula, the long head also acts on the shoulder joint and is also involved in retroversion and adduction of the arm.\n\nIt helps stabilise the shoulder joint at the top of the humerus.\n\n== Training ==\n\nThe triceps can be worked through either isolation or compound elbow extension movements and can contract statically to keep the arm straightened against resistance.\n\nIsolation movements include cable push-downs, lying triceps extensions and arm extensions behind the back.\n\nExamples of compound elbow extension include pressing movements like the push up, bench press, close grip bench press (flat, incline or decline), military press and dips.\n\nA closer grip targets the triceps more than wider grip movements.\n\nStatic contraction movements include pullovers, straight-arm pulldowns and bent-over lateral raises, which are also used to build the deltoids and latissimus dorsi.\n\nIt is important to work the triceps muscle through its full range of contraction.\n\nGiven that this is a two joint muscle (with attachments that cross both the elbow and shoulder) the most comprehensive training approach will have you train the triceps with exercises that fully straighten the elbow with the arm behind the body (to fully shorten the triceps long head).\n\nRuptures of the triceps muscle are rare, and typically only occur in anabolic steroid users.\n\n== Clinical significance ==\n\nThe triceps reflex, elicited by hitting the triceps, is often used to test the function of the nerves of the arm.\n\nThis tests spinal nerves C6 and C7, predominately C7.\n\n== History ==\n\n=== Etymology ===\n\nIt is sometimes called a three-headed muscle (Latin literally three-headed, tri - three, and ceps, from caput - head), because there are three bundles of muscles, each of different origins, joining together at the elbow.\n\nThough a similarly named muscle, the triceps surae, is found on the lower leg, the triceps brachii is commonly called the triceps.\n\nHistorically, the plural form of triceps was tricipites, a form not in general use today; instead, triceps is both singular and plural (i.e., when referring to both arms).\n\n== Animals ==\n\nIn the horse, 84%, 15%, and 3% of the total triceps muscle weight correspond to the long, lateral and medial heads, respectively.Many mammals, such as dogs, cattle, and pigs, have a fourth head, the accessory head.\n\nIt lies between the lateral and medial heads.\n\nIn humans, the anconeus is sometimes loosely called \"the fourth head of the triceps brachii\".\n\nhttps://en.wikipedia.org/wiki/Triceps","superficial-head-of-pronator-teres":"The superficial head (or humeral head) of pronator teres arises from the medial supracondylar ridge immediately superior to the medial epicondyle of the humerus, and from the common flexor tendon (which arises from the medial epicondyle).","deep-head-of-pronator-teres":"The deep head (or ulnar head) of pronator teres is a thin fasciculus, which arises from the medial side of the coronoid process of the ulna, and joins the superficial head at an acute angle.","ulnar-head-of-flexor-carpi-ulnaris":"Origin: medial margin of the olecranon and upper two-thirds of the dorsal border of the ulna by an aponeurosis.\n\nInsertion: pisiform bone, hamatum bone, pisihamate ligament, pisometacarpal ligament, pisometacarpal ligament.\n\nBetween the two heads passes the ulnar nerve and ulnar artery.","flexor-carpi-radialis":"In anatomy, flexor carpi radialis is a muscle of the human forearm that acts to flex and (radially) abduct the hand.\n\nThe Latin carpus means wrist; hence flexor carpi is a flexor of the wrist.\n\n== Origin and insertion ==\n\nThe flexor carpi radialis is one of four muscles in the superficial layer of the anterior compartment of the forearm.\n\nThis muscle originates from the medial epicondyle of the humerus as part of the common flexor tendon.\n\nIt runs just laterally of flexor digitorum superficialis and inserts on the anterior aspect of the base of the second metacarpal, and has small slips to both the third metacarpal and trapezium tuberosity.\n\nThe tendon of the flexor carpi radialis is visible on the anterior surface of the forearm, just proximal to the wrist, when the wrist is flexed.\n\nIt is the tendon seen most lateral, closest to the thumb.\n\n== Nerve and artery ==\n\nLike most flexors of the anterior compartment of the forearm, FCR is innervated by the median nerve, specifically by axons from cervical nerve roots C6 and C7.\n\nThe muscle receives its blood supply from the ulnar artery.\n\n== Exercises ==\n\nThe muscle, like all flexors of the forearm, can be strengthened by exercises that resist its flexion.\n\nA wrist roller can be used, and wrist curls with dumbbells can also be performed.\n\nhttps://en.wikipedia.org/wiki/Flexor_carpi_radialis_muscle","palmaris-longus-muscle":"The palmaris longus is a muscle visible as a small tendon located between the flexor carpi radialis and the flexor carpi ulnaris, although it is not always present.\n\nIt is absent in about 14 percent of the population; however, this number can vary in African, Asian, and Native American populations.\n\nAbsence of the palmaris longus does not have an effect on grip strength.\n\nHowever, the lack of palmaris longus muscle results in decreased pinch strength in fourth and fifth fingers in both sexes.\n\nThe absence of palmaris longus muscle is more prevalent in females than males.\n\nThe palmaris longus muscle can be seen by touching the pads of the fourth finger and thumb and flexing the wrist.\n\nThe tendon, if present, will be visible in the midline of the anterior wrist.\n\n== Structure ==\n\nPalmaris longus is a slender, elongated, spindle shaped muscle, lying on the medial side of the flexor carpi radialis.\n\nIt is widest in the middle, and narrowest at the proximal and distal attachments.It arises mainly from the medial epicondyle of the humerus via the common flexor tendon.\n\nIt also takes origin from the adjacent intermuscular septa and from the antebrachial fascia.It ends in a slender, flattened tendon, which passes over the upper part of the flexor retinaculum and inserts onto the central part of the flexor retinaculum and lower part of the palmar aponeurosis.\n\nFrequently, it sends a tendinous slip to the short muscles of the thumb.\n\n=== Nerve supply ===\n\nThe palmaris longus is supplied by the median nerve.\n\n=== Variation ===\n\nThe palmaris longus muscle is a variable muscle.\n\nThe most common variation is its absence.\n\nSeveral in vivo and in vitro studies have documented the prevalence or absence of the PL tendon in different ethnic groups.\n\nBetween 5.5 and 24% of Caucasian populations (European and North American) and 4.6 to 26.6% of Asian populations (Chinese, Japanese, Indian, Turkish, Malaysian) have been reported to lack the PL tendon.There are also variations related to its form.\n\nIt may be tendinous above and muscular below; or it may be muscular in the center with a tendon above and below; or it may present two muscular bundles with a central tendon; or finally it may consist solely of a tendinous band.\n\nThe muscle may be double, or missing entirely.\n\nSlips of origin from the coronoid process or from the radius have been seen.\n\nPartial or complete insertion into the fascia of the forearm, into the tendon of the flexor carpi ulnaris and pisiform bone, into the scaphoid, and into the muscles of the little finger have been observed.\n\n== Clinical significance ==\n\n=== Use in tendon grafts ===\n\nThe palmaris longus muscle is the most popular for use in tendon grafts for the wrist due to the length and diameter of the palmaris longus tendon, and the fact that it can be used without producing any functional deformities.\n\nWhen a tendon becomes ruptured in the wrist, the palmaris longus tendon may be removed from the flexor retinaculum and grafted to take the place of the ruptured tendon.\n\nThe tendons most commonly replaced or supplemented by the palmaris longus tendon when ruptured are the long flexors of the fingers and the flexor pollicis longus tendon.\n\nThe palmaris longus muscle itself is a weak flexor, and provides no substantial flexing force that would inhibit movement in the wrist if its tendon were cut and moved elsewhere.\n\nThe palmaris longus may contribute and assist in thumb abduction movements; an action necessary to open the hand.\n\nIf the palmaris longus muscle is not available for harvesting in an individual, the anatomically homologous plantaris muscle in the leg may be taken instead.\n\nUsing the patient’s own tendon is advantageous, as it does not introduce foreign material into the body.\n\n=== Carpal tunnel syndrome and palmaris longus variants ===\n\nOf the known anatomical variants of the palmaris longus, the reverse belly of the palmaris longus may be localized within the carpal tunnel producing symptoms of carpal tunnel syndrome.\n\nKnowledge of this variation is important to prevent unnecessary carpal tunnel release surgery, in which, the median nerve compression may remain unresolved due to the presence of this palmaris longus variant.\n\n== Other animals ==\n\n=== Evolution ===\n\nThe evolutionary interpretation of the muscle's absence is that humans inherited the muscle through common descent, and numerous animals that humans share a common ancestor with (such as the orangutan) still actively employ the muscle.\n\nClose primate relatives (such as the chimpanzee and gorilla) also do not actively employ the muscle, and hence they also demonstrate the same variability.\n\nThe common descent principle suggests that at some stage our ancestors employed the muscle actively.\n\nThe thumb apparatus (and particularly the thenar muscle group) then started developing in the primate branch, and consequently the Palmaris longus became vestigial.\n\nAs there is no apparent evolutionary pressure (positive or negative) concerning the muscle, it has remained largely unaffected by evolutionary processes.\n\nhttps://en.wikipedia.org/wiki/Palmaris_longus_muscle","radial-head-of-flexor-digitorum-superficialis":"The flexor digitorum superficialis muscle has two heads:\n-the Humero-ulnar head of flexor digitorum superficialis\n-and the Radial head of flexor digitorum superficialis\n\nThe median nerve and ulnar artery pass between these heads.\n\nThe ulnar collateral ligament of elbow joint gives its origin to part of this muscle.\n\nhttps://en.wikipedia.org/wiki/Flexor_digitorum_superficialis_muscle","flexor-digitorum-profundus":"The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits).\n\nIt is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.\n\nTogether the flexor pollicis longus, pronator quadratus, and flexor digitorum profundus form the deep layer of ventral forearm muscles.\n\nThe muscle is named from Latin 'deep bender of the fingers'.\n\n== Structure ==\n\nFlexor digitorum profundus originates in the upper 3/4 of the anterior and medial surfaces of the ulna, interosseous membrane and deep fascia of the forearm.\n\nThe muscle fans out into four tendons (one to each of the second to fifth fingers) to the palmar base of the distal phalanx.\n\nAlong with the flexor digitorum superficialis, it has long tendons that run down the arm and through the carpal tunnel and attach to the palmar side of the phalanges of the fingers.\n\nFlexor digitorum profundus lies deep to the superficialis, but it attaches more distally.\n\nTherefore, profundus's tendons go through the tendons of superficialis, and end up attaching to the distal phalanx.\n\nFor this reason profundus is also called the perforating muscle.The lumbricals of the hand arise from the radial side of its tendons.\n\n=== Nerve supply ===\n\nFlexor digitorum profundus is a composite muscle innervated by the anterior interosseous nerve and ulnar nerves.\n\nThe medial aspect of the muscle (which flexes the 4th and 5th digit) is supplied by the ulnar nerve (C8, T1).\n\nThe lateral aspect (which flexes the 2nd and 3rd digit) is innervated by the median nerve, specifically the anterior interosseous branch (C8, T1).\n\nIt is one of two flexor muscles that is not exclusively supplied by the median nerve (the other is flexor carpi ulnaris).\n\nIn the forearm, the median nerve travels distally between the flexor digitorum superficialias and the flexor digitorum profundus.\n\n=== Variation ===\n\nThe tendon of the index finger often has a separate muscle belly.\n\n== Function ==\n\nFlexor digitorum profundus is a flexor of the wrist (midcarpal), metacarpophalangeal and interphalangeal joints.\n\nThe lumbricals, intrinsic muscles of the hand, attach to the tendon of flexor digitorum profundus.\n\nThus, the flexor muscle is used to aid the lumbrical muscles in their role as extensors of the interphalangeal joints.\n\nAs the lumbrical muscles originate on the palmar side of the hand and attach on the dorsal aponeurosis, power is transferred from the flexor digitorum profundus muscle to fully extend the fingers as well as flex the metacarpophalangeal joints.\n\nThe tension generated by flexor digitorum profundus at the more distal joints is determined by wrist position.\n\nFlexion of the wrist causes muscle shortening at that point, reducing tension that can be generated more distally.\n\nFingers cannot be fully flexed if the wrist is fully flexed.\n\n== Other animals ==\n\nIn many primates, the FDP is fused with the flexor pollicis longus (FPL).\n\nIn great apes the belly of the FDP has a separate tendon for the FDP.\n\nIn lesser apes, both muscles have separate bellies in the forearm, but in Old World monkeys they separate in the carpal tunnel.\n\nThe lack of differentiation in the FDP musculature in baboons makes it unlikely that this monkey can control individual fingers independently.\n\nhttps://en.wikipedia.org/wiki/Flexor_digitorum_profundus_muscle","flexor-pollicis-longus":"The flexor pollicis longus (; FPL, Latin flexor, bender; pollicis, of the thumb; longus, long) is a muscle in the forearm and hand that flexes the thumb.\n\nIt lies in the same plane as the flexor digitorum profundus.\n\nThis muscle is unique to humans, being either rudimentary or absent in other primates.\n\nA meta-analysis indicated accessory flexor pollicis longus is present in around 48% of the population.\n\n== Human anatomy ==\n\n=== Origin and insertion ===\n\nIt arises from the grooved anterior (side of palm) surface of the body of the radius, extending from immediately below the radial tuberosity and oblique line to within a short distance of the pronator quadratus muscle.\n\nAn occasionally present accessory long head of the flexor pollicis longus muscle is called 'Gantzer's muscle'.\n\nIt may cause compression of the anterior interosseous nerve.\n\nIt arises also from the adjacent part of the interosseous membrane of the forearm, and generally by a fleshy slip from the medial border of the coronoid process of the ulna.\n\nIn 40 percent of cases, it is also inserted from the medial epicondyle of the humerus, and in those cases a tendinous connection with the humeral head of the flexor digitorum superficialis is present.\n\nThe fibers end in a flattened tendon, which passes beneath the flexor retinaculum of the hand through the carpal tunnel.\n\nIt is then lodged between the lateral head of the flexor pollicis brevis and the oblique part of the adductor pollicis, and, entering an osseoaponeurotic canal similar to those for the flexor tendons of the fingers, is inserted into the base of the distal phalanx of the thumb.\n\n=== Relations ===\n\nThe anterior interosseous nerve (a branch of the median nerve) and the anterior interosseous artery and vein pass downward on the front of the interosseous membrane between the flexor pollicis longus and flexor digitorum profundus.\n\nInjuries to tendons are particularly difficult to recover from due to the limited blood supply they receive.\n\n=== Actions ===\n\nThe flexor pollicis longus is a flexor of the phalanges of the thumb; when the thumb is fixed, it assists in flexing the wrist.\n\n=== Innervation ===\n\nThe flexor pollicis longus is supplied by the anterior interosseous(C8-T1) branch of the median nerve (C5-T1).\n\n=== Variations ===\n\nSlips may connect with flexor digitorum superficialis muscle, flexor digitorum profundus muscle (resulting in the Linburg-Comstock syndrome), or the pronator teres muscle.\n\nAn additional tendon to the index finger is sometimes found.\n\n== Evolutionary variation ==\n\nModern humans are unique among hominids in having a flexor pollicis longus (FPL) muscle belly that is separate from that of the flexor digitorum profundus (FDP).\n\nWhile the FPL is not a separate muscle belly in extant great apes, a distinct tendon from the FDP belly might be present.\n\nIn some individuals, this tendon tend to act more like a ligament, which restricts extension of the interphalangeal joint of the thumb.\n\nIn orangutans there is a tendon similar in insertion and function to the FPL in humans, but which has an intrinsic origin on the oblique head of the adductor pollicis.\n\nLesser apes (i.e. gibbons) and Old World monkeys (e.g. baboons) share an extrinsic FPL muscle tendon with humans.\n\nIn most lesser apes, the FPL belly is separate from the FDP belly, but in baboons, the FPL tendon bifurcates from the FDP tendon at the wrist within the carpal tunnel and, because of the lack of differentiation in both the FDP and FPL musculature, it is unlikely that baboons can control individual digits independently.\n\nhttps://en.wikipedia.org/wiki/Flexor_pollicis_longus_muscle","pronator-quadratus":"Pronator quadratus is a square-shaped muscle on the distal forearm that acts to pronate (turn so the palm faces downwards) the hand.\n\n== Structure ==\n\nIts fibres run perpendicular to the direction of the arm, running from the most distal quarter of the anterior ulna to the distal quarter of the radius.\n\nIt has two heads: the superficial head originates from the anterior distal aspect of the diaphysis (shaft) of the ulna and inserts into the anterior distal diaphysis of the radius, as well as its anterior metaphysis.\n\nThe deep head has the same origin, but inserts proximal to the ulnar notch.\n\nIt is the only muscle that attaches only to the ulna at one end and the radius at the other end.\n\nArterial blood comes via the anterior interosseous artery.\n\n=== Innervation ===\n\nPronator quadratus muscle is innervated by the anterior interosseous nerve, a branch of the median nerve.\n\n== Function ==\n\nWhen pronator quadratus contracts, it pulls the lateral side of the radius towards the ulna, thus pronating the hand.\n\nIts deep fibers serve to keep the two bones in the forearm bound together.\n\nMoreover, this muscle can be absent in some humans, however, that does not affect the action of pronation very notably, as the pronator teres does the major role in that action.\n\n== Spinal tracts ==\n\nThe lateral corticospinal tract is responsible for the motor pathway of the pronator quadratus.\n\nThis tract begins in the precentral gyrus of the motor cortex where a signal is transmitted from the upper motor nerve through the progression tracts of the internal capsule and through the cerebral peduncles of the midbrain.\n\nIt decussates in the medulla and travels down the lateral corticospinal tract in the lateral column of the spinal cord.\n\nIt then decussates in the spinal cord and synapses at the anterior horn to the lower motor neurons of the skeletal muscles.\n\nThe cuneate fasciculus tract is responsible for the sensation of the pronator quadratus position and movement, deep touch, visceral pain, and vibration.\n\nThis tract begins in the dorsal nerve root where the signal is transmitted through the dorsal horn and up the posterior column of the spinal cord.\n\nIt synapses with an interneuron in the gracile nucleus.\n\nIt then decussates in the medial lemniscus of the medulla, travels through the cuneate nucleus and through the medial lemniscus of the midbrain to synapse in the thalamus.\n\nIt synapses with a third order neuron and transmits the signal to the postcentral gyrus of the somesthetic cortex.\n\nThis could apply to any muscle in the upper limb and not specific to this muscle.\n\nhttps://en.wikipedia.org/wiki/Pronator_quadratus_muscle","extensor-digitorum":"The extensor digitorum muscle (also known as extensor digitorum communis) is a muscle of the posterior forearm present in humans and other animals.\n\nIt extends the medial four digits of the hand.\n\nExtensor digitorum is innervated by the posterior interosseous nerve, which is a branch of the radial nerve.\n\n== Structure ==\n\nThe extensor digitorum muscle arises from the lateral epicondyle of the humerus, by the common tendon; from the intermuscular septa between it and the adjacent muscles, and from the antebrachial fascia.\n\nIt divides below into four tendons, which pass, together with that of the extensor indicis proprius, through a separate compartment of the dorsal carpal ligament, within a mucous sheath.\n\nThe tendons then diverge on the back of the hand, and are inserted into the middle and distal phalanges of the fingers in the following manner.\n\nOpposite the metacarpophalangeal articulation each tendon is bound by fasciculi to the collateral ligaments and serves as the dorsal ligament of this joint; after having crossed the joint, it spreads out into a broad aponeurosis, which covers the dorsal surface of the first phalanx and is reinforced, in this situation, by the tendons of the interossei and lumbricalis.\n\nOpposite the first interphalangeal joint this aponeurosis divides into three slips; an intermediate and two collateral: the former is inserted into the base of the second phalanx; and the two collateral, which are continued onward along the sides of the second phalanx, unite by their contiguous margins, and are inserted into the dorsal surface of the last phalanx.\n\nAs the tendons cross the interphalangeal joints, they furnish them with dorsal ligaments.\n\nThe tendon to the index finger is accompanied by the tendon of extensor indicis, which lies on its ulnar side.\n\nOn the back of the hand, the tendons to the middle, ring, and little fingers are connected by two obliquely placed bands, one from the third tendon passing inferior and laterally to the second tendon, and the other passing from the same tendon inferior and medially to the fourth.\n\nThe extensor tendons are connected to the second by a thin transverse band, known as the juncturae tendinum; they serve to maintain the central alignment of the extensor tendons over the metacarpal head, thus increasing the available leverage.\n\nInjuries (such as by an external flexion force during active extension) may allow the tendon to dislocate into the intermetacarpal space; the extensor tendon then acts as a flexor and the finger may no longer be actively extended.\n\nThis may be corrected surgically by using a slip of the extensor tendon to replace the damaged ligamentous band.\n\n== Function ==\n\nThe extensor digitorum muscle extends the phalanges, then the wrist, and finally the elbow.\n\nIt tends to separate the fingers as it extends them.\nIn the fingers, the extensor digitorum acts principally on the proximal phalanges, acting to extend the metacarpophalangeal joint.\n\nExtension of the proximal and distal interphalangeal joints, however, is mediated predominantly by the dorsal and palmar interossei and lumbricals of the hand.\n\nhttps://en.wikipedia.org/wiki/Extensor_digitorum_muscle","ulnar-head-of-extensor-carpi-ulnaris":"Origin: Posterior surface of ulna.\n\nSee also: Extensor carpi ulnaris","humeral-head-of-extensor-carpi-ulnaris":"Origin: Lateral apicondyle of humerus, radial collateral ligament.\n\nSee also: Extensor carpi ulnaris","brachioradialis-muscle":"The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow.\n\nIt is also capable of both pronation and supination, depending on the position of the forearm.\n\nIt is attached to the distal styloid process of the radius by way of the brachioradialis tendon, and to the lateral supracondylar ridge of the humerus.\n\n== Structure ==\n\nThe brachioradialis is a superficial, fusiform muscle on the lateral side of the forearm.\n\nIt originates proximally on the lateral supracondylar ridge of the humerus.\n\nIt inserts distally on the radius, at the base of its styloid process.\n\nNear the elbow, it forms the lateral limit of the cubital fossa, or elbow pit.\n\n=== Nerve supply ===\n\nDespite the bulk of the muscle body being visible from the anterior aspect of the forearm, the brachioradialis is a posterior compartment muscle and consequently is innervated by the radial nerve.\n\nOf the muscles that receive innervation from the radial nerve, it is one of only four that receive input directly from the radial nerve.\n\nThe other three are the triceps, anconeus, and extensor carpi radialis longus. (All other posterior compartment muscles that receive radial innervation are supplied by the deep branch of the radial nerve.)\n\n== Function ==\n\nThe brachioradialis flexes the forearm at the elbow.\n\nWhen the forearm is pronated, the brachioradialis tends to supinate as it flexes.\n\nIn a supinated position, it tends to pronate as it flexes.\n\nThis also assists the biceps brachii.The brachioradialis is a stronger elbow flexor when the forearm is in a midposition between supination and pronation at the radioulnar joint.\n\nWhen pronated, the brachioradialis is more active during elbow flexion since the biceps brachii is in a mechanical disadvantage.\n\nWith the insertion of the muscle so far from the fulcrum of the elbow, the brachioradialis does not generate as much joint torque as the brachialis or the biceps.\n\nIt is effective mainly when those muscles have already partially flexed at the elbow.\n\nThe brachioradialis flexes the forearm at the elbow, especially when quick movement is required and when a weight is lifted during slow flexion of the forearm.\nThe muscle is used to stabilize the elbow during rapid flexion and extension while in a midposition, such as in hammering.\n\nThe brachioradialis is synergistic with the brachialis and biceps brachii; the triceps brachii and anconeus are antagonistic.\n\nhttps://en.wikipedia.org/wiki/Brachioradialis","extensor-carpi-radialis-longus":"The extensor carpi radialis longus is one of the five main muscles that control movements at the wrist.\n\nThis muscle is quite long, starting on the lateral side of the humerus, and attaching to the base of the second metacarpal bone (metacarpal of the index finger).\n\n== Structure ==\n\nIt originates from the lateral supracondylar ridge of the humerus, from the lateral intermuscular septum, and by a few fibers from the lateral epicondyle of the humerus.\n\nThe fibers end at the upper third of the forearm in a flat tendon, which runs along the lateral border of the radius, beneath the abductor pollicis longus and extensor pollicis brevis; it then passes beneath the dorsal carpal ligament, where it lies in a groove on the back of the radius common to it and the extensor carpi radialis brevis, immediately behind the styloid process.\n\nOne of the three muscles of the radial forearm group, it initially lies beside the brachioradialis, but becomes mostly tendon early on.\n\nPassing between the brachioradialis and the extensor carpi radialis brevis, this tendon continues into the second tendon compartment together with the latter muscle.\n\nIt is inserted into the dorsal surface of the base of the second metacarpal bone, on its radial side.\n\n=== Innervation ===\n\nThe extensor carpi radialis longus is a wrist extensor that is innervated by the radial nerve, from spinal roots C6 and C7.\n\nAll other major extensor muscles in the superficial layer of the posterior compartment (the extensor digitorum, extensor carpi radialis brevis, extensor carpi ulnaris, and extensor digiti minimi) are innervated by the posterior interosseous branch of the radial nerve.\n\n== Function ==\n\nAs the name suggests, this muscle is an extensor at the wrist joint and travels along the radial side of the arm, so it will also abduct (radial abduction) the hand at the wrist.\n\nThat is, it manipulates the wrist so as to move the hand towards the thumb (i.e. abduction—away from the mid-position of the hand) and away from the palmar side (i.e. extension—increased angle between the palm and the front of the forearm).\n\n== Society and culture ==\n\n=== Exercises ===\n\nThe muscle, like all extensors of the forearm, can be strengthened by exercise that resist its extension; Reverse wrist curls with dumbbells can be performed.\n\nhttps://en.wikipedia.org/wiki/Extensor_carpi_radialis_longus_muscle","extensor-carpi-radialis-brevis":"In human anatomy, extensor carpi radialis brevis is a muscle in the forearm that acts to extend and abduct the wrist.\n\nIt is shorter and thicker than its namesake extensor carpi radialis longus which can be found above the proximal end of the extensor carpi radialis brevis.\n\n== Origin and insertion ==\n\nIt arises from the lateral epicondyle of the humerus, by the common extensor tendon; from the radial collateral ligament of the elbow-joint; from a strong aponeurosis which covers its surface; and from the intermuscular septa between it and the adjacent muscles.\n\nThe fibres end approximately at the middle of the forearm in the form of a flat tendon, which is closely connected with that of the extensor carpi radialis longus, and accompanies it to the wrist; it passes beneath the abductor pollicis longus and extensor pollicis brevis, beneath the extensor retinaculum, and inserts into the lateral dorsal surface of the base of the third metacarpal bone, with a few fibres inserting into the medial dorsal surface of the second metacarpal bone.\n\n== Relations ==\n\nUnder the extensor retinaculum the tendon lies on the back of the radius in a shallow groove, to the ulnar side of that which lodges the tendon of the extensor carpi radialis longus, and separated from it by a faint ridge.\n\n== Innervation ==\n\nLike all the muscles in the posterior forearm, ECR brevis is supplied by a branch of the radial nerve.\n\n== Function ==\n\nIt is an extensor, and an abductor of the hand at the wrist joint.\n\nThat is, it serves to manipulate the wrist so that the fingers moves away from the palm.\n\nThe muscle, like all extensors of the forearm, can be strengthened by exercise that resist its extension; Reverse wrist curls with dumbbells can be performed.\n\nhttps://en.wikipedia.org/wiki/Extensor_carpi_radialis_brevis_muscle","anconeus-muscle":"The anconeus muscle (or anconaeus/anconæus) is a small muscle on the posterior aspect of the elbow joint.\nSome consider anconeus to be a continuation of the triceps brachii muscle.\n\nSome sources consider it to be part of the posterior compartment of the arm, while others consider it part of the posterior compartment of the forearm.The anconeus muscle can easily be palpated just lateral to the olecranon process of the ulna.\n\n== Structure ==\n\nAnconeus originates on the posterior surface of the lateral epicondyle of the humerus and inserts distally on the superior posterior surface of the ulna and the lateral aspect of the olecranon.\n\n=== Innervation ===\n\nAnconeus is innervated by a branch of the radial nerve (cervical roots 7 and 8) from the posterior cord of the brachial plexus called the nerve to the anconeus.\n\nThe somatomotor portion of radial nerve innervating anconeus bifurcates from the main branch in the radial groove of the humerus.\n\nThis innervation pattern follows the rules of innervation of the musculature of the posterior forearm (extensor) compartment by the radial nerve.\n\n== Function ==\n\nIts role in elbow extension is trivial in humans.\n\nIt assists in extension of the elbow, where the triceps brachii is the principal agonist, and supports the elbow in full extension.\n\nIt also prevents the elbow joint capsule being pinched in the olecranon fossa during extension of the elbow.\n\nAnconeus also abducts the ulna and stabilizes the elbow joint.\n\nAnconeus serves to make minute movements with the radius on the ulna.\n\nIn making slight abduction of the ulna, it allows any finger to be used as an axis of rotation of the forearm.\n\n=== Blood supply ===\n\nAnconeus is supplied by the middle collateral artery from the profunda brachii artery.\n\n== Clinical significance ==\n\nTrauma to the nerve supply of the anconeus muscle can usually result from a shoulder dislocation or fractures of the upper part of the humerus or around the olecranon, or any injury that damages the radial nerve.\n\nHarm inflicted upon the radial nerve through these mechanisms can paralyze the anconeus muscle as well as other extensors of the elbow and wrist.\n\nThere are no specific acquired injuries that exclusively affect the anconeus muscle; however, any disease that compromises muscular functions, particularly arm extension (i.e. muscular dystrophy) will affect this particular accessory muscle.\n\nHeterotopic ossification can result from certain trauma as it is an abnormal growth of osseous tissue in non-osseous tissue (e.g. muscle tissue).\n\nThe condition is usually found in the hips, although there have been documented cases of certain individuals with it occurring in the arms and legs.\n\nThe cause for the process to initiate is not well understood, only that it typically results from surgery or trauma.\n\n== History ==\n\n=== Etymology and spelling ===\n\nAnconeus muscle is the anglicized form of the Latin expression musculus anconaeus, as can be found in the Nomina Anatomica as ratified in Basel in 1895 and in Jena in 1935.\n\nThe anatomic Latin adjective anconaeus was written as anconeus in the subsequent edition of the Nomina Anatomica as authorized in 1955 in Paris, without any further explanation of this specific diphthong reduction.\n\nThe following edition of 1961 specified its policy by stating that: All diphthongs should be eliminated.\n\nAlthough a selected number of monophthongizations was reverted, subsequent editions of the Nomina Anatomica and its most recent outing Terminologia Anatomica insisted on writing musculus anconeus.\n\nDespite the earlier preference of the Nomina Anatomica for anconaeus no ancient Greek form ἀγκωναῖος is attested.\n\nIn modern Greek the expression ἀγκωνιαίος μυς is used, with the from anconaeus deviating adjective ἀγκωνιαίος.Anconaeus is derived from the ancient Greek noun, ἀγκών. 'Ακών can be translated as bend of the arm or elbow.\n\nThe expression musculus anconaeus was translated into English as elbow muscle in 1907 in the English translation of the first edition of the Nomina Anatomica.\n\nhttps://en.wikipedia.org/wiki/Anconeus_muscle","extensor-digiti-minimi":"The extensor digiti minimi (extensor digiti quinti proprius) is a slender muscle of the forearm, placed on the ulnar side of the extensor digitorum communis, with which it is generally connected.\n\nIt arises from the common extensor tendon by a thin tendinous slip and frequently from the intermuscular septa between it and the adjacent muscles.\n\nIts tendon passes through a compartment of the extensor retinaculum, posterior to distal radio-ulnar joint, then divides into two as it crosses the dorsum of the hand, and finally joins the extensor digitorum tendon.\n\nAll three tendons attach to the dorsal digital expansion of the fifth digit (little finger).\n\nThere may be a slip of tendon to the fourth digit.\n\n== Variations ==\n\nAn additional fibrous slip from the lateral epicondyle; the tendon of insertion may not divide or may send a slip to the ring finger.\n\nAbsence of muscle rare; fusion of the belly with the extensor digitorum communis not uncommon.\n\nVariations to the fifth extensor compartment, which the extensor digiti minimi runs through, may cause tenosynovitis and can limit the use of the extensor digiti minimi.\n\nExtensor digiti minimi can also be bifurcated, which means split, at many different points in the muscle.\n\n== Functions ==\n\nThe extensor digiti minimi is a two joint muscle.\n\nIt acts as an extensor in both joints.\n\nIt extends the wrist, which means it moves the back of the hand toward the back of the forearm.\n\nIt also extends the little finger, which means it straightens the little finger from a fist.\n\nhttps://en.wikipedia.org/wiki/Extensor_digiti_minimi_muscle","supinator":"In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius.\n\nIts function is to supinate the forearm.\n\n== Structure ==\n\nSupinator consists of two planes of fibers, between which the deep branch of the radial nerve ls.\n\nThe two planes arise in common — the superficial one by tendinous (the initial portion of the muscle is actually just tendon) and the deeper by muscular fibers — from the supinator crest of the ulna, the lateral epicondyle of humerus, the radial collateral ligament, and the annular radial ligament.\n\nThe superficial fibers (pars superficialis) surround the upper part of the radius, and are inserted into the lateral edge of the radial tuberosity and the oblique line of the radius, as low down as the insertion of the pronator teres.\n\nThe upper fibers (pars profunda) of the deeper plane form a sling-like fasciculus, which encircles the neck of the radius above the tuberosity and is attached to the back part of its medial surface; the greater part of this portion of the muscle is inserted into the dorsal and lateral surfaces of the body of the radius, midway between the oblique line and the head of the bone.\n\nThe proximal aspect of the superficial head is known as the arcade of Frohse or the supinator arch.\n\n=== Innervation ===\n\nIt is innervated by the deep branch of the radial nerve.\n\nThe deep branch then becomes the posterior interosseous nerve upon exiting the supinator muscle.\n\nIts nerve roots are primarily from C6, with some C5 involvement.\n\nThere is also possible additional C7 innervation.\n\nThe radial nerve divides into deep and sensory superficial branches just proximal to the supinator muscle — an arrangement that can lead to entrapment and compression of the deep part, potentially resulting in selective paralysis of the muscles served by this nerve (the extensor muscles and the abductor pollicis longus.)\n\nMany possible causes are known for this nerve syndrome, known as supinator entrapment syndrome, including compression by various soft-tissued masses surrounding the nerve, and stress caused by repetitive supination and pronation.\n\n=== Variation ===\n\nThe deep radial nerve passes through the belly of supinator in 70% of cases and via the arcade of Frohse in remaining cases.\n\n== Function ==\n\nEncircling the radius, supinator brings the hand into the supinated position.\n\nIn contrast to the biceps brachii, it is able to do this in all positions of elbow flexion and extension.\n\nSupinator always acts together with biceps, except when the elbow joint is extended.\n\nIt is the most active muscle in forearm supination during unresisted supination, while biceps becomes increasingly active with heavy loading.\n\nSupination strength decreases by 64% if supinator is disabled by, for example, injury.\n\n== History ==\n\n=== Etymology ===\n\nThe term \"supinator\" can also refer more generally to a muscle that causes supination of a part of the body.\n\nIn older texts, the term \"supinator longus\" was used to refer to the brachioradialis, and \"supinator brevis\" was used to describe the muscle now known as the supinator.\n\nhttps://en.wikipedia.org/wiki/Supinator_muscle","abductor-pollicis-longus":"In human anatomy, the abductor pollicis longus (APL) is one of the extrinsic muscles of the hand.\n\nIts major function is to abduct the thumb at the wrist.\n\nIts tendon forms the anterior border of the anatomical snuffbox.\n\n== Structure ==\n\nThe abductor pollicis longus lies immediately below the supinator and is sometimes united with it.\n\nIt arises from the lateral part of the dorsal surface of the body of the ulna, below the insertion of the anconeus, from the interosseous membrane, and from the middle third of the dorsal surface of the body of the radius.\n\nPassing obliquely downward and lateralward, it ends in a tendon, which runs through a groove on the lateral side of the lower end of the radius, accompanied by the tendon of the extensor pollicis brevis.\n\nThe insertion is divided into a distal, superficial part and a proximal, deep part.\n\nThe superficial part is inserted with one or more tendons into the radial side of the base of the first metacarpal bone, and the deep part is variably inserted into the trapezium, the joint capsule and its ligaments, and into the belly of abductor pollicis brevis (APB) or opponens pollicis.\n\n=== Innervation ===\n\nThe abductor pollicis longus muscle is innervated by the posterior interosseous nerve, which is a continuation of the deep branch of the radial nerve after it passes through the supinator muscle.\n\nAbductor pollicis longus lies close to the radial nerve.\n\nThe posterior interosseous nerve is derived from spinal segments C7 & C8.\n\n=== Blood supply ===\n\nAbductor pollicis longus is supplied by the posterior interosseous artery.\n\n=== Variation ===\n\nAn accessory abductor pollicis longus (AAPL) tendon is present in more than 80% of people and a separate muscle belly is present in 20% of people.\n\nIn one study, the accessory tendon was inserted into the trapezium (41%); proximally on the abductor pollicis brevis (22%) and opponens pollicis brevis (5%); had a double insertion on the trapezium and thenar muscles (15%); or the base of the first metacarpal (1%).\n\nUp to seven tendons have been reported in rare cases.Multiple APL tendons can be regarded as a functional advantage since injured tendons can be compensated by the healthy ones.\n\n== Function ==\n\nThe chief action of abductor pollicis longus is to abduct the thumb at the carpometacarpal joint, thereby moving the thumb anteriorly.\n\nIt also assists in extending and rotating the thumb.By its continued action it helps to abduct the wrist (radial deviation) and flex the hand.\n\nThe APL insertion on the trapezium and the APB origin on the same bone is the only connection between the thumb's intrinsic and extrinsic muscles.\n\nAs the thumb is brought into action, these two muscles must coordinate to keep the trapezium stable in the carpus, which is important for the proper functioning of the thumb (i.e. precision and power grip.)\n\n== In other animals ==\n\nThe only primates to have an APL completely separated from the extensor pollicis brevis are modern humans and gibbons.\n\nIn gibbons, however, the APL originates proximally on the radius and ulna, whereas it originates in the middle part of these bones in crab-eating monkeys, bonobos, and humans.\n\nIn all these primates, the muscle is inserted onto the base of the first metacarpal and sometimes onto the trapezium (siamangs and bonobos) and thumb sesamoids (crab-eating monkeys).\n\nIn chimpanzees, the APL flexes the thumb rather than extends it like in modern humans.\n\nCompared to the wrists of chimpanzees, the human wrist is derived (compared to the Pan-Homo LCA) in having considerably longer muscle moment arms for a range of hand muscles.\n\nIt is possible that these differences are due to supinated position of the trapezium in humans which, in its turn, is a result of the expansion of the trapezoid on the side of the palm.\n\nA small, lens-shaped radial sesamoid embedded into the APL tendon is a primitive state found in all known Carnivora genera except in the red and giant pandas and the extinct Simocyon where it is hypertrophied (enlarged) into a sixth digit or a so-called \"false thumb\", a derived trait that first appeared in ursids.\n\nThe APL sesamoid is present in all non-human primates, but only in about half of gorillas, and normally absent in humans.\n\nhttps://en.wikipedia.org/wiki/Abductor_pollicis_longus_muscle","extensor-indicis":"In human anatomy, the extensor indicis [proprius] is a narrow, elongated skeletal muscle in the deep layer of the dorsal forearm, placed medial to, and parallel with, the extensor pollicis longus.\n\nIts tendon goes to the index finger, which it extends.\n\n== Structure ==\n\nIt arises from the distal third of the dorsal part of the body of ulna and from the interosseous membrane.\n\nIt runs through the fourth tendon compartment together with the extensor digitorum, from where it projects into the dorsal aponeurosis of the index finger.\n\nOpposite the head of the second metacarpal bone, it joins the ulnar side of the tendon of the extensor digitorum which belongs to the index finger.\n\nLike the extensor digiti minimi (i.e. the extensor of the little finger), the tendon of the extensor indicis runs and inserts on the ulnar side of the tendon of the common extensor digitorum.\n\nThe extensor indicis lacks the juncturae tendinum interlinking the tendons of the extensor digitorum on the dorsal side of the hand.\n\n=== Variation ===\n\nThe extensor indicis proprius does not show much variation.\n\nIt exists as a single tendon most of the time.\n\nDouble tendons of the extensor indicis proprius was also reported.\n\nIt is known that the extensor indicis proprius inserts to the index finger on the ulnar side of the extensor digitorum.\n\nHowever, the insertion on the radial side of the common extensor digitorum infrequently seen, namely the extensor indicis radialis.\n\nSplit tendons of the muscle inserting on both ulnar and the radial side of the common extensor digitorum was also reported.\n\nAnomalous hand extensors including the extensor medii proprius and the extensor indicis et medii communis are often seen as variations of the extensor indicis due to the shared characteristics and embryonic origin.\n\n== Function ==\n\nThe extensor indicis extends the index finger, and by its continued action assists in extending (dorsiflexion) the wrist and the midcarpal joints.\n\nBecause the index finger and little finger have separate extensors, these fingers can be moved more independently than the other fingers.\n\nhttps://en.wikipedia.org/wiki/Extensor_indicis_muscle","extensor-pollicis-brevis":"In human anatomy, the extensor pollicis brevis is a skeletal muscle on the dorsal side of the forearm.\n\nIt lies on the medial side of, and is closely connected with, the abductor pollicis longus.\n\nThe extensor pollicis brevis (EPB) belongs to the deep group of the posterior fascial compartment of the forearm.[1] It is a part of the lateral border of the anatomical snuffbox.\n\n== Structure ==\n\nThe extensor pollicis brevis arises from the ulna distal to the abductor pollicis longus, from the interosseous membrane, and from the dorsal surface of the radius.\n\nIts direction is similar to that of the abductor pollicis longus, its tendon passing the same groove on the lateral side of the lower end of the radius, to be inserted into the base of the first phalanx of the thumb.\n\n=== Variation ===\n\nAbsence; fusion of tendon with that of the extensor pollicis longus or abductor pollicis longus muscle.\n\n== Function ==\n\nIn a close relationship to the abductor pollicis longus, the extensor pollicis brevis both extends and abducts the thumb at the carpometacarpal and metacarpophalangeal joints.\n\nhttps://en.wikipedia.org/wiki/Extensor_pollicis_brevis_muscle","extensor-pollicis-longus":"In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm.\n\nIt is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together with this muscle.\n\n== Structure ==\n\nThe extensor pollicis longus arises from the dorsal surface of the ulna and from the interosseous membrane, next to the origins of abductor pollicis longus and extensor pollicis brevis.\n\nPassing through the third tendon compartment, lying in a narrow, oblique groove on the back of the lower end of the radius, it crosses the wrist close to the dorsal midline before turning towards the thumb using Lister's tubercle on the distal end of the radius as a pulley.\n\nIt obliquely crosses the tendons of the extensores carpi radialis longus and brevis, and is separated from the extensor pollicis brevis by a triangular interval, the anatomical snuff box in which the radial artery is found.\n\nAt the proximal phalanx, the tendon is joined by expansions from abductor pollicis brevis and adductor pollicis.\n\nThe tendon is finally inserted on the base of the distal phalanx of the thumb.6.7 to 9.7 centimetres (2.6 to 3.8 in) in length, the tendon passes through a long and superficial synovial sheath which, passing obliquely from the radial border of the forearm into the thumb, extends from the proximal border of the extensor retinaculum to the first carpometacarpal joint.\n\nIn the synovial sheath a proximal and a distal mesotendon connect the tendon to the floor of the sheath.\n\n=== Relations ===\n\nTogether with the tendons of the extensor pollicis brevis and the abductor pollicis longus, its tendon crosses the radial artery.\n\n=== Blood supply ===\n\nThe tendon of extensor pollicis longus is supplied by branches from various arteries.\n\nBefore the tendon enters its synovial sheath, arteries from the anterior interosseous artery or its muscular branches enter the tendon.\n\nThe sheath itself is supplied by the posterior ramus of the same artery.\n\nIn the metacarpal region, beyond the synovial sheath, the tendon is supplied directly from the radial artery.\n\nAt the phalanges, the tendon forms a dorsal aponeurosis which is supplied by a digital branch of the first dorsal metacarpal artery.\n\n=== Innervation ===\n\nThe extensor pollicis longus muscle receives innervation from the posterior interosseous nerve (C7 and C8) which is the continuation of the deep branch of the radial nerve.\n\n== Function ==\n\nExtensor pollicis longus extends the terminal phalanx of the thumb.\n\nWhile abductor pollicis brevis and adductor pollicis, both attached to the extensor pollicis longus tendon, can extend the thumb's interphalangeal joint to the neutral position, only extensor pollicis longus can achieve full hyperextension at the interphalangeal joint.\n\nThis complete extension at the interphalangeal joint is not possible, or considerably more difficult, with the carpal, carpometacarpal, and metacarpophalangeal joints simultaneously extended.\n\nLikewise, flexion at the interphalangeal joint by flexor pollicis longus is considerably reduced in wrist flexion.\n\nIt also applies an extensor force at the metacarpophalangeal joint together with the extensor pollicis brevis and extends and adducts at the carpometacarpal joint of the thumb.\n\n== Clinical significance ==\n\n=== Injury ===\n\nTenosynovitis, inflammatory irritation of the synovial sheath, is relatively common in the third compartment after repetitive activities such as drum playing.\n\nhttps://en.wikipedia.org/wiki/Extensor_pollicis_longus_muscle","superficial-head-of-flexor-pollicis-brevis":"The flexor pollicis brevis is a muscle in the hand that flexes the thumb.\n\nIt is one of three thenar muscles.\n\nIt has both a superficial part and a deep part.\n\n== Origin and insertion ==\n\nThe muscle's superficial head arises from the distal edge of the flexor retinaculum and the tubercle of the trapezium, the most lateral bone in the distal row of carpal bones.\n\nIt passes along the radial side of the tendon of the flexor pollicis longus.\nThe deeper (and medial) head \"varies in size and may be absent.\" It arises from the trapezoid and capitate bones on the floor of the carpal tunnel, as well as the ligaments of the distal carpal row.Both heads become tendinous and insert together into the radial side of the base of the proximal phalanx of the thumb; at the junction between the tendinous heads there is a sesamoid bone.\n\n== Innervation ==\n\nThe superficial head is usually innervated by the lateral terminal branch of the median nerve.\n\nThe deep part is often innervated by the deep branch of the ulnar nerve (C8, T1).\n\n== Blood supply ==\n\nThe flexor pollicis brevis receives its blood supply from the superficial palmar branches of radial artery.\n\n== Action ==\n\nThe flexor pollicis brevis flexes the thumb at the metacarpophalangeal joint, as well as flexion and medial rotation of the 1st metacarpal bone at the carpometacarpal joint.\n\n== Pathology ==\n\nFlexor pollicis brevis can, rarely, be completely absent at birth due to a congenital issue (as can the other muscles of the thenar eminence).\n\nhttps://en.wikipedia.org/wiki/Flexor_pollicis_brevis_muscle","deep-head-of-flexor-pollicis-brevis":"The flexor pollicis brevis is a muscle in the hand that flexes the thumb.\n\nIt is one of three thenar muscles.\n\nIt has both a superficial part and a deep part.\n\n== Origin and insertion ==\n\nThe muscle's superficial head arises from the distal edge of the flexor retinaculum and the tubercle of the trapezium, the most lateral bone in the distal row of carpal bones.\n\nIt passes along the radial side of the tendon of the flexor pollicis longus.\nThe deeper (and medial) head \"varies in size and may be absent.\" It arises from the trapezoid and capitate bones on the floor of the carpal tunnel, as well as the ligaments of the distal carpal row.Both heads become tendinous and insert together into the radial side of the base of the proximal phalanx of the thumb; at the junction between the tendinous heads there is a sesamoid bone.\n\n== Innervation ==\n\nThe superficial head is usually innervated by the lateral terminal branch of the median nerve.\n\nThe deep part is often innervated by the deep branch of the ulnar nerve (C8, T1).\n\n== Blood supply ==\n\nThe flexor pollicis brevis receives its blood supply from the superficial palmar branches of radial artery.\n\n== Action ==\n\nThe flexor pollicis brevis flexes the thumb at the metacarpophalangeal joint, as well as flexion and medial rotation of the 1st metacarpal bone at the carpometacarpal joint.\n\n== Pathology ==\n\nFlexor pollicis brevis can, rarely, be completely absent at birth due to a congenital issue (as can the other muscles of the thenar eminence).\n\nhttps://en.wikipedia.org/wiki/Flexor_pollicis_brevis_muscle","oblique-head-of-adductor-pollicis":"In human anatomy, the adductor pollicis muscle is a muscle in the hand that functions to adduct the thumb.\n\nIt has two heads: transverse and oblique.\n\nIt is a fleshy, flat, triangular, and fan-shaped muscle deep in the thenar compartment beneath the long flexor tendons and the lumbrical muscles at the center of the palm.\n\nIt overlies the metacarpal bones and the interosseous muscles.\n\n== Structure ==\n\n=== Oblique head ===\n\nThe oblique head (Latin: adductor obliquus pollicis) arises by several slips from the capitate bone, the bases of the second and third metacarpals, the intercarpal ligaments, and the sheath of the tendon of the flexor carpi radialis.\n\nFrom this origin the greater number of fibers pass obliquely downward and converge to a tendon, which, uniting with the tendons of the medial portion of the flexor pollicis brevis and the transverse head of the adductor pollicis, is inserted into the ulnar side of the base of the proximal phalanx of the thumb, a sesamoid bone being present in the tendon.\n\nA considerable fasciculus, however, passes more obliquely beneath the tendon of the flexor pollicis longus to join the lateral portion of the flexor pollicis brevis and the abductor pollicis brevis.\n\n=== Transverse head ===\n\nThe transverse head (Latin: adductor transversus pollicis) is deeply seated.\n\nIt is triangular, arising by a broad base from the lower two-thirds of the palmar surface of the third metacarpal bone; the fibers converge, to be inserted with the medial part of the flexor pollicis brevis and the oblique head into the ulnar side of the base of the proximal phalanx of the thumb.\n\n=== Relations ===\n\nThe radial artery passes between the two heads, travelling from the back of the hand into the palm, where it forms the deep palmar arch.\n\n=== Innervation ===\n\nThe adductor pollicis is innervated by the deep branch of the ulnar nerve (C8–T1).Between the oblique and transverse heads is a thin fibrous arcade which the nerve passes as it traverses the palm laterally.\n\nThe nerve is accompanied by the deep palmar arch.\n\n== Function ==\n\nWhile adduction of the thumb (bringing it back into the plane of the palm of the hand from its previously abducted position) is mainly produced by the adductor pollicis, it can also bring the thumb to the side of the palm and index finger and the flexor pollicis brevis and the opponens pollicis help in thumb adduction.\n\n== Clinical significance ==\n\nFroment's sign is used to test for a compromised adductor pollicis muscle.\n\nIn neuromuscular monitoring, the ulnar nerve is stimulated and the strength of adductor pollicis contraction is measured.\n\n== Other animals ==\n\nThe adductor pollicis evolved from the contrahens I muscle as man's ancestors' thumbs and big toes became opposable.\n\nIt might also contain an element of the thumb's interosseous muscle.\n\nIn the Pan-Homo LCA the oblique head of the adductor pollicis probably had a relatively small physiological cross sectional area (PCSA) and both heads probably acted as extensors and adductors at the carpometacarpal joint.\n\nIn humans the PCSA of the oblique head is relatively enlarged and both heads act as flexors at this joint.\n\nhttps://en.wikipedia.org/wiki/Adductor_pollicis_muscle","transverse-head-of-adductor-pollicis":"In human anatomy, the adductor pollicis muscle is a muscle in the hand that functions to adduct the thumb.\n\nIt has two heads: transverse and oblique.\n\nIt is a fleshy, flat, triangular, and fan-shaped muscle deep in the thenar compartment beneath the long flexor tendons and the lumbrical muscles at the center of the palm.\n\nIt overlies the metacarpal bones and the interosseous muscles.\n\n== Structure ==\n\n=== Oblique head ===\n\nThe oblique head (Latin: adductor obliquus pollicis) arises by several slips from the capitate bone, the bases of the second and third metacarpals, the intercarpal ligaments, and the sheath of the tendon of the flexor carpi radialis.\n\nFrom this origin the greater number of fibers pass obliquely downward and converge to a tendon, which, uniting with the tendons of the medial portion of the flexor pollicis brevis and the transverse head of the adductor pollicis, is inserted into the ulnar side of the base of the proximal phalanx of the thumb, a sesamoid bone being present in the tendon.\n\nA considerable fasciculus, however, passes more obliquely beneath the tendon of the flexor pollicis longus to join the lateral portion of the flexor pollicis brevis and the abductor pollicis brevis.\n\n=== Transverse head ===\n\nThe transverse head (Latin: adductor transversus pollicis) is deeply seated.\n\nIt is triangular, arising by a broad base from the lower two-thirds of the palmar surface of the third metacarpal bone; the fibers converge, to be inserted with the medial part of the flexor pollicis brevis and the oblique head into the ulnar side of the base of the proximal phalanx of the thumb.\n\n=== Relations ===\n\nThe radial artery passes between the two heads, travelling from the back of the hand into the palm, where it forms the deep palmar arch.\n\n=== Innervation ===\n\nThe adductor pollicis is innervated by the deep branch of the ulnar nerve (C8–T1).Between the oblique and transverse heads is a thin fibrous arcade which the nerve passes as it traverses the palm laterally.\n\nThe nerve is accompanied by the deep palmar arch.\n\n== Function ==\n\nWhile adduction of the thumb (bringing it back into the plane of the palm of the hand from its previously abducted position) is mainly produced by the adductor pollicis, it can also bring the thumb to the side of the palm and index finger and the flexor pollicis brevis and the opponens pollicis help in thumb adduction.\n\n== Clinical significance ==\n\nFroment's sign is used to test for a compromised adductor pollicis muscle.\n\nIn neuromuscular monitoring, the ulnar nerve is stimulated and the strength of adductor pollicis contraction is measured.\n\n== Other animals ==\n\nThe adductor pollicis evolved from the contrahens I muscle as man's ancestors' thumbs and big toes became opposable.\n\nIt might also contain an element of the thumb's interosseous muscle.\n\nIn the Pan-Homo LCA the oblique head of the adductor pollicis probably had a relatively small physiological cross sectional area (PCSA) and both heads probably acted as extensors and adductors at the carpometacarpal joint.\n\nIn humans the PCSA of the oblique head is relatively enlarged and both heads act as flexors at this joint.\n\nhttps://en.wikipedia.org/wiki/Adductor_pollicis_muscle","abductor-pollicis-brevis":"The abductor pollicis brevis is a muscle in the hand that functions as an abductor of the thumb.\n\n== Structure ==\n\nThe abductor pollicis brevis is a flat, thin muscle located just under the skin.\n\nIt is a thenar muscle, and therefore contributes to the bulk of the palm's thenar eminence.\n\nIt originates from the flexor retinaculum of the hand, the tubercle of the scaphoid bone, and additionally sometimes from the tubercle of the trapezium.\n\nRunning lateralward and downward, it is inserted by a thin, flat tendon into the lateral side of the base of the first phalanx of the thumb, and the capsule of the metacarpophalangeal joint.\n\n=== Nerve supply ===\n\nThe abductor pollicis brevis is supplied by the recurrent branch of the median nerve (Roots C5- C7 and C8-T1 in the brachial plexus lateral and medial cords respectively).\n\n== Function ==\n\nAbduction of the thumb is defined as the movement of the thumb anteriorly, a direction perpendicular to the palm.\n\nThe abductor pollicis brevis does this by acting across both the carpometacarpal joint and the metacarpophalangeal joint.\n\nIt also assists in opposition and extension of the thumb.\n\nhttps://en.wikipedia.org/wiki/Abductor_pollicis_brevis_muscle","opponens-pollicis-muscle":"The opponens pollicis is a small, triangular muscle in the hand, which functions to oppose the thumb.\n\nIt is one of the three thenar muscles.\n\nIt lies deep to the abductor pollicis brevis and lateral to the flexor pollicis brevis.\n\n== Structure ==\n\nThe opponens pollicis muscle is one of the three thenar muscles.\n\nIt originates from the flexor retinaculum of the hand and the tubercle of the trapezium.\n\nIt passes downward and laterally, and is inserted into the whole length of the metacarpal bone of the thumb on its radial side.\n\n=== Innervation ===\n\nLike the other thenar muscles, the opponens pollicis is innervated by the recurrent branch of the median nerve.\n\nIn 20% of the population, opponens pollicis is innervated by the ulnar nerve.\n\n=== Blood supply ===\n\nThe opponens pollicis receives its blood supply from the superficial palmar arch.\n\n== Function ==\n\nOpposition of the thumb is a combination of actions that allows the tip of the thumb to touch the tips of other fingers.\n\nThe part of apposition that this muscle is responsible for is the flexion of the thumb's metacarpal at the first carpometacarpal joint.\n\nThis specific action cups the palm.\n\nMany texts, for simplicity, use the term opposition to represent this component of true apposition.\n\nIn order to truly appose the thumb, the actions of a number of other muscles are needed at the thumb's metacarpophalangeal joint.\n\nNote that the two opponens muscles (opponens pollicis and opponens digiti minimi) are named so because they oppose each other, but their actions appose the bones.\n\nhttps://en.wikipedia.org/wiki/Opponens_pollicis_muscle","abductor-digiti-minimi-of-hand":"In human anatomy, the abductor digiti minimi (abductor minimi digiti, abductor digiti quinti, ADM) is a skeletal muscle situated on the ulnar border of the palm of the hand.\n\nIt forms the ulnar border of the palm and its spindle-like shape defines the hypothenar eminence of the palm together with the skin, connective tissue, and fat surrounding it.\n\nIts main function is to pull the little finger away from the other fingers (i.e. abduction).\n\n== Structure ==\n\nThe abductor digiti minimi arises from the pisiform bone, the pisohamate ligament, and the flexor retinaculum.\n\nIts distal tendon ends in three slips that are inserted into the ulnopalmar margin of the proximal phalanx, the palmar plate of the metacarpophalangeal joint, and the sesamoid bone when present.\n\nSome fibers insert into the finger's dorsal aponeurosis, which is why the muscle acts similar to a dorsal interosseus muscle.\n\nAdditionally, the ulnar-most portion of the tendon inserts into the little finger's digital cord, and the muscle thus forms part of a structure that flexes the metacarpophalangeal joint and extends the interphalangeal joints.\n\n=== Innervation ===\n\nIt is innervated by the deep branch of the ulnar nerve (C8–T1).\n\n=== Development ===\n\nThe abductor digit minimi develops at an early stage from an ulnar muscle primordium of the superficial layer of the original undifferentiated mesenchyme of the hand, together with the flexor digitorum superficialis (medial primordia) and the abductor pollicis brevis (radial).\n\nIn contrast, the remaining hypothenar muscles are derived from the deep layer at a later stage.\n\n=== Variation ===\n\nIn rare cases accessory fascicles of the abductor digiti minimi have been found arising from the antebrachial fascia, the radius, and the ulna.\n\nThe abductor digiti minimi is the most variable hypothenar muscle, and might be joined by accessory slips from the tendon of the flexor carpi ulnaris, the flexor retinaculum, the fascia of the distal forearm, or the tendon of the palmaris longus.\n\nOccasionally, the muscle is partially inserted onto the fifth metacarpal bone.In case of polydactyly it may insert to the sixth finger instead, if there is one.\n\n== Function ==\n\nIt is an abductor of the little finger at the metacarpophalangeal joint.It is also possible that the muscle contributes to extension of the middle phalanx of the little finger through its connection to finger's extensor mechanism.It plays an important role when the hand is grasping large objects with outspread fingers.\n\n== Etymology ==\n\nThe name is derived from the Latin -ab \"away from\"; ducere \"to draw\"; digitus, \"digit\"; and minimum, smallest; or quintus, \"fifth\", meaning \"abductor of the smallest or fifth finger\".\n\nhttps://en.wikipedia.org/wiki/Abductor_digiti_minimi_muscle_of_hand","flexor-digiti-minimi-of-hand":"The flexor digiti minimi brevis is a hypothenar muscle in the hand that flexes the little finger (digit V) at the metacarpophalangeal joint.\n\nIt lies lateral to the abductor digiti minimi when the hand is in anatomical position.\n\n== Structure ==\n\nThe flexor digiti minimi brevis arises from the hamulus of the hamate bone and the palmar surface of the flexor retinaculum of the hand.\n\nIt is inserted into the medial side of the base of the proximal phalanx of digit V.\n\nIt is separated from the abductor digiti minimi, at its origin, by the deep branches of the ulnar artery and the ulnar nerve.\n\nThe flexor digiti minimi brevis is sometimes not present; in these cases, the abductor digiti minimi is usually larger than normal.\n\nThe flexor digiti minimi brevis is one of three muscles in the hypothenar muscle group.\n\nThese three muscles form the fleshy mass at the base of the little finger, and are solely concerned with the movement of digit V.\n\nThe other two muscles that make up the hypothenar muscle group are the abductor digiti minimi and the opponens digiti minimi.\n\nIn anatomical position from medial to lateral is the abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi.\n\n== Innervation ==\n\nThe flexor digiti minimi brevis, like other hypothenar muscles, is innervated by the deep branch of the ulnar nerve.\n\nThe ulnar nerve arises from the spinal nerve levels C8-T1.\n\nThe spinal roots of C8 and T1 then merge to form the lower trunk, anterior division, medial cord, and finally produce the ulnar nerve.\n\nThe ulnar nerve has a superficial and deep branch, but it is the deep branch that innervates the flexor digiti minimi brevis.\n\n== Actions ==\n\nThe flexor digiti minimi brevis flexes the little finger at the metacarpophalangeal joint.\n\n== Etymology ==\n\nThe name of this muscle is Latin for the 'short flexor of the little finger'.\n\nNote that brevis is usually included to differentiate it from a longus muscle of the same name.\n\nThe flexor digiti minimi longus, however, is not found in the typical human, but instead is a rare anatomical variation.\n\nhttps://en.wikipedia.org/wiki/Flexor_digiti_minimi_brevis_muscle_(hand)","opponens-digiti-minimi-muscle-of-hand":"The opponens digiti minimi (opponens digiti quinti in older texts) is a muscle in the hand.\n\nIt is of a triangular form, and placed immediately beneath the palmaris brevis, abductor digiti minimi and flexor digiti minimi brevis.\n\nIt is one of the three hypothenar muscles that control the little finger.\n\nIt arises from the convexity of the hamulus of the hamate bone and the contiguous portion of the transverse carpal ligament; it is inserted into the whole length of the metacarpal bone of the little finger, along its ulnar margin.\n\nThe opponens digiti minimi muscle serves to flex and laterally rotate the 5th metacarpal about the 5th carpometacarpal joint, as when bringing the little finger and thumb into opposition.\n\nIt is innervated by the deep branch of the ulnar nerve.\n\nhttps://en.wikipedia.org/wiki/Opponens_digiti_minimi_muscle_of_hand","lumbrical-muscles-of-hand":"LUMBRICALS OF THE HAND\n\nThe lumbricals are intrinsic muscles of the hand that flex the metacarpophalangeal joints, and extend the interphalangeal joints.\n\nThe lumbrical muscles of the foot also have a similar action, though they are of less clinical concern.\n\n== Structure ==\n\nThe lumbricals are four, small, worm-like muscles on each hand.\n\nThese muscles are unusual in that they do not attach to bone.\n\nInstead, they attach proximally to the tendons of flexor digitorum profundus, and distally to the extensor expansions.\n\nThe first and second lumbricals are unipennate, while the third and fourth lumbricals are bipennate.\n\n=== Nerve supply ===\n\nThe first and second lumbricals (the most radial two) are innervated by the median nerve.\n\nThe third and fourth lumbricals (most ulnar two) are innervated by the ulnar nerve.This is the usual innervation of the lumbricals (occurring in 60% of individuals).\n\nHowever 1:3 (median:ulnar - 20% of individuals) and 3:1 (median:ulnar - 20% of individuals) also exist.\n\nThe lumbrical innervation always follows the innervation pattern of the associated muscle unit of flexor digitorum profundus (i.e. if the muscle units supplying the tendon to the middle finger are innervated by the median nerve, the second lumbrical will also be innervated by the median nerve).\n\n=== Blood supply ===\n\nFour separate sources supply blood to these muscles: the superficial palmar arch, the common palmar digital artery, the deep palmar arch, and the dorsal digital artery.\n\n== Function ==\n\nThe lumbrical muscles, with the help of the interosseous muscles, simultaneously flex the metacarpophalangeal joints while extending both interphalangeal joints of the digit on which it inserts.\n\nThe lumbricals are used during an upstroke in writing.\n\n== Etymology ==\n\nThe term \"lumbrical\" comes from the Latin, meaning \"worm\".\n\nhttps://en.wikipedia.org/wiki/Lumbricals_of_the_hand","dorsal-interossei-muscles-of-hand":"In human anatomy, the dorsal interossei (DI) are four muscles in the back of the hand that act to abduct (spread) the index, middle, and ring fingers away from hand's midline (ray of middle finger) and assist in flexion at the metacarpophalangeal joints and extension at the interphalangeal joints of the index, middle and ring fingers.\n\n== Structure ==\n\nThere are four dorsal interossei in each hand.\n\nThey are specified as 'dorsal' to contrast them with the palmar interossei, which are located on the anterior side of the metacarpals.\n\nThe dorsal interosseous muscles are bipennate, with each muscle arising by two heads from the adjacent sides of the metacarpal bones, but more extensively from the metacarpal bone of the finger into which the muscle is inserted.\n\nThey are inserted into the bases of the proximal phalanges and into the extensor expansion of the corresponding extensor digitorum tendon.\n\nThe middle digit has two dorsal interossei insert onto it while the first digit (thumb) and the fifth digit (little finger) have none.\n\nEach finger is provided with two interossei (palmar or dorsal), with the exception of the little finger, in which the abductor digiti minimi muscle takes the place of one of the dorsal interossei.\n\nThe first dorsal interosseous muscle is larger than the others.\n\nBetween its two heads, the radial artery passes from the back of the hand into the palm.\n\nBetween the heads of dorsal interossei two, three, and four, a perforating branch from the deep palmar arch is transmitted.\n\n=== Origins and insertions ===\n\n=== Proximal and distal interossei ===\n\nWith some individual variations, the interossei muscles are attached either proximally or distally on the extensor expansion.\n\nThe first dorsal interosseous, the most consistent, is inserted entirely into the base of its proximal phalanx and the extensor hood there.\n\nThe second, third, and fourth dorsal interossei have insertions both proximally on the base of the metacarpal and hood, and distally on the lateral bands and central tendon of the extensor mechanism.\n\nThe abductor digiti minimi, effectively the \"fifth dorsal interosseus\" or the dorsal interosseus of the little finger, has only a proximal insertion.\n\nThe palmar interossei, in contrast, have only distal insertions.\n\nThe interossei can, thus, be divided into a proximal and a distal group: the proximal interossei are mainly affecting the metacarpophalangeal (MP) joints, whereas the distal interossei are mainly affecting the interphalangeal (IP) joints (but, with continued action, will also affect the MP joints.)\n\n=== Innervation ===\n\nAll interosseous muscles of the hand, with the exception of the first and second lumbricals (the most radial two are innervated by the median nerve), are innervated by the deep branch of the ulnar nerve.\n\n== Function ==\n\nThe dorsal interossei abduct the index, middle, and ring fingers.\n\nThe first dorsal interosseous is also able to rotate the index finger slightly at the metacarpophalangeal joint and assist adductor pollicis in thumb adduction.\n\n=== Metacarpophalangeal joint flexion ===\n\nAll interossei pass dorsal to the transverse metacarpal ligament but slightly volar to the flexion-extension axes of rotation of the MP joints.\n\nIn effect, their ability to flex at the MP joints will depend on the position of the MP joints:When the MP joints are extended, all interossei pass through the flexion-extension axes of the MP joints and their contribution there is therefore negligible, though they still play important roles as joint stabilizers (i.e. preventing MP hyperextension).\n\nAt the same time, the interossei (and abductor digiti minimi) lie relatively far from the anterior-posterior axis of the MP joints and are consequently effective abductors and adductors during MP extension.\n\nBecause the dorsal interossei are predominantly in the proximal group they are more effective at the MP joints than the palmar interossei and, therefore, abduction is stronger than adduction at the MP joints.When the MP joints are being flexed, the position of the interossei moves away volarly from the flexion-extension axes of the MP joints until they are nearly perpendicular to the proximal phalanx.\n\nAt the same time, the increasingly taut collateral ligaments of the MP joints cancel out the abduction-adduction component to increase the force of flexion (resulting in a strong grip).\n\nAt full flexion, the transverse metacarpal ligament restricts the interossei.\n\n=== Interphalangeal joint extension ===\n\nWhen the MP joints are extended, effective IP joint extension can be achieved by all interossei in the distal group (i.e. all except the two outermost muscles, the first interosseus and abductor digiti minimi) because they are attached directly to the extension mechanism.\n\nThis IP extension is therefore stronger than MP abduction/adduction which is produced by continued action except for the index and little fingers.\n\nWhen the MP joints are flexed, the transverse metacarpal ligament enhances the function of the distal interossei by acting as a pulley and preventing them from becoming slack, further increasing the effectiveness of IP extension.\n\n== Clinical relevance ==\n\n=== First dorsal interosseous compartment syndrome ===\n\nCompartment syndrome rarely occurs in the first dorsal interosseous compartment of hand.\n\nThis condition is caused by excessive use of hand, resulting in pain and swelling on the dorsum of the hand.\n\nIt can be treated by simple fasciotomy.\n\nhttps://en.wikipedia.org/wiki/Dorsal_interossei_of_the_hand","palmar-interossei-muscles":"In human anatomy, the palmar or volar interossei (interossei volares in older literature) are three small, unipennate muscles in the hand that lie between the metacarpal bones and are attached to the index, ring, and little fingers.\n\nThey are smaller than the dorsal interossei of the hand.\n\n== Structure ==\n\nAll palmar interossei originate along the shaft of the metacarpal bone of the digit on which they act.\n\nThey are inserted into the base of the proximal phalanx and the extensor expansion of the extensor digitorum of the same digit.\n\n=== Pollical palmar interosseous ===\n\nThe first palmar interosseous is located at the thumb's medial side.\n\nPassing between the first dorsal interosseous and the oblique head of adductor pollicis, it is inserted on the base of the thumb's proximal phalanx together with adductor pollicis.\n\nThe \"pollical\" palmar interosseous muscle (PPIM), is present in more than 80% of individuals and was first described by Henle 1858.\n\nIts presence has been verified by numerous anatomists since, but others have either failed to mention it or considered it part of either adductor pollicis or flexor pollicis brevis.\n\nHowever, the deep head of the flexor pollicis brevis originates on the thumb's ulnar sesamoid bone and the oblique portion of the adductor pollicis on several carpal bones, as well as the bases of the second and third metacarpal bones and not on the first metacarpal.\n\n=== Central palmar interossei ===\n\nThe other three palmar interossei originate on the side of the metacarpal facing the hand's midline (ray of long finger); the second is attached to the medial side of the index finger; the third to the lateral side of the ring finger; and the fourth to the lateral side of the little finger.\n\nThe tendons of these three muscles pass posterior to the deep transverse ligament before being inserted onto the extensor expansion.\n\n=== Innervation ===\n\nAll of the interosseous muscles of the hand are innervated by the deep branch of the ulnar nerve.\n\n=== Blood supply ===\n\nThe palmar interossei are supplied by the palmar metacarpal artery of the deep palmar arch.\n\n== Function ==\n\nThe palmar interosseous muscles adduct the fingers towards the middle finger.\n\nThis is in contrast to the dorsal interossei, which abduct the fingers away from the middle finger.\n\nIn addition (like dorsal interossei) they flex the finger at the metacarpo-phalangeal joint and extend the finger at the interphalangeal joint and thus assist the lumbricals.\n\nThe palmar interossei, together with the dorsal interossei and the lumbricals, are active components of the finger's extensor mechanism.\n\nFibers from some of the interossei contribute directly to the extensor hoods that wrap around the proximal phalanges, while other fibers may contribute to the central tendon and lateral bands of the mechanism.\n\nAll three intrinsic groups of muscles pass palmar to the axis of the metacarpophalangeal joints, and therefore contribute to flexion there.\n\nExtension at the interphalangeal joints cannot be produced by the extensor digitorum alone, but active contraction of one of the three aforementioned intrinsic groups will because of their direct contribution to the extensor mechanism.\n\n== Other animals ==\n\nThe pollical palmar interosseous muscle (PPIM) is absent in non-human primates, and is probably an autapomorphic muscle unique to the human thumb (together with flexor pollicis longus) which probably evolved from the oblique portion of adductor pollicis.\n\nIn African apes, adductor pollicis is notably well-developed, with an origin on the carpus and its ligaments, and an insertion that has migrated distally, in some cases as far as the distal phalanx.\n\nThe insertion of the PPIM into the extensor mechanism is likely to have evolved with tool usage in early hominids.\n\nAs comparative anatomy studies of the human PPIM strongly suggest that the muscle is evolutionarily derived from the adductor pollicis, it has been proposed that PPIM should be designated by the name musculus adductor pollicis accessorius, which indicates that the muscle is most likely a de novo structure derived from the adductor pollicis.\n\nhttps://en.wikipedia.org/wiki/Palmar_interossei_muscles","medial-intermuscular-septum-of-arm":"The medial intermuscular septum, is thicker than the lateral intermuscular septum.\n\nIt extends from the lower part of the crest of the lesser tubercle of the humerus below the teres major, and passes along the medial supracondylar ridge to the medial epicondyle; it is blended with the tendon of the coracobrachialis, and gives attachment to the triceps brachii behind and the brachialis in front.\n\nIt is perforated by the ulnar nerve, the superior ulnar collateral artery, and the posterior branch of the inferior ulnar collateral artery.\n\nhttps://en.wikipedia.org/wiki/Fascial_compartments_of_arm","deltoid-fascia":"The deltoid fascia contributes to the brachial fascia and is connected to the medial and lateral intermuscular septa.","brachial-fascia":"The brachial fascia (deep fascia of the arm) is continuous with that covering the deltoideus and the pectoralis major muscle, by means of which it is attached, above, to the clavicle, acromion, and spine of the scapula; it forms a thin, loose, membranous sheath for the muscles of the arm, and sends septa between them; it is composed of fibers disposed in a circular or spiral direction, and connected together by vertical and oblique fibers.\n\nIt differs in thickness at different parts, being thin over the biceps brachii, but thicker where it covers the triceps brachii, and over the epicondyles of the humerus: it is strengthened by fibrous aponeuroses, derived from the pectoralis major and latissimus dorsi medially, and from the deltoideus laterally.\n\nOn either side it gives off a strong intermuscular septum, which is attached to the corresponding supracondylar ridge and epicondyle of the humerus.\n\nhttps://en.wikipedia.org/wiki/Brachial_fascia","antebrachial-fascia":"The antebrachial fascia (antibrachial fascia or deep fascia of forearm) continuous above with the brachial fascia, is a dense, membranous investment, which forms a general sheath for the muscles in this region; it is attached, behind, to the olecranon and dorsal border of the ulna, and gives off from its deep surface numerous intermuscular septa, which enclose each muscle separately.\n\nOver the flexor muscles tendons as they approach the wrist it is especially thickened, and forms the volar carpal ligament.\n\nThis is continuous with the transverse carpal ligament, and forms a sheath for the tendon of the palmaris longus which passes over the transverse carpal ligament to be inserted into the palmar aponeurosis.\n\nBehind, near the wrist-joint, it is thickened by the addition of many transverse fibers, and forms the dorsal carpal ligament.\n\nIt is much thicker on the dorsal than on the volar surface, and at the lower than at the upper part of the forearm, and is strengthened above by tendinous fibers derived from the Biceps brachii in front, and from the Triceps brachii behind.\n\nIt gives origin to muscular fibers, especially at the upper part of the medial and lateral sides of the forearm, and forms the boundaries of a series of cone-shaped cavities, in which the muscles are contained.\n\nBesides the vertical septa separating the individual muscles, transverse septa are given off both on the volar and dorsal surfaces of the forearm, separating the deep from the superficial layers of muscles.\n\nApertures exist in the fascia for the passage of vessels and nerves; one of these apertures of large size, situated at the front of the elbow, serves for the passage of a communicating branch between the superficial and deep veins.\n\nhttps://en.wikipedia.org/wiki/Antebrachial_fascia","extensor-retinaculum-of-wrist":"The extensor retinaculum (dorsal carpal ligament, or posterior annular ligament) is an anatomical term for the thickened part of the antebrachial fascia that holds the tendons of the extensor muscles in place.\n\nIt is located on the back of the forearm, just proximal to the hand.\n\nIt is continuous with the palmar carpal ligament, which is located on the anterior side of the forearm.\n\n== Structure ==\n\nThe extensor retinaculum is a strong, fibrous band, extending obliquely downward and medialward across the back of the wrist.\n\nIt consists of part of the deep fascia of the back of the forearm, strengthened by the addition of some transverse fibers.\nThe extensor retinaculum is attached laterally to the lateral margin of the radius.\n\nHowever, it is not attached to the ulna, as the distance between these two bones varies with supination and pronation of the forearm.\n\nInstead the medial attachment is to the pisiform bone, the fifth metacarpal bone, and the pisometacarpal ligament.\n\nThe retinaculum is also attached in its passage across the wrist, to the ridges on the dorsal surface of the radius.\n\n== Histology ==\n\nStructurally, the retinaculum consists of three layers.\n\nThe deepest layer, the gliding layer, consists of hyaluronic acid-secreting cells.\n\nThe thick middle layer consists of interspersed elastin fibers, collagen bundles, and fibroblasts.\n\nThe most superficial layer is made up of loose connective tissue which contains vascular channels.\n\nCombined these three layers create a smooth gliding surface as well as mechanically strong tissue which prevents tendon bowstringing.\n\nThe extensor retinaculum of the foot has similar structure.\n\n== Clinical significance ==\n\nStudies conducted on the retinaculum have exhibited it to have several possible surgical treatments uses.\n\nA graft of the extensor retinaculum was shown to be useful in treating boxer's knuckle when direct repair of the damaged capsule is not possible.\n\nBecause of their similarities in histological structure, studies also show the extensor retinaculum to be a reasonable biological replacement for reconstruction of a deficient annular pulley.\n\nhttps://en.wikipedia.org/wiki/Extensor_retinaculum_of_the_hand","flexor-retinaculum-of-wrist":"FLEXOR RETINACULUM OF THE HAND\n\nThe flexor retinaculum (transverse carpal ligament, or anterior annular ligament) is a fibrous band on the palmar side of the hand near the wrist.\n\nIt arches over the carpal bones of the hands, covering them and forming the carpal tunnel.\n\n== Structure ==\n\nThe flexor retinaculum is a strong, fibrous band that covers the carpal bones on the palmar side of the hand near the wrist.\n\nIt attaches to the bones near the radius and ulna.\n\nOn the ulnar side, the flexor retinaculum attaches to the pisiform bone and the hook of the hamate bone.\n\nOn the radial side, it attaches to the tubercle of the scaphoid bone, and to the medial part of the palmar surface and the ridge of the trapezium bone.\nThe flexor retinaculum is continuous with the palmar carpal ligament, and deeper with the palmar aponeurosis.\n\nThe ulnar artery and ulnar nerve, and the cutaneous branches of the median and ulnar nerves, pass on top of the flexor retinaculum.\n\nOn the radial side of the retinaculum is the tendon of the flexor carpi radialis, which lies in the groove on the greater multangular between the attachments of the ligament to the bone.\nThe tendons of the palmaris longus and flexor carpi ulnaris are partly attached to the surface of the retinaculum; below, the short muscles of the thumb and little finger originate from the flexor retinaculum.\n\n== Function ==\n\nThe flexor retinaculum is the roof of the carpal tunnel, through which the median nerve and tendons of muscles which flex the hand pass.\n\n== Clinical significance ==\n\nIn carpal tunnel syndrome, one of the tendons or tissues in the carpal tunnel is inflamed, swollen, or fibrotic and puts pressure on the other structures in the tunnel, including the median nerve.\n\nCarpal tunnel syndrome is the most commonly reported nerve entrapment syndrome.\n\nCarpal tunnel syndrome is often associated with repetitive motions of the wrist and fingers; jobs like typists, pianists, and meat cutters are at particularly high risk.\n\nThe tough flexor retinaculum along with the rest of the carpal tunnel cannot expand, putting pressure on the median nerve running through the carpal tunnel with the flexor tendons of the wrist.\n\nThis results in the symptoms of carpal tunnel syndrome.Symptoms of carpal tunnel syndrome include tingling sensations and muscle weakness in the palm and lateral side of the hand and palm.\n\nIt is possible that the syndrome may extend and radiate up the nerve causing pain to the arm and shoulder.Carpal tunnel syndrome may be treated surgically; although this is usually done after all non-surgical methods of treatment have been exhausted.\n\nNon-surgical treatment methods include anti-inflammatory drugs.\n\nAdditionally, the wrist may also be immobilized in order to prevent further use and inflammation.\n\nWhen surgery is needed, the flexor retinaculum is either completely severed or lengthened.\n\nWhen surgery is done to divide the flexor retinaculum, by far the more common procedure, scar tissue will eventually fill the gap left by surgery.\n\nThe intent is that this will lengthen the flexor retinaculum enough to accommodate inflamed or damaged tendons and reduce the effects of compression on the median nerve.\n\nIn a 2004 double blind-study, researchers concluded that there was no perceivable benefit gained from lengthening the flexor retinaculum during surgery and so division of the ligament remains the preferred method of surgery.\n\nhttps://en.wikipedia.org/wiki/Flexor_retinaculum_of_the_hand","dorsal-fascia-of-hand":"Covers superficially the dorsum of hand.","superficial-transverse-metacarpal-ligament":"TRANSVERSE LIGAMENT OF THE PALMAR APONEUROSIS\n\nThe Transverse Ligament of the Palmar Aponeurosis (TLPA) is a thin band of transverse fibers of the distal portion of the palmar aponeurosis.\n\nIt runs deep and transverse to the longitudinally oriented pretendinous bands of the palmar fascial complex, and serves as an attachment point for the septa of Legueu and Juvara.\n\nThe TLPA is also known as the \"Ligament of Skoog\".\n\nIt should not be confused with the Natatory Ligament (also known as the \"Superficial Transverse Metacarpal Ligament\"), which runs parallel and distal to the TLPA, forming the webbing in between the bases of the fingers.\n\nhttps://en.wikipedia.org/wiki/Transverse_Ligament_of_the_Palmar_Aponeurosis","palmar-aponeurosis":"The palmar aponeurosis (palmar fascia) invests the muscles of the palm, and consists of central, lateral, and medial portions.\n\n== Structure ==\n\nThe central portion occupies the middle of the palm, is triangular in shape, and of great strength.\n\nIts apex is continuous with the lower margin of the transverse carpal ligament, and receives the expanded tendon of the palmaris longus.\n\nIts base divides below into four slips, one for each finger.\n\nEach slip gives off superficial fibers to the skin of the palm and finger, those to the palm joining the skin at the furrow corresponding to the metacarpophalangeal articulations, and those to the fingers passing into the skin at the transverse fold at the bases of the fingers.\n\nThe deeper part of each slip subdivides into two processes, which are inserted into the fibrous sheaths of the flexor tendons.\n\nFrom the sides of these processes offsets are attached to the transverse metacarpal ligament.\n\nBy this arrangement short channels are formed on the front of the heads of the metacarpal bones; through these the flexor tendons pass.\n\nThe intervals between the four slips transmit the digital vessels and nerves, and the tendons of the lumbricales.\n\nAt the points of division into the slips mentioned, numerous strong, transverse fasciculi bind the separate processes together.\n\nThe central part of the palmar aponeurosis is intimately bound to the integument by dense fibroareolar tissue forming the superficial palmar fascia, and gives origin by its medial margin to the palmaris brevis.\n\nIt covers the superficial volar arch, the tendons of the flexor muscles, and the branches of the median and ulnar nerves; and on either side it gives off a septum, which is continuous with the interosseous aponeurosis, and separates the intermediate from the collateral groups of muscles.\n\n=== Lateral and medial portions ===\n\nThe lateral and medial portions of the palmar aponeurosis are thin, fibrous layers, which cover, on the radial side, the muscles of the ball of the thumb, and, on the ulnar side, the muscles of the little finger; they are continuous with the central portion and with the fascia on the dorsum of the hand.\n\nhttps://en.wikipedia.org/wiki/Palmar_aponeurosis","iliacus-muscle":"The iliacus is a flat, triangular muscle which fills the iliac fossa.\n\nIt forms the lateral portion of iliopsoas, providing flexion of the thigh and lower limb at the acetabulofemoral joint.\n\n== Structure ==\n\nThe iliacus arises from the iliac fossa on the interior side of the hip bone, and also from the region of the anterior inferior iliac spine (AIIS).\n\nIt joins the psoas major to form the Iliopsoas.\n\nIt proceeds across the iliopubic eminence through the muscular lacuna to its insertion on the lesser trochanter of the femur.\n\nIts fibers are often inserted in front of those of the psoas major and extend distally over the lesser trochanter.\n\n=== Nerve supply ===\n\nThe iliopsoas is innervated by the femoral nerve and direct branches from the lumbar plexus.\n\n== Function ==\n\nIn open-chain exercises, as part of the iliopsoas, the iliacus is important for lifting (flexing) the femur forward (e.g. front scale).\n\nIn closed-chain exercises, the iliopsoas bends the trunk forward and can lift the trunk from a lying posture (e.g. sit-ups, back scale) because the psoas major crosses several vertebral joints and the sacroiliac joint.\n\nFrom its origin in the lesser pelvis the iliacus acts exclusively on the hip joint.\n\nhttps://en.wikipedia.org/wiki/Iliacus_muscle","psoas-major":"The psoas major ( or ) is a long fusiform muscle located in the lateral lumbar region between the vertebral column and the brim of the lesser pelvis.\n\nIt joins the iliacus muscle to form the iliopsoas.\n\nIn animals, this muscle is equivalent to the tenderloin.\nIts name derives from Greek ψόας, psóās, meaning 'of the loins' (genitive singular form of ψόα, psóa: 'the loins').\n\n== Structure ==\n\nThe psoas major is divided into a superficial and deep part.\n\nThe deep part originates from the transverse processes of lumbar vertebrae I-V.\n\nThe superficial part originates from the lateral surfaces of the last thoracic vertebra, lumbar vertebrae I-IV, and from the neighboring intervertebral discs.\n\nThe lumbar plexus lies between the two layers.Together, the illiacus muscle and the psoas major form the illiopsoas, which is surrounded by the iliac fascia.\n\nThe iliopsoas runs across the iliopubic eminence through the muscular lacuna to its insertion on the lesser trochanter of the femur.\n\nThe iliopectineal bursa separates the tendon of the iliopsoas muscle from the external surface of the hip joint capsule at the level of the iliopubic eminence.\n\nThe iliac subtendinous bursa lies between the lesser trochanter and the attachment of the iliopsoas.\n\n=== Nerve supply ===\n\nInnervation of the psoas major is through the anterior rami of L1 to L3 nerves.\n\n=== Variation ===\n\nIn fewer than 50 percent of human subjects, the psoas major is accompanied by the psoas minor.\n\nOne study using autopsy data found that the psoas major muscle is substantially thicker in men of African descent than in Caucasian men, and that the occurrence of the psoas minor is also ethnically variant, being present in most of the white subjects and absent in most of the black subjects.\n\nIn mice, it is mostly a fast-twitching, type II muscle, while in human it combines slow and fast-twitching fibers.\n\n== Function ==\n\nThe psoas major joins the upper body and the lower body, the axial to the appendicular skeleton, the inside to the outside, and the back to the front.\n\nAs part of the iliopsoas, psoas major contributes to flexion in the hip joint.\n\nOn the lumbar spine, unilateral contraction bends the trunk laterally, while bilateral contraction raises the trunk from its supine position.\n\nIn addition, attachment to the lesser trochanter, located on the postero-medial aspect of the femur, causes lateral rotation and weak adduction of the hip.\n\nIt forms part of a group of muscles called the hip flexors, whose action is primarily to lift the upper leg towards the body when the body is fixed or to pull the body towards the leg when the leg is fixed.\n\nFor example, when doing a sit-up that brings the torso (including the lower back) away from the ground and towards the front of the leg, the hip flexors (including the iliopsoas) will flex the spine upon the pelvis.\n\nOwing to the frontal attachment on the vertebrae, rotation of the spine will stretch the psoas.\n\n== Clinical significance ==\n\nTightness of the psoas can result in spasms or lower back pain by compressing the lumbar discs.\n\nA hypertonic and inflamed psoas can lead to irritation and entrapment of the ilioinguinal and the iliohypogastric nerves, resulting in a sensation of heat or water running down the front of the thigh.\n\nPsoas can be palpated with active flexion of the hip.\n\nA positive psoas contracture test and pain with palpation reported by the patient indicate clinical significance.\n\nCare should be taken around the abdominal organs, especially the colon when palpating deeply.\n\nThe appearance of a protruding belly can visually indicate a hypertonic psoas, which pulls the spine forward while pushing the abdominal contents outward.\n\nThe psoas lies postero-lateral to the lumbar sympathetic ganglia, and the needle tip will often pass through the psoas major during a lumbar sympathetic block.\n\nThe genitofemoral nerve is formed in the midsection of the psoas muscle by the union of branches from the anterior rami of L1 and L2 nerve roots.\n\nThe nerve then courses inferiorly within the psoas muscle and finally \"pierces\" the muscle and emerges on the anterior surface of the psoas distally.\n\nThe nerve then traverses the retroperitoneum, descending over the anterior surface of the psoas.\n\nhttps://en.wikipedia.org/wiki/Psoas_major_muscle","gluteus-medius-muscle":"The gluteus medius, one of the three gluteal muscles, is a broad, thick, radiating muscle.\n\nIt is situated on the outer surface of the pelvis.\n\nIts posterior third is covered by the gluteus maximus, its anterior two-thirds by the gluteal aponeurosis, which separates it from the superficial fascia and integument.\n\n== Structure ==\n\nThe gluteus medius muscle starts, or \"originates\", on the outer surface of the ilium between the iliac crest and the posterior gluteal line above, and the anterior gluteal line below; the gluteus medius also originates from the gluteal aponeurosis that covers its outer surface.\n\nThe fibers of the muscle converge into a strong flattened tendon that inserts on the lateral surface of the greater trochanter.\n\nMore specifically, the muscle's tendon inserts into an oblique ridge that runs downward and forward on the lateral surface of the greater trochanter.\n\n=== Relations ===\n\nA bursa separates the tendon of the muscle from the surface of the trochanter over which it glides.\n\n=== Variations ===\n\nThe posterior border may be more or less closely united to the piriformis, or some of the fibers end on its tendon.\n\nThe posterior fibres of gluteus medius contract to produce hip extension, lateral rotation and abduction.\n\nDuring gait, the posterior fibres help to decelerate internal rotation of the femur at the end of swing phase.\n\n== Function ==\n\n• The anterior part acting alone helps to flex and internally rotate the hip.\n• The posterior part acting alone helps to extend and externally rotate the hip.\n• The anterior and posterior parts working together abduct the hip and stabilize the pelvis in the coronal plane.\n\n== Clinical significance ==\n\nDysfunction of the gluteus medius or the superior gluteal nerve can potentially be indicated by a positive Trendelenburg's sign.\n\nhttps://en.wikipedia.org/wiki/Gluteus_medius","gluteus-maximus-muscle":"The gluteus maximus is the main extensor muscle of the hip.\n\nIt is the largest and outermost of the three gluteal muscles and makes up a large part of the shape and appearance of each side of the hips.\n\nIts thick fleshy mass, in a quadrilateral shape, forms the prominence of the buttocks.\n\nThe other gluteal muscles are the medius and minimus, and sometimes informally these are collectively referred to as the \"glutes\".\n\nIts large size is one of the most characteristic features of the muscular system in humans, connected as it is with the power of maintaining the trunk in the erect posture.\n\nOther primates have much flatter hips and can not sustain standing erectly.\n\nThe muscle is made up of muscle fascicles lying parallel with one another, and collected together into larger bundles separated by fibrous septa.\n\n== Structure ==\n\nThe gluteus maximus is the outermost muscle of the buttocks.\n\nIt arises from connections to nearby structures in this area.\n\nIt arises from the posterior gluteal line of the inner upper ilium, a bone of the pelvis, as well as above it to the iliac crest and slightly below it; from the lower part of the sacrum and the side of the coccyx, the tailbone; from the aponeurosis of the erector spinae (lumbodorsal fascia), the sacrotuberous ligament, and the fascia covering the gluteus medius (gluteal aponeurosis).\n\nThe fibers are directed obliquely downward and lateralward;\nThe gluteus maximus ends in two main areas:\n\nthose forming the upper and larger portion of the muscle, together with the superficial fibers of the lower portion, end in a thick tendinous lamina, which passes across the greater trochanter, and inserts into the iliotibial band of the fascia lata;\nthe deeper fibers of the lower portion are inserted into the gluteal tuberosity of the linea aspera, between the vastus lateralis and adductor magnus.\n\nIf present, the third trochanter also serves as an attachment.\n\n=== Bursae ===\n\nThree bursae are usually found in relation with the deep surface of this muscle:\n\nOne of these, of large size, separates it from the greater trochanter;\na second, (often missing), is situated on the tuberosity of the ischium;\na third is found between the tendon of the muscle and that of the vastus lateralis.\n\n== Function ==\n\nThe gluteus maximus straighten the leg at the hip; when the leg is flexed at the hip, the gluteus maximus extends it to bring the leg into a straight line with the body.\n\nTaking its fixed point from below, it acts upon the pelvis, supporting it and the trunk upon the head of the femur; this is particularly obvious in standing on one leg.\n\nIts most powerful action is to cause the body to regain the erect position after stooping, by drawing the pelvis backward, being assisted in this action by the biceps femoris (long head), semitendinosus, semimembranosus, and adductor magnus.\n\nThe gluteus maximus is a tensor of the fascia lata, and by its connection with the iliotibial band steadies the femur on the articular surfaces of the tibia during standing, when the extensor muscles are relaxed.\n\nThe lower part of the muscle also acts as an adductor and external rotator of the limb.\n\nThe upper fibers act as abductors of the hip joints.\n\n== Society and culture ==\n\n=== Training ===\n\nThe gluteus maximus is involved in a number of sports, from running to weight-lifting.\n\nA number of exercises focus on the gluteus maximus as well as other muscles of the upper leg.\n\nHip thrusts\nGlute bridge\nQuadruped hip extensions\nKettlebell swings\nSquats and variations like split squats, pistol squats and wide-stance lunges\nDeadlift (and variations)\nReverse hyperextension\nFour-way hip extensions\nGlute-ham raise\n\n=== In art ===\n\nIn cultural terms the glutes are often considered to be a symbol of health and strength, and to be aesthetically appealing.\n\nAs such, they frequently feature in artwork which seeks to emphasise and celebrate physicality, and the ability to move dynamically and powerfully.\n\nFor this kind of representation the glutes are usually shown to be efficiently proportioned and prominent.\n\nEvidence of such depictions of the gluteal muscles extends from at least Ancient Greece to the modern day.\nThe glutes in art and photography\n\n== Clinical significance ==\n\nFunctional assessment can be useful in assessing injuries to the gluteus maximus and surrounding muscles.\n\nThese tests include:\n\n30 second chair to stand testThis test measures a participant's ability to stand up from a seated position as many times as possible in a thirty-second period of time.\n\nTesting the number of times a person can stand up in a thirty-second period helps assess strength, flexibility, pain, and endurance, which can help determine how far along a person is in rehabilitation, or how much work is still to be done.\n\nPassive piriformis stretchThe piriformis test measures flexibility of the gluteus maximus.\n\nThis requires a trained professional and is based on the angle of external and internal rotation in relation to normal range of motion without injury or impingement.\n\n== Other animals ==\n\nThe gluteus maximus is larger in size and thicker in humans than in other primates.\n\nIts large size is one of the most characteristic features of the muscular system in humans, connected as it is with the power of maintaining the trunk in the erect posture.\n\nOther primates have much flatter hips and can not sustain standing erectly.In other primates, gluteus maximus consists of ischiofemoralis, a small muscle that corresponds to the human gluteus maximus and originates from the ilium and the sacroiliac ligament, and gluteus maximus proprius, a large muscle that extends from the ischial tuberosity to a relatively more distant insertion on the femur.\n\nIn adapting to bipedal gait, reorganization of the attachment of the muscle as well as the moment arm was required.\n\nhttps://en.wikipedia.org/wiki/Gluteus_maximus","gluteus-minimus-muscle":"The gluteus minimus, or glutæus minimus, the smallest of the three gluteal muscles, is situated immediately beneath the gluteus medius.\n\n== Origin and insertion ==\n\nIt is fan-shaped, arising from the outer surface of the ilium, between the anterior and inferior gluteal lines, and behind, from the margin of the greater sciatic notch.\n\nThe fibers converge to the deep surface of a radiated aponeurosis, and this ends in a tendon which is inserted into an impression on the anterior border of the greater trochanter, and gives an expansion to the capsule of the hip joint.\n\nIt is also a local stabilizer for the hip.\n\n== Relations ==\n\nA bursa is interposed between the tendon and the greater trochanter.\n\nBetween the gluteus medius and gluteus minimus are the deep branches of the superior gluteal vessels and the superior gluteal nerve.\n\nThe deep surface of the gluteus minimus is in relation with the reflected tendon of the rectus femoris and the capsule of the hip joint.\n\n== Function ==\n\nThe gluteus medius and gluteus minimus abduct the thigh, when the limb is extended, and are principally called into action in supporting the body on one limb, in conjunction with the tensor fasciæ latæ.\n\nTheir anterior fibers also flex the hip, and by drawing the greater trochanter forward, rotate the thigh inward, in which action they are also assisted by the Tensor fasciæ latæ.\n\nAdditionally, with the hip flexed, the gluteus medius and minimus internally rotate the thigh.\n\nWith the hip extended, the gluteus medius and gluteus minimus externally rotate the thigh.\n\nThe attachment to the superior capsule of the hip may also serve to retract the capsule away from the joint during motion.\n\nThis mechanism may prevent capsular impingement similar to the role of the articularis genus in the knee.\n\n== Variations ==\n\nThe muscle may be divided into an anterior and a posterior part, or it may send slips to the piriformis, the superior gemellus or the outer part of the origin of the vastus lateralis.\n\n== Pathology ==\n\nParalysis of this muscle or gluteus medius, such as may be caused by the superior gluteal nerve palsy, can lead to difficulty abducting the leg.\n\nPatients will compensate for their difficulty walking by adopting a Trendelenburg gait.\n\nhttps://en.wikipedia.org/wiki/Gluteus_minimus","tensor-fasciae-latae":"The tensor fasciae latae (or tensor fasciæ latæ or, formerly, tensor vaginae femoris) is a muscle of the thigh.\n\nTogether with the gluteus maximus, it acts on the iliotibial band and is continuous with the iliotibial tract, which attaches to the tibia.\n\nThe muscle assists in keeping the balance of the pelvis while standing, walking, or running.\n\n== Structure ==\n\nIt arises from the anterior part of the outer lip of the iliac crest; from the outer surface of the anterior superior iliac spine, and part of the outer border of the notch below it, between the gluteus medius and sartorius; and from the deep surface of the fascia lata.\n\nIt is inserted between the two layers of the iliotibial tract of the fascia lata about the junction of the middle and upper thirds of the thigh.\n\nThe tensor fasciae latae tautens the iliotibial tract and braces the knee, especially when the opposite foot is lifted.\n\nThe terminal insertion point lies on the lateral condyle of the tibia.\n\n=== Nerve supply ===\n\nTensor fasciae latae is innervated by the superior gluteal nerve, L5 and S1.\n\nAt its origins of the anterior rami of L4, L5, and S1 nerves, the superior gluteal nerve exits the pelvis via greater sciatic foramen superior to the piriformis.\n\nThe nerve also courses between the gluteus medius and minimus.\n\nThe superior gluteal artery also supplies the tensor fasciae latae.\n\nThe superior gluteal nerve arises from the sacral plexus and only has muscular innervation associated with it.\n\nThere is no cutaneous innervation for sensation that stems from the superior gluteal nerve.\n\n== Function ==\n\nThe tensor fasciae latae is a tensor of the fascia lata; continuing its action, the oblique direction of its fibers enables it to stabilize the hip in extension (assists gluteus maximus during hip extension).\n\nThe fascia lata is a fibrous sheath that encircles the thigh like a subcutaneous stocking and tightly binds its muscles.\n\nOn the lateral surface, it combines with the tendons of the gluteus maximus and tensor fasciae latae to form the iliotibial tract, which extends from the iliac crest to the lateral condyle of the tibia.\n\nIn the erect posture, acting from below, it will serve to steady the pelvis upon the head of the femur; and by means of the iliotibial tract it steadies the condyles of the femur on the articular surfaces of the tibia, and assists the gluteus maximus in supporting the knee in a position of extension.\n\nThe basic functional movement of tensor fasciae latae is walking.\n\nThe tensor fasciae latae is heavily utilized in horse riding, hurdling and water skiing.\n\nSome problems that arise when this muscle is tight or shortened are pelvic imbalances that lead to pain in hips, as well as pain in the lower back and lateral area of knees.Because of its insertion point on the lateral condyle of the tibia, it also aids in the lateral rotation of the tibia.\n\nThis lateral rotation may be initiated in conjunction with hip abduction and medial rotation of the femur while kicking a soccer ball.\n\nThe tensor fasciae latae works in synergy with the gluteus medius and gluteus minimus muscles to abduct and medially rotate the femur.\nThe TFL is a hip abductor muscle.\n\nTo stretch the tensor fasciae latae, the knee may be brought medially across the body (adducted).\n\nIf one leans against a wall with crossed legs (externally/laterally rotated hips) and pushes the pelvis away from the wall (leaning the upper body towards it) sidebending the lumbar spine (i.e.: curving the spine to the side) should be avoided as it stretches the lumbar region rather than the tensor fasciae latae and other muscles which cross the hip rather than the spine.\n\n== Clinical significance ==\n\nBecause it is used for so many movements and is in a shortened position when seated, the TFL becomes tight easily.\n\nTFL stretches lengthen this important muscle.\n\n=== Strain ===\n\nA small case notes that “it seems possible that a sloped or banked surface could predispose an individual to a TFL strain.” In such a case, “treatment usually consists of rest, heat, and flexibility exercises”, such as lliotibial band stretching.\n\n== Etymology ==\n\n\"Tensor fasciae latae\" translates from Latin to English as \"stretcher of the side band\".\n\n\"Tensor\" is an agent noun that comes from the past participle stem \"tens-\" of the Latin verb \"tendere\", meaning \"to stretch\".\n\n\"Fasciae\" is the Latin term for \"of the band\" and is in the singular genitive case. \"Latae\" is the respective singular, genitive, feminine form of the Latin adjective \"latus\" meaning \"side\".\n\nhttps://en.wikipedia.org/wiki/Tensor_fasciae_latae_muscle","piriformis-muscle":"The piriformis muscle (from Latin piriformis 'pear-shaped') is a muscle in the gluteal region of the lower limbs.\n\nIt is one of the six muscles in the lateral rotator group.\n\n== Structure ==\n\nThe piriformis muscle originates from the anterior (front) part of the sacrum, the part of the spine in the gluteal region.\n\nIt uses three fleshy digitations, attached to the second sacral vertebra, the third sacral vertebra, and the fourth sacral vertebra.\n\nIt also arises from the superior margin of the greater sciatic notch (as well as the sacroiliac joint capsule and the sacrotuberous ligament).\n\nA few fibers also arise from the margin of the greater sciatic foramen, and from the anterior surface of the sacrotuberous ligament.\n\nIt exits the pelvis through the greater sciatic foramen.\n\nIt then inserts onto the greater trochanter of the femur.\n\nIts tendon often joins with the tendons of the superior gemellus, inferior gemellus, and obturator internus muscles prior to insertion.\n\nThe piriformis is a flat muscle, pyramidal in shape.\n\nIt lies almost parallel with the posterior margin of the gluteus medius.\n\nIt is situated partly within the pelvis against its posterior wall, and partly at the back of the hip-joint.\n\n=== Innervation ===\n\nThe piriformis muscle is innervated by the piriformis nerve.\n\n=== Variation ===\n\nIn around 80% of the population, the sciatic nerve travels below the piriformis muscle.\n\nIn 17% of people, the piriformis muscle is pierced by parts or all of the sciatic nerve.\n\nSeveral variations occur, but the most common type of anomaly (81% of anomalies) is the Beaton's type B which is when the common peroneal nerve pierces the piriformis muscle.\n\nIt may be united with the gluteus medius, send fibers to the gluteus minimus, or receive fibers from the superior gemellus.\n\nIt may have one or two sacral attachments; or it may be inserted into the capsule of the hip joint.\n\n== Function ==\n\nThe piriformis muscle is part of the lateral rotators of the hip, along with the quadratus femoris, gemellus inferior, gemellus superior, obturator externus, and obturator internus.\n\nThe piriformis laterally rotates the femur with hip extension and abducts the femur with hip flexion.\n\nAbduction of the flexed thigh is important in the action of walking because it shifts the body weight to the opposite side of the foot being lifted, which prevents falling.\n\nThe action of the lateral rotators can be understood by crossing the legs to rest an ankle on the knee of the other leg.\n\nThis causes the femur to rotate and point the knee laterally.\n\nThe lateral rotators also oppose medial rotation by the gluteus medius and gluteus minimus.\n\nWhen the hip is flexed to 90 degrees, piriformis abducts the femur at the hip and reverses primary function, internally rotating the hip when the hip is flexed at 90 degrees or more. (Netter's Clinical Anatomy, 2010)\n\n== Clinical significance ==\n\nPiriformis syndrome occurs when the piriformis irritates the sciatic nerve, which comes into the gluteal region beneath the muscle, causing pain in the buttocks and referred pain along the sciatic nerve.\n\nThis referred pain is known as sciatica.\n\nSeventeen percent of the population has their sciatic nerve coursing through the piriformis muscle.\n\nThis subgroup of the population is predisposed to developing sciatica.\n\nSciatica can be described by pain, tingling, or numbness deep in the buttocks and along the sciatic nerve.\n\nSitting down, stretching, climbing stairs, and performing squats usually increases pain.\n\nDiagnosing the syndrome is usually based on symptoms and on the physical exam.\n\nMore testing, including MRIs, X-rays, and nerve conduction tests can be administered to exclude other possible diseases.\n\nIf diagnosed with piriformis syndrome, the first treatment involves progressive stretching exercises, massage therapy (including neuromuscular therapy) and physical treatment.\n\nCorticosteroids can be injected into the piriformis muscle if pain continues.\n\nFindings suggest the possibility that Botulinum toxin type B may be of potential benefit in the treatment of pain attributed to piriformis syndrome.\n\nA more invasive, but sometimes necessary treatment involves surgical exploration; however, the side effects of the surgery could be much worse than alternative treatments such as physical therapy.\n\nSurgery should always be a last resort.\n\n=== Landmark ===\n\nThe piriformis is a very important landmark in the gluteal region.\n\nAs it travels through the greater sciatic foramen, it effectively divides it into an inferior and superior part.\nThis determines the name of the vessels and nerves in this region – the nerve and vessels that emerge superior to the piriformis are the superior gluteal nerve and superior gluteal vessels.\n\nInferiorly, it is the same, and the sciatic nerve also travels inferiorly to the piriformis.\n\n== History ==\n\nThe piriformis muscle was first named by Adriaan van den Spiegel, a professor from the University of Padua in the 16th century.\n\nhttps://en.wikipedia.org/wiki/Piriformis_muscle","quadratus-femoris-muscle":"The quadratus femoris is a flat, quadrilateral skeletal muscle.\n\nLocated on the posterior side of the hip joint, it is a strong external rotator and adductor of the thigh, but also acts to stabilize the femoral head in the acetabulum.\n\nQuadratus femoris use in the Meyer's muscle pedicle grafting to prevent avascular necrosis of femur head.\n\n== Course ==\n\nIt originates on the lateral border of the ischial tuberosity of the ischium of the pelvis.\n\nFrom there, it passes laterally to its insertion on the posterior side of the head of the femur: the quadrate tubercle on the intertrochanteric crest and along the quadrate line, the vertical line which runs downward to bisect the lesser trochanter on the medial side of the femur.\n\nAlong its course, quadratus is aligned edge to edge with the inferior gemellus above and the adductor magnus below, so that its upper and lower borders run horizontal and parallel.\n\nAt its origin, the upper margin of the adductor magnus is separated from it by the terminal branches of the medial femoral circumflex vessels.\n\nA bursa is often found between the front of this muscle and the lesser trochanter.\n\nSometimes absent.\n\n== Clinical significance ==\n\nGroin pain can be a disabling ailment with many potential root causes: one such cause, often overlooked, is quadratus femoris tendinitis.\n\nMagnetic resonance imaging can show abnormal signal intensity at the insertion of the right quadratus femoris tendon, which suggests inflammation of the area.\n\nSince the muscle works to laterally rotate and adduct the femur, actions involving the lower body can strain the muscle.\n\nIn addition, patients present with hip pain and an increased signal intensity of the MRI of the quadratus femoris have been shown to also have a significantly narrower ischiofemoral space compared to the general populace.\n\nThe ischiofemoral impingement may be a cause of the hip pain associated with quadratus femoris tendinitis.\n\nhttps://en.wikipedia.org/wiki/Quadratus_femoris_muscle","inferior-gemellus-muscle":"The gemelli muscles are the inferior gemellus muscle\nand the superior gemellus muscle, two small accessory fasciculi to the tendon of the internal obturator muscle.\n\nThe gemelli muscles belong to the lateral rotator group of six muscles of the hip that rotate the femur in the hip joint.\n\n== Superior gemellus muscle ==\n\nThe gemelli muscles are two small muscular fasciculi, accessories to the tendon of the internal obturator muscle which is received into a groove between them.\n\nThe superior gemellus muscle is the higher placed gemellus muscle that arises from the outer (gluteal) surface of the ischial spine, and blends with the upper part of the tendon of the internal obturator.\n\nIt is smaller than the inferior gemellus.\n\nIn some people, the fibres of the gemellus superior extend further than average, and are prolonged onto the medial surface of the greater trochanter of the femur.\n\nThe superior and inferior gemelli are supplied by the inferior gluteal artery.\n\nNerve supply to the superior gemellus is from the supply to the internal obturator – L5, S1, and S2.\n\n== Inferior gemellus muscle ==\n\nThe inferior gemellus muscle arises from the upper part of the ischial tuberosity, immediately below the groove for the internal obturator tendon.\n\nIt blends with the lower part of the tendon, and is inserted with it into the medial surface of the greater trochanter.\n\nIt is rarely absent.\nLike the internal obturator muscle, the gemellus superior and gemellus inferior help to steady the femoral head in the acetabulum.\n\nBoth muscles also help to laterally rotate the extended thigh and abduct the flexed thigh at the hip by assisting the internal obturator.\n\nThe gemelli muscles act to compensate the reduced power of the internal obturator as it turns around the lesser sciatic notch.Blood supply is from the inferior gluteal artery.\n\nNerve supply is from the supply to the quadratus femoris – L4 to S1.Etymology: Gemellus is the diminutive of \"geminus\" meaning twin, doubled or duplicated.\n\nThe superior and inferior gemellus muscles are paired and perform the same action.\n\nhttps://en.wikipedia.org/wiki/Gemelli_muscles","obturator-internus":"The internal obturator muscle or obturator internus muscle originates on the medial surface of the obturator membrane, the ischium near the membrane, and the rim of the pubis.\n\nIt exits the pelvic cavity through the lesser sciatic foramen.\nThe internal obturator is situated partly within the lesser pelvis, and partly at the back of the hip-joint.\n\nIt functions to help laterally rotate femur with hip extension and abduct femur with hip flexion, as well as to steady the femoral head in the acetabulum.\n\n== Structure ==\n\n=== Origin ===\n\nThe internal obturator muscle arises from the inner surface of the antero-lateral wall of the pelvis.\n\nIt surrounds the obturator foramen.\n\nIt is attached to the inferior pubic ramus and ischium, and at the side to the inner surface of the hip bone below and behind the pelvic brim.\n\nIt reaches from the upper part of the greater sciatic foramen above and behind to the obturator foramen below and in front.\n\nIt also arises from the pelvic surface of the obturator membrane.\n\nThis is except in the posterior part, from the tendinous arch which completes the canal for the passage of the obturator vessels and nerve, and to a slight extent from the obturator fascia, which covers the muscle.\n\n=== Passage ===\n\nThe fibers converge through the lesser sciatic foramen.\n\nThese end in four or five tendinous bands, which are found on the deep surface of the muscle.\n\nThese bands are reflected at a right angle over the grooved surface of the ischium between its spine and tuberosity.\n\nThe obturator nerve passes on the superficial surface of the internal obturator muscle.\n\nThe pudendal nerve passes on the lateral surface of the internal obturator muscle and the coccygeus muscle.\n\nThe sciatic nerve passes superficial to the internal obturator muscle on the posterior surface.\n\n=== Insertion ===\n\nThe tendon inserts on the greater trochanter of the proximal femur.\n\n=== Nerve supply ===\n\nThe internal obturator muscle is supplied by the obturator internus nerve (L5, S1, and S2).\n\n=== Bursa/bands ===\n\nThis bony surface is covered by smooth cartilage, which is separated from the tendon by a bursa, and presents one or more ridges corresponding with the furrows between the tendinous bands.\n\nThese bands leave the pelvis through the lesser sciatic foramen and unite into a single flattened tendon, which passes horizontally across the capsule of the hip-joint, and, after receiving the attachments of the superior and inferior gemellus muscles, is inserted into the forepart of the medial surface of the greater trochanter above the trochanteric fossa.\n\nA bursa, narrow and elongated in form, is usually found between the tendon and the capsule of the hip-joint.\n\nIt occasionally communicates with the bursa between the tendon and the ischium.\n\n== Function ==\n\nThe internal obturator muscle helps to support the urinary bladder as part of the pelvic floor.\n\nhttps://en.wikipedia.org/wiki/Internal_obturator_muscle","superior-gemellus-muscle":"The gemelli muscles are the inferior gemellus muscle\nand the superior gemellus muscle, two small accessory fasciculi to the tendon of the internal obturator muscle.\n\nThe gemelli muscles belong to the lateral rotator group of six muscles of the hip that rotate the femur in the hip joint.\n\n== Superior gemellus muscle ==\n\nThe gemelli muscles are two small muscular fasciculi, accessories to the tendon of the internal obturator muscle which is received into a groove between them.\n\nThe superior gemellus muscle is the higher placed gemellus muscle that arises from the outer (gluteal) surface of the ischial spine, and blends with the upper part of the tendon of the internal obturator.\n\nIt is smaller than the inferior gemellus.\n\nIn some people, the fibres of the gemellus superior extend further than average, and are prolonged onto the medial surface of the greater trochanter of the femur.\n\nThe superior and inferior gemelli are supplied by the inferior gluteal artery.\n\nNerve supply to the superior gemellus is from the supply to the internal obturator – L5, S1, and S2.\n\n== Inferior gemellus muscle ==\n\nThe inferior gemellus muscle arises from the upper part of the ischial tuberosity, immediately below the groove for the internal obturator tendon.\n\nIt blends with the lower part of the tendon, and is inserted with it into the medial surface of the greater trochanter.\n\nIt is rarely absent.\nLike the internal obturator muscle, the gemellus superior and gemellus inferior help to steady the femoral head in the acetabulum.\n\nBoth muscles also help to laterally rotate the extended thigh and abduct the flexed thigh at the hip by assisting the internal obturator.\n\nThe gemelli muscles act to compensate the reduced power of the internal obturator as it turns around the lesser sciatic notch.Blood supply is from the inferior gluteal artery.\n\nNerve supply is from the supply to the quadratus femoris – L4 to S1.Etymology: Gemellus is the diminutive of \"geminus\" meaning twin, doubled or duplicated.\n\nThe superior and inferior gemellus muscles are paired and perform the same action.\n\nhttps://en.wikipedia.org/wiki/Gemelli_muscles","lateral-patellar-retinaculum":"The lateral retinaculum is the fibrous tissue on the lateral (outer) side of the kneecap (patella).\n\nThe kneecap has both a medial (on the inner aspect) and a lateral (on the outer side) retinaculum, and these help to support the kneecap in its position in relation to the femur bone underneath it.\n\nhttps://en.wikipedia.org/wiki/Lateral_retinaculum","medial-patellar-retinaculum":"The medial patellar retinaculum is the branch of the tendon of insertion of the quadriceps femoris that crosses the knee on the medial side of the patella.\n\nMost of the fibers of the medial patellar retinaculum originate in the medial femoral region from the vastus medialis muscle, just superior to the patella.","rectus-femoris-muscle":"The quadriceps femoris muscle, also called the quadriceps extensor, quadriceps or quads) is a large muscle group that includes the four prevailing muscles on the front of the thigh.\n\nIt is the great extensor muscle of the knee, forming a large fleshy mass which covers the front and sides of the femur.\n\nThe name derives from Latin four-headed muscle of the femur.\n\n== Structure ==\n\n=== Parts ===\n\nThe quadriceps femoris muscle is subdivided into four separate muscles (the 'heads'), with the first superficial to the other three over the femur (from the trochanters to the condyles):\n\nThe rectus femoris muscle occupies the middle of the thigh, covering most of the other three quadriceps muscles.\n\nIt originates on the ilium.\n\nIt is named for its straight course.\n\nThe vastus lateralis muscle is on the lateral side of the femur (i.e. on the outer side of the thigh).\n\nThe vastus medialis muscle is on the medial side of the femur (i.e. on the inner part thigh).\n\nThe vastus intermedius muscle lies between vastus lateralis and vastus medialis on the front of the femur (i.e. on the top or front of the thigh), but deep to the rectus femoris muscle.\n\nTypically, it cannot be seen without dissection of the rectus femoris.\n\n=== Attachments ===\n\nThe rectus femoris arises from the anterior inferior iliac spine and from the superior edge of the acetabulum.\n\nIt is thus a biarticular muscle.\n\nThe other parts of the quadriceps arise from the surface of the femur.\n\nAll four parts of the quadriceps muscle ultimately insert into the tuberosity of the tibia via the patella, where the quadriceps tendon becomes the patellar ligament.\n\n=== Other muscles ===\n\nThere is a small fifth muscle of the quadriceps complex — the articularis genus muscle — that is not often included.\n\nIn addition, cadaver studies have confirmed the presence of a sixth muscle, the tensor vastus intermedius.\n\nWhile this muscle has avariable presentation, it consistently originates at the proximal femur, runs between the vastus lateralis and vastus intermedius muscles, and inserts distally at the medial aspect of the patellar base.\n\nHistorically considered a part of the vastus lateralis muscle, the tensor vastus intermedius muscle is innervated by an independent branch of the femoral nerve and its tendinous belly can be separated from the vasti lateralis and intermedius muscles in most cases.\n\n=== Innervation ===\n\nThe quadriceps femoris is innervated by the femoral nerve, which originates from L2, L3, L4.\n\n== Function ==\n\nAll four quadriceps are powerful extensors of the knee joint.\n\nThey are crucial in walking, running, jumping and squatting.\n\nBecause the rectus femoris attaches to the ilium, it is also a flexor of the hip.\n\nThis action is also crucial to walking or running, as it swings the leg forward into the ensuing step.\n\nThe quadriceps, specifically the vastus medialis, play the important role of stabilizing the patella and the knee joint during gait.\n\n== Clinical significance ==\n\nThe quadriceps femoris muscle is a target for manual therapy and physical therapy from repetitive strain injuries, such as from skiing.The quadriceps femoris muscle is the most common site of myositis ossificans.\n\n== Society and culture ==\n\n=== Training ===\n\nIn strength training, the quadriceps are trained by several leg exercises.\n\nEffective exercises include the squat and leg press.\n\nThe isolation movement (i.e. targeting solely the quadriceps) is the leg extension.\n\n== Etymology ==\n\nThe proper Latin plural form of the adjective quadriceps would be quadricipites.\n\nIn modern English usage, quadriceps is used in both the singular and plural form.\n\nThe singular form quadricep, produced by back-formation, is frequently used.\n\nhttps://en.wikipedia.org/wiki/Quadriceps_femoris_muscle","vastus-lateralis-muscle":"The quadriceps femoris muscle, also called the quadriceps extensor, quadriceps or quads) is a large muscle group that includes the four prevailing muscles on the front of the thigh.\n\nIt is the great extensor muscle of the knee, forming a large fleshy mass which covers the front and sides of the femur.\n\nThe name derives from Latin four-headed muscle of the femur.\n\n== Structure ==\n\n=== Parts ===\n\nThe quadriceps femoris muscle is subdivided into four separate muscles (the 'heads'), with the first superficial to the other three over the femur (from the trochanters to the condyles):\n\nThe rectus femoris muscle occupies the middle of the thigh, covering most of the other three quadriceps muscles.\n\nIt originates on the ilium.\n\nIt is named for its straight course.\n\nThe vastus lateralis muscle is on the lateral side of the femur (i.e. on the outer side of the thigh).\n\nThe vastus medialis muscle is on the medial side of the femur (i.e. on the inner part thigh).\n\nThe vastus intermedius muscle lies between vastus lateralis and vastus medialis on the front of the femur (i.e. on the top or front of the thigh), but deep to the rectus femoris muscle.\n\nTypically, it cannot be seen without dissection of the rectus femoris.\n\n=== Attachments ===\n\nThe rectus femoris arises from the anterior inferior iliac spine and from the superior edge of the acetabulum.\n\nIt is thus a biarticular muscle.\n\nThe other parts of the quadriceps arise from the surface of the femur.\n\nAll four parts of the quadriceps muscle ultimately insert into the tuberosity of the tibia via the patella, where the quadriceps tendon becomes the patellar ligament.\n\n=== Other muscles ===\n\nThere is a small fifth muscle of the quadriceps complex — the articularis genus muscle — that is not often included.\n\nIn addition, cadaver studies have confirmed the presence of a sixth muscle, the tensor vastus intermedius.\n\nWhile this muscle has avariable presentation, it consistently originates at the proximal femur, runs between the vastus lateralis and vastus intermedius muscles, and inserts distally at the medial aspect of the patellar base.\n\nHistorically considered a part of the vastus lateralis muscle, the tensor vastus intermedius muscle is innervated by an independent branch of the femoral nerve and its tendinous belly can be separated from the vasti lateralis and intermedius muscles in most cases.\n\n=== Innervation ===\n\nThe quadriceps femoris is innervated by the femoral nerve, which originates from L2, L3, L4.\n\n== Function ==\n\nAll four quadriceps are powerful extensors of the knee joint.\n\nThey are crucial in walking, running, jumping and squatting.\n\nBecause the rectus femoris attaches to the ilium, it is also a flexor of the hip.\n\nThis action is also crucial to walking or running, as it swings the leg forward into the ensuing step.\n\nThe quadriceps, specifically the vastus medialis, play the important role of stabilizing the patella and the knee joint during gait.\n\n== Clinical significance ==\n\nThe quadriceps femoris muscle is a target for manual therapy and physical therapy from repetitive strain injuries, such as from skiing.The quadriceps femoris muscle is the most common site of myositis ossificans.\n\n== Society and culture ==\n\n=== Training ===\n\nIn strength training, the quadriceps are trained by several leg exercises.\n\nEffective exercises include the squat and leg press.\n\nThe isolation movement (i.e. targeting solely the quadriceps) is the leg extension.\n\n== Etymology ==\n\nThe proper Latin plural form of the adjective quadriceps would be quadricipites.\n\nIn modern English usage, quadriceps is used in both the singular and plural form.\n\nThe singular form quadricep, produced by back-formation, is frequently used.\n\nhttps://en.wikipedia.org/wiki/Quadriceps_femoris_muscle","vastus-medialis-muscle":"The quadriceps femoris muscle, also called the quadriceps extensor, quadriceps or quads) is a large muscle group that includes the four prevailing muscles on the front of the thigh.\n\nIt is the great extensor muscle of the knee, forming a large fleshy mass which covers the front and sides of the femur.\n\nThe name derives from Latin four-headed muscle of the femur.\n\n== Structure ==\n\n=== Parts ===\n\nThe quadriceps femoris muscle is subdivided into four separate muscles (the 'heads'), with the first superficial to the other three over the femur (from the trochanters to the condyles):\n\nThe rectus femoris muscle occupies the middle of the thigh, covering most of the other three quadriceps muscles.\n\nIt originates on the ilium.\n\nIt is named for its straight course.\n\nThe vastus lateralis muscle is on the lateral side of the femur (i.e. on the outer side of the thigh).\n\nThe vastus medialis muscle is on the medial side of the femur (i.e. on the inner part thigh).\n\nThe vastus intermedius muscle lies between vastus lateralis and vastus medialis on the front of the femur (i.e. on the top or front of the thigh), but deep to the rectus femoris muscle.\n\nTypically, it cannot be seen without dissection of the rectus femoris.\n\n=== Attachments ===\n\nThe rectus femoris arises from the anterior inferior iliac spine and from the superior edge of the acetabulum.\n\nIt is thus a biarticular muscle.\n\nThe other parts of the quadriceps arise from the surface of the femur.\n\nAll four parts of the quadriceps muscle ultimately insert into the tuberosity of the tibia via the patella, where the quadriceps tendon becomes the patellar ligament.\n\n=== Other muscles ===\n\nThere is a small fifth muscle of the quadriceps complex — the articularis genus muscle — that is not often included.\n\nIn addition, cadaver studies have confirmed the presence of a sixth muscle, the tensor vastus intermedius.\n\nWhile this muscle has avariable presentation, it consistently originates at the proximal femur, runs between the vastus lateralis and vastus intermedius muscles, and inserts distally at the medial aspect of the patellar base.\n\nHistorically considered a part of the vastus lateralis muscle, the tensor vastus intermedius muscle is innervated by an independent branch of the femoral nerve and its tendinous belly can be separated from the vasti lateralis and intermedius muscles in most cases.\n\n=== Innervation ===\n\nThe quadriceps femoris is innervated by the femoral nerve, which originates from L2, L3, L4.\n\n== Function ==\n\nAll four quadriceps are powerful extensors of the knee joint.\n\nThey are crucial in walking, running, jumping and squatting.\n\nBecause the rectus femoris attaches to the ilium, it is also a flexor of the hip.\n\nThis action is also crucial to walking or running, as it swings the leg forward into the ensuing step.\n\nThe quadriceps, specifically the vastus medialis, play the important role of stabilizing the patella and the knee joint during gait.\n\n== Clinical significance ==\n\nThe quadriceps femoris muscle is a target for manual therapy and physical therapy from repetitive strain injuries, such as from skiing.The quadriceps femoris muscle is the most common site of myositis ossificans.\n\n== Society and culture ==\n\n=== Training ===\n\nIn strength training, the quadriceps are trained by several leg exercises.\n\nEffective exercises include the squat and leg press.\n\nThe isolation movement (i.e. targeting solely the quadriceps) is the leg extension.\n\n== Etymology ==\n\nThe proper Latin plural form of the adjective quadriceps would be quadricipites.\n\nIn modern English usage, quadriceps is used in both the singular and plural form.\n\nThe singular form quadricep, produced by back-formation, is frequently used.\n\nhttps://en.wikipedia.org/wiki/Quadriceps_femoris_muscle","vastus-intermedius-muscle":"The quadriceps femoris muscle, also called the quadriceps extensor, quadriceps or quads) is a large muscle group that includes the four prevailing muscles on the front of the thigh.\n\nIt is the great extensor muscle of the knee, forming a large fleshy mass which covers the front and sides of the femur.\n\nThe name derives from Latin four-headed muscle of the femur.\n\n== Structure ==\n\n=== Parts ===\n\nThe quadriceps femoris muscle is subdivided into four separate muscles (the 'heads'), with the first superficial to the other three over the femur (from the trochanters to the condyles):\n\nThe rectus femoris muscle occupies the middle of the thigh, covering most of the other three quadriceps muscles.\n\nIt originates on the ilium.\n\nIt is named for its straight course.\n\nThe vastus lateralis muscle is on the lateral side of the femur (i.e. on the outer side of the thigh).\n\nThe vastus medialis muscle is on the medial side of the femur (i.e. on the inner part thigh).\n\nThe vastus intermedius muscle lies between vastus lateralis and vastus medialis on the front of the femur (i.e. on the top or front of the thigh), but deep to the rectus femoris muscle.\n\nTypically, it cannot be seen without dissection of the rectus femoris.\n\n=== Attachments ===\n\nThe rectus femoris arises from the anterior inferior iliac spine and from the superior edge of the acetabulum.\n\nIt is thus a biarticular muscle.\n\nThe other parts of the quadriceps arise from the surface of the femur.\n\nAll four parts of the quadriceps muscle ultimately insert into the tuberosity of the tibia via the patella, where the quadriceps tendon becomes the patellar ligament.\n\n=== Other muscles ===\n\nThere is a small fifth muscle of the quadriceps complex — the articularis genus muscle — that is not often included.\n\nIn addition, cadaver studies have confirmed the presence of a sixth muscle, the tensor vastus intermedius.\n\nWhile this muscle has avariable presentation, it consistently originates at the proximal femur, runs between the vastus lateralis and vastus intermedius muscles, and inserts distally at the medial aspect of the patellar base.\n\nHistorically considered a part of the vastus lateralis muscle, the tensor vastus intermedius muscle is innervated by an independent branch of the femoral nerve and its tendinous belly can be separated from the vasti lateralis and intermedius muscles in most cases.\n\n=== Innervation ===\n\nThe quadriceps femoris is innervated by the femoral nerve, which originates from L2, L3, L4.\n\n== Function ==\n\nAll four quadriceps are powerful extensors of the knee joint.\n\nThey are crucial in walking, running, jumping and squatting.\n\nBecause the rectus femoris attaches to the ilium, it is also a flexor of the hip.\n\nThis action is also crucial to walking or running, as it swings the leg forward into the ensuing step.\n\nThe quadriceps, specifically the vastus medialis, play the important role of stabilizing the patella and the knee joint during gait.\n\n== Clinical significance ==\n\nThe quadriceps femoris muscle is a target for manual therapy and physical therapy from repetitive strain injuries, such as from skiing.The quadriceps femoris muscle is the most common site of myositis ossificans.\n\n== Society and culture ==\n\n=== Training ===\n\nIn strength training, the quadriceps are trained by several leg exercises.\n\nEffective exercises include the squat and leg press.\n\nThe isolation movement (i.e. targeting solely the quadriceps) is the leg extension.\n\n== Etymology ==\n\nThe proper Latin plural form of the adjective quadriceps would be quadricipites.\n\nIn modern English usage, quadriceps is used in both the singular and plural form.\n\nThe singular form quadricep, produced by back-formation, is frequently used.\n\nhttps://en.wikipedia.org/wiki/Quadriceps_femoris_muscle","sartorius-muscle":"The sartorius muscle is the longest muscle in the human body.\n\nIt is a long, thin, superficial muscle that runs down the length of the thigh in the anterior compartment.\n\n== Structure ==\n\nThe sartorius muscle originates from the anterior superior iliac spine, and part of the notch between the anterior superior iliac spine and anterior inferior iliac spine.\n\nIt runs obliquely across the upper and anterior part of the thigh in an inferomedial direction.\n\nIt passes behind the medial condyle of the femur to end in a tendon.\n\nThis tendon curves anteriorly to join the tendons of the gracilis and semitendinosus muscles in the pes anserinus, where it inserts into the superomedial surface of the tibia.\n\nIts upper portion forms the lateral border of the femoral triangle, and the point where it crosses adductor longus marks the apex of the triangle.\n\nDeep to sartorius and its fascia is the adductor canal, through which the saphenous nerve, femoral artery and vein, and nerve to vastus medialis pass.\n\n=== Innervation ===\n\nLike the other muscles in the anterior compartment of the thigh, the sartorius is innervated by the femoral nerve.\n\n=== Variation ===\n\nIt may originate from the outer end of the inguinal ligament, the notch of the ilium, the ilio-pectineal line or the pubis.\n\nThe muscle may be split into two parts, and one part may be inserted into the fascia lata, the femur, the ligament of the patella or the tendon of the semitendinosus.\n\nThe tendon of insertion may end in the fascia lata, the capsule of the knee-joint, or the fascia of the leg.\nThe muscle may be absent in some people.\n\n== Function ==\n\nThe sartorius muscle can move the hip joint and the knee joint, but all of its actions are weak, making it a synergist muscle.\n\nAt the hip, it can flex, weakly abduct, and laterally rotate the femur.\n\nAt the knee, it can flex the leg; when the knee is flexed, sartorius medially rotates the leg.\n\nSitting cross-legged demonstrates all four actions of the sartorius.\n\n== Clinical significance ==\n\nOne of the many conditions that can disrupt the use of the sartorius is pes anserine bursitis, an inflammatory condition of the medial portion of the knee.\n\nThis condition usually occurs in athletes from overuse and is characterized by pain, swelling and tenderness.\n\nThe pes anserinus involves the tendons of the gracilis, semitendinosus, and sartorius muscles; these tendons attach onto the anteromedial proximal tibia.\n\nWhen inflammation of the bursa underlying the tendons occurs, they separate from the head of the tibia.\n\n== History ==\n\nThe name sartorius comes from the Latin word sartor, meaning tailor, and it is sometimes called the tailor's muscle.\n\nThis name was chosen in reference to the cross-legged position in which tailors once sat.\n\nIn French, a muscle name itself \"couturier\" comes from this specific position which is referred to as \"sitting as a tailor\" (in French: \"s'asseoir en tailleur\").\n\nThere are other hypotheses as to the origin of the name.\n\nOne is that it refers to the location of the inferior portion of the muscle being the \"inseam\" or area of the inner thigh that tailors commonly measure when fitting trousers.\n\nAnother is that the muscle closely resembles a tailor's ribbon.\n\nAdditionally, antique sewing machines required continuous crossbody pedaling.\n\nThis combination of lateral rotation and flexion of the hip and flexion of the knee gave tailors particularly developed sartorius muscles.\n\nhttps://en.wikipedia.org/wiki/Sartorius_muscle","adductor-magnus":"The adductor magnus is a large triangular muscle, situated on the medial side of the thigh.\n\nIt consists of two parts.\n\nThe portion which arises from the ischiopubic ramus (a small part of the inferior ramus of the pubis, and the inferior ramus of the ischium) is called the pubofemoral portion, adductor portion, or adductor minimus, and the portion arising from the tuberosity of the ischium is called the ischiocondylar portion, extensor portion, or \"hamstring portion\".\n\nDue to its common embryonic origin, innervation, and action the ischiocondylar portion (or hamstring portion) is often considered part of the hamstring group of muscles.\n\nThe ischiocondylar portion of the adductor magnus is considered a muscle of the posterior compartment of the thigh while the pubofemoral portion of the adductor magnus is considered a muscle of the medial compartment.\n\n== Structure ==\n\n=== Pubofemoral (adductor) portion ===\n\nThose fibers which arise from the ramus of the pubis are short, horizontal in direction, and are inserted into the rough line of the femur leading from the greater trochanter to the linea aspera, medial to the gluteus maximus.\n\nThose fibers from the ramus of the ischium are directed downward and laterally with different degrees of obliquity, to be inserted, by means of a broad aponeurosis, into the linea aspera and the upper part of its medial prolongation below.\n\n=== Ischiocondylar (hamstring) portion ===\n\nThe medial portion of the muscle, composed principally of the fibers arising from the tuberosity of the ischium, forms a thick fleshy mass consisting of coarse bundles which descend almost vertically, and end about the lower third of the thigh in a rounded tendon which is inserted into the adductor tubercle on the medial condyle of the femur, and is connected by a fibrous expansion to the line leading upward from the tubercle to the linea aspera.\n\n=== Relations ===\n\nBy its anterior surface the adductor magnus is in relation with the pectineus, adductor brevis, adductor longus, femoral artery and vein, profunda artery and vein, with their branches, and with the posterior branches of the obturator artery, obturator vein and obturator nerve.\n\nBy its posterior surface with the semitendinosus, semimembranosus, biceps, and gluteus maximus muscle.\n\nBy its inner border with the gracilis and sartorius.\nBy its upper border with the obturator externus, and quadratus femoris.\n\n=== Nerve supply ===\n\nIt is a composite muscle as the adductor and hamstring portions of the muscle are innervated by two different nerves.\n\nThe adductor portion is innervated by the posterior division of the obturator nerve while the hamstring portion is innervated by the sciatic nerve.\n\n=== Osseoaponeurotic openings ===\n\nAt the insertion of the muscle, there is a series of osseoaponeurotic openings, formed by tendinous arches attached to the bone.\n\nThe upper four openings are small, and give passage to the perforating branches of the profunda femoris artery.\n\nThe lowest (often referred to as the adductor hiatus) is large, and transmits the femoral vessels to the popliteal fossa.\n\n=== Variation ===\n\nThe upper, lateral part of the adductor magnus is an incompletely separated division often considered a separate muscle — the adductor minimus.\n\nThese two muscles are frequently separated by a branch of the superior perforating branch of the profunda femoris artery.\n\n== Function ==\n\nThe adductor magnus is a powerful adductor of the thigh, made especially active when the legs are moved from a wide spread position to one in which the legs parallel each other.\n\nThe part attached to the linea aspera acts as a lateral rotator.\n\nThe part which reaches the medial epicondyle acts as a medial rotator when the leg is rotated outwards and flexed, and also acts to extend the hip joint.\n\n== Other animals ==\n\nIn other tetrapods, the adductor magnus crosses the knee joint and inserts into the tibia.\n\nIn humans, the distal part of the tendon detaches and becomes the medial collateral ligament of the knee.\n\nBecause of this, the medial collateral ligament of the knee in humans may contain a few muscle fibres as an atavistic variation.\n\nhttps://en.wikipedia.org/wiki/Adductor_magnus_muscle","adductor-longus":"In the human body, the adductor longus is a skeletal muscle located in the thigh.\n\nOne of the adductor muscles of the hip, its main function is to adduct the thigh and it is innervated by the obturator nerve.\n\nIt forms the medial wall of the femoral triangle.\n\n== Origin and insertion ==\n\nThe adductor longus arises from the body of pubis inferior to pubic crest and lateral to pubic symphysis.\n\nIt lies ventrally on the adductor magnus, and near the femur, the adductor brevis is interposed between these two muscles.\n\nDistally, the fibers of the adductor longus extend into the adductor canal.It is inserted into the middle third of the medial lip of the linea aspera.\n\n== Relations ==\n\nThe adductor longus is in relation by its anterior surface with the pubic portion of the fascia lata, and near its insertion with the femoral artery and vein.\n\nBy its posterior surface with the adductor brevis and magnus, the anterior branches of the obturator artery, vein, and nerves, and near its insertion with the profunda artery and vein.\n\nBy its outer border with the pectineus, and by the inner border with the gracilis.\n\n== Actions ==\n\nIts main actions is to adduct and laterally rotate the thigh; it can also produce some degree of flexion/anteversion.\n\n== Innervation ==\n\nAs part of the medial compartment of the thigh, the adductor longus is innervated by the anterior division (sometimes the posterior division) of the obturator nerve.\n\nThe obturator nerve exits via the anterior rami of the spinal cord from L2, L3, and L4.\n\n== Development ==\n\nAdductor longus is derived from the myotome of spinal roots L2, L3, and L4.\n\nhttps://en.wikipedia.org/wiki/Adductor_longus_muscle","pectineus-muscle":"The pectineus muscle (, from the Latin word pecten, meaning comb) is a flat, quadrangular muscle, situated at the anterior (front) part of the upper and medial (inner) aspect of the thigh.\n\nThe pectineus muscle is the most anterior adductor of the hip.\n\nThe muscle does adduct and internally rotate the thigh but its primary function is hip flexion.\n\nIt can be classified in the medial compartment of thigh (when the function is emphasized) or the anterior compartment of thigh (when the nerve is emphasized).\n\n== Structure ==\n\nThe pectineus muscle arises from the pectineal line of the pubis and to a slight extent from the surface of bone in front of it, between the iliopectineal eminence and pubic tubercle, and from the fascia covering the anterior surface of the muscle; the fibers pass downward, backward, and lateral, to be inserted into the pectineal line of the femur which leads from the lesser trochanter to the linea aspera.\n\n=== Relations ===\n\nThe pectineus is in relation by its anterior surface with the pubic portion of the fascia lata, which separates it from the femoral artery and vein and internal saphenous vein, and lower down with the profunda artery.\n\nBy its posterior surface with the capsule of the hip joint, and with the obturator externus and adductor brevis, the obturator artery and vein being interposed.\n\nBy its external border with the psoas major, the femoral artery resting upon the line of interval.\n\nBy its internal border with the outer edge of the adductor longus.\nObturator foramen is situated directly behind this muscle, which forms one of its coverings.\n\nIt forms part of the floor of the femoral triangle.\n\n=== Innervation ===\n\nThe lumbar plexus is formed from the anterior rami of nerves L1 to L4 and some fibers from T12.\n\nWith only five roots and two divisions, it is less complex than the brachial plexus and gives rise to a number of nerves including the femoral nerve and accessory obturator nerve.\n\nThe pectineus muscle is considered a composite muscle as the innervation is by the femoral nerve (L2 and L3) and occasionally (20% of the population) a branch of the obturator nerve called the accessory obturator nerve.\n\nWhen it is present, the accessory obturator nerve innervates a portion of the pectineus muscle, entering the muscle on its dorsomedial aspect.\n\nThe greater nerve to the muscle is the femoral nerve.\n\nUnlike the obturator accessory nerve, the femoral nerve is always present and provides the sole innervation for the pectineus muscle in over 90% of cases.\n\nThe muscle is also innervated by the accessory obturator nerve in the 8.7% of cases in which the nerve occurs.\n\n== Function ==\n\nIt is one of the muscles primarily responsible for hip flexion.\n\nIt also adducts the thigh.\n\nhttps://en.wikipedia.org/wiki/Pectineus_muscle","adductor-brevis":"The adductor brevis is a muscle in the thigh situated immediately deep to the pectineus and adductor longus.\n\nIt belongs to the adductor muscle group.\n\nThe main function of the adductor brevis is to pull the thigh medially.\n\nThe adductor brevis and the rest of the adductor muscle group is also used to stabilize left to right movements of the trunk, when standing on both feet, or to balance when standing on a moving surface.\n\nThe adductor muscle group is used pressing the thighs together to ride a horse, and kicking with the inside of the foot in soccer or swimming.\n\nLast, they contribute to flexion of the thigh when running or against resistance (squats, jumping, etc.).\n\n== Structure ==\n\nIt is somewhat triangular in form, and arises by a narrow origin from the outer surfaces of the body of the pubis and inferior ramus of the pubis, between the gracilis and obturator externus.\n\nThe Adductor brevis muscle widens in triangular fashion to be inserted into the upper part of the linea aspera immediately lateral to the insertion of pectineus and above that of adductor longus.\n\n=== Relations ===\n\nBy its anterior surface, the adductor brevis is in relation with the pectineus, adductor longus, and anterior branches of the obturator artery, the obturator vein, and the obturator nerve.\n\nBy its posterior surface with the adductor magnus and the posterior branches of the obturator artery, the obturator vein, and the obturator nerve.\n\nBy its outer border with the obturator externus, and the iliopsoas.\n\nBy its inner border with the gracilis and adductor magnus.\nIt is pierced near its insertion by the middle perforating artery.\n\n=== Innervation ===\n\nThe adductor brevis is innervated dually by the anterior and posterior branches of the obturator nerve.\n\n== Function ==\n\nThe muscle is primarily known as a hip adductor.\n\nIt also functions as a hip flexor.\n\nWhether it acts to rotate the femur laterally or medially is dependent on position.\n\nhttps://en.wikipedia.org/wiki/Adductor_brevis_muscle","adductor-minimus":"Small and flat skeletal muscle in the thigh which constitutes the upper, lateral part of the adductor magnus muscle.\n\nIt adducts and laterally rotates the femur.\n\nThe adductor minimus originates on the pelvis at the inferior ramus of the pubis as the anterior-most part of the adductor magnus.\n\nIt is inserted on the back of the femur at the medial lip of the linea aspera and thus crosses the proximal part of the true adductor magnus.\n\n=== Innervation ===\n\n -obturator nerve\n -tibial nerve (L3-5),\n -a branch of the sciatic nerve\n\nhttps://en.wikipedia.org/wiki/Adductor_minimus_muscle","gracilis-muscle":"The gracilis muscle (; Latin for \"slender\") is the most superficial muscle on the medial side of the thigh.\n\nIt is thin and flattened, broad above, narrow and tapering below.\n\n== Structure ==\n\nIt arises by a thin aponeurosis from the anterior margins of the lower half of the symphysis pubis and the upper half of the pubic arch.\n\nThe muscle's fibers run vertically downward, ending in a rounded tendon.\n\nThis tendon passes behind the medial condyle of the femur, curves around the medial condyle of the tibia where it becomes flattened, and inserts into the upper part of the medial surface of the body of the tibia, below the condyle.\n\nFor this reason, the muscle is a lower limb adductor.\n\nAt its insertion the tendon is situated immediately above that of the semitendinosus muscle, and its upper edge is overlapped by the tendon of the sartorius muscle, which it joins to form the pes anserinus.\n\nThe pes anserinus is separated from the medial collateral ligament of the knee-joint by a bursa.\nA few of the fibers of the lower part of the tendon are prolonged into the deep fascia of the leg.\n\n=== Relations ===\n\nBy its inner or superficial surface gracilis is in relation with the fascia lata, and below with the sartorius and internal saphenous nerve; the internal saphenous vein crosses it lying superficially to the fascia lata.\n\nBy its outer or deep surface with the adductor longus, brevis, and magnus, and the internal lateral ligament of the knee-joint, from which it is separated by a synovial bursa common to the tendons of the gracilis and semitendinosus.\n\n=== Nerve supply ===\n\nThe obturator nerve innervates the gracilis muscle via the lumbar spinal vertebrae.\n\n== Function ==\n\nThe muscle adducts, medially rotates (with hip flexion), laterally rotates, and flexes the hip as above, and also aids in flexion of the knee.\n\n== Clinical significance ==\n\nThe gracilis muscle is commonly used as a flap in microsurgery.\n\nAccording to the classification of Mathes and Nahai, it presents a type II blood supply, allowing it to be transferred on its artery derived from the medial circumflex femoral artery.\n\nThis artery enters the muscle about 10 cm from the pubic symphysis.\n\nAt this point (or 1 cm proximal) the nerve also enters.\n\nGracilis muscle is widely used in reconstructive surgery (graciloplasty), either as a pedicled flap or as a free microsurgical flap.\n\nBoth pedicled and free flaps can be muscular or musculocutaneos (the so- called \"composite flaps\").\n\nAs a pedicled flap, gracilis muscle can be used in perineal and vaginal reconstruction, after oncological surgery, in the treatment of recurrent anovaginal and rectovaginal fistulas as well in the coverage of the neurovascular bundle after vascular surgery.As a functioning pedicled flap, the gracilis muscle can be transferred for the treatment of anal incontinence.\n\nThis technique called graciloplasty was described in the 1950s by Pickrell and was revolutionized in the late 1980s by the introduction of chronic muscle electro-stimulation.\n\nThe gracilis microsurgical free flap is commonly used in the reconstruction of upper and lower limbs, in breast reconstruction and – as a free functioning flap – to restore forearm function or in dynamic reconstruction of facial paralysis.Gracilis Muscles Clinical Role\n\n=== Transplantation sites ===\n\nThe muscle may be split to reduce bulk for facial reanimation, as well as to repair hand muscles.\n\nIt can be used to fashion an external anal sphincter.\n\nhttps://en.wikipedia.org/wiki/Gracilis_muscle","obturator-externus":"The external obturator muscle, obturator externus muscle (; OE) is a flat, triangular muscle, which covers the outer surface of the anterior wall of the pelvis.\n\nIt is sometimes considered part of the medial compartment of thigh, and sometimes considered part of the gluteal region.\n\n== Structure ==\n\nIt arises from the margin of bone immediately around the medial side of the obturator membrane and surrounding bone, viz., from the inferior pubic ramus, and the ramus of the ischium; it also arises from the medial two-thirds of the outer surface of the obturator membrane, and from the tendinous arch which completes the canal for the passage of the obturator vessels and nerves.\n\nThe fibers springing from the pubic arch extend on to the inner surface of the bone, where they obtain a narrow origin between the margin of the foramen and the attachment of the obturator membrane.\n\nThe fibers converge and pass posterolateral and upward, and end in a tendon which runs across the back of the neck of the femur and lower part of the capsule of the hip joint and is inserted into the trochanteric fossa of the femur.\n\n=== Relations ===\n\nThe obturator vessels lie between the muscle and the obturator membrane; the anterior branch of the obturator nerve reaches the thigh by passing in front of the muscle, and the posterior branch by piercing it.\n\n=== Variation ===\n\nIn 33% of people a supernumerary muscle is found between the adductor brevis and minimus.\n\nWhile this muscle, when present, is similar to its neighbouring adductors, it is formed by separation from the superficial layer of the external obturator, and is thus not ontogenetically related to the adductor muscles of the hip.\n\nThis muscle originates from the upper part of the inferior pubic ramus from where it runs downwards and laterally.\n\nIn half of cases, it inserts into the anterior surface of the insertion aponeurosis of the adductor minimus.\n\nIn the remaining cases, it is either inserted into the upper part of the pectineal line or the posterior part of the lesser trochanter.\n\nIt has been demonstrated by the course of the posterior branch of obturator nerve that the obturator externus is divided into a superior muscle fascicle and a main belly.\n\nThe supernumerary muscle described above originates from the superior fascicle, while an anomalous fascicle — also derived from the external obturator — originates from the main belly.\n\nThe \"original\" external obturator, i.e. without these supernumerary muscular parts, actually occurs in only 20% of cases, and apparently the external obturator readily undergoes ontogenetic variations.\n\n== Function ==\n\nThe external obturator muscle acts as the lateral rotator of the hip joint.\n\nAs a short muscle around the hip joint, it stabilizes the hip joint as a postural muscle.\n\nIt also helps to aduct the hip joint when in flexion.\n\nhttps://en.wikipedia.org/wiki/External_obturator_muscle","long-head-of-biceps-femoris":"The biceps femoris is a muscle of the thigh located to the posterior, or back.\n\nAs its name implies, it has two parts, one of which (the long head) forms part of the hamstrings muscle group.\n\n== Structure ==\n\nIt has two heads of origin:\n\nthe long head arises from the lower and inner impression on the posterior part of the tuberosity of the ischium.\n\nThis is a common tendon origin with the semitendinosus muscle, and from the lower part of the sacrotuberous ligament.\n\nThe short head, arises from the lateral lip of the linea aspera, between the adductor magnus and vastus lateralis extending up almost as high as the insertion of the gluteus maximus, from the lateral prolongation of the linea aspera to within 5 cm. of the lateral condyle; and from the lateral intermuscular septum.\n\nThe two muscle heads joint together distally and unite in an intricate fashion.\n\nThe fibers of the long head form a fusiform belly, which passes obliquely downward and lateralward across the sciatic nerve to end in an aponeurosis which covers the posterior surface of the muscle and receives the fibers of the short head.\n\nInferiorly, the aponeurosis condenses to form a tendon which predominantly inserts onto the lateral side of the head of the fibula.\n\nThere is a second small insertional attachment by a small tendon slip into the lateral condyle of the tibia.\n\nAt its insertion the tendon divides into two portions, which embrace the fibular collateral ligament of the knee-joint.\n\nTogether, this joining of tendons is commonly referred to as the conjoined tendon of the knee.From the posterior border of the tendon a thin expansion is given off to the fascia of the leg.\n\nThe tendon of insertion of this muscle forms the lateral hamstring; the common fibular (peroneal) nerve descends along its medial border.\n\n=== Variations ===\n\nThe short head may be absent; additional heads may arise from the ischial tuberosity, the linea aspera, the medial supracondylar ridge of the femur, or from various other parts.\n\nThe tendon of insertion may be attached to the Iliotibial band and to retinacular fibers of the lateral joint capsule.\n\nA slip may pass to the gastrocnemius.\n\n=== Innervation ===\n\nIt is a composite muscle as the short head of the biceps femoris develops in the flexor compartment of the thigh and is thus innervated by common fibular branch of the sciatic nerve (L5, S1), while the long head is innervated by the tibial branch of the sciatic nerve (L5, S1).\n\n=== Blood supply ===\n\nThe muscle's vascular supply is derived from the anastomoses of several arteries: the perforating branches of the profunda femoris artery, the inferior gluteal artery, and the popliteal artery.\n\n== Function ==\n\nBoth heads of the biceps femoris perform knee flexion.\n\nSince the long head originates in the pelvis it is involved in hip extension.\n\nThe long head of the biceps femoris is a weaker knee flexor when the hip is extended (because of active insufficiency).\n\nFor the same reason the long head is a weaker hip extender when the knee is flexed.\n\nWhen the knee is semi-flexed, the biceps femoris in consequence of its oblique direction rotates the leg slightly outward.\n\n== Clinical significance ==\n\nAvulsion of the biceps femoris tendon is common in sports that require explosive bending of the knee as seen in sprinting.\n\nhttps://en.wikipedia.org/wiki/Biceps_femoris_muscle","short-head-of-biceps-femoris":"The short head, arises from the lateral lip of the linea aspera, between the adductor magnus and vastus lateralis extending up almost as high as the insertion of the gluteus maximus, from the lateral prolongation of the linea aspera to within 5 cm. of the lateral condyle; and from the lateral intermuscular septum.","semimembranosus-muscle":"The semimembranosus muscle () is the most medial of the three hamstring muscles in the thigh.\n\nIt is so named because it has a flat tendon of origin.\n\nIt lies posteromedially in the thigh, deep to the semitendinosus muscle.\n\nIt extends the hip joint and flexes the knee joint.\n\n== Structure ==\n\nThe semimembranosus muscle, so called from its membranous tendon of origin, is situated at the back and medial side of the thigh.\n\nIt is wider, flatter, and deeper than the semitendinosus (with which it shares very close insertion and attachment points).\n\nThe muscle overlaps the upper part of the popliteal vessels.\n\n=== Origin ===\n\nThe semimembranosus muscle originates by a thick tendon from the superolateral aspect of the ischial tuberosity.\n\nIt arises above and medial to the biceps femoris muscle and semitendinosus muscle.\n\nThe tendon of origin expands into an aponeurosis, which covers the upper part of the anterior surface of the muscle; from this aponeurosis, muscular fibers arise, and converge to another aponeurosis which covers the lower part of the posterior surface of the muscle and contracts into the tendon of insertion.\n\n=== Insertion ===\n\nThe semimembranosus muscle inserts on the:\n\n-medial condyle of the tibia.\n-medial margin of the tibia.\n-intercondylar fossa of femur.\n-lateral condyle of femur.\n-fascia of the popliteus muscle.\n\nThe tendon of insertion gives off certain fibrous expansions: one, of considerable size, passes upward and laterally to be inserted into the posterior lateral condyle of the femur, forming part of the oblique popliteal ligament of the knee-joint; a second is continued downward to the fascia which covers the popliteus muscle; while a few fibers join the medial collateral ligament of the joint and the fascia of the leg.\n\n=== Nerve supply ===\n\nThe semimembranosus is innervated by the tibial part of the sciatic nerve.\n\nThe sciatic nerve consists of the anterior divisions of ventral nerve roots from L4 through S3.\n\nThese nerve roots are part of the larger nerve network–the sacral plexus.\n\nThe tibial part of the sciatic nerve is also responsible for innervation of semitendinosus and the long head of biceps femoris.\n\n=== Variation ===\n\nThe semimembranosus muscle may be reduced or absent, or double, arising mainly from the sacrotuberous ligament and giving a slip to the femur or adductor magnus.\n\n== Function ==\n\nThe semimembranosus muscle extends (straightens) the hip joint.\n\nIt also flexes (bends) the knee joint.\n\nIt also helps to medially rotate the knee: the tibia medially rotates on the femur when the knee is flexed.\n\nIt medially rotates the femur when the hip is extended.\n\nThe muscle can also aid in counteracting the forward bending at the hip joint.\n\n== Clinical significance ==\n\nThe semitendinosus muscle may be dry needled.\n\nhttps://en.wikipedia.org/wiki/Semimembranosus_muscle","semitendinosus-muscle":"The semitendinosus is a long superficial muscle in the back of the thigh.\n\nIt is so named because it has a very long tendon of insertion.\n\nIt lies posteromedially in the thigh, superficial to the semimembranosus.\n\n== Structure ==\n\nThe semitendinosus, remarkable for the great length of its tendon of insertion, is situated at the posterior and medial aspect of the thigh.\n\nIt arises from the lower and medial impression on the upper part of the tuberosity of the ischium, by a tendon common to it and the long head of the biceps femoris; it also arises from an aponeurosis which connects the adjacent surfaces of the two muscles to the extent of about 7.5 cm. from their origin.\n\nThe muscle is fusiform and ends a little below the middle of the thigh in a long round tendon which lies along the medial side of the popliteal fossa; it then curves around the medial condyle of the tibia and passes over the medial collateral ligament of the knee-joint, from which it is separated by a bursa, and is inserted into the upper part of the medial surface of the body of the tibia, nearly as far forward as its anterior crest.\n\nThe semitendinosus is more superficial than the semimembranosus (with which it shares very close insertion and attachment points).\n\nHowever, because the semimembranosus is wider and flatter than the semitendinosus, it is still possible to palpate the semimembranosus directly.\n\nAt its insertion it gives off from its lower border a prolongation to the deep fascia of the leg and lies behind the tendon of the sartorius, and below that of the gracilis, to which it is united.\n\nThese three tendons form what is known as the pes anserinus, so named because it looks like the foot of a goose.\n\n=== Innervation ===\n\nA lower motor neuron exits to the sacral plexus exiting through the spinal levels L5-S2.\n\nFrom the sacral plexus, the lower motor neuron travels down the sciatic nerve.\n\nThe sciatic nerve branches into the deep fibular nerve and the tibial nerve.\n\nThe tibial nerve innervates the semitendinosus as well as the other hamstring muscles, the semimembranosus and biceps femoris.\n\n== Function ==\n\nThe semitendinosus muscle is one of three hamstring muscles that are located at the back of the thigh.\n\nThe other two are the semimembranosus muscle and the biceps femoris.\n\nThe semitendinosus muscle lies between the other two.\n\nThese three muscles work collectively to flex the knee and extend the hip.\n\nThe muscle also helps to medially rotate the tibia on the femur when the knee is flexed and medially rotate the femur when the hip is extended.\n\nIt counteracts forward bending at the hips as well.\n\n== Clinical significance ==\n\nAlong with patellar ligament and quadriceps femoris, semitendinosus/gracilis (STG) tendon autografts has been used commonly and successfully for anterior cruciate ligament reconstruction.\n\nSufficient graft size could typically be obtained using either a semitendinosus/gracilis tendon double-bundle technique, or a quadruple-bundle technique using a single tendon.\n\nhttps://en.wikipedia.org/wiki/Semitendinosus_muscle","extensor-digitorum-longus":"The extensor digitorum longus is a pennate muscle, situated at the lateral part of the front of the leg.\n\n== Origin and insertion ==\n\nIt arises from the lateral condyle of the tibia; from the upper three-quarters of the anterior surface of the body of the fibula; from the upper part of the interosseous membrane; from the deep surface of the fascia; and from the intermuscular septa between it and the tibialis anterior on the medial, and the peroneal muscles on the lateral side.\n\nBetween it and the tibialis anterior are the upper portions of the anterior tibial vessels and deep peroneal nerve.\n\nThe muscle passes under the superior and inferior extensor retinaculum of foot in company with the fibularis tertius, and divides into four slips, which run forward on the dorsum of the foot, and are inserted into the second and third phalanges of the four lesser toes.\n\nThe tendons to the second, third, and fourth toes are each joined, opposite the metatarsophalangeal articulations, on the lateral side by a tendon of the extensor digitorum brevis.\n\nThe tendons are inserted in the following manner: each receives a fibrous expansion from the interossei and lumbricals, and then spreads out into a broad aponeurosis, which covers the dorsal surface of the first phalanx: this aponeurosis, at the articulation of the first with the second phalanx, divides into three slips—an intermediate, which is inserted into the base of the second phalanx; and two collateral slips, which, after uniting on the dorsal surface of the second phalanx, are continued onward, to be inserted into the base of the third phalanx.\n\n== Variations ==\n\nThis muscle varies considerably in the modes of origin and the arrangement of its various tendons.\n\nThe tendons to the second and fifth toes may be found doubled, or extra slips are given off from one or more tendons to their corresponding metatarsal bones, or to the short extensor, or to one of the interosseous muscles.\n\nA slip to the great toe from the innermost tendon has been found.\n\n== Additional Images ==\n\nhttps://en.wikipedia.org/wiki/Extensor_digitorum_longus_muscle","tibialis-anterior-muscle":"The tibialis anterior muscle is a muscle in humans that originates along the upper two-thirds of the lateral (outside) surface of the tibia and inserts into the medial cuneiform and first metatarsal bones of the foot.\n\nIt acts to dorsiflex and invert the foot.\n\nThis muscle is mostly located near the shin.\n\nIt is situated on the lateral side of the tibia; it is thick and fleshy above, tendinous below.\n\nThe tibialis anterior overlaps the anterior tibial vessels and deep peroneal nerve in the upper part of the leg.\n\n== Structure ==\n\nThe tibialis anterior muscle arises from:\n\n-the lateral condyle of the tibia.\n-the upper 2/3 of the lateral surface of the tibia.\n-the adjoining part of the interosseous membrane.\n-the deep surface of the fascia.\n-the intermuscular septum between it and the extensor digitorum longus.The fibers of this circumpennate muscle are relatively parallel to the plane of insertion, ending in a tendon, apparent on the anteriomedial dorsal aspect of the foot close to the ankle.\n\nIt passes through the most medial compartments of the transverse and cruciate crural ligaments.\n\nIt is inserted into the medial and under surface of the medial cuneiform bone and the base of the first metatarsal bone.\n\n=== Nerve supply ===\n\nThe tibialis anterior muscle is supplied by the deep fibular nerve (L4, L5), a branch of common fibular nerve.\n\n=== Variation ===\n\nA deep portion of the muscle is rarely inserted into the talus, or a tendinous slip may pass to the head of the first metatarsal bone or the base of the first phalanx of the great toe.\nThe tibiofascialis anterior, a small muscle from the lower part of the tibia to the transverse or cruciate crural ligaments or deep fascia.\n\n== Function ==\n\nThe tibialis anterior muscle is the most medial muscle of the anterior compartment of the leg.\n\nIt is responsible for dorsiflexing and inverting the foot, and is the largest dorsiflexor of the foot.\n\nThe muscle has two origins, one being the lateral tibial condyle and the other being the upper lateral surface of the tibia, and inserts on the medial surface of the medial cuneiform and adjoining part of base of the first metatarsal of the foot allowing the toe to be pulled up and held in a locked position.\n\nIt also allows for the ankle to be inverted giving the ankle horizontal movement allowing for some cushion if the ankle were to be rolled.\n\nIt is innervated by the deep peroneal nerve and acts as both an antagonist and a synergist of the tibialis posterior.\n\nHowever, the most accurate antagonist of the tibialis anterior is the peroneus longus.\n\nThe tibialis anterior aides in the activities of walking, running, hiking, kicking a ball, or any activity that requires moving the leg or keeping the leg vertical.\n\nIt functions to stabilize the ankle as the foot hits the ground during the contact phase of walking (eccentric contraction) and acts later to pull the foot clear of the ground during the swing phase (concentric contraction).\n\nIt also functions to 'lock' the ankle, as in toe-kicking a ball, when held in an isometric contraction.\nAntagonists are plantar-flexors of the posterior compartment such as soleus and gastrocnemius.\nThe movements of tibialis anterior are dorsiflexion and inversion of the ankle.\n\nHowever, actions of tibialis anterior are dependent on whether the foot is weight bearing or not (closed or open kinetic chain).\n\nWhen the foot is on the ground, the muscle helps to balance the leg and talus on the other tarsal bones so that the leg is kept vertical even when walking on uneven ground.\n\n== Clinical significance ==\n\nSome clinicians attempt to treat tibialis anterior muscle issues with acupuncture techniques, such as dry needling.\n\nThere is significant bias in studies evaluating the efficacy of acupuncture versus medical treatments, and the decision to use acupuncture should be made carefully.\n\nhttps://en.wikipedia.org/wiki/Tibialis_anterior_muscle","fibularis-tertius-muscle":"In human anatomy, the fibularis tertius (also known as the peroneus tertius) is a muscle in the anterior compartment of the leg.\n\nIt acts to tilt the sole of the foot away from the midline of the body (eversion) and to pull the foot upward toward the body (dorsiflexion).\n\n== Structure ==\n\nThe fibularis tertius arises from the lower third of the front surface of the fibula, the lower part of the interosseous membrane, and septum, or connective tissue, between it and the fibularis brevis.\n\nThe septum is sometimes called the intermuscular septum of Otto.\nThe muscle passes downward and ends in a tendon that passes under the superior extensor retinaculum and the inferior extensor retinaculum of the foot in the same canal as the extensor digitorum longus muscle.\n\nIt may be mistaken as a fifth tendon of the extensor digitorum longus.\n\nThe tendon inserts into the medial part of the posterior surface of the shaft of the fifth metatarsal bone.\n\nThe fibularis tertius is supplied by the deep fibular nerve.\n\nIn rare cases, it may also be supplied by the common fibular nerve.\n\nThis is unlike the other fibularis muscles, which are located in the lateral compartment of the leg and are supplied by the superficial fibular nerve, since the fibularis tertius is found in the anterior compartment of the leg.\n\nThe fibularis tertius may be absent in humans.\n\nIt may be absent in as few as 5% of people, or as many as 72%, depending on the population surveyed.\n\nIt is rarely found in other primates, which is one reason its function has been linked to efficient bipedalism.\n\n== Function ==\n\nAs a weak dorsiflexor of the ankle joint, the fibularis tertius assists in pulling the foot upward toward the body.\n\nIt also assists in tilting the sole of the foot away from midline of the body at the ankle (eversion).\n\nIt is likely to be helpful though not essential in bipedal walking.\n\n== Clinical significance ==\n\nThe fibularis tertius may be involved in ankle injuries and may rupture.\n\nThis is caused by hyperextension.The fibularis tertius may be imaged using medical ultrasound.\n\n== Nomenclature and etymology ==\n\nTerminologia Anatomica designates \"fibularis\" as the preferred word over \"peroneus.\"\n\nThe word \"peroneus\" comes from the Greek word \"perone,\" meaning pin of a brooch or a buckle.\n\nIn medical terminology, the word refers to being of or relating to the fibula or to the outer portion of the leg.\n\n== Other animals ==\n\nThe fibularis tertius muscle in horses originates from the near the lateral condyle of the femur, passes through the extensor sulcus on the head of the tibia, and inserts onto the third metatarsal bone, the third and fourth tarsal bones, and the calcaneus.\n\nRupture of the muscle may cause the Achilles tendon to have a slight dip.\n\nhttps://en.wikipedia.org/wiki/Fibularis_tertius","extensor-hallucis-longus":"The extensor hallucis longus muscle is a thin skeletal muscle, situated between the tibialis anterior and the extensor digitorum longus.\n\nIt extends the big toe and dorsiflects the foot.\n\nIt also assists with foot eversion and inversion.\n\n== Structure ==\n\nThe extensor hallucis longus muscle arises from the anterior surface of the fibula for about the middle two-fourths of its extent, medial to the origin of the extensor digitorum longus muscle.\n\nIt also arises from the interosseous membrane of the leg to a similar extent.\n\nThe anterior tibial vessels and deep fibular nerve lie between it and the tibialis anterior.\n\nThe fibers pass downward, and end in a tendon, which occupies the anterior border of the muscle, passes through a distinct compartment in the cruciate crural ligament, crosses from the lateral to the medial side of the anterior tibial vessels near the bend of the ankle, and is inserted into the base of the distal phalanx of the great toe.\n\nOpposite the metatarsophalangeal articulation, the tendon gives off a thin prolongation on either side, to cover the surface of the joint.\n\nAn expansion from the medial side of the tendon is usually inserted into the base of the proximal phalanx.\n\n=== Nerve supply ===\n\nThe extensor hallucis longus muscle is supplied by the deep fibular nerve, a branch of common fibular nerve, which includes L4, L5, and S1 spinal nerve roots.\n\n=== Variations ===\n\nOccasionally united at its origin with the extensor digitorum longus.\nThe extensor ossis metatarsi hallucis, a small muscle, sometimes found as a slip from the extensor hallucis longus, or from the tibialis anterior, or from the extensor digitorum longus, or as a distinct muscle; it traverses the same compartment of the transverse ligament with the extensor hallucis longus.\n\n== Function ==\n\nThe extensor hallucis longus muscle extends the big toe, dorsiflects the foot, and also assists with foot eversion and inversion.\n\nhttps://en.wikipedia.org/wiki/Extensor_hallucis_longus_muscle","fibularis-longus-muscle":"In human anatomy, the fibularis longus (also known as peroneus longus) is a superficial muscle in the lateral compartment of the leg, and acts to evert and plantarflex the ankle.\n\nThe muscle, the longest and most superficial of the three peroneus muscles, is attached proximally to the head of the fibula and its 'belly' runs down most of this bone.\n\nIt becomes a tendon that goes posteriorly around the lateral malleolus of the ankle, then continues under the foot to attach to the medial cuneiform and first metatarsal.\n\nIt is innervated by the superficial peroneal nerve, which arises from the fifth lumbar and first sacral roots of the spinal cord.\n\n== Structure ==\n\nIt arises from the head and upper two-thirds of the lateral surface of the body of the fibula, from the deep surface of the fascia, and from the intermuscular septa between it and the muscles on the front and back of the leg; occasionally also by a few fibers from the lateral condyle of the tibia.\n\nBetween its attachments to the head and to the body of the fibula there is a gap through which the common peroneal nerve passes to the front of the leg.\n\nIt ends in a long tendon, which runs behind the lateral malleolus, in a groove common to it and the tendon of the peroneus brevis; the groove is converted into a canal by the superior peroneal retinaculum, and the tendons in it are contained in a common mucous sheath.\n\nThe tendon then extends obliquely forward across the lateral side of the foot, below the peroneal tubercle, and the tendon of the peroneus brevis, and under cover of the inferior peroneal retinaculum.\n\nIt crosses the lateral side of the cuboid, and then runs on the under surface of that bone in a groove which is converted into the peroneal canal by the long plantar ligament; the tendon then crosses the sole of the foot obliquely, and is inserted into the lateral side of the base of the first metatarsal bone and the lateral side of the medial cuneiform.\n\nOccasionally it sends a slip to the base of the second metatarsal bone.\n\nThe tendon changes its direction at two points: first, behind the lateral malleolus; secondly, on the cuboid bone; in both of these situations the tendon is thickened, and, in the latter, a sesamoid fibrocartilage (sometimes a bone), is usually developed in its substance.\n\n=== Nerve supply ===\n\nThe fibularis longus muscle is supplied by the superficial fibular nerve.\n\n== Function ==\n\nThe peroneus longus and brevis muscles plantarflex the foot, in conjunction with the tibialis posterior, antagonizing the tibialis anterior and peroneus tertius, which are dorsiflexors of the foot.\n\nThe peroneus longus also everts the sole of the foot, and from the oblique direction of the tendon across the sole of the foot is an important agent in the maintenance of the transverse arch.\n\nTaking their fixed points below, the peroneus muscles serve to steady the leg upon the foot.\n\nThis is especially the case in standing upon one leg, when the tendency of the superincumbent weight is to throw the leg medialward; the peroneus longus overcomes this tendency by drawing on the lateral side of the leg.\n\n== History ==\n\n=== Etymology ===\n\nThe terms Peroneus (i.e., Longus and Brevis) and Peroneal (i.e., Artery, Retinaculum) are derived from the Greek word Perone (pronounced Pair-uh-knee) meaning pin of a brooch or a buckle.\n\nIn medical terminology, both terms refer to being of or relating to the fibula or to the outer portion of the leg.\n\nhttps://en.wikipedia.org/wiki/Peroneus_longus","fibularis-brevis-muscle":"The Fibularis brevis muscle (or peroneus brevis muscle) lies under cover of the peroneus longus, and is the shorter and smaller of the peroneus muscles.\n\n== Structure ==\n\nIt arises from the lower two-thirds of the lateral surface of the body of the fibula, medial to the peroneus longus, and from the intermuscular septa separating it from the adjacent muscles on the front and back of the leg.\n\nThe fibers pass vertically downward, and end in a tendon which runs behind the lateral malleolus along with but in front of that of the preceding muscle, the two tendons being enclosed in the same compartment and lubricated by a common mucous sheath.\n\nIt then runs forward on the lateral side of the calcaneus, above the calcaneal tubercle and the tendon of the peroneus longus, and is inserted into the tuberosity at the base of the fifth metatarsal bone, on its lateral side.\n\nWhen the base of the fifth metatarsal is fractured, the peroneus brevis may pull on and displace the proximal fragment (Jones Fracture).\n\nAn inversion sprain of the foot may pull the tendon such that it avulses the tuberosity at the base of the fifth metatarsal.\n\n=== Nerve supply ===\n\nIt is innervated by the superficial fibular nerve, also known as the superficial peroneal nerve.\n\n== Function ==\n\nThe peroneus brevis muscle is the strongest abductor of the foot.\n\nIt also assists in weak plantarflexion and eversion of the foot.\n\nIt provides lateral stability to the foot and ankle.\n\n== History ==\n\n=== Etymology ===\n\nThe terms \"Peroneal\" (i.e., Artery, Retinaculum) and \"Peroneus\" (i.e., Longus and Brevis) are derived from the Greek word Perone (pronounced Pair-uh-knee) meaning pin of a brooch or a buckle.\n\nIn medical terminology, both terms refer to being of or relating to the fibula or to the outer portion of the leg.\n\nhttps://en.wikipedia.org/wiki/Peroneus_brevis","lateral-head-of-gastrocnemius":"The gastrocnemius muscle (plural gastrocnemii) is a superficial two-headed muscle that is in the back part of the lower leg of humans.\n\nIt runs from its two heads just above the knee to the heel, a three joint muscle (knee, ankle and subtalar joints).\n\nThe muscle is named via Latin, from Greek γαστήρ (gaster) 'belly' or 'stomach' and κνήμη (knḗmē) 'leg', meaning 'stomach of leg' (referring to the bulging shape of the calf).\n\n== Structure ==\n\nThe gastrocnemius is located with the soleus in the posterior (back) compartment of the leg.\n\nThe lateral head originates from the lateral condyle of the femur, while the medial head originates from the medial condyle of the femur.\n\nIts other end forms a common tendon with the soleus muscle; this tendon is known as the calcaneal tendon or Achilles tendon and inserts onto the posterior surface of the calcaneus, or heel bone.\n\nIt is considered a superficial muscle as it is located directly under skin, and its shape may often be visualized through the skin.\n\nDeep to the gastrocnemius (farther from the skin) is the soleus muscle.\n\nSome anatomists consider both to be a single muscle—the triceps surae or \"three-headed [muscle] of the calf\"—since they share a common insertion via the Achilles tendon.\n\nThe plantaris muscle and a portion of its tendon run between the two muscles, which is involved in \"locking\" the knee from the standing position.\n\nSince the anterior compartment of the leg is lateral to the tibia, the bulge of muscle medial to the tibia on the anterior side is actually the posterior compartment.\n\nThe soleus is superficial to the mid-shaft of the tibia.\n\n=== Variation ===\n\n10% to 30% of individuals have a sesamoid bone called the \"fabella\" in the lateral (outer) head of the gastrocnemius muscle.\n\n== Function ==\n\nAlong with the soleus muscle, the gastrocnemius forms half of the calf muscle.\n\nIts function is plantar flexing the foot at the ankle joint and flexing the leg at the knee joint.\n\nThe gastrocnemius is primarily involved in running, jumping and other \"fast\" movements of leg, and to a lesser degree in walking and standing.\n\nThis specialization is connected to the predominance of white muscle fibers (type II fast twitch) present in the gastrocnemius, as opposed to the soleus, which has more red muscle fibers (type I slow twitch) and is the primary active muscle when standing still, as determined by EMG studies.\n\n=== Motor pathway ===\n\nThe plan to use the gastrocnemius in running, jumping, knee and plantar flexing is created in the precentral gyrus in the cerebrum of the brain.\n\nOnce a plan is produced, the signal is sent to and down an upper motor neuron.\n\nThe signal is passed through the internal capsule and decussates, or crosses, in the medulla oblongata, specifically in the lateral corticospinal tract.\n\nThe signal continues down through the anterior horn of the spinal cord where the upper motor neuron synapses with the lower motor neuron.\n\nSignal propagation continues down the anterior rami (Lumbar 4-5 and Sacral 1-5) of the sacral plexus.\n\nThe sciatic nerve branches off of the sacral plexus in which the tibial and common fibular nerves are wrapped in one sheath.\n\nThe tibial nerve eventually separates from the sciatic nerve and innervates the gastrocnemius muscle.\n\nThus, completing the plan the brain had originally started with, so that the actions of running, standing, and jumping could be executed.\n\n== Clinical significance ==\n\nThe gastrocnemius muscle is prone to spasms, which are painful, involuntary contractions of the muscle that may last several minutes.\n\nA severe ankle dorsiflexion force may result in an Medial Gastrocnemius Strain (MGS) injury of the muscle, commonly referred to as a \"torn\" or \"strained\" calf muscle, which is acutely painful and disabling.\n\nThe gastrocnemius muscle may also become inflamed due to overuse.\n\nAnti-inflammatory medications and physical therapy (heat, massage, and stretching) may be useful.\n\nAnatomical abnormalities involving the medial head of gastrocnemius muscle result in popliteal artery entrapment syndrome.\n\n== History ==\n\nIn a 1967 EMG study, Herman and Bragin concluded that its most important role was plantar flexing in large contractions and in rapid development of tension.\n\nhttps://en.wikipedia.org/wiki/Gastrocnemius_muscle","medial-head-of-gastrocnemius":"The gastrocnemius muscle (plural gastrocnemii) is a superficial two-headed muscle that is in the back part of the lower leg of humans.\n\nIt runs from its two heads just above the knee to the heel, a three joint muscle (knee, ankle and subtalar joints).\n\nThe muscle is named via Latin, from Greek γαστήρ (gaster) 'belly' or 'stomach' and κνήμη (knḗmē) 'leg', meaning 'stomach of leg' (referring to the bulging shape of the calf).\n\n== Structure ==\n\nThe gastrocnemius is located with the soleus in the posterior (back) compartment of the leg.\n\nThe lateral head originates from the lateral condyle of the femur, while the medial head originates from the medial condyle of the femur.\n\nIts other end forms a common tendon with the soleus muscle; this tendon is known as the calcaneal tendon or Achilles tendon and inserts onto the posterior surface of the calcaneus, or heel bone.\n\nIt is considered a superficial muscle as it is located directly under skin, and its shape may often be visualized through the skin.\n\nDeep to the gastrocnemius (farther from the skin) is the soleus muscle.\n\nSome anatomists consider both to be a single muscle—the triceps surae or \"three-headed [muscle] of the calf\"—since they share a common insertion via the Achilles tendon.\n\nThe plantaris muscle and a portion of its tendon run between the two muscles, which is involved in \"locking\" the knee from the standing position.\n\nSince the anterior compartment of the leg is lateral to the tibia, the bulge of muscle medial to the tibia on the anterior side is actually the posterior compartment.\n\nThe soleus is superficial to the mid-shaft of the tibia.\n\n=== Variation ===\n\n10% to 30% of individuals have a sesamoid bone called the \"fabella\" in the lateral (outer) head of the gastrocnemius muscle.\n\n== Function ==\n\nAlong with the soleus muscle, the gastrocnemius forms half of the calf muscle.\n\nIts function is plantar flexing the foot at the ankle joint and flexing the leg at the knee joint.\n\nThe gastrocnemius is primarily involved in running, jumping and other \"fast\" movements of leg, and to a lesser degree in walking and standing.\n\nThis specialization is connected to the predominance of white muscle fibers (type II fast twitch) present in the gastrocnemius, as opposed to the soleus, which has more red muscle fibers (type I slow twitch) and is the primary active muscle when standing still, as determined by EMG studies.\n\n=== Motor pathway ===\n\nThe plan to use the gastrocnemius in running, jumping, knee and plantar flexing is created in the precentral gyrus in the cerebrum of the brain.\n\nOnce a plan is produced, the signal is sent to and down an upper motor neuron.\n\nThe signal is passed through the internal capsule and decussates, or crosses, in the medulla oblongata, specifically in the lateral corticospinal tract.\n\nThe signal continues down through the anterior horn of the spinal cord where the upper motor neuron synapses with the lower motor neuron.\n\nSignal propagation continues down the anterior rami (Lumbar 4-5 and Sacral 1-5) of the sacral plexus.\n\nThe sciatic nerve branches off of the sacral plexus in which the tibial and common fibular nerves are wrapped in one sheath.\n\nThe tibial nerve eventually separates from the sciatic nerve and innervates the gastrocnemius muscle.\n\nThus, completing the plan the brain had originally started with, so that the actions of running, standing, and jumping could be executed.\n\n== Clinical significance ==\n\nThe gastrocnemius muscle is prone to spasms, which are painful, involuntary contractions of the muscle that may last several minutes.\n\nA severe ankle dorsiflexion force may result in an Medial Gastrocnemius Strain (MGS) injury of the muscle, commonly referred to as a \"torn\" or \"strained\" calf muscle, which is acutely painful and disabling.\n\nThe gastrocnemius muscle may also become inflamed due to overuse.\n\nAnti-inflammatory medications and physical therapy (heat, massage, and stretching) may be useful.\n\nAnatomical abnormalities involving the medial head of gastrocnemius muscle result in popliteal artery entrapment syndrome.\n\n== History ==\n\nIn a 1967 EMG study, Herman and Bragin concluded that its most important role was plantar flexing in large contractions and in rapid development of tension.\n\nhttps://en.wikipedia.org/wiki/Gastrocnemius_muscle","calcaneal-tendon":"The calcaneal tendon or heel cord, also known as the Achilles tendon, is a tendon at the back of the lower leg, and is the thickest in the human body.\n\nIt serves to attach the plantaris, gastrocnemius (calf) and soleus muscles to the calcaneus (heel) bone.\n\nThese muscles, acting via the tendon, cause plantar flexion of the foot at the ankle joint, and (except the soleus) flexion at the knee.\n\nAbnormalities of the calcaneal tendon include inflammation (calcaneal tendinitis), degeneration, rupture, and becoming embedded with cholesterol deposits (xanthomas).\n\nThe calcaneal tendon was named in 1693 after the Greek hero calcaneal.\n\n== Structure ==\n\nThe calcaneal tendon connects muscle to bone, like other tendons, and is located at the back of the lower leg.\n\nThe calcaneal tendon connects the gastrocnemius and soleus muscles to the calcaneal tuberosity on the calcaneus (heel bone).\n\nThe tendon begins near the middle of the calf, and receives muscle fibers on its inner surface, particularly from the soleus muscle, almost to its lower end.\n\nGradually thinning below, it inserts into the middle part of the back of the calcaneus bone.\n\nThe tendon spreads out somewhat at its lower end so that its narrowest part is about 4 cm (1.6 in) above its insertion.The tendon is covered by the fascia and skin, and stands out prominently behind the bone; the gap is filled up with areolar and adipose tissue.\n\nA bursa lies between the tendon and the upper part of the calcaneus.\n\nIt is about 15 centimetres (6 in) long.\nAlong the side of the muscle, and superficial to it, is the small saphenous vein.\n\nThe sural nerve accompanies the small saphenous vein as it descends in the posterior leg, traveling inferolateral to it as it crosses the lateral border of the calcaneal tendon.\n\nThe tendon is the thickest tendon in the human body.\n\nIt can receive a load stress 3.9 times body weight during walking and 7.7 times body weight when running.The blood supply to the calcaneal tendon is poor, and mostly via a recurrent branch of the posterior tibial artery, and some through arterial branches passing through surrounding muscles.\n\n== Function ==\n\nActing via the calcaneal tendon, the gastrocnemius and soleus muscles cause plantar flexion of the foot at the ankle.\n\nThis action brings the sole of the foot closer to the back of the leg.\n\nThe gastrocnemius also flexes the leg at the knee.\n\nBoth muscles are innervated by the tibial nerve.\n\nBecause the fibres of the tendon spiral about 90 degrees, fibres from the gastrocnemius tend to attach to the outer part of the bone, whereas fibres from the soleus tend to attach closer to the midline.Vibration of the tendon without vision has a major impact on postural orientation.\n\nVibration of the tendon causes movement backwards and the illusion of a forward body tilt in standing subjects.\n\nThis is because vibrations stimulate muscle spindles in the calf muscles.\n\nThe muscle spindles alert the brain that the body is moving forward, so the central nervous system compensates by moving the body backwards.\n\n== Clinical significance ==\n\n=== Inflammation ===\n\nInflammation of the calcaneal tendon is called calcaneal tendinitis.\n\ncalcaneal tendinosis is the soreness or stiffness of the tendon, particularly worse when exercising, and generally due to overuse.\n\nThe most common symptoms are pain and swelling around the affected tendon.\n\nThe pain is typically worse at the start of exercise and decreases thereafter.\n\nStiffness of the ankle may also be present.\n\nOnset is generally gradual.It commonly occurs as a result of overuse such as running.\n\nOther risk factors include trauma, a lifestyle that includes little exercise, high-heel shoes, rheumatoid arthritis, and medications of the fluoroquinolone or steroid class.\n\nDiagnosis is generally based on symptoms and examination.While stretching and exercises to strengthen the back are often recommended for prevention, evidence to support these measures is poor.\n\nTreatment typically involves rest, ice, non-steroidal antiinflammatory agents (NSAIDs), and physical therapy.\n\nA heel lift or orthotics may also be helpful.\n\nIn those in who symptoms last more than six months despite other treatments, surgery may be considered.\n\ncalcaneal tendinitis is relatively common.\n\n=== Degeneration ===\n\ncalcaneal tendon degeneration (tendinosis) is typically investigated with either MRI or ultrasound.\n\nIn both cases, the tendon is thickened, may demonstrate surrounding inflammation by virtue of the presence of paratenonitis, retrocalcaneal or retro-calcaneal bursitis.\n\nWithin the tendon, increased blood flow, tendon fibril disorganisation, and partial thickness tears may be identified.\n\ncalcaneal tendinosis frequently involves the mid portion of the tendon but may involve the insertion, which is then known as enthesopathy.\n\nThough enthesopathy may be seen in the context of advancing age, it is also associated with arthritis such as gout and the seronegative spondyloarthitides.\n\ncalcaneal tendinosis is a known risk factor for calf muscle tears.\n\n=== Rupture ===\n\ncalcaneal tendon rupture is when the calcaneal tendon breaks.\n\nSymptoms include the sudden onset of sharp pain in the heel.\n\nA snapping sound may be heard as the tendon breaks and walking becomes difficult.Rupture typically occurs as a result of a sudden bending up of the foot when the calf muscle is engaged, direct trauma, or long-standing tendonitis.\n\nOther risk factors include the use of fluoroquinolones, a significant change in exercise, rheumatoid arthritis, gout, or corticosteroid use.\n\nDiagnosis is typically based on symptoms and examination and supported by medical imaging.\n\ncalcaneal tendon rupture occurs in about 1 per 10,000 people per year.\n\nMales are more commonly affected than females.\n\nPeople in their 30s to 50s are most commonly affected.Prevention may include stretching before activity.\n\nTreatment may be by surgery or casting with the toes somewhat pointed down.\n\nRelatively rapid return to weight bearing (within 4 weeks) appears okay.\n\nThe risk of re-rupture is about 25% with casting.\n\nIf appropriate treatment does not occur within 4 weeks of the injury outcomes are not as good.\n\n=== Xanthomas ===\n\nTendon xanthomas are cholesterol deposits that commonly develop in the calcaneal tendon of people with lipid metabolism disorders such as familial hypercholesterolemia.\n\n=== Neurological exam ===\n\nThe calcaneal' tendon is often tested as part of a neurological examination.\n\nIn this examination, the tendon is hit with a tendon hammer.\n\nThis tests the S1 and S2 spinal nerves: a normal response is plantar flexion (downward movement) of the foot.Level or portion of tendon affected\nParatendinopathy: The inflammation of a connective tissue sleeve which surrounds the tendon and protects it from friction, irritation, and repeated trauma\nInsertional: Eminently overuse-injury which frequently occurs in running and jumping athletes.\n\nPatients affected by insertional calcaneal tendinopathy complain of pain on the posterior aspect of the heel and may have morning stiffness, swelling with activity and tenderness at the tendon insertion level.\n\nIf this condition becomes chronic, calcific deposits at the calcaneal insertional level may be developed (due to microfractures and healing of the osteotendinous union) which can degenerate, if it persists over time, in the abnormal bony prominence on the posterior aspect of heel, condition known as Haglund deformity, which can be painful and difficult close-shoes fitting due to friction and irritation.\nMid-portion: Occurs approximately 2 – 7 cm proximal from the calcaneal insertion into the calcaneus.\n\nCharacterized by a combination of pain and swelling at this level.\n\nIt has associated a remarkable impaired performance.\n\n== Other animals ==\n\nApart from humans, the calcaneal tendon is short or absent in great apes, but long in arboreal gibbons and humans.\n\nIt provides elastic energy storage in hopping, walking, and running.\n\nComputer models suggest this energy storage calcaneal tendon increases top running speed by >80% and reduces running costs by more than three-quarters.\n\nIt has been suggested that the \"absence of a well-developed calcaneal tendon in the nonhuman African apes would preclude them from effective running, both at high speeds and over extended distances.\"\n\n== History ==\n\nThe oldest-known written record of the tendon being named for calcaneal is in 1693 by the Flemish/Dutch anatomist Philip Verheyen.\n\nIn his widely used text Corporis Humani Anatomia he described the tendon's location and said that it was commonly called \"the cord of calcaneal.\" The tendon has been described as early as the time of Hippocrates, who described it as the \"tendo magnus\" (Latin: great tendon) and by subsequent anatomists prior to Verheyen as \"chorda Hippocratis\".Verheyen referred to the mythological account of calcaneal being held by the heel by his mother Thetis when she dipped him in the River Styx as a baby to render his body invulnerable.\n\nAs the heel by which she held him was not touched by the water, it was his one vulnerable spot (hence the expression \"calcaneal' heel\") and he was eventually killed by a poison dart to the heel.\n\nThe name thus also refers to the particularly disabling and painful effect of an injury to this tendon.\n\nThe first closed rupture was described by Ambroise Pare in the sixteenth century.The calcaneal tendon is also known as the \"tendo calcaneus\" (Latin: calcaneal tendon).\n\nBecause eponyms (names relating to people) have no relationship to the subject matter, most anatomical eponyms also have scientifically descriptive terms.\n\nThe term calcaneal comes from the Latin calcaneum, meaning heel.\n\n== References ==\n\nhttps://en.wikipedia.org/wiki/calcaneal_tendon","soleus-muscle":"In humans and some other mammals, the soleus is a powerful muscle in the back part of the lower leg (the calf).\n\nIt runs from just below the knee to the heel, and is involved in standing and walking.\n\nIt is closely connected to the gastrocnemius muscle and some anatomists consider them to be a single muscle, the triceps surae.\n\nIts name is derived from the Latin word \"solea\", meaning \"sandal\".\n\n== Structure ==\n\nThe soleus is located in the superficial posterior compartment of the leg.\n\nThe soleus exhibits significant morphological differences across species.\n\nIt is unipennate in many species.\n\nIn some animals, such as the rabbit, it is fused for much of its length with the gastrocnemius muscle.\n\nIn humans, the soleus is a complex, multi-pennate muscle, usually having a separate (posterior) aponeurosis from the gastrocnemius muscle.\n\nA majority of soleus muscle fibers originate from each side of the anterior aponeurosis, attached to the tibia and fibula.\n\nOther fibers originate from the posterior (back) surfaces of the head of the fibula and its upper quarter, as well as the middle third of the medial border of the tibia.\n\nThe fibers originating from the anterior surface of the anterior aponeurosis insert onto the median septum and the fibers originating from the posterior surface of the anterior aponeurosis insert onto the posterior aponeurosis.\n\nThe posterior aponeurosis and median septum join in the lower quarter of the muscle and then join with the anterior aponeuroses of the gastrocnemius muscles to form the calcaneal tendon or Achilles tendon and inserts onto the posterior surface of the calcaneus, or heel bone.\n\nIn contrast to some animals, the human soleus and gastrocnemius muscles are relatively separate, such that shear can be detected between the soleus and gastrocnemius aponeuroses.The Soleus is vestigial in the horse.\n\n=== Relations ===\n\nThe gastrocnemius muscle is superficial to (closer to the skin than) the soleus, which lies below the gastrocnemius.\nThe plantaris muscle and a portion of its tendon run between the two muscles.\n\nDeep to it (farther from the skin) is the transverse intermuscular septum, which separates the superficial posterior compartment of the leg from the deep posterior compartment.\n\nOn the other side of the fascia are the tibialis posterior muscle, the flexor digitorum longus muscle, and the flexor hallucis longus muscle, along with the posterior tibial artery and posterior tibial vein and the tibial nerve.\n\nSince the anterior compartment of the leg is lateral to the tibia, the bulge of muscle medial to the tibia on the anterior side is actually the posterior compartment.\n\nThe soleus is superficial middle of the tibia.\n\n== Function ==\n\nThe action of the calf muscles, including the soleus, is plantarflexion of the foot (that is, they increase the angle between the foot and the leg).\n\nThey are powerful muscles and are vital in walking, running, and keeping balance.\n\nThe soleus specifically plays an important role in maintaining standing posture; if not for its constant pull, the body would fall forward.\n\nAlso, in upright posture, the soleus is responsible for pumping venous blood back into the heart from the periphery, and is often called the skeletal-muscle pump, peripheral heart or the sural (tricipital) pump.\n\nSoleus muscles have a higher proportion of slow muscle fibers than many other muscles.\n\nIn some animals, such as the guinea pig and cat, soleus consists of 100% slow muscle fibers.\n\nHuman soleus fiber composition is quite variable, containing between 60 and 100% slow fibers.The soleus is the most effective muscle for plantarflexion in a bent knee position (Hence called the first gear muscle).\n\nThis is because the gastrocnemius originates on the femur, so bending the leg limits its effective tension.\n\nDuring regular movement (i.e., walking) the soleus is the primary muscle utilized for plantarflexion due to the slowtwitch fibers resisting fatigue.\n\n== Clinical significance ==\n\n=== Disease ===\n\nDue to the thick fascia covering the muscles of the leg, they are prone to compartment syndrome.\n\nThis pathology relates to the inflammation of tissue affecting blood flow and compressing nerves.\n\nIf left untreated compartment syndrome can lead to atrophy of muscles, blood clots, and neuropathy.\n\nhttps://en.wikipedia.org/wiki/Soleus_muscle","plantaris-muscle":"The plantaris is one of the superficial muscles of the superficial posterior compartment of the leg, one of the fascial compartments of the leg.\nIt is composed of a thin muscle belly and a long thin tendon.\n\nWhile not as thick as the achilles tendon, the plantaris tendon (which tends to be between 30–45 centimetres (12–18 in) in length) is the longest tendon in the human body.\n\nNot including the tendon, the plantaris muscle is approximately 5–10 centimetres (2.0–3.9 in) long and is absent in 8-12% of the population.\n\nIt is one of the plantar flexors in the posterior compartment of the leg, along with the gastrocnemius and soleus muscles.\n\nThe plantaris is considered to have become an unimportant muscle when human ancestors switched from climbing trees to bipedalism and in anatomically modern humans it mainly acts with the gastrocnemius.\n\n== Structure ==\n\nThe plantaris muscle arises from the inferior part of the lateral supracondylar ridge of the femur at a position slightly superior to the origin of the lateral head of gastrocnemius.\n\nIt passes posterior to the knee joint in an inferomedial direction and becomes tendinous distally to insert into the Achilles tendon.\n\nIt occasionally separately inserts into the medial side of the calcaneus.\n\n=== Innervation ===\n\nThe plantaris muscle is innervated by the tibial nerve, a branch of the sciatic nerve in the sacral plexus.\n\nSignaling for contraction begins in the frontal lobe of the brain with the pre-central gyrus (primary motor cortex).\n\nUpper motor neurons are stimulated and send a signal through the internal capsule and down the corticospinal tract.\n\nDecussation of the lateral corticospinal tract occurs in the medullary pyramids, then the fibers continue down the contralateral side of the spinal cord.\n\nUpper motor neurons synapse with lower motor neurons at the anterior horn of the spinal cord in the sacral plexus (formed from the anterior rami of spinal nerves L4, L5, S1–4).\n\nThe lower motor neuron fibers continue down the sciatic nerve and then diverge into the tibial and common fibular nerves.\n\nThe tibial nerve runs medially at the knee joint.\n\nWhen the tibial nerve receives an action potential, the plantaris muscle contracts, providing weak plantar flexion of the foot and weak flexion of the knee.\n\n=== Variation ===\n\nThe muscle may arise from the oblique popliteal ligament.\n\nInterdigitations with the lateral head of the gastrocnemius and a fibrous extension of the muscle to the patella are not unusual.\n\n== Function ==\n\nThe plantaris acts to weakly plantar flex the ankle joint and flex the knee joint.\nThe plantaris muscle may also provide proprioceptive feedback information to the central nervous system regarding the position of the foot.\n\nThe unusually high density of proprioceptive receptor end organs supports this notion.Its motor function is so minimal that its long tendon can readily be harvested for reconstruction elsewhere with little functional deficit.\n\nOften mistaken for a nerve by new medical students (and thus called the \"freshman's nerve\"), the muscle was useful to other primates for grasping with their feet.\n\n== Clinical significance ==\n\nA common injury that is normally attributed to the plantaris muscle is a condition called tennis leg.\n\nAlthough pain in the calf can be attributed to a rupture of the plantaris muscle, recent ultrasound research has shown that tennis leg more commonly arises from tears in the musculotendinous junction of the medial gastrocnemius.\n\nIn one clinical study, 94 out of 141 patients (66.7%) diagnosed with tennis leg were found with a partial rupture of the gastrocnemius muscle, while rupture of the plantaris tendon was only seen in 2 patients (1.4%).Injury may occur from running, jumping, or pushing off one leg in sports such as tennis, basketball and soccer, which require quick foot movement in a certain direction.\n\nIsolated plantaris muscle strains are rare, and ruptures normally occur in conjunction with injury to other muscles in the posterior compartment of the lower leg.\n\nSymptoms of a plantaris muscle rupture may include an audible popping sound in the area during physical activity, swelling, pain in the back of the lower leg, and persistent soreness.\n\nAnkle flexion may also be painful.\n\nhttps://en.wikipedia.org/wiki/Plantaris_muscle","flexor-digitorum-longus":"The flexor digitorum longus muscle is situated on the tibial side of the leg.\n\nAt its origin it is thin and pointed, but it gradually increases in size as it descends.\n\nIt serves to flex the second, third, fourth, and fifth toes.\n\n== Structure ==\n\nThe flexor digitorum longus muscle arises from the posterior surface of the body of the tibia, from immediately below the soleal line to within 7 or 8 cm of its lower extremity, medial to the tibial origin of the tibialis posterior muscle.\n\nIt also arises from the fascia covering the tibialis posterior muscle.\n\nThe fibers end in a tendon, which runs nearly the whole length of the posterior surface of the muscle.\n\nThis tendon passes behind the medial malleolus, in a groove, common to it and the tibialis posterior, but separated from the latter by a fibrous septum, each tendon being contained in a special compartment lined by a separate mucous sheath.\n\nThe tendon of the tibialis posterior and the tendon of the flexor digitorum longus cross each other, in a spot above the medial malleolus, the crural tendinous chiasm.\n\nIt passes through the tarsal tunnel.\n\nIt passes obliquely forward and lateralward, superficial to the deltoid ligament of the ankle-joint, into the sole of the foot, where it crosses over the tendon of the flexor hallucis longus at the level of the navicular bone at a location known as the knot of henry (also referred to as plantar tendinous chiasm), and receives from it a strong tendinous slip.\n\nIt then expands and is joined by the quadratus plantæ muscle, and finally divides into four tendons, which are inserted into the bases of the last phalanges of the second, third, fourth, and fifth toes, each tendon passing through an opening in the corresponding tendon of the flexor digitorum brevis muscle opposite the base of the first interphalangeal joint.\n\n=== Variation ===\n\nFlexor accessorius longus digitorum, not infrequent, origin from fibula, or tibia, or the deep fascia and ending in a tendon which, after passing beneath the laciniate ligament, joins the tendon of the long flexor or the quadratus plantæ.\n\n== Function ==\n\nSimilar to the flexor hallucis longus and tibialis posterior muscles, the flexor digitorum longus muscle functions to plantar flex and invert the foot.\n\nThe flexor digitorum longus muscle is responsible for the movement and curling of the second, third, fourth and fifth toes.\n\nThis muscle makes it possible for the toes to grip the surface of floors, which is important when it comes to maintaining postural balance on surfaces that are rough or uneven.\n\nThe other deep muscles are the flexor hallucis longus and tibialis posterior; the tibialis posterior is the most powerful of these deep muscles.\n\nAll three muscles are innervated by the tibial nerve which comprises half of the sciatic nerve.\n\n== Clinical significance ==\n\nAfter passing through the tarsal tunnel, the flexor digitorum longus tendon must curve around a bony landmark called the sustenaculum tali.\n\nFlexor digitorum longus pain can occur with a trip and fall on uneven surface when the toes are not able to grip the surface totally.\n\nOne can also injure the flexor digitorum longus muscle while running on a beach in the sand without any footwear, making the muscle vulnerable at the calcaneus attachment for injuries.\n\nIn case of flexor digitorum longus pain or strain, the patient will find it tough to walk and will have excruciating pain in the feet and ankles.\n\nSupport braces along with warm compresses are the most preferred way of treating flexor digitorum longus pain or strain.\n\nhttps://en.wikipedia.org/wiki/Flexor_digitorum_longus_muscle","popliteus-muscle":"The popliteus muscle in the leg is used for unlocking the knees when walking, by laterally rotating the femur on the tibia during the closed chain portion of the gait cycle (one with the foot in contact with the ground).\n\nIn open chain movements (when the involved limb is not in contact with the ground), the popliteus muscle medially rotates the tibia on the femur.\n\nIt is also used when sitting down and standing up.\n\nIt is the only muscle in the posterior (back) compartment of the lower leg that acts just on the knee and not on the ankle.\n\nThe gastrocnemius muscle acts on both joints.\n\n== Structure ==\n\nThe popliteus muscle originates from the lateral surface of the lateral condyle of the femur by a rounded tendon.\n\nIts fibers pass downward and medially.\n\nIt inserts onto the posterior surface of tibia, above the soleal line.\n\nThe muscle arises within the capsule of knee joint and its tendon separates the lateral meniscus from the lateral ligament of the joint.\n\n=== Nerve supply ===\n\nThe popliteus muscle is supplied by the tibial nerve, from spinal roots L5 and S1.\n\n=== Variation ===\n\nThere is sometimes an additional head from the sesamoid bone in the lateral (outer) head of the gastrocnemius muscle.\nRarely an additional inconstant muscle; the popliteus minor is seen.\n\nIt originates from the femur on the inner side of the plantaris muscle and inserts into the posterior ligament of the knee-joint.\nPeroneotibialis, 14% of population.\n\nOrigin is inner side of the head of the fibula, insertion into the upper end of the oblique line of the tibia, it lies beneath the popliteus.Another variant, the cyamella, is a small sesamoid bone embedded in the tendon of the popliteus muscle.\n\nIt is rarely seen in humans, but has been described more often in other primates and certain other animals.\n\n== Function ==\n\nThe popliteus assists in flexing the leg upon the thigh; when the leg is flexed, it will rotate the tibia inward.\nIt is especially called into action at the beginning of the act of bending the knee, in as much as it produces the slight inward rotation of the tibia, which is essential in the early stage of this movement.When the knee is in full extension, the femur slightly medially rotates on the tibia to lock the knee joint in place.\n\nPopliteus is often referred to as the \"Key\" to unlocking the knee since it begins knee flexion by laterally rotating the femur on the tibia.Popliteus is also attached to the lateral meniscus in the knee and draws it posteriorly during knee flexion to prevent crushing the meniscus between the tibia and femur as the knee flexes.\n\nhttps://en.wikipedia.org/wiki/Popliteus_muscle","tibialis-posterior-muscle":"The tibialis posterior muscle is the most central of all the leg muscles, and is located in the deep posterior compartment of the leg.\n\nIt is the key stabilizing muscle of the lower leg.\n\n== Structure ==\n\nThe tibialis posterior muscle originates on the inner posterior border of the fibula laterally.\n\nIt is also attached to the interosseous membrane medially, which attaches to the tibia and fibula.\n\nThe tendon of the tibialis posterior muscle (sometimes called the posterior tibial tendon) descends posterior to the medial malleolus.\n\nIt terminates by dividing into plantar, main, and recurrent components.\n\nThe main portion inserts into the tuberosity of the navicular bone.\n\nThe smaller portion inserts into the plantar surface of the medial cuneiform.\n\nThe plantar portion inserts into the bases of the second, third and fourth metatarsals, the intermediate and lateral cuneiforms and the cuboid.\n\nThe recurrent portion inserts into the sustentaculum tali of the calcaneus.\n\nBlood is supplied to the muscle by the posterior tibial artery.\n\n=== Nerve supply ===\n\nThe tibialis posterior muscle is suppled by the tibial nerve.\n\n== Function ==\n\nThe tibialis posterior muscle is a key muscle for stabilization of the lower leg.\n\nIt also contracts to produce inversion of the foot, and assists in the plantarflexion of the foot at the ankle.\n\nThe tibialis posterior has a major role in supporting the medial arch of the foot.\n\nDysfunction of the tibialis posterior, including rupture of the tibialis posterior tendon, can lead to flat feet in adults, as well as a valgus deformity due to unopposed eversion when inversion is lost.\n\n== Clinical significance ==\n\nInjury to the distal tendon of the tibialis posterior muscle is rare.\n\nIt may be caused during exercise.\n\nIt usually presents with pain on the medial side of the ankle.\n\nThis may be treated with dry needling acupuncture.\n\nhttps://en.wikipedia.org/wiki/Tibialis_posterior_muscle","flexor-hallucis-longus":"The flexor hallucis longus muscle (FHL) is one of the three deep muscles of the posterior compartment of the leg that attaches to the plantar surface of the distal phalanx of the great toe.\n\nThe other deep muscles are the flexor digitorum longus and tibialis posterior; the tibialis posterior is the most powerful of these deep muscles.\n\nAll three muscles are innervated by the tibial nerve which comprises half of the sciatic nerve.\n\n== Structure ==\n\nThe flexor hallucis longus is situated on the fibular side of the leg.\n\nIt arises from the inferior two-thirds of the posterior surface of the body of the fibula, with the exception of 2.5 cm. at its lowest part; from the lower part of the interosseous membrane; from an intermuscular septum between it and the peronius muscles, laterally, and from the fascia covering the tibialis posterior, medially.\n\nThe fibers pass obliquely downward and backward, where it passes through the tarsal tunnel on the medial side of the foot and end in a tendon which occupies nearly the whole length of the posterior surface of the muscle.\n\nThis tendon lies in a groove which crosses the posterior surface of the lower end of the tibia, between the medial and lateral tubercles of the posterior surface of the talus, and the under surface of the sustentaculum tali of the calcaneus; in the sole of the foot it runs forward between the two heads of the flexor hallucis brevis, and is inserted into the base of the last phalanx of the great toe.\n\nThe grooves on the talus and calcaneus, which contain the tendon of the muscle, are converted by tendinous fibers into distinct canals, lined by a mucous sheath.\n\nAs the tendon passes forward in the sole of the foot, it is situated above, and crosses from the lateral to the medial side of the tendon of the flexor digitorum longus, to which it is connected by a fibrous slip.\n\n=== Variation ===\n\nUsually a slip runs to the flexor digitorum and frequently an additional slip runs from the flexor digitorum to the flexor hallucis.\n\nPeroneocalcaneus internus, rare, arises below or outside the flexor hallucis from the back of the fibula, passes over the sustentaculum tali with the flexor hallucis and inserts into the calcaneum.\n\n== Function ==\n\nSimilar to the flexor digitorum longus and tibialis posterior muscles, the flexor hallucis longus muscle functions to plantar flex and invert the foot.\n\nHowever, it is unique in that it also functions to flex the great toe and helps supinate the ankle.\n\n== Injury and treatment ==\n\nCommon injuries associated with the FHL tendon are tenosynovitis, tendinopathies, and muscle strains.\n\nBecause the FHL muscle is small, injuries associated with this muscle and its tendon are often overlooked.\n\nAn MRI can be used to evaluate the cause and condition of the FHL tendon.\n\nTears and areas of impingement can be found using this method.\n\nA diagnostic ultrasound can also be used to diagnose FHL injuries, as it shows the muscle in movement and potential areas of impingement.\n\nConservatively, an FHL injury can be evaluated by determining if movements caused by the FHL muscle cause pain along the inner ankle or under the big toe.\n\nAfter passing through the tarsal tunnel, the flexor hallucis longus tendon must curve around a bony landmark called the sustentaculum tali.\n\nFriction at this site is likely to cause pain on the posteromedial aspect of the ankle.\n\nWhile commonly referred to as \"dancer's tendinitis,\" FHL tendinitis occurs commonly in ballet dancers, gymnasts, and runners.\n\nDue to their excessive use of toe flexion, which results in ten times their body weight being applied to this small muscle and tendon, inflammation and irritation is common at the site of the sustentaculum tali.\n\nHallux saltans is a condition that develops as a result of overusing the FHL muscle.\n\nWith this condition, a nodule develops along the FHL tendon which may produce a popping effect during contraction because it drags along surrounding tissues.\n\nIf left untreated and continually irritated, stenosis of the tendon may occur, resulting in the big toe becoming stiff and relatively immobile.\n\nThis condition is known as Hallux Rigidus.\nMost FHL injuries can be managed through conservative treatment.\n\nRest is usually the first indicated intervention for minor FHL injuries.\n\nIce and ultrasound therapy can also help with the inflammation and pain.\n\nPhysical therapy exercises and stretches can help rehabilitate the muscle and tendon and potentially address biomechanical errors that cause the inflammation and microtears in the tendon.\n\nSome FHL injuries can be treated through rest, physical therapy, splints, and anti-inflammatory medication.\n\nHowever, more serious or chronic injuries may require surgery.\n\nIf surgery is indicated, tears in the FHL will be repaired, and debris will be removed from the area.\n\nIt is worth noting that an os trigonum may cause similar symptoms to the ones caused by FHL tendinitis or tenosynovitis.\n\nA radiograph should be taken to rule out this condition.\n\nhttps://en.wikipedia.org/wiki/Flexor_hallucis_longus_muscle","medial-head-of-flexor-hallucis-brevis":"The flexor hallucis brevis divides in front into two portions, which are inserted into the medial and lateral sides of the base of the first phalanx of the great toe, a sesamoid bone being present in each tendon at its insertion.\n\nThe medial head of flexor hallucis brevis is blended with the abductor hallucis muscle previous to its insertion; the lateral head of adductor hallucis brevis (sometimes described as the first plantar interosseus) with the adductor hallucis muscle.","lateral-head-of-flexor-hallucis-brevis":"The flexor hallucis brevis divides in front into two portions, which are inserted into the medial and lateral sides of the base of the first phalanx of the great toe, a sesamoid bone being present in each tendon at its insertion.\n\nThe medial head of flexor hallucis brevis is blended with the abductor hallucis muscle previous to its insertion; the lateral head of flexor hallucis brevis (sometimes described as the first plantar interosseus) with the adductor hallucis muscle.","oblique-head-of-adductor-hallucis":"The oblique head is a large, thick, fleshy mass, crossing the foot obliquely and occupying the hollow space under the first, second, third and fourth metatarsal bones.\n\nIt arises from the bases of the second, third, and fourth metatarsal bones, and from the sheath of the tendon of the Peroneus longus, and is inserted, together with the lateral portion of the Flexor hallucis brevis, into the lateral side of the base of the first phalanx of the great toe.","transverse-head-of-adductor-hallucis":"The transverse head (Transversus pedis) is a narrow, flat fasciculus which arises from the plantar metatarsophalangeal ligaments of the third, fourth, and fifth toes (sometimes only from the third and fourth), and from the transverse ligament of the metatarsals.\n\nIt is inserted into the lateral side of the base of the first phalanx of the great toe, its fibers blending with the tendon of insertion of the oblique head.","abductor-digiti-minimi-of-foot":"The abductor digiti minimi (abductor minimi digiti, abductor digiti quinti) is a muscle which lies along the lateral (outer) border of the foot, and is in relation by its medial margin with the lateral plantar artery, vein and nerves.\n\nIts homolog in the arm is the abductor digiti minimi muscle in the hand.\n\n== Origin and insertion ==\n\nIt arises, by a broad origin, from the lateral process of the tuberosity of the calcaneus, from the under surface of the calcaneus between the two processes of the tuberosity, from the forepart of the medial process, from the plantar aponeurosis, and from the intermuscular septum between it and the flexor digitorum brevis.\n\nIts tendon, after gliding over a smooth facet on the under surface of the base of the fifth metatarsal bone, is inserted, with the flexor digiti quinti brevis, into the fibular side of the base of the first phalanx of the fifth toe.\n\n== Innervation ==\n\nThe abductor digiti minimi is innervated by the lateral plantar nerve, a branch of the tibial nerve.\n\n== Function ==\n\nIts function is flexion and abduction of the fifth (little) toe at the metatarsophalangeal joint.\n\n== Clinical relevance ==\n\nDue to its role in posture during all physical activity while in an upright position, the abductor digiti minimi is often the target of injury.\n\nIn case of polydactyly it may insert to the sixth toe instead, if there is one.\n\n== Etymology ==\n\nThe Latin name abductor digiti minimi translates to abductor of the small digit while the alternative name abductor digiti quinti means abductor of fifth digit.\n\nhttps://en.wikipedia.org/wiki/Abductor_digiti_minimi_muscle_of_foot","abductor-hallucis":"The abductor hallucis muscle is an intrinsic muscle of the foot.\n\nIt participates in the abduction and flexion of the great toe.\n\n== Structure ==\n\nThe abductor hallucis muscle is located in the medial border of the foot and contributes to form the prominence that is observed on the region.\n\nIt is inserted behind on the tuberosity of the calcaneus, the flexor retinaculum, and the plantar aponeurosis.\n\nIts muscle body, relatively thick behind, flattens as it goes forward.\n\nIt ends in a common tendon with the medial head of the flexor hallucis brevis that inserts on the medial surface of the base of the first proximal phalanx and its related sesamoid bone.\n\nIts medial surface is superficial and covered with the muscle's fascia and the skin.\n\n=== Nerve supply ===\n\nAbductor hallucis is supplied by the medial plantar nerve.\n\nThe nerves that supply it enter the muscle from its upper border.\n\nhttps://en.wikipedia.org/wiki/Abductor_hallucis_muscle","extensor-digitorum-brevis":"The extensor digitorum brevis muscle (sometimes EDB) is a muscle on the upper surface of the foot that helps extend digits 2 through 4.\n\n== Structure ==\n\nThe muscle originates from the forepart of the upper and lateral surface of the calcaneus (in front of the groove for the peroneus brevis tendon), from the interosseous talocalcaneal ligament and the stem of the inferior extensor retinaculum.\n\nThe fibres pass obliquely forwards and medially across the dorsum of the foot and end in four tendons.\n\nThe medial part of the muscle, also known as extensor hallucis brevis, ends in a tendon which crosses the dorsalis pedis artery and inserts into the dorsal surface of the base of the proximal phalanx of the great toe.\n\nThe other three tendons insert into the lateral sides of the tendons of extensor digitorum longus for the second, third and fourth toes.\n\n=== Nerve supply ===\n\nNerve supply: lateral terminal branch of Deep Peroneal Nerve (deep fibular nerve) (proximal sciatic branches L4-L5, but most clinically relevant L5 with L4/L5 spinal disc herniation causing L5 lesion).\n\nSame innervation of Extensor Hallucis Brevis\n\n== Function ==\n\nExtensor digitorum brevis extends the first four digits at the metatarsophalangeal joint and assists in extending the second, third and fourth digits at the interphalangeal joint.\n\nThe fifth digit, lacking any insertion from extensor digitorum brevis, can only be raised by the long extensor.\n\nhttps://en.wikipedia.org/wiki/Extensor_digitorum_brevis_muscle","extensor-hallucis-brevis":"The extensor hallucis brevis is a muscle on the top of the foot that helps to extend the big toe.\n\n== Structure ==\n\nThe extensor hallucis brevis is essentially the medial part of the extensor digitorum brevis muscle.\n\nSome anatomists have debated whether these two muscles are distinct entities.\n\nThe extensor hallucis brevis arises from the calcaneus and inserts on the proximal phalanx of the digit 1 (the big toe).\n\n=== Nerve supply ===\n\nNerve supplied by lateral terminal branch of Deep Peroneal Nerve (deep fibular nerve) (proximal sciatic branches S1, S2).\n\nSame innervation of Extensor Digitorum Brevis\n\n== Function ==\n\nThe extensor hallucis brevis helps to extend the big toe.\n\nhttps://en.wikipedia.org/wiki/Extensor_hallucis_brevis_muscle","dorsal-interossei-muscles-of-foot":"In human anatomy, the dorsal interossei of the foot are four muscles situated between the metatarsal bones.\n\n== Origin ==\n\nThe four interossei muscles are bipenniform muscles each originating by two heads from the proximal half of the sides of adjacent metatarsal bones.\n\n== Insertion ==\n\nThe two heads of each muscle form a central tendon which passes forwards deep to the deep transverse metatarsal ligament.\n\nThe tendons are inserted on the bases of the second, third, and fourth proximal phalanges and into the aponeurosis of the tendons of the extensor digitorum longus without attaching to the extensor hoods of the toes.\n\nThus, the first is inserted into the medial side of the second toe; the other three are inserted into the lateral sides of the second, third, and fourth toes.\n\n== Action ==\n\nThe dorsal interossei abduct at the metatarsophalangeal joints of the third and fourth toes.\n\nBecause there is a pair of dorsal interossei muscles attached on both sides of the second toe, simultaneous contraction of these muscles results in no movement.\n\nThis arrangement of dorsal interossei makes the second toe the midline of the foot, whereas the midline of the hand (marked by dorsal interossei of hand) is in the third finger.\n\nAbduction is of little importance in the foot, but, together with the plantar interossei, the dorsal interossei also produce flexion at the metatarsophalangeal joints.\n\nAlthough small, the dorsal interossei are powerful muscles that, together with their plantar counterparts, control the direction of the toes during violent activity, thus allowing the long and short flexors to perform their actions.\n\nBecause of the relationship to the metatarsophalangeal joints, the interossei muscles also contribute to maintaining the anterior metatarsal arch of the foot and also, to a limited extent, the medial and lateral longitudinal arches of the foot.\n\n== Innervation ==\n\nAll dorsal interossei are innervated by the lateral plantar nerve (S2–3).\n\nThose in the fourth interosseous space are innervated by the superficial branch and the other by the deep branch.\n\nThe first and second dorsal interossei muscles additionally receive innervation from the lateral branch of the deep fibular nerve.\n\n== Relations ==\n\nIn the angular interval left between the heads of each of the three lateral muscles, one of the perforating arteries passes to the dorsum of the foot; through the space between the heads of the first muscle the deep plantar branch of the dorsalis pedis artery enters the sole of the foot.\n\nhttps://en.wikipedia.org/wiki/Dorsal_interossei_of_the_foot","flexor-digitorum-brevis":"The flexor digitorum brevis is a muscle which lies in the middle of the sole of the foot, immediately above the central part of the plantar aponeurosis, with which it is firmly united.\n\nIts deep surface is separated from the lateral plantar vessels and nerves by a thin layer of fascia.\n\n== Structure ==\n\nIt arises by a narrow tendon, from the medial process of the tuberosity of the calcaneus, from the central part of the plantar aponeurosis, and from the intermuscular septa between it and the adjacent muscles.\n\nIt passes forward, and divides into four tendons, one for each of the four lesser toes.\n\nOpposite the bases of the first phalanges, each tendon divides into two slips, to allow of the passage of the corresponding tendon of the flexor digitorum longus; the two portions of the tendon then unite and form a grooved channel for the reception of the accompanying long Flexor tendon.\n\nFinally, it divides a second time, and is inserted into the sides of the second phalanx about its middle.\n\nThe mode of division of the tendons of the flexor digitorum brevis, and of their insertion into the phalanges, is analogous to that of the tendons of the flexor digitorum superficialis in the hand.\n\n=== Innervation ===\n\nInnervation is by the medial plantar nerve.\n\n=== Variation ===\n\nSlip to the little toe may occasionally be absent, where it may be replaced by a small fusiform muscle arising from the long flexor tendon or from the quadratus plantæ.\n\nhttps://en.wikipedia.org/wiki/Flexor_digitorum_brevis_muscle","flexor-digiti-minimi-of-foot":"The Flexor digiti minimi brevis (Flexor brevis minimi digiti, Flexor digiti quinti brevis) lies under the metatarsal bone on the little toe, and resembles one of the Interossei.\n\nIt arises from the base of the fifth metatarsal bone, and from the sheath of the Fibularis longus; its tendon is inserted into the lateral side of the base of the first phalanx of the fifth toe.\n\nOccasionally a few of the deeper fibers are inserted into the lateral part of the distal half of the fifth metatarsal bone; these are described by some as a distinct muscle, the opponens digiti quinti.\n\nhttps://en.wikipedia.org/wiki/Flexor_digiti_minimi_brevis_muscle_of_foot","lumbrical-muscles-of-foot":"The lumbricals are four small skeletal muscles, accessory to the tendons of the flexor digitorum longus muscle.\n\nThey are numbered from the medial side of the foot.\n\n== Structure ==\n\nThe lumbricals arise from the tendons of the flexor digitorum longus muscle, as far back as their angles of division, each springing from two tendons, except the first.\n\nThe first lumbrical is unipennate, while the second, third and fourth are bipennate.\n\nThe muscles end in tendons, which pass forward on the medial sides of the four lesser toes, and are inserted into the expansions of the tendons of the extensor digitorum longus muscle on the dorsal surfaces of the proximal phalanges.\n\nAll four lumbricals insert into extensor hoods of the phalanges, thus creating extension at the inter-phalangeal (PIP and DIP) joints.\n\nHowever, as the tendons also pass inferior to the metatarsal phalangeal (MTP) joints it creates flexion at this joint.\n\n=== Innervation ===\n\nThe most medial lumbrical is innervated by the medial plantar nerve while the remaining three lumbricals are supplied by the lateral plantar nerve.\n\n=== Variation ===\n\nAbsence of one or more; doubling of the third or fourth even the fifth.\n\nInsertion partly or wholly into the first phalanges.\n\n== History ==\n\nThe term \"lumbrical\" comes from the Latin, meaning \"worm\".\n\nhttps://en.wikipedia.org/wiki/Lumbricals_of_the_foot","opponens-digiti-minimi-muscle-of-foot":"The Flexor digiti minimi brevis (Flexor brevis minimi digiti, Flexor digiti quinti brevis) lies under the metatarsal bone on the little toe, and resembles one of the Interossei.\n\nIt arises from the base of the fifth metatarsal bone, and from the sheath of the Fibularis longus; its tendon is inserted into the lateral side of the base of the first phalanx of the fifth toe.\n\nOccasionally a few of the deeper fibers are inserted into the lateral part of the distal half of the fifth metatarsal bone; these are described by some as a distinct muscle, the opponens digiti quinti.\n\nhttps://en.wikipedia.org/wiki/Flexor_digiti_minimi_brevis_muscle_of_foot","plantar-interossei-muscles":"In human anatomy, plantar interossei muscles are three muscles located between the metatarsal bones in the foot.\n\n== Structure ==\n\nThe three plantar interosseous muscles are unipennate, as opposed to the bipennate structure of dorsal interosseous muscles, and originate on a single metatarsal bone.\n\nThe three muscles originate on the medial aspect of metatarsals III-V.\n\nThe muscles cross the metatarsophalangeal joint of toes III-V so the insertions correspond with the origin and there is no crossing between toes.The muscles then continue distally along the foot and insert in the proximal phalanges III-V.\n\nThe muscles cross the metatarsophalangeal joint of toes III-V so the insertions correspond with the origin and there is no crossing between toes.\n\n=== Innervation ===\n\nAll three plantar interosseous muscles are innervated by the lateral plantar nerve.\n\nThe lateral plantar nerve is a branch from the tibial nerve, which originally branches off the sciatic nerve from the sacral plexus.\n\n== Function ==\n\nSince the intersseous muscles cross on the metatarsophalangeal joint, then they act on that specific joint and cause adduction of toes III, IV, and V.Adduction itself is not of extreme importance to the toes, but these muscles work together with the dorsal interosseous muscles in flexion of the foot.\n\nThey also work together to strengthen the metatarsal arch.\n\nhttps://en.wikipedia.org/wiki/Plantar_interossei_muscles","quadratus-plantae-muscle":"The quadratus plantae (flexor accessorius) is separated from the muscles of the first layer by the lateral plantar vessels and nerve.\n\nIt acts to aid in flexing the 2nd to 5th toes (offsetting the oblique pull of the flexor digitorum longus) and is one of the few muscles in the foot with no homolog in the hand.\n\n== Origin and insertion ==\n\nIt arises by two heads, which are separated from each other by the long plantar ligament: the medial or larger head is muscular, and is attached to the medial concave surface of the calcaneus, below the groove which lodges the tendon of the flexor hallucis longus; the lateral head, flat and tendinous, arises from the lateral border of the inferior surface of the calcaneus, in front of the lateral process of its tuberosity, and from the long plantar ligament.\nThe two portions join at an acute angle, and end in a flattened band which is inserted into the lateral margin and upper and under surfaces of the tendon of the flexor digitorum longus, forming a kind of groove, in which the tendon is lodged.\n\nIt usually sends slips to those tendons of the Flexor digitorum longus which pass to the second, third, and fourth toes.\n\n== Variations ==\n\nLateral head often wanting; entire muscle absent.\n\nVariation in the number of digital tendons to which fibers can be traced.\n\nMost frequent offsets are sent to the second, third and fourth toes; in many cases to the fifth as well; occasionally to two toes only.\n\nhttps://en.wikipedia.org/wiki/Quadratus_plantae_muscle","iliotibial-tract":"The iliotibial tract or iliotibial band (also known as Maissiat's band or the IT band) is a longitudinal fibrous reinforcement of the fascia lata.\n\nThe action of the muscles associated with the ITB (tensor fasciae latae and some fibers of gluteus maximus) flex, extend, abduct, and laterally and medially rotate the hip.\n\nThe ITB contributes to lateral knee stabilization.\n\nDuring knee extension the ITB moves anterior to the lateral condyle of the femur, while ~30 degrees knee flexion, the ITB moves posterior to the lateral condyle.\n\nHowever, it has been suggested that this is only an illusion due to the changing tension in the anterior and posterior fibers during movement.\n\nIt originates at the anterolateral iliac tubercle portion of the external lip of the iliac crest and inserts at the lateral condyle of the tibia at Gerdy's tubercle.\n\nThe figure shows only the proximal part of the iliotibial tract.\n\nThe part of the iliotibial band which lies beneath the tensor fasciae latae is prolonged upward to join the lateral part of the capsule of the hip-joint.\n\nThe tensor fasciae latae effectively tightens the iliotibial band around the area of the knee.\n\nThis allows for bracing of the knee especially in lifting the opposite foot.The gluteus maximus muscle and the tensor fasciae latae insert upon the tract.\n\n== Clinical significance ==\n\nThe IT band stabilizes the knee both in extension and in partial flexion, and is therefore used constantly during walking and running.\n\nWhen a person is leaning forwards with a slightly flexed knee, the tract is the knee's main support against gravity.\n\nIliotibial band syndrome (ITBS or ITBFS, for iliotibial band friction syndrome) is a common thigh injury generally associated with running.\n\nIt can also be caused by cycling or hiking. The onset of iliotibial band syndrome occurs most commonly in cases of overuse.\n\nThe iliotibial band itself becomes inflamed in response to repeated compression on the outside of the knee or swelling of the fat pad between the bone and the tendon on the side of the knee.\n\nITB syndrome can also be caused by poor physical condition, lack of warming up before exercise, or drastic changes in activity levels.\n\nUntil recent anatomical studies showed differently, the previously held belief was that the distal portion of the iliotibial band rubbed over a bursa, however this bursa was found not to exist.\n\nAdditionally, the theory that the iliotibial band needs to stretch has been questioned as, in cadaveric studies under extreme load, the flexibility of the iliotibial band has been shown to be minimal with greater stiffness than capsular fibers.\n\nSymptoms of iliotibial band syndrome may include pain on the outside of the knee at the beginning of exercise which persists through the exercise or specific movements like running downhill and having the knee bent for prolonged periods of time.\n\nThis syndrome is usually developed by people who suddenly increase their level of activity, such as runners who increase their mileage.\n\nOther risk factors for ITBS include gait abnormalities such as overpronation, leg length discrepancies, or bow-leggedness.\n\nITB Syndrome is an overuse condition of the distal ITB near the lateral femoral condyle and at Gerdy's tubercle.\n\nThe most vulnerable range of knee flexion for this condition is at 30-40 degrees; this is where the ITB crosses the lateral femoral epicondyle.\n\n== Postural function ==\n\nThe IT band is of critical importance to asymmetrical standing (pelvic slouch).\n\nThe upward pull on the lower attachment of the IT band thrusts the knee back into hyperextension, thereby locking the knee and converting the limb into a rigid supportive pillar.\n\nhttps://en.wikipedia.org/wiki/Iliotibial_tract","fascia-lata":"The fascia lata is the deep fascia of the thigh.\n\nIt encloses the thigh muscles and forms the outer limit of the fascial compartments of thigh, which are internally separated by intermuscular septa.\n\nThe fascia lata is thickened at its lateral side where it forms the iliotibial tract, a structure that runs to the tibia and serves as a site of muscle attachment.\n\n== Structure ==\n\nThe fascia lata is an investment for the whole of the thigh, but varies in thickness in different parts.\n\nIt is thicker in the upper and lateral part of the thigh, where it receives a fibrous expansion from the gluteus maximus, and where the tensor fasciae latae is inserted between its layers; it is very thin behind and at the upper and medial part, where it covers the adductor muscles, and again becomes stronger around the knee, receiving fibrous expansions from the tendon of the biceps femoris laterally, from the sartorius medially, and from the quadriceps femoris in front.\n\n=== Function ===\n\nThe fascia lata surrounds the tensor fasciae latae muscle.\n\nIt is a fibrous sheath that encircles the thigh subcutaneously.\n\nThis encircling of the muscle allows the muscles to be bound together tightly.\n\n=== Above and behind ===\n\nThe fascia lata is attached, above and behind (i.e. proximal and posterior), to the back of the sacrum and coccyx; laterally, to the iliac crest; in front, to the inguinal ligament, and to the superior ramus of the pubis; and medially, to the inferior ramus of the pubis, to the inferior ramus and tuberosity of the ischium, and to the lower border of the sacrotuberous ligament.\n\nFrom its attachment to the iliac crest it passes down over the gluteus medius to the upper border of the gluteus maximus, where it splits into two layers, one passing superficial to and the other beneath this muscle; at the lower border of the muscle the two layers reunite.\n\n=== Laterally ===\n\nLaterally, the fascia lata receives the greater part of the tendon of insertion of the gluteus maximus, and becomes proportionately thickened.\nThe portion of the fascia lata attached to the front part of the iliac crest, and corresponding to the origin of the tensor fasciae latae, extends down the lateral side of the thigh as two layers, one superficial to and the other beneath this muscle; at the lower end of the muscle these two layers unite and form a strong band, having first received the insertion of the muscle.\n\nThis band is continued downward under the name of the iliotibial band and is attached to the lateral condyle of the tibia.\n\nThe part of the iliotibial band which lies beneath the tensor fasciae latae is prolonged upward to join the lateral part of the capsule of the hip joint.\n\n=== Below ===\n\nBelow, the fascia lata is attached to all the prominent points around the knee joint, viz., the condyles of the femur and tibia, and the head of the fibula.\nOn either side of the kneecap it is strengthened by transverse fibers from the lower parts of the vasti muscles (three of the four quadriceps) which are attached to and support this bone.\n\nOf these the lateral are the stronger, and are continuous with the iliotibial band.\n\nThe deep surface of the fascia lata gives off two strong intermuscular septa, which are attached to the whole length of the linea aspera and its prolongations above and below; the lateral intermuscular septum, the stronger of the two, extends from the insertion of the gluteus maximus to the lateral condyle, separates the vastus lateralis in front from the short head of the biceps femoris behind, and gives partial origin to these muscles; the medial intermuscular septum is the thinner one and separates the vastus medialis from the adductor muscles.\n\nBesides these there are numerous smaller septa, separating the individual muscles, and enclosing each in a distinct sheath.\n\n=== Deep fascia of leg ===\n\nThe deep fascia of the lower leg is a continuation of the fascia lata.\n\n== Clinical significance ==\n\n=== Transplantation ===\n\nSince the 1920s fasciae latae from deceased donors have been used in reconstructive surgery.\n\nIn 1999 preserved mashed fasciae latae became FDA-approved as a tissue product designed to replace areas of lost fascia or collagen.\n\nThe fascia lata normally performs the function of encircling and tightening the muscles in the thigh.\n\nBecause of this function, it has been used as grafts for patients with facial paralysis.\n\nThe fascia lata offers supports to the muscles that make up the face and this support increases the recovery of the facial muscles.\n\nThe surgeons use the fascia lata as a sort of facial sling to support up the paralyzed face and loops the fascia lata around the center of the lower lip, the corner of the mouth and the center of the upper lip.\n\nA small portion of fascia lata harvested through a sub centimeter skin incision on the lower lateral side of the thigh is used for reconstructing the ear drum in tympanoplasty surgery.\nA larger portion is used in nasal endoscopic skull base surgery.\n\n== History ==\n\n=== Etymology ===\n\nIt is named from its great extent. \"Latus\" give the superlative \"Latissimus\" meaning broadest or widest.\n\nhttps://en.wikipedia.org/wiki/Fascia_lata","popliteal-fascia":"POPlITEAL FASCIA\n\nThe popliteal fascia covers the popliteal fossa, continuous with fascia lata superiorly and crural fascia inferiorly.","crural-fascia":"DEEP FASCIA OF LEG\n\nThe deep fascia of leg, or crural fascia forms a complete investment to the muscles, and is fused with the periosteum over the subcutaneous surfaces of the bones.\n\nThe deep fascia of the leg is continuous above with the fascia lata (deep fascia of the thigh), and is attached around the knee to the patella, the patellar ligament, the tuberosity and condyles of the tibia, and the head of the fibula.\n\nBehind, it forms the popliteal fascia, covering in the popliteal fossa; here it is strengthened by transverse fibers, and perforated by the small saphenous vein.\n\nIt receives an expansion from the tendon of the biceps femoris laterally, and from the tendons of the sartorius, gracilis, semitendinosus, and semimembranosus medially; in front, it blends with the periosteum covering the subcutaneous surface of the tibia, and with that covering the head and malleolus of the fibula; below, it is continuous with the transverse crural and laciniate ligaments.\n\nIt is thick and dense in the upper and anterior part of the leg, and gives attachment, by its deep surface, to the tibialis anterior and extensor digitorum longus; but thinner behind, where it covers the gastrocnemius and soleus.\n\nIt gives off from its deep surface, on the lateral side of the leg, two strong intermuscular septa, the anterior and posterior peroneal septa, which enclose the peroneus longus and brevis muscles and separate them from the muscles of the anterior and posterior crural regions, and several more slender processes which enclose the individual muscles in each region.\n\nA broad transverse intermuscular septum, called the deep transverse fascia of the leg, intervenes between the superficial and deep posterior crural muscles.\n\nhttps://en.wikipedia.org/wiki/Deep_fascia_of_leg","anterior-intermuscular-septum-of-leg":"The anterior intermuscular septum of leg or anterior crural intermuscular septum is a band of fascia which separates the lateral from the anterior compartment of leg.\nThe deep fascia of leg gives off from its deep surface, on the lateral side of the leg, two strong intermuscular septa, the anterior and posterior peroneal septa, which enclose the peroneus longus and brevis, and separate them from the muscles of the anterior and posterior crural regions, and several more slender processes which enclose the individual muscles in each region.\n\nhttps://en.wikipedia.org/wiki/Anterior_intermuscular_septum_of_leg","posterior-intermuscular-septum-of-leg":"The posterior intermuscular septum of leg, or posterior crural intermuscular septum is a band of fascia which separates the lateral compartment of leg.\nThe deep fascia of leg gives off from its deep surface, on the lateral side of the leg, two strong intermuscular septa, the anterior and posterior peroneal septa, which enclose the Peronæi longus and brevis, and separate them from the muscles of the anterior and posterior crural regions, and several more slender processes which enclose the individual muscles in each region.\n\nhttps://en.wikipedia.org/wiki/Posterior_intermuscular_septum_of_leg","transverse-intermuscular-septum-of-leg":"The deep transverse fascia or transverse intermuscular septum of leg is a transversely placed, intermuscular septum, from the deep fascia, between the superficial and deep muscles of the back of the leg.\n\nAt the sides it is connected to the margins of the tibia and fibula.\n\nAbove, where it covers the popliteus, it is thick and dense, and receives an expansion from the tendon of the semimembranosus.\n\nIt is thinner in the middle of the leg; but below, where it covers the tendons passing behind the malleoli, it is thickened and continuous with the laciniate ligament.\n\nhttps://en.wikipedia.org/wiki/Deep_transverse_fascia","superior-extensor-retinaculum-of-ankle":"The superior extensor retinaculum of the foot (transverse crural ligament) is the upper part of the extensor retinaculum of foot which extends from the ankle to the heelbone.\n\nThe superior extensor retinaculum binds down the tendons of extensor digitorum longus, extensor hallucis longus, peroneus tertius, and tibialis anterior as they descend on the front of the tibia and fibula; under it are found also the anterior tibial vessels and deep peroneal nerve.\n\nIt is found on the lateral side of the lower leg, attached laterally to the lower end of the fibula, and medially to the tibia; above it is continuous with the fascia of the leg.\n\nhttps://en.wikipedia.org/wiki/Superior_extensor_retinaculum_of_foot","inferior-extensor-retinaculum-of-ankle":"The inferior extensor retinaculum of the foot (cruciate crural ligament, lower part of anterior annular ligament) is a Y-shaped band placed in front of the ankle-joint, the stem of the Y being attached laterally to the upper surface of the calcaneus, in front of the depression for the interosseous talocalcaneal ligament; it is directed medialward as a double layer, one lamina passing in front of, and the other behind, the tendons of the peroneus tertius and extensor digitorum longus.\n\nAt the medial border of the latter tendon, these two layers join, forming a compartment in which the tendons are enclosed.\n\nFrom the medial extremity of this sheath, the two limbs of the Y diverge: one is directed upward and medialward, to be attached to the tibial malleolus, passing over the extensor hallucis longus and the vessels and nerves but enclosing the tibialis anterior by a splitting of its fibers.\n\nThe other limb extends downward and medialward, to be attached to the border of the plantar aponeurosis, and passes over the tendons of the extensor hallucis longus and tibialis anterior and also the vessels and nerves.\n\nhttps://en.wikipedia.org/wiki/Inferior_extensor_retinaculum_of_foot","superior-fibular-retinaculum":"Superior ligament for the fibular muscles going from the lateral malleolus to the calcaneus.","inferior-fibular-retinaculum":"Inferior ligament for the fibularis longus muscle and fibularis brevis muscle, going from the inferior extensor retinaculum of ankle to the lateral surface of calcaneus.\n\nA bundle of fibers goes to the fibular trochlea and separates the fibularis brevis muscle from the fibularis longus muscle.\n\nStrengthening ligament of the dorsal fascia of foot.","superficial-transverse-metatarsal-ligament":"The transverse metatarsal ligament is a narrow band which runs across and connects together the heads of all the metatarsal bones.\n\nIt is blended anteriorly with the plantar (glenoid) ligaments of the metatarsophalangeal articulations.\n\nIts plantar surface is concave where the Flexor tendons run below it.\n\nAbove it, the tendons of the Interossei pass to their insertions.\n\nIts homologue in the hand is the transverse metacarpal ligament, which connects the metacarpals to each other.\n\nhttps://en.wikipedia.org/wiki/Transverse_metatarsal_ligament","plantar-aponeurosis":"The plantar fascia is the thick connective tissue (aponeurosis) which supports the arch on the bottom (plantar side) of the foot.\n\nIt runs from the tuberosity of the calcaneus (heel bone) forward to the heads of the metatarsal bones (the bone between each toe and the bones of the mid-foot).\n\nThe plantar fascia is a broad structure that spans between the medial calcaneal tubercle and the proximal phalanges of the toes.\n\nRecent studies suggest that the plantar fascia is actually an aponeurosis rather than true fascia.\n\nThe Dorland’s Medical Dictionary defines an aponeurosis as: (i) a white, flattened or ribbon-like tendinous expansion, serving mainly to connect a muscle with the parts that it moves, (ii) a term formerly applied to certain fasciae.\n\nFurther, it defines the plantar aponeurosis as bands of fibrous connective tissue radiating toward the bases of the toes from the medial process of the tuber calcanei (posterior half of the calcaneus).\n\nThe plantar fascia is made up of predominantly longitudinally oriented collagen fibers.\n\nThere are three distinct structural components: the medial component, the central component (plantar aponeurosis), and the lateral component (see diagram at right).\n\nThe central component is the largest and most prominent.\n\nIn younger people the plantar fascia is also intimately related to the Achilles tendon, with a continuous fascial connection between the two from the distal aspect of the Achilles to the origin of the plantar fascia at the calcaneal tubercle.\n\nHowever, the continuity of this connection decreases with age to a point that in the elderly there are few, if any, connecting fibers.\n\nThere are also distinct attachments of the plantar fascia and the Achilles tendon to the calcaneus so the two do not directly contact each other.\n\nNevertheless, there is an indirect relationship whereby if the toes are dorsiflexed, the plantar fascia tightens via the windlass mechanism.\n\nIf a tensile force is then generated in the Achilles tendon it will increase tensile strain in the plantar fascia.\n\nClinically, this relationship has been used as a basis for treatment for plantar fasciitis, with stretches and night stretch splinting being applied to the gastrocnemius/soleus muscle unit.\n\n==Function==\n\nThe effect of dorsiflexing the toes on arch height (A). The windlass mechanism (B).\n\nThe plantar fascia contributes to support of arch of the foot by acting as a tie-rod, where it undergoes tension when the foot bears weight. One biomechanical model estimated it carries as much as 14% of the total load of the foot.\n\nIn an experiment using cadavers, it was found that failure of the plantar fascia averaged at loads of 1189 ± 244 newtons (121 ± 24 kgf or 267 ± 55 lbf).\n\nFailure most often occurred at the proximal attachment to the calcaneus, which is consistent with the usual location of symptoms (i.e. in plantar fasciitis).\n\nComplete rupture or surgical release of the plantar fascia leads to a decrease in arch stiffness and a significant collapse of the longitudinal arch of the foot.\n\nBy modeling it was predicted such conditions would result in a 17% increase in vertical displacement and a 15% increase in horizontal elongation of the foot when it was loaded at 683 newtons (154 lbf).\n\nSurgical release also significantly increases both stress in the plantar ligaments and plantar pressures under the metatarsal heads.\n\nAlthough most of the figures mentioned above are from either cadaver studies or investigations using models, they highlight the relatively large load the plantar fascia is subjected to while contributing to the structural integrity of the foot.\n\n==Gait==\n\nThe plantar fascia also has an important role in dynamic function during gait.\n\nIt was found the plantar fascia continuously elongated during the contact phase of gait.\n\nIt went through rapid elongation before and immediately after mid-stance, reaching a maximum of 9% to 12% elongation between mid-stance and toe-off.\n\nDuring this phase the plantar fascia behaves like a spring, which may assist in conserving energy.\n\nIn addition, the plantar fascia has a critical role in normal mechanical function of the foot, contributing to the \"windlass mechanism\".\n\nWhen the toes are dorsiflexed in the propulsive phase of gait, the plantar fascia becomes tense, resulting in elevation of the longitudinal arch and shortening of the foot.\n\nOne can liken this mechanism to a cable being wound around the drum of a windlass (see 3B); the plantar fascia being the cable, the metatarsal head the drum, and the handle, the proximal phalanx.\n\nhttps://en.wikipedia.org/wiki/Plantar_fascia","flexor-retinaculum-of-ankle":"The flexor retinaculum of foot (laciniate ligament, internal annular ligament) is a strong fibrous band in the foot.\n\n== Structure ==\n\nThe flexor retinaculum of the foot extends from the medial malleolus above, to the calcaneus below.\n\nThis converts a series of bony grooves into canals for the passage of the tendons of the flexor muscles and the posterior tibial vessels and tibial nerve into the sole of the foot, known as the tarsal tunnel.\n\nIt is continuous by its upper border with the deep fascia of the leg, and by its lower border with the plantar aponeurosis and the fibers of origin of the abductor hallucis muscle.\n\nEnumerated from the medial side, the four canals which it forms transmit the tendons of the tibialis posterior and flexor digitorum longus muscles; the posterior tibial artery and tibial nerve, which run through a broad space beneath the ligament; and lastly, in a canal formed partly by the talus, the tendon of the flexor hallucis longus.\n\n== Clinical significance ==\n\nTarsal tunnel syndrome can be caused by entrapment of the tibial nerve beneath the flexor retinaculum of the foot.\n\nThis is characterized by pain, numbness, and tingling of the medial plantar surface of the foot.\n\nThis is made worse by standing and walking, and often worse at night.\n\nTinel's sign can be elicited by tapping the part of the flexor retinaculum of the foot over the tibial nerve.\n\nhttps://en.wikipedia.org/wiki/Flexor_retinaculum_of_foot","external-anal-sphincter":"The external anal sphincter (or sphincter ani externus ) is a flat plane of skeletal muscle fibers, elliptical in shape and intimately adherent to the skin surrounding the margin of the anus.\n\n== Anatomy ==\n\nThe external anal sphincter measures about 8 to 10 cm in length, from its anterior to its posterior extremity, and is about 2.5 cm opposite the anus, the sphincter muscle retracts on defecating.\n\nIt consists of two layers: superficial and deep.\n\nThe superficial layer, constitutes the main portion of the muscle, and arises from a narrow tendinous band, the anococcygeal raphe, which stretches from the tip of the coccyx to the posterior margin of the anus; it forms two flattened planes of muscular tissue, which encircle the anus and meet in front to be inserted into the central tendinous point of the perineum, joining with the superficial transverse perineal muscle, the levator ani, and the bulbospongiosus muscle also known as the bulbocavernosus.\n\nThe deeper layer forms a complete sphincter to the anal canal.\n\nIts fibers surround the canal, closely applied to the internal anal sphincter, and in front blend with the other muscles at the central point of the perineum.\n\nIn a considerable proportion of cases the fibers decussate in front of the anus, and are continuous with the superficial transverse perineal muscle.\n\nPosteriorly, they are not attached to the coccyx, but are continuous with those of the opposite side behind the anal canal.\n\nThe upper edge of the muscle is ill-defined, since fibers are given off from it to join the levator ani.\n\n== Actions ==\n\n(1) Like other muscles, it is always in a state of tonic contraction, and having no antagonistic muscle it keeps the anal canal and orifice shut.\n\n(2) It can be put into a condition of greater contraction under the influence of the will, so as more firmly to occlude the anal aperture, in expiratory efforts unconnected with defecation.\n\n(3) Taking its fixed point at the coccyx, it helps to fix the central point of the perineum, so that the bulbospongiosus muscle may act from this fixed point.\n\nhttps://en.wikipedia.org/wiki/External_anal_sphincter","clavipectoral-fascia":"The clavipectoral fascia (costocoracoid membrane; coracoclavicular fascia) is a strong fascia situated under cover of the clavicular portion of the pectoralis major.\n\nIt occupies the interval between the pectoralis minor and subclavius, and protects the axillary vein and artery, and axillary nerve.\n\nTraced upward, it splits to enclose the subclavius, and its two layers are attached to the clavicle, one in front of and the other behind the muscle; the deep layer fuses with the deep cervical fascia and with the sheath of the axillary vessels.\n\nMedially, it blends with the fascia covering the first two intercostal spaces, and is attached also to the first rib medial to the origin of the subclavius.\n\nLaterally, it is very thick and dense, and is attached to the coracoid process.\n\nThe portion extending from the first rib to the coracoid process is often whiter and denser than the rest, and is sometimes called the costocoracoid membrane.\n\nBelow this it is thin, and at the upper border of the pectoralis minor it splits into two layers to invest the muscle; from the lower border of the pectoralis minor it is continued downward to join the axillary fascia, and lateralward to join the fascia over the short head of the biceps brachii.\n\nThe clavipectoral fascia is pierced by the cephalic vein, thoracoacromial artery and vein, lymphatics and lateral pectoral nerve.\n\nhttps://en.wikipedia.org/wiki/Clavipectoral_fascia","iliopsoas-fascia":"ILIAC FASCIA\n\nThe iliac fascia, or Abernethy's fascia, is a fascia in the region of the ilium of the pelvis.\n\nIt has the following connections:\n\n-laterally, to the whole length of the inner lip of the iliac crest.\nmedially, to the linea terminalis of the lesser pelvis, where it is continuous with the periosteum.\n\n-At the iliopectineal eminence it receives the tendon of insertion of the Psoas minor, when that muscle exists.\n\n-Lateral to the femoral vessels it is intimately connected to the posterior margin of the inguinal ligament, and is continuous with the transversalis fascia.\n\n-Immediately lateral to the femoral vessels the iliac fascia is prolonged backward and medialward from the inguinal ligament as a band, the iliopectineal fascia, which is attached to the iliopectineal eminence.\n\nThis fascia divides the space between the inguinal ligament and the hip bone into two lacunæ or compartments:\n\n-the medial vascular lacuna transmits the femoral vessels.\n-the lateral muscular lacuna transmits the Psoas major and Iliacus and the femoral nerve.Medial to the vessels the iliac fascia is attached to the pectineal line behind the conjoint tendon, where it is again continuous with the transversalis fascia.\n\nhttps://en.wikipedia.org/wiki/Iliac_fascia","transversalis-fascia":"The transversalis fascia (or transverse fascia) is a thin aponeurotic membrane which lies between the inner surface of the transverse abdominal muscle and the parietal peritoneum.\n\nIt forms part of the general layer of fascia lining the abdominal parietes, and is directly continuous with the iliac fascia, internal spermatic, and pelvic fasciae.\n\nIn the inguinal region, the transversalis fascia is thick and dense in structure and is joined by fibers from the aponeurosis of the transverse abdominal.\n\nIt becomes thin as it ascends to the diaphragm and blends with the fascia covering the under surface of this muscle.\n\n== Borders ==\n\nBehind, it is lost in the fat which covers the posterior surfaces of the kidneys.\n\nBelow, it has the following attachments: posteriorly, to the whole length of the iliac crest, between the attachments of the transverse abdominal and Iliacus; between the anterior superior iliac spine and the femoral vessels it is connected to the posterior margin of the inguinal ligament, and is there continuous with the iliac fascia.\n\nMedial to the femoral vessels it is thin and attached to the pubis and pectineal line, behind the inguinal falx, with which it is united; it descends in front of the femoral vessels to form the anterior wall of the femoral sheath.\n\nBeneath the inguinal ligament it is strengthened by a band of fibrous tissue, which is only loosely connected to the ligament, and is specialized as the iliopubic tract.\n\n== Opening ==\n\nThe spermatic cord in the male and the round ligament of the uterus in the female pass through the transverse fascia at the deep inguinal ring the entrance to the inguinal canal.\n\nThis opening is not visible externally.\n\nIn the male the transverse fascia extends downwards as the internal spermatic fascia.\n\nhttps://en.wikipedia.org/wiki/Transversalis_fascia","diaphragmatic-fascia":"Part of the endo-abdominal fascia that covers the abdominal surface of the diaphragm.","tendinous-arch-of-levator-ani":"Tendinous arch strengthening the obturator fascia, more or less developed.\n\nIt gives origin to the levator ani.","subacromial-bursa":"The subacromial bursa is the synovial cavity located just below the acromion, which communicates with the subdeltoid bursa in most individuals, forming the so-called subacromial-subdeltoid bursa (SSB).\n\nThe SSB bursa is located deep to the deltoid muscle and the coracoacromial arch and extends laterally beyond the humeral attachment of the rotator cuff, anteriorly to overlie the intertubercular groove, medially to the acromioclavicular joint, and posteriorly over the rotator cuff.\n\nThe SSB decreases friction, and allows free motion of the rotator cuff relative to the coracoacromial arch and the deltoid muscle.\n\nSince then, histologic studies have documented that synovial membrane may undergo inflammatory and/or degenerative changes and many now believe that they correspond to different stages in the spectrum of disease, with long-lasting inflammation leading to degeneration and fibrosis.\n\nhttps://en.wikipedia.org/wiki/Subacromial_bursa","bicipitoradial-bursa":"The bicipitoradial bursa is a bursa located between the distal tendon of the biceps brachii muscle and the anterior part of the tuberosity of the radius.\n\nIt partially or completely wraps around the biceps tendon.\n\nIt ensures frictionless motion between the biceps tendon and the proximal radius during pronation and supination of the forearm.\n\nWith pronation, the tuberosity of the radius rotates posteriorly, causing compression of the bursa between the biceps tendon and the radial tuberosity.\n\nThe bicipitoradial bursa is one of the two bursae in the cubital fossa, the other being the interosseous bursa.\n\nInflammation of the bicipitoradial bursa or bicipitoradial bursitis is a rare condition and only few reports can be found in literature.\n\nIn severe cases, the bursa is distended by synovial debris and can cause compression of the posterior interosseous nerve.\n\nhttps://en.wikipedia.org/wiki/Bicipitoradial_bursa","iliopectineal-bursa":"The iliopectineal bursa or the iliopsoas bursa is a large synovial bursa that separates the external surface of the hip joint capsule from the normally just the tendon of the iliopsoas muscle.\n\nThe most proximal of part the iliopectineal bursa lies on the iliopubic eminence of the superior pubic ramus.\n\nThe iliopectineal bursa passes across the front of the capsule of the hip joint and extends distally downwards almost as far as to the lesser trochanter.\n\nThe iliopectineal bursa frequently communicates by a circular aperture with the cavity of the hip joint.\n\nIn 13% of all cases the iliopectineal bursa is partly separated by a septum into two cavities.\n\nHere the tendon of the psoas major muscle passes over the medial chamber and the tendon of the iliacus muscle runs over the lateral chamber.\n\nInflammation of the iliopectineal bursa is called iliopectineal bursitis or iliopsoas bursitis.\n\nhttps://en.wikipedia.org/wiki/Iliopectineal_bursa","anserine-bursa":"The anserine bursa (tibial intertendinous bursa) is a sub muscular bursa located deep to the pes anserinus on the anteromedial proximal tibia.\n\nPes anserine bursitis is a common inflammatory condition of the anserine bursa.\n\nhttps://en.wikipedia.org/wiki/Anserine_bursa","stylomandibular-ligament":"The stylomandibular ligament is the thickened posterior portion of the investing cervical fascia around the neck.\n\nIt extends from near the apex of the styloid process of the temporal bone to the angle and posterior border of the angle of the mandible, between the masseter muscle and medial pterygoid muscle.\n\nThe stylomandibular ligament limits mandibular movements, such as preventing excessive opening.\n\n== Structure ==\n\nThe stylomandibular ligament extends from near the apex of the styloid process of the temporal bone to the angle and posterior border of the angle of the mandible, between the masseter muscle and medial pterygoid muscle.\n\nFrom its deep surface, some fibers of the styloglossus muscle originate.\n\nAlthough classed among the ligaments of the temporomandibular joint, it can only be considered as accessory to it.\n\n== Function ==\n\nThe stylomandibular ligament, along with the sphenomandibular ligament, limits mandibular movements, such as preventing excessive opening.\n\n== Clinical significance ==\n\nThe stylomandibular ligament is important for maintaining stability of the mandible after maxillofacial surgery.\n\nhttps://en.wikipedia.org/wiki/Stylomandibular_ligament","stylohyoid-ligament":"The stylohyoid ligament is a ligament that connects the hyoid bone to the temporal styloid process (of the temporal bone of the skull).\n\n== Structure ==\n\nThe stylohyoid ligament connects the lesser horn of hyoid bone to the styloid process of the temporal bone of the skull.\n\n== Clinical significance ==\n\nThe stylohyoid ligament frequently contains a little cartilage in its center, which is sometimes partially ossified in Eagle syndrome.\n\n== Other animals ==\n\nIn many animals, the epihyal is a distinct bone in the centre of the stylohyoid ligament, which is similar to that seen in Eagle syndrome.\n\nhttps://en.wikipedia.org/wiki/Stylohyoid_ligament","pterygospinous-ligament":"The pterygospinous ligament stretches from the upper part of the posterior border of the lateral pterygoid plate to the spinous process of the sphenoid.\n\n== Structure ==\n\n=== Variation ===\n\nIt occasionally ossifies, and in such cases, between its upper border and the base of the skull, a foramen is formed - pterygospinous foramen (Civinini) which transmits the branches of the mandibular nerve to the muscles of mastication.\n\nhttps://en.wikipedia.org/wiki/Pterygospinous_ligament","sphenomandibular-ligament":"The sphenomandibular ligament (internal lateral ligament) is a flat, thin band which is attached superiorly to the spina angularis (spine) of the sphenoid bone, and, becoming broader as it descends, is fixed to the lingula of the mandibular foramen.\n\nThe function of the sphenomandibular ligament is to limit distension of the mandible in an inferior direction.\n\nIt is slack when the temporomandibular joint (TMJ) is in closed position.\n\nIt is taut as the condyle of the mandible is in front of the temporomandibular ligament.\n\nLateral pterygoid and the auriculotemporal nerve are lateral relations, the chorda tympani nerve lies medial near its upper end and medial pterygoid is an inferomedial relation.\n\nThe sphenomandibular ligament is separated from the neck of the mandible below lateral pterygoid by the maxillary artery and from the ramus of the mandible by the inferior alveolar vessels and nerve and a parotid lobule.\n\nThe ligament is derived from Meckel's cartilage.\n\nhttps://en.wikipedia.org/wiki/Sphenomandibular_ligament","articular-capsule-of-temporomandibular-joint":"In anatomy, the temporomandibular joints (TMJ) are the two joints connecting the jawbone to the skull.\n\nIt is a bilateral synovial articulation between the temporal bone of the skull above and the mandible below; it is from these bones that its name is derived.\n\nThis joint is unique in that it is a bilateral joint that functions as one unit.\n\nSince the TMJ is connected to the mandible, the right and left joints must function together and therefore are not independent of each other.\n\n== Structure ==\n\nThe main components are the joint capsule, articular disc, mandibular condyles, articular surface of the temporal bone, temporomandibular ligament, stylomandibular ligament, sphenomandibular ligament, and lateral pterygoid muscle.\n\n=== Capsule ===\n\nThe articular capsule (capsular ligament) is a thin, loose envelope, attached above to the circumference of the mandibular fossa and the articular tubercle immediately in front; below, to the neck of the condyle of the mandible.\n\n=== Articular disc ===\n\nThe unique feature of the temporomandibular joint is the articular disc.\n\nThe disc is composed of dense fibrocartilagenous tissue that is positioned between the head of the mandibular condyle and the mandibular fossa of the temporal bone.\n\nThe temporomandibular joints are one of the few synovial joints in the human body with an articular disc, another being the sternoclavicular joint.\n\nThe disc divides each joint into two compartments, the lower and upper compartments.\n\nThese two compartments are synovial cavities, which consist of an upper and a lower synovial cavity.\n\nThe synovial membrane lining the joint capsule produces the synovial fluid that fills these cavities.\n\nThe central area of the disc is avascular and lacks innervation, thus getting its nutrients from the surrounding synovial fluid.\n\nIn contrast, the posterior ligament and the surrounding capsules along have both blood vessels and nerves.\n\nFew cells are present, but fibroblasts and white blood cells are among these.\n\nThe central area is also thinner but of denser consistency than the peripheral region, which is thicker but has a more cushioned consistency.\n\nThe synovial fluid in the synovial cavities provides nutrition for the avascular central area of the disc.\n\nWith age, the entire disc thins and may undergo the addition of cartilage in the central part, changes that may lead to impaired movement of the joint.\n\nThe synovial membrane covers the inner surface of the articular capsule in the TMJ, except for the surface of the articular disc and condylar cartilage.\n\nThe lower joint compartment formed by the mandible and the articular disc is involved in rotational movement—this is the initial movement of the jaw when the mouth opens.\n\nThe upper joint compartment formed by the articular disc and the temporal bone is involved in translational movement—this is the secondary gliding motion of the jaw as it is opened widely.\n\nThe part of the mandible which mates to the under-surface of the disc is the condyle and the part of the temporal bone which mates to the upper surface of the disk is the articular fossa or glenoid fossa or mandibular fossa.\n\nThe articular disc is a fibrous extension of the capsule in between the two bones of the joint.\n\nThe disc functions as articular surfaces against both the temporal bone and the condyles and divides the joint into two sections, as already described.\n\nIt is biconcave in structure and attaches to the condyle medially and laterally.\n\nThe anterior portion of the disc splits in the vertical dimension, coincident with the insertion of the superior head of the lateral pterygoid.\n\nThe posterior portion also splits in the vertical dimension, and the area between the split continues posteriorly and is referred to as the retrodiscal tissue.\n\nUnlike the disc itself, this piece of connective tissue is vascular and innervated, and in some cases of anterior disc displacement, the pain felt during movement of the mandible is due to the condyle compressing this area against the articular surface of the temporal bone.\n\n=== Ligaments ===\n\nThere are three ligaments associated with the temporomandibular joints: one major and two minor ligaments.\n\nThese ligaments are important in that they define the border movements, or in other words, the farthest extents of movements, of the mandible.\n\nMovements of the mandible made past the extents functionally allowed by the muscular attachments will result in painful stimuli, and thus, movements past these more limited borders are rarely achieved in normal function.\n\nThe major ligament, the temporomandibular ligament, is actually the thickened lateral portion of the capsule, and it has two parts: an outer oblique portion (OOP) and an inner horizontal portion (IHP).\n\nThe base of this triangular ligament is attached to the zygomatic process of the temporal bone and the articular tubercle; its apex is fixed to the lateral side of the neck of the mandible.\n\nThis ligament prevents excessive retraction or moving backward of the mandible, a situation that might lead to problems with the joint.\n\nThe two minor ligaments, the stylomandibular and sphenomandibular ligaments are accessory and are not directly attached to any part of the joint.\n\nThe stylomandibular ligament separates the infratemporal region (anterior) from the parotid region (posterior), and runs from the styloid process to the angle of the mandible; it separates the parotid and submandibular salivary glands.\n\nIt also becomes taut when the mandible is protruded.\nThe sphenomandibular ligament runs from the spine of the sphenoid bone to the lingula of mandible.\n\nThe inferior alveolar nerve descends between the sphenomandibular ligament and the ramus of the mandible to gain access to the mandibular foramen.\n\nThe sphenomandibular ligament, because of its attachment to the lingula, overlaps the opening of the foramen.\n\nIt is a vestige of the embryonic lower jaw, Meckel cartilage.\n\nThe ligament becomes accentuated and taut when the mandible is protruded.\n\nOther ligaments, called \"oto-mandibular ligaments\", connect the middle ear (malleus) with the temporomandibular joint:\n\ndiscomallear (or disco-malleolar) ligament,\nmalleomandibular (or malleolar-mandibular) ligament.\n\n=== Nerve supply ===\n\nSensory innervation of the temporomandibular joint is derived from the auriculotemporal and masseteric branches of V3 or mandibular branch of the trigeminal nerve.\n\nThese are only sensory innervation.\n\nRecall that motor is to the muscles.\nThe specific mechanics of proprioception in the temporomandibular joint involve four receptors.\n\nRuffini endings function as static mechanoreceptors which position the mandible.\n\nPacinian corpuscles are dynamic mechanoreceptors that accelerate movement during reflexes.\n\nGolgi tendon organs function as static mechanoreceptors for the protection of ligaments around the temporomandibular joint.\n\nFree nerve endings are the pain receptors for the protection of the temporomandibular joint itself.\n\nFree nerve endings, many of which act as nociceptors, innervate the bones, ligaments, and muscles of the TMJ.\n\nThe fibrocartilage that overlays the TMJ condyle is not innervated and is avascular in healthy TMJs.\n\nWhen bone tissue, ligaments, or muscles become inflamed or injured, sensory signals are relayed along small-diameter primary afferent nerve fibers that form the trigeminal nerve.\n\nSignals are directed through the trigeminal nerve and modulated by neuronal cell bodies in the trigeminal ganglion.\n\nNociceptive signals are subsequently routed to the spinal trigeminal nucleus, which contains second-order sensory neurons.\n\nFrom the trigeminal nucleus, sensory signals are relayed to higher-order brain regions, including the somatosensory cortex and thalamus.\n\n=== Blood supply ===\n\nIts arterial blood supply is provided by branches of the external carotid artery, predominately the superficial temporal branch.\n\nOther branches of the external carotid artery, namely the deep auricular artery, anterior tympanic artery, ascending pharyngeal artery, and maxillary artery, may also contribute to the arterial blood supply of the joint.\n\n=== Development ===\n\nFormation of the temporomandibular joints occurs at around 12 weeks in utero when the joint spaces and the articular disc develop.\n\nAt approximately 10 weeks the component of the fetus future joint becomes evident in the mesenchyme between condylar cartilage of the mandible and the developing temporal bone.\n\nTwo slits like joint cavities and intervening disk make their appearance in this region by 12 weeks.\n\nThe mesenchyme around the joint begins to form the fibrous joint capsule.\n\nVery little is known about the significance of newly forming muscles in joint formation.\n\nThe developing superior head of the lateral pterygoid muscle attaches to the anterior portion of the fetal disk.\n\nThe disk also continues posteriorly through the petrotympanic fissure and attaches to the malleus of the middle ear.\n\nA growth center is located in the head of each mandibular condyle before an individual reaches maturity.\n\nThis growth center consists of hyaline cartilage underneath the periosteum on the articulating surface of the condyle.\n\nThis is the last growth center of bone in the body and is multidirectional in its growth capacity, unlike a typical long bone.\n\nThis area of cartilage within the bone grows in length by appositional growth as the individual grows to maturity.\n\nOver time, the cartilage is replaced by bone, using endochondral ossification.\n\nThis mandibular growth center in the condyle allows the increased length of the mandible needed for the larger permanent teeth, as well as for the larger brain capacity of the adult.\n\nThis growth of the mandible also influences the overall shape of the face and thus is charted and referred to during orthodontic therapy.\n\nWhen an individual reaches full maturity, the growth center of bone within the condyle has disappeared.\n\n== Function ==\n\nEach temporomandibular joint is classed as a \"ginglymoarthrodial\" joint since it is both a ginglymus (hinging joint) and an arthrodial (sliding) joint.\n\nThe condyle of the mandible articulates with the temporal bone in the mandibular fossa.\n\nThe mandibular fossa is a concave depression in the squamous portion of the temporal bone.\nThese two bones are actually separated by an articular disc, which divides the joint into two distinct compartments.\n\nThe inferior compartment allows for rotation of the condylar head around an instantaneous axis of rotation, corresponding to the first 20mm or so of the opening of the mouth.\n\nAfter the mouth is open to this extent, the mouth can no longer open without the superior compartment of the temporomandibular joints becoming active.\nAt this point, if the mouth continues to open, not only are the condylar heads rotating within the lower compartment of the temporomandibular joints, but the entire apparatus (condylar head and articular disc) translates.\n\nAlthough this had traditionally been explained as a forward and downward sliding motion, on the anterior concave surface of the mandibular fossa and the posterior convex surface of the articular eminence, this translation actually amounts to a rotation around another axis.\n\nThis effectively produces an evolute which can be termed the resultant axis of mandibular rotation, which lies in the vicinity of the mandibular foramen, allowing for a low-tension environment for the vasculature and innervation of the mandible.The necessity of translation to produce further opening past that which can be accomplished with a sole rotation of the condyle can be demonstrated by placing a resistant fist against the chin and trying to open the mouth more than 20 or so mm.\nThe resting position of the temporomandibular joint is not with the teeth biting together.\n\nInstead, the muscular balance and proprioceptive feedback allow a physiologic rest for the mandible, an interocclusal clearance, or freeway space, which is 2 to 4 mm between the teeth.\n\n=== Jaw movement ===\n\nNormal full jaw opening is 40-50 millimeters as measured from the edge of lower front teeth to edge of upper front teeth.\nWhen measuring the vertical range of motion, the measurement must be adjusted for the overbite.\n\nFor example, if the measurement from the edge of the lower front teeth to the edge of the upper front teeth is 40 millimeters and the overbite is 3 millimeters, then the jaw opening is 43 millimeters.\nDuring jaw movements, only the mandible moves.\n\nNormal movements of the mandible during function, such as mastication, or chewing, are known as excursions.\n\nThere are two lateral excursions (left and right) and the forward excursion, known as protrusion.\n\nThe reversal of protrusion is retrusion.\n\nWhen the mandible is moved into protrusion, the mandibular incisors, or front teeth of the mandible, are moved so that they first come edge to edge with the maxillary (upper) incisors and then surpass them, producing a temporary underbite.\n\nThis is accomplished by translation of the condyle down the articular eminence (in the upper portion of the joint) without any more than the slightest amount of rotation taking place (in the lower portion of the joint), other than that necessary to allow the mandibular incisors to come in front of the maxillary incisors without running into them. (This is all assuming an ideal Class I or Class II occlusion.)\n\nDuring chewing, the mandible moves in a specific manner as delineated by the two temporomandibular joints.\n\nThe side of the mandible that moves laterally is referred to as either the working or rotating side, while the other side is referred to as either the balancing or orbiting side.\n\nThe latter terms, although a bit outdated, are actually more precise, as they define the sides by the movements of the respective condyles.\nWhen the mandible is moved into a lateral excursion, the working side condyle (the condyle on the side of the mandible that moves outwards) only performs rotation (in the horizontal plane), while the balancing side condyle performs the translation.\n\nDuring actual functional chewing, when the teeth are not only moved side to side but also up and down when biting of the teeth is incorporated as well, rotation (in a vertical plane) also plays a part in both condyles.\n\nThe mandible is moved primarily by the four muscles of mastication: the masseter, medial pterygoid, lateral pterygoid and the temporalis.\n\nThese four muscles, all innervated by V3, or the mandibular division of the trigeminal nerve, work in different groups to move the mandible in different directions.\n\nContraction of the lateral pterygoid acts to pull the disc and condyle forward within the glenoid fossa and down the articular eminence; thus, the action of this muscle serves to protrude the jaw, it with the assistance of gravity, and the digastricus muscle also opens the jaw.\n\nThe other three muscles close the mouth; the masseter and the medial pterygoid by pulling up the angle of the mandible and the temporalis by pulling up on the coronoid process of the mandible.\n\n== Clinical significance ==\n\n=== Pain ===\n\nTemporomandibular joint pain is generally due to one of four reasons.\n\nMyofascial pain dysfunction syndrome, primarily involving the muscles of mastication.\n\nThis is the most common cause.\n\nInternal derangements, an abnormal relationship of the disc to any of the other components of the joint.\n\nDisc displacement is an example of internal derangement.\n\nOsteoarthritis of the temporomandibular joint, a degenerative joint disease of the articular surfaces.\n\nTemporal arteritis, for which it is considered a reliable diagnostic criteriaPain or dysfunction of the temporomandibular joint (TMJ) is sometimes referred to as temporomandibular joint dysfunction or temporomandibular joint disorder (TMD).\n\nThis term is used to refer to a group of problems involving the temporomandibular joints and the muscles, tendons, ligaments, blood vessels, and other tissues associated with them.\n\nAlthough rare, other pathologic conditions may also affect the function of temporomandibular joints, causing pain and swelling.\n\nThese conditions include chondrosarcoma, osteosarcoma, giant cell tumor, and aneurysmal bone cyst.\n\n=== Examination ===\n\nThe temporomandibular joints can be felt in front of or within the external acoustic meatus during movements of the mandible.\n\nAuscultation of the joint can also be performed.\n\n=== Disc displacement ===\n\nThe most common disorder of a temporomandibular joint is disc displacement.\n\nIn essence, this is when the articular disc, attached anteriorly to the superior head of the lateral pterygoid muscle and posteriorly to the retrodiscal tissue, moves out from between the condyle and the fossa so that the mandible and temporal bone contact is made on something other than the articular disc.\n\nThis, as explained above, is usually very painful, because, unlike these adjacent tissues, the central portion of the disc contains no sensory innervation.\n\nIn most instances of disorder, the disc is displaced anteriorly upon translation, or the anterior and inferior sliding motion of the condyle forward within the fossa and down the articular eminence.\n\nOn opening, a \"pop\" or \"click\" can sometimes be heard and usually felt also, indicating the condyle is moving back onto the disk, known as \"reducing the joint\" (disc displacement with reduction).\n\nUpon closing, the condyle will slide off the back of the disc, hence another \"click\" or \"pop\" at which point the condyle is posterior to the disc.\n\nUpon clenching, the condyle compresses the bilaminar area, and the nerves, arteries, and veins against the temporal fossa, causing pain and inflammation.\nIn disc displacement without reduction the disc stays anterior to the condylar head upon opening.\n\nMouth opening is limited and there is no \"pop\" or \"click\" sound on opening.\n\n=== Congenital disorders ===\n\nAplasia of mandible or cranial bone\nHypoplasia of mandible or cranial bone\nHyperplasia of mandible or cranial bone\nDysplasia abnormal tissue development\n\n=== Traumatic disorders ===\n\nMandibular dislocation\nFracture\nSubluxation\n\n=== Inflammatory disorders ===\n\nSynovitis\nCapsulitis\nMyositis\n\n=== Degenerative disorders ===\n\nOsteoarthritis\nRheumatoid arthritis\nJuvenile idiopathic arthritis\n\n=== Idiopathic disorders ===\n\nTemporomandibular disorder (TMD, also termed \"temporomandibular joint pain-dysfunction syndrome\") is pain and dysfunction of the TMJ and the muscles of mastication (the muscles that move the jaw).\n\nTMD does not fit neatly into any one etiologic category since the pathophysiology is poorly understood and it represents a range of distinct disorders with multifactorial etiology.\n\nTMD accounts for the majority of pathology of the TMJ, and it is the second most frequent cause of orofacial pain after dental pain (i.e. toothache).\n\nFibromyalgia\n\nhttps://en.wikipedia.org/wiki/Temporomandibular_joint","lateral-temporomandibular-ligament":"The temporomandibular ligament, also known as the external lateral ligament, is a ligament that connects the lower articular tubercle of the zygomatic arch to the lateral and posterior border of the neck of the mandible.\n\nIt prevents posterior displacement of the mandible.\n\nIt also prevents the condyloid process from being driven upward by a blow to the jaw, which would otherwise fracture the base of the skull.\n\n== Structure ==\n\nThe temporomandibular ligament originates from the lower articular tubercle of the zygomatic arch.\n\nThis usually has a rough surface for the ligament to attach to.\n\nIt attaches to the lateral and posterior border of the neck of the mandible.It consists of two short, narrow fasciculi, one in front of the other.\n\nIt is broader above than below, and its fibers are directed obliquely downward and backward.It is covered by the parotid gland, and by the integument.\n\n== Function ==\n\nThe temporomandibular ligament constrains the mandible as it opens, keeping the condyloid process close to the joint.\n\nIt prevents posterior displacement of the mandible.\n\nIt also prevents the condyloid process from being driven upward by a blow to the jaw, which would otherwise fracture the base of the skull.\n\nhttps://en.wikipedia.org/wiki/Temporomandibular_ligament","articular-disc-of-temporomandibular-joint":"The articular disk of the temporomandibular joint is a thin, oval plate made of non-vascular fibrous connective tissue, which is located between the mandible's condyloid process and the cranium's mandibular fossa.\n\nIts upper surface is concavo-convex from before backward, to accommodate itself to the form of the mandibular fossa and the articular tubercle.\n\nIts lower surface, in contact with the condyle, is concave.\n\nIts circumference is connected to the articular capsule, and in front to the tendon of the lateral pterygoid muscle.\n\nIt is thicker at its periphery, especially behind, than at its center.\n\nThe fibers of which the disc is composed have a concentric arrangement, more apparent at the circumference than at the center.\n\nIt divides the joint into two cavities, each of which is furnished with a synovial membrane.\n\nIt is attached as follows.\n\n The anterior portion of the disc attaches inferiorly to the anterior condyle and superiorly to the eminence by bending with the joint capsule.\n\n Posteriorly, the disc attaches superiorly to the temporal bone and inferiorly to the posterior condyle (the posterior attachments are frequently called the bilaminar zone).\n\n Laterally and medially, the disc attachments blend into the joint capsule near its attachment to the condylar head.\n\nThe disc prevents the mandible from moving posteriorly.\n\nhttps://en.wikipedia.org/wiki/Articular_disk_of_the_temporomandibular_joint","lateral-thyrohyoid-ligament":"The lateral thyrohyoid ligament (lateral hyothyroid ligament) is a round elastic cord, which forms the posterior border of the thyrohyoid membrane and passes between the tip of the superior cornu of the thyroid cartilage and the extremity of the greater cornu of the hyoid bone.\n\nThe internal branch of the superior laryngeal nerve typical lies lateral to this ligament.\n\n== Triticeal cartilage ==\n\nA small cartilaginous nodule (cartilago triticea), sometimes bony, is frequently found in the lateral thyrohyoid ligament.\n\nhttps://en.wikipedia.org/wiki/Lateral_thyrohyoid_ligament","median-thyrohyoid-ligament":"The median thyrohyoid ligament (also middle hyothyroid ligament or middle thyrohyoid ligament) is the thicker, middle part of the thyrohyoid membrane.\n\nIts lateral thinner portions are pierced by the superior laryngeal vessels and the internal branch of the superior laryngeal nerve.\n\nIts anterior surface is in relation with the thyrohyoideus, sternohyoideus, and omohyoideus muscles, and with the body of the hyoid bone.\n\nhttps://en.wikipedia.org/wiki/Median_thyrohyoid_ligament","quadrangular-membrane":"The quadrangular membrane is a layer of submucosa.\n\nIt contains the cuneiform cartilages.\n\nThe membrane runs between the lateral aspects of the epiglottis and arytenoid cartilages on each side.\n\nThe free inferior border of the quadrangular membrane is the vestibular fold which is the vestibular ligament when covered by mucosa.\n\nThe superior border is in the aryepiglottic fold.\n\nhttps://en.wikipedia.org/wiki/Quadrangular_membrane","median-cricothyroid-ligament":"The cricothyroid ligament (also known as the cricothyroid membrane or cricovocal membrane) is a ligament in the neck.\n\nIt connects the cricoid cartilage to the thyroid cartilage.\n\nIt prevents these cartilages from moving too far apart.\n\nIt is cut during an emergency cricothyrotomy to treat upper airway obstruction.\n\n== Structure ==\n\nThe cricothyroid ligament is composed of two parts:\n\nthe median cricothyroid ligament along the midline (a thickening of the cricothyroid membrane).\n\nIt is a flat band of white connective tissue that connects the front parts of the contiguous margins of the cricoid and thyroid cartilages.\n\nIt is a thick and strong ligament, narrow above and broad below.\n\nEach lateral ligament is known as the conus elasticus.\n\nthe lateral cricothyroid ligaments on each side (these are also called conus elasticus).\n\nEach is overlapped on either side by laryngeal muscles.\n\nThe conus elasticus (which means elastic cone in Latin) is the lateral portion of the cricothyroid ligament.\n\nThe lateral portions are thinner and lie close under the mucous membrane of the larynx; they extend from the upper border of the cricoid cartilage to the lower margin of the vocal ligaments, with which they are continuous.\n\nThe vocal ligaments may therefore be regarded as the free borders of each conus elasticus.\n\nThey extend from the vocal processes of the arytenoid cartilages to the angle of the thyroid cartilage about midway between its upper and lower borders.\n\n=== Relations ===\n\nThe prelaryngeal lymph node (also known as the Delphian lymph node) sits anterior to the median cricothyroid ligament.\n\n== Function ==\n\nThe cricothyroid ligament prevents the cricoid cartilage and the thyroid cartilage from moving too far apart.\n\n== Clinical significance ==\n\nThe cricothyroid ligament is cut during an emergency cricothyrotomy.\n\nThis kind of surgical intervention is necessary during airway obstruction above the level of vocal folds.\n\n== History ==\n\nThe cricothyroid ligament is named after the two structures it connects: the cricoid cartilage and the thyroid cartilage.\n\nIt is also known as the cricothyroid membrane, and the cricovocal membrane.\n\nThe various parts of the cricothyroid ligament have been named in many different ways, which can cause confusion.\n\n== Other animals ==\n\nThe cricothyroid ligament can be found in many other animals, such as cats, dogs, and horses.\n\nThe trachea can be accessed through the cricothyroid ligament, such as for aspiration.\n\nIt can be an important landmark.\n\nhttps://en.wikipedia.org/wiki/Cricothyroid_ligament","cricopharyngeal-ligament":"The Cricopharyngeal ligament extends from the cricoid lamina to the midline of the pharynx.\n\nhttps://en.wikipedia.org/wiki/Cricopharyngeal_ligament","supraspinous-ligament":"The supraspinous ligament, also known as the supraspinal ligament, is a ligament found along the vertebral column.\n\n== Structure ==\n\nThe supraspinous ligament connects the tips of the spinous processes from the seventh cervical vertebra to the sacrum.\n\nAbove the seventh cervical vertebra, the supraspinous ligament is continuous with the nuchal ligament.: 45\n\nBetween the spinous processes it is continuous with the interspinous ligaments.\n\nIt is thicker and broader in the lumbar than in the thoracic region, and intimately blended, in both situations, with the neighboring fascia.\n\nThe most superficial fibers of this ligament extend over three or four vertebrae; those more deeply seated pass between two or three vertebrae while the deepest connect the spinous processes of neighboring vertebrae.\n\n=== Development ===\n\n== Function ==\n\nThe supraspinous ligament, along with the posterior longitudinal ligament, interspinous ligaments and ligamentum flavum, help to limit hyperflexion of the vertebral column.\n\n== Clinical significance ==\n\nLesions to the supraspinous ligament may result in palpable thickening.\n\nUltrasound is effective for detecting lesions.\n\nA strain injury can also damage the supraspinous ligament.\n\nThe supraspinous ligament creates resistance during midline epidural anaesthetics when the needle is being inserted.\n\nThis increased resistance needs to be taken into account, and is one of the first subcutaneous tissues.\n\nhttps://en.wikipedia.org/wiki/Supraspinous_ligament","interspinous-ligaments":"The interspinous ligaments (interspinal ligaments) are thin and membranous ligaments, that connect adjoining spinous processes of the vertebra in the spine.\n\nThey extend from the root to the apex of each spinous process.\n\nThey meet the ligamenta flava in front and blend with the supraspinous ligament behind.\n\nThe ligaments are narrow and elongated in the thoracic region, broader, thicker, and quadrilateral in form in the lumbar region, and only slightly developed in the neck.\n\nIn the neck they are often considered part of the nuchal ligament.The function of the interspinous ligaments is to limit flexion of the spine.\n\nhttps://en.wikipedia.org/wiki/Interspinous_ligament","anterior-longitudinal-ligament":"The anterior longitudinal ligament is a ligament that runs down the anterior surface of the spine.\n\nIt traverses all of the vertebral bodies and intervertebral discs on their ventral side.\n\nIt may be partially to treat certain abnormal curvatures in the vertebral column, such as kyphosis.\n\n== Structure ==\n\nThe anterior longitudinal ligament runs down the vertebral bodies and intervertebral discs of all of the vertebrae on their ventral side.\n\nThe ligament is thick and slightly more narrow over the vertebral bodies and thinner but slightly wider over the intervertebral discs.\n\nThis effect is much less pronounced than that seen in the posterior longitudinal ligament.\n\nIt tends to be narrower and thicker around thoracic vertebrae, but wider and thinner around cervical vertebrae and lumbar vertebrae.\n\nThe anterior longitudinal ligament has three layers: superficial, intermediate and deep.\n\nThe superficial layer traverses 3 – 4 vertebrae, the intermediate layer covers 2 – 3 and the deep layer is only between individual vertebrae.\n\n== Clinical significance ==\n\nThe anterior longitudinal ligament may become calcified, causing back pain.\n\n=== Surgical release ===\n\nThe anterior longitudinal ligament may be \"released\", or partially cut, between two adjacent vertebrae.\n\nThis may be done to treat abnormal curvature in the vertebral column, such as kyphosis.\n\nOsteoporosis, some infections, and past back surgery may prevent this surgery.\n\nhttps://en.wikipedia.org/wiki/Anterior_longitudinal_ligament","posterior-longitudinal-ligament":"The posterior longitudinal ligament is a ligament connecting the posterior surfaces of the vertebral bodies of all of the vertebrae.\n\nIt weakly prevents hyperflexion of the vertebral column.\n\nIt also prevents posterior spinal disc herniation, although problems with the ligament can cause it.\n\n== Structure ==\n\nThe posterior longitudinal ligament is situated within the vertebral canal.\n\nIt extends along the posterior surfaces of the bodies of the vertebrae, from the body of the axis to the sacrum and possibly the coccyx.\n\nIt is continuous with the tectorial membrane of atlanto-axial joint.\n\nThe ligament is thicker in the thoracic than in the cervical and lumbar regions.\n\nIn the thoracic and lumbar regions, it presents a series of dentations with intervening concave margins.\n\nThe posterior longitudinal ligament is narrow at the vertebral bodies, where it covers the basivertebral veins, and widens at the intervertebral disc space.\n\nIt is generally quite wide and thin.\n\nThis ligament is composed of smooth, shining, longitudinal fibers, denser and more compact than those of the anterior ligament, and consists of superficial layers occupying the interval between three or four vertebræ, and deeper layers which extend between adjacent vertebrae.\n\nDeep fibres run between each vertebral body.\n\nSuperficial fibres run between multiple vertebrae.\n\n== Function ==\n\nThe posterior longitudinal ligament weakly prevents hyperflexion of the vertebral column.\n\nIt also limits spinal disc herniation, although it is much narrower than the anterior longitudinal ligament.\n\n== Clinical significance ==\n\nThe posterior longitudinal ligament is much narrower than the anterior longitudinal ligament.\n\nBecause of this, spinal disc herniations usually occur in a posterolateral direction.\n\nThe posterior longitudinal ligament contains a higher density of nociceptors than many ligaments, so can cause back pain.\n\nIt may ossify, particularly around cervical vertebrae.\n\nThe posterior longitudinal ligament has a high density of vasomotor fibres, allowing for increased blood flow to respond to damage to the ligament.\n\nhttps://en.wikipedia.org/wiki/Posterior_longitudinal_ligament","nuchal-ligament":"The nuchal ligament is a ligament at the back of the neck that is continuous with the supraspinous ligament.\n\n== Structure ==\n\nThe nuchal ligament extends from the external occipital protuberance on the skull and median nuchal line to the spinous process of the seventh cervical vertebra in the lower part of the neck.\n\nFrom the anterior border of the nuchal ligament, a fibrous lamina is given off.\n\nThis is attached to the posterior tubercle of the atlas, and to the spinous processes of the cervical vertebrae, and forms a septum between the muscles on either side of the neck.\n\nThe trapezius and splenius capitis muscle attach to the nuchal ligament.\n\n== Function ==\n\nIt is a tendon-like structure that has developed independently in humans and other animals well adapted for running.\n\nIn some four-legged animals, particularly ungulates, the nuchal ligament serves to sustain the weight of the head.\n\n== Clinical significance ==\n\nIn Chiari malformation treatment, decompression and duraplasty with a harvested nuchal ligament showed similar outcomes to pericranial and artificial grafts.\n\n== Other animals ==\n\nIn sheep and cattle it is known as the paxwax.\n\nIt relieves the animal of the weight of its head.\n\nDried paxwax is commonly packaged and sold as a dog treat.In most other mammals, including the great apes, the nuchal ligament is absent or present only as a thin fascia.\n\nAs it is required for running, not all animals have one.\n\nAll dogs (and all living Canidae - wolves, foxes, and wild dogs) possess a similar ligament connecting the spinous process of their first thoracic (or chest) vertebrae to the back of the axis bone (second cervical or neck bone), which supports the weight of the head without active muscle exertion, thus saving energy.\n\nThis ligament is analogous in function (but different in exact structural detail) to the nuchal ligament found in ungulates.\n\nThis ligament allows dogs to carry their heads while running long distances, such as while following scent trails with their nose to the ground, without expending much energy.\n\nIn horses, the parasite Culicoides can spread onchocerca cervicalis by living in the nuchal ligament, causing dermatitis.\n\nhttps://en.wikipedia.org/wiki/Nuchal_ligament","intertransverse-ligaments":"The intertransverse ligaments are ligaments that are placed between the transverse processes of the spine.\n\nIn the cervical region they consist of a few irregular, scattered fibers that are often replaced by muscles.\n\nIn the thoracic region they are rounded cords intimately connected with the deep muscles of the back.\n\nIn the lumbar region they are thin and membranous.\n\nThe intertransverse ligaments often blend with the intertransverse muscles.\n\nThe function of the intertransverse ligaments is to limit lateral flexion of the spine.\n\nhttps://en.wikipedia.org/wiki/Intertransverse_ligament","ligamenta-flava":"The ligamenta flava (singular, ligamentum flavum, Latin for yellow ligament) are a series of ligaments that connect the ventral parts of the laminae of adjacent vertebrae.\n\nThey help to preserve upright posture, preventing hyperflexion, and ensuring that the vertebral column straightens after flexion.\n\nHypertrophy can cause spinal stenosis.\n\n== Structure ==\n\nEach ligamentum flavum connects the laminae two adjacent vertebrae.\n\nThey begin with the junction of the axis and third cervical vertebra, continuing down to the junction of the fifth lumbar vertebra and the sacrum.\n\nThey are best seen from the interior of the vertebral canal, when looked at from the outer surface they appear short, being overlapped by the lamina of the vertebral arch.\n\nEach ligament consists of two lateral portions which commence one on either side of the roots of the articular processes, and extend backward to the point where the laminae meet to form the spinous process; the posterior margins of the two portions are in contact and to a certain extent united, slight intervals being left for the passage of small vessels.\n\nEach consists of yellow elastic tissue, the fibers of which, almost perpendicular in direction, are attached to the anterior surface of the lamina above, some distance from its inferior margin, and to the posterior surface and upper margin of the lamina below.\n\nIn the neck region the ligaments are thin, but broad and long; they are thicker in the thoracic region, and thickest in the lumbar region.\n\nThey are thinnest between the atlas bone (C1) and the axis bone (C2), and may not be present in some people.\n\nThey become longer inferiorly in the cervical spine, as the distance between adjacent laminae increases.\n\n== Function ==\n\nThe marked elasticity of the ligamenta flava serves to preserve upright posture, and to assist the vertebral column in resuming it after flexion.\n\nThe elastin, fairly unique to the ligamenta flava among other ligaments, prevents buckling of the ligament into the spinal canal during extension, which would cause spinal cord compression.\n\n== Clinical significance ==\n\nBecause these ligaments lie in the posterior part of the vertebral canal, their hypertrophy can cause spinal stenosis, particularly in patients with diffuse idiopathic skeletal hyperostosis.\n\nThe ligamenta flava may also become fatty or calcify during ageing.\n\nThese cause degeneration of elastin.\n\nSome studies indicate that the hypertrophy of these ligaments may be linked to a fibrotic process associated with increased collagen VI, which could represent an adaptive and reparative process in response to the rupture of elastic fibers.\n\n=== Epidural ===\n\nDuring an epidural, the needle has to be inserted into the spinal space through a ligamentum flavum.\n\nOnce it passes through, this is felt as a decrease in the pressure requited to further advance the needle.\n\nThis makes the ligamentum flavum an important landmark to overcome to ensure proper needle placement.\n\n=== Removal ===\n\nDuring a microdiscectomy, a procedure to reshape an intervertebral disc that is pressing on the spinal nerves, the ligamenta flava may need to be removed or reshaped.\n\nA hook can be placed underneath a ligamentum flavum to ensure it is separated from the dura mater.\n\nhttps://en.wikipedia.org/wiki/Ligamenta_flava","intercornual-ligament":"The intercornual ligament connects the sacral horn to the coccygeal horn on each side.\n\nThis definition has to be verifies, there is a lack of information about this ligament.","intervertebral-disc-c2-c3":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-c3-c4":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-c4-c5":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-c5-c6":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-c6-c7":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-c7-t1":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-l1-l2":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-l2-l3":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-l3-l4":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-l4-l5":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-l5-s1":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-t1-t2":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-t10-t11":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-t11-t12":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-t12-l1":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-t2-t3":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-t3-t4":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-t4-t5":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-t5-t6":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-t6-t7":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-t7-t8":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-t8-t9":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","intervertebral-disc-t9-t10":"An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.\n\nEach disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold the vertebrae together, and to function as a shock absorber for the spine.\n\n== Structure ==\n\nIntervertebral discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis, which surrounds an inner gel-like center, the nucleus pulposus.\n\nThe anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen.\n\nType I is concentrated toward the edge of the ring, where it provides greater strength.\n\nThe stiff laminae can withstand compressive forces.\n\nThe fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.\n\nThis prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates.\n\nThe nucleus pulposus contains loose fibers suspended in a mucoprotein gel.\n\nThe nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.\n\nIt is the remnant of the notochord.There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas.\n\nThe atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment).\n\nThe axis acts as a post around which the atlas can rotate, allowing the neck to swivel.\n\nThere are 23 discs in the human spine: 6 in the neck (cervical) region, 12 in the middle back (thoracic) region, and 5 in the lower back (lumbar) region Discs are named by the vertebral body above and below.\n\nFor example, the disc between the fifth and sixth cervical vertebrae is designated \"C5-6\".\n\n=== Development ===\n\nDuring development and at birth, vertebral discs have some vascular supply to the cartilage endplates and the anulus fibrosus.\n\nThese quickly deteriorate leaving almost no direct blood supply in healthy adults.\n\n=== Intervertebral disc space ===\n\nThe intervertebral disc space is typically defined on an X-ray photograph as the space between adjacent vertebrae.\n\nIn healthy patients, this corresponds to the size of the intervertebral disc.\n\nThe size of the space can be altered in pathological conditions such as discitis (infection of the intervertebral disc).\n\n== Function ==\n\nThe intervertebral disc functions to separate the vertebrae from each other and provides the surface for the shock-absorbing gel of the nucleus pulposus.\n\nThe nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads.\n\nThe nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.\n\nAttached to each aggrecan molecule are glycosaminoglycan (GAG) chains of chondroitin sulfate and keratan sulfate.\n\nIncreasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.\n\nThe amount of glycosaminoglycans (and hence water) decreases with age and degeneration.\n\n== Clinical significance ==\n\nAnything arising from the intervertebral disc may be termed discogenic in particular when referring to associated pain as discogenic pain.\n\n=== Herniation ===\n\nA spinal disc herniation, commonly referred to as a slipped disc, can happen when unbalanced mechanical pressures substantially deform the anulus fibrosus, allowing part of the nucleus to obtrude.\n\nThese events can occur during peak physical performance, during traumas, or as a result of chronic deterioration, typically accompanied with poor posture and has been associated with a Propionbacterium acnes infection.\n\nBoth the deformed anulus and the gel-like material of the nucleus pulposus can be forced laterally or posteriorly, distorting local muscle function and putting pressure on the nearby nerve.\n\nThis can give the symptoms typical of nerve root entrapment.\n\nThese symptoms can vary between paresthesia, numbness, chronic and/or acute pain, either locally or along the dermatome served by the entrapped nerve, loss of muscle tone and decreased homeostatic performance .\n\nThe disc is not physically slipped; it bulges, usually in just one direction.\n\nRisk of Cauda Equina.\nAnother kind of herniation, of the nucleus pulposus, can also happen as a result of the formation of Schmorl's nodes on the intervertebral disc.\n\nThis is referred to as vertical disc herniation.\n\n=== Degeneration ===\n\nBefore age 40, approximately 25% of people show evidence of disc degeneration at one or more levels.\n\nBeyond age 40, more than 60% of people show evidence of disc degeneration at one or more levels on magnetic resonance imaging (MRI).\n\nThese degenerative changes are a normal part of the ageing process and do not correlate to pain.\n\nOne effect of aging and disc degeneration is that the nucleus pulposus begins to dehydrate and the concentration of proteoglycans in the matrix decreases, thus limiting the ability of the disc to absorb shock.\n\nThis general shrinking of disc size is partially responsible for the common decrease in height as humans age.\n\nThe anulus fibrosus also becomes weaker with age and has an increased risk of tearing.\n\nIn addition, the cartilage endplates begin thinning, fissures begin to form, and there is sclerosis of the subchondral bone.\n\nSince the fissures are formed in the anulus fibrosus due to osteo-arthritic bones or degeneration in general, the inner nucleus pulposus can seep out and put pressure on any number of vertebral nerves.\n\nA herniated disc can cause mild to severe pain such as sciatica and treatment for herniated discs range from physical therapy to surgery.\n\nOther degeneration of the vertebral column includes diffuse idiopathic skeletal hyperostosis (DISH) which is the calcification or ossification of the ligaments surrounding the vertebrae.\n\nThis degeneration causes stiffness and sometimes even curvature in the lumbar and thoraco-lumbar spinal region.\nBurgeoning evidence suggests that long-term running may mitigate age-related degeneration within lumbar intervertebral discs\n\n=== Scoliosis ===\n\nWhile this may not cause pain in some people, in others it may cause chronic pain.\n\nOther spinal disorders can affect the morphology of intervertebral discs.\n\nFor example, patients with scoliosis commonly have calcium deposits (ectopic calcification) in the cartilage endplate and sometimes in the disc itself.\nHerniated discs are also found to have a higher degree of cellular senescence than non-herniated discs.\n\nIn addition to scoliosis, which is the lateral 'S' curvature of the spine, the fused vertebrae can also experience other abnormalities such as kyphosis (hunchback) which shows in old age, or lordosis (swayback), which is often present in pregnancy and obesity.\n\n== Etymology ==\n\nThe Latin word anulus means \"little ring\"; it is the diminutive of anus (\"ring\").\n\nThe misspelling annulus is also common.\n\nhttps://en.wikipedia.org/wiki/Intervertebral_disc","external-intercostal-membrane":"Unlike the other two intercostal muscles, the external intercostal muscle does not retain its muscular character all the way to the sternum, and so the tissue in this location is called the external intercostal membrane.\n\nThe fibers of the external intercostal muscles run downward and forward between adjacent ribs.\n\nEach muscle begins posteriorly at the tubercles of the ribs and extends anteriorly to the costochondral junction, the junction between the costal cartilage and the sternal end of the rib.\n\nThe muscle between the costal cartilages is replaced by a membranous layer called the external intercostal membrane.\n\nLinks and References:\n\n-Grant's: 1.15, 1.20\n-Netter: 176\n-Rohen/Yokochi: 193, 194\n\nhttps://en.wikipedia.org/wiki/External_intercostal_membrane","internal-intercostal-membrane":"The internal or posterior intercostal membrane is an aponeurosis located between the ribs and is a continuation of the internal intercostal muscles.","intra-articular-ligament-of-head-of-rib":"The intra-articular ligament of head of rib (interarticular in older texts; ligamentum capitis costae intraarticulare) is situated in the interior of the articulation of head of rib between the superior costal facet and the inferior costal facet.\n\nIt consists of a short ligament, a band of fibers, flattened from top to bottom, attached at one end to the crest separating the two costal facets on the head of the rib, and at the other end to the intervertebral disc between the two vertebrae; it divides the joint into two cavities.\n\nThis ligament is the homologue of the conjugate ligament present in some mammals, and uniting the heads of opposite ribs, across the back of the intervertebral fibrocartilage.\n\nIn the joints of the first, tenth, eleventh, and twelfth ribs, the intra-articular ligament does not exist; consequently, there is only one cavity in each of these articulations.","radiate-ligament-of-head-of-rib":"The radiate ligament connects the anterior part of the head of each rib with the side of the bodies of two vertebrae, and the intervertebral fibrocartilage between them.\n\nIt consists of three flat fasciculi, which are attached to the anterior part of the head of the rib, just beyond the articular surface.\n\nThe superior fasciculus ascends and is connected with the body of the vertebra above.\n\nThe inferior one descends to the body of the vertebra below.\nThe middle one, the smallest and least distinct, is horizontal and is attached to the intervertebral fibrocartilage.\n\nThe radiate ligament is in relation, in front, with the thoracic ganglia of the sympathetic trunk, the pleura, and, on the right side, with the azygos vein; behind, with the interarticular ligament and synovial membranes.\n\nIn the case of the first rib, this ligament is not divided into three fasciculi, but its fibers are attached to the body of the last cervical vertebra, as well as to that of the first thoracic.\n\nIn the articulations of the heads of the tenth, eleventh, and twelfth ribs, each of which articulates with a single vertebra, the triradiate arrangement does not exist; but the fibers of the ligament in each case are connected to the vertebra above, as well as to that with which the rib articulates.\n\nhttps://en.wikipedia.org/wiki/Radiate_ligament_of_head_of_rib","costotransverse-ligament":"A costotransverse ligament is a short fibrous band that connects a rib with the transverse process of vertebra.\n\nThey are some of the ligaments that surround the costovertebral joint.\n\n== Types ==\n\nThere are three types of costotransverse ligaments in the human body: costo-transverse ligament (connects the posterior surface of the neck of the rib with the transverse process of the corresponding vertebra); lateral costotransverse ligament (connects the non-articular part of the rib with the tip of transverse process); and superior costotransverse ligament (connects the upper border of the neck of the rib to the inferior border of the transverse process of the vertebra above).\n\nIn addition, some sources also list the inferior costotransverse ligament, and the posterior costotransverse ligament in this grouping.\n\n== Functions ==\n\nSupport and prevent dislocation of ribs and limit the costotransverse joint to perform a gliding movement.\nTheir posterior surfaces provide attachment points for the extensor muscles (deep group) of the back.\n\nhttps://en.wikipedia.org/wiki/Costotransverse_ligament","coraco-acromial-ligament":"CORACOACROMIAL LIGAMENT\n\nThe coracoacromial ligament is a strong triangular ligament between the coracoid process and the acromion.\n\n== Structure ==\n\nThe coracoacromial ligament originates from the summit of the acromion of the scapula, just in front of the articular surface for the clavicle.\n\nIt inserts by its broad base along the whole length of the lateral border of the coracoid process of the scapula.\n\nIt is in relation, above, with the clavicle and under surface of the deltoid muscle; below, with the tendon of the supraspinatus, a bursa being interposed.\n\nIts lateral border is continuous with a dense lamina that passes beneath the deltoid muscle upon the tendons of the supraspinatus and infraspinatus.\n\nThe ligament is sometimes described as consisting of two marginal bands and a thinner intervening portion, the two bands being attached respectively to the apex and the base of the coracoid process, and joining together at the acromion.\n\nWhen the pectoralis minor is inserted, as occasionally is the case, into the capsule of the shoulder-joint instead of into the coracoid process, it passes between these two bands, and the intervening portion of the ligament is then deficient.\n\n== Function ==\n\nTogether with the coracoid process and the acromion, the coracoacromial ligament forms a vault for the protection of the head of the humerus.\n\nhttps://en.wikipedia.org/wiki/Coracoacromial_ligament","superior-transverse-scapular-ligament":"The superior transverse ligament (transverse or suprascapular ligament) converts the suprascapular notch into a foramen or opening.\n\nIt is a thin and flat fascicle, narrower at the middle than at the extremities, attached by one end to the base of the coracoid process and by the other to the medial end of the scapular notch.\n\nThe suprascapular nerve always runs through the foramen; while the suprascapular vessels cross over the ligament in most of the cases.\n\nThe suprascapular ligament can become completely or partially ossified.\n\nThe ligament also been found to split forming doubled space within the suprascapular notch.\n\nhttps://en.wikipedia.org/wiki/Superior_transverse_scapular_ligament","trapezoid-ligament":"The trapezoid ligament, the anterior and lateral fasciculus, is broad, thin, and quadrilateral: it is placed obliquely between the coracoid process and the clavicle.\n\nIt is attached, below, to the upper surface of the coracoid process; above, to the oblique ridge on the under surface of the clavicle.\n\nIts anterior border is free; its posterior border is joined with the conoid ligament, the two forming, by their junction, an angle projecting backward.\n\nhttps://en.wikipedia.org/wiki/Trapezoid_ligament","conoid-ligament":"The conoid ligament is the posterior and medial fasciculus of the coracoclavicular ligament.\n\nIt is formed by a dense band of fibers, conical in form, with its base directed upward.\n\nIt is attached by its apex to a rough impression at the base of the coracoid process on the scapula, medial to the trapezoid ligament; above, by its expanded base, to the conoid tubercle on the under surface of the clavicle, and to a line proceeding medialward from it for 1.25 cm.\n\nThese ligaments are in relation, in front, with the subclavius and deltoid muscles; behind, with the trapezius.\n\nhttps://en.wikipedia.org/wiki/Conoid_ligament","acromioclavicular-ligament":"The acromioclavicular ligament is part of the acromioclavicular joint.\n\nIt is divided into two parts: superior and inferior.\n\n== Superior acromioclavicular ligament ==\n\nThis ligament is a quadrilateral band, covering the superior part of the articulation, and extending between the upper part of the lateral end of the clavicle and the adjoining part of the upper surface of the acromion.\n\nIt is composed of parallel fibers, which interlace with the aponeuroses of the trapezius and deltoideus; below, it is in contact with the articular disk when this is present.\n\nThis ligament provides horizontal stability to the acromioclavicular joint\n\n== Inferior acromioclavicular ligament ==\n\nThis ligament is somewhat thinner than the preceding; it covers the under part of the articulation, and is attached to the adjoining surfaces of the two bones.\n\nIt is in relation, above, in rare cases with the articular disk; below, with the tendon of the supraspinatus.\n\nhttps://en.wikipedia.org/wiki/Acromioclavicular_ligament","articular-disc-of-acromioclavicular-joint":"Intermediate plate in fibrocartilage.\n\nIt is in contact with the superior acromioclavicular ligament, and sometimes with the inferior acromioclavicular ligament.\n\n==Variation==\n\nThis meniscus may be a blade of fibrocartilage that extends nearly halfway into the joint or it may form a complete disc that divides the joint into two parts.","articular-disc-of-sternoclavicular-joint":"The articular disc of the sternoclavicular joint is flat and nearly circular, interposed between the articulating surfaces of the sternum and clavicle.\n\nIt is attached, above, to the upper and posterior border of the articular surface of the clavicle; below, to the cartilage of the first rib, near its junction with the sternum; and by its circumference to the interclavicular and anterior and posterior sternoclavicular ligaments.\n\nIt is thicker at the circumference, especially its upper and back part, than at its center.\n\nIt divides the joint into two cavities, each of which is furnished with a synovial membrane.\n\nhttps://en.wikipedia.org/wiki/Articular_disc_of_sternoclavicular_joint","anterior-sternoclavicular-ligament":"The anterior sternoclavicular ligament is a broad band of fibers, covering the anterior (front) surface of the joint between the sternum and clavicle (sternoclavicular articulation).\n\nIt is attached above to the upper and front part of the sternal end of the clavicle, and, passing obliquely downward and medialward, is attached below to the front of the upper part of the manubrium on the sternum.\n\nThis ligament is covered by the sternal portion of the sternocleidomastoideus and the integument; behind, it is in relation with the capsule, the articular disk, and the two synovial membranes.\n\nhttps://en.wikipedia.org/wiki/Anterior_sternoclavicular_ligament","costoclavicular-ligament":"The costoclavicular ligament also known as the rhomboid ligament or Halsted's ligament is a ligament of the shoulder girdle.\n\nIt is short, flat, and rhomboid in form.\n\nIt is the major stabilizing factor of the sternoclavicular joint and is the axis of movement of the joint, especially during elevation of the clavicle.\n\nAttached below to the upper and medial part of the cartilage of the first rib, it ascends at an angle posteriorly and laterally, and is fixed above to the costal tuberosity on the inferior aspect of the clavicle.\n\nIt is in relation, in front, with the tendon of origin of the subclavius; behind, with the subclavian vein.\n\nhttps://en.wikipedia.org/wiki/Costoclavicular_ligament","interclavicular-ligament":"The interclavicular ligament is a flattened band, which varies considerably in form and size in different individuals, it passes in a curved direction from the upper part of the sternal end of one clavicle to that of the other, and is also attached to the upper margin of the sternum.\n\nIt is in relation, in front, with the integument and Sternocleidomastoid muscles; behind, with the Sternothyreoid muscles.\n\nhttps://en.wikipedia.org/wiki/Interclavicular_ligament","posterior-sternoclavicular-ligament":"The posterior sternoclavicular ligament is a band of fibers, covering the posterior surface of the sternoclavicular joint.\n\nIt is attached above to the upper and back part of the sternal end of the clavicle, and, passing obliquely downward and medialward, is fixed below to the back of the upper part of the manubrium sterni.\n\nIt is in relation, in front, with the articular disk and synovial membranes; behind, with the Sternohyoideus and Sternothyreoideus.\n\nhttps://en.wikipedia.org/wiki/Posterior_sternoclavicular_ligament","oblique-cord":"The oblique cord is a ligament between the ulnar and radius bones in the forearm near the elbow.\n\nIt takes the form of a small, flattened band, extending downward and lateralward, from the lateral side of the ulnar tuberosity at the base of the coronoid process to the radius a little below the radial tuberosity.\n\nIts fibers run in the opposite direction to those of the Interosseous membrane of the forearm.\n\nIt is called by other names including oblique ligament, chorda obliqua, radio-ulnar ligament, chorda oblique antebrachii anterior, proximal interosseous band, dorsal oblique accessory cord, proximal band of the interosseous membrane, superior oblique ligament, oblique ligament proper, round ligament, and ligament of Weitbrecht.\n\nIt has no known function and can be cut without apparent consequence.\n\n== Structure ==\n\nA study upon the arms of 38 people found that its mean length is 3.4 cm (range 2.4 to 4.2 cm) and in most people it tapers from the ulna to the radius end, being at the ulna 9 mm, in its middle, 7mm and its radius end 4 mm.\n\n=== Variation ===\n\nThe shape and form of the ligament have been found in humans cadavers to vary from a rounded cord to a flat membrane.\n\nFurther, it is not found in all humans being variably found to be absent in half of arms, and a third or 15% of people.\n\nIt is found in most primates though not in the family of New World monkeys that includes spider and woolly monkeys called atelines.\n\n== Function ==\n\nIt has been suggested to strengthen the interosseus membrane proximally, provide restraint for the rotatory movements of the forearm, or that the ligament may stop bone bending and preventing buckling failure.\n\nHowever, due to the orientation of its fibers, the oblique cord is unlikely to transfer force due to limb loading from the radius to the ulna.One recent comparative study upon primates concluded:\n\nThe oblique cord does not limit supination, nor does it seem to have a role in preventing radial buckling failure or\nreducing bending strain.\n\nWhat, then, is the oblique cord for?\n\nThe oblique cord may simply be an additional tie between the radius and ulna aiding other soft tissue structures such as the annular ligament and interosseous membrane.\n\nAdditionally, the oblique cord may prevent anterior shearing of the proximal radius under extreme compressive loads.\n\nA study on humans concluded that it \"appears insignificant in stability of the proximal forearm.\"\n\nIt has been suggested that its presence in modern humans may be a vestigial body part for a biped that was important due to the load-bearing function of the upper limb in evolutionarily earlier quadruped human ancestors.\n\nhttps://en.wikipedia.org/wiki/Oblique_cord","superior-glenohumeral-ligament":"In human anatomy, the glenohumeral ligaments (GHL) are three ligaments on the anterior side of the glenohumeral joint (i.e. between the glenoid cavity of the scapula and the head of the humerus; colloquially called the shoulder joint).\n\nReinforcing the anterior glenohumeral joint capsule, the superior, middle, and inferior glenohumeral ligaments play different roles in the stability of the head of the humerus depending on arm position and degree of rotation.\n\n== Location ==\n\nThe ligaments may be best seen by opening the capsule at the back of the joint and removing the head of the humerus:\n\n-One on the medial side of the joint passes from the medial edge of the glenoid cavity to the lower part of the lesser tubercle of the humerus.\n\n-A second at the lower part of the joint extends from the under edge of the glenoid cavity to the under part of the anatomical neck of the humerus.\n\n-A third at the upper part of the joint is fixed above to the apex of the glenoid cavity close to the root of the coracoid process, and passing downward along the medial edge of the tendon of the Biceps brachii, is attached below to a small depression above the lesser tubercle of the humerus.\n\n-In addition to these, the capsule is strengthened in front by two bands derived from the tendons of the Pectoralis major and Teres major respectively.\n\n== Function ==\n\nThe most important ligament involved in shoulder joint stability is the Inferior Glenohumeral Ligament.\n\nDuring abduction of the arm the middle and inferior ligaments become taut while the superior ligament relaxes.\n\nThe radius of curvature of the head of the humerus is greater superiorly than inferiorly, which further stretches these ligaments so that they keep the articular surfaces of the joint in their close-packed position.\n\nDuring abduction the greater tubercle of the humerus comes in contact with the upper margin of the glenoid cavity, which limits maximum abduction.\n\nBy rotating the humerus laterally, this contact is delayed because the greater tubercle is pulled back so that the bicipital groove faces the coracoacromial ligament.\n\nThis slightly slackens the inferior fibres of the glenohumeral ligament, allowing an abduction of 90°.\n\nCombining abduction with 30° flexion in the plane of the scapula causes a delay in the tightening of the ligament resulting in a maximum abduction of 110°.\n\nDuring rotation of the arm lateral rotation stretches all three ligaments while medial rotation relaxes them.\n\nhttps://en.wikipedia.org/wiki/Glenohumeral_ligaments","middle-glenohumeral-ligament":"In human anatomy, the glenohumeral ligaments (GHL) are three ligaments on the anterior side of the glenohumeral joint (i.e. between the glenoid cavity of the scapula and the head of the humerus; colloquially called the shoulder joint).\n\nReinforcing the anterior glenohumeral joint capsule, the superior, middle, and inferior glenohumeral ligaments play different roles in the stability of the head of the humerus depending on arm position and degree of rotation.\n\n== Location ==\n\nThe ligaments may be best seen by opening the capsule at the back of the joint and removing the head of the humerus:\n\n-One on the medial side of the joint passes from the medial edge of the glenoid cavity to the lower part of the lesser tubercle of the humerus.\n\n-A second at the lower part of the joint extends from the under edge of the glenoid cavity to the under part of the anatomical neck of the humerus.\n\n-A third at the upper part of the joint is fixed above to the apex of the glenoid cavity close to the root of the coracoid process, and passing downward along the medial edge of the tendon of the Biceps brachii, is attached below to a small depression above the lesser tubercle of the humerus.\n\n-In addition to these, the capsule is strengthened in front by two bands derived from the tendons of the Pectoralis major and Teres major respectively.\n\n== Function ==\n\nThe most important ligament involved in shoulder joint stability is the Inferior Glenohumeral Ligament.\n\nDuring abduction of the arm the middle and inferior ligaments become taut while the superior ligament relaxes.\n\nThe radius of curvature of the head of the humerus is greater superiorly than inferiorly, which further stretches these ligaments so that they keep the articular surfaces of the joint in their close-packed position.\n\nDuring abduction the greater tubercle of the humerus comes in contact with the upper margin of the glenoid cavity, which limits maximum abduction.\n\nBy rotating the humerus laterally, this contact is delayed because the greater tubercle is pulled back so that the bicipital groove faces the coracoacromial ligament.\n\nThis slightly slackens the inferior fibres of the glenohumeral ligament, allowing an abduction of 90°.\n\nCombining abduction with 30° flexion in the plane of the scapula causes a delay in the tightening of the ligament resulting in a maximum abduction of 110°.\n\nDuring rotation of the arm lateral rotation stretches all three ligaments while medial rotation relaxes them.\n\nhttps://en.wikipedia.org/wiki/Glenohumeral_ligaments","inferior-glenohumeral-ligament":"In human anatomy, the glenohumeral ligaments (GHL) are three ligaments on the anterior side of the glenohumeral joint (i.e. between the glenoid cavity of the scapula and the head of the humerus; colloquially called the shoulder joint).\n\nReinforcing the anterior glenohumeral joint capsule, the superior, middle, and inferior glenohumeral ligaments play different roles in the stability of the head of the humerus depending on arm position and degree of rotation.\n\n== Location ==\n\nThe ligaments may be best seen by opening the capsule at the back of the joint and removing the head of the humerus:\n\n-One on the medial side of the joint passes from the medial edge of the glenoid cavity to the lower part of the lesser tubercle of the humerus.\n\n-A second at the lower part of the joint extends from the under edge of the glenoid cavity to the under part of the anatomical neck of the humerus.\n\n-A third at the upper part of the joint is fixed above to the apex of the glenoid cavity close to the root of the coracoid process, and passing downward along the medial edge of the tendon of the Biceps brachii, is attached below to a small depression above the lesser tubercle of the humerus.\n\n-In addition to these, the capsule is strengthened in front by two bands derived from the tendons of the Pectoralis major and Teres major respectively.\n\n== Function ==\n\nThe most important ligament involved in shoulder joint stability is the Inferior Glenohumeral Ligament.\n\nDuring abduction of the arm the middle and inferior ligaments become taut while the superior ligament relaxes.\n\nThe radius of curvature of the head of the humerus is greater superiorly than inferiorly, which further stretches these ligaments so that they keep the articular surfaces of the joint in their close-packed position.\n\nDuring abduction the greater tubercle of the humerus comes in contact with the upper margin of the glenoid cavity, which limits maximum abduction.\n\nBy rotating the humerus laterally, this contact is delayed because the greater tubercle is pulled back so that the bicipital groove faces the coracoacromial ligament.\n\nThis slightly slackens the inferior fibres of the glenohumeral ligament, allowing an abduction of 90°.\n\nCombining abduction with 30° flexion in the plane of the scapula causes a delay in the tightening of the ligament resulting in a maximum abduction of 110°.\n\nDuring rotation of the arm lateral rotation stretches all three ligaments while medial rotation relaxes them.\n\nhttps://en.wikipedia.org/wiki/Glenohumeral_ligaments","articular-capsule-of-glenohumeral-joint":"The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons.\n\nThe articulations between the bones of the shoulder make up the shoulder joints.\n\nThe shoulder joint, also known as the glenohumeral joint, is the major joint of the shoulder, but can more broadly include the acromioclavicular joint.\n\nIn human anatomy, the shoulder joint comprises the part of the body where the humerus attaches to the scapula, and the head sits in the glenoid cavity.\n\nThe shoulder is the group of structures in the region of the joint.The shoulder joint is the main joint of the shoulder.\n\nIt is a ball and socket joint that allows the arm to rotate in a circular fashion or to hinge out and up away from the body.\n\nThe joint capsule is a soft tissue envelope that encircles the glenohumeral joint and attaches to the scapula, humerus, and head of the biceps.\n\nIt is lined by a thin, smooth synovial membrane.\n\nThe rotator cuff is a group of four muscles that surround the shoulder joint and contribute to the shoulder's stability.\n\nThe muscles of the rotator cuff are supraspinatus, subscapularis, infraspinatus, and teres minor.\n\nThe cuff adheres to the glenohumeral capsule and attaches to the humeral head.\n\nThe shoulder must be mobile enough for the wide range actions of the arms and hands, but stable enough to allow for actions such as lifting, pushing, and pulling.\n\n== Structure ==\n\nThe shoulder consists of a ball-and-socket joint formed by the humerus and scapula and their surrounding structures - ligaments, muscles, tendons - which support the bones and maintain the relationship of one to another.\n\nThese supporting structures attach to the clavicle, humerus, and scapula, the latter providing the glenoid cavity, acromion and coracoid processes.\n\nThe main joint of the shoulder is the shoulder joint (or glenohumeral joint), between the humerus and the glenoid process of the scapular.\n\nThe acromioclavicular joint and sternoclavicular joint also play a role in shoulder movements.\n\nWhite hyaline cartilage on the ends of the bones (called articular cartilage) allows the bones to glide and move on each other, and the joint space is surrounded by a synovial membrane.\n\nAround the joint space are muscles - the rotator cuff, which directly surrounds and attaches to the shoulder joint - and other muscles that help provide stability and facilitate movement.\n\nTwo filmy sac-like structures called bursae permit smooth gliding between bone, muscle, and tendon.\n\nThey cushion and protect the rotator cuff from the bony arch of the acromion.The glenoid labrum is the second kind of cartilage in the shoulder which is distinctly different from the articular cartilage.\n\nThis cartilage is more fibrous or rigid than the cartilage on the ends of the ball and socket.\n\nAlso, this cartilage is also found only around the socket where it is attached.\n\n=== Joint ===\n\nThe shoulder joint (also known as the glenohumeral joint) is the main joint of the shoulder.\n\nIt is a ball and socket joint that allows the arm to rotate in a circular fashion or to hinge out and up away from the body.\n\nIt is formed by the articulation between the head of the humerus and the lateral scapula (specifically-the glenoid cavity of the scapula).\n\nThe \"ball\" of the joint is the rounded, medial anterior surface of the humerus and the \"socket\" is formed by the glenoid cavity, the dish-shaped portion of the lateral scapula.\n\nThe shallowness of the cavity and relatively loose connections between the shoulder and the rest of the body allows the arm to have tremendous mobility, at the expense of being much easier to dislocate than most other joints in the body.\n\nThere is an approximately 4-to-1 disproportion in size between the large head of the humerus and the shallow glenoid cavity.The glenoid cavity is made deeper by the addition of the fibrocartilaginous ring of the glenoid labrum.\n\nThe capsule is a soft tissue envelope that encircles the glenohumeral joint and attaches to the scapula, humerus, and head of the biceps.\n\nIt is lined by a thin, smooth synovial membrane.\n\nThis capsule is strengthened by the coracohumeral ligament which attaches the coracoid process of the scapula to the greater tubercle of the humerus.\n\nThere are also three other ligaments attaching the lesser tubercle of the humerus to lateral scapula and are collectively called the glenohumeral ligaments.\n\nThe transverse humeral ligament, which passes from the lesser tubercle to the greater tubercle of humerus, covers the intertubercular groove, in which the long head of biceps brachii travels.\n\n=== Rotator cuff ===\n\nThe rotator cuff is an anatomical term given to the group of four muscles and their tendons that act to stabilize the shoulder.\n\nThese muscles are the supraspinatus, infraspinatus, teres minor and subscapularis and that hold the head of the humerus in the glenoid cavity during movement.\n\nThe cuff adheres to the glenohumeral capsule and attaches to the head of the humerus.\n\nTogether, these keep the humeral head in the glenoid cavity, preventing upward migration of the humeral head caused by the pull of the deltoid muscle at the beginning of arm elevation.\n\nThe infraspinatus and the teres minor, along with the anterior fibers of the deltoid muscle, are responsible for external rotation of the arm.The four tendons of these muscles converge to form the rotator cuff tendon.\n\nThis tendon, along with the articular capsule, the coracohumeral ligament, and the glenohumeral ligament complex, blend into a confluent sheet before insertion into the humeral tuberosities.\n\nThe infraspinatus and teres minor fuse near their musculotendinous junctions, while the supraspinatus and subscapularis tendons join as a sheath that surrounds the biceps tendon at the entrance of the bicipital groove.\n\n=== Other muscles ===\n\nMuscles from the shoulder region\nIn addition to the four muscles of the rotator cuff, the deltoid muscle and teres major muscles arise and exist in the shoulder region itself.\n\nThe deltoid muscle covers the shoulder joint on three sides, arising from the front upper third of the clavicle, the acromion, and the spine of the scapula, and travelling to insert on the deltoid tubercle of the humerus.\n\nContraction of each part of the deltoid assists in different movements of the shoulder - flexion (clavicular part), abduction (middle part) and extension (scapular part).\n\nThe teres major attaches to the outer part of the back of the scapula, beneath the teres minor, and attaches to the upper part of the humerus.\n\nIt helps with medial rotation of the humerus.Muscles from the front\nMuscles from the chest wall that contribute to the shoulder are:\nMuscles from the back\n\n=== Armpit ===\n\nThe armpit (Latin: axilla) is formed by the space between the muscles of the shoulder.\n\nThe nerves and blood vessels of the arm travel through the armpit, and it possesses several sets of lymph nodes that are able to be examined.\n\nThe armpit is formed by the pectoralis major and minor muscles at the front, the latissimus dorsi and teres major muscles at the back, the serratus anterior muscle on its inner surface, and the intertubercular groove of the humerus on the outer side.\n\n=== Nerve supply and passage ===\n\nThe skin around the shoulder is supplied by C2-C4 (upper), and C7 and T2 (lower area).\n\nThe brachial plexus emerges as nerve roots from the cervical vertebrae C5-T1.\n\nBranches of the plexus, in particular from C5-C6, supply the majority of the muscles of the shoulder.\n\n=== Blood vessels ===\n\nThe subclavian artery arises from the brachiocephalic trunk on the right and directly from the aorta from the left.\n\nThis becomes the axillary artery as it passes beyond the first rib.\n\nThe axillary artery also supplies blood to the arm, and is one of the major sources of blood to the shoulder region.\n\nThe other major sources are the transverse cervical artery and the suprascapular artery, both branches of the thyrocervical trunk which itself is a branch of the subclavian artery.\n\nThe blood vessels form a network (anastamosis) behind the shoulder that helps to supply blood to the arm even when the axillary artery is compromised.\n\n== Function ==\n\nThe muscles and joints of the shoulder allow it to move through a remarkable range of motion, making it one of the most mobile joints in the human body.\n\nThe shoulder can abduct, adduct, rotate, be raised in front of and behind the torso and move through a full 360° in the sagittal plane.\n\nThis tremendous range of motion also makes the shoulder extremely unstable, far more prone to dislocation and injury than other jointsThe following describes the terms used for different movements of the shoulder:\n\n== Development ==\n\n=== Puberty ===\n\nUnder the influence of testosterone and growth hormone, the shoulders broaden in males during puberty.\n\n== Clinical significance ==\n\nThe shoulder is the most movable joint in the body.\n\nHowever, it is an unstable joint because of the range of motion allowed.\n\nThis instability increases the likelihood of joint injury, which often leads to a degenerative process in which tissues break down and no longer function well.\n\n=== Fracture ===\n\nFractures of shoulder bones can include clavicular fractures, scapular fractures, and fractures of the upper humerus.\n\n=== Pain ===\n\nShoulder problems, including pain, are common and can relate to any of the structures within the shoulder.\n\nThe primary cause of shoulder pain is a rotator cuff tear.\n\nThe supraspinatus is most commonly involved in a rotator cuff tear.\n\nWhen this type of cartilage starts to wear out (a process called arthritis), the joint becomes painful and stiff.\n\n-Arthritis\n-Frozen shoulder\n-Impingement syndrome\n-Shoulder dislocation\n\n=== Imaging ===\n\nImaging of the shoulder includes ultrasound, X-ray and MRI, and is guided by the suspected diagnosis and presenting symptoms.\n\nConventional x-rays and ultrasonography are the primary tools used to confirm a diagnosis of injuries sustained to the rotator cuff.\n\nFor extended clinical questions, imaging through Magnetic Resonance with or without intraarticular contrast agent is indicated.\n\nHodler et al. recommend starting scanning with conventional x-rays taken from at least two planes, since this method gives a wide first impression and even has the chance of exposing any frequent shoulder pathologies, i.e., decompensated rotator cuff tears, tendinitis calcarea, dislocations, fractures, usures, and/or osteophytes.\n\nFurthermore, x-rays are required for the planning of an optimal CT or MR image.\n\nThe conventional invasive arthrography is nowadays being replaced by the non-invasive MRI and ultrasound, and is used as an imaging reserve for patients who are contraindicated for MRI, for example pacemaker-carriers with an unclear and unsure ultrasonography.\n\n==== X-ray ====\n\nProjectional radiography views of the shoulder include:\n\nAP-projection 40° posterior oblique after GrasheyThe body has to be rotated about 30 to 45 degrees towards the shoulder to be imaged, and the standing or sitting patient lets the arm hang.\n\nThis method reveals the joint gap and the vertical alignment towards the socket.\n\nTransaxillary projectionThe arm should be abducted 80 to 100 degrees.\n\nThis method reveals:\n\n-The horizontal alignment of the humerus head in respect to the socket and the lateral clavicle in respect to the acromion\n\n-Lesions of the anterior and posterior socket border, or of the tuberculum minus\n\n-The eventual non-closure of the acromial apophysis\n\n-The coraco-humeral intervalY-projectionThe lateral contour of the shoulder should be positioned in front of the film in a way that the longitudinal axis of the scapula continues parallel to the path of the rays.\n\nThis method reveals:\n\n-The horizontal centralization of the humerus head and socket\n\n-The osseous margins of the coraco-acromial arch and hence the supraspinatus outlet canal\n\n-The shape of the acromionThis projection has a low tolerance for errors and, accordingly, needs proper execution.\n\n-The Y-projection can be traced back to Wijnblath’s 1933 published cavitas-en-face projection.\n\n==== Ultrasound ====\n\nThere are several advantages of ultrasound.\n\nIt is relatively cheap, does not emit any radiation, is accessible, is capable of visualizing tissue function in real time, and allows the performance of provocative maneuvers in order to replicate the patient’s pain.\n\nThose benefits have helped ultrasound become a common initial choice for assessing tendons and soft tissues.\n\nLimitations include, for example, the high degree of operator dependence and the inability to define pathologies in bones.\n\nOne also has to have an extensive anatomical knowledge of the examined region and keep an open mind to normal variations and artifacts created during the scan.\n\nAlthough musculoskeletal ultrasound training, like medical training in general, is a lifelong process, Kissin et al. suggests that rheumatologists who taught themselves how to manipulate ultrasound can use it just as well as international musculo-skeletal ultrasound experts to diagnose common rheumatic conditions.\n\nAfter the introduction of high-frequency transducers in the mid-1980s, ultrasound has become a conventional tool for taking accurate and precise images of the shoulder to support diagnosis.Adequate for the examination are high-resolution, high-frequency transducers with a transmission frequency of 5, 7.5, and 10 MHz.\n\nTo improve the focus on structures close to the skin an additional \"water start-up length\" is advisable.\n\nDuring the examination the patient is asked to be seated, the affected arm is then adducted and the elbow is bent to 90 degrees.\n\nSlow and cautious passive lateral and/or medial rotations have the effect of being able to visualize different sections of the shoulder.\n\nIn order to also demonstrate those parts which are hidden under the acromion in the neutral position, a maximum medial rotation with hyperextension behind the back is required.\n\nTo avoid the different tendon echogenicities caused by different instrument settings, Middleton compared the tendon’s echogenicity with that of the deltoid muscle, which is still lege artis.Usually the echogenicity compared to the deltoid muscle is homogeneous intensified without dorsal echo extinction.\n\nVariability with reduced or intensified echo has also been found in healthy tendons.\n\nBilateral comparison is very helpful when distinguishing and setting boundaries between physiological variants and a possible pathological finding.\n\nDegenerative changes at the rotator cuff often are found on both sides of the body.\n\nConsequently, unilateral differences rather point to a pathological source and bilateral changes rather to a physiological variation.\n\nIn addition, a dynamic examination can help to differentiate between an ultrasound artifact and a real pathology.\n\nTo accurately evaluate the echogenicity of an ultrasound, one has to take into account the physical laws of reflection, absorption and dispersion.\n\nIt is at all times important to acknowledge that the structures in the joint of the shoulder are not aligned in the transversal, coronal or sagittal plane, and that therefore during imaging of the shoulder the transducer head has to be held perpendicularly or parallel to the structures of interest.\n\nOtherwise the appearing echogenicity may not be evaluated.\n\n==== MRI ====\n\nOrthopedics established the MRI early on as the tool of choice for joint- and soft tissue-imaging because of its non-invasiveness, lack of radiation exposure, multi planar slicing possibilities and the high soft tissue contrast.\n\nMRIs can provide joint details to the treating orthopedist, helping them to diagnose and decide the next appropriate therapeutic step.\n\nTo examine the shoulder, the patient should lay down with the concerned arm is in lateral rotation.\n\nFor signal detection it is recommended to use a surface-coil.\n\nTo find pathologies of the rotator cuff in the basic diagnostic investigation, T2-weighted sequences with fat-suppression or STIR sequences have proven value.\n\nIn general, the examination should occur in the following three main planes: axial, oblique coronal and sagittal.\n\nMost morphological changes and injuries are sustained to the supraspinatus tendon.\n\nTraumatic rotator cuff changes are often located antero-superior, meanwhile degenerative changes more likely are supero-posterior.\nTendons are predominantly composed of dense collagen fiber bundles.\n\nBecause of their extreme short T2-relaxation time they appear typically signal-weak, respectively, dark.\n\nDegenerative changes, inflammations and also partial and complete tears cause loss of the original tendon structure.\n\nFatty deposits, mucous degeneration and hemorrhages lead to an increased intratendinal T1-image.\n\nEdema formations, inflammatory changes and ruptures increase the signals in a T2-weighted image.\n\n==== MRA ====\n\nWhile using MRI, true lesions at the rotator interval region between the parts of the supraspinatus and subscapularis are all but impossible to distinguish from normal synovium and capsule.\n\nIn 1999, Weishaupt D. et al. reached through two readers a significant better visibility of pulley lesions at the rotator interval and the expected location of the reflection pulley of the long biceps and subscapularis tendon on parasagittal (reader1/reader2 sensitivity: 86%/100%; specificity: 90%/70%) and axial (reader1/reader2 sensitivity: 86%/93%; specificity: 90%/80%) MRA images.When examining the rotator cuff, the MRA has a couple of advantages compared to the native MRI.\n\nThrough a fat suppressed T2-weighted spin echo, MRA can reproduce an extreme high fat-water-contrast, which helps to detect water-deposits with better damage diagnosis in structurally changed collagen fiber bundles.\n\n== Other animals ==\n\nTetrapod forelimbs are characterised by a high degree of mobility in the shoulder-thorax connection.\n\nLacking a solid skeletal connection between the shoulder girdle and the vertebral column, the forelimb's attachment to the trunk is instead mainly controlled by serratus lateralis and levator scapulae.\n\nDepending on locomotor style, a bone connects the shoulder girdle to the trunk in some animals; the coracoid bone in reptiles and birds, and the clavicle in primates and bats; but cursorial mammals lack this bone.\n\nIn primates, the shoulder shows characteristics that differ from other mammals, including a well developed clavicle, a dorsally shifted scapula with prominent acromion and spine, and a humerus featuring a straight shaft and a spherical head.\n\n\"In terms of comparative anatomy the human scapula represents two bones that have become fused together; the (dorsal) scapula proper and the (ventral) coracoid.\n\nThe epiphyseal line across the glenoid cavity is the line of fusion.\n\nThey are the counterparts of the ilium and ischium of the pelvic girdle.\"\n\nhttps://en.wikipedia.org/wiki/Shoulder","glenoid-labrum":"The glenoid labrum (glenoid ligament) is a fibrocartilaginous structure (not a fibrocartilage as previously thought) rim attached around the margin of the glenoid cavity in the shoulder blade.\n\nThe shoulder joint is considered a ball and socket joint.\n\nHowever, in bony terms the 'socket' (the glenoid fossa of the scapula) is quite shallow and small, covering at most only a third of the 'ball' (the head of the humerus).\n\nThe socket is deepened by the glenoid labrum, stabilizing the shoulder joint.The labrum is triangular in section; the base is fixed to the circumference of the cavity, while the free edge is thin and sharp.\nIt is continuous above with the tendon of the long head of the biceps brachii, which gives off two fascicles to blend with the fibrous tissue of the labrum.\n\n== Structure ==\n\n== Clinical significance ==\n\n=== Injury ===\n\nTearing of the labrum can occur from either acute trauma or repetitive shoulder motion such as in the sports of swimming, baseball and football.\n\nAcute trauma may be from dislocation of the shoulder, direct blows to the shoulder, and other accidents of the sort.\n\nTears are classified as either superior or inferior in regards to where the tear is in the glenoid cavity.\n\nA SLAP lesion (superior labrum, anterior to posterior) is a tear where the glenoid labrum meets the tendon of the long head of the biceps muscle.\n\nSymptoms include increased pain with overhead activity, popping or grinding, loss of strength, and trouble localizing a specific point of pain.\n\nBecause a SLAP lesion involves the biceps, pain and weakness may also be felt when performing elbow flexion with resistance.\n\n=== Diagnosis ===\n\nClinicians can use any combination of the following manual tests to assist in determining if a labral tear has occurred; Jobe Relocation, O'Brien, Anterior Apprehension, Bicipital Groove Tenderness, Crank, Speed, and Yergason tests.\n\nAs a general rule, abnormal pain experienced during any of these tests will indicate a positive result, or a tear of the glenoid labrum.\n\nAll of the tests take advantage of the fact that the labrum meets the tendon of the long head of the biceps muscle, and thus will normally produce pain in the region if a tear is present.\n\nAdditionally, clinicians may order an MRI (Magnetic Resonance Imaging) or CT (Computed Tomography) scan to be conducted utilizing contrast injections to highlight where tears may be present.\n\nHowever, due to inherent variability between humans, manual tests, when possible, are more accurate in determining the presence of a labral tear.\n\n=== Treatment ===\n\nDetachment of the glenoid labrum often requires surgery to reattach it to the glenoid fossa.\n\nArthroscopic surgical techniques can also be used for more minor detachments.\n\nhttps://en.wikipedia.org/wiki/Glenoid_labrum","coracohumeral-ligament":"The coracohumeral ligament is a broad ligament which strengthens the upper part of the capsule of the shoulder joint.\n\nIt arises from the lateral border of the coracoid process, and passes obliquely downwards and laterally to the front of the greater tubercle of the humerus, blending with the tendon of the supraspinatus muscle.\n\nIt also blends with the subscapularis muscle.\n\nIt has two bands, anterior and posterior, that insert into the lesser and greater tubercles of the humerus respectively.\n\nThis ligament is intimately united to the capsule by its posterior and lower border, but its anterior and upper border presents a free edge, which overlaps the capsule.\n\nhttps://en.wikipedia.org/wiki/Coracohumeral_ligament","transverse-humeral-ligament":"The transverse humeral ligament (Brodie's ligament) forms a broad band bridging the lesser and greater tubercle of the humerus.\n\nIts attachments are limited superior to the epiphysial line.\n\nBy enclosing the canal of the bicipital groove (intertubercular groove), it functions to hold the long head of the biceps tendon within the bicipital groove.\n\nhttps://en.wikipedia.org/wiki/Transverse_humeral_ligament","articular-capsule-of-elbow-joint":"The elbow is the visible joint between the upper and lower parts of the arm.\n\nIt includes prominent landmarks such as the olecranon, the elbow pit, the lateral and medial epicondyles, and the elbow joint.\n\nThe elbow joint is the synovial hinge joint between the humerus in the upper arm and the radius and ulna in the forearm which allows the forearm and hand to be moved towards and away from the body.\n\nMedical Subject Headings defines the elbow specifically for humans and other primates, though the term is frequently used for the anterior joints of other mammals, such as dogs.\n\nThe name for the elbow in Latin is cubitus, and so the word cubital is used in some elbow-related terms, as in cubital nodes for example.\n\n== Structure ==\n\n=== Joint ===\n\nThe elbow joint has three different portions surrounded by a common joint capsule.\n\nThese are joints between the three bones of the elbow, the humerus of the upper arm, and the radius and the ulna of the forearm.\n\nWhen in anatomical position there are four main bony landmarks of the elbow.\n\nAt the lower part of the humerus are the medial and lateral epicondyles, on the side closest to the body (medial) and on the side away from the body (lateral) surfaces.\n\nThe third landmark is the olecranon found at the head of the ulna.\n\nThese lie on a horizontal line called the Hueter line.\n\nWhen the elbow is flexed, they form a triangle called the Hueter triangle, which resembles an equilateral triangle.\n\nAt the surface of the humerus where it faces the joint is the trochlea.\n\nIn most people, the groove running across the trochlea is vertical on the anterior side but it spirals off on the posterior side.\n\nThis results in the forearm being aligned to the upper arm during flexion, but forming an angle to the upper arm during extension — an angle known as the carrying angle.\n\nThe superior radioulnar joint shares the joint capsule with the elbow joint but plays no functional role at the elbow.\n\n==== Joint capsule ====\n\nThe elbow joint and the superior radioulnar joint are enclosed by a single fibrous capsule.\n\nThe capsule is strengthened by ligaments at the sides but is relatively weak in front and behind.On the anterior side, the capsule consists mainly of longitudinal fibres.\n\nHowever, some bundles among these fibers run obliquely or transversely, thickening and strengthening the capsule.\n\nThese bundles are referred to as the capsular ligament.\n\nDeep fibres of the brachialis muscle insert anteriorly into the capsule and act to pull it and the underlying membrane during flexion in order to prevent them from being pinched.On the posterior side, the capsule is thin and mainly composed of transverse fibres.\n\nA few of these fibres stretch across the olecranon fossa without attaching to it and form a transverse band with a free upper border.\n\nOn the ulnar side, the capsule reaches down to the posterior part of the annular ligament.\n\nThe posterior capsule is attached to the triceps tendon which prevents the capsule from being pinched during extension.\n\n==== Synovial membrane ====\nThe synovial membrane of the elbow joint is very extensive.\n\nOn the humerus, it extends up from the articular margins and covers the coronoid and radial fossae anteriorly and the olecranon fossa posteriorly.\n\nDistally, it is prolonged down to the neck of the radius and the superior radioulnar joint.\n\nIt is supported by the quadrate ligament below the annular ligament where it also forms a fold which gives the head of the radius freedom of movement.\n\nSeveral synovial folds project into the recesses of the joint.\n\nThese folds or plicae are remnants of normal embryonic development and can be categorized as either anterior (anterior humeral recess) or posterior (olecranon recess).\n\nA crescent-shaped fold is commonly present between the head of the radius and the capitulum of the humerus.\n\nOn the humerus there are extrasynovial fat pads adjacent to the three articular fossae.\n\nThese pads fill the radial and coronoid fossa anteriorly during extension, and the olecranon fossa posteriorly during flexion.\n\nThey are displaced when the fossae are occupied by the bony projections of the ulna and radius.\n\n==== Ligaments ====\n\nThe elbow, like other joints, has ligaments on either side.\n\nThese are triangular bands which blend with the joint capsule.\n\nThey are positioned so that they always lie across the transverse joint axis and are, therefore, always relatively tense and impose strict limitations on abduction, adduction, and axial rotation at the elbow.\n\nThe ulnar collateral ligament has its apex on the medial epicondyle.\n\nIts anterior band stretches from the anterior side of the medial epicondyle to the medial edge of the coronoid process, while the posterior band stretches from posterior side of the medial epicondyle to the medial side of the olecranon.\n\nThese two bands are separated by a thinner intermediate part and their distal attachments are united by a transverse band below which the synovial membrane protrudes during joint movements.\n\nThe anterior band is closely associated with the tendon of the superficial flexor muscles of the forearm, even being the origin of flexor digitorum superficialis.\n\nThe ulnar nerve crosses the intermediate part as it enters the forearm.The radial collateral ligament is attached to the lateral epicondyle below the common extensor tendon.\n\nLess distinct than the ulnar collateral ligament, this ligament blends with the annular ligament of the radius and its margins are attached near the radial notch of the ulna.\n\n=== Muscles ===\n\n==== Flexion ====\n\nThere are three main flexor muscles at the elbow:\n\nBrachialis acts exclusively as an elbow flexor and is one of the few muscles in the human body with a single function.\n\nIt originates low on the anterior side of the humerus and is inserted into the tuberosity of the ulna.\n\nBrachioradialis acts essentially as an elbow flexor but also supinates during extreme pronation and pronates during extreme supination.\n\nIt originates at the lateral supracondylar ridge distally on the humerus and is inserted distally on the radius at the styloid process.\n\nBiceps brachii is the main elbow flexor but, as a biarticular muscle, also plays important secondary roles as a stabiliser at the shoulder and as a supinator.\n\nIt originates on the scapula with two tendons: That of the long head on the supraglenoid tubercle just above the shoulder joint and that of the short head on the coracoid process at the top of the scapula.\n\nIts main insertion is at the radial tuberosity on the radius.Brachialis is the main muscle used when the elbow is flexed slowly.\n\nDuring rapid and forceful flexion all three muscles are brought into action assisted by the superficial forearm flexors originating at the medial side of the elbow.\n\nThe efficiency of the flexor muscles increases dramatically as the elbow is brought into midflexion (flexed 90°) — biceps reaches its angle of maximum efficiency at 80–90° and brachialis at 100–110°.\n\nActive flexion is limited to 145° by the contact between the anterior muscles of the upper arm and forearm, more so because they are hardened by contraction during flexion.\n\nPassive flexion (forearm is pushed against the upper arm with flexors relaxed) is limited to 160° by the bony projections on the radius and ulna as they reach to shallow depressions on the humerus; i.e. the head of radius being pressed against the radial fossa and the coronoid process being pressed against the coronoid fossa.\n\nPassive flexion is further limited by tension in the posterior capsular ligament and in triceps brachii.\n\nA small accessory muscle, so called epitrochleoanconeus muscle, may be found on the medial aspect of the elbow running from the medial epicondyle to the olecranon.\n\n==== Extension ====\n\nElbow extension is simply bringing the forearm back to anatomical position.\n\nThis action is performed by triceps brachii with a negligible assistance from anconeus.\n\nTriceps originates with two heads posteriorly on the humerus and with its long head on the scapula just below the shoulder joint.\n\nIt is inserted posteriorly on the olecranon.Triceps is maximally efficient with the elbow flexed 20–30°.\n\nAs the angle of flexion increases, the position of the olecranon approaches the main axis of the humerus which decreases muscle efficiency.\n\nIn full flexion, however, the triceps tendon is \"rolled up\" on the olecranon as on a pulley which compensates for the loss of efficiency.\n\nBecause triceps' long head is biarticular (acts on two joints), its efficiency is also dependent on the position of the shoulder.Extension is limited by the olecranon reaching the olecranon fossa, tension in the anterior ligament, and resistance in flexor muscles.\n\nForced extension results in a rupture in one of the limiting structures: olecranon fracture, torn capsule and ligaments, and, though the muscles are normally left unaffected, a bruised brachial artery.\n\n=== Blood supply ===\n\nThe arteries supplying the joint are derived from an extensive circulatory anastomosis between the brachial artery and its terminal branches.\n\nThe superior and inferior ulnar collateral branches of the brachial artery and the radial and middle collateral branches of the profunda brachii artery descend from above to reconnect on the joint capsule, where they also connect with the anterior and posterior ulnar recurrent branches of the ulnar artery; the radial recurrent branch of the radial artery; and the interosseous recurrent branch of the common interosseous artery.\n\nThe blood is brought back by vessels from the radial, ulnar, and brachial veins.\n\nThere are two sets of lymphatic nodes at the elbow, normally located above the medial epicondyle — the deep and superficial cubital nodes (also called epitrochlear nodes).\n\nThe lymphatic drainage at the elbow is through the deep nodes at the bifurcation of the brachial artery, the superficial nodes drain the forearm and the ulnar side of the hand.\n\nThe efferent lymph vessels from the elbow proceed to the lateral group of axillary lymph nodes.\n\n=== Nerve supply ===\n\nThe elbow is innervated anteriorly by branches from the musculocutaneous, median, and radial nerve, and posteriorly from the ulnar nerve and the branch of the radial nerve to anconeus.\n\n=== Development ===\n\nThe elbow undergoes dynamic development of ossification centers through infancy and adolescence, with the order of both the appearance and fusion of the apophyseal growth centers being crucial in assessment of the pediatric elbow on radiograph, in order to distinguish a traumatic fracture or apophyseal separation from normal development.\n\nThe order of appearance can be understood by the mnemonic CRITOE, referring to the capitellum, radial head, internal epicondyle, trochlea, olecranon, and external epicondyle at ages 1, 3, 5, 7, 9 and 11 years.\n\nThese apophyseal centers then fuse during adolescence, with the internal epicondyle and olecranon fusing last.\n\nThe ages of fusion are more variable than ossification, but normally occur at 13, 15, 17, 13, 16 and 13 years, respectively.\n\nIn addition, the presence of a joint effusion can be inferenced by the presence of the fat pad sign, a structure that is normally physiologically present, but pathologic when elevated by fluid, and always pathologic when posterior.\n\n== Function ==\n\nThe function of the elbow joint is to extend and flex the arm grasp and reach for objects.\n\nThe range of movement in the elbow is from 0 degrees of elbow extension to 150 of elbow flexion.\n\nMuscles contributing to function are all flexion (biceps brachii, brachialis, and brachioradialis) and extension muscles (triceps and anconeus).\n\nIn humans, the main task of the elbow is to properly place the hand in space by shortening and lengthening the upper limb.\n\nWhile the superior radioulnar joint shares joint capsule with the elbow joint, it plays no functional role at the elbow.With the elbow extended, the long axis of the humerus and that of the ulna coincide.\n\nAt the same time, the articular surfaces on both bones are located in front of those axes and deviate from them at an angle of 45°.\n\nAdditionally, the forearm muscles that originate at the elbow are grouped at the sides of the joint in order not to interfere with its movement.\n\nThe wide angle of flexion at the elbow made possible by this arrangement — almost 180° — allows the bones to be brought almost in parallel to each other.\n\n=== Carrying angle ===\n\nWhen the arm is extended, with the palm facing forward or up, the bones of the upper arm (humerus) and forearm (radius and ulna) are not perfectly aligned.\n\nThe deviation from a straight line occurs in the direction of the thumb, and is referred to as the \"carrying angle\" (visible in the right half of the picture, right).\n\nThe carrying angle permits the arm to be swung without contacting the hips.\n\nWomen on average have smaller shoulders and wider hips than men, which tends to produce a larger carrying angle (i.e., larger deviation from a straight line than that in men).\n\nThere is, however, extensive overlap in the carrying angle between individual men and women, and a sex-bias has not been consistently observed in scientific studies.\n\nThis could however be attributed to the very small sample sizes in those cited earlier studies.\n\nThe angle is greater in the dominant limb than the non-dominant limb of both sexes, suggesting that natural forces acting on the elbow modify the carrying angle.\n\nDevelopmental, aging and possibly racial influences add further to the variability of this parameter.\n\n== Pathology ==\n\nThe types of disease most commonly seen at the elbow are due to injury.\n\n=== Tendonitis ===\n\nTwo of the most common injuries at the elbow are overuse injuries: tennis elbow and golfer's elbow.\n\nGolfer's elbow involves the tendon of the common flexor origin which originates at the medial epicondyle of the humerus (the \"inside\" of the elbow).\n\nTennis elbow is the equivalent injury, but at the common extensor origin (the lateral epicondyle of the humerus).\n\n=== Fractures ===\n\nThere are three bones at the elbow joint, and any combination of these bones may be involved in a fracture of the elbow.\n\nPatients who are able to fully extend their arm at the elbow are unlikely to have a fracture (98% certainty) and an X-ray is not required as long as an olecranon fracture is ruled out.\n\nAcute fractures may not be easily visible on X-ray.\n\n=== Dislocation ===\n\nElbow dislocations constitute 10% to 25% of all injuries to the elbow.\n\nThe elbow is one of the most commonly dislocated joints in the body, with an average annual incidence of acute dislocation of 6 per 100,000 persons.\n\nAmong injuries to the upper extremity, dislocation of the elbow is second only to a dislocated shoulder.\n\nA full dislocation of the elbow will require expert medical attention to re-align, and recovery can take approximately 8–14 weeks.\n\n=== Infection ===\n\nInfection of the elbow joint (septic arthritis) is uncommon.\n\nIt may occur spontaneously, but may also occur in relation to surgery or infection elsewhere in the body (for example, endocarditis).\n\n=== Arthritis ===\n\nElbow arthritis is usually seen in individuals with rheumatoid arthritis or after fractures that involve the joint itself.\n\nWhen the damage to the joint is severe, fascial arthroplasty or elbow joint replacement may be considered.\n\n=== Bursitis ===\n\nOlecranon bursitis, tenderness, warmth, swelling, pain in both flexion and extension-in chronic case great flexion-is extremely painful.\n\n=== Elbow Pain ===\n\nElbow pain occurs when the tenderness of the tissues in the elbow become inflamed.\n\nFrequent exercise of the inflamed elbow will assist with healing.\n\n== Clinical significance ==\n\nElbow pain can occur for a multitude of reasons, including injury, disease, and other conditions.\n\nCommon conditions include tennis elbow, golfer's elbow, distal radioulnar joint rheumatoid arthritis, and cubital tunnel syndrome.\n\n=== Tennis elbow ===\n\nTennis elbow is a very common type of overuse injury.\n\nIt can occur both from chronic repetitive motions of the hand and forearm, and from trauma to the same areas.\n\nThese repetitions can injure the tendons that connect the extensor supinator muscles (which rotate and extend the forearm) to the olecranon process (also known as “the elbow”).\n\nPain occurs, often radiating from the lateral forearm.\n\nWeakness, numbness, and stiffness are also very common, along with tenderness upon touch.\nA non-invasive treatment for pain management is rest.\n\nIf achieving rest is an issue, a wrist brace can also be worn.\n\nThis keeps the wrist in flexion, thereby relieving the extensor muscles and allowing rest.\n\nIce, heat, ultrasound, steroid injections, and compression can also help alleviate pain.\n\nAfter the pain has been reduced, exercise therapy is important to prevent injury in the future.\n\nExercises should be low velocity, and weight should increase progressively.\n\nStretching the flexors and extensors is helpful, as are strengthening exercises.\n\nMassage can also be useful, focusing on the extensor trigger points.\n\n=== Golfer’s elbow ===\n\nGolfer's elbow is very similar to tennis elbow, but less common.\n\nIt is caused by overuse and repetitive motions like a golf swing.\n\nIt can also be caused by trauma.\n\nWrist flexion and pronation (rotating of the forearm) causes irritation to the tendons near the medial epicondyle of the elbow.\n\nIt can cause pain, stiffness, loss of sensation, and weakness radiating from the inside of the elbow to the fingers.\n\nRest is the primary intervention for this injury.\n\nIce, pain medication, steroid injections, strengthening exercises, and avoiding any aggravating activities can also help.\n\nSurgery is a last resort, and rarely used.\n\nExercises should focus on strengthening and stretching the forearm, and utilizing proper form when performing movements.\n\n=== Rheumatoid arthritis ===\n\nRheumatoid arthritis is a chronic disease that affects joints.\n\nIt is very common in the wrist, and is most common at the radioulnar joint.\n\nIt results in pain, stiffness, and deformities.\n\nThere are many different treatments for rheumatoid arthritis, and there is no one consensus for which methods are best.\n\nMost common treatments include wrist splints, surgery, physical and occupational therapy, and antirheumatic medication.\n\n=== Cubital tunnel syndrome ===\n\nCubital tunnel syndrome, more commonly known as ulnar neuropathy, occurs when the ulnar nerve is irritated and becomes inflamed.\n\nThis can often happen where the ulnar nerve is most superficial, at the elbow.\n\nThe ulnar nerve passes over the elbow, at the area known as the “funny bone”.\n\nIrritation can occur due to constant, repeated stress and pressure at this area, or from a trauma.\n\nIt can also occur due to bone deformities, and oftentimes from sports.\n\nSymptoms include tingling, numbness, and weakness, along with pain.\n\nFirst line pain management techniques include the use of nonsteroidal anti-inflammatory oral medicines.\n\nThese help to reduce inflammation, pressure, and irritation of the nerve and around the nerve.\n\nOther simple fixes include learning more ergonomically friendly habits that can help prevent nerve impingement and irritation in the future.\n\nProtective equipment can also be very helpful.\n\nExamples of this include a protective elbow pad, and an arm splint.\n\nMore serious cases often involve surgery, in which the nerve or the surrounding tissue is moved to relieve the pressure.\n\nRecovery from surgery can take awhile, but the prognosis is often a good one.\n\nRecovery often includes movement restrictions, and range of motion activities, and can last a few months (cubital and radial tunnel syndrome, 2).\n\n== Society and culture ==\n\nThe now obsolete length unit ell relates closely to the elbow.\n\nThis becomes especially visible when considering the Germanic origins of both words, Elle (ell, defined as the length of a male forearm from elbow to fingertips) and Ellbogen (elbow).\n\nIt is unknown when or why the second \"l\" was dropped from English usage of the word.\n\nThe ell as in the English measure could also be taken to come from the letter L, being bent at right angles, as an elbow.\n\nThe ell as a measure was taken as six handbreadths; three to the elbow and three from the elbow to the shoulder.\n\nAnother measure was the cubit (from cubital).\n\nThis was taken to be the length of a man's arm from the elbow to the end of the middle finger.\n\n== Other primates ==\n\nThough the elbow is similarly adapted for stability through a wide range of pronation-supination and flexion-extension in all apes, there are some minor difference.\n\nIn arboreal apes such as orangutans, the large forearm muscles originating on the epicondyles of the humerus generate significant transverse forces on the elbow joint.\n\nThe structure to resist these forces is a pronounced keel on the trochlear notch on the ulna, which is more flattened in, for example, humans and gorillas.\n\nIn knuckle-walkers, on the other hand, the elbow has to deal with large vertical loads passing through extended forearms and the joint is therefore more expanded to provide larger articular surfaces perpendicular to those forces.\n\nDerived traits in catarrhini (apes and Old World monkeys) elbows include the loss of the entepicondylar foramen (a hole in the distal humerus), a non-translatory (rotation-only) humeroulnar joint, and a more robust ulna with a shortened trochlear notch.\n\nThe proximal radioulnar joint is similarly derived in higher primates in the location and shape of the radial notch on the ulna; the primitive form being represented by New World monkeys, such as the howler monkey, and by fossil catarrhines, such as Aegyptopithecus.\n\nIn these taxa, the oval head of the radius lies in front of the ulnar shaft so that the former overlaps the latter by half its width.\n\nWith this forearm configuration, the ulna supports the radius and maximum stability is achieved when the forearm is fully pronated.\n\nhttps://en.wikipedia.org/wiki/Elbow","radial-collateral-ligament":"The radial collateral ligament (RCL), lateral collateral ligament (LCL), or external lateral ligament is a ligament in the elbow on the side of the radius.\n\n== Structure ==\n\nThe composition of the triangular ligamentous structure on the lateral side of the elbow varies widely between individuals and can be considered either a single ligament, in which case multiple distal attachments are generally mentioned and the annular ligament is described separately, or as several separate ligaments, in which case parts of those ligaments are often described as indistinguishable from each other.\n\nIn the latter case, the ligaments are collectively referred to as the lateral collateral ligament complex (LCLC), consisting of four ligaments:\n\n-the radial collateral ligament [proper] (RCL), from the lateral epicondyle to the annular ligament deep to the common extensor tendon\n-the lateral ulnar collateral ligament (LUCL), from the lateral epicondyle to the supinator crest on the ulna.\n\nNear the attachment on the humerus this ligament is normally indistinguishable from the RCL and can be considered the posterior portion of it.\n\nMartin 1958 described the distal part of the LUCL as \"a definite bundle which normally crosses the annular band and gains attachment to the supinator crest, frequently to a special tubercle on that crest\" but didn't name it.\n\nthe annular ligament (AL), from the posterior to the anterior margins of radial notch on the ulna, encircles the head of radius and holds it against the radial notch of ulna.\n\nthe accessory lateral collateral ligament (ALCL). from the inferior margin of the annular ligament to the supinator crest.\n\n== Clinical significance ==\n\nThe radial collateral ligament may be involved in lateral epicondylitis.\n\nhttps://en.wikipedia.org/wiki/Radial_collateral_ligament_of_elbow_joint","ulnar-collateral-ligament":"The ulnar collateral ligament (UCL) or internal lateral ligament is a thick triangular ligament at the medial aspect of the elbow uniting the distal aspect of the humerus to the proximal aspect of the ulna.\n\n== Structure ==\n\nIt consists of two portions, an anterior and posterior united by a thinner intermediate portion.\n\nNote that this ligament is also referred to as the medial collateral ligament and should not be confused with the lateral ulnar collateral ligament (LUCL).\n\nThe anterior portion, directed obliquely forward, is attached, above, by its apex, to the front part of the medial epicondyle of the humerus; and, below, by its broad base to the medial margin of the coronoid process of the ulna.\n\nThe posterior portion, also of triangular form, is attached, above, by its apex, to the lower and back part of the medial epicondyle; below, to the medial margin of the olecranon.\n\nBetween these two bands a few intermediate fibers descend from the medial epicondyle to blend with a transverse band which bridges across the notch between the olecranon and the coronoid process.\n\nThis ligament is in relation with the triceps brachii and flexor carpi ulnaris and the ulnar nerve, and gives origin to part of the flexor digitorum superficialis.\n\n== Injury ==\n\nDuring activities such as overhand baseball pitching, this ligament is subjected to extreme tension, which places the overhand-throwing athlete at risk for injury.\n\nAcute or chronic disruption and/or attenuation of the ulnar collateral ligament often result in medial elbow pain, valgus instability, neurologic deficiency, and impaired throwing performance.\n\nThere are both non-surgical and surgical treatment options.\n\nhttps://en.wikipedia.org/wiki/Ulnar_collateral_ligament_of_elbow_joint","annular-ligament-of-radius":"The annular ligament (orbicular ligament) is a strong band of fibers that encircles the head of the radius, and retains it in contact with the radial notch of the ulna.\n\nPer Terminologia Anatomica, the spelling is \"anular\", but the spelling \"annular\" is frequently encountered.\n\n== Anatomy ==\n\nThe annular ligament is attached by both its ends to the anterior and posterior margins of the radial notch of the ulna, together with which it forms the articular surface that surrounds the head and neck of the radius.\n\nThe ligament is strong and well defined, yet its flexibility permits the slightly oval head of the radius to rotate freely during pronation and supination.\n\nThe head of the radius is wider than the bone's neck, and, because the annular ligament embraces both, the radial head is \"trapped\" inside the ligament which thus acts to prevent distal displacement of the radius.\n\nIt helps to stabilise the proximal radial head, and the radioulnar joint.Superiorly, the ligament is supported by attachments to the radial collateral ligament and the fibrous capsule of the elbow joint.\n\nInferiorly, a few fibres attached to the neck of the radius support a fold of the synovial membrane without interfering with the movements at the joint.\n\nThe fibrocartilage on the upper part of the ligament is continuous with the hyaline cartilage of the radial notch.\n\nAt the posterior attachment the ligament widens to reach above and below the radial notch.\n\nA thickened band which extends from the inferior border of the annular ligament below the radial notch to the neck of the radius is known as the quadrate ligament.\n\n== Clinical significance ==\n\nChildren who have not finished fusing their proximal radial epiphyseal plate may suffer dislocations of this joint, called pulled elbow or Nursemaid's elbow.\n\nThis frequently happens when parents sharply jerk their children by their arms, e.g. the act of grabbing a child away from traffic.\n\nhttps://en.wikipedia.org/wiki/Annular_ligament_of_radius","quadrate-ligament":"In human anatomy, the quadrate ligament or ligament of Denucé is one of the ligaments of the proximal radioulnar joint in the upper forearm.\n\n== Structure ==\n\nThe quadrate ligament is a fibrous band attached to the inferior border of the radial notch on the ulna and to the neck of the radius.\n\nIts borders are strengthened by fibers from the upper border of the annular ligament.\n\nThe ligament is 11 mm (0.43 in) long, 8 mm (0.31 in) wide, and 1 mm (0.039 in) thick.\n\n== Function ==\n\nThe quadrate ligament reinforces the inferior part of the capsule of the elbow joint and contributes to joint stability by securing the proximal radius against the radial notch and by restricting excessive supination (10–20° restriction) and, to a lesser degree, pronation (5–8°).\n\n== History ==\n\nThe quadrate ligament was first described by the French anatomist Jean-Paul-Louis Denucé in 1854, but its function and even presence has been disputed in anatomical literature ever since.\n\nIt received little attention before Nomina Anatomica Parisiensia recognized it as a functional structure in 1955.\n\nMartin 1958, nevertheless, found no evidence of the ligament, and described it as \"nothing more than a thin fibrous layer\" of the joint capsule — somewhat in line with Denucé's note that the ligament could be considered a simple extension of the synovial recess or an extension of the annular ligament.\n\nSpinner & Kaplan 1970, on the other hand, described the ligament as having an anterior border denser and stronger than the posterior, with a thin central portion.\n\nThis description was, however, not corroborated by Tubbs et al. 2006 who, while recognizing the ligament's importance, found it to be of even thickness.\n\nhttps://en.wikipedia.org/wiki/Quadrate_ligament","articular-disc-of-distal-radio-ulnar-joint":"The radiocarpal joint or wrist joint is an ellipsoid joint formed by the radius and the triangular articular disc proximally and the proximal row of carpal bones distally.\n\nOn the other hand, the distal articular surface is made up of proximal surfaces of the scaphoid, triquetral and lunate bones.\n\nhttps://en.wikipedia.org/wiki/Wrist","palmar-radio-ulnar-ligament":"The palmar radio-ulnar ligament is a narrow band of fibers extending from the anterior margin of the ulnar notch of the radius to the front of the head of the ulna.\n\nIt provides stability to the distal radio-ulnar joint.","dorsal-radio-ulnar-ligament":"The dorsal radio-ulnar ligament connets posterior surfaces of the distal extremity the radius and of the head of ulna, taking part in the distal radio-ulnar joint.\n\nhttps://en.wikipedia.org/wiki/Dorsal_radioulnar_ligament","dorsal-intercarpal-ligaments":"The dorsal intercarpal ligament consists of a series of fibrous bands that extend transversely across the dorsal surfaces of the carpal bones, connecting them to each other.\n\nhttps://en.wikipedia.org/wiki/Dorsal_intercarpal_ligament","pisohamate-ligament":"The pisohamate ligament is a ligament in the hand.\n\nIt connects the pisiform to the hook of the hamate.\n\nIt is a prolongation of the tendon of the flexor carpi ulnaris.\nIt serves as part of the origin for the abductor digiti minimi.\n\nIt also forms the floor of the ulnar canal, a canal that allows the ulnar nerve and ulnar artery into the hand.\n\nhttps://en.wikipedia.org/wiki/Pisohamate_ligament","pisometacarpal-ligament":"The pisometacarpal ligament joins the pisiform to the base of the fifth metacarpal bone.\n\nIt is a continuation of the tendon of the flexor carpi ulnaris.\n\nhttps://en.wikipedia.org/wiki/Pisometacarpal_ligament","dorsal-carpometacarpal-ligaments":"The dorsal carpometacarpal ligaments, the strongest and most distinct carpometacarpal ligaments, connect the carpal and metacarpal bones on their dorsal surfaces.\n\nThe second metacarpal bone receives two fasciculi, one from the greater, the other from the lesser multangular.\n\nThe third metacarpal receives two, one each from the lesser multangular and capitate.\n\nThe fourth two, one each from the capitate and hamate.\n\nThe fifth receives a single fasciculus from the hamate, and this is continuous with a similar ligament on the volar surface, forming an incomplete capsule.\n\nhttps://en.wikipedia.org/wiki/Dorsal_carpometacarpal_ligaments","palmar-carpometacarpal-ligaments":"The Palmar carpometacarpal ligaments (or volar) are a series of bands on the palmar surface of the carpometacarpal joints that connect the carpal bones to the second through fifth metacarpal bones.\n\nThe second metacarpal is connected to the trapezium.\n\nThe third metacarpal is connected to the trapezium, to the capitate, and to the hamate.\n\nThe fourth and fifth metacarpals are connected to the hamate.\n\nThe palmar carpometacarpal ligaments have a somewhat similar arrangement to the dorsal carpometacarpal ligaments, with the exception of those of the third metacarpal, which are three in number:\n\n-a lateral one from the greater multangular, situated superficial to the sheath of the tendon of the Flexor carpi radialis;\n-an intermediate one from the capitate;\n-and a medial one from the hamate.\n\nhttps://en.wikipedia.org/wiki/Palmar_carpometacarpal_ligaments","dorsal-metacarpal-ligaments":"The dorsal metacarpal ligaments connect the metacarpal bone's bases with each other, passing transversely from one bone to the other on the dorsal surface.","palmar-metacarpal-ligaments":"The palmar metacarpal ligament serves as the connective tissue, bonding the metacarpal bones together, passing transversely from one bone to another.\n\nThey are slightly concave.","interosseous-metacarpal-ligaments":"The interosseous metacarpal ligaments (ligamenta metacarpalia interossea) connect their contiguous surfaces, just distal to their collateral articular facets.\n\nhttps://en.wikipedia.org/wiki/Intermetacarpal_joints","collateral-metacarpophalangeal-ligaments":"In human anatomy, the radial (RCL) and ulnar (UCL) collateral ligaments of the metacarpophalangeal joints (MCP) of the hand are the primary stabilisers of the MCP joints.\n\nThey have two parts: the cord-like collateral ligaments proper located more dorsally and the accessory collateral ligaments located more volarly.\n\nThey enable us to spread our fingers with an open hand but not with the hand closed into a fist.\n\nOrigin and insertion\n\nThe collateral ligaments originate on depressions on each side of the metacarpal heads dorsal to axis of rotation.\n\nFrom there, they extend obliquely and distally to their insertions onto tubercles at the base of the proximal phalanx.\n\nThe accessory collateral ligaments originate volar to the collateral ligaments and are inserted on the palmar plate.\nFunction\n\nDue to the relation between their insertions on the sides of the metacarpal head and the axis of rotation in the joint, the collateral ligaments are taut in flexion but lax in extension, while the accessory collateral ligaments are lax in flexion but taut in extension.\n\nThe collateral ligaments are lengthened 3–4 mm when the joint flexes 0-80° while the accessory collateral ligaments are shortened 1–2 mm.\n\nDuring hyperextension the accessory ligaments are lengthened while the proper ligaments are shortened.\n\nAs a result, the joint is stable during full flexion while the relaxed collateral ligaments allows lateral and rotation movements during extension.\n\nThe tendons of interosseous and lumbricales add to the lateral stability of the joint.\n\nhttps://en.wikipedia.org/wiki/Collateral_ligaments_of_metacarpophalangeal_joints","deep-transverse-metacarpal-ligament":"The deep transverse metacarpal ligament (also called the deep transverse palmar ligament) is a narrow fibrous band which runs across the palmar surfaces of the heads of the second, third, fourth and fifth metacarpal bones, connecting them together.\n\n== Structure ==\n\nThe deep transverse metacarpal ligament connects the palmar surfaces of the heads of the second, third, fourth, and fifth metacarpal bones.\n\nIt is blended with the palmar metacarpophalangeal ligaments.Its palmar surface is concave where the flexor tendons pass over it.\n\nBehind it, the tendons of the interosseous muscles of the hand pass to their insertions.\n\n== Clinical significance ==\n\nRarely, the deep transverse metacarpal ligament may rupture.\n\nhttps://en.wikipedia.org/wiki/Deep_transverse_metacarpal_ligament","collateral-interphalangeal-ligaments-of-hand":"On each side of the interphalangeal joints of the fingers are diagonally placed fibrous bands.\n\nThe proximal ends of the bands are near the dorsal phalanges of the hand and the distal ends of the bands are near the palmar margins of the digits.\n\nhttps://en.wikipedia.org/wiki/Collateral_ligament_of_interphalangeal_joints_of_hand","palmar-interphalangeal-ligaments":"Metacarpophalangeal joint and joints of digit.\n\nPalmar aspect.\n\nPalmar ligament labelled as volar ligament.\n\nThe palmar ligament is thinner and more flexible in its central-proximal part.\n\nOn both sides it is reinforced by the so-called check rein ligaments.\n\nThe accessory collateral ligaments (ACL) originate at the proximal phalanx and are inserted distally at the base of the middle phalanx below the collateral ligaments.\n\nThe accessory ligament and the proximal margin of the palmar plate are flexible and fold back upon themselves during flexion.\n\nThe flexor tendon sheaths are firmly attached to the proximal and middle phalanges by annular pulleys A2 and A4, while the A3 pulley and the proximal fibres of the C1 ligament attach the sheaths to the mobile volar ligament at the PIP joint.\n\nDuring flexion this arrangement produces a space at the neck of the proximal phalanx which is filled by the folding palmar plate.[2]\n\nThe palmar plate is supported by a ligament on either side of the joint called the collateral ligaments, which prevent deviation of the joint from side to side.\n\nThe ligaments can partially or fully tear and can avulse with a small fracture fragment when the finger is forced backwards into hyperextension.\n\nThis is called a \"palmar plate, or volar plate injury\".\n\nThe palmar plate forms a semi-rigid floor and the collateral ligaments the walls in a mobile box which moves together with the distal part of the joint and provides stability to the joint during its entire range of motion.\n\nBecause the palmar plate adheres to the flexor digitorum superficialis near the distal attachment of the muscle, it also increases the moment of flexor action.\n\nIn the PIP joint, extension is more limited because of the two so called check-rein ligaments, which attach the palmar plate to the proximal phalanx.\n\nhttps://en.wikipedia.org/wiki/Interphalangeal_joints_of_the_hand#Palmar_ligament","articular-capsule-of-radiocarpal-joint":"In human anatomy, the wrist is variously defined as\n\n(1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand;\n\n(2) the wrist joint or radiocarpal joint, the joint between the radius and the carpus and;\n\n(3) the anatomical region surrounding the carpus including the distal parts of the bones of the forearm and the proximal parts of the metacarpus or five metacarpal bones and the series of joints between these bones, thus referred to as wrist joints.\n\nThis region also includes the carpal tunnel, the anatomical snuff box, bracelet lines, the flexor retinaculum, and the extensor retinaculum.\n\nAs a consequence of these various definitions, fractures to the carpal bones are referred to as carpal fractures, while fractures such as distal radius fracture are often considered fractures to the wrist.\n\n== Structure ==\n\nThe distal radioulnar joint is a pivot joint located between the bones of the forearm, the radius and ulna.\n\nFormed by the head of the ulna and the ulnar notch of the radius, this joint is separated from the radiocarpal joint by an articular disk lying between the radius and the styloid process of the ulna.\n\nThe capsule of the joint is lax and extends from the inferior sacciform recess to the ulnar shaft.\n\nTogether with the proximal radioulnar joint, the distal radioulnar joint permits pronation and supination.\n\nThe radiocarpal joint or wrist joint is an ellipsoid joint formed by the radius and the articular disc proximally and the proximal row of carpal bones distally.\n\nThe carpal bones on the ulnar side only make intermittent contact with the proximal side — the triquetrum only makes contact during ulnar abduction.\n\nThe capsule, lax and un-branched, is thin on the dorsal side and can contain synovial folds.\n\nThe capsule is continuous with the midcarpal joint and strengthened by numerous ligaments, including the palmar and dorsal radiocarpal ligaments, and the ulnar and radial collateral ligaments.\n\nThe parts forming the radiocarpal joint are the lower end of the radius and under surface of the articular disk above; and the scaphoid, lunate, and triquetral bones below.\n\nThe articular surface of the radius and the undersurface of the articular disk form together with a transversely elliptical concave surface, the receiving cavity.\n\nThe superior articular surfaces of the scaphoid, lunate, and triquetrum form a smooth convex surface, the condyle, which is received into the concavity.Carpal bones of the hand:\n\nProximal: A=Scaphoid, B=Lunate, C=Triquetrum, D=Pisiform\n\nDistal: E=Trapezium, F=Trapezoid, G=Capitate, H=Hamate\n\nIn the hand proper a total of 13 bones form part of the wrist: eight carpal bones—scaphoid, lunate, triquetral, pisiform, trapezium, trapezoid, capitate, and hamate— and five metacarpal bones—the first, second, third, fourth, and fifth metacarpal bones.\n\nThe midcarpal joint is the S-shaped joint space separating the proximal and distal rows of carpal bones.\n\nThe intercarpal joints, between the bones of each row, are strengthened by the radiate carpal and pisohamate ligaments and the palmar, interosseous, and dorsal intercarpal ligaments.\n\nSome degree of mobility is possible between the bones of the proximal row while the bones of the distal row are connected to each other and to the metacarpal bones —at the carpometacarpal joints— by strong ligaments —the pisometacarpal and palmar and dorsal carpometacarpal ligament— that makes a functional entity of these bones.\n\nAdditionally, the joints between the bases of the metacarpal bones —the intermetacarpal articulations— are strengthened by dorsal, interosseous, and palmar intermetacarpal ligaments.\n\n=== Articulations ===\n\nThe radiocarpal, intercarpal, midcarpal, carpometacarpal, and intermetacarpal joints often intercommunicate through a common synovial cavity.\n\n==== Articular Surfaces ====\n\nIt has two articular surfaces named, proximal and distal articular surfaces respectively.\n\nThe proximal articular surface is made up of the lower end of the radius and a triangular articular disc of the inferior radio-ulnar joint.\n\nOn the other hand, the distal articular surface is made up of proximal surfaces of the scaphoid, triquetral and lunate bones.\n\n== Function ==\n\n=== Movement ===\n\nThe extrinsic hand muscles are located in the forearm where their bellies form the proximal fleshy roundness.\n\nWhen contracted, most of the tendons of these muscles are prevented from standing up like taut bowstrings around the wrist by passing under the flexor retinaculum on the palmar side and the extensor retinaculum on the dorsal side.\n\nOn the palmar side the carpal bones form the carpal tunnel, through which some of the flexor tendons pass in tendon sheaths that enable them to slide back and forth through the narrow passageway (see carpal tunnel syndrome).\n\nStarting from the mid-position of the hand, the movements permitted in the wrist proper are (muscles in order of importance):\n\nMarginal movements: radial deviation (abduction, movement towards the thumb) and ulnar deviation (adduction, movement towards the little finger).\n\nThese movements take place about a dorsopalmar axis (back to front) at the radiocarpal and midcarpal joints passing through the capitate bone.\n\n-Radial abduction (up to 20°): extensor carpi radialis longus, abductor pollicis longus, extensor pollicis longus, flexor carpi radialis, flexor pollicis longus\n\n-Ulnar adduction (up to 30°): extensor carpi ulnaris, flexor carpi ulnaris, extensor digitorum, extensor digiti minimi\n\n-Movements in the plane of the hand: flexion (palmar flexion, tilting towards the palm) and extension (dorsiflexion, tilting towards the back of the hand).\n\nThese movements take place through a transverse axis passing through the capitate bone.\n\nPalmar flexion is the most powerful of these movements because the flexors, especially the finger flexors, are considerably stronger than the extensors.\n\n-Extension (up to 60°): extensor digitorum, extensor carpi radialis longus, extensor carpi radialis brevis, extensor indicis, extensor pollicis longus, extensor digiti minimi, extensor carpi ulnaris\n\n-Palmar flexion (up to 70°): flexor digitorum superficialis, flexor digitorum profundus, flexor carpi ulnaris, flexor pollicis longus, flexor carpi radialis, abductor pollicis longus.\n\nIntermediate or combined movementsHowever, movements at the wrist can not be properly described without including movements in the distal radioulnar joint in which the rotary actions of supination and pronation occur and this joint is therefore normally regarded as part of the wrist.\n\n== Clinical significance ==\n\nWrist pain has a number of causes, including carpal tunnel syndrome, ganglion cyst, tendinitis, and osteoarthritis.\n\nTests such as Phalen's test involve palmarflexion at the wrist.\nThe hand may deviate at the wrist in some conditions, such as rheumatoid arthritis.\n\nOssification of the bones around the wrist is one indicator used in taking a bone age.\n\nA wrist fracture usually means a fracture of the distal radius.\n\n== History ==\n\n=== Etymology ===\n\nThe English word \"wrist\" is etymologically derived from the ancient German word wristiz from which are derived modern German rist (\"instep\", \"wrist\") and modern Swedish vrist (\"instep\", \"ankle\").\n\nThe base writh- and its variants are associated with Old English words \"wreath\", \"wrest\", and \"writhe\".\n\nThe wr- sound of this base seems originally to have been symbolic of the action of twisting.\n\nhttps://en.wikipedia.org/wiki/Wrist","radioscaphocapitate-ligament":"The radioscaphocapitate ligament, together with the radiolunate, radiotriquetral form the palmar radiocarpal ligament.\n\nThis broad membranous band is attached above to the distal end of the radius, and passes downward to the scaphoid, lunate, triquetrum and capitate of the carpal bones in the wrist.\n\nIn addition to this broad membrane, there is a rounded fasciculus, superficial to the rest, which reaches from the base of the styloid process of the ulna to the lunate and triangular bones.\n\n==Perforations==\n\nThe ligament is perforated by apertures for the passage of vessels,\n\n==Relations==\n\nIt is in relation, in front, with the tendons of the flexor digitorum profundus and flexor pollicis longus.\n\nBehind, it is closely adherent to the anterior border of the articular disk of the distal radioulnar articulation.\n\n==Components==\n\nSome sources break down the components of the ligament as follows: radiolunate, radiocapitate, radiotriquetral, and radioscaphoid.\n\nOther sources combine the radioscaphoid and radiocapitate into a \"radioscaphocapitate\".","ulnocapitate-ligament":"Together with the ulnolunate and ulnotriquetral ligaments, they form the palmar ulnocarpal ligament, which is one of the major ligaments of the radiocarpal joint, with the\n\n-dorsal radiocarpal ligament\n-palmar radiocarpal ligament\n-dorsal ulnocarpal ligament\n\nand the\n-ulnar collateral ligament of wrist joint\n-radial collateral ligament of wrist joint.\n\nhttps://en.wikipedia.org/wiki/Palmar_ulnocarpal_ligament","ulnopisiform-ligament":"The ulnopisiform ligament if a part of the palmar ulnocarpal ligament, as the:\n\n-Ulnocapitate ligament\n-Ulnolunate ligament\n-Ulnotriquetral ligament\n\nThe palmar ulnocarpal ligament is one of the major ligaments of the radiocarpal joint (wrist) as the:\n\n-Dorsal radiocarpal ligament\n-Palmar radiocarpal ligament\n-Dorsal ulnocarpal ligament\n\nand the\n-Ulnar collateral ligament of wrist joint\n-Radial collateral ligament of wrist joint","ulnotriquetral-ligament":"Together with the ulnocapitate ligament, the ulnolunate ligament and the ulnopisiform ligament, they form the palmar ulnocarpal ligament.\n\nThe palmar ulnocarpal ligament is one of the major ligaments of the wrist joint, as the:\n\n-dorsal radiocarpal ligament\n-palmar radiocarpal ligament\n-dorsal ulnocarpal ligament\n-palmar ulnocarpal ligament\n\nand the\n-ulnar collateral ligament of wrist joint\n-radial collateral ligament of wrist joint","ulnolunate-ligament":"The ulnolunate ligament if a part of the palmar ulnocarpal ligament, as the:\n\n-Ulnocapitate ligament\n-Ulnolunate ligament\n-Ulnotriquetral ligament\n-Ulnopisiform ligament\n\nThe palmar ulnocarpal ligament is one of the major ligaments of the radiocarpal joint (wrist) as the:\n\n-Dorsal radiocarpal ligament\n-Palmar radiocarpal ligament\n-Dorsal ulnocarpal ligament\n\nand the\n-Ulnar collateral ligament of wrist joint\n-Radial collateral ligament of wrist joint","dorsal-radiocarpal-ligament":"The dorsal radiocarpal ligament (posterior ligament) is less thick and strong than its volar (anterior) counterpart, and has a proximal attachment to the posterior border of the distal radius.\n\nIts fibers run medially and inferiorly to form a distal attachment at the dorsal surfaces of the scaphoid (navicular bone of the hand), lunate, and triquetral.\n\nThe fibres of the dorsal radiocarpal ligament blend with those of the dorsal intercarpal ligament.\n\nIt is in relation, behind, with the Extensor tendons of the fingers; in front, it is blended with the articular disk.\n\nhttps://en.wikipedia.org/wiki/Dorsal_radiocarpal_ligament","ulnar-collateral-ligament-of-wrist-joint":"The ulnar collateral ligament (internal lateral ligament, ulnar carpal collateral ligament or ulnar collateral ligament of the wrist joint) is a rounded cord, attached above to the end of the styloid process of the ulna, and dividing below into two fasciculi, one of which is attached to the medial side of the triquetral bone, the other to the pisiform and flexor retinaculum.\n\nhttps://en.wikipedia.org/wiki/Ulnar_carpal_collateral_ligament","radial-collateral-ligament-of-wrist-joint":"The radial collateral ligament (external lateral ligament, radial carpal collateral ligament) extends from the tip of the styloid process of the radius and attaches to the radial side of the scaphoid (formerly Navicular bone of the hand), immediately adjacent to its proximal articular surface and some fibres extend to the lateral side of the trapezium (greater multangular bone).\n\nIt is in relation with the radial artery, which separates the ligament from the tendons of the Abductor pollicis longus and Extensor pollicis brevis.\n\nThe radial collateral ligament's role is to limit ulnar deviation at the wrist.\n\nhttps://en.wikipedia.org/wiki/Radial_collateral_ligament_of_wrist_joint","dorsal-ulnocarpal-ligament":"The dorsal ulnocarpal ligament is one of the major ligament of the radiocarpal joint (wrist joint), together with the:\n\n-Dorsal radiocarpal ligament\n-Palmar radiocarpal ligament\n-Palmar ulnocarpal ligament\n\nand the\n-Ulnar collateral ligament of wrist joint\n-Radial collateral ligament of wrist joint","radiate-carpal-ligament":"The radiate carpal ligament is a group of about seven fibrous bands which diverge in all directions on the palmar surface of the carpal bones.\n\nThe majority of the bands radiate from the capitate to the scaphoid, lunate, and triquetral bones.\n\nhttps://en.wikipedia.org/wiki/Radiate_carpal_ligament","obturator-membrane":"The obturator membrane is a thin fibrous sheet, which almost completely closes the obturator foramen.\n\nIts fibers are arranged in interlacing bundles mainly transverse in direction; the uppermost bundle is attached to the obturator tubercles and completes the obturator canal for the passage of the obturator vessels and nerve.\n\nThe membrane is attached to the sharp margin of the obturator foramen except at its lower lateral angle, where it is fixed to the pelvic surface of the inferior ramus of the ischium, i. e., within the margin.\n\nBoth obturator muscles are connected with this membrane.\n\nhttps://en.wikipedia.org/wiki/Obturator_membrane","sacrotuberous-ligament":"The sacrotuberous ligament (great or posterior sacrosciatic ligament) is situated at the lower and back part of the pelvis.\n\nIt is flat, and triangular in form; narrower in the middle than at the ends.\n\n== Structure ==\n\nIt runs from the sacrum (the lower transverse sacral tubercles, the inferior margins sacrum and the upper coccyx) to the tuberosity of the ischium.\nIt is a remnant of part of Biceps femoris muscle.\nThe sacrotuberous ligament is attached by its broad base to the posterior superior iliac spine, the posterior sacroiliac ligaments (with which it is partly blended), to the lower transverse sacral tubercles and the lateral margins of the lower sacrum and upper coccyx.\n\nIts oblique fibres descend laterally, converging to form a thick, narrow band that widens again below and is attached to the medial margin of the ischial tuberosity.\n\nIt then spreads along the ischial ramus as the falciform process, whose concave edge blends with the fascial sheath of the internal pudendal vessels and pudendal nerve.\n\nThe lowest fibres of gluteus maximus are attached to the posterior surface of the ligament; superficial fibres of the lower part of the ligament continue into the tendon of biceps femoris.\n\nThe ligament is pierced by the coccygeal branches of the inferior gluteal artery, the perforating cutaneous nerve and filaments of the coccygeal plexus.\n\n=== Variation ===\n\nThe membranous falciform process of the sacrotuberous ligament was found to be absent in 13% of cadavers.\n\nWhen present it extends towards the ischioanal fossa travelling along the ischial ramus and fusing with the obturator fascia.\nThe lower border of the ligament was found to be directly continuous with the tendon of origin of the long head of the Biceps femoris in approximately 50% of subjects.\n\nBiceps femoris could therefore act to stabilise the sacroiliac joint via the sacrotuberous ligament.\n\n== Function ==\n\nThe sacrotuberous ligament contains the coccygeal branch of the inferior gluteal artery.\n\n== Clinical significance ==\n\nIf the pudendal nerve becomes entrapped between this ligament and the sacrospinous ligament causing perineal pain, the sacrotuberous ligament is surgically severed to relieve the pain.\n\nhttps://en.wikipedia.org/wiki/Sacrotuberous_ligament","sacrospinous-ligament":"The sacrospinous ligament (small or anterior sacrosciatic ligament) is a thin, triangular ligament in the human pelvis.\n\nThe base of the ligament is attached to the outer edge of the sacrum and coccyx, and the tip of the ligament attaches to the spine of the ischium, a bony protuberance on the human pelvis.\n\nIts fibres are intermingled with the sacrotuberous ligament.\n\n== Structure ==\n\nThe sacrotuberous ligament passes behind the sacrospinous ligament.\n\nIn its entire length, the sacrospinous ligament covers the equally triangular coccygeus muscle, to which its closely connected.\n\n== Function ==\n\nThe presence of the ligament in the greater sciatic notch creates an opening (foramen), the greater sciatic foramen, and also converts the lesser sciatic notch into the lesser sciatic foramen.\n\nThe greater sciatic foramen lies above the ligament, and the lesser sciatic foramen lies below it.\n\nThe pudendal vessels and nerve pass behind the sacrospinous ligament directly medially and inferiorly to the ischial spine.\n\nThe inferior gluteal artery, from a branch of the internal iliac artery, pass behind the sciatic nerve and the sacrospinous ligament and is left uncovered in a small opening above the top of the sacrospinous ligament.\n\nThe coccygeal branch of the inferior gluteal artery passes behind the mid-portion of the sacrospinous ligament and pierces the sacrotuberous ligament at multiple locations.\n\nThe main body of the inferior gluteal artery leaves the pelvis posteriorly to the upper border of the sacrospinous ligament, to follow the inferior portion of the sciatic nerve out of the greater sciatic foramen.\n\nThe main function of the ligament is to prevent rotation of the ilium past the sacrum.\n\nLaxity of this ligament and the sacrotuberous ligament allows this rotation to occur.\n\nStresses to these ligaments occur most often when leaning forward or getting out of a chair.\n\n== Clinical significance ==\n\nVaginal prolapse or uterine prolapse may occur in women when other pelvic ligaments and supportive structures are weakened.\n\nOne treatment is sacrospinous fixation.\n\nIn this surgery, the apex of the vagina is sutured to the sacrospinous ligament, which may offer a sturdier support than weakened pelvic ligaments, ideally preventing further prolapse.\n\nhttps://en.wikipedia.org/wiki/Sacrospinous_ligament","iliolumbar-ligament":"The iliolumbar ligament is a strong ligament passing from the tip of the transverse process of the fifth lumbar vertebra to the posterior part of the inner lip of the iliac crest (upper margin of ilium).\n\n== Course ==\n\nIt forms the thickened lower border of two of the layers of the thoracolumbar fascia.\n\nOccasionally, a small ligamentous band stretches from the tip of the transverse process of the fourth vertebra down to the iliac crest behind the main ligament.\n\nUsually, fibrous strands are found between this latter process and the iliac crest, but these are only considered a true ligament when dense enough.\n\nIt radiates as it passes laterally and is attached by two main bands to the pelvis.\n\nThe lower bands run to the base of the sacrum, blending with the anterior sacroiliac ligament; the upper is attached to the crest of the ilium immediately in front of the sacroiliac articulation, and is continuous above with the lumbodorsal fascia.\n\nIn front, it is in relation with the psoas major; behind, with the muscles occupying the vertebral groove; above, with the Quadratus lumborum.\n\n== Function ==\n\nThe iliolumbar ligament strengthens the lumbosacral joint assisted by the lateral lumbosacral ligament, and, like all other vertebral joints, by the posterior and anterior longitudinal ligaments, the ligamenta flava, and the interspinous and supraspinous ligaments.\n\nIt reduces the range of movement of the lumbosacral joint.\n\nhttps://en.wikipedia.org/wiki/Iliolumbar_ligament","pubic-symphysis":"The pubic symphysis is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones.\n\nIt is in front of and below the urinary bladder.\n\nIn males, the suspensory ligament of the penis attaches to the pubic symphysis.\n\nIn females, the pubic symphysis is close to the clitoris.\n\nIn most adults it can be moved roughly 2 mm and with 1 degree rotation.\n\nThis increases for women at the time of childbirth.\n\nThe name comes from the Greek word symphysis, meaning 'growing together'.\n\n== Structure ==\n\nThe pubic symphysis is a nonsynovial amphiarthrodial joint.\n\nThe width of the pubic symphysis at the front is 3–5 mm greater than its width at the back.\n\nThis joint is connected by fibrocartilage and may contain a fluid-filled cavity; the center is avascular, possibly due to the nature of the compressive forces passing through this joint, which may lead to harmful vascular disease.\n\nThe ends of both pubic bones are covered by a thin layer of hyaline cartilage attached to the fibrocartilage.\n\nThe fibrocartilaginous disk is reinforced by a series of ligaments.\n\nThese ligaments cling to the fibrocartilaginous disk to the point that fibers intermix with it.\n\nTwo such ligaments are the superior pubic ligament and the inferior pubic ligament, which provide the most stability; the anterior and posterior ligaments are weaker.\n\nThe strong and thicker superior ligament is reinforced by the tendons of the rectus abdominis muscle, the abdominal external oblique muscle, the gracilis muscle, and by muscles of the hip.\n\nThe superior pubic ligament connects together the two pubic bones superiorly, extending laterally as far as the pubic tubercles.\n\nThe inferior ligament in the pubic arch is also known as the arcuate pubic ligament or subpubic ligament; it is a thick, triangular arch of ligamentous fibers, connecting together the two pubic bones below, and forming the upper boundary of the pubic arch.\n\nAbove, it is blended with the interpubic fibrocartilaginous lamina; laterally, it is attached to the inferior rami of the pubic bones; below, it is free, and is separated from the fascia of the urogenital diaphragm by an opening through which the deep dorsal vein of the penis passes into the pelvis.\n\n=== Fibrocartilage ===\n\nFibrocartilage is composed of small, chained bundles of thick, clearly defined, type I collagen fibers.\n\nThis fibrous connective tissue bundles have cartilage cells between them; these cells to a certain extent resemble tendon cells.\n\nThe collagenous fibers are usually placed in an orderly arrangement parallel to tension on the tissue.\n\nIt has a low content of glycosaminoglycans (2% of dry weight).\n\nGlycosaminoglycans are long, unbranched polysaccharides (relatively complex carbohydrates) consisting of repeating disaccharide units.\n\nFibrocartilage does not have a surrounding perichondrium.\n\nPerichondrium surrounds the cartilage of developing bone; it has a layer of dense, irregular connective tissue and functions in the growth and repair of cartilage.\n\n=== Hyaline cartilage ===\n\nHyaline cartilage is the white, shiny gristle at the end of long bones.\n\nThis cartilage has poor healing potential, and efforts to induce it to repair itself frequently end up with a similar, but poorer fibrocartilage.\n\n=== Development ===\n\nIn the newborn, the symphysis pubis is 9–10 mm in width, with thick cartilaginous end-plates.\n\nBy mid-adolescence the adult size is achieved.\n\nDuring adulthood the end-plates decrease in width to a thinner layer.\n\nDegeneration of the symphysis pubis accompanies aging and postpartum.\n\nWomen have a greater thickness of this pubic disc which allows more mobility of the pelvic bones, hence providing a greater diameter of pelvic cavity during childbirth.\n\n== Function ==\n\nAnalysis of the pelvis shows the skinny regions function as arches, transferring the weight of the upright trunk from the sacrum to the hips.\n\nThe symphysis pubis connects these two weight-bearing arches, and the ligaments that surround this pelvic region maintain the mechanical integrity.\n\nThe main motions of the symphysis pubis are superior/inferior glide and separation/compression.\n\nThe functions of the joint are to absorb shock during walking and allow delivery of a baby.\n\n== Clinical significance ==\n\n=== Injury ===\n\nThe pubic symphysis widens slightly when the legs are stretched far apart.\n\nIn sports where these movements are often performed, the risk of a pubic symphysis blockage is high, in which case, after completion of the movement, the bones at the symphysis do not realign correctly and can get jammed in a dislocated position.\n\nThe resulting pain can be severe, especially when further strain is put upon the affected joint.\n\nIn most cases, the joint can only be successfully reduced into its normal position by a trained medical professional.\n\n=== Disease ===\n\nMetabolic diseases, such as renal osteodystrophy, produce widening, while ochronosis results in calcific deposits in the symphysis.\n\nInflammatory diseases, such as ankylosing spondylitis, result in bony fusion of the symphysis.\n\nOsteitis pubis, the most common inflammatory disease in this area, is treated with anti-inflammatory medication and rest.\n\nDegenerative joint disease of the symphysis, which can cause groin pain, results from instability or from abnormal pelvic mechanics.\n\nSymphysiolysis is separation or slipping of the symphysis.\n\nIt has been estimated to occur in 0.2% of pregnancies.\n\n=== Pregnancy ===\n\nDuring pregnancy in the human, hormones such as relaxin remodel this ligamentous capsule allowing the pelvic bones to be more flexible for delivery.\n\nThe gap of the symphysis pubis, normally is 4–5 mm but during pregnancy there will be an increase of at least 2–3 mm, therefore, it is considered that a total width of up to 9 mm between the two bones is normal for a pregnant woman.\n\nThe symphysis pubis separates to some degree during childbirth.\n\nIn some women this separation can become a diastasis of the symphysis pubis.\n\nThe diastasis could be the result of a rapid birth, or a forceps delivery, or may be a prenatal condition.\n\nA diastasis of the symphysis pubis is a cause of pelvic girdle pain (PGP).\n\nOverall, about 45% of all pregnant women and 25% of all women postpartum suffer from PGP.\n\n=== Symphysiotomy ===\n\nSymphysiotomy is a surgical procedure in which the cartilage of the pubic symphysis is divided to widen the pelvis allowing childbirth when there is a mechanical problem.\n\nIt allows the safe delivery of the fetus where Caesarean section is not an option.\n\nSymphysiotomy is suggested for woman in isolated areas experiencing obstructed labor where other medical intervention is unavailable.\n\nThis practice was carried out in Europe before the introduction of the Caesarean section.\n\nHistorically, during obstructed labor, the skull of the fetus was also, at least occasionally, crushed in order to further facilitate the delivery.\n\n== Society and culture ==\n\n=== Use in forensic anthropology ===\n\nPubic symphyses have importance in the field of forensic anthropology, as they can be used to estimate the age of adult skeletons.\n\nThroughout life, the surfaces are worn at a fairly predictable rate.\n\nBy examining the wear of the pubic symphysis, it is possible to estimate the age of the person at death.\n\nhttps://en.wikipedia.org/wiki/Pubic_symphysis","interpubic-disc":"The disc of fibrocartilage that unites the pubic bones of the coxal bones at the pubic symphysis, closing the pelvic girdle.\n\nThe pubic symphysis is a nonsynovial amphiarthrodial joint.\n\nThe width of the pubic symphysis at the front is 3–5 mm greater than its width at the back.\n\nThis joint is connected by fibrocartilage and may contain a fluid-filled cavity; the center is avascular, possibly due to the nature of the compressive forces passing through this joint, which may lead to harmful vascular disease.\n\nThe ends of both pubic bones are covered by a thin layer of hyaline cartilage attached to the fibrocartilage.\n\nThe fibrocartilaginous disk is reinforced by a series of ligaments.\n\nThese ligaments cling to the fibrocartilaginous disk to the point that fibers intermix with it.","inferior-pubic-ligament":"SUPERIOR PUBIC LIGAMENT\n\nThe superior pubic ligament and the inferior pubic ligament provide stability to the pubic symphysis; the anterior and posterior ligaments are weaker.\n\nThe inferior ligament in the pubic arch is also known as the arcuate pubic ligament or subpubic ligament; it is a thick, triangular arch of ligamentous fibers, connecting together the two pubic bones below, and forming the upper boundary of the pubic arch.\n\nBelow, it is free, and is separated from the fascia of the urogenital diaphragm by an opening through which the deep dorsal vein of the penis passes into the pelvis.\n\nhttps://en.wikipedia.org/wiki/Pubic_symphysis","superior-pubic-ligament":"The superior pubic ligament and the inferior pubic ligament provide stability to the pubic symphysis; the anterior and posterior ligaments are weaker.\n\nThe strong and thicker superior ligament is reinforced by the tendons of the rectus abdominis muscle, the abdominal external oblique muscle, the gracilis muscle, and by muscles of the hip.\n\nThe superior pubic ligament connects together the two pubic bones superiorly, extending laterally as far as the pubic tubercles.\n\nAbove, it is blended with the interpubic fibrocartilaginous lamina; laterally, it is attached to the inferior rami of the pubic bones; below, it is free, and is separated from the fascia of the urogenital diaphragm by an opening through which the deep dorsal vein of the penis passes into the pelvis.\n\nhttps://en.wikipedia.org/wiki/Pubic_symphysis","triradiate-cartilage":"The triradiate cartilage (in Latin cartilago ypsiloformis) is the 'Y'-shaped epiphyseal plate between the ilium, ischium and pubis to form the acetabulum of the os coxae.\n\n===Human development===\n\nIn children, the triradiate cartilage closes at an approximate bone age of 12 years for girls and 14 years for boys.\n\n===Clinical use===\n\nEvaluating the position of the triradiate cartilage on an AP radiograph of the pelvis with both Perkin's line and Hilgenreiner's line can help establish a diagnosis of developmental dysplasia of the hip.\n\nhttps://en.wikipedia.org/wiki/Triradiate_cartilage","anterior-sacro-iliac-ligament":"The anterior sacroiliac ligament consists of numerous thin bands, which connect the anterior surface of the lateral part of the sacrum to the margin of the auricular surface of the ilium and to the preauricular sulcus.","posterior-sacro-iliac-ligament":"The posterior sacroiliac ligament is situated in a deep depression between the sacrum and ilium behind; it is strong and forms the chief bond of union between the bones.\n\nIt consists of numerous fasciculi, which pass between the bones in various directions.\n\nThe upper part (short posterior sacroiliac ligament) is nearly horizontal in direction, and pass from the first and second transverse tubercles on the back of the sacrum to the tuberosity of the ilium.\n\nThe lower part (long posterior sacroiliac ligament) is oblique in direction; it is attached by one extremity to the third transverse tubercle of the back of the sacrum, and by the other to the posterior superior spine of the ilium.\n\nhttps://en.wikipedia.org/wiki/Posterior_sacroiliac_ligament","interosseous-sacro-iliac-ligament":"The interosseous sacroiliac ligament, also known as the axial interosseous ligament, is a ligament of the sacroiliac joint that lies deep to the posterior ligament.\n\nIt connects the tuberosities of the sacrum and the ilium of the pelvis.\n\n== Structure ==\n\nThe interosseous sacroiliac ligament consists of a series of short, strong fibers connecting the tuberosities of the sacrum and ilium.\n\nIt is one of the strongest ligaments in the body.\n\n== Function ==\n\nThe major function of the interosseous sacroiliac ligament is to keep the sacrum and ilium together.\n\nThis prevents abduction or distraction of the sacroiliac joint.\n\nIt also helps to bear the weight of the thorax, upper limbs, head, and neck.\n\nThis is performed by the nearly horizontal direction of the fibers running perpendicular from the sacrum to the ilium.\n\nhttps://en.wikipedia.org/wiki/Interosseous_sacroiliac_ligament","anterior-tibiofibular-ligament":"The anterior ligament of the lateral malleolus (anterior tibiofibular ligament or anterior inferior ligament) is a flat, trapezoidal band of fibers, broader below than above, which extends obliquely downward and lateralward between the adjacent margins of the tibia and fibula, on the front aspect of the syndesmosis.\nIt is in relation, in front, with the fibularis tertius, the aponeurosis of the leg, and the integument; behind, with the interosseous ligament; and lies in contact with the cartilage covering the talus.\n\n== Additional images ==\n\nhttps://en.wikipedia.org/wiki/Anterior_tibiofibular_ligament","posterior-tibiofibular-ligament":"The posterior ligament of the lateral malleolus (posterior tibiofibular ligament, posterior inferior ligament).\n\nIt is smaller than the anterior ligament of the lateral malleolus and is disposed in a similar manner on the posterior surface of the syndesmosis.\n\nIt connects the tibia and fibular on the inferior part of both bones.\n\nhttps://en.wikipedia.org/wiki/Posterior_tibiofibular_ligament","transverse-tibiofibular-ligament":"This inferior transverse ligament of the tibiofibular syndesmosis is a connective tissue structure in the lower leg that lies in front of the posterior ligament.\n\nIt is a strong, thick band, of yellowish fibers which passes transversely across the back of the ankle joint, from the lateral malleolus to the posterior border of the articular surface of the tibia, almost as far as its malleolar process.\n\nThis ligament projects below the margin of the bones, and forms part of the articulating surface for the talus.\n\nhttps://en.wikipedia.org/wiki/Inferior_transverse_ligament_of_the_tibiofibular_syndesmosis","interosseous-membrane-of-leg":"The interosseous membrane of the leg (middle tibiofibular ligament) extends between the interosseous crests of the tibia and fibula, helps stabilize the Tib-Fib relationship and separates the muscles on the front from those on the back of the leg.\n\nIt consists of a thin, aponeurotic joint lamina composed of oblique fibers, which for the most part run downward and lateralward; some few fibers, however, pass in the opposite direction.\nIt is broader above than below.\n\nIts upper margin does not quite reach the tibiofibular joint, but presents a free concave border, above which is a large, oval aperture for the passage of the anterior tibial vessels to the front of the leg.\n\nIn its lower part is an opening for the passage of the anterior peroneal vessels.\n\nIt is continuous below with the interosseous ligament of the tibiofibular syndesmosis, and presents numerous perforations for the passage of small vessels.\n\nIt is in relation, in front, with the Tibialis anterior, Extensor digitorum longus, Extensor hallucis proprius, Peronæus tertius, and the anterior tibial vessels and deep peroneal nerve; behind, with the Tibialis posterior and Flexor hallucis longus.\n\nhttps://en.wikipedia.org/wiki/Interosseous_membrane_of_leg","transverse-part-of-iliofemoral-ligament":"Lateral segment with an oblique direction.\n\nIt limits the external rotation and the abduction.","transverse-acetabular-ligament":"The transverse acetabular ligament (transverse ligament) is a portion of the acetabular labrum, though differing from it in having no cartilage cells among its fibers.\nIt consists of strong, flattened fibers, which cross the acetabular notch, and convert it into a foramen through which the nutrient vessels enter the joint.\n\nIt is an intra-articular structure of the hip.\n\n== Function ==\n\nThe transverse acetabular ligament prevents inferior displacement of head of femur.\n\n== Additional Images ==\n\nhttps://en.wikipedia.org/wiki/Transverse_acetabular_ligament","acetabular-labrum":"The acetabular labrum (glenoidal labrum of the hip joint or cotyloid ligament in older texts) is a ring of cartilage that surrounds the acetabulum of the hip.\n\nThe anterior portion is most vulnerable when the labrum tears.\nIt provides an articulating surface for the acetabulum, allowing the head of the femur to articulate with the pelvis.\n\n== Acetabular labrum tear ==\n\n=== Mechanisms of Injury ===\n\nIt is estimated that 75% of acetabular labrum tears have an unknown cause.\n\nTears of the labrum have been credited to a variety of causes such as excessive force, hip dislocation, capsular hip hypermobility, hip dysplasia, and hip degeneration.\n\nA tight iliopsoas tendon has also been attributed to labrum tears by causing compression or traction injuries that eventually lead to a labrum tear.\n\nMost labrum tears are thought to be from gradual tear due to repetitive microtrauma.\n\nIncidents of labrum tears increase with age, suggesting that they may also be caused by deterioration through the aging process.\n\nLabrum tears in athletes can occur from a single event or recurring trauma.\n\nRunning can cause labrum tears due to the labrum being used more for weight bearing and taking excessive forces while at the end-range motion of the leg: hyperabduction, hyperextension, hyperflexion, excessive external rotation.\n\nSporting activities are likely causes, specifically those that require frequent lateral rotation or pivoting on a loaded femur as in hockey or ballet.\n\nConstant hip rotation places increased stress on the capsular tissue and damage to the iliofemoral ligament.\n\nThis in turn causes hip rotational instability putting increased pressure on the labrum.\n\nTraumatic injuries are most commonly seen in athletes who participate in contact or high impact sports like football, soccer, or golf.\n\nThe prevalence rate for traumatic hip injuries that causes a tear of the labrum is very low.\n\nLess than 25% of all patients can relate a specific incident to their torn labrum, however they are often a result of a dislocation or fracture.\n\nFalling on one's side causes a blunt trauma to the greater trochanter of the femur.\n\nSince there is very little soft tissue to diminish the force between the impact and the greater trochanter, the entire blow is transferred to the surface of the hip joint.\n\nAnd since bone density does not reach its peak until the age of 30, hip traumas could result in a fracture.\n\nTears of the hip labrum can be classified in a variety of ways, including morphology, etiology, location, or severity.Anatomical modifications of the femur and or hip socket cause a slow buildup of damage to the cartilage.\n\nFemur or acetabular dysplasia can lead to femoral acetabular impingement (FAI).\n\nImpingement occurs when the femoral head rubs abnormally or lacks a full range of motion in the acetabular socket.\n\nThere are three different forms of FAI.\n\nThe first form is caused by a cam-deformity where extra bone is present on the femoral head, which leads to the head being non-spherical.\n\nThe second deformity is referred to as a pincer deformity and it is due to an excess growth of the acetabular socket.\n\nThe third type of FAI is a combination of the first two deformities.\n\nWhen either abnormality is present, it changes the position that the femoral head occupies in the hip socket.\n\nThe increased stresses that the femur and or acetabulum experience may lead to a fracture of the acetabular rim or a detachment of the overstressed labrum.\n\n=== Diagnosis ===\n\nA acetabular labrum tear is assessed by physical examination followed by medical imagfing.\n\nAn MR arthrogram is more reliable than magnetic resonance imaging.\n\nA full confirmation can be done by arthroscopy.\n\n=== Epidemiology ===\n\nIn the United States acetabular labrum tears usually occur in the anterior or anterior-superior area, possibly due to a sudden change from labrum to acetabular cartilage.\n\nThe most common labrum tears in Japan are in the posterior region, likely due to the customary practice of sitting on the floor.\n\nPosterior labrum tears in the Western world usually occur when a force drives the femoral head posteriorly which transfers shear and compressive forces to the posterior labrum.\n\n=== Rehabilitation ===\n\nWith physical therapy, there is only a small amount of evidence on rehabilitation techniques for the acetabular labrum.\n\nIt is even thought that physical therapy could be controversial due to there not being any evidence of a specific effective therapy routine.\nThere are, however, some studies that report physical therapy could benefit the patient by bringing them back to “sports-ready” capabilities.\n\nIt is advised that physical therapists keep up on the new findings and stay in close contact with the orthopaedic surgeon so they have the best idea of how to approach their patient's case.\n\nFollowing surgery, crutches will be used for up to six weeks and there should be no expectation to return to activities such as running for at least a period of six months.Some things to note when rehabilitation occurs is that it is important to know the size and placement of the tear.\n\nThere are usually four phases in the rehabilitation process noted as: \"Phase I: initial exercises (weeks 1–4), Phase II: intermediate exercises (weeks 5–7), Phase III: advanced exercises (weeks 8–12), and Phase IV: return to sports (weeks 12+)\".\nAll physical therapy regimens should be individualized from person to person based on all adequate criteriaIn phase I of the rehabilitation process the first objective is to minimize the pain and inflammation.\n\nIt is important to begin conducting small motion exercises that have up to 50% weight bearing capacity by the patient.\n\nA symmetrical gait pattern is imperative as not to create an imbalance in the muscles of the hip.\n\nAquatic therapy is highly encouraged and looked upon due to its ability to help the patient move more freely without the pressure of gravity.\n\nTo progress to phase II of the rehabilitation process patients should be able to complete straight leg raises while lying on their side to strengthen the sartorius and tensor fasciate latae muscles to build support in the leg.\nIn phase II the physical therapist should be trying to promote more flexibility in the soft tissue.\n\nThere should be more emphasis on the beginning aspects of strength training while adding some resistance over time.\n\nIn order to progress to phase III, the patient should be able to demonstrate a normal gait pattern and minimal pain with exercises like the single leg bridging to help strengthen the hamstring muscles to help with leg equality.\nIn phase III the focus is to begin building functional strength.\n\nMovements should include single leg exercises to build the muscle and challenge the strength of the hip.\nIn order to progress to phase IV the flexibility of the patient should be adequate.\n\nPhase IV is the final stage in which the physical therapist would assess and prescribe any further exercise up until the patient is ready to return to the sport.\n\nUsually the therapist would start using complex movements like squatting, kicking, and running.\n\nThe therapist would look for symmetrical movements on both sides of the body without pain.\n\nIf the patient demonstrates the symmetrical movements without pain, the physical therapist would use their discretion for the patient's clearance.\n\nSome things to avoid from while rehabilitating are sitting with \"knees lower than the hips, legs crossed where hip is rotated, and sitting on the edge of the seat and contracting the hip flexor muscles.\"\n\n=== Prevention ===\n\nHip labrum tear can occur in a variety of ways such as frequent twisting movement,\ndirect trauma, or degeneration.\n\nDespite the many different possibilities, a large percentage\nof hip labral tears are not directly related to any specific action, making it difficult to\nprevent such an injury.\n\nBut it may be possible to lower the risk by strengthening the gluteus,\nstretching before exercise, and discontinued use of repetitive twisting activities.\nOne way to prevent a hip labrum tear is to decrease the pressure on the anterior region.\nThe labrum is about 2 to 3 mm thick but is wider and thinner in the anterior portion.\n\nStudies have found that in the United States and European countries, hip labral tears are commonly found in the anterior region.\n\nMuscular imbalance of the pelvis can develop lower crossed\nsyndrome.\n\nIt is caused by tight hip flexors and erector spinae with inhibited weak gluteals and\nabdominals.\n\nImbalance of the muscles can lead to an anterior pelvic tilt, increased hip\nflexion, and lumbar hyperlordosis of the lumbar spine.\n\nThis increases the pressure in the anterior\nlabrum.\n\nWeak gluteals during hip extension has also shown increased joint pressure in the\nanterior labrum.\n\nTo prevent a hip labrum tear, you will have to strengthen muscles or\nstretch tight muscles that might cause any muscular imbalance.\n\nA great exercise to strengthen\nthe gluteus is the side lying hip abduction.\n\nYou will be lying on your side with your legs on top of each other.\n\nYou will raise the top leg up while keeping the knee and hip straight.\n\nThis exercise\ntargets the gluteus medius and is effective especially in those with an anterior pelvic tilt.\n\nTo stretch a tight hip flexor, you can do the kneeling hip flexor stretch that targets\nthe iliopsoas.\n\nThese exercises are a great way to strengthen and stabilize the pelvis\nand hip joint to prevent a hip labrum tear.\nStretching before exercise will affect the cartilage through \"creep\".\n\nIt will place a\nconstant load on the labrum, allowing fluid the leak out and deform to the applied load.\n\nThis is\nsignificant for the viscoelasticity of the labrum.\n\nThe hip labrum acts as a shock absorber, joint\nlubricator, stabilizer and pressure distributor.\n\nWith this essential warm up, it is possible for it\nto be better prepared to prevent a hip labrum tear.\n\nBody weight squats are a great example of\nstretching and warming up the body to induce creep before exercise.\n\n== References ==\n\nhttps://en.wikipedia.org/wiki/Acetabular_labrum","pubofemoral-ligament":"The pubofemoral ligament (pubocapsular ligament) is a ligament on the inferior side of the hip joint.\nThis ligament is attached, above, to the obturator crest and the superior ramus of the pubis; below, it blends with the capsule and with the deep surface of the vertical band of the iliofemoral ligament.\n\nThis ligament prevents hyper-abduction of the hip joint.\n\nhttps://en.wikipedia.org/wiki/Pubofemoral_ligament","zona-orbicularis":"The zona orbicularis or annular ligament is a ligament on the neck of the femur formed by the circular fibers of the articular capsule of the hip joint.\n\nIt is also known as the orbicular zone, ring ligament, and zonular band.\n\n== Structure ==\n\nThe zona orbicularis forms a ring around the neck of the femur.\n\nThe articular capsule is much thicker above and in front of the joint, where the greatest amount of resistance is required, and thin and loose behind and below the joint.\nThe capsule consists of two sets of fibers, circular and longitudinal.\n\nThe circular fibers, the zona orbicularis, are most abundant at the lower and back part of the capsule where they form a sling or collar around the femoral neck.\n\nAnteriorly, they blend with the deep surface of the iliofemoral ligament, and gain an attachment to the anterior inferior iliac spine.\n\n== Function ==\n\nThe zona orbicularis and proximal hip joint capsule are poorly understood.\n\nRecent studies seem to confirm that the proximal to middle part of the articular capsule, including the zona orbicularis, acts biomechanically as a locking ring wrapped around the femoral neck and thus is a key structure for hip stability in distraction.\n\nIt tightens the joint capsule of the hip when iliopsoas muscle contracts.\n\n== Notes ==\n\n This article incorporates text in the public domain from page 334 of the 20th edition of Gray's Anatomy (1918)\n\nhttps://en.wikipedia.org/wiki/Zona_orbicularis","ischiofemoral-ligament":"The ischiofemoral ligament, (ischiocapsular ligament, ischiocapsular band) consists of a triangular band of strong fibers on the posterior side of the hip joint.\n\nIts fibers span from the ischium at a point below and behind the acetabulum to blend with the circular fibers at the posterior end of the joint capsule and attach at the intertrochanteric line of the femur.\nStudies of human cadavers found that this ligament limits internal rotation of the hip, regardless of whether the hip is flexed, extended, or in neutral position.\n\nhttps://en.wikipedia.org/wiki/Ischiofemoral_ligament","ligament-of-head-of-femur":"In human anatomy, the ligament of the head of the femur (round ligament of the femur, ligamentum teres femoris, the foveal ligament, or Fillmore’s ligament) is a ligament located in the hip.\n\nIt is triangular in shape and somewhat flattened.\n\nThe ligament is implanted by its apex into the antero-superior part of the fovea capitis femoris and its base is attached by two bands, one into either side of the acetabular notch, and between these bony attachments it blends with the transverse ligament.It is ensheathed by the synovial membrane, and varies greatly in strength in different subjects; occasionally only the synovial fold exists, and in rare cases even this is absent.The ligament of the head of the femur contains within it the acetabular branch of the obturator artery.\n\n== Function ==\n\nThe ligament is made tense when the thigh is semiflexed and the limb then adducted or rotated outward; it is, on the other hand, relaxed when the limb is abducted.Research suggests it contributes little influence as a ligament past childhood, although it may still be important in transmitting arterial supply to the femoral head.\nIn humans, it has been suggested that it is not the ligamentum teres but the hip capsule (specifically the iliofemoral, ischiofemoral and pubofemoral ligaments) that provides the primary resistance to dislocation in the extended hip.\n\nHowever, recent research has suggested the ligamentum teres of the femur may have a number of functions, including a significant biomechanical role on the basis of cadaveric studies where increases of range of motion were seen after sectioning of the ligament.\n\n== Other animals ==\n\nIt has been suggested that some animals, such as the orangutan and Indian elephant, lack a ligamentum teres.\n\nHowever, the presence of a ligamentum teres, albeit with a morphology different from the human version, has been found upon dissection in both these animals.\n\nIn the orangutan, it is believed to play a significant role in preventing dislocation of the femoral head within extreme ranges of motion.\n\nIn the Indian elephant, it is the primary support of the hip joint when the hind limbs are abducted.\n\nhttps://en.wikipedia.org/wiki/Ligament_of_head_of_femur","articular-capsule-of-hip-joint":"In vertebrate anatomy, hip (or \"coxa\" in medical terminology) refers to either an anatomical region or a joint.\n\nThe hip region is located lateral and anterior to the gluteal region, inferior to the iliac crest, and overlying the greater trochanter of the femur, or \"thigh bone\".\n\nIn adults, three of the bones of the pelvis have fused into the hip bone or acetabulum which forms part of the hip region.\n\nThe hip joint, scientifically referred to as the acetabulofemoral joint (art. coxae), is the joint between the head of the femur and acetabulum of the pelvis and its primary function is to support the weight of the body in both static (e.g., standing) and dynamic (e.g., walking or running) postures.\n\nThe hip joints have very important roles in retaining balance, and for maintaining the pelvic inclination angle.\n\nPain of the hip may be the result of numerous causes, including nervous, osteoarthritic, infectious, traumatic, and genetic.\n\n== Structure ==\n\n=== Region ===\n\nThe proximal femur is largely covered by muscles and, as a consequence, the greater trochanter is often the only palpable bony structure in the hip region.\n\n=== Articulation ===\n\nThe hip joint is a synovial joint formed by the articulation of the rounded head of the femur and the cup-like acetabulum of the pelvis.\n\nIt forms the primary connection between the bones of the lower limb and the axial skeleton of the trunk and pelvis.\n\nBoth joint surfaces are covered with a strong but lubricated layer called articular hyaline cartilage.\n\nThe cuplike acetabulum forms at the union of three pelvic bones — the ilium, pubis, and ischium.\n\nThe Y-shaped growth plate that separates them, the triradiate cartilage, is fused definitively at ages 14–16.\n\nIt is a special type of spheroidal or ball and socket joint where the roughly spherical femoral head is largely contained within the acetabulum and has an average radius of curvature of 2.5 cm.\n\nThe acetabulum grasps almost half the femoral ball, a grip augmented by a ring-shaped fibrocartilaginous lip, the acetabular labrum, which extends the joint beyond the equator.\n\nThe joint space between the femoral head and the superior acetabulum is normally between 2 and 7 mm.The head of the femur is attached to the shaft by a thin neck region that is often prone to fracture in the elderly, which is mainly due to the degenerative effects of osteoporosis.\n\nThe acetabulum is oriented inferiorly, laterally and anteriorly, while the femoral neck is directed superiorly, medially, and slightly anteriorly.\n\n=== Articular angles ===\n\nThe transverse angle of the acetabular inlet (also called Sharp's angle and is generally the angle referred to by acetabular angle without further specification) can be determined by measuring the angle between a line passing from the superior to the inferior acetabular rim and the horizontal plane; an angle which normally measures 51° at birth and 40° in adults, and which affects the acetabular lateral coverage of the femoral head and several other parameters.\n\nThe sagittal angle of the acetabular inlet is an angle between a line passing from the anterior to the posterior acetabular rim and the sagittal plane.\n\nIt measures 7° at birth and increases to 17° in adults.\n\nWiberg's centre-edge angle (CE angle) is an angle between a vertical line and a line from the centre of the femoral head to the most lateral part of the acetabulum, as seen on an anteroposterior radiograph.\n\nThe vertical-centre-anterior margin angle (VCA) is an angle formed from a vertical line (V) and a line from the centre of the femoral head (C) and the anterior (A) edge of the dense shadow of the subchondral bone slightly posterior to the anterior edge of the acetabulum, with the radiograph being taken from the false angle, that is, a lateral view rotated 25 degrees towards becoming frontal.\n\nThe articular cartilage angle (AC angle, also called acetabular index or Hilgenreiner angle) is an angle formed parallel to the weight bearing dome, that is, the acetabular sourcil or \"roof\", and the horizontal plane, or a line connecting the corner of the triangular cartilage and the lateral acetabular rim.\n\nIn normal hips in children aged between 11 and 24 months, it has been estimated to be on average 20°, ranging between 18° to 25°.\n\nIt becomes progressively lower with age.\n\nSuggested cutoff values to classify the angle as abnormally increased include:30° up to 4 months of age.\n25° up to 2 years of age.\n\n=== Femoral neck angle ===\n\nThe angle between the longitudinal axes of the femoral neck and shaft, called the caput-collum-diaphyseal angle or CCD angle, normally measures approximately 150° in newborn and 126° in adults (coxa norma).An abnormally small angle is known as coxa vara and an abnormally large angle as coxa valga.\n\nBecause changes in shape of the femur naturally affects the knee, coxa valga is often combined with genu varum (bow-leggedness), while coxa vara leads to genu valgum (knock-knees).\n\nChanges in the CCD angle is the result of changes in the stress patterns applied to the hip joint.\n\nSuch changes, caused for example by a dislocation, change the trabecular patterns inside the bones.\n\nTwo continuous trabecular systems emerging on the auricular surface of the sacroiliac joint meander and criss-cross each other down through the hip bone, the femoral head, neck, and shaft.\n\nIn the hip bone, one system arises on the upper part of the auricular surface to converge onto the posterior surface of the greater sciatic notch, from where its trabeculae are reflected to the inferior part of the acetabulum.\n\nThe other system emerges on the lower part of the auricular surface, converges at the level of the superior gluteal line, and is reflected laterally onto the upper part of the acetabulum.\n\nIn the femur, the first system lines up with a system arising from the lateral part of the femoral shaft to stretch to the inferior portion of the femoral neck and head.\n\nThe other system lines up with a system in the femur stretching from the medial part of the femoral shaft to the superior part of the femoral head.\n\nOn the lateral side of the hip joint the fascia lata is strengthened to form the iliotibial tract which functions as a tension band and reduces the bending loads on the proximal part of the femur.\n\n=== Capsule ===\n\nThe capsule attaches to the hip bone outside the acetabular hip which thus projects into the capsular space.\n\nOn the femoral side, the distance between the head's cartilaginous rim and the capsular attachment at the base of the neck is constant, which leaves a wider extracapsular part of the neck at the back than at the front.\n\nThe strong but loose fibrous capsule of the hip joint permits the hip joint to have the second largest range of movement (second only to the shoulder) and yet support the weight of the body, arms and head.\n\nThe capsule has two sets of fibers: longitudinal and circular.\n\nThe circular fibers form a collar around the femoral neck called the zona orbicularis.\n\nThe longitudinal retinacular fibers travel along the neck and carry blood vessels.\n\n=== Ligaments ===\n\nThe hip joint is reinforced by four ligaments, of which three are extracapsular and one intracapsular.\n\nThe extracapsular ligaments are the iliofemoral, ischiofemoral, and pubofemoral ligaments attached to the bones of the pelvis (the ilium, ischium, and pubis respectively).\n\nAll three strengthen the capsule and prevent an excessive range of movement in the joint.\n\nOf these, the Y-shaped and twisted iliofemoral ligament is the strongest ligament in the human body.\n\nIn the upright position, it prevents the trunk from falling backward without the need for muscular activity.\n\nIn the sitting position, it becomes relaxed, thus permitting the pelvis to tilt backward into its sitting position.\n\nThe pubofemoral ligament prevents excess abduction and extension, ischiofemoral prevents excess extension, and the iliofemoral prevents hyperextension.\n\nThe zona orbicularis, which lies like a collar around the most narrow part of the femoral neck, is covered by the other ligaments which partly radiate into it.\n\nThe zona orbicularis acts like a buttonhole on the femoral head and assists in maintaining the contact in the joint.\n\nAll three ligaments become taut when the joint is extended - this stabilises the joint, and reduces the energy demand of muscles when standing.\n\nThe intracapsular ligament, the ligamentum teres, is attached to a depression in the acetabulum (the acetabular notch) and a depression on the femoral head (the fovea of the head).\n\nIt is only stretched when the hip is dislocated, and may then prevent further displacement.\n\nIt is not that important as a ligament but can often be vitally important as a conduit of a small artery to the head of the femur, that is, the foveal artery.\n\nThis artery is not present in everyone but can become the only blood supply to the bone in the head of the femur when the neck of the femur is fractured or disrupted by injury in childhood.\n\n=== Blood supply ===\n\nThe hip joint is supplied with blood from the medial circumflex femoral and lateral circumflex femoral arteries, which are both usually branches of the deep artery of the thigh (profunda femoris), but there are numerous variations and one or both may also arise directly from the femoral artery.\n\nThere is also a small contribution from the foveal artery, a small vessel in the ligament of the head of the femur which is a branch of the posterior division of the obturator artery, which becomes important to avoid avascular necrosis of the head of the femur when the blood supply from the medial and lateral circumflex arteries are disrupted (e.g. through fracture of the neck of the femur along their course).\n\nThe hip has two anatomically important anastomoses, the cruciate and the trochanteric anastomoses, the latter of which provides most of the blood to the head of the femur.\n\nThese anastomoses exist between the femoral artery or profunda femoris and the gluteal vessels.\n\n=== Muscles and movements ===\n\nThe hip muscles act on three mutually perpendicular main axes, all of which pass through the center of the femoral head, resulting in three degrees of freedom and three pair of principal directions:\n\nFlexion and extension around a transverse axis (left-right); lateral rotation and medial rotation around a longitudinal axis (along the thigh); and abduction and adduction around a sagittal axis (forward-backward); and a combination of these movements (i.e. circumduction, a compound movement in which the leg describes the surface of an irregular cone).\n\nSome of the hip muscles also act on either the vertebral joints or the knee joint, that with their extensive areas of origin and/or insertion, different part of individual muscles participate in very different movements, and that the range of movement varies with the position of the hip joint.\n\nAdditionally, the inferior and Superior gemelli muscles assist the obturator internus and the three muscles together form the three-headed muscle known as the triceps coxae.\n\nThe movements of the hip joint is thus performed by a series of muscles which are here presented in order of importance with the range of motion from the neutral zero-degree position indicated:\n\nLateral or external rotation (30° with the hip extended, 50° with the hip flexed): gluteus maximus; quadratus femoris; obturator internus; dorsal fibers of gluteus medius and minimus; iliopsoas (including psoas major from the vertebral column); obturator externus; adductor magnus, longus, brevis, and minimus; piriformis; and sartorius.\n\nThe iliofemoral ligament inhibits lateral rotation and extension, this is why the hip can rotate laterally to a greater degree when it is flexed.\n\nMedial or internal rotation (40°): anterior fibers of gluteus medius and minimus; tensor fasciae latae; the part of adductor magnus inserted into the adductor tubercle; and, with the leg abducted also the pectineus.\n\nExtension or retroversion (20°): gluteus maximus (if put out of action, active standing from a sitting position is not possible, but standing and walking on a flat surface is); dorsal fibers of gluteus medius and minimus; adductor magnus; and piriformis.\n\nAdditionally, the following thigh muscles extend the hip: semimembranosus, semitendinosus, and long head of biceps femoris.\n\nMaximal extension is inhibited by the iliofemoral ligament.\nFlexion or anteversion (140°): the hip flexors: iliopsoas (with psoas major from vertebral column); tensor fasciae latae, pectineus, adductor longus, adductor brevis, and gracilis.\n\nThigh muscles acting as hip flexors: rectus femoris and sartorius.\n\nMaximal flexion is inhibited by the thigh coming in contact with the chest.\n\nAbduction (50° with hip extended, 80° with hip flexed): gluteus medius; tensor fasciae latae; gluteus maximus with its attachment at the fascia lata; gluteus minimus; piriformis; and obturator internus.\n\nMaximal abduction is inhibited by the neck of the femur coming into contact with the lateral pelvis.\n\nWhen the hips are flexed, this delays the impingement until a greater angle.\n\nAdduction (30° with hip extended, 20° with hip flexed): adductor magnus with adductor minimus; adductor longus, adductor brevis, gluteus maximus with its attachment at the gluteal tuberosity; gracilis (extends to the tibia); pectineus, quadratus femoris; and obturator externus.\n\nOf the thigh muscles, semitendinosus is especially involved in hip adduction.\n\nMaximal adduction is impeded by the thighs coming into contact with one another.\n\nThis can be avoided by abducting the opposite leg, or having the legs alternately flexed/extended at the hip so they travel in different planes and do not intersect.\n\n== Clinical significance ==\n\nA hip fracture is a break that occurs in the upper part of the femur.\n\nSymptoms may include pain around the hip particularly with movement and shortening of the leg.\n\nThe hip joint can be replaced by a prosthesis in a hip replacement operation due to fractures or illnesses such as osteoarthritis.\n\nHip pain can have multiple sources and can also be associated with lower back pain.\n\n== Sexual dimorphism and cultural significance ==\n\nIn humans, unlike other animals, the hip bones are substantially different in the two sexes.\n\nThe hips of human females widen during puberty.\n\nThe femora are also more widely spaced in females, so as to widen the opening in the hip bone and thus facilitate childbirth.\n\nFinally, the ilium and its muscle attachment are shaped so as to situate the buttocks away from the birth canal, where contraction of the buttocks could otherwise damage the baby.\n\nThe female hips have long been associated with both fertility and general expression of sexuality.\n\nSince broad hips facilitate child birth and also serve as an anatomical cue of sexual maturity, they have been seen as an attractive trait for women for thousands of years.\n\nMany of the classical poses women take when sculpted, painted or photographed, such as the Grande Odalisque, serve to emphasize the prominence of their hips.\n\nSimilarly, women's fashion through the ages has often drawn attention to the girth of the wearer's hips.\n\nhttps://en.wikipedia.org/wiki/Hip","medial-meniscus":"The medial meniscus is a fibrocartilage semicircular band that spans the knee joint medially, located between the medial condyle of the femur and the medial condyle of the tibia.\n\nIt is also referred to as the internal semilunar fibrocartilage.\n\nThe medial meniscus has more of a crescent shape while the lateral meniscus is more circular.\n\nThe anterior aspects of both menisci are connected by the transverse ligament.\n\nIt is a common site of injury, especially if the knee is twisted.\n\n== Structure ==\n\nThe meniscus attaches to the tibia via coronary ligaments.\nIts anterior end, thin and pointed, is attached to the anterior intercondyloid fossa of the tibia, in front of the anterior cruciate ligament;\nIts posterior end is fixed to the posterior intercondyloid fossa of the tibia, between the attachments of the lateral meniscus and the posterior cruciate ligament.\nIt is fused with the tibial collateral ligament which makes it far less mobile than the lateral meniscus.\n\nThe points of attachment are relatively widely separated and, because the meniscus is wider posteriorly than anteriorly, the anterior crus is considerably thinner than the posterior crus.\n\nThe greatest displacement of the meniscus is caused by external rotation, while internal rotation relaxes it.During rotational movements of the tibia (with the knee flexed 90 degrees), the medial meniscus remains relatively fixed while the lateral part of the lateral meniscus is displaced across the tibial condyle below.\n\n== Function ==\n\nThe medial meniscus separates the tibia and femur to decrease the contact area between the bones, and serves as a shock absorber reducing the peak contact force experienced.\n\nIt also reduces friction between the two bones to allow smooth movement in the knee and distribute load during movement.\n\n== Clinical significance ==\n\n=== Injury ===\n\nAcute injury to the medial meniscus frequently accompanies an injury to the ACL (anterior cruciate ligament) or MCL (medial collateral ligament).\n\nA person occasionally injures the medial meniscus without harming the ligaments.\n\nHealing of the medial meniscus is generally not possible unless the patient is very young, usually <15 years old.\n\nDamage to the outer third of the meniscus has the best healing potential because of the blood supply, but the inner two thirds of the medial meniscus has a limited blood supply and thus limited healing ability.\n\nLarge tears to the meniscus may require surgical repair or removal.\n\nIn terms of a meniscus tear, the doctor can categorize the injury in a plethora of ways.\n\nFor example, a tear on the outer edge of the meniscus has great chance of healing.\n\nDoctors call this site the “red zone” because this outer portion of the meniscus is highly vascularized; therefore, it receives the amount of nutrients and support needed for a successful recovery.\n\nConversely, the inner two-thirds of the meniscus are called the “white zone.” This portion of the meniscus is not highly vascularized; it receives its nourishment from only the synovial fluid via diffusion.\n\nConsidering these facts, doctors consider different treatments to different kinds of tears:If the meniscus has to be removed (menisectomy) because of injury (either because it cannot heal or because the damage is too severe), the patient has an increased risk of developing osteoarthritis in the knee later in life.\n\nIf the meniscus is removed and there is no arthritis, there are now meniscus transplant options if the patient is young and has normal alignment.More chronic injury occurs with osteoarthritis, made worse by obesity and high-impact activity.\n\nThe medial meniscus and the medial compartment are more commonly affected than the lateral compartment.\n\n=== Books ===\n\nPlatzer, Werner (2004).\n\nColor Atlas of Human Anatomy, Vol. 1: Locomotor System (5th ed.).\n\nThieme.\n\nISBN 3-13-533305-1.\nThieme Atlas of Anatomy: General Anatomy and Musculoskeletal System.\n\nThieme. 2006.\n\nISBN 1-58890-419-9.\nBlahd and Freddie (2010). \"Meniscus Repair\".\n\nHealthwise Staff.\nBrindle, T; Nyland, J; Johnson, D.\n\nL. (2001). \"The meniscus: Review of basic principles with application to surgery and rehabilitation\".\n\nJournal of Athletic Training. 36 (2): 160–9.\n\nPMC 155528.\n\nPMID 16558666.\n\nhttps://en.wikipedia.org/wiki/Medial_meniscus","superficial-part-of-tibial-collateral-ligament":"The tibial collateral ligament (TCL), or Medial collateral ligament (MCL) is one of the four major ligaments of the knee.\n\nIt is on the medial (inner) side of the knee joint in humans and other primates.\n\nIts primary function is to resist outward turning forces on the knee.\n\n== Structure ==\n\nIt is a broad, flat, membranous band, situated slightly posterior on the medial side of the knee joint.\n\nIt is attached proximally to the medial epicondyle of the femur immediately below the adductor tubercle; below to the medial condyle of the tibia and medial surface of its body.\n\nIt resists forces that would push the knee medially, which would otherwise produce valgus deformity.\n\nThe fibers of the posterior part of the ligament are short and incline backward as they descend; they are inserted into the tibia above the groove for the semimembranosus muscle.\n\nThe anterior part of the ligament is a flattened band, about 10 centimeters long, which inclines forward as it descends.\n\nIt is inserted into the medial surface of the body of the tibia about 2.5 centimeters below the level of the condyle.\n\nCrossing on top of the lower part of the MCL is the pes anserinus, the joined tendons of the sartorius, gracilis, and semitendinosus muscles; a bursa is interposed between the two.\n\nThe TCL's deep surface covers the inferior medial genicular vessels and nerve and the anterior portion of the tendon of the semimembranosus muscle, with which it is connected by a few fibers; it is intimately adherent to the medial meniscus.\n\n=== Development ===\n\nEmbryologically and phylogenically, the ligament represents the distal portion of the tendon of adductor magnus muscle.\n\nIn lower animals, adductor magnus inserts into the tibia.\n\nBecause of this, the ligament occasionally contains muscle fibres.\n\nThis is an atavistic variation.\n\n== Clinical significance ==\n\n=== Injury ===\n\nAn MCL injury can be very painful and is caused by a valgus stress to a slightly bent knee, often when landing, bending or on high impact.\n\nIt may be difficult to apply pressure on the injured leg for at least a few days.\n\nIt can be caused by a direct blow to lateral side of knee.\n\nThe most common knee structure damaged in skiing is the medial collateral ligament, although the carve turn has diminished the incidence somewhat.\n\nMCL strains and tears are also fairly common in American football.\n\nThe center and the guards are the most common victims of this type of injury due to the grip trend on their cleats, although sometimes it can be caused by a helmet striking the knee.\n\nThe number of football players who get this injury has increased in recent years.\n\nCompanies are currently trying to develop better cleats that will prevent the injury.\n\nMCL is also crucially affected in breaststroke and many professional swimmers suffer from chronic MCL pains.\n\nThere are three distinct levels in a MCL injury.\n\nGrade 1 is a minor sprain, grade 2 in a major sprain or a minor tear, and grade 3 is a major tear.\n\nBased on the grade of the injury treatment options will vary.\n\n==== Treatment ====\n\nDepending on the grade of the injury, the lowest grade (grade 1) can take between 2 and 10 weeks for the injury to fully heal.\n\nRecovery times for grades 2 and 3 can take several weeks to several months.\n\nTreatment of a partial tear or stretch injury is usually conservative.\n\nSports medicine therapists should be a first choice option for diagnosis and treatment of injuries to this structure.\n\nThis includes measures to control inflammation as well as bracing.\n\nKannus has shown good clinical results with conservative care of grade II sprains, but poor results in grade III sprains.\n\nAs a result, more severe grade III and IV injuries to the MCL that lead to ongoing instability may require arthroscopic surgery.\n\nHowever, the medical literature considers surgery for most MCL injuries to be controversial.\n\nIsolated MCL sprains are common.\n\nFor higher grade tears of the MCL with ongoing instability, the MCL can be sutured or replaced.\n\nOther non-surgical approaches for more severe MCL injuries may include prolotherapy, which has been shown by Reeves in a small RCT to reduce translation on KT-1000 arthrometer versus placebo.\n\nThe future of non-surgical care for a non-healing MCL injury with laxity (partial ligament tear) is likely bioengineering.\n\nFan et al. (2008) have demonstrated that knee ligament reconstruction is possible using mesenchymal stem cells and a silk scaffold.\n\nhttps://en.wikipedia.org/wiki/Medial_collateral_ligament","deep-part-of-tibial-collateral-ligament":"The tibial collateral ligament (TCL), or Medial collateral ligament (MCL) is one of the four major ligaments of the knee.\n\nIt is on the medial (inner) side of the knee joint in humans and other primates.\n\nIts primary function is to resist outward turning forces on the knee.\n\n== Structure ==\n\nIt is a broad, flat, membranous band, situated slightly posterior on the medial side of the knee joint.\n\nIt is attached proximally to the medial epicondyle of the femur immediately below the adductor tubercle; below to the medial condyle of the tibia and medial surface of its body.\n\nIt resists forces that would push the knee medially, which would otherwise produce valgus deformity.\n\nThe fibers of the posterior part of the ligament are short and incline backward as they descend; they are inserted into the tibia above the groove for the semimembranosus muscle.\n\nThe anterior part of the ligament is a flattened band, about 10 centimeters long, which inclines forward as it descends.\n\nIt is inserted into the medial surface of the body of the tibia about 2.5 centimeters below the level of the condyle.\n\nCrossing on top of the lower part of the MCL is the pes anserinus, the joined tendons of the sartorius, gracilis, and semitendinosus muscles; a bursa is interposed between the two.\n\nThe TCL's deep surface covers the inferior medial genicular vessels and nerve and the anterior portion of the tendon of the semimembranosus muscle, with which it is connected by a few fibers; it is intimately adherent to the medial meniscus.\n\n=== Development ===\n\nEmbryologically and phylogenically, the ligament represents the distal portion of the tendon of adductor magnus muscle.\n\nIn lower animals, adductor magnus inserts into the tibia.\n\nBecause of this, the ligament occasionally contains muscle fibres.\n\nThis is an atavistic variation.\n\n== Clinical significance ==\n\n=== Injury ===\n\nAn MCL injury can be very painful and is caused by a valgus stress to a slightly bent knee, often when landing, bending or on high impact.\n\nIt may be difficult to apply pressure on the injured leg for at least a few days.\n\nIt can be caused by a direct blow to lateral side of knee.\n\nThe most common knee structure damaged in skiing is the medial collateral ligament, although the carve turn has diminished the incidence somewhat.\n\nMCL strains and tears are also fairly common in American football.\n\nThe center and the guards are the most common victims of this type of injury due to the grip trend on their cleats, although sometimes it can be caused by a helmet striking the knee.\n\nThe number of football players who get this injury has increased in recent years.\n\nCompanies are currently trying to develop better cleats that will prevent the injury.\n\nMCL is also crucially affected in breaststroke and many professional swimmers suffer from chronic MCL pains.\n\nThere are three distinct levels in a MCL injury.\n\nGrade 1 is a minor sprain, grade 2 in a major sprain or a minor tear, and grade 3 is a major tear.\n\nBased on the grade of the injury treatment options will vary.\n\n==== Treatment ====\n\nDepending on the grade of the injury, the lowest grade (grade 1) can take between 2 and 10 weeks for the injury to fully heal.\n\nRecovery times for grades 2 and 3 can take several weeks to several months.\n\nTreatment of a partial tear or stretch injury is usually conservative.\n\nSports medicine therapists should be a first choice option for diagnosis and treatment of injuries to this structure.\n\nThis includes measures to control inflammation as well as bracing.\n\nKannus has shown good clinical results with conservative care of grade II sprains, but poor results in grade III sprains.\n\nAs a result, more severe grade III and IV injuries to the MCL that lead to ongoing instability may require arthroscopic surgery.\n\nHowever, the medical literature considers surgery for most MCL injuries to be controversial.\n\nIsolated MCL sprains are common.\n\nFor higher grade tears of the MCL with ongoing instability, the MCL can be sutured or replaced.\n\nOther non-surgical approaches for more severe MCL injuries may include prolotherapy, which has been shown by Reeves in a small RCT to reduce translation on KT-1000 arthrometer versus placebo.\n\nThe future of non-surgical care for a non-healing MCL injury with laxity (partial ligament tear) is likely bioengineering.\n\nFan et al. (2008) have demonstrated that knee ligament reconstruction is possible using mesenchymal stem cells and a silk scaffold.\n\nhttps://en.wikipedia.org/wiki/Medial_collateral_ligament","lateral-meniscus":"The lateral meniscus (external semilunar fibrocartilage) is a fibrocartilaginous band that spans the lateral side of the interior of the knee joint.\n\nIt is one of two menisci of the knee, the other being the medial meniscus.\n\nIt is nearly circular and covers a larger portion of the articular surface than the medial.\n\nIt can occasionally be injured or torn by twisting the knee or applying direct force, as seen in contact sports.\n\n== Structure ==\n\nThe lateral meniscus is grooved laterally for the tendon of the popliteus, which separates it from the fibular collateral ligament.\nIts anterior end is attached in front of the intercondyloid eminence of the tibia, lateral to, and behind, the anterior cruciate ligament, with which it blends; the posterior end is attached behind the intercondyloid eminence of the tibia and in front of the posterior end of the medial meniscus.\nThe anterior attachment of the lateral meniscus is twisted on itself so that its free margin looks backward and upward, its anterior end resting on a sloping shelf of bone on the front of the lateral process of the intercondyloid eminence.\nClose to its posterior attachment it sends off a strong fasciculus, the ligament of Wrisberg, which passes upward and medialward, to be inserted into the medial condyle of the femur, immediately behind the attachment of the posterior cruciate ligament.\nThe lateral meniscus gives off from its anterior convex margin a fasciculus which forms the transverse ligament.\n\n=== Variation ===\n\nOccasionally a small fasciculus passes forward to be inserted into the lateral part of the anterior cruciate ligament.\n\n== Clinical significance ==\n\nThe lateral meniscus is less likely to be injured or torn than the medial meniscus.\n\nDiagnosis of lateral meniscus tear is done with McMurray's test.\n\nIf a tear is detected, treatment depends on the type and size of the tear.\n\nSmall tears can be treated conservatively, with rest, ice, and pain medications until the pain is under control, then exercise may be started with gradually increasing intensity, to improve range of motion and decrease swelling.\n\nMore severe tears of the lateral meniscus require surgical repair or removal, which can often be done arthroscopically.\n\nSwelling and stiffness of the knee can occur when you have a torn lateral meniscus.\n\nhttps://en.wikipedia.org/wiki/Lateral_meniscus","articular-capsule-of-knee-joint":"In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint).\n\nIt is the largest joint in the human body.\n\nThe knee is a modified hinge joint, which permits flexion and extension as well as slight internal and external rotation.\n\nThe knee is vulnerable to injury and to the development of osteoarthritis.\n\nIt is often termed a compound joint having tibiofemoral and patellofemoral components. (The fibular collateral ligament is often considered with tibiofemoral components.)\n\n== Structure ==\n\nThe knee is a modified hinge joint, a type of synovial joint, which is composed of three functional compartments: the patellofemoral articulation, consisting of the patella, or \"kneecap\", and the patellar groove on the front of the femur through which it slides; and the medial and lateral tibiofemoral articulations linking the femur, or thigh bone, with the tibia, the main bone of the lower leg.\n\nThe joint is bathed in synovial fluid which is contained inside the synovial membrane called the joint capsule.\n\nThe posterolateral corner of the knee is an area that has recently been the subject of renewed scrutiny and research.\n\nThe knee is the largest joint and one of the most important joints in the body.\n\nIt plays an essential role in movement related to carrying the body weight in horizontal (running and walking) and vertical (jumping) directions.\n\nAt birth, the kneecap is just formed from cartilage, and this will ossify (change to bone) between the ages of three and five years.\n\nBecause it is the largest sesamoid bone in the human body, the ossification process takes significantly longer.\n\n=== Articular bodies ===\n\nThe main articular bodies of the femur are its lateral and medial condyles.\n\nThese diverge slightly distally and posteriorly, with the lateral condyle being wider in front than at the back while the medial condyle is of more constant width.\n\nThe radius of the condyles' curvature in the sagittal plane becomes smaller toward the back.\n\nThis diminishing radius produces a series of involute midpoints (i.e. located on a spiral).\n\nThe resulting series of transverse axes permit the sliding and rolling motion in the flexing knee while ensuring the collateral ligaments are sufficiently lax to permit the rotation associated with the curvature of the medial condyle about a vertical axis.\n\nThe pair of tibial condyles are separated by the intercondylar eminence: 206  composed of a lateral and a medial tubercle.: 202 The patella also serves an articular body, and its posterior surface is referred to as the trochlea of the knee.\n\nIt is inserted into the thin anterior wall of the joint capsule.\n\nOn its posterior surface is a lateral and a medial articular surface, both of which communicate with the patellar surface which unites the two femoral condyles on the anterior side of the bone's distal end.\n\n=== Articular capsule ===\n\nThe articular capsule has a synovial and a fibrous membrane separated by fatty deposits.\n\nAnteriorly, the synovial membrane is attached on the margin of the cartilage both on the femur and the tibia, but on the femur, the suprapatellar bursa or recess extends the joint space proximally.\n\nThe suprapatellar bursa is prevented from being pinched during extension by the articularis genus muscle.\n\nBehind, the synovial membrane is attached to the margins of the two femoral condyles which produces two extensions similar to the anterior recess.\n\nBetween these two extensions, the synovial membrane passes in front of the two cruciate ligaments at the center of the joint, thus forming a pocket direct inward.\n\n=== Bursae ===\n\nNumerous bursae surround the knee joint.\n\nThe largest communicative bursa is the suprapatellar bursa described above.\n\nFour considerably smaller bursae are located on the back of the knee.\n\nTwo non-communicative bursae are located in front of the patella and below the patellar tendon, and others are sometimes present.\n\n=== Cartilage ===\n\nCartilage is a thin, elastic tissue that protects the bone and makes certain that the joint surfaces can slide easily over each other.\n\nCartilage ensures supple knee movement.\n\nThere are two types of joint cartilage in the knees: fibrous cartilage (the meniscus) and hyaline cartilage.\n\nFibrous cartilage has tensile strength and can resist pressure.\n\nHyaline cartilage covers the surface along which the joints move.\n\nCollagen fibres within the articular cartilage have been described by Benninghoff as arising from the subchondral bone in a radial manner, building so called Gothic arches.\n\nOn the surface of the cartilage these fibres appear in a tangential orientation and increase the abrasion resistance.\n\nThere are no blood vessels inside of the hyaline cartilage, the alimentation is performed per diffusion.\n\nSynovial fluid and the subchondral bone marrow serve both as nutrition sources for the hyaline cartilage.\n\nLack of at least one source induces a degeneration.\n\nCartilage will wear over the years.\n\nCartilage has a very limited capacity for self-restoration.\n\nThe newly formed tissue will generally consist of a large part of fibrous cartilage of lesser quality than the original hyaline cartilage.\n\nAs a result, new cracks and tears will form in the cartilage over time.\n\n=== Menisci ===\n\nThe articular disks of the knee-joint are called menisci because they only partly divide the joint space.\n\nThese two disks, the medial meniscus and the lateral meniscus, consist of connective tissue with extensive collagen fibers containing cartilage-like cells.\n\nStrong fibers run along the menisci from one attachment to the other, while weaker radial fibers are interlaced with the former.\n\nThe menisci are flattened at the center of the knee joint, fused with the synovial membrane laterally, and can move over the tibial surface.\n\nThe menisci serve to protect the ends of the bones from rubbing on each other and to effectively deepen the tibial sockets into which the femur attaches.\n\nThey also play a role in shock absorption, and may be cracked, or torn, when the knee is forcefully rotated and/or bent.\n\n=== Ligaments ===\n\nThe ligaments surrounding the knee joint offer stability by limiting movements and, together with the menisci and several bursae, protect the articular capsule.\n\n==== Intracapsular ====\n\nThe knee is stabilized by a pair of cruciate ligaments.\n\nThe anterior cruciate ligament (ACL) stretches from the lateral condyle of femur to the anterior intercondylar area.\n\nThe ACL is critically important because it prevents the tibia from being pushed too far anterior relative to the femur.\n\nIt is often torn during twisting or bending of the knee.\n\nThe posterior cruciate ligament (PCL) stretches from medial condyle of femur to the posterior intercondylar area.\n\nInjury to this ligament is uncommon but can occur as a direct result of forced trauma to the ligament.\n\nThis ligament prevents posterior displacement of the tibia relative to the femur.\n\nThe transverse ligament stretches from the lateral meniscus to the medial meniscus.\n\nIt passes in front of the menisci.\n\nIt is divided into several strips in 10% of cases.: 208  The two menisci are attached to each other anteriorly by the ligament.\n\nThe posterior and anterior meniscofemoral ligaments stretch from the posterior horn of the lateral meniscus to the medial femoral condyle.\n\nThey pass posteriorly behind the posterior cruciate ligament.\n\nThe posterior meniscofemoral ligament is more commonly present (30%); both ligaments are present less often.\n\nThe meniscotibial ligaments (or \"coronary\") stretches from inferior edges of the menisci to the periphery of the tibial plateaus.\n\n==== Extracapsular ====\n\nThe patellar ligament connects the patella to the tuberosity of the tibia.\n\nIt is also occasionally called the patellar tendon because there is no definite separation between the quadriceps tendon (which surrounds the patella) and the area connecting the patella to the tibia.\n\nThis very strong ligament helps give the patella its mechanical leverage\n\nand also functions as a cap for the condyles of the femur.\n\nLaterally and medially to the patellar ligament the lateral and medial retinacula connect fibers from the vasti lateralis and medialis muscles to the tibia.\n\nSome fibers from the iliotibial tract radiate into the lateral retinaculum and the medial retinaculum receives some transverse fibers arising on the medial femoral epicondyle.\n\nThe medial collateral ligament (MCL a.k.a. \"tibial\") stretches from the medial epicondyle of the femur to the medial tibial condyle.\n\nIt is composed of three groups of fibers, one stretching between the two bones, and two fused with the medial meniscus.\n\nThe MCL is partly covered by the pes anserinus and the tendon of the semimembranosus passes under it.\n\nIt protects the medial side of the knee from being bent open by a stress applied to the lateral side of the knee (a valgus force).\n\nThe fibular collateral ligament (LCL a.k.a. \"fibular\") stretches from the lateral epicondyle of the femur to the head of fibula.\n\nIt is separate from both the joint capsule and the lateral meniscus.: 206  It protects the lateral side from an inside bending force (a varus force).\n\nThe anterolateral ligament (ALL) is situated in front of the LCL.Lastly, there are two ligaments on the dorsal side of the knee.\n\nThe oblique popliteal ligament is a radiation of the tendon of the semimembranosus on the medial side, from where it is direct laterally and proximally.\n\nThe arcuate popliteal ligament originates on the apex of the head of the fibula to stretch proximally, crosses the tendon of the popliteus muscle, and passes into the capsule.\n\n== Muscles ==\n\nThe muscles responsible for the movement of the knee joint belong to either the anterior, medial or posterior compartment of the thigh.\n\nThe extensors generally belong to the anterior compartment and the flexors to the posterior.\n\nThe two exceptions to this is gracilis, a flexor, which belongs to the medial compartment and sartorius, a flexor, in the anterior compartment.\n\n=== Extensors ===\n\n=== Flexors ===\n\nPosterior compartment\n\nMedial compartment:\n\n=== Blood supply ===\n\nThe femoral artery and the popliteal artery help form the arterial network or plexus, surrounding the knee joint.\n\nThere are six main branches: two superior genicular arteries, two inferior genicular arteries, the descending genicular artery and the recurrent branch of anterior tibial artery.\n\nThe medial genicular arteries penetrate the knee joint.\n\n== Function ==\n\nThe knee permits flexion and extension about a virtual transverse axis, as well as a slight medial and lateral rotation about the axis of the lower leg in the flexed position.\n\nThe knee joint is called \"mobile\" because the femur and lateral meniscus move over the tibia during rotation, while the femur rolls and glides over both menisci during extension-flexion.\n\nThe center of the transverse axis of the extension/flexion movements is located where both collateral ligaments and both cruciate ligaments intersect.\n\nThis center moves upward and backward during flexion, while the distance between the center and the articular surfaces of the femur changes dynamically with the decreasing curvature of the femoral condyles.\n\nThe total range of motion is dependent on several parameters such as soft-tissue restraints, active insufficiency, and hamstring tightness.\n\n=== Extended position ===\n\nWith the knee extended, both the lateral and medial collateral ligaments, as well as the anterior part of the anterior cruciate ligament, are taut.\n\nDuring extension, the femoral condyles glide and roll into a position which causes the complete unfolding of the tibial collateral ligament.\n\nDuring the last 10° of extension, an obligatory terminal rotation is triggered in which the knee is rotated medially 5°.\n\nThe final rotation is produced by a lateral rotation of the tibia in the non-weight-bearing leg, and by a medial rotation of the femur in the weight-bearing leg.\n\nThis terminal rotation is made possible by the shape of the medial femoral condyle, assisted by contraction of the popliteus muscle and the iliotibial tract and is caused by the stretching of the anterior cruciate ligament.\n\nBoth cruciate ligaments are slightly unwinded and both lateral ligaments become taut.\n\n=== Flexed position ===\n\nIn the flexed position, the collateral ligaments are relaxed while the cruciate ligaments are taut.\n\nRotation is controlled by the twisted cruciate ligaments; the two ligaments get twisted around each other during medial rotation of the tibia—which reduces the amount of rotation possible—while they become unwound during lateral rotation of the tibia.\n\nBecause of the oblique position of the cruciate ligaments, at least a part of one of them is always tense and these ligaments control the joint as the collateral ligaments are relaxed.\n\nFurthermore, the dorsal fibers of the tibial collateral ligament become tensed during extreme medial rotation and the ligament also reduces the lateral rotation to 45–60°.\n\n== Clinical significance ==\n\nKnee pain is caused by trauma, misalignment, and degeneration as well as by conditions like arthritis.\n\nThe most common knee disorder is generally known as patellofemoral syndrome.\n\nThe majority of minor cases of knee pain can be treated at home with rest and ice but more serious injuries do require surgical care.\n\nOne form of patellofemoral syndrome involves a tissue-related problem that creates pressure and irritation in the knee between the patella and the trochlea (patellar compression syndrome), which causes pain.\n\nThe second major class of knee disorder involves a tear, slippage, or dislocation that impairs the structural ability of the knee to balance the leg (patellofemoral instability syndrome).\n\nPatellofemoral instability syndrome may cause either pain, a sense of poor balance, or both.Prepatellar bursitis also known as housemaid's knee is painful inflammation of the prepatellar bursa (a frontal knee bursa) often brought about by occupational activity such as roofing.\nAge also contributes to disorders of the knee.\n\nParticularly in older people, knee pain frequently arises due to osteoarthritis.\n\nIn addition, weakening of tissues around the knee may contribute to the problem.\n\nPatellofemoral instability may relate to hip abnormalities or to tightness of surrounding ligaments.Cartilage lesions can be caused by:\n\n-Accidents (fractures)\n-Injuries\n-The removal of a meniscus\n-Anterior cruciate ligament injury\n-Posterior cruciate ligament injury\n-Posterolateral corner injury\n-Medial knee injuries\n-Considerable strain on the knee.\n\nAny kind of work during which the knees undergo heavy stress may also be detrimental to cartilage.\n\nThis is especially the case in professions in which people frequently have to walk, lift, or squat.\n\nOther causes of pain may be excessive on, and wear off, the knees, in combination with such things as muscle weakness and overweight.\nCommon complaints:\n\nA painful, blocked, locked or swollen knee.\n\nSufferers sometimes feel as if their knees are about to give way, or may feel uncertain about their movement.\n\n=== Overall fitness and knee injury ===\n\nPhysical fitness is related integrally to the development of knee problems.\n\nThe same activity such as climbing stairs may cause pain from patellofemoral compression for someone who is physically unfit, but not for someone else (or even for that person at a different time).\n\nObesity is another major contributor to knee pain.\n\nFor instance, a 30-year-old woman who weighed 120 lb at age 18 years, before her three pregnancies, and now weighs 285 lb, had added 660 lb of force across her patellofemoral joint with each step.\n\n=== Common injuries due to physical activity ===\n\nIn sports that place great pressure on the knees, especially with twisting forces, it is common to tear one or more ligaments or cartilages.\n\nSome of the most common knee injuries are those to the medial side: medial knee injuries.\n\n=== Anterior cruciate ligament injury ===\n\nThe anterior cruciate ligament is the most commonly injured ligament of the knee.\n\nThe injury is common during sports.\n\nTwisting of the knee is a common cause of over-stretching or tearing the ACL.\n\nWhen the ACL is injured a popping sound may be heard, and the leg may suddenly give out.\n\nBesides swelling and pain, walking may be painful and the knee will feel unstable.\n\nMinor tears of the anterior cruciate ligament may heal over time, but a torn ACL requires surgery.\n\nAfter surgery, recovery is prolonged and low impact exercises are recommended to strengthen the joint.\n\n=== Torn meniscus injury ===\n\nThe menisci act as shock absorbers and separate the two ends of bone in the knee joint.\n\nThere are two menisci in the knee, the medial (inner) and the lateral (outer).\n\nWhen there is torn cartilage, it means that the meniscus has been injured.\n\nMeniscus tears occur during sports often when the knee is twisted.\n\nMenisci injury may be innocuous and one may be able to walk after a tear, but soon swelling and pain set in.\n\nSometimes the knee will lock while bending.\n\nPain often occurs when one squats.\n\nSmall meniscus tears are treated conservatively but most large tears require surgery.\n\n=== Fractures ===\n\nKnee fractures are rare but do occur, especially as a result of road accident.\n\nKnee fractures include a patella fracture, and a type of avulsion fracture called a Segond fracture.\n\nThere is usually immediate pain and swelling, and a difficulty or inability to stand on the leg.\n\nThe muscles go into spasm and even the slightest movements are painful.\n\nX-rays can easily confirm the injury and surgery will depend on the degree of displacement and type of fracture.\n\n=== Ruptured tendon ===\n\nTendons usually attach muscle to bone.\n\nIn the knee the quadriceps and patellar tendon can sometimes tear.\n\nThe injuries to these tendons occur when there is forceful contraction of the knee.\n\nIf the tendon is completely torn, bending or extending the leg is impossible.\n\nA completely torn tendon requires surgery but a partially torn tendon can be treated with leg immobilization followed by physical therapy.\n\n=== Overuse ===\n\nOveruse injuries of the knee include tendonitis, bursitis, muscle strains, and iliotibial band syndrome.\n\nThese injuries often develop slowly over weeks or months.\n\nActivities that induce pain usually delay healing.\n\nRest, ice and compression do help in most cases.\n\nOnce the swelling has diminished, heat packs can increase blood supply and promote healing.\n\nMost overuse injuries subside with time but can flare up if the activities are quickly resumed.\n\nIndividuals may reduce the chances of overuse injuries by warming up prior to exercise, by limiting high impact activities and keep their weight under control.\n\n=== Varus or valgus deformity ===\n\nThere are two disorders relating to an abnormal angle in the coronal plane at the level of the knee:\n\nGenu valgum is a valgus deformity in which the tibia is turned outward in relation to the femur, resulting in a knock-kneed appearance.\n\nGenu varum is a varus deformity in which the tibia is turned inward in relation to the femur, resulting in a bowlegged deformity.\n\nThe degree of varus or valgus deformity can be quantified by the hip-knee-ankle angle, which is an angle between the femoral mechanical axis and the center of the ankle joint.\n\nIt is normally between 1.0° and 1.5° of varus in adults.\n\nNormal ranges are different in children.\n\n=== Surgical interventions ===\n\nBefore the advent of arthroscopy and arthroscopic surgery, patients having surgery for a torn ACL required at least nine months of rehabilitation, having initially spent several weeks in a full-length plaster cast.\n\nWith current techniques, such patients may be walking without crutches in two weeks, and playing some sports in a few months.\n\nIn addition to developing new surgical procedures, ongoing research is looking into underlying problems which may increase the likelihood of an athlete suffering a severe knee injury.\n\nThese findings may lead to effective preventive measures, especially in female athletes, who have been shown to be especially vulnerable to ACL tears from relatively minor trauma.\n\nArticular cartilage repair treatment:\n\n-Arthroscopic debridement of the knee (arthroscopic lavage)\n-Mosaïc-plasty\n-Microfracture (Ice-picking)\n-Autologous chondrocyte implantation\n-Osteochondral Autograft and Allografts\n-PLC Reconstruction\n\n== Other animals ==\n\nIn humans, the term \"knee\" refers to the joints between the femur, tibia, and patella, in the leg.\n\nIn quadrupeds such as dogs, horses, and mice, the homologous joints between the femur, tibia, and patella, in the hind leg, are known as the stifle joint.\n\nAlso in quadrupeds, particularly horses, ungulates, and elephants, the layman's term \"knee\" also commonly refers to the forward-facing joint in the foreleg, the carpus, which is homologous to the human wrist.\n\nIn birds, the \"knee\" refers to the joints between the femur and tibiotarsus, and also the patella (when present).\n\nThe layman's term \"knee\" may also refer to the (lower and often more visible due to not being covered by feathers) joint between the tibiotarsus and tarsometatarsus, which is homologous to the human ankle.\n\nIn insects and other animals, the term knee widely refers to any hinge joint.\n\nhttps://en.wikipedia.org/wiki/Knee","meniscopatellar-ligament":"No description has been found anywhere for this structure.","transverse-ligament-of-knee":"The transverse or [anterior] meniscomeniscal ligament is a ligament in the knee joint that connects the anterior convex margin of the lateral meniscus to the anterior end of the medial meniscus.\nIt is divided into several strips in ten percent of subjects and its thickness varies considerably in different subjects.\n\n== Function ==\n\nWhen the knee is being extended the ligament prevents the anterior horns of the menisci from moving forward, and the condylar surfaces of the femur and tibia from exerting pressure on the menisci.\nIt has a restricting effect on anterior-posterior excursion of the anterior horn of the medial meniscus at lower degrees of knee flexion.\n\n== Prevalence of meniscomeniscal ligaments ==\n\nThe transverse ligament is reported in 58 per cent of subjects and is thus the most prevalent of four described meniscomeniscal ligaments.\n\nThe other ligaments, all three of which are reported with a frequency of less than 4 per cent, are the posterior transverse ligament, described as a bundle of fibers connecting the posterior horns of the menisci; and the medial and lateral oblique ligaments, both of which originate on the anterior horn of their namesake meniscus, passes between the cruciate ligaments, and attaches to the posterior horn of the opposite meniscus.\n\nNone of the oblique ligaments have a known function.\n\n== Formation ==\n\nThe formation of the transverse ligament has been investigated in human embryos aged 7–8 weeks (stages 18–23).\n\nAt the early end of the range (stage 19), condensation of the mesenchymal interzone of the knee joint (i.e. the area of densely packed cells indicating the location of the future joint) was recognizable, and near the end of the range (stage 22) clearly visible cellular primordium of the ligament connected to both menisci was observed before all major intraarticular elements were finally evident (stage 23).\n\n== Notes ==\n\n== Additional Images ==\n\nhttps://en.wikipedia.org/wiki/Transverse_ligament_of_knee","posterior-cruciate-ligament":"The posterior cruciate ligament (PCL) is a ligament in each knee of humans and various other animals.\n\nIt works as a counterpart to the anterior cruciate ligament (ACL).\n\nIt connects the posterior intercondylar area of the tibia to the medial condyle of the femur.\n\nThis configuration allows the PCL to resist forces pushing the tibia posteriorly relative to the femur.\nThe PCL and ACL are intracapsular ligaments because they lie deep within the knee joint.\n\nThey are both isolated from the fluid-filled synovial cavity, with the synovial membrane wrapped around them.\n\nThe PCL gets its name by attaching to the posterior portion of the tibia.The PCL, ACL, MCL, and LCL are the four main ligaments of the knee in primates.\n\n== Structure ==\n\nThe PCL is located within the knee joint where it stabilizes the articulating bones, particularly the femur and the tibia, during movement.\n\nIt originates from the lateral edge of the medial femoral condyle and the roof of the intercondyle notch then stretches, at a posterior and lateral angle, toward the posterior of the tibia just below its articular surface.\n\n== Function ==\n\nAlthough each PCL is a unified unit, they are described as separate anterolateral and posteromedial sections based on where each section's attachment site and function.\n\nDuring knee joint movement, the PCL rotates such that the anterolateral section stretches in knee flexion but not in knee extension and the posteromedial bundle stretches in extension rather than flexion.The function of the PCL is to prevent the femur from sliding off the anterior edge of the tibia and to prevent the tibia from displacing posterior to the femur.\n\nThe posterior cruciate ligament is located within the knee.\n\nLigaments are sturdy bands of tissues that connect bones.\n\nSimilar to the anterior cruciate ligament, the PCL connects the femur to the tibia.\n\n== Clinical significance ==\n\nCommon causes of injuries are direct blows to the flexed knee, such as the knee hitting the dashboard in a car accident or falling hard on the knee, both instances displacing the tibia posterior to the femur.An additional test of posterior cruciate ligament injury is the posterior sag test, where, in contrast to the drawer test, no active force is applied.\n\nRather, the person lies supine with the leg held by another person so that the hip is flexed to 90 degrees and the knee 90 degrees.\n\nThe main parameter in this test is step-off, which is the shortest distance from the femur to a hypothetical line that tangents the surface of the tibia from the tibial tuberosity and upwards.\n\nNormally, the step-off is approximately 1 cm, but is decreased (Grade I) or even absent (Grade II) or inverse (Grade III) in injuries to the posterior cruciate ligament.\n\nThe posterior drawer test is one of the tests used by doctors and physiotherapists to detect injury to the PCL.\n\nPatients who are suspected to have a posterior cruciate ligament injury should always be evaluated for other knee injuries that often occur in combination with an PCL injuries.\n\nThese include cartilage/meniscus injuries, bone bruises, ACL tears, fractures, posterolateral injuries and collateral ligament injuries.\nThere are four different grades of classification in which medical doctors classify a PCL injury:\n\nGrade I, the PCL has a slight tear.\nGrade II, the PCL ligament is minimally torn and becomes loose.\nGrade III, the PCL is torn completely and the knee can now be categorized as unstable.\nGrade IV, the ligament is damaged along with another ligament housed in the knee (i.e.\n\nACL).With these grades of PCL injuries, there are different treatments available for such injuries.\n\n=== Mechanism ===\n\nIn this position, the PCL functions to prevent movement of the tibia in the posterior direction and to prevent the tilting or shifting of the patella.\n\nHowever, the respective laxity of the two sections makes the PCL susceptible to injury during hyperflexion, hyperextension, and in a mechanism known as a dashboard injury.\n\nBecause ligaments are viscoelastic) they can handle higher amounts of stress only when the load is increased slowly.\n\nWhen hyperflexion and hyperextension occur suddenly in combination with this viscoelastic behavior, the PCL deforms or tears.\n\nIn the third and most common mechanism, the dashboard injury mechanism, the knee experiences impact in a posterior direction during knee flexion toward the space above the tibia.\n\nThese mechanisms occur in excessive external tibial rotation and during falls that induce a combination of extension and adduction of the tibia, which is referred to as varus-extension stress, or that occur while the knee is flexed.\n\n=== Treatment ===\n\nIt is possible for the PCL to heal on its own.\n\nEven if the PCL does not heal normally, it is unusual for surgery to be required.\n\nTreatment is usually physiotherapy to strengthen the muscles around the knee; usually they provide adequate stability even without a functional PCL.\n\nOnly if there are ongoing symptoms down the track, or if there are other injuries in the knee (eg posterolateral corner injury) will ligament reconstruction be required.\n\nLigament reconstruction is used to replace the torn PCL with a new ligament, which is usually a graft taken from the hamstring or Achilles tendon from a host cadaver.\n\nAn arthroscope allows a complete evaluation of the entire knee joint, including the knee cap (patella), the cartilage surfaces, the meniscus, the ligaments (ACL & PCL), and the joint lining.\n\nThen, the new ligament is attached to the bone of the thigh and lower leg with screws to hold it in place.\n\nSurgery to repair the posterior cruciate ligament is controversial due to its placement and technical difficulty.It is possible for the PCL to heal on its own without surgery when it is a Grade I or Grade II injury.\n\nPCL injuries that are diagnosed in these categories can have their recovery times reduced by performing certain rehabilitative exercises.\n\nFernandez and Pugh(2012) found that following a PCL grade II diagnosis, a multimodal treatment that spanned the course of 8 weeks consisting of chiropractic lumbopelvic manipulation, physiotherapy, and implementing an exercise program that emphasized eccentric muscle contraction (lunges, 1-leg squats, and trunk stabilization proved to be an effective way to recover from the PCL injury.\n\nFor Grades III and IV, operative surgery is recommended or is usually needed.\n\nGrafts is the method when addressing PCL injuries that are in need of operative surgery.\n\nWith grafts, there are different methods such as the tibial inlay or tunnel method.\n\n== Other animals ==\n\nIn the quadruped stifle (analogous to the human knee), based on its anatomical position, it is referred to as the caudal cruciate ligament.\n\nhttps://en.wikipedia.org/wiki/Posterior_cruciate_ligament","anterior-cruciate-ligament":"The anterior cruciate ligament (ACL) is one of a pair of cruciate ligaments (the other being the posterior cruciate ligament) in the human knee.\n\nThe two ligaments are also called \"cruciform\" ligaments, as they are arranged in a crossed formation.\n\nIn the quadruped stifle joint (analogous to the knee), based on its anatomical position, it is also referred to as the cranial cruciate ligament.\n\nThe term cruciate translates to cross.\n\nThis name is fitting because the ACL crosses the posterior cruciate ligament to form an “X”.\n\nIt is composed of strong, fibrous material and assists in controlling excessive motion.\n\nThis is done by limiting mobility of the joint.\n\nThe anterior cruciate ligament is one of the four main ligaments of the knee, providing 85% of the restraining force to anterior tibial displacement at 30 and 90° of knee flexion.\n\nThe ACL is the most injured ligament of the four located in the knee.\n\n== Structure ==\n\nThe ACL originates from deep within the notch of the distal femur.\n\nIts proximal fibers fan out along the medial wall of the lateral femoral condyle.\n\nThe two bundles of the ACL are the anteromedial and the posterolateral, named according to where the bundles insert into the tibial plateau.\n\nThe tibial plateau is a critical weight-bearing region on the upper extremity of the tibia.\n\nThe ACL attaches in front of the intercondyloid eminence of the tibia, where it blends with the anterior horn of the medial meniscus.\n\n== Purpose ==\n\nThe purpose of the ACL is to resist the motions of anterior tibial translation and internal tibial rotation; this is important to have rotational stability.\n\nThis function prevents anterior tibial subluxation of the lateral and medial tibiofemoral joints, which is important for the pivot-shift phenomenon.\n\nThe ACL has mechanoreceptors that detect changes in direction of movement, position of the knee joint, and changes in acceleration, speed, and tension.\n\nA key factor in instability after ACL injuries is having altered neuromuscular function secondary to diminished somatosensory information.\n\nFor athletes who participate in sports involving cutting, jumping, and rapid deceleration, the knee must be stable in terminal extension, which is the screw-home mechanism.\n\n== Clinical significance ==\n\n=== Injury ===\n\nAn ACL tear is one of the most common knee injuries, with over 100,000 tears occurring annually in the US.\n\nMost ACL tears are a result of a non-contact mechanism such as a sudden change in a direction causing the knee to rotate inward.\n\nAs the knee rotates inward, additional strain is placed on the ACL, since the femur and tibia, which are the two bones that articulate together forming the knee joint, move in opposite directions, causing the ACL to tear.\n\nMost athletes require reconstructive surgery on the ACL, in which the torn or ruptured ACL is completely removed and replaced with a piece of tendon or ligament tissue from the patient (autograft) or from a donor (allograft).\n\nConservative treatment has poor outcomes in ACL injury, since the ACL is unable to form a fibrous clot, as it receives most of its nutrients from synovial fluid; this washes away the reparative cells, making the formation of fibrous tissue difficult.\n\nThe two most common sources for tissue are the patellar ligament and the hamstrings tendon.\n\nThe patellar ligament is often used, since bone plugs on each end of the graft are extracted, which helps integrate the graft into the bone tunnels during reconstruction.\n\nThe surgery is arthroscopic, meaning that a tiny camera is inserted through a small surgical cut.\n\nThe camera sends video to a large monitor so the surgeon can see any damage to the ligaments.\n\nIn the event of an autograft, the surgeon makes a larger cut to get the needed tissue.\n\nIn the event of an allograft, in which material is donated, this is not necessary, since no tissue is taken directly from the patient's own body.\n\nThe surgeon drills a hole forming the tibial bone tunnel and femoral bone tunnel, allowing for the patient's new ACL graft to be guided through.\n\nOnce the graft is pulled through the bone tunnels, two screws are placed into the tibial and femoral bone tunnel.\n\nRecovery time usually ranges between one and two years, but is sometimes longer, depending if the patient chose an autograft or allograft.\n\nA week or so after the occurrence of the injury, the athlete is usually deceived by the fact that he/she is walking normally and not feeling much pain.\n\nThis is dangerous, as some athletes start resuming some of their activities such as jogging, which with a wrong move or twist, could damage the bones, as the graft has not completely become integrated into the bone tunnels.\n\nInjured athletes must understand the significance of each step of an ACL injury to avoid complications and ensure a proper recovery.\n\n=== Nonoperative treatment of the ACL ===\n\nACL reconstruction is the most common treatment for an ACL tear, but it is not the only treatment available for individuals.\n\nSome may find it more beneficial to complete a nonoperative rehabilitation program.\n\nIndividuals who are going to continue with physical activity that involves cutting and pivoting, and individuals who are no longer participating in those specific activities both are candidates for the nonoperative route.\n\nIn comparing operative and nonoperative approaches to ACL tears, few differences were noted between surgical and nonsurgical groups, with no significant differences in regard to knee function or muscle strength reported by the patients.The main goals to achieve during rehabilitation (rehab) of an ACL tear is to regain sufficient functional stability, maximize full muscle strength, and decrease risk of reinjury.\n\nTypically, three phases are involved in nonoperative treatment - the acute phase, the neuromuscular training phase, and the return to sport phase.\n\nDuring the acute phase, the rehab is focusing on the acute symptoms that occur right after the injury and are causing an impairment.\n\nThe use of therapeutic exercises and appropriate therapeutic modalities is crucial during this phase to assist in repairing the impairments from the injury.\n\nThe neuromuscular training phase is used to focus on the patient regaining full strength in both the lower extremity and the core muscles.\n\nThis phase begins when the patient regains full range of motion, no effusion, and adequate lower extremity strength.\n\nDuring this phase, the patient completes advanced balance, proprioception, cardiovascular conditioning, and neuromuscular interventions.\n\nIn the final, return to sport phase, the patient focuses on sport-specific activities and agility.\n\nA functional performance brace is suggested to be used during the phase to assist with stability during pivoting and cutting activities.\n\n=== Operative treatment of the ACL ===\n\nAnterior cruciate ligament surgery is a complex operation that requires expertise in the field of orthopedic and sports medicine.\n\nMany factors should be considered when discussing surgery, including the athlete's level of competition, age, previous knee injury, other injuries sustained, leg alignment, and graft choice.\n\nTypically, four graft types are possible, the bone-patella tendon-bone graft, the semitendinosus and gracilis tendons (quadrupled hamstring tendon), quadriceps tendon, and an allograft.\n\nAlthough extensive research has been conducted on which grafts are the best, the surgeon typically chooses the type of graft with which he or she is most comfortable.\n\nIf rehabilitated correctly, the reconstruction should last.\n\nIn fact, 92.9% of patients are happy with graft choice.Prehabilitation has become an integral part of the ACL reconstruction process.\n\nThis means that the patient exercises before getting surgery to maintain factors such as range of motion and strength.\n\nBased on a single leg hop test and self-reported assessment, prehab improved function; these effects were sustained 12 weeks postoperatively.Postsurgical rehabilitation is essential in the recovery from the reconstruction.\n\nThis typically takes a patient 6 to 12 months to return to life as it was prior to the injury.\n\nThe rehab can be divided into protection of the graft, improving range of motion, decrease swelling, and regaining muscle control.\n\nEach phase has different exercises based on the patients' needs.\n\nFor example, while the ligament is healing, a patient's joint should not be used for full weight-bearing, but the patient should strengthen the quadriceps and hamstrings by doing quad sets and weight shifting drills.\n\nPhase two would require full weight-bearing and correcting gait patterns, so exercises such as core strengthening and balance exercises would be appropriate.\n\nIn phase three, the patient begins running, and can do aquatic workouts to help with reducing joint stresses and cardiorespiratory endurance.\n\nPhase four includes multiplanar movements, thus enhancing a running program and beginning agility and plyometric drills.\n\nLastly, phase five focuses on sport- or life-specific motions, depending on the patient.A 2010 Los Angeles Times review of two medical studies discussed whether ACL reconstruction was advisable.\n\nOne study found that children under 14 who had ACL reconstruction fared better after early surgery than those who underwent a delayed surgery.\n\nFor adults 18 to 35, though, patients who underwent early surgery followed by rehabilitation fared no better than those who had rehabilitative therapy and a later surgery.The first report focused on children and the timing of an ACL reconstruction.\n\nACL injuries in children are a challenge because children have open growth plates in the bottom of the femur or thigh bone and on the top of the tibia or shin.\n\nAn ACL reconstruction typically crosses the growth plates, posing a theoretical risk of injury to the growth plate, stunting leg growth, or causing the leg to grow at an unusual angle.The second study noted focused on adults.\n\nIt found no significant statistical difference in performance and pain outcomes for patients who receive early ACL reconstruction vs. those who receive physical therapy with an option for later surgery.\n\nThis would suggest that many patients without instability, buckling, or giving way after a course of rehabilitation can be managed nonoperatively, but was limited to outcomes after two years and did not involve patients who were serious athletes.\n\nPatients involved in sports requiring significant cutting, pivoting, twisting, or rapid acceleration or deceleration may not be able to participate in these activities without ACL reconstruction.\n\n=== ACL injuries in women ===\n\nRisk differences between outcomes in men and women can be attributed to a combination of multiple factors, including anatomical, hormonal, genetic, positional, neuromuscular, and environmental factors.\n\nThe size of the anterior cruciate ligament is often the most reported difference.\n\nStudies look at the length, cross-sectional area, and volume of ACLs.\n\nResearchers use cadavers, and in vivo placement to study these factors, and most studies confirm that women have smaller anterior cruciate ligaments.\n\nOther factors that could contribute to higher risks of ACL tears in women include patient weight and height, the size and depth of the intercondylar notch, the diameter of the ACL, the magnitude of the tibial slope, the volume of the tibial spines, the convexity of the lateral tibiofemoral articular surfaces, and the concavity of the medial tibial plateau.\n\nWhile anatomical factors are most talked about, extrinsic factors, including dynamic movement patterns, might be the most important risk factor when it comes to ACL injury.\n\nEnvironmental factors also play a big role.\n\nExtrinsic factors are controlled by the individual.\n\nThese could be strength, conditioning, shoes, and motivation.\n\n== Gallery ==\n\nhttps://en.wikipedia.org/wiki/Anterior_cruciate_ligament","fibular-collateral-ligament":"The lateral collateral ligament (LCL, long external lateral ligament or fibular collateral ligament) is a ligament located on the lateral (outer) side of the knee, and thus belongs to the extrinsic knee ligaments and posterolateral corner of the knee.\n\n== Structure ==\n\nRounded, more narrow and less broad than the medial collateral ligament, the lateral collateral ligament stretches obliquely downward and backward from the lateral epicondyle of the femur above, to the head of the fibula below.\n\nIn contrast to the medial collateral ligament, it is fused with neither the capsular ligament nor the lateral meniscus.\nBecause of this, the lateral collateral ligament is more flexible than its medial counterpart, and is therefore less susceptible to injury.Both collateral ligaments are taut when the knee joint is in extension.\n\nWith the knee in flexion, the radius of curvatures of the condyles is decreased and the origin and insertions of the ligaments are brought closer together which make them lax.\n\nThe pair of ligaments thus stabilize the knee joint in the coronal plane.\n\nTherefore, damage and rupture of these ligaments can be diagnosed by examining the knee's mediolateral (side) stability.Immediately below its origin is the groove for the tendon of the popliteus.\nThe greater part of its lateral surface is covered by the tendon of the biceps femoris; the tendon, however, divides at its insertion into two parts, which are separated by the ligament.\nDeep to the ligament are the tendon of the popliteus, and the inferior lateral genicular vessels and nerve.\n\n== Causes of injury ==\n\nThe LCL is usually injured as a result of varus force across the knee, which is a force pushing the knee from the medial (inner) side of the joint, causing stress on the outside.\n\nAn example of this would be a direct blow to the inside of the knee.\n\nThe LCL can also be injured by a noncontact injury, such as a hyperextension stress, again causing varus force across the knee.An LCL injury usually occurs simultaneously as the other ligaments of the knee are injured.\n\nMultiple knee ligament tears and stresses can result from a significant trauma that includes direct blunt force to the knee, such as an automobile crash.\n\n== Symptoms ==\n\nSymptoms of a sprain or tear of the LCL includes pain to the lateral aspect of the knee, instability of the knee when walking, swelling and ecchymosis (bruising) at the site of trauma.\n\nDirect trauma to the medial aspect of the knee may also affect the peroneal nerve, which could result in a foot drop or paresthesias below the knee which could present itself as a tingling sensation.\n\n== Treatment ==\n\nAn isolated LCL tear or sprain rarely requires surgery.\n\nIf the injury is a Grade 1 or Grade II, microscopic or partial macroscopic tearing respectively, the injury is treated with rest and rehabilitation.\n\nIce, electrical stimulation and elevation are all methods to reduce the pain and swelling felt in the initial stages after the injury takes place.\n\nPhysical therapy focuses on regaining full range-of-motion, such as biking, stretching and careful applications of pressure on the joint.\n\nFull recovery of Grade I or Grade II tears should take between 6 weeks and 3 months.\n\nContinued pain, swelling and instability to the joint after this time period may require surgical repair or reconstruction to the ligament.\n\nhttps://en.wikipedia.org/wiki/Fibular_collateral_ligament","oblique-popliteal-ligament":"The oblique popliteal ligament (posterior ligament) is a broad, flat, fibrous band, on the posterior knee.\n\n== Structure ==\n\nThe oblique popliteal ligament originates from the adductor tubercle of the medial side of the femur.\n\nIt is also attached to the upper margin of the intercondyloid fossa and posterior surface of the femur close to the articular margins of the condyles.\n\nIt crosses the popliteal fossa from medial to lateral.\n\nIt is attached below to the posterior margin of the head of the tibia.It is one of the five insertions of the semimembranosus muscle.The oblique popliteal ligament forms part of the floor of the popliteal fossa, and the popliteal artery rests upon it.\n\nIt is formed of fasciculi separated from one another by apertures for the passage of vessels and nerves.\nIt is pierced by posterior division of the obturator nerve, as well as the middle genicular nerve, the middle genicular artery, and the middle genicular vein.\n\n== Function ==\n\nThe oblique popliteal ligament reduces rotation around the knee joint.\n\nWhen the knee is in full extension, it prevents valgus deformity.\n\nIt reduces external rotation of the tibia, and internal rotation of the femur.\n\n== Clinical significance ==\n\nThe oblique popliteal ligament may be damaged, causing a valgus deformity.\n\nSurgical repair of the ligament often leads to better outcomes than conservative management.The oblique popliteal ligament may be cut during arthroscopic meniscus repair surgery.\n\nhttps://en.wikipedia.org/wiki/Oblique_popliteal_ligament","infrapatellar-fat-pad":"The infrapatellar fat pad (Hoffa's fat pad) is a cylindrical piece of fat that is situated under and behind the patella bone within the knee.\n\n== Clinical significance ==\n\nThe fat pad is a normal structure but it can sometimes become a problem:\n\nIt can become damaged and painful\nIt can be deliberately removed at arthroscopic surgery to make it easier for the surgeon to see what they are doing - but this can also lead to scarring and pain.\nIt can become hypertrophic and may become impinged between the patella and the femoral condyle, causing sharp pain when the leg is extended.\n\nThis is called infrapatellar fat pad syndrome or Hoffa syndrome.\nIt can become involved in the process of arthrofibrosis and become scarred (fibrotic) and contracted, pulling the patella down into an abnormally low position.\n\n== References ==\n\nhttps://en.wikipedia.org/wiki/Infrapatellar_fat_pad","arcuate-popliteal-ligament":"The arcuate popliteal ligament is an extracapsular ligament of the knee.\n\nIt is Y-shaped and is attached to the posterior portion of the head of the fibula.\n\nFrom there it goes to its two insertions; the medial one goes over popliteus muscle and blends with the oblique popliteal ligament, the lateral one to the Lateral epicondyle of the femur and blends there with the lateral head of gastrocnemius muscle.\n\nhttps://en.wikipedia.org/wiki/Arcuate_popliteal_ligament","popliteofibular-ligament":"The popliteofibular ligament (PFL) connects the popliteus muscle at the musculotendinous junction to the posterior and medial portion of the fibular styloid.\n\nIt has two divisions, anterior and posterior, and acts to stabilize the knee during external rotation.","anterior-ligament-of-fibular-head":"The anterior ligament of the head of the fibula (anterior superior ligament) consists of two or three broad and flat bands, which pass obliquely upward from the front of the head of the fibula to the front of the lateral condyle of the tibia.\n\nThis fibrous band crosses obliquely and superiorly from the anterior aspect of the head of the fibula to the lateral condyle of the tibia.\n\nIt merges with the fibrous capsule of the proximal tibiofibular joint and restrains its movements further.","posterior-ligament-of-fibular-head":"The posterior ligament of the head of the fibula is a part of the knee.\n\nIt is a single thick and broad band, which passes obliquely upward from the back of the head of the fibula to the back of the lateral condyle of the tibia.\n\nIt is covered by the tendon of the Popliteus.","tibiocalcaneal-ligament":"TIBiOCALCANEAL LIGAMENT\n\nOf th superficial fibers of the medial collateral ligament of ankle, the tibiocalcaneal descend almost perpendicularly to be inserted into the whole length of the sustentaculum tali of the calcaneus.","tibionavicular-ligament":"Of the superficial fibres of the medial collateral ligament of ankle, the tibionavicular ligament passes forward to be inserted into the tuberosity of the navicular bone, and immediately behind this they blend with the medial margin of the plantar calcaneonavicular ligament;","posterior-talofibular-ligament":"The posterior talofibular ligament is a ligament that connects the fibula to the talus bone.\n\nIt runs almost horizontally from the malleolar fossa of the lateral malleolus of the fibula to the lateral tubercle on the posterior surface of the talus.\n\nThis insertion lies immediately lateral to the groove for the tendon of the flexor hallucis longus.\n\nhttps://en.wikipedia.org/wiki/Posterior_talofibular_ligament","anterior-talofibular-ligament":"The anterior talofibular ligament is a ligament in the ankle.\nIt passes from the anterior margin of the fibular malleolus, anteriorly and laterally, to the talus bone, in front of its lateral articular facet.\n\nIt is one of the lateral ligaments of the ankle and prevents the foot from sliding forward in relation to the shin.\n\nIt is the most commonly injured ligament in a sprained ankle—from an inversion injury—and will allow a positive anterior drawer test of the ankle if completely torn.\n\n== Further reading ==\n\nMatsui K, Takao M, Tochigi Y, Ozeki S, Glazebrook M (June 2017). \"Anatomy of anterior talofibular ligament and calcaneofibular ligament for minimally invasive surgery: a systematic review\".\n\nKnee Surgery, Sports Traumatology, Arthroscopy (Review). 25 (6): 1892–1902. doi:10.1007/s00167-016-4194-y.\n\nPMID 27295109.\n\nS2CID 25598007.\n\nhttps://en.wikipedia.org/wiki/Anterior_talofibular_ligament","calcaneofibular-ligament":"The calcaneofibular ligament is a narrow, rounded cord, running from the tip of the lateral malleolus of the fibula downward and slightly backward to a tubercle on the lateral surface of the calcaneus.\n\nIt is part of the lateral collateral ligament, which opposes the hyperinversion of the subtalar joint, as in a common type of ankle sprain.It is covered by the tendons of the fibularis longus and brevis muscles.\n\n== Clinical significance ==\n\nThe calcaneofibular ligament is commonly sprained ligament in ankle injuries.\n\nIt may be injured individually, or in combination with other ligaments such as the anterior talofibular ligament and the posterior talofibular ligament.\n\n== Further reading ==\n\nMatsui K, Takao M, Tochigi Y, Ozeki S, Glazebrook M (June 2017). \"Anatomy of anterior talofibular ligament and calcaneofibular ligament for minimally invasive surgery: a systematic review\".\n\nKnee Surgery, Sports Traumatology, Arthroscopy (Review). 25 (6): 1892–1902. doi:10.1007/s00167-016-4194-y.\n\nPMID 27295109.\n\nS2CID 25598007.\n\nhttps://en.wikipedia.org/wiki/Calcaneofibular_ligament","lateral-talocalcaneal-ligament":"The lateral talocalcaneal ligament (external calcaneo-astragaloid ligament) is a ligament in the ankle.\n\nIt is a short, strong fasciculus, passing from the lateral surface of the talus, immediately beneath its fibular facet to the lateral surface of the calcaneus.\nIt is placed in front of, but on a deeper plane than, the calcaneofibular ligament, with the fibers of which it is parallel.\n\nhttps://en.wikipedia.org/wiki/Lateral_talocalcaneal_ligament","medial-talocalcaneal-ligament":"The medial talocalcaneal ligament (internal calcaneo-astragaloid ligament) connects the medial tubercle of the back of the talus with the back of the sustentaculum tali.\nIts fibers blend with those of the plantar calcaneonavicular ligament.\n\nhttps://en.wikipedia.org/wiki/Medial_talocalcaneal_ligament","posterior-talocalcaneal-ligament":"The posterior talocalcaneal ligament (posterior calcaneo-astragaloid ligament) connects the lateral tubercle of the talus with the upper and medial part of the calcaneus; it is a short band, and its fibers radiate from their narrow attachment to the talus.\n\nhttps://en.wikipedia.org/wiki/Posterior_talocalcaneal_ligament","anterior-talocalcaneal-ligament":"The anterior talocalcaneal ligament (anterior calcaneo-astragaloid ligament or anterior interosseous ligament) is a ligament in the foot.\nThe anterior talocalcaneal ligament extends from the front and lateral surface of the neck of the talus to the sinus tarsi of the calcaneus.\nIt forms the posterior boundary of the talocalcaneonavicular joint.\n\nhttps://en.wikipedia.org/wiki/Anterior_talocalcaneal_ligament","calcaneonavicular-ligament":"The calcaneonavicular ligament is the upper of two parts of the bifurcate ligament that is divided in front in a Y-shaped manner into a calcaneocuboid ligament and a calcaneonavicular part.\n\nThey are both attached behind to the deep hollow on the upper surface of the calcaneus, but the calcaneonavicular ligament is attached to the lateral side of the navicular.\n\n(Note this is NOT the spring ligament which is commonly called the plantar calcaneonavicular ligament).\n\nIt is commonly injured in \"sprain-type\" inversion injuries producing an avulsion fracture at the anterolateral process of the calcaneus.","calcaneocuboid-ligament":"The Calcaneocuboid ligament is a fibrous band that connects the superior surface of the calcaneus to the dorsal surface of the cuboid bone.\nIt forms part of the bifurcated ligament.\n\n== References ==\n\nhttps://en.wikipedia.org/wiki/Calcaneocuboid_ligament","plantar-calcaneonavicular-ligament":"The plantar calcaneonavicular ligament (also known as the spring ligament or spring ligament complex) is a complex of three ligaments on the underside of the foot that connect the calcaneus with the navicular bone.\n\n== Structure ==\n\nThe plantar calcaneonavicular ligamentous complex is a broad and thick band with three constituent ligaments.\n\nThese connect the anterior margin of the sustentaculum tali of the calcaneus to the plantar surface of the navicular bone.\n\nIts individual components are the:\n\nsuperomedial calcaneonavicular ligament.\nmedioplantar oblique ligament.\ninferior calcaneonavicular ligament.These ligament components attach to different parts of the navicular bone.The dorsal or superomedial component of the ligament presents a fibrocartilaginous facet, lined by the synovial membrane, upon which a portion of the head of the talus rests.\n\nIts plantar surface, consisting of the intermedial and lateral ligaments, is supported by the tendon of the tibialis posterior; its medial border is blended with the forepart of the deltoid ligament of the ankle-joint.\n\n== Function ==\n\nThis ligamentous complex not only serves to connect the calcaneus and navicular bone, but supports the head of the talus, forming part of the articular cavity in which it is received.\n\nIt helps to maintain the medial longitudinal arch of the foot.\n\nBy providing support to the head of the talus, it bears most of the body weight in a normally functioning foot.\n\n== Clinical significance ==\n\nA sprain to the plantar calcaneonavicular ligament can result in flatfoot deformity, which can impair mobility.\n\nhttps://en.wikipedia.org/wiki/Plantar_calcaneonavicular_ligament","talonavicular-ligament":"The (dorsal) talonavicular ligament is a broad, thin band, which connects the neck of the talus to the dorsal surface of the navicular bone; it is covered by the Extensor tendons.\n\nhttps://en.wikipedia.org/wiki/Dorsal_talonavicular_ligament","plantar-calcaneocuboid-ligament":"The plantar calcaneocuboid ligament (short calcaneocuboid ligament; short plantar ligament) is a ligament on the bottom of the foot that connects the calcaneus to the cuboid bone.\n\nIt lies deep to the long plantar ligament.\n\n== Structure ==\n\nThe plantar calcaneocuboid ligament lies nearer to the bones than the long plantar ligament, from which it is separated by a little areolar tissue.\nIt is a short but wide band of great strength, and extends from the anterior tubercle of calcaneus and the depression in front of it, on the forepart of the plantar surface of the calcaneus, to the plantar surface of the cuboid posterior to the groove for the fibularis longus tendon.\n\nhttps://en.wikipedia.org/wiki/Plantar_calcaneocuboid_ligament","dorsal-calcaneocuboid-ligament":"The dorsal calcaneocuboid ligament (superior calcaneocuboid ligament)\nis a thin but broad fasciculus, which passes between the contiguous surfaces of the calcaneus and cuboid, on the dorsal surface of the joint.\n\nhttps://en.wikipedia.org/wiki/Dorsal_calcaneocuboid_ligament","long-plantar-ligament":"The long plantar ligament (long calcaneocuboid ligament; superficial long plantar ligament) is a long ligament on the underside of the foot that connects the calcaneus with the cuboid bone.\n\n== Structure ==\n\nThe long plantar ligament is the longest of all the ligaments of the tarsus.\n\nIt is attached behind to the plantar surface of the calcaneus in front of the tuberosity, and in front to the tuberosity on the plantar surface of the cuboid bone, the more superficial fibers being continued forward to the bases of the second, third, and fourth metatarsal bones.\nThis ligament converts the groove on the plantar surface of the cuboid into a canal for the tendon of the fibularis longus.\nDeep to this ligament is the short plantar ligament.\nThe long plantar ligament separates the two heads of the quadratus plantae muscle.\n\nhttps://en.wikipedia.org/wiki/Long_plantar_ligament","dorsal-cuneonavicular-ligaments":"The dorsal cuneonavicular ligaments consist of fibrous bands that join the dorsal surface of the navicular bone to the dorsal surfaces of the three cuneiform bones.\n\nhttps://en.wikipedia.org/wiki/Dorsal_cuneonavicular_ligaments","plantar-cuneonavicular-ligaments":"The Plantar cuneonavicular ligaments are fibrous bands that connect the plantar surface of the navicular bone to the adjacent plantar surfaces of the three cuneiform bones.\n\nhttps://en.wikipedia.org/wiki/Plantar_cuneonavicular_ligaments","dorsal-cuneocuboid-ligament":"The dorsal cuneocuboid ligament consists of fibrous bands that connect the dorsal surfaces of the cuboid and lateral surfaces of the cuneiform bones.\n\nhttps://en.wikipedia.org/wiki/Dorsal_cuneocuboid_ligament","plantar-cuneocuboid-ligament":"The Plantar cuneocuboid ligament is a fibrous band that connects the plantar surfaces of the cuboid to the lateral surface of the cuneiform bones.\n\n== References ==\n\nhttps://en.wikipedia.org/wiki/Plantar_cuneocuboid_ligament","plantar-cuboideonavicular-ligament":"The Plantar cuboideonavicular ligament is a fibrous band that connects the plantar surfaces of the cuboid and navicular bones.\n\nhttps://en.wikipedia.org/wiki/Plantar_cuboideonavicular_ligament","dorsal-cuboideonavicular-ligament":"The dorsal cuboideonavicular ligament is a fibrous bundle connecting the dorsal surfaces of the cuboid and navicular bones.\n\nhttps://en.wikipedia.org/wiki/Dorsal_cuboideonavicular_ligament","dorsal-intercuneiform-ligaments":"The Dorsal intercuneiform ligaments are fibrous bands that connect the dorsal surfaces of the three cuneiform bones.\n\nhttps://en.wikipedia.org/wiki/Dorsal_intercuneiform_ligaments","plantar-intercuneiform-ligaments":"The Plantar intercuneiform ligaments are fibrous bands that connect the plantar surfaces of adjacent cuneiform bones.\n\nhttps://en.wikipedia.org/wiki/Plantar_intercuneiform_ligaments","dorsal-tarsometatarsal-ligaments":"The dorsal tarsometatarsal ligaments are ligaments located in the foot.\n\nThey are strong, flat bands that stretch from the tarsal bones to the metatarsals .\nThe first metatarsal is joined to the first cuneiform by a broad, thin band; the second has three, one from each cuneiform bone; the third has one from the third cuneiform; the fourth has one from the third cuneiform and one from the cuboid; and the fifth, one from the cuboid.\n\nhttps://en.wikipedia.org/wiki/Dorsal_tarsometatarsal_ligaments","plantar-tarsometatarsal-ligaments":"The plantar tarsometatarsal ligaments consist of longitudinal and oblique bands, disposed with less regularity than the dorsal ligaments.\nThose for the first and second metatarsals are the strongest; the second and third metatarsals are joined by oblique bands to the first cuneiform; the fourth and fifth metatarsals are connected by a few fibers to the cuboid.\n\nhttps://en.wikipedia.org/wiki/Plantar_tarsometatarsal_ligaments","dorsal-metatarsal-ligaments":"The dorsal metatarsal ligaments are ligaments in the foot.\n\nhttps://en.wikipedia.org/wiki/Dorsal_metatarsal_ligaments","plantar-metatarsal-ligaments":"The former term 'plantar plate'refered to:\n\n-the plantar metatarsophalangeal ligaments,\n-the plantar interphalangeal ligaments,\n-the palmar metacarpophalangeal ligaments,\n-and the palmar interphalangeal ligaments\n\nTheir proximal origins are thin but the distal insertions are stouts.\n\nDue to the weight-bearing nature of the human foot, the plantar plates are exposed to extension forces not present in the human hand.\n\nThe plantar plate supports the weight of the body and restricts dorsiflexion, whilst the main collateral ligament and the accessory collateral ligament (together referred as the collateral ligament complex, CLC) prevent motions in the transverse and sagittal planes.\n\nThe major difference between the plantar plates of the MTP and IP joints is that they blend with the transverse metatarsal ligament in the MTP joints (not present in the toes).\n\nThe MTP joint of the first toe differs from those of the other toes in that other muscles act on the joint, and in the presence of two sesamoid bones.\n\nThe plantar plate is firm but flexible fibrocartilage with a composition similar to that found in the menisci of the knee (composed roughly of 75% type-I collagen), and can thus withstand compressive loads and act as a supportive articular surface.\n\nMost of its fibers are oriented longitudinally, in the same direction as the plantar fascia, and the plate can thus sustain substantial tensile loads in this direction.\n\nhttps://en.wikipedia.org/wiki/Plantar_plate","metatarsal-interosseous-ligaments":"Ligaments located between the bases of the metatarsal bones and filling the distal parts of the articular spaces.\n\nFeneis 92-14","intersesamoid-ligament":"Connects the two sesamoid bones of the foot, located under the head of the head of metatarsal bone of hallux (Great toe).","collateral-metatarsophalangeal-ligaments":"The collateral ligaments of metatarsophalangeal joints are strong, rounded cords, placed one on either side of each joint, and attached, by one end, to the posterior tubercle on the side of the head of the metatarsal bone, and, by the other, to the contiguous extremity of the phalanx.\n\nThe place of dorsal ligaments is supplied by the extensor tendons on the dorsal surfaces of the joints.\n\nhttps://en.wikipedia.org/wiki/Collateral_ligaments_of_metatarsophalangeal_joints","plantar-metatarsophalangeal-ligaments":"The former term 'plantar plate'refered to:\n\n-the plantar metatarsophalangeal ligaments,\n-the plantar interphalangeal ligaments,\n-the palmar metacarpophalangeal ligaments,\n-and the palmar interphalangeal ligaments\n\nTheir proximal origins are thin but the distal insertions are stouts.\n\nDue to the weight-bearing nature of the human foot, the plantar plates are exposed to extension forces not present in the human hand.\n\nThe plantar plate supports the weight of the body and restricts dorsiflexion, whilst the main collateral ligament and the accessory collateral ligament (together referred as the collateral ligament complex, CLC) prevent motions in the transverse and sagittal planes.\n\nThe major difference between the plantar plates of the MTP and IP joints is that they blend with the transverse metatarsal ligament in the MTP joints (not present in the toes).\n\nThe MTP joint of the first toe differs from those of the other toes in that other muscles act on the joint, and in the presence of two sesamoid bones.\n\nThe plantar plate is firm but flexible fibrocartilage with a composition similar to that found in the menisci of the knee (composed roughly of 75% type-I collagen), and can thus withstand compressive loads and act as a supportive articular surface.\n\nMost of its fibers are oriented longitudinally, in the same direction as the plantar fascia, and the plate can thus sustain substantial tensile loads in this direction.\n\nMetatarsophalangeal joints\n\nAt the metatarsophalangeal joint the plantar plate plays an important role in the foot's weight-bearing function.\n\nThe plantar plate is attached to the proximal phalanx, to the major longitudinal bands of the plantar fascia, and to the collateral ligaments.\n\nTogether with the collateral ligaments, it forms a soft tissue box which is connected to the sides of the metatarsal head.\n\nThe plate from the substantial distal insertion of the plantar fascia and can withstand tensile loads in line with the fascia itself.\n\nThe plate can withstand compressive loads from the metatarsal head because of the orientation of the fibers in its fibrocartilage.\n\nThe skeleton of the foot rests on a multi-layered ligamentous system of beams and trusses that responds to weight-bearing on irregular surfaces.\n\nA transverse system at the MTP joints is formed by the plantar plates and the deep transverse metatarsal ligament.\n\nThe strong, longitudinal fibres of the deep plantar fascia are inserted along this transverse system to form a strong longitudinal system.\n\nThe longitudinal system controls the longitudinal arches of the foot, whilst the transverse system controls the splay of the forefoot.\n\nBoth systems are centered on the plantar plates and activated weight-bearing pressure on the metatarsal heads.\n\nThe tendon of the extensor digitorum longus muscle extends the MTP joint by using the plantar fibroaponeurotic structure as a sling.\n\nThe muscle becomes a deforming force if the MTP joint is held in an extended position over a long time, such as in a high-heeled footwear.\n\nThe muscle extends at the IP joints when the MTP joint is flexed or in neutral position.\n\nFlexion is primarily performed by intrinsic foot muscles; the second toe (the) is unique as it has two dorsal interossei but no plantar interossei muscles.\n\nThe lumbrical muscles, attached to the medial side of the lesser toes, act as unopposed adductor, but become insufficient plantar flexors with chronic extension.\n\nhttps://en.wikipedia.org/wiki/Plantar_plate","deep-transverse-metatarsal-ligament":"The transverse metatarsal ligament is a narrow band which runs across and connects together the heads of all the metatarsal bones.\n\nIt is blended anteriorly with the plantar (glenoid) ligaments of the metatarsophalangeal articulations.\n\nIts plantar surface is concave where the Flexor tendons run below it.\n\nAbove it, the tendons of the Interossei pass to their insertions.\n\nIts homologue in the hand is the transverse metacarpal ligament, which connects the metacarpals to each other.\n\n==Clinical significance==\n\nThe dorsal digital nerves of the foot may be compressed by the transverse metatarsal ligament.\n\nThis causes Morton's neuroma, which causes foot pain.\n\nSee also: 'Deep transverse metacarpal ligament'\n\nhttps://en.wikipedia.org/wiki/Transverse_metatarsal_ligament","collateral-interphalangeal-ligaments-of-foot":"The collateral ligaments of the interphalangeal joints of the foot are fibrous bands that are situated on both sides of the interphalangeal joints of the toes.","plantar-interphalangeal-ligaments":"The former term 'plantar plate'refered to:\n\n-the plantar metatarsophalangeal ligaments,\n-the plantar interphalangeal ligaments,\n-the palmar metacarpophalangeal ligaments,\n-and the palmar interphalangeal ligaments\n\nTheir proximal origins are thin but the distal insertions are stouts.\n\nDue to the weight-bearing nature of the human foot, the plantar plates are exposed to extension forces not present in the human hand.\n\nThe plantar plate supports the weight of the body and restricts dorsiflexion, whilst the main collateral ligament and the accessory collateral ligament (together referred as the collateral ligament complex, CLC) prevent motions in the transverse and sagittal planes.\n\nThe major difference between the plantar plates of the MTP and IP joints is that they blend with the transverse metatarsal ligament in the MTP joints (not present in the toes).\n\nThe MTP joint of the first toe differs from those of the other toes in that other muscles act on the joint, and in the presence of two sesamoid bones.\n\nThe plantar plate is firm but flexible fibrocartilage with a composition similar to that found in the menisci of the knee (composed roughly of 75% type-I collagen), and can thus withstand compressive loads and act as a supportive articular surface.\n\nMost of its fibers are oriented longitudinally, in the same direction as the plantar fascia, and the plate can thus sustain substantial tensile loads in this direction.\n\nhttps://en.wikipedia.org/wiki/Plantar_plate","interosseous-membrane-of-forearm":"The interosseous membrane of the forearm (rarely middle or intermediate radioulnar joint) is a fibrous sheet that connects the interosseous margins of the radius and the ulna.\n\nIt is the main part of the radio-ulnar syndesmosis, a fibrous joint between the two bones.\n\n== Function ==\n\nThe interosseous membrane divides the forearm into anterior and posterior compartments, serves as a site of attachment for muscles of the forearm, and transfers loads placed on the forearm.\n\nThe interosseous membrane is designed to shift compressive loads (as in doing a hand-stand) from the distal radius to the proximal ulna.\n\nThe fibers within the interosseous membrane are oriented obliquely so that when force is applied the fibers are drawn taut, shifting more of the load to the ulna.\n\nThis reduces the wear and tear of placing the whole load on a single joint.\n\nThe role of the membrane in load shifting is illustrated when the interosseous membrane is cut; the forces on each bone equalize from their natural proportions.\n\nAdditionally, as the forearm moves from pronation to supination, the interosseous membrane fibers change from a relaxed state, to a tense state in the neutral position.\n\nThey once again become relaxed as the forearm enters pronation.\nThe interosseous membrane is composed of five ligaments:\n\n- Central band (key portion to be reconstructed in case of injury)\n- Accessory band\n- Distal oblique bundle\n- Proximal oblique cord\n- Dorsal oblique accessory cord\n\n== Injury ==\n\nSevere forearm injuries involving separation of the radius and ulna may be due to rupture of the interosseous membrane.\n\nRupture can lead to proximal migration of the radius and an apparent lengthening of the ulna at the wrist.\n\nOften interosseous membrane tears are associated with adverse impacts on forearm rotation.\n\nMRI-assisted diagnosis has been used for mid-substance tears of the interosseous membrane but is expensive and not widely available.\n\nOn the contrary, ultrasound has proven useful in diagnosing tears of the tibiofibular interosseous membrane of the leg, and this technique may also be applied to acute cases of membrane tears in the forearm due to its low cost and portability.\n\nhttps://en.wikipedia.org/wiki/Interosseous_membrane_of_forearm","tentorium-cerebelli":"/CEREBELLAR TENTORIUM\n\nThe cerebellar tentorium or tentorium cerebelli (Latin for \"tent of the cerebellum\") is an extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes.\n\n== Structure ==\n\nThe cerebellar tentorium is an arched lamina, elevated in the middle, and inclining downward toward the circumference.\n\nIt covers the top of the cerebellum, and supports the occipital lobes of the brain.\n\nIts anterior border is free and concave, and bounds a large oval opening, the tentorial incisure, through which pass the cerebral peduncles.\n\nIt is attached, behind, by its convex border, to the transverse ridges upon the inner surface of the occipital bone, and there encloses the transverse sinuses; in front, to the superior angle of the petrous part of the temporal bone on either side, enclosing the superior petrosal sinuses.\n\nAt the apex of the petrous part of the temporal bone the free and attached borders meet, and, crossing one another, are continued forward to be fixed to the anterior and posterior clinoid processes (respectively) of the sphenoid bone.\n\nTo the middle line of its upper surface the posterior border of the falx cerebri is attached, the straight sinus being placed at their line of junction.\n\n== Clinical significance ==\n\nBrain tumors are often characterized as supratentorial (above the tentorium) and infratentorial (below the tentorium).\n\nThe location of the tumor can help in determining the type of tumor, as different tumors occur with different frequencies at each location.\n\nAdditionally, most childhood primary brain tumors are infratentorial, while most adult primary brain tumors are supratentorial.\n\nThe location of the tumor may have prognostic significance as well.\n\nSince the tentorium is a hard structure, if there is an expansion of the volume of the brain or its surrounding matter above the tentorium, such as because of a tumour or bleeding, the brain can get pushed down partly through the tentorium.\n\nThis is called herniation and will often cause an enlarged pupil on the affected side, due to pressure on the oculomotor nerve.\n\nTentorial herniation is a serious symptom, especially since the brainstem is likely to be compressed as well if the intracranial pressure rises further.\n\nA common type of herniation is uncal herniation.\n\nCalcifications within the cerebellar tentorium are relatively common in elderly people; they seem to rarely cause symptoms.\n\nhttps://en.wikipedia.org/wiki/Cerebellar_tentorium","falx-cerebri":"The falx cerebri, also known as the cerebral falx, is a large, crescent-shaped fold of meningeal layer of dura mater that descends vertically in the longitudinal fissure between the cerebral hemispheres of the human brain.\n\nThe falx cerebri attaches anteriorly at the crista galli in proximity to the cribriform plate and to the frontal and ethmoid sinuses.\n\nPosteriorly, it is connected with the upper surface of the cerebellar tentorium.\n\nIts superior margin is attached at midline to the internal surface of skull, as far back as the internal occipital protuberance.\n\nThe superior sagittal sinus is contained in the superior margin of the falx cerebri and overlies the longitudinal fissure of the brain.\n\nThe inferior sagittal sinus is contained in the inferior margin of the falx cerebri and arches over the corpus callosum, deep in the longitudinal fissure.\n\nThe falx cerebri is named for its sickle-like form.\n\n== Calcification ==\n\nCalcification of the falx cerebri is more prevalent in older patients, often without a determinable cause, and without pathogenic symptoms.\n\n== Meningioma ==\n\nFalcine meningioma is a meningioma arising from the falx cerebri and completely concealed by the overlying cortex.\n\nFalcine meningioma tends to grow predominately into one cerebral hemisphere but is often bilateral, and in some patients the tumor grows into the inferior edge of the sagittal sinus.\n\nHowever, although much information is available regarding meningiomas, little is known about falcine meningiomas.\n\nhttps://en.wikipedia.org/wiki/Falx_cerebri","spinal-dura":"Dura mater is a thick membrane made of dense irregular connective tissue that surrounds the brain and spinal cord.\n\nIt is the outermost of the three layers of membrane called the meninges that protect the central nervous system.\n\nThe other two meningeal layers are the arachnoid mater and the pia mater.\n\nThe dura surrounds the brain and the spinal cord.\n\nIt envelops the arachnoid mater, which is responsible for keeping in the cerebrospinal fluid.\n\nIt is derived primarily from the neural crest cell population, with postnatal contributions of the paraxial mesoderm.\n\n== Structure ==\n\nThe dura mater has several functions and layers.\n\nThe dura mater is a membrane that envelops the arachnoid mater.\n\nIt surrounds and supports the dural sinuses (also called dural venous sinuses, cerebral sinuses, or cranial sinuses) and carries blood from the brain toward the heart.\n\nCranial dura mater has two layers called lamellae, a superficial layer (also called the periosteal layer), which serves as the skull's inner periosteum, called the endocranium and a deep layer called the meningeal layer.\n\nWhen it covers the spinal cord it is known as the dural sac or thecal sac.\n\nUnlike cranial dura mater, spinal dura mater only has one layer, known as the meningeal layer.\n\nThe potential space between these two layers is known as the epidural space.\n\n=== Folds and reflections ===\n\nThe dura separates into two layers at dural reflections (also known as dural folds), places where the inner dural layer is reflected as sheet-like protrusions into the cranial cavity.\n\nThere are two main dural reflections:\n\nThe tentorium cerebelli exists between and separates the cerebellum and brainstem from the occipital lobes of the cerebrum.\n\nThe falx cerebri, which separates the two hemispheres of the brain, is located in the longitudinal cerebral fissure between the hemispheres.\n\nTwo other dural infoldings are the cerebellar falx and the sellar diaphragm:\n\nThe cerebellar falx (falx cerebelli) is a vertical dural infolding that lies inferior to the cerebellar tentorium in the posterior part of the posterior cranial fossa.\n\nIt partially separates the cerebellar hemispheres.\n\nThe sellar diaphragm is the smallest dural infolding and is a circular sheet of dura that is suspended between the clinoid processes, forming a partial roof over the hypophysial fossa.\n\nThe sellar diaphgram covers the pituitary gland in this fossa and has an aperture for passage of the infundibulum (pituitary stalk) and hypophysial veins.\n\n=== Blood supply ===\n\nThis depends upon the area of the cranial cavity:\n in the anterior cranial fossa the anterior meningeal artery (branch from the ethmoidal artery) is responsible for blood supply,\n in the middle cranial fossa the middle meningeal artery and some accessory arteries are responsible for blood supply, the middle meningeal artery is a direct branch from the maxillary artery and enter the cranial cavity through the foramen spinosum and then divides into anterior (which runs usually in vertical direction across the pterion) and posterior (which runs posteriosuperiorly) branches, while the accessory meningeal arteries (which are branches from the maxillary artery) enter the skull through foramen ovale and supply area between the two foramina,\n and the in posterior cranial fossa the dura mater has numerous blood supply from different possible arteries:\n\nA. posterior meningeal artery (from the ascending pharyngeal artery through the jugular foramen)\nB. meningeal arteries (from the ascending pharyngeal artery through hypoglossal canal)\nC. meningeal arteries (from occipital artery through jugular or mastoid foramen)\nD. meningeal arteries (from vertebral artery through foramen magnum)\n\n=== Drainage ===\n\nThe two layers of dura mater run together throughout most of the skull.\n\nWhere they separate, the gap between them is called a dural venous sinus.\n\nThese sinuses drain blood and cerebrospinal fluid (CSF) from the brain and empty into the internal jugular vein.\n\nArachnoid villi, which are outgrowths of the arachnoid mater (the middle meningeal layer), extend into the dural venous sinuses to drain CSF.\n\nThese villi act as one-way valves.\nMeningeal veins, which course through the dura mater, and bridging veins, which drain the underlying neural tissue and puncture the dura mater, empty into these dural sinuses.\n\nA rupture of a bridging vein causes a subdural hematoma.\n\n=== Nerve supply ===\n\nThe supratentorial dura mater membrane is supplied by small meningeal branches of the trigeminal nerve (V1, V2 and V3).\n\nThe innervation for the infratentorial dura mater are via upper cervical nerves and the meningeal branch of the vagus nerve.\n\n== Clinical significance ==\n\nMany medical conditions involve the dura mater.\n\nA subdural hematoma occurs when there is an abnormal collection of blood between the dura and the arachnoid, usually as a result of torn bridging veins secondary to head trauma.\n\nAn epidural hematoma is a collection of blood between the dura and the inner surface of the skull, and is usually due to arterial bleeding.\n\nIntradural procedures, such as removal of a brain tumour or treatment of trigeminal neuralgia via a microvascular decompression, require that an incision is made to the dura mater.\n\nTo achieve a watertight repair and avoid potential post-operative complications, the dura is typically closed with sutures.\n\nIf there is a dural deficiency, then a dural substitute may be used to replace this membrane.\n\nSmall gaps in the dura can be covered with a surgical sealant film.\nIn 2011, researchers discovered a connective tissue bridge from the rectus capitis posterior major to the cervical dura mater.\n\nVarious clinical manifestations may be linked to this anatomical relationship such as headaches, trigeminal neuralgia and other symptoms that involved the cervical dura.\n\nThe rectus capitis posterior minor has a similar attachment.The dura-muscular, dura-ligamentous connections in the upper cervical spine and occipital areas may provide anatomic and physiologic answers to the cause of the cervicogenic headache.\n\nThis proposal would further explain manipulation's efficacy in the treatment of cervicogenic headache.\n\nThe American Red Cross and some other agencies accepting blood donations consider dura mater transplants, along with receipt of pituitary-derived growth hormone, a risk factor due to concerns about Creutzfeldt–Jakob disease.Cerebellar tonsillar ectopia, or Chiari, is a condition that was previously thought to be congenital but can be induced by trauma, particularly whiplash trauma.\n\nDural strain may be pulling the cerebellum inferiorly, or skull distortions may be pushing the brain inferiorly.\n\nDural ectasia is the enlargement of the dura and is common in connective tissue disorders, such as Marfan syndrome and Ehlers–Danlos syndrome.\n\nThese conditions are sometimes found in conjunction with Arnold–Chiari malformation.\n\nSpontaneous cerebrospinal fluid leak is the fluid and pressure loss of spinal fluid due to holes in the dura mater.\n\n== Etymology ==\n\nThe name dura mater derives from the Latin for tough mother (or hard mother), a loan translation of Arabic أم الدماغ الصفيقة (umm al-dimāgh al-ṣafīqah), literally 'thick mother of the brain', matrix of the brain, and is also referred to by the term \"pachymeninx\" (plural \"pachymeninges\").\n\nhttps://en.wikipedia.org/wiki/Dura_mater","choroid-plexus":"The choroid plexus, or plica choroidea, is a plexus of cells that arises from the tela choroidea in each of the ventricles of the brain.\n\nThe choroid plexus produces most of the cerebrospinal fluid (CSF) of the central nervous system.\n\nCSF is produced and secreted by the regions of the choroid plexus.\n\nThe choroid plexus consists of modified ependymal cells surrounding a core of capillaries and loose connective tissue.\n\n== Structure ==\n\n=== Location ===\n\nThere is a choroid plexus in each of the four ventricles.\n\nIn the lateral ventricles it is found in the body, and continued in an enlarged amount in the atrium.\n\nThere is no choroid plexus in the anterior horn.\n\nIn the third ventricle there is a small amount in the roof that is continuous with that in the body, via the interventricular foramina, the channels that connect the lateral ventricles with the third ventricle.\n\nA choroid plexus is in part of the roof of the fourth ventricle.\n\n=== Microanatomy ===\n\nThe choroid plexus consists of a layer of cuboidal epithelial cells surrounding a core of capillaries and loose connective tissue.\n\nThe epithelium of the choroid plexus is continuous with the ependymal cell layer (ventricular layer) that lines the ventricular system.\n\nProgenitor ependymal cells are monociliated but they differentiate into multiciliated ependymal cells.\n\nUnlike the ependyma, the choroid plexus epithelial layer has tight junctions between the cells on the side facing the ventricle (apical surface).\n\nThese tight junctions prevent the majority of substances from crossing the cell layer into the cerebrospinal fluid (CSF); thus the choroid plexus acts as a blood–CSF barrier.\n\nThe choroid plexus folds into many villi around each capillary, creating frond-like processes that project into the ventricles.\n\nThe villi, along with a brush border of microvilli, greatly increase the surface area of the choroid plexus.\n\nCSF is formed as plasma is filtered from the blood through the epithelial cells.\n\nChoroid plexus epithelial cells actively transport sodium ions into the ventricles and water follows the resulting osmotic gradient.\n\nThe choroid plexus consists of many capillaries, separated from the ventricles by choroid epithelial cells.\n\nFluid filters through these cells from blood to become cerebrospinal fluid.\n\nThere is also much active transport of substances into, and out of, the CSF as it is made.\n\n== Function ==\n\nThe choroid plexus regulates the production and composition of cerebrospinal fluid (CSF), that provides the protective buoyancy for the brain.\n\nCSF acts as a medium for the glymphatic filtration system that facilitates the removal of metabolic waste from the brain, and the exchange of biomolecules and xenobiotics into and out of the brain.\n\nIn this way the choroid plexus has a very important role in helping to maintain the delicate extracellular environment required by the brain to function optimally.\n\nThe choroid plexus is also a major source of transferrin secretion that plays a part in iron homeostasis in the brain.\n\n=== Blood–cerebrospinal fluid barrier ===\n\nThe blood–cerebrospinal fluid barrier (BCSFB) is a fluid–brain barrier that is composed of a pair of membranes that separate blood from CSF at the capillary level and CSF from brain tissue.\n\nThe blood–CSF boundary at the choroid plexus is a membrane composed of epithelial cells and tight junctions that link them.\n\nThere is a CSF-brain barrier at the level of the pia mater, but only in the embryo.\n\nSimilar to the blood–brain barrier, the blood–CSF barrier functions to prevent the passage of most blood-borne substances into the brain, while selectively permitting the passage specific substances into the brain and facilitating the removal of brain metabolites and metabolic products into the blood.\n\nDespite the similar function between the BBB and BCSFB, each facilitates the transport of different substances into the brain due to the distinctive structural characteristics of each of the two barrier systems.\n\nFor a number of substances, the BCSFB is the primary site of entry into brain tissue.\n\nThe blood–cerebrospinal fluid barrier has also been shown to modulate the entry of leukocytes from the blood to the central nervous system.\n\nThe choroid plexus cells secrete cytokines that recruit monocyte-derived macrophages, among other cells, to the brain.\n\nThis cellular trafficking has implications both in normal brain homeostasis and in neuroinflammatory processes.\n\n== Clinical significance ==\n\n=== Choroid plexus cysts ===\n\nDuring fetal development, some choroid plexus cysts may form.\n\nThese fluid-filled cysts can be detected by a detailed second trimester ultrasound.\n\nThe finding is relatively common, with a prevalence of ~1%.\n\nChoroid plexus cysts are usually an isolated finding.\n\nThe cysts typically disappear later during pregnancy, and are usually harmless.\n\nThey have no effect on infant and early childhood development.Cysts confers a 1% risk of fetal aneuploidy.\n\nThe risk of aneuploidy increases to 10.5-12% if other risk factors or ultrasound findings are noted.\n\nSize, location, disappearance or progression, and whether the cysts are found on both sides or not do not affect the risk of aneuploidy.\n\n44-50% of Edwards syndrome (trisomy 18) cases will present with choroid plexus cysts, as well 1.4% of Down syndrome (trisomy 21) cases.\n\n~75% of abnormal karyotypes associated with choroid plexus cysts are trisomy 18, while the remainder are trisomy 21.\n\n=== Other ===\n\nThere are three graded types of choroid plexus tumor that mainly affect young children.\n\nThese types of cancer are rare.\n\n== Etymology ==\n\nChoroid plexus translates from the Latin plexus chorioides, which mirrors Ancient Greek χοριοειδές πλέγμα.\n\nThe word chorion was used by Galen to refer to the outer membrane enclosing the fetus.\n\nBoth meanings of the word plexus are given as pleating, or braiding.\n\nAs often happens language changes and the use of both choroid or chorioid is both accepted.\n\nNomina Anatomica (now Terminologia Anatomica) reflected this dual usage.\n\nhttps://en.wikipedia.org/wiki/Choroid_plexus","temporal-pole":"There are three known poles of the cerebral hemispheres: the occipital pole, the frontal pole, and the temporal pole.","occipital-pole":"There are three known poles of the cerebral hemispheres: the occipital pole, the frontal pole, and the temporal pole.","central-sulcus":"The central sulcus is a sulcus, or groove, in the cerebral cortex in the brains of vertebrates.\n\nAlso called the central fissure, or the fissure of Rolando or the Rolandic fissure, after Luigi Rolando.\n\nIt is sometimes confused with the longitudinal fissure.\n\nThe central sulcus is a prominent landmark of the brain, separating the parietal lobe from the frontal lobe and the primary motor cortex from the primary somatosensory cortex.\n\n== Evolution of the central sulcus ==\n\nThe evolution of the central sulcus is theorized to have occurred in mammals when the complete dissociation of the original somatosensory cortex from its mirror duplicate developed in placental mammals such as primates, though the development did not stop there as time progressed the distinction between the two cortices grew.\n\n=== Evolution in primates ===\n\nThe central sulcus is more prominent in apes as a result of fine-tuning of the motor system in apes.\n\nHominins (bipedal apes) continued this trend through increased use of their hands due to the advent of bipedalism.\n\nThis allowed for their hands to be freed up from their use in locomotion to focus on more complex manipulative actions such as grasping, tool use, tool making, and many others.\n\nPrevious studies have also shown that the location where the split in the central sulcus occurs is at the division point between the wrist and the individual digits in primary motor cortex, further implicating the relation between the development of this region through the use of their digits.\n\nThe KNOB is also a suggested cortical substrate of the hand, as there have been anatomical asymmetries which have been linked to hand preference and skill, further suggesting the development of hands in the formation of the central sulcus seeing as the KNOB is the central portion of the central sulcus folded over the buried gyrus.\n\n== Development in humans ==\n\nThe central sulcus begins developing around 13 weeks of gestational age undergoes the fastest period of growth between 13 and 15 weeks of gestational age.\n\nHowever, the most active period of development is at approximately 18 to 19 weeks of gestational age.\n\nThis is determined by when there is the greatest amount of migration of neurons and fibers occurring.\n\nIt begins as a point or groove in the parasagittal region of the brain.\n\nIt then becomes a distinct invagination that lengthens towards the lateral sulcus and towards the longitudinal fissure at approximately 22 to 23 weeks of gestational age.\n\nBetween 2 and 3 years of age, the landmark ‘Pli de Passage Frontoparietal Moyen’ (PPFM), which is a depression buried at the central part of the central sulcus, begins to appear.\n\nAt 3 years of age, the average depth curve of the central sulcus is similar to that of adults.\n\n=== Influences on development ===\n\nThe development of the shape of the central sulcus is influenced by both genetic and non-genetic factors.\n\nThe deep structure of the central sulcus has been found to be more consistent in different brains than its superficial structure, suggesting that the superficial structure is more susceptible to non-genetic factors.\n\nThe shape of the central sulcus has been found to be different between people of different biological sex.\n\nThose of male biological sex have been found to have a less convoluted (small fractal dimension) right anterior wall of the central sulcus.\n\nIn addition, while the width of the central sulcus varies, the central sulcus of males has shown to have a larger average width than the central sulcus of females.\n\nHowever, this is specific to the right hemisphere since the central sulcus of the left hemisphere has not shown significant results regarding gender differences.\n\nWith regard to gender differences between hemispheres, females have been shown to have a larger average width of the central sulcus on the left side compared to that of the central sulcus on the right side.\n\nAge also affects the shape of the central sulcus.\n\nIn adults, the distance between the anterior and posterior walls (sulcal span) increases, while the surface area of walls, the sulcal length of the posterior wall, and the convolution (fractal dimension) for the right posterior wall of the central sulcus decrease.\n\nThe posterior walls of the central sulcus appear to be affected more with age.\n\nDifferences between genders regarding the average width of the central sulcus as one ages has also been shown.\n\nThe average width of the central sulcus in males tends to increase more rapidly over time than that of females.\n\nThe surface area of the central sulcus has proven to have an effect on the handedness of an individual.\n\nStudies have found that when the central sulcus is larger in the left hemisphere, the individual tends to me more right hand dominant.\n\nThis is also true about the central sulcus for left handed individuals; there is a greater surface area of the central sulcus in the right hemisphere.\n\nWhile the surface area of the central sulcus is shown to affect the handedness of an individual, it is not understood what the shape of the central sulcus affects as it is not widely explored.\n\nThere is a region of the central sulcus, called the “hand knob”, which is a notch in the area of the hand motor region.\n\nThe position of this “knob” can be indicative as well of someone's handedness.As motor functions develop, it is expected that the shape of the central sulcus will change.\n\nThis is due to the role of the central sulcus in separating the primary motor cortex and primary somatosensory cortex.\n\nFor example, differences along the central sulcus have been reported in musicians, particularly with regard to an omega formation along the center portion of the central sulcus, commonly referred to as the \"hand knob\".\n\nAmong musicians who specialize in string instruments, this omega formation is specific to the right central sulcus.\n\nHowever, among pianists, this omega formation occurs on both sides but more prominently on the left side.\n\n== Clinical significance ==\n\n=== Attention deficit hyperactivity disorder ===\n\nAttention deficit hyperactivity disorder (ADHD) has been associated with sensorimotor deficits and the central sulcus divides both somatosensory and primary motor areas prompting research into how the shape of the central sulcus and ADHD may alter brain development in these individuals.\n\nThe cortical thickness and average and maximum depth of the central sulcus has been shown to be larger for ADHD individuals when compared to neurotypical individuals.\n\nAdditionally, changes in the middle sections of the central sulcus have been linked to children with ADHD.\n\n=== Williams syndrome ===\n\nThe morphology of the central sulcus has been suggested to play a role in individuals with the generic condition known as Williams syndrome.\n\nThe foreshortening of the central sulcus has been found to be an abnormality associated with this syndrome.\n\nThis can be seen with the abnormal dorsal end of the central sulcus in individuals with Williams syndrome.\n\nHowever, the abnormal dorsal end of the central sulcus has not been found to be linked to impaired general intelligence.\n\nThe functional importance of this abnormal part of the central sulcus is still not fully understood though.\n\n=== Severe cerebral small vessel disease ===\n\nThe shape of the central sulcus has been linked to the degree of disability in individuals who have a small subcortical ischemic stroke as a result of severe cerebral small vessel disease.\n\nHowever, the severity of the disability has been found to not be fully dependent upon the morphology of the central sulcus.\n\nIt was found to possibly be due to the hand knobs’ vertical position and size.\n\nhttps://en.wikipedia.org/wiki/Central_sulcus","parieto-occipital-sulcus":"The parieto-occipital sulcus (also called the parieto-occipital fissure) is a deep sulcus in the cerebral cortex that marks the boundary between the cuneus and precuneus, and also between the parietal and occipital lobes.\n\nOnly a small part can be seen on the lateral surface of the hemisphere, its chief part being on the medial surface.\n\nThe lateral part of the parieto-occipital sulcus is situated about 5 cm in front of the occipital pole of the hemisphere, and measures about 1.25 cm. in length.\n\nThe medial part of the parieto-occipital sulcus runs downward and forward as a deep cleft on the medial surface of the hemisphere, and joins the calcarine fissure below and behind the posterior end of the corpus callosum.\n\nIn most cases, it contains a submerged gyrus.\n\n== Function ==\n\nThe parieto-occipital lobe has been found in various neuroimaging studies, including PET (positron-emission-tomography) studies, and SPECT (single-photon emission computed tomography) studies, to be involved along with the dorsolateral prefrontal cortex during planning.\n\nhttps://en.wikipedia.org/wiki/Parieto-occipital_sulcus","subparietal-sulcus":"The subparietal sulcus (Sulcus subparietalis) or suprasplenial sulcus is a sulcus, or crevice, on the medial surface of each cerebral hemisphere, above the splenium of the corpus callosum.\n\nIt separates the precuneus from the posterior part of the cingulate gyrus.\n\nIt is the posterior continuation of the cingulate sulcus.\n\nThe cingulate sulcus actually \"terminates\" as the marginal sulcus of the cingulate sulcus (margin of cingulate gyrus).\n\nIt extends posteriorly toward the calcarine sulcus.\n\nThe precuneus is bordered anteriorly by the marginal branch of the cingulate sulcus (margin of cingulate sulcus), posteriorly by the parietooccipital sulcus, and inferiorly by the subparietal sulcus.\n\nhttps://en.wikipedia.org/wiki/Subparietal_sulcus","cingulate-sulcus-marginal-part":"The cingulate sulcus is a sulcus (brain fold) on the cingulate cortex in the medial wall of the cerebral cortex.\n\nThe frontal and parietal lobes are separated from the cingulate gyrus by the cingulate sulcus.\n\nIt terminates as the marginal sulcus of the cingulate sulcus.\n\nIt sends a ramus to separate the paracentral lobule from the frontal gyri, the paracentral sulcus.\n\nhttps://en.wikipedia.org/wiki/Cingulate_sulcus","circular-sulcus-of-insula":"The insular cortex (also insula and insular lobe) is a portion of the cerebral cortex folded deep within the lateral sulcus (the fissure separating the temporal lobe from the parietal and frontal lobes) within each hemisphere of the mammalian brain.\n\nThe insulae are believed to be involved in consciousness and play a role in diverse functions usually linked to emotion or the regulation of the body's homeostasis.\n\nThese functions include compassion, empathy, taste, perception, motor control, self-awareness, cognitive functioning, interpersonal experience, and awareness of homeostatic emotions such as hunger, pain and fatigue.\n\nIn relation to these, it is involved in psychopathology.\n\nThe insular cortex is divided into two parts: the anterior insula and the posterior insula in which more than a dozen field areas have been identified.\n\nThe cortical area overlying the insula toward the lateral surface of the brain is the operculum (meaning lid).\n\nThe opercula are formed from parts of the enclosing frontal, temporal, and parietal lobes.\n\n== Structure ==\n\n=== Connections ===\n\nThe anterior part of the insula is subdivided by shallow sulci into three or four short gyri.\n\nThe anterior insula receives a direct projection from the basal part of the ventral medial nucleus of the thalamus and a particularly large input from the central nucleus of the amygdala.\n\nIn addition, the anterior insula itself projects to the amygdala.\n\nOne study on rhesus monkeys revealed widespread reciprocal connections between the insular cortex and almost all subnuclei of the amygdaloid complex.\n\nThe posterior insula projects predominantly to the dorsal aspect of the lateral and to the central amygdaloid nuclei.\n\nIn contrast, the anterior insula projects to the anterior amygdaloid area as well as the medial, the cortical, the accessory basal magnocellular, the medial basal, and the lateral amygdaloid nuclei.\n\nThe posterior part of the insula is formed by a long gyrus.\n\nThe posterior insula connects reciprocally with the secondary somatosensory cortex and receives input from spinothalamically activated ventral posterior inferior thalamic nuclei.\n\nIt has also been shown that this region receives inputs from the ventromedial nucleus (posterior part) of the thalamus that are highly specialized to convey homeostatic information such as pain, temperature, itch, local oxygen status, and sensual touch.\n\nA human neuroimaging study using diffusion tensor imaging revealed that the anterior insula is interconnected to regions in the temporal and occipital lobe, opercular and orbitofrontal cortex, triangular and opercular parts of the inferior frontal gyrus.\n\nThe same study revealed differences in the anatomical connection patterns between the left and right hemisphere.\n\nThe 'circular sulcus of insula' (or sulcus of Reil) is a semi-circular sulcus or fissure that separates the insula from the neighboring gyri of the operculum in the front, above, and\nbehind.\n\n=== Cytoarchitecture ===\n\nThe insular cortex has regions of variable cell structure or cytoarchitecture, changing from granular in the posterior portion to agranular in the anterior portion.\n\nThe insula also receives differential cortical and thalamic input along its length.\n\nThe anterior insular cortex contains a population of spindle neurons (also called von Economo neurons), identified as characterising a distinctive subregion as the agranular frontal insula.\n\n=== Development ===\n\nThe insular cortex is considered a separate lobe of the telencephalon by some authorities.\n\nOther sources see the insula as a part of the temporal lobe.\n\nIt is also sometimes grouped with limbic structures deep in the brain into a limbic lobe.\n\nAs a paralimbic cortex, the insular cortex is considered to be a relatively old structure.\n\n== Function ==\n\n=== Multimodal sensory processing, sensory binding ===\n\nFunctional imaging studies show activation of the insula during audio-visual integration tasks.\n\n=== Taste ===\n\nThe anterior insula is part of the primary gustatory cortex.\n\n=== Interoceptive awareness ===\n\nThere is evidence that, in addition to its base functions, the insula may play a role in certain higher-level functions that operate only in humans and other great apes.\n\nThe spindle neurons found at a higher density in the right frontal insular cortex are also found in the anterior cingulate cortex, which is another region that has reached a high level of specialization in great apes.\n\nIt has been speculated that these neurons are involved in cognitive-emotional processes that are specific to primates including great apes, such as empathy and metacognitive emotional feelings.\n\nThis is supported by functional imaging results showing that the structure and function of the right frontal insula is correlated with the ability to feel one's own heartbeat, or to empathize with the pain of others.\n\nIt is thought that these functions are not distinct from the lower-level functions of the insula but rather arise as a consequence of the role of the insula in conveying homeostatic information to consciousness.\n\nThe right anterior insula is engaged in interoceptive awareness of homeostatic emotions such as thirst, pain and fatigue, and the ability to time one's own heartbeat.\n\nMoreover, greater right anterior insular gray matter volume correlates with increased accuracy in this subjective sense of the inner body, and with negative emotional experience.\n\nIt is also involved in the control of blood pressure, in particular during and after exercise, and its activity varies with the amount of effort a person believes he/she is exerting.\n\nThe insular cortex also is where the sensation of pain is judged as to its degree.\n\nFurther, the insula is where a person imagines pain when looking at images of painful events while thinking about their happening to one's own body.\n\nThose with irritable bowel syndrome have abnormal processing of visceral pain in the insular cortex related to dysfunctional inhibition of pain within the brain.Another perception of the right anterior insula is the degree of nonpainful warmth or nonpainful coldness of a skin sensation.\n\nOther internal sensations processed by the insula include stomach or abdominal distension.\n\nA full bladder also activates the insular cortex.One brain imaging study suggests that the unpleasantness of subjectively perceived dyspnea is processed in the right human anterior insula and amygdala.\n\nThe cerebral cortex processing vestibular sensations extends into the insula, with small lesions in the anterior insular cortex being able to cause loss of balance and vertigo.\n\nOther noninteroceptive perceptions include passive listening to music, laughter, and crying, empathy and compassion, and language.\n\n=== Motor control ===\n\nIn motor control, it contributes to hand-and-eye motor movement, swallowing, gastric motility, and speech articulation.\n\nIt has been identified as a \"central command” centre that ensures that heart rate and blood pressure increase at the onset of exercise.\n\nResearch upon conversation links it to the capacity for long and complex spoken sentences.\n\nIt is also involved in motor learning and has been identified as playing a role in the motor recovery from stroke.\n\n=== Homeostasis ===\n\nIt plays a role in a variety of homeostatic functions related to basic survival needs, such as taste, visceral sensation, and autonomic control.\n\nThe insula controls autonomic functions through the regulation of the sympathetic and parasympathetic systems.\n\nIt has a role in regulating the immune system.\n\n=== Self ===\n\nThe insula has been identified as playing a role in the experience of bodily self-awareness, sense of agency, and sense of body ownership.\n\n=== Social emotions ===\n\nThe anterior insula processes a person's sense of disgust both to smells and to the sight of contamination and mutilation — even when just imagining the experience.\n\nThis associates with a mirror neuron-like link between external and internal experiences.\n\nIn social experience, it is involved in the processing of norm violations, emotional processing, empathy, and orgasms.The insula is active during social decision making.\n\nTiziana Quarto et al. measured emotional intelligence (EI) (the ability to identify, regulate, and process emotions of themselves and of others) of sixty-three healthy subjects.\n\nUsing fMRI EI was measured in correlation with left insular activity.\n\nThe subjects were shown various pictures of facial expressions and tasked with deciding to approach or avoid the person in the picture.\n\nThe results of the social decision task yielded that individuals with high EI scores had left insular activation when processing fearful faces.\n\nIndividuals with low EI scores had left insular activation when processing angry faces.\n\n=== Emotions ===\n\nThe insular cortex, in particular its most anterior portion, is considered a limbic-related cortex.\n\nThe insula has increasingly become the focus of attention for its role in body representation and subjective emotional experience.\n\nIn particular, Antonio Damasio has proposed that this region plays a role in mapping visceral states that are associated with emotional experience, giving rise to conscious feelings.\n\nThis is in essence a neurobiological formulation of the ideas of William James, who first proposed that subjective emotional experience (i.e., feelings) arise from our brain's interpretation of bodily states that are elicited by emotional events.\n\nThis is an example of embodied cognition.\nIn terms of function, the insula is believed to process convergent information to produce an emotionally relevant context for sensory experience.\n\nTo be specific, the anterior insula is related more to olfactory, gustatory, viscero-autonomic, and limbic function, whereas the posterior insula is related more to auditory-somesthetic-skeletomotor function.\n\nFunctional imaging experiments have revealed that the insula has an important role in pain experience and the experience of a number of basic emotions, including anger, fear, disgust, happiness, and sadness.The anterior insular cortex (AIC) is believed to be responsible for emotional feelings, including maternal and romantic love, anger, fear, sadness, happiness, sexual arousal, disgust, aversion, unfairness, inequity, indignation, uncertainty, disbelief, social exclusion, trust, empathy, sculptural beauty, a ‘state of union with God’, and hallucinogenic states.\n\nFunctional imaging studies have also implicated the insula in conscious desires, such as food craving and drug craving.\n\nWhat is common to all of these emotional states is that they each change the body in some way and are associated with highly salient subjective qualities.\n\nThe insula is well-situated for the integration of information relating to bodily states into higher-order cognitive and emotional processes.\n\nThe insula receives information from \"homeostatic afferent\" sensory pathways via the thalamus and sends output to a number of other limbic-related structures, such as the amygdala, the ventral striatum, and the orbitofrontal cortex, as well as to motor cortices.\n\nA study using magnetic resonance imaging found that the right anterior insula is significantly thicker in people that meditate.\n\nOther research into brain activity and meditation has shown an increase in grey matter in areas of the brain including the insular cortex.\n\nAnother study using voxel-based morphometry and MRI on experienced Vipassana meditators was done to extend the findings of Lazar et al., which found increased grey matter concentrations in this and other areas of the brain in experienced meditators.\n\nThe strongest evidence against a causative role for the insula cortex in emotion comes from Damasio et al. (2012) which showed that a patient who suffered bilateral lesions of the insula cortex expressed the full complement of human emotions, and was fully capable of emotional learning.\n\n=== Salience ===\n\nFunctional neuroimaging research suggests the insula is involved in two types of salience.\n\nInteroceptive information processing that links interoception with emotional salience to generate a subjective representation of the body.\n\nThis involves, first, the anterior insular cortex with the pregenual anterior cingulate cortex (Brodmann area 33) and the anterior and posterior mid-cingulate cortices, and, second, a general salience network concerned with environmental monitoring, response selection, and skeletomotor body orientation that involves all of the insular cortex and the mid-cingulate cortex.\n\nAn alternative or perhaps complementary proposal is that the right anterior insular regulates the interaction between the salience of the selective attention created to achieve a task (the dorsal attention system) and the salience of arousal created to keep focused upon the relevant part of the environment (ventral attention system).\n\nThis regulation of salience might be particularly important during challenging tasks where attention might fatigue and so cause careless mistakes but if there is too much arousal it risks creating poor performance by turning into anxiety.\n\n=== Auditory perception ===\n\nRecent research indicates that the insular cortex is involved in auditory perception.\n\nResponses to sound stimuli were obtained using intracranial EEG recordings acquired from patients with epilepsy.\n\nThe posterior part of the insula showed auditory responses that resemble those observed in Heschl’s gyrus, whereas the anterior part responded to the emotional contents of the auditory stimuli.\n\nDirect recordings from the posterior part of the insula showed responses to unexpected sounds within regular auditory streams, a process known as auditory deviance detection.\n\nResearchers observed a mismatch negativity (MMN) potential, a well known event related potential, as well as the high frequency activity signals originating from local neurons.\n\nSimple auditory illusions and hallucinations were elicited by electrical functional mapping.\n\n== Clinical significance ==\n\n=== Progressive expressive aphasia ===\n\nProgressive expressive aphasia is the deterioration of normal language function that causes individuals to lose the ability to communicate fluently while still being able to comprehend single words and intact other non-linguistic cognition.\n\nIt is found in a variety of degenerative neurological conditions including Pick's disease, motor neuron disease, corticobasal degeneration, frontotemporal dementia, and Alzheimer's disease.\n\nIt is associated with hypometabolism and atrophy of the left anterior insular cortex.\n\n=== Addiction ===\n\nA number of functional brain imaging studies have shown that the insular cortex is activated when drug users are exposed to environmental cues that trigger cravings.\n\nThis has been shown for a variety of drugs, including cocaine, alcohol, opiates, and nicotine.\n\nDespite these findings, the insula has been ignored within the drug addiction literature, perhaps because it is not known to be a direct target of the mesocortical dopamine system, which is central to current dopamine reward theories of addiction.\n\nResearch published in 2007 has shown that cigarette smokers suffering damage to the insular cortex, from a stroke for instance, have their addiction to cigarettes practically eliminated.\n\nThese individuals were found to be up to 136 times more likely to undergo a disruption of smoking addiction than smokers with damage in other areas.\n\nDisruption of addiction was evidenced by self-reported behavior changes such as quitting smoking less than one day after the brain injury, quitting smoking with great ease, not smoking again after quitting, and having no urge to resume smoking since quitting.\n\nThe study was conducted on average eight years after the strokes, which opens up the possibility that recall bias could have affected the results.\n\nMore recent prospective studies, which overcome this limitation, have corroborated these findings.\n\nThis suggests a significant role for the insular cortex in the neurological mechanisms underlying addiction to nicotine and other drugs, and would make this area of the brain a possible target for novel anti-addiction medication.\n\nIn addition, this finding suggests that functions mediated by the insula, especially conscious feelings, may be particularly important for maintaining drug addiction, although this view is not represented in any modern research or reviews of the subject.\n\nA recent study in rats by Contreras et al. corroborates these findings by showing that reversible inactivation of the insula disrupts amphetamine conditioned place preference, an animal model of cue-induced drug craving.\n\nIn this study, insula inactivation also disrupted \"malaise\" responses to lithium chloride injection, suggesting that the representation of negative interoceptive states by the insula plays a role in addiction.\n\nHowever, in this same study, the conditioned place preference took place immediately after the injection of amphetamine, suggesting that it is the immediate, pleasurable interoceptive effects of amphetamine administration, rather than the delayed, aversive effects of amphetamine withdrawal that are represented within the insula.\n\nA model proposed by Naqvi et al. (see above) is that the insula stores a representation of the pleasurable interoceptive effects of drug use (e.g., the airway sensory effects of nicotine, the cardiovascular effects of amphetamine), and that this representation is activated by exposure to cues that have previously been associated with drug use.\n\nA number of functional imaging studies have shown the insula to be activated during the administration of addictive psychoactive drugs.\n\nSeveral functional imaging studies have also shown that the insula is activated when drug users are exposed to drug cues, and that this activity is correlated with subjective urges.\n\nIn the cue-exposure studies, insula activity is elicited when there is no actual change in the level of drug in the body.\n\nTherefore, rather than merely representing the interoceptive effects of drug use as it occurs, the insula may play a role in memory for the pleasurable interoceptive effects of past drug use, anticipation of these effects in the future, or both.\n\nSuch a representation may give rise to conscious urges that feel as if they arise from within the body.\n\nThis may make addicts feel as if their bodies need to use a drug, and may result in persons with lesions in the insula reporting that their bodies have forgotten the urge to use, according to this study.\n\n=== Subjective certainty in ecstatic seizures ===\n\nA common quality in mystical experiences is a strong feeling of certainty which cannot be expressed in words.\n\nFabienne Picard proposes a neurological explanation for this subjective certainty, based on clinical research of epilepsy.\n\nAccording to Picard, this feeling of certainty may be caused by a dysfunction of the anterior insula, a part of the brain which is involved in interoception, self-reflection, and in avoiding uncertainty about the internal representations of the world by \"anticipation of resolution of uncertainty or risk\".\n\nThis avoidance of uncertainty functions through the comparison between predicted states and actual states, that is, \"signaling that we do not understand, i.e., that there is ambiguity.\"\n\nPicard notes that \"the concept of insight is very close to that of certainty,\" and refers to Archimedes' \"Eureka!\" Picard hypothesizes that during ecstatic seizures the comparison between predicted states and actual states no longer functions, and that mismatches between predicted state and actual state are no longer processed, blocking \"negative emotions and negative arousal arising from predictive uncertainty,\" which will be experienced as emotional confidence.\n\nPicard concludes that \"[t]his could lead to a spiritual interpretation in some individuals.\"\n\n=== Other clinical conditions ===\n\nThe insular cortex has been suggested to have a role in anxiety disorders, emotion dysregulation, and anorexia nervosa.\n\n== History ==\n\nThe insula was first described by Johann Christian Reil while describing cranial and spinal nerves and plexuses.\n\nHenry Gray in Gray's Anatomy is responsible for it being known as the Island of Reil.\n\nJohn Allman and colleagues showed that anterior insular cortex contains spindle neurons.\n\nhttps://en.wikipedia.org/wiki/Insular_cortex","collateral-sulcus":"COLLATERAL FISSURE\n\nThe collateral fissure (or sulcus) is on the tentorial surface of the hemisphere and extends from near the occipital pole to within a short distance of the temporal pole.\n\nBehind, it lies below and lateral to the calcarine fissure, from which it is separated by the lingual gyrus; in front, it is situated between the parahippocampal gyrus and the anterior part of the fusiform gyrus.\n\nhttps://en.wikipedia.org/wiki/Collateral_fissure","opercular-part-of-inferior-frontal-gyrus":"The inferior frontal gyrus is highly convoluted and has three cytoarchitecturally diverse regions.\n\nThe three subdivisions are an opercular part, a triangular part, and an orbital part.\n\nThese divisions are marked by two rami arising from the lateral sulcus.\n\nThe ascending ramus separates the opercular and triangular parts.\n\nThe anterior (horizontal) ramus separates the triangular and orbital parts.\n\nOpercular part of inferior frontal gyrus (pars opercularis), (cortex posterior to the ascending ramus of the lateral sulcus), is the part of frontal lobe that overlies the insular cortex and may be associated with recognizing a tone of voice in spoken native languages.\n\nThis expands on previous work indicating that comprehension of inflectional morpheme processing is associated with the inferior frontal gyrus.\n\nCytoarchitecturally the opercular part of the inferior frontal gyrus is known as Brodmann area 44 (BA44).","orbital-part-of-inferior-frontal-gyrus":"Orbital part of inferior frontal gyrus (pars orbitalis) (cortex inferior and anterior to the horizontal ramus of the lateral sulcus).\n\nThe orbital part of the inferior frontal gyrus is known as Brodmann area 47.","triangular-part-of-inferior-frontal-gyrus":"Triangular part of inferior frontal gyrus (pars triangularis), (cortex between the ascending ramus and the horizontal ramus of the lateral sulcus).\n\nIt may be associated with the ability to translate from a secondary or tertiary language back to one's native language.\n\nThe triangular part of the inferior frontal gyrus is known as Brodmann area 45 (BA45), and the orbital part of the inferior frontal gyrus is known as Brodmann area 47.\n\nhttps://en.wikipedia.org/wiki/Inferior_frontal_gyrus","orbital-gyri-frontomarginal-gyrus-and-sulcus":"The inferior or orbital surface of the frontal lobe is concave, and rests on the orbital plate of the frontal bone.\n\nIt is divided into four orbital gyri by a well-marked H-shaped orbital sulcus.\n\nThese are named, from their position, the medial, anterior, lateral, and posterior, orbital gyri.\n\nThe medial orbital gyrus presents a well-marked antero-posterior sulcus, the olfactory sulcus, for the olfactory tract; the portion medial to this is named the straight gyrus, and is continuous with the superior frontal gyrus on the medial surface.\n\n== Function ==\n\nBailey and Bremer reported that stimulation to the central end of the vagus nerve caused electrical activity in the inferior orbital surface (http://brain.oxfordjournals.org/cgi/pdf_extract/75/2/244)\n\nhttps://en.wikipedia.org/wiki/Orbital_gyri","paracentral-gyrus-and-sulcus":"The paracentral sulcus is a sulcus of the brain.\n\nIt forms the paracentral lobule's anterior border.\n\nIt is part of the cingulate sulcus.\n\nhttps://en.wikipedia.org/wiki/Paracentral_sulcus","straight-gyrus-gyrus-rectus":"The portion of the inferior frontal lobe immediately adjacent to the longitudinal fissure (and medial to the medial orbital gyrus and olfactory tract) is named the straight gyrus,(or gyrus rectus) and is continuous with the superior frontal gyrus on the medial surface.\n\nA specific function for the straight gyrus has not yet been brought to light; however, in males, greater activation of the straight gyrus within the medial orbitofrontal cortex while observing sexually visual pictures has been strongly linked to HSDD (hypoactive sexual desire disorder).\n\nhttps://en.wikipedia.org/wiki/Straight_gyrus","inferior-frontal-sulcus":"The inferior frontal sulcus is a sulcus between the middle frontal gyrus and the inferior frontal gyrus.\n\nhttps://en.wikipedia.org/wiki/Inferior_frontal_sulcus","middle-frontal-gyrus":"The middle frontal gyrus makes up about one-third of the frontal lobe of the human brain. (A gyrus is one of the prominent \"bumps\" or \"ridges\" on the surface of the human brain.)\n\nThe middle frontal gyrus, like the inferior frontal gyrus and the superior frontal gyrus, is more of a region in the frontal gyrus than a true gyrus.\n\nThe borders of the middle frontal gyrus are the inferior frontal sulcus below; the superior frontal sulcus above; and the precentral sulcus behind.\n\nhttps://en.wikipedia.org/wiki/Middle_frontal_gyrus","orbital-gyri":"The inferior or orbital surface of the frontal lobe is concave, and rests on the orbital plate of the frontal bone.\n\nIt is divided into four orbital gyri by a well-marked H-shaped orbital sulcus.\n\nThese are named, from their position, the medial, anterior, lateral, and posterior, orbital gyri.\n\nThe medial orbital gyrus presents a well-marked antero-posterior sulcus, the olfactory sulcus, for the olfactory tract; the portion medial to this is named the straight gyrus, and is continuous with the superior frontal gyrus on the medial surface.\n\n== Function ==\n\nBailey and Bremer reported that stimulation to the central end of the vagus nerve caused electrical activity in the inferior orbital surface (http://brain.oxfordjournals.org/cgi/pdf_extract/75/2/244)\n\nhttps://en.wikipedia.org/wiki/Orbital_gyri","precentral-gyrus":"The precentral gyrus is a prominent gyrus on the surface of the posterior frontal lobe of the brain.\n\nIt is the site of the primary motor cortex that in humans is cytoarchitecturally defined as Brodmann area 4.\n\n== Structure ==\n\nThe precentral gyrus lies in front of the postcentral gyrus - mostly on the lateral (convex) side of each cerebral hemisphere - from which it is separated by the central sulcus.\n\nIts anterior border is represented by the precentral sulcus, while inferiorly it borders to the lateral sulcus (Sylvian fissure).\n\nMedially, it is contiguous with the paracentral lobule.\n\nThe internal pyramidal layer (layer V) of the precentral cortex contains giant (70-100 micrometers) pyramidal neurons called Betz cells, which send long axons to the contralateral motor nuclei of the cranial nerves and to the lower motor neurons in the ventral horn of the spinal cord.\n\nThese axons form the corticospinal tract.\n\nThe Betz cells along with their long axons are referred to as upper motor neurons (UMN).\n\nThere is a precise somatotopic representation of the different body parts in the primary motor cortex, with the leg area located medially (close to the midline), and the head and face area located laterally on the convex side of the cerebral hemisphere (cortical homunculus).\n\nThe arm and hand motor area is the largest and occupies the part of precentral gyrus, located inbetween the leg and face area.\n\n== Function ==\n\nAs they travel down through the cerebral white matter, the motor axons move closer together and form part of the posterior limb of the internal capsule.\n\nThey continue down into the brainstem, where some of them, after crossing over to the contralateral side, distribute to the cranial nerve motor nuclei.\n\n(Note: a few motor fibers synapse with lower motor neurons on the same side of the brainstem).\n\nAfter crossing over to the contralateral side in the medulla oblongata (pyramidal decussation), the axons travel down the spinal cord as the lateral corticospinal tract.\n\nFibers that do not cross over in the brainstem travel down the separate ventral corticospinal tract and most of them cross over to the contralateral side in the spinal cord, shortly before reaching the lower motor neurons.\n\n== Blood supply ==\n\nBranches of the middle cerebral artery provide most of the arterial blood supply for the primary motor cortex.\n\nThe medial aspect (leg areas) is supplied by branches of the anterior cerebral artery.\n\n== Clinical significance ==\n\nLesions of the precentral gyrus result in paralysis of the contralateral side of the body (facial palsy, arm-/leg monoparesis, hemiparesis) - see upper motor neuron.\n\nhttps://en.wikipedia.org/wiki/Precentral_gyrus","superior-frontal-gyrus":"The superior frontal gyrus (SFG) also marginal gyrus, makes up about one third of the frontal lobe of the human brain.\n\nIt is bounded laterally by the superior frontal sulcus.The superior frontal gyrus is one of the frontal gyri.\n\n== Function ==\n\n=== Self-awareness ===\n\nIn fMRI experiments, Goldberg et al. have found evidence that the superior frontal gyrus is involved in self-awareness, in coordination with the action of the sensory system.\n\n=== Laughter ===\n\nIn 1998, neurosurgeon Itzhak Fried described a 16-year-old female patient (referred to as \"patient AK\") who laughed when her SFG was stimulated with electric current during treatment for epilepsy.\n\nElectrical stimulation was applied to the cortical surface of AK's left frontal lobe while an attempt was made to locate the focus of her epileptic seizures (which were never accompanied by laughter).\n\nFried identified a 2 cm by 2 cm area on the left SFG where stimulation produced laughter consistently (over several trials).\n\nAK reported that the laughter was accompanied by a sensation of merriment or mirth.\n\nAK gave a different explanation for the laughter each time, attributing it to an (unfunny) external stimulus.\n\nThus, laughter was attributed to the picture she was asked to name (saying \"the horse is funny\"), or to the sentence she was asked to read, or to persons present in the room (\"you guys are just so funny... standing around\").\n\nIncreasing the level of stimulation current increased the duration and intensity of laughter.\n\nFor example, at low currents only a smile was present, while at higher currents a louder, contagious laughter was induced.\n\nThe laughter was also accompanied by the stopping of all activities involving speech or hand movements.\n\nhttps://en.wikipedia.org/wiki/Superior_frontal_gyrus","superior-frontal-sulcus":"The superior frontal sulcus is a sulcus between the superior frontal gyrus and the middle frontal gyrus.\n\nhttps://en.wikipedia.org/wiki/Superior_frontal_sulcus","orbital-sulci-h-shaped-orbital-sulci":"The inferior or orbital surface of the frontal lobe is concave, and rests on the orbital plate of the frontal bone.\n\nIt is divided into four orbital gyri by a well-marked H-shaped orbital sulcus\n\nhttps://en.wikipedia.org/wiki/Orbital_sulcus","orbital-sulci-lateral-orbital-sulcus":"The inferior or orbital surface of the frontal lobe is concave, and rests on the orbital plate of the frontal bone.\n\nIt is divided into four orbital gyri by a well-marked H-shaped orbital sulcus\n\nhttps://en.wikipedia.org/wiki/Orbital_sulcus","olfactory-sulcus":"The olfactory tract is a bilateral bundle of afferent nerve fibers from the mitral and tufted cells of the olfactory bulb that connects to several target regions in the brain, including the piriform cortex, amygdala, and entorhinal cortex.\n\nIt is a narrow white band, triangular on coronal section, the apex being directed upward.\n\n== Structure ==\n\nThe olfactory tract and olfactory bulb lie in the olfactory sulcus a sulcus formed by the medial orbital gyrus on the inferior surface of each frontal lobe.\n\nThe olfactory tracts lie in the sulci which run closely parallel to the midline.\n\nFibers of the olfactory tract appear to end in the antero-lateral part of the olfactory tubercle, the dorsal and external parts of the anterior olfactory nucleus, the frontal and temporal parts of the prepyriform area, the cortico-medial group of amygdala nuclei and the nucleus of the stria terminalis.\n\nThe olfactory tract divides posteriorly into a medial and a lateral stria.\n\nCaudal to this is the olfactory trigone, and the anterior perforated substance.\n\n=== Medial olfactory stria ===\n\nThe medial olfactory stria turns medially behind the parolfactory area and ends in the subcallosal gyrus; in some cases a small intermediate stria is seen running backward to the anterior perforated substance.\n\n=== Lateral olfactory stria ===\n\nThe lateral olfactory stria is directed across the lateral part of the anterior perforated substance and then bends abruptly medially toward the uncus of the parahippocampal gyrus.\n\n== Clinical significance ==\n\nDestruction to the olfactory tract results in ipsilateral anosmia (loss of the ability to smell).\n\nAnosmia either total or partial is a symptom of Kallmann syndrome a genetic disorder that results in disruption of the development of the olfactory tract.\n\nThe depth of the olfactory sulcus is an indicator of such congenital anosmia.\n\nhttps://en.wikipedia.org/wiki/Olfactory_tract","precentral-sulcus-inferior-part":"The precentral sulcus is a part of the human brain that lies parallel to, and in front of, the central sulcus.\n\n(A sulcus is one of the prominent grooves on the surface of the human brain.)\n\nThe precentral sulcus divides the inferior, middle and superior frontal gyri from the precentral gyrus.\n\nIn most brains, the precentral sulcus is divided into two parts: the inferior precentral sulcus and the superior precentral sulcus.\n\nHowever, the precentral sulcus may sometimes be divided into three parts or form one continuous sulcus.\n\nhttps://en.wikipedia.org/wiki/Precentral_sulcus","precentral-sulcus-superior-part":"The precentral sulcus is a part of the human brain that lies parallel to, and in front of, the central sulcus.\n\n(A sulcus is one of the prominent grooves on the surface of the human brain.)\n\nThe precentral sulcus divides the inferior, middle and superior frontal gyri from the precentral gyrus.\n\nIn most brains, the precentral sulcus is divided into two parts: the inferior precentral sulcus and the superior precentral sulcus.\n\nHowever, the precentral sulcus may sometimes be divided into three parts or form one continuous sulcus.\n\nhttps://en.wikipedia.org/wiki/Precentral_sulcus","angular-gyrus":"The angular gyrus is a region of the brain lying mainly in the anterolateral region of parietal lobe, that lies near the superior edge of the temporal lobe, and immediately posterior to the supramarginal gyrus.\n\nIts significance is in transferring visual information to Wernicke's area, in order to make meaning out of visually perceived words.\n\nIt is also involved in a number of processes related to language, number processing and spatial cognition, memory retrieval, attention, and theory of mind.\n\nIt is Brodmann area 39 of the human brain.\n\n== Anatomy ==\n\nLeft and right angular gyri are connected by the dorsal splenium and isthmus of the corpus callosum.\n\nBoth gyri lie between the four lobes.\n\n== Function ==\n\nThe angular gyrus is the part of the brain associated with complex language functions (i.e. reading, writing and interpretation of what is written).\n\nLesion to this part of the brain shows symptoms of the Gerstmann syndrome:\n effects include finger agnosia, alexia (inability to read), acalculia (inability to use arithmetic operations), agraphia (inability to copy), and left-right confusion.\n\n=== Language ===\n\nGeschwind proposed that written word is translated to internal monologue via the angular gyrus.\n\nRamachandran, and Edward Hubbard published a paper in 2003 in which they speculated that the angular gyrus is at least partially responsible for understanding metaphors.\n\nThey stated:\n There may be neurological disorders that disturb metaphor and synaesthesia.\n\nThis has not been studied in detail but we have seen disturbances in the Bouba/Kiki effect (Ramachandran & Hubbard, 2001a) as well as with proverbs in patients with angular gyrus lesions.\n\nIt would be interesting to see whether they have deficits in other types of synaesthetic metaphor, e.g. 'sharp cheese' or 'loud shirt'.\n\nThere are also hints that patients with right hemisphere lesions show problems with metaphor.\n\nIt is possible that their deficits are mainly with spatial metaphors, such as 'He stepped down as director'.\n\nThe fact that the angular gyrus is proportionately much larger in hominids than other primates, and its strategic location at the crossroads of areas specialized for processing touch, hearing and vision, leads Ramachandran to believe that it is critical both to conceptual metaphors and to cross-modal abstractions more generally.\n\nHowever, recent research challenges this theory.\n\nResearch by Krish Sathian (Emory University) using functional magnetic resonance imaging (fMRI) suggests that the angular gyrus does not play a role in creating conceptual metaphors.\n\nSathian theorizes that conceptual metaphors activate the texture-selective somatosensory cortex in the parietal operculum.\n\nBrownsett and Wise highlight the role of the left angular gyrus in both speaking and writing.\n\n=== Arithmetic and spatial cognition ===\n\nSince 1919, brain injuries to the angular gyrus have been known to often cause arithmetic deficits.\n\nFunctional imaging has shown that while other parts of the parietal lobe bilaterally are involved in approximate calculations due to its link with spatiovisual abilities, the left angular gyrus together with left Inferior frontal gyrus are involved in exact calculation due to verbal arithmetic fact retrieval.\n\nWhen activation in the left angular gyrus is greater, a person's arithmetic skills are also more competent.\n\n=== Attention ===\n\nThe right angular gyrus has been associated with spatiovisual attention toward salient features.\n\nIt may allocate attention by employing a bottom-up strategy which draws on the area's ability to attend to retrieved memories.\n\nFor example, the angular gyrus plays a critical role in distinguishing left from right by integrating the conceptual understanding of the language term \"left\" or \"right\" with its location in space.\n\nFurthermore, the angular gyrus has been associated with orienting in three dimensional space, not because it interprets space, but because it may control attention shifts in space.\n\n=== Other functions ===\n\n==== Default mode network ====\n\nThe angular gyrus is part of the default mode network, a network of brain regions activated during multi-modal activities that are independent of external stimuli.\n\n==== Awareness ====\n\nThe angular gyrus reacts differently to intended and consequential movement.\n\nThis suggests that the angular gyrus monitors the self's intended movements and uses the added information to compute differently, as it does for consequential movements.\n\nBy recording the discrepancy, the angular gyrus maintains an awareness of the self.\n\n==== Memory retrieval ====\n\nActivation of the angular gyrus shows that not only does it mediate memory retrieval, but it also notes contradictions between what is expected from the retrieval, and what is unusual.\n\nThe angular gyrus can access both content and episodic memories and is useful in inferring from these the intentions of human characters.\n\nFurthermore, the angular gyrus may use a feedback strategy to ascertain whether a retrieval is expected or unusual.\n\n==== Out-of-body experiences ====\n\nRecent experiments have demonstrated the possibility that stimulation of the right angular gyrus is the cause of out-of-body experiences.\n\nStimulation of the left angular gyrus in one experiment caused a woman to perceive a shadowy person lurking behind her.\n\nThe shadowy figure is actually a perceived double of the self.\n\nAnother such experiment gave the test subject the sensation of being on the ceiling.\n\nThis is attributed to a discrepancy in the actual position of the body, and the mind's perceived location of the body.\n\n== Clinical significance ==\n\nDamage to the angular gyrus manifests as Gerstmann syndrome.\n\nDamage may impair one or more of the below functions.\n\n-Dysgraphia/agraphia: deficiency in the ability to write\n-Dyscalculia/acalculia: difficulty in learning or comprehending mathematics\n-Finger agnosia: inability to distinguish the fingers on the hand\n-Left-right disorientation\n\nhttps://en.wikipedia.org/wiki/Angular_gyrus","supramarginal-gyrus":"The supramarginal gyrus is a portion of the parietal lobe.\n\nThis area of the brain is also known as Brodmann area 40 based on the brain map created by Korbinian Brodmann to define the structures in the cerebral cortex.\n\nIt is probably involved with language perception and processing, and lesions in it may cause receptive aphasia.\n\n== Important functions ==\n\nThe supramarginal gyrus is part of the somatosensory association cortex, which interprets tactile sensory data and is involved in perception of space and limbs location.\n\nIt is also involved in identifying postures and gestures of other people and is thus a part of the mirror neuron system.\n\nThe right-hemisphere supramarginal gyrus appears to play a central role in controlling empathy towards other people.\n\nWhen this structure isn't working properly or when having to make very quick judgements, empathy becomes severely limited.\n\nResearch has shown that disrupting the neurons in the right supramarginal gyrus causes humans to project emotions on others, inhibiting the ability to be empathetic.\n\nIn addition, this disruption also causes people to be more egocentric, mainly because they are not able to perceive the emotions of those around them.\n\nBoth the left and right supramarginal gyri of healthy, right-handed individuals are shown to be active when making phonological word choices.\n\nIndividuals who had lesions to the left hemisphere had more difficulty than those with lesions to the right hemisphere, reinforcing the dominance of the left hemisphere in language.\n\n== Relationships to surrounding structures ==\n\nThe supramarginal gyrus is located just anterior to the angular gyrus allowing these two structures (which compose the inferior parietal lobule) to form a multimodal complex that receives somatosensory, visual, and auditory inputs from the brain.\n\nAlthough the supramarginal gyrus is not considered a major portion of the language circuit, it still works with the angular gyrus to attempt to link words with meanings.\n\nIt is also bound caudally by the lateral sulcus, one of the most prominent structures found in the brain.\n\nhttps://en.wikipedia.org/wiki/Supramarginal_gyrus","postcentral-gyrus":"The postcentral gyrus is a prominent gyrus in the lateral parietal lobe of the human brain.\n\nIt is the location of the primary somatosensory cortex, the main sensory receptive area for the sense of touch.\n\nLike other sensory areas, there is a map of sensory space in this location, called the sensory homunculus.\n\nThe primary somatosensory cortex was initially defined from surface stimulation studies of Wilder Penfield, and parallel surface potential studies of Bard, Woolsey, and Marshall.\n\nAlthough initially defined to be roughly the same as Brodmann areas 3, 1 and 2, more recent work by Kaas has suggested that for homogeny with other sensory fields only area 3 should be referred to as \"primary somatosensory cortex\", as it receives the bulk of the thalamocortical projections from the sensory input fields.\n\n== Structure ==\n\nThe lateral postcentral gyrus is bounded by:\n\n-medial longitudinal fissure medially (to the middle)\n-central sulcus rostrally (in front)\n-postcentral sulcus caudally (in back)\n-lateral sulcus inferiorly (underneath)The postcentral gyrus includes Brodmann areas 1, 2, and 3.\n\nBrodmann area 1 occupies the apex of the postcentral gyrus.\n\nhttps://en.wikipedia.org/wiki/Postcentral_gyrus","postcentral-sulcus":"The postcentral sulcus of the parietal lobe lies parallel to, and behind, the central sulcus in the human brain.\n\n(A sulcus is one of the prominent grooves on the surface of the brain.)\n\nThe postcentral sulcus divides the postcentral gyrus from the remainder of the parietal lobe.\n\nhttps://en.wikipedia.org/wiki/Postcentral_sulcus","precuneus":"The precuneus is the portion of the superior parietal lobule on the medial surface of each brain hemisphere.\n\nIt is located in front of the cuneus (the upper portion of the occipital lobe).\n\nThe precuneus is bounded in front by the marginal branch of the cingulate sulcus, at the rear by the parietooccipital sulcus, and underneath by the subparietal sulcus.\n\nIt is involved with episodic memory, visuospatial processing, reflections upon self, and aspects of consciousness.\n\nThe location of the precuneus makes it difficult to study.\n\nFurthermore, it is rarely subject to isolated injury due to strokes, or trauma such as gunshot wounds.\n\nThis has resulted in it being \"one of the less accurately mapped areas of the whole cortical surface\".\n\nWhile originally described as homogeneous by Korbinian Brodmann, it is now appreciated to contain three subdivisions.\n\nIt is also known after Achille-Louis Foville as the quadrate lobule of Foville.\n\nThe Latin form of praecuneus was first used in 1868 and the English precuneus in 1879.\n\n== Structure ==\n\nThe precuneus is located on the inside between the two cerebral hemispheres in the rear region between the somatosensory cortex and forward of the cuneus (which contains the visual cortex).\n\nIt is above the posterior cingulate.\n\nFollowing Korbinian Brodmann it has traditionally been considered a homogeneous structure and with limited distinction between it and the neighboring posterior cingulate area.\n\nBrodmann mapped it as the medial continuation of lateral parietal area 7.\n\nAxon tracing research on macaque monkeys has established that it consists of three subdivisions which now have been confirmed by fMRI upon resting-state functional connectivity to also exist in humans (parallel fMRI research has also been done upon monkeys).\n\n=== Subdivisions ===\n\nSensorimotor Anterior RegionThis occurs around the margin of the cingulate sulcus ( blue in figure) and is connected with sensorimotor areas of the cerebral cortex such as the paracentral lobule, supplementary motor area, premotor cortex, somatosensory area (Brodmann area 2), parietal operculum and insula.\n\nfMRI Research upon humans finds a connection with the caudalmost part of parahippocampus and superior temporal gyrus.\n\nNo connections with the inferior parietal lobule, prefrontal cortex nor primary motor cortex.\n\nCognitive/Associative Central Region.\n\nThis occurs around the precuneal sulcus ( green in figure) and is connected with the inferior parietal lobule particularly the angular gyrus and prefrontal areas 10, 46 and 8.\n\nNo connections exist with premotor, motor, or somatosensory areas.\n\nThe areas with which it links are involved in executive functions, working memory and motor planning.\n\nVisual Posterior Region\n\nThis occurs along the parieto-occipital fissure ( yellow in figure).\n\nThis connects with visual areas in the cuneus and primary visual cortex.\n\n=== Subcortical connections ===\n\nBelow the cerebral cortex, the precuneus is connected with the dorsalmost nuclei of the thalamus, including the ventral lateral nucleus, the central and anterior nuclei of the intralaminar nuclear group, and the lateral pulvinar.\n\nOther connections include the claustrum, the dorsolateral caudate nucleus, putamen, and the zona incerta.\n\nIt also has links with the brainstem areas such as the pretectal area, the superior colliculus, the nucleus reticularis tegmenti pontis, and the basis pontis.\n\n== Function ==\n\nThe mental imagery concerning the self has been located in the forward part of the precuneus with posterior areas being involved with episodic memory.\n\nAnother area has been linked to visuospatial imagery.\n\n(It is not though clear how these—and the functions noted below—link with the above three subdivisions.)\n\nThe precuneus plays a role in itch sensations (there are many different types of itch) and their brain processing “‘We can’t [yet] pinpoint what the precuneus does in itch, but it’s uniquely activated with itch and not pain.’”\n\n=== Self ===\n\nFunctional imaging has linked the precuneus to the processes involved in self-consciousness, such as reflective self-awareness, that involve rating one's own personality traits compared to those judged of other people.\n\n=== Memory ===\n\nThe precuneus is involved in memory tasks, such as when people look at images and try to respond based on what they have remembered in regard to verbal questions about their spatial details.\n\nIt is involved with the left prefrontal cortex in the recall of episodic memories including past episodes related to the self.\n\nThe precuneus is also involved in source memory (in which the \"source\" circumstances of a memory are recalled) with the left inferior prefrontal cortex:\n here its role is postulated to be providing rich episodic contextual associations used by the prefrontal cortex to select the correct past memory.\n\nIn the recollection of memories, it has been postulated that the precuneus discerns whether contextual information exists that can be useful for involving the aid of the hippocampus.\n\nAlternatively it has a different involvement when judging the familiarity as it decides whether the processing of perceptual features would be more useful.\n\nIn this way the precuneus gets involved in diverse processes such as attention, episodic memory retrieval, working memory and conscious perception.\n\n=== Visuospatial ===\n\nThe precuneus has been suggested to be involved in directing attention in space both when an individual makes movements and when imaging or preparing them.\n\nIt is involved in motor imagery and shifting attention between motor targets.\n\nIt is also involved in motor coordination that requires shifting attention to different spatial locations.\n\nIt is also together with the dorsal premotor cortex involved in visuospatial mental operations (such as in a modified form of the game of Amidakuji).\n\nIt is suggested that while the premotor area engages in the mental operation, the precuneus aids monitoring the success of that operation in terms of internally represented visual images.\n\nThe precuneus' role in mental imagery has been suggested to extend to that of modeling other people's views.\n\nIt is activated when a person takes a third-person versus first-person visual point of view.\n\nTogether with the superior frontal gyrus and orbitofrontal cortex, the precuneus is activated when people make judgments that requires understanding whether to act out of empathy and forgiveness.\n\n=== Executive functions ===\n\nPrecuneus is thought to be related to response inhibition.\n\n=== Consciousness ===\n\nIt has been suggested that together with the posterior cingulate, the precuneus is \"pivotal for conscious information processing\".\n\nThe evidence for this link with consciousness comes from the effects of its disruption in epilepsy, brain lesions and vegetative state.\n\nAlso, cerebral glucose metabolism is at its highest in these two areas during wakefulness but is most reduced in them during anesthesia.\n\nIn addition, it is one of the areas of the brain most deactivated during slow-wave sleep and rapid eye movement sleep.\n\nTogether with the prefrontal cortex, the precuneus, is more activated upon the learning of words briefly flashed when they are supraliminal (and so enter consciousness) than subliminal (and so do not enter consciousness).\n\n=== Default network ===\n\nIt has been suggested to be the 'core node' or 'hub' of the default mode network that is activated during \"resting consciousness\" in which people do not engage intentionally in sensory or motor activity.\n\nThis involvement in the default network is suggested to underlie its role in self-consciousness.\n\nHowever its involvement in the default network has been questioned.\n\nThough one of the authors raising these doubts noted \"our findings in this regard should be treated as preliminary.\"\n\nA recent study showed that only ventral precuneus is involved in the default network.\n\n=== Parietal prefrontal central hub ===\n\nOlaf Sporns and Ed Bullmore have proposed that its functions link to its role as a central and well connected \"small-world network\" hub between parietal and prefrontal regions.\n\nThese clusters or modules are interlinked by specialized hub regions, ensuring that overall path lengths across the network are short.\n\nMost studies identified [such] hubs among parietal and prefrontal regions, providing a potential explanation for their well-documented activation by many cognitive functions.\n\nParticularly notable is the prominent structural role of the precuneus, a region that is homologous to the highly connected posteromedial cortex in the macaque.\n\nThe precuneus is involved in self-referential processing, imagery and memory, and its deactivation is associated with anaesthetic-induced loss of consciousness.\n\nAn intriguing hypothesis suggests that these functional aspects can be explained on the basis of its high centrality in the cortical network.\n\n== Correlation of grey matter volume and subjective happiness score ==\n\nA positive relationship has been found between the volume of grey matter in the right precuneus and the subject's subjective happiness score.\n\n== Impact of mindfulness ==\n\nA 6-week mindfulness based intervention was found to correlate with a significant grey matter increase within the precuneus.\n\n== Other animals ==\n\nThe precuneus seems to be a recently expanded part of the brain, as in less developed primates such as New world monkeys \"the superior parietal and precuneate regions are poorly developed\".\n\nIt has been noted that \"the precuneus is more highly developed (i.e. comprises a larger portion of the brain volume) in human beings than in non-human primates or other animals, has the most complex columnar cortical organization and is among the last regions to myelinate\".\n\nhttps://en.wikipedia.org/wiki/Precuneus","superior-parietal-lobule":"The superior parietal lobule is bounded in front by the upper part of the postcentral sulcus, but is usually connected with the postcentral gyrus above the end of the sulcus.\n\nThe superior parietal lobule contains Brodmann's areas 5 and 7.\n\nBehind it is the lateral part of the parietooccipital fissure, around the end of which it is joined to the occipital lobe by a curved gyrus, the arcus parietooccipitalis.\n\nBelow, it is separated from the inferior parietal lobule by the horizontal portion of the intraparietal sulcus.\n\nThe superior parietal lobule is involved with spatial orientation, and receives a great deal of visual input as well as sensory input from one's hand.\n\nIt is also involved with other functions of the parietal lobe in general.\n\nThere are major white matter pathway connections with the superior parietal lobule such as the Cingulum, SLF I, superior parietal lobule connections of the Medial longitudinal fasciculus and other newly described superior parietal white matter connections.\n\nDamage to the superior parietal lobule can cause contralateral astereognosis and hemispatial neglect.\n\nIt is also associated with deficits on tests involving the manipulation and rearrangement of information in working memory, but not on working memory tests requiring only rehearsal and retrieval processes.\n\nhttps://en.wikipedia.org/wiki/Superior_parietal_lobule","intraparietal-sulcus":"The intraparietal sulcus (IPS) is located on the lateral surface of the parietal lobe, and consists of an oblique and a horizontal portion.\n\nThe IPS contains a series of functionally distinct subregions that have been intensively investigated using both single cell neurophysiology in primates and human functional neuroimaging.\n\nIts principal functions are related to perceptual-motor coordination (e.g., directing eye movements and reaching) and visual attention, which allows for visually-guided pointing, grasping, and object manipulation that can produce a desired effect.\n\nThe IPS is also thought to play a role in other functions, including processing symbolic numerical information, visuospatial working memory and interpreting the intent of others.\n\n== Function ==\n\nFive regions of the intraparietal sulcus (IPS): anterior, lateral, ventral, caudal, and medial\n\n-LIP & VIP: involved in visual attention and saccadic eye movements\n-VIP & MIP: visual control of reaching and pointing\n-AIP: visual control of grasping and manipulating hand movements\n-CIP: perception of depth from stereopsisAll of these areas have projections to the frontal lobe for executive control.\n\nActivity in the intraparietal sulcus has also been associated with the learning of sequences of finger movements.\n\nThe dorsal attention network includes the intraparietal sulcus of each hemisphere.\n\nThe intraparietal sulcus is activated during voluntary orientation of attention.\n\n=== Understanding numbers ===\n\nBehavioral studies suggest that the IPS is associated with impairments of basic numerical magnitude processing and that there is a pattern of structural and functional alternations in the IPS and in the PFC in dyscalculia.\n\nChildren with developmental dyscalculia were found to have less gray matter in the left IPS.\n\nStudies have shown that electrical activity in a particular group of nerve cells in the intraparietal sulcus spiked when, and only when, volunteers were performing calculations.\n\nOutside experimental settings it was also found that when a patient mentioned a number—or even a quantitative reference, such as \"some more\", \"many\" or \"bigger than the other one\"—there was a spike of electrical activity in the same nerve-cell population of the intraparietal sulcus that was activated when the patient was doing calculations under experimental conditions.\n\nhttps://en.wikipedia.org/wiki/Intraparietal_sulcus","inferior-occipital-gyrus-and-sulcus":"The occipital gyri (OcG) are three gyri in parallel, along the lateral portion of the occipital lobe, also referred to as a composite structure in the brain.\n\nThe gyri are the superior occipital gyrus, the middle occipital gyrus, and the inferior occipital gyrus, and these are also known as the occipital face area.\n\nThe superior and inferior occipital sulci separates the three occipital gyri.\n\nThe intraoccipital sulcus, also known as the superior occipital sulcus, stems from the intraparietal sulcus and continues until the sulcus reaches the transverse occipital sulcus, separating the superior occipital gyrus from the middle occipital gyrus.\n\nThe transverse occipital sulcus comes down along the lateral occipital surface or the inferior occipital sulcus.\n\n== Structural anatomy ==\n\nThe border between the occipital lobe and the parietal and temporal lobes is characterized by different gyri:\n the superior occipital gyrus (also known as gyrus occipitalis superior), middle occipital gyrus (or gyrus occipitalis medius), inferior occipital gyrus (or gyrus occipitalis inferior), and descending occipital gyrus (gyrus occipitalis descendens).\n\n== Function ==\n\nThe occipital complex is primarily responsible for object recognition, including the functional properties and our perception of said objects.\n\nThe middle occipital gyrus (MOG) was observed in a study of the early blind, which showed that it was activated more during spatial than nonspatial tactile and auditory tasks.\n\nEarly blind people have an occipital cortex that is incorporates more senses than people with standard vision, but the MOG still keeps its functional role in processing space around a person.\n\nThe lingual gyrus (also known as medial occipitotemporal gyrus) has been studied and found to be included in processing overall shapes, rather than the individual components that make up a shape.\n\nThis shows that the lingual gyrus is active during visual processing.The inferior occipital gyrus has been found to be related to the visual function of processing faces.\n\nThe IOG is connected to the amygdala via white matter connectivity.\n\nThis allows the IOG to form a network for facial recognition with the amygdala.\n\n== Development ==\n\nThe occipital lobe becomes distinct at 18 weeks gestation, but the gyri are not clear until many weeks later.\n\nDuring development, the occipital lobe develops a lingual gyrus at 27 weeks of gestation.\n\nSecondary gyri develop by 30 weeks, and tertiary gyri develop during 40 to 42 weeks of gestation.\n\nThe superior and inferior occipital gyri develop at the same time, usually shown somewhere between week 24 and 27 in brain development.\n\nDue to the unclear distinction in early neuroscience research as to whether there are two or three occipital gyri, there is not any data on when the middle occipital gyrus starts its formation, but it is likely at the same time.\n\nhttps://en.wikipedia.org/wiki/Occipital_gyri","lateral-occipital-gyrus-middle-occipital-gyrus":"The occipital gyri (OcG) are three gyri in parallel, along the lateral portion of the occipital lobe, also referred to as a composite structure in the brain.\n\nThe gyri are the superior occipital gyrus, the middle occipital gyrus, and the inferior occipital gyrus, and these are also known as the occipital face area.\n\nThe superior and inferior occipital sulci separates the three occipital gyri.\n\nThe intraoccipital sulcus, also known as the superior occipital sulcus, stems from the intraparietal sulcus and continues until the sulcus reaches the transverse occipital sulcus, separating the superior occipital gyrus from the middle occipital gyrus.\n\nThe transverse occipital sulcus comes down along the lateral occipital surface or the inferior occipital sulcus.\n\n== Structural anatomy ==\n\nThe border between the occipital lobe and the parietal and temporal lobes is characterized by different gyri:\n the superior occipital gyrus (also known as gyrus occipitalis superior), middle occipital gyrus (or gyrus occipitalis medius), inferior occipital gyrus (or gyrus occipitalis inferior), and descending occipital gyrus (gyrus occipitalis descendens).\n\n== Function ==\n\nThe occipital complex is primarily responsible for object recognition, including the functional properties and our perception of said objects.\n\nThe middle occipital gyrus (MOG) was observed in a study of the early blind, which showed that it was activated more during spatial than nonspatial tactile and auditory tasks.\n\nEarly blind people have an occipital cortex that is incorporates more senses than people with standard vision, but the MOG still keeps its functional role in processing space around a person.\n\nThe lingual gyrus (also known as medial occipitotemporal gyrus) has been studied and found to be included in processing overall shapes, rather than the individual components that make up a shape.\n\nThis shows that the lingual gyrus is active during visual processing.The inferior occipital gyrus has been found to be related to the visual function of processing faces.\n\nThe IOG is connected to the amygdala via white matter connectivity.\n\nThis allows the IOG to form a network for facial recognition with the amygdala.\n\n== Development ==\n\nThe occipital lobe becomes distinct at 18 weeks gestation, but the gyri are not clear until many weeks later.\n\nDuring development, the occipital lobe develops a lingual gyrus at 27 weeks of gestation.\n\nSecondary gyri develop by 30 weeks, and tertiary gyri develop during 40 to 42 weeks of gestation.\n\nThe superior and inferior occipital gyri develop at the same time, usually shown somewhere between week 24 and 27 in brain development.\n\nDue to the unclear distinction in early neuroscience research as to whether there are two or three occipital gyri, there is not any data on when the middle occipital gyrus starts its formation, but it is likely at the same time.\n\nhttps://en.wikipedia.org/wiki/Occipital_gyri","calcarine-sulcus":"The calcarine sulcus (or calcarine fissure) is an anatomical landmark located at the caudal end of the medial surface of the brain of humans and other primates.\n\nIts name comes from the Latin \"calcar\" meaning \"spur\".\n\nIt is very deep and known as a complete sulcus.\n\n== Anatomy ==\n\nThe calcarine sulcus begins near the occipital pole in two converging rami and runs forward to a point a little below the splenium of the corpus callosum, where it is joined at an acute angle by the medial part of the parieto-occipital sulcus.\n\nThe anterior part of this sulcus gives rise to the prominence of the calcar avis in the posterior cornu of the lateral ventricle.\n\n== Function ==\n\nThe calcarine sulcus is where the primary visual cortex (V1) is concentrated.\n\nThe central visual field is located in the posterior portion of the calcarine sulcus and the peripheral visual field in the anterior portion.\n\nhttps://en.wikipedia.org/wiki/Calcarine_sulcus","cuneus":"The cuneus (Latin for \"wedge\"; plural, cunei) is a smaller lobe in the occipital lobe of the brain.\n\nThe cuneus is bounded anteriorly by the parieto-occipital sulcus, inferiorly by the calcarine sulcus.\n\n== Function ==\n\nThe cuneus (Brodmann area 17) receives visual information from the same-sided superior quadrantic retina (corresponding to contralateral inferior visual field).\n\nIt is most known for its involvement in basic visual processing.\n\nPyramidal cells in the visual cortex (or striate cortex) of the cuneus, project to extrastriate cortices (BA 18,19).\n\nThe mid-level visual processing that occurs in the extrastriate projection fields of the cuneus are modulated by extraretinal effects, like attention, working memory, and reward expectation.\n\n== Clinical research ==\n\nIn addition to its traditional role as a site for basic visual processing, gray matter volume in the cuneus is associated with better inhibitory control in bipolar depression patients.\n\nPathologic gamblers have higher activity in the dorsal visual processing stream including the cuneus relative to controls.\n\nhttps://en.wikipedia.org/wiki/Cuneus","superior-occipital-gyri":"The occipital gyri (OcG) are three gyri in parallel, along the lateral portion of the occipital lobe, also referred to as a composite structure in the brain.\n\nThe gyri are the superior occipital gyrus, the middle occipital gyrus, and the inferior occipital gyrus, and these are also known as the occipital face area.\n\nThe superior and inferior occipital sulci separates the three occipital gyri.\n\nThe intraoccipital sulcus, also known as the superior occipital sulcus, stems from the intraparietal sulcus and continues until the sulcus reaches the transverse occipital sulcus, separating the superior occipital gyrus from the middle occipital gyrus.\n\nThe transverse occipital sulcus comes down along the lateral occipital surface or the inferior occipital sulcus.\n\n== Structural anatomy ==\n\nThe border between the occipital lobe and the parietal and temporal lobes is characterized by different gyri:\n the superior occipital gyrus (also known as gyrus occipitalis superior), middle occipital gyrus (or gyrus occipitalis medius), inferior occipital gyrus (or gyrus occipitalis inferior), and descending occipital gyrus (gyrus occipitalis descendens).\n\n== Function ==\n\nThe occipital complex is primarily responsible for object recognition, including the functional properties and our perception of said objects.\n\nThe middle occipital gyrus (MOG) was observed in a study of the early blind, which showed that it was activated more during spatial than nonspatial tactile and auditory tasks.\n\nEarly blind people have an occipital cortex that is incorporates more senses than people with standard vision, but the MOG still keeps its functional role in processing space around a person.\n\nThe lingual gyrus (also known as medial occipitotemporal gyrus) has been studied and found to be included in processing overall shapes, rather than the individual components that make up a shape.\n\nThis shows that the lingual gyrus is active during visual processing.The inferior occipital gyrus has been found to be related to the visual function of processing faces.\n\nThe IOG is connected to the amygdala via white matter connectivity.\n\nThis allows the IOG to form a network for facial recognition with the amygdala.\n\n== Development ==\n\nThe occipital lobe becomes distinct at 18 weeks gestation, but the gyri are not clear until many weeks later.\n\nDuring development, the occipital lobe develops a lingual gyrus at 27 weeks of gestation.\n\nSecondary gyri develop by 30 weeks, and tertiary gyri develop during 40 to 42 weeks of gestation.\n\nThe superior and inferior occipital gyri develop at the same time, usually shown somewhere between week 24 and 27 in brain development.\n\nDue to the unclear distinction in early neuroscience research as to whether there are two or three occipital gyri, there is not any data on when the middle occipital gyrus starts its formation, but it is likely at the same time.\n\nhttps://en.wikipedia.org/wiki/Occipital_gyri","lunate-sulcus":"In brain anatomy, the lunate sulcus or simian sulcus also known as the sulcus lunatus is a fissure in the occipital lobe variably found in humans and more often larger when present in apes and monkeys.\n\nThe lunate sulcus marks the transition between V1 and V2.The lunate sulcus lies further back in human brains but has a more forward location in chimpanzees.\n\nThe evolutionary expansion of the frontal areas of the lunate sulcus would have caused a shift in the particular location of the fissure.\n\nIt has been hypothesized that evolutionary pressures resulted in the human brain undergoing internal reorganization to develop the capability of human language.\n\nFurthermore, this reorganization must have been implemented during early maturity and is likely responsible for eidetic imagery in some adolescents.During early development, the neural connections in prefrontal cortex and posterior parietal lobe rapidly expand to allow capability for human language, while visual memory capacity of human brain would become limited.\n\nBiological studies have demonstrated that the lunate sulcus is subject to white matter growth, and dental fossil and tomography studies have shown that the brain organization of Australopithecus africanus is pongid-like.\n\n== History ==\n\nThe lunate sulcus was first identified during the early 1900s in the human brain as a homologue of the Affenspalte, a major sulcus defining the primary visual cortex (V1) in apes and other monkey species, by anatomist and Egyptologist Sir Grafton Elliot Smith.\n\nBased on Smith’s observations from studying over 400 Egyptian and ape brains, he noticed that the sulcal patterns between humans and apes were very similar.\n\nHis methodology involved mapping cortical areas via simple visual inspection of endocasts from mummies, as well as of fresh whole and sectioned brains.\n\nPaleoneurologists and scientists study endocasts in order to gather information about brain size and shape, as well as sulcal patterns resulting from pressure-induced impressions by the brain’s surface.\n\nComparison of data gathered from endocasts and the brains of living hominoids allows scientists to study the evolution of the human brain, both anatomically and cognitively.\n\nUltimately, Smith argued that the lunate sulcus was responsible for delineating the rostrolateral boundary of the V1 in both humans and non-human primates, and even pointed out the specific location of the lunate sulcus in chimpanzee versus human brains.\n\nNotably, Smith noticed that the position of the lunate sulcus was more posterior in human, especially those of European descent, as compared to monkey brains.\n\nBased on this observation, he was the first to hypothesize that the caudal shift of the lunate sulcus in Homo sapiens was due to the evolutionary rapid overgrowth of the cerebral cortex that is unique to human neurodevelopment.\n\nSmith’s observation that the caudal shift of the lunate sulcus could also be used as a predictor for determining both the evolutionary posterolateral shift of the occipital lobes/V1 and the corresponding expansion of the neighboring parietotemporo-occipital visual association cortices was supported by recent research.\n\nHowever, some scientists today disagree with Smith’s assertion that a lunate sulcus exists in humans, arguing that there is only an Affenspalte which is solely unique to apes.\n\nSpecifically, in a high-resolution MRI study conducted by Allen et al. (2006), the researchers scanned and analyzed 220 human brains and found no sign of the lunate sulcus homologue.\n\nBased on this finding, they suggested that the claim asserting humans have a lunate sulcus homologue fails to account for and show appreciation of the extensive evolutionary reorganization of the visual cortex in humans.\n\n== Evolution ==\n\nAnalyzing variability in the location of gross anatomical landmarks, like sulci, is an accepted method for studying evolutionary hominin brain reorganization.\n\nNotably, the position of the lunate sulcus in the occipital lobe has been studied in humans, early hominin endocasts, apes, and other monkey species by researchers seeking to make inferences about the morphological evolution of brain regions associated with human visual versus cognitive behaviors.\n\nHowever, some scientists remain skeptical about whether the lunate sulcus is a valid and reliable indicator for studying volumetric changes in the V1 due to the inconsistencies of the sulcus’ presence and lack of histological correspondence with cytoarchitectonic boundaries in hominoids.\n\nDespite this, previous allometry studies have suggested that the lunate sulcus shifts from a lateral-anterior to a medial-posterior position as brain size increases.\n\nSuch shifts have been accredited with predicting whether the lunate sulcus will occur or not based on an increase or reduction in V1 volume, thus providing an explanation for inconsistencies in its presence and position in the occipital lobes.\n\nMoreover, a study conducted by de Sousa et al. (2010) compared the volumes of the V1 relative to the position of the lunate sulcus in three-dimensional reconstructed non-human hominoid brains in order to determine if an allometric relationship existed between V1 volume and lunate sulcus position.\n\nThe researchers found that the position of the lunate sulcus does accurately predict V1 volume in apes, and that V1 volume in humans is smaller than would be expected based on our large brain size.\n\nFurthermore, other research suggests a more posteriorly positioned lunate sulcus from the early hominin fossil record.\n\nBased on all these findings, de Sousa et al. (2010) concluded V1 reduction began during early hominin evolution given the more lateral-anterior position of the lunate sulcus in human and other primate brains today.\n\nhttps://en.wikipedia.org/wiki/Lunate_sulcus","transverse-occipital-sulcus":"The transverse occipital sulcus is a structure in the occipital lobe.\n\nThe transverse occipital sulcus is continuous with the posterior end of the occipital ramus of the intraparietal sulcus, and runs across the upper part of the lobe, a short distance behind the parietooccipital fissure.\n\nhttps://en.wikipedia.org/wiki/Transverse_occipital_sulcus","transverse-temporal-gyri":"The transverse temporal gyri, also called Heschl's gyri () or Heschl's convolutions, are gyri found in the area of primary auditory cortex buried within the lateral sulcus of the human brain, occupying Brodmann areas 41 and 42.\n\nTransverse temporal gyri are superior to and separated from the planum temporale (cortex involved in language production) by Heschl’s sulcus.\n\nTransverse temporal gyri are found in varying numbers in both the right and left hemispheres of the brain and one study found that this number is not related to the hemisphere or dominance of hemisphere studied in subjects.\n\nTransverse temporal gyri can be viewed in the sagittal plane as either an omega shape (if one gyrus is present) or a heart shape (if two gyri and a sulcus are present).Transverse temporal gyri are the first cortical structures to process incoming auditory information.\n\nAnatomically, the transverse temporal gyri are distinct in that they run mediolaterally (toward the center of the brain), rather than front to back as all other temporal lobe gyri run.\n\nThe Heschl's gyri are named after Richard L. Heschl.\n\n== Processing tone ==\n\nThe transverse temporal gyri are active during auditory processing under fMRI for tone and semantic tasks.\n\nTransverse temporal gyri were found in one study to have significantly faster processing rates (33 Hz) in the left hemisphere compared to those in the right hemisphere (3 Hz).\n\nAdditionally this difference in processing rate was found to be related to the volume of rate-related cortex in the gyri; right transverse temporal gyri were found to be more active during temporal processing, and these gyri were found to have more “rate-related cortex”.\n\nWhite and grey matter volumes of transverse temporal gyri were not found to relate to this processing speed, although larger white matter volumes in subjects are associated with increased sensitivity to “rapid auditory input”.\n\nThe role of transverse temporal gyri in auditory processing of tone is demonstrated by a study by Wong, Warrier et. al. (2008).\n\nThis study revealed the following: subjects who could successfully form an association between Mandarin Chinese “pitch patterns” and word meaning were found to have transverse temporal gyri with larger volume than subjects who had “difficulty learning these associations.”\n\nSuccessful completion of the previous task also was found to be associated with a “greater concentration of white matter” in the left transverse temporal gyri of the subject.\n\nIn general, larger transverse temporal gyri “could be associated with more efficient processing of speech-related cues which could facilitate learning and perceiving new speech sounds.”\n\n== Inner voice ==\n\nResearch on the inner voice perceived by humans led to the identification of these gyri as the area of the brain activated during such dialogue with oneself.\n\nSpecifically, Heschl's gyrus responded to spontaneous inner speech, while it was hypoactive during task-elicited inner speech (repeating words prompted by an experimenter).\n\n== Mismatch negativity ==\n\nOne of the famous event-related potential (ERP) components is mismatch negativity.\n\nThis component is consider to represent a prediction error process in the brain.\n\nThis ERP has probably two generators, one in the right prefrontal lobe, and the other in the primary auditory regions - the transverse temporal gyrus and the superior temporal gyrus.\n\nhttps://en.wikipedia.org/wiki/Transverse_temporal_gyrus","temporal-plane":"SUPERIOR TEMPORAL GYRUS\n\nThe superior temporal gyrus (STG) is one of three (sometimes two) gyri in the temporal lobe of the human brain, which is located laterally to the head, situated somewhat above the external ear.\n\nThe superior temporal gyrus is bounded by:\n\n-the lateral sulcus above;\n-the superior temporal sulcus (not always present or visible) below;\n-an imaginary line drawn from the preoccipital notch to the lateral sulcus posteriorly.\n\nThe superior temporal gyrus contains several important structures of the brain, including:\n\nBrodmann areas 41 and 42, marking the location of the auditory cortex, the cortical region responsible for the sensation of sound;\nWernicke's area, Brodmann 22p, an important region for the processing of speech so that it can be understood as language.\n\nThe superior temporal gyrus contains the auditory cortex, which is responsible for processing sounds.\n\nSpecific sound frequencies map precisely onto the auditory cortex.\n\nThis auditory (or tonotopic) map is similar to the homunculus map of the primary motor cortex.\n\nSome areas of the superior temporal gyrus are specialized for processing combinations of frequencies, and other areas are specialized for processing changes in amplitude or frequency.\n\nThe superior temporal gyrus also includes Wernicke's area, which (in most people) is located in the left hemisphere.\n\nIt is the major area involved in the comprehension of language.\n\nThe superior temporal gyrus is involved in auditory processing, including language, but also has been implicated as a critical structure in social cognition.Various parts of the STG might be referred to as anterior (aSTG), middle (mSTG), and posterior (pSTG).\n\n== Function ==\n\nThe superior temporal gyrus has been involved in the perception of emotions in facial stimuli.)\n\nFurthermore, the superior temporal gyrus is an essential structure involved in auditory processing, as well as in the function of language in individuals who may have an impaired vocabulary, or are developing a sense of language.\n\nThe superior temporal gyrus has been discovered to be an important structure in the pathway consisting of the amygdala and prefrontal cortex, which are all involved in social cognition processes.\n\nIncluding the superior temporal gyrus, areas more anterior and dorsal within the temporal lobe have been linked to the ability of processing information the many changeable characteristics of a face.\n\nResearch conducted with the use of neuroimaging have found patients with schizophrenia have structural abnormalities in their superior temporal gyrus.\n\nfMRI analysis has evidenced a link between insight based problem solving and activity in the right anterior superior-temporal gyrus, specifically in relation to the sudden flash of understanding commonly referred to as an 'Aha!' moment.\n\n=== Social context ===\n\nThe superior temporal gyrus (STG) is important for language comprehension, but studies also suggest that it plays a functional role in the cocktail party effect.\n\nA magnetoencephalography study was conducted on participants that were exposed to five differing listening conditions each with a different level of background noise.\n\nIt was discovered that the STG has a strong connection with the attended speech stream in a cocktail party setting.\n\nWhen the attended speech stream wasn’t disrupted by background noise a bilateral connection was displayed, but as more background noise was introduced the connection became left-hemisphere-dependent.\n\nhttps://en.wikipedia.org/wiki/Superior_temporal_gyrus","superior-temporal-gyrus-lateral-part":"The superior temporal gyrus (STG) is one of three (sometimes two) gyri in the temporal lobe of the human brain, which is located laterally to the head, situated somewhat above the external ear.\n\nThe superior temporal gyrus is bounded by:\n\nthe lateral sulcus above;\nthe superior temporal sulcus (not always present or visible) below;\nan imaginary line drawn from the preoccipital notch to the lateral sulcus posteriorly.\n\nThe superior temporal gyrus contains several important structures of the brain, including:\n\nBrodmann areas 41 and 42, marking the location of the auditory cortex, the cortical region responsible for the sensation of sound;\nWernicke's area, Brodmann 22p, an important region for the processing of speech so that it can be understood as language.\n\nThe superior temporal gyrus contains the auditory cortex, which is responsible for processing sounds.\n\nSpecific sound frequencies map precisely onto the auditory cortex.\n\nThis auditory (or tonotopic) map is similar to the homunculus map of the primary motor cortex.\n\nSome areas of the superior temporal gyrus are specialized for processing combinations of frequencies, and other areas are specialized for processing changes in amplitude or frequency.\n\nThe superior temporal gyrus also includes Wernicke's area, which (in most people) is located in the left hemisphere.\n\nIt is the major area involved in the comprehension of language.\n\nThe superior temporal gyrus is involved in auditory processing, including language, but also has been implicated as a critical structure in social cognition.Various parts of the STG might be referred to as anterior (aSTG), middle (mSTG), and posterior (pSTG).\n\n== Function ==\n\nThe superior temporal gyrus has been involved in the perception of emotions in facial stimuli.)\n\nFurthermore, the superior temporal gyrus is an essential structure involved in auditory processing, as well as in the function of language in individuals who may have an impaired vocabulary, or are developing a sense of language.\n\nThe superior temporal gyrus has been discovered to be an important structure in the pathway consisting of the amygdala and prefrontal cortex, which are all involved in social cognition processes.\n\nIncluding the superior temporal gyrus, areas more anterior and dorsal within the temporal lobe have been linked to the ability of processing information the many changeable characteristics of a face.\n\nResearch conducted with the use of neuroimaging have found patients with schizophrenia have structural abnormalities in their superior temporal gyrus.\n\nfMRI analysis has evidenced a link between insight based problem solving and activity in the right anterior superior-temporal gyrus, specifically in relation to the sudden flash of understanding commonly referred to as an 'Aha!' moment.\n\n=== Social context ===\n\nThe superior temporal gyrus (STG) is important for language comprehension, but studies also suggest that it plays a functional role in the cocktail party effect.\n\nA magnetoencephalography study was conducted on participants that were exposed to five differing listening conditions each with a different level of background noise.\n\nIt was discovered that the STG has a strong connection with the attended speech stream in a cocktail party setting.\n\nWhen the attended speech stream wasn’t disrupted by background noise a bilateral connection was displayed, but as more background noise was introduced the connection became left-hemisphere-dependent.\n\nhttps://en.wikipedia.org/wiki/Superior_temporal_gyrus","lateral-occipitotemporal-gyrus":"FUSIFORM GYRUS\n\nThe fusiform gyrus, also known as the lateral occipitotemporal gyrus, is part of the temporal lobe and occipital lobe in Brodmann area 37.\n\nThe fusiform gyrus is located between the lingual gyrus and parahippocampal gyrus above, and the inferior temporal gyrus below.\n\nThough the functionality of the fusiform gyrus is not fully understood, it has been linked with various neural pathways related to recognition.\n\nAdditionally, it has been linked to various neurological phenomena such as synesthesia, dyslexia, and prosopagnosia.\n\n== Anatomy ==\n\nAnatomically, the fusiform gyrus is the largest macro-anatomical structure within the ventral temporal cortex, which mainly includes structures involved in high-level vision.\n\nThe term fusiform gyrus (lit. „spindle-shaped convolution“) refers to the fact that the shape of the gyrus is wider at its centre than at its ends.\n\nThis term is based on the description of the gyrus by Emil Huschke in 1854. (see also section on history).\n\nThe fusiform gyrus is situated at the basal surface of the temporal and occipital lobes and is delineated by the collateral sulcus (CoS) and occipitotemporal sulcus (OTS), respectively.\n\nThe OTS separates the fusiform gyrus from the inferior temporal gyrus (located laterally in respect to the fusiform gyrus) and the CoS separates the fusiform gyrus from the parahippocampal gyrus (located medially in respect to the fusiform gyrus).\n\nThe fusiform gyrus can be further delineated into a lateral and medial portion, as it is separated in its middle by the relatively shallow mid-fusiform sulcus (MFS).\n\nThus, the lateral fusiform gyrus is delineated by the OTS laterally and the MFS medially.\n\nLikewise, the medial fusiform gyrus is delineated by the MFS laterally and the CoS medially.\n\nImportantly, the mid-fusiform sulcus serves as a macroanatomical landmark for the fusiform face area (FFA), a functional subregion of the fusiform gyrus assumed to play a key role in processing faces.\n\n== History ==\n\nThe fusiform gyrus has a contentious history that has recently been clarified.\n\nThe term was first used in 1854 by Emil Huschke from Jena, Germany, who called the fusiform gyrus a “Spindelwulst” (lit. spindle bulge).\n\nHe chose this term because of the similarity that the respective cerebral gyrus bears to the shape of a spindle, or fusil, due to its wider central section.\n\nAt first, researchers located the fusiform gyrus in other mammals as well, without taking into account the variations in gross organizations of other species’ brains.\n\nToday, the fusiform gyrus is considered to be specific to hominoids.\n\nThis is supported by research showing only three temporal gyri and no fusiform gyrus in macaques.\n\nThe first accurate definition of the mid-fusiform sulcus was coined by Gustav Retzius in 1896.\n\nHe was the first to describe the sulcus sagittalis gyri fusiformis (today: mid-fusiform sulcus), and correctly determined that a sulcus divides the fusiform gyrus into lateral and\nmedial partitions.\n\nW.\n\nJulius Mickle mentioned the mid-fusiform sulcus in 1897 and attempted to clarify the relation between temporal sulci and the fusiform gyrus, calling it the “intra-gyral sulcus of the fusiform lobule”.\n\n== Function ==\n\nThe exact functionality of the fusiform gyrus is still disputed, but there is relative consensus on its involvement in the following pathways:\n\n=== Processing of color information ===\n\nIn 2003, V. S.Ramachandran collaborated with scientists from the Salk Institute for Biological Studies in order to identify the potential role of the fusiform gyrus within the color processing pathway in the brain.\n\nExamining the relationship within the pathway specifically in cases of synesthesia, Ramachandran found that synesthetes on average have a higher density of fibers surrounding the angular gyrus.\n\nThe angular gyrus is involved in higher processing of colors.\n\nThe fibers relay shape information from the fusiform gyrus to the angular gyrus in order to produce the association of colors and shapes in grapheme-color synesthesia.\n\nCross-activation between the angular and fusiform gyri has been observed in the average brain, implying that the fusiform gyrus regularly communicates with the visual pathway.\n\n=== Face and body recognition ===\n\nPortions of the fusiform gyrus are critical for face and body recognition.\n\n=== Word recognition ===\n\nIt is believed that portions of the left hemisphere fusiform gyrus are used in word recognition.\n\n=== Within-category identification ===\n\nFurther research by MIT scientists showed that the left and right fusiform gyri played different roles, which subsequently interlinked.\n\nThe left fusiform gyrus recognizes \"face-like\" features in objects that may or may not be actual faces, whereas the right fusiform gyrus determines if that recognized face-like feature is, in fact, a face.\n\n== Related neural transmitter system ==\n\nIn a 2015 study, dopamine was proposed to play a key role in face recognition task and was considered to be related to neural activity in fusiform gyrus.\n\nBy studying the correlation between the binding potential (BP) of dopamine D1 receptor by PET and blood-oxygen-level-dependent (BOLD) in fMRI scan during a face recognition task, higher availability of D1 receptor was shown to be associated with higher BOLD level.\n\nThis study showed that this association with D1 BP is only significant for FFG, not other brain regions.\n\nThe researchers also showed the possibility that higher availability of dopamine D1 receptor may underlie better performance in face recognition task.\n\nDopamine is known to be related to the reward system.\n\nThe dopaminergic system shows an active response to stimuli that predict possible rewards.\n\nAs a social demand, a face recognition task could be a cognition process that involves dopamine, which can elicit a reinforcement feedback.\n\nA 2007 study investigated how dopamine may regulate FFG activity during a face recognition task.\n\nIt indicated that BOLD activity can be modulated by dopamine's influence on postsynaptic D1 receptors.\n\nThe regulation is achieved in a way that dopamine first influence post-synaptic potential, and then further cause BOLD activity increase in the local area.\n\nThis link between post-synaptic BOLD activity increase and dopamine release can be explained by blockage of dopamine reuptake.\n\n== Associated neurological phenomena ==\n\nThe fusiform gyrus has been speculated to be associated with various neurological phenomena.\n\n=== Prosopagnosia ===\n\nSome researchers think that the fusiform gyrus may be related to the disorder known as prosopagnosia, or face blindness.\n\nResearch has also shown that the fusiform face area, the area within the fusiform gyrus, is heavily involved in face perception but only to any generic within-category identification that is shown to be one of the functions of the fusiform gyrus.\n\nAbnormalities of the fusiform gyrus have also been linked to Williams syndrome.\n\nFusiform gyrus has also been involved in the perception of emotions in facial stimuli.\n\nHowever, individuals with autism show little to no activation in the fusiform gyrus in response to seeing a human face.\n\n=== Synaesthesia ===\n\nRecent research has seen activation of the fusiform gyrus during subjective grapheme–color perception in people with synaesthesia.\n\nThe effect of the fusiform gyrus in grapheme sense seems somewhat more clear as the fusiform gyrus seems to play a key role in word recognition.\n\nThe connection to color may be due to cross wiring of (being directly connected to) areas of the fusiform gyrus and other areas of the visual cortex associated with experiencing color.\n\n=== Dyslexia ===\n\nFor those with dyslexia, it has been seen that the fusiform gyrus is underactivated and has reduced gray matter density.\n\n=== Face hallucinations ===\n\nIncreased neurophysiological activity in the fusiform face area may produce hallucinations of faces, whether realistic or cartoonesque, as seen in Charles Bonnet syndrome, hypnagogic hallucinations, peduncular hallucinations, or drug-induced hallucinations.\n\nhttps://en.wikipedia.org/wiki/Fusiform_gyrus","medial-occipitotemporal-gyrus-parahippocampal":"PARAHIPPOCAMPAL GYRUS\n\nThe parahippocampal gyrus (or hippocampal gyrus) is a grey matter cortical region of the brain that surrounds the hippocampus and is part of the limbic system.\n\nThe region plays an important role in memory encoding and retrieval.\n\nIt has been involved in some cases of hippocampal sclerosis.\n\nAsymmetry has been observed in schizophrenia.\n\n== Structure ==\n\nThe anterior part of the gyrus includes the perirhinal and entorhinal cortices.\n\nThe term parahippocampal cortex is used to refer to an area that encompasses both the posterior parahippocampal gyrus and the medial portion of the fusiform gyrus.\n\n== Function ==\n\n=== Scene recognition ===\n\nThe parahippocampal place area (PPA) is a sub-region of the parahippocampal cortex that lies medially in the inferior temporo-occipital cortex.\n\nPPA plays an important role in the encoding and recognition of environmental scenes (rather than faces).\n\nfMRI studies indicate that this region of the brain becomes highly active when human subjects view topographical scene stimuli such as images of landscapes, cityscapes, or rooms (i.e. images of \"places\").\n\nFurthermore, according to work by Pierre Mégevand et al. in 2014, stimulation of the region via intracranial electrodes yields intense topographical visual hallucinations of places and situations.\n\nThe region was first described by Russell Epstein and Nancy Kanwisher in 1998 at MIT, see also other similar reports by Geoffrey Aguirre and Alumit Ishai.\n\nDamage to the PPA (for example, due to stroke) often leads to a syndrome in which patients cannot visually recognize scenes even though they can recognize the individual objects in the scenes (such as people, furniture, etc.).\n\nThe PPA is often considered the complement of the fusiform face area (FFA), a nearby cortical region that responds strongly whenever faces are viewed, and that is believed to be important for face recognition.\n\n=== Social context ===\n\nAdditional research has suggested that the right parahippocampal gyrus in particular has functions beyond the contextualizing of visual background.\n\nTests by a California-based group led by Katherine P.\n\nRankin indicate that the lobe may play a crucial role in identifying social context as well, including paralinguistic elements of verbal communication.\n\nFor example, Rankin's research suggests that the right parahippocampal gyrus enables people to detect sarcasm.\n\nhttps://en.wikipedia.org/wiki/Parahippocampal_gyrus","inferior-temporal-sulcus":"The inferior surface of the temporal lobe is concave, and is continuous posteriorly with the tentorial surface of the occipital lobe.\n\nIt is traversed by the inferior temporal sulcus, which extends from near the occipital pole behind, to within a short distance of the temporal pole in front, but is frequently subdivided by bridging gyri.\n\nhttps://en.wikipedia.org/wiki/Inferior_temporal_sulcus","inferior-temporal-gyrus":"The inferior temporal gyrus is one of three gyri of the temporal lobe and is located below the middle temporal gyrus, connected behind with the inferior occipital gyrus; it also extends around the infero-lateral border on to the inferior surface of the temporal lobe, where it is limited by the inferior sulcus.\n\nThis region is one of the higher levels of the ventral stream of visual processing, associated with the representation of objects, places, faces, and colors.\n\nIt may also be involved in face perception, and in the recognition of numbers.\n\nThe inferior temporal gyrus is the anterior region of the temporal lobe located underneath the central temporal sulcus.\n\nThe primary function of the occipital temporal gyrus – otherwise referenced as IT cortex – is associated with visual stimuli processing, namely visual object recognition, and has been suggested by recent experimental results as the final location of the ventral cortical visual system.\n\nThe IT cortex in humans is also known as the Inferior Temporal Gyrus since it has been located to a specific region of the human temporal lobe.\n\nThe IT processes visual stimuli of objects in our field of vision, and is involved with memory and memory recall to identify that object; it is involved with the processing and perception created by visual stimuli amplified in the V1, V2, V3, and V4 regions of the occipital lobe.\n\nThis region processes the color and form of the object in the visual field and is responsible for producing the “what” from this visual stimuli, or in other words identifying the object based on the color and form of the object and comparing that processed information to stored memories of objects to identify that object.\n\nThe IT cortex’s neurological significance is not just its contribution to the processing of visual stimuli in object recognition but also has been found to be a vital area with regards to simple processing of the visual field, difficulties with perceptual tasks and spatial awareness, and the location of unique single cells that possibly explain the IT cortex’s relation to memory.\n\n== Structure ==\n\nThe temporal lobe is unique to primates.\n\nIn humans, the IT cortex is more complex than their relative primate counterparts.\n\nThe human inferior temporal cortex consists of the inferior temporal gyrus, the middle temporal gyrus, and the fusiform gyrus.\n\nWhen looking at the brain laterally – that is from the side and looking at the surface of the temporal lobe – the inferior temporal gyrus is along the bottom portion of the temporal lobe, and is separated from the middle temporal gyrus located directly above by the inferior temporal sulcus.\n\nAdditionally, some processing of the visual field that corresponds to the ventral stream of visual processing occurs in the lower portion of the superior temporal gyrus closest to the superior temporal sulcus.\n\nThe medial and ventral view of the brain – meaning looking at the medial surface from below the brain, facing upwards – reveals that the inferior temporal gyrus is separated from the fusiform gyrus by the occipital-temporal sulcus.\n\nThis human inferior temporal cortex is much more complex than that of other primates: non-human primates have an inferior temporal cortex that is not divided into unique regions such as humans' inferior temporal gyrus, fusiform gyrus, or middle temporal gyrus.\n\nThis region of the brain corresponds to the inferior temporal cortex and is responsible for visual object recognition and receives processed visual information.\n\nThe inferior temporal cortex in primates has specific regions dedicated to processing different visual stimuli processed and organized by the different layers of the striate cortex and extra-striate cortex.\n\nThe information from the V1 –V5 regions of the geniculate and tectopulvinar pathways are radiated to the IT cortex via the ventral stream: visual information specifically related to the color and form of the visual stimuli.\n\nThrough comparative research between primates – humans and non-human primates – results indicate that the IT cortex plays a significant role in visual shape processing.\n\nThis is supported by functional magnetic resonance imaging (fMRI) data collected by researchers comparing this neurological process between humans and macaques.\n\n== Function ==\n\n=== Receiving information ===\n\nThe light energy that comes from the rays bouncing off of an object is converted into chemical energy by the cells in the retina of the eye.\n\nThis chemical energy is then converted into action potentials that are transferred through the optic nerve and across the optic chiasm, where it is first processed by the lateral geniculate nucleus of the thalamus.\n\nFrom there the information is sent to the primary visual cortex, region V1.\n\nIt then travels from the visual areas in the occipital lobe to the parietal and temporal lobes via two distinct anatomical streams.\n\nThese two cortical visual systems were classified by Ungerleider and Mishkin (1982, see two-streams hypothesis).\n\nOne stream travels ventrally to the inferior temporal cortex (from V1 to V2 then through V4 to ITC) while the other travels dorsally to the posterior parietal cortex.\n\nThey are labeled the “what” and “where” streams, respectively.\n\nThe Inferior Temporal Cortex receives information from the ventral stream, understandably so, as it is known to be a region essential in recognizing patterns, faces, and objects.\n\n=== Single-cell function in the inferior temporal gyrus ===\n\nThe understanding at the single-cell level of the IT cortex and its role of utilizing memory to identify objects and or process the visual field based on color and form visual information is a relatively recent in neuroscience.\n\nEarly research indicated that the cellular connections of the temporal lobe to other memory associated areas of the brain – namely the hippocampus, the amygdala, the prefrontal cortex, among others.\n\nThese cellular connections have recently been found to explain unique elements of memory, suggesting that unique single-cells can be linked to specific unique types and even specific memories.\n\nResearch into the single-cell understanding of the IT cortex reveals many compelling characteristics of these cells:\n single-cells with similar selectivity of memory are clustered together across the cortical layers of the IT cortex; the temporal lobe neurons have recently been shown to display learning behaviors and possibly relate to long-term memory; and, cortical memory within the IT cortex is likely to be enhanced over time thanks to the influence of the afferent-neurons of the medial-temporal region.\n\nFurther research of the single-cells of the IT cortex suggests that these cells not only have a direct link to the visual system pathway but also are deliberate in the visual stimuli they respond to:\n in certain cases, the single-cell IT cortex neurons do not initiate responses when spots or slits, namely simple visual stimuli, are present in the visual field; however, when complicated objects are put in place, this initiates a response in the single-cell neurons of the IT cortex.\n\nThis provides evidence that not only are the single-cell neurons of the IT cortex related in having a unique specific response to visual stimuli but rather that each individual single-cell neuron has a specific response to a specific stimuli.\n\nThe same study also reveals how the magnitude of the response of these single-cell neurons of the IT cortex do not change due to color and size but are only influenced by the shape.\n\nThis led to even more interesting observations where specific IT neurons have been linked to the recognition of faces and hands.\n\nThis is very interesting as to the possibility of relating to neurological disorders of prosopagnosia and explaining the complexity and interest in the human hand.\n\nAdditional research form this study goes into more depth on the role of \"face neurons\" and \"hand neurons\" involved in the IT cortex.\n\nThe significance of the single-cell function in the IT cortex is that it is another pathway in addition to the lateral geniculate pathway that processes most visual system:\n this raises questions about how does it benefit our visual information processing in addition to normal visual pathways and what other functional units are involved in additional visual information processing.\n\n=== Information processing ===\n\nThe information for color and form comes from P-cells that receive their information mainly from cones, so they are sensitive to differences in form and color, as opposed to the M-cells that receive information about motion mainly from rods.\n\nThe neurons in the inferior temporal cortex, also called the inferior temporal visual association cortex, process this information from the P-cells.\n\nThe neurons in the ITC have several unique properties that offer an explanation as to why this area is essential in recognizing patterns.\n\nThey only respond to visual stimuli and their receptive fields always include the fovea, which is one of the densest areas of the retina and is responsible for acute central vision.\n\nThese receptive fields tend to be larger than those in the striate cortex and often extend across the midline to unite the two visual half fields for the first time.\n\nIT neurons are selective for shape and/or color of stimulus and are usually more responsive to complex shapes as opposed to simple ones.\n\nA small percentage of them are selective for specific parts of the face.\n\nFaces and likely other complex shapes are seemingly coded by a sequence of activity across a group of cells, and IT cells can display both short or long term memory for visual stimuli based on experience.\n\n=== Object recognition ===\n\nThere are a number of regions within the ITC that work together for processing and recognizing the information of “what” something is.\n\nIn fact, discrete categories of objects are even associated with different regions.\n\nThe fusiform gyrus or Fusiform Face Area (FFA) deals more with facial and body recognition rather than objects.\n\nThe Parahippocampal Place Area (PPA) helps differentiate between scenes and objects.\n\nThe Extrastriate Body Area (EBA) tells apart body parts from other objects.\n\nAnd the Lateral Occipital Complex (LOC) is used to determine shapes vs. scrambled stimuli.\n\nThese areas must all work together, as well as with the hippocampus, in order to create an array of understanding of the physical world.\n\nThe hippocampus is key for storing the memory of what an object is/what it looks like for future use so that it can be compared and contrasted with other objects.\n\nCorrectly being able to recognize an object is highly dependent on this organized network of brain areas that process, share, and store information.\n\nIn a study by Denys et al., functional magnetic resonance imaging (FMRI) was used to compare the processing of visual shape between humans and macaques.\n\nThey found, amongst other things, that there was a degree of overlap between shape and motion sensitive regions of the cortex, but that the overlap was more distinct in humans.\n\nThis would suggest that the human brain is better evolved for a high level of functioning in a distinct, three-dimensional, visual world.\n\n== Clinical significance ==\n\n=== Prosopagnosia ===\n\nProsopagnosia, also called face blindness, is a disorder that results in the inability to recognize or discriminate between faces.\n\nIt can often be associated with other forms of recognition impairment, such as place, car, or emotional recognition.\n\nA study conducted by Gross et all in 1969 found that certain cells were selective for the shape of a monkey hand, and they observed that as the stimulus they provided began to further resemble a monkey hand, those cells became more active.\n\nA few years later, in 1972, Gross et al. discovered that certain IT cells were selective for faces.\n\nAlthough it is not conclusive, ‘face-selective’ IT cortex cells are assumed to play a large role in facial recognition in monkeys.\n\nAfter the extensive research into the result of damage to the IT cortex in monkeys, it is theorized that lesions in the IT gyrus in humans result in prosopagnosia.\n\nRubens and Benson’s 1971 study of a subject in life with prosopagnosia reveals that the patient is able to name common objects on visual presentation flawlessly, however she cannot recognize faces.\n\nUpon necropsy conducted by Benson et al., it was apparent that a discrete lesion in the right fusiform gyrus, a part of the inferior temporal gyrus, was one of the main causes of the subject’s symptoms.\n\nA more in depth observation can be seen with the example of patient L.H. in the study conducted by N.L.\n\nEtcoff and colleagues in 1991.\n\nThis 40-year-old man was involved in an automobile accident when he was 18, which resulted in severe brain injury.\n\nUpon recovery, L.H. was unable to recognize or discriminate between faces, or even recognize faces that were familiar to him before the accident.\n\nL.H. and other patients with prosopagnosia are often able to live relatively normal and productive lives despite their deficit.\n\nL.H. was still able to recognize common objects, subtle differences in shapes, and even age, sex, and “likeability” of faces.\n\nHowever, they use non-facial cues, such as height, hair color, and voice to differentiate between people.\n\nNon-invasive brain imaging revealed that L.H.’s prosopagnosia was a result of damage to the right temporal lobe, which contains the inferior temporal gyrus.\n\n=== Deficits in semantic memory ===\n\nCertain disorders, such as Alzheimer's disease and semantic dementia, are characterized by a patient’s inability to integrate semantic memories, which results in patients being unable to form new memories, lacking awareness of time period, as well as lacking other important cognitive processes.\n\nChan et al 2001 conducted a study that used volumetric magnetic resonance imaging to quantify the global and temporal lobe atrophy in semantic dementia and Alzheimer's disease.\n\nThe subjects were selected and confirmed to be in the middle of the spectrum of their respective disorders clinically, and then further confirmation came from a series of neuropsychological tests given to the subjects.\n\nThe study treated the inferior temporal cortex and the middle temporal cortex as one and the same, because of the, \"often indistinct,\" border between the gyri.\n\nThe study concluded that in Alzheimer's disease, deficits in inferior temporal structures were not the main source of the disease.\n\nRather, atrophy in the entorhinal cortex, amygdala, and hippocampus was prominent in the Alzheimer’s inflicted subjects of the study.\n\nWith respect to semantic dementia, the study concluded that “the middle and inferior temporal gyri [cortices] may play a key role” in semantic memory, and as a result, unfortunately, when these anterior temporal lobe structures are injured, the subject is left with semantic dementia.\n\nThis information shows how, despite often being grouped in the same category, Alzheimer's disease and semantic dementia are very different diseases, and are characterized by marked differences in the subcortical structures they are associated with.\n\n=== Cerebral achromatopsia ===\n\nCerebral achromatopsia is a medical disorder characterized by the inability to perceive color and to achieve satisfactory visual acuity in high light levels.\n\nCongenital achromatopsia is characterized the same way, however it is genetic, while Cerebral Achromatopsia occurs as a result of damage to certain parts of the brain.\n\nOne part of the brain that is particularly integral to color discrimination is the inferior temporal gyrus.\n\nA 1995 study conducted by Heywood et al. was meant to highlight the parts of the brain that are important in achromatopsia in monkeys, however, it obviously sheds light on the areas of the brain related to achromatopsia in humans.\n\nIn the study, one group of monkeys (group AT) received lesions in the temporal lobe anterior to V4 and the other group (group MOT) received lesions to the occipito-temporal area that corresponds in cranial location to the lesion that produces cerebral achromatopsia in humans.\n\nThe study concluded that group MOT had no impairment of their color vision while the subjects in group AT all had severe impairments to their color vision, consistent with humans diagnosed with cerebral achromatopsia.\n\nThis study shows that temporal lobe areas anterior to V4, which includes the inferior temporal gyrus, play a large role in patients with Cerebral Achromatopsia.\n\nhttps://en.wikipedia.org/wiki/Inferior_temporal_gyrus","middle-temporal-gyrus":"Middle temporal gyrus is a gyrus in the brain on the temporal lobe.\n\nIt is located between the superior temporal gyrus and inferior temporal gyrus.\n\nIt corresponds largely to Brodmann area 21.\nThe middle temporal gyrus is bounded by:\n\nthe superior temporal sulcus above;\nthe inferior temporal sulcus below;\nan imaginary line drawn from the preoccipital notch to the lateral sulcus posteriorly.\n\nIt has been connected with processes as different as contemplating distance, recognition of known faces, audio-visual emotional recognition, and accessing word meaning while reading.\n\nSome studies indicate that lesions of the posterior region of the middle temporal gyrus, in the left cerebral hemisphere, may result in alexia and agraphia for kanji characters (characters of Chinese origin used in Japanese writing).\n\nThe left middle temporal gyrus is also activated during poem composition.\n\nhttps://en.wikipedia.org/wiki/Middle_temporal_gyrus","superior-temporal-sulcus":"The superior temporal sulcus (STS) is the sulcus separating the superior temporal gyrus from the middle temporal gyrus in the temporal lobe of the brain.\n\nA sulcus (plural sulci) is a deep groove that curves into the largest part of the brain, the cerebrum, and a gyrus (plural gyri) is a ridge that curves outward of the cerebrum.\n\nThe STS is located under the lateral fissure, which is the fissure that separates the temporal lobe, parietal lobe, and frontal lobe.\n\nThe STS has an asymmetric structure between the left and right hemisphere, with the STS being longer in the left hemisphere, but deeper in the right hemisphere.\n\nThis asymmetrical structural organization between hemispheres has only been found to occur in the STS of the human brain.\n\nThe STS has been shown to produce strong responses when subjects perceive stimuli in research areas that include theory of mind, biological motion, faces, voices, and language.\n\n== Language Processing ==\n\n=== Spoken language processing ===\n\nThe superior temporal sulcus also activates when hearing human voices.\n\nIt is thought to be a source of sensory encoding linked to motor output through the superior parietal-temporal areas of the brain inferred from the time course of activation.\n\nThe conclusion of pertinence to vocal processing can be drawn from data showing that the regions of the STS are more active when people are listening to vocal sounds rather than non-vocal environmentally based sounds and corresponding control sounds, which can be scrambled or modulated voices.\n\nThese experimental results indicate the involvement of the STS in the areas of speech and language recognition.\n\nThe majority of studies find it is the middle to the posterior portion of the STS that is involved in phonological processing, with bilateral activation indicated though including a mild left hemisphere bias due to greater observed activation.\n\nHowever, the role of the anterior STS in the ventral pathway of speech comprehension and production has not been ruled out.\n\nEvidence for the involvement of the middle portion of the STS in phonological processing comes from repetition-suppression studies, which use fMRI to pinpoint areas of the brain responsible for specialized stimulus involvement by habituating the brain to the stimulus and recording differences in stimulation response.\n\nThe resulting pattern showed expected results in the middle portion of the STS.\n\nStudies using fMRI analysis to measure superior temporal sulcus activation have found that phonemes, words, sentences, and phonological cues all lead to increased activation throughout a posterior-anterior axis in the temporal lobe.\n\nThis pattern of activation, which most frequently occurs in the left hemisphere, has been termed the ventral stream of speech perception.\n\nMany studies consistently indicate that the superior temporal sulcus activation is associated with the interpretation of phonological signals.\n\nAlthough present research suggest that the left hemisphere of the superior temporal sulcus and its associated left ventral stream plays a role in phonological processing, the right hemisphere of the superior temporal sulcus has been connected to the perception of voice and the prosody of speech.\n\nAccording to the audiological pathway model supplied by Hickok and Poeppel, after the spectrotemporal analysis conducted by the auditory cortex, the STS is responsible for interpretation of vocal input through the phonological network.\n\nThis implication is shown in the activation of the region in tasks of speech perception and processing, which necessarily involves access to and continuance of phonological information.\n\nBy manipulating the interactions of phonological data, represented by the provision of words with high or low neighborhood density (words associated with many or few other words), the fluctuation of activity of the STS region can be seen.\n\nThis changing activation links the STS with the phonological pathway.\n\n=== Sign language processing ===\n\nResearch shows that the Broca's area of the brain is activated during sign language production and processing.\n\nAlthough Broca's area is found in the frontal lobe, it receives connection from the superior temporal gyrus, including the STS.\n\nNative signers are people who learned and have been using sign language, such as American Sign Language (ASL), from birth, and/or use it as their first language.\n\nThey often learn sign language from their parents and continue its use throughout their lifetime.\n\nSign language activates language regions of the brain, including the STS.\n\nThere have been studies that show activation of the STS while deaf and hearing native signers perceive sign language, suggesting the STS is tied to the linguistic processing aspect of sign language.\n\nStudies also show that there is greater activation of the middle STS in both deaf and hearing signers who acquired ASL earlier than those who acquired it later.\n\n== Social processing ==\n\nStudies reveal multiple social processing capabilities.\n\nResearch has documented activation in the STS as a result of five specific social inputs, and thus the STS is assumed to be implicated in social perception.\n\nIt showed increased activation related to: theory of mind (false belief stories versus false physical stories) voices versus environmental sounds, stories versus nonsense speech, moving faces versus moving objects, and biological motion.\n\nIt is involved in the perception of where others are gazing (joint attention) and is important in determining where others' emotions are being directed.\n\n=== Theory of mind ===\n\nNeuroimaging studies examining the theory of mind, otherwise known as the ability to attribute mental states to others, have identified the posterior superior temporal sulcus of the right hemisphere as being involved in its processing.\n\nActivation of this region in the theory of mind has been found to be best predicted by independent ratings from other groups of participants, or more specifically, how much each item in the study made them consider the protagonist’s point of view.\n\nReports noted in other studies suggest a number of inconsistencies with the localization of theory of mind processing, such as the middle and anterior portions of the superior temporal sulcus having increased activation in response to theory of mind tasks.\n\nThus, further research is needed to expand upon the precise functional role of the superior temporal sulcus in the perception of theory of mind.\n\n=== Face perception ===\n\nA recent study identified a region of the posterior superior temporal sulcus that is preferentially activated in the interpretation of facial expressions.\n\nSimilarly, another study found that transcranial magnetic stimulation disrupted the neural response to faces, but not the neural response to bodies or objects.\n\nThe patterns of activations found in this study suggests that facial information is processed by projections in the right hemisphere from the posterior superior temporal sulcus, through the anterior superior temporal sulcus, and into the amygdala.\n\nAnother study showed that the resting-state functional connectivity between the right posterior superior temporal sulcus, the right occipital face area, early visual cortex, and bilateral superior temporal sulcus was positively correlated with each subject’s ability to recognize facial expression.\n\n=== Face-voice audiovisual integration ===\n\nMany studies have suggested that the posterior superior temporal sulcus is associated the crossmodal binding of auditory and visual stimuli.\n\nThe activation of this posterior portion of the superior temporal sulcus was reported in the detection of audio-visual incongruences and in voice perception.\n\nThe posterior superior temporal sulcus has also been shown to be preferentially activated by lip reading.\n\nAn area of the right posterior superior temporal sulcus was characterized by a recent study by a stronger response to audiovisual stimuli compared to that of auditory or visual stimuli alone.\n\nThis study also identified this same region to preferentially activated in the processing of stimuli associated with people, such as faces and voices.\n\nAnother fMRI study found that the neural representations of audiovisual integration, non-verbal emotional signals, voice sensitivity, and face sensitivity are all localized to separate regions of the superior temporal sulcus.\n\nLikewise, this study also noted that the area most sensitive to voice is located in the trunk section of the superior temporal sulcus, the area most sensitive to facial expressions is located in the posterior terminal ascending branch, and audiovisual integration of emotional signals occurs in regions that overlap with face and voice recognition areas at the bifurcation of the superior temporal sulcus.\n\n=== Biological motion ===\n\nThe superior temporal sulcus has been found to have a unique sensitivity to observable manifestations of movement understanding, which suggest that the superior temporal sulcus is heavily involved in the recognition of movements and gestures required for normal social information processing in humans.\n\nIn fMRI studies evaluating the interpretation of a point-light display that represents a moving human figure as a pattern of dots, a cluster of significant brain activity was observed in the posterior superior temporal sulcus of the right hemisphere in subjects that correctly identified the biological motion being shown in the point-light display.\n\nFurthermore, movement perception and movement interpretation are believed to be localized in different regions of the superior temporal sulcus, with movement perception being processed in a posterior region of the superior temporal sulcus and movement understanding being processed in a more anterior region.\n\n== Neurological disorders ==\n\nIn studies on dysfunctional social cognition in neurological disorders, such as what is observed in people with high-functioning autism, the role of the superior temporal sulcus in processing social information has been identified as the mechanism that lies at the root of these impairments in social interpretation.\n\n=== Autism ===\n\nChildren with high-functioning autism have been reported to have no significant change in superior temporal sulcus activation for biological motion compared to non-biological motion, which suggests that the superior temporal sulcus is not specifically activated in the processing of biological motion like it is in children without autism.\n\nIn subjects with schizophrenia, another neurological disorder associated with significant impairments to social cognition, these social impairment have been linked to an alteration in posterior superior temporal sulcus activation in affective theory of mind, emotional recognition, and the interpretation of neutral facial expressions.\n\nMore specifically, it was determined that schizophrenic subjects exhibited hyperactivity within the posterior superior temporal sulcus of the right hemisphere in processing neutral facial expressions, but they also exhibited hypoactivity within this same region for emotional recognition and affective theory of mind.\n\nThis same study also found impaired connectivity between the right and left hemispheres of the posterior superior temporal sulcus in the processing of affective theory of mind.\n\nAnother recent study showed an inverse relationship between glutamate concentrations within the superior temporal sulcus and neuroticism scores assessed by questionnaire was found in subjects with schizophrenia, which suggests that elevations in glutamate concentrations may act as a compensatory mechanism that allows those with schizophrenia to prevent neuroticism.\n\n=== Agnosia ===\n\nVarious disorders of the STS have been documented in which patients fail to recognize a certain stimulus, but still exhibit subcortical processing of the stimulus, this is known as an agnosia.\n\nPure auditory agnosia (agnosia without aphasia) is found in a patients who can't identify non-speech sounds such as coughing, whistling, and crying but have no deficit in speech comprehension.\n\nSpeech agnosia is known as an incapability to comprehend spoken words despite intact hearing, speech production, and reading ability.\n\nPatients show a recognition of the familiarity of a word, but are not able to recall its meaning.\n\nPhonagnosia is characterized as an inability to recognize familiar voices, while having other auditory abilities.\n\nPatients exhibited a double dissociation with either an inability to match names or faces with a certain famous voice, or to discriminate familiar voices from unfamiliar ones.\n\nVisual agnosia can be broken into separate disorders in regard to what is being recognized.\n\nAn inability to recognize written words is known as alexia or word blindness, while an inability to recognize familiar faces is known as prosopagnosia.\n\nProsopagnosia has been shown to have a similar double dissociation as phonagnosia in that some patients show an impairment of memory for familiar faces while others show impairment when discriminating familiar faces from unfamiliar ones.\n\nhttps://en.wikipedia.org/wiki/Superior_temporal_sulcus","insula-subcentral-gyrus-and-ant-and-post-sulci":"The insular cortex (also insula and insular lobe) is a portion of the cerebral cortex folded deep within the lateral sulcus (the fissure separating the temporal lobe from the parietal and frontal lobes) within each hemisphere of the mammalian brain.\n\nThe insulae are believed to be involved in consciousness and play a role in diverse functions usually linked to emotion or the regulation of the body's homeostasis.\n\nThese functions include compassion, empathy, taste, perception, motor control, self-awareness, cognitive functioning, interpersonal experience, and awareness of homeostatic emotions such as hunger, pain and fatigue.\n\nIn relation to these, it is involved in psychopathology.\n\nThe insular cortex is divided into two parts: the anterior insula and the posterior insula in which more than a dozen field areas have been identified.\n\nThe cortical area overlying the insula toward the lateral surface of the brain is the operculum (meaning lid).\n\nThe opercula are formed from parts of the enclosing frontal, temporal, and parietal lobes.\n\n== Structure ==\n\n=== Connections ===\n\nThe anterior part of the insula is subdivided by shallow sulci into three or four short gyri.\n\nThe anterior insula receives a direct projection from the basal part of the ventral medial nucleus of the thalamus and a particularly large input from the central nucleus of the amygdala.\n\nIn addition, the anterior insula itself projects to the amygdala.\n\nOne study on rhesus monkeys revealed widespread reciprocal connections between the insular cortex and almost all subnuclei of the amygdaloid complex.\n\nThe posterior insula projects predominantly to the dorsal aspect of the lateral and to the central amygdaloid nuclei.\n\nIn contrast, the anterior insula projects to the anterior amygdaloid area as well as the medial, the cortical, the accessory basal magnocellular, the medial basal, and the lateral amygdaloid nuclei.\n\nThe posterior part of the insula is formed by a long gyrus.\n\nThe posterior insula connects reciprocally with the secondary somatosensory cortex and receives input from spinothalamically activated ventral posterior inferior thalamic nuclei.\n\nIt has also been shown that this region receives inputs from the ventromedial nucleus (posterior part) of the thalamus that are highly specialized to convey homeostatic information such as pain, temperature, itch, local oxygen status, and sensual touch.\n\nA human neuroimaging study using diffusion tensor imaging revealed that the anterior insula is interconnected to regions in the temporal and occipital lobe, opercular and orbitofrontal cortex, triangular and opercular parts of the inferior frontal gyrus.\n\nThe same study revealed differences in the anatomical connection patterns between the left and right hemisphere.\n\nThe 'circular sulcus of insula' (or sulcus of Reil) is a semi-circular sulcus or fissure that separates the insula from the neighboring gyri of the operculum in the front, above, and\nbehind.\n\n=== Cytoarchitecture ===\n\nThe insular cortex has regions of variable cell structure or cytoarchitecture, changing from granular in the posterior portion to agranular in the anterior portion.\n\nThe insula also receives differential cortical and thalamic input along its length.\n\nThe anterior insular cortex contains a population of spindle neurons (also called von Economo neurons), identified as characterising a distinctive subregion as the agranular frontal insula.\n\n=== Development ===\n\nThe insular cortex is considered a separate lobe of the telencephalon by some authorities.\n\nOther sources see the insula as a part of the temporal lobe.\n\nIt is also sometimes grouped with limbic structures deep in the brain into a limbic lobe.\n\nAs a paralimbic cortex, the insular cortex is considered to be a relatively old structure.\n\n== Function ==\n\n=== Multimodal sensory processing, sensory binding ===\n\nFunctional imaging studies show activation of the insula during audio-visual integration tasks.\n\n=== Taste ===\n\nThe anterior insula is part of the primary gustatory cortex.\n\n=== Interoceptive awareness ===\n\nThere is evidence that, in addition to its base functions, the insula may play a role in certain higher-level functions that operate only in humans and other great apes.\n\nThe spindle neurons found at a higher density in the right frontal insular cortex are also found in the anterior cingulate cortex, which is another region that has reached a high level of specialization in great apes.\n\nIt has been speculated that these neurons are involved in cognitive-emotional processes that are specific to primates including great apes, such as empathy and metacognitive emotional feelings.\n\nThis is supported by functional imaging results showing that the structure and function of the right frontal insula is correlated with the ability to feel one's own heartbeat, or to empathize with the pain of others.\n\nIt is thought that these functions are not distinct from the lower-level functions of the insula but rather arise as a consequence of the role of the insula in conveying homeostatic information to consciousness.\n\nThe right anterior insula is engaged in interoceptive awareness of homeostatic emotions such as thirst, pain and fatigue, and the ability to time one's own heartbeat.\n\nMoreover, greater right anterior insular gray matter volume correlates with increased accuracy in this subjective sense of the inner body, and with negative emotional experience.\n\nIt is also involved in the control of blood pressure, in particular during and after exercise, and its activity varies with the amount of effort a person believes he/she is exerting.\n\nThe insular cortex also is where the sensation of pain is judged as to its degree.\n\nFurther, the insula is where a person imagines pain when looking at images of painful events while thinking about their happening to one's own body.\n\nThose with irritable bowel syndrome have abnormal processing of visceral pain in the insular cortex related to dysfunctional inhibition of pain within the brain.Another perception of the right anterior insula is the degree of nonpainful warmth or nonpainful coldness of a skin sensation.\n\nOther internal sensations processed by the insula include stomach or abdominal distension.\n\nA full bladder also activates the insular cortex.One brain imaging study suggests that the unpleasantness of subjectively perceived dyspnea is processed in the right human anterior insula and amygdala.\n\nThe cerebral cortex processing vestibular sensations extends into the insula, with small lesions in the anterior insular cortex being able to cause loss of balance and vertigo.\n\nOther noninteroceptive perceptions include passive listening to music, laughter, and crying, empathy and compassion, and language.\n\n=== Motor control ===\n\nIn motor control, it contributes to hand-and-eye motor movement, swallowing, gastric motility, and speech articulation.\n\nIt has been identified as a \"central command” centre that ensures that heart rate and blood pressure increase at the onset of exercise.\n\nResearch upon conversation links it to the capacity for long and complex spoken sentences.\n\nIt is also involved in motor learning and has been identified as playing a role in the motor recovery from stroke.\n\n=== Homeostasis ===\n\nIt plays a role in a variety of homeostatic functions related to basic survival needs, such as taste, visceral sensation, and autonomic control.\n\nThe insula controls autonomic functions through the regulation of the sympathetic and parasympathetic systems.\n\nIt has a role in regulating the immune system.\n\n=== Self ===\n\nThe insula has been identified as playing a role in the experience of bodily self-awareness, sense of agency, and sense of body ownership.\n\n=== Social emotions ===\n\nThe anterior insula processes a person's sense of disgust both to smells and to the sight of contamination and mutilation — even when just imagining the experience.\n\nThis associates with a mirror neuron-like link between external and internal experiences.\n\nIn social experience, it is involved in the processing of norm violations, emotional processing, empathy, and orgasms.The insula is active during social decision making.\n\nTiziana Quarto et al. measured emotional intelligence (EI) (the ability to identify, regulate, and process emotions of themselves and of others) of sixty-three healthy subjects.\n\nUsing fMRI EI was measured in correlation with left insular activity.\n\nThe subjects were shown various pictures of facial expressions and tasked with deciding to approach or avoid the person in the picture.\n\nThe results of the social decision task yielded that individuals with high EI scores had left insular activation when processing fearful faces.\n\nIndividuals with low EI scores had left insular activation when processing angry faces.\n\n=== Emotions ===\n\nThe insular cortex, in particular its most anterior portion, is considered a limbic-related cortex.\n\nThe insula has increasingly become the focus of attention for its role in body representation and subjective emotional experience.\n\nIn particular, Antonio Damasio has proposed that this region plays a role in mapping visceral states that are associated with emotional experience, giving rise to conscious feelings.\n\nThis is in essence a neurobiological formulation of the ideas of William James, who first proposed that subjective emotional experience (i.e., feelings) arise from our brain's interpretation of bodily states that are elicited by emotional events.\n\nThis is an example of embodied cognition.\nIn terms of function, the insula is believed to process convergent information to produce an emotionally relevant context for sensory experience.\n\nTo be specific, the anterior insula is related more to olfactory, gustatory, viscero-autonomic, and limbic function, whereas the posterior insula is related more to auditory-somesthetic-skeletomotor function.\n\nFunctional imaging experiments have revealed that the insula has an important role in pain experience and the experience of a number of basic emotions, including anger, fear, disgust, happiness, and sadness.The anterior insular cortex (AIC) is believed to be responsible for emotional feelings, including maternal and romantic love, anger, fear, sadness, happiness, sexual arousal, disgust, aversion, unfairness, inequity, indignation, uncertainty, disbelief, social exclusion, trust, empathy, sculptural beauty, a ‘state of union with God’, and hallucinogenic states.\n\nFunctional imaging studies have also implicated the insula in conscious desires, such as food craving and drug craving.\n\nWhat is common to all of these emotional states is that they each change the body in some way and are associated with highly salient subjective qualities.\n\nThe insula is well-situated for the integration of information relating to bodily states into higher-order cognitive and emotional processes.\n\nThe insula receives information from \"homeostatic afferent\" sensory pathways via the thalamus and sends output to a number of other limbic-related structures, such as the amygdala, the ventral striatum, and the orbitofrontal cortex, as well as to motor cortices.\n\nA study using magnetic resonance imaging found that the right anterior insula is significantly thicker in people that meditate.\n\nOther research into brain activity and meditation has shown an increase in grey matter in areas of the brain including the insular cortex.\n\nAnother study using voxel-based morphometry and MRI on experienced Vipassana meditators was done to extend the findings of Lazar et al., which found increased grey matter concentrations in this and other areas of the brain in experienced meditators.\n\nThe strongest evidence against a causative role for the insula cortex in emotion comes from Damasio et al. (2012) which showed that a patient who suffered bilateral lesions of the insula cortex expressed the full complement of human emotions, and was fully capable of emotional learning.\n\n=== Salience ===\n\nFunctional neuroimaging research suggests the insula is involved in two types of salience.\n\nInteroceptive information processing that links interoception with emotional salience to generate a subjective representation of the body.\n\nThis involves, first, the anterior insular cortex with the pregenual anterior cingulate cortex (Brodmann area 33) and the anterior and posterior mid-cingulate cortices, and, second, a general salience network concerned with environmental monitoring, response selection, and skeletomotor body orientation that involves all of the insular cortex and the mid-cingulate cortex.\n\nAn alternative or perhaps complementary proposal is that the right anterior insular regulates the interaction between the salience of the selective attention created to achieve a task (the dorsal attention system) and the salience of arousal created to keep focused upon the relevant part of the environment (ventral attention system).\n\nThis regulation of salience might be particularly important during challenging tasks where attention might fatigue and so cause careless mistakes but if there is too much arousal it risks creating poor performance by turning into anxiety.\n\n=== Auditory perception ===\n\nRecent research indicates that the insular cortex is involved in auditory perception.\n\nResponses to sound stimuli were obtained using intracranial EEG recordings acquired from patients with epilepsy.\n\nThe posterior part of the insula showed auditory responses that resemble those observed in Heschl’s gyrus, whereas the anterior part responded to the emotional contents of the auditory stimuli.\n\nDirect recordings from the posterior part of the insula showed responses to unexpected sounds within regular auditory streams, a process known as auditory deviance detection.\n\nResearchers observed a mismatch negativity (MMN) potential, a well known event related potential, as well as the high frequency activity signals originating from local neurons.\n\nSimple auditory illusions and hallucinations were elicited by electrical functional mapping.\n\n== Clinical significance ==\n\n=== Progressive expressive aphasia ===\n\nProgressive expressive aphasia is the deterioration of normal language function that causes individuals to lose the ability to communicate fluently while still being able to comprehend single words and intact other non-linguistic cognition.\n\nIt is found in a variety of degenerative neurological conditions including Pick's disease, motor neuron disease, corticobasal degeneration, frontotemporal dementia, and Alzheimer's disease.\n\nIt is associated with hypometabolism and atrophy of the left anterior insular cortex.\n\n=== Addiction ===\n\nA number of functional brain imaging studies have shown that the insular cortex is activated when drug users are exposed to environmental cues that trigger cravings.\n\nThis has been shown for a variety of drugs, including cocaine, alcohol, opiates, and nicotine.\n\nDespite these findings, the insula has been ignored within the drug addiction literature, perhaps because it is not known to be a direct target of the mesocortical dopamine system, which is central to current dopamine reward theories of addiction.\n\nResearch published in 2007 has shown that cigarette smokers suffering damage to the insular cortex, from a stroke for instance, have their addiction to cigarettes practically eliminated.\n\nThese individuals were found to be up to 136 times more likely to undergo a disruption of smoking addiction than smokers with damage in other areas.\n\nDisruption of addiction was evidenced by self-reported behavior changes such as quitting smoking less than one day after the brain injury, quitting smoking with great ease, not smoking again after quitting, and having no urge to resume smoking since quitting.\n\nThe study was conducted on average eight years after the strokes, which opens up the possibility that recall bias could have affected the results.\n\nMore recent prospective studies, which overcome this limitation, have corroborated these findings.\n\nThis suggests a significant role for the insular cortex in the neurological mechanisms underlying addiction to nicotine and other drugs, and would make this area of the brain a possible target for novel anti-addiction medication.\n\nIn addition, this finding suggests that functions mediated by the insula, especially conscious feelings, may be particularly important for maintaining drug addiction, although this view is not represented in any modern research or reviews of the subject.\n\nA recent study in rats by Contreras et al. corroborates these findings by showing that reversible inactivation of the insula disrupts amphetamine conditioned place preference, an animal model of cue-induced drug craving.\n\nIn this study, insula inactivation also disrupted \"malaise\" responses to lithium chloride injection, suggesting that the representation of negative interoceptive states by the insula plays a role in addiction.\n\nHowever, in this same study, the conditioned place preference took place immediately after the injection of amphetamine, suggesting that it is the immediate, pleasurable interoceptive effects of amphetamine administration, rather than the delayed, aversive effects of amphetamine withdrawal that are represented within the insula.\n\nA model proposed by Naqvi et al. (see above) is that the insula stores a representation of the pleasurable interoceptive effects of drug use (e.g., the airway sensory effects of nicotine, the cardiovascular effects of amphetamine), and that this representation is activated by exposure to cues that have previously been associated with drug use.\n\nA number of functional imaging studies have shown the insula to be activated during the administration of addictive psychoactive drugs.\n\nSeveral functional imaging studies have also shown that the insula is activated when drug users are exposed to drug cues, and that this activity is correlated with subjective urges.\n\nIn the cue-exposure studies, insula activity is elicited when there is no actual change in the level of drug in the body.\n\nTherefore, rather than merely representing the interoceptive effects of drug use as it occurs, the insula may play a role in memory for the pleasurable interoceptive effects of past drug use, anticipation of these effects in the future, or both.\n\nSuch a representation may give rise to conscious urges that feel as if they arise from within the body.\n\nThis may make addicts feel as if their bodies need to use a drug, and may result in persons with lesions in the insula reporting that their bodies have forgotten the urge to use, according to this study.\n\n=== Subjective certainty in ecstatic seizures ===\n\nA common quality in mystical experiences is a strong feeling of certainty which cannot be expressed in words.\n\nFabienne Picard proposes a neurological explanation for this subjective certainty, based on clinical research of epilepsy.\n\nAccording to Picard, this feeling of certainty may be caused by a dysfunction of the anterior insula, a part of the brain which is involved in interoception, self-reflection, and in avoiding uncertainty about the internal representations of the world by \"anticipation of resolution of uncertainty or risk\".\n\nThis avoidance of uncertainty functions through the comparison between predicted states and actual states, that is, \"signaling that we do not understand, i.e., that there is ambiguity.\"\n\nPicard notes that \"the concept of insight is very close to that of certainty,\" and refers to Archimedes' \"Eureka!\" Picard hypothesizes that during ecstatic seizures the comparison between predicted states and actual states no longer functions, and that mismatches between predicted state and actual state are no longer processed, blocking \"negative emotions and negative arousal arising from predictive uncertainty,\" which will be experienced as emotional confidence.\n\nPicard concludes that \"[t]his could lead to a spiritual interpretation in some individuals.\"\n\n=== Other clinical conditions ===\n\nThe insular cortex has been suggested to have a role in anxiety disorders, emotion dysregulation, and anorexia nervosa.\n\n== History ==\n\nThe insula was first described by Johann Christian Reil while describing cranial and spinal nerves and plexuses.\n\nHenry Gray in Gray's Anatomy is responsible for it being known as the Island of Reil.\n\nJohn Allman and colleagues showed that anterior insular cortex contains spindle neurons.\n\nhttps://en.wikipedia.org/wiki/Insular_cortex","cingulate-gyrus-and-sulcus-middle-anterior-part":"The cingulate cortex is a part of the brain situated in the medial aspect of the cerebral cortex.\n\nThe cingulate cortex includes the entire cingulate gyrus, which lies immediately above the corpus callosum, and the continuation of this in the cingulate sulcus.\n\nThe cingulate cortex is usually considered part of the limbic lobe.\n\nIt receives inputs from the thalamus and the neocortex, and projects to the entorhinal cortex via the cingulum.\n\nIt is an integral part of the limbic system, which is involved with emotion formation and processing, learning, and memory.\n\nThe combination of these three functions makes the cingulate gyrus highly influential in linking motivational outcomes to behavior (e.g. a certain action induced a positive emotional response, which results in learning).\n\nThis role makes the cingulate cortex highly important in disorders such as depression and schizophrenia.\n\nIt also plays a role in executive function and respiratory control.\n\n== Etymology ==\n\nThe term cingulate is derived from the Latin cingulātus (meaning \"girdled\").\n\n== Structure ==\n\nBased on cerebral cytoarchitectonics it has been divided into the Brodmann areas 23, 24, 26, 29, 30, 31, 32 and 33.\n\nThe areas 26, 29 and 30 are usually referred to as the retrosplenial areas.\n\n=== Anterior cingulate cortex ===\n\nThis corresponds to areas 24, 32 and 33 of Brodmann and LA of Constantin von Economo and Bailey and von Bonin.\n\nIt is continued anteriorly by the subgenual area (Brodmann area 25), located below the genu of the corpus callosum).\nIt is cytoarchitectonically agranular.\n\nIt has a gyral and a sulcal part.\n\nAnterior cingulate cortex can further be divided in the perigenual anterior cingulate cortex (near the genu) and midcingulate cortex.\n\nThe anterior cingulate cortex receives primarily its afferent axons from the intralaminar and midline thalamic nuclei (see thalamus).\nThe nucleus anterior receives mamillo-thalamic afferences.\n\nThe mamillary neurons receive axons from the subiculum.\n\nThe whole forms a neural circuit in the limbic system known as the Papez circuit.\n\nThe anterior cingulate cortex sends axons to the anterior nucleus and through the cingulum to other Broca's limbic areas.\n\nThe ACC is involved in error and conflict detection processes.\n\n=== Posterior cingulate cortex ===\n\nThis corresponds to areas 23 and 31 of Brodmann LP of von Economo and Bailey and von Bonin.\n\nIts cellular structure is granular.\n\nIt is followed posteriorly by the retrosplenial cortex (area 29).\nDorsally is the granular area 31.\n\nThe posterior cingulate cortex receives a great part of its afferent axons from the superficial nucleus (or nucleus superior- falsely LD-) of the thalamus (see thalamus), which itself receives axons from the subiculum.\n\nTo some extent it thus duplicates Papez' circuit.\n\nIt receives also direct afferents from the subiculum of the hippocampus.\n\nPosterior cingulate cortex hypometabolism (with 18F-FDG PET) has been defined in Alzheimer's disease.\n\n=== Inputs of the anterior cingulate gyrus ===\n\nA retrograde tracing experiment on macaque monkeys revealed that the ventral anterior nucleus (VA) and the ventral lateral nucleus (VL) of the thalamus are connected with motor areas of the cingulate sulcus.\n\nThe retrosplenial region (Brodmann's area 26, 29 and 30) of cingulate gyrus can be divided into three parts: i.e., retrosplenial granular cortex A, retrosplenial granular cortex B and retrosplenial dysgranular cortex.\n\nThe hippocampal formation sends dense projections to retrosplenial granular cortex A and B and fewer projections to the retrosplenial dysgranular cortex.\n\nThe postsubiculum sends projections to retrosplenial granular cortex A and B and to the retrosplenial dysgranular cortex.\n\nThe dorsal subiculum sends projections to retrosplenial granular cortex B, while ventral subiculum sends projections to retrosplenial granular cortex A.\n\nEntorhinal cortex – caudal parts – sends projections to the retrosplenial dysgranular cortex.\n\n=== Outputs of the anterior cingulate gyrus ===\n\nThe rostral cingulate gyrus (Brodmanns's area 32) projects to the rostral superior temporal gyrus, midorbitofrontal cortex and lateral prefrontal cortex.\n\nThe ventral anterior cingulate (Brodmann's area 24) sends projections to the anterior insular cortex, premotor cortex (Brodmann's area 6), Brodmann's area 8, the perirhinal area, the orbitofrontal cortex (Brodmann's area 12), the laterobasal nucleus of amygdala, and the rostral part of the inferior parietal lobule.\n\nInjecting wheat germ agglutinin and horseradish peroxidase conjugate into the anterior cingulate gyrus of cats, revealed that the anterior cingulate gyrus has reciprocal connections with the rostral part of the thalamic posterior lateral nucleus and rostral end of the pulvinar.\n\nThe postsubiculum receives projections from the retrospleinal dysgranular cortex and the retrosplenial granular cortex A and B.\n\nThe parasubiculum receives projections from the retrosplenial dysgranular cortex and retrosplenial granular cortex A.\n\nCaudal and lateral parts of the entorhinal cortex get projections from the retrosplenial dysgranular cortex, while the caudal medial entorhinal cortex receives projections from the retrosplenial granular cortex A.\n\nThe retrosplenial dysgranular cortex sends projections to the perirhinal cortex.\n\nThe retrospleinal granular cortex A sends projection to the rostral presubiculum.\n\n=== Outputs of the posterior cingulate gyrus ===\n\nThe posterior cingulate cortex (Brodmann's area 23) sends projections to dorsolateral prefrontal cortex (Brodmann's area 9), anterior prefrontal cortex (Brodmann's area 10), orbitofrontal cortex (Brodmanns’ area 11), the parahippocampal gyrus, posterior part of the inferior parietal lobule, the presubiculum, the superior temporal sulcus and the retrosplenial region.\n\nThe retrosplenial cortex and caudal part of the cingulate cortex are connected with rostral prefrontal cortex via cingulate fascicule in macaque monkeys.\n\nVentral posterior cingulate cortex was found to be reciprocally connected with the caudal part of the posterior parietal lobe in rhesus monkeys.\n\nAlso the medial posterior parietal cortex is connected with posterior ventral bank of the cingulate sulcus.\n\n=== Other connections ===\n\nThe anterior cingulate is connected to the posterior cingulate at least in rabbits.\n\nPosterior cingulate gyrus is connected with retrosplenial cortex and this connection is part of the dorsal splenium of the corpus callosum.\n\nThe anterior and posterior cingulate gyrus and retrosplenial cortex send projections to subiculum and presubiculum.\n\n== Clinical significance in schizophrenia ==\n\nUsing a three-dimensional magnetic resonance imaging procedure to measure the volume of the rostral anterior cingulate gyrus (perigenual cingulate gyrus), Takahashi et al. (2003) found that the rostral anterior cingulate gyrus is larger in control (healthy) females than males, but this sex difference was not found in people with schizophrenia.\n\nPeople with schizophrenia also had a smaller volume of perigenual cingulate gyrus than control subjects.\n\nHaznedar et al. (2004) studied metabolic rate of glucose in anterior and posterior cingulate gyrus in people with schizophrenia, schizotypal personality disorder (SPD) and compared them with a control group.\n\nThe metabolic rate of glucose was found to be lower in the left anterior cingulate gyrus and the right posterior cingulate gyrus in people with schizophrenia relative to controls.\n\nAlthough people with SPD were expected to show a glucose metabolic rate somewhere between the individual with schizophrenia and controls, they actually had higher metabolic glucose rate in the left posterior cingulate gyrus.\n\nThe volume of the left anterior cingulate gyrus was reduced in people with schizophrenia as compared with controls, but there was not any difference between people with SPD and people with schizophrenia.\n\nFrom these results it appears that the schizophrenia and SPD are two different disorders.\n\nA study of the volume of the gray and white matter in the anterior cingulate gyrus in people with schizophrenia and their healthy first and second degree relatives revealed no significant difference in the volume of the white matter in the people with schizophrenia and their healthy relatives.\n\nNonetheless a significant difference in the volume of gray matter was detected, people with schizophrenia had smaller volume of gray matter than their second degree relatives, but not relative to their first degree relatives.\n\nBoth the person with schizophrenia and their first degree healthy relatives have smaller gray matter volume than the second degree healthy relatives.\n\nIt appears that genes are responsible for the decreased volume of gray matter in people with schizophrenia.\n\nFujiwara et al. (2007) did an experiment in which they correlated the size of anterior cingulate gyrus in people with schizophrenia with their functioning on social cognition, psychopathology and emotions with control group.\n\nThe smaller the size of anterior cingulate gyrus, the lower was the level of social functioning and the higher was the psychopathology in the people with schizophrenia.\n\nThe anterior cingulate gyrus was found to be bilaterally smaller in people with schizophrenia as compared with control group.\n\nNo difference in IQ tests and basic visuoperceptual ability with facial stimuli was found between people with schizophrenia and the control.\n\n=== Summary ===\n\nPeople with schizophrenia have differences in the anterior cingulate gyrus when compared with controls.\n\nThe anterior cingulate gyrus was found to be smaller in people with schizophrenia.\n\nThe volume of the gray matter in the anterior cingulate gyrus was found to be lower in people with schizophrenia.\n\nHealthy females have larger rostral anterior cingulate gyrus than males, this sex difference in size is absent in people with schizophrenia.\n\nThe metabolic rate of glucose was lower in the left anterior cingulate gyrus and in the right posterior cingulate gyrus.\n\nIn addition to changes in the cingulate cortex more brain structures show changes in people with schizophrenia as compared to controls.\n\nThe hippocampus in people with schizophrenia was found to be smaller in size when compared with controls of the same age group, and, similarly, the caudate and putamen were found to be smaller in volume in a longitudinal study of people with schizophrenia.\n\nWhile the volume of gray matter is smaller, the size of the lateral and third ventricles is larger in people with schizophrenia.\n\n== History ==\n\nCingulum means \"belt\" in Latin.\n\nThe name was likely chosen because this cortex, in great part, surrounds the corpus callosum.\n\nThe cingulate cortex is a part of the \"grand lobe limbique\" of Broca (1878) that consisted of a superior cingulate part (supracallosa) and an inferior hippocampic part (infracallosal).\n\nThe limbic lobe was separated from the remainder of the cortex by Broca for two reasons:\n first because it is not convoluted, and second because the gyri are directed parasagittally (contrary to the transverse gyrification).\n\nSince the parasagittal gyrification is observed in non-primate species, the limbic lobe was thus declared to be \"bestial\".\n\nAs with other parts of the cortex, there have been and continue to be discrepancies concerning boundaries and naming.\n\nBrodmann (1909) further distinguished Areas 24 (anterior cingulate) and 23 (posterior) based on granularity.\n\nMost recently, it was included as a part of the limbic lobe in the Terminologia Anatomica (1998) following von Economo's (1925) system.\n\nhttps://en.wikipedia.org/wiki/Cingulate_cortex","cingulate-gyrus-and-sulcus-middle-posterior-part":"The cingulate sulcus is a sulcus (brain fold) on the cingulate cortex in the medial wall of the cerebral cortex.\n\nThe frontal and parietal lobes are separated from the cingulate gyrus by the cingulate sulcus.\n\nIt terminates as the marginal sulcus of the cingulate sulcus.\n\nIt sends a ramus to separate the paracentral lobule from the frontal gyri, the paracentral sulcus.\n\nhttps://en.wikipedia.org/wiki/Cingulate_sulcus","cingulate-gyrus-posteroventral-part":"The cingulate cortex is a part of the brain situated in the medial aspect of the cerebral cortex.\n\nThe cingulate cortex includes the entire cingulate gyrus, which lies immediately above the corpus callosum, and the continuation of this in the cingulate sulcus.\n\nThe cingulate cortex is usually considered part of the limbic lobe.\n\nIt receives inputs from the thalamus and the neocortex, and projects to the entorhinal cortex via the cingulum.\n\nIt is an integral part of the limbic system, which is involved with emotion formation and processing, learning, and memory.\n\nThe combination of these three functions makes the cingulate gyrus highly influential in linking motivational outcomes to behavior (e.g. a certain action induced a positive emotional response, which results in learning).\n\nThis role makes the cingulate cortex highly important in disorders such as depression and schizophrenia.\n\nIt also plays a role in executive function and respiratory control.\n\n== Etymology ==\n\nThe term cingulate is derived from the Latin cingulātus (meaning \"girdled\").\n\n== Structure ==\n\nBased on cerebral cytoarchitectonics it has been divided into the Brodmann areas 23, 24, 26, 29, 30, 31, 32 and 33.\n\nThe areas 26, 29 and 30 are usually referred to as the retrosplenial areas.\n\n=== Anterior cingulate cortex ===\n\nThis corresponds to areas 24, 32 and 33 of Brodmann and LA of Constantin von Economo and Bailey and von Bonin.\n\nIt is continued anteriorly by the subgenual area (Brodmann area 25), located below the genu of the corpus callosum).\nIt is cytoarchitectonically agranular.\n\nIt has a gyral and a sulcal part.\n\nAnterior cingulate cortex can further be divided in the perigenual anterior cingulate cortex (near the genu) and midcingulate cortex.\n\nThe anterior cingulate cortex receives primarily its afferent axons from the intralaminar and midline thalamic nuclei (see thalamus).\nThe nucleus anterior receives mamillo-thalamic afferences.\n\nThe mamillary neurons receive axons from the subiculum.\n\nThe whole forms a neural circuit in the limbic system known as the Papez circuit.\n\nThe anterior cingulate cortex sends axons to the anterior nucleus and through the cingulum to other Broca's limbic areas.\n\nThe ACC is involved in error and conflict detection processes.\n\n=== Posterior cingulate cortex ===\n\nThis corresponds to areas 23 and 31 of Brodmann LP of von Economo and Bailey and von Bonin.\n\nIts cellular structure is granular.\n\nIt is followed posteriorly by the retrosplenial cortex (area 29).\nDorsally is the granular area 31.\n\nThe posterior cingulate cortex receives a great part of its afferent axons from the superficial nucleus (or nucleus superior- falsely LD-) of the thalamus (see thalamus), which itself receives axons from the subiculum.\n\nTo some extent it thus duplicates Papez' circuit.\n\nIt receives also direct afferents from the subiculum of the hippocampus.\n\nPosterior cingulate cortex hypometabolism (with 18F-FDG PET) has been defined in Alzheimer's disease.\n\n=== Inputs of the anterior cingulate gyrus ===\n\nA retrograde tracing experiment on macaque monkeys revealed that the ventral anterior nucleus (VA) and the ventral lateral nucleus (VL) of the thalamus are connected with motor areas of the cingulate sulcus.\n\nThe retrosplenial region (Brodmann's area 26, 29 and 30) of cingulate gyrus can be divided into three parts: i.e., retrosplenial granular cortex A, retrosplenial granular cortex B and retrosplenial dysgranular cortex.\n\nThe hippocampal formation sends dense projections to retrosplenial granular cortex A and B and fewer projections to the retrosplenial dysgranular cortex.\n\nThe postsubiculum sends projections to retrosplenial granular cortex A and B and to the retrosplenial dysgranular cortex.\n\nThe dorsal subiculum sends projections to retrosplenial granular cortex B, while ventral subiculum sends projections to retrosplenial granular cortex A.\n\nEntorhinal cortex – caudal parts – sends projections to the retrosplenial dysgranular cortex.\n\n=== Outputs of the anterior cingulate gyrus ===\n\nThe rostral cingulate gyrus (Brodmanns's area 32) projects to the rostral superior temporal gyrus, midorbitofrontal cortex and lateral prefrontal cortex.\n\nThe ventral anterior cingulate (Brodmann's area 24) sends projections to the anterior insular cortex, premotor cortex (Brodmann's area 6), Brodmann's area 8, the perirhinal area, the orbitofrontal cortex (Brodmann's area 12), the laterobasal nucleus of amygdala, and the rostral part of the inferior parietal lobule.\n\nInjecting wheat germ agglutinin and horseradish peroxidase conjugate into the anterior cingulate gyrus of cats, revealed that the anterior cingulate gyrus has reciprocal connections with the rostral part of the thalamic posterior lateral nucleus and rostral end of the pulvinar.\n\nThe postsubiculum receives projections from the retrospleinal dysgranular cortex and the retrosplenial granular cortex A and B.\n\nThe parasubiculum receives projections from the retrosplenial dysgranular cortex and retrosplenial granular cortex A.\n\nCaudal and lateral parts of the entorhinal cortex get projections from the retrosplenial dysgranular cortex, while the caudal medial entorhinal cortex receives projections from the retrosplenial granular cortex A.\n\nThe retrosplenial dysgranular cortex sends projections to the perirhinal cortex.\n\nThe retrospleinal granular cortex A sends projection to the rostral presubiculum.\n\n=== Outputs of the posterior cingulate gyrus ===\n\nThe posterior cingulate cortex (Brodmann's area 23) sends projections to dorsolateral prefrontal cortex (Brodmann's area 9), anterior prefrontal cortex (Brodmann's area 10), orbitofrontal cortex (Brodmanns’ area 11), the parahippocampal gyrus, posterior part of the inferior parietal lobule, the presubiculum, the superior temporal sulcus and the retrosplenial region.\n\nThe retrosplenial cortex and caudal part of the cingulate cortex are connected with rostral prefrontal cortex via cingulate fascicule in macaque monkeys.\n\nVentral posterior cingulate cortex was found to be reciprocally connected with the caudal part of the posterior parietal lobe in rhesus monkeys.\n\nAlso the medial posterior parietal cortex is connected with posterior ventral bank of the cingulate sulcus.\n\n=== Other connections ===\n\nThe anterior cingulate is connected to the posterior cingulate at least in rabbits.\n\nPosterior cingulate gyrus is connected with retrosplenial cortex and this connection is part of the dorsal splenium of the corpus callosum.\n\nThe anterior and posterior cingulate gyrus and retrosplenial cortex send projections to subiculum and presubiculum.\n\n== Clinical significance in schizophrenia ==\n\nUsing a three-dimensional magnetic resonance imaging procedure to measure the volume of the rostral anterior cingulate gyrus (perigenual cingulate gyrus), Takahashi et al. (2003) found that the rostral anterior cingulate gyrus is larger in control (healthy) females than males, but this sex difference was not found in people with schizophrenia.\n\nPeople with schizophrenia also had a smaller volume of perigenual cingulate gyrus than control subjects.\n\nHaznedar et al. (2004) studied metabolic rate of glucose in anterior and posterior cingulate gyrus in people with schizophrenia, schizotypal personality disorder (SPD) and compared them with a control group.\n\nThe metabolic rate of glucose was found to be lower in the left anterior cingulate gyrus and the right posterior cingulate gyrus in people with schizophrenia relative to controls.\n\nAlthough people with SPD were expected to show a glucose metabolic rate somewhere between the individual with schizophrenia and controls, they actually had higher metabolic glucose rate in the left posterior cingulate gyrus.\n\nThe volume of the left anterior cingulate gyrus was reduced in people with schizophrenia as compared with controls, but there was not any difference between people with SPD and people with schizophrenia.\n\nFrom these results it appears that the schizophrenia and SPD are two different disorders.\n\nA study of the volume of the gray and white matter in the anterior cingulate gyrus in people with schizophrenia and their healthy first and second degree relatives revealed no significant difference in the volume of the white matter in the people with schizophrenia and their healthy relatives.\n\nNonetheless a significant difference in the volume of gray matter was detected, people with schizophrenia had smaller volume of gray matter than their second degree relatives, but not relative to their first degree relatives.\n\nBoth the person with schizophrenia and their first degree healthy relatives have smaller gray matter volume than the second degree healthy relatives.\n\nIt appears that genes are responsible for the decreased volume of gray matter in people with schizophrenia.\n\nFujiwara et al. (2007) did an experiment in which they correlated the size of anterior cingulate gyrus in people with schizophrenia with their functioning on social cognition, psychopathology and emotions with control group.\n\nThe smaller the size of anterior cingulate gyrus, the lower was the level of social functioning and the higher was the psychopathology in the people with schizophrenia.\n\nThe anterior cingulate gyrus was found to be bilaterally smaller in people with schizophrenia as compared with control group.\n\nNo difference in IQ tests and basic visuoperceptual ability with facial stimuli was found between people with schizophrenia and the control.\n\n=== Summary ===\n\nPeople with schizophrenia have differences in the anterior cingulate gyrus when compared with controls.\n\nThe anterior cingulate gyrus was found to be smaller in people with schizophrenia.\n\nThe volume of the gray matter in the anterior cingulate gyrus was found to be lower in people with schizophrenia.\n\nHealthy females have larger rostral anterior cingulate gyrus than males, this sex difference in size is absent in people with schizophrenia.\n\nThe metabolic rate of glucose was lower in the left anterior cingulate gyrus and in the right posterior cingulate gyrus.\n\nIn addition to changes in the cingulate cortex more brain structures show changes in people with schizophrenia as compared to controls.\n\nThe hippocampus in people with schizophrenia was found to be smaller in size when compared with controls of the same age group, and, similarly, the caudate and putamen were found to be smaller in volume in a longitudinal study of people with schizophrenia.\n\nWhile the volume of gray matter is smaller, the size of the lateral and third ventricles is larger in people with schizophrenia.\n\n== History ==\n\nCingulum means \"belt\" in Latin.\n\nThe name was likely chosen because this cortex, in great part, surrounds the corpus callosum.\n\nThe cingulate cortex is a part of the \"grand lobe limbique\" of Broca (1878) that consisted of a superior cingulate part (supracallosa) and an inferior hippocampic part (infracallosal).\n\nThe limbic lobe was separated from the remainder of the cortex by Broca for two reasons:\n first because it is not convoluted, and second because the gyri are directed parasagittally (contrary to the transverse gyrification).\n\nSince the parasagittal gyrification is observed in non-primate species, the limbic lobe was thus declared to be \"bestial\".\n\nAs with other parts of the cortex, there have been and continue to be discrepancies concerning boundaries and naming.\n\nBrodmann (1909) further distinguished Areas 24 (anterior cingulate) and 23 (posterior) based on granularity.\n\nMost recently, it was included as a part of the limbic lobe in the Terminologia Anatomica (1998) following von Economo's (1925) system.\n\nhttps://en.wikipedia.org/wiki/Cingulate_cortex","hippocampus":"The hippocampus (via Latin from Greek ἱππόκαμπος, 'seahorse') is a major component of the brain of humans and other vertebrates.\n\nHumans and other mammals have two hippocampi, one in each side of the brain.\n\nThe hippocampus is part of the limbic system, and plays important roles in the consolidation of information from short-term memory to long-term memory, and in spatial memory that enables navigation.\n\nThe hippocampus is located in the allocortex, with neural projections into the neocortex in humans, as well as primates.\n\nThe hippocampus, as the medial pallium, is a structure found in all vertebrates.\n\nIn humans, it contains two main interlocking parts: the hippocampus proper (also called Ammon's horn), and the dentate gyrus.In Alzheimer's disease (and other forms of dementia), the hippocampus is one of the first regions of the brain to suffer damage; short-term memory loss and disorientation are included among the early symptoms.\n\nDamage to the hippocampus can also result from oxygen starvation (hypoxia), encephalitis, or medial temporal lobe epilepsy.\n\nPeople with extensive, bilateral hippocampal damage may experience anterograde amnesia: the inability to form and retain new memories.\nSince different neuronal cell types are neatly organized into layers in the hippocampus, it has frequently been used as a model system for studying neurophysiology.\n\nThe form of neural plasticity known as long-term potentiation (LTP) was initially discovered to occur in the hippocampus and has often been studied in this structure.\n\nLTP is widely believed to be one of the main neural mechanisms by which memories are stored in the brain.\nIn rodents as model organisms, the hippocampus has been studied extensively as part of a brain system responsible for spatial memory and navigation.\n\nMany neurons in the rat and mouse hippocampus respond as place cells: that is, they fire bursts of action potentials when the animal passes through a specific part of its environment.\n\nHippocampal place cells interact extensively with head direction cells, whose activity acts as an inertial compass, and conjecturally with grid cells in the neighboring entorhinal cortex.\n\n== Name ==\n\nThe earliest description of the ridge running along the floor of the temporal horn of the lateral ventricle comes from the Venetian anatomist Julius Caesar Aranzi (1587), who likened it first to a silkworm and then to a seahorse (Latin hippocampus, from Greek ἱππόκαμπος, from Greek ἵππος, \"horse\" + κάμπος, \"sea monster\").\n\nThe German anatomist Duvernoy (1729), the first to illustrate the structure, also wavered between \"seahorse\" and \"silkworm\". \"Ram's horn\" was proposed by the Danish anatomist Jacob Winsløw in 1732; and a decade later his fellow Parisian, the surgeon de Garengeot, used \"cornu Ammonis\" – horn of (the ancient Egyptian god) Amun, who was often represented as having a ram's head.\n\nThis has survived in abbreviated form as CA in naming the subfields of the hippocampus.Another reference appeared with the term pes hippocampi, which may date back to Diemerbroeck in 1672, introducing a comparison with the shape of the folded back forelimbs and webbed feet of the mythological hippocampus, a sea monster with a horse's forequarters and a fish's tail.\n\nThe hippocampus was then described as pes hippocampi major, with an adjacent bulge in the occipital horn, described as the pes hippocampi minor and later renamed as the calcar avis.\n\nThe renaming of the hippocampus as hippocampus major, and the calcar avis as hippocampus minor, has been attributed to Félix Vicq-d'Azyr systematizing nomenclature of parts of the brain in 1786.\n\nMayer mistakenly used the term hippopotamus in 1779, and was followed by some other authors until Karl Friedrich Burdach resolved this error in 1829.\n\nIn 1861 the hippocampus minor became the center of a dispute over human evolution between Thomas Henry Huxley and Richard Owen, satirized as the Great Hippocampus Question.\n\nThe term hippocampus minor fell from use in anatomy textbooks and was officially removed in the Nomina Anatomica of 1895.\n\nToday, the structure is just called the hippocampus, with the term Cornu Ammonis (also known as Ammon's horn) surviving in the names of the hippocampal subfields CA1-CA4.\n\n== Relation to limbic system ==\n\nThe term limbic system was introduced in 1952 by Paul MacLean to describe the set of structures that line the edge of the cortex (Latin limbus meaning border): These include the hippocampus, cingulate cortex, olfactory cortex, and amygdala.\n\nPaul MacLean later suggested that the limbic structures comprise the neural basis of emotion.\n\nThe hippocampus is anatomically connected to parts of the brain that are involved with emotional behavior – the septum, the hypothalamic mammillary body, and the anterior nuclear complex in the thalamus, and is generally accepted to be part of the limbic system.\n\n== Anatomy ==\n\nThe hippocampus can be seen as a ridge of gray matter tissue, elevating from the floor of each lateral ventricle in the region of the inferior or temporal horn.\n\nThis ridge can also be seen as an inward fold of the archicortex into the medial temporal lobe.\n\nThe hippocampus can only be seen in dissections as it is concealed by the parahippocampal gyrus.\n\nThe cortex thins from six layers to the three or four layers that make up the hippocampus.The term hippocampal formation is used to refer to the hippocampus proper and its related parts.\n\nHowever, there is no consensus as to what parts are included.\n\nSometimes the hippocampus is said to include the dentate gyrus and the subiculum.\n\nSome references include the dentate gyrus and the subiculum in the hippocampal formation, and others also include the presubiculum, parasubiculum, and entorhinal cortex.\n\nThe neural layout and pathways within the hippocampal formation are very similar in all mammals.The hippocampus, including the dentate gyrus, has the shape of a curved tube, which has been compared to a seahorse, and a ram's horn (Cornu Ammonis).\n\nIts abbreviation CA is used in naming the hippocampal subfields CA1, CA2, CA3, and CA4.\n\nIt can be distinguished as an area where the cortex narrows into a single layer of densely packed pyramidal neurons, which curl into a tight U shape.\n\nOne edge of the \"U,\" – CA4, is embedded into the backward-facing, flexed dentate gyrus.\n\nThe hippocampus is described as having an anterior and posterior part (in primates) or a ventral and dorsal part in other animals.\n\nBoth parts are of similar composition but belong to different neural circuits.\n\nIn the rat, the two hippocampi resemble a pair of bananas, joined at the stems by the commissure of fornix (also called the hippocampal commissure).\n\nIn primates, the part of the hippocampus at the bottom, near the base of the temporal lobe, is much broader than the part at the top.\n\nThis means that in cross-section the hippocampus can show a number of different shapes, depending on the angle and location of the cut.\nIn a cross-section of the hippocampus, including the dentate gyrus, several layers will be shown.\n\nThe dentate gyrus has three layers of cells (or four if the hilus is included).\n\nThe layers are from the outer in – the molecular layer, the inner molecular layer, the granular layer, and the hilus.\n\nThe CA3 in the hippocampus proper has the following cell layers known as strata: lacunosum-moleculare, radiatum, lucidum, pyramidal, and oriens.\n\nCA2 and CA1 also have these layers except the lucidum stratum.\nThe input to the hippocampus (from varying cortical and subcortical structures) comes from the entorhinal cortex via the perforant path.\n\nThe entorhinal cortex (EC) is strongly and reciprocally connected with many cortical and subcortical structures as well as with the brainstem.\n\nDifferent thalamic nuclei, (from the anterior and midline groups), the medial septal nucleus, the supramammillary nucleus of the hypothalamus, and the raphe nuclei and locus coeruleus of the brainstem all send axons to the EC, so that it serves as the interface between the neocortex and the other connections, and the hippocampus.\nThe EC is located in the parahippocampal gyrus, a cortical region adjacent to the hippocampus.\n\nThis gyrus conceals the hippocampus.\n\nThe parahippocampal gyrus is adjacent to the perirhinal cortex, which plays an important role in the visual recognition of complex objects.\n\nThere is also substantial evidence that it makes a contribution to memory, which can be distinguished from the contribution of the hippocampus.\n\nIt is apparent that complete amnesia occurs only when both the hippocampus and the parahippocampus are damaged.\n\n=== Circuitry ===\n\nThe major input to the hippocampus is through the entorhinal cortex (EC), whereas its major output is via CA1 to the subiculum.\n\nInformation reaches CA1 via two main pathways, direct and indirect.\n\nAxons from the EC that originate in layer III are the origin of the direct perforant pathway and form synapses on the very distal apical dendrites of CA1 neurons.\n\nConversely, axons originating from layer II are the origin of the indirect pathway, and information reaches CA1 via the trisynaptic circuit.\n\nIn the initial part of this pathway, the axons project through the perforant pathway to the granule cells of the dentate gyrus (first synapse).\n\nFrom then, the information follows via the mossy fibres to CA3 (second synapse).\n\nFrom there, CA3 axons called Schaffer collaterals leave the deep part of the cell body and loop up to the apical dendrites and then extend to CA1 (third synapse).\n\nAxons from CA1 then project back to the entorhinal cortex, completing the circuit.Basket cells in CA3 receive excitatory input from the pyramidal cells and then give an inhibitory feedback to the pyramidal cells.\n\nThis recurrent inhibition is a simple feedback circuit that can dampen excitatory responses in the hippocampus.\n\nThe pyramidal cells gives a recurrent excitation which is an important mechanism found in some memory processing microcircuits.Several other connections play important roles in hippocampal function.\n\nBeyond the output to the EC, additional output pathways go to other cortical areas including the prefrontal cortex.\n\nA major output goes via the fornix to the lateral septal area and to the mammillary body of the hypothalamus (which the fornix interconnects with the hippocampus).\n\nThe hippocampus receives modulatory input from the serotonin, norepinephrine, and dopamine systems, and from the nucleus reuniens of the thalamus to field CA1.\n\nA very important projection comes from the medial septal nucleus, which sends cholinergic, and gamma amino butyric acid (GABA) stimulating fibers (GABAergic fibers) to all parts of the hippocampus.\n\nThe inputs from the medial septal nucleus play a key role in controlling the physiological state of the hippocampus; destruction of this nucleus abolishes the hippocampal theta rhythm and severely impairs certain types of memory.\n\n=== Regions ===\n\nAreas of the hippocampus are shown to be functionally and anatomically distinct.\n\nThe dorsal hippocampus (DH), ventral hippocampus (VH) and intermediate hippocampus serve different functions, project with differing pathways, and have varying degrees of place cells.\n\nThe dorsal hippocampus serves for spatial memory, verbal memory, and learning of conceptual information.\n\nUsing the radial arm maze, lesions in the DH were shown to cause spatial memory impairment while VH lesions did not.\n\nIts projecting pathways include the medial septal nucleus and supramammillary nucleus.\n\nThe dorsal hippocampus also has more place cells than both the ventral and intermediate hippocampal regions.The intermediate hippocampus has overlapping characteristics with both the ventral and dorsal hippocampus.\n\nUsing anterograde tracing methods, Cenquizca and Swanson (2007) located the moderate projections to two primary olfactory cortical areas and prelimbic areas of the medial prefrontal cortex.\n\nThis region has the smallest number of place cells.\n\nThe ventral hippocampus functions in fear conditioning and affective processes.\n\nAnagnostaras et al. (2002) showed that alterations to the ventral hippocampus reduced the amount of information sent to the amygdala by the dorsal and ventral hippocampus, consequently altering fear conditioning in rats.\n\nHistorically, the earliest widely held hypothesis was that the hippocampus is involved in olfaction.\n\nThis idea was cast into doubt by a series of anatomical studies that did not find any direct projections to the hippocampus from the olfactory bulb.\n\nHowever, later work did confirm that the olfactory bulb does project into the ventral part of the lateral entorhinal cortex, and field CA1 in the ventral hippocampus sends axons to the main olfactory bulb, the anterior olfactory nucleus, and to the primary olfactory cortex.\n\nThere continues to be some interest in hippocampal olfactory responses, in particular, the role of the hippocampus in memory for odors, but few specialists today believe that olfaction is its primary function.\n\n== Function ==\n\n=== Theories of hippocampal functions ===\n\nOver the years, three main ideas of hippocampal function have dominated the literature: response inhibition, episodic memory, and spatial cognition.\n\nThe behavioral inhibition theory (caricatured by John O'Keefe and Lynn Nadel as \"slam on the brakes!\") was very popular up to the 1960s.\n\nIt derived much of its justification from two observations: first, that animals with hippocampal damage tend to be hyperactive; second, that animals with hippocampal damage often have difficulty learning to inhibit responses that they have previously been taught, especially if the response requires remaining quiet as in a passive avoidance test.\n\nBritish psychologist Jeffrey Gray developed this line of thought into a full-fledged theory of the role of the hippocampus in anxiety.\n\nThe inhibition theory is currently the least popular of the three.The second major line of thought relates the hippocampus to memory.\n\nAlthough it had historical precursors, this idea derived its main impetus from a famous report by American neurosurgeon William Beecher Scoville and British-Canadian neuropsychologist Brenda Milner describing the results of surgical destruction of the hippocampi when trying to relieve epileptic seizures in an American man Henry Molaison, known until his death in 2008 as \"Patient H.M.\" The unexpected outcome of the surgery was severe anterograde and partial retrograde amnesia; Molaison was unable to form new episodic memories after his surgery and could not remember any events that occurred just before his surgery, but he did retain memories of events that occurred many years earlier extending back into his childhood.\n\nThis case attracted such widespread professional interest that Molaison became the most intensively studied subject in medical history.\n\nIn the ensuing years, other patients with similar levels of hippocampal damage and amnesia (caused by accident or disease) have also been studied, and thousands of experiments have studied the physiology of activity-driven changes in synaptic connections in the hippocampus.\n\nThere is now universal agreement that the hippocampi play some sort of important role in memory; however, the precise nature of this role remains widely debated.\n\nA recent theory proposed – without questioning its role in spatial cognition – that the hippocampus encodes new episodic memories by associating representations in the newborn granule cells of the dentate gyrus and arranging those representations sequentially in the CA3 by relying on the phase precession generated in the entorhinal cortex\n\nThe third important theory of hippocampal function relates the hippocampus to space.\n\nThe spatial theory was originally championed by O'Keefe and Nadel, who were influenced by American psychologist E.C.\n\nTolman's theories about \"cognitive maps\" in humans and animals.\n\nO'Keefe and his student Dostrovsky in 1971 discovered neurons in the rat hippocampus that appeared to them to show activity related to the rat's location within its environment.\n\nDespite skepticism from other investigators, O'Keefe and his co-workers, especially Lynn Nadel, continued to investigate this question, in a line of work that eventually led to their very influential 1978 book The Hippocampus as a Cognitive Map.\n\nThere is now almost universal agreement that hippocampal function plays an important role in spatial coding, but the details are widely debated.Later research has focused on trying to bridge the disconnect between the two main views of hippocampal function as being split between memory and spatial cognition.\n\nIn some studies, these areas have been expanded to the point of near convergence.\n\nIn an attempt to reconcile the two disparate views, it is suggested that a broader view of the hippocampal function is taken and seen to have a role that encompasses both the organisation of experience (mental mapping, as per Tolman's original concept in 1948) and the directional behaviour seen as being involved in all areas of cognition, so that the function of the hippocampus can be viewed as a broader system that incorporates both the memory and the spatial perspectives in its role that involves the use of a wide scope of cognitive maps.\n\nThis relates to the purposive behaviorism born of Tolman's original goal of identifying the complex cognitive mechanisms and purposes that guided behaviour.It has also been proposed that the spiking activity of hippocampal neurons is associated spatially, and it was suggested that the mechanisms of memory and planning both evolved from mechanisms of navigation and that their neuronal algorithms were basically the same.Many studies have made use of neuroimaging techniques such as functional magnetic resonance imaging (fMRI), and a functional role in approach-avoidance conflict has been noted.\n\nThe anterior hippocampus is seen to be involved in decision-making under approach-avoidance conflict processing.\n\nIt is suggested that the memory, spatial cognition, and conflict processing functions may be seen as working together and not mutually exclusive.\n\n=== Role in memory ===\n\nPsychologists and neuroscientists generally agree that the hippocampus plays an important role in the formation of new memories about experienced events (episodic or autobiographical memory).\n\nPart of this function is hippocampal involvement in the detection of new events, places and stimuli.\n\nSome researchers regard the hippocampus as part of a larger medial temporal lobe memory system responsible for general declarative memory (memories that can be explicitly verbalized – these would include, for example, memory for facts in addition to episodic memory).\n\nThe hippocampus also encodes emotional context from the amygdala.\n\nThis is partly why returning to a location where an emotional event occurred may evoke that emotion.\n\nThere is a deep emotional connection between episodic memories and places.Due to bilateral symmetry the brain has a hippocampus in each cerebral hemisphere.\n\nIf damage to the hippocampus occurs in only one hemisphere, leaving the structure intact in the other hemisphere, the brain can retain near-normal memory functioning.\n\nSevere damage to the hippocampi in both hemispheres results in profound difficulties in forming new memories (anterograde amnesia) and often also affects memories formed before the damage occurred (retrograde amnesia).\n\nAlthough the retrograde effect normally extends many years back before the brain damage, in some cases older memories remain.\n\nThis retention of older memories leads to the idea that consolidation over time involves the transfer of memories out of the hippocampus to other parts of the brain.\n\nExperiments using intrahippocampal transplantation of hippocampal cells in primates with neurotoxic lesions of the hippocampus have shown that the hippocampus is required for the formation and recall, but not the storage, of memories.\n\nIt has been shown that a decrease in the volume of various parts of the hippocampus in people leads to specific memory impairments.\n\nIn particular, efficiency of verbal memory retention is related to the anterior parts of the right and left hippocampus.\n\nThe right head of the hippocampus is more involved in executive functions and regulation during verbal memory recall.\n\nThe tail of the left hippocampus tends to be closely related to verbal memory capacity.Damage to the hippocampus does not affect some types of memory, such as the ability to learn new skills (playing a musical instrument or solving certain types of puzzles, for example).\n\nThis fact suggests that such abilities depend on different types of memory (procedural memory) and different brain regions.\n\nFurthermore, amnesic patients frequently show \"implicit\" memory for experiences even in the absence of conscious knowledge.\n\nFor example, patients asked to guess which of two faces they have seen most recently may give the correct answer most of the time in spite of stating that they have never seen either of the faces before.\n\nSome researchers distinguish between conscious recollection, which depends on the hippocampus, and familiarity, which depends on portions of the medial temporal lobe.When rats are exposed to an intense learning event, they may retain a life-long memory of the event even after a single training session.\n\nThe memory of such an event appears to be first stored in the hippocampus, but this storage is transient.\n\nMuch of the long-term storage of the memory seems to take place in the anterior cingulate cortex.\n\nWhen such an intense learning event was experimentally applied, more than 5,000 differently methylated DNA regions appeared in the hippocampus neuronal genome of the rats at one hour and at 24 hours after training.\n\nThese alterations in methylation pattern occurred at many genes that were down-regulated, often due to the formation of new 5-methylcytosine sites in CpG rich regions of the genome.\n\nFurthermore, many other genes were upregulated, likely often due to the removal of methyl groups from previously existing 5-methylcytosines (5mCs) in DNA.\n\nDemethylation of 5mC can be carried out by several proteins acting in concert, including TET enzymes as well as enzymes of the DNA base excision repair pathway (see Epigenetics in learning and memory).\n\n=== Role in spatial memory and navigation ===\n\nStudies on freely moving rats and mice have shown many hippocampal neurons to act as place cells that cluster in place fields, and these fire bursts of action potentials when the animal passes through a particular location.\n\nThis place-related neural activity in the hippocampus has also been reported in monkeys that were moved around a room whilst in a restraint chair.\n\nHowever, the place cells may have fired in relation to where the monkey was looking rather than to its actual location in the room.\n\nOver many years, many studies have been carried out on place-responses in rodents, which have given a large amount of information.\n\nPlace cell responses are shown by pyramidal cells in the hippocampus and by granule cells in the dentate gyrus.\n\nOther cells in smaller proportion are inhibitory interneurons, and these often show place-related variations in their firing rate that are much weaker.\n\nThere is little, if any, spatial topography in the representation; in general, cells lying next to each other in the hippocampus have uncorrelated spatial firing patterns.\n\nPlace cells are typically almost silent when a rat is moving around outside the place field but reach sustained rates as high as 40 Hz when the rat is near the center.\n\nNeural activity sampled from 30 to 40 randomly chosen place cells carries enough information to allow a rat's location to be reconstructed with high confidence.\n\nThe size of place fields varies in a gradient along the length of the hippocampus, with cells at the dorsal end showing the smallest fields, cells near the center showing larger fields, and cells at the ventral tip showing fields that cover the entire environment.\n\nIn some cases, the firing rate of hippocampal cells depends not only on place but also the direction a rat is moving, the destination toward which it is traveling, or other task-related variables.\n\nThe firing of place cells is timed in relation to local theta waves, a process termed phase precession.In humans, cells with location-specific firing patterns have been reported during a study of patients with drug-resistant epilepsy.\n\nThey were undergoing an invasive procedure to localize the source of their seizures, with a view to surgical resection.\n\nThe patients had diagnostic electrodes implanted in their hippocampus and then used a computer to move around in a virtual reality town.\n\nSimilar brain imaging studies in navigation have shown the hippocampus to be active.\n\nA study was carried out on taxi drivers.\n\nLondon’s black cab drivers need to learn the locations of a large number of places and the fastest routes between them in order to pass a strict test known as The Knowledge in order to gain a license to operate.\n\nA study showed that the posterior part of the hippocampus is larger in these drivers than in the general public, and that a positive correlation exists between the length of time served as a driver and the increase in the volume of this part.\n\nIt was also found the total volume of the hippocampus was unchanged, as the increase seen in the posterior part was made at the expense of the anterior part, which showed a relative decrease in size.\n\nThere have been no reported adverse effects from this disparity in hippocampal proportions.\n\nAnother study showed opposite findings in blind individuals.\n\nThe anterior part of the right hippocampus was larger and the posterior part was smaller, compared with sighted individuals.There are several navigational cells in the brain that are either in the hippocampus itself or are strongly connected to it, such as the speed cells present in the medial entorhinal cortex.\n\nTogether these cells form a network that serves as spatial memory.\n\nThe first of such cells discovered in the 1970s were the place cells, which led to the idea of the hippocampus acting to give a neural representation of the environment in a cognitive map.\n\nWhen the hippocampus is dysfunctional, orientation is affected; people may have difficulty in remembering how they arrived at a location and how to proceed further.\n\nGetting lost is a common symptom of amnesia.\n\nStudies with animals have shown that an intact hippocampus is required for initial learning and long-term retention of some spatial memory tasks, in particular ones that require finding the way to a hidden goal.\n\nOther cells have been discovered since the finding of the place cells in the rodent brain that are either in the hippocampus or the entorhinal cortex.\n\nThese have been assigned as head direction cells, grid cells and boundary cells.\n\nSpeed cells are thought to provide input to the hippocampal grid cells.\n\n=== Role in approach-avoidance conflict processing ===\n\nApproach-avoidance conflict happens when a situation is presented that can either be rewarding or punishing, and the ensuing decision-making has been associated with anxiety. fMRI findings from studies in approach-avoidance decision-making found evidence for a functional role that is not explained by either long-term memory or spatial cognition.\n\nOverall findings showed that the anterior hippocampus is sensitive to conflict, and that it may be part of a larger cortical and subcortical network seen to be important in decision making in uncertain conditions.A review makes reference to a number of studies that show the involvement of the hippocampus in conflict tasks.\n\nThe authors suggest that a challenge is to understand how conflict processing relates to the functions of spatial navigation and memory and how all of these functions need not be mutually exclusive.\n\n== Electroencephalography ==\n\nThe hippocampus shows two major \"modes\" of activity, each associated with a distinct pattern of neural population activity and waves of electrical activity as measured by an electroencephalogram (EEG).\n\nThese modes are named after the EEG patterns associated with them: theta and large irregular activity (LIA).\n\nThe main characteristics described below are for the rat, which is the animal most extensively studied.The theta mode appears during states of active, alert behavior (especially locomotion), and also during REM (dreaming) sleep.\n\nIn the theta mode, the EEG is dominated by large regular waves with a frequency range of 6 to 9 Hz, and the main groups of hippocampal neurons (pyramidal cells and granule cells) show sparse population activity, which means that in any short time interval, the great majority of cells are silent, while the small remaining fraction fire at relatively high rates, up to 50 spikes in one second for the most active of them.\n\nAn active cell typically stays active for half a second to a few seconds.\n\nAs the rat behaves, the active cells fall silent and new cells become active, but the overall percentage of active cells remains more or less constant.\n\nIn many situations, cell activity is determined largely by the spatial location of the animal, but other behavioral variables also clearly influence it.\nThe LIA mode appears during slow-wave (non-dreaming) sleep, and also during states of waking immobility such as resting or eating.\n\nIn the LIA mode, the EEG is dominated by sharp waves that are randomly timed large deflections of the EEG signal lasting for 25–50 milliseconds.\n\nSharp waves are frequently generated in sets, with sets containing up to 5 or more individual sharp waves and lasting up to 500 ms.\n\nThe spiking activity of neurons within the hippocampus is highly correlated with sharp wave activity.\n\nMost neurons decrease their firing rate between sharp waves; however, during a sharp wave, there is a dramatic increase in firing rate in up to 10% of the hippocampal population\nThese two hippocampal activity modes can be seen in primates as well as rats, with the exception that it has been difficult to see robust theta rhythmicity in the primate hippocampus.\n\nThere are, however, qualitatively similar sharp waves and similar state-dependent changes in neural population activity.\n\n=== Theta rhythm ===\n\nThe underlying currents producing the theta wave are generated mainly by densely packed neural layers of the entorhinal cortex, CA3, and the dendrites of pyramidal cells.\n\nThe theta wave is one of the largest signals seen on EEG, and is known as the hippocampal theta rhythm.\n\nIn some situations the EEG is dominated by regular waves at 3 to 10 Hz, often continuing for many seconds.\n\nThese reflect subthreshold membrane potentials and strongly modulate the spiking of hippocampal neurons and synchronise across the hippocampus in a travelling wave pattern.\n\nThe trisynaptic circuit is a relay of neurotransmission in the hippocampus that interacts with many brain regions.\n\nFrom rodent studies it has been proposed that the trisynaptic circuit generates the hippocampal theta rhythm.Theta rhythmicity is very obvious in rabbits and rodents and also clearly present in cats and dogs.\n\nWhether theta can be seen in primates is not yet clear.\n\nIn rats (the animals that have been the most extensively studied), theta is seen mainly in two conditions: first, when an animal is walking or in some other way actively interacting with its surroundings; second, during REM sleep.\n\nThe function of theta has not yet been convincingly explained although numerous theories have been proposed.\n\nThe most popular hypothesis has been to relate it to learning and memory.\n\nAn example would be the phase with which theta rhythms, at the time of stimulation of a neuron, shape the effect of that stimulation upon its synapses.\n\nWhat is meant here is that theta rhythms may affect those aspects of learning and memory that are dependent upon synaptic plasticity.\n\nIt is well established that lesions of the medial septum – the central node of the theta system – cause severe disruptions of memory.\n\nHowever, the medial septum is more than just the controller of theta; it is also the main source of cholinergic projections to the hippocampus.\n\nIt has not been established that septal lesions exert their effects specifically by eliminating the theta rhythm.\n\n=== Sharp waves ===\n\nDuring sleep or during resting, when an animal is not engaged with its surroundings, the hippocampal EEG shows a pattern of irregular slow waves, somewhat larger in amplitude than theta waves.\n\nThis pattern is occasionally interrupted by large surges called sharp waves.\n\nThese events are associated with bursts of spike activity lasting 50 to 100 milliseconds in pyramidal cells of CA3 and CA1.\n\nThey are also associated with short-lived high-frequency EEG oscillations called \"ripples\", with frequencies in the range 150 to 200 Hz in rats, and together they are known as sharp waves and ripples.\n\nSharp waves are most frequent during sleep when they occur at an average rate of around 1 per second (in rats) but in a very irregular temporal pattern.\n\nSharp waves are less frequent during inactive waking states and are usually smaller.\n\nSharp waves have also been observed in humans and monkeys.\n\nIn macaques, sharp waves are robust but do not occur as frequently as in rats.One of the most interesting aspects of sharp waves is that they appear to be associated with memory.\n\nWilson and McNaughton 1994, and numerous later studies, reported that when hippocampal place cells have overlapping spatial firing fields (and therefore often fire in near-simultaneity), they tend to show correlated activity during sleep following the behavioral session.\n\nThis enhancement of correlation, commonly known as reactivation, has been found to occur mainly during sharp waves.\n\nIt has been proposed that sharp waves are, in fact, reactivations of neural activity patterns that were memorized during behavior, driven by strengthening of synaptic connections within the hippocampus.\n\nThis idea forms a key component of the \"two-stage memory\" theory, advocated by Buzsáki and others, which proposes that memories are stored within the hippocampus during behavior and then later transferred to the neocortex during sleep.\n\nSharp waves in Hebbian theory are seen as persistently repeated stimulations by presynaptic cells, of postsynaptic cells that are suggested to drive synaptic changes in the cortical targets of hippocampal output pathways.\n\nSuppression of sharp waves and ripples in sleep or during immobility can interfere with memories expressed at the level of the behavior, nonetheless, the newly formed CA1 place cell code can re-emerge even after a sleep with abolished sharp waves and ripples, in spatially non-demanding tasks.\n\n=== Long-term potentiation ===\n\nSince at least the time of Ramon y Cajal (1852–1934), psychologists have speculated that the brain stores memory by altering the strength of connections between neurons that are simultaneously active.\n\nThis idea was formalized by Donald Hebb in 1949, but for many years remained unexplained.\n\nIn 1973, Tim Bliss and Terje Lømo described a phenomenon in the rabbit hippocampus that appeared to meet Hebb's specifications: a change in synaptic responsiveness induced by brief strong activation and lasting for hours or days or longer.\n\nThis phenomenon was soon referred to as long-term potentiation (LTP).\n\nAs a candidate mechanism for long-term memory, LTP has since been studied intensively, and a great deal has been learned about it.\n\nHowever, the complexity and variety of the intracellular signalling cascades that can trigger LTP is acknowledged as preventing a more complete understanding.The hippocampus is a particularly favorable site for studying LTP because of its densely packed and sharply defined layers of neurons, but similar types of activity-dependent synaptic change have also been observed in many other brain areas.\n\nThe best-studied form of LTP has been seen in CA1 of the hippocampus and occurs at synapses that terminate on dendritic spines and use the neurotransmitter glutamate.\n\nThe synaptic changes depend on a special type of glutamate receptor, the N-methyl-D-aspartate (NMDA) receptor, a cell surface receptor which has the special property of allowing calcium to enter the postsynaptic spine only when presynaptic activation and postsynaptic depolarization occur at the same time.\n\nDrugs that interfere with NMDA receptors block LTP and have major effects on some types of memory, especially spatial memory.\n\nGenetically modified mice that are modified to disable the LTP mechanism, also generally show severe memory deficits.\n\n== Disorders ==\n\n=== Aging ===\n\nAge-related conditions such as Alzheimer's disease and other forms of dementia (for which hippocampal disruption is one of the earliest signs) have a severe impact on many types of cognition including memory.\n\nEven normal aging is associated with a gradual decline in some types of memory, including episodic memory and working memory (or short-term memory).\n\nBecause the hippocampus is thought to play a central role in memory, there has been considerable interest in the possibility that age-related declines could be caused by hippocampal deterioration.\n\nSome early studies reported substantial loss of neurons in the hippocampus of elderly people, but later studies using more precise techniques found only minimal differences.\n\nSimilarly, some MRI studies have reported shrinkage of the hippocampus in elderly people, but other studies have failed to reproduce this finding.\n\nThere is, however, a reliable relationship between the size of the hippocampus and memory performance; so that where there is age-related shrinkage, memory performance will be impaired.\n\nThere are also reports that memory tasks tend to produce less hippocampal activation in the elderly than in the young.\n\nFurthermore, a randomized control trial published in 2011 found that aerobic exercise could increase the size of the hippocampus in adults aged 55 to 80 and also improve spatial memory.\n\n=== Stress ===\n\nThe hippocampus contains high levels of glucocorticoid receptors, which make it more vulnerable to long-term stress than most other brain areas.\n\nThere is evidence that humans having experienced severe, long-lasting traumatic stress show atrophy of the hippocampus more than of other parts of the brain.\n\nThese effects show up in post-traumatic stress disorder, and they may contribute to the hippocampal atrophy reported in schizophrenia and severe depression.\n\nAnterior hippocampal volume in children is positively correlated with parental family income and this correlation is thought to be mediated by income related stress.\n\nA recent study has also revealed atrophy as a result of depression, but this can be stopped with anti-depressants even if they are not effective in relieving other symptoms.Chronic stress resulting in elevated levels of glucocorticoids, notably of cortisol, is seen to be a cause of neuronal atrophy in the hippocampus.\n\nThis atrophy results in a smaller hippocampal volume which is also seen in Cushing’s syndrome.\n\nThe higher levels of cortisol in Cushing’s syndrome is usually the result of medications taken for other conditions.\n\nNeuronal loss also occurs as a result of impaired neurogenesis.\n\nAnother factor that contributes to a smaller hippocampal volume is that of dendritic retraction where dendrites are shortened in length and reduced in number, in response to increased glucocorticoids.\n\nThis dendritic retraction is reversible.\n\nAfter treatment with medication to reduce cortisol in Cushing’s syndrome, the hippocampal volume is seen to be restored by as much as 10%.\n\nThis change is seen to be due to the reforming of the dendrites.\n\nThis dendritic restoration can also happen when stress is removed.\n\nThere is, however, evidence derived mainly from studies using rats that stress occurring shortly after birth can affect hippocampal function in ways that persist throughout life.Sex-specific responses to stress have also been demonstrated in the rat to have an effect on the hippocampus.\n\nChronic stress in the male rat showed dendritic retraction and cell loss in the CA3 region but this was not shown in the female.\n\nThis was thought to be due to neuroprotective ovarian hormones.\n\nIn rats, DNA damage increases in the hippocampus under conditions of stress.\n\n=== Epilepsy ===\n\nThe hippocampus is one of the few brain regions where new neurons are generated.\n\nThis process of neurogenesis is confined to the dentate gyrus.\n\nThe production of new neurons can be positively affected by exercise or negatively affected by epileptic seizures.Seizures in temporal lobe epilepsy can affect the normal development of new neurons and can cause tissue damage.\n\nHippocampal sclerosis including Ammon's horn sclerosis that is specific to the mesial temporal lobe, is the most common type of such tissue damage.\n\nIt is not yet clear, however, whether the epilepsy is usually caused by hippocampal abnormalities or whether the hippocampus is damaged by cumulative effects of seizures.\n\nHowever, in experimental settings where repetitive seizures are artificially induced in animals, hippocampal damage is a frequent result.\n\nThis may be a consequence of the concentration of excitable glutamate receptors in the hippocampus.\n\nHyperexcitability can lead to cytotoxicity and cell death.\n\nIt may also have something to do with the hippocampus being a site where new neurons continue to be created throughout life, and to abnormalities in this process.\n\n=== Schizophrenia ===\n\nThe causes of schizophrenia are not well understood, but numerous abnormalities of brain structure have been reported.\n\nThe most thoroughly investigated alterations involve the cerebral cortex, but effects on the hippocampus have also been described.\n\nMany reports have found reductions in the size of the hippocampus in people with schizophrenia.\n\nThe left hippocampus seems to be affected more than the right.\n\nThe changes noted have largely been accepted to be the result of abnormal development.\n\nIt is unclear whether hippocampal alterations play any role in causing the psychotic symptoms that are the most important feature of schizophrenia.\n\nIt has been suggested that on the basis of experimental work using animals, hippocampal dysfunction might produce an alteration of dopamine release in the basal ganglia, thereby indirectly affecting the integration of information in the prefrontal cortex.\n\nIt has also been suggested that hippocampal dysfunction might account for the disturbances in long-term memory frequently observed.MRI studies have found a smaller brain volume and larger ventricles in people with schizophrenia – however researchers do not know if the shrinkage is from the schizophrenia or from the medication.\n\nThe hippocampus and thalamus have been shown to be reduced in volume; and the volume of the globus pallidus is increased.\n\nCortical patterns are altered, and a reduction in the volume and thickness of the cortex particularly in the frontal and temporal lobes has been noted.\n\nIt has further been proposed that many of the changes seen are present at the start of the disorder which gives weight to the theory that there is abnormal neurodevelopment.The hippocampus has been seen as central to the pathology of schizophrenia, both in the neural and physiological effects.\n\nIt has been generally accepted that there is an abnormal synaptic connectivity underlying schizophrenia.\n\nSeveral lines of evidence implicate changes in the synaptic organization and connectivity, in and from the hippocampus Many studies have found dysfunction in the synaptic circuitry within the hippocampus and its activity on the prefrontal cortex.\n\nThe glutamatergic pathways have been seen to be largely affected.\n\nThe subfield CA1 is seen to be the least involved of the other subfields, and CA4 and the subiculum have been reported elsewhere as being the most implicated areas.\n\nThe review concluded that the pathology could be due to genetics, faulty neurodevelopment or abnormal neural plasticity.\n\nIt was further concluded that schizophrenia is not due to any known neurodegenerative disorder.\n\nOxidative DNA damage is substantially increased in the hippocampus of elderly patients with chronic schizophrenia.\n\n=== Transient global amnesia ===\n\nTransient global amnesia is a dramatic, sudden, temporary, near-total loss of short-term memory.\n\nVarious causes have been hypothesized including ischemia, epilepsy, migraine and disturbance of cerebral venous blood flow, leading to ischemia of structures such as the hippocampus that are involved in memory.There has been no scientific proof of any cause.\n\nHowever, diffusion weighted MRI studies taken from 12 to 24 hours following an episode has shown there to be small dot-like lesions in the hippocampus.\n\nThese findings have suggested a possible implication of CA1 neurons made vulnerable by metabolic stress.\n\n=== PTSD ===\n\nSome studies shows correlation of reduced hippocampus volume and posttraumatic stress disorder (PTSD).\n\nA study of Vietnam War combat veterans with PTSD showed a 20% reduction in the volume of their hippocampus compared with veterans having suffered no such symptoms.\n\nThis finding was not replicated in chronic PTSD patients traumatized at an air show plane crash in 1988 (Ramstein, Germany).\n\nIt is also the case that non-combat twin brothers of Vietnam veterans with PTSD also had smaller hippocampi than other controls, raising questions about the nature of the correlation.\n\nA 2016 study strengthened theory that a smaller hippocampus increases the risk for post-traumatic stress disorder, and a larger hippocampus increases the likelihood of efficacious treatment.\n\n=== Microcephaly ===\n\nHippocampus atrophy has been characterized in microcephaly patients and mouse models with WDR62 mutations which recapitulate human point mutations shown a deficiency in hippocampal development and neurogenesis.\n\n== Other animals ==\n\n=== Other mammals ===\n\nThe hippocampus has a generally similar appearance across the range of mammals, from monotremes such as the echidna to primates such as humans.\n\nThe hippocampal-size-to-body-size ratio broadly increases, being about twice as large for primates as for the echidna.\n\nIt does not, however, increase at anywhere close to the rate of the neocortex-to-body-size ratio.\n\nTherefore, the hippocampus takes up a much larger fraction of the cortical mantle in rodents than in primates.\n\nIn adult humans the volume of the hippocampus on each side of the brain is about 3.0 to 3.5 cm3 as compared to 320 to 420 cm3 for the volume of the neocortex.There is also a general relationship between the size of the hippocampus and spatial memory.\n\nWhen comparisons are made between similar species, those that have a greater capacity for spatial memory tend to have larger hippocampal volumes.\n\nThis relationship also extends to sex differences; in species where males and females show strong differences in spatial memory ability they also tend to show corresponding differences in hippocampal volume.\n\n=== Other vertebrates ===\n\nNon-mammalian species do not have a brain structure that looks like the mammalian hippocampus, but they have one that is considered homologous to it.\n\nThe hippocampus, as pointed out above, is in essence part of the allocortex.\n\nOnly mammals have a fully developed cortex, but the structure it evolved from, called the pallium, is present in all vertebrates, even the most primitive ones such as the lamprey or hagfish.\n\nThe pallium is usually divided into three zones: medial, lateral and dorsal.\n\nThe medial pallium forms the precursor of the hippocampus.\n\nIt does not resemble the hippocampus visually because the layers are not warped into an S shape or enfolded by the dentate gyrus, but the homology is indicated by strong chemical and functional affinities.\n\nThere is now evidence that these hippocampal-like structures are involved in spatial cognition in birds, reptiles, and fish.\n\n==== Birds ====\nIn birds, the correspondence is sufficiently well established that most anatomists refer to the medial pallial zone as the \"avian hippocampus\".\n\nNumerous species of birds have strong spatial skills, in particular those that cache food.\n\nThere is evidence that food-caching birds have a larger hippocampus than other types of birds and that damage to the hippocampus causes impairments in spatial memory.\n\n==== Fish ====\nThe story for fish is more complex.\n\nIn teleost fish (which make up the great majority of existing species), the forebrain is distorted in comparison to other types of vertebrates: most neuroanatomists believe that the teleost forebrain is in essence everted, like a sock turned inside-out, so that structures that lie in the interior, next to the ventricles, for most vertebrates, are found on the outside in teleost fish, and vice versa.\n\nOne of the consequences of this is that the medial pallium (\"hippocampal\" zone) of a typical vertebrate is thought to correspond to the lateral pallium of a typical fish.\n\nSeveral types of fish (particularly goldfish) have been shown experimentally to have strong spatial memory abilities, even forming \"cognitive maps\" of the areas they inhabit.\n\nThere is evidence that damage to the lateral pallium impairs spatial memory.\n\nIt is not yet known whether the medial pallium plays a similar role in even more primitive vertebrates, such as sharks and rays, or even lampreys and hagfish.\n\n=== Insects and molluscs ===\n\nSome types of insects, and molluscs such as the octopus, also have strong spatial learning and navigation abilities, but these appear to work differently from the mammalian spatial system, so there is as yet no good reason to think that they have a common evolutionary origin; nor is there sufficient similarity in brain structure to enable anything resembling a \"hippocampus\" to be identified in these species.\n\nSome have proposed, however, that the insect's mushroom bodies may have a function similar to that of the hippocampus.\n\n== Notes ==\n\n== Further reading ==\n\nHippocampus (Wiley)\nDocampo-Seara A, Lagadec R, Mazan S, Rodríguez MA, Quintana-Urzainqui I, Candal E (July 2018). \"Study of pallial neurogenesis in shark embryos and the evolutionary origin of the subventricular zone\".\n\nBrain Structure and Function. 223 (8): 3593–3612. doi:10.1007/s00429-018-1705-2.\n\nPMID 29980930.\nDerdikman D, Knierim JJ, eds. (2014).\n\nSpace, Time and Memory in the Hippocampal Formation.\n\nSpringer.\n\nISBN 978-3-7091-1292-2.\n\nhttps://en.wikipedia.org/wiki/Hippocampus","amygdaloid-body":"The amygdala (; plural: amygdalae or amygdalas; also corpus amygdaloideum; Latin from Greek, ἀμυγδαλή, amygdalē, 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex vertebrates, including humans.\n\nShown to perform a primary role in the processing of memory, decision making, and emotional responses (including fear, anxiety, and aggression), the amygdalae are considered part of the limbic system.\n\nThe term amygdala was first introduced by Karl Friedrich Burdach in 1822.\n\n== Structure ==\n\nThe regions described as amygdala nuclei encompass several structures of the cerebrum with distinct connectional and functional characteristics in humans and other animals.\n\nAmong these nuclei are the basolateral complex, the cortical nucleus, the medial nucleus, the central nucleus, and the intercalated cell clusters.\n\nThe basolateral complex can be further subdivided into the lateral, the basal, and the accessory basal nuclei.Anatomically, the amygdala, and more particularly its central and medial nuclei, have sometimes been classified as a part of the basal ganglia.\n\n=== Hemispheric specializations ===\n\nIn one study, electrical stimulations of the right amygdala induced negative emotions, especially fear and sadness.\n\nIn contrast, stimulation of the left amygdala was able to induce either pleasant (happiness) or unpleasant (fear, anxiety, sadness) emotions.\n\nOther evidence suggests that the left amygdala plays a role in the brain's reward system.Each side holds a specific function in how we perceive and process emotion.\n\nThe right and left portions of the amygdala have independent memory systems, but work together to store, encode, and interpret emotion.\nThe right hemisphere of the amygdala is associated with negative emotion.\n\nIt plays a role in the expression of fear and in the processing of fear-inducing stimuli.\n\nFear conditioning, which occurs when a neutral stimulus acquires aversive properties, occurs within the right hemisphere.\n\nWhen an individual is presented with a conditioned, aversive stimulus, it is processed within the right amygdala, producing an unpleasant or fearful response.\n\nThis emotional response conditions the individual to avoid fear-inducing stimuli and more importantly, to assess threats in the environment.\nThe right hemisphere is also linked to declarative memory, which consists of facts and information from previously experienced events and must be consciously recalled.\n\nIt also plays a significant role in the retention of episodic memory.\n\nEpisodic memory consists of the autobiographical aspects of memory, permitting recall of emotional and sensory experience of an event.\n\nThis type of memory does not require conscious recall.\n\nThe right amygdala plays a role in the association of time and places with emotional properties.\n\n== Development and sex distinction ==\n\nThe amygdala is one of the best-understood brain regions with regard to differences between the sexes.\n\nThe amygdala is larger in males than females in children aged 7 to 11, adult humans, and adult rats.There is considerable growth within the first few years of structural development in both male and female amygdalae.\n\nWithin this early period, female limbic structures grow at a more rapid pace than the male ones.\n\nAmongst female subjects, the amygdala reaches its full growth potential approximately 1.5 years before the peak of male development.\n\nThe structural development of the male amygdala occurs over a longer period than in women.\n\nDespite the early development of female amygdalae, they reach their growth potential sooner than males, whose amygdalae continue to develop.\n\nThe larger relative size of the male amygdala may be attributed to this extended developmental period.\nHormonal factors may also contribute to sex-specific developmental differences.\n\nThe amygdala is rich in androgen receptors – nuclear receptors that bind to testosterone.\n\nAndrogen receptors play a role in the DNA binding that regulates gene expression.\n\nThough testosterone is present within the female hormonal systems, women have lower levels of testosterone than men.\n\nThe abundance of testosterone in the male hormonal system may contribute to development.\n\nIn addition, the grey matter volume on the amygdala is predicted by testosterone levels, which may also contribute to the increased mass of the male amygdala.\nThere are observable developmental differences between the right and left amygdala.\n\nThe left amygdala reaches its developmental peak approximately 1.5–2 years prior to the right amygdala.\n\nDespite the early growth of the left amygdala, the right increases in volume for a longer period of time.\n\nThe right amygdala is associated with response to fearful stimuli as well as face recognition.\n\nIt is inferred that the early development of the left amygdala functions to provide infants the ability to detect danger.\n\nIn childhood, the amygdala is found to react differently to same-sex versus opposite-sex individuals.\n\nThis reactivity decreases until a person enters adolescence, where it increases dramatically at puberty.Other functional and structural differences between male and female amygdalae have been observed.\n\nSubjects' amygdala activation was observed when watching a horror film and subliminal stimuli.\n\nThe results of the study showed a different lateralization of the amygdala in men and women.\n\nEnhanced memory for the film was related to enhanced activity of the left, but not the right, amygdala in women, whereas it was related to enhanced activity of the right, but not the left, amygdala in men.\n\nSimilarly, a study of decision-making ability in patients with unilateral amygdala damage suggested that men with right (but not left) amygdala damage were more likely to be impaired in decision-making ability, while women with left (but not right) amygdala damage were more likely to be impaired in decision-making ability.\n\nOne study found evidence that on average, women tend to retain stronger memories for emotional events than men.\n\n== Function ==\n\n=== Connections ===\n\nA simple view of the information processing through the amygdala follows as: the amygdala sends projections to the hypothalamus, the dorsomedial thalamus, the thalamic reticular nucleus, the nuclei of the trigeminal nerve and the facial nerve, the ventral tegmental area, the locus coeruleus, and the laterodorsal tegmental nucleus.\n\nThe basolateral amygdala projects to the nucleus accumbens, including the medial shell.\n\nThe medial nucleus is involved in the sense of smell and pheromone-processing.\n\nIt receives input from the olfactory bulb and olfactory cortex.\n\nThe lateral amygdalae, which send impulses to the rest of the basolateral complexes and to the centromedial nuclei, receive input from the sensory systems.\n\nThe centromedial nuclei are the main outputs for the basolateral complexes, and are involved in emotional arousal in rats and cats.\n\n=== Emotional learning ===\n\nIn complex vertebrates, including humans, the amygdalae perform primary roles in the formation and storage of memories associated with emotional events.\n\nResearch indicates that, during fear conditioning, sensory stimuli reach the basolateral complexes of the amygdalae, particularly the lateral nuclei, where they form associations with memories of the stimuli.\n\nThe association between stimuli and the aversive events they predict may be mediated by long-term potentiation, a sustained enhancement of signaling between affected neurons.\n\nThere have been studies that show that damage to the amygdala can interfere with memory that is strengthened by emotion.\n\nOne study examined a patient with bilateral degeneration of the amygdala.\n\nHe was told a violent story accompanied by matching pictures and was observed based on how much he could recall from the story.\n\nThe patient had less recollection of the story than patients with functional amygdala, showing that the amygdala has a strong connection with emotional learning.Emotional memories are thought to be stored in synapses throughout the brain.\n\nFear memories, for example, are considered to be stored in the neuronal connections from the lateral nuclei to the central nucleus of the amygdalae and the bed nuclei of the stria terminalis (part of the extended amygdala).\n\nThese connections are not the sole site of fear memories given that the nuclei of the amygdala receive and send information to other brain regions that are important for memory such as the hippocampus.\n\nSome sensory neurons project their axon terminals to the central nucleus.\n\nThe central nuclei are involved in the genesis of many fear responses such as defensive behavior (freezing or escape responses), autonomic nervous system responses (changes in blood pressure and heart rate/tachycardia), neuroendocrine responses (stress-hormone release), etc.\n\nDamage to the amygdalae impairs both the acquisition and expression of Pavlovian fear conditioning, a form of classical conditioning of emotional responses.\n\nAccumulating evidence has suggested that multiple neuromodulators acting in the amygdala regulates the formation of emotional memories.The amygdalae are also involved in appetitive (positive) conditioning.\n\nIt seems that distinct neurons respond to positive and negative stimuli, but there is no clustering of these distinct neurons into clear anatomical nuclei.\n\nHowever, lesions of the central nucleus in the amygdala have been shown to reduce appetitive learning in rats.\n\nLesions of the basolateral regions do not exhibit the same effect.\n\nResearch like this indicates that different nuclei within the amygdala have different functions in appetitive conditioning.\nNevertheless, researchers found an example of appetitive emotional learning showing an important role for the basolateral amygdala: The naïve female mice are innately attracted to non-volatile pheromones contained in male-soiled bedding, but not by the male-derived volatiles, become attractive if associated with non-volatile attractive pheromones, which act as unconditioned stimulus in a case of Pavlovian associative learning.\n\nIn the vomeronasal, olfactory and emotional systems, Fos (gene family) proteins show that non-volatile pheromones stimulate the vomeronasal system, whereas air-borne volatiles activate only the olfactory system.\n\nThus, the acquired preference for male-derived volatiles reveals an olfactory-vomeronasal associative learning.\n\nMoreover, the reward system is differentially activated by the primary pheromones and secondarily attractive odorants.\n\nExploring the primary attractive pheromone activates the basolateral amygdala and the shell of nucleus accumbens but neither the ventral tegmental area nor the orbitofrontal cortex.\n\nIn contrast, exploring the secondarily attractive male-derived odorants involves activation of a circuit that includes the basolateral amygdala, prefrontal cortex and ventral tegmental area.\n\nTherefore, the basolateral amygdala stands out as the key center for vomeronasal-olfactory associative learning.\n\n=== Reward ===\n\nGlutamatergic neurons in the basolateral amygdala send projections to the nucleus accumbens shell and core.\n\nActivation of these projections drive motivational salience.\n\nThe ability of these projections to drive incentive salience is dependent upon dopamine receptor D1.\n\n=== Memory modulation ===\n\nThe amygdala is also involved in the modulation of memory consolidation.\n\nFollowing any learning event, the long-term memory for the event is not formed instantaneously.\n\nRather, information regarding the event is slowly assimilated into long-term (potentially lifelong) storage over time, possibly via long-term potentiation.\n\nRecent studies suggest that the amygdala regulates memory consolidation in other brain regions.\n\nAlso, fear conditioning, a type of memory that is impaired following amygdala damage, is mediated in part by long-term potentiation.During the consolidation period, the memory can be modulated.\n\nIn particular, it appears that emotional arousal following the learning event influences the strength of the subsequent memory for that event.\n\nGreater emotional arousal following a learning event enhances a person's retention of that event.\n\nExperiments have shown that administration of stress hormones to mice immediately after they learn something enhances their retention when they are tested two days later.The amygdala, especially the basolateral nuclei, are involved in mediating the effects of emotional arousal on the strength of the memory for the event, as shown by many laboratories including that of James McGaugh.\n\nThese laboratories have trained animals on a variety of learning tasks and found that drugs injected into the amygdala after training affect the animals' subsequent retention of the task.\n\nThese tasks include basic classical conditioning tasks such as inhibitory avoidance, where a rat learns to associate a mild footshock with a particular compartment of an apparatus, and more complex tasks such as spatial or cued water maze, where a rat learns to swim to a platform to escape the water.\n\nIf a drug that activates the amygdalae is injected into the amygdalae, the animals had better memory for the training in the task.\n\nIf a drug that inactivates the amygdalae is injected, the animals had impaired memory for the task.\nIn rats, DNA damage was found to increase in the amygdala immediately after exposure to stress.\n\nStress was induced by 30 minutes of restraint or by forced swimming.\n\nBy seven days after exposure to these stresses, increased DNA damage was no longer detectable in the amygdala, probably because of DNA repair.Buddhist monks who do compassion meditation have been shown to modulate their amygdala, along with their temporoparietal junction and insula, during their practice.\n\nIn an fMRI study, more intensive insula activity was found in expert meditators than in novices.\n\nIncreased activity in the amygdala following compassion-oriented meditation may contribute to social connectedness.Amygdala activity at the time of encoding information correlates with retention for that information.\n\nHowever, this correlation depends on the relative \"emotionalness\" of the information.\n\nMore emotionally arousing information increases amygdalar activity, and that activity correlates with retention.\n\nAmygdala neurons show various types of oscillation during emotional arousal, such as theta activity.\n\nThese synchronized neuronal events could promote synaptic plasticity (which is involved in memory retention) by increasing interactions between neocortical storage sites and temporal lobe structures involved in declarative memory.\n\nResearch using Rorschach test blot 03 finds that the number of unique responses to this random figure links to larger sized amygdalae.\n\nThe researchers note, \"Since previous reports have indicated that unique responses were observed at higher frequency in the artistic population than in the nonartistic normal population, this positive correlation suggests that amygdalar enlargement in the normal population might be related to creative mental activity.\"\n\n== Neuropsychological correlates of amygdala activity ==\n\nEarly research on primates provided explanations as to the functions of the amygdala, as well as a basis for further research.\n\nAs early as 1888, rhesus monkeys with a lesioned temporal cortex (including the amygdala) were observed to have significant social and emotional deficits.\n\nHeinrich Klüver and Paul Bucy later expanded upon this same observation by showing that large lesions to the anterior temporal lobe produced noticeable changes, including overreaction to all objects, hypoemotionality, loss of fear, hypersexuality, and hyperorality, a condition in which inappropriate objects are placed in the mouth.\n\nSome monkeys also displayed an inability to recognize familiar objects and would approach animate and inanimate objects indiscriminately, exhibiting a loss of fear towards the experimenters.\n\nThis behavioral disorder was later named Klüver-Bucy syndrome accordingly, and later research proved it was specifically due to amygdala lesions.\n\nMonkey mothers who had amygdala damage showed a reduction in maternal behaviors towards their infants, often physically abusing or neglecting them.\n\nIn 1981, researchers found that selective radio frequency lesions of the whole amygdala caused Klüver-Bucy syndrome.With advances in neuroimaging technology such as MRI, neuroscientists have made significant findings concerning the amygdala in the human brain.\n\nA variety of data shows the amygdala has a substantial role in mental states, and is related to many psychological disorders.\n\nSome studies have shown children with anxiety disorders tend to have a smaller left amygdala.\n\nIn the majority of the cases, there was an association between an increase in the size of the left amygdala with the use of SSRIs (antidepressant medication) or psychotherapy.\n\nThe left amygdala has been linked to social anxiety, obsessive and compulsive disorders, and post traumatic stress, as well as more broadly to separation and general anxiety.\n\nIn a 2003 study, subjects with borderline personality disorder showed significantly greater left amygdala activity than normal control subjects.\n\nSome borderline patients even had difficulties classifying neutral faces or saw them as threatening.\n\nIndividuals with psychopathy show reduced autonomic responses to instructed fear cues than otherwise healthy individuals.\n\nIn 2006, researchers observed hyperactivity in the amygdala when patients were shown threatening faces or confronted with frightening situations.\n\nPatients with severe social phobia showed a correlation with increased response in the amygdala.\n\nSimilarly, depressed patients showed exaggerated left amygdala activity when interpreting emotions for all faces, and especially for fearful faces.\n\nThis hyperactivity was normalized when patients were administered antidepressant medication.\n\nBy contrast, the amygdala has been observed to respond differently in people with bipolar disorder.\n\nA 2003 study found that adult and adolescent bipolar patients tended to have considerably smaller amygdala volumes and somewhat smaller hippocampal volumes.\n\nMany studies have focused on the connections between the amygdala and autism.Studies in 2004 and 2006 showed that normal subjects exposed to images of frightened faces or faces of people from another race will show increased activity of the amygdala, even if that exposure is subliminal.\n\nHowever, the amygdala is not necessary for the processing of fear-related stimuli, since persons in whom it is bilaterally damaged show rapid reactions to fearful faces, even in the absence of a functional amygdala.\n\n=== Sexual orientation ===\n\nRecent studies have suggested possible correlations between brain structure, including differences in hemispheric ratios and connection patterns in the amygdala, and sexual orientation.\n\nHomosexual men tend to exhibit more feminine patterns in the amygdala than heterosexual males do, just as homosexual females tend to show more masculine patterns in the amygdala than heterosexual women do.\n\nIt was observed that amygdala connections were more widespread from the left amygdala in homosexual males, as is also found in heterosexual females.\n\nAmygdala connections were more widespread from the right amygdala in homosexual females, as in heterosexual males.\n\n=== Social interaction ===\n\nAmygdala volume correlates positively with both the size (the number of contacts a person has) and the complexity (the number of different groups to which a person belongs) of social networks.\n\nIndividuals with larger amygdalae had larger and more complex social networks.\n\nThe amygdala is responsible for facial recognition and allows others to respond appropriately to different emotional expressions.\n\nThey were also better able to make accurate social judgments about other persons' faces.\n\nThe amygdala's role in the analysis of social situations stems specifically from its ability to identify and process changes in facial features.\n\nIt does not, however, process the direction of the gaze of the person being perceived.The amygdala is also thought to be a determinant of the level of a person's emotional intelligence.\n\nIt is particularly hypothesized that larger amygdalae allow for greater emotional intelligence, enabling greater societal integration and cooperation with others.The amygdala processes reactions to violations concerning personal space.\n\nThese reactions are absent in persons in whom the amygdala is damaged bilaterally.\n\nFurthermore, the amygdala is found to be activated in fMRI when people observe that others are physically close to them, such as when a person being scanned knows that an experimenter is standing immediately next to the scanner, versus standing at a distance.\n\n=== Aggression ===\n\nAnimal studies have shown that stimulating the amygdala appears to increase both sexual and aggressive behavior.\n\nLikewise, studies using brain lesions have shown that harm to the amygdala may produce the opposite effect.\n\nThus, it appears that this part of the brain may play a role in the display and modulation of aggression.\n\n=== Fear ===\n\nThere are cases of human patients with focal bilateral amygdala lesions due to the rare genetic condition Urbach-Wiethe disease.\n\nSuch patients fail to exhibit fear-related behaviors, leading one, S.M., to be dubbed the \"woman with no fear\".\n\nThis finding reinforces the conclusion that the amygdala \"plays a pivotal role in triggering a state of fear\".\n\n=== Alcoholism and binge drinking ===\n\nThe amygdala appears to play a role in binge drinking, being damaged by repeated episodes of intoxication and withdrawal.\n\nProtein kinase C-epsilon in the amygdala is important for regulating behavioral responses to morphine, ethanol, and controlling anxiety-like behavior.\n\nThe protein is involved in controlling the function of other proteins and plays a role in development of the ability to consume a large amount of ethanol.\n\nThe duration of chronic alcohol consumption and abstinence may affect dynamic brain network adaptations.\n\nWhen excessive drinking occurs, the amygdala is affected through behavioral changes and reduces the brains plasticity.\n\nBrain plasticity is how our brain grows and develops; it is also how our neurons can make connections with other neurons.\n\nThis ultimately increases our neural pathways allowing us to increase our knowledge of the world around us.\n\nWhen our brain plasticity decreases it makes it difficult for neurons to make connections to other neurons.\n\nOften when binge drinking, or alcoholism occurs, our amygdala is affected and leads to behavior damage.\n\nThese behavioral damages can be lack of control, inability to conduct oneself in a mature manner, aggressive behavior, loss of conduct, anxiety, depression, personality disorders, excessive drug intake, bi-polar disorder, confusion, higher tolerance levels, irritability, and inappropriate sexual behaviors with others and self.\n\n=== Anxiety ===\n\nThere may also be a link between the amygdala and anxiety.\n\nIn particular, there is a higher prevalence of females that are affected by anxiety disorders.\n\nIn an experiment, degu pups were removed from their mother but allowed to hear her call.\n\nIn response, the males produced increased serotonin receptors in the amygdala but females lost them.\n\nThis led to the males being less affected by the stressful situation.\nThe clusters of the amygdala are activated when an individual expresses feelings of fear or aggression.\n\nThis occurs because the amygdala is the primary structure of the brain responsible for fight or flight response.\n\nAnxiety and panic attacks can occur when the amygdala senses environmental stressors that stimulate fight or flight response.\n\nThe amygdala is directly associated with conditioned fear.\n\nConditioned fear is the framework used to explain the behavior produced when an originally neutral stimulus is consistently paired with a stimulus that evokes fear.\n\nThe amygdala represents a core fear system in the human body, which is involved in the expression of conditioned fear.\n\nFear is measured by changes in autonomic activity including increased heart rate, increased blood pressure, as well as in simple reflexes such as flinching or blinking.\nThe central nucleus of the amygdala has direct correlations to the hypothalamus and brainstem – areas directly related to fear and anxiety.\n\nThis connection is evident from studies of animals that have undergone amygdalae removal.\n\nSuch studies suggest that animals lacking an amygdala have less fear expression and indulge in non-species-like behavior.\n\nMany projection areas of the amygdala are critically involved in specific signs that are used to measure fear and anxiety.\nMammals have very similar ways of processing and responding to danger.\n\nScientists have observed similar areas in the brain – specifically in the amygdala – lighting up or becoming more active when a mammal is threatened or beginning to experience anxiety.\n\nSimilar parts of the brain are activated when rodents and when humans observe a dangerous situation, the amygdala playing a crucial role in this assessment.\n\nBy observing the amygdalae's functions, it can determined why one rodent may be much more anxious than another.\n\nThere is a direct relationship between the activation of the amygdala and the level of anxiety the subject feels.\nFeelings of anxiety start with a catalyst – an environmental stimulus that provokes stress.\n\nThis can include various smells, sights, and internal sensations that result in anxiety.\n\nThe amygdala reacts to this stimuli by preparing to either stand and fight or to turn and run.\n\nThis response is triggered by the release of adrenaline into the bloodstream.\n\nConsequently, blood sugar rises, becoming immediately available to the muscles for quick energy.\n\nShaking may occur in an attempt to return blood to the rest of the body.\n\nApart from initiation of stress, long-term changes in amygdala neurons may also increase anxiety after long-term or traumatic stress, led by the action of stress-related hormones within the amygdala.\n\nOn the flip side, blocking the action of stress hormones in the amygdala reduces anxiety.\n\nA better understanding of the amygdala and its various functions may lead to a new way of treating clinical anxiety.\n\n=== Posttraumatic stress disorder ===\n\nThere seems to be a connection with the amygdalae and how the brain processes posttraumatic stress disorder.\n\nMultiple studies have found that the amygdalae may be responsible for the emotional reactions of PTSD patients.\n\nOne study in particular found that when PTSD patients are shown pictures of faces with fearful expressions, their amygdalae tended to have a higher activation than someone without PTSD.\n\n=== Bipolar disorder ===\n\nAmygdala dysfunction during face emotion processing is well-documented in bipolar disorder.\n\nIndividuals with bipolar disorder showed greater amygdala activity (especially the amygdala/medial-prefrontal-cortex circuit).\n\n=== Political orientation ===\n\nAmygdala size has been correlated with cognitive styles with regard to political thinking.\n\nA study found that \"greater liberalism was associated with increased gray matter volume in the anterior cingulate cortex, whereas greater conservatism was associated with increased volume of the right amygdala.\" These findings suggest that the volume of the amygdala and anterior cingulate gyrus may be associated with an individual's ability to tolerate uncertainty and conflict.\n\nhttps://en.wikipedia.org/wiki/Amygdala","septal-nuclei":"The septal area (medial olfactory area), consisting of the lateral septum and medial septum, is an area in the lower, posterior part of the medial surface of the frontal lobe, and refers to the nearby septum pellucidum.\n\nThe septal nuclei are located in this area.\n\nThe septal nuclei are composed of medium-size neurons which are classified into dorsal, ventral, medial, and caudal groups.\n\nThe septal nuclei receive reciprocal connections from the olfactory bulb, hippocampus, amygdala, hypothalamus, midbrain, habenula, cingulate gyrus, and thalamus.\n\nThe septal nuclei are essential in generating the theta rhythm of the hippocampus.\n\nThe septal area (medial olfactory area) has no relation to the sense of smell, but it is considered a pleasure zone in animals.\nThe septal nuclei play a role in reward and reinforcement along with the nucleus accumbens.\n\nIn the 1950s, Olds & Milner showed that rats with electrodes implanted in this area will self-stimulate repeatedly (i.e., press a bar to receive electric current that stimulate the neurons).\n\nExperiments on the septal area of humans have taken place since the 1960s.\n\n== Connections ==\n\nThe septal area is located on the lower posterior part of the frontal lobe.\n\nThe septal area refers to the nearby septum pellucidum.\n\nIt is located underneath the corpus callosum and in front of the lamina terminalis.\n\nThe lamina terminalis is a layer of gray matter that connects the optic chiasma and the anterior commissure.\n\nThe septal nuclei are in the septal area, and are essential\nin generating the theta rhythm of the hippocampus.\n\nThe dorsal septum projects to the lateral preoptic area, lateral hypothalamus, periventricular hypothalamus and midline thalamus.\n\nFibers from the ventral half of the septum project topographically to the hippocampal formation, thalamus, hypothalamus and midbrain.\n\nSpecifically, neurons located along the midline in the vertical limb of the diagonal band of Broca project through the dorsal fornix to all CA fields of the dorsal hippocampus and adjacent subicular cortex.\n\nOther fibers from this region project through the stria medullaris to the medial and lateral habenular nuclei, the paratenial and anteromedial nucleus of the thalamus, and through the medial forebrain bundle to the pars posterior of the medial mammillary nucleus.\n\nCells located in the intermediolateral septum also project through the lateral part of the fimbria to all CA fields of the ventral hippocampus and adjacent subicular and entorhinal cortices.\n\nThese cells also send fibers through the stria medullaris to the lateral habenular nucleus and mediodorsal thalamic nucleus.\n\nOther axons arising from these cells descend through the medial forebrain bundle to terminate in a region dorsal to the interpeduncular nucleus.\n\nThe lateral septum is a relay center for connections from the CA3 of the hippocampus to the ventral tegmental area.\n\nThese connections help link reward signals with the context in which they occur.Fibers from the most lateral part of the ventral septum (i.e., bed nucleus of the anterior commissure) project through the stria terminalis to the ventral subiculum.\n\nIn addition, cells located in the horizontal limb of the diagonal band project massively to the pars posterior of the medial mammillary nucleus, the ventral tegmental area, and amygdala.\n\n== Functions of the lateral septum ==\n\n=== The lateral septum and movement and reward ===\n\nThe lateral septum is involved in a variety of functions, including emotional, motivational, and spatial behavior.\n\nIt has been suggested that the LS may regulate interactions between the hippocampus and other regions that mediate goal directed behavior, such as the ventral tegmental area.\n\nFiring of LS neurons is modulated by both speed and acceleration and spatial location, and that firing is also related to reward and context.\n\nIt has thus been suggested that the lateral septum may incorporate movement into the evaluation of environmental context with respect to motivation and reward.\n\n=== Lateral septum and social behavior ===\n\nInhibitory GABA, and excitatory glutamate, which regulate lateral septum (LS) activity, have been found to be increased during social play in juvenile rats.\n\nNo sex differences were found in extracellular GABA concentrations during social playing, however, glutamate plays a major role in female social playing.\n\nWhen glutamate receptors are blocked in the LS pharmacologically, there is a significant decrease in female social playing, while males had no decrease in playing.\n\nThis suggests that in the lateral septum, GABA neurotransmission is involved in social play behavior regulation in both sexes, while glutamate neurotransmission is sex-specific, involved in regulation of social play only in female juvenile rats.\n\nhttps://en.wikipedia.org/wiki/Septal_area","caudate-nucleus":"The caudate nucleus is one of the structures that make up the corpus striatum, which is a component of the basal ganglia.\n\nWhile the caudate nucleus has long been associated with motor processes due to its role in Parkinson's disease, it plays important roles in various other nonmotor functions as well, including procedural learning, associative learning and inhibitory control of action, among other functions.\n\nThe caudate is also one of the brain structures which compose the reward system and functions as part of the cortico–basal ganglia–thalamic loop.\n\n== Structure ==\n\nTogether with the putamen, the caudate forms the dorsal striatum, which is considered a single functional structure; anatomically, it is separated by a large white matter tract, the internal capsule, so it is sometimes also referred to as two structures: the medial dorsal striatum (the caudate) and the lateral dorsal striatum (the putamen).\n\nIn this vein, the two are functionally distinct not as a result of structural differences, but merely due to the topographical distribution of function.\nThe caudate nuclei are located near the center of the brain, sitting astride the thalamus.\n\nThere is a caudate nucleus within each hemisphere of the brain.\n\nIndividually, they resemble a C-shape structure with a wider \"head\" (caput in Latin) at the front, tapering to a \"body\" (corpus) and a \"tail\" (cauda).\n\nSometimes a part of the caudate nucleus is referred to as the \"knee\" (genu).\n\nThe caudate head receives its blood supply from the lenticulostriate artery while the tail of the caudate receives its blood supply from the anterior choroidal artery.\n\nThe head and body of the caudate nucleus form part of the floor of the anterior horn of the lateral ventricle.\n\nAfter the body travels briefly towards the back of the head, the tail curves back toward the anterior, forming the roof of the inferior horn of the lateral ventricle.\n\nThis means that a coronal (on a plane parallel to the face) section that cuts through the tail will also cross the body and head of the caudate nucleus.\n\n=== Neurochemistry ===\n\nThe caudate is highly innervated by dopaminergic neurons that originate from the substantia nigra pars compacta (SNc).\n\nThe SNc is located in the midbrain and contains cell projections to the caudate and putamen, utilizing the neurotransmitter dopamine.\n\nThere are also additional inputs from various association cortices.\n\n== Motor functions ==\n\n=== Spatial mnemonic processing ===\n\nThe caudate nucleus integrates spatial information with motor behavior formulation.\n\nSelective impairment of spatial working memory in subjects with Parkinson's disease and the knowledge of the disease's impact on the amount of dopamine supplied to the striatum have linked the caudate nucleus to spatial and nonspatial mnemonic processing.\n\nSpatially dependent motor preparation has been linked to the caudate nucleus through event-related fMRI analysis techniques.\n\nActivity in the caudate nucleus was demonstrated to be greater during tasks featuring spatial and motoric memory demands than those that involved nonspatial tasks.\nSpecifically, spatial working memory activity has been observed, via fMRI studies of delayed recognition, to be greater in the caudate nucleus when the activity immediately preceded a motor response.\n\nThese results indicate that the caudate nucleus could be involved in coding a motor response.\n\nWith this in mind, the caudate nucleus could be involved in the recruitment of the motor system to support working memory performance by the mediation of sensory-motor transformations.\n\n=== Directed movements ===\n\nThe caudate nucleus contributes importantly to body and limbs posture and the speed and accuracy of directed movements.\n\nDeficits in posture and accuracy during paw usage tasks were observed following the removal of caudate nuclei in felines.\n\nA delay in initiating performance and the need to constantly shift body position were both observed in cats following partial removal of the nuclei.Following the application of cocaine to the caudate nucleus and the resulting lesions produced, a \"leaping or forward movement\" was observed in monkeys.\n\nDue to its association with damage to the caudate, this movement demonstrates the inhibitory nature of the caudate nucleus.\n\nThe \"motor release\" observed as a result of this procedure indicates that the caudate nucleus inhibits the tendency for an animal to move forward without resistance.\n\n== Cognitive functions ==\n\n=== Goal-directed action ===\n\nA review of neuroimaging studies, anatomical studies of caudate connectivity, and behavioral studies reveals a role for the caudate in executive functioning.\n\nA study of Parkinson's patients (see below) may also contribute to a growing body of evidence.\nA two-pronged approach of neuroimaging (including PET and fMRI) and anatomical studies expose a strong relationship between the caudate and cortical areas associated with executive functioning: \"non-invasive measures of anatomical and functional connectivity in humans demonstrate a clear link between the caudate and executive frontal areas.\"Meanwhile, behavioral studies provide another layer to the argument: recent studies suggest that the caudate is fundamental to goal-directed action, that is, \"the selection of behavior based on the changing values of goals and a knowledge of which actions lead to what outcomes.\" One such study presented rats with levers that triggered the release of a cinnamon flavored solution.\n\nAfter the rats learned to press the lever, the researchers changed the value of the outcome (the rats were taught to dislike the flavor either by being given too much of the flavor, or by making the rats ill after drinking the solution) and the effects were observed.\n\nNormal rats pressed the lever less frequently, while rats with lesions in the caudate did not suppress the behavior as effectively.\n\nIn this way, the study demonstrates the link between the caudate and goal-directed behavior; rats with damaged caudate nuclei had difficulty assessing the changing value of the outcome.\n\nIn a 2003-human behavioral study, a similar process was repeated, but the decision this time was whether or not to trust another person when money was at stake.\n\nWhile here the choice was far more complex––the subjects were not simply asked to press a lever, but had to weigh a host of different factors––at the crux of the study was still behavioral selection based on changing values of outcomes.\nIn short, neuroimagery and anatomical studies support the assertion that the caudate plays a role in executive functioning, while behavioral studies deepen our understanding of the ways in which the caudate guides some of our decision-making processes.\n\n=== Memory ===\n\nThe dorsal-prefrontal cortex subcortical loop involving the caudate nucleus has been linked to deficits in working memory, specifically in schizophrenic patients.\n\nFunctional imaging has shown activation of this subcortical loop during working memory tasks in primates and healthy human subjects.\n\nThe caudate may be affiliated with deficits involving working memory from before illness onset as well.\n\nCaudate nucleus volume has been found to be inversely associated with perseverative errors on spatial working memory tasks.The amygdala sends direct projections to the caudate nucleus.\n\nBoth the amygdala and the caudate nucleus have direct and indirect projections to the hippocampus.\n\nThe influence of the amygdala on memory processing in the caudate nucleus has been demonstrated with the finding that lesions involving the connections between these two structures \"block the memory-enhancing effects of oxotremorine infused into the caudate nucleus\".\n\nIn a study involving rats given water-maze training, the caudate nucleus was discovered to enhance memory of visually cued training after amphetamine was infused post-training into the caudate.\n\n=== Learning ===\n\nIn a 2005 study, subjects were asked to learn to categorize visual stimuli by classifying images and receiving feedback on their responses.\n\nActivity associated with successful classification learning (correct categorization) was concentrated to the body and tail of the caudate, while activity associated with feedback processing (the result of incorrect categorization) was concentrated to the head of the caudate.\n\n=== Sleep ===\n\nBilateral lesions in the head of the caudate nucleus in cats were correlated with a decrease in the duration of deep slow wave sleep during the sleep-wakefulness cycle.\n\nWith a decrease in total volume of deep slow wave sleep, the transition of short-term memory to long-term memory may also be affected negatively.\nHowever, the effects of caudate nuclei removal on the sleep-wakefulness pattern of cats have not been permanent.\n\nNormalization has been discovered after a period of three months following caudate nuclei ablation.\n\nThis discovery could be due to the inter-related nature of the roles of the caudate nucleus and the frontal cortex in controlling levels of central nervous system activation.\n\nThe cats with caudate removal, although permanently hyperactive, had a significant decrease in rapid eye movement sleep (REMS) time that only lasted for about two months.\n\nHowever, afrontal cats had a permanent decrease in REMS time and only a temporary period of hyperactivity.Contrasting with associations between \"deep\", REM sleep and the caudate nucleus, a study involving EEG and fMRI measures during human sleep cycles has indicated that the caudate nucleus demonstrates reduced activity during non-REM sleep across all sleep stages.\n\nAdditionally, studies of human caudate nuclei volume in congenital central hypoventilation syndrome (CCHS) subjects established a correlation between CCHS and a significant reduction in left and right caudate volume.\n\nCCHS is a genetic disorder that affects the sleep cycle due to a reduced drive to breathe.\n\nTherefore, the caudate nucleus has been suggested to play a role in human sleep cycles.\n\n=== Emotion ===\n\nThe caudate nucleus has been implicated in responses to visual beauty, and has been suggested as one of the \"neural correlates of romantic love\".Approach-attachment behavior and affect are also controlled by the caudate nucleus.\n\nCats with bilateral removal of the caudate nuclei persistently approached and followed objects, attempting to contact the target, while exhibiting a friendly disposition by the elicitation of treading of the forelimbs and purring.\n\nThe magnitude of the behavioral responses was correlated to the extent of the removal of the nuclei.\n\nReports of human patients with selective damage to the caudate nucleus show unilateral caudate damage resulting in loss of drive, obsessive-compulsive disorder, stimulus-bound perseverative behavior, and hyperactivity.\n\nMost of these deficits can be classified as relating to approach-attachment behaviors, from approaching a target to romantic love.\n\n=== Language ===\n\nNeuroimaging studies reveal that people who can communicate in multiple languages activate exactly the same brain regions regardless of the language.\n\nA 2006 publication studies this phenomenon and identifies the caudate as a center for language control.\n\nIn perhaps the most illustrative case, a trilingual subject with a lesion to the caudate was observed.\n\nThe patient maintained language comprehension in her three languages, but when asked to produce language, she involuntarily switched between the three languages.\n\nIn short, \"these and other findings with bilingual patients suggest that the left caudate is required to monitor and control lexical and language alternatives in production tasks.\"Local shape deformations of the medial surface of the caudate have been correlated with verbal learning capacity for females and the number of perseverance errors on spatial and verbal fluency working memory tasks for males.\n\nSpecifically, a larger caudate nucleus volume has been linked with better verbal fluency performance.A neurological study of glossolalia showed a significant reduction in activity in the left caudate nucleus during glossolalia compared to singing in English.\n\n=== Threshold control ===\n\nThe brain contains large collections of neurons reciprocally connected by excitatory synapses, thus forming large network of elements with positive feedback.\n\nIt is difficult to see how such a system can operate without some mechanism to prevent explosive activation.\n\nThere is some indirect evidence that the caudate may perform this regulatory role by measuring the general activity of cerebral cortex and controlling the threshold potential.\n\n== Clinical significance ==\n\n=== Alzheimer's disease ===\n\nA 2013 study has suggested a link between Alzheimer's patients and the caudate nucleus.\n\nMRI images were used to estimate the volume of caudate nuclei in patients with Alzheimer's and normal volunteers.\n\nThe study found a \"significant reduction in the caudate volume\" in Alzheimer's patients when compared to the normal volunteers.\n\nWhile the correlation does not indicate causation, the finding may have implications for early diagnosis.\n\n=== Parkinson's disease ===\n\nParkinson's disease is likely the most studied basal ganglia disorder.\n\nPatients with this progressive neurodegenerative disorder often first experience movement related symptoms (the three most common being tremors at rest, muscular rigidity, and akathisia) which are later combined with various cognitive deficiencies, including dementia.\n\nParkinson's disease depletes dopaminergic neurons in the nigrostriatal tract, a dopamine pathway that is connected to the head of the caudate.\n\nAs such, many studies have correlated the loss of dopaminergic neurons that send axons to the caudate nucleus and the degree of dementia in Parkinson's patients.\n\nAnd while a relationship has been drawn between the caudate and Parkinson's motor deficiencies, the caudate has also been associated with Parkinson's concomitant cognitive impairments.\n\nOne review contrasts the performance of patients with Parkinson's and patients that strictly suffered from frontal-lobe damage in the Tower of London test.\n\nThe differences in performance between the two types of patients (in a test that, in short, requires subjects to select appropriate intermediate goals with a larger goal in mind) draws a link between the caudate and goal-directed action.\n\nHowever, the studies are not conclusive.\n\nWhile the caudate has been associated with executive function (see \"Goal-Directed Action\"), it remains \"entirely unclear whether executive deficits in [Parkinson's patients] reflect pre-dominantly their cortical or subcortical damage.\"\n\n=== Huntington's disease ===\n\nIn Huntington's disease, a genetic mutation occurs in the HTT gene which encodes for Htt protein.\n\nThe Htt protein interacts with over 100 other proteins, and appears to have multiple biological functions.\n\nThe behavior of this mutated protein is not completely understood, but it is toxic to certain cell types, particularly in the brain.\n\nEarly damage is most evident in the striatum, but as the disease progresses, other areas of the brain are also more conspicuously affected.\n\nEarly symptoms are attributable to functions of the striatum and its cortical connections—namely control over movement, mood and higher cognitive function.\n\n=== Attention-deficit hyperactivity disorder ===\n\nA 2002 study draws a relationship between caudate asymmetry and symptoms related to ADHD.\n\nThe authors used MR images to compare the relative volumes of the caudate nuclei (as the caudate is a bilateral structure), and drew a connection between any asymmetries and symptoms of ADHD: \"The degree of caudate asymmetry significantly predicted cumulative severity ratings of inattentive behaviors.\" This correlation is congruent with previous associations of the caudate with attentional functioning.\n\nA more recent 2018 study replicated these findings, and demonstrated that the caudate asymmetries related to ADHD were more pronounced in the dorsal medial regions of the caudate.\n\n=== Schizophrenia ===\n\nThe volume of white matter in the caudate nucleus has been linked with patients diagnosed with Schizophrenia.\n\nA 2004 study uses magnetic resonance imaging to compare the relative volume of white matter in the caudate among Schizophrenia patients.\n\nThose patients who suffer from the disorder have \"smaller absolute and relative volumes of white matter in the caudate nucleus than healthy subjects.\"\n\n=== Bipolar type I ===\n\nA 2014 study found Type I Bipolar patients had relatively higher volume of gray and white matter in the caudate nucleus and other areas associated with reward processing and decision making, compared to controls and Bipolar II subjects.\n\nOverall the amount of gray and white matter in Bipolar patients was lower than controls.\n\n=== Obsessive-compulsive disorder ===\n\nIt has been theorized that the caudate nucleus may be dysfunctional in persons with obsessive compulsive disorder (OCD), in that it may perhaps be unable to properly regulate the transmission of information regarding worrying events or ideas between the thalamus and the orbitofrontal cortex.\nA neuroimaging study with positron emission tomography found that the right caudate nucleus had the largest change in glucose metabolism after patients had been treated with paroxetine.\n\nRecent SDM meta-analyses of voxel-based morphometry studies comparing people with OCD and healthy controls have found people with OCD to have increased grey matter volumes in bilateral lenticular nuclei, extending to the caudate nuclei, while decreased grey matter volumes in bilateral dorsal medial frontal/anterior cingulate gyri.\n\nThese findings contrast with those in people with other anxiety disorders, who evince decreased (rather than increased) grey matter volumes in bilateral lenticular / caudate nuclei, while also decreased grey matter volumes in bilateral dorsal medial frontal/anterior cingulate gyri.\n\nhttps://en.wikipedia.org/wiki/Caudate_nucleus","putamen":"The putamen (; from Latin, meaning \"nutshell\") is a round structure located at the base of the forebrain (telencephalon).\n\nThe putamen and caudate nucleus together form the dorsal striatum.\n\nIt is also one of the structures that compose the basal nuclei.\n\nThrough various pathways, the putamen is connected to the substantia nigra, the globus pallidus, the claustrum, and the thalamus, in addition to many regions of the cerebral cortex.\n\nA primary function of the putamen is to regulate movements at various stages (e.g. preparation and execution) and influence various types of learning.\n\nIt employs GABA, acetylcholine, and enkephalin to perform its functions.\n\nThe putamen also plays a role in degenerative neurological disorders, such as Parkinson's disease.\n\n== History ==\n\nThe word \"putamen\" is from Latin, referring to that which \"falls off in pruning\", from \"putare\", meaning \"to prune, to think, or to consider\".Until recently, most MRI research focused broadly on the basal ganglia as a whole, for various reasons (e.g. image resolution, rarity of isolated infarct or hemorrhage within the putamen, etc.).\n\nHowever, many studies have been done on the basal ganglia and relevant brain-behavior relationships.\n\nIn the 1970s, the first single unit recordings were done with monkeys monitoring pallidal neuron activity related to movement.\n\nSince then, more extensive neuronal tracing, stimulation, and imaging research methods (e.g. fMRI, DWI) that allow for investigation of the putamen have been developed.\n\n== Anatomy ==\n\nThe putamen is a structure in the forebrain.\n\nAlong with the caudate nucleus it forms the dorsal striatum.\n\nThe caudate and putamen contain the same types of neurons and circuits – many neuroanatomists consider the dorsal striatum to be a single structure, divided into two parts by a large fiber tract, the internal capsule, passing through the middle.\n\nThe putamen, together with the globus pallidus, makes up the lentiform nucleus.\n\nThe putamen is the outermost portion of the basal ganglia.\n\nThese are a group of nuclei in the brain that are interconnected with the cerebral cortex, thalamus, and brainstem.\n\nBasal ganglia include the dorsal striatum, substantia nigra, nucleus accumbens, and the subthalamic nucleus.\n\nIn mammals, the basal ganglia are associated with motor control, cognition, emotions, learning, and domain-general functions important for executive functioning as well as support for domain-specific languages.\n\nThe basal ganglia are located bilaterally, and have rostral and caudal divisions.\n\nThe putamen is located in the rostral division as part of the striatum.\n\nThe basal ganglia receive input from the cerebral cortex, via the striatum.\nThe putamen is interconnected with the following structures:\n\nThis description is rudimentary and does not nearly exhaust even the basic established circuitry of the putamen.\n\nThe cortico-subcortico-cortical circuits with putaminal involvement are dense and complicated, consisting of a wide range of axonal, dendritic, chemical, afferent, and efferent substrates.\n\nThe putamen's outputs are highly arborized across output structures, and cortical efferents arise from layers III-VI of the cortex, dependent on gyri and location within the putamen.\n\nTopographical organization of the putamen combines the following elements: anterior-to-posterior functional and somatotopic gradients, lateral-to-medial functional and somatotopic gradients, diffuse terminal output, patchy localized terminal output, segregated terminals from adjacent regions, finely interdigitated terminals from distal cortical regions in a seemingly overlapping fashion.\n\n=== Caudate nucleus ===\n\nThe caudate works with the putamen to receive the input from cerebral cortex.\n\nCollectively, they can be considered the \"entrance\" to the basal ganglia.\n\nProjections from the putamen reach the caudate directly via the caudolenticular grey bridges.\n\nThe putamen and caudate are jointly connected with the substantia nigra, however the caudate outputs more densely to the substantia nigra pars reticulata while the putamen sends more afferents to the internal globus pallidus.\n\n=== Substantia nigra ===\n\nThe substantia nigra contains two parts: the substantia nigra pars compacta (SNpc) and the substantia nigra pars reticulata (SNpr).\n\nThe SNpc obtains input from the putamen and caudate, and sends information back.\n\nThe SNpr also obtains input from the putamen and caudate.\n\nHowever, it sends the input outside the basal ganglia to control head and eye movements.\n\nThe SNpc produces dopamine, which is crucial for movements.\n\nThe SNpc is the part that degenerates during Parkinson's disease.\n\n=== Globus pallidus ===\n\nThe globus pallidus contains two parts: the globus pallidus pars externa (GPe) and the globus pallidus pars interna (GPi).\n\nBoth regions acquire input from the putamen and caudate and communicate with the subthalamic nucleus.\n\nHowever, mostly the GPi sends GABAergic inhibitory output to the thalamus.\n\nThe GPi also sends projections to parts of the midbrain, which have been assumed to affect posture control.\n\n== Physiology ==\n\n=== Types of pathways ===\n\nThe putamen (and striatum in general) has numerous, parallel circuits that allow for cortico-subcortico-cortico communication loops.\n\nThese have been described, broadly, as the direct, indirect, and hyper direct pathways.\n\nGABAergic projections of the putamen have an inhibitory effect on the thalamus.\n\nThalamic projections from the centromedian and parafascicular nuclei have an excitatory effect on the putamen.\n\nUnlike the thalamus, which has broad reciprocal connectivity, cortical projections with the putamen are afferent, thus sending information as opposed to receiving it.\n\nCortical communication is accomplished via multi-fiber pathways as outlined previously (i.e. via other subcortical structures).\n\n=== Dopamine ===\n\nDopamine is a neurotransmitter that has a dominant role in the putamen, most of it is supplied from the substantia nigra.\n\nWhen a cell body of a neuron (in the putamen or caudate nuclei) fires an action potential, dopamine is released from the presynaptic terminal.\n\nSince projections from the putamen and caudate nuclei modulate the dendrites of the substantia nigra, the dopamine influences the substantia nigra, which affects motor planning.\n\nThis same mechanism is involved in drug addiction.\n\nIn order to control the amount of dopamine in the synaptic cleft, and the amount of dopamine binding to post synaptic terminals, presynaptic dopaminergic neurons function to reuptake the excess dopamine.\n\n=== Other neurotransmitters ===\n\nThe putamen also plays a role in modulation of other neurotransmitters.\n\nIt releases GABA, enkephalin, substance P, and acetylcholine.\n\nIt receives serotonin and glutamate.\n\n== Function: motor skills ==\n\nThe putamen is interconnected with many other structures, and works in conjunction with them to influence many types of motor behaviors.\n\nThese include motor planning, learning, and execution, motor preparation, specifying amplitudes of movement, and movement sequences.\n\nSome neurologists hypothesize that the putamen also plays a role in the selection of movement (e.g.\n\nTourette syndrome) and the \"automatic\" performance of previously learned movements (e.g.\n\nParkinson's disease).In one study it was found that the putamen controls limb movement.\n\nThe goal of this study was to determine whether particular cell activity in the putamen of primates was related to the direction of limb movement or to the underlying pattern of muscular activity.\n\nTwo monkeys were trained to perform tasks that involved the movement of loads.\n\nThe tasks were created so that movement could be distinguished from muscle activity.\n\nNeurons in the putamen were selected for monitoring only if they were related both to the task and to arm movements outside the task.\n\nIt was shown that 50% of the neurons that were monitored were related to the direction of movement, independent of the load.\n\nAnother study was done to investigate movement extent and speed using PET mapping of regional cerebral blood flow in 13 humans.\n\nMovement tasks were performed with a joystick-controlled cursor.\n\nStatistical tests were done to calculate the extent of movements and what regions of the brain the movements correlate to.\n\nIt was found that \"increasing movement extent was associated with parallel increases of rCBF in bilateral basal ganglia (BG; putamen and globus pallidus) and ipsilateral cerebellum.\n\n\" This not only shows that the putamen affects movement but it also shows that the putamen integrates with other structures in order to perform tasks.One study was done in order to specifically investigate how the basal ganglia influences the learning of sequential movements.\n\nTwo monkeys were trained to press a series of buttons in sequence.\n\nThe methods used were designed to be able to monitor the well-learned tasks versus the new tasks.\n\nMuscimol was injected into various parts of the basal ganglia, and it was found that \"the learning of new sequences became deficient after injections in the anterior caudate and putamen, but not the middle-posterior putamen\".\n\nThis shows that different areas of the striatum are utilized when performing various aspects of the learning of sequential movements.\n\n== Role in learning ==\n\nIn many studies, it has become apparent that the putamen plays a role in many types of learning.\n\nSome examples are listed below:\n\n=== Reinforcement and implicit learning ===\n\nAlong with various types of movement, the putamen also affects reinforcement learning and implicit learning.Reinforcement learning is interacting with the environment and catering actions to maximize the outcome.\n\nImplicit learning is a passive process where people are exposed to information and acquire knowledge through exposure.\n\nAlthough the exact mechanisms are not known, it is clear that dopamine and tonically active neurons play a key role here.\n\nTonically active neurons are cholinergic interneurons that fire during the entire duration of the stimulus and fire at about 0.5–3 impulses per second.\n\nPhasic neurons are the opposite and only fire an action potential when movement occurs.\n\n=== Category learning ===\n\nOne particular study used patients with focal lesions on the basal ganglia (specifically the putamen) due to stroke in order to study category learning.\n\nThe advantage to using these types of patients is that dopaminergic projections to the prefrontal cortex are more likely to be intact.\n\nAlso, in these patients, it is easier to relate specific brain structures to function because the lesion only occurs in a specific place.\n\nThe goal of this study was to determine whether or not these lesions affect rule-based and information-integration task learning.\n\nRule-based tasks are learned via hypothesis-testing dependent on working memory.\n\nInformation-integration tasks are ones wherein the accuracy is maximized when information from two sources are integrated at a pre-decisional stage, which follows a procedural-based system.\n\nSeven participants with basal ganglia lesions were used in the experiment, along with nine control participants.\n\nIt is important to note that the caudate was not affected.\n\nThe participants were tested for each type of learning during separate sessions, so the information processes would not interfere with each other.\n\nDuring each session, participants sat in front of a computer screen and various lines were displayed.\n\nThese lines were created by using a randomization technique where random samples were taken from one of four categories.\n\nFor ruled-based testing, these samples were used to construct lines of various length and orientation that fell into these four separate categories.\n\nAfter the stimulus was displayed, the subjects were asked to press 1 of 4 buttons to indicate which category the line fell into.\n\nThe same process was repeated for information-integration tasks, and the same stimuli were used, except that the category boundaries were rotated 45°.\n\nThis rotation causes the subject to integrate the quantitative information about the line before determining what category it is in.\n\nIt was found that subjects in the experimental group were impaired while performing rule-based tasks, but not information-integration ones.\n\nAfter statistical testing, it was also hypothesized that the brain began using information-integration techniques to solve the rule-based learning tasks.\n\nSince rule-based tasks use the hypothesis-testing system of the brain, it can be concluded that the hypothesis-testing system of the brain was damaged/weakened.\n\nIt is known that the caudate and working memories are part of this system.\n\nTherefore, it was confirmed that the putamen is involved in category learning, competition between the systems, feed-back processing in rule-based tasks, and is involved in the processing of pre-frontal regions (which relate to working memory and executive functioning).\n\nNow it is known that not only the basal ganglia and caudate affect category learning.\n\n== Role in \"hate circuit\" ==\n\nTentative studies have suggested that the putamen may play a role in the so-called \"hate circuit\" of the brain.\n\nA recent study was done in London by the department of cell and developmental biology at University College London.\n\nAn fMRI was done on patients while they viewed a picture of people they hated and people who were \"neutral\".\n\nDuring the experiment, a \"hate score\" was recorded for each picture.\n\nThe activity in sub-cortical areas of the brain implied that the \"hate circuit\" involves the putamen and the insula.\n\nIt has been theorized that the \"putamen plays a role in the perception of contempt and disgust, and may be part of the motor system that's mobilized to take action.\"\n\nIt was also found that the amount of activity in the hate circuit correlates with the amount of hate a person declares, which could have legal implications concerning malicious crimes.\n\n== Role in transgender individuals ==\n\nThe putamen was found to have significantly larger amounts of grey matter in male to female transgender individuals compared to the putamen of a typical cisgender man.\n\nThis possibly suggests that a fundamental difference in brain composition may or may not exist between trans women and cisgender men.\n\n== Pathology ==\n\n=== Parkinson's disease ===\n\nAfter discovering the function of the putamen, it has become apparent to neurologists that the putamen and other parts of the basal ganglia play an important role in Parkinson's disease and other diseases that involve the degeneration of neurons.Parkinson's disease is the slow and steady loss of dopaminergic neurons in substantia nigra pars compacta.\n\nIn Parkinson's disease the putamen plays a key role because its inputs and outputs are interconnected to the substantia nigra and the globus pallidus.\n\nIn Parkinson's disease the activity in direct pathways to interior globus pallidus decreases and activity in indirect pathways to external globus pallidus increases.\n\nIt has also been noted that Parkinson's patients have a difficult time with motor planning.\n\n=== Other diseases and disorders ===\n\nThe following diseases and disorders are linked with the putamen:\n\nCognitive decline in Alzheimer's disease\nHuntington's disease\nWilson's disease\nDementia with Lewy bodies\nCorticobasal degeneration\nTourette syndrome\nSchizophrenia\nDepression\nAttention deficit hyperactivity disorder\nChorea\nObsessive-Compulsive Disorder\nKernicterus\nOther anxiety disorders\n\n== In other animals ==\n\nThe putamen in humans is relatively similar in structure and function to other animals.\n\nTherefore, many studies on the putamen have been done on animals (monkeys, rats, cats, etc.), as well as humans.\n\nHowever, inter-species variation are indeed observed in mammals, and have been documented for white matter putaminal connectivity.\n\nVariation is primarily related to structural connectivity patterns, while somatotopic organization principles are retained.\n\nPrimate research since the 1980s through to the present has established that cortical regions relation to higher-order cognition primarily send afferent neurons to the rostal-most portion of the putamen, while the remainder of this structure in primates primarily serves sensori-motor functions and is densely interconnected with primary and supplementary motor regions.\n\nhttps://en.wikipedia.org/wiki/Putamen","corpus-callosum":"The corpus callosum (Latin for \"tough body\"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain.\n\nThe corpus callosum is only found in placental mammals.\n\nIt spans part of the longitudinal fissure, connecting the left and right cerebral hemispheres, enabling communication between them.\n\nIt is the largest white matter structure in the human brain, about ten centimetres in length and consisting of 200–300 million axonal projections.\n\nA number of separate nerve tracts, classed as subregions of the corpus callosum, connect different parts of the hemispheres.\n\nThe main ones are known as the genu, the rostrum, the trunk or body, and the splenium.\n\n== Structure ==\n\nThe corpus callosum forms the floor of the longitudinal fissure that separates the two cerebral hemispheres.\n\nPart of the corpus callosum forms the roof of the lateral ventricles.The corpus callosum has four main parts; individual nerve tracts that connect different parts of the hemispheres.\n\nThese are the rostrum, the genu, the trunk or body, and the splenium.\n\nA narrowed part between the trunk and the splenium is known as the isthmus.\n\nFibres from the trunk and the splenium known together as the tapetum form the roof of each lateral ventricle.\n\nThe front part of the corpus callosum, towards the frontal lobes is called the genu (\"knee\").\n\nThe genu curves downward and backward in front of the septum pellucidum, diminishing greatly in thickness.\n\nThe lower much thinner part is the rostrum and is connected below with the lamina terminalis, which stretches from the interventricular foramina to the recess at the base of the optic stalk.\n\nThe rostrum is named for its resemblance to a bird's beak.\nThe end part of the corpus callosum, towards the cerebellum, is called the splenium.\n\nThis is the thickest part, and overlaps the tela choroidea of the third ventricle and the midbrain, and ends in a thick, convex, free border.\n\nSplenium translates as bandage in Greek.\nThe trunk of the corpus callosum lies between the splenium and the genu.\n\nThe callosal sulcus separates the corpus callosum from the cingulate gyrus.\n\n=== Relations ===\n\nOn either side of the corpus callosum, the fibers radiate in the white matter and pass to the various parts of the cerebral cortex; those curving forward from the genu into the frontal lobes constitute the forceps minor (also forceps anterior) and those curving backward from the splenium into the occipital lobes, the forceps major (also forceps posterior).\n\nBetween these two parts is the main body of the fibers which constitute the tapetum and extend laterally on either side into the temporal lobe, and cover in the central part of the lateral ventricle.\n\nThe tapetum and anterior commissure share the function of connecting left and right temporal lobes.\n\nThe anterior cerebral arteries are in contact with the under surface of the rostrum, they arch over the front of the genu and are carried along the trunk, supplying the front four-fifths of the corpus callosum.\n\n=== Neuronal fibers ===\n\nThe size, amount of myelination, and density of the fibers in the subregions relate to the functions of the brain regions they connect.\n\nMyelination is the process of coating neurons with myelin, which helps the transfer of information between neurons.\n\nThe process is believed to occur until an individual's thirties with peak growth in the first decade of one’s life.\n\nThinner, lightly myelinated fibers are slower conducting and they connect the association and prefrontal areas.\n\nThicker and fast-conducting fibers connect the visual and motor areas.\n\nThe tractogram pictured shows the nerve tracts from six segments of the corpus callosum, providing linking of the cortical regions between the cerebral hemispheres.\n\nThose of the genu are shown in coral, of the premotor – green, of the sensory-motor – purple, of the parietal – pink, of the temporal – yellow, and of the splenium – blue.Thinner axons in the genu connect the prefrontal cortex between the two halves of the brain; these fibers arise from a fork-like bundle of fibers from the tapetum, the forceps minor.\n\nThicker axons in the trunk of the corpus callosum, interconnect areas of the motor cortex, with proportionately more of the corpus callosum dedicated to supplementary motor regions including Broca's area.\n\nThe splenium, communicates somatosensory information between the two halves of the parietal lobe and the visual cortex at the occipital lobe, these are the fibers of the forceps major.\n\nIn a study of five- to eighteen-year-olds there was found to be a positive correlation between age and callosal thickness.\n\n=== Variation between sexes ===\n\nThe corpus callosum and its relation to sex has been a subject of debate in the scientific and lay communities for over a century.\n\nInitial research in the early 20th century claimed the corpus to be different in size between men and women.\n\nThat research was in turn questioned, and ultimately gave way to more advanced imaging techniques that appeared to refute earlier correlations.\n\nHowever, advanced analytical techniques of computational neuroanatomy developed in the 1990s showed that sex differences were clear but confined to certain parts of the corpus callosum, and that they correlated with cognitive performance in certain tests.\n\nAn MRI study found that the midsagittal corpus callosum cross-sectional area is, after controlling for brain size, on average, proportionately larger in females.Using diffusion tensor sequences on MRI machines, the rate at which molecules diffuse in and out of a specific area of tissue, anisotropy can be measured and used as an indirect measurement of anatomical connection strength.\n\nThese sequences have found consistent sex differences in human corpus callosal shape and microstructure.\n\nAnalysis by shape and size has also been used to study specific three-dimensional mathematical relationships with MRIs, and have found consistent and statistically significant differences across sexes.\n\nSpecific algorithms have found significant differences between the two sexes in over 70% of cases in one review.\n\nA 2005 study on the sizes and structures of the corpus callosum in transgender people found it to be structurally more in line with their declared gender than their assigned sex.\n\n== Correlates of size with handedness ==\n\nOne study reported that the front portion of the human corpus callosum was 0.75 cm2 or 11% larger in left-handed and ambidextrous people than right-handed people.\n\nThis difference was evident in the anterior and posterior regions of the corpus callosum, but not in the splenium.\n\nHowever, this has been challenged and others have instead suggested that the degree of handedness negatively correlates with the size of the corpus callosum, meaning that individuals who are capable of using both hands with dexterity would have the largest corpus callosum and vice versa for either left or right hand.\n\n== Clinical significance ==\n\n=== Epilepsy ===\n\nThe symptoms of refractory (difficult to treat) epilepsy can be reduced by cutting through the corpus callosum in an operation known as a corpus callosotomy lobotomy paralysis.\n\nThis is usually reserved for cases in which complex or grand mal seizures are produced by an epileptogenic focus on one side of the brain, causing an interhemispheric electrical storm.\n\nThe diagnostic work up for this procedure involves an electroencephalogram, MRI, PET scan, and evaluation by a neurologist, neurosurgeon, psychiatrist, and neuroradiologist before a partial lobotomy surgery can be considered.\n\n=== Failure to develop ===\n\nThe formation of the corpus callosum begins with the first midline crossing of pioneer axons around week 12 in the prenatal development of the human, or day 15 in the embryogenesis of the mouse.\n\nAgenesis of the corpus callosum (ACC) is a rare congenital disorder that is one of the most common brain malformations observed in human beings, in which the corpus callosum is partially or completely absent.\n\nACC is usually diagnosed within the first two years of life, and may manifest as a severe syndrome in infancy or childhood, as a milder condition in young adults, or as an asymptomatic incidental finding.\n\nInitial symptoms of ACC usually include seizures, which may be followed by feeding problems and delays in holding the head erect, sitting, standing, and walking.\n\nOther possible symptoms may include impairments in mental and physical development, hand-eye coordination, and visual and auditory memory.\n\nHydrocephaly may also occur.\n\nIn mild cases, symptoms such as seizures, repetitive speech, or headaches may not appear for years.\n\nSome syndromes that are often associated with ACC are Aicardi syndrome, Andermann syndrome, Shapiro syndrome, and acrocallosal syndrome.\nACC is usually not fatal.\n\nTreatment usually involves management of symptoms, such as hydrocephaly and seizures, if they occur.\n\nAlthough many children with the disorder lead normal lives and have average intelligence, careful neuropsychological testing reveals subtle differences in higher cortical function compared to individuals of the same age and education without ACC.\n\nChildren with ACC accompanied by developmental delay and/or seizure disorders should be screened for metabolic disorders.\n\nIn addition to agenesis of the corpus callosum, similar conditions are hypogenesis (partial formation), dysgenesis (malformation), and hypoplasia (underdevelopment, including too thin).\n\nOther studies have also linked possible correlations between corpus callosum malformation and autism spectrum disorders.Kim Peek, a savant and the inspiration behind the movie Rain Man, was found with agenesis of the corpus callosum, as part of FG syndrome.\n\n=== Other disease ===\n\nAnterior corpus callosum lesions may result in akinetic mutism or anomic aphasia.\nSee also:\n\nAlien hand syndrome\nDyslexia without agraphia (seen with damage to splenium of corpus callosum)\nMarchiafava–Bignami disease a degenerative disease characterised by loss of myelin and necrosis of the corpus callosum\nMultiple sclerosis with the Dawson's fingers sign\nReversible splenial lesion syndrome – a rare encephalopathy of unknown origin with a transient lesion in the splenium, mostly associated with infectious diseases\nSepto-optic dysplasia (de Morsier syndrome)\nSplit-brain\nSusac's syndrome characterised by lesions as small holes in the corpus callosum\n\n== History ==\n\nThe first study of the corpus with relation to gender was by R.\n\nB.\n\nBean, a Philadelphia anatomist, who suggested in 1906 that \"exceptional size of the corpus callosum may mean exceptional intellectual activity\" and that there were measurable differences between men and women.\n\nPerhaps reflecting the political climate of the times, he went on to claim differences in the size of the callosum across different races.\n\nHis research was ultimately refuted by Franklin Mall, the director of his own laboratory.Of more mainstream impact was a 1982 Science article by Holloway and Utamsing that suggested sex difference in human brain morphology, which related to differences in cognitive ability.\n\nTime published an article in 1992 that suggested that, because the corpus is \"often wider in the brains of women than in those of men, it may allow for greater cross-talk between the hemispheres—possibly the basis for women’s intuition.\"Later publications in the psychology literature have raised doubt as to whether the anatomic size of the corpus is actually different.\n\nA meta-analysis of 49 studies since 1980 found that, contrary to de Lacoste-Utamsing and Holloway, no sex difference could be found in the size of the corpus callosum, whether or not any account was taken of larger male brain size.\n\nA study in 2006 using thin slice MRI showed no difference in thickness of the corpus when accounting for the size of the subject.\n\n== Other animals ==\n\nThe corpus callosum is found only in placental mammals, while it is absent in monotremes and marsupials, as well as other vertebrates such as birds, reptiles, amphibians and fish.\n\n(Other groups do have other brain structures that allow for communication between the two hemispheres, such as the anterior commissure, which serves as the primary mode of interhemispheric communication in marsupials, and which carries all the commissural fibers arising from the neocortex (also known as the neopallium), whereas in placental mammals, the anterior commissure carries only some of these fibers.) In primates, the speed of nerve transmission depends on its degree of myelination, or lipid coating.\n\nThis is reflected by the diameter of the nerve axon.\n\nIn most primates, axonal diameter increases in proportion to brain size to compensate for the increased distance to travel for neural impulse transmission.\n\nThis allows the brain to coordinate sensory and motor impulses.\n\nHowever, the scaling of overall brain size and increased myelination have not occurred between chimpanzees and humans.\n\nThis has resulted in the human corpus callosum's requiring double the time for interhemispheric communication as a macaque's.\n\nThe fibrous bundle at which the corpus callosum appears, can and does increase to such an extent in humans that it encroaches upon and wedges apart the hippocampal structures.\n\nhttps://en.wikipedia.org/wiki/Corpus_callosum","anterior-commissure":"The anterior commissure (also known as the precommissure) is a white matter tract (a bundle of axons) connecting the two temporal lobes of the cerebral hemispheres across the midline, and placed in front of the columns of the fornix.\n\nIn most existing mammals, the great majority of fibers connecting the two hemispheres travel through the corpus callosum, which is over 10 times larger than the anterior commissure, and other routes of communication pass through the hippocampal commissure or, indirectly, via subcortical connections.\n\nNevertheless, the anterior commissure is a significant pathway that can be clearly distinguished in the brains of all mammals.\n\nThe anterior commissure plays a key role in pain sensation, more specifically sharp, acute pain.\n\nIt also contains decussating fibers from the olfactory tracts, vital for the sense of smell and chemoreception.\n\nThe anterior commissure works with the posterior commissure to link the two cerebral hemispheres of the brain and also interconnects the amygdalae and temporal lobes, contributing to the role of memory, emotion, speech and hearing.\n\nIt also is involved in olfaction, instinct, and sexual behavior.\n\nIn a sagittal section, the anterior commissure is oval in shape, having a long vertical axis that measures about 5 mm.\n\n== Structure ==\n\nThe fibers of the anterior commissure can be traced laterally and posteriorly on either side beneath the striatum into the substance of the temporal lobe.\n\nIt serves in this way to connect the two temporal lobes, but it also contains decussating fibers from the olfactory tracts, and is a part of the neospinothalamic tract for pain.\n\nThe anterior commissure also serves to connect the two amygdalae.\n\nThe corpus callosum allows for communication between the two hemispheres and is found only in placental mammals (the eutherians), while it is absent in monotremes and marsupials, as well as other vertebrates such as birds, reptiles, amphibians and fish.\n\nThe anterior commissure serves as the primary mode of interhemispheric communication in marsupials, and which carries all the commissural fibers arising from the neocortex (also known as the neopallium), whereas in placental mammals the anterior commissure carries only some of these fibers).\n\n== Function ==\n\nThe functionality of the anterior commissure is still not completely understood.\n\nResearchers have implicated it in functions ranging from colour perception to attention.\n\nOne such study supported colour perception in callosal agenesis (Those born without a corpus callosum; Barr & Corballis, 2002).\n\nOther studies have built on this to imply that the anterior commissure can be a compensatory pathway in those without a corpus callosum, presenting diffusion tensor imaging (DTI) techniques to better elucidate the anterior commissure and how it might be implicated in various functions (Winter & Franz, 2014).\n\n=== Sexuality ===\n\nIn 1992 Laura Allen and Roger Gorski of UCLA measured the anterior commissures of 30 homosexual men, 30 heterosexual men, and 30 heterosexual women.\n\nThey found that all three groups' commissures were significantly different from one another, with homosexual males having the largest anterior commissure, followed by heterosexual women, and then heterosexual men, who had the smallest anterior commissures.\n\nIn 1993, a review by Byne and Parsons criticized this research, noting that 27 of the 33 homosexual males fell within the range of heterosexual males in the study.\n\nHowever, because range is defined only by the two most extreme data points in a group, the existence of a single heterosexual male with an exceptionally large anterior commissure for his group (an outlier) would cause this large range irrespective of the data from the rest of the individuals in the group.\n\nThis individual's existence would not change the fact that the groups on average were quite different from one another, and that these differences were statistically significant.\n\nA later report by Byne et al. (2001) noted that We also measured the anterior commissure in the same blocks of tissue used for the present hypothalamic study (data not shown) and were unable to replicate a report [by Allen and Gorski] that its cross-sectional area is larger in women than in men.\n\nAlso, a study by Lasco et al. (2002) said:We examined the cross-sectional area of the AC in postmortem material from 120 individuals, and found no variation in the size of the AC with age, HIV status, sex, or sexual orientation.\n\nhttps://en.wikipedia.org/wiki/Anterior_commissure","hippocampal-commissure":"The lateral portions of the body of the fornix are joined by a thin triangular lamina, named the psalterium (lyra).\n\nThis lamina contains some commissural fibers that connect the two hippocampi across the middle line and constitute the commissure of fornix (also called the hippocampal commissure).\n\nThe terminal lamina creates the commissure plate.\n\nThis structure gives existence to the corpus callosum, the septum pellucidum, and the fornix.\n\nThe fornix splits into two columns at the front (anterior pillars), and then splits into two posterior crura.\n\nThese two crura are joined together through the hippocampal commissure.\n\nThe beginning of the splitting is called the psalterium or Lyra Davidis.\n\nThe latter name is used because the structure resembles a lyra (or triangular harp):\n\n The two crura are the \"chassis\" of the lyra, and the commissure connections are the fibers.\n\nhttps://en.wikipedia.org/wiki/Fornix_(neuroanatomy)#Commissure","fornix":"The fornix (meaning \"arch\" in Latin) is a C-shaped bundle of nerve fibers in the brain that acts as the major output tract of the hippocampus.\n\nThe fornix also carries some afferent fibers to the hippocampus from structures in the diencephalon and basal forebrain.\n\nThe fornix is part of the limbic system.\n\nWhile its exact function and importance in the physiology of the brain are still not entirely clear, it has been demonstrated in humans that surgical transection – the cutting of the fornix along its body – can cause memory loss.\n\nThere is some debate over what type of memory is affected by this damage, but it has been found to most closely correlate with recall memory rather than recognition memory.\n\nThis means that damage to the fornix can cause difficulty in recalling long-term information such as details of past events, but it has little effect on the ability to recognize objects or familiar situations.\n\n STRUCTURE\n\nThe fibers begin in the hippocampus on each side of the brain as fimbriae; the separate left and right sides are each called the crus of the fornix (plural crura).\n\nThe bundles of fibers come together in the midline of the brain, forming the body of the fornix.\n\nThe lower edge of the septum pellucidum (the membrane that separates the lateral ventricles) is attached to the upper face of the fornix body.\n\nThe body of the fornix travels anteriorly and divides again near the anterior commissure.\n\nThe left and right parts separate, but there is also an anterior/posterior divergence.\n\n -The posterior fibers (called the postcommissural fornix) of each side continue through the hypothalamus to the mammillary bodies; then to the anterior nuclei of thalamus.\n -The anterior fibers (precommissural fornix) end at the septal nuclei of the basal forebrain and nucleus accumbens of each half of the brain.\n\n COMMISSURE\n\nThe lateral portions of the body of the fornix are joined by a thin triangular lamina, named the psalterium (lyra).\n\nThis lamina contains some commissural fibers that connect the two hippocampi across the middle line and constitute the commissure of fornix (also called the hippocampal commissure).\n\nThe terminal lamina creates the commissure plate.\n\nThis structure gives existence to the corpus callosum, the septum pellucidum, and the fornix.\n\nThe fornix splits into two columns at the front (anterior pillars), and then splits into two posterior crura.\n\nThese two crura are joined together through the hippocampal commissure.\n\nThe beginning of the splitting is called the psalterium or Lyra Davidis.\n\nThe latter name is used because the structure resembles a lyra (or triangular harp): The two crura are the \"chassis\" of the lyra, and the commissure connections are the fibers.\n\n COLUMNS\n\nThe columns (anterior pillars; fornicolumns) of the fornix arch downward in front of the interventricular foramina and behind the anterior commissure, and each descends through the grey matter in the lateral wall of the third ventricle to the base of the brain, where it ends in the mammillary bodies.\n\n CRUS\n\nThe crura (posterior pillars) of the fornix are prolonged backward from the body.\n\nThey are flattened bands, and, at their commencement, are intimately connected with the under surface of the corpus callosum.\n\nDiverging from one another, each curves around the posterior end of the thalamus, and passes downward and forward into the temporal horn of lateral ventricle.\n\nHere, it lies along the concavity of the hippocampus, on the surface of which some of its fibers are spread out to form the alveus, while the remainder is continued as a narrow white band, the fimbria of hippocampus, which is prolonged into the uncus of the parahippocampal gyrus.\n\nhttps://en.wikipedia.org/wiki/Fornix_(neuroanatomy)","stria-terminalis":"The stria terminalis (or terminal stria) is a structure in the brain consisting of a band of fibers running along the lateral margin of the ventricular surface of the thalamus.\n\nServing as a major output pathway of the amygdala, the stria terminalis runs from its centromedial division to the ventromedial nucleus of the hypothalamus.\n\n== Anatomy ==\n\nThe stria terminalis covers the superior thalamostriate vein, marking a line of separation between the thalamus and the caudate nucleus as seen upon gross dissection of the ventricles of the brain, viewed from the superior aspect.\n\nThe stria terminalis extends from the region of the interventricular foramina to the temporal horn of the lateral ventricle, carrying fibers from the amygdala to the septal nuclei, hypothalamic, and thalamic areas of the brain.\n\nIt also carries fibers projecting from these areas back to the amygdala.\n\n== Bed nucleus of the stria terminalis (BNST) ==\n\nThe activity of the bed nucleus of the stria terminalis correlates with anxiety in response to threat monitoring.\n\nIt is thought to act as a relay site within the hypothalamic-pituitary-adrenal axis and regulate its activity in response to acute stress.\n\nHowever, the stress response is time related and the BNST does not activate for contextual fear.\n\nThis means that a sudden scary situation that is under ten minutes long, does not activate the BNST.\n\nIt is also thought to promote behavioral inhibition in response to unfamiliar individuals, by input from the orbitofrontal cortex.\n\nBilateral disruption of this pathway has been shown to attenuate reinstatement of drug seeking behaviour in rodents.\n\nThis nucleus is known to project inhibitory fibers to the lateral hypothalamus and participate in the control of feeding in rodents.\n\nOptogenetic activation of this inhibitory pathway rapidly produced voracious feeding behavior in well-fed mice and optogenetic inhibition of this pathway reduces food intake even in starved animals.\n\n== Sexual dimorphism ==\n\nThe central subdivision of the bed nucleus of the stria terminalis (BSTc) is sexually dimorphic.\n\nOn average, the BSTc is twice as large in men as in women and contains twice the number of somatostatin neurons.\n\nA sample of six post-mortem, long-term hormone replacement therapy (HRT) treated trans women (male-to-female) were found to have a female-typical number of cells in the BSTc, whereas a trans man (female-to-male) was found to have a male-typical number.\n\nThe authors (Jiang-Ning Zhou, Frank PM Kruijver, Dick Swaab) also examined subjects with hormone-related disorders and found no pattern between those disorders and the BSTc while the single untreated male-to-female transsexual had a female-typical number of cells.\n\nThey concluded that the BSTc provides evidence for a neurobiological basis of gender identity and proposed that such was determined before birth.\n\nHormone replacement therapy has been shown to influence hypothalamic size, even though the study tried to do this by including non-transsexual male and female controls which, for a variety of medical reasons, had experienced hormone reversal.\n\nThe statement about the neurobiological basis from birth has later been brought to question, though not refuted, by a follow up study by the same group which found that the sexual dimorphism of the BSTc is not present before adulthood (approximately 22 years of age) even though transsexuals report being aware of their gender identity since childhood.\n\nSince somatostatin-expressing neurons typically block dendritic inputs to the postsynaptic neuron, thus inhibiting signals traveling through associated structures, it is believed that the larger bed nucleus of the stria terminalis found in men (including transgender men) reduce the startle response in men and may be responsible for the higher incidence of specific phobias in women, and a possible source for the stereotype of women being afraid of mice.\n\nOxytocin receptor activity in the BNST is important for social recognition in rats.\n\nBoth male and female rats that received a microinjection of oxytocin receptor antagonist had lower social recognition scores than rats that received a vehicle injection, and microinjections of oxytocin into the BNST enhanced social memory in male, but not female, rats.\n\nReduction of the size of the bed nucleus of the stria terminalis has been observed in pedophilic male perpetrators, in addition to reductions in the right amygdala, hypothalamus and abnormalities in related structures.\n\nThe authors propose that childhood deficits in the BNST and medial amygdala may cause inhibition of sexual maturity.\n\nhttps://en.wikipedia.org/wiki/Stria_terminalis","white-matter-of-telencephalon":"White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts.\n\nLong thought to be passive tissue, white matter affects learning and brain functions, modulating the distribution of action potentials, acting as a relay and coordinating communication between different brain regions.White matter is named for its relatively light appearance resulting from the lipid content of myelin.\n\nHowever, the tissue of the freshly cut brain appears pinkish-white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries.\n\nIts white color in prepared specimens is due to its usual preservation in formaldehyde.\n\n== Structure ==\n\n=== White matter ===\n\nWhite matter is composed of bundles, which connect various grey matter areas (the locations of nerve cell bodies) of the brain to each other, and carry nerve impulses between neurons.\n\nMyelin acts as an insulator, which allows electrical signals to jump, rather than coursing through the axon, increasing the speed of transmission of all nerve signals.\n\nThe total number of long range fibers within a cerebral hemisphere is 2% of the total number of cortico-cortical fibers (across cortical areas) and is roughly the same number as those that communicate between the two hemispheres in the brain's largest white tissue structure, the corpus callosum.\n\nSchüz and Braitenberg note \"As a rough rule, the number of fibres of a certain range of lengths is inversely proportional to their length.\"White matter in nonelderly adults is 1.7–3.6% blood.\n\n=== Grey matter ===\n\nThe other main component of the brain is grey matter (actually pinkish tan due to blood capillaries), which is composed of neurons.\n\nThe substantia nigra is a third colored component found in the brain that appears darker due to higher levels of melanin in dopaminergic neurons than its nearby areas.\n\nNote that white matter can sometimes appear darker than grey matter on a microscope slide because of the type of stain used.\n\nCerebral- and spinal white matter do not contain dendrites, neural cell bodies, or shorter axons, which can only be found in grey matter.\n\n=== Location ===\n\nWhite matter forms the bulk of the deep parts of the brain and the superficial parts of the spinal cord.\n\nAggregates of grey matter such as the basal ganglia (caudate nucleus, putamen, globus pallidus, substantia nigra, subthalamic nucleus, nucleus accumbens) and brainstem nuclei (red nucleus, cranial nerve nuclei) are spread within the cerebral white matter.\n\nThe cerebellum is structured in a similar manner as the cerebrum, with a superficial mantle of cerebellar cortex, deep cerebellar white matter (called the \"arbor vitae\") and aggregates of grey matter surrounded by deep cerebellar white matter (dentate nucleus, globose nucleus, emboliform nucleus, and fastigial nucleus).\n\nThe fluid-filled cerebral ventricles (lateral ventricles, third ventricle, cerebral aqueduct, fourth ventricle) are also located deep within the cerebral white matter.\n\n=== Myelinated axon length ===\n\nMen have more white matter than women both in volume and in length of myelinated axons.\n\nAt the age of 20, the total length of myelinated fibers in men is 176,000 km while that of a woman is 149,000 km.\n\nThere is a decline in total length with age of about 10% each decade such that a man at 80 years of age has 97,200 km and a female 82,000 km.\n\nMost of this reduction is due to the loss of thinner fibers.\n\nHowever, this study only included 36 participants.\n\n== Function ==\n\nWhite matter is the tissue through which messages pass between different areas of grey matter within the central nervous system.\n\nThe white matter is white because of the fatty substance (myelin) that surrounds the nerve fibers (axons).\n\nThis myelin is found in almost all long nerve fibers, and acts as an electrical insulation.\n\nThis is important because it allows the messages to pass quickly from place to place.\n\nUnlike grey matter, which peaks in development in a person's twenties, the white matter continues to develop, and peaks in middle age.\n\n== Research ==\n\nMultiple sclerosis (MS) is the most common of the inflammatory demyelinating diseases of the central nervous system which affect white matter.\n\nIn MS lesions, the myelin sheath around the axons is deteriorated by inflammation.\n\nAlcohol use disorders are associated with a decrease in white matter volume.Amyloid plaques in white matter may be associated with Alzheimer's disease and other neurodegenerative diseases.\n\nOther changes that commonly occur with age include the development of leukoaraiosis, which is a rarefaction of the white matter that can be correlated with a variety of conditions, including loss of myelin pallor, axonal loss, and diminished restrictive function of the blood–brain barrier.\n\nWhite matter lesions on magnetic resonance imaging are linked to several adverse outcomes, such as cognitive impairment and depression.\n\nWhite matter hyperintensity are more than often present with vascular dementia, particularly among small vessel/subcortical subtypes of vascular dementia.\n\n=== Volume ===\n\nSmaller volumes (in terms of group averages) of white matter might be associated with larger deficits in attention, declarative memory, executive functions, intelligence, and academic achievement.\n\nHowever, volume change is continuous throughout one's lifetime due to neuroplasticity, and is a contributing factor rather than determinant factor of certain functional deficits due to compensating effects in other brain regions.\n\nThe integrity of white matter declines due to aging.\n\nNonetheless, regular aerobic exercise appears to either postpone the aging effect or in turn enhance the white matter integrity in the long run.\n\nChanges in white matter volume due to inflammation or injury may be a factor in the severity of obstructive sleep apnea.\n\n== Imaging ==\n\nThe study of white matter has been advanced with the neuroimaging technique called diffusion tensor imaging where magnetic resonance imaging (MRI) brain scanners are used.\n\nAs of 2007, more than 700 publications have been published on the subject.A 2009 paper by Jan Scholz and colleagues used diffusion tensor imaging (DTI) to demonstrate changes in white matter volume as a result of learning a new motor task (e.g. juggling).\n\nThe study is important as the first paper to correlate motor learning with white matter changes.\n\nPreviously, many researchers had considered this type of learning to be exclusively mediated by dendrites, which are not present in white matter.\n\nThe authors suggest that electrical activity in axons may regulate myelination in axons.\n\nOr, gross changes in the diameter or packing density of the axon might cause the change.\n\nA more recent DTI study by Sampaio-Baptista and colleagues reported changes in white matter with motor learning along with increases in myelination.\n\nhttps://en.wikipedia.org/wiki/White_matter","lateral-ventricle":"The lateral ventricles are the two largest ventricles of the brain and contain cerebrospinal fluid (CSF).\n\nEach cerebral hemisphere contains a lateral ventricle, known as the left or right ventricle, respectively.\n\nEach lateral ventricle resembles a C-shaped cavity that begins at an inferior horn in the temporal lobe, travels through a body in the parietal lobe and frontal lobe, and ultimately terminates at the interventricular foramina where each lateral ventricle connects to the single, central third ventricle.\n\nAlong the path, a posterior horn extends backward into the occipital lobe, and an anterior horn extends farther into the frontal lobe.\n\n== Structure ==\n\nEach lateral ventricle takes the form of an elongated curve, with an additional anterior-facing continuation emerging inferiorly from a point near the posterior end of the curve; the junction is known as the trigone of the lateral ventricle.\n\nThe centre of the superior curve is referred to as the body, while the three remaining portions are known as horns (cornua in Latin); they are usually referred to by their position relative to the body (anterior, posterior, or inferior), or sometimes by the lobe of the cerebral cortex into which they extend.\n\nThough somewhat flat, the lateral ventricles have a vaguely triangular cross-section.\n\nEpendyma, which are neuroepithelial cells, line the ventricular system including the lateral ventricles.\n\nBetween the inferior horn and the main body of the ventricle is the putamen, which emerges from the head of the caudate nucleus, and sits above the tapetum; a small number of further connections passing through the occipital tapetum to join the putamen to portions of the caudate nucleus tail adjoining the anterior horn.\n\nBelow the putamen sits the globus pallidus, with which it connects.\n\nThese structures bounding the lateral ventricles form a frame curving around the thalamus, which itself constitutes the main structure bounding the third ventricle.\n\nWere it not for the choroid plexus, a cleft-like opening would be all that lay between the lateral ventricle and the thalamus; this cleft constitutes the lower part of the choroid fissure.\n\nThe thalamus primarily communicates with the structures bounding the lateral ventricles via the globus pallidus, and the anterior extremities of the fornix (the mamillary bodies).\n\n=== Anterior horns of lateral ventricle ===\n\nThe anterior horn of the lateral ventricle is also known as the frontal horn as it extends into the frontal lobe.\n\nThe anterior horn connects to the third ventricle, via the interventricular foramen.\n\nThis portion of the lateral ventricle impinges on the frontal lobe, passing anteriorly and laterally, with slight inclination inferiorly.\n\nIt is separated from the anterior horn of the other lateral ventricle by a thin neural sheet - septum pellucidum, which thus forms its medial boundary.\n\nThe boundary facing exterior to the ventricle curvature is formed by the corpus callosum - the floor at the limit of the ventricle is the upper surface of the rostrum (the reflected portion of the corpus callosum), while nearer the body of the ventricle, the roof consists of the posterior surface of the genu.\n\nThe remaining boundary - that facing interior to the ventricle curvature - comprises the posterior edge of the caudate nucleus.\n\n=== Body of the lateral ventricle ===\n\nThe body of the lateral ventricle, or central part is the part of the ventricle between the anterior horn and the trigone.\n\nIts roof is bound by the tapetum of the corpus callosum - and is separated medially from the other lateral ventricle by the septum pellucidum.\n\nThe tail of the caudate nucleus forms the upper portion of the lateral edge, but it is not large enough to cover the whole boundary.\n\nImmediately below the tail of the caudate nucleus, the next portion of the lateral edge is formed by the comparatively narrow stria terminalis, which sits upon the superior thalamostriate vein.\n\nThe main part of the fornix of the brain forms the next narrow portion of the lateral boundary, which is completed medially by a choroid plexus, which serves both ventricles.\n\n=== Trigone of lateral ventricle ===\n\nThe trigone of the lateral ventricle is the area where the part of the body forms a junction with the inferior horn and the posterior horn.\n\nThis area is referred to as the atrium of the lateral ventricle, and is where the choroid plexus is enlarged as the choroid glomus.\n\nAs a triangular surface feature of the floor of this part of the lateral ventricle it is known as the collateral trigone.\n\n=== Posterior horn of lateral ventricle ===\n\nThe posterior horn of lateral ventricle, or occipital horn, impinges into the occipital lobe in a posterior direction, initially laterally but subsequently curving medially and lilting inferiorly on the lateral side.\n\nThe tapetum of the Corpus Callosum continues to form the roof, which due to the lilt is also the lateral edge.\n\nHowever, the posterior and anterior ends of the Corpus Callosum are characterised by tighter bundling, known as forceps (due to the resulting shape), to curve around the central sulci; the edge of these forceps form the upper part of the medial side of the posterior horn.\n\nThe remainder of the medial edge of the ventricle is directly in contact with white matter of the cortex of the occipital lobe.\n\n=== Inferior horn of lateral ventricle ===\n\nThe inferior horn of the lateral ventricle, or temporal horn, is the largest of the horns.\n\nIt impinges on the temporal lobe in a lateral and anterior direction, initially inferiorly, until it comes within 2.5 cm. of the lobe's apex; its direction is fairly well indicated on the brain surface by the superior temporal sulcus.\n\nThe horn lilts inferiorly towards its lateral edge.\n\nAs a continuation of the interior side of the ventricular curve, the floor of the body of the ventricle becomes the roof of the inferior horn, hence the tail of the caudate nucleus forms the lateral edge of the inferior horn's roof, until, at the extremity of the ventricle, the caudate nucleus becomes the amygdala.\n\nThe stria terminalis forms the remainder of the roof, which is much narrower than at the body - the choroid plexus moves to the medial wall.\n\nThe tapetum for the temporal lobe comprises the lateral boundary of the inferior horn, on its way to join the main tapetum above the body of the ventricle (passing over the Caudate Nucleus as it does so).\n\nThe majority of the inferior horn's floor is formed by the fimbria hippocampi (from which the fornix emerges), and then, more anteriorly, by the hippocampus itself.\n\nAs with the posterior horn, the remainder of the boundary - in this case the lateral side of the floor - is directly in contact with the white matter of the surrounding lobe.\n\n=== Development ===\n\nThe lateral ventricles, similarly to other parts of the ventricular system of the brain, develop from the central canal of the neural tube.\n\nSpecifically, the lateral ventricles originate from the portion of the tube that is present in the developing prosencephalon, and subsequently in the developing telencephalon.\n\nDuring the first three months of prenatal development, the central canal expands into lateral, third, and fourth ventricles, connected by thinner channels.\n\nIn the lateral ventricles, specialized areas – choroid plexuses – appear, which produce cerebrospinal fluid.\n\nThe neural canal that does not expand and remains the same at the level of the midbrain superior to the fourth ventricle forms the cerebral aqueduct.\n\nThe fourth ventricle narrows at the obex (in the caudal medulla), to become the central canal of the spinal cord.\n\nDuring development, pressure from exterior structures causes a number of concave bulges to form within the lateral ventricles, which can be extremely variable in their degree of development; in some individuals they are ill-defined, while in others they can be prominent:\n\n-from the forceps against the posterior horn - creating the bulb of the posterior cornu on the upper medial side of the horn\n\n-from the calcarine sulcus against the posterior horn - creating the calcar avis (historically called the hippocampus minor, for visual reasons) on the lower medial side of the horn\n\n-from the hippocampus against the inferior horn (on the medial floor of the horn)\n\n-from the collateral sulcus against the inferior horn - creating the\n\nCollateral eminence on the lateral floor of the horn.\n\nFetal lateral ventricles may be diagnosed using linear or planar measurements.\n\n== Clinical significance ==\n\nThe volume of the lateral ventricles are known to increase with age.\n\nThey are also enlarged in a number of neurological conditions and are on average larger in patients with schizophrenia, bipolar disorder, major depressive disorder and Alzheimer's disease.\n\nAsymmetry as an anatomical variation, in the size of the lateral ventricles is found in about 5–12% of the population.\n\nThis has been associated with handedness, where right-handed people have been found to have a larger right lateral ventricle and a longer left posterior horn, whereas left-handed people have been found to have longer right posterior horns.\n\nA severe asymmetry, or an asymmetry with midline shift or diffuse enlargement, may indicate brain injury early in life, particularly in cases of a longer right posterior horn.\n\nIf the production of cerebrospinal fluid is bigger than its reabsorption, or if its circulation is blocked – the ventricles may enlarge and cause hydrocephalus.\n\nCalcification of the choroid plexus can occur, usually in the atrium.\n\nhttps://en.wikipedia.org/wiki/Lateral_ventricles","septum-pellucidum":"The septum pellucidum (Latin for \"translucent wall\") is a thin, triangular, vertical double membrane separating the anterior horns of the left and right lateral ventricles of the brain.\n\nIt runs as a sheet from the corpus callosum down to the fornix.\nThe septum is not present in the syndrome septo-optic dysplasia.\n\n== Structure ==\n\nThe septum pellucidum is located in the septal area in the midline of the brain between the two cerebral hemispheres.\n\nThe septal area is also the location of the septal nuclei.\n\nIt is attached to the lower part of the corpus callosum, the large collection of nerve fibers that connect the two cerebral hemispheres.\n\nIt is attached to the front forward part of the fornix.\n\nThe lateral ventricles sit on either side of the septum.\n\nThe septum pellucidum consists of two layers or laminae of both white and gray matter.\n\nDuring fetal development, there is a space between the two laminae called the cave of septum pellucidum that, in ninety percent of cases, disappears during infancy.\n\nThe cavum was occasionally referred to as the fifth ventricle, but this is no longer used because the space is usually not continuous with the ventricular system.\n\nThe fifth ventricle is recognised as the terminal enlargement of the spinal cord.\n\n== Clinical significance ==\n\nAbsence of the septum pellucidum occurs in septo-optic dysplasia, a rare developmental disorder usually characterized by abnormal development of the optic disk and pituitary deficiencies.\n\nSymptoms of septo-optic dysplasia are highly variable and may include vision difficulties, low muscle tone, hormonal problems, seizures, intellectual problems, and jaundice at birth.\n\nManagement is directed at the symptoms a person is affected with.\n\nhttps://en.wikipedia.org/wiki/Septum_pellucidum","habenula":"In neuroanatomy, habenula (diminutive of Latin habena meaning rein) originally denoted the stalk of the pineal gland (pineal habenula; pedunculus of pineal body), but gradually came to refer to a neighboring group of nerve cells with which the pineal gland was believed to be associated, the habenular nucleus.\n\nThe habenular nucleus is a set of well-conserved structures in all vertebrate animals.Currently, this term refers to this separate cell mass in the caudal portion of the dorsal diencephalon, known as the epithalamus, found in all vertebrates on both sides of the third ventricle.\n\nIt is embedded in the posterior end of the stria medullaris from which it receives most of its afferent fibers.\n\nBy way of the fasciculus retroflexus (habenulointerpeduncular tract) it projects to the interpeduncular nucleus and other paramedian cell groups of the midbrain tegmentum.\nFunctionally, the habenula is involved in nociception, sleep-wake cycles, reproductive behavioural, and mood (see section on depression below).\n\nIt is one of the few areas known to influence virtually all monoaminergic systems in the brainstem, such as dopamine, norepinephrine, and serotonin.\n\n== Anatomy ==\n\nThe habenula was traditionally divided into lateral (limbic) and medial (motor) parts.\n\nDetailed examination of the region in the cat, however, suggested that the lateral part should be further divided into ten distinct subnuclei and the medial into five distinct subnuclei.\n\n=== Asymmetry ===\n\nVarious species exhibit left-right asymmetric differentiation of habenular neurons.\n\nIn many fishes and amphibians, the habenula on one side is significantly larger and better organized into distinct nuclei in the dorsal diencephalon than its smaller pair.\n\nThe sidedness of such differentiation (whether the left or the right is more developed) varies with the species.\n\nIn birds and mammals, however, both habenulae are more symmetrical (although not entirely) and consist of a medial and a lateral nucleus on each side which is in fish and amphibians equivalent to dorsal habenula and the ventral habenula, respectively.\n\n=== Lateral habenula ===\n\nThe primary input regions to the lateral habenula (LHb) are the lateral preoptic area (bringing input from the hippocampus and lateral septum), the ventral pallidum (bringing input from the nucleus accumbens and mediodorsal nucleus of the thalamus), the lateral hypothalamus, the medial habenula, and the internal segment of the globus pallidus (bringing input from other basal ganglia structures).Neurons in the lateral habenula are 'reward-negative' as they are activated by stimuli associated with unpleasant events, the absence of the reward or the presence of punishment especially when this is unpredictable.\n\nReward information to the lateral habenula comes from the internal part of the globus pallidus.The outputs of the lateral habenula target dopaminergic regions (substantia nigra pars compacta and the ventral tegmental area), serotonergic regions (median raphe and dorsal raphe nuclei), and a cholinergic region (the laterodorsal tegmental nucleus).\n\nThis output inhibits dopamine neurons in substantia nigra pars compacta and the ventral tegmental area, with activation in the lateral habenula linking to deactivation in them, and vice versa, deactivation in the lateral habenula with their activation.\n\nThe lateral habenula functions to oppose the action of the laterodorsal tegmental nucleus in the acquisition of avoidance responses but not the processing of avoidance later on when it is a memory, motivation or its execution.\n\nNew research suggests that lateral habenula may play a crucial role in decision making.\n\n=== Medial habenula ===\n\nInput to the medial habenula (MHb) comes from a variety of regions and carries a number of different chemicals.\n\nInput regions include septal nuclei (the nucleus fimbrialis septi and the nucleus triangularis septi), dopaminergic inputs from the interfascicular nucleus of the ventral tegmental area, noradrenergic inputs from the locus ceruleus, and GABAergic inputs from the diagonal band of Broca.\n\nThe medial habenula sends outputs of glutamate, substance P and acetylcholine to the periaqueductal gray via the interpeduncular nucleus as well as to the pineal gland.\n\n=== Olfactory coding in the habenula ===\n\nIn lower vertebrates (lampreys and teleost fishes), mitral cell (principal olfactory neurons) axons project exclusively to the right hemisphere of the habenula in an asymmetric manner.\n\nIt is reported that the dorsal habenulae (DHb) are functionally asymmetric with predominantly odor responses in the right hemisphere.\n\nIt was also shown that DHb neurons are spontaneously active even in the absence of olfactory stimulation.\n\nThese spontaneously-active DHb neurons are organized into functional clusters which were proposed to govern olfactory responses. (Jetti, SK. et al 2014, Current Biology)\n\n== Functions ==\n\nThe habenular nuclei are involved in pain processing, reproductive behavior, nutrition, sleep-wake cycles, stress responses, and learning.\n\nRecent demonstrations using fMRI and single unit electrophysiology have closely linked the function of the lateral habenula with reward processing, in particular with regard to encoding negative feedback or negative rewards.\n\nMatsumoto and Hikosaka suggested in 2007 that this reward and reward-negative information in the brain might \"be elaborated through the interplay among the lateral habenula, the basal ganglia, and monoaminergic (dopaminergic and serotonergic) systems\" and that the lateral habenula may play a pivotal role in this \"integrative function\".\n\nRecent evidence suggests that neurons in the lateral habenula signal positive and negative information-prediction errors in addition to positive and negative reward-prediction errors.\n\n== Depression ==\n\nBoth the medial and lateral habenula show reduced volume in those with depression.\n\nNeuron cell numbers were also reduced on the right side.\n\nSuch changes are not seen in those with schizophrenia.\n\nDeep brain stimulation of the major afferent bundle (i.e., stria medullaris thalami) of the lateral habenula has been used for treatment of depression where it is severe, protracted and therapy-resistant.Methyl-D-aspartate (NMDA) receptor-dependent burst firing in the lateral habenula has been associated with depression in animal studies, and it has been shown that the general anesthetic ketamine blocks this firing by acting as a receptor antagonist.\n\nKetamine has been the subject of numerous studies after having shown fast-acting antidepressant effects in humans.\n\nhttps://en.wikipedia.org/wiki/Habenula","optic-tract":"The optic tract (from the Latin tractus opticus) is a part of the visual system in the brain.\n\nIt is a continuation of the optic nerve that relays information from the optic chiasm to the ipsilateral lateral geniculate nucleus (LGN), pretectal nuclei, and superior colliculus.\n\nIt is composed of two individual tracts, the left optic tract and the right optic tract, each of which conveys visual information exclusive to its respective contralateral half of the visual field.\n\nEach of these tracts is derived from a combination of temporal and nasal retinal fibers from each eye that corresponds to one half of the visual field.\n\nIn more specific terms, the optic tract contains fibers from the ipsilateral temporal hemiretina and contralateral nasal hemiretina.\n\n== Visual system ==\n\nThe optic tract carries retinal information relating to the whole visual field.\n\nSpecifically, the left optic tract corresponds to the right visual field, while the right optic tract corresponds to the left visual field.\n\nTo form the right visual field, temporal retinal fibers from the left eye and nasal retinal fibers from the right eye form the left optic tract, and to form the left visual field, temporal retinal fibers from the right eye and nasal retinal fibers from the left eye form the right optic tract.\n\n== Autonomics ==\n\nSeveral autonomic ocular motor responses are consensual.\n\nThe optic tract is primarily responsible for relaying visual information to the LGN, but it is also peripherally responsible for transducing these bilateral autonomic reflexes, including the pupillary light reflex and pupillary dark reflex.\n\n=== Pupillary light reflex ===\n\nThe pupillary light reflex is an autonomic reflex that controls pupil diameter to accommodate for increases in illumination as perceived by the retina.\n\nHigher light intensity causes pupil constriction, and the increase of light stimulation of one eye will cause pupillary constriction of both eyes.\n\nThe neural circuitry of the pupillary light reflex includes the optic tract which joins the optic nerve to the brachium of the superior colliculus.\n\n=== Pupillary dark reflex ===\n\nSimilarly to the pupillary light reflex, the pupillary dark reflex is an autonomic reflex that controls pupil diameter to accommodate for decreases in illumination as perceived by the retina.\n\nLower light intensity causes pupil dilation, and the decrease of light stimulation of one eye will cause pupillary dilation of both eyes.\n\nSimilarly, the neural circuitry of the pupillary dark reflex includes the optic tract which joins the optic nerve to the hypothalamus.\n\n== Damage and pathologies ==\n\n=== Lesions ===\n\nLesions in the optic tract correspond to visual field loss on the left or right half of the vertical midline, also known as homonymous hemianopsia.\n\nA lesion in the left optic tract will cause right-sided homonymous hemianopsia, while a lesion in the right optic tract will cause left-sided homonymous hemianopsia.\n\nStroke, congenital defects, tumors, infection, and surgery are all possible causes of optic tract damage.\n\nPeripheral prism expanders and vision restitution therapy are often employed in patients with visual field loss resultant of permanent optic tract damage.\n\n=== Split-brain ===\n\nIn certain split-brain patients who have undergone a corpus callosotomy to treat severe epilepsy, the information from one optic tract does not get transmitted to both hemispheres.\n\nFor instance, a split-brain patient shown an image in the left visual field will be unable to vocally name what has been seen as the speech-control center is in the left hemisphere of the brain.\n\n=== Pupillary reflexes ===\n\nPupillary reflexes, particularly the pupillary light reflex, are a powerful diagnostic tool often employed in clinical and emergency medical practice.\n\nA lack of equal consensual pupillary constriction to a light stimulus, especially a Marcus Gunn pupil, can be indicative of optic nerve damage, brainstem death, or optic tract damage in between.\n\nhttps://en.wikipedia.org/wiki/Optic_tract","thalamus":"The thalamus (from Greek θάλαμος, \"chamber\") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain).\n\nNerve fibers project out of the thalamus to the cerebral cortex in all directions, allowing hub-like exchanges of information.\n\nIt has several functions, such as the relaying of sensory signals, including motor signals to the cerebral cortex and the regulation of consciousness, sleep, and alertness.Anatomically, it is a paramedian symmetrical structure of two halves (left and right), within the vertebrate brain, situated between the cerebral cortex and the midbrain.\n\nIt forms during embryonic development as the main product of the diencephalon, as first recognized by the Swiss embryologist and anatomist Wilhelm His Sr. in 1893.\n\n== Anatomy ==\n\nThe thalamus is a paired structure of gray matter located in the forebrain which is superior to the midbrain, near the center of the brain, with nerve fibers projecting out to the cerebral cortex in all directions.\n\nThe medial surface of the thalamus constitutes the upper part of the lateral wall of the third ventricle, and is connected to the corresponding surface of the opposite thalamus by a flattened gray band, the interthalamic adhesion.\n\nThe lateral part of the thalamus is the phylogenetically newest part of the thalamus (neothalamus), and includes the lateral nuclei, the pulvinar and the medial and lateral geniculate nuclei.\n\nThere are areas of white matter in the thalamus including the stratum zonale that covers the dorsal surface, and the external and internal medullary laminae.\n\nThe external lamina covers the lateral surface and the internal lamina divides the nuclei into anterior, medial and lateral groups.\n\n=== Blood supply ===\n\nThe thalamus derives its blood supply from a number of arteries: the polar artery (posterior communicating artery), paramedian thalamic-subthalamic arteries, inferolateral (thalamogeniculate) arteries, and posterior (medial and lateral) choroidal arteries.\n\nThese are all branches of the posterior cerebral artery.Some people have the artery of Percheron, which is a rare anatomic variation in which a single arterial trunk arises from the posterior cerebral artery to supply both parts of the thalamus.\n\n=== Thalamic nuclei ===\n\nDerivatives of the diencephalon include the dorsally-located epithalamus (essentially the habenula and annexes) and the perithalamus (prethalamus) containing the zona incerta and the thalamic reticular nucleus.\n\nDue to their different ontogenetic origins, the epithalamus and the perithalamus are formally distinguished from the thalamus proper.\n\nThe metathalamus is made up of the lateral geniculate and medial geniculate nuclei.\nThe thalamus comprises a system of lamellae (made up of myelinated fibers) separating different thalamic subparts.\n\nOther areas are defined by distinct clusters of neurons, such as the periventricular nucleus, the intralaminar elements, the \"nucleus limitans\", and others.\n\nThese latter structures, different in structure from the major part of the thalamus, have been grouped together into the allothalamus as opposed to the isothalamus.\n\nThis distinction simplifies the global description of the thalamus.\n\n=== Connections ===\n\nThe thalamus has many connections to the hippocampus via the mammillothalamic tract, this tract comprises the mammillary bodies and fornix.The thalamus is connected to the cerebral cortex via the thalamocortical radiations.The spinothalamic tract is a sensory pathway originating in the spinal cord.\n\nIt transmits information to the thalamus about pain, temperature, itch and crude touch.\n\nThere are two main parts: the lateral spinothalamic tract, which transmits pain and temperature, and the anterior (or ventral) spinothalamic tract, which transmits crude touch and pressure.\n\n== Function ==\n\nThe thalamus has multiple functions, generally believed to act as a relay station, or hub, relaying information between different subcortical areas and the cerebral cortex.\n\nIn particular, every sensory system (with the exception of the olfactory system) includes a thalamic nucleus that receives sensory signals and sends them to the associated primary cortical area.\n\nFor the visual system, for example, inputs from the retina are sent to the lateral geniculate nucleus of the thalamus, which in turn projects to the visual cortex in the occipital lobe.\n\nThe thalamus is believed to both process sensory information as well as relay it—each of the primary sensory relay areas receives strong feedback connections from the cerebral cortex.\n\nSimilarly the medial geniculate nucleus acts as a key auditory relay between the inferior colliculus of the midbrain and the primary auditory cortex.\n\nThe ventral posterior nucleus is a key somatosensory relay, which sends touch and proprioceptive information to the primary somatosensory cortex.The thalamus also plays an important role in regulating states of sleep and wakefulness.\n\nThalamic nuclei have strong reciprocal connections with the cerebral cortex, forming thalamo-cortico-thalamic circuits that are believed to be involved with consciousness.\n\nThe thalamus plays a major role in regulating arousal, the level of awareness, and activity.\n\nDamage to the thalamus can lead to permanent coma.The role of the thalamus in the more anterior pallidal and nigral territories in the basal ganglia system disturbances is recognized but still poorly understood.\n\nThe contribution of the thalamus to vestibular or to tectal functions is almost ignored.\n\nThe thalamus has been thought of as a \"relay\" that simply forwards signals to the cerebral cortex.\n\nNewer research suggests that thalamic function is more selective.\n\nMany different functions are linked to various regions of the thalamus.\n\nThis is the case for many of the sensory systems (except for the olfactory system), such as the auditory, somatic, visceral, gustatory and visual systems where localized lesions provoke specific sensory deficits.\n\nA major role of the thalamus is support of motor and language systems, and much of the circuitry implicated for these systems is shared.\n\nThe thalamus is functionally connected to the hippocampus as part of the extended hippocampal system at the thalamic anterior nuclei with respect to spatial memory and spatial sensory datum they are crucial for human episodic event memory.\n\nThe thalamic region's connection to the mesio-temporal lobe provide differentiation of the functioning of recollective and familiarity memory.The neuronal information processes necessary for motor control were proposed as a network involving the thalamus as a subcortical motor center.\n\nThrough investigations of the anatomy of the brains of primates the nature of the interconnected tissues of the cerebellum to the multiple motor cortices suggested that the thalamus fulfills a key function in providing the specific channels from the basal ganglia and cerebellum to the cortical motor areas.\n\nIn an investigation of the saccade and antisaccade motor response in three monkeys, the thalamic regions were found to be involved in the generation of antisaccade eye-movement (that is, the ability to inhibit the reflexive jerking movement of the eyes in the direction of a presented stimulus).Recent research suggests that the mediodorsal thalamus (MD) may play a broader role in cognition.\n\nSpecifically, the mediodorsal thalamus may \"amplify the connectivity (signaling strength) of just the circuits in the cortex appropriate for the current context and thereby contribute to the flexibility (of the mammalian brain) to make complex decisions by wiring the many associations on which decisions depend into weakly connected cortical circuits.\" Researchers found that \"enhancing MD activity magnified the ability of mice to \"think,\" driving down by more than 25 percent their error rate in deciding which conflicting sensory stimuli to follow to find the reward.\"\n\n== Development ==\n\nThe thalamic complex is composed of the perithalamus (or prethalamus, previously also known as ventral thalamus), the mid-diencephalic organiser (which forms later the zona limitans intrathalamica (ZLI) ) and the thalamus (dorsal thalamus).\n\nThe development of the thalamus can be subdivided into three steps.\nThe thalamus is the largest structure deriving from the embryonic diencephalon, the posterior part of the forebrain situated between the midbrain and the cerebrum.\n\n=== Early brain development ===\n\nAfter neurulation the anlage of the prethalamus and the thalamus is induced within the neural tube.\n\nData from different vertebrate model organisms support a model in which the interaction between two transcription factors, Fez and Otx, are of decisive importance.\n\nFez is expressed in the prethalamus, and functional experiments show that Fez is required for prethalamus formation.\n\nPosteriorly, Otx1 and Otx2 abut the expression domain of Fez and are required for proper development of the thalamus.\n\n=== Formation of progenitor domains ===\n\nEarly in thalamic development two progenitor domains form, a caudal domain, and a rostral domain.\n\nThe caudal domain gives rise to all of the glutamatergic neurons in the adult thalamus while the rostral domain gives rise to all of the GABAergic neurons in the adult thalamus.\n\n=== The formation of the mid-diencephalic organiser (MDO) ===\n\nAt the interface between the expression domains of Fez and Otx, the mid-diencephalic organizer (MDO, also called the ZLI organiser) is induced within the thalamic anlage.\n\nThe MDO is the central signalling organizer in the thalamus.\n\nA lack of the organizer leads to the absence of the thalamus.\n\nThe MDO matures from ventral to dorsal during development.\n\nMembers of the SHH family and of the Wnt family are the main principal signals emitted by the MDO.\nBesides its importance as signalling center, the organizer matures into the morphological structure of the zona limitans intrathalamica (ZLI).\n\n=== Maturation and parcellation of the thalamus ===\n\nAfter its induction, the MDO starts to orchestrate the development of the thalamic anlage by release of signalling molecules such as SHH.\n\nIn mice, the function of signaling at the MDO has not been addressed directly due to a complete absence of the diencephalon in SHH mutants.Studies in chicks have shown that SHH is both necessary and sufficient for thalamic gene induction.\n\nIn zebrafish, it was shown that the expression of two SHH genes, SHH-a and SHH-b (formerly described as twhh) mark the MDO territory, and that SHH signaling is sufficient for the molecular differentiation of both the prethalamus and the thalamus but is not required for their maintenance and SHH signaling from the MDO/alar plate is sufficient for the maturation of prethalamic and thalamic territory while ventral Shh signals are dispensable.The exposure to SHH leads to differentiation of thalamic neurons.\n\nSHH signaling from the MDO induces a posterior-to-anterior wave of expression the proneural gene Neurogenin1 in the major (caudal) part of the thalamus, and Ascl1 (formerly Mash1) in the remaining narrow stripe of rostral thalamic cells immediately adjacent to the MDO, and in the prethalamus.This zonation of proneural gene expression leads to the differentiation of glutamatergic relay neurons from the Neurogenin1+ precursors and of GABAergic inhibitory neurons from the Ascl1+ precursors.\n\nIn fish, selection of these alternative neurotransmitter fates is controlled by the dynamic expression of Her6 the homolog of HES1.\n\nExpression of this hairy-like bHLH transcription factor, which represses Neurogenin but is required for Ascl1, is progressively lost from the caudal thalamus but maintained in the prethalamus and in the stripe of rostral thalamic cells.\n\nIn addition, studies on chick and mice have shown that blocking the Shh pathway leads to absence of the rostral thalamus and substantial decrease of the caudal thalamus.\n\nThe rostral thalamus will give rise to the reticular nucleus mainly whereby the caudal thalamus will form the relay thalamus and will be further subdivided in the thalamic nuclei.In humans, a common genetic variation in the promoter region of the serotonin transporter (the SERT-long and -short allele: 5-HTTLPR) has been shown to affect the development of several regions of the thalamus in adults.\n\nPeople who inherit two short alleles (SERT-ss) have more neurons and a larger volume in the pulvinar and possibly the limbic regions of the thalamus.\n\nEnlargement of the thalamus provides an anatomical basis for why people who inherit two SERT-ss alleles are more vulnerable to major depression, posttraumatic stress disorder, and suicide.\n\n== Clinical significance ==\n\nA thalamus damaged by a stroke can lead to thalamic pain syndrome, which involves a one-sided burning or aching sensation often accompanied by mood swings.\n\nBilateral ischemia of the area supplied by the paramedian artery can cause serious problems including akinetic mutism, and be accompanied by oculomotor problems.\n\nA related concept is thalamocortical dysrhythmia.\n\nThe occlusion of the artery of Percheron can lead to a bilateral thalamus infarction.\nAlcoholic Korsakoff syndrome stems from damage to the mammillary body, the mammillothalamic fasciculus or the thalamus.Fatal familial insomnia is a hereditary prion disease in which degeneration of the thalamus occurs, causing the patient to gradually lose their ability to sleep and progressing to a state of total insomnia, which invariably leads to death.\n\nIn contrast, damage to the thalamus can result in coma.\n\nhttps://en.wikipedia.org/wiki/Thalamus","hypothalamus":"The hypothalamus (from Ancient Greek ὑπό (hupó) 'under', and θάλαμος (thálamos) 'chamber') is a portion of the brain that contains a number of small nuclei with a variety of functions.\n\nOne of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland.\n\nThe hypothalamus is located below the thalamus and is part of the limbic system.\n\nIn the terminology of neuroanatomy, it forms the ventral part of the diencephalon.\n\nAll vertebrate brains contain a hypothalamus.\n\nIn humans, it is the size of an almond.\nThe hypothalamus is responsible for the regulation of certain metabolic processes and other activities of the autonomic nervous system.\n\nIt synthesizes and secretes certain neurohormones, called releasing hormones or hypothalamic hormones, and these in turn stimulate or inhibit the secretion of hormones from the pituitary gland.\n\nThe hypothalamus controls body temperature, hunger, important aspects of parenting and attachment behaviours, thirst, fatigue, sleep, and circadian rhythms.\n\n== Structure ==\n\nThe hypothalamus is divided into 3 regions (supraoptic, tuberal, mammillary) in a parasagittal plane, indicating location anterior-posterior; and 3 areas (periventricular, medial, lateral) in the coronal plane, indicating location medial-lateral.\n\nHypothalamic nuclei are located within these specific regions and areas.\n\nIt is found in all vertebrate nervous systems.\n\nIn mammals, magnocellular neurosecretory cells in the paraventricular nucleus and the supraoptic nucleus of the hypothalamus produce neurohypophysial hormones, oxytocin and vasopressin.\n\nThese hormones are released into the blood in the posterior pituitary.\n\nMuch smaller parvocellular neurosecretory cells, neurons of the paraventricular nucleus, release corticotropin-releasing hormone and other hormones into the hypophyseal portal system, where these hormones diffuse to the anterior pituitary.\n\n=== Nuclei ===\n\nThe hypothalamic nuclei include the following:\nSee alsoventrolateral preoptic nucleus\nperiventricular nucleus\n\n=== Connections ===\n\nThe hypothalamus is highly interconnected with other parts of the central nervous system, in particular the brainstem and its reticular formation.\n\nAs part of the limbic system, it has connections to other limbic structures including the amygdala and septum, and is also connected with areas of the autonomous nervous system.\nThe hypothalamus receives many inputs from the brainstem, the most notable from the nucleus of the solitary tract, the locus coeruleus, and the ventrolateral medulla.\nMost nerve fibres within the hypothalamus run in two ways (bidirectional).\n\nProjections to areas caudal to the hypothalamus go through the medial forebrain bundle, the mammillotegmental tract and the dorsal longitudinal fasciculus.\nProjections to areas rostral to the hypothalamus are carried by the mammillothalamic tract, the fornix and terminal stria.\nProjections to areas of the sympathetic motor system (lateral horn spinal segments T1-L2/L3) are carried by the hypothalamospinal tract and they activate the sympathetic motor pathway.\n\n=== Sexual dimorphism ===\n\nSeveral hypothalamic nuclei are sexually dimorphic; i.e., there are clear differences in both structure and function between males and females.\n\nSome differences are apparent even in gross neuroanatomy: most notable is the sexually dimorphic nucleus within the preoptic area, in which the differences are subtle changes in the connectivity and chemical sensitivity of particular sets of neurons.\n\nThe importance of these changes can be recognized by functional differences between males and females.\n\nFor instance, males of most species prefer the odor and appearance of females over males, which is instrumental in stimulating male sexual behavior.\n\nIf the sexually dimorphic nucleus is lesioned, this preference for females by males diminishes.\n\nAlso, the pattern of secretion of growth hormone is sexually dimorphic; this is why in many species, adult males are visibly distinct sizes from females.\n\n==== Responsiveness to ovarian steroids ====\nOther striking functional dimorphisms are in the behavioral responses to ovarian steroids of the adult.\n\nMales and females respond to ovarian steroids in different ways, partly because the expression of estrogen-sensitive neurons in the hypothalamus is sexually dimorphic; i.e., estrogen receptors are expressed in different sets of neurons.\nEstrogen and progesterone can influence gene expression in particular neurons or induce changes in cell membrane potential and kinase activation, leading to diverse non-genomic cellular functions.\n\nEstrogen and progesterone bind to their cognate nuclear hormone receptors, which translocate to the cell nucleus and interact with regions of DNA known as hormone response elements (HREs) or get tethered to another transcription factor's binding site.\n\nEstrogen receptor (ER) has been shown to transactivate other transcription factors in this manner, despite the absence of an estrogen response element (ERE) in the proximal promoter region of the gene.\n\nIn general, ERs and progesterone receptors (PRs) are gene activators, with increased mRNA and subsequent protein synthesis following hormone exposure.Male and female brains differ in the distribution of estrogen receptors, and this difference is an irreversible consequence of neonatal steroid exposure.\n\nEstrogen receptors (and progesterone receptors) are found mainly in neurons in the anterior and mediobasal hypothalamus, notably:\n\nthe preoptic area (where LHRH neurons are located, regulating dopamine responses and maternal behavior;\nthe periventricular nucleus where somatostatin neurons are located, regulating stress levels;\nthe ventromedial hypothalamus which regulates hunger and sexual arousal.\n\n=== Development ===\n\nIn neonatal life, gonadal steroids influence the development of the neuroendocrine hypothalamus.\n\nFor instance, they determine the ability of females to exhibit a normal reproductive cycle, and of males and females to display appropriate reproductive behaviors in adult life.\n\nIf a female rat is injected once with testosterone in the first few days of postnatal life (during the \"critical period\" of sex-steroid influence), the hypothalamus is irreversibly masculinized; the adult rat will be incapable of generating an LH surge in response to estrogen (a characteristic of females), but will be capable of exhibiting male sexual behaviors (mounting a sexually receptive female).\nBy contrast, a male rat castrated just after birth will be feminized, and the adult will show female sexual behavior in response to estrogen (sexual receptivity, lordosis behavior).In primates, the developmental influence of androgens is less clear, and the consequences are less understood.\n\nWithin the brain, testosterone is aromatized (to estradiol), which is the principal active hormone for developmental influences.\n\nThe human testis secretes high levels of testosterone from about week 8 of fetal life until 5–6 months after birth (a similar perinatal surge in testosterone is observed in many species), a process that appears to underlie the male phenotype.\n\nEstrogen from the maternal circulation is relatively ineffective, partly because of the high circulating levels of steroid-binding proteins in pregnancy.Sex steroids are not the only important influences upon hypothalamic development; in particular, pre-pubertal stress in early life (of rats) determines the capacity of the adult hypothalamus to respond to an acute stressor.\n\nUnlike gonadal steroid receptors, glucocorticoid receptors are very widespread throughout the brain; in the paraventricular nucleus, they mediate negative feedback control of CRF synthesis and secretion, but elsewhere their role is not well understood.\n\n== Function ==\n\n=== Hormone release ===\n\nThe hypothalamus has a central neuroendocrine function, most notably by its control of the anterior pituitary, which in turn regulates various endocrine glands and organs.\n\nReleasing hormones (also called releasing factors) are produced in hypothalamic nuclei then transported along axons to either the median eminence or the posterior pituitary, where they are stored and released as needed.\nAnterior pituitaryIn the hypothalamic–adenohypophyseal axis, releasing hormones, also known as hypophysiotropic or hypothalamic hormones, are released from the median eminence, a prolongation of the hypothalamus, into the hypophyseal portal system, which carries them to the anterior pituitary where they exert their regulatory functions on the secretion of adenohypophyseal hormones.\n\nThese hypophysiotropic hormones are stimulated by parvocellular neurosecretory cells located in the periventricular area of the hypothalamus.\n\nAfter their release into the capillaries of the third ventricle, the hypophysiotropic hormones travel through what is known as the hypothalamo-pituitary portal circulation.\n\nOnce they reach their destination in the anterior pituitary, these hormones bind to specific receptors located on the surface of pituitary cells.\n\nDepending on which cells are activated through this binding, the pituitary will either begin secreting or stop secreting hormones into the rest of the bloodstream.\nOther hormones secreted from the median eminence include vasopressin, oxytocin, and neurotensin.\nPosterior pituitaryIn the hypothalamic-neurohypophyseal axis, neurohypophysial hormones are released from the posterior pituitary, which is actually a prolongation of the hypothalamus, into the circulation.\n\nIt is also known that hypothalamic-pituitary-adrenal axis (HPA) hormones are related to certain skin diseases and skin homeostasis.\n\nThere is evidence linking hyperactivity of HPA hormones to stress-related skin diseases and skin tumors.\n\n=== Stimulation ===\n\nThe hypothalamus coordinates many hormonal and behavioural circadian rhythms, complex patterns of neuroendocrine outputs, complex homeostatic mechanisms, and important behaviours.\n\nThe hypothalamus must, therefore, respond to many different signals, some of which are generated externally and some internally.\n\nDelta wave signalling arising either in the thalamus or in the cortex influences the secretion of releasing hormones; GHRH and prolactin are stimulated whilst TRH is inhibited.\nThe hypothalamus is responsive to:\n\nLight: daylength and photoperiod for regulating circadian and seasonal rhythms\nOlfactory stimuli, including pheromones\nSteroids, including gonadal steroids and corticosteroids\nNeurally transmitted information arising in particular from the heart, enteric nervous system (of the gastrointestinal tract), and the reproductive tract.\nAutonomic inputs\nBlood-borne stimuli, including leptin, ghrelin, angiotensin, insulin, pituitary hormones, cytokines, plasma concentrations of glucose and osmolarity etc.\nStress\nInvading microorganisms by increasing body temperature, resetting the body's thermostat upward.\n\n==== Olfactory stimuli ====\nOlfactory stimuli are important for sexual reproduction and neuroendocrine function in many species.\n\nFor instance if a pregnant mouse is exposed to the urine of a 'strange' male during a critical period after coitus then the pregnancy fails (the Bruce effect).\n\nThus, during coitus, a female mouse forms a precise 'olfactory memory' of her partner that persists for several days.\n\nPheromonal cues aid synchronization of oestrus in many species; in women, synchronized menstruation may also arise from pheromonal cues, although the role of pheromones in humans is disputed.\n\n==== Blood-borne stimuli ====\nPeptide hormones have important influences upon the hypothalamus, and to do so they must pass through the blood–brain barrier.\n\nThe hypothalamus is bounded in part by specialized brain regions that lack an effective blood–brain barrier; the capillary endothelium at these sites is fenestrated to allow free passage of even large proteins and other molecules.\n\nSome of these sites are the sites of neurosecretion - the neurohypophysis and the median eminence.\n\nHowever, others are sites at which the brain samples the composition of the blood.\n\nTwo of these sites, the SFO (subfornical organ) and the OVLT (organum vasculosum of the lamina terminalis) are so-called circumventricular organs, where neurons are in intimate contact with both blood and CSF.\n\nThese structures are densely vascularized, and contain osmoreceptive and sodium-receptive neurons that control drinking, vasopressin release, sodium excretion, and sodium appetite.\n\nThey also contain neurons with receptors for angiotensin, atrial natriuretic factor, endothelin and relaxin, each of which important in the regulation of fluid and electrolyte balance.\n\nNeurons in the OVLT and SFO project to the supraoptic nucleus and paraventricular nucleus, and also to preoptic hypothalamic areas.\n\nThe circumventricular organs may also be the site of action of interleukins to elicit both fever and ACTH secretion, via effects on paraventricular neurons.It is not clear how all peptides that influence hypothalamic activity gain the necessary access.\n\nIn the case of prolactin and leptin, there is evidence of active uptake at the choroid plexus from the blood into the cerebrospinal fluid (CSF).\n\nSome pituitary hormones have a negative feedback influence upon hypothalamic secretion; for example, growth hormone feeds back on the hypothalamus, but how it enters the brain is not clear.\n\nThere is also evidence for central actions of prolactin.Findings have suggested that thyroid hormone (T4) is taken up by the hypothalamic glial cells in the infundibular nucleus/ median eminence, and that it is here converted into T3 by the type 2 deiodinase (D2).\n\nSubsequent to this, T3 is transported into the thyrotropin-releasing hormone (TRH)-producing neurons in the paraventricular nucleus.\n\nThyroid hormone receptors have been found in these neurons, indicating that they are indeed sensitive to T3 stimuli.\n\nIn addition, these neurons expressed MCT8, a thyroid hormone transporter, supporting the theory that T3 is transported into them.\n\nT3 could then bind to the thyroid hormone receptor in these neurons and affect the production of thyrotropin-releasing hormone, thereby regulating thyroid hormone production.The hypothalamus functions as a type of thermostat for the body.\n\nIt sets a desired body temperature, and stimulates either heat production and retention to raise the blood temperature to a higher setting or sweating and vasodilation to cool the blood to a lower temperature.\n\nAll fevers result from a raised setting in the hypothalamus; elevated body temperatures due to any other cause are classified as hyperthermia.\n\nRarely, direct damage to the hypothalamus, such as from a stroke, will cause a fever; this is sometimes called a hypothalamic fever.\n\nHowever, it is more common for such damage to cause abnormally low body temperatures.\n\n==== Steroids ====\nThe hypothalamus contains neurons that react strongly to steroids and glucocorticoids – (the steroid hormones of the adrenal gland, released in response to ACTH).\n\nIt also contains specialized glucose-sensitive neurons (in the arcuate nucleus and ventromedial hypothalamus), which are important for appetite.\n\nThe preoptic area contains thermosensitive neurons; these are important for TRH secretion.\n\n==== Neural ====\nOxytocin secretion in response to suckling or vagino-cervical stimulation is mediated by some of these pathways; vasopressin secretion in response to cardiovascular stimuli arising from chemoreceptors in the carotid body and aortic arch, and from low-pressure atrial volume receptors, is mediated by others.\n\nIn the rat, stimulation of the vagina also causes prolactin secretion, and this results in pseudo-pregnancy following an infertile mating.\n\nIn the rabbit, coitus elicits reflex ovulation.\n\nIn the sheep, cervical stimulation in the presence of high levels of estrogen can induce maternal behavior in a virgin ewe.\n\nThese effects are all mediated by the hypothalamus, and the information is carried mainly by spinal pathways that relay in the brainstem.\n\nStimulation of the nipples stimulates release of oxytocin and prolactin and suppresses the release of LH and FSH.\nCardiovascular stimuli are carried by the vagus nerve.\n\nThe vagus also conveys a variety of visceral information, including for instance signals arising from gastric distension or emptying, to suppress or promote feeding, by signalling the release of leptin or gastrin, respectively.\n\nAgain this information reaches the hypothalamus via relays in the brainstem.\nIn addition hypothalamic function is responsive to—and regulated by—levels of all three classical monoamine neurotransmitters, noradrenaline, dopamine, and serotonin (5-hydroxytryptamine), in those tracts from which it receives innervation.\n\nFor example, noradrenergic inputs arising from the locus coeruleus have important regulatory effects upon corticotropin-releasing hormone (CRH) levels.\n\n=== Control of food intake ===\n\nThe extreme lateral part of the ventromedial nucleus of the hypothalamus is responsible for the control of food intake.\n\nStimulation of this area causes increased food intake.\n\nBilateral lesion of this area causes complete cessation of food intake.\n\nMedial parts of the nucleus have a controlling effect on the lateral part.\n\nBilateral lesion of the medial part of the ventromedial nucleus causes hyperphagia and obesity of the animal.\n\nFurther lesion of the lateral part of the ventromedial nucleus in the same animal produces complete cessation of food intake.\nThere are different hypotheses related to this regulation:\nLipostatic hypothesis: This hypothesis holds that adipose tissue produces a humoral signal that is proportionate to the amount of fat and acts on the hypothalamus to decrease food intake and increase energy output.\n\nIt has been evident that a hormone leptin acts on the hypothalamus to decrease food intake and increase energy output.\nGutpeptide hypothesis: gastrointestinal hormones like Grp, glucagons, CCK and others claimed to inhibit food intake.\n\nThe food entering the gastrointestinal tract triggers the release of these hormones, which act on the brain to produce satiety.\n\nThe brain contains both CCK-A and CCK-B receptors.\nGlucostatic hypothesis: The activity of the satiety center in the ventromedial nuclei is probably governed by the glucose utilization in the neurons.\n\nIt has been postulated that when their glucose utilization is low and consequently when the arteriovenous blood glucose difference across them is low, the activity across the neurons decrease.\n\nUnder these conditions, the activity of the feeding center is unchecked and the individual feels hungry.\n\nFood intake is rapidly increased by intraventricular administration of 2-deoxyglucose therefore decreasing glucose utilization in cells.\nThermostatic hypothesis: According to this hypothesis, a decrease in body temperature below a given set-point stimulates appetite, whereas an increase above the set-point inhibits appetite.\n\n=== Fear processing ===\n\nThe medial zone of hypothalamus is part of a circuitry that controls motivated behaviors, like defensive behaviors.\n\nAnalyses of Fos-labeling showed that a series of nuclei in the \"behavioral control column\" is important in regulating the expression of innate and conditioned defensive behaviors.\nAntipredatory defensive behaviorExposure to a predator (such as a cat) elicits defensive behaviors in laboratory rodents, even when the animal has never been exposed to a cat.\n\nIn the hypothalamus, this exposure causes an increase in Fos-labeled cells in the anterior hypothalamic nucleus, the dorsomedial part of the ventromedial nucleus, and in the ventrolateral part of the premammillary nucleus (PMDvl).\n\nThe premammillary nucleus has an important role in expression of defensive behaviors towards a predator, since lesions in this nucleus abolish defensive behaviors, like freezing and flight.\n\nThe PMD does not modulate defensive behavior in other situations, as lesions of this nucleus had minimal effects on post-shock freezing scores.\n\nThe PMD has important connections to the dorsal periaqueductal gray, an important structure in fear expression.\n\nIn addition, animals display risk assessment behaviors to the environment previously associated with the cat.\n\nFos-labeled cell analysis showed that the PMDvl is the most activated structure in the hypothalamus, and inactivation with muscimol prior to exposure to the context abolishes the defensive behavior.\n\nTherefore, the hypothalamus, mainly the PMDvl, has an important role in expression of innate and conditioned defensive behaviors to a predator.\n\nSocial defeatLikewise, the hypothalamus has a role in social defeat: Nuclei in medial zone are also mobilized during an encounter with an aggressive conspecific.\n\nThe defeated animal has an increase in Fos levels in sexually dimorphic structures, such as the medial pre-optic nucleus, the ventrolateral part of ventromedial nucleus, and the ventral premammilary nucleus.\n\nSuch structures are important in other social behaviors, such as sexual and aggressive behaviors.\n\nMoreover, the premammillary nucleus also is mobilized, the dorsomedial part but not the ventrolateral part.\n\nLesions in this nucleus abolish passive defensive behavior, like freezing and the \"on-the-back\" posture.\n\nhttps://en.wikipedia.org/wiki/Hypothalamus","stria-medullaris-thalami":"The stria medullaris is a part of the epithalamus.\n\nIt is a fiber bundle containing afferent fibers from the septal nuclei, lateral preoptico-hypothalamic region, and anterior thalamic nuclei to the habenula.\n\nIt forms a horizontal ridge on the medial surface of the thalamus, and is found on the border between dorsal and medial surfaces of thalamus.\n\nSuperior and lateral to habenular trigone.\nIt projects to the habenular nuclei,\nfrom anterior perforated substance and hypothalamus, to habenular trigone, to habenular commissure, to habenular nucleus.\n\nhttps://en.wikipedia.org/wiki/Stria_medullaris_of_thalamus","posterior-commissure":"The posterior commissure (also known as the epithalamic commissure) is a rounded band of white fibers crossing the middle line on the dorsal aspect of the rostral end of the cerebral aqueduct.\n\nIt is important in the bilateral pupillary light reflex.\nIts fibers acquire their medullary sheaths early, but their connections have not been definitively determined.\n\nMost of them have their origin in a nucleus, the nucleus of the posterior commissure (nucleus of Darkschewitsch), which lies in the periaqueductal grey at rostral end of the cerebral aqueduct, in front of the oculomotor nucleus.\n\nSome are thought to be derived from the posterior part of the thalamus and from the superior colliculus, whereas others are believed to be continued downward into the medial longitudinal fasciculus.\nFor the pupillary light reflex, the olivary pretectal nucleus innervates both Edinger-Westphal nuclei.\n\nTo reach the contralateral Edinger-Westphal nucleus, the axons cross in the posterior commissure.\n\n== External links ==\n\nhttps://en.wikipedia.org/wiki/Posterior_commissure","third-ventricle":"The third ventricle is one of the four connected ventricles of the ventricular system within the mammalian brain.\n\nIt is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and left lateral ventricles, and is filled with cerebrospinal fluid (CSF).Running through the third ventricle is the interthalamic adhesion, which contains thalamic neurons and fibers that may connect the two thalami.\n\n== Structure ==\n\nThe third ventricle is a narrow, laterally flattened, vaguely rectangular region, filled with cerebrospinal fluid, and lined by ependyma.\n\nIt is connected at the superior anterior corner to the lateral ventricles, by the interventricular foramina, and becomes the cerebral aqueduct (aqueduct of Sylvius) at the posterior caudal corner.\n\nSince the interventricular foramina are on the lateral edge, the corner of the third ventricle itself forms a bulb, known as the anterior recess (it is also known as the bulb of the ventricle).\n\nThe roof of the ventricle comprises choroid plexus, forming the inferior central portion of the tela choroidea; immediately above the superior central portion of the tela choroidea is the fornix.\nThe lateral side of the ventricle is marked by a sulcus – the hypothalamic sulcus – from the inferior side of the interventricular foramina to the anterior side of the cerebral aqueduct.\n\nThe lateral border posterior/superior of the sulcus constitutes the thalamus, while anterior/inferior of the sulcus it constitutes the hypothalamus.\n\nThe interthalamic adhesion usually tunnels through the thalamic portion of the ventricle, joining together the left and right halves of the thalamus, although it is sometimes absent, or split into more than one tunnel through the ventricle; it is currently unknown whether any nerve fibres pass between the left and right thalamus via the adhesion (it has more resemblance to a herniation than a commissure).\nThe posterior border of the ventricle primarily constitutes the epithalamus.\n\nThe superior part of the posterior border constitutes the habenular commissure, while more centrally it the pineal gland, which regulates sleep and reacts to light levels.\n\nCaudal of the pineal gland is the posterior commissure; nerve fibres reach the posterior commissure from the adjacent midbrain, but their onward connection is currently uncertain.\n\nThe commissures create concavity to the shape of the posterior ventricle border, causing the suprapineal recess above the habenular, and the deeper pineal recess between the habenular and posterior commissures; the recesses being so-named due to the pineal recess being bordered by the pineal gland.\n\nThe anterior wall of the ventricle forms the lamina terminalis, within which the vascular organ monitors and regulates the osmotic concentration of the blood; the cerebrum lies beyond the lamina, and causes it to have a slightly concave shape.\n\nThe optic recess – marks the inferior end of the lamina terminalis, with the optic chiasm forming the immediately adjacent floor.\nThe portion of the floor immediately posterior of the optic chiasm distends inferiorly, and slightly anteriorly, to form a funnel (the infundibulum); the recess leading to the funnel is known as the infundibular recess.\n\nThe border of the funnel is the tuber cinereum, which constitutes a bundle of nerve fibres from the hypothalamus.\n\nThe funnel ends in the posterior lobe of the pituitary gland, which is thus neurally connected to the hypothalamus via the tuber cinereum.\n\nA venous sinus (the circular sinus) surrounds the superior portion of the tuber cinereum; the circular sinus is in fact simply a portion of the two lateral cavernous sinuses, joined together by a posterior and anterior intercavernous sinus.\nThe mammillary bodies form the floor posterior of the tuber cinereum, acting as the link between the fornix and the hypothalamus.\n\nPosterior of the mamillary bodies, the ventricle becomes the opening of the cerebral aqueduct, the inferior borders becoming the crus cerebri (sometimes historically called the cerebral peduncle) of the midbrain.\n\n== Development ==\n\nThe third ventricle, like other parts of the ventricular system of the brain, develops from the neural canal of the neural tube.\n\nSpecifically, it originates from the most rostral portion of the neural tube which initially expands to become the prosencephalon.\n\nThe lamina terminalis is the rostral termination of the neural tube.\n\nAfter about five weeks, different portions of the prosencephalon begin to take distinct developmental paths from one another – the more rostral portion becomes the telencephalon, while the more caudal portion becomes the diencephalon.\n\nThe telencephalon gradually expands laterally to a much greater extent than it does dorsally or ventrally, and its connection to the remainder of the neural tube reduces to the interventricula foramina.\n\nThe diencephalon expands more evenly, but caudally of the diencephalon the canal remains narrow.\n\nThe third ventricle is the space formed by the expanding canal of the diencephalon.\nThe hypothalamic region of the ventricle develops from the ventral portion of the neural tube, while the thalamic region develops from the dorsal portion; the wall of the tube thickens and becomes the hypothalamus and thalamus respectively.\n\nThe hypothalamic area of the ventricle begins to distend ventrally during the 5th week of development, creating the infundibulum and posterior pituitary; an outgrowth from the stomodeum (the future mouth) gradually extends towards it, to form the anterior pituitary.\nThe optic recess is noticeable by the end of the 6th week, by which time a bend is distinguishable in the dorsal portion of the ventricle border.\n\nRostral of the bend, the medial dorsal portion of the ventrical begins to flatten, and become secretory (i.e. choroid plexus), forming the roof of the ventricle.\n\nCaudal of the bend, the ventricle border forms the epithalamus, and begins to distend towards the parietal bone (in lower vertebrates, it distends more specifically to the parietal eye); the border of the distention forms the pineal gland.\n\n== Clinical significance ==\n\nThe floor of the third ventricle is formed by hypothalamic structures and this can be opened surgically between the mamillary bodies and the pituitary gland in a procedure called an endoscopic third ventriculostomy.\n\nAn endoscopic third ventriculostomy can be performed in order to release extra fluid caused by hydrocephalus.\nSeveral studies have found evidence of ventricular enlargement to be associated with major depression, particularly enlargement of the third ventricle.\n\nThese observations are interpreted as indicating a loss of neural tissue in brain regions adjacent to the enlarged ventricle, leading to suggestions that cytokines and related mediators of neurodegeneration may play a role in giving rise to the disease.A chordoid glioma is a rare tumour that can arise in the third ventricle.\n\nhttps://en.wikipedia.org/wiki/Third_ventricle","lateral-geniculate-body":"/LATERAL GENICULATE NUCLEUS\n\nThe lateral geniculate nucleus (LGN; also called the lateral geniculate body or lateral geniculate complex) is a relay center in the thalamus for the visual pathway.\n\nIt is a small, ovoid, ventral projection of the thalamus where the thalamus connects with the optic nerve.\n\nThere are two LGNs, one on the left and another on the right side of the thalamus.\n\nIn humans, both LGNs have six layers of neurons (grey matter) alternating with optic fibers (white matter).\n\nThe LGN receives information directly from the ascending retinal ganglion cells via the optic tract and from the reticular activating system.\n\nNeurons of the LGN send their axons through the optic radiation, a direct pathway to the primary visual cortex.\n\nIn addition, the LGN receives many strong feedback connections from the primary visual cortex.\n\nIn humans as well as other mammals, the two strongest pathways linking the eye to the brain are those projecting to the dorsal part of the LGN in the thalamus, and to the superior colliculus.\n\n== Structure ==\n\nBoth the left and right hemisphere of the brain have a lateral geniculate nucleus, named after its resemblance to a bent knee (genu is Latin for \"knee\").\n\nIn humans as well as in many other primates, the LGN has layers of magnocellular cells and parvocellular cells that are interleaved with layers of koniocellular cells.\n\nIn humans the LGN is normally described as having six distinctive layers.\n\nThe inner two layers, (1 and 2) are magnocellular layers, while the outer four layers, (3,4,5 and 6), are parvocellular layers.\n\nAn additional set of neurons, known as the koniocellular layers, are found ventral to each of the magnocellular and parvocellular layers.\n\nThis layering is variable between primate species, and extra leafleting is variable within species.\n\n== M, P, K cells ==\n\nSize relates to cell body, dendritic tree and receptive fieldThe magnocellular, parvocellular, and koniocellular layers of the LGN correspond with the similarly named types of retinal ganglion cells.\n\nRetinal P ganglion cells send axons to a parvocellular layer, M ganglion cells send axons to a magnocellular layer, and K ganglion cells send axons to a koniocellular layer.\n\nKoniocellular cells are functionally and neurochemically distinct from M and P cells and provide a third channel to the visual cortex.\n\nThey project their axons between the layers of the lateral geniculate nucleus where M and P cells project.\n\nTheir role in visual perception is presently unclear; however, the koniocellular system has been linked with the integration of somatosensory system-proprioceptive information with visual perception, and it may also be involved in color perception.\n\nThe parvo- and magnocellular fibers were previously thought to dominate the Ungerleider–Mishkin ventral stream and dorsal stream, respectively.\n\nHowever, new evidence has accumulated showing that the two streams appear to feed on a more even mixture of different types of nerve fibers.\n\nThe other major retino–cortical visual pathway is the tectopulvinar pathway, routing primarily through the superior colliculus and thalamic pulvinar nucleus onto posterior parietal cortex and visual area MT.\n\n== Ipsilateral and contralateral layers ==\n\nLayer 1, 2\n\nLarge cells, called magnocellular pathways\nInput from Y-ganglion cells\nVery rapid conduction\nColour blind systemLayer 3–6\n\nParvocellular\nInput from X- ganglion cells\nColour vision\nModerate velocity.Both the LGN in the right hemisphere and the LGN in the left hemisphere receive input from each eye.\n\nHowever, each LGN only receives information from one half of the visual field.\n\nThis occurs due to axons of the ganglion cells from the inner halves of the retina (the nasal sides) decussating (crossing to the other side of the brain) through the optic chiasma (khiasma means \"cross-shaped\").\n\nThe axons of the ganglion cells from the outer half of the retina (the temporal sides) remain on the same side of the brain.\n\nTherefore, the right hemisphere receives visual information from the left visual field, and the left hemisphere receives visual information from the right visual field.\n\nWithin one LGN, the visual information is divided among the various layers as follows:\n\nthe eye on the same side (the ipsilateral eye) sends information to layers 2, 3 and 5\nthe eye on the opposite side (the contralateral eye) sends information to layers 1, 4 and 6.This description applies to the LGN of many primates, but not all.\n\nThe sequence of layers receiving information from the ipsilateral and contralateral (opposite side of the head) eyes is different in the tarsier.\n\nSome neuroscientists suggested that \"this apparent difference distinguishes tarsiers from all other primates, reinforcing the view that they arose in an early, independent line of primate evolution\".\n\nIn visual perception, the right eye gets information from the right side of the world (the right visual field), as well as the left side of the world (the left visual field).\n\nYou can confirm this by covering your left eye: the right eye still sees to your left and right, although on the left side your field of view may be partially blocked by your nose.\n\n== Input ==\n\nThe LGN receives input from the retina and many other brain structures, especially visual cortex.\n\nThe principal neurons in the LGN receive strong inputs from the retina.\n\nHowever, the retina only accounts for a small percentage of LGN input.\n\nAs much as 95% of input in the LGN comes from the visual cortex, superior colliculus, pretectum, thalamic reticular nuclei, and local LGN interneurons.\n\nRegions in the brainstem that are not involved in visual perception also project to the LGN, such as the mesencephalic reticular formation, dorsal raphe nucleus, periaqueuctal grey matter, and the locus coeruleus.\n\nThe LGN also receives some inputs from the optic tectum (also known as the superior colliculus).\n\nThese non-retinal inputs can be excitatory, inhibitory, or modulatory.\n\n== Output ==\n\nInformation leaving the LGN travels out on the optic radiations, which form part of the retrolenticular portion of the internal capsule.\n\nThe axons that leave the LGN go to V1 visual cortex.\n\nBoth the magnocellular layers 1–2 and the parvocellular layers 3–6 send their axons to layer 4 in V1.\n\nWithin layer 4 of V1, layer 4cβ receives parvocellular input, and layer 4cα receives magnocellular input.\n\nHowever, the koniocellular layers, intercalated between LGN layers 1–6 send their axons primarily to the cytochrome-oxidase rich blobs of layers 2 and 3 in V1.\n\nAxons from layer 6 of visual cortex send information back to the LGN.\n\nStudies involving blindsight have suggested that projections from the LGN travel not only to the primary visual cortex but also to higher cortical areas V2 and V3.\n\nPatients with blindsight are phenomenally blind in certain areas of the visual field corresponding to a contralateral lesion in the primary visual cortex; however, these patients are able to perform certain motor tasks accurately in their blind field, such as grasping.\n\nThis suggests that neurons travel from the LGN to both the primary visual cortex and higher cortex regions.\n\n== Function in visual perception ==\n\nThe functions of the LGN are multiple.\n\nIts unique folding contributes to its utility by performing a range of anatomical calculations without requiring mathematical computations.\n\nThese include both temporal correlations/decorrelations as well as spatial correlations.\n\nThe resulting outputs include time correlated and spatially correlated signals resulting from summing the signals received from the left and right semifields of view captured by each of the two eyes.\n\nThese signals are correlated in order to achieve a three-dimensional representation of object space as well as obtain information for controlling the precision (previously auxiliary) optical system (POS) of the visual modality.\n\nThe outputs serve several functions.\n\nA signal is provided to control the vergence of the two eyes so they converge at the principal plane of interest in object space.\n\nA signal is provided to control the focus of the eyes based on the calculated distance to the principal plane of interest.\n\nComputations are achieved to determine the position of every major element in object space relative to the principal plane.\n\nThrough subsequent motion of the eyes, a larger stereoscopic mapping of the visual field is achieved.A tag is provided for each major element in the central 1.2 degree field of view of object space.\n\nThe accumulated tags are attached to the features in the merged visual fields forwarded to area 17 of the cerebral cortex (often described as the \"primary\" visual cortex or V1).\n\nA tag is also provided for each major element in the visual field describing the velocity of the major elements based on its change in coordinates with time.\n\nThe velocity tags (particularly those associated with the peripheral field of view) are also used to determine the direction the organism is moving relative to object space.\n\nThese position and velocity tags are extracted prior to the information reaching area 17.\n\nThey constitute the major source of information reported in blindsight experiments where an individual reports motion in a portion of the visual field associated with one hemisphere of area 17 that has been damaged by laceration, stroke, etc.\n\nThe output signals from the LGN determine the spatial dimensions of the stereoscopic and monoscopic portions of the horopter of the visual system.\n\nIt has been shown that while the retina accomplishes spatial decorrelation through center surround inhibition, the LGN accomplishes temporal decorrelation.\n\nThis spatial–temporal decorrelation makes for much more efficient coding.\n\nHowever, there is almost certainly much more going on.\nLike other areas of the thalamus, particularly other relay nuclei, the LGN likely helps the visual system focus its attention on the most important information.\n\nThat is, if you hear a sound slightly to your left, the auditory system likely \"tells\" the visual system, through the LGN via its surrounding peri-reticular nucleus, to direct visual attention to that part of space.\n\nThe LGN is also a station that refines certain receptive fields.\n\nAxiomatically determined functional models of LGN cells have been determined by Lindeberg in terms of Laplacian of Gaussian kernels over the spatial domain in combination with temporal derivatives of either non-causal or time-causal scale-space kernels over the temporal domain.\n\nIt has been shown that this theory both leads to predictions about receptive fields with good qualitative agreement with the biological receptive field measurements performed by DeAngelis et al. and guarantees good theoretical properties of the mathematical receptive field model, including covariance and invariance properties under natural image transformations.\n\nSpecifically according to this theory, non-lagged LGN cells correspond to first-order temporal derivatives, whereas lagged LGN cells correspond to second-order temporal derivatives.\n\nFor an extensive overview of the function of the LGN in visual perception, see Ghodrati et al.\n\n== Rodents ==\n\nIn rodents, the lateral geniculate nucleus contains the dorsal lateral geniculate nucleus (dLGN), the ventral lateral geniculate nucleus (vLGN), and the region in between called the intergeniculate leaflet (IGL).\n\nThese are distinct subcortical nuclei with differences in function.\n\n=== dLGN ===\n\nThe dorsolateral geniculate nucleus is the main division of the lateral geniculate body.\n\nThe majority of input to the dLGN comes from the retina.\n\nIt is laminated and shows retinotopic organization.\n\n=== vLGN ===\n\nThe ventrolateral geniculate nucleus has been found to be relatively large in several species such as lizards, rodents, cows, cats, and primates.\n\nAn initial cytoarchitectural scheme, which has been confirmed in several studies, suggests that the vLGN is divided into two parts.\n\nThe external and internal divisions are separated by a group of fine fibers and a zone of thinly dispersed neurons.\n\nAdditionally, several studies have suggested further subdivisions of the vLGN in other species.\n\nFor example, studies indicate that the cytoarchitecture of the vLGN in the cat differs from rodents.\n\nAlthough five subdivisions of the vLGN in the cat have been identified by some, the scheme that divides the vLGN into three regions (medial, intermediate, and lateral) has been more widely accepted.\n\n=== IGL ===\n\nThe intergeniculate leaflet is a relatively small area found dorsal to the vLGN.\n\nEarlier studies had referred to the IGL as the internal dorsal division of the vLGN.\n\nSeveral studies have described homologous regions in several species, including humans.\n\nThe vLGN and IGL appear to be closely related based on similarities in neurochemicals, inputs and outputs, and physiological properties.\n\nThe vLGN and IGL have been reported to share many neurochemicals that are found concentrated in the cells, including neuropeptide Y, GABA, encephalin, and nitric oxide synthase.\n\nThe neurochemicals serotonin, acetylcholine, histamine, dopamine, and noradrenaline have been found in the fibers of these nuclei.\nBoth the vLGN and IGL receive input from the retina, locus coreuleus, and raphe.\n\nOther connections that have been found to be reciprocal include the superior colliculus, pretectum, and hypothalamus, as well as other thalamic nuclei.\n\nPhysiological and behavioral studies have shown spectral-sensitive and motion-sensitive responses that vary with species.\n\nThe vLGN and IGL seem to play an important role in mediating phases of the circadian rhythms that are not involved with light, as well as phase shifts that are light-dependent.\n\nhttps://en.wikipedia.org/wiki/Lateral_geniculate_nucleus","medial-geniculate-body":"/MEDIAL GENICULATE NUCLEUS\n\nThe medial geniculate nucleus (MGN) or medial geniculate body (MGB) is part of the auditory thalamus and represents the thalamic relay between the inferior colliculus (IC) and the auditory cortex (AC).\n\nIt is made up of a number of sub-nuclei that are distinguished by their neuronal morphology and density, by their afferent and efferent connections, and by the coding properties of their neurons.\n\nIt is thought that the MGN influences the direction and maintenance of attention.\n\n== Divisions ==\n\nThe MGN has three major divisions; ventral (VMGN), dorsal (DMGN) and medial (MMGN).\n\nWhilst the VMGN is specific to auditory information processing, the DMGN and MMGN also receive information from non-auditory pathways.\n\n=== Ventral subnucleus ===\n\n==== Cell types ====\n\nThere are two main cell types in the ventral subnucleus of the medial geniculate body (VMGN):\n\nThalamocortical relay cells (or principal neurons):\n\n The dendritic input to these cells comes from two sets of dendritic trees oriented on opposite poles of the cell.\n\nThe long axis of the relay cells lie parallel to each other running superior-inferiorly with the dendritic trees of cells within the same iso-frequency band overlapping.\n\nThis is similar to the dendritic organization of the IC, but with a different orientation.\n\nThe dendrites of relay cells form a synaptic nest with ascending axons from the inferior colliculus and intrathalamic interneurons.\n\nIn this synapse, relay cells are excited by input from the IC axons.\n\nAt the same time, they are inhibited by dendritic synapses from the interneurons of the VMGB.\n\nThis type of synaptic nesting is characteristic of other regions in the thalamus as well.\n\nIntrathalamic Interneurons: These interneurons provide inhibitory (GABA) input to the relay cells at the synaptic nests.\n\nThe target of their axons however, is not clear.\n\nSome interneurons appear to target relay cells, while others target other interneurons.\n\nThere is also at least one type of interneuron that appears to not be involved in the synaptic nests.\n\n==== Function ====\n\nThe VMGN is thought to be primarily responsible for relaying frequency, intensity and binaural information to the cortex.\n\nThe responses in the VMGN appear to be organized in a tonotopically similar way to those in the IC.\n\nThe primary difference being that the iso-frequency bands are arranged such that lateral regions are most responsive to low frequencies and medial regions are responsive to high frequencies.\n\nSpatiotopic and modulotopic maps (as in the IC) however have not been well supported by mammalian studies.\n\nBoth monaural (10%) and binaural cells (90%) exist in the MGN.\n\nThe monaural cells are primarily responsive to sound in the contralateral hemifield.\n\nBinaural cells are typically similar to the EE or EI type found in the IC.\n\nDefinitions of abbreviations\n\nIC = Inferior colliculus\n\nEE (Excitatory excitatory) type neurons are characterized by excitatory responses to monaural stimulations of both years.\n\nThis response may either be higher than the monaural response\n(EE– facilitation) Or lower (EE– occlusion)\n\nEI (Excitatory inhibitory) type neurons Are characterized by monaural excitation (usually from the contralateral ear).\n\nThe ipsilateral neuron is inhibited when contralateral ear is stimulated at the same time\n\n=== Dorsal subnucleus ===\n\n==== Cell types ====\n\nThere are a large number of cell types present in the dorsal subnucleus of the medial geniculate body (DMGN):\nAt least two principal cell types have been found, along with two distinct types of interneurons.\n\nSeveral sub-nuclei have been identified based on morphology.\n\nNo frequency-specific layering has been found in the DMGN.\n\n==== Function ====\n\nMany types of responses are present in the DMGB that appear to vary by sub-nuclei.\n\nGenerally, the responses are broadly tuned, but some cells appear to respond only to complex stimuli.\n\nOther cells are multi modal, often responding to somatosensory as well as auditory stimuli.\n\n=== Medial subnucleus ===\n\n==== Cell types ====\n\nCells in the medial subnucleus of the medial geniculate body (MMGN) have large irregular shaped dendritic trees.\n\nThere is no clear segregation based on the source of these inputs.\n\n==== Function ====\n\nThe MMGN seems to functionally be responsible for detection of the relative intensity and duration of a sound.\n\nIt shows a wide range of responses to auditory stimuli.\n\nBinaural interactions found in the MMGN include EE, EI, and IE types.\n\nBoth broadly and narrowly tuned cells have been observed.\n\nA type of intensity tuning has also been observed.\n\nIn this type of cell, the response actually decreases as sound intensity increases above a specific level.\n\nAlmost all cells in the MMGN appear to respond for the duration of the stimulus, and have very little adaptation.\n\nIndividual cells still appear to be preferentially tuned to certain frequencies, but they often have more than one and are broadly tuned within these cell frequencies.\n\nIt is not clear whether there truly is one, none, or many tonotopic organizations maps present in the MMGN.\n\nAnaesthetics tend to have large effects on cells within the MMGN, making responses difficult to study.\n\nFinally, the behaviour of MMGN cells are complicated by the fact that sensory stimulation from other modalities modifies the responsiveness of many, but not all, cells in the MMGN.\n\nhttps://en.wikipedia.org/wiki/Medial_geniculate_nucleus","optic-chiasm":"The optic chiasm, or optic chiasma is the part of the brain where the optic nerves cross.\n\nIt is located at the bottom of the brain immediately inferior to the hypothalamus.\n\nThe optic chiasm is found in all vertebrates, although in cyclostomes (lampreys and hagfishes), it is located within the brain.\n\nThis article is about the optic chiasm of vertebrates, which is the best known nerve chiasm, but not every chiasm denotes a crossing of the body midline (e.g., in some invertebrates, see Chiasm (anatomy)).\n\nA midline crossing of nerves inside the brain is called a decussation (see Definition of types of crossings).\n\n== Structure ==\n\nFor the different types of optic chiasm, see\n\nIn all vertebrates, the optic nerves of the left and the right eye meet in the body midline, ventral to the brain.\n\nIn many vertebrates the left optic nerve crosses over the right one without fusing with it.\n\nIn vertebrates with a large overlap of the visual fields of the two eyes, i.e., most mammals and birds, but also amphibians, reptiles such as chameleons, the two optic nerves merge in the optic chiasm.\n\nIn such a merged optic chiasm, part of the nerve fibres do not cross the midline, but continue towards the optic tract of the ipsilateral side.\n\nBy this partial decussation, the part of the visual field that is covered by both eyes is fused so that the processing of binocular depth perception by stereopsis is enabled.\n\nIn the case of such partial decussation, the optic nerve fibres on the medial sides of each retina (which correspond to the lateral side of each visual hemifield, because the image is inverted) cross over to the opposite side of the body midline.\n\nThe inferonasal retina are related to the anterior portion of the optic chiasm whereas superonasal retinal fibers are related to the posterior portion of the optic chiasm.\n\nThe partial crossing over of optic nerve fibres at the optic chiasm allows the visual cortex to receive the same hemispheric visual field from both eyes.\n\nSuperimposing and processing these monocular visual signals allow the visual cortex to generate binocular and stereoscopic vision.\n\nThe net result is that the right cerebral hemisphere processes left visual hemifield, and the left cerebral hemisphere processes the right visual hemifield.\n\nBeyond the optic chiasm, with crossed and uncrossed fibers, the optic nerves are called optic tracts.\n\nThe optic tract inserts on the optic tectum (in mammals known as superior colliculus) of the midbrain.\n\nIn mammals they also branch off to the lateral geniculate body of the thalamus, in turn giving them to the occipital cortex of the cerebrum.\n\n== Development in mammals ==\n\nDuring development, the crossing of the optic nerves is guided primarily by cues such as netrin, slit, semaphorin and ephrin; and by morphogens such as sonic hedgehog (Shh) and Wnt.\n\nThis navigation is mediated by the neuronal growth cone, a structure that responds to the cues by ligand-receptor signalling systems that activate downstream pathways inducing changes in the cytoskeleton.\n\nRetinal ganglion cell (RGC) axons leaving the eye through the optic nerve are blocked from exiting the developing pathway by Slit2 and Sema5A inhibition, expressed bordering the optic nerve pathway.\n\nSsh expressed at the central nervous system midline inhibits crossing prior to the chiasm, where it is downregulated.\n\nThe organization of RGC axons changes from retinotopic to a flat sheet-like orientation as they approach the chiasm site.\n\nMost RGC axons cross the midline at the ventral diencephalon and continue to the contralateral superior colliculus.\n\nThe number of axons that do not cross the midline and project ipsilaterally depends on the degree of binocular vision of the animal (3% in mice and 45% in humans do not cross).\n\nEphrin-B2 is expressed at the chiasm midline by radial glia and acts as a repulsive signal to axons originating from the ventrotemporal retina expressing EphB1 receptor protein, giving rise to the ipsilateral, or uncrossed, projection.\n\nRGC axons that do cross at the optic chiasm are guided by the vascular endothelial growth factor, VEGF-A, expressed at the midline, which signals through the receptor Neuropilin-1 (NRP1) expressed on RGC axons.\n\nChiasm crossing is also promoted by Nr-CAM (Ng-CAM-related cell adhesion molecule) and Semaphorin6D (Sema6D) expressed at the midline, which form a complex that signals to Nr-CAM/Plexin-A1 receptors on crossing RGC axons.\n\n== Other animals ==\n\n=== Mammals ===\n\nSince all vertebrates, even the earliest fossils and modern jawless ones, possess an optic chiasm, it is not known how it evolved.\n\nA number of theories have been proposed for the function of the optic chiasm in vertebrates (see theories).\n\nAccording to the axial twist hypothesis the optic chiasm develops as a consequence of a twist in the early embryo.\n\nIn Siamese cats with certain genotypes of the albino gene, the wiring is disrupted, with more of the nerve-crossing than normal.\n\nSince siamese cats, like albino tigers, also tend to cross their eyes (strabismus), it has been proposed that this behavior might compensate the abnormal amount of decussation.\n\n=== Cephalopods and insects ===\n\nIn cephalopods and insects the optic tracts do not cross the body midline, so each side of the brain processes the ipsilateral eye.\n\n== History ==\n\nThe crossing of nerve fibres, and the impact on vision that this had, was probably first identified by Persian physician \"Esmail Jorjani\", who appears to be Zayn al-Din Gorgani (1042–1137).\n\nhttps://en.wikipedia.org/wiki/Optic_chiasm","nucleus-of-oculomotor-nerve":"OCULOMOTOR NUCLEUS\n\nThe fibers of the oculomotor nerve arise from a nucleus in the midbrain, which lies in the gray substance of the floor of the cerebral aqueduct and extends in front of the aqueduct for a short distance into the floor of the third ventricle.\n\nFrom this nucleus the fibers pass forward through the tegmentum, the red nucleus, and the medial part of the substantia nigra, forming a series of curves with a lateral convexity, and emerge from the oculomotor sulcus on the medial side of the cerebral peduncle.\n\nThe nucleus of the oculomotor nerve does not consist of a continuous column of cells, but is broken up into a number of smaller nuclei, which are arranged in two groups, anterior and posterior.\n\nThose of the posterior group are six in number, five of which are symmetrical on the two sides of the middle line, while the sixth is centrally placed and is common to the nerves of both sides.\n\nThe anterior group consists of two nuclei, an antero-medial and an antero-lateral.\n\nThe nucleus of the oculomotor nerve, considered from a physiological standpoint, can be subdivided into several smaller groups of cells, each group controlling a particular muscle.\n\nA nearby nucleus, the Edinger-Westphal nucleus lies dorsal to the main oculomotor nucleus.\n\nIt is responsible for the autonomic functions of the oculomotor nerve, including pupillary constriction and lens accommodation.\n\nhttps://en.wikipedia.org/wiki/Oculomotor_nucleus","accessory-nucleus-of-oculomotor-nerve":"OCULOMOTOR NUCLEUS\n\nThe fibers of the oculomotor nerve arise from a nucleus in the midbrain, which lies in the gray substance of the floor of the cerebral aqueduct and extends in front of the aqueduct for a short distance into the floor of the third ventricle.\n\nFrom this nucleus the fibers pass forward through the tegmentum, the red nucleus, and the medial part of the substantia nigra, forming a series of curves with a lateral convexity, and emerge from the oculomotor sulcus on the medial side of the cerebral peduncle.\n\nThe nucleus of the oculomotor nerve does not consist of a continuous column of cells, but is broken up into a number of smaller nuclei, which are arranged in two groups, anterior and posterior.\n\nThose of the posterior group are six in number, five of which are symmetrical on the two sides of the middle line, while the sixth is centrally placed and is common to the nerves of both sides.\n\nThe anterior group consists of two nuclei, an antero-medial and an antero-lateral.\n\nThe nucleus of the oculomotor nerve, considered from a physiological standpoint, can be subdivided into several smaller groups of cells, each group controlling a particular muscle.\n\nA nearby nucleus, the Edinger-Westphal nucleus lies dorsal to the main oculomotor nucleus.\n\nIt is responsible for the autonomic functions of the oculomotor nerve, including pupillary constriction and lens accommodation.\n\nhttps://en.wikipedia.org/wiki/Oculomotor_nucleus","red-nucleus":"The red nucleus or nucleus ruber is a structure in the rostral midbrain involved in motor coordination.\n\nThe red nucleus is pale pink, which is believed to be due to the presence of iron in at least two different forms: hemoglobin and ferritin.\n\nThe structure is located in the tegmentum of the midbrain next to the substantia nigra and comprises caudal magnocellular and rostral parvocellular components.\n\nThe red nucleus and substantia nigra are subcortical centers of the extrapyramidal motor system.\n\n== Function ==\n\nIn a vertebrate without a significant corticospinal tract, gait is mainly controlled by the red nucleus.\n\nHowever, in primates, where the corticospinal tract is dominant, the rubrospinal tract may be regarded as vestigial in motor function.\n\nTherefore, the red nucleus is less important in primates than in many other mammals.\n\nNevertheless, the crawling of babies is controlled by the red nucleus, as is arm swinging in typical walking.\n\nThe red nucleus may play an additional role in controlling muscles of the shoulder and upper arm via projections of its magnocellular part.\n\nIn humans, the red nucleus also has limited control over hands, as the rubrospinal tract is more involved in large muscle movement such as that for the arms (but not for the legs, as the tract terminates in the superior thoracic region of the spinal cord).\n\nFine control of the fingers is not modified by the functioning of the red nucleus but relies on the corticospinal tract.\n\nThe majority of red nucleus axons do not project to the spinal cord but, via its parvocellular part, relay information from the motor cortex to the cerebellum through the inferior olivary complex, an important relay center in the medulla.\n\n== Input and output ==\n\nThe red nucleus receives many inputs from the cerebellum (interposed nucleus and the lateral cerebellar nucleus) of the opposite side and an input from the motor cortex of the same side.The red nucleus has two sets of efferents:\n\nIn humans, the majority of the output goes to the bundle of fibers continues through the medial tegmental field toward the inferior olive of the same side, to form part of a pathway that ultimately influence the cerebellum.\n\nThe other output (the rubrospinal projection) goes to the rhombencephalic reticular formation and spinal cord of the opposite side, making up the rubrospinal tract, which runs ventral to the lateral corticospinal tract.\n\nAs stated earlier, the rubrospinal tract is more important in non-primate species: in primates, because of the well-developed cerebral cortex, the corticospinal tract has taken over the role of the rubrospinal.\n\nhttps://en.wikipedia.org/wiki/Red_nucleus","superior-colliculus":"The superior colliculus (Latin for upper hill) is a structure lying on the roof of the mammalian midbrain.\n\nIn non-mammalian vertebrates, the homologous structure is known as the optic tectum, or optic lobe.\n\nThe adjective form tectal is commonly used for both structures.\n\nIn mammals, the superior colliculus forms a major component of the midbrain.\n\nIt is a paired structure and together with the paired inferior colliculi forms the lamina quadrigemina.\n\nThe superior colliculus is a layered structure, with a pattern that is similar to all mammals.\n\nThe layers can be grouped into the superficial layers (stratum opticum and above) and the deeper remaining layers.\n\nNeurons in the superficial layers receive direct input from the retina and respond almost exclusively to visual stimuli.\n\nMany neurons in the deeper layers also respond to other modalities, and some respond to stimuli in multiple modalities.\n\nThe deeper layers also contain a population of motor-related neurons, capable of activating eye movements as well as other responses.\n\nIn other vertebrates the number of layers in the homologous optic tectum varies.\n\nThe general function of the tectal system is to direct behavioral responses toward specific points in body-centered space.\n\nEach layer contains a topographic map of the surrounding world in retinotopic coordinates, and activation of neurons at a particular point in the map evokes a response directed toward the corresponding point in space.\n\nIn primates, the superior colliculus has been studied mainly with respect to its role in directing eye movements.\n\nVisual input from the retina, or \"command\" input from the cerebral cortex, create a \"bump\" of activity in the tectal map, which, if strong enough, induces a saccadic eye movement.\n\nEven in primates, however, the superior colliculus is also involved in generating spatially directed head turns, arm-reaching movements, and shifts in attention that do not involve any overt movements.\n\nIn other species, the superior colliculus is involved in a wide range of responses, including whole-body turns in walking rats.\n\nIn mammals, and especially primates, the massive expansion of the cerebral cortex reduces the superior colliculus to a much smaller fraction of the whole brain.\n\nIt remains nonetheless important in terms of function as the primary integrating center for eye movements.\n\nIn non-mammalian species the optic tectum is involved in many responses including swimming in fish, flying in birds, tongue-strikes toward prey in frogs, and fang-strikes in snakes.\n\nIn some species, including fish and birds, the optic tectum, also known as the optic lobe, is one of the largest components of the brain.\n\nNote on terminology:\n\n This article follows terminology established in the literature, using the term \"superior colliculus\" when discussing mammals and \"optic tectum\" when discussing either specific non-mammalian species or vertebrates in general.\n\n== Structure ==\n\nThe superior colliculus is a synaptic layered structure.\n\nThe two superior colliculi sit below the thalamus and surround the pineal gland in the mammalian midbrain.\n\nIt comprises the dorsal aspect of the midbrain, posterior to the periaqueductal gray and immediately superior to the inferior colliculus.\n\nThe inferior and superior colliculi are known collectively as the corpora quadrigemina (Latin for quadruplet bodies).\n\nThe superior colliculi are larger than the inferior colliculi, though the inferior colliculi are more prominent.\n\nThe brachium of superior colliculus (or superior brachium) is a branch that extends laterally from the superior colliculus, and, passing to the thalamus between the pulvinar and the medial geniculate nuclei, is partly continued into an eminence called the lateral geniculate nucleus, and partly into the optic tract.\n\nThe superior colliculus is associated with a nearby structure called the parabigeminal nucleus, often referred to as its satellite.\n\nIn the optic tectum this nearby structure is known as the nucleus isthmi.\n\n=== Neural circuitry ===\n\nThe microstructure of the superior colliculus and of the optic tectum, varies across species.\n\nAs a general rule, there is always a clear distinction between superficial layers, which receive input primarily from the visual system and show primarily visual responses, and deeper layers, which receive many types of input and project to numerous motor-related brain areas.\n\nThe distinction between these two zones is so clear and consistent that some anatomists have suggested that they should be considered separate brain structures.\n\nIn mammals, neuroanatomists conventionally identify seven layers The top three layers are called superficial:\n\nLamina I or SZ, the stratum zonale, is a thin layer consisting of small myelinated axons together with marginal and horizontal cells.\n\nLamina II or SGS, the stratum griseum superficiale (\"superficial gray layer\"), contains many neurons of various shapes and sizes.\n\nLamina III or SO, the stratum opticum (\"optic layer\"), consists mainly of axons coming from the optic tract.Next come two intermediate layers:\n\nLamina IV or SGI, the stratum griseum intermedium (\"intermediate gray layer\"), is the thickest layer, and is filled with many neurons of many sizes.\n\nThis layer is often as thick as all the other layers together.\n\nIt is often subdivided into \"upper\" and \"lower\" parts.\nLamina V or SAI, the stratum album intermedium (\"intermediate white layer\"), consists mainly of fibers from various sources.Finally come the two deep layers:\n\nLamina VI or SGP, the stratum griseum profundum (\"deep gray layer\"), consists of loosely packed neurons and myelinated fibers.\n\nLamina VII or SAP, the stratum album profundum (\"deep white layer\"), lying directly above the periaqueductal gray, consists entirely of fibers.\n\nThe superficial layers receive input mainly from the retina, vision-related areas of the cerebral cortex, and two tectal-related structures called the pretectum and parabigeminal nucleus.\n\nThe retinal input encompasses the entire superficial zone, and is bilateral, although the contralateral portion is more extensive.\n\nThe cortical input comes most heavily from the primary visual cortex (area 17, V1), the secondary visual cortex (areas 18 and 19), and the frontal eye fields.\n\nThe parabigeminal nucleus plays a very important role in tectal function that is described below.\n\nIn contrast to the vision-dominated inputs to the superficial layers, the intermediate and deep layers receive inputs from a very diverse set of sensory and motor structures.\n\nMost areas of the cerebral cortex project to these layers, although the input from \"association\" areas tends to be heavier than the input from primary sensory or motor areas.\n\nHowever, the cortical areas involved, and the strength of their relative projections differs across species.\n\nAnother important input comes from the substantia nigra, pars reticulata, a component of the basal ganglia.\n\nThis projection uses the inhibitory neurotransmitter GABA, and is thought to exert a \"gating\" effect on the superior colliculus.\n\nThe intermediate and deep layers also receive input from the spinal trigeminal nucleus, which conveys somatosensory information from the face, as well as the hypothalamus, zona incerta, thalamus, and inferior colliculus.\n\nIn addition to their distinctive inputs, the superficial and deep zones of the superior colliculus also have distinctive outputs.\n\nOne of the most important outputs goes to the pulvinar and lateral intermediate areas of the thalamus, which in turn project to areas of the cerebral cortex that are involved in controlling eye movements.\n\nThere are also projections from the superficial zone to the pretectal nuclei, lateral geniculate nucleus of the thalamus, and the parabigeminal nucleus.\n\nThe projections from the deeper layers are more extensive.\n\nThere are two large descending pathways, traveling to the brainstem and spinal cord, and numerous ascending projections to a variety of sensory and motor centers, including several that are involved in generating eye movements.\n\nBoth colliculi also have descending projections to the paramedian pontine reticular formation and spinal cord, and thus can be involved in responses to stimuli faster than cortical processing would allow.\n\n=== Mosaic structure ===\n\nOn detailed examination the collicular layers are actually not smooth sheets, but divided into a honeycomb arrangement of discrete columns.\n\nThe clearest indication of columnar structure comes from the cholinergic inputs arising from the parabigeminal nucleus, whose terminals form evenly spaced clusters that extend from top to bottom of the tectum.\n\nSeveral other neurochemical markers including calretinin, parvalbumin, GAP-43, and NMDA receptors, and connections with numerous other brain structures in the brainstem and diencephalon, also show a corresponding inhomogeneity.\n\nThe total number of columns has been estimated at around 100.\n\nThe functional significance of this columnar architecture is not clear, but it is interesting that recent evidence has implicated the cholinergic inputs as part of a recurrent circuit producing winner-take-all dynamics within the tectum, as described in more detail below.\n\nAll species that have been examined — including mammals and non-mammals — show compartmentalization, but there are some systematic differences in the details of the arrangement.\n\nIn species with a streak-type retina (mainly species with laterally placed eyes, such as rabbits and deer), the compartments cover the full extent of the SC.\n\nIn species with a centrally placed fovea, however, the compartmentalization breaks down in the front (rostral) part of the SC.\n\nThis portion of the SC contains many \"fixation\" neurons that fire continually while the eyes remain fixed in a constant position.\n\n== Function ==\n\nThe history of investigation of the optic tectum has been marked by several large shifts in opinion.\n\nBefore about 1970, most studies involved non-mammals — fish, frogs, birds - that is, species in which the optic tectum is the dominant structure that receives input from the eyes.\n\nThe general view then was that the optic tectum, in these species, is the main visual center in the non-mammalian brain, and, as a consequence, is involved in a wide variety of behaviors.\n\nFrom the 1970s to 1990s, however, neural recordings from mammals, mostly monkeys, focused primarily on the role of the superior colliculus in controlling eye movements.\n\nThis line of investigation came to dominate the literature to such a degree that the majority opinion was that eye-movement control is the only important function in mammals, a view still reflected in many current textbooks.\n\nIn the late 1990s, however, experiments using animals whose heads were free to move showed clearly that the SC actually produces gaze shifts, usually composed of combined head and eye movements, rather than eye movements per se.\n\nThis discovery reawakened interest in the full breadth of functions of the superior colliculus, and led to studies of multisensory integration in a variety of species and situations.\n\nNevertheless, the role of the SC in controlling eye movements is understood in much greater depth than any other function.\n\nBehavioral studies have shown that the SC is not needed for object recognition, but plays a critical role in the ability to direct behaviors toward specific objects, and can support this ability even in the absence of the cerebral cortex.\n\nThus, cats with major damage to the visual cortex cannot recognize objects, but may still be able to follow and orient toward moving stimuli, although more slowly than usual.\n\nIf one half of the SC is removed, however, the cats will circle constantly toward the side of the lesion, and orient compulsively toward objects located there, but fail to orient at all toward objects located in the opposite hemifield.\n\nThese deficits diminish over time but never disappear.\n\n=== Eye movements ===\n\nIn primates, eye movements can be divided into several types: fixation, in which the eyes are directed toward a motionless object, with eye movements only to compensate for movements of the head; smooth pursuit, in which the eyes move steadily to track a moving object; saccades, in which the eyes move very rapidly from one location to another; and vergence, in which the eyes move simultaneously in opposite directions to obtain or maintain single binocular vision.\n\nThe superior colliculus is involved in all of these, but its role in saccades has been studied most intensively.\n\nEach of the two colliculi — one on each side of the brain — contains a two-dimensional map representing half of the visual field.\n\nThe fovea — the region of maximum sensitivity — is represented at the front edge of the map, and the periphery at the back edge.\n\nEye movements are evoked by activity in the deep layers of the SC.\n\nDuring fixation, neurons near the front edge — the foveal zone — are tonically active.\n\nDuring smooth pursuit, neurons a small distance from the front edge are activated, leading to small eye movements.\n\nFor saccades, neurons are activated in a region that represents the point to which the saccade will be directed.\n\nJust prior to a saccade, activity rapidly builds up at the target location and decreases in other parts of the SC.\n\nThe coding is rather broad, so that for any given saccade the activity profile forms a \"hill\" that encompasses a substantial fraction of the collicular map:\n\n The location of the peak of this \"hill\" represents the saccade target.\n\nThe SC encodes the target of a gaze shift, but it does not seem to specify the precise movements needed to get there.\n\nThe decomposition of a gaze shift into head and eye movements and the precise trajectory of the eye during a saccade depend on integration of collicular and non-collicular signals by downstream motor areas, in ways that are not yet well understood.\n\nRegardless of how the movement is evoked or performed, the SC encodes it in \"retinotopic\" coordinates: that is, the location of the SC 'hill\" corresponds to a fixed location on the retina.\n\nThis seems to contradict the observation that stimulation of a single point on the SC can result in different gaze shift directions, depending on initial eye orientation.\n\nHowever, it has been shown that this is because the retinal location of a stimulus is a non-linear function of target location, eye orientation, and the spherical geometry of the eye.\n\nThere has been some controversy about whether the SC merely commands eye movements, and leaves the execution to other structures, or whether it actively participates in the performance of a saccade.\n\nIn 1991, Munoz et al., on the basis of data they collected, argued that, during a saccade, the \"hill\" of activity in the SC moves gradually, to reflect the changing offset of the eye from the target location while the saccade is progressing.\n\nAt present, the predominant view is that, although the \"hill\" does shift slightly during a saccade, it does not shift in the steady and proportionate way that the \"moving hill\" hypothesis predicts.\n\nHowever, moving hills may play another role in the superior colliculus; more recent experiments have demonstrated a continuously moving hill of visual memory activity when the eyes move slowly while a separate saccade target is retained.\n\nThe output from the motor sector of the SC goes to a set of midbrain and brainstem nuclei, which transform the \"place\" code used by the SC into the \"rate\" code used by oculomotor neurons.\n\nEye movements are generated by six muscles, arranged in three orthogonally-aligned pairs.\n\nThus, at the level of the final common path, eye movements are encoded in essentially a Cartesian coordinate system.\n\nAlthough the SC receives a strong input directly from the retina, in primates it is largely under the control of the cerebral cortex, which contains several areas that are involved in determining eye movements.\n\nThe frontal eye fields, a portion of the motor cortex, are involved in triggering intentional saccades, and an adjoining area, the supplementary eye fields, are involved in organizing groups of saccades into sequences.\n\nThe parietal eye fields, farther back in the brain, are involved mainly in reflexive saccades, made in response to changes in the view.\n\nRecent evidence suggests that the primary visual cortex (V1) guides reflexive eye movements, according to V1 Saliency Hypothesis, using a bottom-up saliency map of the visual field generated in V1 from external visual inputs.\n\nThe SC only receives visual inputs in its superficial layers, whereas the deeper layers of the colliculus receive also auditory and somatosensory inputs and are connected to many sensorimotor areas of the brain.\n\nThe colliculus as a whole is thought to help orient the head and eyes toward something seen and heard.\n\nThe superior colliculus also receives auditory information from the inferior colliculus.\n\nThis auditory information is integrated with the visual information already present to produce the ventriloquism effect.\n\n=== Distractibility ===\n\nAs well as being related to eye movements, the SC appears to have an important role to play in the circuitry underpinning distractibility.\n\nHeightened distractibility occurs in normal aging and is also a central feature in a number of medical conditions, including attention deficit hyperactivity disorder (ADHD).\n\nResearch has shown that lesions to the SC in a number of species can result in heightened distractibility and, in humans, removing the inhibitory control on the SC from the pre-frontal cortex, therefore increasing activity in the area, also increases distractibility.\n\nResearch in an animal model of ADHD, the spontaneously hypertensive rat, also shows altered collicular-dependent behaviours and physiology.\n\nFurthermore, amphetamine (a mainstay treatment for ADHD) also suppresses activity in the colliculus in healthy animals.\n\nhttps://en.wikipedia.org/wiki/Superior_colliculus","inferior-colliculus":"The inferior colliculus (IC) (Latin for lower hill) is the principal midbrain nucleus of the auditory pathway and receives input from several peripheral brainstem nuclei in the auditory pathway, as well as inputs from the auditory cortex.\n\nThe inferior colliculus has three subdivisions: the central nucleus, a dorsal cortex by which it is surrounded, and an external cortex which is located laterally.\n\nIts bimodal neurons are implicated in auditory-somatosensory interaction, receiving projections from somatosensory nuclei.\n\nThis multisensory integration may underlie a filtering of self-effected sounds from vocalization, chewing, or respiration activities.\n\nThe inferior colliculi together with the superior colliculi form the eminences of the corpora quadrigemina, and also part of the tectal region of the midbrain.\n\nThe inferior colliculus lies caudal to its counterpart – the superior colliculus – above the trochlear nerve, and at the base of the projection of the medial geniculate nucleus and the lateral geniculate nucleus.\n\n== Subdivisions ==\n\nThe inferior colliculus has three subdivisions – the central nucleus, the dorsal cortex by which it is surrounded, and an external cortex which is located laterally.\n\n== Relationship to auditory system ==\n\nThe inferior colliculi of the midbrain are located just below the visual processing centers known as the superior colliculi.\n\nThe inferior colliculus is the first place where vertically orienting data from the fusiform cells in the dorsal cochlear nucleus can finally synapse with horizontally orienting data.\n\nSound location data thus becomes fully integrated by the inferior colliculus.\n\nIC are large auditory nuclei on the right and left sides of the midbrain.\n\nOf the three subdivisions the central nucleus of IC (CNIC) is the principal way station for ascending auditory information in the IC.\n\n=== Input and output connections of IC ===\n\nThe input connections to the inferior colliculus are composed of many brainstem nuclei.\n\nAll nuclei except the contralateral ventral nucleus of the lateral lemniscus send projections to the central nucleus (CNIC) bilaterally.\n\nIt has been shown that great majority of auditory fibers ascending in the lateral lemniscus terminate in the CNIC.\n\nIn addition, the IC receives inputs from the auditory cortex, the medial division of the medial geniculate body, the posterior limitans, suprapeduncular nucleus and subparafascicular intralaminar nuclei of the thalamus, the substantia nigra pars compacta lateralis, the dorsolateral periaqueductal gray, the nucleus of the brachium of the inferior colliculus (or inferior brachium) and deep layers of the superior colliculus.\n\nThe inferior brachium carries auditory afferent fibers from the inferior colliculus of the mesencephalon to the medial geniculate nucleus.\n\nThe inferior colliculus receives input from both the ipsilateral and contralateral cochlear nucleus and respectively the corresponding ears.\n\nThere is some lateralization, the dorsal projections (containing vertical data) only project to the contralateral inferior colliculus.\n\nThis inferior colliculus contralateral to the ear it is receiving the most information from, then projects to its ipsilateral medial geniculate nucleus.\n\nThe inferior colliculus also receives descending inputs from the auditory cortex and auditory thalamus (or medial geniculate nucleus).\n\nThe medial geniculate body (MGB) is the output connection from inferior colliculus and the last subcortical way station.\n\nThe MGB is composed of ventral, dorsal, and medial divisions, which are relatively similar in humans and other mammals.\n\nThe ventral division receives auditory signals from the central nucleus of the IC.\n\n=== Function of IC ===\n\nThe majority of the ascending fibers from the lateral lemniscus project to IC, which means major ascending auditory pathways converge here.\n\nIC appears as an integrative station and switchboard as well.\n\nIt is involved in the integration and routing of multi-modal sensory perception, mainly the startle response and vestibulo-ocular reflex.\n\nIt is also responsive to specific amplitude modulation frequencies and this might be responsible for detection of pitch.\n\nIn addition, spatial localization by binaural hearing is a related function of IC as well.\nThe inferior colliculus has a relatively high metabolism in the brain.\n\nThe Conrad Simon Memorial Research Initiative measured the blood flow of the IC and put a number at 1.80 cc/g/min in the cat brain.\n\nFor reference, the runner up in the included measurements was the somatosensory cortex at 1.53.\n\nThis indicates that the inferior colliculus is metabolically more active than many other parts of the brain.\n\nThe hippocampus, normally considered to use up a disproportionate amount of energy, was not measured or compared.\n\nSkottun et al. measured the interaural time difference sensitivity of single neurons in the inferior colliculus, and used these to predict behavioural performance.\n\nThe predicted just noticeable difference was comparable to that achieved by humans in behavioral tests.\n\nThis suggested that by the level of the inferior colliculus, integration of information over multiple neurons is unnecessary (see population code).\n\nAxiomatically determined functional models of spectro-temporal receptive fields in inferior colliculus have been determined by Lindeberg and Friberg in terms of derivatives of Gaussian functions over the log-spectral domain and either Gaussian kernels over time in the case of non-causal time or first-order integrators (truncated exponential kernels) coupled in cascade in the case of truly time-causal operations, optionally in combination with local glissando transformations to account for variations in frequencies over time.\n\nThe shapes of the receptive field functions in these models can be determined by necessity from structural properties of the environment combined with requirements about the internal structure of the auditory system to enable theoretically well-founded processing of sound signals at different temporal and log-spectral scales.\n\nThereby, the receptive fields in inferior colliculus can be seen as well adapted to handling natural sound transformations.\n\nhttps://en.wikipedia.org/wiki/Inferior_colliculus","midbrain":"The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal (alertness), and temperature regulation.\n\nThe name comes from the Greek mesos, \"middle\", and enkephalos, \"brain\".\n\n== Structure ==\n\nThe principal regions of the midbrain are the tectum, the cerebral aqueduct, tegmentum, and the cerebral peduncles.\n\nRostrally the midbrain adjoins the diencephalon (thalamus, hypothalamus, etc.), while caudally it adjoins the hindbrain (pons, medulla and cerebellum).\n\nIn the rostral direction, the midbrain noticeably splays laterally.\nSectioning of the midbrain is usually performed axially, at one of two levels – that of the superior colliculi, or that of the inferior colliculi.\n\nOne common technique for remembering the structures of the midbrain involves visualizing these cross-sections (especially at the level of the superior colliculi) as the upside-down face of a bear, with the cerebral peduncles forming the ears, the cerebral aqueduct the mouth, and the tectum the chin; prominent features of the tegmentum form the eyes and certain sculptural shadows of the face.\n\n=== Tectum ===\n\nThe tectum (Latin for roof) is the dorsal side of the midbrain.\n\nThe position of the tectum is contrasted with the tegmentum, which refers to the region in front of the ventricular system, or floor of the midbrain.\n\nIt is involved in certain reflexes in response to visual or auditory stimuli.\n\nThe reticulospinal tract, which exerts some control over alertness, takes input from the tectum, and travels both rostrally and caudally from it.\n\nThe corpora quadrigemina are four mounds, called colliculi, in two pairs – a superior and an inferior pair, on the surface of the tectum.\n\nThe superior colliculi process some visual information, aid the decussation of several fibres of the optic nerve (some fibres remain ipsilateral), and are involved with saccadic eye movements.\n\nThe tectospinal tract connects the superior colliculi to the cervical nerves of the neck, and co-ordinates head and eye movements.\n\nEach superior colliculus also sends information to the corresponding lateral geniculate nucleus, with which it is directly connected.\n\nThe homologous structure to the superior colliculus in non mammalian vertebrates including fish and amphibians, is called the optic tectum; in those animals, the optic tectum integrates sensory information from the eyes and certain auditory reflexes.The inferior colliculi – located just above the trochlear nerve – process certain auditory information.\n\nEach inferior colliculus sends information to the corresponding medial geniculate nucleus, with which it is directly connected.\n\n=== Cerebral aqueduct ===\n\nThe cerebral aqueduct is the part of the ventricular system which links the third ventricle (rostrally) with the fourth ventricle (caudally); as such it is responsible for continuing the circulation of cerebrospinal fluid.\n\nThe cerebral aqueduct is a narrow channel located between the tectum and the tegmentum, and is surrounded by the periaqueductal grey, which has a role in analgesia, quiescence, and bonding.\n\nThe dorsal raphe nucleus (which releases serotonin in response to certain neural activity) is located at the ventral side of the periaqueductal grey, at the level of the inferior colliculus.\n\nThe nuclei of two pairs of cranial nerves are similarly located at the ventral side of the periaqueductal grey – the pair of oculomotor nuclei (which control the eyelid, and most eye movements) is located at the level of the superior colliculus, while the pair of trochlear nuclei (which helps focus vision on more proximal objects) is located caudally to that, at the level of the inferior colliculus, immediately lateral to the dorsal raphe nucleus.\n\nThe oculomotor nerve emerges from the nucleus by traversing the ventral width of the tegmentum, while the trochlear nerve emerges via the tectum, just below the inferior colliculus itself; the trochlear is the only cranial nerve to exit the brainstem dorsally.\n\nThe Edinger-Westphal nucleus (which controls the shape of the lens and size of the pupil) is located between the oculomotor nucleus and the cerebral aqueduct.\n\n=== Tegmentum ===\n\nThe midbrain tegmentum is the portion of the midbrain ventral to the cerebral aqueduct, and is much larger in size than the tectum.\n\nIt communicates with the cerebellum by the superior cerebellar peduncles, which enter at the caudal end, medially, on the ventral side; the cerebellar peduncles are distinctive at the level of the inferior colliculus, where they decussate, but they dissipate more rostrally.\n\nBetween these peduncles, on the ventral side, is the median raphe nucleus, which is involved in memory consolidation.\n\nThe main bulk of the tegmentum contains a complex synaptic network of neurons, primarily involved in homeostasis and reflex actions.\n\nIt includes portions of the reticular formation.\n\nA number of distinct nerve tracts between other parts of the brain pass through it.\n\nThe medial lemniscus – a narrow ribbon of fibres – passes through in a relatively constant axial position; at the level of the inferior colliculus it is near the lateral edge, on the ventral side, and retains a similar position rostrally (due to widening of the tegmentum towards the rostral end, the position can appears more medial).\n\nThe spinothalamic tract – another ribbon-like region of fibres – are located at the lateral edge of the tegmentum; at the level of the inferior colliculus it is immediately dorsal to the medial lemiscus, but due to the rostral widening of the tegmentum, is lateral of the medial lemiscus at the level of the superior colliculus.\n\nA prominent pair of round, reddish, regions – the red nuclei (which have a role in motor co-ordination) – are located in the rostral portion of the midbrain, somewhat medially, at the level of the superior colliculus.\n\nThe rubrospinal tract emerges from the red nucleus and descends caudally, primarily heading to the cervical portion of the spine, to implement the red nuclei's decisions.\n\nThe area between the red nuclei, on the ventral side – known as the ventral tegmental area – is the largest dopamine-producing area in the brain, and is heavily involved in the neural reward system.\n\nThe ventral tegmental area is in contact with parts of the forebrain – the mammillary bodies (from the Diencephalon) and hypothalamus (of the diencephalon).\n\n=== Cerebral peduncles ===\n\nThe cerebral peduncles each form a lobe ventrally of the tegmentum, on either side of the midline.\n\nBeyond the midbrain, between the lobes, is the interpeduncular fossa, which is a cistern filled with cerebrospinal fluid.\n\nThe majority of each lobe constitutes the cerebral crus.\n\nThe cerebral crus are the main tracts descending from the thalamus to caudal parts of the central nervous system; the central and medial ventral portions contain the corticobulbar and corticospinal tracts, while the remainder of each crus primarily contains tracts connecting the cortex to the pons.\n\nOlder texts refer to the crus cerebri as the cerebral peduncle; however, the latter term actually covers all fibres communicating with the cerebrum (usually via the diencephalon), and therefore would include much of the tegmentum as well.\n\nThe remainder of the crus pedunculi – small regions around the main cortical tracts – contain tracts from the internal capsule.\n\nThe portion of the lobes in connection with the tegmentum, except the most lateral portion, is dominated by a blackened band – the substantia nigra (literally black substance) – which is the only part of the basal ganglia system outside the forebrain.\n\nIt is ventrally wider at the rostral end.\n\nBy means of the basal ganglia, the substantia nigra is involved in motor-planning, learning, addiction, and other functions.\n\nThere are two regions within the substantia nigra – one where neurons are densely packed (the pars compacta) and one where they aren't (the pars reticulata), which serve a different role from one another within the basal ganglia system.\n\nThe substantia nigra has extremely high production of melanin (hence the colour), dopamine, and noradrenalin; the loss of dopamine-producing neurons in this region contributes to the progression of Parkinson's disease.\n\n== Development ==\n\nDuring embryonic development, the midbrain (also known as the mesencephalon) arises from the second vesicle of the neural tube, while the interior of this portion of the tube becomes the cerebral aqueduct.\n\nUnlike the other two vesicles – the forebrain and hindbrain – the midbrain does not develop further subdivision for the remainder of neural development.\n\nIt does not split into other brain areas. while the forebrain, for example, divides into the telencephalon and the diencephalon.\n\nThroughout embryonic development, the cells within the midbrain continually multiply; this happens to a much greater extent ventrally than it does dorsally.\n\nThe outward expansion compresses the still-forming cerebral aqueduct, which can result in partial or total obstruction, leading to congenital hydrocephalus.\n\nThe tectum is derived in embryonic development from the alar plate of the neural tube.\n\n== Function ==\n\nThe mesencephalon is considered part of the brainstem.\n\nIts substantia nigra is closely associated with motor system pathways of the basal ganglia.\n\nThe human mesencephalon is archipallian in origin, meaning that its general architecture is shared with the most ancient of vertebrates.\n\nDopamine produced in the substantia nigra and ventral tegmental area plays a role in movement, movement planning, excitation, motivation and habituation of species from humans to the most elementary animals such as insects.\n\nLaboratory house mice from lines that have been selectively bred for high voluntary wheel running have enlarged midbrains.\n\nThe midbrain helps to relay information for vision and hearing.\n\n== Related terms ==\n\nThe term \"tectal plate\" or \"quadrigeminal plate\" is used to describe the junction of the gray and white matter in the embryo. (ancil-453 at NeuroNames).\n\nhttps://en.wikipedia.org/wiki/Midbrain","interpeduncular-fossa":"The interpeduncular fossa is a somewhat rhomboid-shaped area of the base of the brain, limited in front by the optic chiasma, behind by the antero-superior surface of the pons, antero-laterally by the converging optic tracts, and postero-laterally by the diverging cerebral peduncles.\n\nThe floor of interpeduncular fossa, from behind forward, are the posterior perforated substance, corpora mamillaria, tuber cinereum, infundibulum, and pituitary gland.\n\nContents of interpeduncular fossa include oculomotor nerve, and circle of Willis.\n\n== Anatomy ==\n\nThe interpeduncular fossa is located in the posterior portion of the brain, in the brain stem.\n\nIt has been found in humans and macaques, but not in rats or mice, showing that this is a relatively new evolutionary region.\n\n== Clinical significance ==\n\nThe most common locations for neurocutaneous melanosis have occurred along the interpeduncular fossa, ventral brainstem, upper cervical cord, and ventral lumbosacral cord.\n\nhttps://en.wikipedia.org/wiki/Interpeduncular_fossa","vestibular-nuclei":"The vestibular nuclei (VN) are the cranial nuclei for the vestibular nerve located in the brainstem.\nIn Terminologia Anatomica they are grouped in both the pons and the medulla in the brainstem.\n\n== Structure ==\n\n=== Path ===\n\nThe fibers of the vestibular nerve enter the medulla oblongata on the medial side of those of the cochlear, and pass between the inferior peduncle and the spinal tract of the trigeminal nerve.\nThey then divide into ascending and descending fibers.\n\nThe latter end by arborizing around the cells of the medial nucleus, which is situated in the area acustica of the rhomboid fossa.\n\nThe ascending fibers either end in the same manner or in the lateral nucleus, which is situated lateral to the area acustica and farther from the ventricular floor.\nSome of the axons of the cells of the lateral nucleus, and possibly also of the medial nucleus, are continued upward through the inferior peduncle to the roof nuclei of the opposite side of the cerebellum, to which also other fibers of the vestibular root are prolonged without interruption in the nuclei of the medulla oblongata.\nA second set of fibers from the medial and lateral nuclei end partly in the tegmentum, while the remainder ascend in the medial longitudinal fasciculus to arborize around the cells of the nuclei of the oculomotor nerve.\nFibers from the lateral vestibular nucleus also pass via the vestibulospinal tract, to anterior horn cells at many levels in the spinal cord, in order to co-ordinate head and trunk movements.\n\n=== Subnuclei ===\n\nThere are 4 subnuclei; they are situated at the floor of the fourth ventricle.\n\nhttps://en.wikipedia.org/wiki/Vestibular_nuclei","nucleus-of-abducens-nerve":"ABDUCENS NUCLEUS\n\nThe abducens nucleus is the originating nucleus from which the abducens nerve (VI) emerges—a cranial nerve nucleus.\n\nThis nucleus is located beneath the fourth ventricle in the caudal portion of the pons, medial to the sulcus limitans.\n\nThe abducens nucleus along with the internal genu of the facial nerve make up the facial colliculus, a hump at the caudal end of the medial eminence on the dorsal aspect of the pons.\n\n== Structure ==\n\nTwo primary neuron types are located in the abducens nucleus: motorneurons and interneurons.\n\nThe former directly drive the contraction of the ipsilateral lateral rectus muscle via the abducens nerve (sixth cranial nerve); contraction of this muscle rotates the eye outward (abduction).\n\nThe latter relay signals from the abducens nucleus to the contralateral oculomotor nucleus, where motoneurons drive the contraction of the ipsilateral medial rectus muscle (hence, contralateral to the abducens nucleus that issues the command) ; contraction of this muscle rotates the eye inward (adduction).\n\n== Function ==\n\nThis \"wiring\" pattern suggests that the main function of the abducens nucleus is to generate coordinated movements of both eyes in the same direction.\n\nIndeed, electrical stimulation of the abducens nucleus has been shown to generate conjugate eye movements (i.e. both eyes rotate in the same direction, and by the same angle).\n\nSuch eye movements occur whenever we look between targets located in the distance.\n\nMoreover, lesions to the axonal tract of interneurons (in the medial longitudinal fasciculus) have been shown to disrupt conjugate eye movements through the paralysis of the contralateral eye.\n\nImportantly, despite the lesions, this muscle remains functional during convergence eye movements.\n\nFinally, experiments where the electrical activity of single neurons in the abducens nucleus has been recorded during slow and fast conjugate eye movements have demonstrated very little differences in the discharge patterns of motoneurons and interneurons.\n\nAltogether, it is now well accepted that the abducens nucleus is a key structure for the conjugated movements of both eyes.\n\n== Clinical significance ==\n\nDamage to the abducens nerve causes monocular ipsilateral lateral ophthalmoparesis: specifically, loss of the ability to move the ipsilateral eye outward (abduction).\n\nIn contrast, damage to the abducens nucleus causes lateral gaze palsy.\n\nThis is due to damage to both the lower motor neurons that innervate the ipsilateral lateral rectus and internuclear neurons that projecting through the contra lateral medial longitudinal fasciculus to the medial rectus subnucleus of the oculomotor nucleus.\n\nNote, however, that the eye contralateral to the lesion can still move in the direction of the lesion during convergence movements.\n\nhttps://en.wikipedia.org/wiki/Abducens_nucleus","motor-nucleus-of-facial-nerve":"FACIAL MOTOR NUCLEUS\n\nThe facial motor nucleus is a collection of neurons in the brainstem that belong to the facial nerve (cranial nerve VII).\n\nThese lower motor neurons innervate the muscles of facial expression and the stapedius.\n\n== Structure ==\n\nThe nucleus is situated in the caudal portion of the ventrolateral pontine tegmentum.\n\nIts axons take an unusual course, traveling dorsally and looping around the abducens nucleus, then traveling ventrally to exit the ventral pons medial to the spinal trigeminal nucleus.\n\nThese axons form the motor component of the facial nerve, with parasympathetic and sensory components forming the intermediate nerve.\n\nThe nucleus has a dorsal and ventral region, with neurons in the dorsal region innervating muscles of the upper face and neurons in the ventral region innervating muscles of the lower face.\n\n== Function ==\n\nBecause it innervates muscles derived from pharyngeal arches, the facial motor nucleus is considered part of the special visceral efferent (SVE) cell column, which also includes the trigeminal motor nucleus, nucleus ambiguus, and (arguably) the spinal accessory nucleus.\n\n=== Cortical input ===\n\nLike all lower motor neurons, cells of the facial motor nucleus receive cortical input from the primary motor cortex in the frontal lobe of the brain.\n\nUpper motor neurons of the cortex send axons that descend through the internal capsule and synapse on neurons in the facial motor nucleus.\n\nThis pathway from the cortex to the brainstem is called the corticobulbar tract.\n\nThe neurons in the dorsal aspect of the facial motor nucleus receive inputs from both sides of the cortex, while those in the ventral aspect mainly receive contralateral inputs (i.e. from the opposite side of the cortex).\n\nThe result is that both sides of the brain control the muscles of the upper face, while the right side of the brain controls the lower left side of the face, and the left side of the brain controls the lower right side of the face.\n\n== Clinical significance ==\n\nAs a result of the corticobulbar input to the facial motor nucleus, an upper motor neuron lesion to fibers innervating the facial motor nucleus results in central seven.\n\nThe syndrome is characterized by spastic paralysis of the contralateral lower face.\n\nFor example, a left corticobulbar lesion results in paralysis of the muscles that control the lower right quadrant of the face.\n\nBy contrast, a lower motor neuron lesion to the facial motor nucleus results in paralysis of facial muscles on the same side of the injury.\n\nIf a cause, such as trauma or infection, cannot be identified (this situation is called idiopathic palsy) this condition is known as Bell's palsy.\n\nOtherwise it is described by its cause.\n\n=== Mechanism of Facial Nerve Upper vs Lower Motor Neuron Lesions ===\n\nAny lesion occurring within or affecting the corticobulbar tract is known as an upper motor neuron lesion.\n\nAny lesion affecting the individual branches (temporal, zygomatic, buccal, mandibular and cervical) is known as a lower motor neuron lesion.\n\nBranches of the facial nerve leaving the facial motor nucleus (FMN) for the muscles do so via both left and right posterior (dorsal) and anterior (ventral) routes.\n\nIn other words, this means lower motor neurons of the facial nerve can leave either from the left anterior, left posterior, right anterior or right posterior facial motor nucleus.\n\nThe temporal branch travels out from the left and right posterior components.\n\nThe inferior four branches do so via the left and right anterior components.\n\nThe left and right branches supply their respective sides of the face (ipsilateral innervation).\n\nAccordingly, the posterior components receive motor input from both hemispheres of the cerebral cortex (bilaterally), whereas the anterior components receive strictly contralateral input.\n\nThis means that the temporal branch of the facial nerve receives motor input from both hemispheres of the cerebral cortex whereas the zygomatic, buccal, mandibular and cervical branches receive information from only contralateral hemispheres.\n\nNow, because the anterior FMN receives only contralateral cortical input whereas the posterior receives that which is bilateral, a corticobulbar lesion (UMN lesion) occurring in the left hemisphere would eliminate motor input to the right anterior FMN component, thus removing signaling to the inferior four facial nerve branches, thereby paralyzing the right mid- and lower-face.\n\nThe posterior component, however, although now only receiving input from the right hemisphere, is still able to allow the temporal branch to sufficiently innervate the entire forehead.\n\nThis means that the forehead will not be paralyzed.\nThe same mechanism applies for an upper motor neuron lesion in the right hemisphere.\n\nThe left anterior FMN component no longer receives cortical motor input due to its strict contralateral innervation, whereas the posterior component is still sufficiently supplied by the left hemisphere.\n\nThe result is paralysis of the left mid- and lower-face with an unaffected forehead.\n\nOn the other hand, a lower motor neuron lesion is a bit different.\nA lesion on either the left or right side would affect both the anterior and posterior routes on that side because of their close physical proximity to one another.\n\nSo, a lesion on the left side would inhibit muscle innervation from both the left posterior and anterior routes, thus paralyzing the whole left side of the face (Bell’s palsy).\n\nWith this type of lesion, the bilateral and contralateral inputs of the posterior and anterior routes, respectively, become irrelevant because the lesion is below the level of the medulla and the facial motor nucleus.\n\nWhereas at a level above the medulla a lesion occurring in one hemisphere would mean that the other hemisphere could still sufficiently innervate the posterior facial motor nucleus, a lesion affecting a lower motor neuron would eliminate innervation altogether because the nerves no longer have a means to receive compensatory contralateral input at a downstream decussation.\n\nThus, the main distinction between an UMN and LMN lesion is that in the former, there is hemiplegia of the contralateral mid- and lower-face, whereas in the latter, there is complete hemiplegia of the ipsilateral face.\n\nhttps://en.wikipedia.org/wiki/Facial_motor_nucleus","superior-salivatory-nucleus":"The salivatory nuclei are the superior salivatory nucleus, and the inferior salivatory nucleus that innervate the salivary glands.\n\nThey are located in the pontine tegmentum in the brainstem.\n\nThey both are examples of cranial nerve nuclei.\n\nThe superior salivatory nucleus innervates the submandibular gland and the sublingual gland and is part of the facial nerve.\n\nThe inferior salivatory nucleus innervates the parotid gland by way of the otic ganglion and forms the parasympathetic component of the glossopharyngeal nerve.\n\n== Superior salivatory nucleus ==\n\nThe superior salivatory nucleus (or nucleus salivatorius superior) of the facial nerve is a visceromotor cranial nerve nucleus located in the pontine tegmentum.\n\nIt is one of the salivatory nuclei.\nParasympathetic efferent fibers of the facial nerve (preganglionic fibers) arise according to some authors from the small cells of the facial nucleus, or according to others from a special nucleus of cells scattered in the reticular formation, dorso-medial to the facial nucleus – the superior salivatory nucleus.\n\nSome of the preganglionic fibers travel along the greater petrosal nerve through the pterygoid canal, where they join the postsynaptic fibers of the deep petrosal nerve to become the nerve of the pterygoid canal.\n\nThese fibers synapse in the pterygopalatine ganglion, whereupon the postganglionic, postsynaptic, efferent fibers travel to innervate the lacrimal gland and the mucosal glands of the nose, palate, and pharynx.\n\nPreganglionic parasympathetic fibers are also distributed partly via the chorda tympani and lingual nerves to the submandibular ganglion, thence by postganglionic (vasodilator) fibers to the submandibular and sublingual salivary glands.\n\nThe term \"lacrimal nucleus\" is sometimes used to refer to a portion of the superior salivatory nucleus.\n\n== Inferior salivatory nucleus ==\n\nThe inferior salivatory nucleus (or nucleus salivatorius inferior) is a cluster of neurons in the pontine tegmentum (dorsal part of the pons), just above its junction with the medulla.\n\nIt is the general visceral efferent (GVE) component of the glossopharyngeal nerve supplying the parasympathetic input to the parotid gland for salivation.\n\nIt lies immediately caudal to the superior salivatory nucleus and just above the upper end of the dorsal nucleus of the vagus nerve in the medulla.\n\nThe preganglionic parasympathetic fibres originate in the inferior salivatory nucleus of the glossopharyngeal nerve.\n\nThey leave the glossopharngeal nerve by its tympanic branch and then pass via the tympanic plexus and the lesser petrosal nerve to the otic ganglion.\n\nHere, the fibres synapse, and the postganglionic fibers pass by communicating branches to the auriculotemporal nerve, which conveys them to the parotid gland.\n\nThey produce vasodilator and secretomotor effects.\n\n=== Function ===\n\nParasympathetic input from fibers of the inferior salivatory nucleus stimulates the parotid gland to produce vasodilation and secrete saliva.\n\nhttps://en.wikipedia.org/wiki/Salivatory_nuclei","pons":"The pons (from Latin pons, \"bridge\") is part of the brainstem that in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum.\nThe pons is also called the pons Varolii (\"bridge of Varolius\"), after the Italian anatomist and surgeon Costanzo Varolio (1543–75).\n\nThis region of the brainstem includes neural pathways and tracts that conduct signals from the brain down to the cerebellum and medulla, and tracts that carry the sensory signals up into the thalamus.\n\n== Structure ==\n\nThe pons is in the brainstem situated between the midbrain and the medulla oblongata, and in front of the cerebellum.\n\nA separating groove between the pons and the medulla is the inferior pontine sulcus.\n\nThe superior pontine sulcus separates the pons from the midbrain.\n\nThe pons can be broadly divided into two parts: the basilar part of the pons (ventral pons), and the pontine tegmentum (dorsal pons).\n\nRunning down the midline of the ventral surface is the basilar sulcus, a groove for the basilar artery.\n\nMost of the pons is supplied by the pontine arteries, which arise from the basilar artery.\n\nA smaller portion of the pons is supplied by the anterior and posterior inferior cerebellar arteries.\nThe pons in humans measures about 2.5 centimetres (0.98 in) in length.\n\nMost of it appears as a broad anterior bulge above the medulla.\n\nPosteriorly, it consists mainly of two pairs of thick stalks called cerebellar peduncles.\n\nThey connect the cerebellum to the pons (middle cerebellar peduncle) and midbrain (superior cerebellar peduncle).\n\n=== Development ===\n\nDuring embryonic development, the metencephalon develops from the rhombencephalon and gives rise to two structures: the pons and the cerebellum.\n\nThe alar plate produces sensory neuroblasts, which will give rise to the solitary nucleus and its special visceral afferent (SVA) column; the cochlear and vestibular nuclei, which form the special somatic afferent (SSA) fibers of the vestibulocochlear nerve, the spinal and principal trigeminal nerve nuclei, which form the general somatic afferent column (GSA) of the trigeminal nerve, and the pontine nuclei which relays to the cerebellum.\nBasal plate neuroblasts give rise to the abducens nucleus, which forms the general somatic efferent fibers (GSE); the facial and motor trigeminal nuclei, which form the special visceral efferent (SVE) column, and the superior salivatory nucleus, which forms the general visceral efferent fibers (GVE) of the facial nerve.\n\n=== Nuclei ===\n\nA number of cranial nerve nuclei are present in the pons:\n\nmid-pons: the 'chief' or 'pontine' nucleus of the trigeminal nerve sensory nucleus (V)\nmid-pons: the motor nucleus for the trigeminal nerve (V)\nlower down in the pons: abducens nucleus (VI)\nlower down in the pons: facial nerve nucleus (VII)\nlower down in the pons: vestibulocochlear nuclei (vestibular nuclei and cochlear nuclei) (VIII)\n\n== Function ==\n\nFunctions of these four cranial nerves (V-VIII) include regulation of respiration, control of involuntary actions, sensory roles in hearing, equilibrium, and taste, and in facial sensations such as touch and pain, as well as motor roles in eye movement, facial expressions, chewing, swallowing, and the secretion of saliva and tears.The pons contains nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.Within the pons is the pneumotaxic center consisting of the subparabrachial and the medial parabrachial nuclei.\n\nThis center regulates the change from inhalation to exhalation.The pons is implicated in sleep paralysis, and may also play a role in generating dreams.\n\n== Clinical significance ==\n\nCentral pontine myelinolysis is a demyelinating disease that causes difficulty with sense of balance, walking, sense of touch, swallowing and speaking.\n\nIn a clinical setting, it is often associated with transplant or rapid correction of blood sodium.\n\nUndiagnosed, it can lead to death or locked-in syndrome.\n\n== Other animals ==\n\n=== Evolution ===\n\nThe pons first evolved as an offshoot of the medullary reticular formation.\n\nSince lampreys possess a pons, it has been argued that it must have evolved as a region distinct from the medulla by the time the first agnathans appeared, 525 million years ago.\n\nhttps://en.wikipedia.org/wiki/Pons","fourth-ventricle":"The fourth ventricle is one of the four connected fluid-filled cavities within the human brain.\n\nThese cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle.\n\nThe fourth ventricle extends from the cerebral aqueduct (aqueduct of Sylvius) to the obex, and is filled with cerebrospinal fluid (CSF).\nThe fourth ventricle has a characteristic diamond shape in cross-sections of the human brain.\n\nIt is located within the pons or in the upper part of the medulla oblongata.\n\nCSF entering the fourth ventricle through the cerebral aqueduct can exit to the subarachnoid space of the spinal cord through two lateral apertures and a single, midline median aperture.\n\n== Boundaries ==\n\nThe fourth ventricle has a roof at its upper (posterior) surface and a floor at its lower (anterior) surface, and side walls formed by the cerebellar peduncles (nerve bundles joining the structure on the posterior side of the ventricle to the structures on the anterior side).\n\nThe caudal tip of the fourth ventricle - where it becomes the central canal - is known as the obex; the obex is also a marker for the level of the foramen magnum of the skull and therefore is a marker for the imaginary dividing line between the medulla and spinal cord\nThe superior portion of the roof (i.e. of the posterior edge) is a thin lamina - the superior medullary velum - connecting the left and right superior cerebellar peduncles together.\n\nThe inferior portion of the roof - the inferior medullary velum - has a tricorn cross section, directed caudally and laterally, and is formed by the Cerebellum directly.\n\nNear each of the 3 corners of the inferior roof is an opening into the cisterna magna, the caudal opening being the foramen Magendie, while the lateral openings are the foramina of Luschka.\n\nThe roof rises (i.e. posteriorly) to a peak, known as the fastigium (Latin for \"summit\"); the fastigial nucleus lies immediately above the roof of the fourth ventricle, in the cerebellum.\nThe floor (i.e. the anterior edge) of the fourth ventricle constitutes the rhomboid fossa, and comprises a number of general features.\n\nA sulcus - the median sulcus - extends the length of the ventricle (from the cerebral aqueduct of the midbrain to the central canal of the spinal cord), dividing the floor into right and left halves.\n\nEach half is further divided by a further sulcus - the sulcus limitans - along a line parallel to the median sulcus; within the floor, motor neurons are located medially of the sulcus limitans, while sensory neurons are located laterally.\n\nThe elevation between the median sulcus and sulcus limitans (i.e. the region for motor neurons), is known as the medial eminence, while the lateral region (i.e. that for the sensory neurons) is known as the vestibular area.\n\nThe sulcus limitans bifurcates at either end - the superior fovea cerebrally, and the inferior fovea caudally.\nThe pons is located behind the middle and superior portion of the floor.\n\nIn the superior region of the pons is the locus coeruleus, which due to its concentration of noradrenaline has a sky blue appearance, visible (in a colour closer to teal) through the floor of the ventricle, superiorly to the superior fovea.\n\nThe internal part of the facial nerve bulges into the ventricle, forming the facial colliculus, in the process of looping around the abducens nucleus within the inferior region of the Pons.\nThe medulla oblongata is located behind the inferior portion of the floor (and continues caudally of the ventricle).\n\nMedullary striae emerge via the median sulcus and run transversely across the floor to become part of the inferior cerebellar peduncle.\n\nThe hypoglossal nucleus bulges into the floor, creating the hypoglossal trigone, located slightly superiorly to the inferior fovea, within the median eminance.\n\nThe dorsal nucleus of vagus nerve, within the medulla oblongata, comprises cells that are spindle shaped, also creating a bulge—the vagal trigone—in the region of the floor which overlies them; this is the region inferior of the inferior fovea.\n\n== Development ==\n\nThe ventricular system including the fourth ventricle, develops from the central canal of the neural tube.\n\nSpecifically, the fourth ventricle originates from the portion of the tube that is present in the developing rhombencephalon.\n\nDuring the first trimester of pregnancy the central canal expands into the lateral, third and fourth ventricles, connected by thinner channels.\n\nChoroid plexuses appear in the ventricles which produce cerebrospinal fluid.\n\nIf the flow of fluid is blocked ventricles may become enlarged and cause hydrocephalus.\n\n== Clinical significance ==\n\nThe fourth ventricle is a common location of an intracranial ependymomal tumour.\n\nhttps://en.wikipedia.org/wiki/Fourth_ventricle","anterior-cochlear-nucleus":"The cochlear nuclear (CN) complex comprises two cranial nerve nuclei in the human brainstem, the ventral cochlear nucleus (VCN) and the dorsal cochlear nucleus (DCN).\n\nThe ventral (anterior) cochlear nucleus is unlayered whereas the dorsal cochlear nucleus is layered.\n\nAuditory nerve fibers, fibers that travel through the auditory nerve (also known as the cochlear nerve or eighth cranial nerve) carry information from the inner ear, the cochlea, on the same side of the head, to the nerve root in the ventral cochlear nucleus.\n\nAt the nerve root the fibers branch to innervate the ventral cochlear nucleus and the deep layer of the dorsal cochlear nucleus.\n\nAll acoustic information thus enters the brain through the cochlear nuclei, where the processing of acoustic information begins.\n\nThe outputs from the cochlear nuclei are received in higher regions of the auditory brainstem.\n\n== Structure ==\n\nThe cochlear nuclei (CN) are located at the dorso-lateral side of the brainstem, spanning the junction of the pons and medulla.\n\nThe ventral cochlear nucleus (VCN) on the ventral aspect of the brain stem, ventrolateral to the inferior peduncle.\n\nThe dorsal cochlear nucleus (DCN), also known as the tuberculum acusticum or acoustic tubercle, curves over the VCN and wraps around the cerebellar peduncle.\n\nThe VCN is further divided by the nerve root into the posteroventral cochlear nucleus (PVCN) and the anteroventral cochlear nucleus (AVCN).\n\n=== Projections to the cochlear nuclei ===\n\nThe major input to the cochlear nucleus is from the auditory nerve, a part of cranial nerve VIII (the vestibulocochlear nerve).\n\nThe auditory nerve fibers form a highly organized system of connections according to their peripheral innervation of the cochlea.\n\nAxons from the spiral ganglion cells of the lower frequencies innervate the ventrolateral portions of the ventral cochlear nucleus and lateral-ventral portions of the dorsal cochlear nucleus.\n\nThe axons from the higher frequency organ of corti hair cells project to the dorsal portion of the ventral cochlear nucleus and the dorsal-medial portions of the dorsal cochlear nucleus.\n\nThe mid frequency projections end up in between the two extremes; in this way the tonotopic organization that is established in the cochlea is preserved in the cochlear nuclei.\n\nThis tonotopic organization is preserved because only a few inner hair cells synapse on the dendrites of a nerve cell in the spiral ganglion, and the axon from that nerve cell synapses on only a very few dendrites in the cochlear nucleus.\n\nIn contrast with the VCN that receives all acoustic input from the auditory nerve, the DCN receives input not only from the auditory nerve but it also receives acoustic input from neurons in the VCN (T stellate cells).\n\nThe DCN is therefore in a sense a second order sensory nucleus.\nThe cochlear nuclei have long been thought to receive input only from the ipsilateral ear.\n\nThere is evidence, however, for stimulation from the contralateral ear via the contralateral CN, and also the somatosensory parts of the brain.\n\n=== Projections from the cochlear nuclei ===\n\nThere are three major fiber bundles, axons of cochlear nuclear neurons, that carry information from the cochlear nuclei to targets that are mainly on the opposite side of the brain.\n\nThrough the medulla, one projection goes to the contralateral superior olivary complex (SOC) via the trapezoid body, whilst the other half shoots to the ipsilateral SOC.\n\nThis pathway is called the ventral acoustic stria (VAS or, more commonly, the trapezoid body).\n\nAnother pathway, called the dorsal acoustic stria (DAS, also known as the stria of von Monakow), rises above the medulla into the pons where it hits the nuclei of the lateral lemniscus along with its kin, the intermediate acoustic stria (IAS, also known as the stria of Held).\n\nThe IAS decussates across the medulla, before joining the ascending fibers in the contralateral lateral lemniscus.\n\nThe lateral lemniscus contains cells of the nuclei of the lateral lemniscus, and in turn projects to the inferior colliculus.\n\nThe inferior colliculus receives direct, monosynaptic projections from the superior olivary complex, the contralateral dorsal acoustic stria, some classes of stellate neurons of the VCN, as well as from the different nuclei of the lateral lemniscus.\n\nMost of these inputs terminate in the inferior colliculus, although there are a few small projections that bypass the inferior colliculus and project to the medial geniculate, or other forebrain structures.\n\nMedial superior olive (MSO) via trapezoid body (TB) – Ipsilateral and contralateral stimulation for low frequency sounds.\n\nLateral superior olive (LSO) directly and via TB – Ipsilateral stimulation for high frequency sounds.\n\nMedial nucleus of trapezoid body (MNTB) – Contralateral stimulation.\nInferior colliculus – Contralateral stimulation.\n\nPeriolivary nuclei (PON) – Ipsilateral and contralateral stimulation.\nLateral lemniscus (LL) and lemniscal nuclei (LN) – Ipsilateral and contralateral stimulation.\n\n=== Histology ===\n\nThree types of principal cells convey information out of the ventral cochlear nucleus: Bushy cells, stellate cells, and octopus cells.\n\nBushy cells are found mainly in the anterior ventral cochlear nucleus (AVCN).\n\nThese can be further divided into large spherical, small spherical and globular bushy cells, depending on their appearance, and also their location.\n\nWithin the AVCN there is an area of large spherical cells; caudal to this are smaller spherical cells, and globular cells occupy the region around the nerve root.\n\nAn important difference between these subtypes is that they project to differing targets in the superior olivary complex.\n\nLarge spherical bushy cells project to the ipsilateral and contralateral medial superior olive.\n\nGlobular bushy cells project to the contralateral medial nucleus of the trapezoid body, and small spherical bushy cells likely project to the lateral superior olive.\n\nThey have a few (1-4) very short dendrites with numerous small branching, which cause it to resemble a “bush”.\n\nThe bushy cells have specialized electrical properties that allow them to transmit timing information from the auditory nerve to more central areas of the auditory system.\n\nBecause bushy cells receive input from multiple auditory nerve fibers that are tuned to similar frequencies, bushy cells can improve the precision of the timing information by in essence averaging out jitter in timing of the inputs.\n\nBushy cells can also be inhibited by sounds adjacent to the frequency to which they are tuned, leading to even sharper tuning than seen in auditory nerve fibers.\n\nThese cells are usually innervated only by a few auditory nerve fibres, which dominate its firing pattern.\n\nThese afferent nerve fibres wrap their terminal branches around the entire soma, creating a large synapse onto the bushy cells, called an \"endbulb of Held\".\n\nTherefore, a single unit recording of an electrically stimulated bushy neuron characteristically produces exactly one action potential and constitutes the primary response.\n\nStellate cells (aka multipolar cells), have longer dendrites that lie parallel to fascicles of auditory nerve fibers.\n\nThey are also called chopper cells, in reference to their ability to fire a regularly spaced train of action potentials for the duration of a tonal or noise stimulus.\n\nThe chopping pattern is intrinsic to the electrical excitability of the stellate cell, and the firing rate depends on the strength of the auditory input more than on the frequency.\n\nEach stellate cell is narrowly tuned and has inhibitory sidebands, enabling the population of stellate cells to encode the spectrum of sounds, enhancing spectral peaks and valleys.\n\nThese neurons provide acoustic input to the DCN.\nOctopus cells are found in a small region of the posterior ventral cochlear nucleus (PVCN).\n\nThe distinguishing features of these cells are their long, thick and tentacle-shaped dendrites that typically emanate from one side of the cell body.\n\nOctopus cells produce an \"Onset Response\" to simple tonal stimuli.\n\nThat is, they respond only at the onset of a broad-band stimulus.\n\nThe octopus cells can fire with some of the highest temporal precision of any neuron in the brain.\n\nElectrical stimuli to the auditory nerve evoke a graded excitatory postsynaptic potential in the octopus cells.\n\nThese EPSPs are very brief.\n\nThe octopus cells are thought to be important for extracting timing information.\n\nIt has been reported that these cells can respond to click trains at a rate of 800 Hz.Two types of principal cells convey information out of the dorsal cochlear nucleus (DCN) to the contralateral inferior colliculus.\n\nThe principal cells receive two systems of inputs.\n\nAcoustic input comes to the deep layer through several paths.\n\nExcitatory acoustic input comes from auditory nerve fibers and also from stellate cells of the VCN.\n\nAcoustic input is also conveyed through inhibitory interneurons (tuberculoventral cells of the DCN and \"wide band inhibitors\" in the VCN).\n\nThrough the outermost molecular layer, the DCN receives other types of sensory information, most importantly information about the location of the head and ears, through parallel fibers.\n\nThis information is distributed through a cerebellar like circuit that also includes inhibitory interneurons.\n\nFusiform cells (also known as pyramidal cells).\n\nFusiform cells integrate information through two tufts of dendrites, the apical dendrites receiving multisensory, excitatory and inhibitory input through the outermost molecular layer and the basal dendrites receiving excitatory and inhibitory acoustic input from the basal dendrites that extend into the deep layer.\n\nThese neurons are thought to enable mammals to analyze the spectral cues that enable us to localize sounds in elevation and when we lose hearing in one ear.\n\nGiant cells also integrate inputs from the molecular and deep layers but input from the deep layer is predominant.\n\nIt is unclear what their role is in hearing.\n\n== Function ==\n\nThe cochlear nuclear complex is the first integrative, or processing, stage in the auditory system.\n\nInformation is brought to the nuclei from the ipsilateral cochlea via the cochlear nerve.\n\nSeveral tasks are performed in the cochlear nuclei.\n\nBy distributing acoustic input to multiple types of principal cells, the auditory pathway is subdivided into parallel ascending pathways, which can simultaneously extract different types of information.\n\nThe cells of the ventral cochlear nucleus extract information that is carried by the auditory nerve in the timing of firing and in the pattern of activation of the population of auditory nerve fibers.\n\nThe cells of the dorsal cochlear nucleus perform a non-linear spectral analysis and place that spectral analysis into the context of the location of the head, ears and shoulders and that separate expected, self-generated spectral cues from more interesting, unexpected spectral cues using input from the auditory cortex, pontine nuclei, trigeminal ganglion and nucleus, dorsal column nuclei and the second dorsal root ganglion.\n\nIt is likely that these neurons help mammals to use spectral cues for orienting toward those sounds.\n\nThe information is used by higher brainstem regions to achieve further computational objectives (such as sound source location or improvement in signal to noise ratio).\n\nThe inputs from these other areas of the brain probably play a role in sound localization.\n\nIn order to understand in more detail the specific functions of the cochlear nuclei it is first necessary to understand the way sound information is represented by the fibers of the auditory nerve.\n\nBriefly, there are around 30,000 auditory nerve fibres in each of the two auditory nerves.\n\nEach fiber is an axon of a spiral ganglion cell that represents a particular frequency of sound, and a particular range of loudness.\n\nInformation in each nerve fibre is represented by the rate of action potentials as well as the particular timing of individual action potentials.\n\nThe particular physiology and morphology of each cochlear nucleus cell type enhances different aspects of sound information.\n\nhttps://en.wikipedia.org/wiki/Cochlear_nucleus","medulla-oblongata":"The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem.\n\nIt is anterior and partially inferior to the cerebellum.\n\nIt is a cone-shaped neuronal mass responsible for autonomic (involuntary) functions, ranging from vomiting to sneezing.\n\nThe medulla contains the cardiac, respiratory, vomiting and vasomotor centers, and therefore deals with the autonomic functions of breathing, heart rate and blood pressure as well as the sleep wake cycle.\n\nDuring embryonic development, the medulla oblongata develops from the myelencephalon.\n\nThe myelencephalon is a secondary vesicle which forms during the maturation of the rhombencephalon, also referred to as the hindbrain.\n\nThe bulb is an archaic term for the medulla oblongata.\n\nIn modern clinical usage, the word bulbar (as in bulbar palsy) is retained for terms that relate to the medulla oblongata, particularly in reference to medical conditions.\n\nThe word bulbar can refer to the nerves and tracts connected to the medulla, and also by association to those muscles innervated, such as those of the tongue, pharynx and larynx.\n\n== Anatomy ==\n\nThe medulla can be thought of as being in two parts:\n\n-an upper open part or superior part where the dorsal surface of the medulla is formed by the fourth ventricle.\n-a lower closed part or inferior part where the fourth ventricle has narrowed at the obex in the caudal medulla, and surrounds part of the central canal.\n\n=== External surfaces ===\n\nThe anterior median fissure contains a fold of pia mater, and extends along the length of the medulla oblongata.\n\nIt ends at the lower border of the pons in a small triangular area, termed the foramen cecum.\n\nOn either side of this fissure are raised areas termed the medullary pyramids.\n\nThe pyramids house the pyramidal tracts–the corticospinal and the corticobulbar tracts of the nervous system.\n\nAt the caudal part of the medulla these tracts cross over in the decussation of the pyramids obscuring the fissure at this point.\n\nSome other fibers that originate from the anterior median fissure above the decussation of the pyramids and run laterally across the surface of the pons are known as the anterior external arcuate fibers.\n\nThe region between the anterolateral and posterolateral sulcus in the upper part of the medulla is marked by a pair of swellings known as olivary bodies (also called olives).\n\nThey are caused by the largest nuclei of the olivary bodies, the inferior olivary nuclei.\n\nThe posterior part of the medulla between the posterior median sulcus and the posterolateral sulcus contains tracts that enter it from the posterior funiculus of the spinal cord.\n\nThese are the gracile fasciculus, lying medially next to the midline, and the cuneate fasciculus, lying laterally.\n\nThese fasciculi end in rounded elevations known as the gracile and the cuneate tubercles.\n\nThey are caused by masses of gray matter known as the gracile nucleus and the cuneate nucleus.\n\nThe soma (cell bodies) in these nuclei are the second-order neurons of the posterior column-medial lemniscus pathway, and their axons, called the internal arcuate fibers or fasciculi, decussate from one side of the medulla to the other to form the medial lemniscus.\n\nJust above the tubercles, the posterior aspect of the medulla is occupied by a triangular fossa, which forms the lower part of the floor of the fourth ventricle.\n\nThe fossa is bounded on either side by the inferior cerebellar peduncle, which connects the medulla to the cerebellum.\n\nThe lower part of the medulla, immediately lateral to the cuneate fasciculus, is marked by another longitudinal elevation known as the tuberculum cinereum.\n\nIt is caused by an underlying collection of gray matter known as the spinal trigeminal nucleus.\n\nThe gray matter of this nucleus is covered by a layer of nerve fibers that form the spinal tract of the trigeminal nerve.\n\nThe base of the medulla is defined by the commissural fibers, crossing over from the ipsilateral side in the spinal cord to the contralateral side in the brain stem; below this is the spinal cord.\n\n=== Blood supply ===\n\nBlood to the medulla is supplied by a number of arteries.\nAnterior spinal artery: This supplies the whole medial part of the medulla oblongata.\n\nPosterior inferior cerebellar artery:\n This is a major branch of the vertebral artery, and supplies the posterolateral part of the medulla, where the main sensory tracts run and synapse.\n\nIt also supplies part of the cerebellum.\n\nDirect branches of the vertebral artery: The vertebral artery supplies an area between the other two main arteries, including the solitary nucleus and other sensory nuclei and fibers.\n\n=== Development ===\n\nThe medulla oblongata forms in fetal development from the myelencephalon.\n\nThe final differentiation of the medulla is seen at week 20 gestation.Neuroblasts from the alar plate of the neural tube at this level will produce the sensory nuclei of the medulla.\n\nThe basal plate neuroblasts will give rise to the motor nuclei.\n\nAlar plate neuroblasts give rise to:\n\nThe solitary nucleus, which contains the general visceral afferent fibers for taste, as well as the special visceral afferent column.\n\nThe spinal trigeminal nerve nuclei which contains the general somatic afferent column.\n\nThe cochlear and vestibular nuclei, which contain the special somatic afferent column.\n\nThe inferior olivary nucleus, which relays to the cerebellum.\n\nThe dorsal column nuclei, which contain the gracile and cuneate nuclei.\n\nBasal plate neuroblasts give rise to:\n\nThe hypoglossal nucleus, which contains general somatic efferent fibers.\n\nThe nucleus ambiguus, which form the special visceral efferent.\n\nThe dorsal nucleus of vagus nerve and the inferior salivatory nucleus, both of which form the general visceral efferent fibers.\n\n== Function ==\n\nThe medulla oblongata connects the higher levels of the brain to the spinal cord, and is responsible for several functions of the autonomous nervous system which include:\n\nThe control of ventilation via signals from the carotid and aortic bodies.\n\nRespiration is regulated by groups of chemoreceptors.\n\nThese sensors detect changes in the acidity of the blood; if, for example, the blood becomes too acidic, the medulla oblongata sends electrical signals to intercostal and phrenical muscle tissue to increase their contraction rate and increase oxygenation of the blood.\n\nThe ventral respiratory group and the dorsal respiratory group are neurons involved in this regulation.\n\nThe pre-Bötzinger complex is a cluster of interneurons involved in the respiratory function of the medulla.\n\nCardiovascular center – sympathetic, parasympathetic nervous system\nVasomotor center – baroreceptors\nReflex centers of vomiting, coughing, sneezing, and swallowing.\n\nThese reflexes which include the pharyngeal reflex, the swallowing reflex (also known as the palatal reflex), and the masseter reflex can be termed, bulbar reflexes.\n\n== Clinical significance ==\n\nA blood vessel blockage (such as in a stroke) will injure the pyramidal tract, medial lemniscus, and the hypoglossal nucleus.\n\nThis causes a syndrome called medial medullary syndrome.\n\nLateral medullary syndrome can be caused by the blockage of either the posterior inferior cerebellar artery or of the vertebral arteries.\n\nProgressive bulbar palsy (PBP) is a disease that attacks the nerves supplying the bulbar muscles.\n\nInfantile progressive bulbar palsy is progressive bulbar palsy in children.\n\n== Other animals ==\n\nBoth lampreys and hagfish possess a fully developed medulla oblongata.\n\nSince these are both very similar to early agnathans, it has been suggested that the medulla evolved in these early fish, approximately 505 million years ago.\n\nThe status of the medulla as part of the primordial reptilian brain is confirmed by its disproportionate size in modern reptiles such as the crocodile, alligator, and monitor lizard.\n\nhttps://en.wikipedia.org/wiki/Medulla_oblongata","pyramid-of-medulla-oblongata":"MEDULLARY PYRAMIDS (BRAINSTEM)\n\nThe medullary pyramids are paired white matter structures of the brainstem's medulla oblongata that contain motor fibers of the corticospinal and corticobulbar tracts – known together as the pyramidal tracts.\n\nThe lower limit of the pyramids is marked when the fibers cross (decussate).\n\n== Structure ==\n\nThe ventral portion of the medulla oblongata contains the medullary pyramids.\n\nThese two ridge-like structures travel along the length of the medulla oblongata and are bordered medially by the anterior median fissure.\n\nThey each have an anterolateral sulcus along their lateral borders, where the hypoglossal nerve emerges from.\n\nAlso at the side of each pyramid there is a pronounced bulge known as an olive.\n\nFibers of the posterior column, which transmit sensory and proprioceptive information, are located behind the pyramids on the medulla oblongata.\n\nThe medullary pyramids contain motor fibers that are known as the corticobulbar and corticospinal tracts.\n\nThe corticospinal tracts are on the anterior surface of the pyramids.\n\nThese tracts transport motor signals that originated in the precentral gyrus and travelled through the internal capsule to the medulla oblongata and pyramids.\n\nExtrapyramidal tracts are those motor tracts that do not traverse the medullary pyramids.\n\nAt the pyramids' most caudal end, the corticospinal axons decussate (or cross over) the midline and continue down the spinal cord on the contralateral side.\n\nThe fibers that decussated will go down the lateral corticospinal tract while the fibers that did not decussate will travel down the anterior corticospinal tract.\n\nNearly 90 percent of the fibers decussate and travel down the lateral corticospinal tract while the other 10 percent travels down the anterior corticospinal tract.\n\n=== Decussation ===\n\nThe two pyramids contain the motor fibers that pass from the brain to the medulla oblongata and spinal cord.\n\nThese are the corticobulbar and corticospinal fibers that make up the pyramidal tracts.\n\nAbout 90% of these fibers leave the pyramids in successive bundles and decussate (cross over) in the anterior median fissure of the medulla oblongata as the pyramidal decussation or motor decussation.\n\nHaving crossed over at the middle line, they pass down in the posterior part of the lateral funiculus as the lateral corticospinal tract.\n\nThe other 10% of the fibers stay uncrossed in the anterior corticospinal tract.\n\nThe pyramidal decussation marks the border between the spinal cord and the medulla oblongata.\n\n== Function ==\n\nThe medullary pyramids contain the motor fibers of the pyramidal tracts – the corticospinal and corticobulbar tracts.\n\n== Clinical significance ==\n\nWhiplash as a result of a car accident can lead to brainstem injuries that affect the pyramids at the medulla oblongata.\n\nThese pyramid injuries are usually a result of a dislocation at the occiput or spinal level C1.\n\nInjuries to the pyramids of the medulla oblongata can also be caused by the quick hyperextension of the neck (cervical region of the spine).\n\nHyperextension of the neck can pull and tear the pyramids, leading to a variety of symptoms such as weakness in all four limbs, difficulty swallowing, and difficulty speaking.\n\nA bilateral infarction in the pyramids of the medulla can result in motor quadriplegia.\n\nThis is rare, however, as there have only been four cases of this reported.\n\nhttps://en.wikipedia.org/wiki/Medullary_pyramids_(brainstem)","olive":"OLIVARY BODY\n\nIn anatomy, the olivary bodies or simply olives (Latin oliva and olivae, singular and plural, respectively) are a pair of prominent oval structures in the medulla oblongata, the lower portion of the brainstem.\n\nThey contain the olivary nuclei.\n\n== Structure ==\n\nThe olivary body is located on the anterior surface of the medulla lateral to the pyramid, from which it is separated by the antero-lateral sulcus and the fibers of the hypoglossal nerve.\n\nBehind (dorsally), it is separated from the postero-lateral sulcus by the ventral spinocerebellar fasciculus.\n\nIn the depression between the upper end of the olive and the pons lies the vestibulocochlear nerve.\n\nIn humans, it measures about 1.25 cm. in length, and between its upper end and the pons there is a slight depression to which the roots of the facial nerve are attached.\n\nThe external arcuate fibers wind across the lower part of the pyramid and olive and enter the inferior peduncle.\n\n=== Olivary nuclei ===\n\nThe olive consists of two parts:\n\nThe inferior olivary nucleus (or 'complex'), which is a part of the olivo-cerebellar system and is mainly involved in cerebellar motor-learning and function.\n\nThe superior olivary nucleus, considered part of the pons and part of the auditory system, aiding the perception of sound.\n\nThe inferior olive in itself is divided to 3 main nuclei:\n\nThe primary olivary nucleus (PO) which consist of the major laminar structure.\n\nThe medial accessory olivary nucleus (MAO) lies between the primary olivary nucleus and the pyramid, and forms a curved lamina, the concavity of which is directed laterally.\n\nThe dorsal accessory olivary nucleus (DAO) is the smallest, and appears on transverse section as a curved lamina behind the primary olivary nucleus.\n\nSmall additional inferior olivary structures consist of the dorsal cap of Kooy and the ventrolateral outgrowth.\n\nhttps://en.wikipedia.org/wiki/Olivary_body","nucleus-of-accessory-nerve":"The spinal accessory nucleus lies within the cervical spinal cord (C1-C5) in the posterolateral aspect of the anterior horn.\n\nThe nucleus ambiguus is classically said to provide the \"cranial component\" of the accessory nerve.\n\nHowever, the very existence of this cranial component has been recently questioned and seen as contributing exclusively to the vagus nerve.\n\nThe terminology continues to be used in describing both human anatomy, and that of other animals.\n\nhttps://en.wikipedia.org/wiki/Spinal_accessory_nucleus","sensory-root-of-trigeminal-nerve":"PRINCIPAL SENSORY NUCLEUS OF TRIGEMINAL NERVE\n\nThe principal sensory nucleus of trigeminal nerve (or chief sensory nucleus of V, main trigeminal sensory nucleus) is a group of second-order neurons which have cell bodies in the caudal pons.\n\nIt receives information about discriminative sensation and light touch of the face as well as conscious proprioception of the jaw via first order neurons of CN V.\n\nMost of the sensory information crosses the midline and travels to the contralateral ventral posteromedial nucleus (VPM) of the thalamus via the anterior trigeminothalamic tract.\n\nHowever, information of the oral cavity travels to the ipsilateral VPM of the thalamus via the dorsal trigeminothalamic tract.\n\nhttps://en.wikipedia.org/wiki/Principal_sensory_nucleus_of_trigeminal_nerve","motor-root-of-trigeminal-nerve":"TRIGEMINAL MOTOR NUCLEUS\n\nThe trigeminal motor nucleus contains motor neurons that innervate muscles of the first branchial arch, namely the muscles of mastication, the tensor tympani, tensor veli palatini, mylohyoid, and anterior belly of the digastric.\n\nThis nucleus is located in the mid-pons (i.e. in the center of the pons going inferior to superior).\n\n== Lesion ==\n\nThe trigeminal motor nucleus forms the efferent pathway of the jaw jerk reflex.\n\nSince the axons involved in this reflex do not decussate, a lesion involving the trigeminal motor nucleus would cause ipsilateral hemiparesis.\n\nhttps://en.wikipedia.org/wiki/Trigeminal_motor_nucleus","cochlear-nerve":"The cochlear nerve (also auditory nerve or acoustic nerve) is one of two parts of the vestibulocochlear nerve, a cranial nerve present in amniotes, the other part being the vestibular nerve.\n\nThe cochlear nerve carries auditory sensory information from the cochlea of the inner ear directly to the brain.\n\nThe other portion of the vestibulocochlear nerve is the vestibular nerve, which carries spatial orientation information to the brain from the semicircular canals, also known as semicircular ducts.\n\n== Anatomy and connections ==\n\nIn terms of anatomy, an auditory nerve fiber is either bipolar or unipolar, with its distal projection being called the peripheral process, and its proximal projection being called the axon; these two projections are also known as the \"peripheral axon\" and the \"central axon\", respectively.\n\nThe peripheral process is sometimes referred to as a dendrite, although that term is somewhat inaccurate.\n\nUnlike the typical dendrite, the peripheral process generates and conducts action potentials, which then \"jump\" across the cell body (or soma) and continue to propagate along the central axon.\n\nIn this respect, auditory nerve fibers are somewhat unusual in that action potentials pass through the soma.\n\nBoth the peripheral process and the axon are myelinated.\nIn humans, there are on average 30,000 nerve fibers within the cochlear nerve.\n\nThe number of fibers varies significantly across species; the domestic cat, for example, has an average of 50,000 fibers.\n\nThe peripheral axons of auditory nerve fibers form synaptic connections with the hair cells of the cochlea via ribbon synapses using the neurotransmitter glutamate.\n\nThe central axons form synaptic connections with cells in the cochlear nucleus of the brainstem.\nThe cell bodies of the cochlear nerve lie within the cochlea and collectively form the spiral ganglion, named for the spiral shape it shares with the cochlea.\n\nThese central axons exit the cochlea at its base and form a nerve trunk, which, in humans, is approximately one inch long.\n\nThis travels in parallel with the vestibular nerves through the internal auditory canal, through which it connects to the brainstem.\n\nThere, its fibers synapse with the cell bodies of the cochlear nucleus.\n\n== Types of neurons ==\n\nIn mammals, cochlear nerve fibers are classified as either type I or type II.\n\nType I neurons make up 90-95% of the neurons and innervate the inner hair cells.\n\nThey have relatively large diameters, are bipolar, and are myelinated.\n\nEach type I axon innervates only a single inner hair cell, but each inner hair cell is innervated by up to 30 such nerve fibers, depending on species and location within the cochlea.\nType II neurons make up the remaining 5-10% of the neurons and innervate the outer hair cells.\n\nThey have relatively small diameters, are unipolar, and are unmyelinated.\n\n== Cochlear nuclear complex ==\n\nIn mammals, the axons from each cochlear nerve terminate in the cochlear nuclear complex that is ipsilaterally located in the medulla of the brainstem.\n\nThe cochlear nucleus is the first 'relay station' of the central auditory system and receives mainly ipsilateral afferent input.\nThe three major components of the cochlear nuclear complex are (see figure below):\n\nthe dorsal cochlear nucleus (DCN)\nthe anteroventral cochlear nucleus (AVCN)\nthe posteroventral cochlear nucleus (PVCN)Each of the three cochlear nuclei are tonotopically organized.\n\nThe axons from the low-frequency region of the cochlea project to the ventral portion of the dorsal cochlear nucleus and the ventrolateral portions of the anteroventral cochlear nucleus.\n\nThe axons from the high-frequency region project to the dorsal portion of the anteroventral cochlear nucleus and the uppermost dorsal portions of the dorsal cochlear nucleus.\n\nThe axons from the intermediate frequency region project to intermediate targets, such that tonotopy is preserved between the cochlea and the cochlear nuclei.\n\nhttps://en.wikipedia.org/wiki/Cochlear_nerve","ganglia-of-sympathetic-trunk":"SYMPATHETIC GANGLIA\n\nThe sympathetic ganglia, or paravertebral ganglia are autonomic ganglia, of the sympathetic nervous system.\n\nGanglia are 20,000 to 30,000 afferent and efferent nerve cell bodies that run along on either side of the spinal cord.\n\nAfferent nerve cell bodies bring information from the body to the brain and spinal cord, while efferent nerve cell bodies bring information from the brain and spinal cord to the rest of the body.\n\nThe cell bodies create long sympathetic chains that are on either side of the spinal cord.\n\nThey also form para- or pre-vertebral ganglia of gross anatomy.\n\nThe efferent nerve cell bodies bring information from the brain to the body regarding perceptions of danger.\n\nThis perception of danger can instigate the fight-or-flight response associated with the sympathetic nervous system.\n\nThe fight-or-flight response is adaptive when there is a real and present danger which can be avoided or diminished through increased sympathetic activity.\n\nSympathetic activity could be increased heart rate, dilated pupils, or sweaty palms, for example.\n\nThe fight-or-flight response is maladaptive when the danger is imagined, prolonged, or when it lasts after the threat is over.\n\nWhen the intensity or duration of the response is excessive, the individual may meet criteria for a variety of psychological disorders.\n\nNeuroblastoma tumors can arise from the sympathetic ganglia tissue.\n\n== Structure ==\n\n=== Sympathetic chain ganglia ===\n\nThe bilaterally symmetric sympathetic chain ganglia, also called the paravertebral ganglia, are located just ventral and lateral to the spinal cord.\n\nThe chain extends from the upper neck down to the coccyx, forming the unpaired coccygeal ganglion.\n\nEach ganglion within this chain is either cervical, thoracic, lumbar, or sacral.\n\nPreganglionic nerves from the spinal cord synapse at one of the chain ganglia, and the postganglionic fiber extends to an effector, a visceral organ in the thoracic cavity, abdominal cavity, or pelvic cavity.\n\nThere are usually 22-23 pairs of these ganglia:\n 3 in the cervical region (cervical ganglia), 11 in the thoracic region (note the presence of the stellate cervicothoracic ganglia), 4 in the lumbar region and 4-5 in the sacral region.\n\nThroughout human evolution, the first thoracic and inferior cervical ganglia merged - and this resulting ganglion is called the stellate ganglion (so called because of its radiating pattern similar in appearance to a star).\n\nThe general rule of interaction of the nerve fibers in the sympathetic nervous system begins at the spinal cord.\n\nHere they arise from the thoracolumbar (T1-L2) regions' lateral horn of grey and emerge via the ventral root.\n\nThey enter their respective spinal nerve (e.g.\n\nT5), and thus enter the white ramus communicans.\n\nThis myelinated division can then enter the sympathetic chain.\n\nHere four options are available to the fibers:\n(1) they can run up the chain and synapse,\n(2) they can synapse at the level of entry,\n(3) they can pass straight through and synapse elsewhere - such as in the case of T5-12 (the splanchnic nerves), or\n(4) they can enter the chain and descend to synapse.\n\nIt is this ability to move superiorly and inferiorly along the chain that results in the mass response to the sympathetic nervous system.\n\nA preganglionic fibre may synapse to 15-20 postganglionic fibres.\n\nThe postganglionic neurons extend across most of the body.\n\nUpon exiting the sympathetic chain, the fibres enter a less-myelinated gray ramus communicans.\n\nThere is still a myelin sheath present – just in far lower amounts compared to the white ramus communicans.\n\nThis ramus then enters the spinal nerve and is sent to its synapsing target, or becomes a visceral branch to enter a plexus (e.g. the superficial or deep cardiac plexuses), or synapses directly onto a target.\n\n=== Collateral ganglia ===\n\nNeurons of the collateral ganglia, also called the prevertebral ganglia, receive input from the splanchnic nerves and innervate organs of the abdominal and pelvic region.\n\nThese include the celiac ganglia, superior mesenteric ganglia, and inferior mesenteric ganglia.\n\nhttps://en.wikipedia.org/wiki/Sympathetic_ganglia","lacrimal-gland":"The lacrimal glands are paired exocrine glands, one for each eye, found in most terrestrial vertebrates and some marine mammals, that secrete the aqueous layer of the tear film.\n\nIn humans, they are situated in the upper lateral region of each orbit, in the lacrimal fossa of the orbit formed by the frontal bone.\n\nInflammation of the lacrimal glands is called dacryoadenitis.\n\nThe lacrimal gland produces tears which are secreted by the lacrimal ducts, and flow over the ocular surface, and then into canals that connect to the lacrimal sac.\n\nFrom that sac, the tears drain through the lacrimal duct into the nose.\n\nAnatomists divide the gland into two sections, a palpebral lobe, or portion, and an orbital lobe or portion.\n\nThe smaller palpebral lobe lies close to the eye, along the inner surface of the eyelid; if the upper eyelid is everted, the palpebral portion can be seen.\n\nThe orbital lobe of the gland, contains fine interlobular ducts that connect the orbital lobe and the palpebral lobe.\n\nThey unite to form three to five main secretory ducts, joining five to seven ducts in the palpebral portion before the secreted fluid may enter on the surface of the eye.\n\nTears secreted collect in the fornix conjunctiva of the upper lid, and pass over the eye surface to the lacrimal puncta, small holes found at the inner corner of the eyelids.\n\nThese pass the tears through the lacrimal canaliculi on to the lacrimal sac, in turn to the nasolacrimal duct, which dumps them out into the nose.Lacrimal glands are also present in other mammals, such as horses.\n\n== Structure ==\n\n=== Histology ===\n\nThe lacrimal gland is a compound tubuloacinar gland, it is made up of many lobules separated by connective tissue, each lobule contains many acini.\n\nThe acini composed of large serous cells which, produce a watery serous secretion, serous cells are filled with lightly stained secretory granules and surrounded by well-developed myoepithelial cells and a sparse, vascular stroma.\n\nEach acinus consists of a grape-like mass of lacrimal gland cells with their apices pointed to a central lumen.\n\nThe central lumen of many of the units converge to form intralobular ducts, and then they unite to form interlobular ducts.\n\nThe gland lacks striated ducts.\n\n=== Blood supply ===\n\nThe lacrimal gland receives blood from the lacrimal artery, which is a branch of the ophthalmic artery.\n\nBlood from the gland drains to the superior ophthalmic vein.\n\n=== Lymphatic drainage ===\n\nNo lymphatic vessels have been observed draining the lacrimal gland.\n\n=== Nerve supply ===\n\nThe lacrimal gland is innervated by the lacrimal nerve, which is the smallest branch of the ophthalmic nerve, itself a branch of the trigeminal nerve (CN V).\n\nAfter the lacrimal nerve branches from the ophthalmic nerve it receives a communicating branch from the zygomatic nerve.\n\nThis communicating branch carries postganglionic parasympathetic axons from the pterygopalatine ganglion.\n\nThe lacrimal nerve passes anteriorly in the orbit and through the lacrimal gland providing parasympathetic and sympathetic innervation to it.\n\n==== Parasympathetic innervation ====\n\nThe parasympathetic innervation to the lacrimal gland is a complex pathway which traverses through numerous structures in the head.\n\nUltimately this two-neuron pathway involving both a preganglionic and postganglionic parasympathetic neuron increases the secretion of lacrimal fluid from the lacrimal gland.\n\nThe preganglionic parasympathetic neurons are located in the superior salivatory nucleus.\n\nThey project axons which exit the brainstem as part of the facial nerve (CN VII).\n\nWithin the facial canal at the geniculate ganglion the axons branch from the facial nerve forming the greater petrosal nerve.\n\nThis nerve exits the facial canal through the hiatus for the greater petrosal nerve in the petrous part of the temporal bone.\n\nIt emerges to the middle cranial fossa and travels anteromedially to enter the foramen lacerum.\n\nWithin the foramen lacerum it joins to the deep petrosal nerve to form the nerve of the pterygoid canal and then passes through this canal.\n\nIt emerges in the pterygopalatine fossa and enters the pterygopalatine ganglion where the preganglionic parasympathetic axons synapse with the postganglionic parasympathetic neurons.\n\nThe postganglionic neurons then send axons which travel with the zygomatic nerve to enter the inferior orbital fissure.\n\nAs the zygomatic nerve travels anteriorly in the orbit it send a communicating branch to the lacrimal nerve which carries the postganglionic parasympathetic axons.\n\nThe lacrimal nerve completes this long pathway by travelling through the lacrimal gland and sending branches to it which provide parasympathetic innervation to increase the secretion of lacrimal fluid.\n\n==== Sympathetic innervation ====\n\nSympathetic innervation to the lacrimal gland is of less physiologic importance than the parasympathetic innervation, however there are noradrenergic axons found within the lacrimal gland.\n\nTheir cell bodies are located in the superior cervical ganglion.\n\n== Clinical significance ==\n\nIn contrast to the normal moisture of the eyes or even crying, there can be persistent dryness, scratching, itchiness and burning in the eyes, which are signs of dry eye syndrome (DES) or keratoconjunctivitis sicca (KCS).\n\nWith this syndrome, the lacrimal glands produce less lacrimal fluid, which mainly occurs with ageing or certain medications.\n\nThe Schirmer test, conducted by placing a thin strip of filter paper at the edge of the eye, can be used to determine the level of dryness of the eye.\n\nMany medications or diseases that cause dry eye syndrome can also cause hyposalivation with xerostomia.\n\nTreatment varies according to aetiology and includes avoidance of exacerbating factors, tear stimulation and supplementation, increasing tear retention, eyelid cleansing, and treatment of eye inflammation.\n\nIt is located in each and every eye.\nIn addition, the following can be associated with lacrimal gland pathology:\n\nDacryoadenitis\nSjögren's syndrome\n\nhttps://en.wikipedia.org/wiki/Lacrimal_gland","lacrimal-canaliculus":"The lacrimal canaliculi, (sing. canaliculus), are the small channels in each eyelid that drain lacrimal fluid, from the lacrimal puncta to the lacrimal sac.\n\nThis forms part of the lacrimal apparatus that drains lacrimal fluid from the surface of the eye to the nasal cavity.\n\n== Structure ==\n\nThere is a single lacrimal canaliculus in each eyelid, a superior lacrimal canaliculus in the upper eyelid and an inferior lacrimal canaliculus in the lower eyelid.\n\nThe canaliculi travel vertically and then turn medially to travel towards the lacrimal sac.\n\nAt the bend, the canaliculus is dilated and called the ampulla.\n\nUsually, the superior and inferior lacrimal canaliculi join to form a common passage that enters the lateral wall of the lacrimal sac.\n\n=== Superior lacrimal canaliculus ===\n\nThe superior lacrimal canaliculus is located in the upper eyelid.\n\nIt first ascends, then bends medially towards the lacrimal sac.\n\nIt drains lacrimal fluid from the superior lacrimal punctum.\n\nIt is smaller and shorter than the inferior lacrimal canaliculus.\n\n=== Inferior lacrimal canaliculus ===\n\nThe inferior lacrimal canaliculus is located in the lower eyelid.\n\nIt first descends, then bends medially towards the lacrimal sac.\n\nIt drains lacrimal fluid from the inferior lacrimal punctum.\n\n== Histology ==\n\nThe lacrimal canaliculi have a mucosa composed of a non-keratinized stratified squamous epithelium on a basement membrane and a highly elastic lamina propria.\n\nSurrounding the mucosa are skeletal muscle fibres continuous with the orbicularis oculi which forms a sort of sphincter.\n\nThis may facilitate the draining of lacrimal fluid during blinking.\n\n== Clinical significance ==\n\nCanaliculitis is inflammation of the lacrimal canaliculus.\n\nhttps://en.wikipedia.org/wiki/Lacrimal_canaliculi","lacrimal-sac":"The lacrimal sac or lachrymal sac is the upper dilated end of the nasolacrimal duct, and is lodged in a deep groove formed by the lacrimal bone and frontal process of the maxilla.\n\nIt connects the lacrimal canaliculi, which drain tears from the eye's surface, and the nasolacrimal duct, which conveys this fluid into the nasal cavity.\n\nLacrimal sac occlusion leads to dacryocystitis.\n\n== Structure ==\n\nIt is oval in form and measures from 12 to 15 mm. in length; its upper end is closed and rounded; its lower is continued into the nasolacrimal duct.\n\nIts superficial surface is covered by a fibrous expansion derived from the medial palpebral ligament, and its deep surface is crossed by the lacrimal part of the orbicularis oculi, which is attached to the crest on the lacrimal bone.\n\n=== Histology ===\n\nLike the nasolacrimal duct, the sac is lined by stratified columnar epithelium with mucus-secreting goblet cells, with surrounding connective tissue.\n\nThe Lacrimal Sac also drains the eye of debris and microbes.\n\n== Function ==\n\nIt serves as a reservoir for overflow of tears, in which the lacrimal sac pumps inward and outward driven by the orbicularis muscle during blinking.\n\n== Imaging ==\n\nThe lacrimal sac can be imaged by dacrocystography, in which radiocontrast is injected, followed by X-ray imaging.\n\nhttps://en.wikipedia.org/wiki/Lacrimal_sac","nasolacrimal-duct":"The nasolacrimal duct (also called the tear duct) carries tears from the lacrimal sac of the eye into the nasal cavity.\n\nThe duct begins in the eye socket between the maxillary and lacrimal bones, from where it passes downwards and backwards.\n\nThe opening of the nasolacrimal duct into the inferior nasal meatus of the nasal cavity is partially covered by a mucosal fold (valve of Hasner or plica lacrimalis).\n\nExcess tears flow through the nasolacrimal duct which drains into the inferior nasal meatus.\n\nThis is the reason the nose starts to run when a person is crying or has watery eyes from an allergy, and why one can sometimes taste eye drops.\n\nThis is for the same reason when applying some eye drops it is often advised to close the nasolacrimal duct by pressing it with a finger to prevent the medicine from escaping the eye and having unwanted side effects elsewhere in the body as it will proceed through the canal to the Nasal Cavity.\n\nLike the lacrimal sac, the duct is lined by stratified columnar epithelium containing mucus-secreting goblet cells, and is surrounded by connective tissue.\n\n== Clinical significance ==\n\nObstruction of the nasolacrimal duct may occur.\n\nThis leads to the excess overflow of tears called epiphora (chronic low-grade nasolacrimal duct occlusion).\n\nA congenital obstruction can cause cystic expansion of the duct and is called a dacryocystocele or Timo cyst.\n\nPersons with dry eye conditions can be fitted with punctal plugs that seal the ducts to limit the amount of fluid drainage and retain moisture.\n\nDuring an ear infection, excess mucus may drain through the nasolacrimal duct in the opposite way tears drain.\n\nThe canal containing the nasolacrimal duct is called the nasolacrimal canal.\n\nIn humans, the tear ducts in males tend to be larger than the ones in females.\n\nhttps://en.wikipedia.org/wiki/Nasolacrimal_duct","suspensory-ligament-of-eyeball":"The suspensory ligament of eyeball (or Lockwood's ligament) forms a hammock stretching below the eyeball between the medial and lateral check ligaments and enclosing the inferior rectus and inferior oblique muscles of the eye.\n\nIt is a thickening of Tenon's capsule, the dense connective tissue capsule surrounding the globe and separating it from orbital fat.\n\nThis ligament is responsible for maintaining and supporting the position of the eyeball in its normal upward and forward position within the orbit, and prevents downward displacement of the eyeball.\n\nIt can be considered a part of the bulbar sheath.It is named for Charles Barrett Lockwood.\n\nhttps://en.wikipedia.org/wiki/Suspensory_ligament_of_eyeball","tympanic-membrane":"EARDRUM\n\nIn the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear.\n\nIts function is to transmit sound from the air to the ossicles inside the middle ear, and then to the oval window in the fluid-filled cochlea.\n\nHence, it ultimately converts and amplifies vibration in air to vibration in cochlear fluid.\n\nThe malleus bone bridges the gap between the eardrum and the other ossicles.Rupture or perforation of the eardrum can lead to conductive hearing loss.\n\nCollapse or retraction of the eardrum can cause conductive hearing loss or cholesteatoma.\n\n== Structure ==\n\n=== Orientation and relations ===\n\nThe tympanic membrane is oriented obliquely in the anteroposterior, mediolateral, and superoinferior planes.\n\nConsequently, its superoposterior end lies lateral to its anteroinferior end.\n\nAnatomically, it relates superiorly to the middle cranial fossa, posteriorly to the ossicles and facial nerve, inferiorly to the parotid gland, and anteriorly to the temporomandibular joint.\n\n=== Regions ===\n\nThe eardrum is divided into two general regions: the pars flaccida and the pars tensa.\n\nThe relatively fragile pars flaccida lies above the lateral process of the malleus between the notch of Rivinus and the anterior and posterior malleal folds.\n\nConsisting of two layers and appearing slightly pinkish in hue, it is associated with Eustachian tube dysfunction and cholesteatomas.\n\nThe larger pars tensa consists of three layers: skin, fibrous tissue, and mucosa.\n\nIts thick periphery forms a fibrocartilaginous ring called the annulus tympanicus or Gerlach's ligament. while the central umbo tents inward at the level of the tip of malleus.\n\nThe middle fibrous layer, containing radial, circular, and parabolic fibers, encloses the handle of malleus.\n\nThough comparatively robust, the pars tensa is the region more commonly associated with perforations.\n\n=== Umbo ===\n\nThe manubrium (Latin: handle) of the malleus is firmly attached to the medial surface of the membrane as far as its center, drawing it toward the tympanic cavity.\n\nThe lateral surface of the membrane is thus concave.\n\nThe most depressed aspect of this concavity is termed the umbo (Latin: shield boss).\n\n=== Nerve supply ===\n\nSensation of the outer surface of the tympanic membrane is supplied mainly by the auriculotemporal nerve, a branch of the mandibular nerve (cranial nerve V3), with contributions from the auricular branch of the vagus nerve (cranial nerve X), the facial nerve (cranial nerve VII), and possibly the glossopharyngeal nerve (cranial nerve IX).\n\nThe inner surface of the tympanic membrane is innervated by the glossopharyngeal nerve.\n\n== Clinical significance ==\n\n=== Examination ===\n\nWhen the eardrum is illuminated during a medical examination, a cone of light radiates from the tip of the malleus to the periphery in the anteroinferior quadrant, this is what is known clinically as 5 o'clock.\n\n=== Rupture ===\n\nUnintentional perforation (rupture) has been described in blast injuries and air travel, typically in patients experiencing upper respiratory congestion that prevents equalization of pressure in the middle ear.\n\nIt is also known to occur in swimming, diving (including scuba diving), and martial arts.Patients suffering from tympanic membrane rupture may experience bleeding, tinnitus, hearing loss, or disequilibrium (vertigo).\n\nHowever, they rarely require medical intervention, as between 80 and 95 percent of ruptures recover completely within two to four weeks.\n\nThe prognosis becomes more guarded as the force of injury increases.\n\n=== Surgical puncture for treatment of middle ear infections ===\n\nThe pressure of fluid in an infected middle ear onto the eardrum may cause it to rupture.\n\nUsually, this consists of a small hole (perforation), which allows fluid to drain out.\n\nIf this does not occur naturally, a myringotomy (tympanotomy, tympanostomy) can be performed.\n\nA myringotomy is a surgical procedure in which a tiny incision is created in the eardrum to relieve pressure caused by excessive buildup of fluid, or to drain pus from the middle ear.\n\nThe fluid or pus comes from a middle ear infection (otitis media), which is a common problem in children.\n\nA tympanostomy tube is inserted into the eardrum to keep the middle ear aerated for a prolonged time and to prevent reaccumulation of fluid.\n\nWithout the insertion of a tube, the incision usually heals spontaneously in two to three weeks.\n\nDepending on the type, the tube is either naturally extruded in 6 to 12 months or removed during a minor procedure.\n\nThose requiring myringotomy usually have an obstructed or dysfunctional eustachian tube that is unable to perform drainage or ventilation in its usual fashion.\n\nBefore the invention of antibiotics, myringotomy without tube placement was also used as a major treatment of severe acute otitis media.\n\nIn some cases, the pressure of fluid in an infected middle ear is great enough to cause the eardrum to rupture naturally.\n\nUsually, this consists of a small hole (perforation), from which fluid can drain.\n\n== Society and culture ==\n\nThe Bajau people of the Pacific intentionally rupture their eardrums at an early age to facilitate diving and hunting at sea.\n\nMany older Bajau therefore have difficulties hearing.\n\nhttps://en.wikipedia.org/wiki/Eardrum","vestibule":"The vestibule is the central part of the bony labyrinth in the inner ear, and is situated medial to the eardrum (tympanic membrane), behind the cochlea, and in front of the three semicircular canals.The name comes from the Latin vestibulum, literally an entrance hall.\n\n== Structure ==\n\nThe vestibule is somewhat oval in shape, but flattened transversely; it measures about 5 mm from front to back, the same from top to bottom, and about 3 mm across.\n\nIn its lateral or tympanic wall is the oval window (fenestra vestibuli), closed, in the fresh state, by the base of the stapes and annular ligament.\n\nOn its medial wall, at the forepart, is a small circular depression, the recessus sphæricus, which is perforated, at its anterior and inferior part, by several minute holes (macula cribrosa media) for the passage of filaments of the acoustic nerve to the saccule; and behind this depression is an oblique ridge, the crista vestibuli, the anterior end of which is named the pyramid of the vestibule.\n\nThis ridge bifurcates below to enclose a small depression, the fossa cochlearis, which is perforated by a number of holes for the passage of filaments of the acoustic nerve which supply the vestibular end of the ductus cochlearis.\n\nThe orifice of the aquæductus vestibuli is the hind part of the medial wall; it extends to the posterior surface of the petrous portion of the temporal bone.\n\nIt transmits a small vein and contains a tubular prolongation of the membranous labyrinth, the endolymphatic duct, which ends in a cul-de-sac between the layers of the dura mater within the cranial cavity.\n\nOn the upper wall or roof, there is a transversely oval depression, the recessus ellipticus, separated from the recessus sphæricus by the crista vestibuli already mentioned.\n\nThe pyramid and adjoining part of the recessus ellipticus are perforated by a number of holes (macula cribrosa superior).\n\nThe apertures in the pyramid transmit the nerves to the utricle; those in the recessus ellipticus are the nerves to the ampullæ of the superior and lateral semicircular ducts.\n\nBehind, the five orifices of the semicircular canals can be found.\nIn the frontal view, there is an elliptical opening which communicates with the scala vestibuli of the cochlea.\n\nhttps://en.wikipedia.org/wiki/Vestibule_of_the_ear","cochlea":"The cochlea is the part of the inner ear involved in hearing.\n\nIt is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus.\n\nA core component of the cochlea is the Organ of Corti, the sensory organ of hearing, which is distributed along the partition separating the fluid chambers in the coiled tapered tube of the cochlea.\n\nThe name cochlea derives from Ancient Greek κοχλίας (kokhlias) 'spiral, snail shell'.\n\n== Structure ==\n\nThe cochlea (plural is cochleae) is a spiraled, hollow, conical chamber of bone, in which waves propagate from the base (near the middle ear and the oval window) to the apex (the top or center of the spiral).\n\nThe spiral canal of the cochlea is a section of the bony labyrinth of the inner ear that is approximately 30 mm long and makes 2¾ turns about the modiolus.\n\nThe cochlear structures include:\n\nThree scalae or chambers:\nthe vestibular duct or scala vestibuli (containing perilymph), which lies superior to the cochlear duct and abuts the oval window\nthe tympanic duct or scala tympani (containing perilymph), which lies inferior to the cochlear duct and terminates at the round window\nthe cochlear duct or scala media (containing endolymph) a region of high potassium ion concentration that the stereocilia of the hair cells project into\nThe helicotrema, the location where the tympanic duct and the vestibular duct merge, at the apex of the cochlea\nReissner's membrane, which separates the vestibular duct from the cochlear duct\nThe osseous spiral lamina, a main structural element that separates the cochlear duct from the tympanic duct\nThe basilar membrane, a main structural element that separates the cochlear duct from the tympanic duct and determines the mechanical wave propagation properties of the cochlear partition\nThe Organ of Corti, the sensory epithelium, a cellular layer on the basilar membrane, in which sensory hair cells are powered by the potential difference between the perilymph and the endolymph\nhair cells, sensory cells in the Organ of Corti, topped with hair-like structures called stereocilia\nThe spiral ligament.The cochlea is a portion of the inner ear that looks like a snail shell (cochlea is Greek for snail).\n\nThe cochlea receives sound in the form of vibrations, which cause the stereocilia to move.\n\nThe stereocilia then convert these vibrations into nerve impulses which are taken up to the brain to be interpreted.\n\nTwo of the three fluid sections are canals and the third is the 'Organ of Corti' which detects pressure impulses that travel along the auditory nerve to the brain.\n\nThe two canals are called the vestibular canal and the tympanic canal.\n\n=== Microanatomy ===\n\nThe walls of the hollow cochlea are made of bone, with a thin, delicate lining of epithelial tissue.\n\nThis coiled tube is divided through most of its length by an inner membranous partition.\n\nTwo fluid-filled outer spaces (ducts or scalae) are formed by this dividing membrane.\n\nAt the top of the snailshell-like coiling tubes, there is a reversal of the direction of the fluid, thus changing the vestibular duct to the tympanic duct.\n\nThis area is called the helicotrema.\n\nThis continuation at the helicotrema allows fluid being pushed into the vestibular duct by the oval window to move back out via movement in the tympanic duct and deflection of the round window; since the fluid is nearly incompressible and the bony walls are rigid, it is essential for the conserved fluid volume to exit somewhere.\nThe lengthwise partition that divides most of the cochlea is itself a fluid-filled tube, the third 'duct'.\n\nThis central column is called the cochlear duct.\n\nIts fluid, endolymph, also contains electrolytes and proteins, but is chemically quite different from perilymph.\n\nWhereas the perilymph is rich in sodium ions, the endolymph is rich in potassium ions, which produces an ionic, electrical potential.\nThe hair cells are arranged in four rows in the Organ of Corti along the entire length of the cochlear coil.\n\nThree rows consist of outer hair cells (OHCs) and one row consists of inner hair cells (IHCs).\n\nThe inner hair cells provide the main neural output of the cochlea.\n\nThe outer hair cells, instead, mainly 'receive' neural input from the brain, which influences their motility as part of the cochlea's mechanical \"pre-amplifier\".\n\nThe input to the OHC is from the olivary body via the medial olivocochlear bundle.\nThe cochlear duct is almost as complex on its own as the ear itself.\n\nThe cochlear duct is bounded on three sides by the basilar membrane, the stria vascularis, and Reissner's membrane.\n\nThe stria vascularis is a rich bed of capillaries and secretory cells; Reissner's membrane is a thin membrane that separates endolymph from perilymph; and the basilar membrane is a mechanically somewhat stiff membrane, supporting the receptor organ for hearing, the Organ of Corti, and determines the mechanical wave propagation properties of the cochlear system.\n\n== Function ==\n\nThe cochlea is filled with a watery liquid, the endolymph, which moves in response to the vibrations coming from the middle ear via the oval window.\n\nAs the fluid moves, the cochlear partition (basilar membrane and organ of Corti) moves; thousands of hair cells sense the motion via their stereocilia, and convert that motion to electrical signals that are communicated via neurotransmitters to many thousands of nerve cells.\n\nThese primary auditory neurons transform the signals into electrochemical impulses known as action potentials, which travel along the auditory nerve to structures in the brainstem for further processing.\n\n=== Hearing ===\n\nThe stapes (stirrup) ossicle bone of the middle ear transmits vibrations to the fenestra ovalis (oval window) on the outside of the cochlea, which vibrates the perilymph in the vestibular duct (upper chamber of the cochlea).\n\nThe ossicles are essential for efficient coupling of sound waves into the cochlea, since the cochlea environment is a fluid–membrane system, and it takes more pressure to move sound through fluid–membrane waves than it does through air.\n\nA pressure increase is achieved by reducing the area ratio from the tympanic membrane (drum) to the oval window (stapes bone) by 20.\n\nAs pressure = force/area, results in a pressure gain of about 20 times from the original sound wave pressure in air.\n\nThis gain is a form of impedance matching – to match the soundwave travelling through air to that travelling in the fluid–membrane system.\nAt the base of the cochlea, each 'duct' ends in a membranous portal that faces the middle ear cavity: The vestibular duct ends at the oval window, where the footplate of the stapes sits.\n\nThe footplate vibrates when the pressure is transmitted via the ossicular chain.\n\nThe wave in the perilymph moves away from the footplate and towards the helicotrema.\n\nSince those fluid waves move the cochlear partition that separates the ducts up and down, the waves have a corresponding symmetric part in perilymph of the tympanic duct, which ends at the round window, bulging out when the oval window bulges in.\nThe perilymph in the vestibular duct and the endolymph in the cochlear duct act mechanically as a single duct, being kept apart only by the very thin Reissner's membrane.\nThe vibrations of the endolymph in the cochlear duct displace the basilar membrane in a pattern that peaks a distance from the oval window depending upon the soundwave frequency.\n\nThe Organ of Corti vibrates due to outer hair cells further amplifying these vibrations.\n\nInner hair cells are then displaced by the vibrations in the fluid, and depolarise by an influx of K+ via their tip-link-connected channels, and send their signals via neurotransmitter to the primary auditory neurons of the spiral ganglion.\nThe hair cells in the Organ of Corti are tuned to certain sound frequencies by way of their location in the cochlea, due to the degree of stiffness in the basilar membrane.\n\nThis stiffness is due to, among other things, the thickness and width of the basilar membrane, which along the length of the cochlea is stiffest nearest its beginning at the oval window, where the stapes introduces the vibrations coming from the eardrum.\n\nSince its stiffness is high there, it allows only high-frequency vibrations to move the basilar membrane, and thus the hair cells.\n\nThe farther a wave travels towards the cochlea's apex (the helicotrema), the less stiff the basilar membrane is; thus lower frequencies travel down the tube, and the less-stiff membrane is moved most easily by them where the reduced stiffness allows: that is, as the basilar membrane gets less and less stiff, waves slow down and it responds better to lower frequencies.\n\nIn addition, in mammals, the cochlea is coiled, which has been shown to enhance low-frequency vibrations as they travel through the fluid-filled coil.\n\nThis spatial arrangement of sound reception is referred to as tonotopy.\nFor very low frequencies (below 20 Hz), the waves propagate along the complete route of the cochlea – differentially up vestibular duct and tympanic duct all the way to the helicotrema.\n\nFrequencies this low still activate the Organ of Corti to some extent but are too low to elicit the perception of a pitch.\n\nHigher frequencies do not propagate to the helicotrema, due to the stiffness-mediated tonotopy.\nA very strong movement of the basilar membrane due to very loud noise may cause hair cells to die.\n\nThis is a common cause of partial hearing loss and is the reason why users of firearms or heavy machinery often wear earmuffs or earplugs.\n\n=== Hair cell amplification ===\n\nNot only does the cochlea \"receive\" sound, a healthy cochlea generates and amplifies sound when necessary.\n\nWhere the organism needs a mechanism to hear very faint sounds, the cochlea amplifies by the reverse transduction of the OHCs, converting electrical signals back to mechanical in a positive-feedback configuration.\n\nThe OHCs have a protein motor called prestin on their outer membranes; it generates additional movement that couples back to the fluid–membrane wave.\n\nThis \"active amplifier\" is essential in the ear's ability to amplify weak sounds.The active amplifier also leads to the phenomenon of soundwave vibrations being emitted from the cochlea back into the ear canal through the middle ear (otoacoustic emissions).\n\n=== Otoacoustic emissions ===\n\nOtoacoustic emissions are due to a wave exiting the cochlea via the oval window, and propagating back through the middle ear to the eardrum, and out the ear canal, where it can be picked up by a microphone.\n\nOtoacoustic emissions are important in some types of tests for hearing impairment, since they are present when the cochlea is working well, and less so when it is suffering from loss of OHC activity.\n\n=== Role of gap junctions ===\n\nGap-junction proteins, called connexins, expressed in the cochlea play an important role in auditory functioning.\n\nMutations in gap-junction genes have been found to cause syndromic and nonsyndromic deafness.\n\nCertain connexins, including connexin 30 and connexin 26, are prevalent in the two distinct gap-junction systems found in the cochlea.\n\nThe epithelial-cell gap-junction network couples non-sensory epithelial cells, while the connective-tissue gap-junction network couples connective-tissue cells.\n\nGap-junction channels recycle potassium ions back to the endolymph after mechanotransduction in hair cells.\n\nImportantly, gap junction channels are found between cochlear supporting cells, but not auditory hair cells.\n\n== Clinical significance ==\n\n=== Hearing loss ===\n\n=== Bionics ===\n\nIn 2009, engineers at the Massachusetts Institute of Technology created an electronic chip that can quickly analyze a very large range of radio frequencies while using only a fraction of the power needed for existing technologies; its design specifically mimics a cochlea.\n\n== Other animals ==\n\nThe coiled form of cochlea is unique to mammals.\n\nIn birds and in other non-mammalian vertebrates, the compartment containing the sensory cells for hearing is occasionally also called \"cochlea,\" despite not being coiled up.\n\nInstead, it forms a blind-ended tube, also called the cochlear duct.\n\nThis difference apparently evolved in parallel with the differences in frequency range of hearing between mammals and non-mammalian vertebrates.\n\nThe superior frequency range in mammals is partly due to their unique mechanism of pre-amplification of sound by active cell-body vibrations of outer hair cells.\n\nFrequency resolution is, however, not better in mammals than in most lizards and birds, but the upper frequency limit is – sometimes much – higher.\n\nMost bird species do not hear above 4–5 kHz, the currently known maximum being ~ 11 kHz in the barn owl.\n\nSome marine mammals hear up to 200 kHz.\n\nA long coiled compartment, rather than a short and straight one, provides more space for additional octaves of hearing range, and has made possible some of the highly derived behaviors involving mammalian hearing.As the study of the cochlea should fundamentally be focused at the level of hair cells, it is important to note the anatomical and physiological differences between the hair cells of various species.\n\nIn birds, for instance, instead of outer and inner hair cells, there are tall and short hair cells.\n\nThere are several similarities of note in regard to this comparative data.\n\nFor one, the tall hair cell is very similar in function to that of the inner hair cell, and the short hair cell, lacking afferent auditory-nerve fiber innervation, resembles the outer hair cell.\n\nOne unavoidable difference, however, is that while all hair cells are attached to a tectorial membrane in birds, only the outer hair cells are attached to the tectorial membrane in mammals.\n\n== History ==\n\nThe name cochlea is derived from the Latin word for snail shell, which in turn is from the Greek κοχλίας kokhlias (\"snail, screw\"), from κόχλος kokhlos (\"spiral shell\") in reference to its coiled shape; the cochlea is coiled in mammals with the exception of monotremes.\n\nhttps://en.wikipedia.org/wiki/Cochlea","auditory-tube":"In anatomy, the Eustachian tube, also known as the auditory tube or pharyngotympanic tube, is a tube that links the nasopharynx to the middle ear, of which it is also a part.\n\nIn adult humans, the Eustachian tube is approximately 35 mm (1.4 in) long and 3 mm (0.12 in) in diameter.\n\nIt is named after the sixteenth-century Italian anatomist Bartolomeo Eustachi.In humans and other tetrapods, both the middle ear and the ear canal are normally filled with air.\n\nUnlike the air of the ear canal, however, the air of the middle ear is not in direct contact with the atmosphere outside the body; thus, a pressure difference can develop between the atmospheric pressure of the ear canal and the middle ear.\n\nNormally, the Eustachian tube is collapsed, but it gapes open with swallowing and with positive pressure, allowing the middle ear's pressure to adjust to the atmospheric pressure.\n\nWhen taking off in an aircraft, the ambient air pressure goes from higher (on the ground) to lower (in the sky).\n\nThe air in the middle ear expands as the plane gains altitude, and pushes its way into the back of the nose and mouth; on the way down, the volume of air in the middle ear shrinks, and a slight vacuum is produced.\n\nActive opening of the Eustachian tube (through actions like swallowing or the Valsalva maneuver) is required to equalize the pressure between the middle ear and the ambient atmosphere as the plane descends.\n\nA diver also experiences this change in pressure, but with greater rates of pressure change; active opening of the Eustachian tube is required more frequently as the diver goes deeper, into higher pressure.\n\n== Structure ==\n\nThe Eustachian tube extends from the anterior wall of the middle ear to the lateral wall of the nasopharynx, approximately at the level of the inferior nasal concha.\n\nIt consists of a bony part and a cartilaginous part.\n\n=== Bony part ===\n\nThe bony part (1⁄3) nearest to the middle ear is made of bone and is about 12 mm in length.\n\nIt begins in the anterior wall of the tympanic cavity, below the septum canalis musculotubarius, and, gradually narrowing, ends at the angle of junction of the squamous and the petrous parts of the temporal bone, its extremity presenting a jagged margin which serves for the attachment of the cartilaginous part.\n\nThe vestibule of the Eustachian tube is known as the protympanum, The protympanum is also known as the anterior part of the bony part of the tube.\n\n=== Cartilaginous part ===\n\nThe cartilaginous part of the Eustachian tube is about 24 mm in length and is formed of a triangular plate of elastic fibrocartilage, the apex of which is attached to the margin of the medial end of the bony part of the tube, while its base lies directly under the mucous membrane of the nasal part of the pharynx, where it forms an elevation, the torus tubarius or cushion, behind the pharyngeal opening of the auditory tube.\n\nThe upper edge of the cartilage is curled upon itself, being bent laterally so as to present on transverse section the appearance of a hook; a groove or furrow is thus produced, which is open below and laterally, and this part of the canal is completed by fibrous membrane.\n\nThe cartilage lies in a groove between the petrous part of the temporal bone and the great wing of the sphenoid; this groove ends opposite the middle of the medial pterygoid plate.\n\nThe cartilaginous and bony portions of the tube are not in the same plane, the former inclining downward a little more than the latter.\n\nThe diameter of the tube is not uniform throughout, being greatest at the pharyngeal opening, least at the junction of the bony and cartilaginous portions, and again increased toward the tympanic cavity; the narrowest part of the tube is termed the isthmus.\n\nThe position and relations of the pharyngeal opening are described with the nasal part of the pharynx.\n\nThe mucous membrane of the tube is continuous in front with that of the nasal part of the pharynx, and behind with that of the tympanic cavity; it is covered with ciliated pseudostratified columnar epithelia and is thin in the osseous portion, while in the cartilaginous portion it contains many mucous glands and near the pharyngeal orifice a considerable amount of adenoid tissue, which has been named by Gerlach the tube tonsil.\n\n=== Muscles ===\n\nThere are four muscles associated with the function of the Eustachian tube:\n\n-Levator veli palatini (innervated by the vagus nerve)\n-Salpingopharyngeus (innervated by the vagus nerve)\n-Tensor tympani (innervated by the mandibular nerve of CN V)\n-Tensor veli palatini (innervated by the mandibular nerve of CN V)\n\nThe tube is opened during swallowing by contraction of the tensor veli palatini and levator veli palatini, muscles of the soft palate.\n\n=== New anatomical perspectives ===\n\nMore recently, two developments have enhanced our understanding of the anatomy of the eustachian tube: Valsalva computerized tomography and endoscopic ear surgery.\n\nGiven the greater access to the ear anatomy using endoscopic methods, it has been suggested that the bony part of the eustachian tube is really the anterior extension of the middle ear cavity, or the \"Protympanum\".\n\nThe term \"Eustachian Tube\" should be limited to the fibrocartilaginous structure connecting the protympanum to the nasopharynx.\n\nThe Eustachian tube is a sac like irregular structure rather than a tubular structure.\n\nThe ear side of the eustchian tube is by far the narrowest segment, called isthmus, and is probably the site of possible obstructive pathology causing chronic ear disease.\n\n== Development ==\n\nThe Eustachian tube is derived from the dorsal part of the first pharyngeal pouch and second endodermal pouch, which during embryogenesis forms the tubotympanic recess.\n\nThe distal part of the tubotympanic sulcus gives rise to the tympanic cavity, while the proximal tubular structure becomes the Eustachian tube.\n\nIt helps transformation of sound waves.\n\n== Function ==\n\n=== Pressure equalization ===\n\nUnder normal circumstances, the human Eustachian tube is closed, but it can open to let a small amount of air through to prevent damage by equalizing pressure between the middle ear and the atmosphere.\n\nPressure differences cause temporary conductive hearing loss by decreased motion of the tympanic membrane and ossicles of the ear.\n\nVarious methods of ear clearing such as yawning, swallowing, or chewing gum may be used to intentionally open the tube and equalize pressures.\n\nWhen this happens, humans hear a small popping sound, an event familiar to aircraft passengers, scuba divers, or drivers in mountainous regions.\n\nDevices assisting in pressure equalization include an ad hoc balloon applied to the nose, creating inflation by positive air pressure.\n\nSome people learn to voluntarily 'click' their ears, together or separately, performing a pressure equalizing routine by opening their Eustachian tubes when pressure changes are experienced, as in ascending/descending in aircraft, mountain driving, elevator lift/drops, etc.\n\nSome are even able to deliberately keep their Eustachian tubes open for a brief period, and even increase or decrease air pressure in the middle ear.\n\nThe 'clicking' can actually be heard by putting one's ear to another's while performing the clicking sound.\n\nThis voluntary control may be first discovered when yawning or swallowing, or by other means (above).\n\nThose who develop this ability may discover that it can be done deliberately without force even when there are no pressure issues involved.\n\n=== Mucus drainage ===\n\nThe Eustachian tube also drains mucus from the middle ear.\n\nUpper respiratory tract infections or allergies can cause the Eustachian tube, or the membranes surrounding its opening to become swollen, trapping fluid, which serves as a growth medium for bacteria, causing ear infections.\n\nThis swelling can be reduced through the use of decongestants such as pseudoephedrine, oxymetazoline, and phenylephrine.\n\nEar infections are more common in children because the tube is horizontal and shorter, making bacterial entry easier, and it also has a smaller diameter, making the movement of fluid more difficult.\n\nIn addition, children's developing immune systems and poor hygiene habits make them more prone to upper respiratory infections.\n\n== Clinical significance ==\n\nOtitis media, or inflammation of the middle ear, commonly affects the Eustachian tube.\n\nChildren under 7 are more susceptible to this condition, one theory being that this is because the Eustachian tube is shorter and at more of a horizontal angle than in the adult ear.\n\nOthers argue that susceptibility in this age group is related to immunological factors and not Eustachian tube anatomy.\n\nBarotitis, a form of barotrauma, may occur when there is a substantial difference in air or water pressure between the outer and the middle ear – for example, during a rapid ascent while scuba diving, or during sudden decompression of an aircraft at high altitude.\n\nSome people are born with a dysfunctional Eustachian tube that is much slimmer than usual.\n\nThe cause may be genetic, but it has also been posited as a condition in which the patient did not fully recover from the effects of pressure on the middle ear during birth (retained birth compression).\n\nIt is suggested that Eustachian tube dysfunction can result in a large amount of mucus accumulating in the middle ear, often impairing hearing to a degree.\n\nThis condition is known as otitis media with effusion.\n\nA patulous Eustachian tube is a rare condition in which the Eustachian tube remains intermittently open, causing an echoing sound of the person's own heartbeat, breathing, and speech.\n\nThis may be temporarily relieved by holding the head upside down.\n\nSmoking can also cause damage to the cilia that protect the Eustachian tube from mucus, which can result in the clogging of the tube and a buildup of bacteria in the ear, leading to a middle ear infection.\n\nRecurring and chronic cases of sinus infection can result in Eustachian tube dysfunction caused by excessive mucus production which, in turn, causes obstruction to the openings of the Eustachian tubes.\n\n=== Ventilation tubes ===\n\nIn severe cases of childhood middle ear infections and Eustachian tube blockage, ventilation can be provided by a surgical puncturing of the eardrum to permit air equalization, known as myringotomy.\n\nThe eardrum would normally naturally heal and close the hole, so a tiny plastic rimmed grommet is inserted into the hole to hold it open.\n\nThis is known as a tympanostomy tube.\n\nAs a child grows, the tube is eventually naturally expelled by the body.\n\nLonger-lasting vent grommets with larger flanges have been researched, but these can lead to permanent perforation of the eardrum.\n\n=== Dilation of the Eustachian tube ===\n\nMore recently, dilation of the eustachian tube using balloon catheter has gained attention as a method of treating eustachian tube obstruction.\n\nThere are two methods of performing this procedure depending on the route of the catheter introduction and the area of the Eustachian tube to be dilated.\n\nDennis Poe have popularized the transnasal introduction and the dilation of the nose side of the eustachian tube.\n\nMuaaz Tarabichi pioneered the transtympanic (ear) introduction of the balloon catheter and the dilatation of the proximal part (the ear side) of the cartilaginous eustachian tube.\n\n== Other animals ==\n\nIn the equids (horses) and some rodent-like species such as the desert hyrax, an evagination of the Eustachian tube is known as the guttural pouch and is divided into medial and lateral compartments by the stylohyoid bone of the hyoid apparatus.\n\nThis is of great importance in equine medicine as the pouches are prone to infections, and, due to their intimate relationship to the cranial nerves (VII, IX, X, XI) and the internal and external carotid artery, various syndromes may arise relating to which is damaged.\n\nEpistaxis (nosebleed) is a very common presentation to veterinary surgeons and this may often be fatal unless a balloon catheter can be placed in time to suppress bleeding.\n\nhttps://en.wikipedia.org/wiki/Eustachian_tube","tuber-of-vermis":"The tuber of vermis, the most posterior division of the inferior vermis, is of small size, and laterally spreads out into the large inferior semilunar lobules, which comprise at least two-thirds of the inferior surface of the hemisphere.\n\n== Additional Images ==\n\nhttps://en.wikipedia.org/wiki/Tuber_of_vermis","superior-cerebellar-peduncle":"In the human brain, the superior cerebellar peduncle (brachium conjunctivum) is a paired structure of white matter that connects the cerebellum to the midbrain.\n\nIt consists mainly of efferent fibers, the cerebellothalamic tract that runs from a cerebellar hemisphere to the contralateral thalamus, and the cerebellorubral tract that runs from a cerebellar hemisphere to the red nucleus.\n\nIt also contains afferent tracts, most prominent of which is the ventral spinocerebellar tract.\n\nOther afferent tracts are the trigeminothalamic fibers, tectocerebellar fibers, and noradrenergic fibers from the locus coeruleus.\n\nThe superior peduncle emerges from the upper and medial parts of the white matter of each hemisphere and is placed under cover of the upper part of the cerebellum.\n\n== Structure ==\n\nSuperior cerebellar peduncles are connected together by the anterior medullary velum, which can be followed upward as far as the inferior colliculi, under which they disappear.\n\nBelow, they form the upper lateral boundaries of the fourth ventricle, but as they ascend they converge on the dorsal aspect of the ventricle and thus assist in forming its roof.\n\n=== Decussation ===\n\nThe decussation of superior cerebellar peduncle is the crossing of fibers of the superior cerebellar peduncle across the midline, and is located at the level of the inferior colliculi.\n\nIt comprises the cerebellothalamic tract, which arises from the dentate nucleus (therefore also known as dentatothalamic tract), as well as the cerebellorubral tract, which arises from the globose and emboliform nuclei and project to the contralateral red nucleus to eventually become the rubrospinal tract.\n\nIt is also known as horseshoe-shaped commissure of Wernekinck.\n\nIt is important as an anatomical landmark, as lesions above it cause contralateral cerebellar signs, while lesions below it cause ipsilateral cerebellar signs.\n\nhttps://en.wikipedia.org/wiki/Superior_cerebellar_peduncle","nodule-of-vermis":"The nodule (nodular lobe), or anterior end of the inferior vermis, abuts against the roof of the fourth ventricle, and can only be distinctly seen after the cerebellum has been separated from the medulla oblongata and pons.\nOn either side of the nodule is a thin layer of white substance, named the posterior medullary velum.\nIt is semilunar in form, its convex border being continuous with the white substance of the cerebellum; it extends on either side as far as the flocculus.\n\n== Additional Images ==\n\nhttps://en.wikipedia.org/wiki/Nodule_of_vermis","lingula-of-cerebellum":"The lingula is a small tongue-shaped process, consisting of four or five folia; it lies in front of the lobulus centralis, and is concealed by it.\nAnteriorly, it rests on the dorsal surface of the anterior medullary velum, and its white substance is continuous with that of the velum.\n\nhttps://en.wikipedia.org/wiki/Lingula_of_cerebellum","flocculus":"The flocculus (Latin: tuft of wool, diminutive) is a small lobe of the cerebellum at the posterior border of the middle cerebellar peduncle anterior to the biventer lobule.\n\nLike other parts of the cerebellum, the flocculus is involved in motor control.\n\nIt is an essential part of the vestibulo-ocular reflex, and aids in the learning of basic motor skills in the brain.\nIt is associated with the nodulus of the vermis; together, these two structures compose the vestibular part of the cerebellum.\nAt its base, the flocculus receives input from the inner ear's vestibular system and regulates balance.\n\nMany floccular projections connect to the motor nuclei involved in control of eye movement.\n\n== Structure ==\n\nThe flocculus is contained within the flocculonodular lobe which is connected to the cerebellum.\n\nThe cerebellum is the section of the brain that is essential for motor control.\n\nAs a part of the cerebellum, the flocculus plays a part of the vestibulo-ocular reflex system, a system that controls the movement of the eye in coordination with movements of the head.\n\nThere are five separate “zones” in the flocculus and two halves, the caudal and rostral half.\n\n=== Circuitry of the flocculus ===\n\nThe flocculus has a complex circuitry that is reflected in the structure of the zones and halves.\n\nThese \"zones\" of the flocculus refer to five separate groupings of Purkinje cells that project to different areas of the brain.\n\nDepending upon where stimulus occurs in the flocculus, signals can be projected to very different parts of the brain.\n\nThe first and third zones of the flocculus project to the superior vestibular nucleus, the second and fourth zone projects to the medial vestibular nucleus, and the fifth zone projects to the interposed posterior nucleus, a part of the cerebellum.The anatomy of the flocculus shows that it is composed of two disjointed lobes or halves.\n\nThe “halves” of the flocculus refer to the caudal half and the rostral half, and they indicate from where fiber projections are received and the path in which a signal travels.\n\nThe caudal half of the flocculus receives mossy fiber projections mainly from the vestibular system and tegmental pontine reticular nucleus, an area within the floor of the midbrain that affects the axonal projections or images received by the cerebellum.\n\nVestibular inputs are also carried through climbing fibers that project into the flocculus, stimulating Purkinje cells.\n\nLeading research would suggest that climbing fibers play a specific role in motor learning.\n\nThe climbing fibers then send the image or projection to the part of the brain that receives electrical signals and generates movement.\n\nFrom the midbrain, corticopontine fibers carry information from the primary motor cortex.\n\nFrom there, projections are sent to the ipsilateral pontine nucleus in the ventral pons, both of which are associated with projections to the cerebellum.\n\nFinally, pontocerebellar projections carry vestibulo-occular signals to the contralateral cerebellum via the middle cerebellar peduncle.\n\nThe rostral half of the flocculus also receives mossy fiber projections from the pontine nuclei; however, it receives very little projection from the vestibular system.\n\n== Function ==\n\nThe flocculus is a part of the vestibulo-ocular reflex system and is used to help stabilize gaze during head rotation about any axis of space.\n\nNeurons in both the vermis of cerebellum and flocculus transmit an eye velocity signal that correlates with smooth pursuit.\n\n=== Flocculus role In learning basic motor functions ===\n\nThe idea that the flocculus is involved in motor learning gave rise to the “flocculus hypothesis.” This hypothesis argues that the flocculus plays a key role in the vestibulo-ocular system, most importantly the ability for the vestibular system to adapt to a shift in the visual field.\n\nThe learning of basic motor skills, including walking, balancing, and the ability to sit up, can be attributed to early patterns and pathways associated with the vestibulo-occular reflex and the pathways formed in the cerebellum.\n\nWithin the cerebellum pathways that contribute to the learning of basic motor skills.\n\nAlso\nThe flocculus appears to be included a VOR pathway that aids in the adaptation to a repeated shift in the visual field.\n\nA shift in the visual field affects an individuals spatial recognition.\n\nThe leading research would suggest that flocculus aids in the synchronization of eye and motor functions after a visual shift occurs in order for the visual field and the motor skills to function together.\n\nIf this shift is repeated the flocculus essentially trains the brain to fully readjust to this repeated stimuli.\n\n== Location ==\n\nConstituted by two disjointed-shaped lobes, the flocculus is positioned within the lowest level of the cerebellum.\n\nThere are three main subdivisions in the cerebellum and the flocculus is contained within the most primitive the vestibulocerebellum.Its lobes are linked through a circuit of neurons connecting to the vermis, the medial structure in the cerebellum.\n\nExtensions leave the base of the follucular's lobes which then connect to the spinal cord.\n\nThe cerebellum, which houses the flocculus, is located in the back and at the base of the human brain, directly above the brainstem.\n\n== Clinical significance ==\n\nThe flocculus is most important for the pursuit of movements with the eyes.\n\nLesions in the flocculus impair control of the vestibulo-ocular reflex, and gaze holding also known as vestibulocerebellar syndrome.\n\nThe deficits observed in patients with lesions to this area resemble dose-dependent effects of alcohol on pursuit movements.\n\nBilateral lesions of the flocculus reduce the gain of smooth pursuit, which is the steady tracking of a moving object by the eyes.\n\nInstead, the bilateral lesions of the flocculus result in saccadic pursuit, in which smooth tracking is replaced by simultaneous rapid movements, or jerking motions, of the eye to follow an object toward the ipsilateral visual field.\n\nThese lesions also impair the ability to hold the eyes in the eccentric position, resulting in gaze-evoked nystagmus toward the affected side of the cerebellum.\n\nNystagmus is the constant involuntary movements of the eyes; a patient can have either horizontal nystagmus (side-to-side eye movements), vertical nystagmus (up and down eye movements), or rotary nystagmus (circular eye movements).\n\nThe flocculus also plays a role in keeping the body oriented in space.\n\nA lesion in this area will result in ataxia, a neurological disorder that results in the deterioration of the coordination of muscle movements, and unsteady bodily movements such as swaying and staggering.\n\n=== Associated conditions ===\n\nThe conditions and systems associated with floccular loss are considered to be a subset of a vestibular disease.\n\nSome symptoms of common vestibular diseases include: head tilting, an inability to stand, ataxia, dizziness, vomiting and strabismus.\n\nBecause of the flocculus’ role in the vestibular system, the inner ear, equilibrioception, and both peripheral and central vision is affected by any loss or damage to the Flocculus.\n\nThese systems are affected because damage to the flocculus prevents any changes from being stored in regards to visual and motor communication, meaning that although the VOR is still intact these systems are unable to store changes in gain or eye movement as you rotate your head back and forth.\n\nhttps://en.wikipedia.org/wiki/Flocculus","culmen":"A culmen is a top, a summit or a culminating point.\n\nIt may also refer to:\n\nCulmen (bird), the upper ridge of a bird's beak\nCulmen (cerebellum), a structure in the brain\n\nhttps://en.wikipedia.org/wiki/Culmen","central-lobule":"The central lobule is a small square lobule, situated in the anterior cerebellar notch.\n\nIt overlaps the lingula, from which it is separated by the precentral fissure; laterally, it extends along the upper and anterior part of each hemisphere, where it forms a wing-like prolongation (ala), on each side, as the alae of the central lobule or alae lobuli centralis.\n\n== Additional Images ==\n\nhttps://en.wikipedia.org/wiki/Central_lobule","vitreous-body":"The vitreous body (vitreous meaning \"glass-like\", from Latin vitreus, equivalent to vitr(um) glass + -eus -ous) is the clear gel that fills the space between the lens and the retina of the eyeball (the vitreous chamber) in humans and other vertebrates.\n\nIt is often referred to as the vitreous humor (also spelled humour, from Latin meaning liquid) or simply \"the vitreous\".\n\nVitreous fluid or \"liquid vitreous\" is the liquid component of the vitreous gel, found after a vitreous detachment.\n\nIt is not to be confused with the aqueous humor, the other fluid in the eye that is found between the cornea and lens.\n\n== Structure ==\n\nThe vitreous humor is a transparent, colorless, gelatinous mass that fills the space in the eye between the lens and the retina.\n\nIt is surrounded by a layer of collagen called the vitreous membrane (or hyaloid membrane or vitreous cortex) separating it from the rest of the eye.\n\nIt makes up four-fifths of the volume of the eyeball.\n\nThe vitreous humour is fluid-like near the centre, and gel-like near the edges.\nThe vitreous humour is in contact with the vitreous membrane overlying the retina.\n\nCollagen fibrils attach the vitreous at the optic nerve disc and the ora serrata (where the retina ends anteriorly), at the Wieger-band, the dorsal side of the lens.\n\nThe vitreous also firmly attaches to the lens capsule, retinal vessels, and the macula, the area of the retina which provides finer detail and central vision.Aquaporin 4 in Müller cell in rats transports water to the vitreous body.\n\n=== Anatomical features ===\n\nThe vitreous has many anatomical landmarks, including the hyaloid membrane, Berger's space, space of Erggelet, Wieger's ligament, Cloquet's canal and the space of Martegiani.Surface features:\n\nPatella fossa: Shallow saucer-like concavity anteriorly, in which the lens rests, separated by Berger's space\nLigamentum hyaloideocapsulare (Wieger's ligament): Circular thickening of vitreous 8-9mm in diameter, delineates the patella fossa\nAnterior hyaloid: Vitreous surface anterior to ora serrata.\n\nContinuous with and invests in the zonular fibres, and extends forward between the ciliary processes\nVitreous base: Denser cortical area of vitreous.\n\nFirmly attached to the posterior 2mm of the pars plana, and the anterior 2-4mm of retina\nPosterior hyaloid surface: Closely applied to retinal internal limiting membrane.\n\nFirm attachment sites: Along blood vessels and at sites of retinal degeneration\nSpace of Martegioni: A funnel shaped space overlying the optic disc with condensed edge\nCloquet's canal: A 1–2 mm wide canal within the vitreous, from the space of Martegioni to the space of Berger, along an S-shaped course mainly below the horizontal.\nMittendorf's dot: A small circular opacity on the posterior lens capsule, which represents the site of attachment of the hyaloid artery before it subsequently regressed.\nBergmeister's papilla: A tuft of fibrous tissue at the optic disc, which represents a remnant of the sheath associated with the hyaloid artery before it subsequently regressed.Internal structures of the vitreous\n\nThe vitreous body at birth is homogenous with a finely striated pattern.\nWith early aging the vitreous develops narrow transvitreal \"channels\".\nThe cortex is denser than the centre with development.\nFrom adolescence, vitreous tracts form from anterior to posterior.\nThese vitreous tracts are fine sheet-like condensations of vitreous.Named tracts\n\nRetrolental tract: Extends posteriorly from the hyaloideocapsular ligament into central vitreous\nCoronary tract: External to the retrolental tract, and excluding posteriorly from a circular zone overlying the posterior 1/3rd of the ciliary processes\nMedian tract: Extends back from a circular zone external to the coronary tract, at the anterior margin of the vitreous base\nPreretinal tract: Extends back from the ora serrata and vitreous base\n\n=== Biochemical properties ===\n\nIts composition is similar to that of the cornea, but the vitreous contains very few cells.\n\nIt is composed mostly of phagocytes, which remove unwanted cellular debris in the visual field, and hyalocytes, which turn over the hyaluronan.\nThe vitreous humour contains no blood vessels, and 98–99% of its volume is water (as opposed to only 75% in the cornea).\n\nIn addition to water, the vitreous consists of salts, sugars, vitrosin (a type of collagen), a network of collagen type II fibrils with glycosaminoglycan, hyaluronan, opticin, and a wide array of proteins.\n\nDespite having little solid matter, the fluid is substantial enough to fill the eye and give it its spherical shape.\n\nThis contrasts with the aqueous humour, which is more fluid, and the lens, on the other hand, which is elastic in nature and is tightly packed with cells.\n\nThe vitreous humour has a viscosity two to four times that of water, giving it a gelatinous consistency.\n\nIt has a refractive index of 1.336.\n\n== Development ==\n\nThe vitreous fluid is not present at birth (the eye being filled with only the gel-like vitreous body), but found after age 4-5, and increases in size thereafter.Produced by cells in the non-pigmented portion of the ciliary body, the vitreous humour is derived from embryonic mesenchyme cells, which degenerate after birth.The nature and composition of the vitreous humour changes over the course of life.\n\nIn adolescence, the vitreous cortex becomes more dense and vitreous tracts develop; and in adulthood, the tracts become better defined and sinuous.\n\nCentral vitreous liquefies, fibrillar degeneration occurs, and the tracts break up (syneresis).Coarse strands develop with ageing.\n\nThe gel volume decreases with age, and the liquid volume increases.\n\nThe cortex may disappear at sites, allowing liquid vitreous to extrude adjacently into the potential space between vitreous cortex and retina (vitreous detachment).\n\n== Clinical significance ==\n\n=== Injury ===\n\nIf the vitreous pulls away from the retina, it is known as a vitreous detachment.\n\nAs the human body ages, the vitreous often liquefies and may collapse.\n\nThis is more likely to occur, and occurs much earlier, in eyes that are nearsighted (myopia).\n\nIt can also occur after injuries to the eye or inflammation in the eye (uveitis).\nThe collagen fibres of the vitreous are held apart by electrical charges.\n\nWith aging, these charges tend to reduce, and the fibres may clump together.\n\nSimilarly, the gel may liquefy, a condition known as synaeresis, allowing cells and other organic clusters to float freely within the vitreous humour.\n\nThese allow floaters which are perceived in the visual field as spots or fibrous strands.\n\nFloaters are generally harmless, but the sudden onset of recurring floaters may signify a posterior vitreous detachment or other diseases of the eye.\nPosterior vitreous detachment: Once liquid vitreous enters the sub-hyaloid space between the vitreous cortex and the retina, it may strip the vitreous cortex off the retina with each eye movement (see Saccade).\n\n=== Postmortem and forensic ===\n\nAfter death, the vitreous resists putrefaction longer than other body fluids.\n\nWithin the hours, days and weeks after death, the vitreous potassium concentration rises, at such a predictable speed that vitreous potassium levels are frequently used to estimate the time since death (post-mortem interval) of a corpse.The metabolic exchange and equilibration between systemic circulation and vitreous humour is so slow that vitreous humour is sometimes the fluid of choice for postmortem analysis of glucose levels or substances which would be more rapidly diffused, degraded, excreted or metabolized from the general circulation.\nAccording to Jewish religion, extracting the vitreous fluid for forensic chemical analysis is preferred to blood analysis (in case a forensic or post-mortem toxicology test is deemed necessary).\n\nThis avoids the loss of even a few droplets of blood from the body prior to burial.\n\nhttps://en.wikipedia.org/wiki/Vitreous_body","retina":"The retina (from Latin: rete \"net\") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs.\n\nThe optics of the eye create a focused two-dimensional image of the visual world on the retina, which translates that image into electrical neural impulses to the brain to create visual perception.\n\nThe retina serves a function analogous to that of the film or image sensor in a camera.\n\nThe neural retina consists of several layers of neurons interconnected by synapses and is supported by an outer layer of pigmented epithelial cells.\n\nThe primary light-sensing cells in the retina are the photoreceptor cells, which are of two types: rods and cones.\n\nRods function mainly in dim light and provide black-and-white vision.\n\nCones function in well-lit conditions and are responsible for the perception of colour, as well as high-acuity vision used for tasks such as reading.\n\nA third type of light-sensing cell, the photosensitive ganglion cell, is important for entrainment of circadian rhythms and reflexive responses such as the pupillary light reflex.\n\nLight striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses that are sent to various visual centres of the brain through the fibres of the optic nerve.\n\nNeural signals from the rods and cones undergo processing by other neurons, whose output takes the form of action potentials in retinal ganglion cells whose axons form the optic nerve.\n\nSeveral important features of visual perception can be traced to the retinal encoding and processing of light.\n\nIn vertebrate embryonic development, the retina and the optic nerve originate as outgrowths of the developing brain, specifically the embryonic diencephalon; thus, the retina is considered part of the central nervous system (CNS) and is actually brain tissue.\n\nIt is the only part of the CNS that can be visualized non-invasively.\n\n== Structure ==\n\n=== Inverted versus non-inverted retina ===\n\nThe vertebrate retina is inverted in the sense that the light sensing cells are in back of the retina, so that light has to pass through layers of neurons and capillaries before it reaches the rods and cones.\n\nThe ganglion cells, whose axons form the optic nerve, are at the front of the retina; therefore the optic nerve must cross through the retina en route to the brain.\n\nIn this region there are no photoreceptors, giving rise to the blind spot.\n\nIn contrast, in the cephalopod retina the photoreceptors are in front, with processing neurons and capillaries behind them.\n\nBecause of this, cephalopods do not have a blind spot.\nAlthough the overlying neural tissue is partly transparent, and the accompanying glial cells have been shown to act as fibre-optic channels to transport photons directly to the photoreceptors, light scattering does occur.\n\nSome vertebrates, including humans, have an area of the central retina adapted for high-acuity vision.\n\nThis area, termed the fovea centralis, is avascular (does not have blood vessels), and has minimal neural tissue in front of the photoreceptors, thereby minimizing light scattering.The cephalopods have a non-inverted retina which is comparable in resolving power to the eyes of many vertebrates.\n\nSquid eyes do not have an analog of the vertebrate retinal pigment epithelium (RPE).\n\nAlthough their photoreceptors contain a protein, retinochrome, that recycles retinal and replicates one of the functions of the vertebrate RPE, one could argue that cephalopod photoreceptors are not maintained as well as in vertebrates and that, as a result, the useful lifetime of photoreceptors in invertebrates is much shorter than in vertebrates.\n\nHaving easily replaced stalk-eyes (some lobsters) or retinae (some spiders, such as Deinopis) rarely occurs.\nThe cephalopod retina does not originate as an outgrowth of the brain, as the vertebrate one does.\n\nIt is arguable that this difference shows that vertebrate and cephalopod eyes are not homologous but have evolved separately.\n\nFrom an evolutionary perspective, a more complex structure such as the inverted retina can generally come about as a consequence of two alternate processes: (a) an advantageous \"good\" compromise between competing functional limitations, or (b) as a historical maladaptive relic of the convoluted path of organ evolution and transformation.\n\nVision is an important adaptation in higher vertebrates.\nA third view of the \"inverted\" vertebrate eye is that it combines two benefits: the maintenance of the photoreceptors mentioned above, and the reduction in light intensity necessary to avoid blinding the photoreceptors, which are based on the extremely sensitive eyes of the ancestors of modern hagfishes (a fish that lives in very deep, dark water).\n\n=== Retinal layers ===\n\nThe vertebrate retina has ten distinct layers.\n\nFrom closest to farthest from the vitreous body:\n\nInner limiting membrane – basement membrane elaborated by Müller cells.\nNerve fibre layer – axons of the ganglion cell bodies (note that a thin layer of Müller cell footplates exists between this layer and the inner limiting membrane).\nGanglion cell layer – contains nuclei of ganglion cells, the axons of which become the optic nerve fibres, and some displaced amacrine cells.\nInner plexiform layer – contains the synapse between the bipolar cell axons and the dendrites of the ganglion and amacrine cells.\nInner nuclear layer – contains the nuclei and surrounding cell bodies (perikarya) of the amacrine cells, bipolar cells, and horizontal cells.\nOuter plexiform layer – projections of rods and cones ending in the rod spherule and cone pedicle, respectively.\n\nThese make synapses with dendrites of bipolar cells and horizontal cells.\n\nIn the macular region, this is known as the Fiber layer of Henle.\nOuter nuclear layer – cell bodies of rods and cones.\nExternal limiting membrane – layer that separates the inner segment portions of the photoreceptors from their cell nuclei.\nInner segment / outer segment layer – inner segments and outer segments of rods and cones.\n\nThe outer segments contain a highly specialized light-sensing apparatus.\nRetinal pigment epithelium – single layer of cuboidal epithelial cells (with extrusions not shown in diagram).\n\nThis layer is closest to the choroid, and provides nourishment and supportive functions to the neural retina, The black pigment melanin in the pigment layer prevents light reflection throughout the globe of the eyeball; this is extremely important for clear vision.These layers can be grouped into 4 main processing stages: photoreception; transmission to bipolar cells; transmission to ganglion cells, which also contain photoreceptors, the photosensitive ganglion cells; and transmission along the optic nerve.\n\nAt each synaptic stage there are also laterally connecting horizontal and amacrine cells.\nThe optic nerve is a central tract of many axons of ganglion cells connecting primarily to the lateral geniculate body, a visual relay station in the diencephalon (the rear of the forebrain).\n\nIt also projects to the superior colliculus, the suprachiasmatic nucleus, and the nucleus of the optic tract.\n\nIt passes through the other layers, creating the optic disc in primates.Additional structures, not directly associated with vision, are found as outgrowths of the retina in some vertebrate groups.\n\nIn birds, the pecten is a vascular structure of complex shape that projects from the retina into the vitreous humour; it supplies oxygen and nutrients to the eye, and may also aid in vision.\n\nReptiles have a similar, but much simpler, structure.In adult humans, the entire retina is approximately 72% of a sphere about 22 mm in diameter.\n\nThe entire retina contains about 7 million cones and 75 to 150 million rods.\n\nThe optic disc, a part of the retina sometimes called \"the blind spot\" because it lacks photoreceptors, is located at the optic papilla, where the optic-nerve fibres leave the eye.\n\nIt appears as an oval white area of 3 mm².\n\nTemporal (in the direction of the temples) to this disc is the macula, at whose centre is the fovea, a pit that is responsible for our sharp central vision but is actually less sensitive to light because of its lack of rods.\n\nHuman and non-human primates possess one fovea, as opposed to certain bird species, such as hawks, who are bifoviate, and dogs and cats, who possess no fovea but a central band known as the visual streak.\n\nAround the fovea extends the central retina for about 6 mm and then the peripheral retina.\n\nThe farthest edge of the retina is defined by the ora serrata.\n\nThe distance from one ora to the other (or macula), the most sensitive area along the horizontal meridian is about 32 mm.In section, the retina is no more than 0.5 mm thick.\n\nIt has three layers of nerve cells and two of synapses, including the unique ribbon synapse.\n\nThe optic nerve carries the ganglion cell axons to the brain, and the blood vessels that supply the retina.\n\nThe ganglion cells lie innermost in the eye while the photoreceptive cells lie beyond.\n\nBecause of this counter-intuitive arrangement, light must first pass through and around the ganglion cells and through the thickness of the retina, (including its capillary vessels, not shown) before reaching the rods and cones.\n\nLight is absorbed by the retinal pigment epithelium or the choroid (both of which are opaque).\nThe white blood cells in the capillaries in front of the photoreceptors can be perceived as tiny bright moving dots when looking into blue light.\n\nThis is known as the blue field entoptic phenomenon (or Scheerer's phenomenon).\nBetween the ganglion cell layer and the rods and cones there are two layers of neuropils where synaptic contacts are made.\n\nThe neuropil layers are the outer plexiform layer and the inner plexiform layer.\n\nIn the outer neuropil layer, the rods and cones connect to the vertically running bipolar cells, and the horizontally oriented horizontal cells connect to ganglion cells.\nThe central retina predominantly contains cones, while the peripheral retina predominantly contains rods.\n\nIn total, there are about seven million cones and a hundred million rods.\n\nAt the centre of the macula is the foveal pit where the cones are narrow and long, and, arranged in a hexagonal mosaic, the most dense, in contradistinction to the much fatter cones located more peripherally in the retina.\n\nAt the foveal pit the other retinal layers are displaced, before building up along the foveal slope until the rim of the fovea, or parafovea, is reached, which is the thickest portion of the retina.\n\nThe macula has a yellow pigmentation, from screening pigments, and is known as the macula lutea.\n\nThe area directly surrounding the fovea has the highest density of rods converging on single bipolar cells.\n\nSince its cones have a much lesser convergence of signals, the fovea allows for the sharpest vision the eye can attain.Though the rod and cones are a mosaic of sorts, transmission from receptors, to bipolars, to ganglion cells is not direct.\n\nSince there are about 150 million receptors and only 1 million optic nerve fibres, there must be convergence and thus mixing of signals.\n\nMoreover, the horizontal action of the horizontal and amacrine cells can allow one area of the retina to control another (e.g. one stimulus inhibiting another).\n\nThis inhibition is key to lessening the sum of messages sent to the higher regions of the brain.\n\nIn some lower vertebrates (e.g. the pigeon), there is a \"centrifugal\" control of messages – that is, one layer can control another, or higher regions of the brain can drive the retinal nerve cells, but in primates this does not occur.\n\n==== Layers imagable with optical coherence tomography ====\nUsing optical coherence tomography (OCT) there are 18 layers that can be identified in the retina.\n\nThe layers and anatomical correlation are as follows:\n\nFrom innermost to outermost, the layers identifiable by OCT are as follows:\n\n=== Development ===\n\nRetinal development begins with the establishment of the eye fields mediated by the SHH and SIX3 proteins, with subsequent development of the optic vesicles regulated by the PAX6 and LHX2 proteins.\n\nThe role of Pax6 in eye development was elegantly demonstrated by Walter Gehring and colleagues, who showed that ectopic expression of Pax6 can lead to eye formation on Drosophila antennae, wings, and legs.\n\nThe optic vesicle gives rise to three structures: the neural retina, the retinal pigmented epithelium, and the optic stalk.\n\nThe neural retina contains the retinal progenitor cells (RPCs) that give rise to the seven cell types of the retina.\n\nDifferentiation begins with the retinal ganglion cells and concludes with production of the Muller glia.\n\nAlthough each cell type differentiates from the RPCs in a sequential order, there is considerable overlap in the timing of when individual cell types differentiate.\n\nThe cues that determine a RPC daughter cell fate are coded by multiple transcription factor families including the bHLH and homeodomain factors.In addition to guiding cell fate determination, cues exist in the retina to determine the dorsal-ventral (D-V) and nasal-temporal (N-T) axes.\n\nThe D-V axis is established by a ventral to dorsal gradient of VAX2, whereas the N-T axis is coordinated by expression of the forkhead transcription factors FOXD1 and FOXG1.\n\nAdditional gradients are formed within the retina.\n\nThis spatial distribution may aid in proper targeting of RGC axons that function to establish the retinotopic map.\n\n=== Blood supply ===\n\nThe retina is stratified into distinct layers, each containing specific cell types or cellular compartments that have metabolisms with different nutritional requirements.\n\nTo satisfy these requirements, the ophthalmic artery bifurcates and supplies the retina via two distinct vascular networks: the choroidal network, which supplies the choroid and the outer retina, and the retinal network, which supplies the retina's inner layer.\n\n==== Circulatory mechanisms ====\nAt first glance, one may think that the vertebrate retina is \"wired wrongly\" or \"badly designed\"; but in fact, the retina could not function if it were not inverted.\n\nThe photoreceptor layer must be embedded in the retinal pigment epithelium (RPE), which performs at least seven vital functions, one of the most obvious being to supply oxygen and other necessary nutrients needed for the photoreceptors to function.\n\nThese nutrients include glucose, fatty acids, and retinal.\n\nThe mammalian photoreceptor amplification process uses large quantities energy for vision in photopic conditions (requiring less under scotopic conditions) and, thus, requires the large supply nutrients supplied by the blood vessels in the choroid, which lies beyond the RPE.\n\nThe choroid supplies about 75% of these nutrients to the retina and the retinal vasculature only 25%.When light strikes 11-cis-retinal (in the disks in the rods and cones), 11-cis-retinal changes to all-trans-retinal which then triggers changes in the opsins.\n\nNow, the outer segments do not regenerate the retinal back into the cis- form once it has been changed by light.\n\nInstead the retinal is pumped out to the surrounding RPE where it is regenerated and transported back into the outer segments of the photoreceptors.\n\nThis recycling function of the RPE protects the photoreceptors against photo-oxidative damage and allows the photoreceptor cells to have decades-long useful lives.\n\n==== In birds ====\nThe bird retina is devoid of blood vessels, perhaps to give unobscured passage of light for forming images, thus giving better resolution.\n\nIt is, therefore, a considered view that the bird retina depends for nutrition and oxygen supply on a specialized organ, called the \"pecten\" or pecten oculi, located on the blind spot or optic disk.\n\nThis organ is extremely rich in blood vessels and is thought to supply nutrition and oxygen to the bird retina by diffusion through the vitreous body.\n\nThe pecten is highly rich in alkaline phosphatase activity and polarized cells in its bridge portion – both befitting its secretory role.\n\nPecten cells are packed with dark melanin granules, which have been theorized to keep this organ warm with the absorption of stray light falling on the pecten.\n\nThis is considered to enhance metabolic rate of the pecten, thereby exporting more nutritive molecules to meet the stringent energy requirements of the retina during long periods of exposure to light.\n\n=== Biometric identification and diagnosis of disease ===\n\nThe bifurcations and other physical characteristics of the inner retinal vascular network are known to vary among individuals, and these individual variances have been used for biometric identification and for early detection of the onset of disease.\n\nThe mapping of vascular bifurcations is one of the basic steps in biometric identification.\n\nResults of such analyses of retinal blood vessel structure can be evaluated against the ground truth data of vascular bifurcations of retinal fundus images that are obtained from the DRIVE dataset.\n\nIn addition, the classes of vessels of the DRIVE dataset have also been identified, and an automated method for accurate extraction of these bifurcations is also available.\n\nChanges in retinal blood circulation are seen with aging and exposure to air pollution, and may indicate cardiovascular diseases such as hypertension and atherosclerosis.\n\nDetermining the equivalent width of arterioles and venules near the optic disc is also a widely used technique to identify cardiovascular risks.\n\n== Function ==\n\nThe retina translates an optical image into neural impulses starting with the patterned excitation of the colour-sensitive pigments of its rods and cones, the retina's photoreceptor cells.\n\nThe excitation is processed by the neural system and various parts of the brain working in parallel to form a representation of the external environment in the brain.\nThe cones respond to bright light and mediate high-resolution colour vision during daylight illumination (also called photopic vision).\n\nThe rod responses are saturated at daylight levels and don't contribute to pattern vision.\n\nHowever, rods do respond to dim light and mediate lower-resolution, monochromatic vision under very low levels of illumination (called scotopic vision).\n\nThe illumination in most office settings falls between these two levels and is called mesopic vision.\n\nAt mesopic light levels, both the rods and cones are actively contributing pattern information.\n\nWhat contribution the rod information makes to pattern vision under these circumstances is unclear.\nThe response of cones to various wavelengths of light is called their spectral sensitivity.\n\nIn normal human vision, the spectral sensitivity of a cone falls into one of three subtypes, often called blue, green, and red, but more accurately known as short, medium, and long wavelength-sensitive cone subtypes.\n\nIt is a lack of one or more of the cone subtypes that causes individuals to have deficiencies in colour vision or various kinds of colour blindness.\n\nThese individuals are not blind to objects of a particular colour, but are unable to distinguish between colours that can be distinguished by people with normal vision.\n\nHumans have this trichromatic vision, while most other mammals lack cones with red sensitive pigment and therefore have poorer dichromatic colour vision.\n\nHowever, some animals have four spectral subtypes, e.g. the trout adds an ultraviolet subgroup to short, medium, and long subtypes that are similar to humans.\n\nSome fish are sensitive to the polarization of light as well.\nIn the photoreceptors, exposure to light hyperpolarizes the membrane in a series of graded shifts.\n\nThe outer cell segment contains a photopigment.\n\nInside the cell the normal levels of cyclic guanosine monophosphate (cGMP) keep the Na+ channel open, and thus in the resting state the cell is depolarised.\n\nThe photon causes the retinal bound to the receptor protein to isomerise to trans-retinal.\n\nThis causes the receptor to activate multiple G-proteins.\n\nThis in turn causes the Ga-subunit of the protein to activate a phosphodiesterase (PDE6), which degrades cGMP, resulting in the closing of Na+ cyclic nucleotide-gated ion channels (CNGs).\n\nThus the cell is hyperpolarised.\n\nThe amount of neurotransmitter released is reduced in bright light and increases as light levels fall.\n\nThe actual photopigment is bleached away in bright light and only replaced as a chemical process, so in a transition from bright light to darkness the eye can take up to thirty minutes to reach full sensitivity.\nWhen thus excited by light, the photoceptor sends a proportional response synaptically to bipolar cells which in turn signal the retinal ganglion cells.\n\nThe photoreceptors are also cross-linked by horizontal cells and amacrine cells, which modify the synaptic signal before it reaches the ganglion cells, the neural signals being intermixed and combined.\n\nOf the retina's nerve cells, only the retinal ganglion cells and few amacrine cells create action potentials.\nIn the retinal ganglion cells there are two types of response, depending on the receptive field of the cell.\n\nThe receptive fields of retinal ganglion cells comprise a central, approximately circular area, where light has one effect on the firing of the cell, and an annular surround, where light has the opposite effect.\n\nIn ON cells, an increment in light intensity in the centre of the receptive field causes the firing rate to increase.\n\nIn OFF cells, it makes it decrease.\n\nIn a linear model, this response profile is well described by a difference of Gaussians and is the basis for edge detection algorithms.\n\nBeyond this simple difference, ganglion cells are also differentiated by chromatic sensitivity and the type of spatial summation.\n\nCells showing linear spatial summation are termed X cells (also called parvocellular, P, or midget ganglion cells), and those showing non-linear summation are Y cells (also called magnocellular, M, or parasol retinal ganglion cells), although the correspondence between X and Y cells (in the cat retina) and P and M cells (in the primate retina) is not as simple as it once seemed.\nIn the transfer of visual signals to the brain, the visual pathway, the retina is vertically divided in two, a temporal (nearer to the temple) half and a nasal (nearer to the nose) half.\n\nThe axons from the nasal half cross the brain at the optic chiasma to join with axons from the temporal half of the other eye before passing into the lateral geniculate body.\nAlthough there are more than 130 million retinal receptors, there are only approximately 1.2 million fibres (axons) in the optic nerve.\n\nSo, a large amount of pre-processing is performed within the retina.\n\nThe fovea produces the most accurate information.\n\nDespite occupying about 0.01% of the visual field (less than 2° of visual angle), about 10% of axons in the optic nerve are devoted to the fovea.\n\nThe resolution limit of the fovea has been determined to be around 10,000 points.\n\nThe information capacity is estimated at 500,000 bits per second (for more information on bits, see information theory) without colour or around 600,000 bits per second including colour.\n\n=== Spatial encoding ===\n\nWhen the retina sends neural impulses representing an image to the brain, it spatially encodes (compresses) those impulses to fit the limited capacity of the optic nerve.\n\nCompression is necessary because there are 100 times more photoreceptor cells than ganglion cells.\n\nThis is done by \"decorrelation\", which is carried out by the \"centre–surround structures\", which are implemented by the bipolar and ganglion cells.\nThere are two types of centre–surround structures in the retina – on-centres and off-centres.\n\nOn-centres have a positively weighted centre and a negatively weighted surround.\n\nOff-centres are just the opposite.\n\nPositive weighting is more commonly known as excitatory, and negative weighting as inhibitory.\nThese centre–surround structures are not physical apparent, in the sense that one cannot see them by staining samples of tissue and examining the retina's anatomy.\n\nThe centre–surround structures are logical (i.e., mathematically abstract) in the sense that they depend on the connection strengths between bipolar and ganglion cells.\n\nIt is believed that the connection strength between cells is caused by the number and types of ion channels embedded in the synapses between the bipolar and ganglion cells.\nThe centre–surround structures are mathematically equivalent to the edge detection algorithms used by computer programmers to extract or enhance the edges in a digital photograph.\n\nThus, the retina performs operations on the image-representing impulses to enhance the edges of objects within its visual field.\n\nFor example, in a picture of a dog, a cat and a car, it is the edges of these objects that contain the most information.\n\nIn order for higher functions in the brain (or in a computer for that matter) to extract and classify objects such as a dog and a cat, the retina is the first step to separating out the various objects within the scene.\nAs an example, the following matrix is at the heart of a computer algorithm that implements edge detection.\n\nThis matrix is the computer equivalent to the centre–surround structure.\n\nIn this example, each box (element) within this matrix would be connected to one photoreceptor.\n\nThe photoreceptor in the centre is the current receptor being processed.\n\nThe centre photoreceptor is multiplied by the +1 weight factor.\n\nThe surrounding photoreceptors are the \"nearest neighbors\" to the centre and are multiplied by the −1/8 value.\n\nThe sum of all nine of these elements is finally calculated.\n\nThis summation is repeated for every photoreceptor in the image by shifting left to the end of a row and then down to the next line.\n\nThe total sum of this matrix is zero, if all the inputs from the nine photoreceptors are of the same value.\n\nThe zero result indicates the image was uniform (non-changing) within this small patch.\n\nNegative or positive sums mean the image was varying (changing) within this small patch of nine photoreceptors.\nThe above matrix is only an approximation to what really happens inside the retina.\n\nThe differences are:\n\nThe above example is called \"balanced\".\n\nThe term balanced means that the sum of the negative weights is equal to the sum of the positive weights so that they cancel out perfectly.\n\nRetinal ganglion cells are almost never perfectly balanced.\nThe table is square while the centre–surround structures in the retina are circular.\nNeurons operate on spike trains traveling down nerve cell axons.\n\nComputers operate on a single floating point number that is essentially constant from each input pixel. (The computer pixel is basically the equivalent of a biological photoreceptor.)\nThe retina performs all these calculations in parallel while the computer operates on each pixel one at a time.\n\nThe retina performs no repeated summations and shifting as would a computer.\nFinally, the horizontal and amacrine cells play a significant role in this process, but that is not represented here.Here is an example of an input image and how edge detection would modify it.\n\nOnce the image is spatially encoded by the centre–surround structures, the signal is sent out along the optic nerve (via the axons of the ganglion cells) through the optic chiasm to the LGN (lateral geniculate nucleus).\n\nThe exact function of the LGN is unknown at this time.\n\nThe output of the LGN is then sent to the back of the brain.\n\nSpecifically, the output of the LGN \"radiates\" out to the V1 primary visual cortex.\nSimplified signal flow: Photoreceptors → Bipolar → Ganglion → Chiasm → LGN → V1 cortex\n\n== Clinical significance ==\n\nThere are many inherited and acquired diseases or disorders that may affect the retina.\n\nSome of them include:\n\nRetinitis pigmentosa is a group of genetic diseases that affect the retina and cause the loss of night vision and peripheral vision.\nMacular degeneration describes a group of diseases characterized by loss of central vision because of death or impairment of the cells in the macula.\nCone-rod dystrophy (CORD) describes a number of diseases where vision loss is caused by deterioration of the cones and/or rods in the retina.\nIn retinal separation, the retina detaches from the back of the eyeball.\n\nIgnipuncture is an outdated treatment method.\n\nThe term retinal detachment is used to describe a separation of the neurosensory retina from the retinal pigment epithelium.\n\nThere are several modern treatment methods for fixing a retinal detachment: pneumatic retinopexy, scleral buckle, cryotherapy, laser photocoagulation and pars plana vitrectomy.\nBoth hypertension and diabetes mellitus can cause damage to the tiny blood vessels that supply the retina, leading to hypertensive retinopathy and diabetic retinopathy.\nRetinoblastoma is a cancer of the retina.\nRetinal diseases in dogs include retinal dysplasia, progressive retinal atrophy, and sudden acquired retinal degeneration.\nLipemia retinalis is a white appearance of the retina, and can occur by lipid deposition in lipoprotein lipase deficiency.\nRetinal Detachment.\n\nThe neural retina occasionally detaches from the pigment epithelium.\n\nIn some instances, the cause of such detachment is injury to the eyeball that allows fluid or blood to collect between the neural retina and the pigment epithelium.\n\nDetachment is occasionally caused by contracture of fine collagenous fibrils in the vitreous humor, which pull areas of the retina toward the interior of the globe.\nNight Blindness : Night blindness occurs in any person with severe vitamin A deficiency.\n\nThe reason for this is that without vitamin A, the amounts of retinal and rhodopsin that can be formed are severely depressed.\n\nThis condition is called night blindness because the amount of light available at night is too little to permit adequate vision in vitamin A–deficient persons.In addition, the retina has been described as a \"window\" into the brain and body, given that abnormalities detected through an examination of the retina can discover both neurological and systemic diseases.\n\n=== Diagnosis ===\n\nA number of different instruments are available for the diagnosis of diseases and disorders affecting the retina.\n\nOphthalmoscopy and fundus photography have long been used to examine the retina.\n\nRecently, adaptive optics has been used to image individual rods and cones in the living human retina, and a company based in Scotland has engineered technology that allows physicians to observe the complete retina without any discomfort to patients.The electroretinogram is used to non-invasively measure the retina's electrical activity, which is affected by certain diseases.\n\nA relatively new technology, now becoming widely available, is optical coherence tomography (OCT).\n\nThis non-invasive technique allows one to obtain a 3D volumetric or high resolution cross-sectional tomogram of the fine structures of the retina, with histologic quality.\n\nRetinal vessel analysis is a non-invasive method to examine the small arteries and veins in the retina which allows to draw conclusions about the morphology and the function of small vessels elsewhere in the human body.\n\nIt has been established as a predictor of cardiovascular disease and seems to have, according to a study published in 2019, potential in the early detection of Alzheimer's disease.\n\n=== Treatment ===\n\nTreatment depends upon the nature of the disease or disorder.\n\n==== Common treatment modalities ====\nThe following are commonly modalities of management for retinal disease:\n\nIntravitreal medication, such as anti-VEGF or corticosteroid agents\nVitreoretinal surgery\nUse of nutritional supplements\nModification of systemic risk factors for retinal disease\n\n==== Uncommon treatment modalities ====\n\n== History ==\n\nAround 300 BCE, Herophilos identified the retina from dissections of cadaver eyes.\n\nHe called it the arachnoid layer, from its resemblance to a spider web, and retiform, from its resemblance to a casting net.\n\nThe term arachnoid came to refer to a layer around the brain; the term retiform came to refer to the retina.Between 1011 and 1021 CE, Ibn Al-Haytham published numerous experiments demonstrating that sight occurs from light reflecting from objects into the eye.\n\nThis is consistent with intromission theory and against emission theory, the theory that sight occurs from rays emitted by the eyes.\n\nHowever, Ibn Al-Haytham decided that the retina could not be responsible for the beginnings of vision because the image formed on it was inverted.\n\nInstead he decided it must begin at the surface of the lens.In 1604, Johannes Kepler worked out the optics of the eye and decided that the retina must be where sight begins.\n\nHe left it up to other scientists to reconcile the inverted retinal image with our perception of the world as upright.In 1894, Santiago Ramón y Cajal published the first major characterization of retinal neurons in Retina der Wirbelthiere (The Retina of Vertebrates).George Wald, Haldan Keffer Hartline, and Ragnar Granit won the 1967 Nobel Prize in Physiology or Medicine for their scientific research on the retina.A recent University of Pennsylvania study calculated that the approximate bandwidth of human retinas is 8.75 megabits per second, whereas a guinea pig's retinal transfer rate is 875 kilobits per second.MacLaren & Pearson and colleagues at University College London and Moorfields Eye Hospital in London, in 2006, showed that photoreceptor cells could be transplanted successfully in the mouse retina if donor cells were at a critical developmental stage.\n\nRecently Ader and colleagues in Dublin showed, using the electron microscope, that transplanted photoreceptors formed synaptic connections.In 2012, Sebastian Seung and his laboratory at MIT launched EyeWire, an online Citizen science game where players trace neurons in the retina.\n\nThe goals of the EyeWire project are to identify specific cell types within the known broad classes of retinal cells, and to map the connections between neurons in the retina, which will help to determine how vision works.\n\nhttps://en.wikipedia.org/wiki/Retina","sclera":"The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some crucial elastic fiber.\n\nIn humans, and some other vertebrates, the whole sclera is white, contrasting with the coloured iris, but in most mammals, the visible part of the sclera matches the colour of the iris, so the white part does not normally show while other vertebrates have distinct colors for both of them.\n\nIn the development of the embryo, the sclera is derived from the neural crest.\n\nIn children, it is thinner and shows some of the underlying pigment, appearing slightly blue.\n\nIn the elderly, fatty deposits on the sclera can make it appear slightly yellow.\n\nPeople with dark skin can have naturally darkened sclerae, the result of melanin pigmentation.The human eye is relatively rare for having a pale sclera (relative to the iris).\n\nThis makes it easier for one individual to identify where another individual is looking, and the cooperative eye hypothesis suggests this has evolved as a method of nonverbal communication.\n\n== Structure ==\n\nThe sclera forms the posterior five-sixths of the connective tissue coat of the globe.\n\nIt is continuous with the dura mater and the cornea, and maintains the shape of the globe, offering resistance to internal and external forces, and provides an attachment for the extraocular muscle insertions.\n\nThe sclera is perforated by many nerves and vessels passing through the posterior scleral foramen, the hole that is formed by the optic nerve.\n\nAt the optic disc the outer two-thirds of the sclera continues with the dura mater (outer coat of the brain) via the dural sheath of the optic nerve.\n\nThe inner third joins with some choroidal tissue to form a plate (lamina cribrosa) across the optic nerve with perforations through which the optic fibers (fasciculi) pass.\n\nThe thickness of the sclera varies from 1mm at the posterior pole to 0.3 mm just behind the rectus muscle insertions.\n\nThe sclera's blood vessels are mainly on the surface.\n\nAlong with the vessels of the conjunctiva (which is a thin layer covering the sclera), those in the episclera render the inflamed eye bright red.\n\nIn many vertebrates, the sclera is reinforced with plates of cartilage or bone, together forming a circular structure called the sclerotic ring.\n\nIn primitive fish, this ring consists of four plates, but the number is lower in many living ray-finned fishes, and much higher in lobe-finned fishes, various reptiles, and birds.\n\nThe ring has disappeared in many groups, including living amphibians, some reptiles and fish, and all mammals.The eyes of all non-human primates are dark with small, barely visible sclera.\n\n=== Histology ===\n\nThe collagen of the sclera is continuous with the cornea.\n\nFrom outer to innermost, the four layers of the sclera are:\n\nepisclera\nstroma\nlamina fusca\nendotheliumThe sclera is opaque due to the irregularity of the Type I collagen fibers, as opposed to the near-uniform thickness and parallel arrangement of the corneal collagen.\n\nMoreover, the cornea bears more mucopolysaccharide (a carbohydrate that has among its repeating units a nitrogenous sugar, hexosamine) to embed the fibrils.\n\nThe cornea, unlike the sclera, has five layers.\n\nThe middle, thickest layer is also called the stroma.\n\nThe sclera, like the cornea, contains a basal endothelium, above which there is the lamina fusca, containing a high count of pigment cells.\n\nSometimes, very small gray-blue spots can appear on the sclera, a harmless condition called scleral melanocytosis.\n\n== Function ==\n\nHuman eyes are somewhat distinctive in the animal kingdom in that the sclera is very plainly visible whenever the eye is open.\n\nThis is not just due to the white color of the human sclera, which many other species share, but also to the fact that the human iris is relatively small and comprises a significantly smaller portion of the exposed eye surface compared to other animals.\n\nIt is theorized that this adaptation evolved because of our social nature as the eye became a useful communication tool in addition to a sensory organ.\n\nIt is believed that the conspicuous sclera of the human eye makes it easier for one individual to identify where another individual is looking, increasing the efficacy of this particular form of nonverbal communication.\n\nAnimal researchers have also found that, in the course of their domestication, dogs have also developed the ability to pick up visual cues from the eyes of humans.\n\nDogs do not seem to use this form of communication with one another and only look for visual information from the eyes of humans.\n\n== Injury ==\n\n=== Trauma ===\n\nThe bony area that makes up the human eye socket provides exceptional protection to the sclera.\n\nHowever, if the sclera is ruptured by a blunt force or is penetrated by a sharp object, the recovery of full former vision is usually rare.\n\nIf pressure is applied slowly, the eye is actually very elastic.\n\nHowever, most ruptures involve objects moving at some velocity.\n\nThe cushion of orbital fat protects the sclera from head-on blunt forces, but damage from oblique forces striking the eye from the side is not prevented by this cushion.\n\nHemorrhaging and a dramatic drop in intraocular pressure are common, along with a reduction in visual perception to only broad hand movements and the presence or absence of light.\n\nHowever, a low-velocity injury which does not puncture and penetrate the sclera requires only superficial treatment and the removal of the object.\n\nSufficiently small objects which become embedded and which are subsequently left untreated may eventually become surrounded by a benign cyst, causing no other damage or discomfort.\n\n=== Thermal trauma ===\n\nThe sclera is rarely damaged by brief exposure to heat: the eyelids provide exceptional protection, and the fact that the sclera is covered in layers of moist tissue means that these tissues are able to cause much of the offending heat to become dissipated as steam before the sclera itself is damaged.\n\nEven relatively low-temperature molten metals when splashed against an open eye have been shown to cause very little damage to the sclera, even while creating detailed casts of the surrounding eyelashes.\n\nProlonged exposure, however—on the order of 30 seconds—at temperatures above 45 °C (113 °F) will begin to cause scarring, and above 55 °C (131 °F) will cause extreme changes in the sclera and surrounding tissue.\n\nSuch long exposures even in industrial settings are virtually nonexistent.\n\n=== Chemical injury ===\n\nThe sclera is highly resistant to injury from brief exposure to toxic chemicals.\n\nThe reflexive production of tears at the onset of chemical exposure tends to quickly wash away such irritants, preventing further harm.\n\nAcids with a pH below 2.5 are the source of greatest acidic burn risk, with sulfuric acid, the kind present in car batteries and therefore commonly available, being among the most dangerous in this regard.\n\nHowever, acid burns, even severe ones, seldom result in loss of the eye.Alkali burns, on the other hand, such as those resulting from exposure to ammonium hydroxide or ammonium chloride or other chemicals with a pH above 11.5, will cause cellular tissue in the sclera to saponify and should be considered medical emergencies requiring immediate treatment.\n\n== Clinical significance ==\n\nYellowing of the sclera is a visual symptom of jaundice.\n\nIn very rare but severe cases of kidney failure and liver failure, the sclera may turn black.\n\nIn cases of osteogenesis imperfecta, the sclera may appear to have a blue tint.\n\nThe blue tint is caused by the showing of the underlying uveal tract (choroid and retinal pigment epithelium).\n\nhttps://en.wikipedia.org/wiki/Sclera","posterior-segment-of-eyeball":"The posterior segment or posterior cavity is the back two-thirds of the eye that includes the anterior hyaloid membrane and all of the optical structures behind it: the vitreous humor, retina, choroid, and optic nerve.\n\nThe portion of the posterior segment visible during ophthalmoscopy (or fundoscopy) is sometimes referred to as the posterior pole, or fundus.\n\nSome ophthalmologists specialize in the treatment and management of posterior segment disorders and diseases.In some animals, the retina contains a reflective layer (the tapetum lucidum) which increases the amount of light each photosensitive cell perceives, reflecting the light out of the eye, allowing the animal to see better under low light conditions.\n\n== References ==\n\nhttps://en.wikipedia.org/wiki/Posterior_segment_of_eyeball","lens":"The lens is a transparent biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina.\n\nBy changing shape, it functions to change the focal length of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina.\n\nThis adjustment of the lens is known as accommodation (see also below).\n\nAccommodation is similar to the focusing of a photographic camera via movement of its lenses.\n\nThe lens is flatter on its anterior side than on its posterior side.\nThe lens is also known as the aquula (Latin, a little stream, dim. of aqua, water) or crystalline lens.\n\nIn humans, the refractive power of the lens in its natural environment is approximately 18 dioptres, roughly one-third of the eye's total power.\n\n== Structure ==\n\nThe lens is part of the anterior segment of the human eye.\n\nIn front of the lens is the iris, which regulates the amount of light entering into the eye.\n\nThe lens is suspended in place by the suspensory ligament of the lens, a ring of fibrous tissue that attaches to the lens at its equator and connects it to the ciliary body.\n\nPosterior to the lens is the vitreous body, which, along with the aqueous humor on the anterior surface, bathes the lens.\n\nThe lens has an ellipsoid, biconvex shape.\n\nThe anterior surface is less curved than the posterior.\n\nIn the adult, the lens is typically circa 10 mm in diameter and has an axial length of about 4 mm, though it is important to note that the size and shape can change due to accommodation and because the lens continues to grow throughout a person's lifetime.\n\n=== Microanatomy ===\n\nThe lens has three main parts: the lens capsule, the lens epithelium, and the lens fibers.\n\nThe lens capsule forms the outermost layer of the lens and the lens fibers form the bulk of the interior of the lens.\n\nThe cells of the lens epithelium, located between the lens capsule and the outermost layer of lens fibers, are found only on the anterior side of the lens.\n\nThe lens itself lacks nerves, blood vessels, or connective tissue.\n\n==== Lens capsule ====\nThe lens capsule is a smooth, transparent basement membrane that completely surrounds the lens.\n\nThe capsule is elastic and is composed of collagen.\n\nIt is synthesized by the lens epithelium and its main components are type IV collagen and sulfated glycosaminoglycans (GAGs).\n\nThe capsule is very elastic and so allows the lens to assume a more spherical shape when not under the tension of the zonular fibers (also called suspensory ligaments), which connect the lens capsule to the ciliary body.\n\nThe capsule varies from 2 to 28 micrometres in thickness, being thickest near the equator and thinnest near the posterior pole.\n\n==== Lens epithelium ====\nThe lens epithelium, located in the anterior portion of the lens between the lens capsule and the lens fibers, is a simple cuboidal epithelium.\n\nThe cells of the lens epithelium regulate most of the homeostatic functions of the lens.\n\nAs ions, nutrients, and liquid enter the lens from the aqueous humor, Na+/K+-ATPase pumps in the lens epithelial cells pump ions out of the lens to maintain appropriate lens osmotic concentration and volume, with equatorially positioned lens epithelium cells contributing most to this current.\n\nThe activity of the Na+/K+-ATPases keeps water and current flowing through the lens from the poles and exiting through the equatorial regions.\n\nThe cells of the lens epithelium also serve as the progenitors for new lens fibers.\n\nIt constantly lays down fibers in the embryo, fetus, infant, and adult, and continues to lay down fibers for lifelong growth.\n\n==== Lens fibers ====\n\nThe lens fibers form the bulk of the lens.\n\nThey are long, thin, transparent cells, firmly packed, with diameters typically 4–7 micrometres and lengths of up to 12 mm long.\n\nThe lens fibers stretch lengthwise from the posterior to the anterior poles and, when cut horizontally, are arranged in concentric layers rather like the layers of an onion.\n\nIf cut along the equator, it appears as a honeycomb.\n\nThe middle of each fiber lies on the equator.\n\nThese tightly packed layers of lens fibers are referred to as laminae.\n\nThe lens fibers are linked together via gap junctions and interdigitations of the cells that resemble \"ball and socket\" forms.\n\nThe lens is split into regions depending on the age of the lens fibers of a particular layer.\n\nMoving outwards from the central, oldest layer, the lens is split into an embryonic nucleus, the fetal nucleus, the adult nucleus, and the outer cortex.\n\nNew lens fibers, generated from the lens epithelium, are added to the outer cortex.\n\nMature lens fibers have no organelles or nuclei.\n\n=== Development ===\n\nDevelopment of the human lens begins at the 4 mm embryonic stage.\n\nUnlike the rest of the eye, which is derived mostly from the neural ectoderm, the lens is derived from the surface ectoderm.\n\nThe first stage of lens differentiation takes place when the optic vesicle, which is formed from outpocketings in the neural ectoderm, comes in proximity to the surface ectoderm.\n\nThe optic vesicle induces nearby surface ectoderm to form the lens placode.\n\nAt the 4 mm stage, the lens placode is a single monolayer of columnar cells.\n\nAs development progresses, the lens placode begins to deepen and invaginate.\n\nAs the placode continues to deepen, the opening to the surface ectoderm constricts and the lens cells forms a structure known as the lens vesicle.\n\nBy the 10 mm stage, the lens vesicle has completely separated from the surface ectoderm.\n\nAfter the 10 mm stage, signals from the developing neural retina induces the cells closest to the posterior end of the lens vesicle begin to elongate toward the anterior end of the vesicle.\n\nThese signals also induce the synthesis of crystallins.\n\nThese elongating cells eventually fill in the lumen of the vesicle to form the primary fibers, which become the embryonic nucleus in the mature lens.\n\nThe cells of the anterior portion of the lens vesicle give rise to the lens epithelium.\n\nAdditional secondary fibers are derived from lens epithelial cells located toward the equatorial region of the lens.\n\nThese cells lengthen anteriorly and posteriorly to encircle the primary fibers.\n\nThe new fibers grow longer than those of the primary layer, but as the lens gets larger, the ends of the newer fibers cannot reach the posterior or anterior poles of the lens.\n\nThe lens fibers that do not reach the poles form tight, interdigitating seams with neighboring fibers.\n\nThese seams are readily visible and are termed sutures.\n\nThe suture patterns become more complex as more layers of lens fibers are added to the outer portion of the lens.\n\nThe lens continues to grow after birth, with the new secondary fibers being added as outer layers.\n\nNew lens fibers are generated from the equatorial cells of the lens epithelium, in a region referred to as the germinative zone.\n\nThe lens epithelial cells elongate, lose contact with the capsule and epithelium, synthesize crystallin, and then finally lose their nuclei (enucleate) as they become mature lens fibers.\n\nFrom development through early adulthood, the addition of secondary lens fibers results in the lens growing more ellipsoid in shape; after about age 20, however, the lens grows rounder with time and the iris is very important for this development.Several proteins control the embryonic development of the lens: among these, primarily, PAX6, considered the master regulator gene of this organ.\n\nOther effectors of proper lens development include the Wnt signaling components BCL9 and Pygo2.\n\n=== Variation ===\n\nIn many aquatic vertebrates, the lens is considerably thicker, almost spherical, to increase the refraction.\n\nThis difference compensates for the smaller angle of refraction between the eye's cornea and the watery medium, as they have similar refractive indices.\n\nEven among terrestrial animals, however, the lens of primates such as humans is unusually flat.In reptiles and birds, the ciliary body touches the lens with a number of pads on its inner surface, in addition to the zonular fibres.\n\nThese pads compress and release the lens to modify its shape while focusing on objects at different distances; the zonular fibres perform this function in mammals.\n\nIn fish and amphibians, the lens is fixed in shape, and focusing is instead achieved by moving the lens forwards or backwards within the eye.In cartilaginous fish, the zonular fibres are replaced by a membrane, including a small muscle at the underside of the lens.\n\nThis muscle pulls the lens forward from its relaxed position when focusing on nearby objects.\n\nIn teleosts, by contrast, a muscle projects from a vascular structure in the floor of the eye, called the falciform process, and serves to pull the lens backwards from the relaxed position to focus on distant objects.\n\nWhile amphibians move the lens forward, as do cartilaginous fish, the muscles involved are not homologous with those of either type of fish.\n\nIn frogs, there are two muscles, one above and one below the lens, while other amphibians have only the lower muscle.\n\nIn the most primitive vertebrates, the lampreys and hagfish, the lens is not attached to the outer surface of the eyeball at all.\n\nThere is no aqueous humor in these fish, and the vitreous body simply presses the lens against the surface of the cornea.\n\nTo focus its eyes, a lamprey flattens the cornea using muscles outside of the eye and pushes the lens backwards.\n\n== Function ==\n\n=== Accommodation ===\n\nThe lens is flexible and its curvature is controlled by ciliary muscles through the zonules.\n\nBy changing the curvature of the lens, one can focus the eye on objects at different distances from it.\n\nThis process is called accommodation.\n\nAt short focal distance the ciliary muscle contracts, zonule fibers loosen, and the lens thickens, resulting in a rounder shape and thus higher refractive power.\n\nChanging focus to an object at a greater distance requires the relaxation of the lens and thus increasing the focal distance.\n\nThe refractive index of human lens varies from approximately 1.406 in the central layers down to 1.386 in less dense layers of the lens.\n\nThis index gradient enhances the optical power of the lens.\n\nAquatic animals must rely entirely on their lens for both focusing and to provide almost the entire refractive power of the eye as the water-cornea interface does not have a large enough difference in indices of refraction to provide significant refractive power.\n\nAs such, lenses in aquatic eyes tend to be much rounder and harder.\n\n=== Crystallins and transparency ===\n\nCrystallins are water-soluble proteins that compose over 90% of the protein within the lens.\n\nThe three main crystallin types found in the human eye are α-, β-, and γ-crystallins.\n\nCrystallins tend to form soluble, high-molecular weight aggregates that pack tightly in lens fibers, thus increasing the index of refraction of the lens while maintaining its transparency. β and γ crystallins are found primarily in the lens, while subunits of α -crystallin have been isolated from other parts of the eye and the body. α-crystallin proteins belong to a larger superfamily of molecular chaperone proteins, and so it is believed that the crystallin proteins were evolutionarily recruited from chaperone proteins for optical purposes.\n\nThe chaperone functions of α-crystallin may also help maintain the lens proteins, which must last a human for their entire lifetime.\n\nAnother important factor in maintaining the transparency of the lens is the absence of light-scattering organelles such as the nucleus, endoplasmic reticulum, and mitochondria within the mature lens fibers.\n\nLens fibers also have a very extensive cytoskeleton that maintains the precise shape and packing of the lens fibers; disruptions/mutations in certain cytoskeletal elements can lead to the loss of transparency.\n\nThe lens blocks most ultraviolet light in the wavelength range of 300–400 nm; shorter wavelengths are blocked by the cornea.\n\nThe pigment responsible for blocking the light is 3-hydroxykynurenine glucoside, a product of tryptophan catabolism in the lens epithelium.\n\nHigh intensity ultraviolet light can harm the retina, and artificial intraocular lenses are therefore manufactured to also block ultraviolet light.\n\nPeople lacking a lens (a condition known as aphakia) perceive ultraviolet light as whitish blue or whitish-violet.\n\n=== Nourishment ===\n\nThe lens is metabolically active and requires nourishment in order to maintain its growth and transparency.\n\nCompared to other tissues in the eye, however, the lens has considerably lower energy demands.By nine weeks into human development, the lens is surrounded and nourished by a net of vessels, the tunica vasculosa lentis, which is derived from the hyaloid artery.\n\nBeginning in the fourth month of development, the hyaloid artery and its related vasculature begin to atrophy and completely disappear by birth.\n\nIn the postnatal eye, Cloquet's canal marks the former location of the hyaloid artery.\nAfter regression of the hyaloid artery, the lens receives all its nourishment from the aqueous humor.\n\nNutrients diffuse in and waste diffuses out through a constant flow of fluid from the anterior/posterior poles of the lens and out of the equatorial regions, a dynamic that is maintained by the Na+/K+-ATPase pumps located in the equatorially positioned cells of the lens epithelium.Glucose is the primary energy source for the lens.\n\nAs mature lens fibers do not have mitochondria, approximately 80% of the glucose is metabolized via anaerobic metabolism.\n\nThe remaining fraction of glucose is shunted primarily down the pentose phosphate pathway.\n\nThe lack of aerobic respiration means that the lens consumes very little oxygen as well.\n\n== Clinical significance ==\n\nCataracts are opacities of the lens.\n\nWhile some are small and do not require any treatment, others may be large enough to block light and obstruct vision.\n\nCataracts usually develop as the aging lens becomes more and more opaque, but cataracts can also form congenitally or after injury to the lens.\n\nNuclear sclerosis is a type of age-related cataract.\n\nDiabetes is another risk factor for cataract.\n\nCataract surgery involves the removal of the lens and insertion of an artificial intraocular lens.\n\nPresbyopia is the age-related loss of accommodation, which is marked by the inability of the eye to focus on nearby objects.\n\nThe exact mechanism is still unknown, but age-related changes in the hardness, shape, and size of the lens have all been linked to the condition.\n\nEctopia lentis is the displacement of the lens from its normal position.\n\nAphakia is the absence of the lens from the eye.\n\nAphakia can be the result of surgery or injury, or it can be congenital.\n\nhttps://en.wikipedia.org/wiki/Lens_(anatomy)","iris":"In humans and most mammals and birds, the iris (plural: irides or irises) is a thin, annular structure in the eye, responsible for controlling the diameter and size of the pupil, thus the amount of light reaching the retina.\n\nEye color is defined by that of the iris.\n\nIn optical terms, the pupil is the eye's aperture, while the iris is the diaphragm.\n\n== Structure ==\n\nThe iris consists of two layers: the front pigmented fibrovascular layer known as a stroma and, beneath the stroma, pigmented epithelial cells.\n\nThe stroma is connected to a sphincter muscle (sphincter pupillae), which contracts the pupil in a circular motion, and a set of dilator muscles (dilator pupillae), which pull the iris radially to enlarge the pupil, pulling it in folds.\n\nThe circle circumference sphincter constricting muscle is the opposing muscle of the circle-radius dilator muscle.\n\nThe iris inner smaller circle-circumference changes size when constricting or dilating.\n\nThe iris outer larger circle-circumference does not change size.\n\nThe constricting muscle is located on the iris inner smaller circle-circumference.\n\nThe back surface is covered by a heavily pigmented epithelial layer that is two cells thick (the iris pigment epithelium), but the front surface has no epithelium.\n\nThis anterior surface projects as the dilator muscles.\n\nThe high pigment content blocks light from passing through the iris to the retina, restricting it to the pupil.\n\nThe outer edge of the iris, known as the root, is attached to the sclera and the anterior ciliary body.\n\nThe iris and ciliary body together are known as the anterior uvea.\n\nJust in front of the root of the iris is the region referred to as the trabecular meshwork, through which the aqueous humour constantly drains out of the eye, with the result that diseases of the iris often have important effects on intraocular pressure and indirectly on vision.\n\nThe iris along with the anterior ciliary body provide a secondary pathway for aqueous humour to drain from the eye.\n\nThe iris is divided into two major regions:\n\nThe pupillary zone is the inner region whose edge forms the boundary of the pupil.\n\nThe ciliary zone is the rest of the iris that extends to its origin at the ciliary body.The collarette is the thickest region of the iris, separating the pupillary portion from the ciliary portion.\n\nThe collarette is a vestige of the coating of the embryonic pupil.\n\nIt is typically defined as the region where the sphincter muscle and dilator muscle overlap.\n\nRadial ridges extend from the periphery to the pupillary zone, to supply the iris with blood vessels.\n\nThe root of the iris is the thinnest and most peripheral.\n\nThe muscle cells of the iris are smooth muscle in mammals and amphibians, but are striated muscle in reptiles (including birds).\n\nMany fish have neither, and, as a result, their irides are unable to dilate and contract, so that the pupil always remains of a fixed size.\n\n=== Front ===\n\nThe crypts of Fuchs are a series of openings located on either side of the collarette that allow the stroma and deeper iris tissues to be bathed in aqueous humor.\n\nCollagen trabeculae that surround the border of the crypts can be seen in blue irises.\n\nThe midway between the collarette and the origin of the iris:\n\nThese folds result from changes in the surface of the iris as it dilates.\n\nCrypts on the base of the iris are additional openings that can be observed close to the outermost part of the ciliary portion of the iris.\n\n=== Back ===\n\nThe radial contraction folds of Schwalbe are a series of very fine radial folds in the pupillary portion of the iris extending from the pupillary margin to the collarette.\n\nThey are associated with the scalloped appearance of the pupillary ruff.\n\nThe structural folds of Schwalbe are radial folds extending from the border of the ciliary and pupillary zones that are much broader and more widely spaced, continuous with the \"valleys\" between the ciliary processes.\n\nSome of the circular contraction folds are a fine series of ridges that run near the pupillary margin and vary in thickness of the iris pigment epithelium; others are in ciliary portion of iris.\n\n=== Microanatomy ===\n\nFrom anterior (front) to posterior (back), the layers of the iris are:\n\nAnterior limiting layer\nStroma of iris\nIris sphincter muscle\nIris dilator muscle (myoepithelium)\nAnterior pigment epithelium\nPosterior pigment epithelium\n\n=== Development ===\n\nThe stroma and the anterior border layer of the iris are derived from the neural crest, and behind the stroma of the iris, the sphincter pupillae and dilator pupillae muscles, as well as the iris epithelium, develop from optic cup neuroectoderm.\n\n== Eye color ==\n\nThe iris is usually strongly pigmented, with the color typically ranging between brown, hazel, green, gray, and blue.\n\nOccasionally, the color of the iris is due to a lack of pigmentation, as in the pinkish-white of oculocutaneous albinism, or to obscuration of its pigment by blood vessels, as in the red of an abnormally vascularised iris.\n\nDespite the wide range of colors, the only pigment that contributes substantially to normal human iris color is the dark pigment melanin.\n\nThe quantity of melanin pigment in the iris is one factor in determining the phenotypic eye color of a person.\n\nStructurally, this huge molecule is only slightly different from its equivalent found in skin and hair.\n\nIris color is due to variable amounts of eumelanin (brown/black melanins) and pheomelanin (red/yellow melanins) produced by melanocytes.\n\nMore of the former is found in brown-eyed people and of the latter in blue- and green-eyed people.\n\n=== Genetic and physical factors determining iris color ===\n\nIris color is a highly complex phenomenon consisting of the combined effects of texture, pigmentation, fibrous tissue, and blood vessels within the iris stroma, which together make up an individual's epigenetic constitution in this context.\n\nA person's \"eye color\" is actually the color of one's iris, the cornea being transparent and the white sclera entirely outside the area of interest.\n\nMelanin is yellowish-brown to dark brown in the stromal pigment cells, and black in the iris pigment epithelium, which lies in a thin but very opaque layer across the back of the iris.\n\nMost human irises also show a condensation of the brownish stromal melanin in the thin anterior border layer, which by its position has an overt influence on the overall color.\n\nThe degree of dispersion of the melanin, which is in subcellular bundles called melanosomes, has some influence on the observed color, but melanosomes in the iris of humans and other vertebrates are not mobile, and the degree of pigment dispersion cannot be reversed.\n\nAbnormal clumping of melanosomes does occur in disease and may lead to irreversible changes in iris color (see heterochromia, below).\n\nColors other than brown or black are due to selective reflection and absorption from the other stromal components.\n\nSometimes, lipofuscin, a yellow \"wear and tear\" pigment, also enters into the visible eye color, especially in aged or diseased green eyes.\nThe optical mechanisms by which the nonpigmented stromal components influence eye color are complex, and many erroneous statements exist in the literature.\n\nSimple selective absorption and reflection by biological molecules (hemoglobin in the blood vessels, collagen in the vessel and stroma) is the most important element.\n\nRayleigh scattering and Tyndall scattering, (which also happen in the sky) and diffraction also occur.\n\nRaman scattering, and constructive interference, as in the feathers of birds, do not contribute to the color of the human eye, but interference phenomena are important in the brilliantly colored iris pigment cells (iridophores) in many animals.\n\nInterference effects can occur at both molecular and light-microscopic scales, and are often associated (in melanin-bearing cells) with quasicrystalline formations, which enhance the optical effects.\n\nInterference is recognised by characteristic dependence of color on the angle of view, as seen in eyespots of some butterfly wings, although the chemical components remain the same.\n\nWhite babies are usually born blue-eyed since no pigment is in the stroma, and their eyes appear blue due to scattering and selective absorption from the posterior epithelium.\n\nIf melanin is deposited substantially, brown or black color is seen; if not, they will remain blue or gray.All the contributing factors towards eye color and its variation are not fully understood.\n\nAutosomal recessive/dominant traits in iris color are inherent in other species, but coloration can follow a different pattern.\n\n==== Amber eyes ====\nAmber-colored eyes are extremely rare in humans.\n\nThey consist of a solid orange/gold color that may contain lighter shades of the same pigment within the iris.\n\nThis is an unusual occurrence that happens when the yellow pigment pheomelanin is dominant within the iris.\n\nPheomelanin is also found on individuals with green eyes in much smaller amounts.\n\nThis is because green eyes have a strong presence of both melanin and pheomelanin.\n\nOften in poor lighting, one may mistake amber eyes for brown.\n\nThis also happens when viewed from far away or in pictures with poor lighting, as well.\n\nIn natural or well-lit areas, though, telling the difference between the two colors is easy.\n\nAnother common mistake people make is referring to amber eyes as hazel.\n\nAlthough similar, hazel eyes have a stronger presence of melanin with two very distinct colors within the iris (usually green/brown), and often contain many speckles or blotches of mixed hues.\n\n=== Different colors in the two eyes ===\n\nHeterochromia (also known as a heterochromia iridis or heterochromia iridum) is an ocular condition in which one iris is a different color from the other iris (complete heterochromia), or where the part of one iris is a different color from the remainder (partial heterochromia or sectoral heterochromia).\n\nUncommon in humans, it is often an indicator of ocular disease, such as chronic iritis or diffuse iris melanoma, but may also occur as a normal variant.\n\nSectors or patches of strikingly different colors in the same iris are less common.\n\nAnastasius the First was dubbed dikoros (having two irises) for his patent heterochromia since his right iris had a darker color than the left one.In contrast, heterochromia and variegated iris patterns are common in veterinary practice.\n\nSiberian Husky dogs show heterochromia, possibly analogous to the genetically determined Waardenburg syndrome of humans.\n\nSome white cat fancies (e.g., white Turkish Angora or white Turkish van cats) may show striking heterochromia, with the most common pattern being one uniformly blue, the other copper, orange, yellow, or green.\n\nStriking variation within the same iris is also common in some animals, and is the norm in some species.\n\nSeveral herding breeds, particularly those with a blue merle coat color (such as Australian Shepherds and Border Collies) may show well-defined blue areas within a brown iris, as well as separate blue and darker eyes.\n\nSome horses (usually within the white, spotted, palomino, or cremello groups of breeds) may show amber, brown, white and blue all within the same eye, without any sign of eye disease.One eye with a white or bluish-white iris is also known as a \"walleye\".\n\n== Clinical significance ==\n\nAngle closure glaucoma\nAnisocoria\nHorner's syndrome\nIridocyclitis\nIritis\nMiosis/Mydriasis\nSynechia\nThird nerve palsy\nAniridia\n\n== Alternative medicine ==\n\n=== Iridology ===\n\nIridology (also known as iridodiagnosis) is an alternative medicine technique whose proponents believe that patterns, colors, and other characteristics of the iris can be examined to determine information about a patient's systemic health.\n\nPractitioners match their observations to \"iris charts\", which divide the iris into zones corresponding to specific parts of the human body.\n\nIridologists see the eyes as \"windows\" into the body's state of health.Iridology is not supported by quality research studies, and is considered pseudoscience by the majority of medical practitioners and eye-care professionals.\n\n== Etymology ==\n\nThe word \"iris\" is derived from the Greek goddess of the rainbow, because of the many colours of the iris.\n\nhttps://en.wikipedia.org/wiki/Iris_(anatomy)","cornea":"The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber.\n\nAlong with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power.\n\nIn humans, the refractive power of the cornea is approximately 43 dioptres.\n\nThe cornea can be reshaped by surgical procedures such as LASIK.\n\nWhile the cornea contributes most of the eye's focusing power, its focus is fixed.\n\nAccommodation (the refocusing of light to better view near objects) is accomplished by changing the geometry of the lens.\n\nMedical terms related to the cornea often start with the prefix \"kerat-\" from the Greek word κέρας, horn.\n\n== Structure ==\n\nThe cornea has unmyelinated nerve endings sensitive to touch, temperature and chemicals; a touch of the cornea causes an involuntary reflex to close the eyelid.\n\nBecause transparency is of prime importance, the healthy cornea does not have or need blood vessels within it.\n\nInstead, oxygen dissolves in tears and then diffuses throughout the cornea to keep it healthy.\n\nSimilarly, nutrients are transported via diffusion from the tear fluid through the outside surface and the aqueous humour through the inside surface.\n\nNutrients also come via neurotrophins supplied by the nerves of the cornea.\n\nIn humans, the cornea has a diameter of about 11.5 mm and a thickness of 0.5–0.6 mm in the center and 0.6–0.8 mm at the periphery.\n\nTransparency, avascularity, the presence of immature resident immune cells, and immunologic privilege makes the cornea a very special tissue.\nThe most abundant soluble protein in mammalian cornea is albumin.The human cornea borders with the sclera via the corneal limbus.\n\nIn lampreys, the cornea is solely an extension of the sclera, and is separate from the skin above it, but in more advanced vertebrates it is always fused with the skin to form a single structure, albeit one composed of multiple layers.\n\nIn fish, and aquatic vertebrates in general, the cornea plays no role in focusing light, since it has virtually the same refractive index as water.\n\n=== Microanatomy ===\n\nThe human cornea has five layers (possibly six, if the Dua's layer is included).\n\nCorneas of other primates have five known layers.\n\nThe corneas of cats, dogs, wolves, and other carnivores only have four.\n\nFrom the anterior to posterior the layers of the human cornea are:\n\nCorneal epithelium: an exceedingly thin multicellular epithelial tissue layer (non-keratinized stratified squamous epithelium) of fast-growing and easily regenerated cells, kept moist with tears.\n\nIrregularity or edema of the corneal epithelium disrupts the smoothness of the air/tear-film interface, the most significant component of the total refractive power of the eye, thereby reducing visual acuity.\n\nIt is continuous with the conjunctival epithelium, and is composed of about 6 layers of cells which are shed constantly on the exposed layer and are regenerated by multiplication in the basal layer.\n\nBowman's layer (also known as the anterior limiting membrane): when discussed in lieu of a subepithelial basement membrane, Bowman's Layer is a tough layer composed of collagen (mainly type I collagen fibrils), laminin, nidogen, perlecan and other HSPGs that protects the corneal stroma.\n\nWhen discussed as a separate entity from the subepithelial basement membrane, Bowman's Layer can be described as an acellular, condensed region of the apical stroma, composed primarily of randomly organized yet tightly woven collagen fibrils.\n\nThese fibrils interact with and attach onto each other.\n\nThis layer is eight to 14 micrometres (μm) thick and is absent or very thin in non-primates.\n\nCorneal stroma (also substantia propria): a thick, transparent middle layer, consisting of regularly arranged collagen fibers along with sparsely distributed interconnected keratocytes, which are the cells for general repair and maintenance.\n\nThey are parallel and are superimposed like book pages.\n\nThe corneal stroma consists of approximately 200 layers of mainly type I collagen fibrils.\n\nEach layer is 1.5-2.5 μm.\n\nUp to 90% of the corneal thickness is composed of stroma.\n\nThere are 2 theories of how transparency in the cornea comes about:\nThe lattice arrangements of the collagen fibrils in the stroma.\n\nThe light scatter by individual fibrils is cancelled by destructive interference from the scattered light from other individual fibrils.\nThe spacing of the neighboring collagen fibrils in the stroma must be < 200 nm for there to be transparency. (Goldman and Benedek)\nDescemet's membrane (also posterior limiting membrane): a thin acellular layer that serves as the modified basement membrane of the corneal endothelium, from which the cells are derived.\n\nThis layer is composed mainly of collagen type IV fibrils, less rigid than collagen type I fibrils, and is around 5-20 μm thick, depending on the subject's age.\n\nJust anterior to Descemet's membrane, a very thin and strong layer, Dua's layer, 15 microns thick and able to withstand 1.5 to 2 bars of pressure.\n\nCorneal endothelium: a simple squamous or low cuboidal monolayer, approx 5 μm thick, of mitochondria-rich cells.\n\nThese cells are responsible for regulating fluid and solute transport between the aqueous and corneal stromal compartments.\n(The term endothelium is a misnomer here.\n\nThe corneal endothelium is bathed by aqueous humor, not by blood or lymph, and has a very different origin, function, and appearance from vascular endothelia.)\n\nUnlike the corneal epithelium, the cells of the endothelium do not regenerate.\n\nInstead, they stretch to compensate for dead cells which reduces the overall cell density of the endothelium, which affects fluid regulation.\n\nIf the endothelium can no longer maintain a proper fluid balance, stromal swelling due to excess fluids and subsequent loss of transparency will occur and this may cause corneal edema and interference with the transparency of the cornea and thus impairing the image formed.\n\nIris pigment cells deposited on the corneal endothelium can sometimes be washed into a distinct vertical pattern by the aqueous currents - this is known as Krukenberg's Spindle.\n\n=== Nerve supply ===\n\nThe cornea is one of the most sensitive tissues of the body, as it is densely innervated with sensory nerve fibres via the ophthalmic division of the trigeminal nerve by way of 70–80 long ciliary nerves.\n\nResearch suggests the density of pain receptors in the cornea is 300-600 times greater than skin and 20-40 times greater than dental pulp, making any injury to the structure excruciatingly painful.\n\nThe ciliary nerves run under the endothelium and exit the eye through holes in the sclera apart from the optic nerve (which transmits only optic signals).\n\nThe nerves enter the cornea via three levels; scleral, episcleral and conjunctival.\n\nMost of the bundles give rise by subdivision to a network in the stroma, from which fibres supply the different regions.\n\nThe three networks are, midstromal, subepithelial/sub-basal, and epithelial.\n\nThe receptive fields of each nerve ending are very large, and may overlap.\n\nCorneal nerves of the subepithelial layer terminate near the superficial epithelial layer of the cornea in a logarithmic spiral pattern.\n\nThe density of epithelial nerves decreases with age, especially after the seventh decade.\n\n== Function ==\n\n=== Refraction ===\n\nThe optical component is concerned with producing a reduced inverted image on the retina.\n\nThe eye's optical system consists of not only two but four surfaces—two on the cornea, two on the lens.\n\nRays are refracted toward the midline.\n\nDistant rays, due to their parallel nature, converge to a point on the retina.\n\nThe cornea admits light at the greatest angle.\n\nThe aqueous and vitreous humors both have a refractive index of 1.336-1.339, whereas the cornea has a refractive index of 1.376.\n\nBecause the change in refractive index between cornea and aqueous humor is relatively small compared to the change at the air–cornea interface, it has a negligible refractive effect, typically -6 dioptres.\n\nThe cornea is considered to be a positive meniscus lens.\n\nIn some animals, such as species of birds, chameleons and a species of fish, the cornea can also focus.\n\n=== Transparency ===\n\nUpon death or removal of an eye the cornea absorbs the aqueous humor, thickens, and becomes hazy.\n\nTransparency can be restored by putting it in a warm, well-ventilated chamber at 31 °C (88 °F, the normal temperature), allowing the fluid to leave the cornea and become transparent.\n\nThe cornea takes in fluid from the aqueous humor and the small blood vessels of the limbus, but a pump ejects the fluid immediately upon entry.\n\nWhen energy is deficient the pump may fail, or function too slowly to compensate, leading to swelling.\n\nThis arises at death, but a dead eye can be placed in a warm chamber with a reservoir of sugar and glycogen that generally keeps the cornea transparent for at least 24 hours.\n\nThe endothelium controls this pumping action, and as discussed above, damage thereof is more serious, and is a cause of opaqueness and swelling.\n\nWhen damage to the cornea occurs, such as in a viral infection, the collagen used to repair the process is not regularly arranged, leading to an opaque patch (leukoma).\n\n== Clinical significance ==\n\nThe most common corneal disorders are the following:\n\nCorneal abrasion - a medical condition involving the loss of the surface epithelial layer of the eye's cornea as a result of trauma to the surface of the eye.\n\nCorneal dystrophy - a condition in which one or more parts of the cornea lose their normal clarity due to a buildup of cloudy material.\nCorneal ulcer - an inflammatory or infective condition of the cornea involving disruption of its epithelial layer with involvement of the corneal stroma.\n\nCorneal neovascularization - excessive ingrowth of blood vessels from the limbal vascular plexus into the cornea, caused by deprivation of oxygen from the air.\n\nFuchs' dystrophy - cloudy morning vision.\n\nKeratitis - inflammation of the cornea.\n\nKeratoconus - a degenerative disease, the cornea thins and changes shape to be more like a cone.\n\nCorneal Foreign body- one of the most common preventable occupational hazards.\n\n=== Management ===\n\n==== Surgical procedures ====\n\nVarious refractive eye surgery techniques change the shape of the cornea in order to reduce the need for corrective lenses or otherwise improve the refractive state of the eye.\n\nIn many of the techniques used today, reshaping of the cornea is performed by photoablation using the excimer laser.\n\nThere are also synthetic corneas (keratoprostheses) in development.\n\nMost are merely plastic inserts, but there are also those composed of biocompatible synthetic materials that encourage tissue ingrowth into the synthetic cornea, thereby promoting biointegration.\n\nOther methods, such as magnetic deformable membranes and optically coherent transcranial magnetic stimulation of the human retina are still in very early stages of research.\n\n==== Other procedures ====\n\nOrthokeratology is a method using specialized hard or rigid gas-permeable contact lenses to transiently reshape the cornea in order to improve the refractive state of the eye or reduce the need for eyeglasses and contact lenses.\n\nIn 2009, researchers at the University of Pittsburgh Medical center demonstrated that stem cell collected from human corneas can restore transparency without provoking a rejection response in mice with corneal damage.\n\nFor corneal epithelial diseases such as Stevens Johnson Syndrome, persistent corneal ulcer etc., the autologous contralateral (normal) suprabasal limbus derived in vitro expanded corneal limbal stem cells are found to be effective as amniotic membrane based expansion is controversial.\n\nFor endothelial diseases, such as bullous keratopathy, cadaver corneal endothelial precursor cells have been proven to be efficient.\n\nRecently emerging tissue engineering technologies are expected to be capable of making one cadaver-donor's corneal cells be expanded and be usable in more than one patient's eye.\n\n==== Corneal retention and permeability in topical drug delivery to the eye ====\nThe majority of ocular therapeutic agents are administered to the eye via the topical route.\n\nCornea is one of the main barriers for drug diffusion because of its highly impermeable nature.\n\nIts continuous irrigation with a tear fluid also results in poor retention of the therapeutic agents on the ocular surface.\n\nPoor permeability of the cornea and quick wash out of therapeutic agents from ocular surface result in very low bioavailability of the drugs administered via topical route (typically less than 5%).\n\nPoor retention of formulations on ocular surfaces could potentially be improved with the use of mucoadhesive polymers.\n\nDrug permeability through the cornea could be facilitated with addition of penetration enhancers into topical formulations.\n\n=== Transplantation ===\n\nIf the corneal stroma develops visually significant opacity, irregularity, or edema, a cornea of a deceased donor can be transplanted.\n\nBecause there are no blood vessels in the cornea, there are also few problems with rejection of the new cornea.\n\nWhen a cornea is needed for transplant, as from an eye bank, the best procedure is to remove the cornea from the eyeball, preventing the cornea from absorbing the aqueous humor.\n\nThere is a global shortage of corneal donations, severely limiting the availability of corneal transplants across most of the world.\n\nA 2016 study found that 12.7 million visually impaired people were in need of a corneal transplant, with only 1 cornea available for every 70 needed.\n\nMany countries have years-long waitlists for corneal transplant surgery due to the shortage of donated corneas.\n\nOnly a handful of countries consistently have a large enough supply of donated corneas to meet local demand without a waitlist, including the United States, Italy, and Sri Lanka.\n\nhttps://en.wikipedia.org/wiki/Cornea","anterior-segment-of-eyeball":"The anterior segment or anterior cavity is the front third of the eye that includes the structures in front of the vitreous humour:\n the cornea, iris, ciliary body, and lens.\n\nWithin the anterior segment are two fluid-filled spaces:\n\n the anterior chamber between the posterior surface of the cornea (i.e. the corneal endothelium) and the iris.\n\n the posterior chamber between the iris and the front face of the vitreous.\n\nAqueous humour fills these spaces within the anterior segment and provides nutrients to the surrounding structures.\n\nSome ophthalmologists and optometrists specialize in the treatment and management of anterior segment disorders and diseases.\n\nhttps://en.wikipedia.org/wiki/Anterior_segment_of_eyeball","anterior-chamber-of-eyeball":"The anterior chamber (AC) is the aqueous humor-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium.\n\nHyphema, anterior uveitis and glaucoma are three main pathologies in this area.\n\nIn hyphema, blood fills the anterior chamber as a result of a hemorrhage, most commonly after a blunt eye injury.\n\nAnterior uveitis is an inflammatory process affecting the iris and ciliary body, with resulting inflammatory signs in the anterior chamber.\n\nIn glaucoma, blockage of the trabecular meshwork prevents the normal outflow of aqueous humour, resulting in increased intraocular pressure, progressive damage to the optic nerve head, and eventually blindness.\n\nThe depth of the anterior chamber of the eye varies between 1.5 and 4.0 mm, averaging 3.0 mm.\n\nIt tends to become shallower at older age and in eyes with hypermetropia (far sightedness).\n\nAs depth decreases below 2.5 mm, the risk for angle closure glaucoma increases.\n\n== Clinical significance ==\n\n=== Depth measurement ===\n\nDetermining the anterior chamber depth (ACD) is important in estimating the risk of angle closure glaucoma.\n\nThere are various method of measuring ACD, including examination through a slit lamp, ultrasound and Scheimpflug photography.\n\nThese methods require sophisticated examination equipment and expertise.\n\nA simpler clinical method of quantitatively estimating ACD using smartphone photography (EZ ratio) was developed by Dr Ehud Zamir from the Centre for Eye Research Australia, the University of Melbourne, and published in 2016.\n\n== Pathology ==\n\nGlaucoma\nHyphema\nHypopyon\nIntraocular pressure\nOcular hypertension\n\nhttps://en.wikipedia.org/wiki/Anterior_chamber_of_eyeball","nucleus-of-trochlear-nerve":"TROCHLEAR NUCLEUS\n\nThe nucleus of the trochlear nerve () is located in the midbrain, at an intercollicular level between the superior colliculus and inferior colliculus.\n\nIt is a motor nucleus, and so is located near the midline, embedded within the medial longitudinal fasciculus (see diagram at right).\n\nThe oculomotor nerve and trochlear nerve are the only two cranial nerves with nuclei in the midbrain, other than the trigeminal nerve, which has a midbrain nucleus called the mesencephalic nucleus of trigeminal nerve, which functions in preserving dentition.\n\nOddly, fibers from the trochlear nucleus cross over in the trochlear decussation of the midbrain, located in the superior medullary velum to exit dorsally, the only cranial nerve to do so.\n\nThe trochlear nerve then goes around the midbrain, and is visible coming out of the sides.\n\nhttps://en.wikipedia.org/wiki/Trochlear_nucleus","posterior-cochlear-nucleus":"The cochlear nuclear (CN) complex comprises two cranial nerve nuclei in the human brainstem, the ventral cochlear nucleus (VCN) and the dorsal cochlear nucleus (DCN).\n\nThe ventral (anterior) cochlear nucleus is unlayered whereas the dorsal cochlear nucleus is layered.\n\nAuditory nerve fibers, fibers that travel through the auditory nerve (also known as the cochlear nerve or eighth cranial nerve) carry information from the inner ear, the cochlea, on the same side of the head, to the nerve root in the ventral cochlear nucleus.\n\nAt the nerve root the fibers branch to innervate the ventral cochlear nucleus and the deep layer of the dorsal cochlear nucleus.\n\nAll acoustic information thus enters the brain through the cochlear nuclei, where the processing of acoustic information begins.\n\nThe outputs from the cochlear nuclei are received in higher regions of the auditory brainstem.\n\n== Structure ==\n\nThe cochlear nuclei (CN) are located at the dorso-lateral side of the brainstem, spanning the junction of the pons and medulla.\n\nThe ventral cochlear nucleus (VCN) on the ventral aspect of the brain stem, ventrolateral to the inferior peduncle.\n\nThe dorsal cochlear nucleus (DCN), also known as the tuberculum acusticum or acoustic tubercle, curves over the VCN and wraps around the cerebellar peduncle.\n\nThe VCN is further divided by the nerve root into the posteroventral cochlear nucleus (PVCN) and the anteroventral cochlear nucleus (AVCN).\n\n=== Projections to the cochlear nuclei ===\n\nThe major input to the cochlear nucleus is from the auditory nerve, a part of cranial nerve VIII (the vestibulocochlear nerve).\n\nThe auditory nerve fibers form a highly organized system of connections according to their peripheral innervation of the cochlea.\n\nAxons from the spiral ganglion cells of the lower frequencies innervate the ventrolateral portions of the ventral cochlear nucleus and lateral-ventral portions of the dorsal cochlear nucleus.\n\nThe axons from the higher frequency organ of corti hair cells project to the dorsal portion of the ventral cochlear nucleus and the dorsal-medial portions of the dorsal cochlear nucleus.\n\nThe mid frequency projections end up in between the two extremes; in this way the tonotopic organization that is established in the cochlea is preserved in the cochlear nuclei.\n\nThis tonotopic organization is preserved because only a few inner hair cells synapse on the dendrites of a nerve cell in the spiral ganglion, and the axon from that nerve cell synapses on only a very few dendrites in the cochlear nucleus.\n\nIn contrast with the VCN that receives all acoustic input from the auditory nerve, the DCN receives input not only from the auditory nerve but it also receives acoustic input from neurons in the VCN (T stellate cells).\n\nThe DCN is therefore in a sense a second order sensory nucleus.\nThe cochlear nuclei have long been thought to receive input only from the ipsilateral ear.\n\nThere is evidence, however, for stimulation from the contralateral ear via the contralateral CN, and also the somatosensory parts of the brain.\n\n=== Projections from the cochlear nuclei ===\n\nThere are three major fiber bundles, axons of cochlear nuclear neurons, that carry information from the cochlear nuclei to targets that are mainly on the opposite side of the brain.\n\nThrough the medulla, one projection goes to the contralateral superior olivary complex (SOC) via the trapezoid body, whilst the other half shoots to the ipsilateral SOC.\n\nThis pathway is called the ventral acoustic stria (VAS or, more commonly, the trapezoid body).\n\nAnother pathway, called the dorsal acoustic stria (DAS, also known as the stria of von Monakow), rises above the medulla into the pons where it hits the nuclei of the lateral lemniscus along with its kin, the intermediate acoustic stria (IAS, also known as the stria of Held).\n\nThe IAS decussates across the medulla, before joining the ascending fibers in the contralateral lateral lemniscus.\n\nThe lateral lemniscus contains cells of the nuclei of the lateral lemniscus, and in turn projects to the inferior colliculus.\n\nThe inferior colliculus receives direct, monosynaptic projections from the superior olivary complex, the contralateral dorsal acoustic stria, some classes of stellate neurons of the VCN, as well as from the different nuclei of the lateral lemniscus.\n\nMost of these inputs terminate in the inferior colliculus, although there are a few small projections that bypass the inferior colliculus and project to the medial geniculate, or other forebrain structures.\n\nMedial superior olive (MSO) via trapezoid body (TB) – Ipsilateral and contralateral stimulation for low frequency sounds.\n\nLateral superior olive (LSO) directly and via TB – Ipsilateral stimulation for high frequency sounds.\n\nMedial nucleus of trapezoid body (MNTB) – Contralateral stimulation.\nInferior colliculus – Contralateral stimulation.\n\nPeriolivary nuclei (PON) – Ipsilateral and contralateral stimulation.\nLateral lemniscus (LL) and lemniscal nuclei (LN) – Ipsilateral and contralateral stimulation.\n\n=== Histology ===\n\nThree types of principal cells convey information out of the ventral cochlear nucleus: Bushy cells, stellate cells, and octopus cells.\n\nBushy cells are found mainly in the anterior ventral cochlear nucleus (AVCN).\n\nThese can be further divided into large spherical, small spherical and globular bushy cells, depending on their appearance, and also their location.\n\nWithin the AVCN there is an area of large spherical cells; caudal to this are smaller spherical cells, and globular cells occupy the region around the nerve root.\n\nAn important difference between these subtypes is that they project to differing targets in the superior olivary complex.\n\nLarge spherical bushy cells project to the ipsilateral and contralateral medial superior olive.\n\nGlobular bushy cells project to the contralateral medial nucleus of the trapezoid body, and small spherical bushy cells likely project to the lateral superior olive.\n\nThey have a few (1-4) very short dendrites with numerous small branching, which cause it to resemble a “bush”.\n\nThe bushy cells have specialized electrical properties that allow them to transmit timing information from the auditory nerve to more central areas of the auditory system.\n\nBecause bushy cells receive input from multiple auditory nerve fibers that are tuned to similar frequencies, bushy cells can improve the precision of the timing information by in essence averaging out jitter in timing of the inputs.\n\nBushy cells can also be inhibited by sounds adjacent to the frequency to which they are tuned, leading to even sharper tuning than seen in auditory nerve fibers.\n\nThese cells are usually innervated only by a few auditory nerve fibres, which dominate its firing pattern.\n\nThese afferent nerve fibres wrap their terminal branches around the entire soma, creating a large synapse onto the bushy cells, called an \"endbulb of Held\".\n\nTherefore, a single unit recording of an electrically stimulated bushy neuron characteristically produces exactly one action potential and constitutes the primary response.\n\nStellate cells (aka multipolar cells), have longer dendrites that lie parallel to fascicles of auditory nerve fibers.\n\nThey are also called chopper cells, in reference to their ability to fire a regularly spaced train of action potentials for the duration of a tonal or noise stimulus.\n\nThe chopping pattern is intrinsic to the electrical excitability of the stellate cell, and the firing rate depends on the strength of the auditory input more than on the frequency.\n\nEach stellate cell is narrowly tuned and has inhibitory sidebands, enabling the population of stellate cells to encode the spectrum of sounds, enhancing spectral peaks and valleys.\n\nThese neurons provide acoustic input to the DCN.\nOctopus cells are found in a small region of the posterior ventral cochlear nucleus (PVCN).\n\nThe distinguishing features of these cells are their long, thick and tentacle-shaped dendrites that typically emanate from one side of the cell body.\n\nOctopus cells produce an \"Onset Response\" to simple tonal stimuli.\n\nThat is, they respond only at the onset of a broad-band stimulus.\n\nThe octopus cells can fire with some of the highest temporal precision of any neuron in the brain.\n\nElectrical stimuli to the auditory nerve evoke a graded excitatory postsynaptic potential in the octopus cells.\n\nThese EPSPs are very brief.\n\nThe octopus cells are thought to be important for extracting timing information.\n\nIt has been reported that these cells can respond to click trains at a rate of 800 Hz.Two types of principal cells convey information out of the dorsal cochlear nucleus (DCN) to the contralateral inferior colliculus.\n\nThe principal cells receive two systems of inputs.\n\nAcoustic input comes to the deep layer through several paths.\n\nExcitatory acoustic input comes from auditory nerve fibers and also from stellate cells of the VCN.\n\nAcoustic input is also conveyed through inhibitory interneurons (tuberculoventral cells of the DCN and \"wide band inhibitors\" in the VCN).\n\nThrough the outermost molecular layer, the DCN receives other types of sensory information, most importantly information about the location of the head and ears, through parallel fibers.\n\nThis information is distributed through a cerebellar like circuit that also includes inhibitory interneurons.\n\nFusiform cells (also known as pyramidal cells).\n\nFusiform cells integrate information through two tufts of dendrites, the apical dendrites receiving multisensory, excitatory and inhibitory input through the outermost molecular layer and the basal dendrites receiving excitatory and inhibitory acoustic input from the basal dendrites that extend into the deep layer.\n\nThese neurons are thought to enable mammals to analyze the spectral cues that enable us to localize sounds in elevation and when we lose hearing in one ear.\n\nGiant cells also integrate inputs from the molecular and deep layers but input from the deep layer is predominant.\n\nIt is unclear what their role is in hearing.\n\n== Function ==\n\nThe cochlear nuclear complex is the first integrative, or processing, stage in the auditory system.\n\nInformation is brought to the nuclei from the ipsilateral cochlea via the cochlear nerve.\n\nSeveral tasks are performed in the cochlear nuclei.\n\nBy distributing acoustic input to multiple types of principal cells, the auditory pathway is subdivided into parallel ascending pathways, which can simultaneously extract different types of information.\n\nThe cells of the ventral cochlear nucleus extract information that is carried by the auditory nerve in the timing of firing and in the pattern of activation of the population of auditory nerve fibers.\n\nThe cells of the dorsal cochlear nucleus perform a non-linear spectral analysis and place that spectral analysis into the context of the location of the head, ears and shoulders and that separate expected, self-generated spectral cues from more interesting, unexpected spectral cues using input from the auditory cortex, pontine nuclei, trigeminal ganglion and nucleus, dorsal column nuclei and the second dorsal root ganglion.\n\nIt is likely that these neurons help mammals to use spectral cues for orienting toward those sounds.\n\nThe information is used by higher brainstem regions to achieve further computational objectives (such as sound source location or improvement in signal to noise ratio).\n\nThe inputs from these other areas of the brain probably play a role in sound localization.\n\nIn order to understand in more detail the specific functions of the cochlear nuclei it is first necessary to understand the way sound information is represented by the fibers of the auditory nerve.\n\nBriefly, there are around 30,000 auditory nerve fibres in each of the two auditory nerves.\n\nEach fiber is an axon of a spiral ganglion cell that represents a particular frequency of sound, and a particular range of loudness.\n\nInformation in each nerve fibre is represented by the rate of action potentials as well as the particular timing of individual action potentials.\n\nThe particular physiology and morphology of each cochlear nucleus cell type enhances different aspects of sound information.\n\nhttps://en.wikipedia.org/wiki/Cochlear_nucleus","inferior-salivatory-nucleus":"The salivatory nuclei are the superior salivatory nucleus, and the inferior salivatory nucleus that innervate the salivary glands.\n\nThey are located in the pontine tegmentum in the brainstem.\n\nThey both are examples of cranial nerve nuclei.\n\nThe superior salivatory nucleus innervates the submandibular gland and the sublingual gland and is part of the facial nerve.\n\nThe inferior salivatory nucleus innervates the parotid gland by way of the otic ganglion and forms the parasympathetic component of the glossopharyngeal nerve.\n\n== Superior salivatory nucleus ==\n\nThe superior salivatory nucleus (or nucleus salivatorius superior) of the facial nerve is a visceromotor cranial nerve nucleus located in the pontine tegmentum.\n\nIt is one of the salivatory nuclei.\n\nParasympathetic efferent fibers of the facial nerve (preganglionic fibers) arise according to some authors from the small cells of the facial nucleus, or according to others from a special nucleus of cells scattered in the reticular formation, dorso-medial to the facial nucleus – the superior salivatory nucleus.\n\nSome of the preganglionic fibers travel along the greater petrosal nerve through the pterygoid canal, where they join the postsynaptic fibers of the deep petrosal nerve to become the nerve of the pterygoid canal.\n\nThese fibers synapse in the pterygopalatine ganglion, whereupon the postganglionic, postsynaptic, efferent fibers travel to innervate the lacrimal gland and the mucosal glands of the nose, palate, and pharynx.\n\nPreganglionic parasympathetic fibers are also distributed partly via the chorda tympani and lingual nerves to the submandibular ganglion, thence by postganglionic (vasodilator) fibers to the submandibular and sublingual salivary glands.\n\nThe term \"lacrimal nucleus\" is sometimes used to refer to a portion of the superior salivatory nucleus.\n\n== Inferior salivatory nucleus ==\n\nThe inferior salivatory nucleus (or nucleus salivatorius inferior) is a cluster of neurons in the pontine tegmentum (dorsal part of the pons), just above its junction with the medulla.\n\nIt is the general visceral efferent (GVE) component of the glossopharyngeal nerve supplying the parasympathetic input to the parotid gland for salivation.\n\nIt lies immediately caudal to the superior salivatory nucleus and just above the upper end of the dorsal nucleus of the vagus nerve in the medulla.\n\nThe preganglionic parasympathetic fibres originate in the inferior salivatory nucleus of the glossopharyngeal nerve.\n\nThey leave the glossopharngeal nerve by its tympanic branch and then pass via the tympanic plexus and the lesser petrosal nerve to the otic ganglion.\n\nHere, the fibres synapse, and the postganglionic fibers pass by communicating branches to the auriculotemporal nerve, which conveys them to the parotid gland.\n\nThey produce vasodilator and secretomotor effects.\n\n=== Function ===\n\nParasympathetic input from fibers of the inferior salivatory nucleus stimulates the parotid gland to produce vasodilation and secrete saliva.\n\nhttps://en.wikipedia.org/wiki/Salivatory_nuclei","posterior-nucleus-of-vagus-nerve":"The dorsal nucleus of vagus nerve (or posterior nucleus of vagus nerve or dorsal vagal nucleus or nucleus dorsalis nervi vagi or nucleus posterior nervi vagi) is a cranial nerve nucleus for the vagus nerve in the medulla that lies ventral to the floor of the fourth ventricle.\n\nIt mostly serves parasympathetic vagal functions in the gastrointestinal tract, lungs, and other thoracic and abdominal vagal innervations.\n\nThese functions include, among others, bronchoconstriction and gland secretion.\n\nThe cell bodies for the preganglionic parasympathetic vagal neurons that innervate the heart reside in the nucleus ambiguus.\n\nAdditional cell bodies are found in the nucleus ambiguus, which give rise to the branchial efferent motor fibers of the vagus nerve (CN X) terminating in the laryngeal, pharyngeal muscles, and musculus uvulae.\n\nSee also\n\n -Vagovagal reflex, gastrointestinal tract reflex circuits where afferent and efferent fibers of the vagus nerve.\n -Nucleus ambiguus\n\nhttps://en.wikipedia.org/wiki/Dorsal_nucleus_of_vagus_nerve","nucleus-of-hypoglossal-nerve":"The hypoglossal nucleus is a cranial nerve nucleus, found within the medulla.\n\nBeing a motor nucleus, it is close to the midline.\n\nIn the open medulla, it is visible as what is known as the hypoglossal trigone, a raised area (medial to the vagal trigone) protruding slightly into the fourth ventricle.\n\nThe hypoglossal nucleus is located between the dorsal motor nucleus of the vagus and the midline of the medulla.\n\nAxons from the hypoglossal nucleus pass anteriorly through the medulla forming the hypoglossal nerve which exits between the pyramid and olive in a groove called the anterolateral sulcus.\n\nhttps://en.wikipedia.org/wiki/Hypoglossal_nucleus","nucleus-of-solitary-tract":"In the human brainstem, the solitary nucleus, also called nucleus of the solitary tract, nucleus solitarius, and nucleus tractus solitarii, (SN or NTS) is a series of purely sensory nuclei (clusters of nerve cell bodies) forming a vertical column of grey matter embedded in the medulla oblongata.\n\nThrough the center of the SN runs the solitary tract, a white bundle of nerve fibers, including fibers from the facial, glossopharyngeal and vagus nerves, that innervate the SN.\n\nThe SN projects to, among other regions, the reticular formation, parasympathetic preganglionic neurons, hypothalamus and thalamus, forming circuits that contribute to autonomic regulation.\n\nCells along the length of the SN are arranged roughly in accordance with function; for instance, cells involved in taste are located in the rostral part, while those receiving information from cardio-respiratory and gastrointestinal processes are found in the caudal part.\n\nInputs\n\n Taste information from the facial nerve via the chorda tympani (anterior 2/3 of the tongue), glossopharyngeal nerve (posterior 1/3) and vagus nerve (small area on the epiglottis)\n\n Chemoreceptors and mechanoreceptors of the general visceral afferent pathway (GVA) in the carotid body via glossopharyngeal nerve, aortic bodies, and the sinoatrial node, via the vagus nerve\n\n Chemically and mechanically sensitive neurons of the general visceral afferent pathway (GVA) with endings located in the heart, lungs, airways, gastrointestinal system, pharynx, and liver via the glossopharyngeal and vagus nerves.\n\n Additional minor GVA input from the nasal cavity, soft palate and sinus cavities enters via the facial nerve.\n\nNeurons that innervate the SN mediate the gag reflex, the carotid sinus reflex, the aortic reflex, the cough reflex, the baroreceptor and chemoreceptor reflexes, several respiratory reflexes and reflexes within the gastrointestinal system regulating motility and secretion.\n\nNeurons which transmit signals about the gut wall, the stretch of the lungs, and the dryness of mucous membranes also innervate the SN.\n\nThe first central neurons within the SN can participate in simple autonomic reflexes.\n\n==Outputs==\n\nInformation goes from the solitary nucleus to a large number of other regions of the brain including the paraventricular nucleus of the hypothalamus and the central nucleus of the amygdala, as well as to other nuclei in the brainstem (such as the parabrachial area, the locus coeruleus, the dorsal raphe nucleus, and other visceral motor or respiratory networks).\n\nThe signals projected from the SN to the parabrachial area originate in the oral cavity and gastrointestinal tract.\n\nThe pathways for gastric and gustatory (taste) processes are believed to terminate in different subdivisions of the parabrachial area, but still interact in the SN.\n\nSome neuronal subpopulations in the SN, such as the noradrenergic cell group A2 and the aldosterone-sensitive HSD2 neurons project as far ventral as the bed nucleus of the stria terminalis.\n\nhttps://en.wikipedia.org/wiki/Solitary_nucleus","nucleus-ambiguus":"The nucleus ambiguus (\"ambiguous nucleus\" in English) is a group of large motor neurons, situated deep in the medullary reticular formation named by Jacob Clarke.\n\nThe nucleus ambiguus contains the cell bodies of neurons that innervate the muscles of the soft palate, pharynx, and larynx which are associated with speech and swallowing.\n\nAs well as motor neurons, the nucleus ambiguus contains preganglionic parasympathetic neurons which innervate postganglionic parasympathetic neurons in the heart.\n\nIt is a region of histologically disparate cells located just dorsal (posterior) to the inferior olivary nucleus in the lateral portion of the upper (rostral) medulla.\n\nIt receives upper motor neuron innervation directly via the corticobulbar tract.\n\nThis nucleus gives rise to the branchial efferent motor fibers of the vagus nerve (CN X) terminating in the laryngeal, pharyngeal muscles, and musculus uvulae; as well as to the efferent motor fibers of the glossopharyngeal nerve (CN IX) terminating in the stylopharyngeus muscle.\n\n== Function ==\n\nThe nucleus ambiguus controls the motor innervation of ipsilateral muscles of the soft palate, pharynx, larynx and upper esophagus.\n\nLesions of nucleus ambiguus results in nasal speech, dysphagia, dysphonia, and deviation of the uvula toward the contralateral side.\n\nPreganglionic parasympathetics to the heart also flow through the external formation of the nucleus.\n\n== Areas supplied ==\n\nThe muscles supplied by the vagus (included with this is the cranial root of the accessory nerve), such as levator veli palatini, are also necessary to swallow properly through integration by the nucleus of the solitary tract.\n\nThe vagus also supplies the upper part of the esophagus, and other parts of the pharynx and larynx.\n\nAs well as motor neurons, the nucleus ambiguus in its \"external formation\" contains cholinergic preganglionic parasympathetic neurons for the heart.\n\nThese neurons are cardioinhibitory.\n\nThis cardioinhibitory effect is one of the means by which quick changes in blood pressure are achieved by the central nervous system (the primary means being changes in sympathetic nervous system activity, which constricts arterioles and makes the heart pump faster and harder).\n\nThat is, through integrated and antagonistic system with sympathetic outflow from the vasomotor center of the brainstem, the parasympathetic outflow arising from the nucleus ambiguus and dorsal motor nucleus of the vagus nerve acts to decrease cardiac activity in response to fast increases in blood pressure.\n\nThe external formation of the nucleus ambiguus also sends bronchoconstrictor fibers to the bronchopulmonary system, which can produce reflexive decreases in pulmonary bronchial airflow.\n\nThe pathophysiologic relevance of this system, which may act in concert with the cardioinhibitory system, is poorly understood, but likely plays a role in bronchospastic diseases like COPD/emphysema (in which inhaled anticholinergic medications such as Spiriva/tiotropium or ipratropium are standard-of-care treatment) and asthma, particularly for exercise-related asthma exacerbations, which may have a component of autonomic dysregulation.\n\nhttps://en.wikipedia.org/wiki/Nucleus_ambiguus","white-matter-of-spinal-cord":"In cross-section, the peripheral region of the cord contains neuronal white matter tracts containing sensory and motor axons.\n\nInternal to this peripheral region is the grey matter, which contains the nerve cell bodies arranged in the three grey columns that give the region its butterfly-shape.\n\nThis central region surrounds the central canal, which is an extension of the fourth ventricle and contains cerebrospinal fluid.\n\nThe spinal cord is elliptical in cross section, being compressed dorsolaterally.\n\nTwo prominent grooves, or sulci, run along its length.\n\nThe posterior median sulcus is the groove in the dorsal side, and the anterior median fissure is the groove in the ventral side.\n\nhttps://en.wikipedia.org/wiki/Spinal_cord","gracile-fasciculus":"The gracile fasciculus carries sensory information from the lower half of the body entering the spinal cord at the lumbar level.\n\nThe cuneate fasciculus carries sensory information from the upper half of the body (upper limbs, trunk, and neck) entering the spinal cord at the cervical level.\n\nThe gracile fasciculus is wedge-shaped on transverse section and lies next to the posterior median septum.\n\nIts base is at the surface of the spinal cord, and its apex directed toward the posterior gray commissure.\n\nThe gracile fasciculus increases in size from inferior to superior.\n\nhttps://en.wikipedia.org/wiki/Dorsal_column%E2%80%93medial_lemniscus_pathway#Structure","cuneate-fasciculus":"The cuneate fasciculus is triangular on transverse section, and lies between the gracile fasciculus and the posterior column, its base corresponding with the surface of the spinal cord.\n\nIts fibers, larger than those of the gracile fasciculus, are mostly derived from the same source, viz., the posterior nerve roots.\n\nSome ascend for only a short distance in the tract, and, entering the gray matter, come into close relationship with the cells of the dorsal nucleus, while others can be traced as far as the medulla oblongata, where they end in the gracile nucleus and cuneate nucleus.\n\nhttps://en.wikipedia.org/wiki/Dorsal_column%E2%80%93medial_lemniscus_pathway#Structure","central-canal":"The central canal (also known as ependymal canal) is the cerebrospinal fluid-filled space that runs through the spinal cord.\n\nThe central canal lies below and is connected to the ventricular system of the brain, from which it receives cerebrospinal fluid, and shares the same ependymal lining.\n\nThe central canal helps to transport nutrients to the spinal cord as well as protect it by cushioning the impact of a force when the spine is affected.\n\nThe central canal represents the adult remainder of the central cavity of the neural tube.\n\nIt generally occludes (closes off) with age.\n\n== Structure ==\n\nThe central canal below at the ventricular system of the brain, beginning at a region called the obex where the fourth ventricle, a cavity present in the brainstem, narrows.\n\nThe central canal is located in the anterior third of the spinal cord in the cervical and thoracic regions.\n\nIn the lumbar spine it enlarges and is located more centrally.\n\nAt the conus medullaris, where the spinal cord tapers, it is located more posteriorly.\n\n=== Terminal ventricle ===\n\nThe terminal ventricle (ventriculus terminalis, fifth ventricle or ampulla caudalis) is the widest part of the central canal of the spinal cord that is located at or near the conus medullaris.\n\nIt was described by Stilling in 1859 and Krause in 1875.\n\nKrause introduced the term fifth ventricle after observation of normal ependymal cells.\n\nThe central canal expands as a fusiform terminal ventricle, and approximately 8–10 mm in length in the conus medullaris (or conus terminalis).\n\nAlthough the terminal ventricle is visible in the fetus and children, it is usually absent in adults.\n\nSometimes, the terminal ventricle is observed by MRI or ultrasound in children less than 5 years old.\n\n=== Microanatomy ===\n\nThe central canal shares the same ependymal lining as the ventricular system of the brain.\n\nThe canal is lined by ciliated, column-shaped cells, outside of which is a band of gelatinous substance, called the substantia gelatinosa centralis (or central gelatinous substance of spinal cord).\n\nThis gelatinous substance consists mainly of neuroglia, but contains a few nerve cells and fibers; it is traversed by processes from the deep ends of the columnar ciliated cells which line the central canal.\n\nThe substantia gelatinosa of Rolando, is located more dorsally.\n\n=== Development ===\n\nThe central canal represents the adult remainder of the central cavity of the neural tube.\n\nIt generally occludes (closes off) with age.\n\n== Function ==\n\nThe central canal carries cerebrospinal fluid (CSF), which it receives from the ventricular system of the brain.\n\nThe central canal helps to transport nutrients to the spinal cord as well as protect it by cushioning the impact of a force when the spine is affected.\n\n== Clinical significance ==\n\nSyringomyelia is a disease caused by the blockage of the central canal.\n\nBlockage of the central canal usually occurs at the lower cervical and upper thoracic levels.\n\nThis typically damages white matter fibers that cross in anterior white commissure, leading to the loss of temperature, pain, and motor function at the affected levels on side opposite to the damage.\n\nOther relevant conditions include:\n\n-Spina bifida\n-Arnold-Chiari syndrome\n-Spinal tumor\n-Myelomeningocele\n-Syringomyelia\n-Hydromyelia.\n\nIn hydromyelia, a dilation of the central canal of the spinal cord is caused by an increase of cerebrospinal fluid.\n\nSyringohydromyelia (i.e., both Syringomyelia and Hydromyelia)\nTethered cordIn some cases, the terminal ventricle may cause clinical symptoms due to its expansion.\n\nhttps://en.wikipedia.org/wiki/Central_canal","medial-vestibulospinal-tract":"The medial vestibulospinal tract is one of the descending spinal tracts of the ventromedial funiculus of the spinal cord.\n\nIt is found only in the cervical spine and above.\n\nThe medial part of the vestibulospinal tract is the smaller part, and is primarily made of fibers from the medial vestibular nucleus.\n\nIt projects bilaterally down the spinal cord and triggers the ventral horn of the cervical spinal circuits, particularly controlling lower motor neurons associated with the spinal accessory nerve (CN XI).\n\nAdditionally, the pathway projects superiorly to the paramedian pontine reticular formation, indirectly innervating the nuclei of CN VI and III.\n\nThrough this superior projection, the medial vestibulospinal tract is involved in \"yoking\" the eyes together in response to rapid movement of the head.\n\nThus, cumulatively it controls head and whole body orientation.\n\nhttps://en.wikipedia.org/wiki/Medial_vestibulospinal_tract","nucleus-proprius":"The nucleus proprius is a layer of the spinal cord adjacent to the substantia gelatinosa.\n\nThe nucleus proprius can be found in the gray matter in all levels of the spinal cord.\n\nIt constitutes the first synapse of the spinothalamic tract carrying pain and temperature sensations from peripheral nerves.\n\nCells in this nucleus project to deeper laminae of the spinal cord, to the posterior column nuclei, and to other supraspinal relay centers including the midbrain, thalamus, and hypothalamus.\n\nRexed laminae III and IV make up the nucleus proprius.\n\nThe nucleus proprius (NP), along with the substantia gelatinosa of Rolando are involved in sensing pain and temperature.\n\nhttps://en.wikipedia.org/wiki/Nucleus_proprius_of_spinal_cord","intermediolateral-nucleus":"The intermediolateral nucleus (IML) is a region of grey matter found in one of the three grey columns of the spinal cord, the lateral grey column.\n\nThis is Rexed lamina VII.\nThe intermediolateral cell column exists at vertebral levels T1 – L3.\n\nIt mediates the entire sympathetic innervation of the body, but the nucleus resides in the grey matter of the spinal cord.Rexed Lamina VII contains several well defined nuclei including the nucleus dorsalis (Clarke's column), the intermediolateral nucleus, and the sacral autonomic nucleus.\nIt extends from T1 to L3, and contains the autonomic motor neurons that give rise to the preganglionic fibers of the sympathetic nervous system, (preganglionic sympathetic general visceral efferents).\n\n== References ==\n\nhttps://en.wikipedia.org/wiki/Intermediolateral_nucleus","lateral-corticospinal-tract":"The lateral corticospinal tract (also called the crossed pyramidal tract or lateral cerebrospinal fasciculus) is the largest part of the corticospinal tract.\n\nIt extends throughout the entire length of the spinal cord, and on transverse section appears as an oval area in front of the posterior column and medial to the posterior spinocerebellar tract.\n\n== Structure ==\n\nDescending motor pathways carry motor signals from the brain down the spinal cord and to the target muscle or organ.\n\nThey typically consist of an upper motor neuron and a lower motor neuron.\n\nThe lateral corticospinal tract is a descending motor pathway that begins in the cerebral cortex, decussates in the pyramids of the lower medulla (also known as the medulla oblongata or the cervicomedullary junction, which is the most posterior division of the brain) and proceeds down the contralateral side of the spinal cord.\n\nIt is the largest part of the corticospinal tract.\n\nIt extends throughout the entire length of the medulla spinalis, and on transverse section appears as an oval area in front of the posterior column and medial to the posterior spinocerebellar tract.\n\n== Function ==\n\nAxons in the lateral corticospinal tract weave out of the tract and into the anterior horns of the spinal cord.\n\nIt controls fine movement of ipsilateral limbs (albeit contralateral to the corresponding motor cortex) as it lies distal to the pyramidal decussation.\n\nControl of more central axial and girdle muscles comes from the anterior corticospinal tract.Damage to different parts of the body will cause deficits, depending on whether the damage is above (rostral) or below (caudal) the pyramidal decussation.\n\nDamage to the body above the pyramidal decussation will cause contralateral motor deficits.\n\nFor example, if there is a lesion at the pre-central gyrus in the right cerebral cortex, then the left side of the body will be affected.\n\nWhereas damage below the pyramidal decussation will result in ipsilateral motor deficits.\n\nFor example, spinal cord damage on the left side of the lateral corticospinal tract at the thoracic level can cause motor deficits to the left side of the body.\n\n== Clinical significance ==\n\nPoliomyelitis and amyotrophic lateral sclerosis arise out of complications in the lateral corticospinal tract.\n\nBoth of these diseases result in muscle atrophy.\n\nIn poliomyelitis, the poliovirus destroys motor neurons found in the brainstem and anterior horn of the spinal cord.\n\nThis inhibits the lower motor neurons of the lateral corticospinal tract from travelling to the target muscle or organ and delivering the signal from the brain.\nIn amyotrophic lateral sclerosis, the lateral side of the spinal cord undergoes scarring.\n\nThe astrocytes found in the spinal cord, which are vital to the healthy functioning of the central nervous system, fail to reabsorb a specific neurotransmitter.\n\nThis causes the neurotransmitter to reach toxic levels and leads to scarring in the lateral regions of the spinal cord.\n\nThis also disrupts neural signal transmission.\n\nhttps://en.wikipedia.org/wiki/Lateral_corticospinal_tract","rubrospinal-tract":"The rubrospinal tract is a part of the nervous system.\n\nIt is a part of the lateral indirect extra-pyramidal tract.\n\n== Structure ==\n\nIn the midbrain, it originates in the magnocellular red nucleus, crosses to the other side of the midbrain, and descends in the lateral part of the brainstem tegmentum.\n\nIn the spinal cord, it travels through the lateral funiculus of the spinal cord, coursing adjacent to the lateral corticospinal tract.\n\n== Function ==\n\nIn humans, the rubrospinal tract is one of several major motor control pathways.\n\nIt is smaller and has fewer axons than the corticospinal tract, suggesting that it is less important in motor control.\n\nIt is one of the pathways for the mediation of involuntary movement, along with other extra-pyramidal tracts including the vestibulospinal, tectospinal, and reticulospinal tracts.\n\nThe tract is responsible for large muscle movement regulation flexor and inhibiting extensor tone as well as fine motor control.\n\nIt terminates primarily in the cervical and thoracic portions of the spinal cord, suggesting that it functions in upper limb but not in lower limb control.\n\nIt is small and rudimentary in humans.\n\nIn some other primates, however, experiments have shown that over time, the rubrospinal tract can assume almost all the duties of the corticospinal tract when the corticospinal tract is lesioned.\n\nhttps://en.wikipedia.org/wiki/Rubrospinal_tract","lateral-reticulospinal-tract":"The medial reticular formation and lateral reticular formation are two columns of nuclei with ill-defined boundaries that send projections through the medulla and into the midbrain.\n\nThe nuclei can be differentiated by function, cell type, and projections of efferent or afferent nerves.\n\nMoving caudally from the rostral midbrain, at the site of the rostral pons and the midbrain, the medial RF becomes less prominent, and the lateral RF becomes more prominent.\n\n---\n\nThe reticulospinal tracts, also known as the descending or anterior reticulospinal tracts, are extrapyramidal motor tracts that descend from the reticular formation in two tracts to act on the motor neurons supplying the trunk and proximal limb flexors and extensors.\n\nThe reticulospinal tracts are involved mainly in locomotion and postural control, although they do have other functions as well.\n\nThe descending reticulospinal tracts are one of four major cortical pathways to the spinal cord for musculoskeletal activity.\n\nThe reticulospinal tracts works with the other three pathways to give a coordinated control of movement, including delicate manipulations.\n\nThe four pathways can be grouped into two main system pathways – a medial system and a lateral system.\n\nThe medial system includes the reticulospinal pathway and the vestibulospinal pathway, and this system provides control of posture.\n\nThe corticospinal and the rubrospinal tract pathways belong to the lateral system which provides fine control of movement.\n\nhttps://en.wikipedia.org/wiki/Reticular_formation#Descending_reticulospinal_tracts","lateral-vestibulospinal-tract":"The lateral vestibulospinal tract is one of the descending spinal tracts of the ventromedial funiculus.\nThe lateral part of the vestibulospinal tract is the major portion and is composed of fibers originating in the lateral, superior, and inferior vestibular nuclei (primarily the lateral).\n\nIt projects ipsilaterally down to the lumbar region of the spinal cord.\n\nThere it helps to maintain an upright and balanced posture by stimulating extensor motor neurons in the legs.\n\nIt also innervates muscles of the trunk, thus additionally aiding in body posture.\n\nThe lateral vestibular nuclei receive input from cerebellum, particularly the vestibulocerebellum, or the flocculi and nodulus.\n\nThe cerebellum aids in coordinating postural adjustments.\n\nhttps://en.wikipedia.org/wiki/Lateral_vestibulospinal_tract","medial-reticulospinal-tract":"The medial reticular formation and lateral reticular formation are two columns of nuclei with ill-defined boundaries that send projections through the medulla and into the midbrain.\n\nThe nuclei can be differentiated by function, cell type, and projections of efferent or afferent nerves.\n\nMoving caudally from the rostral midbrain, at the site of the rostral pons and the midbrain, the medial RF becomes less prominent, and the lateral RF becomes more prominent.\n\n---\n\nThe reticulospinal tracts, also known as the descending or anterior reticulospinal tracts, are extrapyramidal motor tracts that descend from the reticular formation in two tracts to act on the motor neurons supplying the trunk and proximal limb flexors and extensors.\n\nThe reticulospinal tracts are involved mainly in locomotion and postural control, although they do have other functions as well.\n\nThe descending reticulospinal tracts are one of four major cortical pathways to the spinal cord for musculoskeletal activity.\n\nThe reticulospinal tracts works with the other three pathways to give a coordinated control of movement, including delicate manipulations.\n\nThe four pathways can be grouped into two main system pathways – a medial system and a lateral system.\n\nThe medial system includes the reticulospinal pathway and the vestibulospinal pathway, and this system provides control of posture.\n\nThe corticospinal and the rubrospinal tract pathways belong to the lateral system which provides fine control of movement.\n\nhttps://en.wikipedia.org/wiki/Reticular_formation#Descending_reticulospinal_tracts","anterior-corticospinal-tract":"The anterior corticospinal tract (also called the ventral corticospinal tract, \"Bundle of Turck\", medial corticospinal tract, direct pyramidal tract, or anterior cerebrospinal fasciculus) is a small bundle of descending fibers that connect the cerebral cortex to the spinal cord.\n\nDescending tracts are pathways by which motor signals are sent from upper motor neurons in the brain to lower motor neurons which then directly innervate muscle to produce movement.\n\nThe anterior corticospinal tract is usually small, varying inversely in size with the lateral corticospinal tract, which is the main part of the corticospinal tract.\nIt lies close to the anterior median fissure, and is present only in the upper part of the spinal cord; gradually diminishing in size as it descends, it ends about the middle of the thoracic region.\nIt consists of descending fibers that arise from cells in the motor area of the ipsilateral cerebral hemisphere.\n\nThe impulse travels from these upper motor neurons (located in the pre-central gyrus of the brain) through the anterior column.\n\nIn contrast to the fibers for the lateral corticospinal tract, the fibers for the anterior corticospinal tract do not decussate at the level of the medulla oblongata, although they do cross over in the spinal level they innervate.\n\nThey then synapse at the anterior horn with the lower motor neuron which then synapses with the target muscle at the motor end plate.\n\nIn contrast to the lateral corticospinal tract which controls the movement of the limbs, the anterior corticospinal tract controls the movements of axial muscles (of the trunk).\nA few of its fibers pass to the lateral column of the same side and to the gray matter at the base of the posterior grey column.\n\nhttps://en.wikipedia.org/wiki/Anterior_corticospinal_tract","anterior-spinothalamic-tract":"The anterior spinothalamic tract, (Latin: tractus spinothalamicus anterior) or ventral spinothalamic fasciculus situated in the marginal part of the anterior funiculus and intermingled more or less with the vestibulospinal tract, is derived from cells in the posterior column or intermediate gray matter of the opposite side.\n\nAβ fibres carry sensory information pertaining to crude touch from the skin.\n\nAfter entering the spinal cord the first order neurons synapse (in the nucleus proprius), and the second order neurons decussate via the anterior white commissure.\n\nThese second order neurons ascend synapsing in the VPL of the thalamus.\n\nIncoming first order neurons can ascend or descend via the Lissauer tract.\n\nThis is a somewhat doubtful fasciculus and its fibers are supposed to end in the thalamus and to conduct certain of the touch impulses. More specifically, its fibers convey crude touch information to the VPL (ventral posterolateral nucleus) part of the thalamus.\n\nThe fibers of the anterior spinothalamic tract conduct information about pressure and crude touch (protopathic).\n\nThe fine touch (epicritic) is conducted by fibers of the medial lemniscus.\n\nThe medial lemniscus is formed by the axons of the neurons of the gracilis and cuneatus nuclei of the medulla oblongata which receive information about light touch, vibration and conscient proprioception from the gracilis and cuneatus fasciculus of the spinal cord.\n\nThis fasciculus receive the axons of the first order neuron which is located in the dorsal root ganglion that receives afferent fibers from receptors in the skin, muscles and joints.\n\nhttps://en.wikipedia.org/wiki/Spinothalamic_tract#Anterior_spinothalamic_tract","lateral-spinothalamic-tract":"The lateral spinothalamic tract (or lateral spinothalamic fasciculus), is a bundle of afferent nerve fibers ascending through the white matter of the spinal cord, in the spinothalamic tract, carrying sensory information to the brain.\n\nIt carries pain, and temperature sensory information (protopathic sensation) to the thalamus.\n\nIt is composed primarily of fast-conducting, sparsely myelinated A delta fibers and slow-conducting, unmyelinated C fibers.\n\nThese are secondary sensory neurons which have already synapsed with the primary sensory neurons of the peripheral nervous system in the posterior horn of the spinal cord (one of the three grey columns).\n\nTogether with the anterior spinothalamic tract, the lateral spinothalamic tract is sometimes termed the secondary sensory fasciculus or spinal lemniscus.\n\nAnatomy\n\nThe neurons of the lateral spinothalamic tract originate in the spinal dorsal root ganglia.\n\nThey project peripheral processes to the tissues in the form of free nerve endings which are sensitive to molecules indicative of cell damage.\n\nThe central processes enter the spinal cord in an area at the back of the posterior horn known as the posterolateral tract.\n\nHere, the processes ascend approximately two levels before synapsing on second-order neurons.\n\nThese secondary neurons are situated in the posterior horn, specifically in the Rexed laminae regions I, IV, V and VI.\n\nRegion II is primarily composed of Golgi II interneurons, which are primarily for the modulation of pain, and largely project to secondary neurons in regions I and V.\n\nSecondary neurons from regions I and V decussate across the anterior white commissure and ascend in the (now contralateral) lateral spinothalamic tract.\n\nThese fibers will ascend through the brainstem, including the medulla oblongata, pons and midbrain, as the spinal lemniscus until synapsing in the ventroposteriorlateral (VPL) nucleus of the thalamus.\n\nThe third order neurons in the thalamus will then project through the internal capsule and corona radiata to various regions of the cortex, primarily the main somatosensory cortex, Brodmann areas 3, 1, and 2.\n\nFunction\n\nThe types of sensory information means that the sensation is accompanied by a compulsion to act. For instance, an itch is accompanied by a need to scratch, and a painful stimulus makes us want to withdraw from the pain.[citation needed]\n\nThere are two sub-systems identified:\n\n Direct (for direct conscious appreciation of pain)\n Indirect (for affective and arousal impact of pain). Indirect projections include\n Spino-Reticulo-Thalamo-Cortical (part of the ascending reticular arousal system, aka ARAS)\n Spino-Mesencephalic-Limbic (for affective impact of pain).\n\nhttps://en.wikipedia.org/wiki/Spinothalamic_tract#Lateral_spinothalamic_tract","posterolateral-tract":"The posterolateral tract (fasciculus of Lissauer, Lissauer's tract, tract of Lissauer, dorsolateral fasciculus, dorsolateral tract, zone of Lissauer) is a small strand situated in relation to the tip of the posterior column close to the entrance of the posterior nerve roots.\n\nIt is present throughout the spinal cord, and is most developed in the upper cervical regions.\n\n== Structure ==\n\n The posterolateral tract contains centrally projecting axons from dorsal root ganglion cells carrying crude touch and pressure information (location, intensity and quality).\n\nThese axons enter the spinal column and penetrate the grey matter of the dorsal horn, where they synapse on second-order neurons in either the substantia gelatinosa of Rolando or the nucleus proprius.\n\nThose neurons project their axon to the anterolateral quadrant of the contralateral half of the spinal cord, where they give the spinothalamic tract.\n\nThe axons of second-order neurons ultimately synapse on neurons in the ventral posterior lateral nucleus (VPL) of the thalamus after coursing in the spinal lemniscus.\n\nAfter this, the 3rd order neuron fibers traverse the internal capsule and the corona radiata, ultimately synapsing in the post central gyrus (somatosensory cortex).\n\nThe location of this synapse is dependent upon the somatotopic organisation of the somatosensory cortex, it can be estimated according to the position on the 'somatosensory homunculus'\nThe posterolateral tract consists of fine fibers which do not receive their myelin sheaths until toward the close of fetal life.\n\nIn addition it contains great numbers of fine non-myelinated fibers derived mostly from the dorsal roots but partly endogenous in origin.\nThese fibers are intimately related to the substantia gelatinosa which is probably their terminal nucleus.\nThe non-myelinated fibers ascend or descend for short distances not exceeding one or two segments, but most of them enter the substantia gelatinosa at or near the level of their origin.\n\n== Clinical significance ==\n\nDuring a complete occlusion of the ventral artery of the spinal cord, it is the only tract spared along with the dorsal columns.\nThe posterolateral spinal tracts are involved with neurological deficits seen in pernicious anemia.\n\n== Eponym ==\n\nThe tract of Lissauer was named after German neurologist Heinrich Lissauer (1861-1891).\n\nhttps://en.wikipedia.org/wiki/Posterolateral_tract","posterior-spinocerebellar-tract":"The spinocerebellar tract is a nerve tract originating in the spinal cord and terminating in the same side (ipsilateral) of the cerebellum.\n\n== Origins of proprioceptive information ==\n\nProprioceptive information is obtained by Golgi tendon organs and muscle spindles.\n\nGolgi tendon organs consist of a fibrous capsule enclosing tendon fascicles and bare nerve endings that respond to tension in the tendon by causing action potentials in type Ib afferents.\n\nThese fibers are relatively large, myelinated, and quickly conducting.\n\nMuscle spindles monitor the length within muscles and send information via faster Ia afferents.\n\nThese axons are larger and faster than type Ib (from both nuclear bag fibers and nuclear chain fibers) and type II afferents (solely from nuclear chain fibers).All of these neurons are sensory (first order, or primary) and have their cell bodies in the dorsal root ganglia.\n\nThey pass through Rexed laminae layers I-VI of the posterior grey column (dorsal horn) to form synapses with second order or secondary neurons in layer VII just beneath the dorsal horn.\n\n== Subdivisions of the tract ==\n\nThe tract is divided into:\n\n=== Dorsal spinocerebellar tract ===\n\nThe dorsal spinocerebellar tract (posterior spinocerebellar tract, Flechsig's fasciculus, Flechsig's tract) conveys proprioceptive information from proprioceptors in the skeletal muscles and joints to the cerebellum.It is part of the somatosensory system and runs in parallel with the ventral spinocerebellar tract.\n\nIt carries proprioceptive information from muscle spindles and Golgi tendon organs of ipsilateral part of trunk and lower limb.\nProprioceptive information is taken to the spinal cord via central processes of dorsal root ganglia (first order neurons).\n\nThese central processes travel through the dorsal horn where they synapse with second order neurons of Clarke's nucleus.\n\nAxon fibers from Clarke's Nucleus convey this proprioceptive information in the spinal cord in the peripheral region of the funiculus posterior ipsilaterally.\n\nThe fibers continue to course through the medulla oblongata of the brainstem, at which point they pass through the inferior cerebellar peduncle and into the cerebellum, where unconscious proprioceptive information is processed.\n\nThis tract involves two neurons and ends up on the same side of the body.\n\nThe terms Flechsig's fasciculus and Flechsig's tract are named after German neuroanatomist, psychiatrist and neuropathologist Paul Flechsig.\n\n=== Ventral spinocerebellar tract ===\n\nThe ventral spinocerebellar tract (or anterior spinocerebellar tract) conveys proprioceptive information from the body to the cerebellum.\n\nHistorically, it has also been known as Gowers' column (or fasciculus or tract), after Sir William Richard Gowers.\n\nIt is part of the somatosensory system and runs in parallel with the dorsal spinocerebellar tract.\n\nBoth these tracts involve two neurons.\n\nThe ventral spinocerebellar tract will cross to the opposite side of the body first in the spinal cord as part of the anterior white commissure and then cross again to end in the cerebellum (referred to as a \"double cross\"), as compared to the dorsal spinocerebellar tract, which does not decussate, or cross sides, at all through its path.\n\nThe ventral tract (under L2/L3) gets its proprioceptive/fine touch/vibration information from a first order neuron, with its cell body in a dorsal ganglion.\n\nThe axon runs via the fila radicularia to the dorsal horn of the grey matter.\n\nThere it makes a synapse with the dendrites of two neurons: they send their axons bilaterally to the ventral border of the lateral funiculi.\n\nThe fibers of the ventral spinocerebellar tract then enters the cerebellum via the superior cerebellar peduncle.\n\nThis is in contrast with the dorsal spinocerebellar tract (C8 - L2/L3), which only has 1 unilateral axon that has its cell body in Clarke's column (only at the level of C8 - L2/L3).\n\nOriginates from ventral horn at lumbosacral spinal levels.\n\nAxons first cross midline in the spinal cord and run in the ventral border of the lateral funiculi.\n\nThese axons ascend to the pons where they join the superior cerebellar peduncle to enter the cerebellum.\n\nOnce in the deep white matter of the cerebellum, the axons recross the midline, give off collaterals to the globose and emboliform nuclei, and terminate in the cortex of the anterior lobe and vermis of the posterior lobe.\n\n==== Comparison with dorsal spinocerebellar tract ====\nWhen the dorsal roots are cut in a cat performing a step cycle, peripheral excitation is lost, and the dorsal spinocerebellar tract has no activity; the ventral spinocerebellar tract continues to show activity.\n\nThis suggests that the dorsal spinocerebellar tract carries sensory information to the spinocerebellum through the inferior cerebellar peduncle during movement (since the inferior peduncle is known to contain fibres from the dorsal tract), and that the ventral spinocerebellar tract carries internally generated motor information about the movement through the superior cerebellar peduncle.\n\n=== Posterior external arcuate fibers ===\n\nThe posterior external arcuate fibers (dorsal external arcuate fibers or cuneocerebellar tract) take origin in the accessory cuneate nucleus; they pass to the inferior cerebellar peduncle of the same side.\n\nThe term \"cuneocerebellar tract\" is also used to describe an exteroceptive and proprioceptive components that take origin in the gracile and cuneate nuclei; they pass to the inferior cerebellar peduncle of the same side.\n\nThe posterior external arcuate fibers carry proprioceptive information from the upper limbs and neck.\n\nIt is an analogue to the dorsal spinocerebellar tract for the upper limbs.\n\nIn this context, the \"cuneo-\" derives from the accessory cuneate nucleus, not the cuneate nucleus. (The two nuclei are related in space, but not in function.)\n\nIt is uncertain whether fibers are continued directly from the gracile and cuneate fasciculi into the inferior peduncle.\n\n=== Rostral spinocerebellar tract ===\n\nThe rostral spinocerebellar tract is a tract which transmits information from the golgi tendon organs of the cranial half of the body to the cerebellum.\n\nIt terminates bilaterally in the anterior lobe of the cerebellum (lower cerebellar peduncle) after travelling ipsilaterally from its origin in the cervical portion of the spinal cord.\n\nIt reaches the cerebellum partly through the brachium conjunctivum (superior cerebellar peduncle) and partly through the restiform body (inferior cerebellar peduncle).\n\n== Pathway for dorsal and spinocuneocerebellar tracts ==\n\nThe sensory neurons synapse in an area known as Clarke's nucleus or \"Clarke's column\".\n\nThis is a column of relay neuron cell bodies within the medial gray matter within the spinal cord in layer VII (just beneath the dorsal horn), specifically between T1-L3.\n\nThese neurons then send axons up the spinal cord, and project ipsilaterally to medial zones of the cerebellum through the inferior cerebellar peduncle.\n\nBelow L3, relevant neurons pass into the fasciculus gracilis (usually associated with the dorsal column-medial lemniscal system) until L3 where they synapse with Clarke's nucleus (leading to considerable caudal enlargement).\n\nThe neurons in the accessory cuneate nucleus have axons leading to the ipsilateral cerebellum via the inferior cerebellar peduncle.\n\n== Pathway for ventral and rostral spinocerebellar tracts ==\n\nSome neurons of the ventral spinocerebellar tract instead form synapses with neurons in layer VII of L4-S3.\n\nMost of these fibers cross over to the contralateral lateral funiculus via the anterior white commissure and through the superior cerebellar peduncle.\n\nThe fibers then often cross over again within the cerebellum to end on the ipsilateral side.\n\nFor this reason the tract is sometimes termed the \"double-crosser.\"\nThe Rostral Tract synapses at the dorsal horn lamina (intermediate gray zone) of the spinal cord and ascends ipsilaterally to the cerebellum through the inferior cerebellar peduncle\n\nhttps://en.wikipedia.org/wiki/Spinocerebellar_tract","anterior-spinocerebellar-tract":"The ventral spinocerebellar tract (or anterior spinocerebellar tract) conveys proprioceptive information from the body to the cerebellum.\n\nHistorically, it has also been known as Gowers' column (or fasciculus or tract), after Sir William Richard Gowers.\n\nIt is part of the somatosensory system and runs in parallel with the dorsal spinocerebellar tract. Both these tracts involve two neurons.\n\nThe ventral spinocerebellar tract will cross to the opposite side of the body first in the spinal cord as part of the anterior white commissure and then cross again to end in the cerebellum (referred to as a \"double cross\"), as compared to the dorsal spinocerebellar tract, which does not decussate, or cross sides, at all through its path.\n\nThe ventral tract (under L2/L3) gets its proprioceptive/fine touch/vibration information from a first order neuron, with its cell body in a dorsal ganglion.\n\nThe axon runs via the fila radicularia to the dorsal horn of the grey matter.\n\nThere it makes a synapse with the dendrites of two neurons: they send their axons bilaterally to the ventral border of the lateral funiculi.\n\nThe fibers of the ventral spinocerebellar tract then enters the cerebellum via the superior cerebellar peduncle.\n\nThis is in contrast with the dorsal spinocerebellar tract (C8 - L2/L3), which only has 1 unilateral axon that has its cell body in Clarke's column (only at the level of C8 - L2/L3).\n\nOriginates from ventral horn at lumbosacral spinal levels.\n\nAxons first cross midline in the spinal cord and run in the ventral border of the lateral funiculi.\n\nThese axons ascend to the pons where they join the superior cerebellar peduncle to enter the cerebellum. Once in the deep white matter of the cerebellum, the axons recross the midline, give off collaterals to the globose and emboliform nuclei, and terminate in the cortex of the anterior lobe and vermis of the posterior lobe.\n\nComparison with dorsal spinocerebellar tract:\n\nWhen the dorsal roots are cut in a cat performing a step cycle, peripheral excitation is lost, and the dorsal spinocerebellar tract has no activity; the ventral spinocerebellar tract continues to show activity.\n\nThis suggests that the dorsal spinocerebellar tract carries sensory information to the spinocerebellum through the inferior cerebellar peduncle during movement (since the inferior peduncle is known to contain fibres from the dorsal tract), and that the ventral spinocerebellar tract carries internally generated motor information about the movement through the superior cerebellar peduncle.\n\nhttps://en.wikipedia.org/wiki/Spinocerebellar_tract#Ventral_spinocerebellar_tract","tectospinal-tract":"In humans, the tectospinal tract (or colliculospinal tract) is a nerve tract that coordinates head and eye movements.\n\nThis tract is part of the extrapyramidal system and connects the midbrain tectum, and cervical regions of the spinal cord.It is responsible for motor impulses that arise from one side of the midbrain to muscles on the opposite side of the body (contralateral).\n\nThe function of the tectospinal tract is to mediate reflex postural movements of the head in response to visual and auditory stimuli.\nThe portion of the midbrain from where this tract originates is the superior colliculus, which receives afferents from the visual nuclei (primarily the oculomotor nuclei complex), then projects to the contralateral (decussating dorsal to the mesencephalic duct) and ipsilateral portion of the first cervical neuromeres of the spinal cord, the oculomotor and trochlear nuclei in the midbrain and the abducens nucleus in the caudal portion of the pons.\nThe tract descends to the cervical spinal cord to terminate in Rexed laminae VI, VII, and VIII to coordinate head, neck, and eye movements, primarily in response to visual stimuli.\n\nhttps://en.wikipedia.org/wiki/Tectospinal_tract","lateral-intermediate-substance":"LATERAL GREY COLUMN\n\nThe lateral grey column (lateral column, lateral cornu, lateral horn of spinal cord, intermediolateral column) is one of the three grey columns of the spinal cord (which give the shape of a butterfly); the others being the anterior and posterior grey columns.\n\nThe lateral grey column is primarily involved with activity in the sympathetic division of the autonomic motor system.\n\nIt projects to the side as a triangular field in the thoracic and upper lumbar regions (specifically T1-L2) of the postero-lateral part of the anterior grey column.\n\n== Background information ==\n\n=== Nervous system ===\n\nThe nervous system is the system of neurons, or nerve cells that relay electrical signals through the brain and body.\n\nA nerve cell receives signals from other nerve cells through tree-branch-like extensions called dendrites and passes signals through a long extension called an axon (or nerve fiber).\n\nSynapses are places where one cell's axon passes information to another cell's dendrite by sending chemicals called neurotransmitters across a small gap called a synaptic cleft.\n\nSynapses occur in various locations, including ganglia (singular: ganglion), which are masses of nerve cell bodies.\n\nPreganglionic nerve cells in the sympathetic nervous system (all of which come from the lateral grey column), use the neurotransmitter acetylcholine, while postganglionic sympathetic nerve cells use norepinephrine.\n\nGrey matter in the brain and spinal cord is any accumulation of cell bodies and neuropil (neuropil is tissue rich in nerve cell bodies and dendrites).\n\nWhite matter consists of nerve tracts (groups of axons) and commissures (tracts that cross the brain's midline).\n\n=== Sympathetic nervous system ===\n\nThe nervous system is divided into the central nervous system (brain and spinal cord) and the peripheral nervous system (everything else).\n\nThe peripheral nervous system is divided into the somatic nervous system (voluntary processes) and the autonomic nervous system (involuntary processes).\n\nThe autonomic nervous system is divided into the parasympathetic nervous system (normal functioning) and the sympathetic nervous system (emergency functioning).\n\nThe lateral grey column mediates the functions of the sympathetic nervous system.\n\n=== Spinal cord ===\n\nThe spinal cord is divided into 31 segments, located between the vertebrae.\n\nEach segment is defined by a posterior root entering it and an anterior root exiting it.\n\nEach of these roots is the end of a spinal nerve connecting the spinal cord to the body.\n\nThe vertebral column is divided into four groups of vertebrae: (from top to bottom) cervical, thoracic, lumbar, and sacral.\n\n== Structure ==\n\nThe lateral grey column is present at 17 levels of the spinal cord, specifically through levels T1-L2 (sympathetic outflow) as well as through levels S2-S4 (parasympathetic outflow).\n\nBoth these segments are located within the first thoracic vertebra to the first or second lumbar vertebra as the spinal cord ends here and the nerves form the cauda equina.\n\nThe lateral grey column is composed of sympathetic preganglionic visceral motor neurons which are part of the autonomic nervous system.\n\nAn in-depth study of the lateral grey columns in the thoracic region of rats revealed two types of cells.\n\nOne cell type was characterized by many mitochondria, an indented nucleus, and a long endoplasmic reticulum, while the other cell type had an increased cytoplasmic density and a short endoplasmic reticulum.\n\nLateral column axon terminals were found to contain noradrenaline storage granules and could be divided into four types.\n\nType one terminals contained a few large and many small granular vesicles, and type two terminals had many large vesicles and barely noticeable granules.\n\nType three terminals contained small, spherical vesicles and no granules, and type four were the rarest terminals that had flattened vesicles with small and large granules.\n\nThe cells of the intermediolateral cell column are fusiform or star-shaped, and of a medium size.\n\nThe intermediolateral cell column exists at vertebral levels T1 - L2 and mediates the entire sympathetic innervation of the body.\n\nIn the upper part of the cervical region and lower part of the medulla oblongata, as well as in the third and fourth sacral vertebrae, this column is again differentiated.\n\n== Functions ==\n\nThe lateral grey column's connections mediate the functions of the sympathetic nervous system (SNS), which changes cardiac, pulmonary, hepatic (liver), and gastrointestinal activities to prepare the body for emergency situations (although the sympathetic system is always active to some extent, including in the absence of a stressful environment, to maintain the appropriate level of sympathetic function).\n\nWhen the brain responds to potential threats by sending signals to lateral grey column cells, the lateral column passes on the signals to initiate a variety of physiological changes that prepare the body for a “fight-or-flight” response.\n\nHairs stand up to conserve heat.\n\nThe gut relaxes and digestion slows so that more energy can be directed toward dealing with the threatening situation.\n\nThe adrenal medulla is activated and releases epinephrine (adrenaline) into the bloodstream, where it mediates many changes, such as the preparation of muscles for emergency activity.\n\nA variety of smooth muscles relax; for example, the muscles wrapped around the bronchioles of the lungs relax, allowing more oxygen to enter the bloodstream.\n\nHeart rate increases to ensure all cells are supplied quickly with the substances they need.\n\nThe liver produces glucose (sugar) to fuel the muscles.\n\nBlood vessels contract (vasoconstriction), which reduces bleeding and conserves body heat (the exception is blood vessels fueling large muscles that would be used in running or fighting).\n\nThe pupils dilate, improving vision.\n\nPerspiration increases in certain areas of the body (the purpose of this is not yet fully understood, but there is some evidence that the odor produced by this sweat serves as a signal to other individuals).\n\n=== Sympathetic ===\n\nThe lateral grey column plays an important role in the sympathetic division of the visceral (autonomic) motor system.\n\nNeuron cell bodies in the lateral column send their axons to synapse on sympathetic ganglia that innervate autonomic and pelvic organs; in fact, all preganglionic neurons in the sympathetic nervous system originate in the lateral grey column.\n\nNeurons in the upper and middle thoracic segments control sympathetic activity in organs in the head and thorax, while neurons in the lower thoracic and upper lumbar segments control abdominal and pelvic organs and targets in the lower extremities.\n\nSlightly myelinated preganglionic fibers (aka visceral efferent fibers) leave the lateral grey column through the ventral roots and promptly form fourteen aggregates called white rami communicantes, also known as white communicating rami, which eventually enter the sympathetic trunk, a structure next to the vertebral column that consists of paired chains of sympathetic ganglia connected by nerve fibers.\n\nMost often, the fibers from the lateral grey column will travel along the sympathetic trunk until they synapse on one of the trunk's ganglia, which then passes on the information via postganglionic fibers in a gray ramus communicans.\n\n31 pairs of gray rami communicantes exit the sympathetic trunk to join the 31 pairs of spinal nerves and travel to targets such as sweat glands, hair follicles, and blood vessels.\n\nSome fibers, such as the ones that innervate the heart, join the spinal nerves directly, without first joining a gray ramus communicans.\n\nOther fibers from lateral grey column neurons pass through the sympathetic trunk without synapsing there.\n\nThe greater splanchnic nerve leaves the vertebral levels T5-T9 and synapses in the abdomen in the celiac ganglia, which innervates the celiac artery (splanchnic nerves are the nerves that innervate thoracic and abdominal viscera).\n\nThe lesser splanchnic nerve travels from the vertebral levels T10-T11 to the abdomen's superior mesenteric ganglia, which innervates the superior mesenteric artery, and to the aorticorenal ganglion.\n\nThe least, or lowest, splanchnic nerve connects the T12 level to the renal plexus.\n\nThe lumbar splanchnic nerves from the upper two lumbar segments synapse in the abdomen on the inferior mesenteric ganglia, associated with the inferior mesenteric artery.\n\nIn addition, some thoracic fibers in the splanchnic nerves innervate the adrenal medulla, a ganglion in the abdomen that mediates the sympathetic response to stress.\n\nAxons from the lateral grey column release acetylcholine at their synapses.\n\nThis can excite or inhibit the postsynaptic cell, depending on the type of acetylcholine receptor in its membrane.\n\nPostganglionic cells (that is, nerve cells innervated in ganglia by lateral column neurons) typically release norepinephrine (noradrenaline) on their targets; these synapses can also be either excitatory or inhibitory.\n\nThe lateral grey column receives input signals from preganglionic, myelinated fibers from viscera (internal organs), which course through prevertebral ganglia (between the visceral organ and the sympathetic chain) and paravertebral ganglia (in the sympathetic chain), white rami communicantes, and dorsal roots to synapse on cells of the intermediolateral cell column in the lateral horn.\n\nLateral grey column nerve cells also receive signals from the brainstem and from neurons in the hypothalamus, a brain area involved in mediating many physiological functions and emotional states.\n\n== Clinical significance ==\n\nHorner's syndrome is characterized by small pupils, sunken eyes, partially drooping eyelid, and dryness of the skin on the face.\n\nIt is caused by problems in autonomic pathways such as damage to the lateral grey column.Progressive autonomic failure is a disease associated with autonomic disturbances due to selective neuronal degeneration.\n\nA study estimated the number of nerve cells in the lateral grey columns of 21 people with progressive autonomic failure in comparison with a control group.\n\nThis same study found that an average of 75 percent of the lateral column cells were lost in people with progressive autonomic failure.Multiple system atrophy (MSA) is an adult onset disorder that is a sporadic and progressive.\n\nMSA is characterized by a combination of ataxia, parkinsonism, and autonomic dysfunction.\n\nA study did a comparison with the lateral grey column nerve cell count between 15 cases of patients with MSA and a control group.\n\nAll cases of MSA had lost over 50 percent of their lateral horn cells which shows the involvement of the intermediolateral columns in MSA.\n\nLichtheim's disease (also known as subacute combined degeneration) is the result of a vitamin B12 deficiency and is associated with pernicious anemia.\n\nThe disease is characterized by the degeneration of both the lateral and posterior columns, which results in symptoms such as a spastic ataxic gait and paranoia.\n\nPatients may also feel tingling or weakness in their limbs and torso.\n\nhttps://en.wikipedia.org/wiki/Lateral_grey_column","posterior-fasciculus-proprius":"The proper fasciculi, or spinospinal fasciculi, or propriospinal tracts,[1] are groups of short fibres, ascending and descending, and crossed and uncrossed, within the spinal cord.\n\nThese fibres are grouped into anterior, posterior, and lateral regions and make up a spinal pathway. Descending dorsal root collaterals are often included in the pathway.\n\nThere is an anterior fasciculus proprius, a lateral fasciculus proprius and the posterior fasciculus proprius.\n\nThe posterior fasciculus proprius arises from cells in the posterior column; their axons bifurcate (fork) into ascending and descending branches which occupy the ventral part of the funiculus close to the grey column.\n\nThey are intersegmental and run for varying distances sending off collaterals and terminals to the grey matter.\n\nhttps://en.wikipedia.org/wiki/Proper_fasciculi","lateral-fasciculus-proprius":"The proper fasciculi, or spinospinal fasciculi, or propriospinal tracts, are groups of short fibres, ascending and descending, and crossed and uncrossed, within the spinal cord.\n\nThese fibres are grouped into anterior, posterior, and lateral regions and make up a spinal pathway. Descending dorsal root collaterals are often included in the pathway.\n\nThere is an anterior fasciculus proprius, a lateral fasciculus proprius and a posterior pasciculus proprius.\n\nThe lateral proper fasciculus is made up of the remainder of the lateral column, and is continuous in front with the anterior proper fasciculus.\n\nIt consists chiefly of intersegmental fibres which arise from cells in the grey matter, and, after a longer or shorter course, re-enter the grey matter and ramify in it.\n\nSome of its fibers are, also continued upward into the brain in the medial longitudinal fasciculus.\n\nhttps://en.wikipedia.org/wiki/Proper_fasciculi","posterior-horn-of-spinal-cord":"The posterior grey column (posterior cornu, dorsal horn, spinal dorsal horn, posterior horn, sensory horn[1]) of the spinal cord is one of the three grey columns of the spinal cord.\n\nIt receives several types of sensory information from the body, including fine touch, proprioception, and vibration.\n\nThis information is sent from receptors of the skin, bones, and joints through sensory neurons whose cell bodies lie in the dorsal root ganglion.\n\nAnatomy\n\nThe posterior grey column is subdivided into six layers termed Rexed laminae I-VI\n\n -Marginal nucleus of spinal cord (lamina I)\n -Substantia gelatinosa of Rolando (lamina II)\n -Nucleus proprius (laminae III, IV)\n -Spinal lamina V, the neck of the posterior horn[2]\n -Spinal lamina VI, the base of the posterior horn.\n\nThe other four Rexed laminae are located in the other two grey columns in the spinal cord.\n\nhttps://en.wikipedia.org/wiki/Posterior_grey_column","anterior-fasciculus-proprius":"The proper fasciculi, or spinospinal fasciculi, or propriospinal tracts, are groups of short fibres, ascending and descending, and crossed and uncrossed, within the spinal cord.\n\nThese fibres are grouped into anterior, posterior, and lateral regions and make up a spinal pathway. Descending dorsal root collaterals are often included in the pathway.\n\nThere is an anterior fasciculus proprius, a lateral fasciculus proprius and a posterior fasciculus proprius.\n\nThe anterior fasciculus proprius consists of longitudinal intersegmental fibres which arise from cells in the grey matter, more especially from those of the medial group of the anterior column, and, after a longer or shorter course, re-enter the gray substance; and fibres which cross in the anterior white commissure from the grey matter of the opposite side.\n\nhttps://en.wikipedia.org/wiki/Proper_fasciculi","anterior-horn-of-spinal-cord":"/ANTERIOR GREY COLUMN\n\nThe anterior grey column (also called the anterior cornu, anterior horn of spinal cord, motor horn or ventral horn) is the front column of grey matter in the spinal cord.\n\nIt is one of the three grey columns.\n\nThe anterior grey column contains motor neurons that affect the skeletal muscles while the posterior grey column receives information regarding touch and sensation.\n\nThe anterior grey column is the column where the cell bodies of alpha motor neurons are located.\n\n== Structure ==\n\nThe anterior grey column, directed forward, is broad and of a rounded or quadrangular shape.\n\nIts posterior part is termed the base, and its anterior part the head, but these are not differentiated from each other by any well-defined constriction.\n\nIt is separated from the surface of the medulla spinalis by a layer of white substance which is traversed by the bundles of the anterior nerve roots.\n\nIn the thoracic region, the postero-lateral part of the anterior column projects laterally as a triangular field, which is named the lateral grey column.\n\n== Clinical significance ==\n\nIt is these cells that are affected in the following diseases, – amyotrophic lateral sclerosis, spinal and bulbar muscular atrophy, Charcot–Marie–Tooth disease, progressive muscular atrophy, all spinal muscular atrophies, poliomyelitis, and West Nile virus.\n\n=== Pharmacological interaction ===\n\nThe anterior grey column is the target for some spasmolytic medications.\n\nNorepinephrine release here, (as induced by cyclobenzaprine) reduces spasms by innervation (reducing nerve activity) of alpha motor neurons via interaction with gamma fibers.\n\nhttps://en.wikipedia.org/wiki/Anterior_grey_column","spinotectal-tract":"The spinotectal tract (spinomesencephalic tract, spinotectal fasciculus, spino-quadrigeminal system of Mott) arises in the spinothalamic tract and terminates in the inferior and superior colliculi.It is situated ventral to the lateral spinothalamic tract, but its fibers are more or less intermingled with it.\nIn the brainstem the fibers run lateral from the inferior olive, ventro-lateral from the superior olive, then ventro-medial from the spinal tract of the trigeminal; the fibers come to lie in the medial portion of the lateral lemniscus.\n\nhttps://en.wikipedia.org/wiki/Spinotectal_tract","spinal-ganglion":"A dorsal root ganglion (or spinal ganglion; also known as a posterior root ganglion) is a cluster of neurons (a ganglion) in a dorsal root of a spinal nerve.\n\nThe cell bodies of sensory neurons known as first-order neurons are located in the dorsal root ganglia.\n\nThe axons of dorsal root ganglion neurons are known as afferents.\n\nIn the peripheral nervous system, afferents refer to the axons that relay sensory information into the central nervous system (i.e. the brain and the spinal cord).\n\nStructure\n\nThe neurons comprising the dorsal root ganglion are of the pseudo-unipolar type, meaning they have a cell body (soma) with two branches that act as a single axon, often referred to as a distal process and a proximal process.\n\nUnlike the majority of neurons found in the central nervous system, an action potential in posterior root ganglion neuron may initiate in the distal process in the periphery, bypass the cell body, and continue to propagate along the proximal process until reaching the synaptic terminal in the posterior horn of spinal cord.\n\nDistal section\n\nThe distal section of the axon may either be a bare nerve ending or encapsulated by a structure that helps relay specific information to nerve.\n\nTwo examples where the nerve ending of the distal process is encapsulated as such are, Meissner's corpuscles, which render the distal processes of mechanosensory neurons sensitive to stroking only, and Pacinian corpuscles, which make neurons more sensitive to vibration.\n\nLocation\n\nThe dorsal root ganglia lie in the intervertebral foramina.\n\nThe anterior and posterior spinal nerve roots join just beyond (lateral) to the location of the dorsal root ganglion.\nDevelopment\n\nThe dorsal root ganglia develop in the embryo from neural crest cells, not neural tube. Hence, the spinal ganglia can be regarded as gray matter of the spinal cord that became translocated to the periphery.\n\nFunction\n\nNociception\n\nProton-sensing G protein-coupled receptors are expressed by DRG sensory neurons and might play a role in acid-induced nociception.\n\nMechanosensitive channels\n\nThe nerve endings of dorsal root ganglion neurons have a variety of sensory receptors that are activated by mechanical, thermal, chemical, and noxious stimuli.\n\nIn these sensory neurons, a group of ion channels thought to be responsible for somatosensory transduction have been identified.\n\nCompression of the dorsal root ganglion by a mechanical stimulus lowers the voltage threshold needed to evoke a response and causes action potentials to be fired.\n\nThis firing may even persist after the removal of the stimulus.\n\nTwo distinct types of mechanosensitive ion channels have been found in the posterior root ganglion neurons.\n\nThe two channels are broadly classified as either high-threshold (HT) or low threshold (LT).\n\nAs their names suggest, they have different thresholds as well as different sensitivities to pressure.\n\nThese are cationic channels whose activity appears to be regulated by the proper functioning of the cytoskeleton and cytoskeleton associated proteins.\n\nThe presence of these channels in the posterior root ganglion gives reason to believe that other sensory neurons may contain them as well.\n\nHigh-threshold mechanosensitive channels\n\nHigh-threshold channels have a possible role in nociception.\n\nThese channels are found predominantly in smaller sensory neurons in the dorsal root ganglion cells and are activated by higher pressures, two attributes that are characteristic of nociceptors.\n\nAlso, the threshold of HT channels was lowered in the presence of PGE2 (a compound that sensitizes neurons to mechanical stimuli and mechanical hyperalgesia) which further supports a role for HT channels in the transduction of mechanical stimuli into nociceptive neuronal signals.\n\nPresynaptic control\n\nThe presynaptic regulation of the dorsal nerve ending discharge in the spinal cord can occur through certain types of GABAA receptors but not through the activation of glycine receptors which are absent from these types of terminals.\n\nThus GABAA receptors but not glycine receptors can presynaptically control nociception and pain transmission.","uvula-of-palate":"The palatine uvula, usually referred to as simply the uvula, is a conic projection from the back edge of the middle of the soft palate, composed of connective tissue containing a number of racemose glands, and some muscular fibers.\n\nIt also contains many serous glands, which produce thin saliva.\n\nStructure\nMuscle\n\nThe muscular part of the uvula (Latin: musculus uvulae) shortens and broadens the uvula.\n\nThis changes the contour of the posterior part of the soft palate.\n\nThis change in contour allows the soft palate to adapt closely to the posterior pharyngeal wall to help close the nasopharynx during swallowing.\n\nIts muscles are controlled by the pharyngeal branch of the vagus nerve.\n\n==Function==\n\nDuring swallowing, the soft palate and the uvula move together to close off the nasopharynx, and prevent food from entering the nasal cavity.\n\nIt has also been proposed that the abundant amount of thin saliva produced by the uvula serves to keep the throat well lubricated.\n\nIt has a function in speech as well.\n\nIn many languages, the uvula is used to articulate a range of consonant sounds, known as uvular consonants.\n\nThe voiced uvular trill, written [ʀ] in the International Phonetic Alphabet, is one example; it is used in French, Arabic and Hebrew, among other languages.\n\nDue to the large amount of saliva produced from glands in the uvula that are absent in other mammals, it has been suggested that the uvula is an accessory speech organ.\n\nStimulation of the uvula also causes the gag reflex to initiate.\n\nThis is often a problem for people with uvula piercings, and a common method of inducing vomiting.\n\nhttps://en.wikipedia.org/wiki/Palatine_uvula","gingiva":"/GUMS\n\nThe gums or gingiva (plural: gingivae) consist of the mucosal tissue that lies over the mandible and maxilla inside the mouth.\n\nGum health and disease can have an effect on general health.\n\n== Structure ==\n\nThe gums are part of the soft tissue lining of the mouth.\n\nThey surround the teeth and provide a seal around them.\n\nUnlike the soft tissue linings of the lips and cheeks, most of the gums are tightly bound to the underlying bone which helps resist the friction of food passing over them.\n\nThus when healthy, it presents an effective barrier to the barrage of periodontal insults to deeper tissue.\n\nHealthy gums are usually coral pink in light skinned people, and may be naturally darker with melanin pigmentation.\n\nChanges in color, particularly increased redness, together with swelling and an increased tendency to bleed, suggest an inflammation that is possibly due to the accumulation of bacterial plaque.\n\nOverall, the clinical appearance of the tissue reflects the underlying histology, both in health and disease.\n\nWhen gum tissue is not healthy, it can provide a gateway for periodontal disease to advance into the deeper tissue of the periodontium, leading to a poorer prognosis for long-term retention of the teeth.\n\nBoth the type of periodontal therapy and homecare instructions given to patients by dental professionals and restorative care are based on the clinical conditions of the tissue.\n\nThe gums are divided anatomically into marginal, attached and interdental areas.\n\n=== Marginal gums ===\n\nThe marginal gum is the edge of the gums surrounding the teeth in collar-like fashion.\n\nIn about half of individuals, it is demarcated from the adjacent, attached gums by a shallow linear depression, the free gingival groove.\n\nThis slight depression on the outer surface of the gum does not correspond to the depth of the gingival sulcus but instead to the apical border of the junctional epithelium.\n\nThis outer groove varies in depth according to the area of the oral cavity.\n\nThe groove is very prominent on mandibular anteriors and premolars.\n\nThe marginal gum varies in width from 0.5 to 2.0 mm from the free gingival crest to the attached gingiva.\n\nThe marginal gingiva follows the scalloped pattern established by the contour of the cementoenamel junction (CEJ) of the teeth.\n\nThe marginal gingiva has a more translucent appearance than the attached gingiva, yet has a similar clinical appearance, including pinkness, dullness, and firmness.\n\nIn contrast, the marginal gingiva lacks the presence of stippling, and the tissue is mobile or free from the underlying tooth surface, as can be demonstrated with a periodontal probe.\n\nThe marginal gingiva is stabilized by the gingival fibers that have no bony support.\n\nThe gingival margin, or free gingival crest, at the most superficial part of the marginal gingiva, is also easily seen clinically, and its location should be recorded on a patient's chart.\n\n=== Attached gum ===\n\nThe attached gums are continuous with the marginal gum.\n\nIt is firm, resilient, and tightly bound to the underlying periosteum of alveolar bone.\n\nThe facial aspect of the attached gum extends to the relatively loose and movable alveolar mucosa, from which it is demarcated by the mucogingival junction.\n\nAttached gum may present with surface stippling.\n\nThe tissue when dried is dull, firm, and immobile, with varying amounts of stippling.\n\nThe width of the attached gum varies according to its location.\n\nThe width of the attached gum on the facial aspect differs in different areas of the mouth.\n\nIt is generally greatest in the incisor region (3.5 to 4.5 mm in the maxilla and 3.3 to 3.9 mm in the mandible) and less in the posterior segments, with the least width in the first premolar area (1.9 mm in the maxilla and 1.8 mm in the mandible).\n\nHowever, certain levels of attached gum may be necessary for the stability of the underlying root of the tooth.\n\n=== Interdental gum ===\n\nThe interdental gum lies between the teeth.\n\nThey occupy the gingival embrasure, which is the interproximal space beneath the area of tooth contact.\n\nThe interdental papilla can be pyramidal or have a \"col\" shape.\n\nAttached gums are resistant to the forces of chewing and covered in keratin.\n\nThe col varies in depth and width, depending on the expanse of the contacting tooth surfaces.\n\nThe epithelium covering the col consists of the marginal gum of the adjacent teeth, except that it is nonkeratinized.\n\nIt is mainly present in the broad interdental gingiva of the posterior teeth, and generally is not present with those interproximal tissue associated with anterior teeth because the latter tissue is narrower.\n\nIn the absence of contact between adjacent teeth, the attached gum extends uninterrupted from the facial to the lingual aspect.\n\nThe col may be important in the formation of periodontal disease but is visible clinically only when teeth are extracted.\n\nInterdental AreasIt is the part of gum which extends in between two teeth up to the contact point.\n\nThere is a facial side interdental papilla and a lingual side interdental papilla.\n\nInterdental papilla has a summit and margins that are concave.\n\nThe tip and the margins are unattached and the central portion attached.\n\nIn inflammations the interdental papilla loses its concavity.\n\n== Characteristics of healthy gums ==\n\n=== Color ===\n\nHealthy gums usually have a color that has been described as \"coral pink\".\n\nOther colours like red, white, and blue can signify inflammation (gingivitis) or pathology.\n\nSmoking or drug use can cause discoloring as well (such as \"meth mouth\").\n\nAlthough described as the colour coral pink, variation in colour is possible.\n\nThis can be the result of factors such as: thickness and degree of keratinization of the epithelium, blood flow to the gums, natural pigmentation of the skin, disease, and medications.\n\nSince the colour of the gums can vary, uniformity of colour is more important than the underlying color itself.\n\nExcess deposits of melanin can cause dark spots or patches on the gums (melanin gingival hyperpigmentation), especially at the base of the interdental papillae.\n\nGum depigmentation (aka gum bleaching) is a procedure used in cosmetic dentistry to remove these discolorations.\n\n=== Contour ===\n\nHealthy gums have a smooth curved or scalloped appearance around each tooth.\n\nHealthy gums fill and fit each space between the teeth, unlike the swollen gum papilla seen in gingivitis or the empty interdental embrasure seen in periodontal disease.\n\nHealthy gums hold tight to each tooth in that the gum surface narrows to \"knife-edge\" thin at the free gingival margin.\n\nOn the other hand, inflamed gums have a \"puffy\" or \"rolled\" margin.\n\n=== Texture ===\n\nHealthy gums have a firm texture that is resistant to movement, and the surface texture often exhibits surface stippling.\n\nUnhealthy gums, on the other hand, is often swollen and less firm.\n\nHealthy gums have an orange-peel like texture to it due to the stippling.\n\n=== Reaction to disturbance ===\n\nHealthy gums usually have no reaction to normal disturbance such as brushing or periodontal probing.\n\nUnhealthy gums, conversely, will show bleeding on probing (BOP) and/or purulent exudate.\n\n== Clinical significance ==\n\nThe gingival cavity microecosystem, fueled by food residues and saliva, can support the growth of many microorganisms, of which some can be injurious to health.\n\nImproper or insufficient oral hygiene can thus lead to many gum and periodontal disorders, including gingivitis or periodontitis, which are major causes for tooth failure.\n\nRecent studies have also shown that anabolic steroids are also closely associated with gingival enlargement requiring a gingivectomy for many cases.\n\nGingival recession is when there is an apical movement of the gum margin away from the biting (occlusal) surface.\n\nIt may indicate an underlying inflammation such as periodontitis or pyorrhea, a pocket formation, dry mouth or displacement of the marginal gums away from the tooth by mechanical (such as brushing), chemical, or surgical means.\n\nGingival retraction, in turn, may expose the dental neck and leave it vulnerable to the action of external stimuli, and may cause root sensitivity.\n\nhttps://en.wikipedia.org/wiki/Gums","parotid-gland":"The parotid gland is a major salivary gland in many animals.\n\nIn humans, the two parotid glands are present on either side of the mouth and in front of both ears.\n\nThey are the largest of the salivary glands.\n\nEach parotid is wrapped around the mandibular ramus, and secretes serous saliva through the parotid duct into the mouth, to facilitate mastication and swallowing and to begin the digestion of starches.\n\nThere are also two other types of salivary glands; they are submandibular and sublingual glands.\n\nSometimes accessory parotid glands are found close to the main parotid glands.\n\n== Etymology ==\n\nThe word parotid literally means \"beside the ear\".\n\nFrom Greek παρωτίς (stem παρωτιδ-) : (gland) behind the ear < παρά - pará : in front, and οὖς - ous (stem ὠτ-, ōt-) : ear.\n\n== Structure ==\n\nThe parotid glands are a pair of mainly serous salivary glands located below and in front of each ear canal, draining their secretions into the vestibule of the mouth through the parotid duct.\n\nEach gland lies behind the mandibular ramus and in front of the mastoid process of the temporal bone.\n\nThe gland can be felt on either side, by feeling in front of each ear, along the cheek, and below the angle of the mandible.\n\nThe parotid duct, a long excretory duct, emerges from the front of each gland, superficial to the masseter muscle.\n\nThe duct pierces the buccinator muscle, then opens into the mouth on the inner surface of the cheek, usually opposite the maxillary second molar.\n\nThe parotid papilla is a small elevation of tissue that marks the opening of the parotid duct on the inner surface of the cheek.The gland has four surfaces – superficial or lateral, superior, anteromedial, and posteromedial.\n\nThe gland has three borders – anterior, medial, and posterior.\n\nThe parotid gland has two ends – superior end in the form of small superior surface and an inferior end (apex).\n\nA number of different structures pass through the gland.\n\nFrom lateral to medial, these are:\n\nFacial nerve\nRetromandibular vein\nExternal carotid artery\nSuperficial temporal artery\nBranches of the great auricular nerve\nMaxillary arterySometimes accessory parotid glands are found as an anatomic variation.\n\nThese are close to the main glands and consist of ectopic salivary gland tissue.\n\nCapsule of parotid gland\n\nCapsule of the parotid gland is formed from the investing layer of the deep cervical fascia.\n\nIt is supplied by great auricular nerve.\n\nThe fascia splits to enclose the gland.\n\nThis splitting occurs between the angle of the mandible and the mastoid process.\n\nThe superficial lamina (parotidomassetric fascia) is thick and is attached to zygomatic arch.\n\nThe deep lamina is thin and is attached to styloid process, tympanic plate and the ramus of the mandible.\n\nThe part of deep lamina extending between the styloid process and the mandible is thickened to form stylomastoid ligament.\n\nThe stylomandibular ligament separates parotid gland from the superficial lobe of the submandibular gland.\n\n=== Location ===\n\nSuperficial or lateral relations:\n The gland is situated deep to the skin, superficial fascia, superficial lamina of investing layer of deep cervical fascia and great auricular nerve (anterior ramus of C2 and C3).\n\nAnteromedial relations:\n The gland is situated posterolaterally to the mandibular ramus, masseter and medial pterygoid muscles.\n\nA part of the gland may extend between the ramus and medial pterygoid, as the pterygoid process.\n\nBranches of facial nerve and parotid duct emerge through this surface.\n\nPosteromedial relations:\n The gland is situated anterolaterally to mastoid process of temporal bone with its attached sternocleidomastoid and digastric muscles, styloid process of temporal bone with its three attached muscles (stylohyoid, stylopharyngeus, and styloglossus) and carotid sheath with its contained neurovasculature (internal carotid artery, internal jugular vein, and 9th, 10th, 11th, and 12th cranial nerves).\n\nMedial relations:\n The parotid gland comes into contact with the superior pharyngeal constrictor muscle at the medial border, where the anteromedial and posteromedial surfaces meet.\n\nHence, a need exists to examine the fauces in parotitis.\n\n=== Blood supply ===\n\nThe external carotid artery and its terminal branches within the gland, namely, the superficial temporal and the maxillary artery, also the posterior auricular artery supply the parotid gland.\n\nVenous return is to the retromandibular veins.\n\n=== Lymphatic drainage ===\n\nThe gland is mainly drained into the preauricular or parotid lymph nodes which ultimately drain to the deep cervical chain.\n\n=== Nerve supply ===\n\nThe parotid gland receives both sensory and autonomic innervation.\n\nGeneral sensory innervation to the parotid gland, its sheath, and the overlying skin is provided by the auriculotemporal nerve.\n\nThe autonomic innervation controls the rate of saliva production and is supplied by the glossopharyngeal nerve.\n\nThe cell bodies of the preganglionic sympathetic fibres usually lie in the lateral horns of upper thoracic spinal segments (T1-T3).\n\nPostganglionic sympathetic fibers from superior cervical sympathetic ganglion reach the gland as periarterial nerve plexuses around the external carotid artery and their function is mainly vasoconstriction.\n\nPreganglionic parasympathetic fibers leave the brain stem from inferior salivatory nucleus in the glossopharyngeal nerve and then through its tympanic and then the lesser petrosal branch pass into the otic ganglion.\n\nThere, they synapse with postganglionic fibers which reach the gland by hitch-hiking via the auriculotemporal nerve, a branch of the mandibular nerve.: 255\n\n=== Histology ===\n\nThe gland has a capsule of its own of dense connective tissue, but is also provided with a false capsule by the investing layer of the deep cervical fascia.\n\nThe fascia at the imaginary line between the angle of the mandible and the mastoid process splits into a superficial and a deep lamina to enclose the gland.\n\nThe risorius is a small muscle embedded with this capsule substance.\nThe gland has short, striated ducts and long, intercalated ducts.\n\nThe intercalated ducts are also numerous and lined with cuboidal epithelial cells, and have lumina larger than those of the acini.\n\nThe striated ducts are also numerous and consist of simple columnar epithelium, having striations that represent the infolded basal cell membranes and mitochondria.\n\nThough the parotid gland is the largest, it provides only 25% of the total salivary volume.\n\nThe serous cell predominates in the parotid, making the gland secrete a mainly serous secretory product.\n\nThe parotid gland also secretes salivary alpha-amylase (sAA), which is the first step in the decomposition of starches during mastication.\n\nIt is the main exocrine gland to secrete this.\n\nIt breaks down amylose (straight chain starch) and amylopectin (branched starch) by hydrolyzing alpha 1,4 bonds.\n\nAdditionally, the alpha amylase has been suggested to prevent bacterial attachment to oral surfaces and to enable bacterial clearance from the mouth.\n\n== Development ==\n\nThe parotid salivary glands appear early in the sixth week of the prenatal development and are the first major salivary glands formed.\n\nThe epithelial buds of these glands are located on the inner part of the cheek, near the labial commissures of the primitive mouth (from ectodermal lining near angles of the stomodeum in the 1st/2nd pharyngeal arches; the stomodeum itself is created from the rupturing of the oropharyngeal membrane at about 26 days.)\n\nThese buds grow posteriorly toward the otic placodes of the ears and branch to form solid cords with rounded terminal ends near the developing facial nerve.\n\nLater, at around 10 weeks of prenatal development, these cords are canalized and form ducts, with the largest becoming the parotid duct for the parotid gland.\n\nThe rounded terminal ends of the cords form the acini of the glands.\n\nSecretion by the parotid glands via the parotid duct begins at about 18 weeks of gestation.\n\nAgain, the supporting connective tissue of the gland develops from the surrounding mesenchyme.\n\n== Parotid gland swellings ==\n\n=== Causes ===\n\n==== Mumps ====\n\nMumps is seen to be a common cause of parotid gland swelling – 85% of cases occur in children younger than 15 years.\n\nThe disease is highly contagious and spreads by airborne droplets from salivary, nasal, and urinary secretions.\n\nSymptoms include oedema in the area, trismus as well as otalgia.\n\nThe lesion tends to begin on one side of the face and eventually becomes bilateral.\n\nThe transmission of the paramyxovirus is by contact with the infected persons saliva.\n\nInitial symptoms tend to be a headache and fever.\n\nMumps is not fatal, however further complications can include swelling of the ovaries or the testes.\n\nDiagnosis of mumps is confirmed through viral serology, management of the condition includes hydration and good oral hygiene of the patient requiring excellent motivation.\n\nHowever, since the development of the mumps vaccine, given at the age of between 4–6 years, the incidence of this viral infection has greatly reduced.\n\nThis vaccine has reduced the incidence by 99%.\n\n==== Neoplasms ====\n\n===== Benign =====\n\nNeoplastic lesions of the parotid salivary gland can either be benign or malignant.\n\nWithin the parotid gland, nearly 80% of tumours are benign.\n\nBenign lesions tend to be painless, asymptomatic and slow-growing.\n\nThe most common salivary gland neoplasms in children are hemangiomas, lymphatic malformations, and pleomorphic adenomas.\n\nDiagnosis of benign lesions require a fine-needle-like aspiration biopsy.\n\nWith various benign lesions, most commonly the pleomorphic adenoma, there is a risk of developing malignancy over time.\n\nAs a result, these lesions are typically resected.\n\nPleomorphic adenoma is seen to be a common benign neoplasm of the salivary gland and has an overall incidence of 54–68%.\n\nThe Warthin tumour has a lower incidence of 6–10%; this tumour is associated with smoking and is more common in older men.\n\nBenign lesions of the parotid gland have a significantly higher incidence than malignant lesions.\n\n===== Malignant =====\n\nMalignant salivary gland lesions are rare.\n\nHowever, when a tumour extends to the submandibular, sublingual and the minor salivary glands, they tend to be malignant.\n\nDistinguishing a malignant lesion from a benign one may be difficult as they both present as painless lesions.\n\nA biopsy is crucial in aiding diagnosis.\n\nThere are common signs that can highlight the presence of a malignant lesion.\n\nThese include facial nerve weakness, rapid increase of the size of the lump as well as ulceration of the mucosa of the skin.\n\nMucoepidermoid carcinoma is a common malignant tumour of the salivary glands and has a low incidence of 4–13%.\n\nAdenoid cystic carcinoma is also a common malignant salivary gland lesion and has an incidence of 4–8%.\n\nThis carcinoma tends to invade nerves and can re-occur post-treatment.\n\n==== Polycystic Parotid Disease ====\n\nA developmental polycystic disease of the salivary gland is seen to be extremely rare and is seen to be independent of recurrent parotitis.\n\nThe cause is thought to be a defect in the interactions between activin, follistatin and TGF-β, leading to a developmental disorder of glandular tissue.\n\n== Clinical significance ==\n\n=== Parotitis ===\n\nInflammation of one or both parotid glands is known as parotitis.\n\nThe most common cause of parotitis is mumps.\n\nWidespread vaccination against mumps has markedly reduced the incidence of mumps parotitis.\n\nThe pain of mumps is due to the swelling of the gland within its fibrous capsule.\n\nApart from viral infection, other infections, such as bacterial, can cause parotitis (acute suppurative parotitis or chronic parotitis).\n\nThese infections may cause blockage of the duct by salivary duct calculi or external compression.\n\nParotid gland swellings can also be due to benign lymphoepithelial lesions caused by Mikulicz disease and Sjögren syndrome.\n\nSwelling of the parotid gland may also indicate the eating disorder bulimia nervosa, creating the look of a heavy jaw line.\n\nWith the inflammation of mumps or obstruction of the ducts, increased levels of the salivary alpha amylase secreted by the parotid gland can be detected in the blood stream.\n\n=== Fibrous reactions ===\n\nTuberculosis and syphilis can cause granuloma formation in the parotid glands.\n\n=== Salivary stones ===\n\nSalivary stones mainly occur within the main confluence of the ducts and within the main parotid duct.\n\nThe patient usually complains of intense pain when salivating and tends to avoid foods which produce this symptom.\n\nIn addition, the parotid gland may become enlarged upon trying to eat.\n\nThe pain can be reproduced in clinic by squirting lemon juice into the mouth.\n\nSurgery depends upon the site of the stone: if within the anterior aspect of the duct, a simple incision into the buccal mucosa with sphinterotomy may allow removal; however, if situated more posteriorly within the main duct, complete gland excision may be necessary.\n\n=== Injury ===\n\nThe parotid salivary gland can also be pierced and the facial nerve temporarily traumatized when an inferior alveolar local anesthesia nerve block is incorrectly administered, causing transient facial paralysis.\n\n=== Cancer and tumours ===\n\nAbout 80% of tumors of the parotid gland are benign.\n\nThe most common of these include pleomorphic adenoma (70% of tumors, of which 60% occur in females) and Warthin tumor (i.e. adenolymphoma, which is more common in males than in females).\n\nTheir importance is in relation to their anatomical position and tendency to grow over time.\n\nThe tumorous growth can also change the consistency of the gland and cause facial pain on the involved side.\n\nAround 20% of parotid tumors are malignant, with the most common tumors being mucoepidermoid carcinoma and adenoid cystic carcinoma.\n\nOther malignant tumors of the parotid gland include acinic cell carcinoma, carcinoma expleomorphic adenoma, adenocarcinoma (arising from ductal epithelium of parotid gland), squamous cell carcinoma (arising from parenchyma of parotid gland), and undifferentiated carcinoma.\n\nMetastasis from other sites like phyllodes tumour of breast presenting as parotid swelling have also been described.\n\nCritically, the relationship of the tumor to the branches of the facial nerve (CN VII) must be defined because resection may damage the nerves, resulting in paralysis of the muscles of facial expression.\n\n=== Surgery ===\n\nSurgical treatment of parotid gland tumors is sometimes difficult because of the anatomical relations of the facial nerve parotid lodge, as well as the increased potential for postoperative relapse.\n\nThus, detection of early stages of a parotid tumor is extremely important in terms of postoperative prognosis.\n\nOperative technique is laborious, because of relapses and incomplete previous treatment made in other border specialties.\n\nSurgical techniques in parotid surgery have evolved in the last years with the use of neuromonitoring of the facial nerve and have become safer and less invasive.\n\nAfter surgical removal of the parotid gland (Parotidectomy), the auriculotemporal nerve is liable to damage and upon recovery it fuses with sweat glands.\n\nThis can cause sweating on the cheek on the side of the face of the affected gland.\n\nThis condition is known as Frey's syndrome.\n\n== Infections ==\n\n=== Bacterial infections ===\n\n==== Acute bacterial parotitis ====\n\nCommonly caused by a retrograde bacterial infection as a result of illness, sepsis, trauma, surgery, reduced salivary flow due to medications, diabetes, malnutrition and dehydration.\n\nClassically symptoms of painful swelling in the parotid region when eating seen.\n\nManagement is based upon antibacterials, rehydration combined with gentle massage to encourage salivary flow.\n\n==== Chronic bacterial parotitis ====\n\nA latent infection despite clinical resolution of the disease resulting in impaired function.\n\nHistologically glandular duct dilation, abscess formation and atrophy may be seen.\n\nParotid secretions are viscous.\n\nDisease course shows pain and swelling, waxing and waning.\n\nRadiographic screening should be undertaken to rule out sialolith.\n\nManagement with palliative care with parotidectomy as a last resort.\n\n=== Viral infections ===\n\n==== Mumps ====\n\nAcute non-suppurative disease that often occurs in epidemics.\n\nPrevented by MMR vaccine.\n\nCaused by paramyxovirus that is transmitted by infected saliva and urine.\n\nA prodromal period of 24–28 hours is experienced, followed by rapid and painful swelling of the parotid gland.\n\nTreatment is supportive (bedrest, hydration) as spontaneous resolution occurs within 5–10 days.\n\n==== HIV / AIDS ====\n\nDiffuse gland enlargement is seen, and may affect patients throughout all stages of the infection.\n\nLymphoepithelial cysts seen via imaging help aid diagnosis.\n\nPathogenic process occurs due to circulating CD8 lymphocytes within the salivary gland.\n\nMedical management via use of antiretrovirals, excellent oral hygiene measures and sialogogues.\n\n=== Autoimmune related ===\n\n==== Systemic lupus erythematosus ====\n\nMost commonly seen in fourth and fifth decades in women, and can affect any salivary gland.\n\nPresentation is a slowly enlarging gland, with diagnosis made by identification of the underlying systemic disorder and measurements of salivary chemical levels.\n\nSodium and chloride ion levels will be elevated two or three times normal levels.\n\nTreatment is by addressing the underlying systemic condition.\n\n==== Sarcoidosis ====\n\nSarcoidosis is a chronic systemic disease characterised by the production of non-caseating granulomas of unknown aetiology.\n\nIt can affect any organ of the body, depressing cellular immunity and enhancing humoral immunity.\n\nSalivary gland involvement primarily involves the parotid gland, causing enlargement and swelling.\n\nSalivary gland biopsy with histopathologic examination is needed to make the distinction between whether Sjoren’s syndrome or sarcoidosis is the cause of this.\n\n==== Sjogren's syndrome ====\n\nSalivary gland enlargement occurs in up to 30% of patients with Sjogren’s syndrome, with the parotid gland being most often enlarged, and bilateral parotid gland enlargement seen in 25–60% of patients.\n\nHowever, the parotid glands have a longer-lasting secretory capacity in Sjogren’s syndrome patient and therefore are the last glands to manifest hyposalivation in the disease.\n\nHistopathology shows clustering of lymphocytic infiltrates and epimyoepithelial islands.\n\n=== Mycobacterial infection ===\n\nThe most common head and neck manifestation of tuberculosis mycobacterial disease is infection of cervical lymph nodes.\n\nThe infection is thought to originate in the tonsils or gingiva, ascending to the parotid gland.\n\nTwo clinical forms; acute and chronic lesions.\n\nAcute lesions have diffuse glandular edema, easily confused with acute sialdentitis or abscess.\n\nThe chronic lesions occur as slow growing masses mimicking tumors.\n\n== Examination of the salivary gland ==\n\n=== History and examination ===\n\nA patient with parotid swelling may complain of swelling, pain, xerostomia, bad taste and sometimes sialorrhoea.\n\nThe most common presenting symptom of neoplasms (both benign and malignant) is an asymptomatic swelling.\n\nPain is more common in patients with parotid cancer (10–29% feel pain) than those with benign neoplasms (only 2.5–4%), but pain itself it not diagnostic of malignancy.\n\nEpisodic swelling of major salivary glands accompanied by pain and related to salivary stimuli suggests duct obstruction.\n\nAlso need to assess the facial nerve.\n\nThe facial nerve passes through the parotid so may be affected if there is a change in the parotid gland.\n\nFacial nerve paralysis in a previously untreated patient usually indicates that a tumour is malignant.\n\n=== Physical examination ===\n\nThe superficial location of the salivary glands allows palpation and visual inspection.\n\nThe inspection must be systematic, both intraorally and extraorally, so no area is missed.\n\nFor extraoral examination the patients head should be inclined forwards in order to maximally expose the parotid and submandibular glands.\n\nA normal parotid gland is barely palpable and a normal sublingual gland is not palpable.Intra-oral examination should include observations for asymmetry, discolouration, pulsation and obstructions in the duct orifices.\n\nSwelling of the deep lobe of the parotid gland may be seen intra-orally, and may also displace the tonsil.\n\nThe minor salivary glands should be examined.\n\nThe labial, buccal and posterior palatal mucosa should be dried with an air blower or tissue and pressed to assess the flow of saliva.\n\n=== Salivary testing ===\n\nSalivary stimulation\n\nThis can be done by palpating the parotid gland, thus stimulating it.\n\nAssess to see whether there is saliva flowing from the parotid papilla.Sialography\n\nSialograms can identify changes in salivary gland architecture and are useful in the evaluation of major gland swellings.\n\nIt involves the instillation of a radio-opaque fluid into the major gland ductal system.\n\nThis outlines the major and minor ductal systems, and also gives an outline of the glandular tissue.\n\nFor example, sialadenitis creates an appearance known as “pruning of the tree” on a sialogram, where there are less branches visible from the duct system.\n\nAlso, a space occupying lesion that occurs within or adjacent to a salivary gland can displace the normal anatomy of the gland.\n\nThis may create an appearance known as “ball in hand” on a sialogram, where the ducts are curved around the mass of the lesion.Sialochemistry\n\nThe composition of saliva changes in disease states, and analysis of saliva for enzymes, electrolytes, hormones, drugs and immunisation status can be performed.Radioisotope scintigraphy\n\nGives an objective measure of isotope uptake and excretion using a gamma scintillation camera.\n\nAfter about 20 minutes, a salivary stimulant will be given to promote salivary flow through the gland.\n\nThey are used to assess patients with persistent symptoms of dry mouth and also to evaluate salivary gland swelling due to infection, inflammation or obstruction.\n\n=== Further tests ===\n\n-Imagining techniques\n\n-Ultrasounds, CT Scans or MRIs can aid with disease localisation\n\n-Sialoendoscopy\n\n-A camera is inserted into the duct of a salivary gland to assess blockages\n\n-Biopsy\n\n-This can be done by fine needle aspiration biopsy, which provides an opportunity to obtain information about the histology of a salivary tumour prior to initiation of treatment.\n\nhttps://en.wikipedia.org/wiki/Parotid_gland","sublingual-gland":"The paired sublingual glands are major salivary glands in the mouth.\n\nThey are the smallest, most diffuse, and the only unencapsulated major salivary glands.\n\nThey provide only 3-5% of the total salivary volume.\n\nThere are also two other types of salivary glands; they are submandibular and parotid glands.\n\n== Structure ==\n\nThey lie anterior and superior to the submandibular gland and inferior and lateral to the tongue, as well as beneath the mucous membrane of the floor of the mouth.\n\nThey are bounded laterally by the bone of the mandible and inferolaterally by the mylohyoid muscle.\n\nThe glands can be felt behind each mandibular canine.\n\nPlacing one index finger within the mouth and the fingertips of the opposite hand outside it, the compressed gland is manually palpated between the inner and outer fingers.\nThe sublingual glands are drained by 8-20 excretory ducts called the ducts of Rivinus.\n\nThe largest of all, the sublingual duct (of Bartholin) joins the submandibular duct to drain through the sublingual caruncle.\n\nThe sublingual caruncle is a small papilla near the midline of the floor of the mouth on each side of the lingual frenum.\n\nMost of the remaining small sublingual ducts (of Rivinus) open separate into the mouth on an elevated crest of mucous membrane, the plica sublingualis (aka sublingual fold), formed by the gland and located on either side of the frenulum linguae.\n\n=== Microanatomy ===\n\nThe sublingual gland consists mostly of mucous acini capped with serous demilunes and is therefore categorized as a mixed mucous gland with a mucous product predominating.\n\nStriated and intercalated ducts are also present.\n\n=== Blood supply ===\n\nThe gland receives its blood supply from the sublingual and submental arteries.\n\nLymph from the sublingual salivary gland drains into the submandibular lymph nodes.\n\n=== Nerve supply ===\n\nThe chorda tympani nerve (from the facial nerve via the submandibular ganglion) is secretomotor and provides parasympathetic supply to the sublingual glands.\n\nThe path of the nerve is as follows: junction between pons and medulla, through internal acoustic meatus and facial canal to chorda tympani, through middle ear cavity, out petrotympanic fissure to join the lingual nerve, travels with lingual nerve to synapse at the submandibular ganglion, then postganglionic fibers travels to the sublingual gland.\n\n=== Development ===\n\nThe sublingual salivary glands appear in the eighth week of prenatal development, two weeks later than the other two major salivary glands.\n\nThey develop from epithelial buds in the sulcus surrounding the sublingual folds on the floor of the mouth, lateral to the developing submandibular gland.\n\nThese buds branch and form into cords that canalize to form the sublingual ducts associated with the gland.\n\nThe rounded terminal ends of the cords form acini.\n\n== Clinical significance ==\n\nRanulas are the most common pathologic lesion associated with the sublingual glands.\n\nhttps://en.wikipedia.org/wiki/Sublingual_gland","submandibular-gland":"The paired submandibular glands (historically known as submaxillary glands) are major salivary glands located beneath the floor of the mouth.\n\nThey each weigh about 15 grams and contribute some 60–67% of unstimulated saliva secretion; on stimulation their contribution decreases in proportion as the parotid secretion rises to 50%.\n\nThe average length of the normal human submandibular salivary gland is approximately 27mm, while the average width is approximately 14.3mm.\n\n== Structure ==\n\nLying superior to the digastric muscles, each submandibular gland is divided into superficial and deep lobes, which are separated by the mylohyoid muscle:\nThe superficial lobe comprises most of the gland, with the mylohyoid muscle runs under it\nThe deep lobe is the smaller partSecretions are delivered into the submandibular duct on the deep portion after which they hook around the posterior edge of the mylohyoid muscle and proceed on the superior surface laterally.\n\nThe excretory ducts are then crossed by the lingual nerve, and ultimately drain into the sublingual caruncles – small prominences on either side of the lingual frenulum along with the major sublingual duct.\n\nThe gland can be bilaterally palpated (felt) inferior and posterior to the body of the mandible, moving inward from the inferior border of the mandible near its angle with the head tilted forwards.\n\n=== Microanatomy ===\n\nLobes contain smaller lobules, which contain adenomeres, the secretory units of the gland.\n\nEach adenomer contains one or more acini, or alveoli, which are small clusters of cells that secrete their products into a duct.\n\nThe acini of each adenomere are composed of either serous or mucous cells, with serous adenomeres predominating.\n\nSome mucous adenomeres may also be capped with a serous demilune, a layer of lysozyme-secreting serous cells resembling a half moon.\nLike other exocrine glands, the submandibular gland can be classified by the microscopic anatomy of its secretory cells and how they are arranged.\n\nBecause the glands are branched, and because the tubules forming the branches contain secretory cells, submandibular glands are classified as branched tubuloacinar glands.\n\nFurther, because the secretory cells are of both serous and mucous types, the submandibular gland is a mixed gland, and though most of the cells are serous, the exudate is chiefly mucous.\n\nIt has long striated ducts and short intercalated ducts.The secretory acinar cells of the submandibular gland have distinct functions.\n\nThe mucous cells are the most active and therefore the major product of the submandibular glands is saliva which is mucoid in nature.\n\nMucous cells secrete mucin which aids in the lubrication of the food bolus as it travels through the esophagus.\n\nIn addition, the serous cells produce salivary amylase, which aids in the breakdown of starches in the mouth.\n\nThe submandibular gland's highly active acini account for most of the salivary volume.\n\nThe parotid and sublingual glands account for the remaining.\n\n=== Blood supply ===\n\nThe gland receives its blood supply from the facial and lingual arteries.\n\nThe gland is supplied by sublingual and submental arteries and drained by common facial and lingual veins.\n\n=== Lymphatic drainage ===\n\nThe lymphatics from submandibular gland first drain into submandibular lymph nodes and subsequently into jugulo - digastric lymph nodes.\n\n=== Nerve supply ===\n\nTheir secretions, like the secretions of other salivary glands, are regulated directly by the parasympathetic nervous system and indirectly by the sympathetic nervous system.\n\nParasympathetic innervation to the submandibular glands is provided by the superior salivatory nucleus via the chorda tympani, a branch of the facial nerve, that becomes part of the trigeminal nerve's lingual nerve prior to synapsing on the submandibular ganglion.\n\nIncreased parasympathetic activity promotes the secretion of saliva.\nThe sympathetic nervous system regulates submandibular secretions through vasoconstriction of the arteries that supply it.\n\nIncreased sympathetic activity reduces glandular bloodflow, thereby decreasing the volume of fluid in salivary secretions, producing an enzyme rich mucous saliva.\n\nNevertheless, direct stimulation of sympathetic nerves will cause an increase in salivary enzymatic secretions.\n\nIn sum, the volume decreases, but the secretions are increased by parasympathetic and sympathetic innervation.\n\n=== Development ===\n\nThe submandibular salivary glands develop later than the parotid glands and appear late in the sixth week of prenatal development.\n\nThey develop bilaterally from epithelial buds in the sulcus surrounding the sublingual folds on the floor of the primitive mouth.\n\nSolid cords branch from the buds and grow posteriorly, lateral to the developing tongue.\n\nThe cords of the submandibular gland later branch further and then become canalized to form the ductal part.\n\nThe submandibular gland acini develop from the cords’ rounded terminal ends at 12 weeks, and secretory activity via the submandibular duct begins at 16 weeks.\n\nGrowth of the submandibular gland continues after birth with the formation of more acini.\n\nLateral to both sides of the tongue, a linear groove develops and closes over to form the submandibular duct.\n\n== Function ==\n\nThe submandibular gland releases a host of factors which regulate systemic inflammatory responses and modulate systemic immune and inflammatory reactions.\n\nEarly work in identifying factors that played a role in the cervical sympathetic trunk-submandibular gland (CST-SMG) axis lead to the discovery of a seven amino acid peptide, called the submandibular gland peptide-T.\n\nSGP-T was demonstrated to have biological activity and thermoregulatory properties related to endotoxin exposure.\n\nSGP-T, an isolate of the submandibular gland, demonstrated its immunoregulatory properties and potential role in modulating the CST-SMG axis, and subsequently was shown to play an important role in the control of inflammation.\n\n== Clinical significance ==\n\nThe submandibular gland accounts for 80% of all salivary duct calculi (salivary stones or sialolith), possibly due to the different nature of the saliva that it produces and the tortuous travel of the submandibular duct to its ductal opening for a considerable upward distance.\n\nThe submandibular gland is one of the major three glands that provide the mouth with saliva.\n\nThe\ntwo other types of salivary glands are parotid and sublingual glands.\n\n=== Dissection images ===\n\nhttps://en.wikipedia.org/wiki/Submandibular_gland","tongue":"The tongue is a muscular organ in the mouth of a typical tetrapod.\n\nIt manipulates food for mastication and swallowing as part of the digestive process, and is the primary organ of taste.\n\nThe tongue's upper surface (dorsum) is covered by taste buds housed in numerous lingual papillae.\n\nIt is sensitive and kept moist by saliva and is richly supplied with nerves and blood vessels.\n\nThe tongue also serves as a natural means of cleaning the teeth.\n\nA major function of the tongue is the enabling of speech in humans and vocalization in other animals.\nThe human tongue is divided into two parts, an oral part at the front and a pharyngeal part at the back.\n\nThe left and right sides are also separated along most of its length by a vertical section of fibrous tissue (the lingual septum) that results in a groove, the median sulcus, on the tongue's surface.\nThere are two groups of muscles of the tongue.\n\nThe four intrinsic muscles alter the shape of the tongue and are not attached to bone.\n\nThe four paired extrinsic muscles change the position of the tongue and are anchored to bone.\n\n== Etymology ==\n\nThe word tongue derives from the Old English tunge, which comes from Proto-Germanic *tungōn.\n\nIt has cognates in other Germanic languages—for example tonge in West Frisian, tong in Dutch and Afrikaans, Zunge in German, tunge in Danish and Norwegian, and tunga in Icelandic, Faroese and Swedish.\n\nThe ue ending of the word seems to be a fourteenth-century attempt to show \"proper pronunciation\", but it is \"neither etymological nor phonetic\".\n\nSome used the spelling tunge and tonge as late as the sixteenth century.\n\n== In humans ==\n\n=== Structure ===\n\nThe tongue is a muscular hydrostat that forms part of the floor of the oral cavity.\n\nThe left and right sides of the tongue are separated by a vertical section of fibrous tissue known as the lingual septum.\n\nThis division is along the length of the tongue save for the very back of the pharyngeal part and is visible as a groove called the median sulcus.\n\nThe human tongue is divided into anterior and posterior parts by the terminal sulcus which is a V-shaped groove.\n\nThe apex of the terminal sulcus is marked by a blind foramen, the foramen cecum, which is a remnant of the median thyroid diverticulum in early embryonic development.\n\nThe anterior oral part is the visible part situated at the front and makes up roughly two-thirds the length of the tongue.\n\nThe posterior pharyngeal part is the part closest to the throat, roughly one-third of its length.\n\nThese parts differ in terms of their embryological development and nerve supply.\nThe anterior tongue is, at its apex, thin and narrow.\n\nIt is directed forward against the lingual surfaces of the lower incisor teeth.\n\nThe posterior part is, at its root, directed backward, and connected with the hyoid bone by the hyoglossi and genioglossi muscles and the hyoglossal membrane, with the epiglottis by three glossoepiglottic folds of mucous membrane, with the soft palate by the glossopalatine arches, and with the pharynx by the superior pharyngeal constrictor muscle and the mucous membrane.\n\nIt also forms the anterior wall of the oropharynx.\nThe average length of the human tongue from the oropharynx to the tip is 10 cm.\n\nThe average weight of the human tongue from adult males is 70g and for adult females 60g.In phonetics and phonology, a distinction is made between the tip of the tongue and the blade (the portion just behind the tip).\n\nSounds made with the tongue tip are said to be apical, while those made with the tongue blade are said to be laminal.\n\n==== Upper surface of the tongue ====\n\nThe upper surface of the tongue is called the dorsum, and is divided by a groove into symmetrical halves by the median sulcus.\n\nThe foramen cecum marks the end of this division (at about 2.5 cm from the root of the tongue) and the beginning of the terminal sulcus.\n\nThe foramen cecum is also the point of attachment of the thyroglossal duct and is formed during the descent of the thyroid diverticulum in embryonic development.\nThe terminal sulcus is a shallow groove that runs forward as a shallow groove in a V shape from the foramen cecum, forwards and outwards to the margins (borders) of the tongue.\n\nThe terminal sulcus divides the tongue into a posterior pharyngeal part and an anterior oral part.\n\nThe pharyngeal part is supplied by the glossopharyngeal nerve and the oral part is supplied by the lingual nerve (a branch of the mandibular branch (V3) of the trigeminal nerve) for somatosensory perception and by the chorda tympani (a branch of the facial nerve) for taste perception.\nBoth parts of the tongue develop from different pharyngeal arches.\n\n==== Undersurface of the tongue ====\nOn the undersurface of the tongue is a fold of mucous membrane called the frenulum that tethers the tongue at the midline to the floor of the mouth.\n\nOn either side of the frenulum are small prominences called sublingual caruncles that the major salivary submandibular glands drain into.\n\n==== Muscles ====\nThe eight muscles of the human tongue are classified as either intrinsic or extrinsic.\n\nThe four intrinsic muscles act to change the shape of the tongue, and are not attached to any bone.\n\nThe four extrinsic muscles act to change the position of the tongue, and are anchored to bone.\n\n===== Extrinsic =====\n\nThe four extrinsic muscles originate from bone and extend to the tongue.\n\nThey are the genioglossus, the hyoglossus (often including the chondroglossus) the styloglossus, and the palatoglossus.\n\nTheir main functions are altering the tongue's position allowing for protrusion, retraction, and side-to-side movement.The genioglossus arises from the mandible and protrudes the tongue.\n\nIt is also known as the tongue's \"safety muscle\" since it is the only muscle that propels the tongue forward.\nThe hyoglossus, arises from the hyoid bone and retracts and depresses the tongue.\n\nThe chondroglossus is often included with this muscle.\nThe styloglossus arises from the styloid process of the temporal bone and draws the sides of the tongue up to create a trough for swallowing.\nThe palatoglossus arises from the palatine aponeurosis, and depresses the soft palate, moves the palatoglossal fold towards the midline, and elevates the back of the tongue during swallowing.\n\n===== Intrinsic =====\n\nFour paired intrinsic muscles of the tongue originate and insert within the tongue, running along its length.\n\nThey are the superior longitudinal muscle, the inferior longitudinal muscle, the vertical muscle, and the transverse muscle.\n\nThese muscles alter the shape of the tongue by lengthening and shortening it, curling and uncurling its apex and edges as in tongue rolling, and flattening and rounding its surface.\n\nThis provides shape and helps facilitate speech, swallowing, and eating.The superior longitudinal muscle runs along the upper surface of the tongue under the mucous membrane, and elevates, assists in retraction of, or deviates the tip of the tongue.\n\nIt originates near the epiglottis, at the hyoid bone, from the median fibrous septum.\nThe inferior longitudinal muscle lines the sides of the tongue, and is joined to the styloglossus muscle.\nThe vertical muscle is located in the middle of the tongue, and joins the superior and inferior longitudinal muscles.\nThe transverse muscle divides the tongue at the middle, and is attached to the mucous membranes that run along the sides.\n\n==== Blood supply ====\n\nThe tongue receives its blood supply primarily from the lingual artery, a branch of the external carotid artery.\n\nThe lingual veins drain into the internal jugular vein.\n\nThe floor of the mouth also receives its blood supply from the lingual artery.\n\nThere is also a secondary blood supply to the root of tongue from the tonsillar branch of the facial artery and the ascending pharyngeal artery.\nAn area in the neck sometimes called the Pirogov triangle is formed by the intermediate tendon of the digastric muscle, the posterior border of the mylohyoid muscle, and the hypoglossal nerve.\n\nThe lingual artery is a good place to stop severe hemorrhage from the tongue.\n\n==== Nerve supply ====\nInnervation of the tongue consists of motor fibers, special sensory fibers for taste, and general sensory fibers for sensation.\nMotor supply for all intrinsic and extrinsic muscles of the tongue is supplied by efferent motor nerve fibers from the hypoglossal nerve (CN XII), with the exception of the palatoglossus, which is innervated by the vagus nerve (CN X).Innervation of taste and sensation is different for the anterior and posterior part of the tongue because they are derived from different embryological structures (pharyngeal arch 1 and pharyngeal arches 3 and 4, respectively).\nAnterior two-thirds of tongue (anterior to the vallate papillae):\nTaste: chorda tympani branch of the facial nerve (CN VII) via special visceral afferent fibers\nSensation: lingual branch of the mandibular (V3) division of the trigeminal nerve (CN V) via general visceral afferent fibers\nPosterior one third of tongue:\nTaste and sensation: glossopharyngeal nerve (CN IX) via a mixture of special and general visceral afferent fibers\nBase of tongue\nTaste and sensation: internal branch of the superior laryngeal nerve (itself a branch of the vagus nerve, CN X)\n\n==== Lymphatic drainage ====\nThe tip of tongue drains to the submental nodes.\n\nThe left and right halves of the anterior two-thirds of the tongue drains to submandibular lymph nodes, while the posterior one-third of the tongue drains to the jugulo-omohyoid nodes.\n\n==== Microanatomy ====\n\nThe upper surface of the tongue is covered in masticatory mucosa, a type of oral mucosa which is of keratinized stratified squamous epithelium.\n\nEmbedded in this are numerous papillae, some of which house the taste buds and their taste receptors.\n\nThe lingual papillae consist of filiform, fungiform, vallate and foliate papillae, and only the filiform papillae are not associated with any taste buds.\nThe tongue can divide itself in dorsal and ventral surface.\n\nThe dorsal surface is a stratified squamous keratinized epithelium which is characterized by numerous mucosal projections called papillae.\n\nThe lingual papillae covers the dorsal side of the tongue towards the front of the terminal groove.\n\nThe ventral surface is stratified squamous non-keratinized epithelium which is smooth.\n\n=== Development ===\n\nThe tongue begins to develop in the fourth week of embryonic development from a median swelling – the median tongue bud (tuberculum impar) of the first pharyngeal arch.In the fifth week a pair of lateral lingual swellings, one on the right side and one on the left, form on the first pharyngeal arch.\n\nThese lingual swellings quickly expand and cover the median tongue bud.\n\nThey form the anterior part of the tongue that makes up two-thirds of the length of the tongue, and continue to develop through prenatal development.\n\nThe line of their fusion is marked by the median sulcus.In the fourth week a swelling appears from the second pharyngeal arch, in the midline, called the copula.\n\nDuring the fifth and sixth weeks the copula is overgrown by a swelling from the third and fourth arches (mainly from the third arch) called the hypopharyngeal eminence, and this develops into the posterior part of the tongue (the other third).\n\nThe hypopharyngeal eminence develops mainly by the growth of endoderm from the third pharyngeal arch.\n\nThe boundary between the two parts of the tongue, the anterior from the first arch and the posterior from the third arch is marked by the terminal sulcus.\n\nThe terminal sulcus is shaped like a V with the tip of the V situated posteriorly.\n\nAt the tip of the terminal sulcus is the foramen cecum, which is the point of attachment of the thyroglossal duct where the embryonic thyroid begins to descend.\n\n=== Function ===\n\n==== Taste ====\n\nChemicals that stimulate taste receptor cells are known as tastants.\n\nOnce a tastant is dissolved in saliva, it can make contact with the plasma membrane of the gustatory hairs, which are the sites of taste transduction.The tongue is equipped with many taste buds on its dorsal surface, and each taste bud is equipped with taste receptor cells that can sense particular classes of tastes.\n\nDistinct types of taste receptor cells respectively detect substances that are sweet, bitter, salty, sour, spicy, or taste of umami.\n\nUmami receptor cells are the least understood and accordingly are the type most intensively under research.\n\n==== Mastication ====\nThe tongue is an important accessory organ in the digestive system.\n\nThe tongue is used for crushing food against the hard palate, during mastication and manipulation of food for softening prior to swallowing.\n\nThe epithelium on the tongue's upper, or dorsal surface is keratinised.\n\nConsequently, the tongue can grind against the hard palate without being itself damaged or irritated.\n\n==== Speech ====\nThe intrinsic muscles of the tongue enable the shaping of the tongue which facilitates speech.\n\n==== Intimacy ====\nThe tongue plays a role in physical intimacy and sexuality.\n\nThe tongue is part of the erogenous zone of the mouth and can be used in intimate contact, as in the French kiss and in oral sex.\n\nThe tongue can be used for stimulating the clitoris and other areas of the vulva.\n\n=== Clinical significance ===\n\n==== Disease ====\n\nA congenital disorder of the tongue is that of ankyloglossia also known as tongue-tie.\n\nThe tongue is tied to the floor of the mouth by a very short and thickened frenulum and this affects speech, eating, and swallowing.\nThe tongue is prone to several pathologies including glossitis and other inflammations such as geographic tongue, and median rhomboid glossitis; burning mouth syndrome, oral hairy leukoplakia, oral candidiasis (thrush), black hairy tongue and fissured tongue.\nThere are several types of oral cancer that mainly affect the tongue.\n\nMostly these are squamous cell carcinomas.Food debris, desquamated epithelial cells and bacteria often form a visible tongue coating.\n\nThis coating has been identified as a major factor contributing to bad breath (halitosis), which can be managed by using a tongue cleaner.\n\n==== Medication delivery ====\nThe sublingual region underneath the front of the tongue is an ideal location for the administration of certain medications into the body.\n\nThe oral mucosa is very thin underneath the tongue, and is underlain by a plexus of veins.\n\nThe sublingual route takes advantage of the highly vascular quality of the oral cavity, and allows for the speedy application of medication into the cardiovascular system, bypassing the gastrointestinal tract.\n\nThis is the only convenient and efficacious route of administration (apart from Intravenous therapy) of nitroglycerin to a patient suffering chest pain from angina pectoris.\n\n== Other animals ==\n\nThe muscles of the tongue evolved in amphibians from occipital somites.\n\nMost amphibians show a proper tongue after their metamorphosis.\n\nAs a consequence most vertebrate animals—amphibians, reptiles, birds, and mammals—have tongues (the frog family of pipids lack tongue).\n\nIn mammals such as dogs and cats, the tongue is often used to clean the fur and body by licking.\n\nThe tongues of these species have a very rough texture which allows them to remove oils and parasites.\n\nSome dogs have a tendency to consistently lick a part of their foreleg which can result in a skin condition known as a lick granuloma.\n\nA dog's tongue also acts as a heat regulator.\n\nAs a dog increases its exercise the tongue will increase in size due to greater blood flow.\n\nThe tongue hangs out of the dog's mouth and the moisture on the tongue will work to cool the bloodflow.Some animals have tongues that are specially adapted for catching prey.\n\nFor example, chameleons, frogs, pangolins and anteaters have prehensile tongues.\nOther animals may have organs that are analogous to tongues, such as a butterfly's proboscis or a radula on a mollusc, but these are not homologous with the tongues found in vertebrates and often have little resemblance in function.\n\nFor example, butterflies do not lick with their proboscides; they suck through them, and the proboscis is not a single organ, but two jaws held together to form a tube.\n\nMany species of fish have small folds at the base of their mouths that might informally be called tongues, but they lack a muscular structure like the true tongues found in most tetrapods.\n\n== Society and culture ==\n\n=== Figures of speech ===\n\nThe tongue can be used as a metonym for language.\n\nFor example, the New Testament of the Bible, in the Book of Acts of the Apostles, Jesus' disciples on the Day of Pentecost received a type of spiritual gift: \"there appeared unto them cloven tongues like as of fire, and it sat upon each of them.\n\nAnd they were all filled with the Holy Ghost, and began to speak with other tongues ....\", which amazed the crowd of Jewish people in Jerusalem, who were from various parts of the Roman Empire but could now understand what was being preached.\n\nThe phrase mother tongue is used as a child's first language.\n\nMany languages have the same word for \"tongue\" and \"language\".\nA common temporary failure in word retrieval from memory is referred to as the tip-of-the-tongue phenomenon.\n\nThe expression tongue in cheek refers to a statement that is not to be taken entirely seriously – something said or done with subtle ironic or sarcastic humour.\n\nA tongue twister is a phrase made specifically to be very difficult to pronounce.\n\nAside from being a medical condition, \"tongue-tied\" means being unable to say what you want due to confusion or restriction.\n\nThe phrase \"cat got your tongue\" refers to when a person is speechless.\n\nTo \"bite one's tongue\" is a phrase which describes holding back an opinion to avoid causing offence.\n\nA \"slip of the tongue\" refers to an unintentional utterance, such as a Freudian slip.\n\nThe \"gift of tongues\" refers to when one is uncommonly gifted to be able to speak in a foreign language, often as a type of spiritual gift.\n\nSpeaking in tongues is a common phrase used to describe glossolalia, which is to make smooth, language-resembling sounds that is no true spoken language itself.\n\nA deceptive person is said to have a forked tongue, and a smooth-talking person said to have a silver tongue.\n\n=== Gestures ===\n\nSticking one's tongue out at someone is considered a childish gesture of rudeness or defiance in many countries; the act may also have sexual connotations, depending on the way in which it is done.\n\nHowever, in Tibet it is considered a greeting.\n\nIn 2009, a farmer from Fabriano, Italy, was convicted and fined by the country's highest court for sticking his tongue out at a neighbor with whom he had been arguing.\n\nProof of the affront had been captured with a cell phone camera.\n\n=== Body art ===\n\nTongue piercing and splitting have become more common in western countries in recent decades.\n\nIn one study, one-fifth of young adults were found to have at least one type of oral piercing, most commonly the tongue.\n\n=== As food ===\n\nThe tongues of some animals are consumed and sometimes considered delicacies.\n\nHot tongue sandwiches are frequently found on menus in kosher delicatessens in America.\n\nTaco de lengua (lengua being Spanish for tongue) is a taco filled with beef tongue, and is especially popular in Mexican cuisine.\n\nAs part of Colombian gastronomy, Tongue in Sauce (Lengua en Salsa), is a dish prepared by frying the tongue, adding tomato sauce, onions and salt.\n\nTongue can also be prepared as birria.\n\nPig and beef tongue are consumed in Chinese cuisine.\n\nDuck tongues are sometimes employed in Szechuan dishes, while lamb's tongue is occasionally employed in Continental and contemporary American cooking.\n\nFried cod \"tongue\" is a relatively common part of fish meals in Norway and Newfoundland.\n\nIn Argentina and Uruguay cow tongue is cooked and served in vinegar (lengua a la vinagreta).\n\nIn the Czech Republic and Poland, a pork tongue is considered a delicacy, and there are many ways of preparing it.\n\nIn Eastern Slavic countries, pork and beef tongues are commonly consumed, boiled and garnished with horseradish or jelled; beef tongues fetch a significantly higher price and are considered more of a delicacy.\n\nIn Alaska, cow tongues are among the more common.\nTongues of seals and whales have been eaten, sometimes in large quantities, by sealers and whalers, and in various times and places have been sold for food on shore.\n\nhttps://en.wikipedia.org/wiki/Tongue","pharynx":"The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs).\n\nIt is found in vertebrates and invertebrates, though its structure varies across species.\n\nThe pharynx carries food and air to the esophagus and larynx respectively.\n\nThe flap of cartilage called the epiglottis stops food from entering the larynx.\nIn humans, the pharynx is part of the digestive system and the conducting zone of the respiratory system. (The conducting zone—which also includes the nostrils of the nose, the larynx, trachea, bronchi, and bronchioles—filters, warms and moistens air and conducts it into the lungs).\n\nThe human pharynx is conventionally divided into three sections: the nasopharynx, oropharynx, and laryngopharynx.\n\nIt is also important in vocalization.\nIn humans, two sets of pharyngeal muscles form the pharynx and determine the shape of its lumen.\n\nThey are arranged as an inner layer of longitudinal muscles and an outer circular layer.\n\n== Structure ==\n\n=== Nasopharynx ===\n\nThe upper portion of the pharynx, the nasopharynx, extends from the base of the skull to the upper surface of the soft palate.\n\nIt includes the space between the internal nares and the soft palate and lies above the oral cavity.\n\nThe adenoids, also known as the pharyngeal tonsils, are lymphoid tissue structures located in the posterior wall of the nasopharynx.\n\nWaldeyer's tonsillar ring is an annular arrangement of lymphoid tissue in both the nasopharynx and oropharynx.\n\nThe nasopharynx is lined by respiratory epithelium that is pseudostratified, columnar, and ciliated.\nPolyps or mucus can obstruct the nasopharynx, as can congestion due to an upper respiratory infection.\n\nThe auditory tube, which connects the middle ear to the pharynx, opens into the nasopharynx at the pharyngeal opening of the auditory tube.\n\nThe opening and closing of the auditory tubes serves to equalize the barometric pressure in the middle ear with that of the ambient atmosphere.\n\nThe anterior aspect of the nasopharynx communicates through the choanae with the nasal cavities.\n\nOn its lateral wall is the pharyngeal opening of the auditory tube, somewhat triangular in shape and bounded behind by a firm prominence, the torus tubarius or cushion, caused by the medial end of the cartilage of the tube that elevates the mucous membrane.\nTwo folds arise from the cartilaginous opening:\n\nthe salpingopharyngeal fold, a vertical fold of mucous membrane extending from the inferior part of the torus and containing the salpingopharyngeus muscle\nthe salpingopalatine fold, a smaller fold, in front of the salpingopharyngeal fold, extending from the superior part of the torus to the palate and containing the levator veli palatini muscle.\n\nIt also contains some muscle fibres called salpingopalatine muscle The tensor veli palatini is lateral to the levator and does not contribute to the fold, since the origin is deep to the cartilaginous opening.\n\n=== Oropharynx ===\n\nThe oropharynx lies behind the oral cavity, extending from the uvula to the level of the hyoid bone.\n\nIt opens anteriorly, through the isthmus faucium, into the mouth, while in its lateral wall, between the palatoglossal arch and the palatopharyngeal arch, is the palatine tonsil.\n\nThe anterior wall consists of the base of the tongue and the epiglottic vallecula; the lateral wall is made up of the tonsil, tonsillar fossa, and tonsillar (faucial) pillars; the superior wall consists of the inferior surface of the soft palate and the uvula.\n\nBecause both food and air pass through the pharynx, a flap of connective tissue called the epiglottis closes over the glottis when food is swallowed to prevent aspiration.\n\nThe oropharynx is lined by non-keratinized squamous stratified epithelium.\nThe HACEK organisms (Haemophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella) are part of the normal oropharyngeal flora, which grow slowly, prefer a carbon dioxide-enriched atmosphere, and share an enhanced capacity to produce endocardial infections, especially in young children.\n\nFusobacterium is a pathogen.\n\n=== Laryngopharynx ===\n\nThe laryngopharynx, (Latin: pars laryngea pharyngis), also known as hypopharynx, is the caudal part of the pharynx; it is the part of the throat that connects to the esophagus.\n\nIt lies inferior to the epiglottis and extends to the location where this common pathway diverges into the respiratory (laryngeal) and digestive (esophageal) pathways.\n\nAt that point, the laryngopharynx is continuous with the esophagus posteriorly.\n\nThe esophagus conducts food and fluids to the stomach; air enters the larynx anteriorly.\n\nDuring swallowing, food has the \"right of way\", and air passage temporarily stops.\n\nCorresponding roughly to the area located between the 4th and 6th cervical vertebrae, the superior boundary of the laryngopharynx is at the level of the hyoid bone.\n\nThe laryngopharynx includes three major sites: the pyriform sinus, postcricoid area, and the posterior pharyngeal wall.\n\nLike the oropharynx above it, the laryngopharynx serves as a passageway for food and air and is lined with a stratified squamous epithelium.\n\nIt is innervated by the pharyngeal plexus.\nThe vascular supply to the laryngopharynx includes the superior thyroid artery, the lingual artery and the ascending pharyngeal artery.\n\nThe primary neural supply is from both the vagus and glossopharyngeal nerves.\n\nThe vagus nerve provides an auricular branch also termed \"Arnold's nerve\" which also supplies the external auditory canal, thus laryngopharyngeal cancer can result in referred ear pain.\n\nThis nerve is also responsible for the ear-cough reflex in which stimulation of the ear canal results in a person coughing.\n\n== Function ==\n\nThe pharynx moves food from the mouth to the esophagus.\n\nIt also moves air from the nasal and oral cavities to the larynx.\n\nIt is also used in human speech; pharyngeal consonants are articulated here.\n\n== Clinical significance ==\n\n=== Inflammation ===\n\nInflammation of the pharynx, or pharyngitis, is the painful inflammation of the throat.\n\n=== Pharyngeal cancer ===\n\nPharyngeal cancer is a cancer that originates in the neck and/or throat.\n\n=== Waldeyer's tonsillar ring ===\n\nWaldeyer's tonsillar ring is an anatomical term collectively describing the annular arrangement of lymphoid tissue in the pharynx.\n\nWaldeyer's ring circumscribes the naso- and oropharynx, with some of its tonsillar tissue located above and some below the soft palate (and to the back of the oral cavity).\n\nIt is believed that Waldeyer's ring prevents the invasion of microorganisms from going into the air and food passages and this helps in the defense mechanism of the respiratory and alimentary systems.\n\n== History ==\n\n=== Etymology ===\n\nThe word pharynx () is derived from the Greek φάρυγξ phárynx, meaning \"throat\".\n\nIts plural form is pharynges or pharynxes , and its adjective form is pharyngeal ( or ).\n\n== Other vertebrates ==\n\nAll vertebrates have a pharynx, used in both feeding and respiration.\n\nThe pharynx arises during development in all vertebrates through a series of six or more outpocketings on the lateral sides of the head.\n\nThese outpocketings are pharyngeal arches, and they give rise to a number of different structures in the skeletal, muscular, and circulatory systems.\n\nThe structure of the pharynx varies across the vertebrates.\n\nIt differs in dogs, horses, and ruminants.\n\nIn dogs, a single duct connects the nasopharynx to the nasal cavity.\n\nThe tonsils are a compact mass that points away from the lumen of the pharynx.\n\nIn the horse, the auditory tube opens into the guttural pouch and the tonsils are diffuse and raised slightly.\n\nHorses are unable to breathe through the mouth as the free apex of the rostral epiglottis lies dorsal to the soft palate in a normal horse.\n\nIn ruminants the tonsils are a compact mass that points towards the lumen of the pharynx.\n\n=== Pharyngeal arches ===\n\nPharyngeal arches are characteristic features of vertebrates whose origin can be traced back through chordates to basal deuterostomes who also share endodermal outpocketings of the pharyngeal apparatus.\n\nSimilar patterns of gene expression can be detected in the developing pharynx of amphioxi and hemichordates.\n\nHowever, the vertebrate pharynx is unique in that it gives rise to endoskeletal support through the contribution of neural crest cells.\n\n=== Pharyngeal jaws ===\n\nPharyngeal jaws are a \"second set\" of jaws contained within the pharynx of many species of fish, distinct from the primary (oral) jaws.\n\nPharyngeal jaws have been studied in moray eels where their specific action is noted.\n\nWhen the moray bites prey, it first bites normally with its oral jaws, capturing the prey.\n\nImmediately thereafter, the pharyngeal jaws are brought forward and bite down on the prey to grip it; they then retract, pulling the prey down the eel's esophagus, allowing it to be swallowed.\n\n== Invertebrates ==\n\nInvertebrates also have a pharynx.\n\nInvertebrates with a pharynx include the tardigrades, annelids and arthropods, and the priapulids (which have an eversible pharynx).The \"pharynx\" of the nematode worm is a muscular food pump in the head, triangular in cross-section, that grinds food and transports it directly to the intestines.\n\nA one-way valve connects the pharynx to the excretory canal.\n\nhttps://en.wikipedia.org/wiki/Pharynx","stomach":"The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates.\n\nThe stomach has a dilated structure and functions as a vital digestive organ.\n\nIn the digestive system the stomach is involved in the second phase of digestion, following chewing.\n\nIt performs a chemical breakdown by means of enzymes and hydrochloric acid.\nIn humans and many other animals, the stomach is located between the oesophagus and the small intestine.\n\nThe stomach secretes digestive enzymes and gastric acid to aid in food digestion.\n\nThe pyloric sphincter controls the passage of partially digested food (chyme) from the stomach into the duodenum, where peristalsis takes over to move this through the rest of intestines.\n\n== Structure ==\n\nIn humans, the stomach lies between the oesophagus and the duodenum (the first part of the small intestine).\n\nIt is in the left upper part of the abdominal cavity.\n\nThe top of the stomach lies against the diaphragm.\n\nLying behind the stomach is the pancreas.\n\nA large double fold of visceral peritoneum called the greater omentum hangs down from the greater curvature of the stomach.\n\nTwo sphincters keep the contents of the stomach contained; the lower oesophageal sphincter (found in the cardiac region), at the junction of the oesophagus and stomach, and the pyloric sphincter at the junction of the stomach with the duodenum.\n\nThe stomach is surrounded by parasympathetic (stimulant) and sympathetic (inhibitor) plexuses (networks of blood vessels and nerves in the anterior gastric, posterior, superior and inferior, celiac and myenteric), which regulate both the secretory activity of the stomach and the motor (motion) activity of its muscles.\n\nBecause it is a distensible organ, it normally expands to hold about one litre of food.\n\nThe stomach of a newborn human baby will only be able to retain about 30 millilitres.\n\nThe maximum stomach volume in adults is between 2 and 4 litres.\n\n=== Sections ===\n\nIn classical anatomy the human stomach is divided into four sections, beginning at the cardia.\n\nThe cardia is where the contents of the esophagus empty into the stomach.\n\nThe fundus (from Latin 'bottom') is formed in the upper curved part.\nThe body is the main, central region of the stomach.\n\nThe pylorus (from Greek 'gatekeeper') is the lower section of the stomach that empties contents into the duodenum.\n\nThe cardia is defined as the region following the \"z-line\" of the gastroesophageal junction, the point at which the epithelium changes from stratified squamous to columnar.\n\nNear the cardia is the lower oesophageal sphincter.\n\nRecent research has shown that the cardia is not an anatomically distinct region of the stomach but a region of the oesophageal lining damaged by reflux.\n\n=== Anatomical proximity ===\n\nThe stomach bed refers to the structures upon which the stomach rests in mammals.\n\nThese include the pancreas, spleen, left kidney, left suprarenal gland, transverse colon and its mesocolon, and the diaphragm.\n\nThe term was introduced around 1896 by Philip Polson of the Catholic University School of Medicine, Dublin.\n\nHowever this was brought into disrepute by surgeon anatomist J Massey.\n\n=== Blood supply ===\n\nThe lesser curvature of the human stomach is supplied by the right gastric artery inferiorly and the left gastric artery superiorly, which also supplies the cardiac region.\n\nThe greater curvature is supplied by the right gastroepiploic artery inferiorly and the left gastroepiploic artery superiorly.\n\nThe fundus of the stomach, and also the upper portion of the greater curvature, is supplied by the short gastric arteries, which arise from the splenic artery.\n\n=== Microanatomy ===\n\n==== Wall ====\n\nLike the other parts of the gastrointestinal tract, the human stomach walls consist of a mucosa, submucosa, muscularis externa, subserosa and serosa.\n\nThe inner part of the lining of the stomach, the gastric mucosa, consists of an outer layer of column-shaped cells, a lamina propria, and a thin layer of smooth muscle called the muscularis mucosa.\n\nBeneath the mucosa lies the submucosa, consisting of fibrous connective tissue.\n\nMeissner's plexus is in this layer interior to the oblique muscle layer.Outside of the submucosa lies another muscular layer, the muscularis externa.\n\nIt consists of three layers of muscular fibres, with fibres lying at angles to each other.\n\nThese are the inner oblique, middle circular, and outer longitudinal layers.\n\nThe presence of the inner oblique layer is distinct from other parts of the gastrointestinal tract, which do not possess this layer.\n\nStomach contains the thickest muscularis layer consisting of three layers, thus maximum peristalsis occurs here.\n\nThe inner oblique layer: This layer is responsible for creating the motion that churns and physically breaks down the food.\n\nIt is the only layer of the three which is not seen in other parts of the digestive system.\n\nThe antrum has thicker skin cells in its walls and performs more forceful contractions than the fundus.\n\nThe middle circular layer: At this layer, the pylorus is surrounded by a thick circular muscular wall, which is normally tonically constricted, forming a functional (if not anatomically discrete) pyloric sphincter, which controls the movement of chyme into the duodenum.\n\nThis layer is concentric to the longitudinal axis of the stomach.\n\nAuerbach's plexus (myenteric plexus) is found between the outer longitudinal and the middle circular layer and is responsible for the innervation of both (causing peristalsis and mixing).\n\nThe outer longitudinal layer is responsible for moving the bolus towards the pylorus of the stomach through muscular shortening.\n\nTo the outside of the muscularis externa lies a serosa, consisting of layers of connective tissue continuous with the peritoneum.\n\n==== Glands ====\n\nThe mucosa lining the stomach is lined with a number of these pits, which receive gastric juice, secreted by between 2 and 7 gastric glands.\n\nGastric juice is an acidic fluid containing hydrochloric acid and the digestive enzyme pepsin.\n\nThe glands contains a number of cells, with the function of the glands changing depending on their position within the stomach.\n\nWithin the body and fundus of the stomach lie the fundic glands.\n\nIn general, these glands are lined by column-shaped cells that secrete a protective layer of mucus and bicarbonate.\n\nAdditional cells present include parietal cells that secrete hydrochloric acid and intrinsic factor, chief cells that secrete pepsinogen (this is a precursor to pepsin- the highly acidic environment converts the pepsinogen to pepsin), and neuroendocrine cells that secrete serotonin.Glands differ where the stomach meets the esophagus and near the pylorus.\n\nNear the junction between the stomach and the oesophagus lie cardiac glands, which primarily secrete mucus.\n\nThey are fewer in number than the other gastric glands and are more shallowly positioned in the mucosa.\n\nThere are two kinds - either simple tubular with short ducts or compound racemose resembling the duodenal Brunner's glands.\n\nNear the pylorus lie pyloric glands located in the antrum of the pylorus.\n\nThey secrete mucus, as well as gastrin produced by their G cells.\n\n=== Gene and protein expression ===\n\nAbout 20,000 protein coding genes are expressed in human cells and nearly 70% of these genes are expressed in the normal stomach.\n\nJust over 150 of these genes are more specifically expressed in the stomach compared to other organs, with only some 20 genes being highly specific.\n\nThe corresponding specific proteins expressed in stomach are mainly involved in creating a suitable environment for handling the digestion of food for uptake of nutrients.\n\nHighly stomach-specific proteins include GKN1, expressed in the mucosa; pepsinogen PGC and the lipase LIPF, expressed in chief cells; and gastric ATPase ATP4A and gastric intrinsic factor GIF, expressed in parietal cells.\n\n== Development ==\n\nIn early human embryogenesis, the ventral part of the embryo abuts the yolk sac.\n\nDuring the third week of development, as the embryo grows, it begins to surround parts of the sac.\n\nThe enveloped portions form the basis for the adult gastrointestinal tract.\n\nThe sac is surrounded by a network of vitelline arteries and veins.\n\nOver time, these arteries consolidate into the three main arteries that supply the developing gastrointestinal tract: the celiac artery, superior mesenteric artery, and inferior mesenteric artery.\n\nThe areas supplied by these arteries are used to define the foregut, midgut, and hindgut.\n\nThe surrounded sac becomes the primitive gut.\n\nSections of this gut begin to differentiate into the organs of the gastrointestinal tract, and the esophagus, and stomach form from the foregut.\n\n== Function ==\n\n=== Digestion ===\n\nIn the human digestive system, a bolus (a small rounded mass of chewed up food) enters the stomach through the esophagus via the lower esophageal sphincter.\n\nThe stomach releases proteases (protein-digesting enzymes such as pepsin) and hydrochloric acid, which kills or inhibits bacteria and provides the acidic pH of 2 for the proteases to work.\n\nFood is churned by the stomach through muscular contractions of the wall called peristalsis – reducing the volume of the bolus, before looping around the fundus and the body of stomach as the boluses are converted into chyme (partially digested food).\n\nChyme slowly passes through the pyloric sphincter and into the duodenum of the small intestine, where the extraction of nutrients begins.\n\nGastric juice in the stomach also contains pepsinogen.\n\nHydrochloric acid activates this inactive form of enzyme into the active form, pepsin.\n\nPepsin breaks down proteins into polypeptides.\n\n=== Absorption ===\n\nAlthough the absorption in the human digestive system is mainly a function of the small intestine, some absorption of certain small molecules nevertheless does occur in the stomach through its lining.\n\nThis includes:\n\nWater, if the body is dehydrated\nMedication, such as aspirin\nAmino acids\n10–20% of ingested ethanol (e.g. from alcoholic beverages)\nCaffeine\nTo a small extent water-soluble vitamins (most are absorbed in the small intestine)\nThe parietal cells of the human stomach are responsible for producing intrinsic factor, which is necessary for the absorption of vitamin B12.\n\nB12 is used in cellular metabolism and is necessary for the production of red blood cells, and the functioning of the nervous system.\n\n=== Control of secretion and motility ===\n\nThe movement and the flow of chemicals into the stomach are controlled by both the autonomic nervous system and by the various digestive hormones of the digestive system:\n\nOther than gastrin, these hormones all act to turn off the stomach action.\n\nThis is in response to food products in the liver and gall bladder, which have not yet been absorbed.\n\nThe stomach needs to push food into the small intestine only when the intestine is not busy.\n\nWhile the intestine is full and still digesting food, the stomach acts as storage for food.\n\n=== Other ===\n\nEffects of EGFEpidermal growth factor (EGF) results in cellular proliferation, differentiation, and survival.\n\nEGF is a low-molecular-weight polypeptide first purified from the mouse submandibular gland, but since then found in many human tissues including the submandibular gland, and the parotid gland.\n\nSalivary EGF, which also seems to be regulated by dietary inorganic iodine, also plays an important physiological role in the maintenance of oro-oesophageal and gastric tissue integrity.\n\nThe biological effects of salivary EGF include healing of oral and gastroesophageal ulcers, inhibition of gastric acid secretion, stimulation of DNA synthesis, and mucosal protection from intraluminal injurious factors such as gastric acid, bile acids, pepsin, and trypsin and from physical, chemical, and bacterial agents.\n\nStomach as nutrition sensorThe human stomach can \"taste\" sodium glutamate using glutamate receptors and this information is passed to the lateral hypothalamus and limbic system in the brain as a palatability signal through the vagus nerve.\n\nThe stomach can also sense, independently of tongue and oral taste receptors, glucose, carbohydrates, proteins, and fats.\n\nThis allows the brain to link nutritional value of foods to their tastes.\nThyrogastric syndromeThis syndrome defines the association between thyroid disease and chronic gastritis, which was first described in the 1960s.\n\nThis term was coined also to indicate the presence of thyroid autoantibodies or autoimmune thyroid disease in patients with pernicious anemia, a late clinical stage of atrophic gastritis.\n\nIn 1993, has been published a more complete investigation on the stomach and thyroid, reporting that the thyroid is, embryogenetically and phylogenetically, derived from primitive stomach, and that the thyroid cells, such as primitive gastroenteric cells, during vertebrate evolution, migrated and specialized in uptake of iodide and in storage and elaboration of iodine compounds.\n\nIn fact, stomach and thyroid share iodine-concentranting ability and many morphological and functional similarities, such as cell polarity and apical microvilli, similar organ-specific antigens and associated autoimmune diseases, secretion of glycoproteins (thyroglobulin and mucin) and peptide hormones, the digesting and readsorbing ability, and lastly, similar ability to form iodotyrosines by peroxidase activity, where iodide acts as an electron donor in the presence of H2O2.\n\nIn the following years, many researchers published reviews about this syndrome.\n\n== Clinical significance ==\n\n=== Diseases ===\n\nA series of radiographs can be used to examine the stomach for various disorders.\n\nThis will often include the use of a barium swallow.\n\nAnother method of examination of the stomach, is the use of an endoscope.\n\nA gastric emptying scan is considered the gold standard to assess gastric emptying rate.A large number of studies have indicated that most cases of peptic ulcers, and gastritis, in humans are caused by Helicobacter pylori infection, and an association has been seen with the development of stomach cancer.A stomach rumble is actually noise from the intestines.\n\n=== Surgery ===\n\nIn humans, many bariatric surgery procedures involve the stomach, in order to lose weight.\n\nA gastric band may be placed around the cardia area, which can adjust to limit intake.\n\nThe anatomy of the stomach may be modified, or the stomach may be bypassed entirely.\n\nSurgical removal of the stomach is called a gastrectomy, and removal of the cardia area is a called a cardiectomy. \"Cardiectomy\" is a term that is also used to describe the removal of the heart.\n\nA gastrectomy may be carried out because of gastric cancer or severe perforation of the stomach wall.\n\nFundoplication is stomach surgery in which the fundus is wrapped around the lower esophagus and stitched into place.\n\nIt is used to treat gastroesophageal reflux disease (GERD).\n\n== History ==\n\nThere were previously conflicting statements in the academic anatomy community over whether the cardia is part of the stomach, part of the oesophagus or a distinct entity.\n\nModern surgical and medical textbooks have agreed that \"the gastric cardia is now clearly considered to be part of the stomach.\"\n\n=== Etymology ===\n\nThe word stomach is derived from the Latin stomachus which has roots from the Greek word stomachos (στόμαχος), ultimately from stoma (στόμα), \"mouth\".\n\nGastro- and gastric (meaning \"related to the stomach\") are both derived from the Greek word gaster (γαστήρ, meaning \"belly\").\n\n== Other animals ==\n\nAlthough the precise shape and size of the stomach varies widely among different vertebrates, the relative positions of the oesophageal and duodenal openings remain relatively constant.\n\nAs a result, the organ always curves somewhat to the left before curving back to meet the pyloric sphincter.\n\nHowever, lampreys, hagfishes, chimaeras, lungfishes, and some teleost fish have no stomach at all, with the oesophagus opening directly into the intestine.\n\nThese animals all consume diets that require little storage of food, no predigestion with gastric juices, or both.The gastric lining is usually divided into two regions, an anterior portion lined by fundic glands and a posterior portion lined with pyloric glands.\n\nCardiac glands are unique to mammals, and even then are absent in a number of species.\n\nThe distributions of these glands vary between species, and do not always correspond with the same regions as in humans.\n\nFurthermore, in many non-human mammals, a portion of the stomach anterior to the cardiac glands is lined with epithelium essentially identical to that of the oesophagus.\n\nRuminants, in particular, have a complex stomach, the first three chambers of which are all lined with oesophageal mucosa.\n\nIn birds and crocodilians, the stomach is divided into two regions.\n\nAnteriorly is a narrow tubular region, the proventriculus, lined by fundic glands, and connecting the true stomach to the crop.\n\nBeyond lies the powerful muscular gizzard, lined by pyloric glands, and, in some species, containing stones that the animal swallows to help grind up food.In insects there is also a crop.\n\nThe insect stomach is called the midgut.\nInformation about the stomach in echinoderms or molluscs can be found under the respective articles.\n\nhttps://en.wikipedia.org/wiki/Stomach","duodenum":"The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds.\n\nIn fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine may be used instead of duodenum.\n\nIn mammals the duodenum may be the principal site for iron absorption.\nThe duodenum precedes the jejunum and ileum and is the shortest part of the small intestine.\nIn humans, the duodenum is a hollow jointed tube about 25–38 cm (10–15 inches) long connecting the stomach to the jejunum.\n\nIt begins with the duodenal bulb and ends at the suspensory muscle of duodenum.\n\nIt can be divided into four parts.\n\n== Structure ==\n\nThe duodenum is a 25–38 cm (10-15 inch) C-shaped structure lying adjacent to the stomach.\n\nIt is divided anatomically into four sections.\n\nThe first part of the duodenum lies within the peritoneum but its other parts are retroperitoneal.: 273\n\n=== Parts ===\n\nThe first part, or superior part, of the duodenum is a continuation from the pylorus to transpyloric plane.\n\nIt is superior to the rest of the segments, at the vertebral level of L1.\n\nThe duodenal bulb, about 2 cm (0.79 in) long, is the first part of the duodenum and is slightly dilated.\n\nThe duodenal bulb is a remnant of the mesoduodenum, a mesentery that suspends the organ from the posterior abdominal wall in fetal life.\n\nThe first part of the duodenum is mobile, and connected to the liver by the hepatoduodenal ligament of the lesser omentum.\n\nThe first part of the duodenum ends at the corner, the superior duodenal flexure.: 273 Relations:\nAnterior\nGallbladder\nQuadrate lobe of liver\nPosterior\nBile duct\nGastroduodenal artery\nPortal vein\nInferior vena cava\nHead of pancreas\nSuperior\nNeck of gallbladder\nHepatoduodenal ligament (lesser omentum)\nInferior\nNeck of pancreas\nGreater omentum\nHead of pancreasThe second part, or descending part, of the duodenum begins at the superior duodenal flexure.\n\nIt goes inferior to the lower border of vertebral body L3, before making a sharp turn medially into the inferior duodenal flexure, the end of the descending part.: 274 The pancreatic duct and common bile duct enter the descending duodenum, through the major duodenal papilla.\n\nThe second part of the duodenum also contains the minor duodenal papilla, the entrance for the accessory pancreatic duct.\n\nThe junction between the embryological foregut and midgut lies just below the major duodenal papilla.: 274 The third part, or horizontal part or inferior part of the duodenum is 10~12 cm in length.\n\nIt begins at the inferior duodenal flexure and passes transversely to the left, passing in front of the inferior vena cava, abdominal aorta and the vertebral column.\n\nThe superior mesenteric artery and vein are anterior to the third part of duodenum.: 274  This part may be compressed between the aorta and SMA causing superior mesenteric artery syndrome.\nThe fourth part, or ascending part, of the duodenum passes upward, joining with the jejunum at the duodenojejunal flexure.\n\nThe fourth part of the duodenum is at the vertebral level L3, and may pass directly on top, or slightly to the left, of the aorta.: 274\n\n=== Blood supply ===\n\nThe duodenum receives arterial blood from two different sources.\n\nThe transition between these sources is important as it demarcates the foregut from the midgut.\n\nProximal to the 2nd part of the duodenum (approximately at the major duodenal papilla – where the bile duct enters) the arterial supply is from the gastroduodenal artery and its branch the superior pancreaticoduodenal artery.\n\nDistal to this point (the midgut) the arterial supply is from the superior mesenteric artery (SMA), and its branch the inferior pancreaticoduodenal artery supplies the 3rd and 4th sections.\nThe superior and inferior pancreaticoduodenal arteries (from the gastroduodenal artery and SMA respectively) form an anastomotic loop between the celiac trunk and the SMA; so there is potential for collateral circulation here.\nThe venous drainage of the duodenum follows the arteries.\n\nUltimately these veins drain into the portal system, either directly or indirectly through the splenic or superior mesenteric vein and then to portal vein .\n\n=== Lymphatic drainage ===\n\nThe lymphatic vessels follow the arteries in a retrograde fashion.\n\nThe anterior lymphatic vessels drain into the pancreatoduodenal lymph nodes located along the superior and inferior pancreatoduodenal arteries and then into the pyloric lymph nodes (along the gastroduodenal artery).\nThe posterior lymphatic vessels pass posterior to the head of the pancreas and drain into the superior mesenteric lymph nodes.\n\nEfferent lymphatic vessels from the duodenal lymph nodes ultimately pass into the celiac lymph nodes.\n\n=== Microanatomy ===\n\nUnder microscopy, the duodenum has a villous mucosa.\n\nThis is distinct from the mucosa of the pylorus, which directly joins to the duodenum.\n\nLike other structures of the gastrointestinal tract, the duodenum has a mucosa, submucosa, muscularis externa, and adventitia.\n\nGlands line the duodenum, known as Brunner's glands, which secrete mucus and bicarbonate in order to neutralise stomach acids.\n\nThese are distinct glands not found in the ileum or jejunum, the other parts of the small intestine. : 274–275\n\n=== Variation ===\n\n=== Gene and protein expression ===\n\nAbout 20,000 protein coding genes are expressed in human cells and 70% of these genes are expressed in the normal duodenum.\n\nSome 300 of these genes are more specifically expressed in the duodenum with very few genes expressed only in the duodenum.\n\nThe corresponding specific proteins are expressed in the duodenal mucosa, and many of these are also expressed in the small intestine, such as ANPEP, a digestive enzyme, ACE, an enzyme involved in control of blood pressure, and RBP2, a protein involved in the uptake of vitamin A.\n\n== Function ==\n\nThe duodenum is largely responsible for the breakdown of food in the small intestine, using enzymes.\n\nThe duodenum also regulates the rate of emptying of the stomach via hormonal pathways.\n\nSecretin and cholecystokinin are released from cells in the duodenal epithelium in response to acidic and fatty stimuli present there when the pylorus opens and emits gastric chyme into the duodenum for further digestion.\n\nThese cause the liver and gall bladder to release bile, and the pancreas to release bicarbonate and digestive enzymes such as trypsin, lipase and amylase into the duodenum as they are needed.\nThe villi of the duodenum have a leafy-looking appearance, which is a histologically identifiable structure.\n\nBrunner's glands, which secrete mucus, are found in the duodenum only.\n\nThe duodenum wall consists of a very thin layer of cells that form the muscularis mucosae.\n\n== Clinical significance ==\n\n=== Ulceration ===\n\nUlcers of the duodenum commonly occur because of infection by the bacteria Helicobacter pylori.\n\nThese bacteria, through a number of mechanisms, erode the protective mucosa of the duodenum, predisposing it to damage from gastric acids.\n\nThe first part of the duodenum is the most common location of ulcers since it is where the acidic chyme meets the duodenal mucosa before mixing with the alkaline secretions of the duodenum.\n\nDuodenal ulcers may cause recurrent abdominal pain and dyspepsia, and are often investigated using a urea breath test to test for the bacteria, and endoscopy to confirm ulceration and take a biopsy.\n\nIf managed, these are often managed through antibiotics that aim to eradicate the bacteria, and PPIs and antacids to reduce the gastric acidity.\n\n=== Celiac disease ===\n\nThe British Society of Gastroenterology (BSG) guidelines specify that a duodenal biopsy is required for the diagnosis of adult celiac disease.\n\nThe biopsy is ideally performed at a moment when the patient is on a gluten-containing diet.\n\n=== Cancer ===\n\nDuodenal cancer is a cancer in the first section of the small intestine.\n\nCancer of the duodenum is relatively rare compared to stomach cancer and colorectal cancer; Malignant tumors in the duodenum constitute only around 0.3 % of all the gastrointestinal tract tumors but around half of cancerous tissues that develop in the small intestine.\n\nIts histology is often observed to be adenocarcinoma, meaning that the cancerous tissue arises from glandular cells in the epithelial tissue lining the duodenum.\n\n=== Inflammation ===\n\nInflammation of the duodenum is referred to as duodenitis.\n\nThere are multiple known causes.\n\n== History ==\n\nThe name duodenum is from Medieval Latin, short for intestīnum duodēnum digitōrum, which may be translated: intestine of twelve finger-widths (in length), from Latin duodēnum, genitive pl. of duodēnī, twelve each, from duodecim, twelve.\n\nThe Latin phrase intestīnum duodēnum digitōrum is thought to be a loan-translation from the Greek word dodekadaktylon (δωδεκαδάκτυλον), literally \"twelve fingers long.\" The intestinal section was so called by Greek physician Herophilus (c.335–280 B.C.E.) for its length, about equal to the breadth of 12 fingers.\n\n== Accessory organs ==\n\nThe liver has so many functions but the main digestive function is making bile.\n\nThe gallbladder stores bile made from the liver.\n\nIt travels into the duodenum.\n\nThe pancreas makes enzymes that break down protein fat and carbohydrates.\n\nThe pancreas also makes bicarbonate which neutralizes the acid from the stomach.\n\n== Other animals ==\n\nThe duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds.\n\nIn fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine may be used instead of duodenum.\n\nIn mammals the duodenum may be the principal site for iron absorption.\n\nhttps://en.wikipedia.org/wiki/Duodenum","vermiform-appendix":"APPENDIX\n\nThe appendix (or vermiform appendix; also cecal [or caecal] appendix; vermix; or vermiform process) is a finger-like, blind-ended tube connected to the cecum, from which it develops in the embryo.\n\nThe cecum is a pouch-like structure of the large intestine, located at the junction of the small and the large intestines.\n\nThe term \"vermiform\" comes from Latin and means \"worm-shaped.\" The appendix used to be considered a vestigial organ, but this view has changed over the past decades.\n\nResearch suggests that the appendix may serve an important purpose.\n\nIn particular, it may serve as a reservoir for beneficial gut bacteria.\n\n== Structure ==\n\nThe human appendix averages 9 cm (3.5 in) in length but can range from 5 to 35 cm (2.0 to 13.8 in).\n\nThe diameter of the appendix is 6 mm (0.24 in), and more than 6 mm (0.24 in) is considered a thickened or inflamed appendix.\n\nThe longest appendix ever removed was 26 cm (10 in) long.\n\nThe appendix is usually located in the lower right quadrant of the abdomen, near the right hip bone.\n\nThe base of the appendix is located 2 cm (0.79 in) beneath the ileocecal valve that separates the large intestine from the small intestine.\n\nIts position within the abdomen corresponds to a point on the surface known as McBurney's point.\n\nThe appendix is connected to the mesentery in the lower region of the ileum, by a short region of the mesocolon known as the mesoappendix.\n\n=== Variation ===\n\nSome identical twins—known as mirror image twins—can have a mirror-imaged anatomy, a congenital condition with the appendix located in the lower left quadrant of the abdomen instead of the lower right.\n\nIntestinal malrotation may also cause displacement of the appendix to the left side.\n\nWhile the base of the appendix is typically located 2 cm (0.79 in) below the ileocecal valve, the tip of the appendix can be variably located—in the pelvis, outside the peritoneum or behind the cecum.\n\nThe prevalence of the different positions varies amongst populations with the retrocecal position being most common in Ghana and Sudan, with 67.3% and 58.3% occurrence respectively, in comparison to Iran and Bosnia where the pelvic position is most common, with 55.8% and 57.7% occurrence respectively.\n\nIn very rare cases, the appendix may not be present at all (laparotomies for suspected appendicitis have given a frequency of 1 in 100,000).Sometimes there is a semi-circular fold of mucous membrane at the opening of the appendix.\n\nThis valve of the vermiform appendix is also called Gerlach's valve.\n\n== Functions ==\n\n=== Maintaining gut flora ===\n\nAlthough it has been long accepted that the immune tissue surrounding the appendix and elsewhere in the gut—called gut-associated lymphoid tissue—carries out a number of important functions, explanations were lacking for the distinctive shape of the appendix and its apparent lack of specific importance and function as judged by an absence of side effects following its removal.\n\nTherefore, the notion that the appendix is only vestigial became widely held.\nWilliam Parker, Randy Bollinger, and colleagues at Duke University proposed in 2007 that the appendix serves as a haven for useful bacteria when illness flushes the bacteria from the rest of the intestines.\n\nThis proposition is based on an understanding that emerged by the early 2000s of how the immune system supports the growth of beneficial intestinal bacteria, in combination with many well-known features of the appendix, including its architecture, its location just below the normal one-way flow of food and germs in the large intestine, and its association with copious amounts of immune tissue.\n\nResearch performed at Winthrop–University Hospital showed that individuals without an appendix were four times as likely to have a recurrence of Clostridium difficile colitis.\n\nThe appendix, therefore, may act as a \"safe house\" for beneficial bacteria.\n\nThis reservoir of bacteria could then serve to repopulate the gut flora in the digestive system following a bout of dysentery or cholera or to boost it following a milder gastrointestinal illness.\n\n=== Immune and lymphatic systems ===\n\nThe appendix has been identified as an important component of mammalian mucosal immune function, particularly B cell-mediated immune responses and extrathymically derived T cells.\n\nThis structure helps in the proper movement and removal of waste matter in the digestive system, contains lymphatic vessels that regulate pathogens, and lastly, might even produce early defences that prevent deadly diseases.\n\nAdditionally, it is thought that this may provide more immune defences from invading pathogens and getting the lymphatic system's B and T cells to fight the viruses and bacteria that infect that portion of the bowel and training them so that immune responses are targeted and more able to reliably and less dangerously fight off pathogens.\n\nIn addition, there are different immune cells called innate lymphoid cells that function in the gut in order to help the appendix maintain digestive health.\n\nResearch also shows a positive correlation between the existence of appendix and the concentration of cecal lymphoid tissue, which supports that not only does the appendix evolve as a complex with the cecum but also has major immune benefits.\n\n== Clinical significance ==\n\nCommon diseases of the appendix (in humans) are appendicitis and carcinoid tumors (appendiceal carcinoid).\n\nAppendix cancer accounts for about 1 in 200 of all gastrointestinal malignancies.\n\nIn rare cases, adenomas are also present.\n\n=== Appendicitis ===\n\nAppendicitis is a condition characterized by inflammation of the appendix.\n\nPain often begins in the center of the abdomen, corresponding to the appendix's development as part of the embryonic midgut.\n\nThis pain is typically a dull, poorly localized, visceral pain.As the inflammation progresses, the pain begins to localize more clearly to the right lower quadrant, as the peritoneum becomes inflamed.\n\nThis peritoneal inflammation, or peritonitis, results in rebound tenderness (pain upon removal of pressure rather than application of pressure).\n\nIn particular, it presents at McBurney's point, 1/3 of the way along a line drawn from the anterior superior iliac spine to the umbilicus.\n\nTypically, point (skin) pain is not present until the parietal peritoneum is inflamed, as well.\n\nFever and an immune system response are also characteristic of appendicitis.\n\nOther signs and symptoms may include nausea and vomiting, low-grade fever that may get worse, constipation or diarrhea, abdominal bloating, or flatulence.Appendicitis usually requires the removal of the inflamed appendix, in an appendectomy either by laparotomy or laparoscopy.\n\nUntreated, the appendix may rupture, leading to peritonitis, followed by shock, and, if still untreated, death.Recently, practitioners reported good results in treating appendicitis without appendectomy.\n\nManaging appendicitis using only antibiotic treatment and cooling of the appendix was successful in first occurrence acute appendicitis without complication.\n\n=== Surgery ===\n\nThe surgical removal of the appendix is called an appendectomy.\n\nThis removal is normally performed as an emergency procedure when the patient is suffering from acute appendicitis.\n\nIn the absence of surgical facilities, intravenous antibiotics are used to delay or avoid the onset of sepsis.\n\nIn some cases, the appendicitis resolves completely; more often, an inflammatory mass forms around the appendix.\n\nThis is a relative contraindication to surgery.\nThe appendix is also used for the construction of an efferent urinary conduit, in an operation known as the Mitrofanoff procedure, in people with a neurogenic bladder.\n\nThe appendix is also used as a means to access the colon in children with paralysed bowels or major rectal sphincter problems.\n\nThe appendix is brought out to the skin surface and the child/parent can then attach a catheter and easily wash out the colon (via normal defaecation) using an appropriate solution.\n\n== History ==\n\nCharles Darwin suggested that the appendix was mainly used by earlier hominids for digesting fibrous vegetation, then evolved to take on a new purpose over time.\n\nThe very long cecum of some herbivorous animals, such as in the horse or the koala, appears to support this hypothesis.\n\nThe koala's cecum enables it to host bacteria that specifically help to break down cellulose.\n\nHuman ancestors may have also relied upon this system when they lived on a diet rich in foliage.\n\nAs people began to eat more easily digested foods, they may have become less reliant on cellulose-rich plants for energy.\n\nAs the cecum became less necessary for digestion, mutations that were previously deleterious (and would have hindered evolutionary progress) were no longer important, so the mutations survived.\n\nIt is suggested that these alleles became more frequent and the cecum continued to shrink.\n\nAfter millions of years, the once-necessary cecum degraded to be the appendix of modern humans.Dr.\n\nHeather F.\n\nSmith of Midwestern University and colleagues explained:\n\nRecently ... improved understanding of gut immunity has merged with current thinking in biological and medical science, pointing to an apparent function of the mammalian cecal appendix as a safe-house for symbiotic gut microbes, preserving the flora during times of gastrointestinal infection in societies without modern medicine.\n\nThis function is potentially a selective force for the evolution and maintenance of the appendix.\n\nThree morphotypes of cecal-appendices can be described among mammals based primarily on the shape of the cecum: a distinct appendix branching from a rounded or sac-like cecum (as in many primate species), an appendix located at the apex of a long and voluminous cecum (as in the rabbit, greater glider and Cape dune mole rat), and an appendix in the absence of a pronounced cecum (as in the wombat).\n\nIn addition, long narrow appendix-like structures are found in mammals that either lack an apparent cecum (as in monotremes) or lack a distinct junction between the cecum and appendix-like structure (as in the koala).\n\nA cecal appendix has evolved independently at least twice, and apparently represents yet another example of convergence in morphology between Australian marsupials and placentals in the rest of the world.\n\nAlthough the appendix has apparently been lost by numerous species, it has also been maintained for more than 80 million years in at least one clade.\n\nIn a 2013 paper, the appendix was found to have evolved at least 32 times (and perhaps as many as 38 times) and to have been lost no more than six times.\n\nA more recent study using similar methods on an updated database yielded similar, though less spectacular results, with at least 29 gains and at the most 12 losses (all of which were ambiguous), and this is still significantly asymmetrical.\n\nThis suggests that the cecal appendix has a selective advantage in many situations and argues strongly against its vestigial nature.\n\nThis complex evolutionary history of the appendix, along with a great heterogeneity in its evolutionary rate in various taxa, suggests that it is a recurrent trait.\n\nSuch a function may be useful in a culture lacking modern sanitation and healthcare practice, where diarrhea may be prevalent.\n\nCurrent epidemiological data on the cause of death in developed countries collected by the World Health Organization in 2001 show that acute diarrhea is now the fourth leading cause of disease-related death in developing countries (data summarized by The Bill and Melinda Gates Foundation).\n\nTwo of the other leading causes of death are expected to have exerted limited or no selection pressure.\n\nhttps://en.wikipedia.org/wiki/Appendix_(anatomy)","free-taenia":"The taeniae coli (also teniae coli or tenia coli) are three separate longitudinal ribbons (taeniae meaning ribbon in Latin) of smooth muscle on the outside of the ascending, transverse, descending and sigmoid colons.\n\nThey are visible and can be seen just below the serosa or fibrosa.\n\nThere are three teniae coli: mesocolic, free and omental taeniae coli.\n\nThe teniae coli contract lengthwise to produce the haustra, the bulges in the colon.\nThe bands converge at the root of the vermiform appendix.\n\nAt the rectosigmoid junction, the taeniae spread out and unite to form the longitudinal muscle layer.\n\nIn the caecum, the ascending colon, the descending colon and sigmoid colon the positions of these bands are fixed.\n\nThe taenia libera, is placed anteriorly in the caecum, ascending, descending and sigmoid colon, but is placed inferiorly in the transverse colon.\n\nThe taenia mesocolica is present on the posteromedial surface of caecum, ascending, descending and sigmoid colon, but is placed posteriorly on transverse colon at the site of attachment of transverse mesocolon.\n\nThe taenia omentalis is situated posterolaterally in caecum, ascending, descending and sigmoid colon, but is situated on the anterosuperior surface of transverse colon where layers three and four of the greater omentum meet the transverse colon.\n\nThis change in position is due to the twist in transverse colon.\n\nThese bands correspond to the outer layer of the muscularis externa, in other portions of the digestive tract.\n\nThe teniae coli are regulated by the sacral nerves of the spinal cord, which are under control of the parasympathetic nervous system.\n\n== Diverticulosis ==\n\nSpaces between the circular bands of taeniae are weak points in the bowel, and are the sites of diverticulosis.\n\nMost diverticulosis occur in the sigmoid colon as it is the segment with the highest intraluminal pressure.\n\nDiverticulosis does not occur in the rectum as the tenia coli become a continuous muscular layer.\n\nDiverticulosis can then become diverticulitis if the patient develops inflammation of the diverticulosis, this whole spectrum of disease is called diverticular disease.\n\nhttps://en.wikipedia.org/wiki/Taenia_coli","mesocolic-taenia":"The taeniae coli (also teniae coli or tenia coli) are three separate longitudinal ribbons (taeniae meaning ribbon in Latin) of smooth muscle on the outside of the ascending, transverse, descending and sigmoid colons.\n\nThey are visible and can be seen just below the serosa or fibrosa.\n\nThere are three teniae coli: mesocolic, free and omental taeniae coli.\n\nThe teniae coli contract lengthwise to produce the haustra, the bulges in the colon.\nThe bands converge at the root of the vermiform appendix.\n\nAt the rectosigmoid junction, the taeniae spread out and unite to form the longitudinal muscle layer.\n\nIn the caecum, the ascending colon, the descending colon and sigmoid colon the positions of these bands are fixed.\n\nThe taenia libera, is placed anteriorly in the caecum, ascending, descending and sigmoid colon, but is placed inferiorly in the transverse colon.\n\nThe taenia mesocolica is present on the posteromedial surface of caecum, ascending, descending and sigmoid colon, but is placed posteriorly on transverse colon at the site of attachment of transverse mesocolon.\n\nThe taenia omentalis is situated posterolaterally in caecum, ascending, descending and sigmoid colon, but is situated on the anterosuperior surface of transverse colon where layers three and four of the greater omentum meet the transverse colon.\n\nThis change in position is due to the twist in transverse colon.\n\nThese bands correspond to the outer layer of the muscularis externa, in other portions of the digestive tract.\n\nThe teniae coli are regulated by the sacral nerves of the spinal cord, which are under control of the parasympathetic nervous system.\n\n== Diverticulosis ==\n\nSpaces between the circular bands of taeniae are weak points in the bowel, and are the sites of diverticulosis.\n\nMost diverticulosis occur in the sigmoid colon as it is the segment with the highest intraluminal pressure.\n\nDiverticulosis does not occur in the rectum as the tenia coli become a continuous muscular layer.\n\nDiverticulosis can then become diverticulitis if the patient develops inflammation of the diverticulosis, this whole spectrum of disease is called diverticular disease.\n\nhttps://en.wikipedia.org/wiki/Taenia_coli","omental-taenia":"The taeniae coli (also teniae coli or tenia coli) are three separate longitudinal ribbons (taeniae meaning ribbon in Latin) of smooth muscle on the outside of the ascending, transverse, descending and sigmoid colons.\n\nThey are visible and can be seen just below the serosa or fibrosa.\n\nThere are three teniae coli: mesocolic, free and omental taeniae coli.\n\nThe teniae coli contract lengthwise to produce the haustra, the bulges in the colon.\nThe bands converge at the root of the vermiform appendix.\n\nAt the rectosigmoid junction, the taeniae spread out and unite to form the longitudinal muscle layer.\n\nIn the caecum, the ascending colon, the descending colon and sigmoid colon the positions of these bands are fixed.\n\nThe taenia libera, is placed anteriorly in the caecum, ascending, descending and sigmoid colon, but is placed inferiorly in the transverse colon.\n\nThe taenia mesocolica is present on the posteromedial surface of caecum, ascending, descending and sigmoid colon, but is placed posteriorly on transverse colon at the site of attachment of transverse mesocolon.\n\nThe taenia omentalis is situated posterolaterally in caecum, ascending, descending and sigmoid colon, but is situated on the anterosuperior surface of transverse colon where layers three and four of the greater omentum meet the transverse colon.\n\nThis change in position is due to the twist in transverse colon.\n\nThese bands correspond to the outer layer of the muscularis externa, in other portions of the digestive tract.\n\nThe teniae coli are regulated by the sacral nerves of the spinal cord, which are under control of the parasympathetic nervous system.\n\n== Diverticulosis ==\n\nSpaces between the circular bands of taeniae are weak points in the bowel, and are the sites of diverticulosis.\n\nMost diverticulosis occur in the sigmoid colon as it is the segment with the highest intraluminal pressure.\n\nDiverticulosis does not occur in the rectum as the tenia coli become a continuous muscular layer.\n\nDiverticulosis can then become diverticulitis if the patient develops inflammation of the diverticulosis, this whole spectrum of disease is called diverticular disease.\n\nhttps://en.wikipedia.org/wiki/Taenia_coli","sigmoid-colon":"The sigmoid colon (or pelvic colon) is the part of the large intestine that is closest to the rectum and anus.\n\nIt forms a loop that averages about 35–40 centimetres (14–16 in) in length.\n\nThe loop is typically shaped like a Greek letter sigma (ς) or Latin letter S (thus sigma + -oid).\n\nThis part of the colon normally lies within the pelvis, but due to its freedom of movement it is liable to be displaced into the abdominal cavity.\n\n== Structure ==\n\nThe sigmoid colon begins at the superior aperture of the lesser pelvis, where it is continuous with the iliac colon, and passes transversely across the front of the sacrum to the right side of the pelvis.\n\nIt then curves on itself and turns toward the left to reach the middle line at the level of the third piece of the sacrum, where it bends downward and ends in the rectum.\n\nIts function is to expel solid and gaseous waste from the gastrointestinal tract.\n\nThe curving path it takes toward the anus allows it to store gas in the superior arched portion, enabling the colon to expel gas without excreting faeces simultaneously.\n\n=== Coverings ===\n\nThe sigmoid colon is completely surrounded by peritoneum (and thus is not retroperitoneal), which forms a mesentery (sigmoid mesocolon), which diminishes in length from the center toward the ends of the loop, where it disappears, so that the loop is fixed at its junctions with the iliac colon and rectum, but enjoys a considerable range of movement in its central portion.\n\n=== Nerve supply ===\n\nPelvic splanchnic nerves are the primary source for parasympathetic innervation.\n\nLumbar splanchnic nerves provide sympathetic innervation via the inferior mesenteric ganglion.\n\n=== Relations ===\n\nBehind the sigmoid colon are the external iliac vessels, ovary, obturator nerve, the left Piriformis, and left sacral plexus of nerves.\n\nIn front, it is separated from the bladder in the male, and the uterus in the female, by some coils of the small intestine.\n\n== Clinical significance ==\n\nDiverticulosis often occurs in the sigmoid colon in association with increased intraluminal pressure and focal weakness in the colonic wall.\n\nIt is a common cause of hematochezia.\nVolvulus occurs when a portion of the bowel twists around its mesentery, which can lead to obstruction and infarction.\n\nVolvulus in the elderly commonly occurs in the sigmoid colon, whereas in infants and children it is more likely to occur in the midgut.\n\nThis may correct itself spontaneously or the rotation may continue until the blood supply of the gut is cut off completely.\n\nhttps://en.wikipedia.org/wiki/Sigmoid_colon","ascending-colon":"LARGE INTESTINE\n\nThe large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the digestive system in vertebrates.\n\nWater is absorbed here and the remaining waste material is stored as feces before being removed by defecation.\n\nThe colon is the largest portion of the large intestine, so many mentions of the large intestine and colon overlap in meaning whenever precision is not the focus.\n\nMost sources define the large intestine as the combination of the cecum, colon, rectum, and anal canal.\n\nSome other sources exclude the anal canal.\n\nIn humans, the large intestine begins in the right iliac region of the pelvis, just at or below the waist, where it is joined to the end of the small intestine at the cecum, via the ileocecal valve.\n\nIt then continues as the colon ascending the abdomen, across the width of the abdominal cavity as the transverse colon, and then descending to the rectum and its endpoint at the anal canal.\n\nOverall, in humans, the large intestine is about 1.5 metres (5 ft) long, which is about one-fifth of the whole length of the gastrointestinal tract.\n\n== Structure ==\n\nThe colon is the last part of the digestive system.\n\nIt has a segmented appearance due to a series of saccules called haustra.\n\nIt extracts water and salt from solid wastes before they are eliminated from the body and is the site in which flora-aided (largely bacterial) fermentation of unabsorbed material occurs.\n\nUnlike the small intestine, the colon does not play a major role in absorption of foods and nutrients.\n\nAbout 1.5 litres or 45 ounces of water arrives in the colon each day.The length of the average adult human colon is 65 inches or 166 cm (range of 80 to 313 cm) for males, and 61 inches or 155 cm (range of 80 to 214 cm) for females.\n\n=== Sections ===\n\nIn mammals, the colon consists of six sections: the cecum, the ascending colon, the transverse colon, the descending colon, the sigmoid colon, and the rectum.Sections of the colon are:\n\nThe cecum including the appendix\nThe ascending colon\nThe transverse colon including the colic flexures and transverse mesocolon\nThe descending colon\nThe sigmoid colon – the s-shaped region of the large intestine\nThe rectumThe parts of the colon are either intraperitoneal or behind it in the retroperitoneum.\n\nRetroperitoneal organs, in general, do not have a complete covering of peritoneum, so they are fixed in location.\n\nIntraperitoneal organs are completely surrounded by peritoneum and are therefore mobile.\n\nOf the colon, the ascending colon, descending colon and rectum are retroperitoneal, while the cecum, appendix, transverse colon and sigmoid colon are intraperitoneal.\n\nThis is important as it affects which organs can be easily accessed during surgery, such as a laparotomy.\n\nIn terms of diameter, the cecum is the widest, averaging slightly less than 9 cm in healthy individuals, and the transverse colon averages less than 6 cm in diameter.\n\nThe descending and sigmoid colon are slightly smaller, with the sigmoid colon averaging 4–5 cm (1.6–2.0 in) in diameter.\n\nDiameters larger than certain thresholds for each colonic section can be diagnostic for megacolon.\n\n==== Cecum and appendix ====\n\nThe cecum is the first section of the colon and involved in the digestion, while the appendix which develops embryologically from it, is a structure of the colon, not involved in digestion and considered to be part of the gut-associated lymphoid tissue.\n\nThe function of the appendix is uncertain, but some sources believe that the appendix has a role in housing a sample of the colon's microflora, and is able to help to repopulate the colon with bacteria if the microflora has been damaged during the course of an immune reaction.\n\nThe appendix has also been shown to have a high concentration of lymphatic cells.\n\n==== Ascending colon ====\n\nThe ascending colon is the first of four main sections of the large intestine.\n\nIt is connected to the small intestine by a section of bowel called the cecum.\n\nThe ascending colon runs upwards through the abdominal cavity toward the transverse colon for approximately eight inches (20 cm).\n\nOne of the main functions of the colon is to remove the water and other key nutrients from waste material and recycle it.\n\nAs the waste material exits the small intestine through the ileocecal valve, it will move into the cecum and then to the ascending colon where this process of extraction starts.\n\nThe waste material is pumped upwards toward the transverse colon by peristalsis.\n\nThe ascending colon is sometimes attached to the appendix via Gerlach's valve.\n\nIn ruminants, the ascending colon is known as the spiral colon.\nTaking into account all ages and sexes, colon cancer occurs here most often (41%).\n\n==== Transverse colon ====\n\nThe transverse colon is the part of the colon from the hepatic flexure, also known as the right colic, (the turn of the colon by the liver) to the splenic flexure also known as the left colic, (the turn of the colon by the spleen).\n\nThe transverse colon hangs off the stomach, attached to it by a large fold of peritoneum called the greater omentum.\n\nOn the posterior side, the transverse colon is connected to the posterior abdominal wall by a mesentery known as the transverse mesocolon.\n\nThe transverse colon is encased in peritoneum, and is therefore mobile (unlike the parts of the colon immediately before and after it).\n\nThe proximal two-thirds of the transverse colon is perfused by the middle colic artery, a branch of the superior mesenteric artery (SMA), while the latter third is supplied by branches of the inferior mesenteric artery (IMA).\n\nThe \"watershed\" area between these two blood supplies, which represents the embryologic division between the midgut and hindgut, is an area sensitive to ischemia.\n\n==== Descending colon ====\n\nThe descending colon is the part of the colon from the splenic flexure to the beginning of the sigmoid colon.\n\nOne function of the descending colon in the digestive system is to store feces that will be emptied into the rectum.\n\nIt is retroperitoneal in two-thirds of humans.\n\nIn the other third, it has a (usually short) mesentery.\n\nThe arterial supply comes via the left colic artery.\n\nThe descending colon is also called the distal gut, as it is further along the gastrointestinal tract than the proximal gut.\n\nGut flora are very dense in this region.\n\n==== Sigmoid colon ====\n\nThe sigmoid colon is the part of the large intestine after the descending colon and before the rectum.\n\nThe name sigmoid means S-shaped (see sigmoid; cf. sigmoid sinus).\n\nThe walls of the sigmoid colon are muscular and contract to increase the pressure inside the colon, causing the stool to move into the rectum.\n\nThe sigmoid colon is supplied with blood from several branches (usually between 2 and 6) of the sigmoid arteries, a branch of the IMA.\n\nThe IMA terminates as the superior rectal artery.\n\nSigmoidoscopy is a common diagnostic technique used to examine the sigmoid colon.\n\n==== Rectum ====\n\nThe rectum is the last section of the large intestine.\n\nIt holds the formed feces awaiting elimination via defecation.\nIt is about 12 cm long.\n\n=== Appearance ===\n\nThe cecum – the first part of the large intestine\n\nTaeniae coli – three bands of smooth muscle\nHaustra – bulges caused by contraction of taeniae coli\nEpiploic appendages – small fat accumulations on the visceraThe taenia coli run the length of the large intestine.\n\nBecause the taenia coli are shorter than the large bowel itself, the colon becomes sacculated, forming the haustra of the colon which are the shelf-like intraluminal projections.\n\n=== Blood supply ===\n\nArterial supply to the colon comes from branches of the superior mesenteric artery (SMA) and inferior mesenteric artery (IMA).\n\nFlow between these two systems communicates via the marginal artery of the colon that runs parallel to the colon for its entire length.\n\nHistorically, a structure variously identified as the arc of Riolan or meandering mesenteric artery (of Moskowitz) was thought to connect the proximal SMA to the proximal IMA.\n\nThis variably present structure would be important if either vessel were occluded.\n\nHowever, at least one review of the literature questions the existence of this vessel, with some experts calling for the abolition of these terms from future medical literature.\n\nVenous drainage usually mirrors colonic arterial supply, with the inferior mesenteric vein draining into the splenic vein, and the superior mesenteric vein joining the splenic vein to form the hepatic portal vein that then enters the liver.\n\n=== Lymphatic drainage ===\n\nLymphatic drainage from the ascending colon and proximal two-thirds of the transverse colon is to the colic lymph nodes and the superior mesenteric lymph nodes, which drain into the cisterna chyli.\n\nThe lymph from the distal one-third of the transverse colon, the descending colon, the sigmoid colon, and the upper rectum drain into the inferior mesenteric and colic lymph nodes.\n\nThe lower rectum to the anal canal above the pectinate line drain to the internal iliac nodes.\n\nThe anal canal below the pectinate line drains into the superficial inguinal nodes.\n\nThe pectinate line only roughly marks this transition.\n\n=== Nerve supply ===\n\nSympathetic supply : Superior & inferior mesenteric ganglia\nParasympathetic supply : Vagus & pelvic nerves\n\n=== Development ===\n\n=== Variation ===\n\nOne variation on the normal anatomy of the colon occurs when extra loops form, resulting in a colon that is up to five metres longer than normal.\n\nThis condition, referred to as redundant colon, typically has no direct major health consequences, though rarely volvulus occurs, resulting in obstruction and requiring immediate medical attention.\n\nA significant indirect health consequence is that use of a standard adult colonoscope is difficult and in some cases impossible when a redundant colon is present, though specialized variants on the instrument (including the pediatric variant) are useful in overcoming this problem.\n\n== Microanatomy ==\n\n=== Colonic crypts ===\n\nThe wall of the large intestine is lined with simple columnar epithelium with invaginations.\n\nThe invaginations are called the intestinal glands or colonic crypts.\n\nThe colon crypts are shaped like microscopic thick walled test tubes with a central hole down the length of the tube (the crypt lumen).\n\nFour tissue sections are shown here, two cut across the long axes of the crypts and two cut parallel to the long axes.\n\nIn these images the cells have been stained by immunohistochemistry to show a brown-orange color if the cells produce a mitochondrial protein called cytochrome c oxidase subunit I (CCOI).\n\nThe nuclei of the cells (located at the outer edges of the cells lining the walls of the crypts) are stained blue-gray with haematoxylin.\n\nAs seen in panels C and D, crypts are about 75 to about 110 cells long.\n\nBaker et al. found that the average crypt circumference is 23 cells.\n\nThus, by the images shown here, there are an average of about 1,725 to 2,530 cells per colonic crypt.\n\nNooteboom et al. measuring the number of cells in a small number of crypts reported a range of 1,500 to 4,900 cells per colonic crypt.\n\nCells are produced at the crypt base and migrate upward along the crypt axis before being shed into the colonic lumen days later.\n\nThere are 5 to 6 stem cells at the bases of the crypts.As estimated from the image in panel A, there are about 100 colonic crypts per square millimeter of the colonic epithelium.\n\nSince the average length of the human colon is 160.5 cm and the average inner circumference of the colon is 6.2 cm, the inner surface epithelial area of the human colon has an average area of about 995 cm2, which includes 9,950,000 (close to 10 million) crypts.\n\nIn the four tissue sections shown here, many of the intestinal glands have cells with a mitochondrial DNA mutation in the CCOI gene and appear mostly white, with their main color being the blue-gray staining of the nuclei.\n\nAs seen in panel B, a portion of the stem cells of three crypts appear to have a mutation in CCOI, so that 40% to 50% of the cells arising from those stem cells form a white segment in the cross cut area.\n\nOverall, the percent of crypts deficient for CCOI is less than 1% before age 40, but then increases linearly with age.\n\nColonic crypts deficient for CCOI in women reaches, on average, 18% in women and 23% in men by 80–84 years of age.Crypts of the colon can reproduce by fission, as seen in panel C, where a crypt is fissioning to form two crypts, and in panel B where at least one crypt appears to be fissioning.\n\nMost crypts deficient in CCOI are in clusters of crypts (clones of crypts) with two or more CCOI-deficient crypts adjacent to each other (see panel D).\n\n==== Mucosa ====\n\nAbout 150 of the many thousands of protein coding genes expressed in the large intestine, some are specific to the mucous membrane in different regions and include CEACAM7.\n\n== Function ==\n\nThe large intestine absorbs water and any remaining absorbable nutrients from the food before sending the indigestible matter to the rectum.\n\nThe colon absorbs vitamins that are created by the colonic bacteria, such as thiamine, riboflavin, and vitamin K (especially important as the daily ingestion of vitamin K is not normally enough to maintain adequate blood coagulation).\n\nIt also compacts feces, and stores fecal matter in the rectum until it can be discharged via the anus in defecation.\n\nThe large intestine also secretes K+ and Cl-.\n\nChloride secretion increases in cystic fibrosis.\nRecycling of various nutrients takes place in colon.\n\nExamples include fermentation of carbohydrates, short chain fatty acids, and urea cycling.\n\nThe appendix contains a small amount of mucosa-associated lymphoid tissue which gives the appendix an undetermined role in immunity.\n\nHowever, the appendix is known to be important in fetal life as it contains endocrine cells that release biogenic amines and peptide hormones important for homeostasis during early growth and development.\n\nThe appendix can be removed with no apparent damage or consequence to the patient.By the time the chyme has reached this tube, most nutrients and 90% of the water have been absorbed by the body.\n\nAt this point some electrolytes like sodium, magnesium, and chloride are left as well as indigestible parts of ingested food (e.g., a large part of ingested amylose, starch which has been shielded from digestion heretofore, and dietary fiber, which is largely indigestible carbohydrate in either soluble or insoluble form).\n\nAs the chyme moves through the large intestine, most of the remaining water is removed, while the chyme is mixed with mucus and bacteria (known as gut flora), and becomes feces.\n\nThe ascending colon receives fecal material as a liquid.\n\nThe muscles of the colon then move the watery waste material forward and slowly absorb all the excess water, causing the stools to gradually solidify as they move along into the descending colon.\n\nThe bacteria break down some of the fiber for their own nourishment and create acetate, propionate, and butyrate as waste products, which in turn are used by the cell lining of the colon for nourishment.\n\nNo protein is made available.\n\nIn humans, perhaps 10% of the undigested carbohydrate thus becomes available, though this may vary with diet; in other animals, including other apes and primates, who have proportionally larger colons, more is made available, thus permitting a higher portion of plant material in the diet.\n\nThe large intestine produces no digestive enzymes — chemical digestion is completed in the small intestine before the chyme reaches the large intestine.\n\nThe pH in the colon varies between 5.5 and 7 (slightly acidic to neutral).\n\n=== Standing gradient osmosis ===\n\nWater absorption at the colon typically proceeds against a transmucosal osmotic pressure gradient.\n\nThe standing gradient osmosis is the reabsorption of water against the osmotic gradient in the intestines.\n\nCells occupying the intestinal lining pump sodium ions into the intercellular space, raising the osmolarity of the intercellular fluid.\n\nThis hypertonic fluid creates an osmotic pressure that drives water into the lateral intercellular spaces by osmosis via tight junctions and adjacent cells, which then in turn moves across the basement membrane and into the capillaries, while more sodium ions are pumped again into the intercellular fluid.\n\nAlthough water travels down an osmotic gradient in each individual step, overall, water usually travels against the osmotic gradient due to the pumping of sodium ions into the intercellular fluid.\n\nThis allows the large intestine to absorb water despite the blood in capillaries being hypotonic compared to the fluid within the intestinal lumen.\n\n=== Gut flora ===\n\nThe large intestine houses over 700 species of bacteria that perform a variety of functions, as well as fungi, protozoa, and archaea.\n\nSpecies diversity varies by geography and diet.\n\nThe microbes in a human distal gut often number in the vicinity of 100 trillion, and can weigh around 200 grams (0.44 pounds).\n\nThis mass of mostly symbiotic microbes has recently been called the latest human organ to be \"discovered\" or in other words, the \"forgotten organ\".\n\nThe large intestine absorbs some of the products formed by the bacteria inhabiting this region.\n\nUndigested polysaccharides (fiber) are metabolized to short-chain fatty acids by bacteria in the large intestine and absorbed by passive diffusion.\n\nThe bicarbonate that the large intestine secretes helps to neutralize the increased acidity resulting from the formation of these fatty acids.\n\nThese bacteria also produce large amounts of vitamins, especially vitamin K and biotin (a B vitamin), for absorption into the blood.\n\nAlthough this source of vitamins, in general, provides only a small part of the daily requirement, it makes a significant contribution when dietary vitamin intake is low.\n\nAn individual who depends on absorption of vitamins formed by bacteria in the large intestine may become vitamin-deficient if treated with antibiotics that inhibit the vitamin producing species of bacteria as well as the intended disease-causing bacteria.Other bacterial products include gas (flatus), which is a mixture of nitrogen and carbon dioxide, with small amounts of the gases hydrogen, methane, and hydrogen sulfide.\n\nBacterial fermentation of undigested polysaccharides produces these.\n\nSome of the fecal odor is due to indoles, metabolized from the amino acid tryptophan.\n\nThe normal flora is also essential in the development of certain tissues, including the cecum and lymphatics.\n\nThey are also involved in the production of cross-reactive antibodies.\n\nThese are antibodies produced by the immune system against the normal flora, that are also effective against related pathogens, thereby preventing infection or invasion.\n\nThe two most prevalent phyla of the colon are firmicutes and bacteroidetes.\n\nThe ratio between the two seems to vary widely as reported by the Human Microbiome Project.\n\nBacteroides are implicated in the initiation of colitis and colon cancer.\n\nBifidobacteria are also abundant, and are often described as 'friendly bacteria'.A mucus layer protects the large intestine from attacks from colonic commensal bacteria.\n\n== Clinical significance ==\n\n=== Disease ===\n\nFollowing are the most common diseases or disorders of the colon:\n\n=== Colonoscopy ===\n\nColonoscopy is the endoscopic examination of the large intestine and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus.\n\nIt can provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy or removal of suspected colorectal cancer lesions.\n\nColonoscopy can remove polyps as small as one millimetre or less.\n\nOnce polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not.\n\nIt takes 15 years or less for a polyp to turn cancerous.\nColonoscopy is similar to sigmoidoscopy—the difference being related to which parts of the colon each can examine.\n\nA colonoscopy allows an examination of the entire colon (1200–1500 mm in length).\n\nA sigmoidoscopy allows an examination of the distal portion (about 600 mm) of the colon, which may be sufficient because benefits to cancer survival of colonoscopy have been limited to the detection of lesions in the distal portion of the colon.\n\nA sigmoidoscopy is often used as a screening procedure for a full colonoscopy, often done in conjunction with a stool-based test such as a fecal occult blood test (FOBT), fecal immunochemical test (FIT), or multi-target stool DNA test (Cologuard) or blood-based test, SEPT9 DNA methylation test (Epi proColon).\n\nAbout 5% of these screened patients are referred to colonoscopy.\n\nVirtual colonoscopy, which uses 2D and 3D imagery reconstructed from computed tomography (CT) scans or from nuclear magnetic resonance (MR) scans, is also possible, as a totally non-invasive medical test, although it is not standard and still under investigation regarding its diagnostic abilities.\n\nFurthermore, virtual colonoscopy does not allow for therapeutic maneuvers such as polyp/tumour removal or biopsy nor visualization of lesions smaller than 5 millimeters.\n\nIf a growth or polyp is detected using CT colonography, a standard colonoscopy would still need to be performed.\n\nAdditionally, surgeons have lately been using the term pouchoscopy to refer to a colonoscopy of the ileo-anal pouch.\n\n== Other animals ==\n\nThe large intestine is truly distinct only in tetrapods, in which it is almost always separated from the small intestine by an ileocaecal valve.\n\nIn most vertebrates, however, it is a relatively short structure running directly to the anus, although noticeably wider than the small intestine.\n\nAlthough the caecum is present in most amniotes, only in mammals does the remainder of the large intestine develop into a true colon.\n\nIn some small mammals, the colon is straight, as it is in other tetrapods, but, in the majority of mammalian species, it is divided into ascending and descending portions; a distinct transverse colon is typically present only in primates.\n\nHowever, the taeniae coli and accompanying haustra are not found in either carnivorans or ruminants.\n\nThe rectum of mammals (other than monotremes) is derived from the cloaca of other vertebrates, and is, therefore, not truly homologous with the \"rectum\" found in these species.\n\nIn fish, there is no true large intestine, but simply a short rectum connecting the end of the digestive part of the gut to the cloaca.\n\nIn sharks, this includes a rectal gland that secretes salt to help the animal maintain osmotic balance with the seawater.\n\nThe gland somewhat resembles a caecum in structure but is not a homologous structure.\n\nhttps://en.wikipedia.org/wiki/Large_intestine","descending-colon":"LARGE INTESTINE\n\nThe large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the digestive system in vertebrates.\n\nWater is absorbed here and the remaining waste material is stored as feces before being removed by defecation.\n\nThe colon is the largest portion of the large intestine, so many mentions of the large intestine and colon overlap in meaning whenever precision is not the focus.\n\nMost sources define the large intestine as the combination of the cecum, colon, rectum, and anal canal.\n\nSome other sources exclude the anal canal.In humans, the large intestine begins in the right iliac region of the pelvis, just at or below the waist, where it is joined to the end of the small intestine at the cecum, via the ileocecal valve.\n\nIt then continues as the colon ascending the abdomen, across the width of the abdominal cavity as the transverse colon, and then descending to the rectum and its endpoint at the anal canal.\n\nOverall, in humans, the large intestine is about 1.5 metres (5 ft) long, which is about one-fifth of the whole length of the gastrointestinal tract.\n\n== Structure ==\n\nThe colon is the last part of the digestive system.\n\nIt has a segmented appearance due to a series of saccules called haustra.\n\nIt extracts water and salt from solid wastes before they are eliminated from the body and is the site in which flora-aided (largely bacterial) fermentation of unabsorbed material occurs.\n\nUnlike the small intestine, the colon does not play a major role in absorption of foods and nutrients.\n\nAbout 1.5 litres or 45 ounces of water arrives in the colon each day.\n\nThe length of the average adult human colon is 65 inches or 166 cm (range of 80 to 313 cm) for males, and 61 inches or 155 cm (range of 80 to 214 cm) for females.\n\n=== Sections ===\n\nIn mammals, the colon consists of six sections: the cecum, the ascending colon, the transverse colon, the descending colon, the sigmoid colon, and the rectum.Sections of the colon are:\n\n-The cecum including the appendix\n-The ascending colon\n-The transverse colon including the colic flexures and transverse mesocolon\n-The descending colon\n-The sigmoid colon – the s-shaped region of the large intestine\n-The rectum\n\nThe parts of the colon are either intraperitoneal or behind it in the retroperitoneum.\n\nRetroperitoneal organs, in general, do not have a complete covering of peritoneum, so they are fixed in location.\n\nIntraperitoneal organs are completely surrounded by peritoneum and are therefore mobile.\n\nOf the colon, the ascending colon, descending colon and rectum are retroperitoneal, while the cecum, appendix, transverse colon and sigmoid colon are intraperitoneal.\n\nThis is important as it affects which organs can be easily accessed during surgery, such as a laparotomy.\n\nIn terms of diameter, the cecum is the widest, averaging slightly less than 9 cm in healthy individuals, and the transverse colon averages less than 6 cm in diameter.\n\nThe descending and sigmoid colon are slightly smaller, with the sigmoid colon averaging 4–5 cm (1.6–2.0 in) in diameter.\n\nDiameters larger than certain thresholds for each colonic section can be diagnostic for megacolon.\n\n==== Cecum and appendix ====\n\nThe cecum is the first section of the colon and involved in the digestion, while the appendix which develops embryologically from it, is a structure of the colon, not involved in digestion and considered to be part of the gut-associated lymphoid tissue.\n\nThe function of the appendix is uncertain, but some sources believe that the appendix has a role in housing a sample of the colon's microflora, and is able to help to repopulate the colon with bacteria if the microflora has been damaged during the course of an immune reaction.\n\nThe appendix has also been shown to have a high concentration of lymphatic cells.\n\n==== Ascending colon ====\n\nThe ascending colon is the first of four main sections of the large intestine.\n\nIt is connected to the small intestine by a section of bowel called the cecum.\n\nThe ascending colon runs upwards through the abdominal cavity toward the transverse colon for approximately eight inches (20 cm).\n\nOne of the main functions of the colon is to remove the water and other key nutrients from waste material and recycle it.\n\nAs the waste material exits the small intestine through the ileocecal valve, it will move into the cecum and then to the ascending colon where this process of extraction starts.\n\nThe waste material is pumped upwards toward the transverse colon by peristalsis.\n\nThe ascending colon is sometimes attached to the appendix via Gerlach's valve.\n\nIn ruminants, the ascending colon is known as the spiral colon.\nTaking into account all ages and sexes, colon cancer occurs here most often (41%).\n\n==== Transverse colon ====\n\nThe transverse colon is the part of the colon from the hepatic flexure, also known as the right colic, (the turn of the colon by the liver) to the splenic flexure also known as the left colic, (the turn of the colon by the spleen).\n\nThe transverse colon hangs off the stomach, attached to it by a large fold of peritoneum called the greater omentum.\n\nOn the posterior side, the transverse colon is connected to the posterior abdominal wall by a mesentery known as the transverse mesocolon.\n\nThe transverse colon is encased in peritoneum, and is therefore mobile (unlike the parts of the colon immediately before and after it).\n\nThe proximal two-thirds of the transverse colon is perfused by the middle colic artery, a branch of the superior mesenteric artery (SMA), while the latter third is supplied by branches of the inferior mesenteric artery (IMA).\n\nThe \"watershed\" area between these two blood supplies, which represents the embryologic division between the midgut and hindgut, is an area sensitive to ischemia.\n\n==== Descending colon ====\n\nThe descending colon is the part of the colon from the splenic flexure to the beginning of the sigmoid colon.\n\nOne function of the descending colon in the digestive system is to store feces that will be emptied into the rectum.\n\nIt is retroperitoneal in two-thirds of humans.\n\nIn the other third, it has a (usually short) mesentery.\n\nThe arterial supply comes via the left colic artery.\n\nThe descending colon is also called the distal gut, as it is further along the gastrointestinal tract than the proximal gut.\n\nGut flora are very dense in this region.\n\n==== Sigmoid colon ====\n\nThe sigmoid colon is the part of the large intestine after the descending colon and before the rectum.\n\nThe name sigmoid means S-shaped (see sigmoid; cf. sigmoid sinus).\n\nThe walls of the sigmoid colon are muscular and contract to increase the pressure inside the colon, causing the stool to move into the rectum.\n\nThe sigmoid colon is supplied with blood from several branches (usually between 2 and 6) of the sigmoid arteries, a branch of the IMA.\n\nThe IMA terminates as the superior rectal artery.\nSigmoidoscopy is a common diagnostic technique used to examine the sigmoid colon.\n\n==== Rectum ====\n\nThe rectum is the last section of the large intestine.\n\nIt holds the formed feces awaiting elimination via defecation.\nIt is about 12 cm long.\n\n=== Appearance ===\n\nThe cecum – the first part of the large intestine\nTaeniae coli – three bands of smooth muscle\nHaustra – bulges caused by contraction of taeniae coli\nEpiploic appendages – small fat accumulations on the visceraThe taenia coli run the length of the large intestine.\n\nBecause the taenia coli are shorter than the large bowel itself, the colon becomes sacculated, forming the haustra of the colon which are the shelf-like intraluminal projections.\n\n=== Blood supply ===\n\nArterial supply to the colon comes from branches of the superior mesenteric artery (SMA) and inferior mesenteric artery (IMA).\n\nFlow between these two systems communicates via the marginal artery of the colon that runs parallel to the colon for its entire length.\n\nHistorically, a structure variously identified as the arc of Riolan or meandering mesenteric artery (of Moskowitz) was thought to connect the proximal SMA to the proximal IMA.\n\nThis variably present structure would be important if either vessel were occluded.\n\nHowever, at least one review of the literature questions the existence of this vessel, with some experts calling for the abolition of these terms from future medical literature.Venous drainage usually mirrors colonic arterial supply, with the inferior mesenteric vein draining into the splenic vein, and the superior mesenteric vein joining the splenic vein to form the hepatic portal vein that then enters the liver.\n\n=== Lymphatic drainage ===\n\nLymphatic drainage from the ascending colon and proximal two-thirds of the transverse colon is to the colic lymph nodes and the superior mesenteric lymph nodes, which drain into the cisterna chyli.\n\nThe lymph from the distal one-third of the transverse colon, the descending colon, the sigmoid colon, and the upper rectum drain into the inferior mesenteric and colic lymph nodes.\n\nThe lower rectum to the anal canal above the pectinate line drain to the internal iliac nodes.\n\nThe anal canal below the pectinate line drains into the superficial inguinal nodes.\n\nThe pectinate line only roughly marks this transition.\n\n=== Nerve supply ===\n\nSympathetic supply : Superior & inferior mesenteric ganglia\nParasympathetic supply : Vagus & pelvic nerves\n\n=== Development ===\n\n=== Variation ===\n\nOne variation on the normal anatomy of the colon occurs when extra loops form, resulting in a colon that is up to five metres longer than normal.\n\nThis condition, referred to as redundant colon, typically has no direct major health consequences, though rarely volvulus occurs, resulting in obstruction and requiring immediate medical attention.\n\nA significant indirect health consequence is that use of a standard adult colonoscope is difficult and in some cases impossible when a redundant colon is present, though specialized variants on the instrument (including the pediatric variant) are useful in overcoming this problem.\n\n== Microanatomy ==\n\n=== Colonic crypts ===\n\nThe wall of the large intestine is lined with simple columnar epithelium with invaginations.\n\nThe invaginations are called the intestinal glands or colonic crypts.\n\nThe colon crypts are shaped like microscopic thick walled test tubes with a central hole down the length of the tube (the crypt lumen).\n\nFour tissue sections are shown here, two cut across the long axes of the crypts and two cut parallel to the long axes.\n\nIn these images the cells have been stained by immunohistochemistry to show a brown-orange color if the cells produce a mitochondrial protein called cytochrome c oxidase subunit I (CCOI).\n\nThe nuclei of the cells (located at the outer edges of the cells lining the walls of the crypts) are stained blue-gray with haematoxylin.\n\nAs seen in panels C and D, crypts are about 75 to about 110 cells long.\n\nBaker et al. found that the average crypt circumference is 23 cells.\n\nThus, by the images shown here, there are an average of about 1,725 to 2,530 cells per colonic crypt.\n\nNooteboom et al. measuring the number of cells in a small number of crypts reported a range of 1,500 to 4,900 cells per colonic crypt.\n\nCells are produced at the crypt base and migrate upward along the crypt axis before being shed into the colonic lumen days later.\n\nThere are 5 to 6 stem cells at the bases of the crypts.\n\nAs estimated from the image in panel A, there are about 100 colonic crypts per square millimeter of the colonic epithelium.\n\nSince the average length of the human colon is 160.5 cm and the average inner circumference of the colon is 6.2 cm, the inner surface epithelial area of the human colon has an average area of about 995 cm2, which includes 9,950,000 (close to 10 million) crypts.\n\nIn the four tissue sections shown here, many of the intestinal glands have cells with a mitochondrial DNA mutation in the CCOI gene and appear mostly white, with their main color being the blue-gray staining of the nuclei.\n\nAs seen in panel B, a portion of the stem cells of three crypts appear to have a mutation in CCOI, so that 40% to 50% of the cells arising from those stem cells form a white segment in the cross cut area.\n\nOverall, the percent of crypts deficient for CCOI is less than 1% before age 40, but then increases linearly with age.\n\nColonic crypts deficient for CCOI in women reaches, on average, 18% in women and 23% in men by 80–84 years of age.Crypts of the colon can reproduce by fission, as seen in panel C, where a crypt is fissioning to form two crypts, and in panel B where at least one crypt appears to be fissioning.\n\nMost crypts deficient in CCOI are in clusters of crypts (clones of crypts) with two or more CCOI-deficient crypts adjacent to each other (see panel D).\n\n==== Mucosa ====\n\nAbout 150 of the many thousands of protein coding genes expressed in the large intestine, some are specific to the mucous membrane in different regions and include CEACAM7.\n\n== Function ==\n\nThe large intestine absorbs water and any remaining absorbable nutrients from the food before sending the indigestible matter to the rectum.\n\nThe colon absorbs vitamins that are created by the colonic bacteria, such as thiamine, riboflavin, and vitamin K (especially important as the daily ingestion of vitamin K is not normally enough to maintain adequate blood coagulation).\n\nIt also compacts feces, and stores fecal matter in the rectum until it can be discharged via the anus in defecation.\n\nThe large intestine also secretes K+ and Cl-.\n\nChloride secretion increases in cystic fibrosis.\nRecycling of various nutrients takes place in colon.\n\nExamples include fermentation of carbohydrates, short chain fatty acids, and urea cycling.\n\nThe appendix contains a small amount of mucosa-associated lymphoid tissue which gives the appendix an undetermined role in immunity.\n\nHowever, the appendix is known to be important in fetal life as it contains endocrine cells that release biogenic amines and peptide hormones important for homeostasis during early growth and development.\n\nThe appendix can be removed with no apparent damage or consequence to the patient.By the time the chyme has reached this tube, most nutrients and 90% of the water have been absorbed by the body.\n\nAt this point some electrolytes like sodium, magnesium, and chloride are left as well as indigestible parts of ingested food (e.g., a large part of ingested amylose, starch which has been shielded from digestion heretofore, and dietary fiber, which is largely indigestible carbohydrate in either soluble or insoluble form).\n\nAs the chyme moves through the large intestine, most of the remaining water is removed, while the chyme is mixed with mucus and bacteria (known as gut flora), and becomes feces.\n\nThe ascending colon receives fecal material as a liquid.\n\nThe muscles of the colon then move the watery waste material forward and slowly absorb all the excess water, causing the stools to gradually solidify as they move along into the descending colon.\n\nThe bacteria break down some of the fiber for their own nourishment and create acetate, propionate, and butyrate as waste products, which in turn are used by the cell lining of the colon for nourishment.\n\nNo protein is made available.\n\nIn humans, perhaps 10% of the undigested carbohydrate thus becomes available, though this may vary with diet; in other animals, including other apes and primates, who have proportionally larger colons, more is made available, thus permitting a higher portion of plant material in the diet.\n\nThe large intestine produces no digestive enzymes — chemical digestion is completed in the small intestine before the chyme reaches the large intestine.\n\nThe pH in the colon varies between 5.5 and 7 (slightly acidic to neutral).\n\n=== Standing gradient osmosis ===\n\nWater absorption at the colon typically proceeds against a transmucosal osmotic pressure gradient.\n\nThe standing gradient osmosis is the reabsorption of water against the osmotic gradient in the intestines.\n\nCells occupying the intestinal lining pump sodium ions into the intercellular space, raising the osmolarity of the intercellular fluid.\n\nThis hypertonic fluid creates an osmotic pressure that drives water into the lateral intercellular spaces by osmosis via tight junctions and adjacent cells, which then in turn moves across the basement membrane and into the capillaries, while more sodium ions are pumped again into the intercellular fluid.\n\nAlthough water travels down an osmotic gradient in each individual step, overall, water usually travels against the osmotic gradient due to the pumping of sodium ions into the intercellular fluid.\n\nThis allows the large intestine to absorb water despite the blood in capillaries being hypotonic compared to the fluid within the intestinal lumen.\n\n=== Gut flora ===\n\nThe large intestine houses over 700 species of bacteria that perform a variety of functions, as well as fungi, protozoa, and archaea.\n\nSpecies diversity varies by geography and diet.\n\nThe microbes in a human distal gut often number in the vicinity of 100 trillion, and can weigh around 200 grams (0.44 pounds).\n\nThis mass of mostly symbiotic microbes has recently been called the latest human organ to be \"discovered\" or in other words, the \"forgotten organ\".The large intestine absorbs some of the products formed by the bacteria inhabiting this region.\n\nUndigested polysaccharides (fiber) are metabolized to short-chain fatty acids by bacteria in the large intestine and absorbed by passive diffusion.\n\nThe bicarbonate that the large intestine secretes helps to neutralize the increased acidity resulting from the formation of these fatty acids.\n\nThese bacteria also produce large amounts of vitamins, especially vitamin K and biotin (a B vitamin), for absorption into the blood.\n\nAlthough this source of vitamins, in general, provides only a small part of the daily requirement, it makes a significant contribution when dietary vitamin intake is low.\n\nAn individual who depends on absorption of vitamins formed by bacteria in the large intestine may become vitamin-deficient if treated with antibiotics that inhibit the vitamin producing species of bacteria as well as the intended disease-causing bacteria.\n\nOther bacterial products include gas (flatus), which is a mixture of nitrogen and carbon dioxide, with small amounts of the gases hydrogen, methane, and hydrogen sulfide.\n\nBacterial fermentation of undigested polysaccharides produces these.\n\nSome of the fecal odor is due to indoles, metabolized from the amino acid tryptophan.\n\nThe normal flora is also essential in the development of certain tissues, including the cecum and lymphatics.\n\nThey are also involved in the production of cross-reactive antibodies.\n\nThese are antibodies produced by the immune system against the normal flora, that are also effective against related pathogens, thereby preventing infection or invasion.\n\nThe two most prevalent phyla of the colon are firmicutes and bacteroidetes.\n\nThe ratio between the two seems to vary widely as reported by the Human Microbiome Project.\n\nBacteroides are implicated in the initiation of colitis and colon cancer.\n\nBifidobacteria are also abundant, and are often described as 'friendly bacteria'.A mucus layer protects the large intestine from attacks from colonic commensal bacteria.\n\n== Clinical significance ==\n\n=== Disease ===\n\nFollowing are the most common diseases or disorders of the colon:\n\n=== Colonoscopy ===\n\nColonoscopy is the endoscopic examination of the large intestine and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus.\n\nIt can provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy or removal of suspected colorectal cancer lesions.\n\nColonoscopy can remove polyps as small as one millimetre or less.\n\nOnce polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not.\n\nIt takes 15 years or less for a polyp to turn cancerous.\nColonoscopy is similar to sigmoidoscopy—the difference being related to which parts of the colon each can examine.\n\nA colonoscopy allows an examination of the entire colon (1200–1500 mm in length).\n\nA sigmoidoscopy allows an examination of the distal portion (about 600 mm) of the colon, which may be sufficient because benefits to cancer survival of colonoscopy have been limited to the detection of lesions in the distal portion of the colon.\n\nA sigmoidoscopy is often used as a screening procedure for a full colonoscopy, often done in conjunction with a stool-based test such as a fecal occult blood test (FOBT), fecal immunochemical test (FIT), or multi-target stool DNA test (Cologuard) or blood-based test, SEPT9 DNA methylation test (Epi proColon).\n\nAbout 5% of these screened patients are referred to colonoscopy.\n\nVirtual colonoscopy, which uses 2D and 3D imagery reconstructed from computed tomography (CT) scans or from nuclear magnetic resonance (MR) scans, is also possible, as a totally non-invasive medical test, although it is not standard and still under investigation regarding its diagnostic abilities.\n\nFurthermore, virtual colonoscopy does not allow for therapeutic maneuvers such as polyp/tumour removal or biopsy nor visualization of lesions smaller than 5 millimeters.\n\nIf a growth or polyp is detected using CT colonography, a standard colonoscopy would still need to be performed.\n\nAdditionally, surgeons have lately been using the term pouchoscopy to refer to a colonoscopy of the ileo-anal pouch.\n\n== Other animals ==\n\nThe large intestine is truly distinct only in tetrapods, in which it is almost always separated from the small intestine by an ileocaecal valve.\n\nIn most vertebrates, however, it is a relatively short structure running directly to the anus, although noticeably wider than the small intestine.\n\nAlthough the caecum is present in most amniotes, only in mammals does the remainder of the large intestine develop into a true colon.\n\nIn some small mammals, the colon is straight, as it is in other tetrapods, but, in the majority of mammalian species, it is divided into ascending and descending portions; a distinct transverse colon is typically present only in primates.\n\nHowever, the taeniae coli and accompanying haustra are not found in either carnivorans or ruminants.\n\nThe rectum of mammals (other than monotremes) is derived from the cloaca of other vertebrates, and is, therefore, not truly homologous with the \"rectum\" found in these species.\n\nIn fish, there is no true large intestine, but simply a short rectum connecting the end of the digestive part of the gut to the cloaca.\n\nIn sharks, this includes a rectal gland that secretes salt to help the animal maintain osmotic balance with the seawater.\n\nThe gland somewhat resembles a caecum in structure but is not a homologous structure.\n\nhttps://en.wikipedia.org/wiki/Large_intestine","transverse-colon":"LARGE INTESTINE\n\nThe large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the digestive system in vertebrates.\n\nWater is absorbed here and the remaining waste material is stored as feces before being removed by defecation.The colon is the largest portion of the large intestine, so many mentions of the large intestine and colon overlap in meaning whenever precision is not the focus.\n\nMost sources define the large intestine as the combination of the cecum, colon, rectum, and anal canal.\n\nSome other sources exclude the anal canal.In humans, the large intestine begins in the right iliac region of the pelvis, just at or below the waist, where it is joined to the end of the small intestine at the cecum, via the ileocecal valve.\n\nIt then continues as the colon ascending the abdomen, across the width of the abdominal cavity as the transverse colon, and then descending to the rectum and its endpoint at the anal canal.\n\nOverall, in humans, the large intestine is about 1.5 metres (5 ft) long, which is about one-fifth of the whole length of the gastrointestinal tract.\n\n== Structure ==\n\nThe colon is the last part of the digestive system.\n\nIt has a segmented appearance due to a series of saccules called haustra.\n\nIt extracts water and salt from solid wastes before they are eliminated from the body and is the site in which flora-aided (largely bacterial) fermentation of unabsorbed material occurs.\n\nUnlike the small intestine, the colon does not play a major role in absorption of foods and nutrients.\n\nAbout 1.5 litres or 45 ounces of water arrives in the colon each day.The length of the average adult human colon is 65 inches or 166 cm (range of 80 to 313 cm) for males, and 61 inches or 155 cm (range of 80 to 214 cm) for females.\n\n=== Sections ===\n\nIn mammals, the colon consists of six sections: the cecum, the ascending colon, the transverse colon, the descending colon, the sigmoid colon, and the rectum.Sections of the colon are:\n\nThe cecum including the appendix\nThe ascending colon\nThe transverse colon including the colic flexures and transverse mesocolon\nThe descending colon\nThe sigmoid colon – the s-shaped region of the large intestine\nThe rectumThe parts of the colon are either intraperitoneal or behind it in the retroperitoneum.\n\nRetroperitoneal organs, in general, do not have a complete covering of peritoneum, so they are fixed in location.\n\nIntraperitoneal organs are completely surrounded by peritoneum and are therefore mobile.\n\nOf the colon, the ascending colon, descending colon and rectum are retroperitoneal, while the cecum, appendix, transverse colon and sigmoid colon are intraperitoneal.\n\nThis is important as it affects which organs can be easily accessed during surgery, such as a laparotomy.\nIn terms of diameter, the cecum is the widest, averaging slightly less than 9 cm in healthy individuals, and the transverse colon averages less than 6 cm in diameter.\n\nThe descending and sigmoid colon are slightly smaller, with the sigmoid colon averaging 4–5 cm (1.6–2.0 in) in diameter.\n\nDiameters larger than certain thresholds for each colonic section can be diagnostic for megacolon.\n\n==== Cecum and appendix ====\nThe cecum is the first section of the colon and involved in the digestion, while the appendix which develops embryologically from it, is a structure of the colon, not involved in digestion and considered to be part of the gut-associated lymphoid tissue.\n\nThe function of the appendix is uncertain, but some sources believe that the appendix has a role in housing a sample of the colon's microflora, and is able to help to repopulate the colon with bacteria if the microflora has been damaged during the course of an immune reaction.\n\nThe appendix has also been shown to have a high concentration of lymphatic cells.\n\n==== Ascending colon ====\nThe ascending colon is the first of four main sections of the large intestine.\n\nIt is connected to the small intestine by a section of bowel called the cecum.\n\nThe ascending colon runs upwards through the abdominal cavity toward the transverse colon for approximately eight inches (20 cm).\nOne of the main functions of the colon is to remove the water and other key nutrients from waste material and recycle it.\n\nAs the waste material exits the small intestine through the ileocecal valve, it will move into the cecum and then to the ascending colon where this process of extraction starts.\n\nThe waste material is pumped upwards toward the transverse colon by peristalsis.\n\nThe ascending colon is sometimes attached to the appendix via Gerlach's valve.\n\nIn ruminants, the ascending colon is known as the spiral colon.\nTaking into account all ages and sexes, colon cancer occurs here most often (41%).\n\n==== Transverse colon ====\nThe transverse colon is the part of the colon from the hepatic flexure, also known as the right colic, (the turn of the colon by the liver) to the splenic flexure also known as the left colic, (the turn of the colon by the spleen).\n\nThe transverse colon hangs off the stomach, attached to it by a large fold of peritoneum called the greater omentum.\n\nOn the posterior side, the transverse colon is connected to the posterior abdominal wall by a mesentery known as the transverse mesocolon.\nThe transverse colon is encased in peritoneum, and is therefore mobile (unlike the parts of the colon immediately before and after it).\nThe proximal two-thirds of the transverse colon is perfused by the middle colic artery, a branch of the superior mesenteric artery (SMA), while the latter third is supplied by branches of the inferior mesenteric artery (IMA).\n\nThe \"watershed\" area between these two blood supplies, which represents the embryologic division between the midgut and hindgut, is an area sensitive to ischemia.\n\n==== Descending colon ====\nThe descending colon is the part of the colon from the splenic flexure to the beginning of the sigmoid colon.\n\nOne function of the descending colon in the digestive system is to store feces that will be emptied into the rectum.\n\nIt is retroperitoneal in two-thirds of humans.\n\nIn the other third, it has a (usually short) mesentery.\n\nThe arterial supply comes via the left colic artery.\n\nThe descending colon is also called the distal gut, as it is further along the gastrointestinal tract than the proximal gut.\n\nGut flora are very dense in this region.\n\n==== Sigmoid colon ====\nThe sigmoid colon is the part of the large intestine after the descending colon and before the rectum.\n\nThe name sigmoid means S-shaped (see sigmoid; cf. sigmoid sinus).\n\nThe walls of the sigmoid colon are muscular and contract to increase the pressure inside the colon, causing the stool to move into the rectum.\nThe sigmoid colon is supplied with blood from several branches (usually between 2 and 6) of the sigmoid arteries, a branch of the IMA.\n\nThe IMA terminates as the superior rectal artery.\nSigmoidoscopy is a common diagnostic technique used to examine the sigmoid colon.\n\n==== Rectum ====\nThe rectum is the last section of the large intestine.\n\nIt holds the formed feces awaiting elimination via defecation.\nIt is about 12 cm long.\n\n=== Appearance ===\n\nThe cecum – the first part of the large intestine\n\nTaeniae coli – three bands of smooth muscle\nHaustra – bulges caused by contraction of taeniae coli\nEpiploic appendages – small fat accumulations on the visceraThe taenia coli run the length of the large intestine.\n\nBecause the taenia coli are shorter than the large bowel itself, the colon becomes sacculated, forming the haustra of the colon which are the shelf-like intraluminal projections.\n\n=== Blood supply ===\n\nArterial supply to the colon comes from branches of the superior mesenteric artery (SMA) and inferior mesenteric artery (IMA).\n\nFlow between these two systems communicates via the marginal artery of the colon that runs parallel to the colon for its entire length.\n\nHistorically, a structure variously identified as the arc of Riolan or meandering mesenteric artery (of Moskowitz) was thought to connect the proximal SMA to the proximal IMA.\n\nThis variably present structure would be important if either vessel were occluded.\n\nHowever, at least one review of the literature questions the existence of this vessel, with some experts calling for the abolition of these terms from future medical literature.Venous drainage usually mirrors colonic arterial supply, with the inferior mesenteric vein draining into the splenic vein, and the superior mesenteric vein joining the splenic vein to form the hepatic portal vein that then enters the liver.\n\n=== Lymphatic drainage ===\n\nLymphatic drainage from the ascending colon and proximal two-thirds of the transverse colon is to the colic lymph nodes and the superior mesenteric lymph nodes, which drain into the cisterna chyli.\n\nThe lymph from the distal one-third of the transverse colon, the descending colon, the sigmoid colon, and the upper rectum drain into the inferior mesenteric and colic lymph nodes.\n\nThe lower rectum to the anal canal above the pectinate line drain to the internal iliac nodes.\n\nThe anal canal below the pectinate line drains into the superficial inguinal nodes.\n\nThe pectinate line only roughly marks this transition.\n\n=== Nerve supply ===\n\nSympathetic supply : Superior & inferior mesenteric ganglia\nParasympathetic supply : Vagus & pelvic nerves\n\n=== Development ===\n\n=== Variation ===\n\nOne variation on the normal anatomy of the colon occurs when extra loops form, resulting in a colon that is up to five metres longer than normal.\n\nThis condition, referred to as redundant colon, typically has no direct major health consequences, though rarely volvulus occurs, resulting in obstruction and requiring immediate medical attention.\n\nA significant indirect health consequence is that use of a standard adult colonoscope is difficult and in some cases impossible when a redundant colon is present, though specialized variants on the instrument (including the pediatric variant) are useful in overcoming this problem.\n\n== Microanatomy ==\n\n=== Colonic crypts ===\n\nThe wall of the large intestine is lined with simple columnar epithelium with invaginations.\n\nThe invaginations are called the intestinal glands or colonic crypts.\n\nThe colon crypts are shaped like microscopic thick walled test tubes with a central hole down the length of the tube (the crypt lumen).\n\nFour tissue sections are shown here, two cut across the long axes of the crypts and two cut parallel to the long axes.\n\nIn these images the cells have been stained by immunohistochemistry to show a brown-orange color if the cells produce a mitochondrial protein called cytochrome c oxidase subunit I (CCOI).\n\nThe nuclei of the cells (located at the outer edges of the cells lining the walls of the crypts) are stained blue-gray with haematoxylin.\n\nAs seen in panels C and D, crypts are about 75 to about 110 cells long.\n\nBaker et al. found that the average crypt circumference is 23 cells.\n\nThus, by the images shown here, there are an average of about 1,725 to 2,530 cells per colonic crypt.\n\nNooteboom et al. measuring the number of cells in a small number of crypts reported a range of 1,500 to 4,900 cells per colonic crypt.\n\nCells are produced at the crypt base and migrate upward along the crypt axis before being shed into the colonic lumen days later.\n\nThere are 5 to 6 stem cells at the bases of the crypts.As estimated from the image in panel A, there are about 100 colonic crypts per square millimeter of the colonic epithelium.\n\nSince the average length of the human colon is 160.5 cm and the average inner circumference of the colon is 6.2 cm, the inner surface epithelial area of the human colon has an average area of about 995 cm2, which includes 9,950,000 (close to 10 million) crypts.\nIn the four tissue sections shown here, many of the intestinal glands have cells with a mitochondrial DNA mutation in the CCOI gene and appear mostly white, with their main color being the blue-gray staining of the nuclei.\n\nAs seen in panel B, a portion of the stem cells of three crypts appear to have a mutation in CCOI, so that 40% to 50% of the cells arising from those stem cells form a white segment in the cross cut area.\nOverall, the percent of crypts deficient for CCOI is less than 1% before age 40, but then increases linearly with age.\n\nColonic crypts deficient for CCOI in women reaches, on average, 18% in women and 23% in men by 80–84 years of age.Crypts of the colon can reproduce by fission, as seen in panel C, where a crypt is fissioning to form two crypts, and in panel B where at least one crypt appears to be fissioning.\n\nMost crypts deficient in CCOI are in clusters of crypts (clones of crypts) with two or more CCOI-deficient crypts adjacent to each other (see panel D).\n\n==== Mucosa ====\nAbout 150 of the many thousands of protein coding genes expressed in the large intestine, some are specific to the mucous membrane in different regions and include CEACAM7.\n\n== Function ==\n\nThe large intestine absorbs water and any remaining absorbable nutrients from the food before sending the indigestible matter to the rectum.\n\nThe colon absorbs vitamins that are created by the colonic bacteria, such as thiamine, riboflavin, and vitamin K (especially important as the daily ingestion of vitamin K is not normally enough to maintain adequate blood coagulation).\n\nIt also compacts feces, and stores fecal matter in the rectum until it can be discharged via the anus in defecation.\nThe large intestine also secretes K+ and Cl-.\n\nChloride secretion increases in cystic fibrosis.\nRecycling of various nutrients takes place in colon.\n\nExamples include fermentation of carbohydrates, short chain fatty acids, and urea cycling.The appendix contains a small amount of mucosa-associated lymphoid tissue which gives the appendix an undetermined role in immunity.\n\nHowever, the appendix is known to be important in fetal life as it contains endocrine cells that release biogenic amines and peptide hormones important for homeostasis during early growth and development.\n\nThe appendix can be removed with no apparent damage or consequence to the patient.By the time the chyme has reached this tube, most nutrients and 90% of the water have been absorbed by the body.\n\nAt this point some electrolytes like sodium, magnesium, and chloride are left as well as indigestible parts of ingested food (e.g., a large part of ingested amylose, starch which has been shielded from digestion heretofore, and dietary fiber, which is largely indigestible carbohydrate in either soluble or insoluble form).\n\nAs the chyme moves through the large intestine, most of the remaining water is removed, while the chyme is mixed with mucus and bacteria (known as gut flora), and becomes feces.\n\nThe ascending colon receives fecal material as a liquid.\n\nThe muscles of the colon then move the watery waste material forward and slowly absorb all the excess water, causing the stools to gradually solidify as they move along into the descending colon.The bacteria break down some of the fiber for their own nourishment and create acetate, propionate, and butyrate as waste products, which in turn are used by the cell lining of the colon for nourishment.\n\nNo protein is made available.\n\nIn humans, perhaps 10% of the undigested carbohydrate thus becomes available, though this may vary with diet; in other animals, including other apes and primates, who have proportionally larger colons, more is made available, thus permitting a higher portion of plant material in the diet.\n\nThe large intestine produces no digestive enzymes — chemical digestion is completed in the small intestine before the chyme reaches the large intestine.\n\nThe pH in the colon varies between 5.5 and 7 (slightly acidic to neutral).\n\n=== Standing gradient osmosis ===\n\nWater absorption at the colon typically proceeds against a transmucosal osmotic pressure gradient.\n\nThe standing gradient osmosis is the reabsorption of water against the osmotic gradient in the intestines.\n\nCells occupying the intestinal lining pump sodium ions into the intercellular space, raising the osmolarity of the intercellular fluid.\n\nThis hypertonic fluid creates an osmotic pressure that drives water into the lateral intercellular spaces by osmosis via tight junctions and adjacent cells, which then in turn moves across the basement membrane and into the capillaries, while more sodium ions are pumped again into the intercellular fluid.\n\nAlthough water travels down an osmotic gradient in each individual step, overall, water usually travels against the osmotic gradient due to the pumping of sodium ions into the intercellular fluid.\n\nThis allows the large intestine to absorb water despite the blood in capillaries being hypotonic compared to the fluid within the intestinal lumen.\n\n=== Gut flora ===\n\nThe large intestine houses over 700 species of bacteria that perform a variety of functions, as well as fungi, protozoa, and archaea.\n\nSpecies diversity varies by geography and diet.\n\nThe microbes in a human distal gut often number in the vicinity of 100 trillion, and can weigh around 200 grams (0.44 pounds).\n\nThis mass of mostly symbiotic microbes has recently been called the latest human organ to be \"discovered\" or in other words, the \"forgotten organ\".The large intestine absorbs some of the products formed by the bacteria inhabiting this region.\n\nUndigested polysaccharides (fiber) are metabolized to short-chain fatty acids by bacteria in the large intestine and absorbed by passive diffusion.\n\nThe bicarbonate that the large intestine secretes helps to neutralize the increased acidity resulting from the formation of these fatty acids.These bacteria also produce large amounts of vitamins, especially vitamin K and biotin (a B vitamin), for absorption into the blood.\n\nAlthough this source of vitamins, in general, provides only a small part of the daily requirement, it makes a significant contribution when dietary vitamin intake is low.\n\nAn individual who depends on absorption of vitamins formed by bacteria in the large intestine may become vitamin-deficient if treated with antibiotics that inhibit the vitamin producing species of bacteria as well as the intended disease-causing bacteria.Other bacterial products include gas (flatus), which is a mixture of nitrogen and carbon dioxide, with small amounts of the gases hydrogen, methane, and hydrogen sulfide.\n\nBacterial fermentation of undigested polysaccharides produces these.\n\nSome of the fecal odor is due to indoles, metabolized from the amino acid tryptophan.\n\nThe normal flora is also essential in the development of certain tissues, including the cecum and lymphatics.They are also involved in the production of cross-reactive antibodies.\n\nThese are antibodies produced by the immune system against the normal flora, that are also effective against related pathogens, thereby preventing infection or invasion.\nThe two most prevalent phyla of the colon are firmicutes and bacteroidetes.\n\nThe ratio between the two seems to vary widely as reported by the Human Microbiome Project.\n\nBacteroides are implicated in the initiation of colitis and colon cancer.\n\nBifidobacteria are also abundant, and are often described as 'friendly bacteria'.A mucus layer protects the large intestine from attacks from colonic commensal bacteria.\n\n== Clinical significance ==\n\n=== Disease ===\n\nFollowing are the most common diseases or disorders of the colon:\n\n=== Colonoscopy ===\n\nColonoscopy is the endoscopic examination of the large intestine and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus.\n\nIt can provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy or removal of suspected colorectal cancer lesions.\n\nColonoscopy can remove polyps as small as one millimetre or less.\n\nOnce polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not.\n\nIt takes 15 years or less for a polyp to turn cancerous.\nColonoscopy is similar to sigmoidoscopy—the difference being related to which parts of the colon each can examine.\n\nA colonoscopy allows an examination of the entire colon (1200–1500 mm in length).\n\nA sigmoidoscopy allows an examination of the distal portion (about 600 mm) of the colon, which may be sufficient because benefits to cancer survival of colonoscopy have been limited to the detection of lesions in the distal portion of the colon.A sigmoidoscopy is often used as a screening procedure for a full colonoscopy, often done in conjunction with a stool-based test such as a fecal occult blood test (FOBT), fecal immunochemical test (FIT), or multi-target stool DNA test (Cologuard) or blood-based test, SEPT9 DNA methylation test (Epi proColon).\n\nAbout 5% of these screened patients are referred to colonoscopy.Virtual colonoscopy, which uses 2D and 3D imagery reconstructed from computed tomography (CT) scans or from nuclear magnetic resonance (MR) scans, is also possible, as a totally non-invasive medical test, although it is not standard and still under investigation regarding its diagnostic abilities.\n\nFurthermore, virtual colonoscopy does not allow for therapeutic maneuvers such as polyp/tumour removal or biopsy nor visualization of lesions smaller than 5 millimeters.\n\nIf a growth or polyp is detected using CT colonography, a standard colonoscopy would still need to be performed.\n\nAdditionally, surgeons have lately been using the term pouchoscopy to refer to a colonoscopy of the ileo-anal pouch.\n\n== Other animals ==\n\nThe large intestine is truly distinct only in tetrapods, in which it is almost always separated from the small intestine by an ileocaecal valve.\n\nIn most vertebrates, however, it is a relatively short structure running directly to the anus, although noticeably wider than the small intestine.\n\nAlthough the caecum is present in most amniotes, only in mammals does the remainder of the large intestine develop into a true colon.In some small mammals, the colon is straight, as it is in other tetrapods, but, in the majority of mammalian species, it is divided into ascending and descending portions; a distinct transverse colon is typically present only in primates.\n\nHowever, the taeniae coli and accompanying haustra are not found in either carnivorans or ruminants.\n\nThe rectum of mammals (other than monotremes) is derived from the cloaca of other vertebrates, and is, therefore, not truly homologous with the \"rectum\" found in these species.In fish, there is no true large intestine, but simply a short rectum connecting the end of the digestive part of the gut to the cloaca.\n\nIn sharks, this includes a rectal gland that secretes salt to help the animal maintain osmotic balance with the seawater.\n\nThe gland somewhat resembles a caecum in structure but is not a homologous structure.\n\nhttps://en.wikipedia.org/wiki/Large_intestine","left-posterior-lateral-segment-of-liver-ii":"Superior lateral segment of the left lateral division of liver.","left-anterior-lateral-segment-of-liver-iii":"Inferior lateral segment of the left lateral division of liver.","anterior-medial-segment-of-liver-v":"It is located beneath the posterior medial segment of liver (VIII), with which it forms the right medial division of liver.","anterior-lateral-segment-of-liver-vi":"It is located beneath the posterior lateral division of liver (VII), with which it forms the right lateral division of liver.","posterior-lateral-segment-of-liver-vii":"It is located above the anterior lateral segment of liver (VI), with which it forms the right lateral division of liver.","posterior-segment-of-liver-i":"Segment I is the caudate lobe and is situated posterior.\n\nIt may receive its supply from both the right and the left branches of portal vein.\n\nIt contains one or more hepatic veins which drain directly into the inferior vena cava (IVC).\n\nThe caudate lobe is a separate structure which receives blood flow from both the right- and left-sided vascular branches.\n\nhttps://en.wikipedia.org/wiki/Liver_segment","posterior-medial-segment-of-liver-viii":"It is located above the anterior medial segment of liver (V) with which it forms the right medial division of liver.","liver":"The liver is an organ of the digestive system only found in vertebrates which detoxifies various metabolites, synthesizes proteins and produces biochemicals necessary for digestion and growth.\n\nIn humans, it is located in the right upper quadrant of the abdomen, below the diaphragm.\n\nIts other roles in metabolism include the regulation of glycogen storage, decomposition of red blood cells, and the production of hormones.\n\nThe liver is an accessory digestive organ that produces bile, an alkaline fluid containing cholesterol and bile acids, which helps the breakdown of fat.\n\nThe gallbladder, a small pouch that sits just under the liver, stores bile produced by the liver which is afterwards moved to the small intestine to complete digestion.\n\nThe liver's highly specialized tissue, consisting of mostly hepatocytes, regulates a wide variety of high-volume biochemical reactions, including the synthesis and breakdown of small and complex molecules, many of which are necessary for normal vital functions.\n\nEstimates regarding the organ's total number of functions vary, but textbooks generally cite it being around 500.\n\nIt is not known how to compensate for the absence of liver function in the long term, although liver dialysis techniques can be used in the short term.\n\nArtificial livers have not been developed to promote long-term replacement in the absence of the liver.\n\nAs of 2018, liver transplantation is the only option for complete liver failure.\n\n== Structure ==\n\nThe liver is a reddish-brown, wedge-shaped organ with two\nlobes of unequal size and shape.\n\nA human liver normally weighs approximately 1.5 kg (3.3 lb) and has a width of about 15 cm (6 in).\n\nThere is considerable size variation between individuals, with the standard reference range for men being 970–1,860 g (2.14–4.10 lb) and for women 600–1,770 g (1.32–3.90 lb).\n\nIt is both the heaviest internal organ and the largest gland in the human body.\n\nLocated in the right upper quadrant of the abdominal cavity, it rests just below the diaphragm, to the right of the stomach and overlies the gallbladder.\n\nThe liver is connected to two large blood vessels: the hepatic artery and the portal vein.\n\nThe hepatic artery carries oxygen-rich blood from the aorta via the celiac trunk, whereas the portal vein carries blood rich in digested nutrients from the entire gastrointestinal tract and also from the spleen and pancreas.\n\nThese blood vessels subdivide into small capillaries known as liver sinusoids, which then lead to lobules.\nLobules are the functional units of the liver.\n\nEach lobule is made up of millions of hepatic cells (hepatocytes), which are the basic metabolic cells.\n\nThe lobules are held together by a fine, dense, irregular, fibroelastic connective tissue layer extending from the fibrous capsule covering the entire liver known as Glisson's capsule.\n\nThis extends into the structure of the liver by accompanying the blood vessels, ducts, and nerves at the hepatic hilum.\n\nThe whole surface of the liver, except for the bare area, is covered in a serous coat derived from the peritoneum, and this firmly adheres to the inner Glisson's capsule.\n\n=== Gross anatomy ===\n\nTerminology related to the liver often starts in hepat- from ἡπατο-, from the Greek word for liver.\n\n==== Lobes ====\n\nThe liver is grossly divided into two parts when viewed from above – a right and a left lobe - and four parts when viewed from below (left, right, caudate, and quadrate lobes).\n\nThe falciform ligament makes a superficial division of the liver into a left and right lobe.\n\nFrom below, the two additional lobes are located between the right and left lobes, one in front of the other.\n\nA line can be imagined running from the left of the vena cava and all the way forward to divide the liver and gallbladder into two halves.\n\nThis line is called Cantlie's line.\n\nOther anatomical landmarks include the ligamentum venosum and the round ligament of the liver, which further divide the left side of the liver in two sections.\n\nAn important anatomical landmark, the porta hepatis, divides this left portion into four segments, which can be numbered starting at the caudate lobe as I in an anticlockwise manner.\n\nFrom this parietal view, seven segments can be seen, because the eighth segment is only visible in the visceral view.\n\n==== Surfaces ====\n\nOn the diaphragmatic surface, apart from a triangular bare area where it connects to the diaphragm, the liver is covered by a thin, double-layered membrane, the peritoneum, that helps to reduce friction against other organs.\n\nThis surface covers the convex shape of the two lobes where it accommodates the shape of the diaphragm.\n\nThe peritoneum folds back on itself to form the falciform ligament and the right and left triangular ligaments.\n\nThese peritoneal ligaments are not related to the anatomic ligaments in joints, and the right and left triangular ligaments have no known functional importance, though they serve as surface landmarks.\n\nThe falciform ligament functions to attach the liver to the posterior portion of the anterior body wall.\n\nThe visceral surface or inferior surface is uneven and concave.\n\nIt is covered in peritoneum apart from where it attaches the gallbladder and the porta hepatis.\n\nThe fossa of gall bladder lies to the right of the quadrate lobe, occupied by the gallbladder with its cystic duct close to the right end of porta hepatis.\n\n==== Impressions ====\n\nSeveral impressions on the surface of the liver accommodate the various adjacent structures and organs.\n\nUnderneath the right lobe and to the right of the gallbladder fossa are two impressions, one behind the other and separated by a ridge.\n\nThe one in front is a shallow colic impression, formed by the hepatic flexure and the one behind is a deeper renal impression accommodating part of the right kidney and part of the suprarenal gland.\n\nThe suprarenal impression is a small, triangular, depressed area on the liver.\n\nIt is located close to the right of the fossa, between the bare area and the caudate lobe, and immediately above the renal impression.\n\nThe greater part of the suprarenal impression is devoid of peritoneum and it lodges the right suprarenal gland.Medial to the renal impression is a third and slightly marked impression, lying between it and the neck of the gall bladder.\n\nThis is caused by the descending portion of the duodenum, and is known as the duodenal impression.The inferior surface of the left lobe of the liver presents behind and to the left of the gastric impression.\n\nThis is moulded over the upper front surface of the stomach, and to the right of this is a rounded eminence, the tuber omentale, which fits into the concavity of the lesser curvature of the stomach and lies in front of the anterior layer of the lesser omentum.\n\n=== Microscopic anatomy ===\n\nMicroscopically, each liver lobe is seen to be made up of hepatic lobules.\n\nThe lobules are roughly hexagonal, and consist of plates of hepatocytes, and sinusoids radiating from a central vein towards an imaginary perimeter of interlobular portal triads.\n\nThe central vein joins to the hepatic vein to carry blood out from the liver.\n\nA distinctive component of a lobule is the portal triad, which can be found running along each of the lobule's corners.\n\nThe portal triad, consists of the hepatic artery, the portal vein, and the common bile duct.\n\nThe triad may be seen on a liver ultrasound, as a Mickey Mouse sign with the portal vein as the head, and the hepatic artery, and the common bile duct as the ears.\n\nHistology, the study of microscopic anatomy, shows two major types of liver cell: parenchymal cells and nonparenchymal cells.\n\nAbout 70–85% of the liver volume is occupied by parenchymal hepatocytes.\n\nNonparenchymal cells constitute 40% of the total number of liver cells but only 6.5% of its volume.\n\nThe liver sinusoids are lined with two types of cell, sinusoidal endothelial cells, and phagocytic Kupffer cells.\n\nHepatic stellate cells are nonparenchymal cells found in the perisinusoidal space, between a sinusoid and a hepatocyte.\n\nAdditionally, intrahepatic lymphocytes are often present in the sinusoidal lumen.\n\n=== Functional anatomy ===\n\nThe central area or hepatic hilum, includes the opening known as the porta hepatis which carries the common bile duct and common hepatic artery, and the opening for the portal vein.\n\nThe duct, vein, and artery divide into left and right branches, and the areas of the liver supplied by these branches constitute the functional left and right lobes.\n\nThe functional lobes are separated by the imaginary plane, Cantlie's line, joining the gallbladder fossa to the inferior vena cava.\n\nThe plane separates the liver into the true right and left lobes.\n\nThe middle hepatic vein also demarcates the true right and left lobes.\n\nThe right lobe is further divided into an anterior and posterior segment by the right hepatic vein.\n\nThe left lobe is divided into the medial and lateral segments by the left hepatic vein.\n\nThe hilum of the liver is described in terms of three plates that contain the bile ducts and blood vessels.\n\nThe contents of the whole plate system are surrounded by a sheath.\n\nThe three plates are the hilar plate, the cystic plate and the umbilical plate and the plate system is the site of the many anatomical variations to be found in the liver.\n\n=== Couinaud classification system ===\n\nIn the widely used Couinaud system, the functional lobes are further divided into a total of eight subsegments based on a transverse plane through the bifurcation of the main portal vein.\n\nThe caudate lobe is a separate structure that receives blood flow from both the right- and left-sided vascular branches.\n\nThe Couinaud classification divides the liver into eight functionally independent liver segments.\n\nEach segment has its own vascular inflow, outflow and biliary drainage.\n\nIn the centre of each segment are branches of the portal vein, hepatic artery, and bile duct.\n\nIn the periphery of each segment is vascular outflow through the hepatic veins.\n\nThe classification system uses the vascular supply in the liver to separate the functional units (numbered I to VIII) with unit 1, the caudate lobe, receiving its supply from both the right and the left branches of the portal vein.\n\nIt contains one or more hepatic veins which drain directly into the inferior vena cava.\n\nThe remainder of the units (II to VIII) are numbered in a clockwise fashion:\n\n=== Gene and protein expression ===\n\nAbout 20,000 protein coding genes are expressed in human cells and 60% of these genes are expressed in a normal, adult liver.\n\nOver 400 genes are more specifically expressed in the liver, with some 150 genes highly specific for liver tissue.\n\nA large fraction of the corresponding liver specific proteins are mainly expressed in hepatocytes and secreted into the blood and constitute plasma proteins.\n\nOther liver specific proteins are certain liver enzymes such as HAO1 and RDH16, proteins involved in bile synthesis such as BAAT and SLC27A5, and transporter proteins involved in the metabolism of drugs, such as ABCB11 and SLC2A2.\n\nExamples of highly liver-specific proteins include apolipoprotein A II, coagulation factors F2 and F9, complement factor related proteins, and the fibrinogen beta chain protein.\n\n== Development ==\n\nOrganogenesis, the development of the organs, takes place from the third to the eighth week during embryogenesis.\n\nThe origins of the liver lie in both the ventral portion of the foregut endoderm (endoderm being one of the three embryonic germ layers) and the constituents of the adjacent septum transversum mesenchyme.\n\nIn the human embryo, the hepatic diverticulum is the tube of endoderm that extends out from the foregut into the surrounding mesenchyme.\n\nThe mesenchyme of septum transversum induces this endoderm to proliferate, to branch, and to form the glandular epithelium of the liver.\n\nA portion of the hepatic diverticulum (that region closest to the digestive tube) continues to function as the drainage duct of the liver, and a branch from this duct produces the gallbladder.\n\nBesides signals from the septum transversum mesenchyme, fibroblast growth factor from the developing heart also contributes to hepatic competence, along with retinoic acid emanating from the lateral plate mesoderm.\n\nThe hepatic endodermal cells undergo a morphological transition from columnar to pseudostratified resulting in thickening into the early liver bud.\n\nTheir expansion forms a population of the bipotential hepatoblasts.\n\nHepatic stellate cells are derived from mesenchyme.After migration of hepatoblasts into the septum transversum mesenchyme, the hepatic architecture begins to be established, with liver sinusoids and bile canaliculi appearing.\n\nThe liver bud separates into the lobes.\n\nThe left umbilical vein becomes the ductus venosus and the right vitelline vein becomes the portal vein.\n\nThe expanding liver bud is colonized by hematopoietic cells.\n\nThe bipotential hepatoblasts begin differentiating into biliary epithelial cells and hepatocytes.\n\nThe biliary epithelial cells differentiate from hepatoblasts around portal veins, first producing a monolayer, and then a bilayer of cuboidal cells.\n\nIn ductal plate, focal dilations emerge at points in the bilayer, become surrounded by portal mesenchyme, and undergo tubulogenesis into intrahepatic bile ducts.\n\nHepatoblasts not adjacent to portal veins instead differentiate into hepatocytes and arrange into cords lined by sinusoidal epithelial cells and bile canaliculi.\n\nOnce hepatoblasts are specified into hepatocytes and undergo further expansion, they begin acquiring the functions of a mature hepatocyte, and eventually mature hepatocytes appear as highly polarized epithelial cells with abundant glycogen accumulation.\n\nIn the adult liver, hepatocytes are not equivalent, with position along the portocentrovenular axis within a liver lobule dictating expression of metabolic genes involved in drug metabolism, carbohydrate metabolism, ammonia detoxification, and bile production and secretion.\n\nWNT/β-catenin has now been identified to be playing a key role in this phenomenon.At birth, the liver comprises roughly 4% of body weight and weighs on average about 120 g (4 oz).\n\nOver the course of further development, it will increase to 1.4–1.6 kg (3.1–3.5 lb) but will only take up 2.5–3.5% of body weight.\n\n=== Fetal blood supply ===\n\nIn the growing fetus, a major source of blood to the liver is the umbilical vein, which supplies nutrients to the growing fetus.\n\nThe umbilical vein enters the abdomen at the umbilicus and passes upward along the free margin of the falciform ligament of the liver to the inferior surface of the liver.\n\nThere, it joins with the left branch of the portal vein.\n\nThe ductus venosus carries blood from the left portal vein to the left hepatic vein and then to the inferior vena cava, allowing placental blood to bypass the liver.\n\nIn the fetus, the liver does not perform the normal digestive processes and filtration of the infant liver because nutrients are received directly from the mother via the placenta.\n\nThe fetal liver releases some blood stem cells that migrate to the fetal thymus, creating the T-cells or T-lymphocytes.\n\nAfter birth, the formation of blood stem cells shifts to the red bone marrow.\n\nAfter 2–5 days, the umbilical vein and ductus venosus are completely obliterated; the former becomes the round ligament of liver and the latter becomes the ligamentum venosum.\n\nIn the disorders of cirrhosis and portal hypertension, the umbilical vein can open up again.\n\n== Functions ==\n\nThe various functions of the liver are carried out by the liver cells or hepatocytes.\n\nThe liver is thought to be responsible for up to 500 separate functions, usually in combination with other systems and organs.\n\nCurrently, no artificial organ or device is capable of reproducing all the functions of the liver.\n\nSome functions can be carried out by liver dialysis, an experimental treatment for liver failure.\n\nThe liver also accounts for about 20% of resting total body oxygen consumption.\n\n=== Blood supply ===\n\nThe liver receives a dual blood supply from the hepatic portal vein and hepatic arteries.\n\nThe hepatic portal vein delivers around 75% of the liver's blood supply and carries venous blood drained from the spleen, gastrointestinal tract, and its associated organs.\n\nThe hepatic arteries supply arterial blood to the liver, accounting for the remaining quarter of its blood flow.\n\nOxygen is provided from both sources; about half of the liver's oxygen demand is met by the hepatic portal vein, and half is met by the hepatic arteries.\n\nThe hepatic artery also has both alpha- and beta-adrenergic receptors; therefore, flow through the artery is controlled, in part, by the splanchnic nerves of the autonomic nervous system.\n\nBlood flows through the liver sinusoids and empties into the central vein of each lobule.\n\nThe central veins coalesce into hepatic veins, which leave the liver and drain into the inferior vena cava.\n\n=== Biliary flow ===\n\nThe biliary tract is derived from the branches of the bile ducts.\n\nThe biliary tract, also known as the biliary tree, is the path by which bile is secreted by the liver then transported to the first part of the small intestine, the duodenum.\n\nThe bile produced in the liver is collected in bile canaliculi, small grooves between the faces of adjacent hepatocytes.\n\nThe canaliculi radiate to the edge of the liver lobule, where they merge to form bile ducts.\n\nWithin the liver, these ducts are termed intrahepatic bile ducts, and once they exit the liver, they are considered extrahepatic.\n\nThe intrahepatic ducts eventually drain into the right and left hepatic ducts, which exit the liver at the transverse fissure, and merge to form the common hepatic duct.\n\nThe cystic duct from the gallbladder joins with the common hepatic duct to form the common bile duct.\n\nThe biliary system and connective tissue is supplied by the hepatic artery alone.\n\nBile either drains directly into the duodenum via the common bile duct, or is temporarily stored in the gallbladder via the cystic duct.\n\nThe common bile duct and the pancreatic duct enter the second part of the duodenum together at the hepatopancreatic ampulla, also known as the ampulla of Vater.\n\n=== Synthesis ===\n\nThe liver plays a major role in carbohydrate, protein, amino acid, and lipid metabolism.\n\n==== Carbohydrate metabolism ====\n\nThe liver performs several roles in carbohydrate metabolism:\n\nThe liver synthesizes and stores around 100g of glycogen via glycogenesis, the formation of glycogen from glucose.\n\nWhen needed, the liver releases glucose into the blood by performing glycogenolysis, the breakdown of glycogen into glucose.\n\nThe liver is also responsible for gluconeogenesis, which is the synthesis of glucose from certain amino acids, lactate, or glycerol.\n\nAdipose and liver cells produce glycerol by breakdown of fat, which the liver uses for gluconeogenesis.\n\nLiver also does glyconeogenesis which is synthesis of glycogen from lactic acid.\n\n==== Protein metabolism ====\n\nThe liver is responsible for the mainstay of protein metabolism, synthesis as well as degradation.\n\nAll plasma proteins except Gamma-globulins are synthesised in the liver.\n\nIt is also responsible for a large part of amino acid synthesis.\n\nThe liver plays a role in the production of clotting factors, as well as red blood cell production.\n\nSome of the proteins synthesized by the liver include coagulation factors I (fibrinogen), II (prothrombin), V, VII, VIII, IX, X, XI, XII, XIII, as well as protein C, protein S and antithrombin.\n\nThe liver is a major site of production for thrombopoietin, a glycoprotein hormone that regulates the production of platelets by the bone marrow.\n\n==== Lipid metabolism ====\n\nThe liver plays several roles in lipid metabolism: it performs cholesterol synthesis, lipogenesis, and the production of triglycerides, and a bulk of the body's lipoproteins are synthesized in the liver.\n\nThe liver plays a key role in digestion, as it produces and excretes bile (a yellowish liquid) required for emulsifying fats and help the absorption of vitamin K from the diet.\n\nSome of the bile drains directly into the duodenum, and some is stored in the gallbladder.\n\nThe liver produces insulin-like growth factor 1, a polypeptide protein hormone that plays an important role in childhood growth and continues to have anabolic effects in adults.\n\n=== Breakdown ===\n\nThe liver is responsible for the breakdown of insulin and other hormones.\n\nThe liver breaks down bilirubin via glucuronidation, facilitating its excretion into bile.\n\nThe liver is responsible for the breakdown and excretion of many waste products.\n\nIt plays a key role in breaking down or modifying toxic substances (e.g., methylation) and most medicinal products in a process called drug metabolism.\n\nThis sometimes results in toxication, when the metabolite is more toxic than its precursor.\n\nPreferably, the toxins are conjugated to avail excretion in bile or urine.\n\nThe liver converts ammonia into urea as part of the ornithine cycle or the urea cycle, and the urea is excreted in the urine.\n\n=== Blood reservoir ===\n\nBecause the liver is an expandable organ, large quantities of\nblood can be stored in its blood vessels.\n\nIts normal blood volume, including both that in the hepatic veins and that in the hepatic sinuses, is about 450 milliliters, or almost 10 percent of the body's total blood volume.\n\nWhen high pressure in the right atrium causes backpressure in the liver, the liver expands, and 0.5 to 1 liter of extra blood is occasionally stored in the hepatic veins and sinuses.\n\nThis occurs especially in cardiac failure with peripheral congestion.\n\nThus, in effect, the liver is a large, expandable, venous organ capable of acting as a valuable blood reservoir in times of excess blood volume and capable of supplying extra blood in times of diminished blood volume.\n\n=== Lymph production ===\n\nBecause the pores in the hepatic sinusoids are very permeable and allow ready passage of both fluid and proteins into the perisinusoidal space, the lymph draining from the liver usually has a protein concentration of about 6 g/dl, which is only slightly less than the protein concentration of plasma.\n\nAlso, the high permeability of the liver sinusoid epithelium allows large quantities of lymph to form.\n\nTherefore, about half of all the lymph formed in the body under resting conditions arises in the liver.\n\n=== Other ===\n\nThe liver stores a multitude of substances, including vitamin A (1–2 years' supply), vitamin D (1–4 months' supply), vitamin B12 (3–5 years' supply), vitamin K, vitamin E, iron, copper, zinc, cobalt, molybdenum, etc.\n\nHaemopoiesis - The formation of blood cells is called haemopoiesis.\n\nIn embryonic stage RBC and WBC are formed by liver.\n\nIn the first trimester fetus, the liver is the main site of red blood cell production.\n\nBy the 32nd week of gestation, the bone marrow has almost completely taken over that task.\n\nLiver helps in purification of blood.\n\nThe Kupffer cells of liver are phagocytic cells, helps in phagocytosis of dead blood cells and bacteria from the blood.\n\nThe liver is responsible for immunological effects – the mononuclear phagocyte system of the liver contains many immunologically active cells, acting as a 'sieve' for antigens carried to it via the portal system.\n\nThe liver produces albumin, the most abundant protein in blood serum.\n\nIt is essential in the maintenance of oncotic pressure, and acts as a transport for fatty acids and steroid hormones.\n\nThe liver synthesizes angiotensinogen, a hormone that is responsible for raising the blood pressure when activated by renin, an enzyme that is released when the kidney senses low blood pressure.\n\nThe liver produces the enzyme catalase to break down hydrogen peroxide, a toxic oxidising agent, into water and oxygen.\n\n=== With aging ===\n\nThe oxidative capacity of the liver decreases with aging, and therefore any medications that require oxidation (for instance, benzodiazepines) are more likely to accumulate to toxic levels.\n\nHowever, medications with shorter half-lives, such as lorazepam and oxazepam, are preferred in most cases when benzodiazepines are required in regard to geriatric medicine.\n\n== Clinical significance ==\n\n=== Disease ===\n\nThe liver is a vital organ and supports almost every other organ in the body.\n\nBecause of its strategic location and multidimensional functions, the liver is also prone to many diseases.\n\nThe bare area of the liver is a site that is vulnerable to the passing of infection from the abdominal cavity to the thoracic cavity.\n\nLiver diseases may be diagnosed by liver function tests–blood tests that can identify various markers.\n\nFor example, acute-phase reactants are produced by the liver in response to injury or inflammation.\n\nHepatitis is a common condition of inflammation of the liver.\n\nThe most usual cause of this is viral, and the most common of these infections are hepatitis A, B, C, D, and E.\n\nSome of these infections are sexually transmitted.\n\nInflammation can also be caused by other viruses in the family Herpesviridae such as the herpes simplex virus.\n\nChronic (rather than acute) infection with hepatitis B virus or hepatitis C virus is the main cause of liver cancer.\n\nGlobally, about 248 million individuals are chronically infected with hepatitis B (with 843,724 in the U.S.), and 142 million are chronically infected with hepatitis C (with 2.7 million in the U.S.).\n\nGlobally there are about 114 million and 20 million cases of hepatitis A and hepatitis E respectively, but these generally resolve and do not become chronic.\n\nHepatitis D virus is a \"satellite\" of hepatitis B virus (can only infect in the presence of hepatitis B), and co-infects nearly 20 million people with hepatitis B, globally.\n\nHepatic encephalopathy is caused by an accumulation of toxins in the bloodstream that are normally removed by the liver.\n\nThis condition can result in coma and can prove fatal.\n\nBudd–Chiari syndrome is a condition caused by blockage of the hepatic veins (including thrombosis) that drain the liver.\n\nIt presents with the classical triad of abdominal pain, ascites and liver enlargement.\n\nMany diseases of the liver are accompanied by jaundice caused by increased levels of bilirubin in the system.\n\nThe bilirubin results from the breakup of the hemoglobin of dead red blood cells; normally, the liver removes bilirubin from the blood and excretes it through bile.\n\nOther disorders caused by excessive alcohol consumption are grouped under alcoholic liver diseases and these include alcoholic hepatitis, fatty liver, and cirrhosis.\n\nFactors contributing to the development of alcoholic liver diseases are not only the quantity and frequency of alcohol consumption, but can also include gender, genetics, and liver insult.\n\nLiver damage can also be caused by drugs, particularly paracetamol and drugs used to treat cancer.\n\nA rupture of the liver can be caused by a liver shot used in combat sports.\nPrimary biliary cholangitis is an autoimmune disease of the liver.\n\nIt is marked by slow progressive destruction of the small bile ducts of the liver, with the intralobular ducts (Canals of Hering) affected early in the disease.\n\nWhen these ducts are damaged, bile and other toxins build up in the liver (cholestasis) and over time damages the liver tissue in combination with ongoing immune related damage.\n\nThis can lead to scarring (fibrosis) and cirrhosis.\n\nCirrhosis increases the resistance to blood flow in the liver, and can result in portal hypertension.\n\nCongested anastomoses between the portal venous system and the systemic circulation, can be a subsequent condition.\n\nThere are also many pediatric liver diseases, including biliary atresia, alpha-1 antitrypsin deficiency, alagille syndrome, progressive familial intrahepatic cholestasis, Langerhans cell histiocytosis and hepatic hemangioma a benign tumour the most common type of liver tumour, thought to be congenital.\n\nA genetic disorder causing multiple cysts to form in the liver tissue, usually in later life, and usually asymptomatic, is polycystic liver disease.\n\nDiseases that interfere with liver function will lead to derangement of these processes.\n\nHowever, the liver has a great capacity to regenerate and has a large reserve capacity.\n\nIn most cases, the liver only produces symptoms after extensive damage.\n\nHepatomegaly refers to an enlarged liver and can be due to many causes.\n\nIt can be palpated in a liver span measurement.\n\n=== Symptoms ===\n\nThe classic symptoms of liver damage include the following:\n\nPale stools occur when stercobilin, a brown pigment, is absent from the stool.\n\nStercobilin is derived from bilirubin metabolites produced in the liver.\n\nDark urine occurs when bilirubin mixes with urine\n\nJaundice (yellow skin and/or whites of the eyes)\n\nThis is where bilirubin deposits in skin, causing an intense itch.\n\nItching is the most common complaint by people who have liver failure.\n\nOften this itch cannot be relieved by drugs.\n\nSwelling of the abdomen, and swelling of the ankles and feet occurs because the liver fails to make albumin.\n\nExcessive fatigue occurs from a generalized loss of nutrients, minerals and vitamins.\n\nBruising and easy bleeding are other features of liver disease.\n\nThe liver makes clotting factors, substances which help prevent bleeding.\n\nWhen liver damage occurs, these factors are no longer present and severe bleeding can occur.\n\nPain in the upper right quadrant can result from the stretching of Glisson's capsule in conditions of hepatitis and pre-eclampsia.\n\n=== Diagnosis ===\n\nThe diagnosis of liver disease is made by liver function tests, groups of blood tests, that can readily show the extent of liver damage.\n\nIf infection is suspected, then other serological tests will be carried out.\n\nA physical examination of the liver can only reveal its size and any tenderness, and some form of imaging such as an ultrasound or CT scan may also be needed.\n\nSometimes a liver biopsy will be necessary, and a tissue sample is taken through a needle inserted into the skin just below the rib cage.\n\nThis procedure may be helped by a sonographer providing ultrasound guidance to an interventional radiologist.\n\n=== Liver regeneration ===\n\nThe liver is the only human internal organ capable of natural regeneration of lost tissue; as little as 25% of a liver can regenerate into a whole liver.\n\nThis is, however, not true regeneration but rather compensatory growth in mammals.\n\nThe lobes that are removed do not regrow and the growth of the liver is a restoration of function, not original form.\n\nThis contrasts with true regeneration where both original function and form are restored.\n\nIn some other species, such as zebrafish, the liver undergoes true regeneration by restoring both shape and size of the organ.\n\nIn the liver, large areas of the tissues are formed but for the formation of new cells there must be sufficient amount of material so the circulation of the blood becomes more active.\n\nThis is predominantly due to the hepatocytes re-entering the cell cycle.\n\nThat is, the hepatocytes go from the quiescent G0 phase to the G1 phase and undergo mitosis.\n\nThis process is activated by the p75 receptors.\n\nThere is also some evidence of bipotential stem cells, called hepatic oval cells or ovalocytes (not to be confused with oval red blood cells of ovalocytosis), which are thought to reside in the canals of Hering.\n\nThese cells can differentiate into either hepatocytes or cholangiocytes.\n\nCholangiocytes are the epithelial lining cells of the bile ducts.\n\nThey are cuboidal epithelium in the small interlobular bile ducts, but become columnar and mucus secreting in larger bile ducts approaching the porta hepatis and the extrahepatic ducts.\n\nResearch is being carried out on the use of stem cells for the generation of an artificial liver.\n\nScientific and medical works about liver regeneration often refer to the Greek Titan Prometheus who was chained to a rock in the Caucasus where, each day, his liver was devoured by an eagle, only to grow back each night.\n\nThe myth suggests the ancient Greeks may have known about the liver's remarkable capacity for self-repair.\n\n=== Liver transplantation ===\n\nHuman liver transplants were first performed by Thomas Starzl in the United States and Roy Calne in Cambridge, England in 1963 and 1967, respectively.\n\nLiver transplantation is the only option for those with irreversible liver failure.\n\nMost transplants are done for chronic liver diseases leading to cirrhosis, such as chronic hepatitis C, alcoholism, and autoimmune hepatitis.\n\nLess commonly, liver transplantation is done for fulminant hepatic failure, in which liver failure occurs over days to weeks.\n\nLiver allografts for transplant usually come from donors who have died from fatal brain injury.\n\nLiving donor liver transplantation is a technique in which a portion of a living person's liver is removed (hepatectomy) and used to replace the entire liver of the recipient.\n\nThis was first performed in 1989 for pediatric liver transplantation.\n\nOnly 20 percent of an adult's liver (Couinaud segments 2 and 3) is needed to serve as a liver allograft for an infant or small child.\n\nMore recently, adult-to-adult liver transplantation has been done using the donor's right hepatic lobe, which amounts to 60 percent of the liver.\n\nDue to the ability of the liver to regenerate, both the donor and recipient end up with normal liver function if all goes well.\n\nThis procedure is more controversial, as it entails performing a much larger operation on the donor, and indeed there were at least two donor deaths out of the first several hundred cases.\n\nA 2006 publication addressed the problem of donor mortality and found at least fourteen cases.\n\nThe risk of postoperative complications (and death) is far greater in right-sided operations than that in left-sided operations.\n\nWith the recent advances of noninvasive imaging, living liver donors usually have to undergo imaging examinations for liver anatomy to decide if the anatomy is feasible for donation.\n\nThe evaluation is usually performed by multidetector row computed tomography (MDCT) and magnetic resonance imaging (MRI).\n\nMDCT is good in vascular anatomy and volumetry.\n\nMRI is used for biliary tree anatomy.\n\nDonors with very unusual vascular anatomy, which makes them unsuitable for donation, could be screened out to avoid unnecessary operations.\n\n== Society and culture ==\n\nSome cultures regard the liver as the seat of the soul.\n\nIn Greek mythology, the gods punished Prometheus for revealing fire to humans by chaining him to a rock where a vulture (or an eagle) would peck out his liver, which would regenerate overnight.\n\n(The liver is the only human internal organ that actually can regenerate itself to a significant extent.)\n\nMany ancient peoples of the Near East and Mediterranean areas practiced a type of divination called haruspicy or hepatomancy, where they tried to obtain information by examining the livers of sheep and other animals.\n\nIn Plato, and in later physiology, the liver was thought to be the seat of the darkest emotions (specifically wrath, jealousy and greed) which drive men to action.\n\nThe Talmud (tractate Berakhot 61b) refers to the liver as the seat of anger, with the gallbladder counteracting this.\n\nThe Persian, Urdu, and Hindi languages (جگر or jigar) refer to the liver figurative speech to indicate courage and strong feelings, or \"their best\"; e.g., \"This Mecca has thrown to you the pieces of its liver!\".\n\nThe term jan e jigar, literally \"the strength (power) of my liver\", is a term of endearment in Urdu.\n\nIn Persian slang, jigar is used as an adjective for any object which is desirable, especially women.\n\nIn the Zulu language, the word for liver (isibindi) is the same as the word for courage.\n\nIn English the term 'lily-livered' is used to indicate cowardice from the medieval belief that the liver was the seat of courage.\nSpanish hígados also means \"courage\".\n\nHowever the secondary meaning of Basque gibel is \"indolence\".In biblical Hebrew, the word for liver, כבד (Kauved, stemmed KBD or KVD, similar to Arabic الكبد), also means heavy and is used to describe the rich (\"heavy\" with possessions) and honor (presumably for the same reason).\n\nIn the Book of Lamentations (2:11) it is used to describe the physiological responses to sadness by \"my liver spilled to earth\" along with the flow of tears and the overturning in bitterness of the intestines.\n\nOn several occasions in the book of Psalms (most notably 16:9), the word is used to describe happiness in the liver, along with the heart (which beats rapidly) and the flesh (which appears red under the skin).\n\nFurther usage as the self (similar to \"your honor\") is widely available throughout the old testament, sometimes compared to the breathing soul (Genesis 49:6, Psalms 7:6, etc.).\n\nAn honorable hat was also referred to with this word (Job 19:9, etc.) and under that definition appears many times along with פאר Pe'er - grandeur.\n\nThese four meanings were used in preceding ancient Semitic languages such as Accadian and Ancient Egyptian preserved in classical Ethiopic Ge'ez language.\n\n=== Food ===\n\nHumans commonly eat the livers of mammals, fowl, and fish as food.\n\nDomestic pig, ox, lamb, calf, chicken, and goose livers are widely available from butchers and supermarkets.\n\nIn the Romance languages, the anatomical word for \"liver\" (French foie, Spanish hígado, etc.) derives not from the Latin anatomical term, jecur, but from the culinary term ficatum, literally \"stuffed with figs,\" referring to the livers of geese that had been fattened on figs.\n\nAnimal livers are rich in iron, vitamin A and vitamin B12; and cod liver oil is commonly used as a dietary supplement.\n\nLiver can be baked, boiled, broiled, fried, stir-fried, or eaten raw (asbeh nayeh or sawda naye in Lebanese cuisine, or liver sashimi in Japanese cuisine).\n\nIn many preparations, pieces of liver are combined with pieces of meat or kidneys, as in the various forms of Middle Eastern mixed grill (e.g. meurav Yerushalmi).\n\nWell-known examples include liver pâté, foie gras, chopped liver, and leverpastej.\n\nLiver sausages, such as Braunschweiger and liverwurst, are also a valued meal.\n\nLiver sausages may also be used as spreads.\n\nA traditional South African delicacy, skilpadjies, is made of minced lamb's liver wrapped in netvet (caul fat), and grilled over an open fire.\n\nTraditionally, some fish livers were valued as food, especially the stingray liver.\n\nIt was used to prepare delicacies, such as poached skate liver on toast in England, as well as the beignets de foie de raie and foie de raie en croute in French cuisine.\n\n=== Giraffe liver ===\n\nThe Humr, one of the tribes in the Baggara ethnic grouping, native to southwestern Kordofan in Sudan and speakers of Shuwa or Chadian Arabic, prepare a non-alcoholic drink from the liver and bone marrow of the giraffe which they call umm nyolokh, and which they claim is intoxicating ( Arabic سكران sakran ), causing dreams and even waking hallucinations.\n\nAnthropologist Ian Cunnison, who accompanied the Humr on one of their giraffe-hunting expeditions in the late 1950s, notes that:\n\nIt is said that a person, once he has drunk umm nyolokh, will return to giraffe again and again.\n\nHumr, being Mahdists, are strict abstainers [ from alcohol ] and a Humrawi is never drunk ( sakran ) on liquor or beer.\n\nBut he uses this word to describe the effects which umm nyolokh has upon him.\n\nCunnison's remarkable account of an apparently psychoactive mammal found its way from a somewhat obscure scientific paper into more mainstream literature through a conversation between Dr.\n\nWendy James of the Institute of Social and Cultural Anthropology at the University of Oxford and specialist on the use of hallucinogens and intoxicants in society Richard Rudgley, who considered its implications in his popular work The Encyclopedia of Psychoactive Substances.\n\nRudgley hypothesises that the presence of the hallucinogenic compound DMT might account for the putative intoxicating properties of umm nyolokh.Cunnison himself, on the other hand, had found it hard fully to believe in the literal truth of the Humr's assertion that their drink was intoxicating:\n\nI can only assume that there is no intoxicating substance in the drink and that the effect it produces is simply a matter of convention, although it may be brought about subconsciously.\n\nThe study of entheogens in general - including entheogens of animal origin ( e.g. hallucinogenic fish and toad venom ) - has, however, made considerable progress in the sixty-odd years since Cunnison's report and the idea that some intoxicating principle might reside in giraffe liver no longer seems as far-fetched as it was in Cunnison's day, although conclusive proof ( or disproof ) will have to await detailed analyses of the animal organ in question and the drink prepared therefrom.\n\n=== Arrow/bullet poison ===\n\nCertain Tungusic peoples formerly prepared a type of arrow poison from rotting animal livers, which was, in later times, also applied to bullets.\n\nRussian anthropologist Sergei Mikhailovich Shirokogorov notes that: Formerly the using of poisoned arrows was common.\n\nFor instance, among the Kumarčen, [ a subgroup of the Oroqen ] even in recent times a poison was used which was prepared from decaying liver.\n\nThis has been confirmed by the Kumarčen.\n\nI am not competent to judge as to the chemical conditions of production of poison which is not destroyed by the heat of explosion.\n\nHowever, the Tungus themselves compare this method [ of poisoning ammunition ] with the poisoning of arrows.\n\n== Other animals ==\n\nThe liver is found in all vertebrates and is typically the largest internal organ.\n\nIts form varies considerably in different species, and is largely determined by the shape and arrangement of the surrounding organs.\n\nNonetheless, in most species it is divided into right and left lobes; exceptions to this general rule include snakes, where the shape of the body necessitates a simple cigar-like form.\n\nThe internal structure of the liver is broadly similar in all vertebrates.\n\nAn organ sometimes referred to as a liver is found associated with the digestive tract of the primitive chordate Amphioxus.\n\nAlthough it performs many functions of a liver, it is not considered a true liver but a homolog of the vertebrate liver.\n\nThe amphioxus hepatic caecum produces the liver-specific proteins vitellogenin, antithrombin, plasminogen, alanine aminotransferase, and insulin/Insulin-like growth factor (IGF)\n\nhttps://en.wikipedia.org/wiki/Liver","gallbladder":"In vertebrates, the gallbladder, also known as the cholecyst, is a small hollow organ where bile is stored and concentrated before it is released into the small intestine.\n\nIn humans, the pear-shaped gallbladder lies beneath the liver, although the structure and position of the gallbladder can vary significantly among animal species.\n\nIt receives and stores bile, produced by the liver, via the common hepatic duct, and releases it via the common bile duct into the duodenum, where the bile helps in the digestion of fats.\n\nThe gallbladder can be affected by gallstones, formed by material that cannot be dissolved – usually cholesterol or bilirubin, a product of haemoglobin breakdown.\n\nThese may cause significant pain, particularly in the upper-right corner of the abdomen, and are often treated with removal of the gallbladder called a cholecystectomy.\n\nCholecystitis, inflammation of the gallbladder, has a wide range of causes, including result from the impaction of gallstones, infection, and autoimmune disease.\n\n== Structure ==\n\nThe gallbladder is a hollow organ that sits in a shallow depression below the right lobe of the liver, which is grey-blue in life.\n\nIn adults, the gallbladder measures approximately 7 to 10 centimetres (2.8 to 3.9 inches) in length and 4 centimetres (1.6 in) in diameter when fully distended.\n\nThe gallbladder has a capacity of about 50 millilitres (1.8 imperial fluid ounces).\n\nThe gallbladder is shaped like a pear, with its tip opening into the cystic duct.\n\nThe gallbladder is divided into three sections: the fundus, body, and neck.\n\nThe fundus is the rounded base, angled so that it faces the abdominal wall.\n\nThe body lies in a depression in the surface of the lower liver.\n\nThe neck tapers and is continuous with the cystic duct, part of the biliary tree.\n\nThe gallbladder fossa, against which the fundus and body of the gallbladder lie, is found beneath the junction of hepatic segments IVB and V.\n\nThe cystic duct unites with the common hepatic duct to become the common bile duct.\n\nAt the junction of the neck of the gallbladder and the cystic duct, there is an out-pouching of the gallbladder wall forming a mucosal fold known as \"Hartmann's pouch\".Lymphatic drainage of the gallbladder follows the cystic node which is located between cystic duct and common hepatic ducts.\n\nLymphatics from the lower part of the drain into lower hepatic lymph nodes.\n\nAll the lymph finally drains into celiac lymph nodes.\n\n=== Microanatomy ===\n\nThe gallbladder wall is composed of a number of layers.\n\nThe gallbladder wall's innermost surface is lined by a single layer of columnar cells with a brush border of microvilli, very similar to intestinal absorptive cells.\n\nUnderneath the epithelium is an underlying lamina propria, a muscular layer, an outer perimuscular layer and serosa.\n\nUnlike elsewhere in the intestinal tract, the gallbladder does not have a muscularis mucosae, and the muscular fibres are not arranged in distinct layers.\n\nThe mucosa, the inner portion of the gallbladder wall, consists of a lining of a single layer of columnar cells, with cells possessing small hair-like attachments called microvilli.\n\nThis sits on a thin layer of connective tissue, the lamina propria.\n\nThe mucosa is curved and collected into tiny outpouchings called rugae.A muscular layer sits beneath the mucosa.\n\nThis is formed by smooth muscle, with fibres that lie in longitudinal, oblique and transverse directions, and are not arranged in separate layers.\n\nThe muscle fibres here contract to expel bile from the gallbladder.\n\nA distinctive feature of the gallbladder is the presence of Rokitansky–Aschoff sinuses, deep outpouchings of the mucosa that can extend through the muscular layer, and which indicate adenomyomatosis.\n\nThe muscular layer is surrounded by a layer of connective and fat tissue.The outer layer of the fundus of gallbladder, and the surfaces not in contact with the liver, are covered by a thick serosa, which is exposed to the peritoneum.\n\nThe serosa contains blood vessels and lymphatics.\n\nThe surfaces in contact with the liver are covered in connective tissue.\n\n=== Variation ===\n\nThe gallbladder varies in size, shape, and position between different people.\n\nRarely, two or even three gallbladders may coexist, either as separate bladders draining into the cystic duct, or sharing a common branch that drains into the cystic duct.\n\nAdditionally, the gallbladder may fail to form at all.\n\nGallbladders with two lobes separated by a septum may also exist.\n\nThese abnormalities are not likely to affect function and are generally asymptomatic.\n\nThe location of the gallbladder in relation to the liver may also vary, with documented variants including gallbladders found within, above, on the left side of, behind, and detached or suspended from the liver.\n\nSuch variants are very rare: from 1886 to 1998, only 110 cases of left-lying liver, or less than one per year, were reported in scientific literature.An anatomical variation can occur, known as a Phrygian cap, which is an innocuous fold in the fundus, named after its resemblance to the Phrygian cap.\n\n=== Development ===\n\nThe gallbladder develops from an endodermal outpouching of the embryonic gut tube.\n\nEarly in development, the human embryo has three germ layers and abuts an embryonic yolk sac.\n\nDuring the second week of embryogenesis, as the embryo grows, it begins to surround and envelop portions of this sac.\n\nThe enveloped portions form the basis for the adult gastrointestinal tract.\n\nSections of this foregut begin to differentiate into the organs of the gastrointestinal tract, such as the esophagus, stomach, and intestines.During the fourth week of embryological development, the stomach rotates.\n\nThe stomach, originally lying in the midline of the embryo, rotates so that its body is on the left.\n\nThis rotation also affects the part of the gastrointestinal tube immediately below the stomach, which will go on to become the duodenum.\n\nBy the end of the fourth week, the developing duodenum begins to spout a small outpouching on its right side, the hepatic diverticulum, which will go on to become the biliary tree.\n\nJust below this is a second outpouching, known as the cystic diverticulum, that will eventually develop into the gallbladder.\n\n== Function ==\n\nThe main function of the gallbladder is to store bile, also called gall, needed for the digestion of fats in food.\n\nProduced by the liver, bile flows through small vessels into the larger hepatic ducts and ultimately through the cystic duct (parts of the biliary tree) into the gallbladder, where it is stored.\n\nAt any one time, 30 to 60 millilitres (1.0 to 2.0 US fl oz) of bile is stored within the gallbladder.When food containing fat enters the digestive tract, it stimulates the secretion of cholecystokinin (CCK) from I cells of the duodenum and jejunum.\n\nIn response to cholecystokinin, the gallbladder rhythmically contracts and releases its contents into the common bile duct, eventually draining into the duodenum.\n\nThe bile emulsifies fats in partly digested food, thereby assisting their absorption.\n\nBile consists primarily of water and bile salts, and also acts as a means of eliminating bilirubin, a product of hemoglobin metabolism, from the body.\n\nThe bile that is secreted by the liver and stored in the gallbladder is not the same as the bile that is secreted by the gallbladder.\n\nDuring gallbladder storage of bile, it is concentrated 3-10 fold by removal of some water and electrolytes.\n\nThis is through the active transport of sodium and chloride ions across the epithelium of the gallbladder, which creates an osmotic pressure that also causes water and other electrolytes to be reabsorbed.\n\n== Clinical significance ==\n\n=== Gallstones ===\n\nGallstones form when the bile is saturated, usually with either cholesterol or bilirubin.\n\nMost gallstones do not cause symptoms, with stones either remaining in the gallbladder or passed along the biliary system.\n\nWhen symptoms occur, severe \"colicky\" pain in the upper right part of the abdomen is often felt.\n\nIf the stone blocks the gallbladder, inflammation known as cholecystitis may result.\n\nIf the stone lodges in the biliary system, jaundice may occur; if the stone blocks the pancreatic duct, pancreatitis may occur.\n\nGallstones are diagnosed using ultrasound.\n\nWhen a symptomatic gallstone occurs, it is often managed by waiting for it to be passed naturally.\n\nGiven the likelihood of recurrent gallstones, surgery to remove the gallbladder is often considered.\n\nSome medication, such as ursodeoxycholic acid, may be used; lithotripsy, a procedure used to break down the stones, may also be used.\n\n=== Inflammation ===\n\nKnown as cholecystitis, inflammation of the gallbladder is commonly caused by obstruction of the duct with gallstones, which is known as cholelithiasis.\n\nBlocked bile accumulates, and pressure on the gallbladder wall may lead to the release of substances that cause inflammation, such as phospholipase.\n\nThere is also the risk of bacterial infection.\n\nAn inflamed gallbladder is likely to cause sharp and localised pain, fever, and tenderness in the upper, right corner of the abdomen, and may have a positive Murphy's sign.\n\nCholecystitis is often managed with rest and antibiotics, particularly cephalosporins and, in severe cases, metronidazole.\n\nAdditionally the gallbladder may need to be removed surgically if inflammation has progressed far enough.\n\n=== Gallbladder removal ===\n\nA cholecystectomy is a procedure in which the gallbladder is removed.\n\nIt may be removed because of recurrent gallstones and is considered an elective procedure.\n\nA cholecystectomy may be an open procedure, or a laparoscopic one.\n\nIn the surgery, the gallbladder is removed from the neck to the fundus, and so bile will drain directly from the liver into the biliary tree.\n\nAbout 30 percent of patients may experience some degree of indigestion following the procedure, although severe complications are much rarer.\n\nAbout 10 percent of surgeries lead to a chronic condition of postcholecystectomy syndrome.\n\n=== Complication ===\n\nBiliary injury (bile duct injury) is the traumatic damage of the bile ducts.\n\nIt is most commonly an iatrogenic complication of cholecystectomy — surgical removal of gall bladder, but can also be caused by other operations or by major trauma.\n\nThe risk of biliary injury is more during laparoscopic cholecystectomy than during open cholecystectomy.\n\nBiliary injury may lead to several complications and may even cause death if not diagnosed in time and managed properly.\n\nIdeally biliary injury should be managed at a center with facilities and expertise in endoscopy, radiology and surgery.Biloma is collection of bile within the abdominal cavity.\n\nIt happens when there is a bile leak, for example after surgery for removing the gallbladder (laparoscopic cholecystectomy), with an incidence of 0.3–2%.\n\nOther causes are biliary surgery, liver biopsy, abdominal trauma, and, rarely, spontaneous perforation.\n\n=== Cancer ===\n\nCancer of the gallbladder is uncommon and mostly occurs in later life.\n\nWhen cancer occurs, it is mostly of the glands lining the surface of the gallbladder (adenocarcinoma).\n\nGallstones are thought to be linked to the formation of cancer.\n\nOther risk factors include large (>1 cm) gallbladder polyps and having a highly calcified \"porcelain\" gallbladder.\n\nCancer of the gallbladder can cause attacks of biliary pain, yellowing of the skin (jaundice), and weight loss.\n\nA large gallbladder may be able to be felt in the abdomen.\n\nLiver function tests may be elevated, particularly involving GGT and ALP, with ultrasound and CT scans being considered medical imaging investigations of choice.\n\nCancer of the gallbladder is managed by removing the gallbladder, however, as of 2010, the prognosis remains poor.\n\nCancer of the gallbladder may also be found incidentally after surgical removal of the gallbladder, with 1–3% of cancers identified in this way.\n\nGallbladder polyps are mostly benign growths or lesions resembling growths that form in the gallbladder wall, and are only associated with cancer when they are larger in size (>1 cm).\n\nCholesterol polyps, often associated with cholesterolosis (\"strawberry gallbladder\", a change in the gallbladder wall due to excess cholesterol), often cause no symptoms and are thus often detected in this way.\n\n=== Tests ===\n\nTests used to investigate for gallbladder disease include blood tests and medical imaging.\n\nA full blood count may reveal an increased white cell count suggestive of inflammation or infection.\n\nTests such as bilirubin and liver function tests may reveal if there is inflammation linked to the biliary tree or gallbladder, and whether this is associated with inflammation of the liver, and a lipase or amylase may be elevated if there is pancreatitis.\n\nBilirubin may rise when there is obstruction of the flow of bile.\n\nA CA 19-9 level may be taken to investigate for cholangiocarcinoma.An ultrasound is often the first medical imaging test performed when gallbladder disease such as gallstones are suspected.\n\nAn abdominal X-ray or CT scan is another form of imaging that may be used to examine the gallbladder and surrounding organs.\n\nOther imaging options include MRCP (magnetic resonance cholangiopancreatography), ERCP and percutaneous or intraoperative cholangiography.\n\nA cholescintigraphy scan is a nuclear imaging procedure used to assess the condition of the gallbladder.\n\n== Other animals ==\n\nMost vertebrates have gallbladders, but the form and arrangement of the bile ducts may vary considerably.\n\nIn many species, for example, there are several separate ducts running to the intestine, rather than the single common bile duct found in humans.\n\nSeveral species of mammals (including horses, deer, rats, and laminoids), several species of birds (such as pigeons and some psittacine species), lampreys and all invertebrates do not have a gallbladder .\n\nThe bile from several species of bears is used in traditional Chinese medicine; bile bears are kept alive in captivity while their bile is extracted, in an industry characterized by animal cruelty.\n\n== History ==\n\nDepictions of the gallbladder and biliary tree are found in Babylonian models found from 2000 BCE, and in ancient Etruscan model from 200 BCE, with models associated with divine worship.\n\nDiseases of the gallbladder are known to have existed in humans since antiquity, with gallstones found in the mummy of Princess Amenen of Thebes dating to 1500 BCE.\n\nSome historians believe the death of Alexander the Great may have been associated with an acute episode of cholecystitis.\n\nThe existence of the gallbladder has been noted since the 5th century, but it is only relatively recently that the function and the diseases of the gallbladder has been documented, particularly in the last two centuries.\n\nThe first descriptions of gallstones appear to have been in the Renaissance, perhaps because of the low incidence of gallstones in earlier times owing to a diet with more cereals and vegetables and less meat.\n\nAnthonius Benevinius in 1506 was the first to draw a connection between symptoms and the presence of gallstones.\n\nLudwig Georg Courvoisier, after examining a number of cases in 1890 that gave rise to the eponymous Courvoisier's law, stated that in an enlarged, nontender gallbladder, the cause of jaundice is unlikely to be gallstones.\n\nThe first surgical removal of a gallstone (cholecystolithotomy) was in 1676 by physician Joenisius, who removed the stones from a spontaneously occurring biliary fistula.\n\nStough Hobbs in 1867 performed the first recorded cholecystotomy, although such an operation was in fact described earlier by French surgeon Jean Louis Petit in the mid eighteenth century.\n\nGerman surgeon Carl Langenbuch performed the first cholecystectomy in 1882 for a sufferer of cholelithiasis.\n\nBefore this, surgery had focused on creating a fistula for drainage of gallstones.\n\nLangenbuch reasoned that given several other species of mammal have no gallbladder, humans could survive without one.\n\nThe debate whether surgical removal of the gallbladder or simply gallstones was preferred was settled in the 1920s, with the consensus that removal of the gallbladder was preferred.\n\nIt was only in the mid and late parts of the twentieth century that medical imaging techniques such as use of contrast medium and CT scans were used to view the gallbladder.\n\nThe first laparoscopic cholecystectomy performed by Erich Mühe of Germany in 1985, although French surgeons Phillipe Mouret and Francois Dubois are often credited for their operations in 1987 and 1988 respectively.\n\n== Society and culture ==\n\nTo have \"gall\" is associated with bold behaviour, whereas to have \"bile\" is associated with bitterness.\n\nIn the Chinese language, the gallbladder (Chinese: 膽) is associated with courage and a myriad of related idioms, including using terms such as \"a body completely [of] gall\" (Chinese: 渾身是膽) to describe a brave person, and \"single gallbladder hero\" (Chinese: 孤膽英雄) to describe a lone hero.In the Zangfu theory of Chinese medicine, the gallbladder not only has a digestive role, but is seen as the seat of decision-making.\n\nhttps://en.wikipedia.org/wiki/Gallbladder","pancreas":"The pancreas is an organ of the digestive system and endocrine system of vertebrates.\n\nIn humans, it is located in the abdomen behind the stomach and functions as a gland.\n\nThe pancreas is a mixed or heterocrine gland, i.e. it has both an endocrine and a digestive exocrine function. 99% of the pancreas is exocrine and 1% is endocrine.\n\nAs an endocrine gland, it functions mostly to regulate blood sugar levels, secreting the hormones insulin, glucagon, somatostatin, and pancreatic polypeptide.\n\nAs a part of the digestive system, it functions as an exocrine gland secreting pancreatic juice into the duodenum through the pancreatic duct.\n\nThis juice contains bicarbonate, which neutralizes acid entering the duodenum from the stomach; and digestive enzymes, which break down carbohydrates, proteins, and fats in food entering the duodenum from the stomach.\nInflammation of the pancreas is known as pancreatitis, with common causes including chronic alcohol use and gallstones.\n\nBecause of its role in the regulation of blood sugar, the pancreas is also a key organ in diabetes mellitus.\n\nPancreatic cancer can arise following chronic pancreatitis or due to other reasons, and carries a very poor prognosis, as it is often identified when it has spread to other areas of the body.\nThe word pancreas comes from the Greek πᾶν (pân, “all”) & κρέας (kréas, “flesh”).\n\nThe function of the pancreas in diabetes has been known since at least 1889, with its role in insulin production identified in 1921.\n\n== Structure ==\n\nThe pancreas is an organ that in humans lies in the abdomen, stretching from behind the stomach to the left upper abdomen near the spleen.\n\nIn adults, it is about 12–15 centimetres (4.7–5.9 in) long, lobulated, and salmon-coloured in appearance.Anatomically, the pancreas is divided into a head, neck, body, and tail.\n\nThe pancreas stretches from the inner curvature of the duodenum, where the head surrounds two blood vessels: the superior mesenteric artery, and vein.\n\nThe longest part of the pancreas, the body, stretches across behind the stomach, and the tail of the pancreas ends adjacent to the spleen.Two ducts, the main pancreatic duct and a smaller accessory pancreatic duct run through the body of the pancreas.\n\nThe main pancreatic duct joins with the common bile duct forming a small ballooning called the ampulla of Vater (hepatopancreatic ampulla).\n\nThis ampulla is surrounded by a muscle, the sphincter of Oddi.\n\nThis ampulla opens into the descending part of the duodenum.\n\nThe opening of the common bile duct into main pancreatic duct is controlled by sphincter of Boyden.\n\nThe accessory pancreatic duct opens into duodenum with separate openings located above the opening of the main pancreatic duct.\n\n=== Parts ===\n\nThe head of the pancreas sits within the curvature of the duodenum, and wraps around the superior mesenteric artery and vein.\n\nTo the right sits the descending part of the duodenum, and between these travel the superior and inferior pancreaticoduodenal arteries.\n\nBehind rests the inferior vena cava, and the common bile duct.\n\nIn front sits the peritoneal membrane and the transverse colon.\n\nA small uncinate process emerges from below the head, situated behind the superior mesenteric vein and sometimes artery.The neck of the pancreas separates the head of the pancreas, located in the curvature of the duodenum, from the body.\n\nThe neck is about 2 cm (0.79 in) wide, and sits in front of where the portal vein is formed.\n\nThe neck lies mostly behind the pylorus of the stomach, and is covered with peritoneum.\n\nThe anterior superior pancreaticoduodenal artery travels in front of the neck of the pancreas.The body is the largest part of the pancreas, and mostly lies behind the stomach, tapering along its length.\n\nThe peritoneum sits on top of the body of the pancreas, and the transverse colon in front of the peritoneum.\n\nBehind the pancreas are several blood vessels, including the aorta, the splenic vein, and the left renal vein, as well as the beginning of the superior mesenteric artery.\n\nBelow the body of the pancreas sits some of the small intestine, specifically the last part of the duodenum and the jejunum to which it connects, as well as the suspensory ligament of the duodenum which falls between these two.\n\nIn front of the pancreas sits the transverse colon.The pancreas narrows towards the tail, which sits near to the spleen.\n\nIt is usually between 1.3–3.5 cm (0.51–1.38 in) long, and sits between the layers of the ligament between the spleen and the left kidney.\n\nThe splenic artery and vein, which also passes behind the body of the pancreas, pass behind the tail of the pancreas.\n\n=== Blood supply ===\n\nThe pancreas has a rich blood supply, with vessels originating as branches of both the coeliac artery and superior mesenteric artery.\n\nThe splenic artery runs along the top of the pancreas, and supplies the left part of the body and the tail of the pancreas through its pancreatic branches, the largest of which is called the greater pancreatic artery.\n\nThe superior and inferior pancreaticoduodenal arteries run along the back and front surfaces of the head of the pancreas adjacent to the duodenum.\n\nThese supply the head of the pancreas.\n\nThese vessels join together (anastamose) in the middle.The body and neck of the pancreas drain into the splenic vein, which sits behind the pancreas.\n\nThe head drains into, and wraps around, the superior mesenteric and portal veins, via the pancreaticoduodenal veins.The pancreas drains into lymphatic vessels that travel alongside its arteries, and has a rich lymphatic supply.\n\nThe lymphatic vessels of the body and tail drain into splenic lymph nodes, and eventually into lymph nodes that lie in front of the aorta, between the coeliac and superior mesenteric arteries.\n\nThe lymphatic vessels of the head and neck drain into intermediate lymphatic vessels around the pancreaticoduodenal, mesenteric and hepatic arteries, and from there into the lymph nodes that lie in front of the aorta.\n\n=== Microanatomy ===\n\nThe pancreas contains tissue with an endocrine and exocrine role, and this division is also visible when the pancreas is viewed under a microscope.The majority of pancreatic tissue has a digestive role.\n\nThe cells with this role form clusters (Latin: acini) around small ducts, and are arranged in lobes that have thin fibrous walls.\n\nThe cells of each acinus secrete inactive digestive enzymes called zymogens into the small intercalated ducts which they surround.\n\nIn each acinus, the cells are pyramid-shaped and situated around the intercalated ducts, with the nuclei resting on the basement membrane, a large endoplasmic reticulum, and a number of zymogen granules visible within the cytoplasm.\n\nThe intercalated ducts drain into larger intralobular ducts within the lobule, and finally interlobular ducts.\n\nThe ducts are lined by a single layer of column-shaped cells.\n\nThere is more than one layer of cells as the diameter of the ducts increases.The tissues with an endocrine role within the pancreas exist as clusters of cells called pancreatic islets (also called islets of Langerhans) that are distributed throughout the pancreas.\n\nPancreatic islets contain alpha cells, beta cells, and delta cells, each of which releases a different hormone.\n\nThese cells have characteristic positions, with alpha cells (secreting glucagon) tending to be situated around the periphery of the islet, and beta cells (secreting insulin) more numerous and found throughout the islet.\n\nEnterochromaffin cells are also scattered throughout the islets.\n\nIslets are composed of up to 3,000 secretory cells, and contain several small arterioles to receive blood, and venules that allow the hormones secreted by the cells to enter the systemic circulation.\n\n=== Variation ===\n\nThe size of the pancreas varies considerably.\n\nSeveral anatomical variations exist, relating to the embryological development of the two pancreatic buds.\n\nThe pancreas develops from these buds on either side of the duodenum.\n\nThe ventral bud rotates to lie next to the dorsal bud, eventually fusing.\n\nIn about 10% of adults, an accessory pancreatic duct may be present if the main duct of the dorsal bud of the pancreas does not regress; this duct opens into the minor duodenal papilla.\n\nIf the two buds themselves, each having a duct, do not fuse, a pancreas may exist with two separate ducts, a condition known as a pancreas divisum.\n\nThis condition has no physiologic consequence.\n\nIf the ventral bud does not fully rotate, an annular pancreas may exist, where part or all of the duodenum is encircled by the pancreas.\n\nThis may be associated with duodenal atresia.\n\n=== Gene and protein expression ===\n\n10,000 protein coding genes (50% of all genes) are expressed in the normal human pancreas.\n\nLess than 100 of these genes are specifically expressed in the pancreas.\n\nSimilar to the salivary glands, most pancreas-specific genes encode for secreted proteins.\n\nCorresponding pancreas-specific proteins are either expressed in the exocrine cellular compartment and have functions related to digestion or food uptake such as digestive chymotrypsinogen enzymes and pancreatic lipase PNLIP, or are expressed in the various cells of the endocrine pancreatic islets and have functions related to secreted hormones such as insulin, glucagon, somatostatin and pancreatic polypeptide.\n\n== Development ==\n\nThe pancreas forms during development from two buds that arise from the duodenal part of the foregut, an embryonic tube that is a precursor to the gastrointestinal tract.\n\nIt is of endodermal origin.\n\nPancreatic development begins with the formation of a dorsal and ventral pancreatic bud.\n\nEach joins with the foregut through a duct.\n\nThe dorsal pancreatic bud forms the neck, body, and tail of the developed pancreas, and the ventral pancreatic bud forms the head and uncinate process.The definitive pancreas results from rotation of the ventral bud and the fusion of the two buds.\n\nDuring development, the duodenum rotates to the right, and the ventral bud rotates with it, moving to a position that becomes more dorsal.\n\nUpon reaching its final destination, the ventral pancreatic bud is below the larger dorsal bud, and eventually fuses with it.\n\nAt this point of fusion, the main ducts of the ventral and dorsal pancreatic buds fuse, forming the main pancreatic duct.\n\nUsually, the duct of the dorsal bud regresses, leaving the main pancreatic duct.\n\n=== Cellular development ===\n\nPancreatic progenitor cells are precursor cells that differentiate into the functional pancreatic cells, including exocrine acinar cells, endocrine islet cells, and ductal cells.\n\nThese progenitor cells are characterised by the co-expression of the transcription factors PDX1 and NKX6-1.The cells of the exocrine pancreas differentiate through molecules that induce differentiation including follistatin, fibroblast growth factors, and activation of the Notch receptor system.\n\nDevelopment of the exocrine acini progresses through three successive stages.\n\nThese are the predifferentiated, protodifferentiated, and differentiated stages, which correspond to undetectable, low, and high levels of digestive enzyme activity, respectively.Pancreatic progenitor cells differentiate into endocrine islet cells under the influence of neurogenin-3 and ISL1, but only in the absence of notch receptor signaling.\n\nUnder the direction of a Pax gene, the endocrine precursor cells differentiate to form alpha and gamma cells.\n\nUnder the direction of Pax-6, the endocrine precursor cells differentiate to form beta and delta cells.\n\nThe pancreatic islets form as the endocrine cells migrate from the duct system to form small clusters around capillaries.\n\nThis occurs around the third month of development, and insulin and glucagon can be detected in the human fetal circulation by the fourth or fifth month of development.\n\n== Function ==\n\nThe pancreas is involved in blood sugar control and metabolism within the body, and also in the secretion of substances (collectively pancreatic juice) that help digestion.\n\nThese are divided into an \"endocrine\" role, relating to the secretion of insulin and other substances within pancreatic islets that help control blood sugar levels and metabolism within the body, and an \"exocrine\" role, relating to the secretion of enzymes involved in digesting substances in the digestive tract.\n\n=== Blood glucose regulation ===\n\nCells within the pancreas help to maintain blood glucose levels (homeostasis).\n\nThe cells that do this are located within the pancreatic islets that are present throughout the pancreas.\n\nWhen blood glucose levels are low, alpha cells secrete glucagon, which increases blood glucose levels.\n\nWhen blood glucose levels are high beta cells secrete insulin to decrease glucose in blood.\n\nDelta cells in the islet also secrete somatostatin which decreases the release of insulin and glucagon.Glucagon acts to increase glucose levels by promoting the creation of glucose and the breakdown of glycogen to glucose in the liver.\n\nIt also decreases the uptake of glucose in fat and muscle.\n\nGlucagon release is stimulated by low blood glucose or insulin levels, and during exercise.\n\nInsulin acts to decrease blood glucose levels by facilitating uptake by cells (particularly skeletal muscle), and promoting its use in the creation of proteins, fats and carbohydrates.\n\nInsulin is initially created as a precursor form called preproinsulin.\n\nThis is converted to proinsulin and cleaved by C-peptide to insulin which is then stored in granules in beta cells.\n\nGlucose is taken into the beta cells and degraded.\n\nThe end effect of this is to cause depolarisation of the cell membrane which stimulates the release of the insulin.The main factor influencing the secretion of insulin and glucagon are the levels of glucose in blood plasma.\n\nLow blood sugar stimulates glucagon release, and high blood sugar stimulates insulin release.\n\nOther factors also influence the secretion of these hormones.\n\nSome amino acids, that are byproducts of the digestion of protein, stimulate insulin and glucagon release.\n\nSomatostatin acts as an inhibitor of both insulin and glucagon.\n\nThe autonomic nervous system also plays a role.\n\nActivation of Beta-2 receptors of the sympathetic nervous system by catecholamines secreted from sympathetic nerves stimulates secretion of insulin and glucagon, whereas activation of Alpha-1 receptors inhibits secretion.\n\nM3 receptors of the parasympathetic nervous system act when stimulated by the right vagus nerve to stimulate release of insulin from beta cells.\n\n=== Digestion ===\n\nThe pancreas plays a vital role in the digestive system.\n\nIt does this by secreting a fluid that contains digestive enzymes into the duodenum, the first part of the small intestine that receives food from the stomach.\n\nThese enzymes help to break down carbohydrates, proteins and lipids (fats).\n\nThis role is called the \"exocrine\" role of the pancreas.\n\nThe cells that do this are arranged in clusters called acini.\n\nSecretions into the middle of the acinus accumulate in intralobular ducts, which drain to the main pancreatic duct, which drains directly into the duodenum.\n\nAbout 1.5 - 3 liters of fluid are secreted in this manner every day.The cells in each acinus are filled with granules containing the digestive enzymes.\n\nThese are secreted in an inactive form termed zymogens or proenzymes.\n\nWhen released into the duodenum, they are activated by the enzyme enterokinase present in the lining of the duodenum.\n\nThe proenzymes are cleaved, creating a cascade of activating enzymes.\nEnzymes that break down proteins begin with activation of trypsinogen to trypsin.\n\nThe free trypsin then cleaves the rest of the trypsinogen, as well as chymotrypsinogen to its active form chymotrypsin.\nEnzymes secreted involved in the digestion of fats include lipase, phospholipase A2, lysophospholipase, and cholesterol esterase.\nEnzymes that break down starch and other carbohydrates include amylase.These enzymes are secreted in a fluid rich in bicarbonate.\n\nBicarbonate helps maintain an alkaline pH for the fluid, a pH in which most of the enzymes act most efficiently, and also helps to neutralise the stomach acids that enter the duodenum.\n\nSecretion is influenced by hormones including secretin, cholecystokinin, and VIP, as well as acetylcholine stimulation from the vagus nerve.\n\nSecretin is released from the S cells which form part of the lining of the duodenum in response to stimulation by gastric acid.\n\nAlong with VIP, it increases the secretion of enzymes and bicarbonate.\n\nCholecystokinin is released from Ito cells of the lining of the duodenum and jejunum mostly in response to long chain fatty acids, and increases the effects of secretin.\n\nAt a cellular level, bicarbonate is secreted from the acinar cells through a sodium and bicarbonate cotransporter that acts because of membrane depolarisation caused by the cystic fibrosis transmembrane conductance regulator.\n\nSecretin and VIP act to increase the opening of the cystic fibrosis transmembrane conductance regulator, which leads to more membrane depolarisation and more secretion of bicarbonate.A variety of mechanisms act to ensure that the digestive action of the pancreas does not act to digest pancreatic tissue itself.\n\nThese include the secretion of inactive enzymes (zymogens), the secretion of the protective enzyme trypsin inhibitor, which inactivates trypsin, the changes in pH that occur with bicarbonate secretion that stimulate digestion only when the pancreas is stimulated, and the fact that the low calcium within cells causes inactivation of trypsin.\n\n=== Additional functions ===\n\nThe pancreas also secretes vasoactive intestinal peptide and pancreatic polypeptide.\n\nEnterochromaffin cells of the pancreas secrete the hormones motilin, serotonin, and substance P.\n\n== Clinical significance ==\n\n=== Inflammation ===\n\nInflammation of the pancreas is known as pancreatitis.\n\nPancreatitis is most often associated with recurrent gallstones or chronic alcohol use, with other common causes including traumatic damage, damage following an ERCP, some medications, infections such as mumps and very high blood triglyceride levels.\n\nAcute pancreatitis is likely to cause intense pain in the central abdomen, that often radiates to the back, and may be associated with nausea or vomiting.\n\nSevere pancreatitis may lead to bleeding or perforation of the pancreas resulting in shock or a systemic inflammatory response syndrome, bruising of the flanks or the region around the belly button.\n\nThese severe complications are often managed in an intensive care unit.In pancreatitis, enzymes of the exocrine pancreas damage the structure and tissue of the pancreas.\n\nDetection of some of these enzymes, such as amylase and lipase in the blood, along with symptoms and findings on medical imaging such as ultrasound or a CT scan, are often used to indicate that a person has pancreatitis.\n\nPancreatitis is often managed medically with pain reliefs, and monitoring to prevent or manage shock, and management of any identified underlying causes.\n\nThis may include removal of gallstones, lowering of blood triglyceride or glucose levels, the use of corticosteroids for autoimmune pancreatitis, and the cessation of any medication triggers.Chronic pancreatitis refers to the development of pancreatitis over time.\n\nIt shares many similar causes, with the most common being chronic alcohol use, with other causes including recurrent acute episodes and cystic fibrosis.\n\nAbdominal pain, characteristically relieved by sitting forward or drinking alcohol, is the most common symptom.\n\nWhen the digestive function of the pancreas is severely affected, this may lead to problems with fat digestion and the development of steatorrhoea; when the endocrine function is affected, this may lead to diabetes.\n\nChronic pancreatitis is investigated in a similar way to acute pancreatitis.\n\nIn addition to management of pain and nausea, and management of any identified causes (which may include alcohol cessation), because of the digestive role of the pancreas, enzyme replacement may be needed to prevent malabsorption.\n\n=== Cancer ===\n\nPancreatic cancers, particularly the most common type, pancreatic adenocarcinoma, remain very difficult to treat, and are mostly diagnosed only at a stage that is too late for surgery, which is the only curative treatment.\n\nPancreatic cancer is rare in people younger than 40 and the median age of diagnosis is 71.\n\nRisk factors include chronic pancreatitis, older age, smoking, obesity, diabetes, and certain rare genetic conditions including multiple endocrine neoplasia type 1, hereditary nonpolyposis colon cancer and dysplastic nevus syndrome among others.\n\nAbout 25% of cases are attributable to tobacco smoking, while 5–10% of cases are linked to inherited genes.Pancreatic adenocarcinoma is the most common form of pancreatic cancer, and is cancer arising from the exocrine digestive part of the pancreas.\n\nMost occur in the head of the pancreas.\n\nSymptoms tend to arise late in the course of the cancer, when it causes abdominal pain, weight loss, or yellowing of the skin (jaundice).\n\nJaundice occurs when the outflow of bile is blocked by the cancer.\n\nOther less common symptoms include nausea, vomiting, pancreatitis, diabetes or recurrent venous thrombosis.\n\nPancreatic cancer is usually diagnosed by medical imaging in the form of an ultrasound or CT scan with contrast enhancement.\n\nAn endoscopic ultrasound may be used if a tumour is being considered for surgical removal, and biopsy guided by ERCP or ultrasound can be used to confirm an uncertain diagnosis.Because of the late development of symptoms, most cancer presents at an advanced stage.\n\nOnly 10 to 15% of tumours are suitable for surgical resection.\n\nAs of 2018, when chemotherapy is given the FOLFIRINOX regimen containing fluorouracil, irinotecan, oxaliplatin and leucovorin has been shown to extend survival beyond traditional gemcitabine regimens.\n\nFor the most part, treatment is palliative, focus on the management of symptoms that develop.\n\nThis may include management of itch, a choledochojejunostomy or the insertion of stents with ERCP to facilitate the drainage of bile, and medications to help control pain.\n\nIn the United States pancreatic cancer is the fourth most common cause of deaths due to cancer.\n\nThe disease occurs more often in the developed world, which had 68% of new cases in 2012.\n\nPancreatic adenocarcinoma typically has poor outcomes with the average percentage alive for at least one and five years after diagnosis being 25% and 5% respectively.\n\nIn localized disease where the cancer is small (< 2 cm) the number alive at five years is approximately 20%.There are several types of pancreatic cancer, involving both the endocrine and exocrine tissue.\n\nThe many types of pancreatic endocrine tumors are all uncommon or rare, and have varied outlooks.\n\nHowever the incidence of these cancers has been rising sharply; it is not clear to what extent this reflects increased detection, especially through medical imaging, of tumors that would be very slow to develop.\n\nInsulinomas (largely benign) and gastrinomas are the most common types.\n\nFor those with neuroendocrine cancers the number alive after five years is much better at 65%, varying considerably with type.A solid pseudopapillary tumour is a low-grade malignant tumour of the pancreas of papillary architecture that typically afflicts young women.\n\n=== Diabetes mellitus ===\n\n==== Type 1 diabetes ====\n\nDiabetes mellitus type 1 is a chronic autoimmune disease in which the immune system attacks the insulin-secreting beta cells of the pancreas.\n\nInsulin is needed to keep blood sugar levels within optimal ranges, and its lack can lead to high blood sugar.\n\nAs an untreated chronic condition, complications including accelerated vascular disease, diabetic retinopathy, kidney disease and neuropathy can result.\n\nIn addition, if there is not enough insulin for glucose to be used within cells, the medical emergency diabetic ketoacidosis, which is often the first symptom that a person with type 1 diabetes may have, can result.\n\nType 1 diabetes can develop at any age but is most often diagnosed before age 40.\n\nFor people living with type 1 diabetes, insulin injections are critical for survival.\n\nAn experimental procedure to treat type 1 diabetes is pancreas transplantation or isolated transplantation of islet cells to supply a person with functioning beta cells.\n\n==== Type 2 diabetes ====\n\nDiabetes mellitus type 2 is the most common form of diabetes.\n\nThe causes for high blood sugar in this form of diabetes usually are a combination of insulin resistance and impaired insulin secretion, with both genetic and environmental factors playing a role in the development of the disease.\n\nOver time, pancreatic beta cells may become \"exhausted\" and less functional.\n\nThe management of type 2 diabetes involves a combination of lifestyle measures, medications if required and potentially insulin.\nWith relevance to the pancreas, several medications act to enhance the secretion of insulin from beta cells, particularly sulphonylureas, which act directly on beta cells; incretins which replicate the action of the hormones glucagon-like peptide 1, increasing the secretion of insulin from beta cells after meals, and are more resistant to breakdown; and DPP-4 inhibitors, which slow the breakdown of incretins.\n\n=== Removal ===\n\nIt is possible for a person to live without a pancreas, provided that the person takes insulin for proper regulation of blood glucose concentration and pancreatic enzyme supplements to aid digestion.\n\n== History ==\n\nThe pancreas was first identified by Herophilus (335–280 BC), a Greek anatomist and surgeon.\n\nA few hundred years later, Rufus of Ephesus, another Greek anatomist, gave the pancreas its name.\n\nEtymologically, the term \"pancreas\", a modern Latin adaptation of Greek πάγκρεας, [πᾶν (\"all\", \"whole\"), and κρέας (\"flesh\")], originally means sweetbread, although literally meaning all-flesh, presumably because of its fleshy consistency.\n\nIt was only in 1889 when Oskar Minkowski discovered that removing the pancreas from a dog caused it to become diabetic.\n\nInsulin was later isolated from pancreatic islets by Frederick Banting and Charles Herbert Best in 1921.The way the tissue of the pancreas has been viewed has also changed.\n\nPreviously, it was viewed using simple staining methods such as H&E stains.\n\nNow, immunohistochemistry can be used to more easily differentiate cell types.\n\nThis involves visible antibodies to the products of certain cell types, and helps identify with greater ease cell types such as alpha and beta cells.\n\n== Other animals ==\n\nPancreatic tissue is present in all vertebrates, but its precise form and arrangement varies widely.\n\nThere may be up to three separate pancreases, two of which arise from ventral buds, and the other dorsally.\n\nIn most species (including humans), these \"fuse\" in the adult, but there are several exceptions.\n\nEven when a single pancreas is present, two or three pancreatic ducts may persist, each draining separately into the duodenum (or equivalent part of the foregut).\n\nBirds, for example, typically have three such ducts.In teleost fish, and a few other species (such as rabbits), there is no discrete pancreas at all, with pancreatic tissue being distributed diffusely across the mesentery and even within other nearby organs, such as the liver or spleen.\n\nIn a few teleost species, the endocrine tissue has fused to form a distinct gland within the abdominal cavity, but otherwise it is distributed among the exocrine components.\n\nThe most primitive arrangement, however, appears to be that of lampreys and lungfish, in which pancreatic tissue is found as a number of discrete nodules within the wall of the gut itself, with the exocrine portions being little different from other glandular structures of the intestine.\n\n== Cuisine ==\n\nThe pancreas of calf (ris de veau) or lamb (ris d'agneau), and, less commonly, of beef or pork, are used as food under the culinary name of sweetbread.\n\nhttps://en.wikipedia.org/wiki/Pancreas","epiglottis":"The epiglottis is a leaf-shaped flap in the throat that prevents food from entering the windpipe and the lungs.\n\nIt stays open during breathing, allowing air into the larynx.\n\nDuring swallowing, it closes to prevent aspiration of food into the lungs, forcing the swallowed liquids or food to go along the esophagus toward the stomach instead.\n\nIt is thus the valve that diverts passage to either the trachea or the esophagus.\n\nThe epiglottis is made of elastic cartilage covered with a mucous membrane, attached to the entrance of the larynx.\n\nIt projects upwards and backwards behind the tongue and the hyoid bone.\n\nThe epiglottis may be inflamed in a condition called epiglottitis, which is most commonly due to the vaccine-preventable bacteria Haemophilus influenzae.\n\nDysfunction may cause the inhalation of food, called aspiration, which may lead to pneumonia or airway obstruction.\n\nThe epiglottis is also an important landmark for intubation.\nThe epiglottis has been identified as early as Aristotle, and gets its name from being above the glottis (epi- + glottis).\n\n== Structure ==\n\nThe epiglottis sits at the entrance of the larynx.\n\nIt is shaped like a leaf of purslane and has a free upper part that rests behind the tongue, and a lower stalk (Latin: petiolus).\n\nThe stalk originates from the back surface of the thyroid cartilage, connected by a thyroepiglottic ligament.\n\nAt the sides, the stalk is connected to the arytenoid cartilages at the walls of the larynx by folds.The epiglottis originates at the entrance of the larynx, and is attached to the hyoid bone.\n\nFrom there, it projects upwards and backwards behind the tongue.\n\nThe space between the epiglottis and the tongue is called the vallecula.\n\n=== Microanatomy ===\n\nThe epiglottis has two surfaces; a forward-facing anterior surface, and a posterior surface facing the larynx.\n\nThe forward-facing surface is covered with several layers of thin cells (stratified squamous epithelium), and is not covered with keratin, the same surface as the back of the tongue.\n\nThe back surface is covered in a layer of column-shaped cells with cilia, similar to the rest of the respiratory tract.\n\nIt also has mucous-secreting goblet cells.\n\nThere is an intermediate zone between these surfaces that contains cells that transition in shape.\n\nThe body of the epiglottis consists of elastic cartilage.\n\n=== Development ===\n\nThe epiglottis arises from the fourth pharyngeal arch.\n\nIt can be seen as a distinct structure later than the other cartilage of the pharynx, visible around the fifth month of development.\n\nThe position of the epiglottis also changes with ageing.\n\nIn infants, it touches the soft palate, whereas in adults, its position is lower.\n\n=== Variation ===\n\nA high-rising epiglottis is a normal anatomical variation, visible during an examination of the mouth.\n\nIt does not cause any serious problem apart from maybe a mild sensation of a foreign body in the throat.\n\nIt is seen more often in children than adults and does not need any medical or surgical intervention.\n\nThe front surface of the epiglottis is occasionally notched.\n\n== Function ==\n\nThe epiglottis is normally pointed upward during breathing with its underside functioning as part of the pharynx.\n\nThere are taste buds on the epiglottis.\n\n=== Swallowing ===\n\nDuring swallowing, the epiglottis bends backwards, folding over the entrance to the trachea, and preventing food from going into it.\n\nThe folding backwards is a complex movement the causes of which are not completely understood.\n\nIt is likely that during swallowing the hyoid bone and the larynx move upwards and forwards, which increases passive pressure from the back of the tongue; because the aryepiglottic muscles contract; because of the passive weight of the food pushing down; and because of contraction of laryngeal and because of contraction of thyroarytenoid muscles.\n\nThe consequence of this is that during swallowing the bent epiglottis blocks off the trachea, preventing food from going into it; food instead travels down the esophagus, which is behind it.\n\n=== Speech sounds ===\n\nIn many languages, the epiglottis is not essential for producing sounds.\n\nIn some languages, the epiglottis is used to produce epiglottal consonant speech sounds, though this sound-type is rather rare.\n\n== Clinical significance ==\n\n=== Inflammation ===\n\nInflammation of the epiglottis is known as epiglottitis.\n\nEpiglottitis is mainly caused by Haemophilus influenzae.\n\nA person with epiglottitis may have a fever, sore throat, difficulty swallowing, and difficulty breathing.\n\nFor this reason, acute epiglottitis is considered a medical emergency, because of the risk of obstruction of the pharynx.\n\nEpiglottitis is often managed with antibiotics, inhaled aerosolised epinephrine to act as a bronchodilator, and may require tracheal intubation or a tracheostomy if breathing is difficult.\n\nThe incidence of epiglottitis has decreased significantly in countries where vaccination against Haemophilus influenzae is administered.\n\n=== Aspiration ===\n\nWhen food or other objects travel down the respiratory tract rather than down the esophagus to the stomach, this is called aspiration.\n\nThis can lead to airway obstruction, inflammation of lung tissue, and aspiration pneumonia; and in the long term, atelectasis and bronchiectasis.\n\nOne reason aspiration can occur is because of failure of the epiglottis to close completely.\n\nShould food or liquid enter the airway due to the epiglottis failing to close properly, throat clearing or the cough reflex may occur to protect the respiratory system and expel material from the airway.\n\nWhere there is impairment in laryngeal vestibule sensation, silent aspiration (entry of material to the airway that does not result in a cough reflex) may occur.\n\n=== Other ===\n\nThe epiglottis and vallecula are important anatomical landmarks in intubation.\n\nAbnormal positioning of the epiglottis is a rare cause of obstructive sleep apnoea.\n\n== Other animals ==\n\nThe epiglottis is present in mammals, including land mammals and cetaceans, also as a cartilaginous structure.\n\nLike in humans, it functions to prevent entry of food into the trachea during swallowing.\n\nThe position of the larynx is flat in mice and other rodents, including rabbits.\n\nFor this reason, because the epiglottis is located behind the soft palate in rabbits, they are obligate nose breathers, as are mice and other rodents.\n\nIn rodents and mice, there is a unique pouch in front of the epiglottis, and the epiglottis is commonly injured by inhaled substances, particularly at the transition zone between the flattened and cuboidal epithelium.\n\nIt is also common to see taste buds on the epiglottis in these species.\n\n== History ==\n\nThe epiglottis was noted by Aristotle, although the epiglottis' function was first defined by Vesalius in 1543.\n\nThe word has Greek roots.\n\nThe epiglottis gets its name from being above (Ancient Greek: ἐπί, romanized: epi-) the glottis (Ancient Greek: γλωττίς, romanized: glottis, lit. 'tongue').\n\nhttps://en.wikipedia.org/wiki/Epiglottis","trachea":"The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs.\n\nThe trachea extends from the larynx and branches into the two primary bronchi.\n\nAt the top of the trachea the cricoid cartilage attaches it to the larynx.\n\nThe trachea is formed by a number of horseshoe-shaped rings, joined together vertically by overlying ligaments, and by the trachealis muscle at their ends.\n\nThe epiglottis closes the opening to the larynx during swallowing.\nThe trachea begins to form in the second month of embryo development, becoming longer and more fixed in its position over time.\n\nIt is epithelium lined with column-shaped cells that have hair-like extensions called cilia, with scattered goblet cells that produce protective mucins.\n\nThe trachea can be affected by inflammation or infection, usually as a result of a viral illness affecting other parts of the respiratory tract, such as the larynx and bronchi, called croup, that can result in a barking cough.\n\nInfection with bacteria usually affects the trachea only and can cause narrowing or even obstruction.\n\nAs a major part of the respiratory tract, when obstructed the trachea prevents air entering the lungs and so a tracheostomy may be required if the trachea is obstructed.\n\nAdditionally, during surgery if mechanical ventilation is required when a person is sedated, a tube is inserted into the trachea, called intubation.\n\nThe word trachea is used to define a very different organ in invertebrates than in vertebrates.\n\nInsects have an open respiratory system made up of spiracles, tracheae, and tracheoles to transport metabolic gases to and from tissues.\n\n== Structure ==\n\nAn adult's trachea has an inner diameter of about 1.5 to 2 centimetres (0.59 to 0.79 in) and a length of about 10 to 11 centimetres (3.9 to 4.3 in); wider in males than females.\n\nIt begins at the bottom of the larynx and ends at the carina, the point where the trachea branches into the left and right main bronchi.\n\nThe trachea is surrounded by 16–20 rings of hyaline cartilage; these 'rings' are 4 millimetres high in the adult, incomplete and C-shaped.\n\nLigaments connect the rings.\n\nThe trachealis muscle connects the ends of the incomplete rings and runs along the back wall of the trachea.\n\nAlso adventitia, which is the outermost layer of connective tissue that surrounds the hyaline cartilage, contributes to the trachea's ability to bend and stretch with movement.\n\nThe trachea begins at the lower edge of the cricoid cartilage of the larynx and ends at the carina, the point where the trachea branches into left and right main bronchi.\n\nThe trachea begins level with the sixth cervical vertebra (C6), and the carina is found at the level of the fourth thoracic vertebra (T4), although its position may change with breathing.\n\n=== Nearby structures ===\n\nThe trachea passes by many structures of the neck and chest (thorax) along its course.\nIn front of the upper trachea lies connective tissue and skin.\n\nSeveral other structures pass over or sit on the trachea; the jugular arch, which joins the two anterior jugular veins, sits in front of the upper part of the trachea.\n\nThe sternohyoid and sternothyroid muscles stretch along its length.\n\nThe thyroid gland also stretches across the upper trachea, with the isthmus overlying the second to fourth rings, and the lobes stretching to the level of the fifth or sixth cartilage.\n\nThe blood vessels of the thyroid rest on the trachea next to the isthmus; superior thyroid arteries join just above it, and the inferior thyroid veins below it.\n\nIn front of the lower trachea lies the manubrium of the sternum, the remnants of the thymus in adults.\n\nTo the front left lie the large blood vessels the aortic arch and its branches the left common carotid artery and the brachiocephalic trunk; and the left brachiocephalic vein.\n\nThe deep cardiac plexus and lymph nodes are also positioned in front of the lower trachea.Behind the trachea, along its length, sits the oesophagus, followed by connective tissue and the vertebral column.\n\nTo its sides run the carotid arteries and inferior thyroid arteries; and to its sides on its back surface run the recurrent laryngeal nerves in the upper trachea, and the vagus nerves in the lower trachea.\n\nThe trachealis muscle contracts during coughing, reducing the size of the lumen of the trachea.\n\n=== Blood and lymphatic supply ===\n\nThe upper part of trachea receives and drains blood through the inferior thyroid arteries and veins; the lower trachea receives blood from bronchial arteries.\n\nArteries that supply the trachea do so via small branches that supply the trachea from the sides.\n\nAs the branches approach the wall of the trachea, they split into inferior and superior branches, which join with the branches of the arteries above and below; these then split into branches that supply the anterior and posterior parts of the trachea.\n\nThe inferior thyroid arteries arise just below the isthmus of the thyroid, which sits atop the trachea.\n\nThese arteries join (anastamoses) with ascending branches of the bronchial arteries, which are direct branches from the aorta, to supply blood to the trachea.\n\nThe lymphatic vessels of the trachea drain into the pretracheal nodes that lie in front of the trachea, and paratracheal lymph nodes that lie beside it.\n\n=== Development ===\n\nIn the fourth week of development of the human embryo as the respiratory bud grows, the trachea separates from the foregut through the formation of ridges which eventually separate the trachea from the oesophagus, the tracheoesophageal septum.\n\nThis separates the future trachea from the oesophagus and divides the foregut tube into the laryngotracheal tube.\n\nBy the start of the fifth week, the left and right main bronchi have begin to form, initially as buds at the terminal end of the trachea.The trachea is no more than 4mm diameter during the first year of life, expanding to its adult diameter of approximately 2cm by late childhood.\n\nThe trachea is more circular and more vertical in children compared to adults, varies more in size, and also varies more in its position in relation to its surrounding structures.\n\n=== Microanatomy ===\n\nThe trachea is lined with a layer of interspersed layers of column-shaped cells with cilia.\n\nThe epithelium contains goblet cells, which are glandular, column-shaped cells that produce mucins, the main component of mucus.\n\nMucus helps to moisten and protect the airways.\n\nMucus lines the ciliated cells of the trachea to trap inhaled foreign particles that the cilia then waft upward toward the larynx and then the pharynx where it can be either swallowed into the stomach or expelled as phlegm.\n\nThis self-clearing mechanism is termed mucociliary clearance.The trachea is surrounded by 16 to 20 rings of hyaline cartilage; these 'rings' are incomplete and C-shaped.\n\nTwo or more of the cartilages often unite, partially or completely, and they are sometimes bifurcated at their extremities.\n\nThe rings are generally highly elastic but they may calcify with age.\n\n== Function ==\n\nThe trachea is one part of the respiratory tree that is a conduit for air to pass through on its way to or from the alveoli of the lungs.\n\nThis transmits oxygen to the body and removes carbon dioxide.\n\n== Use in killing humans ==\n\nCrushing the trachea is a common tactic for temporarily or permanently disabling another human and is taught in the military, martial arts and police forces around the world.\n\n== Clinical significance ==\n\n=== Inflammation and infection ===\n\nInflammation of the trachea is known as tracheitis, usually due to an infection.\n\nIt is usually caused by viral infections, with bacterial infections occurring almost entirely in children.\n\nMost commonly, infections occur with inflammation of other parts of the respiratory tract, such as the larynx and bronchi, known as croup, however bacterial infections may also affect the trachea alone, although they are often associated with a recent viral infection.\n\nViruses that cause croup are generally the parainfluenza viruses 1–3, with influenza viruses A and B also causing croup, but usually causing more serious infections; bacteria may also cause croup and include Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis.\n\nCauses of bacterial infection of the trachea are most commonly Staphylococcus aureus and Streptococcus pneumoniae.\n\nIn patients who are in hospital, additional bacteria that may cause tracheitis include Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa.A person affected with tracheitis may start with symptoms that suggest an upper respiratory tract infection such as a cough, sore throat, or coryzal symptoms such as a runny nose.\n\nFevers may develop and an affected child may develop difficulty breathing and sepsis.\n\nSwelling of the airway can cause narrowing of the airway, causing a hoarse breathing sound called stridor, or even cause complete blockage.\n\nUnfortunately, up to 80% of people affected by bacterial tracheitis require the use of mechanical ventilation, and treatment may include endoscopy for the purposes of acquiring microbiological specimens for culture and sensitivity, as well as removal of any dead tissue associated with the infection.\n\nTreatment in such situations usually includes antibiotics.\n\n=== Narrowing ===\n\nA trachea may be narrowed or compressed, usually a result of enlarged nearby lymph nodes; cancers of the trachea or nearby structures; large thyroid goitres; or rarely as a result of other processes such as unusually swollen blood vessels.\n\nScarring from tracheobronchial injury or intubation; or inflammation associated with granulomatosis with polyangiitis may also cause a narrowing of the trachea (tracheal stenosis).\n\nObstruction invariably causes a harsh breathing sound known as stridor.\n\nA camera inserted via the mouth down into the trachea, called bronchoscopy, may be performed to investigate the cause of an obstruction.\n\nManagement of obstructions depends on the cause.\n\nObstructions as a result of malignancy may be managed with surgery, chemotherapy or radiotherapy.\n\nA stent may be inserted over the obstruction.\n\nBenign lesions, such as narrowing resulting from scarring, are likely to be surgically excised.One cause of narrowing is tracheomalacia, which is the tendency for the trachea to collapse when there is increased external pressure, such as when airflow is increased during breathing in or out, due to decreased compliance.\n\nIt can be due to congenital causes, or due to things that develop after birth, such as compression from nearby masses or swelling, or trauma.\n\nCongenital tracheomalacia can occur by itself or in association with other abnormalities such as bronchomalacia or laryngomalacia, and abnormal connections between the trachea and the oesophagus, amongst others.\n\nCongenital tracheomalacia often improves without specific intervention; when required, interventions may include beta agonists and muscarinic agonists, which enhance the tone of the smooth muscle surrounding the trachea; positive pressure ventilation, or surgery, which may include the placement of a stent, or the removal of the affected part of the trachea.\n\nIn dogs, particularly miniature dogs and toy dogs, tracheomalacia, as well as bronchomalacia, can lead to tracheal collapse, which often presents with a honking goose-like cough.\n\n=== Intubation ===\n\nTracheal intubation refers to the insertion of a tube down the trachea.\n\nThis procedure is commonly performed during surgery, in order to ensure a person receives enough oxygen when sedated.\n\nThe catheter is connected to a machine that monitors the airflow, oxygenation and several other metrics.\n\nThis is often one of the responsibilities of an anaesthetist during surgery.\nIn an emergency, or when tracheal intubation is deemed impossible, a tracheotomy is often performed to insert a tube for ventilation, usually when needed for particular types of surgery to be carried out so that the airway can be kept open.\n\nThe provision of the opening via a tracheotomy is called a tracheostomy.\n\nAnother method procedure can be carried, in an emergency situation, and this is a cricothyrotomy.\n\n=== Congenital disorders ===\n\nTracheal agenesis is a rare birth defect in which the trachea fails to develop.\n\nThe defect is usually fatal though sometimes surgical intervention has been successful.\nA tracheoesophageal fistula is a congenital defect in which the trachea and esophagus are abnormally connected (a fistula).\n\nThis is because of abnormalities in the separation between the trachea and oesophagus during development.\n\nThis occurs in approximately 1 in 3000 births, and the most common abnormalities is a separation of the upper and lower ends of the oesophagus, with the upper end finishing in a closed pouch.\n\nOther abnormalities may be associated with this, including cardiac abnormalities, or VACTERL syndrome.\n\nSuch fistulas may be detected before a baby is born because of excess amniotic fluid; after birth, they are often associated with pneumonitis and pneumonia because of aspiration of food contents.\n\nCongenital fistulas are often treated by surgical repair.\n\nIn adults, fistulas may occur because of erosion into the trachea from nearby malignant tumours, which erode into both the trachea and the oesophagus.\n\nInitially, these often result in coughing from swallowed contents of the oesophagus that are aspirated through the trachea, often progressing to fatal pneumonia; unfortunately, there is rarely a curative treatment.\n\nA tracheo-oesophageal puncture is a surgically created hole between the trachea and the esophagus in a person who has had their larynx removed.\n\nAir travels upwards from the surgical connection to the upper oesophagus and the pharynx, creating vibrations that create sound that can be used for speech.\n\nThe purpose of the puncture is to restore a person's ability to speak after the vocal cords have been removed.Sometimes as an anatomical variation one or more of the tracheal rings are formed as complete rings, rather than horseshoe shaped rings.\n\nThese O rings are smaller than the normal C-shaped rings and can cause narrowing (stenosis) of the trachea, resulting in breathing difficulties.\n\nAn operation called a slide tracheoplasty can open up the rings and rejoin them as wider rings, shortening the length of the trachea.\n\nSlide tracheoplasty is said to be the best option in treating tracheal stenosis.Mounier-Kuhn syndrome is a rare congenital disorder of an abnormally enlarged trachea, characterised by absent elastic fibres, smooth muscle thinning, and a tendency to get recurrent respiratory tract infections.\n\n=== Replacement ===\n\nFrom 2008, operations have experimentally replaced tracheas, with those grown from stem cells, or with synthetic substitutes, however this is regarded as experimental and there is no standardised method.\n\nDifficulties with ensuring adequate blood supply to the replaced trachea is considered a major challenge to any replacement.\n\nAdditionally, no evidence has been found to support the placement of stem cells taken from bone marrow on the trachea as a way of stimulating tissue regeneration, and such a method remains hypothetical.In January 2021, surgeons at Mount Sinai Hospital in New York performed the first complete trachea transplantation.\n\nThe 18-hour procedure included harvesting a trachea from a donor and implanting it in the patient, connecting numerous veins and arteries to provide sufficient blood flow to the organ.\n\n== Other animals ==\n\nAllowing for variations in the length of the neck, the trachea in other mammals is, in general, similar to that in humans.\n\nGenerally, it is also similar to the reptilian trachea.\n\n=== Vertebrates ===\n\nIn birds, the trachea runs from the pharynx to the syrinx, from which the primary bronchi diverge.\n\nSwans have an unusually elongated trachea, part of which is coiled beneath the sternum; this may act as a resonator to amplify sound.\n\nIn some birds, the tracheal rings are complete, and may even be ossified.In amphibians, the trachea is normally extremely short, and leads directly into the lungs, without clear primary bronchi.\n\nA longer trachea is, however, found in some long-necked salamanders, and in caecilians.\n\nWhile there are irregular cartilagenous nodules on the amphibian trachea, these do not form the rings found in amniotes.The only vertebrates to have lungs, but no trachea, are the lungfish and the Polypterus, in which the lungs arise directly from the pharynx.\n\n=== Invertebrates ===\n\nThe word trachea is used to define a very different organ in invertebrates than in vertebrates.\n\nInsects have an open respiratory system made up of spiracles, tracheae, and tracheoles to transport metabolic gases to and from tissues.\n\nThe distribution of spiracles can vary greatly among the many orders of insects, but in general each segment of the body can have only one pair of spiracles, each of which connects to an atrium and has a relatively large tracheal tube behind it.\n\nThe tracheae are invaginations of the cuticular exoskeleton that branch (anastomose) throughout the body with diameters from only a few micrometres up to 0.8 mm.\n\nDiffusion of oxygen and carbon dioxide takes place across the walls of the smallest tubes, called tracheoles, which penetrate tissues and even indent individual cells.\n\nGas may be conducted through the respiratory system by means of active ventilation or passive diffusion.\n\nUnlike vertebrates, insects do not generally carry oxygen in their haemolymph.\nThis is one of the factors that may limit their size.\nA tracheal tube may contain ridge-like circumferential rings of taenidia in various geometries such as loops or helices.\n\nTaenidia provide strength and flexibility to the trachea.\n\nIn the head, thorax, or abdomen, tracheae may also be connected to air sacs.\n\nMany insects, such as grasshoppers and bees, which actively pump the air sacs in their abdomen, are able to control the flow of air through their body.\n\nIn some aquatic insects, the tracheae exchange gas through the body wall directly, in the form of a gill, or function essentially as normal, via a plastron.\n\nNote that despite being internal, the tracheae of arthropods are lined with cuticular tissue and are shed during moulting (ecdysis).\n\n== References ==\n\nhttps://en.wikipedia.org/wiki/Trachea","superior-lobe-of-right-lung":"LUNG\n\nThe lungs are the primary organs of the respiratory system in humans and most other animals including a few fish, and some snails.\n\nIn mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart.\n\nTheir function in the respiratory system is to extract oxygen from the air and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange.\n\nRespiration is driven by different muscular systems in different species.\n\nMammals, reptiles and birds use their different muscles to support and foster breathing.\n\nIn earlier tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians.\n\nIn humans, the main muscle of respiration that drives breathing is the diaphragm.\n\nThe lungs also provide airflow that makes vocal sounds including human speech possible.\nHumans have two lungs, a right lung, and a left lung.\n\nThey are situated within the thoracic cavity of the chest.\n\nThe right lung is bigger than the left, which shares space in the chest with the heart.\n\nThe lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier.\n\nThe lungs are part of the lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles, and which receive air breathed in via the conducting zone.\n\nThe conducting zone ends at the terminal bronchioles.\n\nThese divide into the respiratory bronchioles of the respiratory zone which divide into alveolar ducts that give rise to the alveolar sacs that contain the alveoli, where gas exchange takes place.\n\nAlveoli are also sparsely present on the walls of the respiratory bronchioles and alveolar ducts.\n\nTogether, the lungs contain approximately 2,400 kilometres (1,500 mi) of airways and 300 to 500 million alveoli.\n\nEach lung is enclosed within a pleural sac of two membranes called pleurae; the membranes are separated by a film of pleural fluid, which allows the inner and outer membranes to slide over each other whilst breathing takes place, without much friction.\n\nThe inner pleura also divides each lung into sections called lobes.\n\nThe right lung has three lobes and the left has two.\n\nThe lobes are further divided into bronchopulmonary segments and pulmonary lobules.\n\nThe lungs have a unique blood supply, receiving deoxygenated blood from the heart in the pulmonary circulation for the purposes of receiving oxygen and releasing carbon dioxide, and a separate supply of oxygenated blood to the tissue of the lungs, in the bronchial circulation.\nThe tissue of the lungs can be affected by a number of respiratory diseases, including pneumonia and lung cancer.\n\nChronic obstructive pulmonary disease includes chronic bronchitis and emphysema, and can be related to smoking or exposure to harmful substances.\n\nA number of occupational lung diseases can be caused by substances such as coal dust, asbestos fibres, and crystalline silica dust.\n\nDiseases such as bronchitis can also affect the respiratory tract.\n\nMedical terms related to the lung often begin with pulmo-, from the Latin pulmonarius (of the lungs) as in pulmonology, or with pneumo- (from Greek πνεύμων \"lung\") as in pneumonia.\nIn embryonic development, the lungs begin to develop as an outpouching of the foregut, a tube which goes on to form the upper part of the digestive system.\n\nWhen the lungs are formed the fetus is held in the fluid-filled amniotic sac and so they do not function to breathe.\n\nBlood is also diverted from the lungs through the ductus arteriosus.\n\nAt birth however, air begins to pass through the lungs, and the diversionary duct closes, so that the lungs can begin to respire.\n\nThe lungs only fully develop in early childhood.\n\n== Structure ==\n\n=== Anatomy ===\n\nThe lungs are located in the chest on either side of the heart in the rib cage.\n\nThey are conical in shape with a narrow rounded apex at the top, and a broad concave base that rests on the convex surface of the diaphragm.\n\nThe apex of the lung extends into the root of the neck, reaching shortly above the level of the sternal end of the first rib.\n\nThe lungs stretch from close to the backbone in the rib cage to the front of the chest and downwards from the lower part of the trachea to the diaphragm.\n\nThe left lung shares space with the heart, and has an indentation in its border called the cardiac notch of the left lung to accommodate this.\n\nThe front and outer sides of the lungs face the ribs, which make light indentations on their surfaces.\n\nThe medial surfaces of the lungs face towards the centre of the chest, and lie against the heart, great vessels, and the carina where the trachea divides into the two main bronchi.\n\nThe cardiac impression is an indentation formed on the surfaces of the lungs where they rest against the heart.\nBoth lungs have a central recession called the hilum at the root of the lung, where the blood vessels and airways pass into the lungs.\n\nThere are also bronchopulmonary lymph nodes on the hilum.The lungs are surrounded by the pulmonary pleurae.\n\nThe pleurae are two serous membranes; the outer parietal pleura lines the inner wall of the rib cage and the inner visceral pleura directly lines the surface of the lungs.\n\nBetween the pleurae is a potential space called the pleural cavity containing a thin layer of lubricating pleural fluid.\n\n==== Lobes ====\nEach lung is divided into sections called lobes by the infoldings of the visceral pleura as fissures.\n\nLobes are divided into segments, and segments have further divisions as lobules.\n\nThere are three lobes in the right lung and two lobes in the left lung.\n\n==== Fissures ====\nThe fissures are formed in early prenatal development by invaginations of the visceral pleura that divide the lobar bronchi, and section the lungs into lobes that helps in their expansion.\n\nThe right lung is divided into three lobes by a horizontal fissure, and an oblique fissure.\n\nThe left lung is divided into two lobes by an oblique fissure which is closely aligned with the oblique fissure in the right lung.\n\nIn the right lung the upper horizontal fissure, separates the upper (superior) lobe from the middle lobe.\n\nThe lower, oblique fissure separates the lower lobe from the middle and upper lobes.Variations in the fissures are fairly common being either incompletely formed\nor present as an extra fissure as in the azygos fissure, or absent.\n\nIncomplete fissures are responsible for interlobar collateral ventilation, airflow between lobes which is unwanted in some lung volume reduction procedures.\n\n==== Segments ====\nThe main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of the lung.\n\nThe lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments.\n\nEach bronchopulmonary segment has its own (segmental) bronchus and arterial supply.\n\nSegments for the left and right lung are shown in the table.\n\nThe segmental anatomy is useful clinically for localising disease processes in the lungs.\n\nA segment is a discrete unit that can be surgically removed without seriously affecting surrounding tissue.\n\n=== Right lung ===\n\nThe right lung has both more lobes and segments than the left.\n\nIt is divided into three lobes, an upper, middle, and a lower lobe by two fissures, one oblique and one horizontal.\n\nThe upper, horizontal fissure, separates the upper from the middle lobe.\n\nIt begins in the lower oblique fissure near the posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage; on the mediastinal surface it may be traced back to the hilum.\n\nThe lower, oblique fissure, separates the lower from the middle and upper lobes and is closely aligned with the oblique fissure in the left lung.The mediastinal surface of the right lung is indented by a number of nearby structures.\n\nThe heart sits in an impression called the cardiac impression.\n\nAbove the hilum of the lung is an arched groove for the azygos vein, and above this is a wide groove for the superior vena cava and right brachiocephalic vein; behind this, and close to the top of the lung is a groove for the brachiocephalic artery.\n\nThere is a groove for the esophagus behind the hilum and the pulmonary ligament, and near the lower part of the esophageal groove is a deeper groove for the inferior vena cava before it enters the heart.The weight of the right lung varies between individuals, with a standard reference range in men of 155–720 g (0.342–1.587 lb) and in women of 100–590 g (0.22–1.30 lb).\n\n=== Left lung ===\n\nThe left lung is divided into two lobes, an upper and a lower lobe, by the oblique fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilum.\n\nThe left lung, unlike the right, does not have a middle lobe, though it does have a homologous feature, a projection of the upper lobe termed the lingula.\n\nIts name means \"little tongue\".\n\nThe lingula on the left lung serves as an anatomic parallel to the middle lobe on the right lung, with both areas being predisposed to similar infections and anatomic complications.\n\nThere are two bronchopulmonary segments of the lingula: superior and inferior.The mediastinal surface of the left lung has a large cardiac impression where the heart sits.\n\nThis is deeper and larger than that on the right lung, at which level the heart projects to the left.On the same surface, immediately above the hilum, is a well-marked curved groove for the aortic arch, and a groove below it for the descending aorta.\n\nThe left subclavian artery, a branch off the aortic arch, sits in a groove from the arch to near the apex of the lung.\n\nA shallower groove in front of the artery and near the edge of the lung, lodges the left brachiocephalic vein.\n\nThe esophagus may sit in a wider shallow impression at the base of the lung.The weight of the left lung, by standard reference range, in men is 110–675 g (0.243–1.488 lb) in women 105–515 g (0.231–1.135 lb).\n\n== Microanatomy ==\n\nThe lungs are part of the lower respiratory tract, and accommodate the bronchial airways when they branch from the trachea.\n\nThe bronchial airways terminate in alveoli which make up the functional tissue (parenchyma) of the lung, and veins, arteries, nerves, and lymphatic vessels.\n\nThe trachea and bronchi have plexuses of lymph capillaries in their mucosa and submucosa.\n\nThe smaller bronchi have a single layer of lymph capillaries, and they are absent in the alveoli.\n\nThe lungs are supplied with the largest lymphatic drainage system of any other organ in the body.\n\nEach lung is surrounded by a serous membrane of visceral pleura, which has an underlying layer of loose connective tissue attached to the substance of the lung.\n\n=== Connective tissue ===\n\nThe connective tissue of the lungs is made up of elastic and collagen fibres that are interspersed between the capillaries and the alveolar walls.\n\nElastin is the key protein of the extracellular matrix and is the main component of the elastic fibres.\n\nElastin gives the necessary elasticity and resilience required for the persistent stretching involved in breathing, known as lung compliance.\n\nIt is also responsible for the elastic recoil needed.\n\nElastin is more concentrated in areas of high stress such as the openings of the alveoli, and alveolar junctions.\n\nThe connective tissue links all the alveoli to form the lung parenchyma which has a sponge-like appearance.\n\nThe alveoli have interconnecting air passages in their walls known as the pores of Kohn.\n\n=== Respiratory epithelium ===\n\nAll of the lower respiratory tract including the trachea, bronchi, and bronchioles is lined with respiratory epithelium.\n\nThis is a ciliated epithelium interspersed with goblet cells which produce mucin the main component of mucus, ciliated cells, basal cells, and in the terminal bronchioles–club cells with actions similar to basal cells, and macrophages.\n\nThe epithelial cells, and the submucosal glands throughout the respiratory tract secrete airway surface liquid (ASL), the composition of which is tightly regulated and determines how well mucociliary clearance works.Pulmonary neuroendocrine cells are found throughout the respiratory epithelium including the alveolar epithelium, though they only account for around 0.5 per cent of the total epithelial population.\n\nPNECs are innervated airway epithelial cells that are particularly focused at airway junction points.\n\nThese cells can produce serotonin, dopamine, and norepinephrine, as well as polypeptide products.\n\nCytoplasmic processes from the pulmonary neuroendocrine cells extend into the airway lumen where they may sense the composition of inspired gas.\n\n=== Bronchial airways ===\n\nIn the bronchi there are incomplete tracheal rings of cartilage and smaller plates of cartilage that keep them open.: 472  Bronchioles are too narrow to support cartilage and their walls are of smooth muscle, and this is largely absent in the narrower respiratory bronchioles which are mainly just of epithelium.: 472  The absence of cartilage in the terminal bronchioles gives them an alternative name of membranous bronchioles.\n\n=== Respiratory zone ===\n\nThe conducting zone of the respiratory tract ends at the terminal bronchioles when they branch into the respiratory bronchioles.\n\nThis marks the beginning of the terminal respiratory unit called the acinus which includes the respiratory bronchioles, the alveolar ducts, alveolar sacs, and alveoli.\n\nAn acinus measures up to 10 mm in diameter.\n\nA primary pulmonary lobule is that part of the acinus that includes the alveolar ducts, sacs, and alveoli but does not include the respiratory bronchioles.\n\nThe unit described as the secondary pulmonary lobule is the lobule most referred to as the pulmonary lobule or respiratory lobule.: 489  This lobule is a discrete unit that is the smallest component of the lung that can be seen without aid.\n\nThe secondary pulmonary lobule is likely to be made up of between 30 and 50 primary lobules.\n\nThe lobule is supplied by a terminal bronchiole that branches into respiratory bronchioles.\n\nThe respiratory bronchioles supply the alveoli in each acinus and is accompanied by a pulmonary artery branch.\n\nEach lobule is enclosed by an interlobular septa.\n\nEach acinus is incompletely separated by an interlobular septa.The respiratory bronchiole gives rise to the alveolar ducts that lead to the alveolar sacs, which contain two or more alveoli.\n\nThe walls of the alveoli are extremely thin allowing a fast rate of diffusion.\n\nThe alveoli have interconnecting small air passages in their walls known as the pores of Kohn.\n\n=== Alveoli ===\n\nAlveoli consist of two types of alveolar cell and an alveolar macrophage.\n\nThe two types of cell are known as type I and type II cells (also known as pneumocytes).\n\nTypes I and II make up the walls and alveolar septa.\n\nType I cells provide 95% of the surface area of each alveoli and are flat (\"squamous\"), and Type II cells generally cluster in the corners of the alveoli and have a cuboidal shape.\n\nDespite this, cells occur in a roughly equal ratio of 1:1 or 6:4.Type I are squamous epithelial cells that make up the alveolar wall structure.\n\nThey have extremely thin walls that enable an easy gas exchange.\n\nThese type I cells also make up the alveolar septa which separate each alveolus.\n\nThe septa consist of an epithelial lining and associated basement membranes.\n\nType I cells are not able to divide, and consequently rely on differentiation from Type II cells.Type II are larger and they line the alveoli and produce and secrete epithelial lining fluid, and lung surfactant.\n\nType II cells are able to divide and differentiate to Type I cells.The alveolar macrophages have an important role in the immune system.\n\nThey remove substances which deposit in the alveoli including loose red blood cells that have been forced out from blood vessels.\n\n=== Microbiota ===\n\nThere is a large presence of microorganisms in the lungs known as the lung microbiota that interacts with the airway epithelial cells; an interaction of probable importance in maintaining homeostasis.\n\nThe microbiota is complex and dynamic in healthy people, and altered in diseases such as asthma and COPD.\n\nFor example significant changes can take place in COPD following infection with rhinovirus.\n\nFungal genera that are commonly found as mycobiota in the microbiota include Candida, Malassezia, Saccharomyces, and Aspergillus.\n\n=== Respiratory tract ===\n\nThe lower respiratory tract is part of the respiratory system, and consists of the trachea and the structures below this including the lungs.\n\nThe trachea receives air from the pharynx and travels down to a place where it splits (the carina) into a right and left primary bronchus.\n\nThese supply air to the right and left lungs, splitting progressively into the secondary and tertiary bronchi for the lobes of the lungs, and into smaller and smaller bronchioles until they become the respiratory bronchioles.\n\nThese in turn supply air through alveolar ducts into the alveoli, where the exchange of gases take place.\n\nOxygen breathed in, diffuses through the walls of the alveoli into the enveloping capillaries and into the circulation, and carbon dioxide diffuses from the blood into the lungs to be breathed out.\nEstimates of the total surface area of lungs vary from 50 to 75 square metres (540 to 810 sq ft); although this is often quoted in textbooks and the media being \"the size of a tennis court\", it is actually less than half the size of a singles court.The bronchi in the conducting zone are reinforced with hyaline cartilage in order to hold open the airways.\n\nThe bronchioles have no cartilage and are surrounded instead by smooth muscle.\n\nAir is warmed to 37 °C (99 °F), humidified and cleansed by the conducting zone.\n\nParticles from the air being removed by the cilia on the respiratory epithelium lining the passageways, in a process called mucociliary clearance.\nPulmonary stretch receptors in the smooth muscle of the airways initiate a reflex known as the Hering–Breuer reflex that prevents the lungs from over-inflation, during forceful inspiration.\n\n=== Blood supply ===\n\nThe lungs have a dual blood supply provided by a bronchial and a pulmonary circulation.\n\nThe bronchial circulation supplies oxygenated blood to the airways of the lungs, through the bronchial arteries that leave the aorta.\n\nThere are usually three arteries, two to the left lung and one to the right, and they branch alongside the bronchi and bronchioles.\n\nThe pulmonary circulation carries deoxygenated blood from the heart to the lungs and returns the oxygenated blood to the heart to supply the rest of the body.The blood volume of the lungs is about 450 millilitres on average, about 9% of the total blood volume of the entire circulatory system.\n\nThis quantity can easily fluctuate from between one-half and twice the normal volume.\n\nAlso, in the event of blood loss through hemorrhage, blood from the lungs can partially compensate by automatically transferring to the systemic circulation.\n\n=== Nerve supply ===\n\nThe lungs are supplied by nerves of the autonomic nervous system.\n\nInput from the parasympathetic nervous system occurs via the vagus nerve.\n\nWhen stimulated by acetylcholine, this causes constriction of the smooth muscle lining the bronchus and bronchioles, and increases the secretions from glands.\n\nThe lungs also have a sympathetic tone from norepinephrine acting on the beta 2 adrenoceptors in the respiratory tract, which causes bronchodilation.The action of breathing takes place because of nerve signals sent by the respiratory center in the brainstem, along the phrenic nerve from the cervical plexus to the diaphragm.\n\n=== Variation ===\n\nThe lobes of the lung are subject to anatomical variations.\n\nA horizontal interlobar fissure was found to be incomplete in 25% of right lungs, or even absent in 11% of all cases.\n\nAn accessory fissure was also found in 14% and 22% of left and right lungs, respectively.\n\nAn oblique fissure was found to be incomplete in 21% to 47% of left lungs.\n\nIn some cases a fissure is absent, or extra, resulting in a right lung with only two lobes, or a left lung with three lobes.A variation in the airway branching structure has been found specifically in the central airway\nbranching.\n\nThis variation is associated with the development of COPD in adulthood.\n\n== Development ==\n\nThe development of the human lungs arise from the laryngotracheal groove and develop to maturity over several weeks in the foetus and for several years following birth.The larynx, trachea, bronchi and lungs that make up the respiratory tract, begin to form during the fourth week of embryogenesis from the lung bud which appears ventrally to the caudal portion of the foregut.\n\nThe respiratory tract has a branching structure, and is also known as the respiratory tree.\n\nIn the embryo this structure is developed in the process of branching morphogenesis, and is generated by the repeated splitting of the tip of the branch.\n\nIn the development of the lungs (as in some other organs) the epithelium forms branching tubes.\n\nThe lung has a left-right symmetry and each bud known as a bronchial bud grows out as a tubular epithelium that becomes a bronchus.\n\nEach bronchus branches into bronchioles.\n\nThe branching is a result of the tip of each tube bifurcating.\n\nThe branching process forms the bronchi, bronchioles, and ultimately the alveoli.\n\nThe four genes mostly associated with branching morphogenesis in the lung are the intercellular signalling protein – sonic hedgehog (SHH), fibroblast growth factors FGF10 and FGFR2b, and bone morphogenetic protein BMP4.\n\nFGF10 is seen to have the most prominent role.\n\nFGF10 is a paracrine signalling molecule needed for epithelial branching, and SHH inhibits FGF10.\n\nThe development of the alveoli is influenced by a different mechanism whereby continued bifurcation is stopped and the distal tips become dilated to form the alveoli.\nAt the end of the fourth week the lung bud divides into two, the right and left primary bronchial buds on each side of the trachea.\n\nDuring the fifth week the right bud branches into three secondary bronchial buds and the left branches into two secondary bronchial buds.\n\nThese give rise to the lobes of the lungs, three on the right and two on the left.\n\nOver the following week, the secondary buds branch into tertiary buds, about ten on each side.\n\nFrom the sixth week to the sixteenth week, the major elements of the lungs appear except the alveoli.\n\nFrom week 16 to week 26, the bronchi enlarge and lung tissue becomes highly vascularised.\n\nBronchioles and alveolar ducts also develop.\n\nBy week 26 the terminal bronchioles have formed which branch into two respiratory bronchioles.\n\nDuring the period covering the 26th week until birth the important blood–air barrier is established.\n\nSpecialised type I alveolar cells where gas exchange will take place, together with the type II alveolar cells that secrete pulmonary surfactant, appear.\n\nThe surfactant reduces the surface tension at the air-alveolar surface which allows expansion of the alveolar sacs.\n\nThe alveolar sacs contain the primitive alveoli that form at the end of the alveolar ducts,\nand their appearance around the seventh month marks the point at which limited respiration would be possible, and the premature baby could survive.\n\n=== Vitamin A deficiency ===\n\nThe developing lung is particularly vulnerable to changes in the levels of vitamin A.\n\nVitamin A deficiency has been linked to changes in the epithelial lining of the lung and in the lung parenchyma.\n\nThis can disrupt the normal physiology of the lung and predispose to respiratory diseases.\n\nSevere nutritional deficiency in vitamin A results in a reduction in the formation of the alveolar walls (septa) and to notable changes in the respiratory epithelium; alterations are noted in the extracellular matrix and in the protein content of the basement membrane.\n\nThe extracellular matrix maintains lung elasticity; the basement membrane is associated with alveolar epithelium and is important in the blood-air barrier.\n\nThe deficiency is associated with functional defects and disease states.\n\nVitamin A is crucial in the development of the alveoli which continues for several years after birth.\n\n=== After birth ===\n\nAt birth, the baby's lungs are filled with fluid secreted by the lungs and are not inflated.\n\nAfter birth the infant's central nervous system reacts to the sudden change in temperature and environment.\n\nThis triggers the first breath, within about 10 seconds after delivery.\n\nBefore birth, the lungs are filled with fetal lung fluid. After the first breath, the fluid is quickly absorbed into the body or exhaled.\n\nThe resistance in the lung's blood vessels decreases giving an increased surface area for gas exchange, and the lungs begin to breathe spontaneously.\n\nThis accompanies other changes which result in an increased amount of blood entering the lung tissues.At birth the lungs are very undeveloped with only around one sixth of the alveoli of the adult lung present.\n\nThe alveoli continue to form into early adulthood, and their ability to form when necessary is seen in the regeneration of the lung.\n\nAlveolar septa have a double capillary network instead of the single network of the developed lung.\n\nOnly after the maturation of the capillary network can the lung enter a normal phase of growth.\n\nFollowing the early growth in numbers of alveoli there is another stage of the alveoli being enlarged.\n\n== Function ==\n\n=== Gas exchange ===\n\nThe major function of the lungs is gas exchange between the lungs and the blood.\n\nThe alveolar and pulmonary capillary gases equilibrate across the thin blood–air barrier.\n\nThis thin membrane (about 0.5 –2 μm thick) is folded into about 300 million alveoli, providing an extremely large surface area (estimates varying between 70 and 145 m2) for gas exchange to occur.\n\nThe lungs are not capable of expanding to breathe on their own, and will only do so when there is an increase in the volume of the thoracic cavity.\n\nThis is achieved by the muscles of respiration, through the contraction of the diaphragm, and the intercostal muscles which pull the rib cage upwards as shown in the diagram.\n\nDuring breathing out the muscles relax, returning the lungs to their resting position.\n\nAt this point the lungs contain the functional residual capacity (FRC) of air, which, in the adult human, has a volume of about 2.5–3.0 litres.During heavy breathing as in exertion, a large number of accessory muscles in the neck and abdomen are recruited, that during exhalation pull the ribcage down, decreasing the volume of the thoracic cavity.\n\nThe FRC is now decreased, but since the lungs cannot be emptied completely there is still about a litre of residual air left.\n\nLung function testing is carried out to evaluate lung volumes and capacities.\n\n=== Protection ===\n\nThe lungs possess several characteristics which protect against infection.\n\nThe respiratory tract is lined by respiratory epithelium or respiratory mucosa, with hair-like projections called cilia that beat rhythmically and carry mucus.\n\nThis mucociliary clearance is an important defence system against air-borne infection.\n\nThe dust particles and bacteria in the inhaled air are caught in the mucosal surface of the airways, and are moved up towards the pharynx by the rhythmic upward beating action of the cilia.: 661–730  The lining of the lung also secretes immunoglobulin A which protects against respiratory infections; goblet cells secrete mucus which also contains several antimicrobial compounds such as defensins, antiproteases, and antioxidants.\n\nA rare type of specialised cell called a pulmonary ionocyte that is suggested may regulate mucus viscosity has been described.\n\nIn addition, the lining of the lung also contains macrophages, immune cells which engulf and destroy debris and microbes that enter the lung in a process known as phagocytosis; and dendritic cells which present antigens to activate components of the adaptive immune system such as T cells and B cells.The size of the respiratory tract and the flow of air also protect the lungs from larger particles.\n\nSmaller particles deposit in the mouth and behind the mouth in the oropharynx, and larger particles are trapped in nasal hair after inhalation.\n\n=== Other ===\n\nIn addition to their function in respiration, the lungs have a number of other functions.\n\nThey are involved in maintaining homeostasis, helping in the regulation of blood pressure as part of the renin–angiotensin system.\n\nThe inner lining of the blood vessels secretes angiotensin-converting enzyme (ACE) an enzyme that catalyses the conversion of angiotensin I to angiotensin II.\n\nThe lungs are involved in the blood's acid–base homeostasis by expelling carbon dioxide when breathing.The lungs also serve a protective role.\n\nSeveral blood-borne substances, such as a few types of prostaglandins, leukotrienes, serotonin and bradykinin, are excreted through the lungs.\n\nDrugs and other substances can be absorbed, modified or excreted in the lungs.\n\nThe lungs filter out small blood clots from veins and prevent them from entering arteries and causing strokes.The lungs also play a pivotal role in speech by providing air and airflow for the creation of vocal sounds, and other paralanguage communications such as sighs and gasps.\nResearch suggests a role of the lungs in the production of blood platelets.\n\n== Gene and protein expression ==\n\nAbout 20,000 protein coding genes are expressed in human cells and almost 75% of these genes are expressed in the normal lung.\n\nA little less than 200 of these genes are more specifically expressed in the lung with less than 20 genes being highly lung specific.\n\nThe highest expression of lung specific proteins are different surfactant proteins, such as SFTPA1, SFTPB and SFTPC, and napsin, expressed in type II pneumocytes.\n\nOther proteins with elevated expression in the lung are the dynein protein DNAH5 in ciliated cells, and the secreted SCGB1A1 protein in mucus-secreting goblet cells of the airway mucosa.\n\n== Clinical significance ==\n\nLungs can be affected by a number of diseases and disorders.\n\nPulmonology is the medical speciality that deals with respiratory diseases involving the lungs and respiratory system.\n\nCardiothoracic surgery deals with surgery of the lungs including lung volume reduction surgery, lobectomy, pneumectomy and lung transplantation.\n\n=== Inflammation and infection ===\n\nInflammatory conditions of the lung tissue are pneumonia, of the respiratory tract are bronchitis and bronchiolitis, and of the pleurae surrounding the lungs pleurisy.\n\nInflammation is usually caused by infections due to bacteria or viruses.\n\nWhen the lung tissue is inflamed due to other causes it is called pneumonitis.\n\nOne major cause of bacterial pneumonia is tuberculosis.\n\nChronic infections often occur in those with immunodeficiency and can include a fungal infection by Aspergillus fumigatus that can lead to an aspergilloma forming in the lung.Alcohol affects the lungs and can cause inflammatory alcoholic lung disease.\n\nAcute exposure to alcohol stimulates the beating of cilia in the respiratory epithelium.\n\nHowever, chronic exposure has the effect of desensitising the ciliary response which reduces mucociliary clearance (MCC).\n\nMCC is an innate defense system protecting against pollutants and pathogens, and when this is disrupted the numbers of alveolar macrophages are decreased.\n\nA subsequent inflammatory response is the release of cytokines.\n\nAnother consequence is the susceptibility to infection.\n\n=== Blood-supply changes ===\n\nA pulmonary embolism is a blood clot that becomes lodged in the pulmonary arteries.\n\nThe majority of emboli arise because of deep vein thrombosis in the legs.\n\nPulmonary emboli may be investigated using a ventilation/perfusion scan, a CT scan of the arteries of the lung, or blood tests such as the D-dimer.\n\nPulmonary hypertension describes an increased pressure at the beginning of the pulmonary artery that has a large number of differing causes.\n\nOther rarer conditions may also affect the blood supply of the lung, such as granulomatosis with polyangiitis, which causes inflammation of the small blood vessels of the lungs and kidneys.A lung contusion is a bruise caused by chest trauma.\n\nIt results in hemorrhage of the alveoli causing a build-up of fluid which can impair breathing, and this can be either mild or severe.\nThe function of the lungs can also be affected by compression from fluid in the pleural cavity pleural effusion, or other substances such as air (pneumothorax), blood (hemothorax), or rarer causes.\n\nThese may be investigated using a chest X-ray or CT scan, and may require the insertion of a surgical drain until the underlying cause is identified and treated.\n\n=== Obstructive lung diseases ===\n\nAsthma, chronic bronchitis, bronchiectasis and chronic obstructive pulmonary disease (COPD) are all obstructive lung diseases characterised by airway obstruction.\n\nThis limits the amount of air that is able to enter alveoli because of constriction of the bronchial tree, due to inflammation.\n\nObstructive lung diseases are often identified because of symptoms and diagnosed with pulmonary function tests such as spirometry.\n\nMany obstructive lung diseases are managed by avoiding triggers (such as dust mites or smoking), with symptom control such as bronchodilators, and with suppression of inflammation (such as through corticosteroids) in severe cases.\n\nA common cause of chronic bronchitis, and emphysema, is smoking; and common causes of bronchiectasis include severe infections and cystic fibrosis.\n\nThe definitive cause of asthma is not yet known.The breakdown of alveolar tissue, often as a result of tobacco-smoking leads to emphysema, which can become severe enough to develop into COPD.\n\nElastase breaks down the elastin in the lung's connective tissue that can also result in emphysema.\n\nElastase is inhibited by the acute-phase protein, alpha-1 antitrypsin, and when there is a deficiency in this, emphysema can develop.\n\nWith persistent stress from smoking, the airway basal cells become disarranged and lose their regenerative ability needed to repair the epithelial barrier.\n\nThe disorganised basal cells are seen to be responsible for the major airway changes that are characteristic of COPD, and with continued stress can undergo a malignant transformation.\n\nStudies have shown that the initial development of emphysema is centred on the early changes in the airway epithelium of the small airways.\n\nBasal cells become further deranged in a smoker's transition to clinically defined COPD.\n\n=== Restrictive lung diseases ===\n\nSome types of chronic lung diseases are classified as restrictive lung disease, because of a restriction in the amount of lung tissue involved in respiration.\n\nThese include pulmonary fibrosis which can occur when the lung is inflamed for a long period of time.\n\nFibrosis in the lung replaces functioning lung tissue with fibrous connective tissue.\n\nThis can be due to a large variety of occupational lung diseases such as Coalworker's pneumoconiosis, autoimmune diseases or more rarely to a reaction to medication.\n\nSevere respiratory disorders, where spontaneous breathing is not enough to maintain life, may need the use of mechanical ventilation to ensure an adequate supply of air.\n\n=== Cancers ===\n\nLung cancer can either arise directly from lung tissue or as a result of metastasis from another part of the body.\n\nThere are two main types of primary tumour described as either small-cell or non-small-cell lung carcinomas.\n\nThe major risk factor for cancer is smoking.\n\nOnce a cancer is identified it is staged using scans such as a CT scan and a sample of tissue from a biopsy is taken.\n\nCancers may be treated surgically by removing the tumour, the use of radiotherapy, chemotherapy or a combination, or with the aim of symptom control.\n\nLung cancer screening is being recommended in the United States for high-risk populations.\n\n=== Congenital disorders ===\n\nCongenital disorders include cystic fibrosis, pulmonary hypoplasia (an incomplete development of the lungs)congenital diaphragmatic hernia, and infant respiratory distress syndrome caused by a deficiency in lung surfactant.\n\nAn azygos lobe is a congenital anatomical variation which though usually without effect can cause problems in thoracoscopic procedures.\n\n=== Others ===\n\nA pneumothorax (collapsed lung) is an abnormal collection of air in the pleural space that causes an uncoupling of the lung from the chest wall.\n\nThe lung cannot expand against the air pressure inside the pleural space.\n\nAn easy to understand example is a traumatic pneumothorax, where air enters the pleural space from outside the body, as occurs with puncture to the chest wall.\n\nSimilarly, scuba divers ascending while holding their breath with their lungs fully inflated can cause air sacs (alveoli) to burst and leak high pressure air into the pleural space.\n\n=== Lung examination ===\n\nAs part of a physical examination in response to respiratory symptoms of shortness of breath, and cough, a lung examination may be carried out.\n\nThis exam includes palpation and auscultation.\n\nThe areas of the lungs that can be listened to using a stethoscope are called the lung fields, and these are the posterior, lateral, and anterior lung fields.\n\nThe posterior fields can be listened to from the back and include: the lower lobes (taking up three quarters of the posterior fields); the anterior fields taking up the other quarter; and the lateral fields under the axillae, the left axilla for the lingual, the right axilla for the middle right lobe.\n\nThe anterior fields can also be auscultated from the front.\n\nAbnormal breathing sounds heard during a lung exam can indicate the presence of a lung condition; wheezing for example is commonly associated with asthma and COPD.\n\n=== Lung function testing ===\n\nLung function testing is carried out by evaluating a person's capacity to inhale and exhale in different circumstances.\n\nThe volume of air inhaled and exhaled by a person at rest is the tidal volume (normally 500-750mL); the inspiratory reserve volume and expiratory reserve volume are the additional amounts a person is able to forcibly inhale and exhale respectively.\n\nThe summed total of forced inspiration and expiration is a person's vital capacity.\n\nNot all air is expelled from the lungs even after a forced breath out; the remainder of the air is called the residual volume.\n\nTogether these terms are referred to as lung volumes.Pulmonary plethysmographs are used to measure functional residual capacity.\n\nFunctional residual capacity cannot be measured by tests that rely on breathing out, as a person is only able to breathe a maximum of 80% of their total functional capacity.\n\nThe total lung capacity depends on the person's age, height, weight, and sex, and normally ranges between 4 and 6 litres.\n\nFemales tend to have a 20–25% lower capacity than males.\n\nTall people tend to have a larger total lung capacity than shorter people.\n\nSmokers have a lower capacity than nonsmokers.\n\nThinner persons tend to have a larger capacity.\n\nLung capacity can be increased by physical training as much as 40% but the effect may be modified by exposure to air pollution.Other lung function tests include spirometry, measuring the amount (volume) and flow of air that can be inhaled and exhaled.\n\nThe maximum volume of breath that can be exhaled is called the vital capacity.\n\nIn particular, how much a person is able to exhale in one second (called forced expiratory volume (FEV1)) as a proportion of how much they are able to exhale in total (FEV).\n\nThis ratio, the FEV1/FEV ratio, is important to distinguish whether a lung disease is restrictive or obstructive.\n\nAnother test is that of the lung's diffusing capacity – this is a measure of the transfer of gas from air to the blood in the lung capillaries.\n\n== Other animals ==\n\n=== Birds ===\n\nThe lungs of birds are relatively small, but are connected to 8 or 9 air sacs that extend through much of the body, and are in turn connected to air spaces within the bones.\n\nOn inhalation, air travels through the trachea of a bird into the air sacs.\n\nAir then travels continuously from the air sacs at the back, through the lungs, which are relatively fixed in size, to the air sacs at the front.\n\nFrom here, the air is exhaled.\n\nThese fixed size lungs are called \"circulatory lungs\", as distinct from the \"bellows-type lungs\" found in most other animals.The lungs of birds contain millions of tiny parallel passages called parabronchi.\n\nSmall sacs called atria radiate from the walls of the tiny passages; these, like the alveoli in other lungs, are the site of gas exchange by simple diffusion.\n\nThe blood flow around the parabronchi and their atria forms a cross-current process of gas exchange (see diagram on the right).The air sacs, which hold air, do not contribute much to gas exchange, despite being thin-walled, as they are poorly vascularised.\n\nThe air sacs expand and contract due to changes in the volume in the thorax and abdomen.\n\nThis volume change is caused by the movement of the sternum and ribs and this movement is often synchronised with movement of the flight muscles.Parabronchi in which the air flow is unidirectional are called paleopulmonic parabronchi and are found in all birds.\n\nSome birds, however, have, in addition, a lung structure where the air flow in the parabronchi is bidirectional.\n\nThese are termed neopulmonic parabronchi.\n\n=== Reptiles ===\n\nThe lungs of most reptiles have a single bronchus running down the centre, from which numerous branches reach out to individual pockets throughout the lungs.\n\nThese pockets are similar to alveoli in mammals, but much larger and fewer in number.\n\nThese give the lung a sponge-like texture.\n\nIn tuataras, snakes, and some lizards, the lungs are simpler in structure, similar to that of typical amphibians.Snakes and limbless lizards typically possess only the right lung as a major respiratory organ; the left lung is greatly reduced, or even absent.\n\nAmphisbaenians, however, have the opposite arrangement, with a major left lung, and a reduced or absent right lung.Both crocodilians and monitor lizards have developed lungs similar to those of birds, providing a unidirectional airflow and even possessing air sacs.\n\nThe now extinct pterosaurs have seemingly even further refined this type of lung, extending the airsacs into the wing membranes and, in the case of lonchodectids, tupuxuara, and azhdarchoids, the hindlimbs.Reptilian lungs typically receive air via expansion and contraction of the ribs driven by axial muscles and buccal pumping.\n\nCrocodilians also rely on the hepatic piston method, in which the liver is pulled back by a muscle anchored to the pubic bone (part of the pelvis) called the diaphragmaticus, which in turn creates negative pressure in the crocodile's thoracic cavity, allowing air to be moved into the lungs by Boyle's law.\n\nTurtles, which are unable to move their ribs, instead use their forelimbs and pectoral girdle to force air in and out of the lungs.\n\n=== Amphibians ===\n\nThe lungs of most frogs and other amphibians are simple and balloon-like, with gas exchange limited to the outer surface of the lung.\n\nThis is not very efficient, but amphibians have low metabolic demands and can also quickly dispose of carbon dioxide by diffusion across their skin in water, and supplement their oxygen supply by the same method.\n\nAmphibians employ a positive pressure system to get air to their lungs, forcing air down into the lungs by buccal pumping.\n\nThis is distinct from most higher vertebrates, who use a breathing system driven by negative pressure where the lungs are inflated by expanding the rib cage.\n\nIn buccal pumping, the floor of the mouth is lowered, filling the mouth cavity with air.\n\nThe throat muscles then presses the throat against the underside of the skull, forcing the air into the lungs.Due to the possibility of respiration across the skin combined with small size, all known lungless tetrapods are amphibians.\n\nThe majority of salamander species are lungless salamanders, which respirate through their skin and tissues lining their mouth.\n\nThis necessarily restricts their size: all are small and rather thread-like in appearance, maximising skin surface relative to body volume.\n\nOther known lungless tetrapods are the Bornean flat-headed frog and Atretochoana eiselti, a caecilian.The lungs of amphibians typically have a few narrow internal walls (septa) of soft tissue around the outer walls, increasing the respiratory surface area and giving the lung a honeycomb appearance.\n\nIn some salamanders even these are lacking, and the lung has a smooth wall.\n\nIn caecilians, as in snakes, only the right lung attains any size or development.\n\n=== Lungfish ===\n\nThe lungs of lungfish are similar to those of amphibians, with few, if any, internal septa.\n\nIn the Australian lungfish, there is only a single lung, albeit divided into two lobes.\n\nOther lungfish and Polypterus, however, have two lungs, which are located in the upper part of the body, with the connecting duct curving around and above the esophagus.\n\nThe blood supply also twists around the esophagus, suggesting that the lungs originally evolved in the ventral part of the body, as in other vertebrates.\n\n=== Invertebrates ===\n\nSome invertebrates have lung-like structures that serve a similar respiratory purpose as, but are not evolutionarily related to, vertebrate lungs.\n\nSome arachnids, such as spiders and scorpions, have structures called book lungs used for atmospheric gas exchange.\n\nSome species of spider have four pairs of book lungs but most have two pairs.\n\nScorpions have spiracles on their body for the entrance of air to the book lungs.The coconut crab is terrestrial and uses structures called branchiostegal lungs to breathe air.\n\nThey cannot swim and would drown in water, yet they possess a rudimentary set of gills.\n\nThey can breathe on land and hold their breath underwater.\n\nThe branchiostegal lungs are seen as a developmental adaptive stage from water-living to enable land-living, or from fish to amphibian.Pulmonates are mostly land snails and slugs that have developed a simple lung from the mantle cavity.\n\nAn externally located opening called the pneumostome allows air to be taken into the mantle cavity lung.\n\n== Evolutionary origins ==\n\nThe lungs of today's terrestrial vertebrates and the gas bladders of today's fish are believed to have evolved from simple sacs, as outpocketings of the esophagus, that allowed early fish to gulp air under oxygen-poor conditions.\n\nThese outpocketings first arose in the bony fish.\n\nIn most of the ray-finned fish the sacs evolved into closed off gas bladders, while a number of carp, trout, herring, catfish, and eels have retained the physostome condition with the sac being open to the esophagus.\n\nIn more basal bony fish, such as the gar, bichir, bowfin and the lobe-finned fish, the bladders have evolved to primarily function as lungs.\n\nThe lobe-finned fish gave rise to the land-based tetrapods.\n\nThus, the lungs of vertebrates are homologous to the gas bladders of fish (but not to their gills).\n\n== Further reading ==\n\nhttps://en.wikipedia.org/wiki/Lung","middle-lobe-of-right-lung":"LUNG\n\nThe lungs are the primary organs of the respiratory system in humans and most other animals including a few fish, and some snails.\n\nIn mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart.\n\nTheir function in the respiratory system is to extract oxygen from the air and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange.\n\nRespiration is driven by different muscular systems in different species.\n\nMammals, reptiles and birds use their different muscles to support and foster breathing.\n\nIn earlier tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians.\n\nIn humans, the main muscle of respiration that drives breathing is the diaphragm.\n\nThe lungs also provide airflow that makes vocal sounds including human speech possible.\nHumans have two lungs, a right lung, and a left lung.\n\nThey are situated within the thoracic cavity of the chest.\n\nThe right lung is bigger than the left, which shares space in the chest with the heart.\n\nThe lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier.\n\nThe lungs are part of the lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles, and which receive air breathed in via the conducting zone.\n\nThe conducting zone ends at the terminal bronchioles.\n\nThese divide into the respiratory bronchioles of the respiratory zone which divide into alveolar ducts that give rise to the alveolar sacs that contain the alveoli, where gas exchange takes place.\n\nAlveoli are also sparsely present on the walls of the respiratory bronchioles and alveolar ducts.\n\nTogether, the lungs contain approximately 2,400 kilometres (1,500 mi) of airways and 300 to 500 million alveoli.\n\nEach lung is enclosed within a pleural sac of two membranes called pleurae; the membranes are separated by a film of pleural fluid, which allows the inner and outer membranes to slide over each other whilst breathing takes place, without much friction.\n\nThe inner pleura also divides each lung into sections called lobes.\n\nThe right lung has three lobes and the left has two.\n\nThe lobes are further divided into bronchopulmonary segments and pulmonary lobules.\n\nThe lungs have a unique blood supply, receiving deoxygenated blood from the heart in the pulmonary circulation for the purposes of receiving oxygen and releasing carbon dioxide, and a separate supply of oxygenated blood to the tissue of the lungs, in the bronchial circulation.\nThe tissue of the lungs can be affected by a number of respiratory diseases, including pneumonia and lung cancer.\n\nChronic obstructive pulmonary disease includes chronic bronchitis and emphysema, and can be related to smoking or exposure to harmful substances.\n\nA number of occupational lung diseases can be caused by substances such as coal dust, asbestos fibres, and crystalline silica dust.\n\nDiseases such as bronchitis can also affect the respiratory tract.\n\nMedical terms related to the lung often begin with pulmo-, from the Latin pulmonarius (of the lungs) as in pulmonology, or with pneumo- (from Greek πνεύμων \"lung\") as in pneumonia.\nIn embryonic development, the lungs begin to develop as an outpouching of the foregut, a tube which goes on to form the upper part of the digestive system.\n\nWhen the lungs are formed the fetus is held in the fluid-filled amniotic sac and so they do not function to breathe.\n\nBlood is also diverted from the lungs through the ductus arteriosus.\n\nAt birth however, air begins to pass through the lungs, and the diversionary duct closes, so that the lungs can begin to respire.\n\nThe lungs only fully develop in early childhood.\n\n== Structure ==\n\n=== Anatomy ===\n\nThe lungs are located in the chest on either side of the heart in the rib cage.\n\nThey are conical in shape with a narrow rounded apex at the top, and a broad concave base that rests on the convex surface of the diaphragm.\n\nThe apex of the lung extends into the root of the neck, reaching shortly above the level of the sternal end of the first rib.\n\nThe lungs stretch from close to the backbone in the rib cage to the front of the chest and downwards from the lower part of the trachea to the diaphragm.\n\nThe left lung shares space with the heart, and has an indentation in its border called the cardiac notch of the left lung to accommodate this.\n\nThe front and outer sides of the lungs face the ribs, which make light indentations on their surfaces.\n\nThe medial surfaces of the lungs face towards the centre of the chest, and lie against the heart, great vessels, and the carina where the trachea divides into the two main bronchi.\n\nThe cardiac impression is an indentation formed on the surfaces of the lungs where they rest against the heart.\nBoth lungs have a central recession called the hilum at the root of the lung, where the blood vessels and airways pass into the lungs.\n\nThere are also bronchopulmonary lymph nodes on the hilum.The lungs are surrounded by the pulmonary pleurae.\n\nThe pleurae are two serous membranes; the outer parietal pleura lines the inner wall of the rib cage and the inner visceral pleura directly lines the surface of the lungs.\n\nBetween the pleurae is a potential space called the pleural cavity containing a thin layer of lubricating pleural fluid.\n\n==== Lobes ====\nEach lung is divided into sections called lobes by the infoldings of the visceral pleura as fissures.\n\nLobes are divided into segments, and segments have further divisions as lobules.\n\nThere are three lobes in the right lung and two lobes in the left lung.\n\n==== Fissures ====\nThe fissures are formed in early prenatal development by invaginations of the visceral pleura that divide the lobar bronchi, and section the lungs into lobes that helps in their expansion.\n\nThe right lung is divided into three lobes by a horizontal fissure, and an oblique fissure.\n\nThe left lung is divided into two lobes by an oblique fissure which is closely aligned with the oblique fissure in the right lung.\n\nIn the right lung the upper horizontal fissure, separates the upper (superior) lobe from the middle lobe.\n\nThe lower, oblique fissure separates the lower lobe from the middle and upper lobes.Variations in the fissures are fairly common being either incompletely formed\nor present as an extra fissure as in the azygos fissure, or absent.\n\nIncomplete fissures are responsible for interlobar collateral ventilation, airflow between lobes which is unwanted in some lung volume reduction procedures.\n\n==== Segments ====\nThe main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of the lung.\n\nThe lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments.\n\nEach bronchopulmonary segment has its own (segmental) bronchus and arterial supply.\n\nSegments for the left and right lung are shown in the table.\n\nThe segmental anatomy is useful clinically for localising disease processes in the lungs.\n\nA segment is a discrete unit that can be surgically removed without seriously affecting surrounding tissue.\n\n=== Right lung ===\n\nThe right lung has both more lobes and segments than the left.\n\nIt is divided into three lobes, an upper, middle, and a lower lobe by two fissures, one oblique and one horizontal.\n\nThe upper, horizontal fissure, separates the upper from the middle lobe.\n\nIt begins in the lower oblique fissure near the posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage; on the mediastinal surface it may be traced back to the hilum.\n\nThe lower, oblique fissure, separates the lower from the middle and upper lobes and is closely aligned with the oblique fissure in the left lung.The mediastinal surface of the right lung is indented by a number of nearby structures.\n\nThe heart sits in an impression called the cardiac impression.\n\nAbove the hilum of the lung is an arched groove for the azygos vein, and above this is a wide groove for the superior vena cava and right brachiocephalic vein; behind this, and close to the top of the lung is a groove for the brachiocephalic artery.\n\nThere is a groove for the esophagus behind the hilum and the pulmonary ligament, and near the lower part of the esophageal groove is a deeper groove for the inferior vena cava before it enters the heart.The weight of the right lung varies between individuals, with a standard reference range in men of 155–720 g (0.342–1.587 lb) and in women of 100–590 g (0.22–1.30 lb).\n\n=== Left lung ===\n\nThe left lung is divided into two lobes, an upper and a lower lobe, by the oblique fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilum.\n\nThe left lung, unlike the right, does not have a middle lobe, though it does have a homologous feature, a projection of the upper lobe termed the lingula.\n\nIts name means \"little tongue\".\n\nThe lingula on the left lung serves as an anatomic parallel to the middle lobe on the right lung, with both areas being predisposed to similar infections and anatomic complications.\n\nThere are two bronchopulmonary segments of the lingula: superior and inferior.The mediastinal surface of the left lung has a large cardiac impression where the heart sits.\n\nThis is deeper and larger than that on the right lung, at which level the heart projects to the left.On the same surface, immediately above the hilum, is a well-marked curved groove for the aortic arch, and a groove below it for the descending aorta.\n\nThe left subclavian artery, a branch off the aortic arch, sits in a groove from the arch to near the apex of the lung.\n\nA shallower groove in front of the artery and near the edge of the lung, lodges the left brachiocephalic vein.\n\nThe esophagus may sit in a wider shallow impression at the base of the lung.The weight of the left lung, by standard reference range, in men is 110–675 g (0.243–1.488 lb) in women 105–515 g (0.231–1.135 lb).\n\n== Microanatomy ==\n\nThe lungs are part of the lower respiratory tract, and accommodate the bronchial airways when they branch from the trachea.\n\nThe bronchial airways terminate in alveoli which make up the functional tissue (parenchyma) of the lung, and veins, arteries, nerves, and lymphatic vessels.\n\nThe trachea and bronchi have plexuses of lymph capillaries in their mucosa and submucosa.\n\nThe smaller bronchi have a single layer of lymph capillaries, and they are absent in the alveoli.\n\nThe lungs are supplied with the largest lymphatic drainage system of any other organ in the body.\n\nEach lung is surrounded by a serous membrane of visceral pleura, which has an underlying layer of loose connective tissue attached to the substance of the lung.\n\n=== Connective tissue ===\n\nThe connective tissue of the lungs is made up of elastic and collagen fibres that are interspersed between the capillaries and the alveolar walls.\n\nElastin is the key protein of the extracellular matrix and is the main component of the elastic fibres.\n\nElastin gives the necessary elasticity and resilience required for the persistent stretching involved in breathing, known as lung compliance.\n\nIt is also responsible for the elastic recoil needed.\n\nElastin is more concentrated in areas of high stress such as the openings of the alveoli, and alveolar junctions.\n\nThe connective tissue links all the alveoli to form the lung parenchyma which has a sponge-like appearance.\n\nThe alveoli have interconnecting air passages in their walls known as the pores of Kohn.\n\n=== Respiratory epithelium ===\n\nAll of the lower respiratory tract including the trachea, bronchi, and bronchioles is lined with respiratory epithelium.\n\nThis is a ciliated epithelium interspersed with goblet cells which produce mucin the main component of mucus, ciliated cells, basal cells, and in the terminal bronchioles–club cells with actions similar to basal cells, and macrophages.\n\nThe epithelial cells, and the submucosal glands throughout the respiratory tract secrete airway surface liquid (ASL), the composition of which is tightly regulated and determines how well mucociliary clearance works.Pulmonary neuroendocrine cells are found throughout the respiratory epithelium including the alveolar epithelium, though they only account for around 0.5 per cent of the total epithelial population.\n\nPNECs are innervated airway epithelial cells that are particularly focused at airway junction points.\n\nThese cells can produce serotonin, dopamine, and norepinephrine, as well as polypeptide products.\n\nCytoplasmic processes from the pulmonary neuroendocrine cells extend into the airway lumen where they may sense the composition of inspired gas.\n\n=== Bronchial airways ===\n\nIn the bronchi there are incomplete tracheal rings of cartilage and smaller plates of cartilage that keep them open.: 472  Bronchioles are too narrow to support cartilage and their walls are of smooth muscle, and this is largely absent in the narrower respiratory bronchioles which are mainly just of epithelium.: 472  The absence of cartilage in the terminal bronchioles gives them an alternative name of membranous bronchioles.\n\n=== Respiratory zone ===\n\nThe conducting zone of the respiratory tract ends at the terminal bronchioles when they branch into the respiratory bronchioles.\n\nThis marks the beginning of the terminal respiratory unit called the acinus which includes the respiratory bronchioles, the alveolar ducts, alveolar sacs, and alveoli.\n\nAn acinus measures up to 10 mm in diameter.\n\nA primary pulmonary lobule is that part of the acinus that includes the alveolar ducts, sacs, and alveoli but does not include the respiratory bronchioles.\n\nThe unit described as the secondary pulmonary lobule is the lobule most referred to as the pulmonary lobule or respiratory lobule.: 489  This lobule is a discrete unit that is the smallest component of the lung that can be seen without aid.\n\nThe secondary pulmonary lobule is likely to be made up of between 30 and 50 primary lobules.\n\nThe lobule is supplied by a terminal bronchiole that branches into respiratory bronchioles.\n\nThe respiratory bronchioles supply the alveoli in each acinus and is accompanied by a pulmonary artery branch.\n\nEach lobule is enclosed by an interlobular septa.\n\nEach acinus is incompletely separated by an interlobular septa.The respiratory bronchiole gives rise to the alveolar ducts that lead to the alveolar sacs, which contain two or more alveoli.\n\nThe walls of the alveoli are extremely thin allowing a fast rate of diffusion.\n\nThe alveoli have interconnecting small air passages in their walls known as the pores of Kohn.\n\n=== Alveoli ===\n\nAlveoli consist of two types of alveolar cell and an alveolar macrophage.\n\nThe two types of cell are known as type I and type II cells (also known as pneumocytes).\n\nTypes I and II make up the walls and alveolar septa.\n\nType I cells provide 95% of the surface area of each alveoli and are flat (\"squamous\"), and Type II cells generally cluster in the corners of the alveoli and have a cuboidal shape.\n\nDespite this, cells occur in a roughly equal ratio of 1:1 or 6:4.Type I are squamous epithelial cells that make up the alveolar wall structure.\n\nThey have extremely thin walls that enable an easy gas exchange.\n\nThese type I cells also make up the alveolar septa which separate each alveolus.\n\nThe septa consist of an epithelial lining and associated basement membranes.\n\nType I cells are not able to divide, and consequently rely on differentiation from Type II cells.Type II are larger and they line the alveoli and produce and secrete epithelial lining fluid, and lung surfactant.\n\nType II cells are able to divide and differentiate to Type I cells.The alveolar macrophages have an important role in the immune system.\n\nThey remove substances which deposit in the alveoli including loose red blood cells that have been forced out from blood vessels.\n\n=== Microbiota ===\n\nThere is a large presence of microorganisms in the lungs known as the lung microbiota that interacts with the airway epithelial cells; an interaction of probable importance in maintaining homeostasis.\n\nThe microbiota is complex and dynamic in healthy people, and altered in diseases such as asthma and COPD.\n\nFor example significant changes can take place in COPD following infection with rhinovirus.\n\nFungal genera that are commonly found as mycobiota in the microbiota include Candida, Malassezia, Saccharomyces, and Aspergillus.\n\n=== Respiratory tract ===\n\nThe lower respiratory tract is part of the respiratory system, and consists of the trachea and the structures below this including the lungs.\n\nThe trachea receives air from the pharynx and travels down to a place where it splits (the carina) into a right and left primary bronchus.\n\nThese supply air to the right and left lungs, splitting progressively into the secondary and tertiary bronchi for the lobes of the lungs, and into smaller and smaller bronchioles until they become the respiratory bronchioles.\n\nThese in turn supply air through alveolar ducts into the alveoli, where the exchange of gases take place.\n\nOxygen breathed in, diffuses through the walls of the alveoli into the enveloping capillaries and into the circulation, and carbon dioxide diffuses from the blood into the lungs to be breathed out.\nEstimates of the total surface area of lungs vary from 50 to 75 square metres (540 to 810 sq ft); although this is often quoted in textbooks and the media being \"the size of a tennis court\", it is actually less than half the size of a singles court.The bronchi in the conducting zone are reinforced with hyaline cartilage in order to hold open the airways.\n\nThe bronchioles have no cartilage and are surrounded instead by smooth muscle.\n\nAir is warmed to 37 °C (99 °F), humidified and cleansed by the conducting zone.\n\nParticles from the air being removed by the cilia on the respiratory epithelium lining the passageways, in a process called mucociliary clearance.\nPulmonary stretch receptors in the smooth muscle of the airways initiate a reflex known as the Hering–Breuer reflex that prevents the lungs from over-inflation, during forceful inspiration.\n\n=== Blood supply ===\n\nThe lungs have a dual blood supply provided by a bronchial and a pulmonary circulation.\n\nThe bronchial circulation supplies oxygenated blood to the airways of the lungs, through the bronchial arteries that leave the aorta.\n\nThere are usually three arteries, two to the left lung and one to the right, and they branch alongside the bronchi and bronchioles.\n\nThe pulmonary circulation carries deoxygenated blood from the heart to the lungs and returns the oxygenated blood to the heart to supply the rest of the body.The blood volume of the lungs is about 450 millilitres on average, about 9% of the total blood volume of the entire circulatory system.\n\nThis quantity can easily fluctuate from between one-half and twice the normal volume.\n\nAlso, in the event of blood loss through hemorrhage, blood from the lungs can partially compensate by automatically transferring to the systemic circulation.\n\n=== Nerve supply ===\n\nThe lungs are supplied by nerves of the autonomic nervous system.\n\nInput from the parasympathetic nervous system occurs via the vagus nerve.\n\nWhen stimulated by acetylcholine, this causes constriction of the smooth muscle lining the bronchus and bronchioles, and increases the secretions from glands.\n\nThe lungs also have a sympathetic tone from norepinephrine acting on the beta 2 adrenoceptors in the respiratory tract, which causes bronchodilation.The action of breathing takes place because of nerve signals sent by the respiratory center in the brainstem, along the phrenic nerve from the cervical plexus to the diaphragm.\n\n=== Variation ===\n\nThe lobes of the lung are subject to anatomical variations.\n\nA horizontal interlobar fissure was found to be incomplete in 25% of right lungs, or even absent in 11% of all cases.\n\nAn accessory fissure was also found in 14% and 22% of left and right lungs, respectively.\n\nAn oblique fissure was found to be incomplete in 21% to 47% of left lungs.\n\nIn some cases a fissure is absent, or extra, resulting in a right lung with only two lobes, or a left lung with three lobes.A variation in the airway branching structure has been found specifically in the central airway\nbranching.\n\nThis variation is associated with the development of COPD in adulthood.\n\n== Development ==\n\nThe development of the human lungs arise from the laryngotracheal groove and develop to maturity over several weeks in the foetus and for several years following birth.The larynx, trachea, bronchi and lungs that make up the respiratory tract, begin to form during the fourth week of embryogenesis from the lung bud which appears ventrally to the caudal portion of the foregut.\n\nThe respiratory tract has a branching structure, and is also known as the respiratory tree.\n\nIn the embryo this structure is developed in the process of branching morphogenesis, and is generated by the repeated splitting of the tip of the branch.\n\nIn the development of the lungs (as in some other organs) the epithelium forms branching tubes.\n\nThe lung has a left-right symmetry and each bud known as a bronchial bud grows out as a tubular epithelium that becomes a bronchus.\n\nEach bronchus branches into bronchioles.\n\nThe branching is a result of the tip of each tube bifurcating.\n\nThe branching process forms the bronchi, bronchioles, and ultimately the alveoli.\n\nThe four genes mostly associated with branching morphogenesis in the lung are the intercellular signalling protein – sonic hedgehog (SHH), fibroblast growth factors FGF10 and FGFR2b, and bone morphogenetic protein BMP4.\n\nFGF10 is seen to have the most prominent role.\n\nFGF10 is a paracrine signalling molecule needed for epithelial branching, and SHH inhibits FGF10.\n\nThe development of the alveoli is influenced by a different mechanism whereby continued bifurcation is stopped and the distal tips become dilated to form the alveoli.\nAt the end of the fourth week the lung bud divides into two, the right and left primary bronchial buds on each side of the trachea.\n\nDuring the fifth week the right bud branches into three secondary bronchial buds and the left branches into two secondary bronchial buds.\n\nThese give rise to the lobes of the lungs, three on the right and two on the left.\n\nOver the following week, the secondary buds branch into tertiary buds, about ten on each side.\n\nFrom the sixth week to the sixteenth week, the major elements of the lungs appear except the alveoli.\n\nFrom week 16 to week 26, the bronchi enlarge and lung tissue becomes highly vascularised.\n\nBronchioles and alveolar ducts also develop.\n\nBy week 26 the terminal bronchioles have formed which branch into two respiratory bronchioles.\n\nDuring the period covering the 26th week until birth the important blood–air barrier is established.\n\nSpecialised type I alveolar cells where gas exchange will take place, together with the type II alveolar cells that secrete pulmonary surfactant, appear.\n\nThe surfactant reduces the surface tension at the air-alveolar surface which allows expansion of the alveolar sacs.\n\nThe alveolar sacs contain the primitive alveoli that form at the end of the alveolar ducts,\nand their appearance around the seventh month marks the point at which limited respiration would be possible, and the premature baby could survive.\n\n=== Vitamin A deficiency ===\n\nThe developing lung is particularly vulnerable to changes in the levels of vitamin A.\n\nVitamin A deficiency has been linked to changes in the epithelial lining of the lung and in the lung parenchyma.\n\nThis can disrupt the normal physiology of the lung and predispose to respiratory diseases.\n\nSevere nutritional deficiency in vitamin A results in a reduction in the formation of the alveolar walls (septa) and to notable changes in the respiratory epithelium; alterations are noted in the extracellular matrix and in the protein content of the basement membrane.\n\nThe extracellular matrix maintains lung elasticity; the basement membrane is associated with alveolar epithelium and is important in the blood-air barrier.\n\nThe deficiency is associated with functional defects and disease states.\n\nVitamin A is crucial in the development of the alveoli which continues for several years after birth.\n\n=== After birth ===\n\nAt birth, the baby's lungs are filled with fluid secreted by the lungs and are not inflated.\n\nAfter birth the infant's central nervous system reacts to the sudden change in temperature and environment.\n\nThis triggers the first breath, within about 10 seconds after delivery.\n\nBefore birth, the lungs are filled with fetal lung fluid. After the first breath, the fluid is quickly absorbed into the body or exhaled.\n\nThe resistance in the lung's blood vessels decreases giving an increased surface area for gas exchange, and the lungs begin to breathe spontaneously.\n\nThis accompanies other changes which result in an increased amount of blood entering the lung tissues.At birth the lungs are very undeveloped with only around one sixth of the alveoli of the adult lung present.\n\nThe alveoli continue to form into early adulthood, and their ability to form when necessary is seen in the regeneration of the lung.\n\nAlveolar septa have a double capillary network instead of the single network of the developed lung.\n\nOnly after the maturation of the capillary network can the lung enter a normal phase of growth.\n\nFollowing the early growth in numbers of alveoli there is another stage of the alveoli being enlarged.\n\n== Function ==\n\n=== Gas exchange ===\n\nThe major function of the lungs is gas exchange between the lungs and the blood.\n\nThe alveolar and pulmonary capillary gases equilibrate across the thin blood–air barrier.\n\nThis thin membrane (about 0.5 –2 μm thick) is folded into about 300 million alveoli, providing an extremely large surface area (estimates varying between 70 and 145 m2) for gas exchange to occur.\n\nThe lungs are not capable of expanding to breathe on their own, and will only do so when there is an increase in the volume of the thoracic cavity.\n\nThis is achieved by the muscles of respiration, through the contraction of the diaphragm, and the intercostal muscles which pull the rib cage upwards as shown in the diagram.\n\nDuring breathing out the muscles relax, returning the lungs to their resting position.\n\nAt this point the lungs contain the functional residual capacity (FRC) of air, which, in the adult human, has a volume of about 2.5–3.0 litres.During heavy breathing as in exertion, a large number of accessory muscles in the neck and abdomen are recruited, that during exhalation pull the ribcage down, decreasing the volume of the thoracic cavity.\n\nThe FRC is now decreased, but since the lungs cannot be emptied completely there is still about a litre of residual air left.\n\nLung function testing is carried out to evaluate lung volumes and capacities.\n\n=== Protection ===\n\nThe lungs possess several characteristics which protect against infection.\n\nThe respiratory tract is lined by respiratory epithelium or respiratory mucosa, with hair-like projections called cilia that beat rhythmically and carry mucus.\n\nThis mucociliary clearance is an important defence system against air-borne infection.\n\nThe dust particles and bacteria in the inhaled air are caught in the mucosal surface of the airways, and are moved up towards the pharynx by the rhythmic upward beating action of the cilia.: 661–730  The lining of the lung also secretes immunoglobulin A which protects against respiratory infections; goblet cells secrete mucus which also contains several antimicrobial compounds such as defensins, antiproteases, and antioxidants.\n\nA rare type of specialised cell called a pulmonary ionocyte that is suggested may regulate mucus viscosity has been described.\n\nIn addition, the lining of the lung also contains macrophages, immune cells which engulf and destroy debris and microbes that enter the lung in a process known as phagocytosis; and dendritic cells which present antigens to activate components of the adaptive immune system such as T cells and B cells.The size of the respiratory tract and the flow of air also protect the lungs from larger particles.\n\nSmaller particles deposit in the mouth and behind the mouth in the oropharynx, and larger particles are trapped in nasal hair after inhalation.\n\n=== Other ===\n\nIn addition to their function in respiration, the lungs have a number of other functions.\n\nThey are involved in maintaining homeostasis, helping in the regulation of blood pressure as part of the renin–angiotensin system.\n\nThe inner lining of the blood vessels secretes angiotensin-converting enzyme (ACE) an enzyme that catalyses the conversion of angiotensin I to angiotensin II.\n\nThe lungs are involved in the blood's acid–base homeostasis by expelling carbon dioxide when breathing.The lungs also serve a protective role.\n\nSeveral blood-borne substances, such as a few types of prostaglandins, leukotrienes, serotonin and bradykinin, are excreted through the lungs.\n\nDrugs and other substances can be absorbed, modified or excreted in the lungs.\n\nThe lungs filter out small blood clots from veins and prevent them from entering arteries and causing strokes.The lungs also play a pivotal role in speech by providing air and airflow for the creation of vocal sounds, and other paralanguage communications such as sighs and gasps.\nResearch suggests a role of the lungs in the production of blood platelets.\n\n== Gene and protein expression ==\n\nAbout 20,000 protein coding genes are expressed in human cells and almost 75% of these genes are expressed in the normal lung.\n\nA little less than 200 of these genes are more specifically expressed in the lung with less than 20 genes being highly lung specific.\n\nThe highest expression of lung specific proteins are different surfactant proteins, such as SFTPA1, SFTPB and SFTPC, and napsin, expressed in type II pneumocytes.\n\nOther proteins with elevated expression in the lung are the dynein protein DNAH5 in ciliated cells, and the secreted SCGB1A1 protein in mucus-secreting goblet cells of the airway mucosa.\n\n== Clinical significance ==\n\nLungs can be affected by a number of diseases and disorders.\n\nPulmonology is the medical speciality that deals with respiratory diseases involving the lungs and respiratory system.\n\nCardiothoracic surgery deals with surgery of the lungs including lung volume reduction surgery, lobectomy, pneumectomy and lung transplantation.\n\n=== Inflammation and infection ===\n\nInflammatory conditions of the lung tissue are pneumonia, of the respiratory tract are bronchitis and bronchiolitis, and of the pleurae surrounding the lungs pleurisy.\n\nInflammation is usually caused by infections due to bacteria or viruses.\n\nWhen the lung tissue is inflamed due to other causes it is called pneumonitis.\n\nOne major cause of bacterial pneumonia is tuberculosis.\n\nChronic infections often occur in those with immunodeficiency and can include a fungal infection by Aspergillus fumigatus that can lead to an aspergilloma forming in the lung.Alcohol affects the lungs and can cause inflammatory alcoholic lung disease.\n\nAcute exposure to alcohol stimulates the beating of cilia in the respiratory epithelium.\n\nHowever, chronic exposure has the effect of desensitising the ciliary response which reduces mucociliary clearance (MCC).\n\nMCC is an innate defense system protecting against pollutants and pathogens, and when this is disrupted the numbers of alveolar macrophages are decreased.\n\nA subsequent inflammatory response is the release of cytokines.\n\nAnother consequence is the susceptibility to infection.\n\n=== Blood-supply changes ===\n\nA pulmonary embolism is a blood clot that becomes lodged in the pulmonary arteries.\n\nThe majority of emboli arise because of deep vein thrombosis in the legs.\n\nPulmonary emboli may be investigated using a ventilation/perfusion scan, a CT scan of the arteries of the lung, or blood tests such as the D-dimer.\n\nPulmonary hypertension describes an increased pressure at the beginning of the pulmonary artery that has a large number of differing causes.\n\nOther rarer conditions may also affect the blood supply of the lung, such as granulomatosis with polyangiitis, which causes inflammation of the small blood vessels of the lungs and kidneys.A lung contusion is a bruise caused by chest trauma.\n\nIt results in hemorrhage of the alveoli causing a build-up of fluid which can impair breathing, and this can be either mild or severe.\nThe function of the lungs can also be affected by compression from fluid in the pleural cavity pleural effusion, or other substances such as air (pneumothorax), blood (hemothorax), or rarer causes.\n\nThese may be investigated using a chest X-ray or CT scan, and may require the insertion of a surgical drain until the underlying cause is identified and treated.\n\n=== Obstructive lung diseases ===\n\nAsthma, chronic bronchitis, bronchiectasis and chronic obstructive pulmonary disease (COPD) are all obstructive lung diseases characterised by airway obstruction.\n\nThis limits the amount of air that is able to enter alveoli because of constriction of the bronchial tree, due to inflammation.\n\nObstructive lung diseases are often identified because of symptoms and diagnosed with pulmonary function tests such as spirometry.\n\nMany obstructive lung diseases are managed by avoiding triggers (such as dust mites or smoking), with symptom control such as bronchodilators, and with suppression of inflammation (such as through corticosteroids) in severe cases.\n\nA common cause of chronic bronchitis, and emphysema, is smoking; and common causes of bronchiectasis include severe infections and cystic fibrosis.\n\nThe definitive cause of asthma is not yet known.The breakdown of alveolar tissue, often as a result of tobacco-smoking leads to emphysema, which can become severe enough to develop into COPD.\n\nElastase breaks down the elastin in the lung's connective tissue that can also result in emphysema.\n\nElastase is inhibited by the acute-phase protein, alpha-1 antitrypsin, and when there is a deficiency in this, emphysema can develop.\n\nWith persistent stress from smoking, the airway basal cells become disarranged and lose their regenerative ability needed to repair the epithelial barrier.\n\nThe disorganised basal cells are seen to be responsible for the major airway changes that are characteristic of COPD, and with continued stress can undergo a malignant transformation.\n\nStudies have shown that the initial development of emphysema is centred on the early changes in the airway epithelium of the small airways.\n\nBasal cells become further deranged in a smoker's transition to clinically defined COPD.\n\n=== Restrictive lung diseases ===\n\nSome types of chronic lung diseases are classified as restrictive lung disease, because of a restriction in the amount of lung tissue involved in respiration.\n\nThese include pulmonary fibrosis which can occur when the lung is inflamed for a long period of time.\n\nFibrosis in the lung replaces functioning lung tissue with fibrous connective tissue.\n\nThis can be due to a large variety of occupational lung diseases such as Coalworker's pneumoconiosis, autoimmune diseases or more rarely to a reaction to medication.\n\nSevere respiratory disorders, where spontaneous breathing is not enough to maintain life, may need the use of mechanical ventilation to ensure an adequate supply of air.\n\n=== Cancers ===\n\nLung cancer can either arise directly from lung tissue or as a result of metastasis from another part of the body.\n\nThere are two main types of primary tumour described as either small-cell or non-small-cell lung carcinomas.\n\nThe major risk factor for cancer is smoking.\n\nOnce a cancer is identified it is staged using scans such as a CT scan and a sample of tissue from a biopsy is taken.\n\nCancers may be treated surgically by removing the tumour, the use of radiotherapy, chemotherapy or a combination, or with the aim of symptom control.\n\nLung cancer screening is being recommended in the United States for high-risk populations.\n\n=== Congenital disorders ===\n\nCongenital disorders include cystic fibrosis, pulmonary hypoplasia (an incomplete development of the lungs)congenital diaphragmatic hernia, and infant respiratory distress syndrome caused by a deficiency in lung surfactant.\n\nAn azygos lobe is a congenital anatomical variation which though usually without effect can cause problems in thoracoscopic procedures.\n\n=== Others ===\n\nA pneumothorax (collapsed lung) is an abnormal collection of air in the pleural space that causes an uncoupling of the lung from the chest wall.\n\nThe lung cannot expand against the air pressure inside the pleural space.\n\nAn easy to understand example is a traumatic pneumothorax, where air enters the pleural space from outside the body, as occurs with puncture to the chest wall.\n\nSimilarly, scuba divers ascending while holding their breath with their lungs fully inflated can cause air sacs (alveoli) to burst and leak high pressure air into the pleural space.\n\n=== Lung examination ===\n\nAs part of a physical examination in response to respiratory symptoms of shortness of breath, and cough, a lung examination may be carried out.\n\nThis exam includes palpation and auscultation.\n\nThe areas of the lungs that can be listened to using a stethoscope are called the lung fields, and these are the posterior, lateral, and anterior lung fields.\n\nThe posterior fields can be listened to from the back and include: the lower lobes (taking up three quarters of the posterior fields); the anterior fields taking up the other quarter; and the lateral fields under the axillae, the left axilla for the lingual, the right axilla for the middle right lobe.\n\nThe anterior fields can also be auscultated from the front.\n\nAbnormal breathing sounds heard during a lung exam can indicate the presence of a lung condition; wheezing for example is commonly associated with asthma and COPD.\n\n=== Lung function testing ===\n\nLung function testing is carried out by evaluating a person's capacity to inhale and exhale in different circumstances.\n\nThe volume of air inhaled and exhaled by a person at rest is the tidal volume (normally 500-750mL); the inspiratory reserve volume and expiratory reserve volume are the additional amounts a person is able to forcibly inhale and exhale respectively.\n\nThe summed total of forced inspiration and expiration is a person's vital capacity.\n\nNot all air is expelled from the lungs even after a forced breath out; the remainder of the air is called the residual volume.\n\nTogether these terms are referred to as lung volumes.Pulmonary plethysmographs are used to measure functional residual capacity.\n\nFunctional residual capacity cannot be measured by tests that rely on breathing out, as a person is only able to breathe a maximum of 80% of their total functional capacity.\n\nThe total lung capacity depends on the person's age, height, weight, and sex, and normally ranges between 4 and 6 litres.\n\nFemales tend to have a 20–25% lower capacity than males.\n\nTall people tend to have a larger total lung capacity than shorter people.\n\nSmokers have a lower capacity than nonsmokers.\n\nThinner persons tend to have a larger capacity.\n\nLung capacity can be increased by physical training as much as 40% but the effect may be modified by exposure to air pollution.Other lung function tests include spirometry, measuring the amount (volume) and flow of air that can be inhaled and exhaled.\n\nThe maximum volume of breath that can be exhaled is called the vital capacity.\n\nIn particular, how much a person is able to exhale in one second (called forced expiratory volume (FEV1)) as a proportion of how much they are able to exhale in total (FEV).\n\nThis ratio, the FEV1/FEV ratio, is important to distinguish whether a lung disease is restrictive or obstructive.\n\nAnother test is that of the lung's diffusing capacity – this is a measure of the transfer of gas from air to the blood in the lung capillaries.\n\n== Other animals ==\n\n=== Birds ===\n\nThe lungs of birds are relatively small, but are connected to 8 or 9 air sacs that extend through much of the body, and are in turn connected to air spaces within the bones.\n\nOn inhalation, air travels through the trachea of a bird into the air sacs.\n\nAir then travels continuously from the air sacs at the back, through the lungs, which are relatively fixed in size, to the air sacs at the front.\n\nFrom here, the air is exhaled.\n\nThese fixed size lungs are called \"circulatory lungs\", as distinct from the \"bellows-type lungs\" found in most other animals.The lungs of birds contain millions of tiny parallel passages called parabronchi.\n\nSmall sacs called atria radiate from the walls of the tiny passages; these, like the alveoli in other lungs, are the site of gas exchange by simple diffusion.\n\nThe blood flow around the parabronchi and their atria forms a cross-current process of gas exchange (see diagram on the right).The air sacs, which hold air, do not contribute much to gas exchange, despite being thin-walled, as they are poorly vascularised.\n\nThe air sacs expand and contract due to changes in the volume in the thorax and abdomen.\n\nThis volume change is caused by the movement of the sternum and ribs and this movement is often synchronised with movement of the flight muscles.Parabronchi in which the air flow is unidirectional are called paleopulmonic parabronchi and are found in all birds.\n\nSome birds, however, have, in addition, a lung structure where the air flow in the parabronchi is bidirectional.\n\nThese are termed neopulmonic parabronchi.\n\n=== Reptiles ===\n\nThe lungs of most reptiles have a single bronchus running down the centre, from which numerous branches reach out to individual pockets throughout the lungs.\n\nThese pockets are similar to alveoli in mammals, but much larger and fewer in number.\n\nThese give the lung a sponge-like texture.\n\nIn tuataras, snakes, and some lizards, the lungs are simpler in structure, similar to that of typical amphibians.Snakes and limbless lizards typically possess only the right lung as a major respiratory organ; the left lung is greatly reduced, or even absent.\n\nAmphisbaenians, however, have the opposite arrangement, with a major left lung, and a reduced or absent right lung.Both crocodilians and monitor lizards have developed lungs similar to those of birds, providing a unidirectional airflow and even possessing air sacs.\n\nThe now extinct pterosaurs have seemingly even further refined this type of lung, extending the airsacs into the wing membranes and, in the case of lonchodectids, tupuxuara, and azhdarchoids, the hindlimbs.Reptilian lungs typically receive air via expansion and contraction of the ribs driven by axial muscles and buccal pumping.\n\nCrocodilians also rely on the hepatic piston method, in which the liver is pulled back by a muscle anchored to the pubic bone (part of the pelvis) called the diaphragmaticus, which in turn creates negative pressure in the crocodile's thoracic cavity, allowing air to be moved into the lungs by Boyle's law.\n\nTurtles, which are unable to move their ribs, instead use their forelimbs and pectoral girdle to force air in and out of the lungs.\n\n=== Amphibians ===\n\nThe lungs of most frogs and other amphibians are simple and balloon-like, with gas exchange limited to the outer surface of the lung.\n\nThis is not very efficient, but amphibians have low metabolic demands and can also quickly dispose of carbon dioxide by diffusion across their skin in water, and supplement their oxygen supply by the same method.\n\nAmphibians employ a positive pressure system to get air to their lungs, forcing air down into the lungs by buccal pumping.\n\nThis is distinct from most higher vertebrates, who use a breathing system driven by negative pressure where the lungs are inflated by expanding the rib cage.\n\nIn buccal pumping, the floor of the mouth is lowered, filling the mouth cavity with air.\n\nThe throat muscles then presses the throat against the underside of the skull, forcing the air into the lungs.Due to the possibility of respiration across the skin combined with small size, all known lungless tetrapods are amphibians.\n\nThe majority of salamander species are lungless salamanders, which respirate through their skin and tissues lining their mouth.\n\nThis necessarily restricts their size: all are small and rather thread-like in appearance, maximising skin surface relative to body volume.\n\nOther known lungless tetrapods are the Bornean flat-headed frog and Atretochoana eiselti, a caecilian.The lungs of amphibians typically have a few narrow internal walls (septa) of soft tissue around the outer walls, increasing the respiratory surface area and giving the lung a honeycomb appearance.\n\nIn some salamanders even these are lacking, and the lung has a smooth wall.\n\nIn caecilians, as in snakes, only the right lung attains any size or development.\n\n=== Lungfish ===\n\nThe lungs of lungfish are similar to those of amphibians, with few, if any, internal septa.\n\nIn the Australian lungfish, there is only a single lung, albeit divided into two lobes.\n\nOther lungfish and Polypterus, however, have two lungs, which are located in the upper part of the body, with the connecting duct curving around and above the esophagus.\n\nThe blood supply also twists around the esophagus, suggesting that the lungs originally evolved in the ventral part of the body, as in other vertebrates.\n\n=== Invertebrates ===\n\nSome invertebrates have lung-like structures that serve a similar respiratory purpose as, but are not evolutionarily related to, vertebrate lungs.\n\nSome arachnids, such as spiders and scorpions, have structures called book lungs used for atmospheric gas exchange.\n\nSome species of spider have four pairs of book lungs but most have two pairs.\n\nScorpions have spiracles on their body for the entrance of air to the book lungs.The coconut crab is terrestrial and uses structures called branchiostegal lungs to breathe air.\n\nThey cannot swim and would drown in water, yet they possess a rudimentary set of gills.\n\nThey can breathe on land and hold their breath underwater.\n\nThe branchiostegal lungs are seen as a developmental adaptive stage from water-living to enable land-living, or from fish to amphibian.Pulmonates are mostly land snails and slugs that have developed a simple lung from the mantle cavity.\n\nAn externally located opening called the pneumostome allows air to be taken into the mantle cavity lung.\n\n== Evolutionary origins ==\n\nThe lungs of today's terrestrial vertebrates and the gas bladders of today's fish are believed to have evolved from simple sacs, as outpocketings of the esophagus, that allowed early fish to gulp air under oxygen-poor conditions.\n\nThese outpocketings first arose in the bony fish.\n\nIn most of the ray-finned fish the sacs evolved into closed off gas bladders, while a number of carp, trout, herring, catfish, and eels have retained the physostome condition with the sac being open to the esophagus.\n\nIn more basal bony fish, such as the gar, bichir, bowfin and the lobe-finned fish, the bladders have evolved to primarily function as lungs.\n\nThe lobe-finned fish gave rise to the land-based tetrapods.\n\nThus, the lungs of vertebrates are homologous to the gas bladders of fish (but not to their gills).\n\n== Further reading ==\n\nhttps://en.wikipedia.org/wiki/Lung","inferior-lobe-of-right-lung":"LUNG\n\nThe lungs are the primary organs of the respiratory system in humans and most other animals including a few fish, and some snails.\n\nIn mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart.\n\nTheir function in the respiratory system is to extract oxygen from the air and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange.\n\nRespiration is driven by different muscular systems in different species.\n\nMammals, reptiles and birds use their different muscles to support and foster breathing.\n\nIn earlier tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians.\n\nIn humans, the main muscle of respiration that drives breathing is the diaphragm.\n\nThe lungs also provide airflow that makes vocal sounds including human speech possible.\nHumans have two lungs, a right lung, and a left lung.\n\nThey are situated within the thoracic cavity of the chest.\n\nThe right lung is bigger than the left, which shares space in the chest with the heart.\n\nThe lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier.\n\nThe lungs are part of the lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles, and which receive air breathed in via the conducting zone.\n\nThe conducting zone ends at the terminal bronchioles.\n\nThese divide into the respiratory bronchioles of the respiratory zone which divide into alveolar ducts that give rise to the alveolar sacs that contain the alveoli, where gas exchange takes place.\n\nAlveoli are also sparsely present on the walls of the respiratory bronchioles and alveolar ducts.\n\nTogether, the lungs contain approximately 2,400 kilometres (1,500 mi) of airways and 300 to 500 million alveoli.\n\nEach lung is enclosed within a pleural sac of two membranes called pleurae; the membranes are separated by a film of pleural fluid, which allows the inner and outer membranes to slide over each other whilst breathing takes place, without much friction.\n\nThe inner pleura also divides each lung into sections called lobes.\n\nThe right lung has three lobes and the left has two.\n\nThe lobes are further divided into bronchopulmonary segments and pulmonary lobules.\n\nThe lungs have a unique blood supply, receiving deoxygenated blood from the heart in the pulmonary circulation for the purposes of receiving oxygen and releasing carbon dioxide, and a separate supply of oxygenated blood to the tissue of the lungs, in the bronchial circulation.\nThe tissue of the lungs can be affected by a number of respiratory diseases, including pneumonia and lung cancer.\n\nChronic obstructive pulmonary disease includes chronic bronchitis and emphysema, and can be related to smoking or exposure to harmful substances.\n\nA number of occupational lung diseases can be caused by substances such as coal dust, asbestos fibres, and crystalline silica dust.\n\nDiseases such as bronchitis can also affect the respiratory tract.\n\nMedical terms related to the lung often begin with pulmo-, from the Latin pulmonarius (of the lungs) as in pulmonology, or with pneumo- (from Greek πνεύμων \"lung\") as in pneumonia.\nIn embryonic development, the lungs begin to develop as an outpouching of the foregut, a tube which goes on to form the upper part of the digestive system.\n\nWhen the lungs are formed the fetus is held in the fluid-filled amniotic sac and so they do not function to breathe.\n\nBlood is also diverted from the lungs through the ductus arteriosus.\n\nAt birth however, air begins to pass through the lungs, and the diversionary duct closes, so that the lungs can begin to respire.\n\nThe lungs only fully develop in early childhood.\n\n== Structure ==\n\n=== Anatomy ===\n\nThe lungs are located in the chest on either side of the heart in the rib cage.\n\nThey are conical in shape with a narrow rounded apex at the top, and a broad concave base that rests on the convex surface of the diaphragm.\n\nThe apex of the lung extends into the root of the neck, reaching shortly above the level of the sternal end of the first rib.\n\nThe lungs stretch from close to the backbone in the rib cage to the front of the chest and downwards from the lower part of the trachea to the diaphragm.\n\nThe left lung shares space with the heart, and has an indentation in its border called the cardiac notch of the left lung to accommodate this.\n\nThe front and outer sides of the lungs face the ribs, which make light indentations on their surfaces.\n\nThe medial surfaces of the lungs face towards the centre of the chest, and lie against the heart, great vessels, and the carina where the trachea divides into the two main bronchi.\n\nThe cardiac impression is an indentation formed on the surfaces of the lungs where they rest against the heart.\nBoth lungs have a central recession called the hilum at the root of the lung, where the blood vessels and airways pass into the lungs.\n\nThere are also bronchopulmonary lymph nodes on the hilum.The lungs are surrounded by the pulmonary pleurae.\n\nThe pleurae are two serous membranes; the outer parietal pleura lines the inner wall of the rib cage and the inner visceral pleura directly lines the surface of the lungs.\n\nBetween the pleurae is a potential space called the pleural cavity containing a thin layer of lubricating pleural fluid.\n\n==== Lobes ====\nEach lung is divided into sections called lobes by the infoldings of the visceral pleura as fissures.\n\nLobes are divided into segments, and segments have further divisions as lobules.\n\nThere are three lobes in the right lung and two lobes in the left lung.\n\n==== Fissures ====\nThe fissures are formed in early prenatal development by invaginations of the visceral pleura that divide the lobar bronchi, and section the lungs into lobes that helps in their expansion.\n\nThe right lung is divided into three lobes by a horizontal fissure, and an oblique fissure.\n\nThe left lung is divided into two lobes by an oblique fissure which is closely aligned with the oblique fissure in the right lung.\n\nIn the right lung the upper horizontal fissure, separates the upper (superior) lobe from the middle lobe.\n\nThe lower, oblique fissure separates the lower lobe from the middle and upper lobes.Variations in the fissures are fairly common being either incompletely formed\nor present as an extra fissure as in the azygos fissure, or absent.\n\nIncomplete fissures are responsible for interlobar collateral ventilation, airflow between lobes which is unwanted in some lung volume reduction procedures.\n\n==== Segments ====\nThe main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of the lung.\n\nThe lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments.\n\nEach bronchopulmonary segment has its own (segmental) bronchus and arterial supply.\n\nSegments for the left and right lung are shown in the table.\n\nThe segmental anatomy is useful clinically for localising disease processes in the lungs.\n\nA segment is a discrete unit that can be surgically removed without seriously affecting surrounding tissue.\n\n=== Right lung ===\n\nThe right lung has both more lobes and segments than the left.\n\nIt is divided into three lobes, an upper, middle, and a lower lobe by two fissures, one oblique and one horizontal.\n\nThe upper, horizontal fissure, separates the upper from the middle lobe.\n\nIt begins in the lower oblique fissure near the posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage; on the mediastinal surface it may be traced back to the hilum.\n\nThe lower, oblique fissure, separates the lower from the middle and upper lobes and is closely aligned with the oblique fissure in the left lung.The mediastinal surface of the right lung is indented by a number of nearby structures.\n\nThe heart sits in an impression called the cardiac impression.\n\nAbove the hilum of the lung is an arched groove for the azygos vein, and above this is a wide groove for the superior vena cava and right brachiocephalic vein; behind this, and close to the top of the lung is a groove for the brachiocephalic artery.\n\nThere is a groove for the esophagus behind the hilum and the pulmonary ligament, and near the lower part of the esophageal groove is a deeper groove for the inferior vena cava before it enters the heart.The weight of the right lung varies between individuals, with a standard reference range in men of 155–720 g (0.342–1.587 lb) and in women of 100–590 g (0.22–1.30 lb).\n\n=== Left lung ===\n\nThe left lung is divided into two lobes, an upper and a lower lobe, by the oblique fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilum.\n\nThe left lung, unlike the right, does not have a middle lobe, though it does have a homologous feature, a projection of the upper lobe termed the lingula.\n\nIts name means \"little tongue\".\n\nThe lingula on the left lung serves as an anatomic parallel to the middle lobe on the right lung, with both areas being predisposed to similar infections and anatomic complications.\n\nThere are two bronchopulmonary segments of the lingula: superior and inferior.The mediastinal surface of the left lung has a large cardiac impression where the heart sits.\n\nThis is deeper and larger than that on the right lung, at which level the heart projects to the left.On the same surface, immediately above the hilum, is a well-marked curved groove for the aortic arch, and a groove below it for the descending aorta.\n\nThe left subclavian artery, a branch off the aortic arch, sits in a groove from the arch to near the apex of the lung.\n\nA shallower groove in front of the artery and near the edge of the lung, lodges the left brachiocephalic vein.\n\nThe esophagus may sit in a wider shallow impression at the base of the lung.The weight of the left lung, by standard reference range, in men is 110–675 g (0.243–1.488 lb) in women 105–515 g (0.231–1.135 lb).\n\n== Microanatomy ==\n\nThe lungs are part of the lower respiratory tract, and accommodate the bronchial airways when they branch from the trachea.\n\nThe bronchial airways terminate in alveoli which make up the functional tissue (parenchyma) of the lung, and veins, arteries, nerves, and lymphatic vessels.\n\nThe trachea and bronchi have plexuses of lymph capillaries in their mucosa and submucosa.\n\nThe smaller bronchi have a single layer of lymph capillaries, and they are absent in the alveoli.\n\nThe lungs are supplied with the largest lymphatic drainage system of any other organ in the body.\n\nEach lung is surrounded by a serous membrane of visceral pleura, which has an underlying layer of loose connective tissue attached to the substance of the lung.\n\n=== Connective tissue ===\n\nThe connective tissue of the lungs is made up of elastic and collagen fibres that are interspersed between the capillaries and the alveolar walls.\n\nElastin is the key protein of the extracellular matrix and is the main component of the elastic fibres.\n\nElastin gives the necessary elasticity and resilience required for the persistent stretching involved in breathing, known as lung compliance.\n\nIt is also responsible for the elastic recoil needed.\n\nElastin is more concentrated in areas of high stress such as the openings of the alveoli, and alveolar junctions.\n\nThe connective tissue links all the alveoli to form the lung parenchyma which has a sponge-like appearance.\n\nThe alveoli have interconnecting air passages in their walls known as the pores of Kohn.\n\n=== Respiratory epithelium ===\n\nAll of the lower respiratory tract including the trachea, bronchi, and bronchioles is lined with respiratory epithelium.\n\nThis is a ciliated epithelium interspersed with goblet cells which produce mucin the main component of mucus, ciliated cells, basal cells, and in the terminal bronchioles–club cells with actions similar to basal cells, and macrophages.\n\nThe epithelial cells, and the submucosal glands throughout the respiratory tract secrete airway surface liquid (ASL), the composition of which is tightly regulated and determines how well mucociliary clearance works.Pulmonary neuroendocrine cells are found throughout the respiratory epithelium including the alveolar epithelium, though they only account for around 0.5 per cent of the total epithelial population.\n\nPNECs are innervated airway epithelial cells that are particularly focused at airway junction points.\n\nThese cells can produce serotonin, dopamine, and norepinephrine, as well as polypeptide products.\n\nCytoplasmic processes from the pulmonary neuroendocrine cells extend into the airway lumen where they may sense the composition of inspired gas.\n\n=== Bronchial airways ===\n\nIn the bronchi there are incomplete tracheal rings of cartilage and smaller plates of cartilage that keep them open.: 472  Bronchioles are too narrow to support cartilage and their walls are of smooth muscle, and this is largely absent in the narrower respiratory bronchioles which are mainly just of epithelium.: 472  The absence of cartilage in the terminal bronchioles gives them an alternative name of membranous bronchioles.\n\n=== Respiratory zone ===\n\nThe conducting zone of the respiratory tract ends at the terminal bronchioles when they branch into the respiratory bronchioles.\n\nThis marks the beginning of the terminal respiratory unit called the acinus which includes the respiratory bronchioles, the alveolar ducts, alveolar sacs, and alveoli.\n\nAn acinus measures up to 10 mm in diameter.\n\nA primary pulmonary lobule is that part of the acinus that includes the alveolar ducts, sacs, and alveoli but does not include the respiratory bronchioles.\n\nThe unit described as the secondary pulmonary lobule is the lobule most referred to as the pulmonary lobule or respiratory lobule.: 489  This lobule is a discrete unit that is the smallest component of the lung that can be seen without aid.\n\nThe secondary pulmonary lobule is likely to be made up of between 30 and 50 primary lobules.\n\nThe lobule is supplied by a terminal bronchiole that branches into respiratory bronchioles.\n\nThe respiratory bronchioles supply the alveoli in each acinus and is accompanied by a pulmonary artery branch.\n\nEach lobule is enclosed by an interlobular septa.\n\nEach acinus is incompletely separated by an interlobular septa.The respiratory bronchiole gives rise to the alveolar ducts that lead to the alveolar sacs, which contain two or more alveoli.\n\nThe walls of the alveoli are extremely thin allowing a fast rate of diffusion.\n\nThe alveoli have interconnecting small air passages in their walls known as the pores of Kohn.\n\n=== Alveoli ===\n\nAlveoli consist of two types of alveolar cell and an alveolar macrophage.\n\nThe two types of cell are known as type I and type II cells (also known as pneumocytes).\n\nTypes I and II make up the walls and alveolar septa.\n\nType I cells provide 95% of the surface area of each alveoli and are flat (\"squamous\"), and Type II cells generally cluster in the corners of the alveoli and have a cuboidal shape.\n\nDespite this, cells occur in a roughly equal ratio of 1:1 or 6:4.Type I are squamous epithelial cells that make up the alveolar wall structure.\n\nThey have extremely thin walls that enable an easy gas exchange.\n\nThese type I cells also make up the alveolar septa which separate each alveolus.\n\nThe septa consist of an epithelial lining and associated basement membranes.\n\nType I cells are not able to divide, and consequently rely on differentiation from Type II cells.Type II are larger and they line the alveoli and produce and secrete epithelial lining fluid, and lung surfactant.\n\nType II cells are able to divide and differentiate to Type I cells.The alveolar macrophages have an important role in the immune system.\n\nThey remove substances which deposit in the alveoli including loose red blood cells that have been forced out from blood vessels.\n\n=== Microbiota ===\n\nThere is a large presence of microorganisms in the lungs known as the lung microbiota that interacts with the airway epithelial cells; an interaction of probable importance in maintaining homeostasis.\n\nThe microbiota is complex and dynamic in healthy people, and altered in diseases such as asthma and COPD.\n\nFor example significant changes can take place in COPD following infection with rhinovirus.\n\nFungal genera that are commonly found as mycobiota in the microbiota include Candida, Malassezia, Saccharomyces, and Aspergillus.\n\n=== Respiratory tract ===\n\nThe lower respiratory tract is part of the respiratory system, and consists of the trachea and the structures below this including the lungs.\n\nThe trachea receives air from the pharynx and travels down to a place where it splits (the carina) into a right and left primary bronchus.\n\nThese supply air to the right and left lungs, splitting progressively into the secondary and tertiary bronchi for the lobes of the lungs, and into smaller and smaller bronchioles until they become the respiratory bronchioles.\n\nThese in turn supply air through alveolar ducts into the alveoli, where the exchange of gases take place.\n\nOxygen breathed in, diffuses through the walls of the alveoli into the enveloping capillaries and into the circulation, and carbon dioxide diffuses from the blood into the lungs to be breathed out.\nEstimates of the total surface area of lungs vary from 50 to 75 square metres (540 to 810 sq ft); although this is often quoted in textbooks and the media being \"the size of a tennis court\", it is actually less than half the size of a singles court.The bronchi in the conducting zone are reinforced with hyaline cartilage in order to hold open the airways.\n\nThe bronchioles have no cartilage and are surrounded instead by smooth muscle.\n\nAir is warmed to 37 °C (99 °F), humidified and cleansed by the conducting zone.\n\nParticles from the air being removed by the cilia on the respiratory epithelium lining the passageways, in a process called mucociliary clearance.\nPulmonary stretch receptors in the smooth muscle of the airways initiate a reflex known as the Hering–Breuer reflex that prevents the lungs from over-inflation, during forceful inspiration.\n\n=== Blood supply ===\n\nThe lungs have a dual blood supply provided by a bronchial and a pulmonary circulation.\n\nThe bronchial circulation supplies oxygenated blood to the airways of the lungs, through the bronchial arteries that leave the aorta.\n\nThere are usually three arteries, two to the left lung and one to the right, and they branch alongside the bronchi and bronchioles.\n\nThe pulmonary circulation carries deoxygenated blood from the heart to the lungs and returns the oxygenated blood to the heart to supply the rest of the body.The blood volume of the lungs is about 450 millilitres on average, about 9% of the total blood volume of the entire circulatory system.\n\nThis quantity can easily fluctuate from between one-half and twice the normal volume.\n\nAlso, in the event of blood loss through hemorrhage, blood from the lungs can partially compensate by automatically transferring to the systemic circulation.\n\n=== Nerve supply ===\n\nThe lungs are supplied by nerves of the autonomic nervous system.\n\nInput from the parasympathetic nervous system occurs via the vagus nerve.\n\nWhen stimulated by acetylcholine, this causes constriction of the smooth muscle lining the bronchus and bronchioles, and increases the secretions from glands.\n\nThe lungs also have a sympathetic tone from norepinephrine acting on the beta 2 adrenoceptors in the respiratory tract, which causes bronchodilation.The action of breathing takes place because of nerve signals sent by the respiratory center in the brainstem, along the phrenic nerve from the cervical plexus to the diaphragm.\n\n=== Variation ===\n\nThe lobes of the lung are subject to anatomical variations.\n\nA horizontal interlobar fissure was found to be incomplete in 25% of right lungs, or even absent in 11% of all cases.\n\nAn accessory fissure was also found in 14% and 22% of left and right lungs, respectively.\n\nAn oblique fissure was found to be incomplete in 21% to 47% of left lungs.\n\nIn some cases a fissure is absent, or extra, resulting in a right lung with only two lobes, or a left lung with three lobes.A variation in the airway branching structure has been found specifically in the central airway\nbranching.\n\nThis variation is associated with the development of COPD in adulthood.\n\n== Development ==\n\nThe development of the human lungs arise from the laryngotracheal groove and develop to maturity over several weeks in the foetus and for several years following birth.The larynx, trachea, bronchi and lungs that make up the respiratory tract, begin to form during the fourth week of embryogenesis from the lung bud which appears ventrally to the caudal portion of the foregut.\n\nThe respiratory tract has a branching structure, and is also known as the respiratory tree.\n\nIn the embryo this structure is developed in the process of branching morphogenesis, and is generated by the repeated splitting of the tip of the branch.\n\nIn the development of the lungs (as in some other organs) the epithelium forms branching tubes.\n\nThe lung has a left-right symmetry and each bud known as a bronchial bud grows out as a tubular epithelium that becomes a bronchus.\n\nEach bronchus branches into bronchioles.\n\nThe branching is a result of the tip of each tube bifurcating.\n\nThe branching process forms the bronchi, bronchioles, and ultimately the alveoli.\n\nThe four genes mostly associated with branching morphogenesis in the lung are the intercellular signalling protein – sonic hedgehog (SHH), fibroblast growth factors FGF10 and FGFR2b, and bone morphogenetic protein BMP4.\n\nFGF10 is seen to have the most prominent role.\n\nFGF10 is a paracrine signalling molecule needed for epithelial branching, and SHH inhibits FGF10.\n\nThe development of the alveoli is influenced by a different mechanism whereby continued bifurcation is stopped and the distal tips become dilated to form the alveoli.\nAt the end of the fourth week the lung bud divides into two, the right and left primary bronchial buds on each side of the trachea.\n\nDuring the fifth week the right bud branches into three secondary bronchial buds and the left branches into two secondary bronchial buds.\n\nThese give rise to the lobes of the lungs, three on the right and two on the left.\n\nOver the following week, the secondary buds branch into tertiary buds, about ten on each side.\n\nFrom the sixth week to the sixteenth week, the major elements of the lungs appear except the alveoli.\n\nFrom week 16 to week 26, the bronchi enlarge and lung tissue becomes highly vascularised.\n\nBronchioles and alveolar ducts also develop.\n\nBy week 26 the terminal bronchioles have formed which branch into two respiratory bronchioles.\n\nDuring the period covering the 26th week until birth the important blood–air barrier is established.\n\nSpecialised type I alveolar cells where gas exchange will take place, together with the type II alveolar cells that secrete pulmonary surfactant, appear.\n\nThe surfactant reduces the surface tension at the air-alveolar surface which allows expansion of the alveolar sacs.\n\nThe alveolar sacs contain the primitive alveoli that form at the end of the alveolar ducts,\nand their appearance around the seventh month marks the point at which limited respiration would be possible, and the premature baby could survive.\n\n=== Vitamin A deficiency ===\n\nThe developing lung is particularly vulnerable to changes in the levels of vitamin A.\n\nVitamin A deficiency has been linked to changes in the epithelial lining of the lung and in the lung parenchyma.\n\nThis can disrupt the normal physiology of the lung and predispose to respiratory diseases.\n\nSevere nutritional deficiency in vitamin A results in a reduction in the formation of the alveolar walls (septa) and to notable changes in the respiratory epithelium; alterations are noted in the extracellular matrix and in the protein content of the basement membrane.\n\nThe extracellular matrix maintains lung elasticity; the basement membrane is associated with alveolar epithelium and is important in the blood-air barrier.\n\nThe deficiency is associated with functional defects and disease states.\n\nVitamin A is crucial in the development of the alveoli which continues for several years after birth.\n\n=== After birth ===\n\nAt birth, the baby's lungs are filled with fluid secreted by the lungs and are not inflated.\n\nAfter birth the infant's central nervous system reacts to the sudden change in temperature and environment.\n\nThis triggers the first breath, within about 10 seconds after delivery.\n\nBefore birth, the lungs are filled with fetal lung fluid. After the first breath, the fluid is quickly absorbed into the body or exhaled.\n\nThe resistance in the lung's blood vessels decreases giving an increased surface area for gas exchange, and the lungs begin to breathe spontaneously.\n\nThis accompanies other changes which result in an increased amount of blood entering the lung tissues.At birth the lungs are very undeveloped with only around one sixth of the alveoli of the adult lung present.\n\nThe alveoli continue to form into early adulthood, and their ability to form when necessary is seen in the regeneration of the lung.\n\nAlveolar septa have a double capillary network instead of the single network of the developed lung.\n\nOnly after the maturation of the capillary network can the lung enter a normal phase of growth.\n\nFollowing the early growth in numbers of alveoli there is another stage of the alveoli being enlarged.\n\n== Function ==\n\n=== Gas exchange ===\n\nThe major function of the lungs is gas exchange between the lungs and the blood.\n\nThe alveolar and pulmonary capillary gases equilibrate across the thin blood–air barrier.\n\nThis thin membrane (about 0.5 –2 μm thick) is folded into about 300 million alveoli, providing an extremely large surface area (estimates varying between 70 and 145 m2) for gas exchange to occur.\n\nThe lungs are not capable of expanding to breathe on their own, and will only do so when there is an increase in the volume of the thoracic cavity.\n\nThis is achieved by the muscles of respiration, through the contraction of the diaphragm, and the intercostal muscles which pull the rib cage upwards as shown in the diagram.\n\nDuring breathing out the muscles relax, returning the lungs to their resting position.\n\nAt this point the lungs contain the functional residual capacity (FRC) of air, which, in the adult human, has a volume of about 2.5–3.0 litres.During heavy breathing as in exertion, a large number of accessory muscles in the neck and abdomen are recruited, that during exhalation pull the ribcage down, decreasing the volume of the thoracic cavity.\n\nThe FRC is now decreased, but since the lungs cannot be emptied completely there is still about a litre of residual air left.\n\nLung function testing is carried out to evaluate lung volumes and capacities.\n\n=== Protection ===\n\nThe lungs possess several characteristics which protect against infection.\n\nThe respiratory tract is lined by respiratory epithelium or respiratory mucosa, with hair-like projections called cilia that beat rhythmically and carry mucus.\n\nThis mucociliary clearance is an important defence system against air-borne infection.\n\nThe dust particles and bacteria in the inhaled air are caught in the mucosal surface of the airways, and are moved up towards the pharynx by the rhythmic upward beating action of the cilia.: 661–730  The lining of the lung also secretes immunoglobulin A which protects against respiratory infections; goblet cells secrete mucus which also contains several antimicrobial compounds such as defensins, antiproteases, and antioxidants.\n\nA rare type of specialised cell called a pulmonary ionocyte that is suggested may regulate mucus viscosity has been described.\n\nIn addition, the lining of the lung also contains macrophages, immune cells which engulf and destroy debris and microbes that enter the lung in a process known as phagocytosis; and dendritic cells which present antigens to activate components of the adaptive immune system such as T cells and B cells.The size of the respiratory tract and the flow of air also protect the lungs from larger particles.\n\nSmaller particles deposit in the mouth and behind the mouth in the oropharynx, and larger particles are trapped in nasal hair after inhalation.\n\n=== Other ===\n\nIn addition to their function in respiration, the lungs have a number of other functions.\n\nThey are involved in maintaining homeostasis, helping in the regulation of blood pressure as part of the renin–angiotensin system.\n\nThe inner lining of the blood vessels secretes angiotensin-converting enzyme (ACE) an enzyme that catalyses the conversion of angiotensin I to angiotensin II.\n\nThe lungs are involved in the blood's acid–base homeostasis by expelling carbon dioxide when breathing.The lungs also serve a protective role.\n\nSeveral blood-borne substances, such as a few types of prostaglandins, leukotrienes, serotonin and bradykinin, are excreted through the lungs.\n\nDrugs and other substances can be absorbed, modified or excreted in the lungs.\n\nThe lungs filter out small blood clots from veins and prevent them from entering arteries and causing strokes.The lungs also play a pivotal role in speech by providing air and airflow for the creation of vocal sounds, and other paralanguage communications such as sighs and gasps.\nResearch suggests a role of the lungs in the production of blood platelets.\n\n== Gene and protein expression ==\n\nAbout 20,000 protein coding genes are expressed in human cells and almost 75% of these genes are expressed in the normal lung.\n\nA little less than 200 of these genes are more specifically expressed in the lung with less than 20 genes being highly lung specific.\n\nThe highest expression of lung specific proteins are different surfactant proteins, such as SFTPA1, SFTPB and SFTPC, and napsin, expressed in type II pneumocytes.\n\nOther proteins with elevated expression in the lung are the dynein protein DNAH5 in ciliated cells, and the secreted SCGB1A1 protein in mucus-secreting goblet cells of the airway mucosa.\n\n== Clinical significance ==\n\nLungs can be affected by a number of diseases and disorders.\n\nPulmonology is the medical speciality that deals with respiratory diseases involving the lungs and respiratory system.\n\nCardiothoracic surgery deals with surgery of the lungs including lung volume reduction surgery, lobectomy, pneumectomy and lung transplantation.\n\n=== Inflammation and infection ===\n\nInflammatory conditions of the lung tissue are pneumonia, of the respiratory tract are bronchitis and bronchiolitis, and of the pleurae surrounding the lungs pleurisy.\n\nInflammation is usually caused by infections due to bacteria or viruses.\n\nWhen the lung tissue is inflamed due to other causes it is called pneumonitis.\n\nOne major cause of bacterial pneumonia is tuberculosis.\n\nChronic infections often occur in those with immunodeficiency and can include a fungal infection by Aspergillus fumigatus that can lead to an aspergilloma forming in the lung.Alcohol affects the lungs and can cause inflammatory alcoholic lung disease.\n\nAcute exposure to alcohol stimulates the beating of cilia in the respiratory epithelium.\n\nHowever, chronic exposure has the effect of desensitising the ciliary response which reduces mucociliary clearance (MCC).\n\nMCC is an innate defense system protecting against pollutants and pathogens, and when this is disrupted the numbers of alveolar macrophages are decreased.\n\nA subsequent inflammatory response is the release of cytokines.\n\nAnother consequence is the susceptibility to infection.\n\n=== Blood-supply changes ===\n\nA pulmonary embolism is a blood clot that becomes lodged in the pulmonary arteries.\n\nThe majority of emboli arise because of deep vein thrombosis in the legs.\n\nPulmonary emboli may be investigated using a ventilation/perfusion scan, a CT scan of the arteries of the lung, or blood tests such as the D-dimer.\n\nPulmonary hypertension describes an increased pressure at the beginning of the pulmonary artery that has a large number of differing causes.\n\nOther rarer conditions may also affect the blood supply of the lung, such as granulomatosis with polyangiitis, which causes inflammation of the small blood vessels of the lungs and kidneys.A lung contusion is a bruise caused by chest trauma.\n\nIt results in hemorrhage of the alveoli causing a build-up of fluid which can impair breathing, and this can be either mild or severe.\nThe function of the lungs can also be affected by compression from fluid in the pleural cavity pleural effusion, or other substances such as air (pneumothorax), blood (hemothorax), or rarer causes.\n\nThese may be investigated using a chest X-ray or CT scan, and may require the insertion of a surgical drain until the underlying cause is identified and treated.\n\n=== Obstructive lung diseases ===\n\nAsthma, chronic bronchitis, bronchiectasis and chronic obstructive pulmonary disease (COPD) are all obstructive lung diseases characterised by airway obstruction.\n\nThis limits the amount of air that is able to enter alveoli because of constriction of the bronchial tree, due to inflammation.\n\nObstructive lung diseases are often identified because of symptoms and diagnosed with pulmonary function tests such as spirometry.\n\nMany obstructive lung diseases are managed by avoiding triggers (such as dust mites or smoking), with symptom control such as bronchodilators, and with suppression of inflammation (such as through corticosteroids) in severe cases.\n\nA common cause of chronic bronchitis, and emphysema, is smoking; and common causes of bronchiectasis include severe infections and cystic fibrosis.\n\nThe definitive cause of asthma is not yet known.The breakdown of alveolar tissue, often as a result of tobacco-smoking leads to emphysema, which can become severe enough to develop into COPD.\n\nElastase breaks down the elastin in the lung's connective tissue that can also result in emphysema.\n\nElastase is inhibited by the acute-phase protein, alpha-1 antitrypsin, and when there is a deficiency in this, emphysema can develop.\n\nWith persistent stress from smoking, the airway basal cells become disarranged and lose their regenerative ability needed to repair the epithelial barrier.\n\nThe disorganised basal cells are seen to be responsible for the major airway changes that are characteristic of COPD, and with continued stress can undergo a malignant transformation.\n\nStudies have shown that the initial development of emphysema is centred on the early changes in the airway epithelium of the small airways.\n\nBasal cells become further deranged in a smoker's transition to clinically defined COPD.\n\n=== Restrictive lung diseases ===\n\nSome types of chronic lung diseases are classified as restrictive lung disease, because of a restriction in the amount of lung tissue involved in respiration.\n\nThese include pulmonary fibrosis which can occur when the lung is inflamed for a long period of time.\n\nFibrosis in the lung replaces functioning lung tissue with fibrous connective tissue.\n\nThis can be due to a large variety of occupational lung diseases such as Coalworker's pneumoconiosis, autoimmune diseases or more rarely to a reaction to medication.\n\nSevere respiratory disorders, where spontaneous breathing is not enough to maintain life, may need the use of mechanical ventilation to ensure an adequate supply of air.\n\n=== Cancers ===\n\nLung cancer can either arise directly from lung tissue or as a result of metastasis from another part of the body.\n\nThere are two main types of primary tumour described as either small-cell or non-small-cell lung carcinomas.\n\nThe major risk factor for cancer is smoking.\n\nOnce a cancer is identified it is staged using scans such as a CT scan and a sample of tissue from a biopsy is taken.\n\nCancers may be treated surgically by removing the tumour, the use of radiotherapy, chemotherapy or a combination, or with the aim of symptom control.\n\nLung cancer screening is being recommended in the United States for high-risk populations.\n\n=== Congenital disorders ===\n\nCongenital disorders include cystic fibrosis, pulmonary hypoplasia (an incomplete development of the lungs)congenital diaphragmatic hernia, and infant respiratory distress syndrome caused by a deficiency in lung surfactant.\n\nAn azygos lobe is a congenital anatomical variation which though usually without effect can cause problems in thoracoscopic procedures.\n\n=== Others ===\n\nA pneumothorax (collapsed lung) is an abnormal collection of air in the pleural space that causes an uncoupling of the lung from the chest wall.\n\nThe lung cannot expand against the air pressure inside the pleural space.\n\nAn easy to understand example is a traumatic pneumothorax, where air enters the pleural space from outside the body, as occurs with puncture to the chest wall.\n\nSimilarly, scuba divers ascending while holding their breath with their lungs fully inflated can cause air sacs (alveoli) to burst and leak high pressure air into the pleural space.\n\n=== Lung examination ===\n\nAs part of a physical examination in response to respiratory symptoms of shortness of breath, and cough, a lung examination may be carried out.\n\nThis exam includes palpation and auscultation.\n\nThe areas of the lungs that can be listened to using a stethoscope are called the lung fields, and these are the posterior, lateral, and anterior lung fields.\n\nThe posterior fields can be listened to from the back and include: the lower lobes (taking up three quarters of the posterior fields); the anterior fields taking up the other quarter; and the lateral fields under the axillae, the left axilla for the lingual, the right axilla for the middle right lobe.\n\nThe anterior fields can also be auscultated from the front.\n\nAbnormal breathing sounds heard during a lung exam can indicate the presence of a lung condition; wheezing for example is commonly associated with asthma and COPD.\n\n=== Lung function testing ===\n\nLung function testing is carried out by evaluating a person's capacity to inhale and exhale in different circumstances.\n\nThe volume of air inhaled and exhaled by a person at rest is the tidal volume (normally 500-750mL); the inspiratory reserve volume and expiratory reserve volume are the additional amounts a person is able to forcibly inhale and exhale respectively.\n\nThe summed total of forced inspiration and expiration is a person's vital capacity.\n\nNot all air is expelled from the lungs even after a forced breath out; the remainder of the air is called the residual volume.\n\nTogether these terms are referred to as lung volumes.Pulmonary plethysmographs are used to measure functional residual capacity.\n\nFunctional residual capacity cannot be measured by tests that rely on breathing out, as a person is only able to breathe a maximum of 80% of their total functional capacity.\n\nThe total lung capacity depends on the person's age, height, weight, and sex, and normally ranges between 4 and 6 litres.\n\nFemales tend to have a 20–25% lower capacity than males.\n\nTall people tend to have a larger total lung capacity than shorter people.\n\nSmokers have a lower capacity than nonsmokers.\n\nThinner persons tend to have a larger capacity.\n\nLung capacity can be increased by physical training as much as 40% but the effect may be modified by exposure to air pollution.Other lung function tests include spirometry, measuring the amount (volume) and flow of air that can be inhaled and exhaled.\n\nThe maximum volume of breath that can be exhaled is called the vital capacity.\n\nIn particular, how much a person is able to exhale in one second (called forced expiratory volume (FEV1)) as a proportion of how much they are able to exhale in total (FEV).\n\nThis ratio, the FEV1/FEV ratio, is important to distinguish whether a lung disease is restrictive or obstructive.\n\nAnother test is that of the lung's diffusing capacity – this is a measure of the transfer of gas from air to the blood in the lung capillaries.\n\n== Other animals ==\n\n=== Birds ===\n\nThe lungs of birds are relatively small, but are connected to 8 or 9 air sacs that extend through much of the body, and are in turn connected to air spaces within the bones.\n\nOn inhalation, air travels through the trachea of a bird into the air sacs.\n\nAir then travels continuously from the air sacs at the back, through the lungs, which are relatively fixed in size, to the air sacs at the front.\n\nFrom here, the air is exhaled.\n\nThese fixed size lungs are called \"circulatory lungs\", as distinct from the \"bellows-type lungs\" found in most other animals.The lungs of birds contain millions of tiny parallel passages called parabronchi.\n\nSmall sacs called atria radiate from the walls of the tiny passages; these, like the alveoli in other lungs, are the site of gas exchange by simple diffusion.\n\nThe blood flow around the parabronchi and their atria forms a cross-current process of gas exchange (see diagram on the right).The air sacs, which hold air, do not contribute much to gas exchange, despite being thin-walled, as they are poorly vascularised.\n\nThe air sacs expand and contract due to changes in the volume in the thorax and abdomen.\n\nThis volume change is caused by the movement of the sternum and ribs and this movement is often synchronised with movement of the flight muscles.Parabronchi in which the air flow is unidirectional are called paleopulmonic parabronchi and are found in all birds.\n\nSome birds, however, have, in addition, a lung structure where the air flow in the parabronchi is bidirectional.\n\nThese are termed neopulmonic parabronchi.\n\n=== Reptiles ===\n\nThe lungs of most reptiles have a single bronchus running down the centre, from which numerous branches reach out to individual pockets throughout the lungs.\n\nThese pockets are similar to alveoli in mammals, but much larger and fewer in number.\n\nThese give the lung a sponge-like texture.\n\nIn tuataras, snakes, and some lizards, the lungs are simpler in structure, similar to that of typical amphibians.Snakes and limbless lizards typically possess only the right lung as a major respiratory organ; the left lung is greatly reduced, or even absent.\n\nAmphisbaenians, however, have the opposite arrangement, with a major left lung, and a reduced or absent right lung.Both crocodilians and monitor lizards have developed lungs similar to those of birds, providing a unidirectional airflow and even possessing air sacs.\n\nThe now extinct pterosaurs have seemingly even further refined this type of lung, extending the airsacs into the wing membranes and, in the case of lonchodectids, tupuxuara, and azhdarchoids, the hindlimbs.Reptilian lungs typically receive air via expansion and contraction of the ribs driven by axial muscles and buccal pumping.\n\nCrocodilians also rely on the hepatic piston method, in which the liver is pulled back by a muscle anchored to the pubic bone (part of the pelvis) called the diaphragmaticus, which in turn creates negative pressure in the crocodile's thoracic cavity, allowing air to be moved into the lungs by Boyle's law.\n\nTurtles, which are unable to move their ribs, instead use their forelimbs and pectoral girdle to force air in and out of the lungs.\n\n=== Amphibians ===\n\nThe lungs of most frogs and other amphibians are simple and balloon-like, with gas exchange limited to the outer surface of the lung.\n\nThis is not very efficient, but amphibians have low metabolic demands and can also quickly dispose of carbon dioxide by diffusion across their skin in water, and supplement their oxygen supply by the same method.\n\nAmphibians employ a positive pressure system to get air to their lungs, forcing air down into the lungs by buccal pumping.\n\nThis is distinct from most higher vertebrates, who use a breathing system driven by negative pressure where the lungs are inflated by expanding the rib cage.\n\nIn buccal pumping, the floor of the mouth is lowered, filling the mouth cavity with air.\n\nThe throat muscles then presses the throat against the underside of the skull, forcing the air into the lungs.Due to the possibility of respiration across the skin combined with small size, all known lungless tetrapods are amphibians.\n\nThe majority of salamander species are lungless salamanders, which respirate through their skin and tissues lining their mouth.\n\nThis necessarily restricts their size: all are small and rather thread-like in appearance, maximising skin surface relative to body volume.\n\nOther known lungless tetrapods are the Bornean flat-headed frog and Atretochoana eiselti, a caecilian.The lungs of amphibians typically have a few narrow internal walls (septa) of soft tissue around the outer walls, increasing the respiratory surface area and giving the lung a honeycomb appearance.\n\nIn some salamanders even these are lacking, and the lung has a smooth wall.\n\nIn caecilians, as in snakes, only the right lung attains any size or development.\n\n=== Lungfish ===\n\nThe lungs of lungfish are similar to those of amphibians, with few, if any, internal septa.\n\nIn the Australian lungfish, there is only a single lung, albeit divided into two lobes.\n\nOther lungfish and Polypterus, however, have two lungs, which are located in the upper part of the body, with the connecting duct curving around and above the esophagus.\n\nThe blood supply also twists around the esophagus, suggesting that the lungs originally evolved in the ventral part of the body, as in other vertebrates.\n\n=== Invertebrates ===\n\nSome invertebrates have lung-like structures that serve a similar respiratory purpose as, but are not evolutionarily related to, vertebrate lungs.\n\nSome arachnids, such as spiders and scorpions, have structures called book lungs used for atmospheric gas exchange.\n\nSome species of spider have four pairs of book lungs but most have two pairs.\n\nScorpions have spiracles on their body for the entrance of air to the book lungs.The coconut crab is terrestrial and uses structures called branchiostegal lungs to breathe air.\n\nThey cannot swim and would drown in water, yet they possess a rudimentary set of gills.\n\nThey can breathe on land and hold their breath underwater.\n\nThe branchiostegal lungs are seen as a developmental adaptive stage from water-living to enable land-living, or from fish to amphibian.Pulmonates are mostly land snails and slugs that have developed a simple lung from the mantle cavity.\n\nAn externally located opening called the pneumostome allows air to be taken into the mantle cavity lung.\n\n== Evolutionary origins ==\n\nThe lungs of today's terrestrial vertebrates and the gas bladders of today's fish are believed to have evolved from simple sacs, as outpocketings of the esophagus, that allowed early fish to gulp air under oxygen-poor conditions.\n\nThese outpocketings first arose in the bony fish.\n\nIn most of the ray-finned fish the sacs evolved into closed off gas bladders, while a number of carp, trout, herring, catfish, and eels have retained the physostome condition with the sac being open to the esophagus.\n\nIn more basal bony fish, such as the gar, bichir, bowfin and the lobe-finned fish, the bladders have evolved to primarily function as lungs.\n\nThe lobe-finned fish gave rise to the land-based tetrapods.\n\nThus, the lungs of vertebrates are homologous to the gas bladders of fish (but not to their gills).\n\n== Further reading ==\n\nhttps://en.wikipedia.org/wiki/Lung","superior-lobe-of-left-lung":"LUNG\n\nThe lungs are the primary organs of the respiratory system in humans and most other animals including a few fish, and some snails.\n\nIn mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart.\n\nTheir function in the respiratory system is to extract oxygen from the air and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange.\n\nRespiration is driven by different muscular systems in different species.\n\nMammals, reptiles and birds use their different muscles to support and foster breathing.\n\nIn earlier tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians.\n\nIn humans, the main muscle of respiration that drives breathing is the diaphragm.\n\nThe lungs also provide airflow that makes vocal sounds including human speech possible.\nHumans have two lungs, a right lung, and a left lung.\n\nThey are situated within the thoracic cavity of the chest.\n\nThe right lung is bigger than the left, which shares space in the chest with the heart.\n\nThe lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier.\n\nThe lungs are part of the lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles, and which receive air breathed in via the conducting zone.\n\nThe conducting zone ends at the terminal bronchioles.\n\nThese divide into the respiratory bronchioles of the respiratory zone which divide into alveolar ducts that give rise to the alveolar sacs that contain the alveoli, where gas exchange takes place.\n\nAlveoli are also sparsely present on the walls of the respiratory bronchioles and alveolar ducts.\n\nTogether, the lungs contain approximately 2,400 kilometres (1,500 mi) of airways and 300 to 500 million alveoli.\n\nEach lung is enclosed within a pleural sac of two membranes called pleurae; the membranes are separated by a film of pleural fluid, which allows the inner and outer membranes to slide over each other whilst breathing takes place, without much friction.\n\nThe inner pleura also divides each lung into sections called lobes.\n\nThe right lung has three lobes and the left has two.\n\nThe lobes are further divided into bronchopulmonary segments and pulmonary lobules.\n\nThe lungs have a unique blood supply, receiving deoxygenated blood from the heart in the pulmonary circulation for the purposes of receiving oxygen and releasing carbon dioxide, and a separate supply of oxygenated blood to the tissue of the lungs, in the bronchial circulation.\nThe tissue of the lungs can be affected by a number of respiratory diseases, including pneumonia and lung cancer.\n\nChronic obstructive pulmonary disease includes chronic bronchitis and emphysema, and can be related to smoking or exposure to harmful substances.\n\nA number of occupational lung diseases can be caused by substances such as coal dust, asbestos fibres, and crystalline silica dust.\n\nDiseases such as bronchitis can also affect the respiratory tract.\n\nMedical terms related to the lung often begin with pulmo-, from the Latin pulmonarius (of the lungs) as in pulmonology, or with pneumo- (from Greek πνεύμων \"lung\") as in pneumonia.\nIn embryonic development, the lungs begin to develop as an outpouching of the foregut, a tube which goes on to form the upper part of the digestive system.\n\nWhen the lungs are formed the fetus is held in the fluid-filled amniotic sac and so they do not function to breathe.\n\nBlood is also diverted from the lungs through the ductus arteriosus.\n\nAt birth however, air begins to pass through the lungs, and the diversionary duct closes, so that the lungs can begin to respire.\n\nThe lungs only fully develop in early childhood.\n\n== Structure ==\n\n=== Anatomy ===\n\nThe lungs are located in the chest on either side of the heart in the rib cage.\n\nThey are conical in shape with a narrow rounded apex at the top, and a broad concave base that rests on the convex surface of the diaphragm.\n\nThe apex of the lung extends into the root of the neck, reaching shortly above the level of the sternal end of the first rib.\n\nThe lungs stretch from close to the backbone in the rib cage to the front of the chest and downwards from the lower part of the trachea to the diaphragm.\n\nThe left lung shares space with the heart, and has an indentation in its border called the cardiac notch of the left lung to accommodate this.\n\nThe front and outer sides of the lungs face the ribs, which make light indentations on their surfaces.\n\nThe medial surfaces of the lungs face towards the centre of the chest, and lie against the heart, great vessels, and the carina where the trachea divides into the two main bronchi.\n\nThe cardiac impression is an indentation formed on the surfaces of the lungs where they rest against the heart.\nBoth lungs have a central recession called the hilum at the root of the lung, where the blood vessels and airways pass into the lungs.\n\nThere are also bronchopulmonary lymph nodes on the hilum.The lungs are surrounded by the pulmonary pleurae.\n\nThe pleurae are two serous membranes; the outer parietal pleura lines the inner wall of the rib cage and the inner visceral pleura directly lines the surface of the lungs.\n\nBetween the pleurae is a potential space called the pleural cavity containing a thin layer of lubricating pleural fluid.\n\n==== Lobes ====\nEach lung is divided into sections called lobes by the infoldings of the visceral pleura as fissures.\n\nLobes are divided into segments, and segments have further divisions as lobules.\n\nThere are three lobes in the right lung and two lobes in the left lung.\n\n==== Fissures ====\nThe fissures are formed in early prenatal development by invaginations of the visceral pleura that divide the lobar bronchi, and section the lungs into lobes that helps in their expansion.\n\nThe right lung is divided into three lobes by a horizontal fissure, and an oblique fissure.\n\nThe left lung is divided into two lobes by an oblique fissure which is closely aligned with the oblique fissure in the right lung.\n\nIn the right lung the upper horizontal fissure, separates the upper (superior) lobe from the middle lobe.\n\nThe lower, oblique fissure separates the lower lobe from the middle and upper lobes.Variations in the fissures are fairly common being either incompletely formed\nor present as an extra fissure as in the azygos fissure, or absent.\n\nIncomplete fissures are responsible for interlobar collateral ventilation, airflow between lobes which is unwanted in some lung volume reduction procedures.\n\n==== Segments ====\nThe main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of the lung.\n\nThe lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments.\n\nEach bronchopulmonary segment has its own (segmental) bronchus and arterial supply.\n\nSegments for the left and right lung are shown in the table.\n\nThe segmental anatomy is useful clinically for localising disease processes in the lungs.\n\nA segment is a discrete unit that can be surgically removed without seriously affecting surrounding tissue.\n\n=== Right lung ===\n\nThe right lung has both more lobes and segments than the left.\n\nIt is divided into three lobes, an upper, middle, and a lower lobe by two fissures, one oblique and one horizontal.\n\nThe upper, horizontal fissure, separates the upper from the middle lobe.\n\nIt begins in the lower oblique fissure near the posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage; on the mediastinal surface it may be traced back to the hilum.\n\nThe lower, oblique fissure, separates the lower from the middle and upper lobes and is closely aligned with the oblique fissure in the left lung.The mediastinal surface of the right lung is indented by a number of nearby structures.\n\nThe heart sits in an impression called the cardiac impression.\n\nAbove the hilum of the lung is an arched groove for the azygos vein, and above this is a wide groove for the superior vena cava and right brachiocephalic vein; behind this, and close to the top of the lung is a groove for the brachiocephalic artery.\n\nThere is a groove for the esophagus behind the hilum and the pulmonary ligament, and near the lower part of the esophageal groove is a deeper groove for the inferior vena cava before it enters the heart.The weight of the right lung varies between individuals, with a standard reference range in men of 155–720 g (0.342–1.587 lb) and in women of 100–590 g (0.22–1.30 lb).\n\n=== Left lung ===\n\nThe left lung is divided into two lobes, an upper and a lower lobe, by the oblique fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilum.\n\nThe left lung, unlike the right, does not have a middle lobe, though it does have a homologous feature, a projection of the upper lobe termed the lingula.\n\nIts name means \"little tongue\".\n\nThe lingula on the left lung serves as an anatomic parallel to the middle lobe on the right lung, with both areas being predisposed to similar infections and anatomic complications.\n\nThere are two bronchopulmonary segments of the lingula: superior and inferior.The mediastinal surface of the left lung has a large cardiac impression where the heart sits.\n\nThis is deeper and larger than that on the right lung, at which level the heart projects to the left.On the same surface, immediately above the hilum, is a well-marked curved groove for the aortic arch, and a groove below it for the descending aorta.\n\nThe left subclavian artery, a branch off the aortic arch, sits in a groove from the arch to near the apex of the lung.\n\nA shallower groove in front of the artery and near the edge of the lung, lodges the left brachiocephalic vein.\n\nThe esophagus may sit in a wider shallow impression at the base of the lung.The weight of the left lung, by standard reference range, in men is 110–675 g (0.243–1.488 lb) in women 105–515 g (0.231–1.135 lb).\n\n== Microanatomy ==\n\nThe lungs are part of the lower respiratory tract, and accommodate the bronchial airways when they branch from the trachea.\n\nThe bronchial airways terminate in alveoli which make up the functional tissue (parenchyma) of the lung, and veins, arteries, nerves, and lymphatic vessels.\n\nThe trachea and bronchi have plexuses of lymph capillaries in their mucosa and submucosa.\n\nThe smaller bronchi have a single layer of lymph capillaries, and they are absent in the alveoli.\n\nThe lungs are supplied with the largest lymphatic drainage system of any other organ in the body.\n\nEach lung is surrounded by a serous membrane of visceral pleura, which has an underlying layer of loose connective tissue attached to the substance of the lung.\n\n=== Connective tissue ===\n\nThe connective tissue of the lungs is made up of elastic and collagen fibres that are interspersed between the capillaries and the alveolar walls.\n\nElastin is the key protein of the extracellular matrix and is the main component of the elastic fibres.\n\nElastin gives the necessary elasticity and resilience required for the persistent stretching involved in breathing, known as lung compliance.\n\nIt is also responsible for the elastic recoil needed.\n\nElastin is more concentrated in areas of high stress such as the openings of the alveoli, and alveolar junctions.\n\nThe connective tissue links all the alveoli to form the lung parenchyma which has a sponge-like appearance.\n\nThe alveoli have interconnecting air passages in their walls known as the pores of Kohn.\n\n=== Respiratory epithelium ===\n\nAll of the lower respiratory tract including the trachea, bronchi, and bronchioles is lined with respiratory epithelium.\n\nThis is a ciliated epithelium interspersed with goblet cells which produce mucin the main component of mucus, ciliated cells, basal cells, and in the terminal bronchioles–club cells with actions similar to basal cells, and macrophages.\n\nThe epithelial cells, and the submucosal glands throughout the respiratory tract secrete airway surface liquid (ASL), the composition of which is tightly regulated and determines how well mucociliary clearance works.Pulmonary neuroendocrine cells are found throughout the respiratory epithelium including the alveolar epithelium, though they only account for around 0.5 per cent of the total epithelial population.\n\nPNECs are innervated airway epithelial cells that are particularly focused at airway junction points.\n\nThese cells can produce serotonin, dopamine, and norepinephrine, as well as polypeptide products.\n\nCytoplasmic processes from the pulmonary neuroendocrine cells extend into the airway lumen where they may sense the composition of inspired gas.\n\n=== Bronchial airways ===\n\nIn the bronchi there are incomplete tracheal rings of cartilage and smaller plates of cartilage that keep them open.: 472  Bronchioles are too narrow to support cartilage and their walls are of smooth muscle, and this is largely absent in the narrower respiratory bronchioles which are mainly just of epithelium.: 472  The absence of cartilage in the terminal bronchioles gives them an alternative name of membranous bronchioles.\n\n=== Respiratory zone ===\n\nThe conducting zone of the respiratory tract ends at the terminal bronchioles when they branch into the respiratory bronchioles.\n\nThis marks the beginning of the terminal respiratory unit called the acinus which includes the respiratory bronchioles, the alveolar ducts, alveolar sacs, and alveoli.\n\nAn acinus measures up to 10 mm in diameter.\n\nA primary pulmonary lobule is that part of the acinus that includes the alveolar ducts, sacs, and alveoli but does not include the respiratory bronchioles.\n\nThe unit described as the secondary pulmonary lobule is the lobule most referred to as the pulmonary lobule or respiratory lobule.: 489  This lobule is a discrete unit that is the smallest component of the lung that can be seen without aid.\n\nThe secondary pulmonary lobule is likely to be made up of between 30 and 50 primary lobules.\n\nThe lobule is supplied by a terminal bronchiole that branches into respiratory bronchioles.\n\nThe respiratory bronchioles supply the alveoli in each acinus and is accompanied by a pulmonary artery branch.\n\nEach lobule is enclosed by an interlobular septa.\n\nEach acinus is incompletely separated by an interlobular septa.The respiratory bronchiole gives rise to the alveolar ducts that lead to the alveolar sacs, which contain two or more alveoli.\n\nThe walls of the alveoli are extremely thin allowing a fast rate of diffusion.\n\nThe alveoli have interconnecting small air passages in their walls known as the pores of Kohn.\n\n=== Alveoli ===\n\nAlveoli consist of two types of alveolar cell and an alveolar macrophage.\n\nThe two types of cell are known as type I and type II cells (also known as pneumocytes).\n\nTypes I and II make up the walls and alveolar septa.\n\nType I cells provide 95% of the surface area of each alveoli and are flat (\"squamous\"), and Type II cells generally cluster in the corners of the alveoli and have a cuboidal shape.\n\nDespite this, cells occur in a roughly equal ratio of 1:1 or 6:4.Type I are squamous epithelial cells that make up the alveolar wall structure.\n\nThey have extremely thin walls that enable an easy gas exchange.\n\nThese type I cells also make up the alveolar septa which separate each alveolus.\n\nThe septa consist of an epithelial lining and associated basement membranes.\n\nType I cells are not able to divide, and consequently rely on differentiation from Type II cells.Type II are larger and they line the alveoli and produce and secrete epithelial lining fluid, and lung surfactant.\n\nType II cells are able to divide and differentiate to Type I cells.The alveolar macrophages have an important role in the immune system.\n\nThey remove substances which deposit in the alveoli including loose red blood cells that have been forced out from blood vessels.\n\n=== Microbiota ===\n\nThere is a large presence of microorganisms in the lungs known as the lung microbiota that interacts with the airway epithelial cells; an interaction of probable importance in maintaining homeostasis.\n\nThe microbiota is complex and dynamic in healthy people, and altered in diseases such as asthma and COPD.\n\nFor example significant changes can take place in COPD following infection with rhinovirus.\n\nFungal genera that are commonly found as mycobiota in the microbiota include Candida, Malassezia, Saccharomyces, and Aspergillus.\n\n=== Respiratory tract ===\n\nThe lower respiratory tract is part of the respiratory system, and consists of the trachea and the structures below this including the lungs.\n\nThe trachea receives air from the pharynx and travels down to a place where it splits (the carina) into a right and left primary bronchus.\n\nThese supply air to the right and left lungs, splitting progressively into the secondary and tertiary bronchi for the lobes of the lungs, and into smaller and smaller bronchioles until they become the respiratory bronchioles.\n\nThese in turn supply air through alveolar ducts into the alveoli, where the exchange of gases take place.\n\nOxygen breathed in, diffuses through the walls of the alveoli into the enveloping capillaries and into the circulation, and carbon dioxide diffuses from the blood into the lungs to be breathed out.\nEstimates of the total surface area of lungs vary from 50 to 75 square metres (540 to 810 sq ft); although this is often quoted in textbooks and the media being \"the size of a tennis court\", it is actually less than half the size of a singles court.The bronchi in the conducting zone are reinforced with hyaline cartilage in order to hold open the airways.\n\nThe bronchioles have no cartilage and are surrounded instead by smooth muscle.\n\nAir is warmed to 37 °C (99 °F), humidified and cleansed by the conducting zone.\n\nParticles from the air being removed by the cilia on the respiratory epithelium lining the passageways, in a process called mucociliary clearance.\nPulmonary stretch receptors in the smooth muscle of the airways initiate a reflex known as the Hering–Breuer reflex that prevents the lungs from over-inflation, during forceful inspiration.\n\n=== Blood supply ===\n\nThe lungs have a dual blood supply provided by a bronchial and a pulmonary circulation.\n\nThe bronchial circulation supplies oxygenated blood to the airways of the lungs, through the bronchial arteries that leave the aorta.\n\nThere are usually three arteries, two to the left lung and one to the right, and they branch alongside the bronchi and bronchioles.\n\nThe pulmonary circulation carries deoxygenated blood from the heart to the lungs and returns the oxygenated blood to the heart to supply the rest of the body.The blood volume of the lungs is about 450 millilitres on average, about 9% of the total blood volume of the entire circulatory system.\n\nThis quantity can easily fluctuate from between one-half and twice the normal volume.\n\nAlso, in the event of blood loss through hemorrhage, blood from the lungs can partially compensate by automatically transferring to the systemic circulation.\n\n=== Nerve supply ===\n\nThe lungs are supplied by nerves of the autonomic nervous system.\n\nInput from the parasympathetic nervous system occurs via the vagus nerve.\n\nWhen stimulated by acetylcholine, this causes constriction of the smooth muscle lining the bronchus and bronchioles, and increases the secretions from glands.\n\nThe lungs also have a sympathetic tone from norepinephrine acting on the beta 2 adrenoceptors in the respiratory tract, which causes bronchodilation.The action of breathing takes place because of nerve signals sent by the respiratory center in the brainstem, along the phrenic nerve from the cervical plexus to the diaphragm.\n\n=== Variation ===\n\nThe lobes of the lung are subject to anatomical variations.\n\nA horizontal interlobar fissure was found to be incomplete in 25% of right lungs, or even absent in 11% of all cases.\n\nAn accessory fissure was also found in 14% and 22% of left and right lungs, respectively.\n\nAn oblique fissure was found to be incomplete in 21% to 47% of left lungs.\n\nIn some cases a fissure is absent, or extra, resulting in a right lung with only two lobes, or a left lung with three lobes.A variation in the airway branching structure has been found specifically in the central airway\nbranching.\n\nThis variation is associated with the development of COPD in adulthood.\n\n== Development ==\n\nThe development of the human lungs arise from the laryngotracheal groove and develop to maturity over several weeks in the foetus and for several years following birth.The larynx, trachea, bronchi and lungs that make up the respiratory tract, begin to form during the fourth week of embryogenesis from the lung bud which appears ventrally to the caudal portion of the foregut.\n\nThe respiratory tract has a branching structure, and is also known as the respiratory tree.\n\nIn the embryo this structure is developed in the process of branching morphogenesis, and is generated by the repeated splitting of the tip of the branch.\n\nIn the development of the lungs (as in some other organs) the epithelium forms branching tubes.\n\nThe lung has a left-right symmetry and each bud known as a bronchial bud grows out as a tubular epithelium that becomes a bronchus.\n\nEach bronchus branches into bronchioles.\n\nThe branching is a result of the tip of each tube bifurcating.\n\nThe branching process forms the bronchi, bronchioles, and ultimately the alveoli.\n\nThe four genes mostly associated with branching morphogenesis in the lung are the intercellular signalling protein – sonic hedgehog (SHH), fibroblast growth factors FGF10 and FGFR2b, and bone morphogenetic protein BMP4.\n\nFGF10 is seen to have the most prominent role.\n\nFGF10 is a paracrine signalling molecule needed for epithelial branching, and SHH inhibits FGF10.\n\nThe development of the alveoli is influenced by a different mechanism whereby continued bifurcation is stopped and the distal tips become dilated to form the alveoli.\nAt the end of the fourth week the lung bud divides into two, the right and left primary bronchial buds on each side of the trachea.\n\nDuring the fifth week the right bud branches into three secondary bronchial buds and the left branches into two secondary bronchial buds.\n\nThese give rise to the lobes of the lungs, three on the right and two on the left.\n\nOver the following week, the secondary buds branch into tertiary buds, about ten on each side.\n\nFrom the sixth week to the sixteenth week, the major elements of the lungs appear except the alveoli.\n\nFrom week 16 to week 26, the bronchi enlarge and lung tissue becomes highly vascularised.\n\nBronchioles and alveolar ducts also develop.\n\nBy week 26 the terminal bronchioles have formed which branch into two respiratory bronchioles.\n\nDuring the period covering the 26th week until birth the important blood–air barrier is established.\n\nSpecialised type I alveolar cells where gas exchange will take place, together with the type II alveolar cells that secrete pulmonary surfactant, appear.\n\nThe surfactant reduces the surface tension at the air-alveolar surface which allows expansion of the alveolar sacs.\n\nThe alveolar sacs contain the primitive alveoli that form at the end of the alveolar ducts,\nand their appearance around the seventh month marks the point at which limited respiration would be possible, and the premature baby could survive.\n\n=== Vitamin A deficiency ===\n\nThe developing lung is particularly vulnerable to changes in the levels of vitamin A.\n\nVitamin A deficiency has been linked to changes in the epithelial lining of the lung and in the lung parenchyma.\n\nThis can disrupt the normal physiology of the lung and predispose to respiratory diseases.\n\nSevere nutritional deficiency in vitamin A results in a reduction in the formation of the alveolar walls (septa) and to notable changes in the respiratory epithelium; alterations are noted in the extracellular matrix and in the protein content of the basement membrane.\n\nThe extracellular matrix maintains lung elasticity; the basement membrane is associated with alveolar epithelium and is important in the blood-air barrier.\n\nThe deficiency is associated with functional defects and disease states.\n\nVitamin A is crucial in the development of the alveoli which continues for several years after birth.\n\n=== After birth ===\n\nAt birth, the baby's lungs are filled with fluid secreted by the lungs and are not inflated.\n\nAfter birth the infant's central nervous system reacts to the sudden change in temperature and environment.\n\nThis triggers the first breath, within about 10 seconds after delivery.\n\nBefore birth, the lungs are filled with fetal lung fluid. After the first breath, the fluid is quickly absorbed into the body or exhaled.\n\nThe resistance in the lung's blood vessels decreases giving an increased surface area for gas exchange, and the lungs begin to breathe spontaneously.\n\nThis accompanies other changes which result in an increased amount of blood entering the lung tissues.At birth the lungs are very undeveloped with only around one sixth of the alveoli of the adult lung present.\n\nThe alveoli continue to form into early adulthood, and their ability to form when necessary is seen in the regeneration of the lung.\n\nAlveolar septa have a double capillary network instead of the single network of the developed lung.\n\nOnly after the maturation of the capillary network can the lung enter a normal phase of growth.\n\nFollowing the early growth in numbers of alveoli there is another stage of the alveoli being enlarged.\n\n== Function ==\n\n=== Gas exchange ===\n\nThe major function of the lungs is gas exchange between the lungs and the blood.\n\nThe alveolar and pulmonary capillary gases equilibrate across the thin blood–air barrier.\n\nThis thin membrane (about 0.5 –2 μm thick) is folded into about 300 million alveoli, providing an extremely large surface area (estimates varying between 70 and 145 m2) for gas exchange to occur.\n\nThe lungs are not capable of expanding to breathe on their own, and will only do so when there is an increase in the volume of the thoracic cavity.\n\nThis is achieved by the muscles of respiration, through the contraction of the diaphragm, and the intercostal muscles which pull the rib cage upwards as shown in the diagram.\n\nDuring breathing out the muscles relax, returning the lungs to their resting position.\n\nAt this point the lungs contain the functional residual capacity (FRC) of air, which, in the adult human, has a volume of about 2.5–3.0 litres.During heavy breathing as in exertion, a large number of accessory muscles in the neck and abdomen are recruited, that during exhalation pull the ribcage down, decreasing the volume of the thoracic cavity.\n\nThe FRC is now decreased, but since the lungs cannot be emptied completely there is still about a litre of residual air left.\n\nLung function testing is carried out to evaluate lung volumes and capacities.\n\n=== Protection ===\n\nThe lungs possess several characteristics which protect against infection.\n\nThe respiratory tract is lined by respiratory epithelium or respiratory mucosa, with hair-like projections called cilia that beat rhythmically and carry mucus.\n\nThis mucociliary clearance is an important defence system against air-borne infection.\n\nThe dust particles and bacteria in the inhaled air are caught in the mucosal surface of the airways, and are moved up towards the pharynx by the rhythmic upward beating action of the cilia.: 661–730  The lining of the lung also secretes immunoglobulin A which protects against respiratory infections; goblet cells secrete mucus which also contains several antimicrobial compounds such as defensins, antiproteases, and antioxidants.\n\nA rare type of specialised cell called a pulmonary ionocyte that is suggested may regulate mucus viscosity has been described.\n\nIn addition, the lining of the lung also contains macrophages, immune cells which engulf and destroy debris and microbes that enter the lung in a process known as phagocytosis; and dendritic cells which present antigens to activate components of the adaptive immune system such as T cells and B cells.The size of the respiratory tract and the flow of air also protect the lungs from larger particles.\n\nSmaller particles deposit in the mouth and behind the mouth in the oropharynx, and larger particles are trapped in nasal hair after inhalation.\n\n=== Other ===\n\nIn addition to their function in respiration, the lungs have a number of other functions.\n\nThey are involved in maintaining homeostasis, helping in the regulation of blood pressure as part of the renin–angiotensin system.\n\nThe inner lining of the blood vessels secretes angiotensin-converting enzyme (ACE) an enzyme that catalyses the conversion of angiotensin I to angiotensin II.\n\nThe lungs are involved in the blood's acid–base homeostasis by expelling carbon dioxide when breathing.The lungs also serve a protective role.\n\nSeveral blood-borne substances, such as a few types of prostaglandins, leukotrienes, serotonin and bradykinin, are excreted through the lungs.\n\nDrugs and other substances can be absorbed, modified or excreted in the lungs.\n\nThe lungs filter out small blood clots from veins and prevent them from entering arteries and causing strokes.The lungs also play a pivotal role in speech by providing air and airflow for the creation of vocal sounds, and other paralanguage communications such as sighs and gasps.\nResearch suggests a role of the lungs in the production of blood platelets.\n\n== Gene and protein expression ==\n\nAbout 20,000 protein coding genes are expressed in human cells and almost 75% of these genes are expressed in the normal lung.\n\nA little less than 200 of these genes are more specifically expressed in the lung with less than 20 genes being highly lung specific.\n\nThe highest expression of lung specific proteins are different surfactant proteins, such as SFTPA1, SFTPB and SFTPC, and napsin, expressed in type II pneumocytes.\n\nOther proteins with elevated expression in the lung are the dynein protein DNAH5 in ciliated cells, and the secreted SCGB1A1 protein in mucus-secreting goblet cells of the airway mucosa.\n\n== Clinical significance ==\n\nLungs can be affected by a number of diseases and disorders.\n\nPulmonology is the medical speciality that deals with respiratory diseases involving the lungs and respiratory system.\n\nCardiothoracic surgery deals with surgery of the lungs including lung volume reduction surgery, lobectomy, pneumectomy and lung transplantation.\n\n=== Inflammation and infection ===\n\nInflammatory conditions of the lung tissue are pneumonia, of the respiratory tract are bronchitis and bronchiolitis, and of the pleurae surrounding the lungs pleurisy.\n\nInflammation is usually caused by infections due to bacteria or viruses.\n\nWhen the lung tissue is inflamed due to other causes it is called pneumonitis.\n\nOne major cause of bacterial pneumonia is tuberculosis.\n\nChronic infections often occur in those with immunodeficiency and can include a fungal infection by Aspergillus fumigatus that can lead to an aspergilloma forming in the lung.Alcohol affects the lungs and can cause inflammatory alcoholic lung disease.\n\nAcute exposure to alcohol stimulates the beating of cilia in the respiratory epithelium.\n\nHowever, chronic exposure has the effect of desensitising the ciliary response which reduces mucociliary clearance (MCC).\n\nMCC is an innate defense system protecting against pollutants and pathogens, and when this is disrupted the numbers of alveolar macrophages are decreased.\n\nA subsequent inflammatory response is the release of cytokines.\n\nAnother consequence is the susceptibility to infection.\n\n=== Blood-supply changes ===\n\nA pulmonary embolism is a blood clot that becomes lodged in the pulmonary arteries.\n\nThe majority of emboli arise because of deep vein thrombosis in the legs.\n\nPulmonary emboli may be investigated using a ventilation/perfusion scan, a CT scan of the arteries of the lung, or blood tests such as the D-dimer.\n\nPulmonary hypertension describes an increased pressure at the beginning of the pulmonary artery that has a large number of differing causes.\n\nOther rarer conditions may also affect the blood supply of the lung, such as granulomatosis with polyangiitis, which causes inflammation of the small blood vessels of the lungs and kidneys.A lung contusion is a bruise caused by chest trauma.\n\nIt results in hemorrhage of the alveoli causing a build-up of fluid which can impair breathing, and this can be either mild or severe.\nThe function of the lungs can also be affected by compression from fluid in the pleural cavity pleural effusion, or other substances such as air (pneumothorax), blood (hemothorax), or rarer causes.\n\nThese may be investigated using a chest X-ray or CT scan, and may require the insertion of a surgical drain until the underlying cause is identified and treated.\n\n=== Obstructive lung diseases ===\n\nAsthma, chronic bronchitis, bronchiectasis and chronic obstructive pulmonary disease (COPD) are all obstructive lung diseases characterised by airway obstruction.\n\nThis limits the amount of air that is able to enter alveoli because of constriction of the bronchial tree, due to inflammation.\n\nObstructive lung diseases are often identified because of symptoms and diagnosed with pulmonary function tests such as spirometry.\n\nMany obstructive lung diseases are managed by avoiding triggers (such as dust mites or smoking), with symptom control such as bronchodilators, and with suppression of inflammation (such as through corticosteroids) in severe cases.\n\nA common cause of chronic bronchitis, and emphysema, is smoking; and common causes of bronchiectasis include severe infections and cystic fibrosis.\n\nThe definitive cause of asthma is not yet known.The breakdown of alveolar tissue, often as a result of tobacco-smoking leads to emphysema, which can become severe enough to develop into COPD.\n\nElastase breaks down the elastin in the lung's connective tissue that can also result in emphysema.\n\nElastase is inhibited by the acute-phase protein, alpha-1 antitrypsin, and when there is a deficiency in this, emphysema can develop.\n\nWith persistent stress from smoking, the airway basal cells become disarranged and lose their regenerative ability needed to repair the epithelial barrier.\n\nThe disorganised basal cells are seen to be responsible for the major airway changes that are characteristic of COPD, and with continued stress can undergo a malignant transformation.\n\nStudies have shown that the initial development of emphysema is centred on the early changes in the airway epithelium of the small airways.\n\nBasal cells become further deranged in a smoker's transition to clinically defined COPD.\n\n=== Restrictive lung diseases ===\n\nSome types of chronic lung diseases are classified as restrictive lung disease, because of a restriction in the amount of lung tissue involved in respiration.\n\nThese include pulmonary fibrosis which can occur when the lung is inflamed for a long period of time.\n\nFibrosis in the lung replaces functioning lung tissue with fibrous connective tissue.\n\nThis can be due to a large variety of occupational lung diseases such as Coalworker's pneumoconiosis, autoimmune diseases or more rarely to a reaction to medication.\n\nSevere respiratory disorders, where spontaneous breathing is not enough to maintain life, may need the use of mechanical ventilation to ensure an adequate supply of air.\n\n=== Cancers ===\n\nLung cancer can either arise directly from lung tissue or as a result of metastasis from another part of the body.\n\nThere are two main types of primary tumour described as either small-cell or non-small-cell lung carcinomas.\n\nThe major risk factor for cancer is smoking.\n\nOnce a cancer is identified it is staged using scans such as a CT scan and a sample of tissue from a biopsy is taken.\n\nCancers may be treated surgically by removing the tumour, the use of radiotherapy, chemotherapy or a combination, or with the aim of symptom control.\n\nLung cancer screening is being recommended in the United States for high-risk populations.\n\n=== Congenital disorders ===\n\nCongenital disorders include cystic fibrosis, pulmonary hypoplasia (an incomplete development of the lungs)congenital diaphragmatic hernia, and infant respiratory distress syndrome caused by a deficiency in lung surfactant.\n\nAn azygos lobe is a congenital anatomical variation which though usually without effect can cause problems in thoracoscopic procedures.\n\n=== Others ===\n\nA pneumothorax (collapsed lung) is an abnormal collection of air in the pleural space that causes an uncoupling of the lung from the chest wall.\n\nThe lung cannot expand against the air pressure inside the pleural space.\n\nAn easy to understand example is a traumatic pneumothorax, where air enters the pleural space from outside the body, as occurs with puncture to the chest wall.\n\nSimilarly, scuba divers ascending while holding their breath with their lungs fully inflated can cause air sacs (alveoli) to burst and leak high pressure air into the pleural space.\n\n=== Lung examination ===\n\nAs part of a physical examination in response to respiratory symptoms of shortness of breath, and cough, a lung examination may be carried out.\n\nThis exam includes palpation and auscultation.\n\nThe areas of the lungs that can be listened to using a stethoscope are called the lung fields, and these are the posterior, lateral, and anterior lung fields.\n\nThe posterior fields can be listened to from the back and include: the lower lobes (taking up three quarters of the posterior fields); the anterior fields taking up the other quarter; and the lateral fields under the axillae, the left axilla for the lingual, the right axilla for the middle right lobe.\n\nThe anterior fields can also be auscultated from the front.\n\nAbnormal breathing sounds heard during a lung exam can indicate the presence of a lung condition; wheezing for example is commonly associated with asthma and COPD.\n\n=== Lung function testing ===\n\nLung function testing is carried out by evaluating a person's capacity to inhale and exhale in different circumstances.\n\nThe volume of air inhaled and exhaled by a person at rest is the tidal volume (normally 500-750mL); the inspiratory reserve volume and expiratory reserve volume are the additional amounts a person is able to forcibly inhale and exhale respectively.\n\nThe summed total of forced inspiration and expiration is a person's vital capacity.\n\nNot all air is expelled from the lungs even after a forced breath out; the remainder of the air is called the residual volume.\n\nTogether these terms are referred to as lung volumes.Pulmonary plethysmographs are used to measure functional residual capacity.\n\nFunctional residual capacity cannot be measured by tests that rely on breathing out, as a person is only able to breathe a maximum of 80% of their total functional capacity.\n\nThe total lung capacity depends on the person's age, height, weight, and sex, and normally ranges between 4 and 6 litres.\n\nFemales tend to have a 20–25% lower capacity than males.\n\nTall people tend to have a larger total lung capacity than shorter people.\n\nSmokers have a lower capacity than nonsmokers.\n\nThinner persons tend to have a larger capacity.\n\nLung capacity can be increased by physical training as much as 40% but the effect may be modified by exposure to air pollution.Other lung function tests include spirometry, measuring the amount (volume) and flow of air that can be inhaled and exhaled.\n\nThe maximum volume of breath that can be exhaled is called the vital capacity.\n\nIn particular, how much a person is able to exhale in one second (called forced expiratory volume (FEV1)) as a proportion of how much they are able to exhale in total (FEV).\n\nThis ratio, the FEV1/FEV ratio, is important to distinguish whether a lung disease is restrictive or obstructive.\n\nAnother test is that of the lung's diffusing capacity – this is a measure of the transfer of gas from air to the blood in the lung capillaries.\n\n== Other animals ==\n\n=== Birds ===\n\nThe lungs of birds are relatively small, but are connected to 8 or 9 air sacs that extend through much of the body, and are in turn connected to air spaces within the bones.\n\nOn inhalation, air travels through the trachea of a bird into the air sacs.\n\nAir then travels continuously from the air sacs at the back, through the lungs, which are relatively fixed in size, to the air sacs at the front.\n\nFrom here, the air is exhaled.\n\nThese fixed size lungs are called \"circulatory lungs\", as distinct from the \"bellows-type lungs\" found in most other animals.The lungs of birds contain millions of tiny parallel passages called parabronchi.\n\nSmall sacs called atria radiate from the walls of the tiny passages; these, like the alveoli in other lungs, are the site of gas exchange by simple diffusion.\n\nThe blood flow around the parabronchi and their atria forms a cross-current process of gas exchange (see diagram on the right).The air sacs, which hold air, do not contribute much to gas exchange, despite being thin-walled, as they are poorly vascularised.\n\nThe air sacs expand and contract due to changes in the volume in the thorax and abdomen.\n\nThis volume change is caused by the movement of the sternum and ribs and this movement is often synchronised with movement of the flight muscles.Parabronchi in which the air flow is unidirectional are called paleopulmonic parabronchi and are found in all birds.\n\nSome birds, however, have, in addition, a lung structure where the air flow in the parabronchi is bidirectional.\n\nThese are termed neopulmonic parabronchi.\n\n=== Reptiles ===\n\nThe lungs of most reptiles have a single bronchus running down the centre, from which numerous branches reach out to individual pockets throughout the lungs.\n\nThese pockets are similar to alveoli in mammals, but much larger and fewer in number.\n\nThese give the lung a sponge-like texture.\n\nIn tuataras, snakes, and some lizards, the lungs are simpler in structure, similar to that of typical amphibians.Snakes and limbless lizards typically possess only the right lung as a major respiratory organ; the left lung is greatly reduced, or even absent.\n\nAmphisbaenians, however, have the opposite arrangement, with a major left lung, and a reduced or absent right lung.Both crocodilians and monitor lizards have developed lungs similar to those of birds, providing a unidirectional airflow and even possessing air sacs.\n\nThe now extinct pterosaurs have seemingly even further refined this type of lung, extending the airsacs into the wing membranes and, in the case of lonchodectids, tupuxuara, and azhdarchoids, the hindlimbs.Reptilian lungs typically receive air via expansion and contraction of the ribs driven by axial muscles and buccal pumping.\n\nCrocodilians also rely on the hepatic piston method, in which the liver is pulled back by a muscle anchored to the pubic bone (part of the pelvis) called the diaphragmaticus, which in turn creates negative pressure in the crocodile's thoracic cavity, allowing air to be moved into the lungs by Boyle's law.\n\nTurtles, which are unable to move their ribs, instead use their forelimbs and pectoral girdle to force air in and out of the lungs.\n\n=== Amphibians ===\n\nThe lungs of most frogs and other amphibians are simple and balloon-like, with gas exchange limited to the outer surface of the lung.\n\nThis is not very efficient, but amphibians have low metabolic demands and can also quickly dispose of carbon dioxide by diffusion across their skin in water, and supplement their oxygen supply by the same method.\n\nAmphibians employ a positive pressure system to get air to their lungs, forcing air down into the lungs by buccal pumping.\n\nThis is distinct from most higher vertebrates, who use a breathing system driven by negative pressure where the lungs are inflated by expanding the rib cage.\n\nIn buccal pumping, the floor of the mouth is lowered, filling the mouth cavity with air.\n\nThe throat muscles then presses the throat against the underside of the skull, forcing the air into the lungs.Due to the possibility of respiration across the skin combined with small size, all known lungless tetrapods are amphibians.\n\nThe majority of salamander species are lungless salamanders, which respirate through their skin and tissues lining their mouth.\n\nThis necessarily restricts their size: all are small and rather thread-like in appearance, maximising skin surface relative to body volume.\n\nOther known lungless tetrapods are the Bornean flat-headed frog and Atretochoana eiselti, a caecilian.The lungs of amphibians typically have a few narrow internal walls (septa) of soft tissue around the outer walls, increasing the respiratory surface area and giving the lung a honeycomb appearance.\n\nIn some salamanders even these are lacking, and the lung has a smooth wall.\n\nIn caecilians, as in snakes, only the right lung attains any size or development.\n\n=== Lungfish ===\n\nThe lungs of lungfish are similar to those of amphibians, with few, if any, internal septa.\n\nIn the Australian lungfish, there is only a single lung, albeit divided into two lobes.\n\nOther lungfish and Polypterus, however, have two lungs, which are located in the upper part of the body, with the connecting duct curving around and above the esophagus.\n\nThe blood supply also twists around the esophagus, suggesting that the lungs originally evolved in the ventral part of the body, as in other vertebrates.\n\n=== Invertebrates ===\n\nSome invertebrates have lung-like structures that serve a similar respiratory purpose as, but are not evolutionarily related to, vertebrate lungs.\n\nSome arachnids, such as spiders and scorpions, have structures called book lungs used for atmospheric gas exchange.\n\nSome species of spider have four pairs of book lungs but most have two pairs.\n\nScorpions have spiracles on their body for the entrance of air to the book lungs.The coconut crab is terrestrial and uses structures called branchiostegal lungs to breathe air.\n\nThey cannot swim and would drown in water, yet they possess a rudimentary set of gills.\n\nThey can breathe on land and hold their breath underwater.\n\nThe branchiostegal lungs are seen as a developmental adaptive stage from water-living to enable land-living, or from fish to amphibian.Pulmonates are mostly land snails and slugs that have developed a simple lung from the mantle cavity.\n\nAn externally located opening called the pneumostome allows air to be taken into the mantle cavity lung.\n\n== Evolutionary origins ==\n\nThe lungs of today's terrestrial vertebrates and the gas bladders of today's fish are believed to have evolved from simple sacs, as outpocketings of the esophagus, that allowed early fish to gulp air under oxygen-poor conditions.\n\nThese outpocketings first arose in the bony fish.\n\nIn most of the ray-finned fish the sacs evolved into closed off gas bladders, while a number of carp, trout, herring, catfish, and eels have retained the physostome condition with the sac being open to the esophagus.\n\nIn more basal bony fish, such as the gar, bichir, bowfin and the lobe-finned fish, the bladders have evolved to primarily function as lungs.\n\nThe lobe-finned fish gave rise to the land-based tetrapods.\n\nThus, the lungs of vertebrates are homologous to the gas bladders of fish (but not to their gills).\n\nhttps://en.wikipedia.org/wiki/Lung","inferior-lobe-of-left-lung":"LUNG\n\nThe lungs are the primary organs of the respiratory system in humans and most other animals including a few fish, and some snails.\n\nIn mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart.\n\nTheir function in the respiratory system is to extract oxygen from the air and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange.\n\nRespiration is driven by different muscular systems in different species.\n\nMammals, reptiles and birds use their different muscles to support and foster breathing.\n\nIn earlier tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians.\n\nIn humans, the main muscle of respiration that drives breathing is the diaphragm.\n\nThe lungs also provide airflow that makes vocal sounds including human speech possible.\nHumans have two lungs, a right lung, and a left lung.\n\nThey are situated within the thoracic cavity of the chest.\n\nThe right lung is bigger than the left, which shares space in the chest with the heart.\n\nThe lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier.\n\nThe lungs are part of the lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles, and which receive air breathed in via the conducting zone.\n\nThe conducting zone ends at the terminal bronchioles.\n\nThese divide into the respiratory bronchioles of the respiratory zone which divide into alveolar ducts that give rise to the alveolar sacs that contain the alveoli, where gas exchange takes place.\n\nAlveoli are also sparsely present on the walls of the respiratory bronchioles and alveolar ducts.\n\nTogether, the lungs contain approximately 2,400 kilometres (1,500 mi) of airways and 300 to 500 million alveoli.\n\nEach lung is enclosed within a pleural sac of two membranes called pleurae; the membranes are separated by a film of pleural fluid, which allows the inner and outer membranes to slide over each other whilst breathing takes place, without much friction.\n\nThe inner pleura also divides each lung into sections called lobes.\n\nThe right lung has three lobes and the left has two.\n\nThe lobes are further divided into bronchopulmonary segments and pulmonary lobules.\n\nThe lungs have a unique blood supply, receiving deoxygenated blood from the heart in the pulmonary circulation for the purposes of receiving oxygen and releasing carbon dioxide, and a separate supply of oxygenated blood to the tissue of the lungs, in the bronchial circulation.\nThe tissue of the lungs can be affected by a number of respiratory diseases, including pneumonia and lung cancer.\n\nChronic obstructive pulmonary disease includes chronic bronchitis and emphysema, and can be related to smoking or exposure to harmful substances.\n\nA number of occupational lung diseases can be caused by substances such as coal dust, asbestos fibres, and crystalline silica dust.\n\nDiseases such as bronchitis can also affect the respiratory tract.\n\nMedical terms related to the lung often begin with pulmo-, from the Latin pulmonarius (of the lungs) as in pulmonology, or with pneumo- (from Greek πνεύμων \"lung\") as in pneumonia.\nIn embryonic development, the lungs begin to develop as an outpouching of the foregut, a tube which goes on to form the upper part of the digestive system.\n\nWhen the lungs are formed the fetus is held in the fluid-filled amniotic sac and so they do not function to breathe.\n\nBlood is also diverted from the lungs through the ductus arteriosus.\n\nAt birth however, air begins to pass through the lungs, and the diversionary duct closes, so that the lungs can begin to respire.\n\nThe lungs only fully develop in early childhood.\n\n== Structure ==\n\n=== Anatomy ===\n\nThe lungs are located in the chest on either side of the heart in the rib cage.\n\nThey are conical in shape with a narrow rounded apex at the top, and a broad concave base that rests on the convex surface of the diaphragm.\n\nThe apex of the lung extends into the root of the neck, reaching shortly above the level of the sternal end of the first rib.\n\nThe lungs stretch from close to the backbone in the rib cage to the front of the chest and downwards from the lower part of the trachea to the diaphragm.\n\nThe left lung shares space with the heart, and has an indentation in its border called the cardiac notch of the left lung to accommodate this.\n\nThe front and outer sides of the lungs face the ribs, which make light indentations on their surfaces.\n\nThe medial surfaces of the lungs face towards the centre of the chest, and lie against the heart, great vessels, and the carina where the trachea divides into the two main bronchi.\n\nThe cardiac impression is an indentation formed on the surfaces of the lungs where they rest against the heart.\nBoth lungs have a central recession called the hilum at the root of the lung, where the blood vessels and airways pass into the lungs.\n\nThere are also bronchopulmonary lymph nodes on the hilum.The lungs are surrounded by the pulmonary pleurae.\n\nThe pleurae are two serous membranes; the outer parietal pleura lines the inner wall of the rib cage and the inner visceral pleura directly lines the surface of the lungs.\n\nBetween the pleurae is a potential space called the pleural cavity containing a thin layer of lubricating pleural fluid.\n\n==== Lobes ====\nEach lung is divided into sections called lobes by the infoldings of the visceral pleura as fissures.\n\nLobes are divided into segments, and segments have further divisions as lobules.\n\nThere are three lobes in the right lung and two lobes in the left lung.\n\n==== Fissures ====\nThe fissures are formed in early prenatal development by invaginations of the visceral pleura that divide the lobar bronchi, and section the lungs into lobes that helps in their expansion.\n\nThe right lung is divided into three lobes by a horizontal fissure, and an oblique fissure.\n\nThe left lung is divided into two lobes by an oblique fissure which is closely aligned with the oblique fissure in the right lung.\n\nIn the right lung the upper horizontal fissure, separates the upper (superior) lobe from the middle lobe.\n\nThe lower, oblique fissure separates the lower lobe from the middle and upper lobes.Variations in the fissures are fairly common being either incompletely formed\nor present as an extra fissure as in the azygos fissure, or absent.\n\nIncomplete fissures are responsible for interlobar collateral ventilation, airflow between lobes which is unwanted in some lung volume reduction procedures.\n\n==== Segments ====\nThe main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of the lung.\n\nThe lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments.\n\nEach bronchopulmonary segment has its own (segmental) bronchus and arterial supply.\n\nSegments for the left and right lung are shown in the table.\n\nThe segmental anatomy is useful clinically for localising disease processes in the lungs.\n\nA segment is a discrete unit that can be surgically removed without seriously affecting surrounding tissue.\n\n=== Right lung ===\n\nThe right lung has both more lobes and segments than the left.\n\nIt is divided into three lobes, an upper, middle, and a lower lobe by two fissures, one oblique and one horizontal.\n\nThe upper, horizontal fissure, separates the upper from the middle lobe.\n\nIt begins in the lower oblique fissure near the posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage; on the mediastinal surface it may be traced back to the hilum.\n\nThe lower, oblique fissure, separates the lower from the middle and upper lobes and is closely aligned with the oblique fissure in the left lung.The mediastinal surface of the right lung is indented by a number of nearby structures.\n\nThe heart sits in an impression called the cardiac impression.\n\nAbove the hilum of the lung is an arched groove for the azygos vein, and above this is a wide groove for the superior vena cava and right brachiocephalic vein; behind this, and close to the top of the lung is a groove for the brachiocephalic artery.\n\nThere is a groove for the esophagus behind the hilum and the pulmonary ligament, and near the lower part of the esophageal groove is a deeper groove for the inferior vena cava before it enters the heart.The weight of the right lung varies between individuals, with a standard reference range in men of 155–720 g (0.342–1.587 lb) and in women of 100–590 g (0.22–1.30 lb).\n\n=== Left lung ===\n\nThe left lung is divided into two lobes, an upper and a lower lobe, by the oblique fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilum.\n\nThe left lung, unlike the right, does not have a middle lobe, though it does have a homologous feature, a projection of the upper lobe termed the lingula.\n\nIts name means \"little tongue\".\n\nThe lingula on the left lung serves as an anatomic parallel to the middle lobe on the right lung, with both areas being predisposed to similar infections and anatomic complications.\n\nThere are two bronchopulmonary segments of the lingula: superior and inferior.The mediastinal surface of the left lung has a large cardiac impression where the heart sits.\n\nThis is deeper and larger than that on the right lung, at which level the heart projects to the left.On the same surface, immediately above the hilum, is a well-marked curved groove for the aortic arch, and a groove below it for the descending aorta.\n\nThe left subclavian artery, a branch off the aortic arch, sits in a groove from the arch to near the apex of the lung.\n\nA shallower groove in front of the artery and near the edge of the lung, lodges the left brachiocephalic vein.\n\nThe esophagus may sit in a wider shallow impression at the base of the lung.The weight of the left lung, by standard reference range, in men is 110–675 g (0.243–1.488 lb) in women 105–515 g (0.231–1.135 lb).\n\n== Microanatomy ==\n\nThe lungs are part of the lower respiratory tract, and accommodate the bronchial airways when they branch from the trachea.\n\nThe bronchial airways terminate in alveoli which make up the functional tissue (parenchyma) of the lung, and veins, arteries, nerves, and lymphatic vessels.\n\nThe trachea and bronchi have plexuses of lymph capillaries in their mucosa and submucosa.\n\nThe smaller bronchi have a single layer of lymph capillaries, and they are absent in the alveoli.\n\nThe lungs are supplied with the largest lymphatic drainage system of any other organ in the body.\n\nEach lung is surrounded by a serous membrane of visceral pleura, which has an underlying layer of loose connective tissue attached to the substance of the lung.\n\n=== Connective tissue ===\n\nThe connective tissue of the lungs is made up of elastic and collagen fibres that are interspersed between the capillaries and the alveolar walls.\n\nElastin is the key protein of the extracellular matrix and is the main component of the elastic fibres.\n\nElastin gives the necessary elasticity and resilience required for the persistent stretching involved in breathing, known as lung compliance.\n\nIt is also responsible for the elastic recoil needed.\n\nElastin is more concentrated in areas of high stress such as the openings of the alveoli, and alveolar junctions.\n\nThe connective tissue links all the alveoli to form the lung parenchyma which has a sponge-like appearance.\n\nThe alveoli have interconnecting air passages in their walls known as the pores of Kohn.\n\n=== Respiratory epithelium ===\n\nAll of the lower respiratory tract including the trachea, bronchi, and bronchioles is lined with respiratory epithelium.\n\nThis is a ciliated epithelium interspersed with goblet cells which produce mucin the main component of mucus, ciliated cells, basal cells, and in the terminal bronchioles–club cells with actions similar to basal cells, and macrophages.\n\nThe epithelial cells, and the submucosal glands throughout the respiratory tract secrete airway surface liquid (ASL), the composition of which is tightly regulated and determines how well mucociliary clearance works.Pulmonary neuroendocrine cells are found throughout the respiratory epithelium including the alveolar epithelium, though they only account for around 0.5 per cent of the total epithelial population.\n\nPNECs are innervated airway epithelial cells that are particularly focused at airway junction points.\n\nThese cells can produce serotonin, dopamine, and norepinephrine, as well as polypeptide products.\n\nCytoplasmic processes from the pulmonary neuroendocrine cells extend into the airway lumen where they may sense the composition of inspired gas.\n\n=== Bronchial airways ===\n\nIn the bronchi there are incomplete tracheal rings of cartilage and smaller plates of cartilage that keep them open.: 472  Bronchioles are too narrow to support cartilage and their walls are of smooth muscle, and this is largely absent in the narrower respiratory bronchioles which are mainly just of epithelium.: 472  The absence of cartilage in the terminal bronchioles gives them an alternative name of membranous bronchioles.\n\n=== Respiratory zone ===\n\nThe conducting zone of the respiratory tract ends at the terminal bronchioles when they branch into the respiratory bronchioles.\n\nThis marks the beginning of the terminal respiratory unit called the acinus which includes the respiratory bronchioles, the alveolar ducts, alveolar sacs, and alveoli.\n\nAn acinus measures up to 10 mm in diameter.\n\nA primary pulmonary lobule is that part of the acinus that includes the alveolar ducts, sacs, and alveoli but does not include the respiratory bronchioles.\n\nThe unit described as the secondary pulmonary lobule is the lobule most referred to as the pulmonary lobule or respiratory lobule.: 489  This lobule is a discrete unit that is the smallest component of the lung that can be seen without aid.\n\nThe secondary pulmonary lobule is likely to be made up of between 30 and 50 primary lobules.\n\nThe lobule is supplied by a terminal bronchiole that branches into respiratory bronchioles.\n\nThe respiratory bronchioles supply the alveoli in each acinus and is accompanied by a pulmonary artery branch.\n\nEach lobule is enclosed by an interlobular septa.\n\nEach acinus is incompletely separated by an interlobular septa.The respiratory bronchiole gives rise to the alveolar ducts that lead to the alveolar sacs, which contain two or more alveoli.\n\nThe walls of the alveoli are extremely thin allowing a fast rate of diffusion.\n\nThe alveoli have interconnecting small air passages in their walls known as the pores of Kohn.\n\n=== Alveoli ===\n\nAlveoli consist of two types of alveolar cell and an alveolar macrophage.\n\nThe two types of cell are known as type I and type II cells (also known as pneumocytes).\n\nTypes I and II make up the walls and alveolar septa.\n\nType I cells provide 95% of the surface area of each alveoli and are flat (\"squamous\"), and Type II cells generally cluster in the corners of the alveoli and have a cuboidal shape.\n\nDespite this, cells occur in a roughly equal ratio of 1:1 or 6:4.Type I are squamous epithelial cells that make up the alveolar wall structure.\n\nThey have extremely thin walls that enable an easy gas exchange.\n\nThese type I cells also make up the alveolar septa which separate each alveolus.\n\nThe septa consist of an epithelial lining and associated basement membranes.\n\nType I cells are not able to divide, and consequently rely on differentiation from Type II cells.Type II are larger and they line the alveoli and produce and secrete epithelial lining fluid, and lung surfactant.\n\nType II cells are able to divide and differentiate to Type I cells.The alveolar macrophages have an important role in the immune system.\n\nThey remove substances which deposit in the alveoli including loose red blood cells that have been forced out from blood vessels.\n\n=== Microbiota ===\n\nThere is a large presence of microorganisms in the lungs known as the lung microbiota that interacts with the airway epithelial cells; an interaction of probable importance in maintaining homeostasis.\n\nThe microbiota is complex and dynamic in healthy people, and altered in diseases such as asthma and COPD.\n\nFor example significant changes can take place in COPD following infection with rhinovirus.\n\nFungal genera that are commonly found as mycobiota in the microbiota include Candida, Malassezia, Saccharomyces, and Aspergillus.\n\n=== Respiratory tract ===\n\nThe lower respiratory tract is part of the respiratory system, and consists of the trachea and the structures below this including the lungs.\n\nThe trachea receives air from the pharynx and travels down to a place where it splits (the carina) into a right and left primary bronchus.\n\nThese supply air to the right and left lungs, splitting progressively into the secondary and tertiary bronchi for the lobes of the lungs, and into smaller and smaller bronchioles until they become the respiratory bronchioles.\n\nThese in turn supply air through alveolar ducts into the alveoli, where the exchange of gases take place.\n\nOxygen breathed in, diffuses through the walls of the alveoli into the enveloping capillaries and into the circulation, and carbon dioxide diffuses from the blood into the lungs to be breathed out.\nEstimates of the total surface area of lungs vary from 50 to 75 square metres (540 to 810 sq ft); although this is often quoted in textbooks and the media being \"the size of a tennis court\", it is actually less than half the size of a singles court.The bronchi in the conducting zone are reinforced with hyaline cartilage in order to hold open the airways.\n\nThe bronchioles have no cartilage and are surrounded instead by smooth muscle.\n\nAir is warmed to 37 °C (99 °F), humidified and cleansed by the conducting zone.\n\nParticles from the air being removed by the cilia on the respiratory epithelium lining the passageways, in a process called mucociliary clearance.\nPulmonary stretch receptors in the smooth muscle of the airways initiate a reflex known as the Hering–Breuer reflex that prevents the lungs from over-inflation, during forceful inspiration.\n\n=== Blood supply ===\n\nThe lungs have a dual blood supply provided by a bronchial and a pulmonary circulation.\n\nThe bronchial circulation supplies oxygenated blood to the airways of the lungs, through the bronchial arteries that leave the aorta.\n\nThere are usually three arteries, two to the left lung and one to the right, and they branch alongside the bronchi and bronchioles.\n\nThe pulmonary circulation carries deoxygenated blood from the heart to the lungs and returns the oxygenated blood to the heart to supply the rest of the body.The blood volume of the lungs is about 450 millilitres on average, about 9% of the total blood volume of the entire circulatory system.\n\nThis quantity can easily fluctuate from between one-half and twice the normal volume.\n\nAlso, in the event of blood loss through hemorrhage, blood from the lungs can partially compensate by automatically transferring to the systemic circulation.\n\n=== Nerve supply ===\n\nThe lungs are supplied by nerves of the autonomic nervous system.\n\nInput from the parasympathetic nervous system occurs via the vagus nerve.\n\nWhen stimulated by acetylcholine, this causes constriction of the smooth muscle lining the bronchus and bronchioles, and increases the secretions from glands.\n\nThe lungs also have a sympathetic tone from norepinephrine acting on the beta 2 adrenoceptors in the respiratory tract, which causes bronchodilation.The action of breathing takes place because of nerve signals sent by the respiratory center in the brainstem, along the phrenic nerve from the cervical plexus to the diaphragm.\n\n=== Variation ===\n\nThe lobes of the lung are subject to anatomical variations.\n\nA horizontal interlobar fissure was found to be incomplete in 25% of right lungs, or even absent in 11% of all cases.\n\nAn accessory fissure was also found in 14% and 22% of left and right lungs, respectively.\n\nAn oblique fissure was found to be incomplete in 21% to 47% of left lungs.\n\nIn some cases a fissure is absent, or extra, resulting in a right lung with only two lobes, or a left lung with three lobes.A variation in the airway branching structure has been found specifically in the central airway\nbranching.\n\nThis variation is associated with the development of COPD in adulthood.\n\n== Development ==\n\nThe development of the human lungs arise from the laryngotracheal groove and develop to maturity over several weeks in the foetus and for several years following birth.The larynx, trachea, bronchi and lungs that make up the respiratory tract, begin to form during the fourth week of embryogenesis from the lung bud which appears ventrally to the caudal portion of the foregut.\n\nThe respiratory tract has a branching structure, and is also known as the respiratory tree.\n\nIn the embryo this structure is developed in the process of branching morphogenesis, and is generated by the repeated splitting of the tip of the branch.\n\nIn the development of the lungs (as in some other organs) the epithelium forms branching tubes.\n\nThe lung has a left-right symmetry and each bud known as a bronchial bud grows out as a tubular epithelium that becomes a bronchus.\n\nEach bronchus branches into bronchioles.\n\nThe branching is a result of the tip of each tube bifurcating.\n\nThe branching process forms the bronchi, bronchioles, and ultimately the alveoli.\n\nThe four genes mostly associated with branching morphogenesis in the lung are the intercellular signalling protein – sonic hedgehog (SHH), fibroblast growth factors FGF10 and FGFR2b, and bone morphogenetic protein BMP4.\n\nFGF10 is seen to have the most prominent role.\n\nFGF10 is a paracrine signalling molecule needed for epithelial branching, and SHH inhibits FGF10.\n\nThe development of the alveoli is influenced by a different mechanism whereby continued bifurcation is stopped and the distal tips become dilated to form the alveoli.\nAt the end of the fourth week the lung bud divides into two, the right and left primary bronchial buds on each side of the trachea.\n\nDuring the fifth week the right bud branches into three secondary bronchial buds and the left branches into two secondary bronchial buds.\n\nThese give rise to the lobes of the lungs, three on the right and two on the left.\n\nOver the following week, the secondary buds branch into tertiary buds, about ten on each side.\n\nFrom the sixth week to the sixteenth week, the major elements of the lungs appear except the alveoli.\n\nFrom week 16 to week 26, the bronchi enlarge and lung tissue becomes highly vascularised.\n\nBronchioles and alveolar ducts also develop.\n\nBy week 26 the terminal bronchioles have formed which branch into two respiratory bronchioles.\n\nDuring the period covering the 26th week until birth the important blood–air barrier is established.\n\nSpecialised type I alveolar cells where gas exchange will take place, together with the type II alveolar cells that secrete pulmonary surfactant, appear.\n\nThe surfactant reduces the surface tension at the air-alveolar surface which allows expansion of the alveolar sacs.\n\nThe alveolar sacs contain the primitive alveoli that form at the end of the alveolar ducts,\nand their appearance around the seventh month marks the point at which limited respiration would be possible, and the premature baby could survive.\n\n=== Vitamin A deficiency ===\n\nThe developing lung is particularly vulnerable to changes in the levels of vitamin A.\n\nVitamin A deficiency has been linked to changes in the epithelial lining of the lung and in the lung parenchyma.\n\nThis can disrupt the normal physiology of the lung and predispose to respiratory diseases.\n\nSevere nutritional deficiency in vitamin A results in a reduction in the formation of the alveolar walls (septa) and to notable changes in the respiratory epithelium; alterations are noted in the extracellular matrix and in the protein content of the basement membrane.\n\nThe extracellular matrix maintains lung elasticity; the basement membrane is associated with alveolar epithelium and is important in the blood-air barrier.\n\nThe deficiency is associated with functional defects and disease states.\n\nVitamin A is crucial in the development of the alveoli which continues for several years after birth.\n\n=== After birth ===\n\nAt birth, the baby's lungs are filled with fluid secreted by the lungs and are not inflated.\n\nAfter birth the infant's central nervous system reacts to the sudden change in temperature and environment.\n\nThis triggers the first breath, within about 10 seconds after delivery.\n\nBefore birth, the lungs are filled with fetal lung fluid. After the first breath, the fluid is quickly absorbed into the body or exhaled.\n\nThe resistance in the lung's blood vessels decreases giving an increased surface area for gas exchange, and the lungs begin to breathe spontaneously.\n\nThis accompanies other changes which result in an increased amount of blood entering the lung tissues.At birth the lungs are very undeveloped with only around one sixth of the alveoli of the adult lung present.\n\nThe alveoli continue to form into early adulthood, and their ability to form when necessary is seen in the regeneration of the lung.\n\nAlveolar septa have a double capillary network instead of the single network of the developed lung.\n\nOnly after the maturation of the capillary network can the lung enter a normal phase of growth.\n\nFollowing the early growth in numbers of alveoli there is another stage of the alveoli being enlarged.\n\n== Function ==\n\n=== Gas exchange ===\n\nThe major function of the lungs is gas exchange between the lungs and the blood.\n\nThe alveolar and pulmonary capillary gases equilibrate across the thin blood–air barrier.\n\nThis thin membrane (about 0.5 –2 μm thick) is folded into about 300 million alveoli, providing an extremely large surface area (estimates varying between 70 and 145 m2) for gas exchange to occur.\n\nThe lungs are not capable of expanding to breathe on their own, and will only do so when there is an increase in the volume of the thoracic cavity.\n\nThis is achieved by the muscles of respiration, through the contraction of the diaphragm, and the intercostal muscles which pull the rib cage upwards as shown in the diagram.\n\nDuring breathing out the muscles relax, returning the lungs to their resting position.\n\nAt this point the lungs contain the functional residual capacity (FRC) of air, which, in the adult human, has a volume of about 2.5–3.0 litres.During heavy breathing as in exertion, a large number of accessory muscles in the neck and abdomen are recruited, that during exhalation pull the ribcage down, decreasing the volume of the thoracic cavity.\n\nThe FRC is now decreased, but since the lungs cannot be emptied completely there is still about a litre of residual air left.\n\nLung function testing is carried out to evaluate lung volumes and capacities.\n\n=== Protection ===\n\nThe lungs possess several characteristics which protect against infection.\n\nThe respiratory tract is lined by respiratory epithelium or respiratory mucosa, with hair-like projections called cilia that beat rhythmically and carry mucus.\n\nThis mucociliary clearance is an important defence system against air-borne infection.\n\nThe dust particles and bacteria in the inhaled air are caught in the mucosal surface of the airways, and are moved up towards the pharynx by the rhythmic upward beating action of the cilia.: 661–730  The lining of the lung also secretes immunoglobulin A which protects against respiratory infections; goblet cells secrete mucus which also contains several antimicrobial compounds such as defensins, antiproteases, and antioxidants.\n\nA rare type of specialised cell called a pulmonary ionocyte that is suggested may regulate mucus viscosity has been described.\n\nIn addition, the lining of the lung also contains macrophages, immune cells which engulf and destroy debris and microbes that enter the lung in a process known as phagocytosis; and dendritic cells which present antigens to activate components of the adaptive immune system such as T cells and B cells.The size of the respiratory tract and the flow of air also protect the lungs from larger particles.\n\nSmaller particles deposit in the mouth and behind the mouth in the oropharynx, and larger particles are trapped in nasal hair after inhalation.\n\n=== Other ===\n\nIn addition to their function in respiration, the lungs have a number of other functions.\n\nThey are involved in maintaining homeostasis, helping in the regulation of blood pressure as part of the renin–angiotensin system.\n\nThe inner lining of the blood vessels secretes angiotensin-converting enzyme (ACE) an enzyme that catalyses the conversion of angiotensin I to angiotensin II.\n\nThe lungs are involved in the blood's acid–base homeostasis by expelling carbon dioxide when breathing.The lungs also serve a protective role.\n\nSeveral blood-borne substances, such as a few types of prostaglandins, leukotrienes, serotonin and bradykinin, are excreted through the lungs.\n\nDrugs and other substances can be absorbed, modified or excreted in the lungs.\n\nThe lungs filter out small blood clots from veins and prevent them from entering arteries and causing strokes.The lungs also play a pivotal role in speech by providing air and airflow for the creation of vocal sounds, and other paralanguage communications such as sighs and gasps.\nResearch suggests a role of the lungs in the production of blood platelets.\n\n== Gene and protein expression ==\n\nAbout 20,000 protein coding genes are expressed in human cells and almost 75% of these genes are expressed in the normal lung.\n\nA little less than 200 of these genes are more specifically expressed in the lung with less than 20 genes being highly lung specific.\n\nThe highest expression of lung specific proteins are different surfactant proteins, such as SFTPA1, SFTPB and SFTPC, and napsin, expressed in type II pneumocytes.\n\nOther proteins with elevated expression in the lung are the dynein protein DNAH5 in ciliated cells, and the secreted SCGB1A1 protein in mucus-secreting goblet cells of the airway mucosa.\n\n== Clinical significance ==\n\nLungs can be affected by a number of diseases and disorders.\n\nPulmonology is the medical speciality that deals with respiratory diseases involving the lungs and respiratory system.\n\nCardiothoracic surgery deals with surgery of the lungs including lung volume reduction surgery, lobectomy, pneumectomy and lung transplantation.\n\n=== Inflammation and infection ===\n\nInflammatory conditions of the lung tissue are pneumonia, of the respiratory tract are bronchitis and bronchiolitis, and of the pleurae surrounding the lungs pleurisy.\n\nInflammation is usually caused by infections due to bacteria or viruses.\n\nWhen the lung tissue is inflamed due to other causes it is called pneumonitis.\n\nOne major cause of bacterial pneumonia is tuberculosis.\n\nChronic infections often occur in those with immunodeficiency and can include a fungal infection by Aspergillus fumigatus that can lead to an aspergilloma forming in the lung.Alcohol affects the lungs and can cause inflammatory alcoholic lung disease.\n\nAcute exposure to alcohol stimulates the beating of cilia in the respiratory epithelium.\n\nHowever, chronic exposure has the effect of desensitising the ciliary response which reduces mucociliary clearance (MCC).\n\nMCC is an innate defense system protecting against pollutants and pathogens, and when this is disrupted the numbers of alveolar macrophages are decreased.\n\nA subsequent inflammatory response is the release of cytokines.\n\nAnother consequence is the susceptibility to infection.\n\n=== Blood-supply changes ===\n\nA pulmonary embolism is a blood clot that becomes lodged in the pulmonary arteries.\n\nThe majority of emboli arise because of deep vein thrombosis in the legs.\n\nPulmonary emboli may be investigated using a ventilation/perfusion scan, a CT scan of the arteries of the lung, or blood tests such as the D-dimer.\n\nPulmonary hypertension describes an increased pressure at the beginning of the pulmonary artery that has a large number of differing causes.\n\nOther rarer conditions may also affect the blood supply of the lung, such as granulomatosis with polyangiitis, which causes inflammation of the small blood vessels of the lungs and kidneys.A lung contusion is a bruise caused by chest trauma.\n\nIt results in hemorrhage of the alveoli causing a build-up of fluid which can impair breathing, and this can be either mild or severe.\nThe function of the lungs can also be affected by compression from fluid in the pleural cavity pleural effusion, or other substances such as air (pneumothorax), blood (hemothorax), or rarer causes.\n\nThese may be investigated using a chest X-ray or CT scan, and may require the insertion of a surgical drain until the underlying cause is identified and treated.\n\n=== Obstructive lung diseases ===\n\nAsthma, chronic bronchitis, bronchiectasis and chronic obstructive pulmonary disease (COPD) are all obstructive lung diseases characterised by airway obstruction.\n\nThis limits the amount of air that is able to enter alveoli because of constriction of the bronchial tree, due to inflammation.\n\nObstructive lung diseases are often identified because of symptoms and diagnosed with pulmonary function tests such as spirometry.\n\nMany obstructive lung diseases are managed by avoiding triggers (such as dust mites or smoking), with symptom control such as bronchodilators, and with suppression of inflammation (such as through corticosteroids) in severe cases.\n\nA common cause of chronic bronchitis, and emphysema, is smoking; and common causes of bronchiectasis include severe infections and cystic fibrosis.\n\nThe definitive cause of asthma is not yet known.The breakdown of alveolar tissue, often as a result of tobacco-smoking leads to emphysema, which can become severe enough to develop into COPD.\n\nElastase breaks down the elastin in the lung's connective tissue that can also result in emphysema.\n\nElastase is inhibited by the acute-phase protein, alpha-1 antitrypsin, and when there is a deficiency in this, emphysema can develop.\n\nWith persistent stress from smoking, the airway basal cells become disarranged and lose their regenerative ability needed to repair the epithelial barrier.\n\nThe disorganised basal cells are seen to be responsible for the major airway changes that are characteristic of COPD, and with continued stress can undergo a malignant transformation.\n\nStudies have shown that the initial development of emphysema is centred on the early changes in the airway epithelium of the small airways.\n\nBasal cells become further deranged in a smoker's transition to clinically defined COPD.\n\n=== Restrictive lung diseases ===\n\nSome types of chronic lung diseases are classified as restrictive lung disease, because of a restriction in the amount of lung tissue involved in respiration.\n\nThese include pulmonary fibrosis which can occur when the lung is inflamed for a long period of time.\n\nFibrosis in the lung replaces functioning lung tissue with fibrous connective tissue.\n\nThis can be due to a large variety of occupational lung diseases such as Coalworker's pneumoconiosis, autoimmune diseases or more rarely to a reaction to medication.\n\nSevere respiratory disorders, where spontaneous breathing is not enough to maintain life, may need the use of mechanical ventilation to ensure an adequate supply of air.\n\n=== Cancers ===\n\nLung cancer can either arise directly from lung tissue or as a result of metastasis from another part of the body.\n\nThere are two main types of primary tumour described as either small-cell or non-small-cell lung carcinomas.\n\nThe major risk factor for cancer is smoking.\n\nOnce a cancer is identified it is staged using scans such as a CT scan and a sample of tissue from a biopsy is taken.\n\nCancers may be treated surgically by removing the tumour, the use of radiotherapy, chemotherapy or a combination, or with the aim of symptom control.\n\nLung cancer screening is being recommended in the United States for high-risk populations.\n\n=== Congenital disorders ===\n\nCongenital disorders include cystic fibrosis, pulmonary hypoplasia (an incomplete development of the lungs)congenital diaphragmatic hernia, and infant respiratory distress syndrome caused by a deficiency in lung surfactant.\n\nAn azygos lobe is a congenital anatomical variation which though usually without effect can cause problems in thoracoscopic procedures.\n\n=== Others ===\n\nA pneumothorax (collapsed lung) is an abnormal collection of air in the pleural space that causes an uncoupling of the lung from the chest wall.\n\nThe lung cannot expand against the air pressure inside the pleural space.\n\nAn easy to understand example is a traumatic pneumothorax, where air enters the pleural space from outside the body, as occurs with puncture to the chest wall.\n\nSimilarly, scuba divers ascending while holding their breath with their lungs fully inflated can cause air sacs (alveoli) to burst and leak high pressure air into the pleural space.\n\n=== Lung examination ===\n\nAs part of a physical examination in response to respiratory symptoms of shortness of breath, and cough, a lung examination may be carried out.\n\nThis exam includes palpation and auscultation.\n\nThe areas of the lungs that can be listened to using a stethoscope are called the lung fields, and these are the posterior, lateral, and anterior lung fields.\n\nThe posterior fields can be listened to from the back and include: the lower lobes (taking up three quarters of the posterior fields); the anterior fields taking up the other quarter; and the lateral fields under the axillae, the left axilla for the lingual, the right axilla for the middle right lobe.\n\nThe anterior fields can also be auscultated from the front.\n\nAbnormal breathing sounds heard during a lung exam can indicate the presence of a lung condition; wheezing for example is commonly associated with asthma and COPD.\n\n=== Lung function testing ===\n\nLung function testing is carried out by evaluating a person's capacity to inhale and exhale in different circumstances.\n\nThe volume of air inhaled and exhaled by a person at rest is the tidal volume (normally 500-750mL); the inspiratory reserve volume and expiratory reserve volume are the additional amounts a person is able to forcibly inhale and exhale respectively.\n\nThe summed total of forced inspiration and expiration is a person's vital capacity.\n\nNot all air is expelled from the lungs even after a forced breath out; the remainder of the air is called the residual volume.\n\nTogether these terms are referred to as lung volumes.Pulmonary plethysmographs are used to measure functional residual capacity.\n\nFunctional residual capacity cannot be measured by tests that rely on breathing out, as a person is only able to breathe a maximum of 80% of their total functional capacity.\n\nThe total lung capacity depends on the person's age, height, weight, and sex, and normally ranges between 4 and 6 litres.\n\nFemales tend to have a 20–25% lower capacity than males.\n\nTall people tend to have a larger total lung capacity than shorter people.\n\nSmokers have a lower capacity than nonsmokers.\n\nThinner persons tend to have a larger capacity.\n\nLung capacity can be increased by physical training as much as 40% but the effect may be modified by exposure to air pollution.Other lung function tests include spirometry, measuring the amount (volume) and flow of air that can be inhaled and exhaled.\n\nThe maximum volume of breath that can be exhaled is called the vital capacity.\n\nIn particular, how much a person is able to exhale in one second (called forced expiratory volume (FEV1)) as a proportion of how much they are able to exhale in total (FEV).\n\nThis ratio, the FEV1/FEV ratio, is important to distinguish whether a lung disease is restrictive or obstructive.\n\nAnother test is that of the lung's diffusing capacity – this is a measure of the transfer of gas from air to the blood in the lung capillaries.\n\n== Other animals ==\n\n=== Birds ===\n\nThe lungs of birds are relatively small, but are connected to 8 or 9 air sacs that extend through much of the body, and are in turn connected to air spaces within the bones.\n\nOn inhalation, air travels through the trachea of a bird into the air sacs.\n\nAir then travels continuously from the air sacs at the back, through the lungs, which are relatively fixed in size, to the air sacs at the front.\n\nFrom here, the air is exhaled.\n\nThese fixed size lungs are called \"circulatory lungs\", as distinct from the \"bellows-type lungs\" found in most other animals.The lungs of birds contain millions of tiny parallel passages called parabronchi.\n\nSmall sacs called atria radiate from the walls of the tiny passages; these, like the alveoli in other lungs, are the site of gas exchange by simple diffusion.\n\nThe blood flow around the parabronchi and their atria forms a cross-current process of gas exchange (see diagram on the right).The air sacs, which hold air, do not contribute much to gas exchange, despite being thin-walled, as they are poorly vascularised.\n\nThe air sacs expand and contract due to changes in the volume in the thorax and abdomen.\n\nThis volume change is caused by the movement of the sternum and ribs and this movement is often synchronised with movement of the flight muscles.Parabronchi in which the air flow is unidirectional are called paleopulmonic parabronchi and are found in all birds.\n\nSome birds, however, have, in addition, a lung structure where the air flow in the parabronchi is bidirectional.\n\nThese are termed neopulmonic parabronchi.\n\n=== Reptiles ===\n\nThe lungs of most reptiles have a single bronchus running down the centre, from which numerous branches reach out to individual pockets throughout the lungs.\n\nThese pockets are similar to alveoli in mammals, but much larger and fewer in number.\n\nThese give the lung a sponge-like texture.\n\nIn tuataras, snakes, and some lizards, the lungs are simpler in structure, similar to that of typical amphibians.Snakes and limbless lizards typically possess only the right lung as a major respiratory organ; the left lung is greatly reduced, or even absent.\n\nAmphisbaenians, however, have the opposite arrangement, with a major left lung, and a reduced or absent right lung.Both crocodilians and monitor lizards have developed lungs similar to those of birds, providing a unidirectional airflow and even possessing air sacs.\n\nThe now extinct pterosaurs have seemingly even further refined this type of lung, extending the airsacs into the wing membranes and, in the case of lonchodectids, tupuxuara, and azhdarchoids, the hindlimbs.Reptilian lungs typically receive air via expansion and contraction of the ribs driven by axial muscles and buccal pumping.\n\nCrocodilians also rely on the hepatic piston method, in which the liver is pulled back by a muscle anchored to the pubic bone (part of the pelvis) called the diaphragmaticus, which in turn creates negative pressure in the crocodile's thoracic cavity, allowing air to be moved into the lungs by Boyle's law.\n\nTurtles, which are unable to move their ribs, instead use their forelimbs and pectoral girdle to force air in and out of the lungs.\n\n=== Amphibians ===\n\nThe lungs of most frogs and other amphibians are simple and balloon-like, with gas exchange limited to the outer surface of the lung.\n\nThis is not very efficient, but amphibians have low metabolic demands and can also quickly dispose of carbon dioxide by diffusion across their skin in water, and supplement their oxygen supply by the same method.\n\nAmphibians employ a positive pressure system to get air to their lungs, forcing air down into the lungs by buccal pumping.\n\nThis is distinct from most higher vertebrates, who use a breathing system driven by negative pressure where the lungs are inflated by expanding the rib cage.\n\nIn buccal pumping, the floor of the mouth is lowered, filling the mouth cavity with air.\n\nThe throat muscles then presses the throat against the underside of the skull, forcing the air into the lungs.Due to the possibility of respiration across the skin combined with small size, all known lungless tetrapods are amphibians.\n\nThe majority of salamander species are lungless salamanders, which respirate through their skin and tissues lining their mouth.\n\nThis necessarily restricts their size: all are small and rather thread-like in appearance, maximising skin surface relative to body volume.\n\nOther known lungless tetrapods are the Bornean flat-headed frog and Atretochoana eiselti, a caecilian.The lungs of amphibians typically have a few narrow internal walls (septa) of soft tissue around the outer walls, increasing the respiratory surface area and giving the lung a honeycomb appearance.\n\nIn some salamanders even these are lacking, and the lung has a smooth wall.\n\nIn caecilians, as in snakes, only the right lung attains any size or development.\n\n=== Lungfish ===\n\nThe lungs of lungfish are similar to those of amphibians, with few, if any, internal septa.\n\nIn the Australian lungfish, there is only a single lung, albeit divided into two lobes.\n\nOther lungfish and Polypterus, however, have two lungs, which are located in the upper part of the body, with the connecting duct curving around and above the esophagus.\n\nThe blood supply also twists around the esophagus, suggesting that the lungs originally evolved in the ventral part of the body, as in other vertebrates.\n\n=== Invertebrates ===\n\nSome invertebrates have lung-like structures that serve a similar respiratory purpose as, but are not evolutionarily related to, vertebrate lungs.\n\nSome arachnids, such as spiders and scorpions, have structures called book lungs used for atmospheric gas exchange.\n\nSome species of spider have four pairs of book lungs but most have two pairs.\n\nScorpions have spiracles on their body for the entrance of air to the book lungs.The coconut crab is terrestrial and uses structures called branchiostegal lungs to breathe air.\n\nThey cannot swim and would drown in water, yet they possess a rudimentary set of gills.\n\nThey can breathe on land and hold their breath underwater.\n\nThe branchiostegal lungs are seen as a developmental adaptive stage from water-living to enable land-living, or from fish to amphibian.Pulmonates are mostly land snails and slugs that have developed a simple lung from the mantle cavity.\n\nAn externally located opening called the pneumostome allows air to be taken into the mantle cavity lung.\n\n== Evolutionary origins ==\n\nThe lungs of today's terrestrial vertebrates and the gas bladders of today's fish are believed to have evolved from simple sacs, as outpocketings of the esophagus, that allowed early fish to gulp air under oxygen-poor conditions.\n\nThese outpocketings first arose in the bony fish.\n\nIn most of the ray-finned fish the sacs evolved into closed off gas bladders, while a number of carp, trout, herring, catfish, and eels have retained the physostome condition with the sac being open to the esophagus.\n\nIn more basal bony fish, such as the gar, bichir, bowfin and the lobe-finned fish, the bladders have evolved to primarily function as lungs.\n\nThe lobe-finned fish gave rise to the land-based tetrapods.\n\nThus, the lungs of vertebrates are homologous to the gas bladders of fish (but not to their gills).\n\nhttps://en.wikipedia.org/wiki/Lung","kidney":"The kidneys are two reddish-brown bean-shaped organs found in vertebrates.\n\nThey are located on the left and right in the retroperitoneal space, and in adult humans are about 12 centimetres (4+1⁄2 inches) in length.\n\nThey receive blood from the paired renal arteries; blood exits into the paired renal veins.\n\nEach kidney is attached to a ureter, a tube that carries excreted urine to the bladder.\n\nThe kidney participates in the control of the volume of various body fluids, fluid osmolality, acid–base balance, various electrolyte concentrations, and removal of toxins.\n\nFiltration occurs in the glomerulus: one-fifth of the blood volume that enters the kidneys is filtered.\n\nExamples of substances reabsorbed are solute-free water, sodium, bicarbonate, glucose, and amino acids.\n\nExamples of substances secreted are hydrogen, ammonium, potassium and uric acid.\n\nThe kidneys also carry out functions independent of the nephron.\n\nFor example, they convert a precursor of vitamin D to its active form, calcitriol; and synthesize the hormones erythropoietin and renin.\n\nThe nephron is the structural and functional unit of the kidney.\n\nEach adult human kidney contains around 1 million nephrons, while a mouse kidney contains only about 12,500 nephrons.\n\nProcedures used in the management of kidney disease include chemical and microscopic examination of the urine (urinalysis), measurement of kidney function by calculating the estimated glomerular filtration rate (eGFR) using the serum creatinine; and kidney biopsy and CT scan to evaluate for abnormal anatomy.\n\nDialysis and kidney transplantation are used to treat kidney failure; one (or both sequentially) of these are almost always used when renal function drops below 15%.\n\nNephrectomy is frequently used to cure renal cell carcinoma.\nRenal physiology is the study of kidney function.\n\nNephrology is the medical specialty which addresses diseases of kidney function: these include chronic kidney disease, nephritic and nephrotic syndromes, acute kidney injury, and pyelonephritis.\n\nUrology addresses diseases of kidney (and urinary tract) anatomy: these include cancer, renal cysts, kidney stones and ureteral stones, and urinary tract obstruction.\n\nThe word “renal” is an adjective meaning “relating to the kidneys”, and its roots are French or late Latin.\n\nWhereas according to some opinions, \"renal\" should be replaced with \"kidney\" in scientific writings such as \"kidney artery\", other experts have advocated preserving the use of renal as appropriate including in \"renal artery\".\n\n== Structure ==\n\nIn humans, the kidneys are located high in the abdominal cavity, one on each side of the spine, and lie in a retroperitoneal position at a slightly oblique angle.\n\nThe asymmetry within the abdominal cavity, caused by the position of the liver, typically results in the right kidney being slightly lower and smaller than the left, and being placed slightly more to the middle than the left kidney.\n\nThe left kidney is approximately at the vertebral level T12 to L3, and the right is slightly lower.\n\nThe right kidney sits just below the diaphragm and posterior to the liver.\n\nThe left kidney sits below the diaphragm and posterior to the spleen.\n\nOn top of each kidney is an adrenal gland.\n\nThe upper parts of the kidneys are partially protected by the 11th and 12th ribs.\n\nEach kidney, with its adrenal gland is surrounded by two layers of fat: the perirenal fat present between renal fascia and renal capsule and pararenal fat superior to the renal fascia.\n\nThe kidney is a bean-shaped structure with a convex and a concave border.\n\nA recessed area on the concave border is the renal hilum, where the renal artery enters the kidney and the renal vein and ureter leave.\n\nThe kidney is surrounded by tough fibrous tissue, the renal capsule, which is itself surrounded by perirenal fat, renal fascia, and pararenal fat.\n\nThe anterior (front) surface of these tissues is the peritoneum, while the posterior (rear) surface is the transversalis fascia.\n\nThe superior pole of the right kidney is adjacent to the liver.\n\nFor the left kidney, it is next to the spleen.\n\nBoth, therefore, move down upon inhalation.\n\nA Danish study measured the median renal length to be 11.2 cm (4+7⁄16 in) on the left side and 10.9 cm (4+5⁄16 in) on the right side in adults.\n\nMedian renal volumes were 146 cm3 (8+15⁄16 cu in) on the left and 134 cm3 (8+3⁄16 cu in) on the right.\n\n=== Gross anatomy ===\n\nThe functional substance, or parenchyma, of the kidney is divided into two major structures: the outer renal cortex and the inner renal medulla.\n\nGrossly, these structures take the shape of eight to 18 cone-shaped renal lobes, each containing renal cortex surrounding a portion of medulla called a renal pyramid.\n\nBetween the renal pyramids are projections of cortex called renal columns.\n\nNephrons, the urine-producing functional structures of the kidney, span the cortex and medulla.\n\nThe initial filtering portion of a nephron is the renal corpuscle, which is located in the cortex.\n\nThis is followed by a renal tubule that passes from the cortex deep into the medullary pyramids.\n\nPart of the renal cortex, a medullary ray is a collection of renal tubules that drain into a single collecting duct.\n\nThe tip, or papilla, of each pyramid empties urine into a minor calyx; minor calyces empty into major calyces, and major calyces empty into the renal pelvis.\n\nThis becomes the ureter.\n\nAt the hilum, the ureter and renal vein exit the kidney and the renal artery enters.\n\nHilar fat and lymphatic tissue with lymph nodes surround these structures.\n\nThe hilar fat is contiguous with a fat-filled cavity called the renal sinus.\n\nThe renal sinus collectively contains the renal pelvis and calyces and separates these structures from the renal medullary tissue.The kidneys possess no overtly moving structures.\n\n=== Blood supply ===\n\nThe kidneys receive blood from the renal arteries, left and right, which branch directly from the abdominal aorta.\n\nDespite their relatively small size, the kidneys receive approximately 20% of the cardiac output.\n\nEach renal artery branches into segmental arteries, dividing further into interlobar arteries, which penetrate the renal capsule and extend through the renal columns between the renal pyramids.\n\nThe interlobar arteries then supply blood to the arcuate arteries that run through the boundary of the cortex and the medulla.\n\nEach arcuate artery supplies several interlobular arteries that feed into the afferent arterioles that supply the glomeruli.\n\nBlood drains from the kidneys, ultimately into the inferior vena cava.\n\nAfter filtration occurs, the blood moves through a small network of small veins (venules) that converge into interlobular veins.\n\nAs with the arteriole distribution, the veins follow the same pattern: the interlobular provide blood to the arcuate veins then back to the interlobar veins, which come to form the renal veins which exiting the kidney .\n\n=== Nerve supply ===\n\nThe kidney and nervous system communicate via the renal plexus, whose fibers course along the renal arteries to reach each kidney.\n\nInput from the sympathetic nervous system triggers vasoconstriction in the kidney, thereby reducing renal blood flow.\n\nThe kidney also receives input from the parasympathetic nervous system, by way of the renal branches of the vagus nerve; the function of this is yet unclear.\n\nSensory input from the kidney travels to the T10-11 levels of the spinal cord and is sensed in the corresponding dermatome.\n\nThus, pain in the flank region may be referred from corresponding kidney.\n\n=== Microanatomy ===\n\nRenal histology is the study of the microscopic structure of the kidney.\n\nDistinct cell types include:\n\nKidney glomerulus parietal cell\nKidney glomerulus podocyte\nKidney proximal tubule brush border cell\nLoop of Henle thin segment cell\nThick ascending limb cell\nKidney distal tubule cell\nCollecting duct principal cell\nCollecting duct intercalated cell\nInterstitial kidney cells\n\n=== Gene and protein expression ===\n\nAbout 20,000 protein coding genes are expressed in human cells and almost 70% of these genes are expressed in normal, adult kidneys.\n\nJust over 300 genes are more specifically expressed in the kidney, with only some 50 genes being highly specific for the kidney.\n\nMany of the corresponding kidney specific proteins are expressed in the cell membrane and function as transporter proteins.\n\nThe highest expressed kidney specific protein is uromodulin, the most abundant protein in urine with functions that prevent calcification and growth of bacteria.\n\nSpecific proteins are expressed in the different compartments of the kidney with podocin and nephrin expressed in glomeruli, Solute carrier family protein SLC22A8 expressed in proximal tubules, calbindin expressed in distal tubules and aquaporin 2 expressed in the collecting duct cells.\n\n=== Development ===\n\nThe mammalian kidney develops from intermediate mesoderm.\n\nKidney development, also called nephrogenesis, proceeds through a series of three successive developmental phases: the pronephros, mesonephros, and metanephros.\n\nThe metanephros are primordia of the permanent kidney.\n\n== Function ==\n\nThe kidneys excrete a variety of waste products produced by metabolism into the urine.\n\nThe microscopic structural and functional unit of the kidney is the nephron.\n\nIt processes the blood supplied to it via filtration, reabsorption, secretion and excretion; the consequence of those processes is the production of urine.\n\nThese include the nitrogenous wastes urea, from protein catabolism, and uric acid, from nucleic acid metabolism.\n\nThe ability of mammals and some birds to concentrate wastes into a volume of urine much smaller than the volume of blood from which the wastes were extracted is dependent on an elaborate countercurrent multiplication mechanism.\n\nThis requires several independent nephron characteristics to operate: a tight hairpin configuration of the tubules, water and ion permeability in the descending limb of the loop, water impermeability in the ascending loop, and active ion transport out of most of the ascending limb.\n\nIn addition, passive countercurrent exchange by the vessels carrying the blood supply to the nephron is essential for enabling this function.\n\nThe kidney participates in whole-body homeostasis, regulating acid–base balance, electrolyte concentrations, extracellular fluid volume, and blood pressure.\n\nThe kidney accomplishes these homeostatic functions both independently and in concert with other organs, particularly those of the endocrine system.\n\nVarious endocrine hormones coordinate these endocrine functions; these include renin, angiotensin II, aldosterone, antidiuretic hormone, and atrial natriuretic peptide, among others.\n\n=== Formation of urine ===\n\n==== Filtration ====\n\nFiltration, which takes place at the renal corpuscle, is the process by which cells and large proteins are retained while materials of smaller molecular weights are filtered from the blood to make an ultrafiltrate that eventually becomes urine.\n\nThe kidney generates 180 liters of filtrate a day.\n\nThe process is also known as hydrostatic filtration due to the hydrostatic pressure exerted on the capillary walls.\n\n==== Reabsorption ====\n\nReabsorption is the transport of molecules from this ultrafiltrate and into the peritubular capillary.\n\nIt is accomplished via selective receptors on the luminal cell membrane.\n\nWater is 55% reabsorbed in the proximal tubule.\n\nGlucose at normal plasma levels is completely reabsorbed in the proximal tubule.\n\nThe mechanism for this is the Na+/glucose cotransporter.\n\nA plasma level of 350 mg/dL will fully saturate the transporters and glucose will be lost in the urine.\n\nA plasma glucose level of approximately 160 is sufficient to allow glucosuria, which is an important clinical clue to diabetes mellitus.\nAmino acids are reabsorbed by sodium dependent transporters in the proximal tubule.\n\nHartnup disease is a deficiency of the tryptophan amino acid transporter, which results in pellagra.\n\n==== Secretion ====\n\nSecretion is the reverse of reabsorption: molecules are transported from the peritubular capillary through the interstitial fluid, then through the renal tubular cell and into the ultrafiltrate.\n\n==== Excretion ====\n\nThe last step in the processing of the ultrafiltrate is excretion: the ultrafiltrate passes out of the nephron and travels through a tube called the collecting duct, which is part of the collecting duct system, and then to the ureters where it is renamed urine.\n\nIn addition to transporting the ultrafiltrate, the collecting duct also takes part in reabsorption.\n\n=== Hormone secretion ===\n\nThe kidneys secrete a variety of hormones, including erythropoietin, calcitriol, and renin.\n\nErythropoietin is released in response to hypoxia (low levels of oxygen at tissue level) in the renal circulation.\n\nIt stimulates erythropoiesis (production of red blood cells) in the bone marrow.\n\nCalcitriol, the activated form of vitamin D, promotes intestinal absorption of calcium and the renal reabsorption of phosphate.\n\nRenin is an enzyme which regulates angiotensin and aldosterone levels.\n\n=== Blood pressure regulation ===\n\nAlthough the kidney cannot directly sense blood, long-term regulation of blood pressure predominantly depends upon the kidney.\n\nThis primarily occurs through maintenance of the extracellular fluid compartment, the size of which depends on the plasma sodium concentration.\n\nRenin is the first in a series of important chemical messengers that make up the renin–angiotensin system.\n\nChanges in renin ultimately alter the output of this system, principally the hormones angiotensin II and aldosterone.\n\nEach hormone acts via multiple mechanisms, but both increase the kidney's absorption of sodium chloride, thereby expanding the extracellular fluid compartment and raising blood pressure.\n\nWhen renin levels are elevated, the concentrations of angiotensin II and aldosterone increase, leading to increased sodium chloride reabsorption, expansion of the extracellular fluid compartment, and an increase in blood pressure.\n\nConversely, when renin levels are low, angiotensin II and aldosterone levels decrease, contracting the extracellular fluid compartment, and decreasing blood pressure.\n\n=== Acid–base balance ===\n\nTwo organ systems, the kidneys and lungs, maintain acid–base homeostasis, which is the maintenance of pH around a relatively stable value.\n\nThe lungs contribute to acid–base homeostasis by regulating carbon dioxide (CO2) concentration.\n\nThe kidneys have two very important roles in maintaining the acid–base balance: to reabsorb and regenerate bicarbonate from urine, and to excrete hydrogen ions and fixed acids (anions of acids) into urine.\n\n=== Regulation of osmolality ===\n\nThe kidneys help maintain the water and salt level of the body.\n\nAny significant rise in plasma osmolality is detected by the hypothalamus, which communicates directly with the posterior pituitary gland.\n\nAn increase in osmolality causes the gland to secrete antidiuretic hormone (ADH), resulting in water reabsorption by the kidney and an increase in urine concentration.\n\nThe two factors work together to return the plasma osmolality to its normal levels.\n\n=== Measuring function ===\n\nVarious calculations and methods are used to try to measure kidney function.\n\nRenal clearance is the volume of plasma from which the substance is completely cleared from the blood per unit time.\n\nThe filtration fraction is the amount of plasma that is actually filtered through the kidney.\n\nThis can be defined using the equation.\n\nThe kidney is a very complex organ and mathematical modelling has been used to better understand kidney function at several scales, including fluid uptake and secretion.\n\n== Clinical significance ==\n\nNephrology is the subspeciality under Internal Medicine that deals with kidney function and disease states related to renal malfunction and their management including dialysis and kidney transplantation.\n\nUrology is the specialty under Surgery that deals with kidney structure abnormalities such as kidney cancer and cysts and problems with urinary tract.\n\nNephrologists are internists, and urologists are surgeons, whereas both are often called \"kidney doctors\".\n\nThere are overlapping areas that both nephrologists and urologists can provide care such as kidney stones and kidney related infections.\nThere are many causes of kidney disease.\n\nSome causes are acquired over the course of life, such as diabetic nephropathy whereas others are congenital, such as polycystic kidney disease.\n\nMedical terms related to the kidneys commonly use terms such as renal and the prefix nephro-.\n\nThe adjective renal, meaning related to the kidney, is from the Latin rēnēs, meaning kidneys; the prefix nephro- is from the Ancient Greek word for kidney, nephros (νεφρός).\n\nFor example, surgical removal of the kidney is a nephrectomy, while a reduction in kidney function is called renal dysfunction.\n\n=== Acquired ===\n\nDiabetic nephropathy\nGlomerulonephritis\nHydronephrosis is the enlargement of one or both of the kidneys caused by obstruction of the flow of urine.\nInterstitial nephritis\nKidney stones (nephrolithiasis) are a relatively common and particularly painful disorder.\n\nA chronic condition can result in scars to the kidneys.\n\nThe removal of kidney stones involves ultrasound treatment to break up the stones into smaller pieces, which are then passed through the urinary tract.\n\nOne common symptom of kidney stones is a sharp to disabling pain in the middle and sides of the lower back or groin.\nKidney tumour\nWilms tumor\nRenal cell carcinoma\nLupus nephritis\nMinimal change disease\nIn nephrotic syndrome, the glomerulus has been damaged so that a large amount of protein in the blood enters the urine.\n\nOther frequent features of the nephrotic syndrome include swelling, low serum albumin, and high cholesterol.\n\nPyelonephritis is infection of the kidneys and is frequently caused by complication of a urinary tract infection.\nKidney failure\nAcute kidney failure\nStage 5 Chronic Kidney Disease\nRenal artery stenosis\nRenovascular hypertension\n\n=== Kidney injury and failure ===\n\nGenerally, humans can live normally with just one kidney, as one has more functioning renal tissue than is needed to survive.\n\nOnly when the amount of functioning kidney tissue is greatly diminished does one develop chronic kidney disease.\n\nRenal replacement therapy, in the form of dialysis or kidney transplantation, is indicated when the glomerular filtration rate has fallen very low or if the renal dysfunction leads to severe symptoms.\n\n=== Dialysis ===\n\nDialysis is a treatment that substitutes for the function of normal kidneys.\n\nDialysis may be instituted when approximately 85%-90% of kidney function is lost, as indicated by a glomerular filtration rate (GFR) of less than 15.\n\nDialysis removes metabolic waste products as well as excess water and sodium (thereby contributing to regulating blood pressure); and maintains many chemical levels within the body.\n\nLife expectancy is 5–10 years for those on dialysis; some live up to 30 years.\n\nDialysis can occur via the blood (through a catheter or arteriovenous fistula), or through the peritoneum (peritoneal dialysis) Dialysis is typically administered three times a week for several hours at free-standing dialysis centers, allowing recipients to lead an otherwise essentially normal life.\n\n=== Congenital disease ===\n\nCongenital hydronephrosis\nCongenital obstruction of urinary tract\nDuplex kidneys, or double kidneys, occur in approximately 1% of the population.\n\nThis occurrence normally causes no complications, but can occasionally cause urinary tract infections.\nDuplicated ureter occurs in approximately one in 100 live births\nHorseshoe kidney occurs in approximately one in 400 live births\nNephroblastoma (Syndromic Wilm's tumour)\nNutcracker syndrome\nPolycystic kidney disease\nAutosomal dominant polycystic kidney disease afflicts patients later in life.\n\nApproximately one in 1000 people will develop this condition\nAutosomal recessive polycystic kidney disease is far less common, but more severe, than the dominant condition.\n\nIt is apparent in utero or at birth.\nRenal agenesis.\n\nFailure of one kidney to form occurs in approximately one in 750 live births.\n\nFailure of both kidneys to form used to be fatal; however, medical advances such as amnioinfusion therapy during pregnancy and peritoneal dialysis have made it possible to stay alive until a transplant can occur.\nRenal dysplasia\nUnilateral small kidney\nMulticystic dysplastic kidney occurs in approximately one in every 2400 live births\nUreteropelvic Junction Obstruction or UPJO; although most cases are congenital, some are acquired.\n\n=== Diagnosis ===\n\nMany renal diseases are diagnosed on the basis of a detailed medical history, and physical examination.\n\nThe medical history takes into account present and past symptoms, especially those of kidney disease; recent infections; exposure to substances toxic to the kidney; and family history of kidney disease.\nKidney function is tested by using blood tests and urine tests.\n\nThe most common blood test are creatinine, urea and electrolytes.\n\nUrine tests such as urinalysis can evaluate for pH, protein, glucose, and the presence of blood.\n\nMicroscopic analysis can also identify the presence of urinary casts and crystals.\n\nThe glomerular filtration rate (GFR) can be directly measured (\"measured GFR\", or mGFR) but this rarely done in everyday practice.\n\nInstead, special equations are used to calculate GFR (\"estimated GFR\", or eGFR).\n\n==== Imaging ====\n\nRenal ultrasonography is essential in the diagnosis and management of kidney-related diseases.\n\nOther modalities, such as CT and MRI, should always be considered as supplementary imaging modalities in the assessment of renal disease.\n\n==== Biopsy ====\n\nThe role of the renal biopsy is to diagnose renal disease in which the etiology is not clear based upon noninvasive means (clinical history, past medical history, medication history, physical exam, laboratory studies, imaging studies).\n\nIn general, a renal pathologist will perform a detailed morphological evaluation and integrate the morphologic findings with the clinical history and laboratory data, ultimately arriving at a pathological diagnosis.\n\nA renal pathologist is a physician who has undergone general training in anatomic pathology and additional specially training in the interpretation of renal biopsy specimens.\n\nIdeally, multiple core sections are obtained and evaluated for adequacy (presence of glomeruli) intraoperatively.\n\nA pathologist/pathology assistant divides the specimen(s) for submission for light microscopy, immunofluorescence microscopy and electron microscopy.\n\nThe pathologist will examine the specimen using light microscopy with multiple staining techniques (hematoxylin and eosin/H&E, PAS, trichrome, silver stain) on multiple level sections.\n\nMultiple immunofluorescence stains are performed to evaluate for antibody, protein and complement deposition.\n\nFinally, ultra-structural examination is performed with electron microscopy and may reveal the presence of electron-dense deposits or other characteristic abnormalities that may suggest an etiology for the patient's renal disease.\n\n== Other animals ==\n\nIn the majority of vertebrates, the mesonephros persists into the adult, albeit usually fused with the more advanced metanephros; only in amniotes is the mesonephros restricted to the embryo.\n\nThe kidneys of fish and amphibians are typically narrow, elongated organs, occupying a significant portion of the trunk.\n\nThe collecting ducts from each cluster of nephrons usually drain into an archinephric duct, which is homologous with the vas deferens of amniotes.\n\nHowever, the situation is not always so simple; in cartilaginous fish and some amphibians, there is also a shorter duct, similar to the amniote ureter, which drains the posterior (metanephric) parts of the kidney, and joins with the archinephric duct at the bladder or cloaca.\n\nIndeed, in many cartilaginous fish, the anterior portion of the kidney may degenerate or cease to function altogether in the adult.In the most primitive vertebrates, the hagfish and lampreys, the kidney is unusually simple: it consists of a row of nephrons, each emptying directly into the archinephric duct.\n\nInvertebrates may possess excretory organs that are sometimes referred to as \"kidneys\", but, even in Amphioxus, these are never homologous with the kidneys of vertebrates, and are more accurately referred to by other names, such as nephridia.\n\nIn amphibians, kidneys and the urinary bladder harbour specialized parasites, monogeneans of the family Polystomatidae.The kidneys of reptiles consist of a number of lobules arranged in a broadly linear pattern.\n\nEach lobule contains a single branch of the ureter in its centre, into which the collecting ducts empty.\n\nReptiles have relatively few nephrons compared with other amniotes of a similar size, possibly because of their lower metabolic rate.Birds have relatively large, elongated kidneys, each of which is divided into three or more distinct lobes.\n\nThe lobes consists of several small, irregularly arranged, lobules, each centred on a branch of the ureter.\n\nBirds have small glomeruli, but about twice as many nephrons as similarly sized mammals.The human kidney is fairly typical of that of mammals.\n\nDistinctive features of the mammalian kidney, in comparison with that of other vertebrates, include the presence of the renal pelvis and renal pyramids and a clearly distinguishable cortex and medulla.\n\nThe latter feature is due to the presence of elongated loops of Henle; these are much shorter in birds, and not truly present in other vertebrates (although the nephron often has a short intermediate segment between the convoluted tubules).\n\nIt is only in mammals that the kidney takes on its classical \"kidney\" shape, although there are some exceptions, such as the multilobed reniculate kidneys of pinnipeds and cetaceans.\n\n=== Evolutionary adaptation ===\n\nKidneys of various animals show evidence of evolutionary adaptation and have long been studied in ecophysiology and comparative physiology.\n\nKidney morphology, often indexed as the relative medullary thickness, is associated with habitat aridity among species of mammals and diet (e.g., carnivores have only long loops of Henle).\n\n== Society and culture ==\n\n=== Significance ===\n\n==== Egyptian ====\n\nIn ancient Egypt, the kidneys, like the heart, were left inside the mummified bodies, unlike other organs which were removed.\n\nComparing this to the biblical statements, and to drawings of human body with the heart and two kidneys portraying a set of scales for weighing justice, it seems that the Egyptian beliefs had also connected the kidneys with judgement and perhaps with moral decisions.\n\n==== Hebrew ====\n\nAccording to studies in modern and ancient Hebrew, various body organs in humans and animals served also an emotional or logical role, today mostly attributed to the brain and the endocrine system.\n\nThe kidney is mentioned in several biblical verses in conjunction with the heart, much as the bowels were understood to be the \"seat\" of emotion – grief, joy and pain.\n\nSimilarly, the Talmud (Berakhoth 61.a) states that one of the two kidneys counsels what is good, and the other evil.\nIn the sacrifices offered at the biblical Tabernacle and later on at the temple in Jerusalem, the priests were instructed to remove the kidneys and the adrenal gland covering the kidneys of the sheep, goat and cattle offerings, and to burn them on the altar, as the holy part of the \"offering for God\" never to be eaten.\n\n==== India: Ayurvedic system ====\n\nIn ancient India, according to the Ayurvedic medical systems, the kidneys were considered the beginning of the excursion channels system, the 'head' of the Mutra Srotas, receiving from all other systems, and therefore important in determining a person's health balance and temperament by the balance and mixture of the three 'Dosha's – the three health elements: Vatha (or Vata) – air, Pitta – bile, and Kapha – mucus.\n\nThe temperament and health of a person can then be seen in the resulting color of the urine.Modern Ayurveda practitioners, a practice which is characterized as pseudoscience, have attempted to revive these methods in medical procedures as part of Ayurveda Urine therapy.\n\nThese procedures have been called \"nonsensical\" by skeptics.\n\n==== Medieval Christianity ====\n\nThe Latin term renes is related to the English word \"reins\", a synonym for the kidneys in Shakespearean English (e.g.\n\nMerry Wives of Windsor 3.5), which was also the time when the King James Version of the Bible was translated.\n\nKidneys were once popularly regarded as the seat of the conscience and reflection, and a number of verses in the Bible (e.g.\n\nPs. 7:9, Rev. 2:23) state that God searches out and inspects the kidneys, or \"reins\", of humans, together with the heart.\n\n== History ==\n\nKidney stones have been identified and recorded about as long as written historical records exist.\n\nThe urinary tract including the ureters, as well as their function to drain urine from the kidneys, has been described by Galen in the second century AD.The first to examine the ureter through an internal approach, called ureteroscopy, rather than surgery was Hampton Young in 1929.\n\nThis was improved on by VF Marshall who is the first published use of a flexible endoscope based on fiber optics, which occurred in 1964.\n\nThe insertion of a drainage tube into the renal pelvis, bypassing the uterers and urinary tract, called nephrostomy, was first described in 1941.\n\nSuch an approach differed greatly from the open surgical approaches within the urinary system employed during the preceding two millennia.\n\nhttps://en.wikipedia.org/wiki/Kidney","urinary-bladder":"The urinary bladder, or simply bladder, is a hollow muscular organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination.\n\nIn humans the bladder is a hollow distensible organ that sits on the pelvic floor.\n\nUrine enters the bladder via the ureters and exits via the urethra.\n\nThe typical human bladder will hold between 300 and 500 ml before the urge to empty occurs, but can hold considerably more.\n\nThe Latin phrase for \"urinary bladder\" is vesica urinaria, and the term vesical or prefix vesico - appear in connection with associated structures such as vesical veins.\n\nThe modern Latin word for \"bladder\" – cystis – appears in associated terms such as cystitis (inflammation of the bladder).\n\n== Structure ==\n\nIn humans, the bladder is a hollow muscular organ situated at the base of the pelvis.\n\nIn gross anatomy, the bladder can be divided into a broad fundus, a body, an apex, and a neck.\n\nThe apex is directed forward toward the upper part of the pubic symphysis, and from there the median umbilical ligament continues upward on the back of the anterior abdominal wall to the umbilicus.\n\nThe peritoneum is carried by it from the apex on to the abdominal wall to form the middle umbilical fold.\n\nThe neck of the bladder is the area at the base of the trigone that surrounds the internal urethral orifice that leads to the urethra.\n\nIn males the neck of the urinary bladder is next to the prostate gland.\nThe bladder has three openings.\n\nThe two ureters enter the bladder at ureteric orifices, and the urethra enters at the trigone of the bladder.\n\nThese ureteric openings have mucosal flaps in front of them that act as valves in preventing the backflow of urine into the ureters, known as vesicoureteral reflux.\n\nBetween the two ureteric openings is a raised area of tissue called the interureteric crest.\n\nThis makes the upper boundary of the trigone.\n\nThe trigone is an area of smooth muscle that forms the floor of the bladder above the urethra.\n\nIt is an area of smooth tissue for the easy flow of urine into and from this part of the bladder - in contrast to the irregular surface formed by the rugae.\n\nThe walls of the bladder have a series of ridges, thick mucosal folds known as rugae that allow for the expansion of the bladder.\n\nThe detrusor muscle is the muscular layer of the wall made of smooth muscle fibers arranged in spiral, longitudinal, and circular bundles.\n\nThe detrusor muscle is able to change its length.\n\nIt can also contract for a long time whilst voiding, and it stays relaxed whilst the bladder is filling.\n\nThe wall of the urinary bladder is normally 3–5 mm thick.\n\nWhen well distended, the wall is normally less than 3 mm.\n\n=== Nearby structures ===\n\nIn men, the prostate gland lies outside the opening for the urethra.\n\nThe middle lobe of the prostate causes an elevation in the mucous membrane behind the internal urethral orifice called the uvula of urinary bladder.\n\nThe uvula can enlarge when the prostate becomes enlarged.\nThe bladder is located below the peritoneal cavity near the pelvic floor and behind the pubic symphysis.\n\nIn men, it lies in front of the rectum, separated by the recto-vesical pouch, and is supported by fibres of the levator ani and of the prostate gland.\n\nIn women, it lies in front of the uterus, separated by the vesico-uterine pouch, and is supported by the elevator ani and the upper part of the vagina.\n\n=== Blood and lymph supply ===\n\nThe bladder receives blood by the vesical arteries and drained into a network of vesical veins.\n\nThe superior vesical artery supplies blood to the upper part of the bladder.\n\nThe lower part of the bladder is supplied by the inferior vesical artery, both of which are branches of the internal iliac arteries.\n\nIn females, the uterine and vaginal arteries provide additional blood supply.\n\nVenous drainage begins in a network of small vessels on the lower lateral surfaces of the bladder, which coalesce and travel with the lateral ligaments of the bladder into the internal iliac veins.\n\nThe lymph drained from the bladder begins in a series of networks throughout the mucosal, muscular and serosal layers.\n\nThese then form three sets of vessels: one set near the trigone draining the bottom of the bladder; one set draining the top of the bladder; and another set draining the outer undersurface of the bladder.\n\nThe majority of these vessels drain into the external iliac lymph nodes.\n\n=== Nerve supply ===\n\nThe bladder receives both sensory and motor supply from sympathetic and the parasympathetic nervous systems.\n\nThe motor supply from both sympathetic fibers, most of which arise from the superior and inferior hypogastric plexuses and nerves, and from parasympathetic fibers, which come from the pelvic splanchnic nerves.Sensation from the bladder, relating to distension or to irritation (such as by infection or a stone) is transmitted primarily through the parasympathetic nervous system.\n\nThese travel via sacral nerves to S2-4.\n\nFrom here, sensation travels to the brain via the dorsal columns in the spinal cord.\n\n=== Microanatomy ===\n\nWhen viewed under a microscope the bladder can be seen to have an inner lining (called epithelium), three layers of muscle fibres, and an outer adventitia.\n\nThe inner wall of the bladder is called urothelium, a type of transitional epithelium formed by three to six layers of cells; the cells may become more cuboidal or flatter depending on whether the bladder is empty or full.\n\nAdditionally, these are lined with a mucous membrane consisting of a surface glycocalyx that protects the cells beneath it from urine.\n\nThe epithelium lies on a thin basement membrane, and a lamina propria.\n\nThe mucosal lining also offers a urothelial barrier against the passing of infections.\n\nThese layers are surrounded by three layers of muscle fibres arranged as an inner layer of fibres orientated longitudinally, a middle layer of circular fibres, and an outermost layer of longitudinal fibres; these form the detrusor muscle, which can be seen with the naked eye.The outside of the bladder is protected by a serous membrane called adventitia.\n\n=== Development ===\n\nIn the developing embryo, at the hind end lies a cloaca.\n\nThis, over the fourth to the seventh week, divides into a urogenital sinus and the beginnings of the anal canal, with a wall forming between these two inpouchings called the urorectal septum.\n\nThe urogenital sinus divides into three parts, with the upper and largest part becoming the bladder; the middle part becoming the urethra, and the lower part changes depending on the biological sex of the embryo.The human urinary bladder derives from the urogenital sinus, and it is initially continuous with the allantois.\n\nThe upper and lower parts of the bladder develop separately and join together around the middle part of development.\n\nAt this time the ureters move from the mesonephric ducts to the trigone.\n\nIn males, the base of the bladder lies between the rectum and the pubic symphysis.\n\nIt is superior to the prostate, and separated from the rectum by the recto-vesical pouch.\n\nIn females, the bladder sits inferior to the uterus and anterior to the vagina; thus its maximum capacity is lower than in males.\n\nIt is separated from the uterus by the vesico-uterine pouch.\n\nIn infants and young children the urinary bladder is in the abdomen even when empty.\n\n== Function ==\n\nUrine, excreted by the kidneys, collects in the bladder because of drainage from two ureters, before disposal by urination (micturition).\n\nUrine leaves the bladder via the urethra, a single muscular tube ending in an opening called the urinary meatus, where it exits the body.\n\nUrination involves coordinated muscle changes involving a reflex based in the spine, with higher inputs from the brain.\n\nDuring urination, the detrusor muscle contracts, and the external urinary sphincter and muscles of the perineum relax, allowing urine to pass through the urethra and out of the body.\n\nThe urge to pass urine stems from stretch receptors that activate when between 300 - 400 mL urine is held within the bladder.\n\nAs urine accumulates, the rugae flatten and the wall of the bladder thins as it stretches, allowing the bladder to store larger amounts of urine without a significant rise in internal pressure.\n\nUrination is controlled by the pontine micturition center in the brainstem.Stretch receptors in the bladder signal the parasympathetic nervous system to stimulate the muscarinic receptors in the detrusor to contract the muscle when the bladder is distended.\n\nThis encourages the bladder to expel urine through the urethra.\n\nThe main receptor activated is the M3 receptor, although M2 receptors are also involved and whilst outnumbering the M3 receptors they are not so responsive.\n\nThe main relaxant pathway is via the adenylyl cyclase cAMP pathway, activated via the β3 adrenergic receptors.\n\nThe β2 adrenergic receptors are also present in the detrusor and even outnumber β3 receptors, but they do not have as important an effect in relaxing the detrusor smooth muscle.\n\n== Clinical significance ==\n\n=== Inflammation and infection ===\n\nCystitis refers to infection or inflammation of the bladder.\n\nIt commonly occurs as part of a urinary tract infection.\n\nIn adults, it is more common in women than men, owing to a shorter urethra.\n\nIt is common in males during childhood, and in older men where an enlarged prostate may cause urinary retention.\n\nOther risk factors include other causes of blockage or narrowing, such as prostate cancer or the presence of vesico-ureteric reflux; the presence of outside structures in the urinary tract, such as urinary catheters; and neurologic problems that make passing urine difficult.\n\nInfections that involve the bladder can cause pain in the lower abdomen (above the pubic symphysis, so called \"suprapubic\" pain), particularly before and after passing urine, and a desire to pass urine frequently and with little warning (urinary urgency).\n\nInfections are usually due to bacteria, of which the most common is E coli.When a urinary tract infection or cystitis is suspected, a medical practitioner may request a urine sample.\n\nA dipstick placed in the urine may be used to see if the urine has white blood cells, or the presence of nitrates which may indicate an infection.\n\nThe urine specimen may be also sent for microbial culture and sensitivity to assess if a particular bacteria grows in the urine, and identify its antibiotic sensitivities.\n\nSometimes, additional investigations may be requested.\n\nThese might include testing the function of the kidneys by assessing electrolytes and creatinine; investigating for blockages or narrowing of the renal tract with a ultrasound, and testing for an enlarged prostate with a digital rectal examination.\n\nUrinary tract infections or cystitis are treated with antibiotics, many of which are consumed by mouth.\n\nSerious infections may require treatment with intravenous antibiotics.Interstitial cystitis refers to a condition in which the bladder is infected due to a cause that is not bacteria.\n\n=== Incontinence and retention ===\n\nFrequent urination can be due to excessive urine production, small bladder capacity, irritability or incomplete emptying.\n\nMales with an enlarged prostate urinate more frequently.\n\nOne definition of an overactive bladder is when a person urinates more than eight times per day.\n\nAn overactive bladder can often cause urinary incontinence.\n\nThough both urinary frequency and volumes have been shown to have a circadian rhythm, meaning day and night cycles, it is not entirely clear how these are disturbed in the overactive bladder.\n\nUrodynamic testing can help to explain the symptoms.\n\nAn underactive bladder is the condition where there is a difficulty in passing urine and is the main symptom of a neurogenic bladder.\n\nFrequent urination at night may indicate the presence of bladder stones.\nDisorders of or related to the bladder include:\n\nBladder exstrophy\nBladder sphincter dyssynergia, a condition in which the sufferer cannot coordinate relaxation of the urethra sphincter with the contraction of the bladder muscles\nParuresis\nTrigonitis\nUrinary retention\n\nDisorders of bladder function may be dealt with surgically, by re-directing the flow of urine or by replacement with an artificial urinary bladder.\n\nThe volume of the bladder may be increased by bladder augmentation.\n\nAn obstruction of the bladder neck may be severe enough to warrant surgery.\n\n=== Cancer ===\n\nCancer of the bladder is known as bladder cancer.\n\nIt is usually due to cancer of the urothelium, the cells that line the surface of the bladder.\n\nBladder cancer is more common after the age of 40, and more common in men than women; other risk factors include smoking and exposure to dyes such as aromatic amines and aldehydes.\n\nWhen cancer is present, the most common symptom in an affected person is blood in the urine; a physical medical examination may be otherwise normal, except in late disease.\n\nBladder cancer is most often due to cancer of the cells lining the ureter, called transitional cell carcinoma, although it can more rarely occur as a squamous cell carcinoma if the type of cells lining the urethra have changed due to chronic inflammation, such as due to stones or schistosomiasis.\n\nInvestigations performed usually include collecting a sample of urine for an inspection for malignant cells under a microscope, called cytology, as well as medical imaging by a CT urogram or ultrasound.\n\nIf a concerning lesion is seen, a flexible camera may be inserted into the bladder, called cystoscopy, in order to view the lesion and take a biopsy, and a CT scan will be performed of other body parts (a CT scan of the chest, abdomen and pelvis) to look for additional metastatic lesions.Treatment depends on the cancer's stage.\n\nCancer present only in the bladder may be removed surgically via cystoscopy; an injection of the chemotherapeutic mitomycin C may be performed at the same time.\n\nCancers that are high grade may be treated with an injection of the BCG vaccine into the bladder wall, and may require surgical removal if it does not resolve.\n\nCancer that is invading through the bladder wall may be managed by complete surgical removal of the bladder (radical cystectomy), with the ureters diverted into a segment of part of ileum connected to a stoma bag on the skin.\n\nPrognosis can vary markedly depending on the cancer's stage and grade, with a better prognosis associated with tumours found only in the bladder, that are low grade, that don't invade through the bladder wall, and that is papillary in visual appearance.\n\n=== Investigation ===\n\nA number of investigations are used to examine the bladder.\n\nThe investigations that are ordered will depend on the taking of a medical history and an examination.\n\nThe examination may involve a medical practitioner feeling in the suprapubic area for tenderness or fullness that might indicate an inflamed or full bladder.\n\nBlood tests may be ordered that may indicate inflammation; for example a full blood count may demonstrate elevated white blood cells, or a C-reactive protein may be elevated in an infection.Some forms of medical imaging exist to visualise the bladder.\n\nA bladder ultrasound may be conducted to view how much urine is within the bladder, indicating urinary retention.\n\nA urinary tract ultrasound, conducted by a more trained operator, may be conducted to view whether there are stones, tumours or sites of obstruction within the bladder and urinary tract.\n\nA CT scan may also be ordered.\nA flexible internal camera, called a cystoscope, can be inserted to view the internal appearance of the bladder and take a biopsy if required.\nUrodynamic testing can help to explain the symptoms.\n\n== Other animals ==\n\n=== Mammals ===\n\nAll mammals have a urinary bladder.\n\nThis structure begins as an embryonic cloaca.\n\nIn the vast majority, this eventually becomes differentiated into a dorsal part connected to the intestine and a ventral part which becomes associated with the urinogenital passage and urinary bladder.\n\nThe only mammals in which this does not take place are the platypus and the spiny anteater both of which retain the cloaca into adulthood.The mammalian bladder is an organ that regularly stores a hyperosmotic concentration of urine.\n\nIt therefore is relatively impermeable and has multiple epithelial layers.\n\nThe urinary bladder of the cetaceans (whales and dolphins) is proportionally smaller than that of land-dwelling mammals.\n\n=== Reptiles ===\n\nIn all reptiles, the urinogenital ducts and the anus both empty into an organ called a cloaca.\n\nIn some reptiles, a midventral wall in the cloaca may open into a urinary bladder, but not all.\n\nIt is present in all turtles and tortoises as well as most lizards but is lacking in the monitor lizard, the legless lizards.\n\nIt is absent in the snakes, alligators, and crocodiles.: p. 474 Many turtles, tortoises, and lizards have proportionally very large bladders.\n\nCharles Darwin noted that the Galapagos tortoise had a bladder which could store up to 20% of its body weight.\n\nSuch adaptations are the result of environments such as remote islands and deserts where water is very scarce.\n\nOther desert-dwelling reptiles have large bladders that can store a long-term reservoir of water for up to several months and aid in osmoregulation.\n\nTurtles have two or more accessory urinary bladders, located lateral to the neck of the urinary bladder and dorsal to the pubis, occupying a significant portion of their body cavity.\n\nTheir bladder is also usually bilobed with a left and right section.\n\nThe right section is located under the liver, which prevents large stones from remaining in that side while the left section is more likely to have calculi.\n\n=== Amphibians ===\n\nMost aquatic and semi-aquatic amphibians have a membranous skin which allows them to absorb water directly through it.\n\nSome semi-aquatic animals also have similarly permeable bladder membrane.\n\nAs a result, they tend to have high rates of urine production to offset this high water intake, and have urine which is low in dissolved salts.\n\nThe urinary bladder assists such animals to retain salts.\n\nSome aquatic amphibian such as Xenopus do not reabsorb water, to prevent excessive water influx.\n\nFor land-dwelling amphibians, dehydration results in reduced urine output.The amphibian bladder is usually highly distensible and among some land-dwelling species of frogs and salamanders may account for between 20% and 50% of their total body weight.\n\n=== Fish ===\n\nThe gills of most teleost fish help to eliminate ammonia from the body, and fish live surrounded by water, but most still have a distinct bladder for storing waste fluid.\n\nThe urinary bladder of teleosts is permeable to water, though this is less true for freshwater dwelling species than saltwater species.\n\nMost fish also have an organ called a swim-bladder which is unrelated to the urinary bladder except in its membranous nature.\n\nThe loaches, pilchards, and herrings are among the few types of fish in which a urinary bladder is poorly developed.\n\nIt is largest in those fish which lack an air bladder, and is situated in front of the oviducts and behind the rectum.\n\n=== Birds ===\n\nIn nearly all bird species, there is no urinary bladder per se.\n\nAlthough all birds have kidneys, the ureters open directly into a cloaca which serves as a reservoir for urine, fecal matter, and eggs.\n\n=== Crustaceans ===\n\nUnlike the urinary bladder of vertebrates, the urinary bladder of crustaceans both stores and modifies urine.\n\nThe bladder consists of two sets of lateral and central lobes.\n\nThe central lobes sit near the digestive organs and the lateral lobes extend along the front and sides of the crustacean's body cavity.\n\nThe tissue of the bladder is thin epithelium.\n\nhttps://en.wikipedia.org/wiki/Urinary_bladder","renal-pelvis":"The renal pelvis or pelvis of the kidney is the funnel-like dilated part of the ureter in the kidney.\n\nIn humans, the renal pelvis is the point where the two or three major calyces join.\n\nIt has a mucous membrane and is covered with transitional epithelium and an underlying lamina propria of loose-to-dense connective tissue.\nThe renal pelvis functions as a funnel for urine flowing to the ureter.\nThe renal pelvis is the location of several kinds of kidney cancer and is affected by infection in pyelonephritis.\n\n== Clinical significance ==\n\nThe renal pelvis is the location of several kinds of kidney cancer and is affected by infection in pyelonephritis.\n\nA large \"staghorn\" kidney stone may block all or part of the renal pelvis.\nThe size of the renal pelvis plays a major role in the grading of hydronephrosis.\n\nNormally, the anteroposterior diameter of the renal pelvis is less than 4 mm in fetuses up to 32 weeks of gestational age and 7 mm afterwards.\n\nIn adults, 13% of the normal population have a transverse pelvic diameter of over 10 mm.\n\n== Etymology and pronunciation ==\n\nLike the bony pelvis, the renal pelvis () gets its English name via New Latin from the older Latin word pelvis, \"basin\", as in \"wash basin\".\n\nIn both cases the name reflects the shape of the structure, and in the case of the renal pelvis, it also reflects the function.\n\nThe name reflects that each renal pelvis collects urine from the calyces and funnels it into the ureter like a wash basin collects water and funnels it into a drain pipe.\n\nThe renal pelvis is occasionally called the pyelum (from Greek πύελος pýelos, \"trough\", ‘anything hollow’), and the combining form pyelo- denotes the renal pelvis (pyelo- is not to be confused with pyo-).\n\nThe words infundibulum and choana are other words for funnel-shaped cavities (which medical English got from the Latin and Greek words for \"funnel\", respectively), and the renal pelvis is sometimes called the renal infundibulum.\n\nThe form *renal choana is logical but is not used.\n\nhttps://en.wikipedia.org/wiki/Renal_pelvis","testis":"TESTICLE\n\nTesticle or testis (plural testes) is the male reproductive gland or gonad in all animals, including humans.\n\nIt is homologous to the female ovary.\n\nThe functions of the testes are to produce both sperm and androgens, primarily testosterone.\n\nTestosterone release is controlled by the anterior pituitary luteinizing hormone, whereas sperm production is controlled both by the anterior pituitary follicle-stimulating hormone and gonadal testosterone.\n\n== Structure ==\n\n=== Appearance ===\n\nMales have two testicles of similar size contained within the scrotum, which is an extension of the abdominal wall.\n\nScrotal asymmetry is not unusual: one testicle extends farther down into the scrotum than the other due to differences in the anatomy of the vasculature.\n\n=== Measurement ===\n\nThe volume of the testicle can be estimated by palpating it and comparing it to ellipsoids of known sizes.\n\nAnother method is to use calipers (an orchidometer) or a ruler either on the person or on an ultrasound image to obtain the three measurements of the x, y, and z axes (length, depth and width).\n\nThese measurements can then be used to calculate the volume, using the formula for the volume of an ellipsoid:\n\nAn average adult testicle measures up to 5 cm × 2 cm × 3 cm (2 in × 3⁄4 in × 1+1⁄4 in).\n\nThe Tanner scale for the maturity of male genitals assigns a maturity stage to the calculated volume ranging from stage I, a volume of less than 1.5 cm3; to stage V, a volume greater than 20 cm3.\n\nNormal volume is 15 to 25 cm3; the average is 18 cm3 per testis (range 12–30 cm3).\n\n=== Internal structure ===\n\n==== Duct system ====\n\nThe testes are covered by a tough membranous shell called the tunica albuginea.\n\nWithin the testes are very fine coiled tubes called seminiferous tubules.\n\nThe tubules are lined with a layer of cells (germ cells) that develop from puberty through old age into sperm cells (also known as spermatozoa or male gametes).\n\nThe developing sperm travel through the seminiferous tubules to the rete testis located in the mediastinum testis, to the efferent ducts, and then to the epididymis where newly created sperm cells mature (see spermatogenesis).\n\nThe sperm move into the vas deferens, and are eventually expelled through the urethra and out of the urethral orifice through muscular contractions.\n\n==== Primary cell types ====\n\nWithin the seminiferous tubules, the germ cells develop into spermatogonia, spermatocytes, spermatids and spermatozoon through the process of spermatogenesis.\n\nThe gametes contain DNA for fertilization of an ovum Sertoli cells – the true epithelium of the seminiferous epithelium, critical for the support of germ cell development into spermatozoa.\n\nSertoli cells secrete inhibin.\n\nPeritubular myoid cells surround the seminiferous tubules.Between tubules (interstitial cells), exist Leydig cells – cells localized between seminiferous tubules that produce and secrete testosterone and other androgens important for sexual development and puberty, secondary sexual characteristics like facial hair, sexual behavior and libido.\n\nThey also support spermatogenesis and erectile function.\n\nTestosterone controls testicular volume.\nImmature Leydig cells and interstitial macrophages and epithelial cells are also present.\n\n==== Blood supply and lymphatic drainage ====\n\nBlood supply and lymphatic drainage of the testes and scrotum are distinct:\n\nThe paired testicular arteries arise directly from the abdominal aorta and descend through the inguinal canal, while the scrotum and the rest of the external genitalia is supplied by the internal pudendal artery (itself a branch of the internal iliac artery).\n\nThe testis has collateral blood supply from\n1. the cremasteric artery (a branch of the inferior epigastric artery, which is a branch of the external iliac artery),\nand\n2. the artery to the ductus deferens (a branch of the inferior vesical artery, which is a branch of the internal iliac artery).\n\nTherefore, if the testicular artery is ligated, e.g., during a Fowler-Stevens orchiopexy for a high undescended testis, the testis will usually survive on these other blood supplies.\n\nLymphatic drainage of the testes follows the testicular arteries back to the paraaortic lymph nodes, while lymph from the scrotum drains to the inguinal lymph nodes.\n\n==== Layers ====\n\nMany anatomical features of the adult testis reflect its developmental origin in the abdomen.\n\nThe layers of tissue enclosing each testicle are derived from the layers of the anterior abdominal wall.\n\nNotably, the cremasteric muscle arises from the internal oblique muscle.\n\n==== The blood–testis barrier ====\n\nLarge molecules cannot pass from the blood into the lumen of a seminiferous tubule due to the presence of tight junctions between adjacent Sertoli cells.\n\nThe spermatogonia are in the basal compartment (deep to the level of the tight junctions) and the more mature forms such as primary and secondary spermatocytes and spermatids are in the adluminal compartment.\n\nThe function of the blood–testis barrier may be to prevent an auto-immune reaction.\n\nMature sperm (and their antigens) arise long after immune tolerance is established in infancy.\n\nSince sperm are antigenically different from self tissue, a male animal can react immunologically to his own sperm.\n\nHe is capable of making antibodies against them.\n\nInjection of sperm antigens causes inflammation of the testis (auto-immune orchitis) and reduced fertility.\n\nThe blood–testis barrier may reduce the likelihood that sperm proteins will induce an immune response, reducing fertility and so progeny.\n\n=== Temperature regulation ===\n\nSpermatogenesis is enhanced at temperatures slightly less than core body temperature.\n\nThe spermatogenesis is less efficient at lower and higher temperatures than 33 °C.\n\nBecause the testes are located outside the body, the smooth tissue of the scrotum can move them closer or further away from the body.\n\nThe temperature of the testes is maintained at 35 degrees Celsius (95 degrees Fahrenheit), i.e. two degrees below the body temperature of 37 degrees Celsius (98.6 degrees Fahrenheit).\n\nHigher temperatures affect spermatogenesis.\n\nThere are a number of mechanisms to maintain the testes at the optimum temperature.\n\nThe cremasteric muscle is part of the spermatic cord.\n\nWhen this muscle contracts, the cord is shortened and the testicle is moved closer up toward the body, which provides slightly more warmth to maintain optimal testicular temperature.\n\nWhen cooling is required, the cremasteric muscle relaxes and the testicle is lowered away from the warm body and is able to cool.\n\nContraction also occurs in response to stress (the testicles rise up toward the body in an effort to protect them in a fight).\n\nThe cremaster muscle can reflexively raise each testicle individually if properly triggered.\n\nThis phenomenon is known as the cremasteric reflex.\n\nThe testicles can also be lifted voluntarily using the pubococcygeus muscle, which partially activates related muscles.\n\n=== Gene and protein expression ===\n\nThe human genome includes approximately 20,000 protein coding genes: 80% of these genes are expressed in adult testes.\n\nThe testes have the highest fraction of tissue type-specific genes compared to other organs and tissues: about 1000 of them are highly specific for the testes, and about 2,200 show an elevated pattern of expression here.\n\nA majority of these genes encode for proteins that are expressed in the seminiferous tubules and have functions related to spermatogenesis.\n\nSperm cells express proteins that result in the development of flagella; these same proteins are expressed in the female in cells lining the fallopian tube, and cause the development of cilia.\n\nIn other words, sperm cell flagella and Fallopian tube cilia are homologous structures.\n\nThe testis-specific proteins that show the highest level of expression are protamines.\n\n== Development ==\n\nThere are two phases in which the testes grow substantially; namely in embryonic and pubertal age.\n\n=== Embryonic ===\n\nDuring mammalian development, the gonads are at first capable of becoming either ovaries or testes.\n\nIn humans, starting at about week 4 the gonadal rudiments are present within the intermediate mesoderm adjacent to the developing kidneys.\n\nAt about week 6, sex cords develop within the forming testes.\n\nThese are made up of early Sertoli cells that surround and nurture the germ cells that migrate into the gonads shortly before sex determination begins.\n\nIn males, the sex-specific gene SRY that is found on the Y-chromosome initiates sex determination by downstream regulation of sex-determining factors, (such as GATA4, SOX9 and AMH), which leads to development of the male phenotype, including directing development of the early bipotential gonad down the male path of development.\n\nTestes follow the \"path of descent\" from high in the posterior fetal abdomen to the inguinal ring and beyond to the inguinal canal and into the scrotum.\n\nIn most cases (97% full-term, 70% preterm), both testes have descended by birth.\n\nIn most other cases, only one testis fails to descend (cryptorchidism) and that will probably express itself within a year.\n\n=== Pubertal ===\n\nThe testes grow in response to the start of spermatogenesis.\n\nSize depends on lytic function, sperm production (amount of spermatogenesis present in testis), interstitial fluid, and Sertoli cell fluid production.\n\nAfter puberty, the volume of the testes can be increased by over 500% as compared to the pre-pubertal size.\n\nTesticles are fully descended before one reaches puberty.\n\n== Clinical significance ==\n\n=== Protection and injury ===\n\nThe testicles are well known to be very sensitive to impact and injury.\n\nThe pain involved travels up from each testicle into the abdominal cavity, via the spermatic plexus, which is the primary nerve of each testicle.\n\nThis will cause pain in the hip and the back.\nThe pain usually goes away in a few minutes.\n\nTesticular torsion is a medical emergency.\n\nTesticular rupture is a medical emergency caused by blunt force impact, sharp edge, or piercing impact to one or both testicles, which can lead to necrosis of the testis in as little as 30 minutes.\n\nPenetrating injuries to the scrotum may cause castration, or physical separation or destruction of the testes, possibly along with part or all of the penis, which results in total sterility if the testicles are not reattached quickly.\n\nSome jockstraps are designed to provide support to the testicles.\n\n=== Diseases and conditions ===\n\n-Testicular cancer and other neoplasms –\n\nTo improve the chances of catching possible cases of testicular cancer or other health issues early, regular testicular self-examination is recommended.\n\n-Varicocele, swollen vein(s) from the testes, usually affecting the left side, the testis usually being normal.\n\n-Hydrocele testis, swelling around testes caused by accumulation of clear liquid within a membranous sac, the testis usually being normal\n\n-Spermatocele, a retention cyst of a tubule of the rete testis or the head of the epididymis distended with barely watery fluid that contains spermatozoa.\n\n-Endocrine disorders can also affect the size and function of the testis.\n\n-Certain inherited conditions involving mutations in key developmental genes also impair testicular descent, resulting in abdominal or inguinal testes which remain nonfunctional and may become cancerous.\n\n-Other genetic conditions can result in the loss of the Wolffian ducts and allow for the persistence of Müllerian ducts.\n\n-Both excess and deficient levels of estrogens can disrupt spermatogenesis and cause infertility.\n\n-Bell-clapper deformity is a deformity in which the testicle is not attached to the scrotal walls, and can rotate freely on the spermatic cord within the tunica vaginalis.\n\nIt is the most common underlying cause of testicular torsion.\n\n-Orchitis inflammation of the testicles\n-Epididymitis, a painful inflammation of the epididymis or epididymides frequently caused by bacterial infection but sometimes of unknown origin.\n-Anorchia, the absence of one or both testicles.\n-Cryptorchidism or \"undescended testicles\", when the testicle does not descend into the scrotum of the infant boy.\n-Testicular enlargement is an unspecific sign of various testicular diseases, and can be defined as a testicular size of more than 5 cm (long axis) × 3 cm (short axis).\n-Blue balls is a slang term for a temporary fluid congestion in the testicles and prostate region caused by prolonged sexual arousal.\n-Testicular prostheses are available to mimic the appearance and feel of one or both testicles, when absent as from injury or as treatment in association to gender dysphoria.\n\nThere have also been some instances of their implantation in dogs.\n\n=== Effects of exogenous hormones ===\n\nTo some extent, it is possible to change testicular size.\n\nShort of direct injury or subjecting them to adverse conditions, e.g., higher temperature than they are normally accustomed to, they can be shrunk by competing against their intrinsic hormonal function through the use of externally administered steroidal hormones.\n\nSteroids taken for muscle enhancement (especially anabolic steroids) often have the undesired side effect of testicular shrinkage.\n\nSimilarly, stimulation of testicular functions via gonadotropic-like hormones may enlarge their size.\n\nTestes may shrink or atrophy during hormone replacement therapy or through chemical castration.\n\nIn all cases, the loss in testes volume corresponds with a loss of spermatogenesis.\n\n== Society and culture ==\n\nThe testicles of calves, lambs, roosters, turkeys, and other animals are eaten in many parts of the world, often under euphemistic culinary names.\n\nTesticles are a by-product of the castration of young animals raised for meat, so they were probably a late-spring seasonal specialty, though nowadays they are generally frozen and available year-round.\n\nAs early as 330 BC, Aristotle prescribed the ligation (tying off) of the left testicle in men wishing to have boys.\n\nIn the Middle Ages, men who wanted a boy sometimes had their left testicle removed.\n\nThis was because people believed that the right testicle made \"boy\" sperm and the left made \"girl\" sperm.\n\n== Etymology and slang ==\n\nOne theory about the etymology of the word testis is based on Roman law.\n\nThe original Latin word testis, \"witness\", was used in the firmly established legal principle \"Testis unus, testis nullus\" (one witness [equals] no witness), meaning that testimony by any one person in court was to be disregarded unless corroborated by the testimony of at least another.\n\nThis led to the common practice of producing two witnesses, bribed to testify the same way in cases of lawsuits with ulterior motives.\n\nSince such \"witnesses\" always came in pairs, the meaning was accordingly extended, often in the diminutive (testiculus, testiculi).\n\nAnother theory says that testis is influenced by a loan translation, from Greek parastatēs \"defender (in law), supporter\" that is \"two glands side by side\".In slang, the testes are usually referred to as \"balls\" as a reference to blue balls.\n\nFrequently, \"nuts\" (sometimes intentionally misspelled as \"nutz\") are also a slang term for the testes due to the geometric resemblance, as evidenced by the various usages of the term \"Deez Nuts\", which include a satirical political candidate in 2016.\n\n== Other animals ==\n\n=== External appearance ===\n\nIn sharks, the testicle on the right side is usually larger, and in many bird and mammal species, the left may be the larger.\n\nThe primitive jawless fish have only a single testis, located in the midline of the body, although even this forms from the fusion of paired structures in the embryo.\n\nIn seasonal breeders, the weight of the testes often increases during the breeding season.\n\nThe testicles of a dromedary camel are 7–10 cm (2.8–3.9 in) long, 4.5 cm (1.8 in) deep and 5 cm (2.0 in) in width.\n\nThe right testicle is often smaller than the left.\n\n=== Location ===\n\n==== Internal ====\n\nThe basal condition for mammals is to have internal testes.\n\nThe testes of monotremes, xenarthrans, and elephants remain within the abdomen.\n\nThere are also some marsupials with external testes and Boreoeutherian mammals with internal testes, such as the rhinoceros.\n\nCetaceans such as whales and dolphins also have internal testes.\n\nAs external testes would increase drag in the water they have internal testes which are kept cool by special circulatory systems that cool the arterial blood going to the testes by placing the arteries near veins bringing cooled venous blood from the skin.\n\nIn odobenids and phocids, the location of the testes is para-abdominal, though otariids have scrotal testes.\n\n==== External ====\n\nBoreoeutherian land mammals, the large group of mammals that includes humans, have externalized testes.\n\nTheir testes function best at temperatures lower than their core body temperature.\n\nTheir testes are located outside of the body, suspended by the spermatic cord within the scrotum.\n\nThere are several hypotheses why most boreotherian mammals have external testes which operate best at a temperature that is slightly less than the core body temperature, e.g. that it is stuck with enzymes evolved in a colder temperature due to external testes evolving for different reasons, that the lower temperature of the testes simply is more efficient for sperm production.\n\n 1) More efficient.\n\nThe classic hypothesis is that cooler temperature of the testes allows for more efficient fertile spermatogenesis.\n\nIn other words, there are no possible enzymes operating at normal core body temperature that are as efficient as the ones evolved, at least none appearing in our evolution so far.\n\nThe early mammals had lower body temperatures and thus their testes worked efficiently within their body.\n\nHowever it is argued that boreotherian mammals have higher body temperatures than the other mammals and had to develop external testes to keep them cool.\n\nIt is argued that those mammals with internal testes, such as the monotremes, armadillos, sloths, elephants, and rhinoceroses, have a lower core body temperatures than those mammals with external testes.\n\nHowever, the question remains why birds despite having very high core body temperatures have internal testes and did not evolve external testes.\n\nIt was once theorized that birds used their air sacs to cool the testes internally, but later studies revealed that birds' testes are able to function at core body temperature.\n\nSome mammals which have seasonal breeding cycles keep their testes internal until the breeding season at which point their testes descend and increase in size and become external.\n\n 2) Irreversible adaptation to sperm competition.\n\nIt has been suggested that the ancestor of the boreoeutherian mammals was a small mammal that required very large testes (perhaps rather like those of a hamster) for sperm competition and thus had to place its testes outside the body.\n\nThis led to enzymes involved in spermatogenesis, spermatogenic DNA polymerase beta and recombinase activities evolving a unique temperature optimum, slightly less than core body temperature.\n\nWhen the boreoeutherian mammals then diversified into forms that were larger and/or did not require intense sperm competition they still produced enzymes that operated best at cooler temperatures and had to keep their testes outside the body.\n\nThis position is made less parsimonious by the fact that the kangaroo, a non-boreoeutherian mammal, has external testicles.\n\nThe ancestors of kangaroos might, separately from boreotherian mammals, have also been subject to heavy sperm competition and thus developed external testes, however, kangaroo external testes are suggestive of a possible adaptive function for external testes in large animals.\n\n 3) Protection from abdominal cavity pressure changes.\n\nOne argument for the evolution of external testes is that it protects the testes from abdominal cavity pressure changes caused by jumping and galloping.\n\n 4) Protection against DNA damage.\n\nMild, transient scrotal heat stress causes DNA damage, reduced fertility and abnormal embryonic development in mice.\n\nDNA strand breaks were found in spermatocytes recovered from testicles subjected to 40 °C or 42 °C for 30 minutes.\n\nThese findings suggest that the external location of the testicles provides the adaptive benefit of protecting spermatogenic cells from heat-induced DNA damage that could otherwise lead to infertility and germline mutation.\n\n=== Size ===\n\nThe relative size of testes is often influenced by mating systems.\n\nTesticular size as a proportion of body weight varies widely.\n\nIn the mammalian kingdom, there is a tendency for testicular size to correspond with multiple mates (e.g., harems, polygamy).\n\nProduction of testicular output sperm and spermatic fluid is also larger in polygamous animals, possibly a spermatogenic competition for survival.\n\nThe testes of the right whale are likely to be the largest of any animal, each weighing around 500 kg (1,100 lb).\n\nAmong the Hominidae, gorillas have little female promiscuity and sperm competition and the testes are small compared to body weight (0.03%).\n\nChimpanzees have high promiscuity and large testes compared to body weight (0.3%).\n\nHuman testicular size falls between these extremes (0.08%).Testis weight also varies in seasonal breeders like red foxes, golden jackals and coyotes.\n\n=== Internal structure ===\n\nUnder a tough membranous shell called the tunica albuginea, the testis of amniotes, as well as some teleost fish, contains very fine coiled tubes called seminiferous tubules.\n\nAmphibians and most fish do not possess seminiferous tubules.\n\nInstead, the sperm are produced in spherical structures called sperm ampullae.\n\nThese are seasonal structures, releasing their contents during the breeding season, and then being reabsorbed by the body.\n\nBefore the next breeding season, new sperm ampullae begin to form and ripen.\n\nThe ampullae are otherwise essentially identical to the seminiferous tubules in higher vertebrates, including the same range of cell types.\n\nhttps://en.wikipedia.org/wiki/Testicle","epididymis":"The epididymis (; plural: epididymides or ) is a tube that connects a testicle to a vas deferens in the male reproductive system.\n\nIt is present in all male reptiles, birds, and mammals.\n\nIt is a single, narrow, tightly-coiled tube in adult humans, 6 to 7 meters (20 to 23 ft) in length connecting the efferent ducts from the rear of each testicle to its vas deferens.\n\n== Structure ==\n\nThe epididymis can be divided into three main regions:\n\nThe head (Latin: caput).\n\nThe head of the epididymis receives spermatozoa via the efferent ducts of the mediastinium of the testis.\n\nIt is characterized histologically by a thick epithelium with long stereocilia (described below) and a little smooth muscle.\n\nIt is involved in absorbing fluid to make the sperm more concentrated.\n\nThe concentration of the sperm here is dilute.\nThe body (Latin: corpus).\n\nThis has an intermediate epithelium and smooth muscle thickness.\nThe tail (Latin: cauda).\n\nThis has the thinnest epithelium of the three regions and the greatest quantity of smooth muscle.In reptiles, there is an additional canal between the testis and the head of the epididymis and which receives the various efferent ducts.\n\nThis is, however, absent in all birds and mammals.\n\n=== Histology ===\n\nThe epididymis is covered by a two layered pseudostratified epithelium.\n\nThe epithelium is separated by a basement membrane from the connective tissue wall which has smooth muscle cells.\n\nThe major cell types in the epithelium are:\n\nPrincipal cells: columnar cells that, with the basal cells, form the majority of the epithelium.\n\nIn the caput (head) region these cells have long stereocilia that are tuft-like extensions that project into the lumen.\n\nThe sterocilia are much shorter in the cauda (tail) segment.\n\nThey also secrete carnitine, sialic acid, glycoproteins, and glycerylphosphorylcholine into the lumen.\nBasal cells: shorter, pyramid-shaped cells which contact the basal lamina but taper off before their apical surfaces reach the lumen.\n\nThese are thought to be undifferentiated precursors of principal cells.\nApical cells: predominantly found in the head region\nClear cells: predominant in the tail region\nIntraepithelial lymphocytes: distributed throughout the tissue.\nIntraepithelial macrophages\n\n==== Stereocilia ====\nThe stereocilia of the epididymis are long cytoplasmic projections that have an actin filament backbone.\n\nThese filaments have been visualized at high resolution using fluorescent phalloidin that binds to actin filaments.\nThe stereocilia in the epididymis are non-motile.\n\nThese membrane extensions increase the surface area of the cell, allowing for greater absorption and secretion.\n\nIt has been shown that epithelial sodium channel ENaC that allows the flow of Na+ ions into the cell is localized on stereocilia.Because sperm are initially non-motile as they leave the seminiferous tubules, large volumes of fluid are secreted to propel them to the epididymis.\n\nThe core function of the stereocilia is to resorb 90% of this fluid as the spermatozoa start to become motile.\n\nThis absorption creates a fluid current that moves the immobile sperm from the seminiferous tubules to the epididymis.\n\nSpermatozoa do not reach full motility until they reach the vagina, where the alkaline pH is neutralized by acidic vaginal fluids.\n\n=== Development ===\n\nIn the embryo, the epididymis develops from tissue that once formed the mesonephros, a primitive kidney found in many aquatic vertebrates.\n\nPersistence of the cranial end of the mesonephric duct will leave behind a remnant called the appendix of the epididymis.\n\nIn addition, some mesonephric tubules can persist as the paradidymis, a small body caudal to the efferent ductules.\nA Gartner's duct is a homologous remnant in the female.\n\n== Function ==\n\n=== Role in storage of sperm and ejaculant ===\n\nSpermatozoa formed in the testis enter the caput epididymis, progress to the corpus, and finally reach the cauda region, where they are stored.\n\nSperm entering the caput epididymis are incomplete—they lack the ability to swim forward (motility) and to fertilize an egg.\n\nEpididymal transit takes 2 to 6 days in humans and 10–13 in rodents.\n\nDuring their transit in the epididymis, sperm undergo maturation processes necessary for them to acquire motility and fertility.\n\nFinal maturation (capacitation) is completed in the female reproductive tract.\nThe epididymis secretes immobilin, a large glycoprotein that is responsible for the creating of the viscoelastic luminal environment that serves to mechanically immobilize spermatozoa until ejaculation.\n\nImmobilin is predominantly secreted into the proximal caput epididymis prior to the acquisition of the potential for sperm motility.\n\nDuring ejaculation, sperm flow from the cauda epididymis (which functions as a storage reservoir) into the vas deferens where they are propelled by the peristaltic action of muscle layers in the wall of the vas deferens, and are mixed with the diluting fluids of the prostate, seminal vesicles, and other accessory glands prior to ejaculation (forming semen).\n\n== Clinical significance ==\n\n=== Inflammation ===\n\nAn inflammation of the epididymis is called epididymitis.\n\nIt is much more common than testicular inflammation, termed orchitis.\n\n=== Surgical removal ===\n\nEpididymotomy is the placing of an incision into the epididymis and is sometimes considered as a treatment option for acute suppurating epididymitis.\nEpididymectomy is the surgical removal of the epididymis sometimes performed for post-vasectomy pain syndrome and for refractory cases of epididymitis.\nEpididymectomy is also performed for sterilization on some male animals of livestock species so they can be used to detect estrus in females ready for artificially insemination.\n\n== Gallery ==\n\n== Notes ==\n\nhttps://en.wikipedia.org/wiki/Epididymis","seminal-gland":"The seminal vesicles (also called vesicular glands, or seminal glands) are a pair of two convoluted tubular glands that lie behind the urinary bladder of some male mammals.\n\nThey secrete fluid that partly composes the semen.\n\nThe vesicles are 5–10 cm in size, 3–5 cm in diameter, and are located between the bladder and the rectum.\n\nThey have multiple outpouchings which contain secretory glands, which join together with the vas deferens as the ejaculatory duct.\n\nThey receive blood from the vesiculodeferential artery, and drain into the vesiculodeferential veins.\n\nThe glands are lined with column-shaped and cuboidal cells.\n\nThe vesicles are present in many groups of mammals, but not marsupials, monotremes or carnivores.\n\nInflammation of the seminal vesicles is called seminal vesiculitis, most often is due to bacterial infection as a result of a sexually transmitted disease or following a surgical procedure.\n\nSeminal vesiculitis can cause pain in the lower abdomen, scrotum, penis or peritoneum, painful ejaculation, and blood in the semen.\n\nIt is usually treated with antibiotics, although may require surgical drainage in complicated cases.\n\nOther conditions may affect the vesicles, including congenital abnormalities such as failure or incomplete formation, and, uncommonly, tumours.\n\nThe seminal vesicles have been described as early as the second century AD by Galen, although the vesicles only received their name much later, as they were initially described using the term from which the word prostate is derived.\n\n== Structure ==\n\nThe seminal vesicles are a pair of glands in males that are positioned below the urinary bladder and at the end of the vasa deferentia, where they enter the prostate.\n\nEach vesicle is a coiled and folded tube, with occasional outpouchings termed diverticula in its wall.\n\nThe lower part of the tube ends as a straight tube called the excretory duct which joins with the vas deferens of that side of the body to form an ejaculatory duct.\n\nThe ejaculatory ducts pass through the prostate gland before opening separately into the verumontanum of the prostatic urethra.\n\nThe vesicles are between 5–10 cm in size, 3–5 cm in diameter, and have a volume of around 13 mL.The vesicles receive blood supply from the vesiculodeferential artery, and also from the inferior vesical artery.\n\nThe vesiculodeferential artery arises from the umbilical arteries, which branch directly from the internal iliac arteries.\n\nBlood is drained into the vesiculodeferential veins and the inferior vesical plexus, which drain into the internal iliac veins.\n\nLymphatic drainage occurs along the venous routes, draining into the internal iliac nodes.The vesicles lie behind the bladder at the end of the vasa deferentia.\n\nThey lie in the space between the bladder and the rectum; the bladder and prostate lie in front, the tip of the ureter as it enters the bladder above, and Denonvilliers fascia and the rectum behind.\n\n=== Development ===\n\nIn the developing embryo, at the hind end lies a cloaca.\n\nThis, over the fourth to the seventh week, divides into a urogenital sinus and the beginnings of the anal canal, with a wall forming between these two inpouchings called the urorectal septum.\n\nTwo ducts form next to each other that connect to the urogenital sinus; the mesonephric duct and the paramesonephric duct, which go on to form the reproductive tracts of the male and female respectively.In the male, under the influence of testosterone, the mesonephric duct proliferates, forming the epididymis, ductus deferens and, via a small outpouching near the developing prostate, the seminal vesicles.\n\nSertoli cells secrete anti-mullerian hormone, which causes the paramesonephric duct to regress.\n\nThe development and maintenance of the seminal vesicles, as well as their secretion and size/weight, are highly dependent on androgens.\n\nThe seminal vesicles contain 5α-reductase, which metabolizes testosterone into its much more potent metabolite, dihydrotestosterone (DHT).\n\nThe seminal vesicles have also been found to contain luteinizing hormone receptors, and hence may also be regulated by the ligand of this receptor, luteinizing hormone.\n\n=== Microanatomy ===\n\nThe inner lining of the seminal vesicles (the epithelium) is made of a lining of interspersed column-shaped and cube-shaped cells.\n\nThere are varying descriptions of the lining as being pseudostratified and consisting of column-shaped cells only.\n\nWhen viewed under a microscope, the cells are seen to have large bubbles in their interior.\n\nThis is because their interior, called cytoplasm, contains lipid droplets involved in secretion during ejaculation.\n\nThe tissue of the seminal vesicles is full of glands, spaced irregularly.\n\nAs well as glands, the seminal vesicles contain smooth muscle and connective tissue.\n\nThis fibrous and muscular tissue surrounds the glands, helping to expel their contents.\n\nThe outer surface of the glands is covered in peritoneum.\n\n== Function ==\n\nThe seminal vesicles secrete a significant proportion of the fluid that ultimately becomes semen.\n\nFluid is secreted from the ejaculatory ducts of the vesicles into the vas deferens, where it becomes part of semen.\n\nThis then passes through the urethra, where it is ejaculated during a male sexual response.About 70-85% of the seminal fluid in humans originates from the seminal vesicles.\n\nThe fluid consists of nutrients including fructose and citric acid, prostaglandins, and fibrinogen.\n\nNutrients help support sperm until fertilisation occurs; prostaglandins may also assist by softening mucous of the cervix, and by causing reverse contractions of parts of the female reproductive tract such as the fallopian tubes, to ensure that sperm are less likely to be expelled.\n\n== Clinical significance ==\n\n=== Disease ===\n\nSeminal vesiculitis (also known as spermatocystitis) is an inflammation of the seminal vesicles, most often caused by bacterial infection.\n\nSymptoms can include vague back or lower abdominal pain; pain of the penis, scrotum or peritoneum; painful ejaculation; blood in the semen on ejaculation; irritative and obstructive voiding symptoms; and impotence.\n\nInfection may be due to sexually transmitted infections, as a complication of a procedure such as prostate biopsy.\n\nIt is usually treated with antibiotics.\n\nIf a person experiences ongoing discomfort, transurethral seminal vesiculoscopy may be considered.\n\nIntervention in the form of drainage through the skin or surgery may also be required if the infection becomes an abscess.\n\nThe seminal vesicles may also be affected by tuberculosis, schistosomiasis and hydatid disease.\n\nThese diseases are investigated, diagnosed and treated according to the underlying disease.\n\nCongenital anomalies associated with the seminal vesicles include failure to develop, either completely (agenesis) or partially (hypoplasia), and cysts.\n\nFailure of the vesicles to form is often associated with absent vas deferens, or an abnormal connection between the vas deferens and the ureter.\n\nThe seminal vesicles may also be affected by cysts, amyloidosis, and stones.\n\nStones or cysts that become infected, or obstruct the vas deferens or seminal vesicles, may require surgical intervention.\n\nBenign tumours of the seminal vesicles are rare.\n\nWhen they do occur, they are usually papillary adenomas and cystadenomas.\n\nThey do not cause elevation of tumour markers, and are usually diagnosed based examination of tissue that has been removed after surgery.\n\nPrimary adenocarcinoma of the seminal vesicles, although rare, constitutes the most common malignant cancer of the seminal vesicles; that said, the majority of malignant cancers affecting the vesicles are lesions that have extended into the vesicles from nearby parts of the body.\n\nWhen adenocarcinoma occurs, it can cause blood in the urine, blood in the semen, painful urination, urinary retention, or even urinary obstruction.\n\nAdenocarcinomata are usually diagnosed after they are excised, based on tissue diagnosis.\n\nSome produce the tumour marker Ca-125, which can be used to monitor for reoccurence afterwards.\n\nEven rarer neoplasms include sarcoma, squamous cell carcinoma, yolk sac tumor, neuroendocrine carcinoma, paraganglioma, epithelial stromal tumors and lymphoma.\n\n=== Investigations ===\n\nSymptoms due to diseases of the seminal vesicles may be vague and not able to be specifically attributable to the vesicles themselves; additionally, some conditions such as tumours or cysts may not cause any symptoms at all.\n\nWhen diseases is suspected, such as due to pain on ejaculation, blood in the urine, infertility, due to urinary tract obstruction, further investigations may be conducted.\n\nA digital rectal examination, which involves a finger inserted by a medical practitioner through the anus, may cause greater than usual tenderness of the prostate gland, or may reveal a large seminal vesicle.\n\nA urine specimen may be collected, and is likely to demonstrate blood within the urine.\n\nLaboratory examination of seminal vesicle fluid requires a semen sample, e.g. for semen culture or semen analysis.\n\nFructose levels provide a measure of seminal vesicle function and, if absent, bilateral agenesis or obstruction is suspected.\n\nImaging of the vesicles is provided by medical imaging; either by transrectal ultrasound, CT or MRI scans.\n\nAn examination using cystoscopy, where a flexible tube is inserted in the urethra, may show disease of the vesicles because of changes in the normal appearance of the nearby bladder trigone, or prostatic urethra.\n\n== Other animals ==\n\nThe evolution of seminal vesicles may have been influenced by sexual selection.\n\nThey occur in many groups of mammals, but are absent in marsupials, monotremes, and carnivores.\n\nThe function is similar in all mammals they are present in, which is to secrete a fluid as part of semen that is ejaculated during the sexual response.\n\n== History ==\n\nThe action of the seminal vesicles has been described as early the second century AD by Galen, as \"glandular bodies\" that secrete substances alongside semen during reproduction.\n\nBy the time of Herophilus the presence of the glands and associated ducts had been described.\n\nAround the time of the early 17th century the word used to describe the vesicles, parastatai, eventually and unambiguously was used to refer to the prostate gland, rather than the vesicles.\n\nThe first time the prostate was portrayed in an individual drawing was by Reiner De Graaf in 1678.\n\nThe first described use of laparoscopic surgery on the vesicles was described in 1993; this is now the preferred approach because of decreased pain, complications, and a shorter hospital stay.\n\nhttps://en.wikipedia.org/wiki/Seminal_vesicles","prostate":"The prostate is both an accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation.\n\nIt is found only in some mammals.\n\nIt differs between species anatomically, chemically, and physiologically.\n\nAnatomically, the prostate is found below the bladder, with the urethra passing through it.\n\nIt is described in gross anatomy as consisting of lobes and in microanatomy by zone.\n\nIt is surrounded by an elastic, fibromuscular capsule and contains glandular tissue as well as connective tissue.\nThe prostate glands produce and contain fluid that forms part of semen, the substance that is emitted during ejaculation as part of the male sexual response.\n\nThis prostatic fluid is slightly alkaline, milky or white in appearance.\n\nThe alkalinity of semen helps neutralize the acidity of the vaginal tract, prolonging the lifespan of sperm.\n\nThe prostatic fluid is expelled in the first part of ejaculate, together with most of the sperm, because of the action of smooth muscle tissue within the prostate.\n\nIn comparison with the few spermatozoa expelled together with mainly seminal vesicular fluid, those in prostatic fluid have better motility, longer survival, and better protection of genetic material.\nDisorders of the prostate include enlargement, inflammation, infection, and cancer.\n\nThe word prostate comes from Ancient Greek προστάτης, prostátēs, meaning \"one who stands before\", \"protector\", \"guardian\", with the term originally used to describe the seminal vesicles.\n\n== Structure ==\n\nThe prostate is a gland of the male reproductive system.\n\nIn adults, it is about the size of a walnut, and has an average weight of about 11 grams, usually ranging between 7 and 16 grams.\n\nThe prostate is located in the pelvis.\n\nIt sits below the urinary bladder and surrounds the urethra.\n\nThe part of the urethra passing through it is called the prostatic urethra, which joins with the two ejaculatory ducts.\n\nThe prostate is covered in a surface called the prostatic capsule or prostatic fascia.The internal structure of the prostate has been described using both lobes and zones.\n\nBecause of the variation in descriptions and definitions of lobes, the zone classification is used more predominantly.The prostate has been described as consisting of three or four zones.\n\nZones are more typically able to be seen on histology, or in medical imaging, such as ultrasound or MRI.\n\nThe zones are:\n\nThe \"lobe\" classification describes lobes that, while originally defined in the fetus, are also visible in gross anatomy, including dissection and when viewed endoscopically.\n\nThe five lobes are the anterior lobe or isthmus, the posterior lobe, the right and left lateral lobes, and the middle or median lobe.\n\nInside of the prostate, adjacent and parallel to the prostatic urethra, there are two longitudinal muscle systems.\n\nOn the front side (ventrally) runs the urethral dilator (musculus dilatator urethrae), on the backside (dorsally) runs the muscle switching the urethra into the ejaculatory state (musculus ejaculatorius).\n\n=== Blood and lymphatic vessels ===\n\nThe prostate receives blood through the inferior vesical artery, internal pudendal artery, and middle rectal arteries.\n\nThese vessels enter the prostate on its outer posterior surface where it meets the bladder, and travel forward to the apex of the prostate.\n\nBoth the inferior vesical and the middle rectal arteries often arise together directly from the internal iliac arteries.\n\nOn entering the bladder, the inferior vesical artery splits into a urethral branch, supplying the urethral prostate; and a capsular branch, which travels around the capsule and has smaller branches which perforate into the prostate.The veins of the prostate form a network – the prostatic venous plexus, primarily around its front and outer surface.\n\nThis network also receives blood from the deep dorsal vein of the penis, and is connected via branches to the vesical plexus and internal pudendal veins.\n\nVeins drain into the vesical and then internal iliac veins.The lymphatic drainage of the prostate depends on the positioning of the area.\n\nVessels surrounding the vas deferens, some of the vessels in the seminal vesicle, and a vessel from the posterior surface of the prostate drain into the external iliac lymph nodes.\n\nSome of the seminal vesicle vessels, prostatic vessels, and vessels from the anterior prostate drain into internal iliac lymph nodes.\n\nVessels of the prostate itself also drain into the obturator and sacral lymph nodes.\n\n=== Microanatomy ===\n\nThe prostate consists of glandular and connective tissue.\n\nTall column-shaped cells form the lining (the epithelium) of the glands.\n\nThese form one layer or may be pseudostratified.\n\nThe epithelium is highly variable and areas of low cuboidal or flat cells can also be present, with transitional epithelium in the outer regions of the longer ducts.\n\nThe glands are formed as many follicles, which in drain into canals and subsequently 12–20 main ducts, These in turn drain into the urethra as it passes through the prostate.\n\nThere are also a small amount of flat cells, which sit next to the basement membranes of glands, and act as stem cells.The connective tissue of the prostate is made up of fibrous tissue and smooth muscle.\n\nThe fibrous tissue separates the gland into lobules.\n\nIt also sits between the glands and is composed of randomly orientated smooth-muscle bundles that are continuous with the bladder.Over time, thickened secretions called corpora amylacea accumulate in the gland.\n\n=== Gene and protein expression ===\n\nAbout 20,000 protein coding genes are expressed in human cells and almost 75% of these genes are expressed in the normal prostate.\n\nAbout 150 of these genes are more specifically expressed in the prostate, with about 20 genes being highly prostate specific.\n\nThe corresponding specific proteins are expressed in the glandular and secretory cells of the prostatic gland and have functions that are important for the characteristics of semen, including prostate-specific proteins, such as the prostate specific antigen (PSA), and the Prostatic acid phosphatase.\n\n=== Development ===\n\nIn the developing embryo, at the hind end lies an inpouching called the cloaca.\n\nThis, over the fourth to the seventh week, divides into a urogenital sinus and the beginnings of the anal canal, with a wall forming between these two inpouchings called the urorectal septum.\n\nThe urogenital sinus divides into three parts, with the middle part forming the urethra; the upper part is largest and becomes the urinary bladder, and the lower part then changes depending on the biological sex of the embryo.The prostatic part of the urethra develops from the middle, pelvic, part of the urogenital sinus, which is of endodermal origin.\n\nAround the end of the third month of embryonic life, outgrowths arise from the prostatic part of the urethra and grow into the surrounding mesenchyme.\n\nThe cells lining this part of the urethra differentiate into the glandular epithelium of the prostate.\n\nThe associated mesenchyme differentiates into the dense connective tissue and the smooth muscle of the prostate.Condensation of mesenchyme, urethra, and Wolffian ducts gives rise to the adult prostate gland, a composite organ made up of several tightly fused glandular and non-glandular components.\n\nTo function properly, the prostate needs male hormones (androgens), which are responsible for male sex characteristics.\n\nThe main male hormone is testosterone, which is produced mainly by the testicles.\n\nIt is dihydrotestosterone (DHT), a metabolite of testosterone, that predominantly regulates the prostate.\n\nThe prostate gland enlarges over time, until the fourth decade of life.\n\n== Function ==\n\nThe prostate secretes fluid which becomes part of semen.\n\nSemen is the fluid emitted (ejaculated) by males during the sexual response.\n\nWhen sperm is emitted, it is transmitted from the vas deferens into the male urethra via the ejaculatory ducts, which lie within the prostate gland.\n\nEjaculation is the expulsion of semen from the urethra.\n\nSemen is moved into the urethra following contractions of the smooth muscle of the vas deferens and seminal vesicles, following stimulation, primarily of the glans penis.\n\nStimulation sends nerve signals via the internal pudendal nerves to the upper lumbar spine; the nerve signals causing contraction act via the hypogastric nerves.\n\nAfter traveling into the urethra, the seminal fluid is ejaculated by contraction of the bulbocavernosus muscle.\n\nThe secretions of the prostate include proteolytic enzymes, prostatic acid phosphatase, fibrinolysin, zinc, and prostate-specific antigen.\n\nTogether with the secretions from the seminal vesicles, these form the major fluid part of semen.It is possible for some men to achieve orgasm solely through stimulation of the prostate gland, such as via prostate massage or anal intercourse.\n\nThis has led to the area of the rectal wall adjacent to the prostate to be popularly (yet inaccurately) referred to as the \"male G-spot\".The prostate's changes of shape, which facilitate the mechanical switch between urination and ejaculation, are mainly driven by the two longitudinal muscle systems running along the prostatic urethra.\n\nThese are the urethral dilator (musculus dilatator urethrae) on the urethra's front side, which contracts during urination and thereby shortens and tilts the prostate in its vertical dimension thus widening the prostatic section of the urethral tube, and the muscle switching the urethra into the ejaculatory state (musculus ejaculatorius) on its backside.In case of an operation, e.g. because of benign prostatic hyperplasia (BPH), damaging or sparing of these two muscle systems varies considerably depending on the choice of operation type and details of the procedure of the chosen technique.\n\nThe effects on postoperational urination and ejaculation vary correspondingly. (See also: Surgery for benign prostatic hyperplasia).\n\n== Clinical significance ==\n\n=== Inflammation ===\n\nProstatitis is inflammation of the prostate gland.\n\nIt can be caused by infection with bacteria, or other noninfective causes.\n\nInflammation of the prostate can cause painful urination or ejaculation, groin pain, difficulty passing urine, or constitutional symptoms such as fever or tiredness.\n\nWhen inflamed, the prostate becomes enlarged and is tender when touched during digital rectal examination.\n\nA culprit bacteria may grow in a urine culture.Acute prostatitis and chronic bacterial prostatitis are treated with antibiotics.\n\nChronic non-bacterial prostatitis, or male chronic pelvic pain syndrome is treated by a large variety of modalities including the medications alpha blockers, nonsteroidal antiinflammatories and amitriptyline, antihistamines, and other anxiolytics.\n\nOther treatments that are not medications may include physical therapy, psychotherapy, nerve modulators, and surgery.\n\nMore recently, a combination of trigger point and psychological therapy has proved effective for category III prostatitis as well.\n\n=== Enlarged prostate ===\n\nAn enlarged prostate is called prostatomegaly, with benign prostatic hyperplasia (BPH) being the most common cause.\n\nBPH refers to an enlargement of the prostate due to an increase in the number of cells that make up the prostate (hyperplasia) from a cause that is not a malignancy.\n\nIt is very common in older men.\n\nIt is often diagnosed when the prostate has enlarged to the point where urination becomes difficult.\n\nSymptoms include needing to urinate often (urinary frequency) or taking a while to get started (urinary hesitancy).\n\nIf the prostate grows too large, it may constrict the urethra and impede the flow of urine, making urination painful and difficult, or in extreme cases completely impossible, causing urinary retention.\n\nOver time, chronic retention may cause the bladder to become larger and cause a backflow of urine into the kidneys (hydronephrosis).BPH can be treated with medication, a minimally invasive procedure or, in extreme cases, surgery that removes the prostate.\n\nIn general, treatment often begins with an alpha-1 adrenergic receptor antagonist medication such as tamsulosin, which reduces the tone of the smooth muscle found in the urethra that passes through the prostate, making it easier for urine to pass through.\n\nFor people with persistent symptoms, procedures may be considered.\n\nThe surgery most often used in such cases is transurethral resection of the prostate, in which an instrument is inserted through the urethra to remove prostate tissue that is pressing against the upper part of the urethra and restricting the flow of urine.\n\nMinimally invasive procedures include transurethral needle ablation of the prostate and transurethral microwave thermotherapy.\n\nThese outpatient procedures may be followed by the insertion of a temporary stent, to allow normal voluntary urination, without exacerbating irritative symptoms.\n\n=== Cancer ===\n\nProstate cancer is one of the most common cancers affecting older men in the UK, US, Northern Europe and Australia, and a significant cause of death for elderly men worldwide.\n\nOften, a person does not have symptoms; when they do occur, symptoms may include urinary frequency, urgency, hesitation and other symptoms associated with BPH.\n\nUncommonly, such cancers may cause weight loss, retention of urine, or symptoms such as back pain due to metastatic lesions that have spread outside of the prostate.A digital rectal examination and the measurement of a prostate-specific antigen (PSA) level are usually the first investigations done to check for prostate cancer.\n\nPSA values are difficult to interpret, because a high value might be present in a person without cancer, and a low value can be present in someone with cancer.\n\nThe next form of testing is often the taking of a biopsy to assess for tumour activity and invasiveness.\n\nBecause of the significant risk of overdiagnosis with widespread screening in the general population, prostate cancer screening is controversial.\n\nIf a tumour is confirmed, medical imaging such as an MRI or bone scan may be done to check for the presence of tumour metastases in other parts of the body.Prostate cancer that is only present in the prostate is often treated with either surgical removal of the prostate or with radiotherapy or by the insertion of small radioactive particles of iodine-125 or palladium-103, called brachytherapy.\n\nCancer that has spread to other parts of the body is usually treated also with hormone therapy, to deprive a tumour of sex hormones (androgens) that stimulate proliferation.\n\nThis is often done through the use of GnRH analogues or agents that block the receptors that androgens act at, such as bicalutamide; occasionally, surgical removal of the testes may be done instead.\n\nCancer that does not respond to hormonal treatment, or that progresses after treatment, might be treated with chemotherapy such as docetaxel.\n\nRadiotherapy may also be used to help with pain associated with bony lesions.Sometimes, the decision may be made not to treat prostate cancer.\n\nIf a cancer is small and localised, the decision may be made to monitor for cancer activity at intervals (\"active surveillance\") and defer treatment.\n\nIf a person, because of frailty or other medical conditions or reasons, has a life expectancy less than ten years, then the impacts of treatment may outweigh any perceived benefits.\n\n=== Surgery ===\n\nSurgery to remove the prostate is called prostatectomy, and is usually done as a treatment for cancer limited to the prostate, or prostatic enlargement.\n\nWhen it is done, it may be done as open surgery or as laparoscopic (keyhole) surgery.\n\nThese are done under general anaesthetic.\n\nUsually the procedure for cancer is a radical prostatectomy, which means that the seminal vesicles are removed and vas deferens is also tied off.\n\nPart of the prostate can also be removed from within the urethra, called transurethral resection of the prostate (TURP).\n\nOpen surgery may involve a cut that is made in the perineum, or via an approach that involves a cut down the midline from the belly button to the pubic bone.\n\nOpen surgery may be preferred if there is a suspicion that lymph nodes are involved and they need to be removed or biopsied during a procedure.\n\nA perineal approach will not involve lymph node removal and may result in less pain and a faster recovery following an operation.\n\nA TURP procedure uses a tube inserted into the urethra via the penis and some form of heat, electricity or laser to remove prostate tissue.The whole prostate can be removed.\n\nComplications that might develop because of surgery include urinary incontinence.\n\nErectile dysfunction because of damage to nerves during the operation, particularly if a cancer is very close to nerves.\n\nEjaculation of semen will not occur during orgasm if the vas deferens are tied off and seminal vesicles removed, such as during a radial prosatectomy.\n\nThis will mean a man becomes infertile.\n\nSometimes, orgasm may not be able to occur or may be painful.\n\nThe penis length may change if the part of the urethra within the prostate is also removed.\n\nGeneral complications due to surgery can also develop, such as infections, bleeding, inadvertent damage to nearby organs or within the abdomen, and the formation of blood clots.\n\n== History ==\n\nThe prostate was first formally identified by Venetian anatomist Niccolò Massa in Anatomiae libri introductorius (Introduction to Anatomy) 1536 and illustrated by Flemish anatomist Andreas Vesalius in Tabulae anatomicae sex (six anatomical tables) in 1538.\n\nMassa described it as a \"glandular flesh upon which rests the neck of the bladder,\" and Vesalius as a \"glandular body\".\n\nThe first time a word similar to 'prostate' was used to describe the gland is credited to André du Laurens in 1600, who described it as a term already in use by anatomists at the time.\n\nThe term was however used at least as early as 1549 by French surgeon Ambroise Pare.At the time, Du Laurens was describing what was considered to be a pair of organs (not the single two-lobed organ), and the Latin term prostatae that was used was a mistranslation of the term for the Ancient Greek word used to describe the seminal vesicles, parastatai; although it has been argued that surgeons in Ancient Greece and Rome must have at least seen the prostate as an anatomical entity.\n\nThe term prostatae was taken rather than the grammatically correct prostator (singular) and prostatores (plural) because the gender of the Ancient Greek term was taken as female, when it was in fact male.The fact that the prostate was one and not two organs was an idea popularised throughout the early 18th century, as was the English language term used to describe the organ, prostate, attributed to William Cheselden.\n\nA monograph, \"Practical observations on the treatment of the diseases of the prostate gland\" by Everard Home in 1811, was important in the history of the prostate by describing and naming anatomical parts of the prostate, including the median lobe.\n\nThe idea of the five lobes of the prostate was popularized following anatomical studies conducted by American urologist Oswald Lowsley in 1912.\n\nJohn E.\n\nMcNeal first proposed the idea of \"zones\" in 1968; McNeal found that the relatively homogeneous cut surface of an adult prostate in no way resembled \"lobes\" and thus led to the description of \"zones\".Prostate cancer was first described in a speech to the Medical and Chiurgical Society of London in 1853 by surgeon John Adams and increasingly described by the late 19th century.\n\nProstate cancer was initially considered a rare disease, probably because of shorter life expectancies and poorer detection methods in the 19th century.\n\nThe first treatments of prostate cancer were surgeries to relieve urinary obstruction.\n\nSamuel David Gross has been credited with the first mention of a prostatectomy, as \"too absurd to be seriously entertained\" The first removal for prostate cancer (radical perineal prostatectomy) was first performed in 1904 by Hugh H.\n\nYoung at Johns Hopkins Hospital; partial removal of the gland was conducted by Theodore Billroth in 1867.Transurethral resection of the prostate (TURP) replaced radical prostatectomy for symptomatic relief of obstruction in the middle of the 20th century because it could better preserve penile erectile function.\n\nRadical retropubic prostatectomy was developed in 1983 by Patrick Walsh.\n\nIn 1941, Charles B.\n\nHuggins published studies in which he used estrogen to oppose testosterone production in men with metastatic prostate cancer.\n\nThis discovery of \"chemical castration\" won Huggins the 1966 Nobel Prize in Physiology or Medicine.The role of the gonadotropin-releasing hormone (GnRH) in reproduction was determined by Andrzej W.\n\nSchally and Roger Guillemin, who both won the 1977 Nobel Prize in Physiology or Medicine for this work.\n\nGnRH receptor agonists, such as leuprorelin and goserelin, were subsequently developed and used to treat prostate cancer.\n\nRadiation therapy for prostate cancer was first developed in the early 20th century and initially consisted of intraprostatic radium implants.\n\nExternal beam radiotherapy became more popular as stronger X-ray radiation sources became available in the middle of the 20th century.\n\nBrachytherapy with implanted seeds (for prostate cancer) was first described in 1983.\n\nSystemic chemotherapy for prostate cancer was first studied in the 1970s.\n\nThe initial regimen of cyclophosphamide and 5-fluorouracil was quickly joined by multiple regimens using a host of other systemic chemotherapy drugs.\n\n== Other animals ==\n\nThe prostate is found only in mammals.\n\nThe prostate glands of male marsupials are proportionally larger than those of placental mammals.\n\nThe presence of a functional prostate in monotremes is controversial, and if monotremes do possess functional prostates, they may not make the same contribution to semen as in other mammals.The structure of the prostate varies, ranging from tubuloalveolar (as in humans) to branched tubular.\n\nThe gland is particularly well developed in dogs, foxes and boars, though in other mammals, such as bulls, it can be small and inconspicuous.\n\nIn other animals, such as marsupials and small ruminants, the prostate is disseminate, meaning not specifically localisable as a distinct tissue, but present throughout the relevant part of the urethra; in other animals, such as red deer and American elk, it may be present as a specific organ and in a disseminate form.\n\nIn some marsupial species, the size of the prostate gland changes seasonally.\n\nThe prostate is the only accessory gland that occurs in male dogs.\n\nDogs can produce in one hour as much prostatic fluid as a human can in a day.\n\nThey excrete this fluid along with their urine to mark their territory.\n\nAdditionally, dogs are the only species apart from humans seen to have a significant incidence of prostate cancer.\n\nIn cetaceans (whales, dolphins, porpoises) the prostate is composed of diffuse urethral glands and is surrounded by a very powerful compressor muscle.The prostate gland originates with tissues in the urethral wall.\n\nThis means the urethra, a compressible tube used for urination, runs through the middle of the prostate.\n\nThis leads to an evolutionary design fault for some mammals, including human males.\n\nThe prostate is prone to infection and enlargement later in life, constricting the urethra so urinating becomes slow and painful.Prostatic secretions vary among species.\n\nThey are generally composed of simple sugars and are often slightly alkaline.\n\n== Skene's gland ==\n\nBecause the Skene's gland and the male prostate act similarly by secreting prostate-specific antigen (PSA), which is an ejaculate protein produced in males, and of prostate-specific acid phosphatase, the Skene's glands is sometimes referred to as the \"female prostate\".\n\nAlthough it is homologous to the male prostate (developed from the same embryological tissues), various aspects of its development in relation to the male prostate are widely unknown and a matter of research.\n\nhttps://en.wikipedia.org/wiki/Prostate","glans-penis":"The glans penis, commonly referred to as the glans, is a structure at the distal end of the penis in male mammals.\n\nIt is the sensitive bulbous structure at the end of the human penis, and is anatomically homologous to the clitoral glans of the human female.\n\nThe glans penis may be smooth, spiny, elongated, or divided in other mammals.\n\nTypically, the glans is completely or partially covered by the foreskin in humans, except in those who have been circumcised.\n\nThe foreskin can generally be retracted over and past the glans, and may automatically retract during an erection.\n\nThe glans is more commonly known as the \"head\" or the \"tip\" of the penis.\n\nThe medical name comes from the Latin words glans (\"acorn\") and penis (\"of the penis\").\n\n== In humans ==\n\n=== Structure ===\n\nThe glans penis is the expanded cap of the corpus spongiosum.\n\nIt is moulded on the rounded ends of the corpora cavernosa penis, extending farther on their upper than on their lower surfaces.\n\nAt the summit of the glans is the slit-like vertical external urethral orifice.\n\nThe circumference of the base of the glans forms a rounded projecting border, the corona glandis, overhanging a deep retroglandular groove known as the coronal sulcus, behind which is the neck of the penis.\n\nThe proportional size of the glans penis can vary greatly.\n\nOn some penises it is much wider in circumference than the shaft, giving the penis a mushroom-like appearance, and on others it is narrower and more akin to a probe in shape.\n\nThe soft cushiony texture of the glans absorbs impact during rigorous instances of copulation.The foreskin maintains the mucosa in a moist environment.\n\nCircumcised penises have a glans which is permanently exposed and dry.\n\nSeveral studies have suggested the glans is equally sensitive in both circumcised and uncircumcised penises, while others have reported it is more sensitive in people who are not circumcised.\n\nHalata & Munger (1986) report that the density of genital corpuscles is greatest in the corona glandis, while Yang & Bradley's (1998) report \"showed no areas in the glans to be more densely innervated than others.\n\n\"Halata & Spathe (1997) reported; \"the glans penis contains a predominance of free nerve endings, numerous genital end bulbs and rarely Pacinian and Ruffinian corpuscles.\n\nMerkel nerve endings and Meissner's corpuscles are not present.\"Yang & Bradley argue; \"the distinct pattern of innervation of the glans emphasizes the role of the glans as a sensory structure\".\n\nSome researchers have suggested that the glans has evolved to become acorn, mushroom or cone shaped so that during copulation it acts to remove any semen still there from previous sex partners, but this is not supported when looking at primate relatives who have different mating behaviors.\n\n=== Clinical significance ===\n\nThe meatus (opening) of the urethra is located at the tip of the glans penis.\nThe epithelium of the glans penis is mucocutaneous tissue.\n\nBirley et al. report that excessive washing with soap may dry the mucous membrane which covers the glans penis and cause non-specific dermatitis.\n\nInflammation of the glans penis is known as balanitis, and, occurs in 3–11% of males (up to 35% of diabetic males).\n\nEdwards reported that it is generally more common in males who have poor hygiene habits or have not been circumcised.\n\nIt has many causes, including irritation, or infection with a wide variety of pathogens.\n\nCareful identification of the cause with the aid of patient history, physical examination, swabs and cultures, and biopsy are essential in order to determine the proper treatment.\n\nMeatal stenosis is a late complication of circumcision, which occurs in about 2 to 20 percent of circumcised boys.\n\n== Other animals ==\n\nMale felids are able to urinate backwards by curving the tip of the glans penis backward.\n\nIn cats, the glans penis is covered with spines, but in dogs, the glans is smooth.\n\nPenile spines also occur on the glans of male and female spotted hyenas.In male dogs, the glans penis consists of two parts called the bulbus glandis and pars longa glandis.\n\nThe glans of a fossa's penis extends about halfway down the shaft and is spiny except at the tip.\n\nIn comparison, the glans of felids is short and spiny, while that of viverrids is smooth and long.\nThe shape of the glans varies among different marsupial species.\n\nIn most marsupials, the glans is divided, but male macropods have an undivided glans penis.\n\nThe glans penis is also divided into two parts in platypuses and echidnas.\n\nThe glans penis of the marsh rice rat is long and robust, averaging 7.3 mm (0.29 in) long and 4.6 mm (0.18 in) broad.\n\nIn Thomasomys ucucha the glans penis is rounded, short, and small and is superficially divided into left and right halves by a trough at the top and a ridge at the bottom.\n\nMost of the glans is covered with spines, except for an area near the tip.\n\nWinkelmann's mouse can most readily be distinguished from its close relatives by its partially corrugated glans penis.\n\nWhen erect, the glans of a horse's penis increases by 3 to 4 times.\n\nThe urethra opens within the urethral fossa, a small pouch at the distal end of the glans.\n\nUnlike the human glans, the glans of a horse's penis extends backwards on its shaft.\n\nMales of Racey's pipistrelle bat have a narrow, egg-shaped glans penis.\n\nThe glans penis of a male cape ground squirrel is large with a prominent baculum.\n\nhttps://en.wikipedia.org/wiki/Glans_penis","corpus-cavernosum-of-penis":"A corpus cavernosum penis (singular) (literally \"cave-like body\" of the penis, plural corpora cavernosa) is one of a pair of sponge-like regions of erectile tissue, which contain most of the blood in the penis during an erection.\n\nSuch a corpus is homologous to the corpus cavernosum clitoridis in the female; the body of the clitoris that contains erectile tissue in a pair of corpora cavernosa with a recognisably similar structure.\n\n== Anatomy ==\n\nThe two corpora cavernosa and corpus spongiosum (also known as the corpus cavernosum urethrae in older texts and in the adjacent diagram) are three expandable erectile tissues along the length of the penis, which fill with blood during penile erection.\n\nThe two corpora cavernosa lie along the penis shaft, from the pubic bones to the head of the penis, where they join.\n\nThese formations are made of a sponge-like tissue containing trabeculae, irregular blood-filled spaces lined by endothelium and separated by septum of the penis.\n\nThe male anatomy has no vestibular bulbs, but instead a corpus spongiosum, a smaller region along the bottom of the penis, which contains the urethra and forms the glans penis.\n\n== Physiology ==\n\nIn some circumstances, release of nitric oxide precedes relaxation of muscles in the corpora cavernosa and corpus spongiosum, in a process similar to female arousal.\n\nThe spongy tissue fills with blood, from arteries down the length of the penis.\n\nA little blood enters the corpus spongiosum; the remainder engorges the corpora cavernosa, which expand to hold 90% of the blood involved in an erection, increasing both in length and in diameter.\n\nThe function of the corpus spongiosum is to prevent compression of the urethra during erection.\n\nBlood can leave the erectile tissue only through a drainage system of veins around the outside wall of the corpus cavernosum.\n\nThe expanding spongy tissue presses against a surrounding dense tissue (tunica albuginea) constricting these veins, preventing blood from leaving.\n\nThe penis becomes rigid as a result.\n\nThe glans penis, the expanded cap of the corpus spongiosum, remains more malleable during erection because its tunica albuginea is much thinner than elsewhere in the penis.\n\nhttps://en.wikipedia.org/wiki/Corpus_cavernosum_penis","corpus-spongiosum-of-penis":"The corpus spongiosum is the mass of spongy tissue surrounding the male urethra within the penis.\n\nIt is also called the corpus cavernosum urethrae in older texts.\n\n== Anatomy ==\n\nPosterior part of the corpus spongiosum is expanded to form the urethral bulb, and lies in apposition with the inferior fascia of the urogenital diaphragm, from which it receives a fibrous investment.\n\nThe urethra enters the bulb nearer to the superior than to the inferior surface.\n\nOn the latter there is a median sulcus (groove), from which a thin fibrous septum (wall) projects into the substance of the bulb and divides it imperfectly into two lateral lobes or hemispheres.\n\nThe portion of the corpus spongiosum in front of the bulb lies in a groove on the under surface of the conjoined corpora cavernosa penis.\n\nIt is cylindrical in form and tapers slightly from behind forward.\n\nIts anterior end is expanded in the form of an obtuse cone, flattened from above downward.\n\nThis expansion, termed the glans penis, is moulded on the rounded ends of the corpus cavernosum penis, extending farther on their upper than on their lower surfaces.\n\nAt the summit of the glans is the slit-like vertical opening known as the external urethral orifice, or the urinary meatus.\n\nThe circumference of the base of the glans forms a rounded projecting border, the corona of glans penis, overhanging a deep retroglandular sulcus, behind which is the neck of the penis.\n\n== Function ==\n\nThe function of the corpus spongiosum in erection is to prevent the urethra from pinching closed, thereby maintaining the urethra as a viable channel for ejaculation.\n\nTo do this, the corpus spongiosum remains pliable during erection while the corpora cavernosa penis become engorged with blood.\n\nhttps://en.wikipedia.org/wiki/Corpus_spongiosum_penis","mesocolon":"Peritoneal fold in which the vessels and nerves travel, for the suspension and the supply of the colon.\n\nFeneis 210.16\n\nThe mesocolon was thought to be a fragmented structure, with all named parts—the ascending, transverse, descending, and sigmoid mesocolons, the mesoappendix, and the mesorectum—separately terminating their insertion into the posterior abdominal wall.\n\nHowever, in 2012, new microscopic and electron microscopic examinations showed the mesocolon to be a single structure derived from the duodenojejunal flexure and extending to the distal mesorectal layer.\n\nThe mesocolon regions were traditionally taught to be separate sections with separate insertions into the posterior abdominal wall.\n\nIn 2012, the first detailed observational and histological studies of the mesocolon were undertaken and this revealed several new findings.\n\nThe study included 109 patients undergoing open, elective, total abdominal colectomy.\n\nAnatomical observations were recorded during the surgery and on the post-operative specimens.\n\nThese studies showed that the mesocolon is continuous from the ileocaecal to the rectosigmoid level.\n\nIt was also shown that a mesenteric confluence occurs at the ileocaecal and rectosigmoid junctions, as well as at the hepatic and splenic flexures and that each confluence involves peritoneal and omental attachments.\n\nThe proximal rectum was shown to originate at the confluence of the mesorectum and mesosigmoid.\n\nA plane occupied by perinephric fascia was shown to separate the entire apposed small intestinal mesentery and the mesocolon from the retroperitoneum.\n\nDeep in the pelvis, this fascia coalesces to give rise to presacral fascia.\n\nhttps://en.wikipedia.org/wiki/Mesentery#Structure","meso-appendix":"The mesentery becomes attached to the colon at the gastrointestinal margin and continues as the several regions of the mesocolon.\n\nThe parts of the mesocolon take their names from the part of the colon to which they attach.\n\nThese are the transverse mesocolon attaching to the transverse colon, the sigmoid mesocolon attaching to the sigmoid colon, the mesoappendix attaching to the appendix, and the mesorectum attaching to the upper third of the rectum.\n\nhttps://en.wikipedia.org/wiki/Mesentery#Segments","greater-omentum":"The greater omentum (also the great omentum, omentum majus, gastrocolic omentum, epiploon, or, especially in animals, caul) is a large apron-like fold of visceral peritoneum that hangs down from the stomach.\n\nIt extends from the greater curvature of the stomach, passing in front of the small intestines and doubles back to ascend to the transverse colon before reaching to the posterior abdominal wall.\n\nThe greater omentum is larger than the lesser omentum, which hangs down from the liver to the lesser curvature.\n\nThe common anatomical term \"epiploic\" derives from \"epiploon\", from the Greek epipleein, meaning to float or sail on, since the greater omentum appears to float on the surface of the intestines.\n\nIt is the first structure observed when the abdominal cavity is opened anteriorly (from the front).\n\n== Structure ==\n\nThe greater omentum is the larger of the two peritoneal folds.\n\nIt consists of a double sheet of peritoneum, folded on itself so that it has four layers.The two layers of the greater omentum descend from the greater curvature of the stomach and the beginning of the duodenum.\n\nThey pass in front of the small intestines, sometimes as low as the pelvis, before turning on themselves, and ascending as far as the transverse colon, where they separate and enclose that part of the intestine.These individual layers are easily seen in the young, but in the adult they are more or less inseparably blended.\nThe left border of the greater omentum is continuous with the gastrosplenic ligament; its right border extends as far as the beginning of the duodenum.\nThe greater omentum is usually thin, and has a perforated appearance.\n\nIt contains some adipose tissue, which can accumulate considerably in obese people.\n\nIt is highly vascularised.\n\n=== Subdivisions ===\n\nThe greater omentum is often defined to encompass a variety of structures.\n\nMost sources include the following three:\nGastrophrenic ligament—extends to the underside of the left dome of the diaphragm\nGastrocolic ligament—extends to the transverse colon (occasionally on its own considered synonymous with \"greater omentum\")\nGastrosplenic ligament (or Gastrolienal) ligament)— extends to the spleen, overlying the kidneyThe splenorenal ligament (or lienorenal ligament) (from the left kidney to the spleen) is occasionally considered part of the greater omentum.\n\nIt is derived from the peritoneum, where the wall of the general peritoneal cavity comes into contact with the lesser sac between the left kidney and the spleen; the splenic artery and vein pass between its two layers.\n\nIt contains the tail of the pancreas, the only intraperitoneal portion of the pancreas, and splenic vessels.\n\nOne or more of the preceding sentences incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)\n\n==== Phrenicosplenic ligament ====\nThe phrenosplenic ligament (lienophrenic ligament or phrenicolienal ligament) is a double fold of peritoneum that connects the thoracic diaphragm and spleen.The phrenicosplenic ligament is part of the greater omentum.\n\nDistinctions between the phrenicosplenic ligament and adjacent ligaments, such as the gastrophrenic, gastrosplenic and splenorenal ligaments, which are all part of the same mesenteric sheet, are often nebulous.\n\n=== Blood supply ===\n\nThe right and left gastroepiploic arteries (also known as gastroomental) provide the sole blood supply to the greater omentum.\n\nBoth are branches of the celiac trunk.\n\nThe right gastroepiploic artery is a branch of the gastroduodenal artery, which is a branch of the common hepatic artery, which is a branch of the celiac trunk.\n\nThe left gastroepiploic artery is the largest branch of the splenic artery, which is a branch of the celiac trunk.\n\nThe right and left gastroepiploic arteries anastomose within the two layers of the anterior greater omentum along the greater curvature of the stomach.\n\n=== Development ===\n\nThe greater omentum develops from the dorsal mesentery that connects the stomach to the posterior abdominal wall.\n\nDuring its development, the stomach undergoes its first 90° rotation along the axis of the embryo, so that posterior structures are moved to the left and structures anterior to the stomach are shifted to the right.\n\nAs a result, the dorsal mesentery folds over on itself, forming a pouch with its blind end on the left side of the embryo.\n\nA second approximately 90° rotation of the stomach, this time in the frontal plane, moves structures inferior if they were originally to the left of the stomach, and superior if they were originally to the stomach's right.\n\nConsequently, the blind-ended sac (also called the lesser sac) formed by the dorsal mesentery is brought inferiorly, where it assumes its final position as the greater omentum.\n\nIt grows to the point that it covers the majority of the small and large intestine.\n\n== Functions ==\n\nThe functions of the greater omentum are:\n\nFat deposition, having varying amounts of adipose tissue\nImmune contribution, having milky spots of macrophage collections\nInfection and wound isolation; It may also physically limit the spread of intraperitoneal infections.\n\nThe greater omentum can often be found wrapped around areas of infection and trauma.\n\n== Clinical significance ==\n\n=== Surgical removal ===\n\nOmentectomy refers to the surgical removal of the omentum, a relatively simple procedure with no documented major side effects, that is performed in cases where there is concern that there may be spread of cancerous tissue into the omentum.\n\nExamples for this are ovarian cancer and advanced or aggressive endometrial cancer as well as intestinal cancer and also appendix cancer.\n\nThe procedure is generally done as an add-on when the primary lesion is removed.\n\n=== Omental flap ===\n\nThe greater omentum may be surgically harvested for reconstruction of the thoracic wall.\n\nIt has also been used experimentally to reinforce bioengineered tissues transplanted to the surface of the heart for cardiac regeneration.\n\n=== Use in brain surgery ===\n\nThe greater omentum may be surgically harvested to provide revascularization of brain tissue after a stroke.\n\n== History ==\n\nThe greater omentum is also known as the great omentum, the omentum majus, the gastrocolic omentum, the epiploon, and the caul.\nIn 1906, the greater omentum was described as the \"abdominal policeman\" by the surgeon James Rutherford Morrison.\n\nThis is due to its immunological function, whereby omental tissue seems to \"surveil\" the abdomen for infection and cover areas of infection when found - walling it off with immunologically active tissue.\n\n== Notes and references ==\n\nhttps://en.wikipedia.org/wiki/Greater_omentum","lesser-omentum":"The lesser omentum (small omentum or gastrohepatic omentum) is the double layer of peritoneum that extends from the liver to the lesser curvature of the stomach, and to the first part of the duodenum.\n\nThe lesser omentum is usually divided into these two connecting parts: the hepatogastric ligament, and the hepatoduodenal ligament.\n\n== Structure ==\n\nThe lesser omentum is extremely thin, and is continuous with the two layers of peritoneum which cover respectively the antero-superior and postero-inferior surfaces of the stomach and first part of the duodenum.\nWhen these two layers reach the lesser curvature of the stomach and the upper border of the duodenum, they join together and ascend as a double fold to the porta hepatis.\nTo the left of the porta, the fold is attached to the bottom of the fossa for the ductus venosus, along which it is carried to the diaphragm, where the two layers separate to embrace the end of the esophagus.\nAt the right border of the lesser omentum, the two layers are continuous, and form a free margin which constitutes the anterior boundary of the omental foramen.\n\n== Divisions ==\n\nAnatomically, the lesser omentum is divided into ligaments, each starting with the prefix \"hepato\" to indicate that it connects to the liver at one end.\nMost sources divide it into two parts:\nhepatogastric ligament: the portion connecting to the lesser curvature of the stomach\nhepatoduodenal ligament: the portion connecting to the duodenumIn some cases, the following ligaments are considered part of the lesser omentum:\n\nhepatophrenic ligament: the portion connecting to the thoracic diaphragm\nhepatoesophageal ligament: the portion connecting to the esophagus\nhepatocolic ligament: the portion connecting to the colon\n\n== Contents ==\n\nBetween the two layers of the lesser omentum, close to the right free margin, are the hepatic artery proper, the common bile duct, the portal vein, lymphatics, and the hepatic plexus of nerves—all these structures being enclosed in a fibrous capsule (Glisson's capsule).\nBetween the layers of the lesser omentum, where they are attached to the stomach, run the right and left gastric arteries, as well as the gastric veins.\n\nhttps://en.wikipedia.org/wiki/Lesser_omentum","adenohypophysis":"A major organ of the endocrine system, the anterior pituitary (also called the adenohypophysis or pars anterior) is the glandular, anterior lobe that together with the posterior lobe (posterior pituitary, or the neurohypophysis) makes up the pituitary gland (hypophysis).\n\nThe anterior pituitary regulates several physiological processes, including stress, growth, reproduction, and lactation.\n\nProper functioning of the anterior pituitary and of the organs it regulates can often be ascertained via blood tests that measure hormone levels.\n\n== Structure ==\n\nThe pituitary gland sits in a protective bony enclosure called the sella turcica (Turkish chair/saddle).\n\nIt is composed of three lobes: the anterior, intermediate, and posterior lobes.\n\nIn many animals, these lobes are distinct.\n\nHowever, in humans, the intermediate lobe is but a few cell layers thick and indistinct; as a result, it is often considered part of the anterior pituitary.\n\nIn all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary.\n\nThe anterior pituitary is composed of three regions:\n\nPars distalisThe pars distalis (distal part) comprises the majority of the anterior pituitary and is where the bulk of pituitary hormone production occurs.\n\nThe pars distalis contains two types of cells, including chromophobe cells and chromophil cells.\n\nThe chromophils can be further divided into acidophils (alpha cells) and basophils (beta cells).\n\nThese cells all together produce hormones of the anterior pituitary and release them into the blood stream.\n\nNota bene: The terms \"basophil\" and \"acidophil\" are used by some books, whereas others prefer not to use these terms.\n\nThis is due to the possible confusion with white blood cells, where one may also find basophils and acidophils.\n\nPars tuberalis\nThe pars tuberalis (tubular part) forms a part of the sheath extending up from the pars distalis, which joins with the pituitary stalk (also known as the infundibular stalk or infundibulum), arising from the posterior lobe.\n\n(The pituitary stalk connects the hypothalamus to the posterior pituitary.) The function of the pars tuberalis is poorly understood.\n\nHowever, it has been seen to be important in receiving the endocrine signal in the form of TSHB (a β subunit of TSH), informing the pars tuberalis of the photoperiod (length of day).\n\nThe expression of this subunit is regulated by the secretion of melatonin in response to light information transmitted to the pineal gland.\n\nEarlier studies have shown localization of melatonin receptors in this region.\n\nPars intermedia\nThe pars intermedia (intermediate part) sits between the pars distalis and the posterior pituitary, forming the boundary between the anterior and posterior pituitaries.\n\nIt is very small and indistinct in humans.\n\n=== Development ===\n\nThe anterior pituitary is derived from the ectoderm, more specifically from that of Rathke’s pouch, part of the developing hard palate in the embryo.Rathke’s pouch is also ectodermal in origin.\n\nThe pouch eventually loses its connection with the pharynx, giving rise to the anterior pituitary.\n\nThe anterior wall of Rathke's pouch proliferates, filling most of the pouch to form the pars distalis and the pars tuberalis.\n\nThe posterior wall of the anterior pituitary forms the pars intermedia.\n\nIts formation from the soft tissues of the upper palate contrasts with the posterior pituitary, which originates from neuroectoderm.\n\n== Function ==\n\nThe anterior pituitary contains five types of endocrine cell, and they are defined by the hormones they secrete: somatotropes (GH); Lactotropes (PRL); gonadotropes (LH and FSH); corticotropes (ACTH) and thyrotropes (TSH).\n\nIt also contains non-endocrine folliculostellate cells which are thought to stimulate and support the endocrine cell populations.\n\nHormones secreted by the anterior pituitary are trophic hormones (Greek: trophe, “nourishment”).\n\nTrophic hormones directly affect growth either as hyperplasia or hypertrophy on the tissue it is stimulating.\n\nTropic hormones are named for their ability to act directly on target tissues or other endocrine glands to release hormones, causing numerous cascading physiological responses.\n\n=== Role in the endocrine system ===\n\nHypothalamic controlHormone secretion from the anterior pituitary gland is regulated by hormones secreted by the hypothalamus.\n\nNeuroendocrine cells in the hypothalamus project axons to the median eminence, at the base of the brain.\n\nAt this site, these cells can release substances into small blood vessels that travel directly to the anterior pituitary gland (the hypothalamo-hypophyseal portal vessels).\n\nOther Control MechanismsAside from hypothalamic control of the anterior pituitary, other systems in the body have been shown to regulate the anterior pituitary’s function.\n\nGABA can either stimulate or inhibit the secretion of luteinizing hormone (LH) and growth hormone (GH) and can stimulate the secretion of thyroid-stimulating hormone (TSH).\n\nProstaglandins are now known to inhibit adrenocorticotropic hormone (ACTH) and also to stimulate TSH, GH and LH release.\n\nGABA, through action with the hypothalamus, has been shown experimentally to influence the level of GH secretion.\n\nClinical evidence supports the experimental findings of the excitatory and inhibitory effects GABA has on GH secretion, dependent on GABA’s site of action within the hypothalamic-pituitary unit.\n\n=== Effects of the anterior pituitary ===\n\nThermal homeostasisThe homeostatic maintenance of the anterior pituitary is crucial to our physiological well being.\n\nIncreased plasma levels of TSH induce hyperthermia through a mechanism involving increased metabolism and cutaneous vasodilation.\n\nIncreased levels of LH also result in hypothermia but through a decreased metabolism action.\n\nACTH increase metabolism and induce cutaneous vasoconstriction, increased plasma levels also result in hyperthermia and prolactin decreases with decreasing temperature values.\n\nFollicle-stimulating hormone (FSH) also may cause hypothermia if increased beyond homeostatic levels through an increased metabolic mechanism only.\n\nGonadal function\nGonadotropes, primarily luteinising hormone (LH) secreted from the anterior pituitary stimulates the ovulation cycle in female mammals, whilst in the males, LH stimulates the synthesis of androgen which drives the ongoing will to mate together with a constant production of sperm.\n\nHPA axis\nHypothalamic-pituitary-adrenal axis\nThe anterior pituitary plays a role in stress response.\n\nCorticotropin releasing hormone (CRH) from the hypothalamus stimulates ACTH release in a cascading effect that ends with the production of glucocorticoids from the adrenal cortex.\n\n=== Behavioral effects ===\n\nDevelopment\nThe release of GH, LH, and FSH are required for correct human development, including gonadal development.\n\nBreast-feeding\nRelease of the hormone prolactin is essential for lactation.\nStress\nOperating through the hypothalamic-pituitary-adrenal axis (HPA), the anterior pituitary gland has a large role in the neuroendocrine system’s stress response.\n\nStress induces a release of corticotropin-releasing hormone (CRH) and vasopressin from the hypothalamus, which activates the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary gland.\n\nThen, this acts on the adrenal cortex to produce glucocorticoids such as cortisol.\n\nThese glucocorticoids act back on the anterior pituitary gland and the hypothalamus with negative feedback to slow the production of CRH and ACTH.\n\nIncreased cortisol under stress conditions can cause the following: metabolic effects (mobilization of glucose, fatty acids, and amino acids), bone re-absorption (calcium mobilization), activation of the sympathetic nervous system response (fight or flight), anti-inflammatory effects, and inhibition of reproduction/growth.\n\nWhen the anterior pituitary gland is removed (hypophysectomy) in rats, their avoidance learning mechanisms were slowed, but injections of ACTH restored their performance.\n\nIn addition, stress may delay the release of reproductive hormones such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH).\n\nThis shows that the anterior pituitary gland is involved in behavioral functions as well as being part of a larger pathway for stress responses.\n\nIt is also known that (HPA) hormones are related to certain skin diseases and skin homeostasis.\n\nThere is evidence linking hyperactivity of HPA hormones to stress-related skin diseases and skin tumors.\n\nAging\nOperating through the hypothalamic-pituitary-gonadal axis, the anterior pituitary gland also affects the reproductive system.\n\nThe hypothalamus releases gonadotropin-releasing hormone (GnRH), which stimulates the release of luteinizing hormone (LH) and follicle-stimulating hormone.\n\nThen the gonads produce estrogen and testosterone.\n\nThe decrease in release of gonadotropins (LH and FSH) caused by normal aging may be responsible for impotence and frailty in elderly men because of the eventual decrease in production of testosterone.\n\nThis lower level of testosterone can have other effects, such as reduced libido, well-being and mood, muscle and bone strength, and metabolism.\n\nTactile responding\nIt has been shown that infant mice who were stroked with a paintbrush (simulating motherly care) had more release and binding of growth hormone (GH) from the anterior pituitary gland.Circadian rhythms\n\nLight information received by the eyes is transmitted to the pineal gland via the circadian pacemaker (the suprachiasmatic nucleus).\n\nDiminishing light stimulates the release of melatonin from the pineal gland which can also affect the secretion levels in the hypothalamic-pituitary-gonadal axis.\n\nMelatonin can lower levels of LH and FSH, which will decrease levels of estrogen and testosterone.\n\nIn addition, melatonin may affect production of prolactin.\n\n== Clinical significance ==\n\n=== Increased activity ===\n\nHyperpituitarism is the condition where the pituitary secretes excessive amounts of hormones.\n\nThis hypersecretion often results in the formation of a pituitary adenoma (tumour), which are benign apart from a tiny fraction.\n\nThere are mainly three types of anterior pituitary tumors and their associated disorders.\n\nFor example, acromegaly results from excessive secretion of growth hormone (GH) often being released by a pituitary adenoma.\n\nThis disorder can cause disfigurement and possibly death and can lead to gigantism, a hormone disorder shown in “giants” such as André the Giant, where it occurs before the epiphyseal plates in bones close in puberty.\n\nThe most common type of pituitary tumour is a prolactinoma which hypersecretes prolactin.\n\nA third type of pituitary adenoma secretes excess ACTH, which in turn, causes an excess of cortisol to be secreted and is the cause of Cushing's disease.\n\n=== Decreased activity ===\n\nHypopituitarism is characterized by a decreased secretion of hormones released by the anterior pituitary.\n\nFor example, hypo-secretion of GH prior to puberty can be a cause of dwarfism.\n\nIn addition, secondary adrenal insufficiency can be caused by hypo-secretion of ACTH which, in turn, does not signal the adrenal cortex to produce a sufficient amount of cortisol.\n\nThis is a life-threatening condition.\n\nHypopituitarism could be caused by the destruction or removal of the anterior pituitary tissue through traumatic brain injury, tumor, tuberculosis, or syphilis, among other causes.\n\nThis disorder used to be referred to as Simmonds' disease but now according to the Diseases Database it is called Sheehan syndrome.\n\nIf the hypopituitarism is caused by the blood loss associated with childbirth, the disorder is referred to as Sheehan syndrome.\n\n== History ==\n\n=== Etymology ===\n\nThe anterior pituitary is also known as the adenohypophysis, meaning \"glandular undergrowth\", from the Greek adeno- (\"gland\"), hypo (\"under\"), and physis (\"growth\").\n\nhttps://en.wikipedia.org/wiki/Anterior_pituitary","neurohypophysis":"The posterior pituitary (or neurohypophysis) is the posterior lobe of the pituitary gland which is part of the endocrine system.\n\nThe posterior pituitary is not glandular as is the anterior pituitary.\n\nInstead, it is largely a collection of axonal projections from the hypothalamus that terminate behind the anterior pituitary, and serve as a site for the secretion of neurohypophysial hormones (oxytocin and vasopressin) directly into the blood.\n\nThe hypothalamic–neurohypophyseal system is composed of the hypothalamus (the paraventricular nucleus and supraoptic nucleus), posterior pituitary, and these axonal projections.\n\n== Structure ==\n\nThe posterior pituitary consists mainly of neuronal projections (axons) of magnocellular neurosecretory cells extending from the supraoptic and paraventricular nuclei of the hypothalamus.\n\nThese axons store and release neurohypophysial hormones oxytocin and vasopressin into the neurohypophyseal capillaries, from there they get into the systemic circulation (and partly back into the hypophyseal portal system).\n\nIn addition to axons, the posterior pituitary also contains pituicytes, specialized glial cells resembling astrocytes assisting in the storage and release of the hormones.\n\nClassification of the posterior pituitary varies, but most sources include the two regions below:\n\nPars nervosa\nAlso called the neural lobe or posterior lobe, this region constitutes the majority of the posterior pituitary and is the storage site of oxytocin and vasopressin.\n\nSometimes (incorrectly) considered synonymous with the posterior pituitary, the pars nervosa includes Herring bodies and pituicytes.\n\nInfundibular stalk\n\nAlso known as the infundibulum or pituitary stalk, the infundibular stalk bridges the hypothalamic and hypophyseal systems.\n\nThe median eminence is only occasionally included as part of the posterior pituitary.\n\nOther sources specifically exclude it from the pituitary.A few sources include the pars intermedia as part of the posterior lobe, but this is a minority view.\n\nIt is based upon the gross anatomical separation of the posterior and anterior pituitary along the cystic remnants of Rathke's pouch, causing the pars intermedia to remain attached to the neurohypophysis.\n\n== Function ==\n\n=== Hormone secretion ===\n\nTwo hormones are classically considered as being related to the posterior pituitary: oxytocin and vasopressin.\n\nThese hormones are created in the hypothalamus and released in the posterior pituitary.\n\nAfter creation, they are stored in neurosecretory vesicles regrouped into Herring bodies before being secreted in the posterior pituitary via the bloodstream.\n\n== Clinical significance ==\n\nInsufficient secretion of vasopressin underlies diabetes insipidus, a condition in which the body loses the capacity to concentrate urine.\n\nAffected individuals excrete as much as 20 liters of dilute urine per day.\n\nOversecretion of vasopressin causes the syndrome of inappropriate antidiuretic hormone (SIADH).\n\nhttps://en.wikipedia.org/wiki/Posterior_pituitary","thyroid-gland":"The thyroid, or thyroid gland, is an endocrine gland in vertebrates.\n\nIn humans it is in the neck and consists of two connected lobes.\n\nThe lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus.\n\nThe thyroid is located at the front of the neck, below the Adam's apple.\n\nMicroscopically, the functional unit of the thyroid gland is the spherical thyroid follicle, lined with follicular cells (thyrocytes), and occasional parafollicular cells that surround a lumen containing colloid.\n\nThe thyroid gland secretes three hormones: the two thyroid hormones – triiodothyronine (T3) and thyroxine (T4) – and a peptide hormone, calcitonin.\n\nThe thyroid hormones influence the metabolic rate and protein synthesis, and in children, growth and development.\n\nCalcitonin plays a role in calcium homeostasis.\n\nSecretion of the two thyroid hormones is regulated by thyroid-stimulating hormone (TSH), which is secreted from the anterior pituitary gland.\n\nTSH is regulated by thyrotropin-releasing hormone (TRH), which is produced by the hypothalamus.\n\nThe thyroid gland develops in the floor of the pharynx at the base of the tongue at 3–4 weeks gestation; it then descends in front of the pharyngeal gut, and ultimately over the next few weeks, it migrates to the base of the neck.\n\nDuring migration, the thyroid remains connected to the tongue by a narrow canal, the thyroglossal duct.\n\nAt the end of the fifth week the thyroglossal duct degenerates, and over the following two weeks the detached thyroid migrates to its final position.\n\nEuthyroid is the term used to describe a state of normal thyroid function in the body.\n\nThyroid disorders include hyperthyroidism, hypothyroidism, thyroid inflammation (thyroiditis), thyroid enlargement (goitre), thyroid nodules, and thyroid cancer.\n\nHyperthyroidism is characterized by excessive secretion of thyroid hormones: the most common cause is the autoimmune disorder Graves' disease.\n\nHypothyroidism is characterized by a deficient secretion of thyroid hormones: the most common cause is iodine deficiency.\n\nIn iodine-deficient regions, hypothyroidism secondary to iodine deficiency is the leading cause of preventable intellectual disability in children.\n\nIn iodine-sufficient regions, the most common cause of hypothyroidism is the autoimmune disorder Hashimoto's thyroiditis.\n\nThe presence of the thyroid and its various diseases have been noted and treated for centuries, although the gland itself has only been described and named since the Renaissance.\n\nKnowledge of the thyroid, its biochemistry, and its disorders developed throughout the late nineteenth and twentieth centuries.\n\nMany modern treatments and investigative modalities evolved throughout the mid-twentieth century, including refinement of surgical techniques for thyroid removal (thyroidectomy) for the treatment of goitre; the use of radioactive iodine and thiouracil for the treatment of Graves' disease; and fine needle aspiration for diagnosis of thyroid nodules.\n\n== Structure ==\n\n=== Features ===\n\nThe thyroid gland is a butterfly-shaped organ composed of two lobes, left and right, connected by a narrow tissue band, called an \"isthmus\".\n\nIt weighs 25 grams in adults, with each lobe being about 5 cm long, 3 cm wide, and 2 cm thick and the isthmus about 1.25 cm in height and width.\n\nThe gland is usually larger in women than in men, and increases in size during pregnancy.\n\nThe thyroid is near the front of the neck, lying against and around the front of the larynx and trachea.\n\nThe thyroid cartilage and cricoid cartilage lie just above the gland, below the Adam's apple.\n\nThe isthmus extends from the second to third rings of the trachea, with the uppermost part of the lobes extending to the thyroid cartilage and the lowermost around the fourth to sixth tracheal rings.\n\nThe infrahyoid muscles lie in front of the gland and the sternocleidomastoid muscle to the side.\n\nBehind the outer wings of the thyroid lie the two carotid arteries.\n\nThe trachea, larynx, lower pharynx and esophagus all lie behind the thyroid.\n\nIn this region, the recurrent laryngeal nerve and the inferior thyroid artery pass next to or in the ligament.\n\nTypically, four parathyroid glands, two on each side, lie on each side between the two layers of the thyroid capsule, at the back of the thyroid lobes.\n\nThe thyroid gland is covered by a thin fibrous capsule, which has an inner and an outer layer.\n\nThe inner layer extrudes into the gland and forms the septae that divides the thyroid tissue into microscopic lobules.\n\nThe outer layer is continuous with the pretracheal fascia, attaching the gland to the cricoid and thyroid cartilages via a thickening of the fascia to form the posterior suspensory ligament of thyroid gland, also known as Berry's ligament.\n\nThis causes the thyroid to move up and down with the movement of these cartilages when swallowing occurs.\n\n=== Blood, lymph and nerve supply ===\n\nThe thyroid is supplied with arterial blood from the superior thyroid artery, a branch of the external carotid artery, and the inferior thyroid artery, a branch of the thyrocervical trunk, and sometimes by an anatomical variant the thyroid ima artery, which has a variable origin.\n\nThe superior thyroid artery splits into anterior and posterior branches supplying the thyroid, and the inferior thyroid artery splits into superior and inferior branches.\n\nThe superior and inferior thyroid arteries join together behind the outer part of the thyroid lobes.\n\nThe venous blood is drained via superior and middle thyroid veins, which drain to the internal jugular vein, and via the inferior thyroid veins.\n\nThe inferior thyroid veins originate in a network of veins and drain into the left and right brachiocephalic veins.\n\nBoth arteries and veins form a plexus between the two layers of the capsule of the thyroid gland.Lymphatic drainage frequently passes the prelaryngeal lymph nodes (located just above the isthmus) and the pretracheal and paratracheal lymph nodes.\n\nThe gland receives sympathetic nerve supply from the superior, middle and inferior cervical ganglion of the sympathetic trunk.\n\nThe gland receives parasympathetic nerve supply from the superior laryngeal nerve and the recurrent laryngeal nerve.\n\n=== Variation ===\n\nThere are many variants in the size and shape of the thyroid gland, and in the position of the embedded parathyroid glands.\n\nSometimes there is a third lobe present called the pyramidal lobe.\n\nWhen present, this lobe often stretches up the hyoid bone from the thyroid isthmus and may be one to several divided lobes.\n\nThe presence of this lobe ranges in reported studies from 18.3% to 44.6%.\n\nIt was shown to more often arise from the left side and occasionally separated.\n\nThe pyramidal lobe is also known as Lalouette's pyramid.\n\nThe pyramidal lobe is a remnant of the thyroglossal duct, which usually wastes away during the thyroid gland's descent.\n\nSmall accessory thyroid glands may in fact occur anywhere along the thyroglossal duct, from the foramen cecum of the tongue to the position of the thyroid in the adult.\n\nA small horn at the back of the thyroid lobes, usually close to the recurrent laryngeal nerve and the inferior thyroid artery, is called Zuckerkandl's tubercle.\n\nOther variants include a levator muscle of thyroid gland, connecting the isthmus to the body of the hyoid bone, and the presence of the small thyroid ima artery.\n\n=== Microanatomy ===\n\nAt the microscopic level, there are three primary features of the thyroid—follicles, follicular cells, and parafollicular cells, first discovered by Geoffery Websterson in 1664.\n\nFolliclesThyroid follicles are small spherical groupings of cells 0.02–0.9mm in diameter that play the main role in thyroid function.\n\nThey consist of a rim that has a rich blood supply, nerve and lymphatic presence, that surrounds a core of colloid that consists mostly of thyroid hormone precursor proteins called thyroglobulin, an iodinated glycoprotein.\n\nFollicular cellsThe core of a follicle is surrounded by a single layer of follicular cells.\n\nWhen stimulated by thyroid stimulating hormone (TSH), these secrete the thyroid hormones T3 and T4.\n\nThey do this by transporting and metabolising the thyroglobulin contained in the colloid.\n\nFollicular cells vary in shape from flat to cuboid to columnar, depending on how active they are.\n\nParafollicular cellsScattered among follicular cells and in spaces between the spherical follicles are another type of thyroid cell, parafollicular cells.\n\nThese cells secrete calcitonin and so are also called C cells.\n\n== Development ==\n\nIn the development of the embryo, at 3–4 weeks gestational age, the thyroid gland appears as an epithelial proliferation in the floor of the pharynx at the base of the tongue between the tuberculum impar and the copula linguae.\n\nThe copula soon becomes covered over by the hypopharyngeal eminence at a point later indicated by the foramen cecum.\n\nThe thyroid then descends in front of the pharyngeal gut as a bilobed diverticulum through the thyroglossal duct.\n\nOver the next few weeks, it migrates to the base of the neck, passing in front of the hyoid bone.\n\nDuring migration, the thyroid remains connected to the tongue by a narrow canal, the thyroglossal duct.\n\nAt the end of the fifth week the thyroglossal duct degenerates, and over the following two weeks the detached thyroid migrates to its final position.\n\nThe fetal hypothalamus and pituitary start to secrete thyrotropin-releasing hormone (TRH) and thyroid-stimulating hormone (TSH).\n\nTSH is first measurable at 11 weeks.\n\nBy 18–20 weeks, the production of thyroxine (T4) reaches a clinically significant and self-sufficient level.\n\nFetal triiodothyronine (T3) remains low, less than 15 ng/dL until 30 weeks, and increases to 50 ng/dL at full-term.\n\nThe fetus needs to be self-sufficient in thyroid hormones in order to guard against neurodevelopmental disorders that would arise from maternal hypothyroidism.\n\nThe presence of sufficient iodine is essential for healthy neurodevelopment.\n\nThe neuroendocrine parafollicular cells, also known as C cells, responsible for the production of calcitonin, are derived from foregut endoderm.\n\nThis part of the thyroid then first forms as the ultimopharyngeal body, which begins in the ventral fourth pharyngeal pouch and joins the primordial thyroid gland during its descent to its final location.\n\nAberrations in prenatal development can result in various forms of thyroid dysgenesis which can cause congenital hypothyroidism, and if untreated this can lead to cretinism.\n\n== Function ==\n\n=== Thyroid hormones ===\n\nThe primary function of the thyroid is the production of the iodine-containing thyroid hormones, triiodothyronine (T3) and thyroxine (T4) and the peptide hormone calcitonin.\n\nThe thyroid hormones are created from iodine and tyrosine.\n\nT3 is so named because it contains three atoms of iodine per molecule and T4 contains four atoms of iodine per molecule.\n\nThe thyroid hormones have a wide range of effects on the human body.\n\nThese include:\n\n-Metabolic.\n\nThe thyroid hormones increase the basal metabolic rate and have effects on almost all body tissues.\n\nAppetite, the absorption of substances, and gut motility are all influenced by thyroid hormones.\n\nThey increase the absorption in the gut, generation, uptake by cells, and breakdown of glucose.\n\nThey stimulate the breakdown of fats, and increase the number of free fatty acids.\n\nDespite increasing free fatty acids, thyroid hormones decrease cholesterol levels, perhaps by increasing the rate of secretion of cholesterol in bile.\n\n-Cardiovascular.\n\nThe hormones increase the rate and strength of the heartbeat.\n\nThey increase the rate of breathing, intake and consumption of oxygen, and increase the activity of mitochondria.\n\nCombined, these factors increase blood flow and the body's temperature.\n\n-Developmental.\n\nThyroid hormones are important for normal development.\n\nThey increase the growth rate of young people, and cells of the developing brain are a major target for the thyroid hormones T3 and T4.\n\nThyroid hormones play a particularly crucial role in brain maturation during fetal development and first few years of postnatal life.\n\nThe thyroid hormones also play a role in maintaining normal sexual function, sleep, and thought patterns.\n\nIncreased levels are associated with increased speed of thought generation but decreased focus.\n\nSexual function, including libido and the maintenance of a normal menstrual cycle, are influenced by thyroid hormones.After secretion, only a very small proportion of the thyroid hormones travel freely in the blood.\n\nMost are bound to thyroxine-binding globulin (about 70%), transthyretin (10%), and albumin (15%).\n\nOnly the 0.03% of T4 and 0.3% of T3 traveling freely have hormonal activity.\n\nIn addition, up to 85% of the T3 in blood is produced following conversion from T4 by iodothyronine deiodinases in organs around the body.\n\nThyroid hormones act by crossing the cell membrane and binding to intracellular nuclear thyroid hormone receptors TR-α1,TR-α2,TR-β1 and TR-β2, which bind with hormone response elements and transcription factors to modulate DNA transcription.\n\nIn addition to these actions on DNA, the thyroid hormones also act within the cell membrane or within cytoplasm via reactions with enzymes, including calcium ATPase, adenylyl cyclase, and glucose transporters.\n\n=== Hormone production ===\n\nThe thyroid hormones are created from thyroglobulin.\n\nThis is a protein within the colloid in the follicular lumen that is originally created within the rough endoplasmic reticulum of follicular cells and then transported into the follicular lumen.\n\nThyroglobulin contains 123 units of tyrosine, which reacts with iodine within the follicular lumen.Iodine is essential for the production of the thyroid hormones.\n\nIodine (I0) travels in the blood as iodide (I−), which is taken up into the follicular cells by a sodium-iodide symporter.\n\nThis is an ion channel on the cell membrane which in the same action transports two sodium ions and an iodide ion into the cell.\n\nIodide then travels from within the cell into the lumen, through the action of pendrin, an iodide-chloride antiporter.\n\nIn the follicular lumen, the iodide is then oxidized to iodine.\n\nThis makes it more reactive, and the iodine is attached to the active tyrosine units in thyroglobulin by the enzyme thyroid peroxidase.\n\nThis forms the precursors of thyroid hormones monoiodotyrosine (MIT), and diiodotyrosine (DIT).When the follicular cells are stimulated by thyroid-stimulating hormone, the follicular cells reabsorb thyroglobulin from the follicular lumen.\n\nThe iodinated tyrosines are cleaved, forming the thyroid hormones T4, T3, DIT, MIT, and traces of reverse triiodothyronine.\n\nT3 and T4 are released into the blood.\n\nThe hormones secreted from the gland are about 80–90% T4 and about 10–20% T3.\n\nDeiodinase enzymes in peripheral tissues remove the iodine from MIT and DIT and convert T4 to T3 and RT3.\n\nThis is a major source of both RT3 (95%) and T3 (87%) in peripheral tissues.\n\n=== Regulation ===\n\nThe production of thyroxine and triiodothyronine is primarily regulated by thyroid-stimulating hormone (TSH), released by the anterior pituitary gland.\n\nTSH release in turn is stimulated by thyrotropin releasing hormone (TRH), released in a pulsatile manner from the hypothalamus.\n\nThe thyroid hormones provide negative feedback to the thyrotropes TSH and TRH: when the thyroid hormones are high, TSH production is suppressed.\n\nThis negative feedback also occurs when levels of TSH are high, causing TRH production to be suppressed.\n\nTRH is secreted at an increased rate in situations such as cold exposure in order to stimulate thermogenesis.\n\nIn addition to being suppressed by the presence of thyroid hormones, TSH production is blunted by dopamine, somatostatin, and glucocorticoids.\n\n=== Calcitonin ===\n\nThe thyroid gland also produces the hormone calcitonin, which helps regulate blood calcium levels.\n\nParafollicular cells produce calcitonin in response to high blood calcium.\n\nCalcitonin decreases the release of calcium from bone, by decreasing the activity of osteoclasts, cells which break down bone.\n\nBone is constantly reabsorbed by osteoclasts and created by osteoblasts, so calcitonin effectively stimulates movement of calcium into bone.\n\nThe effects of calcitonin are opposite those of the parathyroid hormone (PTH) produced in the parathyroid glands.\n\nHowever, calcitonin seems far less essential than PTH, since calcium metabolism remains clinically normal after removal of the thyroid (thyroidectomy), but not the parathyroid glands.\n\n== Gene and protein expression ==\n\nAbout 20,000 protein coding genes are expressed in human cells: 70% of these genes are expressed in thyroid cells.\n\nTwo-hundred fifty of these genes are more specifically expressed in the thyroid, and about 20 genes are highly thyroid specific.\n\nIn the follicular cells, the proteins synthesized by these genes direct thyroid hormone synthesis—thyroglobulin, TPO, and IYD; while in the parafollicular c-cells, they direct calcitonin synthesis—CALCA, and CALCB.\n\n== Clinical significance ==\n\nGeneral practitioners, family physicians, and internal medicine specialists play a role in identifying and monitoring the treatment of thyroid disease.\n\nEndocrinologists and thyroidologists are thyroid specialists.\n\nThyroid surgeons or otolaryngologists are responsible for the surgical management of thyroid disease.\n\n=== Functional disorders ===\n\n==== Hyperthyroidism ====\n\nExcessive production of the thyroid hormones is called hyperthyroidism.\n\nCauses include Graves' disease, toxic multinodular goitre, solitary thyroid adenoma, inflammation, and a pituitary adenoma which secretes excess TSH.\n\nAnother cause is excess iodine availability, either from excess ingestion, induced by the drug amiodarone, or following iodinated contrast imaging.\n\nHyperthyroidism often causes a variety of non-specific symptoms including weight loss, increased appetite, insomnia, decreased tolerance of heat, tremor, palpitations, anxiety and nervousness.\n\nIn some cases it can cause chest pain, diarrhoea, hair loss and muscle weakness.\n\nSuch symptoms may be managed temporarily with drugs such as beta blockers.Long-term management of hyperthyroidism may include drugs that suppress thyroid function such as propylthiouracil, carbimazole and methimazole.\n\nAlternatively, radioactive iodine-131 can be used to destroy thyroid tissue: radioactive iodine is selectively taken up by thyroid cells, which over time destroys them.\n\nThe chosen first-line treatment will depend on the individual and on the country where being treated.\n\nSurgery to remove the thyroid can sometimes be performed as a transoral thyroidectomy, a minimally-invasive procedure.\n\nSurgery does however carry a risk of damage to the parathyroid glands and the recurrent laryngeal nerve, which innervates the vocal cords.\n\nIf the entire thyroid gland is removed, hypothyroidism will inevitably result, and thyroid hormone substitutes will be needed.\n\n==== Hypothyroidism ====\n\nAn underactive thyroid gland results in hypothyroidism.\n\nTypical symptoms are abnormal weight gain, tiredness, constipation, heavy menstrual bleeding, hair loss, cold intolerance, and a slow heart rate.\n\nIodine deficiency is the most common cause of hypothyroidism worldwide, and the autoimmune disease Hashimoto's thyroiditis is the most common cause in the developed world.\n\nOther causes include congenital abnormalities, diseases causing transient inflammation, surgical removal or radioablation of the thyroid, the drugs amiodarone and lithium, amyloidosis, and sarcoidosis.\n\nSome forms of hypothyroidism can result in myxedema and severe cases can result in myxedema coma.Hypothyroidism is managed with replacement of the hormone thyroxine.\n\nThis is usually given daily as an oral supplement, and may take a few weeks to become effective.\n\nSome causes of hypothyroidism, such as Postpartum thyroiditis and Subacute thyroiditis may be transient and pass over time, and other causes such as iodine deficiency may be able to be rectified with dietary supplementation.\n\n=== Diseases ===\n\n==== Graves' disease ====\n\nGraves' disease is an autoimmune disorder that is the most common cause of hyperthyroidism.\n\nIn Graves' disease, for an unknown reason autoantibodies develop against the thyroid stimulating hormone receptor.\n\nThese antibodies activate the receptor, leading to development of a goitre and symptoms of hyperthyroidism, such as heat intolerance, weight loss, diarrhoea and palpitations.\n\nOccasionally such antibodies block but do not activate the receptor, leading to symptoms associated with hypothyroidism.\n\nIn addition, gradual protrusion of the eyes may occur, called Graves' ophthalmopathy, as may swelling of the front of the shins.\n\nGraves' disease can be diagnosed by the presence of pathomnomonic features such as involvement of the eyes and shins, or isolation of autoantibodies, or by results of a radiolabelled uptake scan.\n\nGraves' disease is treated with anti-thyroid drugs such as propylthiouracil, which decrease the production of thyroid hormones, but hold a high rate of relapse.\n\nIf there is no involvement of the eyes, then use of radioactive isotopes to ablate the gland may be considered.\n\nSurgical removal of the gland with subsequent thyroid hormone replacement may be considered, however this will not control symptoms associated with the eye or skin.\n\n==== Nodules ====\n\nThyroid nodules are often found on the gland, with a prevalence of 4–7%.\n\nThe majority of nodules do not cause any symptoms, thyroid hormone secretion is normal, and they are non-cancerous.\n\nNon-cancerous cases include simple cysts, colloid nodules, and thyroid adenomas.\n\nMalignant nodules, which only occur in about 5% of nodules, include follicular, papillary, medullary carcinomas and metastases from other sites Nodules are more likely in females, those who are exposed to radiation, and in those who are iodine deficient.\n\nWhen a nodule is present, thyroid function tests determine whether the nodule is secreting excess thyroid hormones, causing hyperthyroidism.\n\nWhen the thyroid function tests are normal, an ultrasound is often used to investigate the nodule, and provide information such as whether the nodule is fluid-filled or a solid mass, and whether the appearance is suggestive of a benign or malignant cancer.\n\nA needle aspiration biopsy may then be performed, and the sample undergoes cytology, in which the appearance of cells is viewed to determine whether they resemble normal or cancerous cells.\n\nThe presence of multiple nodules is called a multinodular goitre; and if it is associated with hyperthyroidism, it is called a toxic multinodular goitre.\n\n==== Goitre ====\n\nAn enlarged thyroid gland is called a goitre.\n\nGoitres are present in some form in about 5% of people, and are the result of a large number of causes, including iodine deficiency, autoimmune disease (both Graves' disease and Hashimoto's thyroiditis), infection, inflammation, and infiltrative disease such as sarcoidosis and amyloidosis.\n\nSometimes no cause can be found, a state called \"simple goitre\".Some forms of goitre are associated with pain, whereas many do not cause any symptoms.\n\nEnlarged goitres may extend beyond the normal position of the thyroid gland to below the sternum, around the airway or esophagus.\n\nGoitres may be associated with hyperthyroidism or hypothyroidism, relating to the underlying cause of the goitre.\n\nThyroid function tests may be done to investigate the cause and effects of the goitre.\n\nThe underlying cause of the goitre may be treated, however many goitres with no associated symptoms are simply monitored.\n\n==== Inflammation ====\n\nInflammation of the thyroid is called thyroiditis, and may cause symptoms of hyperthyroidism or hypothyroidism.\n\nTwo types of thyroiditis initially present with hyperthyroidism and are sometimes followed by a period of hypothyroidism – Hashimoto's thyroiditis and postpartum thyroiditis.\n\nThere are other disorders that cause inflammation of the thyroid, and these include subacute thyroiditis, acute thyroiditis, silent thyroiditis, Riedel's thyroiditis and traumatic injury, including palpation thyroiditis.\n\nHashimoto's thyroiditis is an autoimmune disorder in which the thyroid gland is infiltrated by the lymphocytes B-cell and T-cells.\n\nThese progressively destroy the thyroid gland.\n\nIn this way, Hasimoto's thyroiditis may have occurred insidiously, and only be noticed when thyroid hormone production decreases, causing symptoms of hypothyroidism.\n\nHashimoto's is more common in females than males, much more common after the age of 60, and has known genetic risk factors.\n\nAlso more common in individuals with Hashimoto's thyroiditis are type 1 diabetes, pernicious anaemia, Addison's disease vitiligo.Postpartum thyroiditis occurs in some females following childbirth.\n\nAfter delivery, the gland becomes inflamed and the condition initially presents with a period of hyperthyroidism followed by hypothyroidism and, usually, a return to normal function.\n\nThe course of the illness takes place over several months, and is characterised by a painless goitre.\n\nAntibodies against thyroid peroxidase can be found on testing.\n\nThe inflammation usually resolves without treatment, although thyroid hormone replacement may be needed during the period of hypothyroidism.\n\n==== Cancer ====\n\nThe most common neoplasm affecting the thyroid gland is a benign adenoma, usually presenting as a painless mass in the neck.\n\nMalignant thyroid cancers are most often carcinomas, although cancer can occur in any tissue that the thyroid consists of, including cancer of C-cells and lymphomas.\n\nCancers from other sites also rarely lodge in the thyroid.\n\nRadiation of the head and neck presents a risk factor for thyroid cancer, and cancer is more common in women than men, occurring at a rate of about 2:1.\n\nIn most cases, thyroid cancer presents as a painless mass in the neck.\n\nIt is very unusual for thyroid cancers to present with other symptoms, although in some cases cancer may cause hyperthyroidism.\n\nMost malignant thyroid cancers are papillary, followed by follicular, medullary, and thyroid lymphoma.\n\nBecause of the prominence of the thyroid gland, cancer is often detected earlier in the course of disease as the cause of a nodule, which may undergo fine needle aspiration.\n\nThyroid function tests will help reveal whether the nodule produces excess thyroid hormones.\n\nA radioactive iodine uptake test can help reveal the activity and location of the cancer and metastases.\n\nThyroid cancers are treated by removing the whole or part of thyroid gland.\n\nRadioactive Iodine 131 may be given to radioablate the thyroid.\n\nThyroxine is given to replace the hormones lost and to suppress TSH production, as TSH may stimulate recurrence.\n\nWith the exception of the rare anaplastic thyroid cancer, which carries a very poor prognosis, most thyroid cancers carry an excellent prognosis and can even be considered curable.\n\n==== Congenital ====\nA persistent thyroglossal duct is the most common clinically significant congenital disorder of the thyroid gland.\n\nA persistent sinus tract may remain as a vestigial remnant of the tubular development of the thyroid gland.\n\nParts of this tube may be obliterated, leaving small segments to form thyroglossal cysts.\n\nPreterm neonates are at risk of hypothyroidism as their thyroid glands are insufficiently developed to meet their postnatal needs.\n\nIn order to detect hypothyroidism in newborn babies, to prevent growth and development abnormalities in later life, many countries have newborn screening programs at birth.\n\nInfants with thyroid hormone deficiency (congenital hypothyroidism) can manifest problems of physical growth and development as well as brain development, termed cretinism.\n\nChildren with congenital hypothyroidism are treated supplementally with levothyroxine, which facilitates normal growth and development.Mucinous, clear secretions may collect within these cysts to form either spherical masses or fusiform swellings, rarely larger than 2 to 3 cm in diameter.\n\nThese are present in the midline of the neck anterior to the trachea.\n\nSegments of the duct and cysts that occur high in the neck are lined by stratified squamous epithelium, which is essentially identical to that covering the posterior portion of the tongue in the region of the foramen cecum.\n\nThe disorders that occur in the lower neck more proximal to the thyroid gland are lined by epithelium resembling the thyroidal acinar epithelium.\n\nCharacteristically, next to the lining epithelium, there is an intense lymphocytic infiltrate.\n\nSuperimposed infection may convert these lesions into abscess cavities, and rarely, give rise to cancers.\n\nAnother disorder is that of thyroid dysgenesis which can result in various presentations of one or more misplaced accessory thyroid glands.\n\nThese can be asymptomatic.\n\n==== Iodine ====\n\nIodine deficiency, most common in inland and mountainous areas, can predispose to goitre – if widespread, known as endemic goitre.\n\nPregnant women deficient of iodine can give birth to infants with thyroid hormone deficiency.\n\nThe use of iodised salt to add iodine to the diet has eliminated endemic cretinism in most developed countries, and over 120 countries have made the iodination of salt mandatory.\n\nBecause the thyroid concentrates iodine, it also concentrates the various radioactive isotopes of iodine produced by nuclear fission.\n\nIn the event of large accidental releases of such material into the environment, the uptake of radioactive iodine isotopes by the thyroid can, in theory, be blocked by saturating the uptake mechanism with a large surplus of non-radioactive iodine, taken in the form of potassium iodide tablets.\n\nOne consequence of the Chernobyl disaster was an increase in thyroid cancers in children in the years following the accident.\n\nExcessive iodine intake is uncommon and usually has no effect on the thyroid function.\n\nSometimes though it may cause hyperthyroidism, and sometimes hypothyroidism with a resulting goitre.\n\n=== Evaluation ===\n\nThe thyroid is examined by observation of the gland and surrounding neck for swelling or enlargement.\n\nIt is then felt, usually from behind, and a person is often asked to swallow to better feel the gland against the fingers of the examiner.\n\nThe gland moves up and down with swallowing because of its attachments to the thyroid and cricoid cartilages.\n\nIn a healthy person the gland is not visible yet is palpable as a soft mass.\n\nExamination of the thyroid gland includes the search for abnormal masses and the assessment of overall thyroid size.\n\nThe character of the thyroid, swellings, nodules, and their consistency may all be able to be felt.\n\nIf a goitre is present, an examiner may also feel down the neck consider tapping the upper part of the chest to check for extension.\n\nFurther tests may include raising the arms (Pemberton's sign), listening to the gland with a stethoscope for bruits, testing of reflexes, and palpation of the lymph nodes in the head and neck.\n\nAn examination of the thyroid will also include observation of the person as a whole, to look for systemic signs such as weight gain or loss, hair loss, and signs in other locations – such as protrusion of the eyes or swelling of the calves in Graves' disease.\n\n=== Tests ===\n\nThyroid function tests include a battery of blood tests, including the measurement of the thyroid hormones, as well as the measurement of thyroid stimulating hormone (TSH).\n\nThey may reveal hyperthyroidism (high T3 and T4), hypothyroidism (low T3, T4), or subclinical hyperthyroidism (normal T3 and T4 with a low TSH).TSH levels are considered the most sensitive marker of thyroid dysfunction.\n\nThey are however not always accurate, particularly if the cause of hypothyroidism is thought to be related to insufficient thyrotropin releasing hormone (TRH) secretion, in which case it may be low or falsely normal.\n\nIn such a case a TRH stimulation test, in which TRH is given and TSH levels are measured at 30 and 60-minutes after, may be conducted.T3 and T4 can be measured directly.\n\nHowever, as the two thyroid hormones travel bound to other molecules, and it is the \"free\" component that is biologically active, free T3 and free T4 levels can be measured.\n\nT4 is preferred, because in hypothyroidism T3 levels may be normal.\n\nThe ratio of bound to unbound thyroid hormones is known as the thyroid hormone binding ratio (THBR).\n\nIt is also possible to measure directly the main carriers of the thyroid hormones, thryoglobulin and throxine-binding globulin.\n\nThyroglobulin will also be measurable in a healthy thyroid, and will increase with inflammation, and may also be used to measure the success of thyroid removal or ablation.\n\nIf successful, thyroglobulin should be undetectable.\n\nLastly, antibodies against components of the thyroid, particularly anti-TPO and anti-thyroglobulin, can be measured.\n\nThese may be present in normal individuals but are highly sensitive for autoimmune-related disease.\n\n==== Imaging ====\n\nUltrasound of the thyroid may be used to reveal whether structures are solid or filled with fluid, helping to differentiate between nodules and goitres and cysts.\n\nIt may also help differentiate between malignant and benign lesions.When further imaging is required, a radiolabelled iodine-123 or technetium-99 uptake scan may take place.\n\nThis can determine the size and shape of lesions, reveal whether nodules or goitres are metabolically active, and reveal and monitor sites of thyroid disease or cancer deposits outside the thyroid.\n\nA fine needle aspiration of a sample of thyroid tissue may be taken in order to evaluate a lesion seen on ultrasound which is then sent for histopathology and cytology.Computed tomography of the thyroid plays an important role in the evaluation of thyroid cancer.\n\nCT scans often incidentally find thyroid abnormalities, and thereby practically becomes the first investigation modality.\n\n== History ==\n\nThe thyroid gland received its modern name in the 1600s, when the anatomist Thomas Wharton likened its shape to that of an Ancient Greek shield or thyos.\n\nHowever, the existence of the gland, and of the diseases associated with it, was known long before then.\n\n=== Antiquity ===\n\nThe presence and diseases of the thyroid have been noted and treated for thousands of years.\n\nIn 1600 BCE burnt sponge and seaweed (which contain iodine) were used within China for the treatment of goitres, a practice which has developed in many parts of the world.\n\nIn Ayurvedic medicine, the book Sushruta Samhita written about 1400 BCE described hyperthyroidism, hypothyroidism and goitre.\n\nAristotle and Xenophon in the fifth century BCE describe cases of diffuse toxic goitre.\n\nHippocrates and Plato in the fourth century BCE provided some of the first descriptions of the gland itself, proposing its function as a salivary gland.\n\nPliny the Elder in the first century BCE referred to epidemics of goitre in the Alps and proposed treatment with burnt seaweed, a practice also referred to by Galen in the second century, referred to burnt sponge for the treatment of goitre.\n\nThe Chinese pharmacology text Shennong Ben Cao Jing, written ca. 200-250, also refers to goitre.\n\n=== Scientific era ===\n\nIn 1500 polymath Leonardo da Vinci provided the first illustration of the thyroid.\n\nIn 1543 anatomist Andreas Vesalius gave the first anatomic description and illustration of the gland.\n\nIn 1656 the thyroid received its modern name, by the anatomist Thomas Wharton.\n\nThe gland was named thyroid, meaning shield, as its shape resembled the shields commonly used in Ancient Greece.\n\nThe English name thyroid gland is derived from the medical Latin used by Wharton – glandula thyreoidea.\n\nGlandula means 'gland' in Latin, and thyreoidea can be traced back to the Ancient Greek word θυρεοειδής, meaning 'shield-like/shield-shaped'.\n\nFrench chemist Bernard Courtois discovered iodine in 1811, and in 1896 Eugen Baumann documented it as the central ingredient in the thyroid gland.\n\nHe did this by boiling the thyroid glands of a thousand sheep, and named the precipitate, a combination of the thyroid hormones, 'iodothyrin'.\n\nDavid Marine in 1907 proved that iodine is necessary for thyroid function.Graves' disease was described by Robert James Graves in 1834.\n\nThe role of the thyroid gland in metabolism was demonstrated in 1895 by Adolf Magnus-Levy.\n\nThyroxine was first isolated in 1914 and synthesized in 1927, and triiodothyroxine in 1952.\n\nThe conversion of T4 to T3 was discovered in 1970.\n\nThe process of discovering TSH took place over the early to mid twentieth century.\n\nTRH was discovered by Polish endocrinologist Andrew Schally in 1970, contributing in part to his Nobel Prize in Medicine in 1977.\n\nIn the nineteenth century numerous authors described both cretinism and myxedema, and their relationship to the thyroid.\n\nCharles Mayo coined the term hyperthyroidism in 1910.\n\nHakaru Hashimoto documented a case of Hashimoto's thyroiditis in 1912, antibodies in this disease were demonstrated in 1956.\n\nKnowledge of the thyroid and its conditions developed throughout the late nineteenth and twentieth centuries, with many modern treatments and investigative modalities evolving throughout the mid twentieth century, including the use of radioactive iodine, thiouracil and fine needle aspiration.\n\n=== Surgery ===\n\nEither Aetius in the sixth century CE or Persian Ali ibn Abbas al-Magusi in 990 CE conducted the first recorded thyroidectomy as a treatment for goitre.\n\nOperations remained risky and generally were not successful until the 19th century, when descriptions emerged from a number of authors including Prussian surgeon Theodor Billroth, Swiss surgeon and physiologist Theodor Kocher, American physician Charles Mayo, American surgeons William Halsted and George Crile.\n\nThese descriptions provided the basis for modern thyroid surgery.\n\nTheodor Kocher went on to win the Nobel Prize in Physiology or Medicine in 1909 \"for his work on the physiology, pathology and surgery of the thyroid gland\".\n\n== Other animals ==\n\nThe thyroid gland is found in all vertebrates.\n\nIn fish, it is usually located below the gills and is not always divided into distinct lobes.\n\nHowever, in some teleosts, patches of thyroid tissue are found elsewhere in the body, associated with the kidneys, spleen, heart, or eyes.\n\nIn tetrapods, the thyroid is always found somewhere in the neck region.\n\nIn most tetrapod species, there are two paired thyroid glands – that is, the right and left lobes are not joined together.\n\nHowever, there is only ever a single thyroid gland in most mammals, and the shape found in humans is common to many other species.\n\nIn larval lampreys, the thyroid originates as an exocrine gland, secreting its hormones into the gut, and associated with the larva's filter-feeding apparatus.\n\nIn the adult lamprey, the gland separates from the gut, and becomes endocrine, but this path of development may reflect the evolutionary origin of the thyroid.\n\nFor instance, the closest living relatives of vertebrates, the tunicates and amphioxi (lancelets), have a structure very similar to that of larval lampreys (the endostyle), and this also secretes iodine-containing compounds, though not thyroxine.\n\nThyroxine is critical to metabolic regulation, and growth throughout the vertebrate clade.\n\nIodine and T4 trigger the change from a plant-eating water-dwelling tadpole into a meat-eating land-dwelling frog, with better neurological, visuospatial, smell and cognitive abilities for hunting, as seen in other predatory animals.\n\nA similar phenomenon happens in the neotenic amphibian salamanders, which, without introducing iodine, don't transform into land-dwelling adults, and live and reproduce in the larval form of aquatic axolotl.\n\nAmong amphibians, administering a thyroid-blocking agent such as propylthiouracil (PTU) can prevent tadpoles from metamorphosing into frogs; in contrast, administering thyroxine will trigger metamorphosis.\n\nIn amphibian metamorphosis, thyroxine and iodine also exert a well-studied experimental model of apoptosis on the cells of gills, tail, and fins of tadpoles.\n\nIodine, via iodolipids, has favored the evolution of terrestrial animal species and has likely played a crucial role in the evolution of the human brain.\n\nhttps://en.wikipedia.org/wiki/Thyroid","inferior-parathyroid-gland":"The two parathyroid glands on each side which are positioned higher are called the superior parathyroid glands, while the lower two are called the inferior parathyroid glands.\n\nhttps://en.wikipedia.org/wiki/Parathyroid_gland#Anatomy","superior-parathyroid-gland":"The two parathyroid glands on each side which are positioned higher are called the superior parathyroid glands, while the lower two are called the inferior parathyroid glands.\n\nhttps://en.wikipedia.org/wiki/Parathyroid_gland#Anatomy","suprarenal-gland":"The suprarenal glands (also known as adrenal glands) are endocrine glands that produce a variety of hormones including suprarenaline and the steroids aldosterone and cortisol.\n\nThey are found above the kidneys.\n\nEach gland has an outer cortex which produces steroid hormones and an inner medulla.\n\nThe suprarenal cortex itself is divided into three main zones: the zona glomerulosa, the zona fasciculata and the zona reticularis.\n\nThe suprarenal cortex produces three main types of steroid hormones: mineralocorticoids, glucocorticoids, and androgens.\n\nMineralocorticoids (such as aldosterone) produced in the zona glomerulosa help in the regulation of blood pressure and electrolyte balance.\n\nThe glucocorticoids cortisol and cortisone are synthesized in the zona fasciculata; their functions include the regulation of metabolism and immune system suppression.\n\nThe innermost layer of the cortex, the zona reticularis, produces androgens that are converted to fully functional sex hormones in the gonads and other target organs.\n\nThe production of steroid hormones is called steroidogenesis, and involves a number of reactions and processes that take place in cortical cells.\n\nThe medulla produces the catecholamines, which function to produce a rapid response throughout the body in stress situations.\n\nA number of endocrine diseases involve dysfunctions of the suprarenal gland.\n\nOverproduction of cortisol leads to Cushing's syndrome, whereas insufficient production is associated with Addison's disease.\n\nCongenital suprarenal hyperplasia is a genetic disease produced by dysregulation of endocrine control mechanisms.\n\nA variety of tumors can arise from suprarenal tissue and are commonly found in medical imaging when searching for other diseases.\n\n== Structure ==\n\nThe suprarenal glands are located on both sides of the body in the retroperitoneum, above and slightly medial to the kidneys.\n\nIn humans, the right suprarenal gland is pyramidal in shape, whereas the left is semilunar or crescent shaped and somewhat larger.\n\nThe suprarenal glands measure approximately 3 cm in width, 5.0 cm in length, and up to 1.0 cm in thickness.\n\nTheir combined weight in an adult human ranges from 7 to 10 grams.\n\nThe glands are yellowish in colour.\n\nThe suprarenal glands are surrounded by a fatty capsule and lie within the renal fascia, which also surrounds the kidneys.\n\nA weak septum (wall) of connective tissue separates the glands from the kidneys.\n\nThe suprarenal glands are directly below the diaphragm, and are attached to the crura of the diaphragm by the renal fascia.\n\nEach suprarenal gland has two distinct parts, each with a unique function, the outer suprarenal cortex and the inner medulla, both of which produce hormones.\n\n=== suprarenal cortex ===\n\nThe suprarenal cortex is the outer region and also the largest part of an suprarenal gland.\n\nIt is divided into three separate zones: zona glomerulosa, zona fasciculata and zona reticularis.\n\nEach zone is responsible for producing specific hormones.\nThe suprarenal cortex is the outermost layer of the suprarenal gland.\n\nWithin the cortex are three layers, called \"zones\".\n\nWhen viewed under a microscope each layer has a distinct appearance, and each has a different function.\n\nThe suprarenal cortex is devoted to production of hormones, namely aldosterone, cortisol, and androgens.\n\n==== Zona glomerulosa ====\nThe outermost zone of the suprarenal cortex is the zona glomerulosa.\n\nIt lies immediately under the fibrous capsule of the gland.\n\nCells in this layer form oval groups, separated by thin strands of connective tissue from the fibrous capsule of the gland and carry wide capillaries.\n\nThis layer is the main site for production of aldosterone, a mineralocorticoid, by the action of the enzyme aldosterone synthase.\n\nAldosterone plays an important role in the long-term regulation of blood pressure.\n\n==== Zona fasciculata ====\nThe zona fasciculata is situated between the zona glomerulosa and zona reticularis.\n\nCells in this layer are responsible for producing glucocorticoids such as cortisol.\n\nIt is the largest of the three layers, accounting for nearly 80% of the volume of the cortex.\n\nIn the zona fasciculata, cells are arranged in columns radially oriented towards the medulla.\n\nCells contain numerous lipid droplets, abundant mitochondria and a complex smooth endoplasmic reticulum.\n\n==== Zona reticularis ====\nThe innermost cortical layer, the zona reticularis, lies directly adjacent to the medulla.\n\nIt produces androgens, mainly dehydroepiandrosterone (DHEA), DHEA sulfate (DHEA-S), and androstenedione (the precursor to testosterone) in humans.\n\nIts small cells form irregular cords and clusters, separated by capillaries and connective tissue.\n\nThe cells contain relatively small quantities of cytoplasm and lipid droplets, and sometimes display brown lipofuscin pigment.\n\n=== Medulla ===\n\nThe suprarenal medulla is at the centre of each suprarenal gland, and is surrounded by the suprarenal cortex.\n\nThe chromaffin cells of the medulla are the body's main source of the catecholamines, such as suprarenaline and norsuprarenaline, released by the medulla.\n\nApproximately 20% norsuprarenaline (norepinephrine) and 80% suprarenaline (epinephrine) are secreted here.\n\nThe suprarenal medulla is driven by the sympathetic nervous system via preganglionic fibers originating in the thoracic spinal cord, from vertebrae T5–T11.\n\nBecause it is innervated by preganglionic nerve fibers, the suprarenal medulla can be considered as a specialized sympathetic ganglion.\n\nUnlike other sympathetic ganglia, however, the suprarenal medulla lacks distinct synapses and releases its secretions directly into the blood.\n\n=== Blood supply ===\n\nThe suprarenal glands have one of the greatest blood supply rates per gram of tissue of any organ: up to 60 small arteries may enter each gland.\n\nThree arteries usually supply each suprarenal gland:\nThe superior suprarenal artery, a branch of the inferior phrenic artery\n-The middle suprarenal artery, a direct branch of the abdominal aorta\n-The inferior suprarenal artery, a branch of the renal arteryThese blood vessels supply a network of small arteries within the capsule of the suprarenal glands.\n\nThin strands of the capsule enter the glands, carrying blood to them.\n\nVenous blood is drained from the glands by the suprarenal veins, usually one for each gland:\n-The right suprarenal vein drains into the inferior vena cava\n-The left suprarenal vein drains into the left renal vein or the left inferior phrenic vein.The central adrenomedullary vein, in the suprarenal medulla, is an unusual type of blood vessel.\n\nIts structure is different from the other veins in that the smooth muscle in its tunica media (the middle layer of the vessel) is arranged in conspicuous, longitudinally oriented bundles.\n\n=== Variability ===\n\nThe suprarenal glands may not develop at all, or may be fused in the midline behind the aorta.\n\nThese are associated with other congenital abnormalities, such as failure of the kidneys to develop, or fused kidneys.\n\nThe gland may develop with a partial or complete absence of the cortex, or may develop in an unusual location.\n\n== Function ==\n\nThe suprarenal gland secretes a number of different hormones which are metabolised by enzymes either within the gland or in other parts of the body.\n\nThese hormones are involved in a number of essential biological functions.\n\n=== Corticosteroids ===\n\nCorticosteroids are a group of steroid hormones produced from the cortex of the suprarenal gland, from which they are named.\nMineralocorticoids such as aldosterone regulate salt (\"mineral\") balance and blood volume.\n\nGlucocorticoids such as cortisol influence metabolism rates of proteins, fats and sugars (\"glucose\").\n\nAndrogens such as dehydroepiandrosterone.MineralocorticoidsThe suprarenal gland produces aldosterone, a mineralocorticoid, which is important in the regulation of salt (\"mineral\") balance and blood volume.\n\nIn the kidneys, aldosterone acts on the distal convoluted tubules and the collecting ducts by increasing the reabsorption of sodium and the excretion of both potassium and hydrogen ions.\n\nAldosterone is responsible for the reabsorption of about 2% of filtered glomerular filtrate.\n\nSodium retention is also a response of the distal colon and sweat glands to aldosterone receptor stimulation.\n\nAngiotensin II and extracellular potassium are the two main regulators of aldosterone production.\n\nThe amount of sodium present in the body affects the extracellular volume, which in turn influences blood pressure.\n\nTherefore, the effects of aldosterone in sodium retention are important for the regulation of blood pressure.\n\nGlucocorticoidsCortisol is the main glucocorticoid in humans.\n\nIn species that do not create cortisol, this role is played by corticosterone instead.\n\nGlucocorticoids have many effects on metabolism.\n\nAs their name suggests, they increase the circulating level of glucose.\n\nThis is the result of an increase in the mobilization of amino acids from protein and the stimulation of synthesis of glucose from these amino acids in the liver.\n\nIn addition, they increase the levels of free fatty acids, which cells can use as an alternative to glucose to obtain energy.\n\nGlucocorticoids also have effects unrelated to the regulation of blood sugar levels, including the suppression of the immune system and a potent anti-inflammatory effect.\n\nCortisol reduces the capacity of osteoblasts to produce new bone tissue and decreases the absorption of calcium in the gastrointestinal tract.The suprarenal gland secretes a basal level of cortisol but can also produce bursts of the hormone in response to adrenocorticotropic hormone (ACTH) from the anterior pituitary.\n\nCortisol is not evenly released during the day – its concentrations in the blood are highest in the early morning and lowest in the evening as a result of the circadian rhythm of ACTH secretion.\n\nCortisone is an inactive product of the action of the enzyme 11β-HSD on cortisol.\n\nThe reaction catalyzed by 11β-HSD is reversible, which means that it can turn administered cortisone into cortisol, the biologically active hormone.\n\nFormation\n\nAll corticosteroid hormones share cholesterol as a common precursor.\n\nTherefore, the first step in steroidogenesis is cholesterol uptake or synthesis.\n\nCells that produce steroid hormones can acquire cholesterol through two paths.\n\nThe main source is through dietary cholesterol transported via the blood as cholesterol esters within low density lipoproteins (LDL).\n\nLDL enters the cells through receptor-mediated endocytosis.\n\nThe other source of cholesterol is synthesis in the cell's endoplasmic reticulum.\n\nSynthesis can compensate when LDL levels are abnormally low.\n\nIn the lysosome, cholesterol esters are converted to free cholesterol, which is then used for steroidogenesis or stored in the cell.\n\nThe initial part of conversion of cholesterol into steroid hormones involves a number of enzymes of the cytochrome P450 family that are located in the inner membrane of mitochondria.\n\nTransport of cholesterol from the outer to the inner membrane is facilitated by steroidogenic acute regulatory protein and is the rate-limiting step of steroid synthesis.\n\nThe layers of the suprarenal gland differ by function, with each layer having distinct enzymes that produce different hormones from a common precursor.\n\nThe first enzymatic step in the production of all steroid hormones is cleavage of the cholesterol side chain, a reaction that forms pregnenolone as a product and is catalyzed by the enzyme P450scc, also known as cholesterol desmolase.\n\nAfter the production of pregnenolone, specific enzymes of each cortical layer further modify it.\n\nEnzymes involved in this process include both mitochondrial and microsomal P450s and hydroxysteroid dehydrogenases.\n\nUsually a number of intermediate steps in which pregnenolone is modified several times are required to form the functional hormones.\n\nEnzymes that catalyze reactions in these metabolic pathways are involved in a number of endocrine diseases.\n\nFor example, the most common form of congenital suprarenal hyperplasia develops as a result of deficiency of 21-hydroxylase, an enzyme involved in an intermediate step of cortisol production.\n\nRegulation\n\nGlucocorticoids are under the regulatory influence of the hypothalamus-pituitary-suprarenal (HPA) axis.\n\nGlucocorticoid synthesis is stimulated by adrenocorticotropic hormone (ACTH), a hormone released into the bloodstream by the anterior pituitary.\n\nIn turn, production of ACTH is stimulated by the presence of corticotropin-releasing hormone (CRH), which is released by neurons of the hypothalamus.\n\nACTH acts on the suprarenal cells first by increasing the levels of StAR within the cells, and then of all steroidogenic P450 enzymes.\n\nThe HPA axis is an example of a negative feedback system, in which cortisol itself acts as a direct inhibitor of both CRH and ACTH synthesis.\n\nThe HPA axis also interacts with the immune system through increased secretion of ACTH at the presence of certain molecules of the inflammatory response.Mineralocorticoid secretion is regulated mainly by the renin–angiotensin–aldosterone system (RAAS), the concentration of potassium, and to a lesser extent the concentration of ACTH.\n\nSensors of blood pressure in the juxtaglomerular apparatus of the kidneys release the enzyme renin into the blood, which starts a cascade of reactions that lead to formation of angiotensin II.\n\nAngiotensin receptors in cells of the zona glomerulosa recognize the substance, and upon binding they stimulate the release of aldosterone.\n\n=== Androgens ===\n\nCells in zona reticularis of the suprarenal glands produce male sex hormones, or androgens, the most important of which is DHEA.\n\nIn general, these hormones do not have an overall effect in the male body, and are converted to more potent androgens such as testosterone and DHT or to estrogens (female sex hormones) in the gonads, acting in this way as a metabolic intermediate.\n\n=== Catecholamines ===\n\nPrimarily referred to in the United States as epinephrine and norepinephrine, suprarenaline and norsuprarenaline are catecholamines, water-soluble compounds that have a structure made of a catechol group and an amine group.\n\nThe suprarenal glands are responsible for most of the suprarenaline that circulates in the body, but only for a small amount of circulating norsuprarenaline.\n\nThese hormones are released by the suprarenal medulla, which contains a dense network of blood vessels.\n\nsuprarenaline and norsuprarenaline act at adrenoreceptors throughout the body, with effects that include an increase in blood pressure and heart rate.\n\nActions of suprarenaline and norsuprarenaline are responsible for the fight or flight response, characterised by a quickening of breathing and heart rate, an increase in blood pressure, and constriction of blood vessels in many parts of the body.\n\nFormationCatecholamines are produced in chromaffin cells in the medulla of the suprarenal gland, from tyrosine, a non-essential amino acid derived from food or produced from phenylalanine in the liver.\n\nThe enzyme tyrosine hydroxylase converts tyrosine to L-DOPA in the first step of catecholamine synthesis.\n\nL-DOPA is then converted to dopamine before it can be turned into norsuprarenaline.\n\nIn the cytosol, norsuprarenaline is converted to epinephrine by the enzyme phenylethanolamine N-methyltransferase (PNMT) and stored in granules.\n\nGlucocorticoids produced in the suprarenal cortex stimulate the synthesis of catecholamines by increasing the levels of tyrosine hydroxylase and PNMT.Catecholamine release is stimulated by the activation of the sympathetic nervous system.\n\nSplanchnic nerves of the sympathetic nervous system innervate the medulla of the suprarenal gland.\n\nWhen activated, it evokes the release of catecholamines from the storage granules by stimulating the opening of calcium channels in the cell membrane.\n\n== Gene and protein expression ==\n\nThe human genome includes approximately 20,000 protein coding genes and 70% of these genes are expressed in the normal adult suprarenal glands.\n\nOnly some 250 genes are more specifically expressed in the suprarenal glands compared to other organs and tissues.\n\nThe suprarenal-gland-specific genes with the highest level of expression include members of the cytochrome P450 superfamily of enzymes.\n\nCorresponding proteins are expressed in the different compartments of the suprarenal gland, such as CYP11A1, HSD3B2 and FDX1 involved in steroid hormone synthesis and expressed in cortical cell layers, and PNMT and DBH involved in norsuprarenaline and suprarenaline synthesis and expressed in the medulla.\n\n== Development ==\n\nThe suprarenal glands are composed of two heterogenous types of tissue.\n\nIn the center is the suprarenal medulla, which produces suprarenaline and norsuprarenaline and releases them into the bloodstream, as part of the sympathetic nervous system.\n\nSurrounding the medulla is the cortex, which produces a variety of steroid hormones.\n\nThese tissues come from different embryological precursors and have distinct prenatal development paths.\n\nThe cortex of the suprarenal gland is derived from mesoderm, whereas the medulla is derived from the neural crest, which is of ectodermal origin.\n\nThe suprarenal glands in a newborn baby are much larger as a proportion of the body size than in an adult.\n\nFor example, at age three months the glands are four times the size of the kidneys.\n\nThe size of the glands decreases relatively after birth, mainly because of shrinkage of the cortex.\n\nThe cortex, which almost completely disappears by age 1, develops again from age 4–5.\n\nThe glands weigh about 1 g at birth and develop to an adult weight of about 4 grams each.\n\nIn a fetus the glands are first detectable after the sixth week of development.\n\n=== Cortex ===\n\nsuprarenal cortex tissue is derived from the intermediate mesoderm.\n\nIt first appears 33 days after fertilisation, shows steroid hormone production capabilities by the eighth week and undergoes rapid growth during the first trimester of pregnancy.\n\nThe fetal suprarenal cortex is different from its adult counterpart, as it is composed of two distinct zones: the inner \"fetal\" zone, which carries most of the hormone-producing activity, and the outer \"definitive\" zone, which is in a proliferative phase.\n\nThe fetal zone produces large amounts of suprarenal androgens (male sex hormones) that are used by the placenta for estrogen biosynthesis.\n\nCortical development of the suprarenal gland is regulated mostly by ACTH, a hormone produced by the pituitary gland that stimulates cortisol synthesis.\n\nDuring midgestation, the fetal zone occupies most of the cortical volume and produces 100–200 mg/day of DHEA-S, an androgen and precursor of both androgens and estrogens (female sex hormones).\n\nsuprarenal hormones, especially glucocorticoids such as cortisol, are essential for prenatal development of organs, particularly for the maturation of the lungs.\n\nThe suprarenal gland decreases in size after birth because of the rapid disappearance of the fetal zone, with a corresponding decrease in androgen secretion.\n\n==== Adrenarche ====\n\nDuring early childhood androgen synthesis and secretion remain low, but several years before puberty (from 6–8 years of age) changes occur in both anatomical and functional aspects of cortical androgen production that lead to increased secretion of the steroids DHEA and DHEA-S.\n\nThese changes are part of a process called adrenarche, which has only been described in humans and some other primates.\n\nAdrenarche is independent of ACTH or gonadotropins and correlates with a progressive thickening of the zona reticularis layer of the cortex.\n\nFunctionally, adrenarche provides a source of androgens for the development of axillary and pubic hair before the beginning of puberty.\n\n=== Medulla ===\n\nThe suprarenal medulla is derived from neural crest cells, which come from the ectoderm layer of the embryo.\n\nThese cells migrate from their initial position and aggregate in the vicinity of the dorsal aorta, a primitive blood vessel, which activates the differentiation of these cells through the release of proteins known as BMPs.\n\nThese cells then undergo a second migration from the dorsal aorta to form the suprarenal medulla and other organs of the sympathetic nervous system.\n\nCells of the suprarenal medulla are called chromaffin cells because they contain granules that stain with chromium salts, a characteristic not present in all sympathetic organs.\n\nGlucocorticoids produced in the suprarenal cortex were once thought to be responsible for the differentiation of chromaffin cells.\n\nMore recent research suggests that BMP-4 secreted in suprarenal tissue is the main responsible for this, and that glucocorticoids only play a role in the subsequent development of the cells.\n\n== Clinical significance ==\n\nThe normal function of the suprarenal gland may be impaired by conditions such as infections, tumors, genetic disorders and autoimmune diseases, or as a side effect of medical therapy.\n\nThese disorders affect the gland either directly (as with infections or autoimmune diseases) or as a result of the dysregulation of hormone production (as in some types of Cushing's syndrome) leading to an excess or insufficiency of suprarenal hormones and the related symptoms.\n\n=== Corticosteroid overproduction ===\n\n==== Cushing's syndrome ====\nCushing's syndrome is the manifestation of glucocorticoid excess.\n\nIt can be the result of a prolonged treatment with glucocorticoids or be caused by an underlying disease which produces alterations in the HPA axis or the production of cortisol.\n\nCauses can be further classified into ACTH-dependent or ACTH-independent.\n\nThe most common cause of endogenous Cushing's syndrome is a pituitary adenoma which causes an excessive production of ACTH.\n\nThe disease produces a wide variety of signs and symptoms which include obesity, diabetes, increased blood pressure, excessive body hair (hirsutism), osteoporosis, depression, and most distinctively, stretch marks in the skin, caused by its progressive thinning.\n\n==== Primary aldosteronism ====\n\nWhen the zona glomerulosa produces excess aldosterone, the result is primary aldosteronism.\n\nCauses for this condition are bilateral hyperplasia (excessive tissue growth) of the glands, or aldosterone-producing adenomas (a condition called Conn's syndrome).\n\nPrimary aldosteronism produces hypertension and electrolyte imbalance, increasing potassium depletion sodium retention.\n\n=== suprarenal insufficiency ===\n\nsuprarenal insufficiency (the deficiency of glucocorticoids) occurs in about 5 in 10,000 in the general population.\n\nDiseases classified as primary suprarenal insufficiency (including Addison's disease and genetic causes) directly affect the suprarenal cortex.\n\nIf a problem that affects the hypothalamic-pituitary-suprarenal axis arises outside the gland, it is a secondary suprarenal insufficiency.\n\n==== Addison's disease ====\n\nAddison's disease refers to primary hyposuprarenalism, which is a deficiency in glucocorticoid and mineralocorticoid production by the suprarenal gland.\n\nIn the Western world, Addison's disease is most commonly an autoimmune condition, in which the body produces antibodies against cells of the suprarenal cortex.\n\nWorldwide, the disease is more frequently caused by infection, especially from tuberculosis.\n\nA distinctive feature of Addison's disease is hyperpigmentation of the skin, which presents with other nonspecific symptoms such as fatigue.\n\nA complication seen in untreated Addison's disease and other types of primary suprarenal insufficiency is the suprarenal crisis, a medical emergency in which low glucocorticoid and mineralocorticoid levels result in hypovolemic shock and symptoms such as vomiting and fever.\n\nAn suprarenal crisis can progressively lead to stupor and coma.\n\nThe management of suprarenal crises includes the application of hydrocortisone injections.\n\n==== Secondary suprarenal insufficiency ====\n\nIn secondary suprarenal insufficiency, a dysfunction of the hypothalamic-pituitary-suprarenal axis leads to decreased stimulation of the suprarenal cortex.\n\nApart from suppression of the axis by glucocorticoid therapy, the most common cause of secondary suprarenal insufficiency are tumors that affect the production of adrenocorticotropic hormone (ACTH) by the pituitary gland.\n\nThis type of suprarenal insufficiency usually does not affect the production of mineralocorticoids, which are under regulation of the renin–angiotensin system instead.\n\n==== Congenital suprarenal hyperplasia ====\n\nCongenital suprarenal hyperplasia is a congenital disease in which mutations of enzymes that produce steroid hormones result in a glucocorticoid deficiency and malfunction of the negative feedback loop of the HPA axis.\n\nIn the HPA axis, cortisol (a glucocorticoid) inhibits the release of CRH and ACTH, hormones that in turn stimulate corticosteroid synthesis.\n\nAs cortisol cannot be synthesized, these hormones are released in high quantities and stimulate production of other suprarenal steroids instead.\n\nThe most common form of congenital suprarenal hyperplasia is due to 21-hydroxylase deficiency. 21-hydroxylase is necessary for production of both mineralocorticoids and glucocorticoids, but not androgens.\n\nTherefore, ACTH stimulation of the suprarenal cortex induces the release of excessive amounts of suprarenal androgens, which can lead to the development of ambiguous genitalia and secondary sex characteristics.\n\n=== suprarenal tumors ===\n\nsuprarenal tumors are commonly found as incidentalomas, unexpected asymptomatic tumors found during medical imaging.\n\nThey are seen in around 3.4% of CT scans, and in most cases they are benign adenomas.\n\nsuprarenal carcinomas are very rare, with an incidence of 1 case per million per year.Pheochromocytomas are tumors of the suprarenal medulla that arise from chromaffin cells.\n\nThey can produce a variety of nonspecific symptoms, which include headaches, sweating, anxiety and palpitations.\n\nCommon signs include hypertension and tachycardia.\n\nSurgery, especially suprarenal laparoscopy, is the most common treatment for small pheochromocytomas.\n\nhttps://en.wikipedia.org/wiki/suprarenal_gland","pineal-gland":"The pineal gland, conarium, or epiphysis cerebri, is a small endocrine gland in the brain of most vertebrates.\n\nThe pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal cycles.\n\nThe shape of the gland resembles a pine cone, which gives it its name.\n\nThe pineal gland is located in the epithalamus, near the center of the brain, between the two hemispheres, tucked in a groove where the two halves of the thalamus join.\n\nThe pineal gland is one of the neuroendocrine secretory circumventricular organs in which capillaries are mostly permeable to solutes in the blood.Nearly all vertebrate species possess a pineal gland.\n\nThe most important exception is a primitive vertebrate, the hagfish.\n\nEven in the hagfish, however, there may be a \"pineal equivalent\" structure in the dorsal diencephalon.\n\nThe lancelet Branchiostoma lanceolatum, the nearest existing relative to vertebrates, also lacks a recognizable pineal gland.\n\nThe lamprey (another primitive vertebrate), however, does possess one.\n\nA few more complex vertebrates have lost pineal glands over the course of their evolution.The results of various scientific research in evolutionary biology, comparative neuroanatomy and neurophysiology have explained the evolutionary history (phylogeny) of the pineal gland in different vertebrate species.\n\nFrom the point of view of biological evolution, the pineal gland is a kind of atrophied photoreceptor.\n\nIn the epithalamus of some species of amphibians and reptiles, it is linked to a light-sensing organ, known as the parietal eye, which is also called the pineal eye or third eye.René Descartes believed the human pineal gland to be the \"principal seat of the soul.\" Academic philosophy among his contemporaries considered the pineal gland as a neuroanatomical structure without special metaphysical qualities; science studied it as one endocrine gland among many.\n\n== Etymology ==\n\nThe word pineal, from Latin pinea (pine-cone), was first used in the late 17th century to refer to the cone shape of the brain gland.\n\n== Structure ==\n\nThe pineal gland is a midline brain structure that is unpaired.\n\nIt takes its name from its pine-cone shape.\n\nThe gland is reddish-gray and about the size of a grain of rice (5–8 mm) in humans.\n\nThe pineal gland, also called the pineal body, is part of the epithalamus, and lies between the laterally positioned thalamic bodies and behind the habenular commissure.\n\nIt is located in the quadrigeminal cistern near to the corpora quadrigemina.\n\nIt is also located behind the third ventricle and is bathed in cerebrospinal fluid supplied through a small pineal recess of the third ventricle which projects into the stalk of the gland.\n\n=== Blood supply ===\n\nUnlike most of the mammalian brain, the pineal gland is not isolated from the body by the blood–brain barrier system; it has profuse blood flow, second only to the kidney, supplied from the choroidal branches of the posterior cerebral artery.\n\n=== Nerve supply ===\n\nThe pineal gland receives a sympathetic innervation from the superior cervical ganglion.\n\nA parasympathetic innervation from the pterygopalatine and otic ganglia is also present.\n\nFurther, some nerve fibers penetrate into the pineal gland via the pineal stalk (central innervation).\n\nAlso, neurons in the trigeminal ganglion innervate the gland with nerve fibers containing the neuropeptide PACAP.\n\n=== Microanatomy ===\n\nThe pineal body in humans consists of a lobular parenchyma of pinealocytes surrounded by connective tissue spaces.\n\nThe gland's surface is covered by a pial capsule.\nThe pineal gland consists mainly of pinealocytes, but four other cell types have been identified.\n\nAs it is quite cellular (in relation to the cortex and white matter), it may be mistaken for a neoplasm.\n\n=== Development ===\n\nThe human pineal gland grows in size until about 1–2 years of age, remaining stable thereafter, although its weight increases gradually from puberty onwards.\n\nThe abundant melatonin levels in children are believed to inhibit sexual development, and pineal tumors have been linked with precocious puberty.\n\nWhen puberty arrives, melatonin production is reduced.\n\n=== Symmetry ===\n\nIn the zebrafish the pineal gland does not straddle the midline, but shows a left-sided bias.\n\nIn humans, functional cerebral dominance is accompanied by subtle anatomical asymmetry.\n\n== Function ==\n\nOne function of the pineal gland is to produce melatonin.\n\nMelatonin has various functions in the central nervous system, the most important of which is to help modulate sleep patterns.\n\nMelatonin production is stimulated by darkness and inhibited by light.\n\nLight sensitive nerve cells in the retina detect light and send this signal to the suprachiasmatic nucleus (SCN), synchronizing the SCN to the day-night cycle.\n\nNerve fibers then relay the daylight information from the SCN to the paraventricular nuclei (PVN), then to the spinal cord and via the sympathetic system to superior cervical ganglia (SCG), and from there into the pineal gland.\nThe compound pinoline is also claimed to be produced in the pineal gland; it is one of the beta-carbolines.\n\nThis claim is subject to some controversy.\n\n=== Regulation of the pituitary gland ===\n\nStudies on rodents suggest that the pineal gland influences the pituitary gland's secretion of the sex hormones, follicle-stimulating hormone (FSH), and luteinizing hormone (LH).\n\nPinealectomy performed on rodents produced no change in pituitary weight, but caused an increase in the concentration of FSH and LH within the gland.\n\nAdministration of melatonin did not return the concentrations of FSH to normal levels, suggesting that the pineal gland influences pituitary gland secretion of FSH and LH through an undescribed transmitting molecule.The pineal gland contains receptors for the regulatory neuropeptide, endothelin-1, which, when injected in picomolar quantities into the lateral cerebral ventricle, causes a calcium-mediated increase in pineal glucose metabolism.\n\n=== Regulation of bone metabolism ===\n\nStudies in mice suggest that the pineal-derived melatonin regulates new bone deposition.\n\nPineal-derived melatonin mediates its action on the bone cells through MT2 receptors.\n\nThis pathway could be a potential new target for osteoporosis treatment as the study shows the curative effect of oral melatonin treatment in a postmenopausal osteoporosis mouse model.\n\n== Clinical significance ==\n\n=== Calcification ===\n\nCalcification of the pineal gland is typical in young adults, and has been observed in children as young as two years of age.\n\nThe internal secretions of the pineal gland are known to inhibit the development of the reproductive glands because when it is severely damaged in children, development of the sexual organs and the skeleton are accelerated.\n\nPineal gland calcification is detrimental to its ability to synthesize melatonin and scientific literature presents inconclusive findings on whether it causes sleep problems.The calcified gland is often seen in skull x-rays.\n\nCalcification rates vary widely by country and correlate with an increase in age, with calcification occurring in an estimated 40% of Americans by age seventeen.\n\nCalcification of the pineal gland is associated with corpora arenacea, also known as \"brain sand\".\n\n=== Tumors ===\n\nTumors of the pineal gland are called pinealomas.\n\nThese tumors are rare and 50% to 70% are germinomas that arise from sequestered embryonic germ cells.\n\nHistologically they are similar to testicular seminomas and ovarian dysgerminomas.A pineal tumor can compress the superior colliculi and pretectal area of the dorsal midbrain, producing Parinaud's syndrome.\n\nPineal tumors also can cause compression of the cerebral aqueduct, resulting in a noncommunicating hydrocephalus.\n\nOther manifestations are the consequence of their pressure effects and consist of visual disturbances, headache, mental deterioration, and sometimes dementia-like behaviour.These neoplasms are divided into three categories: pineoblastomas, pineocytomas, and mixed tumors, based on their level of differentiation, which, in turn, correlates with their neoplastic aggressiveness.\n\nThe clinical course of patients with pineocytomas is prolonged, averaging up to several years.\n\nThe position of these tumors makes them difficult to remove surgically.\n\n=== Other conditions ===\n\nThe morphology of the pineal gland differs markedly in different pathological conditions.\n\nFor instance, it is known that its volume is reduced both in obese patients as well as patients with primary insomnia.\n\n== Other animals ==\n\nMost living vertebrates have pineal glands.\n\nIt is likely that the common ancestor of all vertebrates had a pair of photosensory organs on the top of its head, similar to the arrangement in modern lampreys.\n\nSome extinct Devonian fishes have two parietal foramina in their skulls, suggesting an ancestral bilaterality of parietal eyes.\n\nThe parietal eye and the pineal gland of living tetrapods are probably the descendants of the left and right parts of this organ, respectively.During embryonic development, the parietal eye and the pineal organ of modern lizards and tuataras form together from a pocket formed in the brain ectoderm.\n\nThe loss of parietal eyes in many living tetrapods is supported by developmental formation of a paired structure that subsequently fuses into a single pineal gland in developing embryos of turtles, snakes, birds, and mammals.The pineal organs of mammals fall into one of three categories based on shape.\n\nRodents have more structurally complex pineal glands than other mammals.Crocodilians and some tropical lineages of mammals (some xenarthrans (sloths), pangolins, sirenians (manatees and dugongs), and some marsupials (sugar gliders)) have lost both their parietal eye and their pineal organ.\n\nPolar mammals, such as walruses and some seals, possess unusually large pineal glands.All amphibians have a pineal organ, but some frogs and toads also have what is called a \"frontal organ\", which is essentially a parietal eye.Pinealocytes in many non-mammalian vertebrates have a strong resemblance to the photoreceptor cells of the eye.\n\nEvidence from morphology and developmental biology suggests that pineal cells possess a common evolutionary ancestor with retinal cells.Pineal cytostructure seems to have evolutionary similarities to the retinal cells of the lateral eyes.\n\nModern birds and reptiles express the phototransducing pigment melanopsin in the pineal gland.\n\nAvian pineal glands are thought to act like the suprachiasmatic nucleus in mammals.\n\nThe structure of the pineal eye in modern lizards and tuatara is analogous to the cornea, lens, and retina of the lateral eyes of vertebrates.In most vertebrates, exposure to light sets off a chain reaction of enzymatic events within the pineal gland that regulates circadian rhythms.\n\nIn humans and other mammals, the light signals necessary to set circadian rhythms are sent from the eye through the retinohypothalamic system to the suprachiasmatic nuclei (SCN) and the pineal gland.\nThe fossilized skulls of many extinct vertebrates have a pineal foramen (opening), which in some cases is larger than that of any living vertebrate.\n\nAlthough fossils seldom preserve deep-brain soft anatomy, the brain of the Russian fossil bird Cerebavis cenomanica from Melovatka, about 90 million years old, shows a relatively large parietal eye and pineal gland.Rick Strassman, an author and Clinical Associate Professor of Psychiatry at the University of New Mexico School of Medicine, has theorised that the human pineal gland is capable of producing the hallucinogen N,N-Dimethyltryptamine (DMT) under certain circumstances.\n\nIn 2013 he and other researchers first reported DMT in the pineal gland microdialysate of rodents.\n\n== Society and culture ==\n\nSeventeenth-century philosopher and scientist René Descartes was highly interested in anatomy and physiology.\n\nHe discussed the pineal gland both in his first book, the Treatise of Man (written before 1637, but only published posthumously 1662/1664), and in his last book, The Passions of the Soul (1649) and he regarded it as \"the principal seat of the soul and the place in which all our thoughts are formed.\" In the Treatise of Man, Descartes described conceptual models of man, namely creatures created by God, which consist of two ingredients, a body and a soul.\n\nIn the Passions, Descartes split man up into a body and a soul and emphasized that the soul is joined to the whole body by \"a certain very small gland situated in the middle of the brain's substance and suspended above the passage through which the spirits in the brain's anterior cavities communicate with those in its posterior cavities\".\n\nDescartes attached significance to the gland because he believed it to be the only section of the brain to exist as a single part rather than one-half of a pair.\n\nSome of Descartes's basic anatomical and physiological assumptions were totally mistaken, not only by modern standards, but also in light of what was already known in his time.The notion of a \"pineal-eye\" is central to the philosophy of the French writer Georges Bataille, which is analyzed at length by literary scholar Denis Hollier in his study Against Architecture.\n\nIn this work Hollier discusses how Bataille uses the concept of a \"pineal-eye\" as a reference to a blind-spot in Western rationality, and an organ of excess and delirium.\n\nThis conceptual device is explicit in his surrealist texts, The Jesuve and The Pineal Eye.In the late 19th century Madame Blavatsky (who founded theosophy) identified the pineal gland with the Hindu concept of the third eye, or the Ajna chakra.\n\nThis association is still popular today.In the short story \"From Beyond\" by H.\n\nP.\n\nLovecraft, a scientist creates an electronic device that emits a resonance wave, which stimulates an affected person's pineal gland, thereby allowing them to perceive planes of existence outside the scope of accepted reality, a translucent, alien environment that overlaps our own recognized reality.\n\nIt was adapted as a film of the same name in 1986.\n\nThe 2013 horror film Banshee Chapter is heavily influenced by this short story.\n\n== History ==\n\nThe secretory activity of the pineal gland is only partially understood.\n\nIts location deep in the brain suggested to philosophers throughout history that it possesses particular importance.\n\nThis combination led to its being regarded as a \"mystery\" gland with mystical, metaphysical, and occult theories surrounding its perceived functions.\nThe pineal gland was originally believed to be a \"vestigial remnant\" of a larger organ.\n\nIn 1917, it was known that extract of cow pineals lightened frog skin.\n\nDermatology professor Aaron B.\n\nLerner and colleagues at Yale University, hoping that a substance from the pineal might be useful in treating skin diseases, isolated and named the hormone melatonin in 1958.\n\nThe substance did not prove to be helpful as intended, but its discovery helped solve several mysteries such as why removing the rat's pineal accelerated ovary growth, why keeping rats in constant light decreased the weight of their pineals, and why pinealectomy and constant light affect ovary growth to an equal extent; this knowledge gave a boost to the then new field of chronobiology.Of the endocrine organs, the function of the pineal gland was the last discovered.\nLocated deep in the center of the brain, the pineal gland was once known as the “third eye.”\nThe pineal gland produces melatonin, which helps maintain circadian rhythm and regulate reproductive hormones.\n\nhttps://en.wikipedia.org/wiki/Pineal_gland","mucosa-of-stomach":"GASTRIC MUCOSA\n\nThe gastric mucosa is the mucous membrane layer of the stomach, which contains the glands and the gastric pits.\n\nIn humans, it is about 1 mm thick, and its surface is smooth, soft, and velvety.\n\nIt consists of simple columnar epithelium, lamina propria, and the muscularis mucosae.\n\n== Description ==\n\nIn its fresh state, it is of a pinkish tinge at the pyloric end and of a red or reddish-brown color over the rest of its surface.\n\nIn infancy it is of a brighter hue, the vascular redness being more marked.\n\nIt is thin at the cardiac extremity, but thicker toward the pylorus.\n\nDuring the contracted state of the organ it is thrown into numerous plaits or rugae, which, for the most part, have a longitudinal direction, and are most marked toward the pyloric end of the stomach, and along the greater curvature.\n\nThese folds are entirely obliterated when the organ becomes distended.\n\nWhen examined with a lens, the inner surface of the mucous membrane presents a peculiar honeycomb appearance from being covered with funnel-like depressions or foveolae of a polygonal or hexagonal form, which vary from 0.12 to 0.25 mm. in diameter.\n\nThese are the ducts of the gastric glands, and at the bottom of each may be seen one or more minute orifices, the openings of the gland tubes.\n\nGastric glands are simple or branched tubular glands that emerge on the deeper part of the gastric foveola, inside the gastric areas and outlined by the folds of the mucosa.\n\n== Types of glands ==\n\nThere are three types of glands: cardiac glands (in the proximal part of the stomach), fundic (oxyntic) glands (the dominating type of gland), and pyloric glands.\n\nThe cardiac glands mainly contain mucus-producing cells called foveolar cells.\n\nThe bottom part of the oxyntic glands is dominated by zymogenic (chief) cells that produce pepsinogen (an inactive precursor of the pepsin enzyme).\n\nParietal cells, which secrete hydrochloric acid (HCl) are scattered in the glands, with most of them in the middle part.\n\nThe upper part of the glands consist of mucous neck cells; in this part the dividing cells are seen.\n\nThe pyloric glands contain mucus-secreting cells.\n\nSeveral types of endocrine cells are found in throughout the gastric mucosa.\n\nThe pyloric glands contain gastrin-producing cells (G cells); this hormone stimulates acid production from the parietal cells.\n\nEnterochromaffin-like cells (ECLs), found in the oxyntic glands release histamine, which also is a powerful stimulant of the acid secretion.\n\nThe A cells produce glucagon, which mobilizes the hepatic glycogen, and the enterochromaffin cells produce serotonin, which stimulates the contraction of the smooth muscles.\n\n== Surface ==\n\nThe surface of the mucous membrane is covered by a single layer of columnar epithelium.\n\nThis epithelium commences very abruptly at the cardiac orifice, where there is a sudden transition from the stratified epithelium of the esophagus.\n\nThe epithelial lining of the gland ducts is of the same character and is continuous with the general epithelial lining of the stomach.\n\nAn important iodine concentration by sodium-iodide symporter (NIS) is present in mucinous cells of surface epithelium and gastric pits of the fundus and pyloric part of the stomach.\n\n== Pathology ==\n\nGastritis\nAcute gastritis\nChronic gastritis\nGastric tumors\n\nhttps://en.wikipedia.org/wiki/Gastric_mucosa","pleura":"PULMONARY PLEURAE\n\nThe pulmonary pleurae (sing. pleura) are the two opposing layers of serous membrane overlying the lungs and the inside of the surrounding chest walls.\n\nThe inner pleura, called the visceral pleura, covers the surface of each lung and dips between the lobes of the lung as fissures, and is formed by the invagination of lung buds into each thoracic sac during embryonic development.\n\nThe outer layer, called the parietal pleura, lines the inner surfaces of the thoracic cavity on each side of the mediastinum, and can be subdivided into mediastinal (covering the side surfaces of the fibrous pericardium, oesophagus and thoracic aorta), diaphragmatic (covering the upper surface of the diaphragm), costal (covering the inside of rib cage) and cervical (covering the underside of the suprapleural membrane) pleurae.\n\nThe visceral and the mediastinal parietal pleurae are connected at the root of the lung (\"hilum\") through a smooth fold known as pleural reflections, and a bell sleeve-like extension of visceral pleura hanging under to the hilum is known as the pulmonary ligament.\n\nBetween two pleurae is a potential space called the pleural cavity (also pleural space), which is normally collapsed and filled with only a tiny amount of serous fluid (pleural fluid) secreted by the pleurae, and is clinically considered vacuumous under healthy conditions.\n\nThe two lungs bounded by parietal pleura, almost fill the thoracic cavity.\n\n== Anatomy ==\n\nEach pleura comprises a superficial serosa made of a simple monolayer of flat (squamous) or cuboidal mesothelial cells with microvilli up to 6 μm (0.00024 in) long.\n\nThe mesothelium is without basement membrane, and supported by a well-vascularized underlying loose connective tissue containing two poorly defined layers of elastin-rich laminae.\n\nThe costal parietal pleurae also have adipocytes in the subserosa, which present as subpleural/extrapleural fats and are histologically considered belonging to the endothoracic fascia that separates the subserosa from the inner periosteum of the ribs.\n\nBoth pleurae are quite firmly attached to their underlying structures, and are usually covered by surface glycocalyces that limit fluid loss and reduce friction.\n\nThe enclosed space between the parietal and visceral pleurae, known as the pleural space, is normally filled only by a tiny amount (less than 10 mL or 0.34 US fl oz) of serous fluid secreted from the apical region of the parietal pleura.\n\nThe combination of surface tension, oncotic pressure, and the fluid pressure drop caused by the inward elastic recoil of the lung parenchyma and the rigidity of the chest wall, results in a normally negative pressure of -5 cmH2O (approximately −3.68 mmHg or −0.491 kPa) within the pleural space, causing it to mostly stay collapsed as a potential space that acts as a functionally vacuumous interface between the parietal and visceral pleurae.\n\nContracting the respiratory muscles expands the chest cavity, causing the attached parietal pleura to also expand outwards.\n\nIf the pleural functional vacuum stays intact, the pleural space will remain as collapsed as possible and cause the visceral pleura to be pulled along outwards, which in turn draws the underlying lung also into expansion.\n\nThis transmits the pressure negativity into the alveoli and bronchioli, thus facilitating inhalation.\n\n=== Visceral pleura ===\n\nThe visceral pleura (from Latin: viscera, lit. 'organ') covers the lung surfaces and the hilar structures and extends caudally from the hilum as a mesentery-like band called the pulmonary ligament.\n\nEach lung is divided into lobes by the infoldings of the pleura as fissures.\n\nThe fissures are double folds of pleura that section the lungs and help in their expansion, allowing the lung to ventilate more effectively even if parts of it (usually the basal segments) fail to expand properly due to congestion or consolidation.\n\nThe function of the visceral pleura is to produce and reabsorb fluid.\n\nIt is an area that is insensitive to pain due to its association with the lung and innervation by visceral sensory neurons.Visceral pleura also forms interlobular septa (that separates secondary pulmonary lobules).\n\nInterlobular septa contains connective tissue, pulmonary veins, and lymphatics.\n\n=== Parietal pleura ===\n\nThe parietal pleura (from Latin: paries, lit. 'wall') lines the inside of the thoracic cavity which is set apart from the thoracic wall by the endothoracic fascia.\n\nThe Parietal includes the inner surface of the rib cage and the upper surface of the diaphragm, as well as the side surfaces of the mediastinum, from which it separates the pleural cavity.\n\nIt joins the visceral pleura at the pericardial base of the pulmonary hilum and pulmonary ligament as a smooth but acutely angled circumferential junction known as the hilar reflection.\n\nThe parietal pleura is subdivided according to the surface it covers.\n\nThe costal pleura is the pleural portion covering the inner surfaces of the rib cage, and is separated from the ribs/cartilages and intercostal muscles by the endothoracic fascia.\n\nThe apical part of the costal pleura, sometimes referred to as the cervical pleura or cupula of pleura, bulges beyond the thoracic inlet into the posterior triangle of the neck, where it is covered by an extension of the endothoracic fascia known as the suprapleural membrane.\n\nThis is the most superficial (and thus most vulnerable) part of the pleura and can be punctured by subclavian catheterization or a penetrating neck injury.\n\nThe diaphragmatic pleura is the portion covering the convex upper surface of the diaphragm.\n\nIts junction with the costal pleura at the diaphragmatic margin is a sharp gutter known as the costodiaphragmatic recess, which has diagnostic significance on plain radiography.\n\nThe mediastinal pleura is the portion covering the lateral surfaces of the mediastinum, predominantly the fibrous pericardium, thoracic aorta, superior vena cava/azygos vein, esophagus and (very rarely) an enlarged thymus.\n\nIts anterosuperior part (especially of the left side) not infrequently can bulge into the anterior mediastinum behind the upper sternal body and even touch its contralateral counterpart in forced inhalation, but the left and right pleurae do not communicate unless there is a significant injury (traumatic or iatrogenic) or disease process (e.g. malignancy).\n\n=== Neurovascular supply ===\n\nAs a rule of thumb, the blood and nerve supply of a pleura comes from the structures under it.\n\nThe visceral pleura is supplied by the capillaries that supply the lung surface (from both the pulmonary circulation and the bronchial vessels), and innervated by the nerve endings from the pulmonary plexus.\n\nThe parietal pleura is supplied by blood from the cavity wall under it, which can come from the aorta (intercostal, superior phrenic and inferior phrenic arteries), the internal thoracic arteries (pericardiacophrenic, anterior intercostal and musculophrenic branches), or their anastomoses.\n\nSimilarly, its nerve supply is from its underlying structures — the costal pleura is innervated by the intercostal nerves; the diaphragmatic pleura is innervated by the phrenic nerve in its central portion around the central tendon, and by the intercostal nerves in its periphery near the costal margin; the mediastinal pleura is innervated by branches of the phrenic nerve over the fibrous pericardium.\n\n== Development ==\n\nThe visceral and parietal pleurae, like all mesothelia, both derive from the lateral plate mesoderms.\n\nDuring the third week of embryogenesis, each lateral mesoderm splits into two layers.\n\nThe dorsal layer joins overlying somites and ectoderm to form the somatopleure; and the ventral layer joins the underlying endoderm to form the splanchnopleure.\n\nThe dehiscence of these two layers creates a fluid-filled cavity on each side, and with the ventral infolding and the subsequent midline fusion of the trilaminar disc, forms a pair of intraembryonic coeloms anterolaterally around the gut tube during the fourth week, with the splanchnopleure on the inner cavity wall and the somatopleure on the outer cavity wall.\n\nThe cranial end of the intraembryonic coeloms fuse early to form a single cavity, which rotates anteriorly and apparently descends inverted in front of the thorax, and is later encroached by the growing primordial heart as the pericardial cavity.\n\nThe caudal portions of the coeloms fuse later below the umbilical vein to become the larger peritoneal cavity, separated from the pericardial cavity by the transverse septum.\n\nThe two cavities communicate via a slim pair of remnant coeloms adjacent to the upper foregut called the pericardioperitoneal canal.\n\nDuring the fifth week, the developing lung buds begin to invaginate into these canals, creating a pair of enlarging cavities that encroach into the surrounding somites and further displace the transverse septum caudally — namely the pleural cavities.\n\nThe mesothelia pushed out by the developing lungs arise from the splanchnopleure, and become the visceral pleurae; while the other mesothelial surfaces of the pleural cavities arise from the somatopleure, and become the parietal pleurae.\n\n== Function ==\n\nAs a serous membrane, the pleura secretes a serous fluid (pleural fluid) that contains various lubricating macromolecules such as sialomucin, hyaluronan and phospholipids.\n\nThese, coupled with the smoothness of the glycocalyces and hydrodynamic lubrication of the pleural fluid itself, reduces the frictional coefficient when the opposing pleural surfaces have to slide against each other during ventilation, thus help improving the pulmonary compliance.\n\nThe adhesive property of the pleural fluid to various cellular surfaces, coupled with its oncotic pressure and the negative fluid pressure, also holds the two opposing pleurae in close sliding contact and keeps the pleural space collapsed, maximizing the total lung capacity while maintaining a functional vacuum.\n\nWhen inhalation occurs, the contraction of the diaphragm and the external intercostal muscles (along with the bucket/pump handle movements of the ribs and sternum) increases the volume of the pleural cavity, further increasing the negative pressure within the pleural space.\n\nAs long as the functional vacuum remains intact, the lung will be drawn to expand along with the chest wall, relaying a negative airway pressure that causes an airflow into the lung, resulting in inhalation.\n\nExhalation is however usually passive, caused by elastic recoil of the alveolar walls and relaxation of respiratory muscles.\n\nIn forced exhalation, the pleural fluid provides some hydrostatic cushioning for the lungs against the rapid change of pressure within the pleural cavity.\n\n== Clinical significance ==\n\nPleuritis or pleurisy is a inflammatory condition of pleurae.\n\nDue to the somatic innervation of the parietal pleura, pleural irritations, especially if from acute causes, often produce a sharp chest pain that is worse by breathing, known as pleuritic pain.\n\nPleural disease or lymphatic blockages can lead to a build-up of serous fluid within the pleural space, known as a pleural effusion.\n\nPleural effusion obliterates the pleural vacuum and can collapse the lung (due to hydrostatic pressure), impairing ventilation and leading to type 2 respiratory failure.\n\nThe condition can be treated by mechanically removing the fluid via thoracocentesis (also known as a \"pleural tap\") with a pigtail catheter, a chest tube, or a thoracoscopic procedure.\n\nInfected pleural effusion can lead to pleural empyema, which can create significant adhesion and fibrosis that require division and decortication.\n\nFor recurrent pleural effusions, pleurodesis can be performed to establish permanent obliteration of the pleural space.\n\nhttps://en.wikipedia.org/wiki/Pulmonary_pleurae","oropharynx":"The oropharynx lies behind the oral cavity, extending from the uvula to the level of the hyoid bone.\n\nIt opens anteriorly, through the isthmus faucium, into the mouth, while in its lateral wall, between the palatoglossal arch and the palatopharyngeal arch, is the palatine tonsil.\n\nThe anterior wall consists of the base of the tongue and the epiglottic vallecula; the lateral wall is made up of the tonsil, tonsillar fossa, and tonsillar (faucial) pillars; the superior wall consists of the inferior surface of the soft palate and the uvula.\n\nBecause both food and air pass through the pharynx, a flap of connective tissue called the epiglottis closes over the glottis when food is swallowed to prevent aspiration. The oropharynx is lined by non-keratinized squamous stratified epithelium.\n\nThe HACEK organisms (Haemophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella) are part of the normal oropharyngeal flora, which grow slowly, prefer a carbon dioxide-enriched atmosphere, and share an enhanced capacity to produce endocardial infections, especially in young children.\n\nFusobacterium is a pathogen","nasopharynx":"The upper portion of the pharynx, the nasopharynx, extends from the base of the skull to the upper surface of the soft palate.\n\nIt includes the space between the internal nares and the soft palate and lies above the oral cavity.\n\nThe adenoids, also known as the pharyngeal tonsils, are lymphoid tissue structures located in the posterior wall of the nasopharynx.\n\nWaldeyer's tonsillar ring is an annular arrangement of lymphoid tissue in both the nasopharynx and oropharynx.\n\nThe nasopharynx is lined by respiratory epithelium that is pseudostratified, columnar, and ciliated.\n\nPolyps or mucus can obstruct the nasopharynx, as can congestion due to an upper respiratory infection.\n\nThe auditory tube, which connects the middle ear to the pharynx, opens into the nasopharynx at the pharyngeal opening of the auditory tube.\n\nThe opening and closing of the auditory tubes serves to equalize the barometric pressure in the middle ear with that of the ambient atmosphere.\n\nDetails of torus tubarius\n\nThe anterior aspect of the nasopharynx communicates through the choanae with the nasal cavities.\n\nOn its lateral wall is the pharyngeal opening of the auditory tube, somewhat triangular in shape and bounded behind by a firm prominence, the torus tubarius or cushion, caused by the medial end of the cartilage of the tube that elevates the mucous membrane.\n\nTwo folds arise from the cartilaginous opening:\n\n -the salpingopharyngeal fold, a vertical fold of mucous membrane extending from the inferior part of the torus and containing the salpingopharyngeus muscle\n\n -the salpingopalatine fold, a smaller fold, in front of the salpingopharyngeal fold, extending from the superior part of the torus to the palate and containing the levator veli palatini muscle.\n\n It also contains some muscle fibres called salpingopalatine muscle\n\n The tensor veli palatini is lateral to the levator and does not contribute to the fold, since the origin is deep to the cartilaginous opening.\n\nhttps://en.wikipedia.org/wiki/Pharynx","laryngopharynx":"The laryngopharynx, (Latin: pars laryngea pharyngis), also known as hypopharynx, is the caudal part of the pharynx; it is the part of the throat that connects to the esophagus.\n\nIt lies inferior to the epiglottis and extends to the location where this common pathway diverges into the respiratory (laryngeal) and digestive (esophageal) pathways.\n\nAt that point, the laryngopharynx is continuous with the esophagus posteriorly.\n\nThe esophagus conducts food and fluids to the stomach; air enters the larynx anteriorly.\n\nDuring swallowing, food has the \"right of way\", and air passage temporarily stops.\n\nCorresponding roughly to the area located between the 4th and 6th cervical vertebrae, the superior boundary of the laryngopharynx is at the level of the hyoid bone.\n\nThe laryngopharynx includes three major sites: the pyriform sinus, postcricoid area, and the posterior pharyngeal wall.\n\nLike the oropharynx above it, the laryngopharynx serves as a passageway for food and air and is lined with a stratified squamous epithelium.\n\nIt is innervated by the pharyngeal plexus.\n\nThe vascular supply to the laryngopharynx includes the superior thyroid artery, the lingual artery and the ascending pharyngeal artery.\n\nThe primary neural supply is from both the vagus and glossopharyngeal nerves.\n\nThe vagus nerve provides an auricular branch also termed \"Arnold's nerve\" which also supplies the external auditory canal, thus laryngopharyngeal cancer can result in referred ear pain.\n\nThis nerve is also responsible for the ear-cough reflex in which stimulation of the ear canal results in a person coughing.\n\nhttps://en.wikipedia.org/wiki/Pharynx","soft-palate":"The soft palate (also known as the velum, palatal velum, or muscular palate) is, in mammals, the soft tissue constituting the back of the roof of the mouth.\n\nThe soft palate is part of the palate of the mouth; the other part is the hard palate.\n\nThe soft palate is distinguished from the hard palate at the front of the mouth in that it does not contain bone.\n\n== Structure ==\n\n=== Muscles ===\n\nThe five muscles of the soft palate play important roles in swallowing and breathing.\n\nThe muscles are:\n\nTensor veli palatini, which is involved in swallowing\nPalatoglossus, involved in swallowing\nPalatopharyngeus, involved in breathing\nLevator veli palatini, involved in swallowing\nMusculus uvulae, which moves the uvulaThese muscles are innervated by the pharyngeal plexus via the vagus nerve, with the exception of the tensor veli palatini.\n\nThe tensor veli palatini is innervated by the mandibular division of the trigeminal nerve (V3).\n\n== Function ==\n\nThe soft palate is moveable, consisting of muscle fibers sheathed in mucous membrane.\n\nIt is responsible for closing off the nasal passages during the act of swallowing, and also for closing off the airway.\n\nDuring sneezing, it protects the nasal passage by diverting a portion of the excreted substance to the mouth.\nIn humans, the uvula hangs from the end of the soft palate.\n\nTouching the uvula or the end of the soft palate evokes a strong gag reflex in most people.\n\n=== Speech ===\n\nA speech sound made with the middle part of the tongue (dorsum) touching the soft palate is known as a velar consonant.\nIt is possible for the soft palate to retract and elevate during speech to separate the oral cavity (mouth) from the nasal cavity in order to produce the oral speech sounds.\n\nIf this separation is incomplete, air escapes through the nose, causing speech to be perceived as nasal.\n\n=== Modelling ===\n\nWithin the microstructure of the soft palate lie a variety of variably-oriented fibers that create a nonuniform surface with a nonuniform density distribution.\n\nThe tissue has been characterized as viscoelastic, nonlinear, and anisotropic in the direction of the fibers.\n\nYoung modulus values range from 585 Pa at the posterior free edge of the soft palate to 1409 Pa where the soft palate attaches to the maxilla.\n\nThese properties are useful when quantifying the effects of corrective orthopedic devices such as the Hotz Plate on cleft lip.\nQuantitative analyses have been done on bilateral and unilateral cleft palate to better understand geometric differences in cleft palate throughout the course of its development and correction.\n\nDespite the difficulty in finding common, comparable landmarks between normal soft palates and cleft palates, analytical methods have been devised to assess differences in degree of curvature of the alveolar crest, two-dimensional and three-dimensional surface area, and slope of the alveolar crest.\nFinite element analysis has demonstrated effective modeling of soft-palate extension and movement.\n\nIt has also been an effective tool for evaluating the craniofacial effects of corrective orthopedic devices and cleft lip.\n\n== Clinical significance ==\n\n=== Disease ===\n\nPathology of the soft palate includes mucosal lesions such as pemphigus vulgaris dsg - 3, herpangina and migratory stomatitis, and muscular conditions such as the congenital cleft palate and cleft uvula.\n\nPetechiae on the soft palate are mainly associated with streptococcal pharyngitis, and as such it is an uncommon but highly specific finding. 10 to 30 percent of palatal petechiae cases are estimated to be caused by suction, which can be habitual or secondary to fellatio.\n\nhttps://en.wikipedia.org/wiki/Soft_palate","left-coronary-leaflet":"The two leaflets of the aortic valve that are attached to the (interventricular?) septum are named the left and right leaflets, and correspond to the right and left leaflets of the aortic valve, which they face.\n\nThe third leaflet is called the anterior leaflet or the non-coronary leaflet (to maintain the nomenclature of the aortic valve).","right-atrium":"The atrium (Latin: ātrium, lit. 'entry hall') or auricle is the upper chamber through which blood enters the ventricles of the heart.\n\nThere are two atria in the human heart – the left atrium receives blood from the pulmonary (lung) circulation, and the right atrium receives blood from the venae cavae (venous circulation).\n\nThe atria receive blood while relaxed (diastole), then contract (systole) to move blood to the ventricles.\n\nAll animals with a closed circulatory system have at least one atrium.\n\nHumans have two atria.\nFormerly, the atrium was called the ‘auricle’.\n\nThat term is still used to describe this chamber in some other animals, such as the Mollusca.\n\nThey have thicker muscular walls than the atria do.\n\nEach atrium is roughly cube-shaped except for an ear-shaped projection called an auricle.\n\n== Structure ==\n\nHumans have a four-chambered heart consisting of the right atrium, left atrium, right ventricle, and left ventricle.\n\nThe atria are the two upper chambers.\n\nThe right atrium receives and holds deoxygenated blood from the superior vena cava, inferior vena cava, anterior cardiac veins, smallest cardiac veins and the coronary sinus, which it then sends down to the right ventricle (through the tricuspid valve), which in turn sends it to the pulmonary artery for pulmonary circulation.\n\nThe left atrium receives the oxygenated blood from the left and right pulmonary veins, which it pumps to the left ventricle (through the mitral valve) for pumping out through the aorta for systemic circulation.\n\nThe right atrium and right ventricle are often referred to as the right heart; similarly, the left atrium and left ventricle are often referred to as the left heart.\n\nThe atria do not have valves at their inlets, and as a result, a venous pulsation is normal and can be detected in the jugular vein as the jugular venous pressure.\n\nInternally, there are the rough pectinate muscles and crista terminalis of His, which act as a boundary inside the atrium and the smooth-walled part of the right atrium, the sinus venarum, which are derived from the sinus venosus.\n\nThe sinus venarum is the adult remnant of the sinus venous and it surrounds the openings of the venae cavae and the coronary sinus.\n\nAttached to the right atrium is the right atrial appendage – a pouch-like extension of the pectinate muscles.\n\nThe interatrial septum separates the right atrium from the left atrium; this is marked by a depression in the right atrium – the fossa ovalis.\n\nThe atria are depolarised by calcium.\n\nHigh in the upper part of the left atrium is a muscular ear-shaped pouch – the left atrial appendage.\n\nThis appears to \"function as a decompression chamber during left ventricular systole and during other periods when left atrial pressure is high\".\n\nWith certain conditions, it may be associated with risks of stroke from blood clot formation, because of which surgeons may choose to close it during open-heart surgery.\n\n=== Conduction system ===\n\nThe sinoatrial (SA) node is located in the posterior aspect of the right atrium, next to the superior vena cava.\n\nThis is a group of pacemaker cells which spontaneously depolarize to create an action potential.\n\nThe cardiac action potential then spreads across both atria causing them to contract, forcing the blood they hold into their corresponding ventricles.\n\nThe atrioventricular node (AV node) is another node in the cardiac electrical conduction system.\n\nThis is located between the atria and the ventricles.\n\n=== Blood supply ===\n\nThe left atrium is supplied mainly by the left circumflex coronary artery, and its small branches.\n\nThe oblique vein of the left atrium is partly responsible for venous drainage; it derives from the embryonic left superior vena cava.\n\n=== Development ===\n\nDuring embryogenesis at about two weeks, a primitive atrium begins to be formed.\n\nIt begins as one chamber, which over the following two weeks becomes divided by the septum primum into the left atrium and the right atrium.\n\nThe interatrial septum has an opening in the right atrium, the foramen ovale, which provides access to the left atrium; this connects the two chambers, which is essential for fetal blood circulation.\n\nAt birth, when the first breath is taken fetal blood flow is reversed to travel through the lungs.\n\nThe foramen ovale is no longer needed and it closes to leave a depression (the fossa ovalis) in the atrial wall.\nIn some cases, the foramen ovale fails to close.\n\nThis abnormality is present in approximately 25% of the general population.\n\nThis is known as a patent foramen ovale, an atrial septal defect.\n\nIt is mostly unproblematic, although it can be associated with paradoxical embolization and stroke.\n\nWithin the fetal right atrium, blood from the inferior vena cava and the superior vena cava flow in separate streams to different locations in the heart; this has been reported to occur through the Coandă effect.\n\n== Function ==\n\nIn human physiology, the atria facilitate circulation primarily by allowing uninterrupted venous flow to the heart during ventricular systole.\n\nBy being partially empty and distensible, atria prevent the interruption of venous flow to the heart that would occur during ventricular systole if the veins ended at the inlet valves of the heart.\n\nIn normal physiologic states, the output of the heart is pulsatile, and the venous inflow to the heart is continuous and non-pulsatile.\n\nBut without functioning atria, venous flow becomes pulsatile, and the overall circulation rate decreases significantly.\n\nAtria have four essential characteristics that cause them to promote continuous venous flow.\n\n(1) There are no atrial inlet valves to interrupt blood flow during atrial systole.\n\n(2) The atrial systole contractions are incomplete and thus do not contract to the extent that would block flow from the veins through the atria into the ventricles.\n\nDuring atrial systole, blood not only empties from the atria to the ventricles, but blood continues to flow uninterrupted from the veins right through the atria into the ventricles.\n\n(3) The atrial contractions must be gentle enough so that the force of contraction does not exert significant back pressure that would impede venous flow.\n\n(4) The \"let go\" of the atria must be timed so that they relax before the start of ventricular contraction, to be able to accept venous flow without interruption.\n\nBy preventing the inertia of interrupted venous flow that would otherwise occur at each ventricular systole, atria allow approximately 75% more cardiac output than would otherwise occur.\n\nThe fact that atrial contraction is 15% of the amount of the succeeding ventricular ejection has led to a misplaced emphasis on their role in pumping up the ventricles (the so-called \"atrial kick\"), whereas the key benefit of atria is in preventing circulatory inertia and allowing uninterrupted venous flow to the heart.\n\nAlso of importance in maintaining the blood flow are the presence of atrial volume receptors.\n\nThese are low-pressure baroreceptors in the atria, which send signals to the hypothalamus when a drop in atrial pressure (which indicates a drop in blood volume) is detected.\n\nThis triggers a release of vasopressin.\n\n== Left atrial appendage ==\n\nThe left atrial appendage can be seen on a standard posteroanterior x-ray, where the lower level of the left hilum becomes concave.\n\nThe left atrial appendage can serve as an approach for mitral valve surgery.\n\n== Disorders ==\n\n=== Atrial septal defect ===\n\nIn an adult, an atrial septal defect results in the flow of blood in the reverse direction – from the left atrium to the right – which reduces cardiac output, potentially causing cardiac failure, and in severe or untreated cases cardiac arrest and sudden death.\n\n=== Left atrial appendage thrombosis ===\n\nIn patients with atrial fibrillation, mitral valve disease, and other conditions, blood clots have a tendency to form in the left atrial appendage.\n\nThe clots may dislodge (forming emboli), which may lead to ischemic damage to the brain, kidneys, or other organs supplied by the systemic circulation.\n\nIn those with uncontrollable atrial fibrillation, left atrial appendage excision may be performed at the time of any open heart surgery to prevent future clot formation within the appendage.\n\n=== Functional abnormalities ===\n\nWolff-Parkinson-White syndrome\nAtrial flutter\nAtrial tachycardia\nSinus tachycardia\nMultifocal atrial tachycardia – several types\nPremature atrial contraction\n\n== Other animals ==\n\nMany other animals, including mammals, also have four-chambered hearts, which have a similar function.\n\nSome animals (amphibians and reptiles) have a three-chambered heart, in which the blood from each atrium is mixed in the single ventricle before being pumped to the aorta.\n\nIn these animals, the left atrium still serves the purpose of collecting blood from the pulmonary veins.\n\nIn some fish, the circulatory system is very simple: a two-chambered heart including one atrium and one ventricle.\n\nAmong sharks, the heart consists of four chambers arranged serially (and therefore called a serial heart): blood flows into the most posterior chamber, the sinus venosus, and then to the atrium which moves it to the third chamber, the ventricle, before it reaches the conus anteriosus, which itself is connected to the ventral aorta.\n\nThis is considered a primitive arrangement, and many vertebrates have condensed the atrium with the sinus venosus and the ventricle with the conus anteriosus.\n\nWith the advent of lungs came a partitioning of the atrium into two parts divided by a septum.\n\nAmong frogs, the oxygenated and deoxygenated blood is mixed in the ventricle before being pumped out to the body's organs; in turtles, the ventricle is almost entirely divided by a septum, but retains an opening through which some mixing of blood occurs.\n\nIn birds, mammals, and some other reptiles (alligators in particular) the partitioning of both chambers is complete.\n\nhttps://en.wikipedia.org/wiki/Atrium_(heart)","right-ventricle":"A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs.\n\nThe atrium (an adjacent/upper heart chamber that is smaller than a ventricle) primes the pump.\n\nIn a four-chambered heart, such as that in humans, there are two ventricles that operate in a double circulatory system: the right ventricle pumps blood into the pulmonary circulation to the lungs, and the left ventricle pumps blood into the systemic circulation through the aorta.\n\nThe term \"interventricular\" means between the ventricles (for example the interventricular septum), while \"intraventricular\" means within one ventricle (for example an intraventricular block).\n\n== Structure ==\n\nVentricles have thicker walls than atria and generate higher blood pressures.\n\nThe physiological load on the ventricles requiring pumping of blood throughout the body and lungs is much greater than the pressure generated by the atria to fill the ventricles.\n\nFurther, the left ventricle has thicker walls than the right because it needs to pump blood to most of the body while the right ventricle fills only the lungs.On the inner walls of the ventricles are irregular muscular columns called trabeculae carneae which cover all of the inner ventricular surfaces except that of the conus arteriosus, in the right ventricle.\n\nThere are three types of these muscles.\n\nThe third type, the papillary muscles, give origin at their apices to the chordae tendinae which attach to the cusps of the tricuspid valve and to the mitral valve.\n\nThe mass of the left ventricle, as estimated by magnetic resonance imaging, averages 143 g ± 38.4 g, with a range of 87––224 g.\n\nThe right ventricle is equal in size to the left ventricle and contains roughly 85 millilitres (3 imp fl oz; 3 US fl oz) in the adult.\n\nIts upper front surface is circled and convex, and forms much of the sternocostal surface of the heart.\n\nIts under surface is flattened, forming part of the diaphragmatic surface of the heart that rests upon the diaphragm.\n\nIts posterior wall is formed by the ventricular septum, which bulges into the right ventricle, so that a transverse section of the cavity presents a semilunar outline.\n\nIts upper and left angle forms a conical pouch, the conus arteriosus, from which the pulmonary artery arises.\n\nA tendinous band, called the tendon of the conus arteriosus, extends upward from the right atrioventricular fibrous ring and connects the posterior surface of the conus arteriosus to the aorta.\n\n=== Shape ===\n\nThe left ventricle is longer and more conical in shape than the right, and on transverse section its concavity presents an oval or nearly circular outline.\n\nIt forms a small part of the sternocostal surface and a considerable part of the diaphragmatic surface of the heart; it also forms the apex of the heart.\n\nThe left ventricle is thicker and more muscular than the right ventricle because it pumps blood at a higher pressure.\n\nThe right ventricle is triangular in shape and extends from the tricuspid valve in the right atrium to near the apex of the heart.\n\nIts wall is thickest at the apex and thins towards its base at the atrium.\n\nWhen viewed via cross section however, the right ventricle seems to be crescent shaped.\n\nThe right ventricle is made of two components: the sinus and the conus.\n\nThe Sinus is the inflow which flows away from the tricuspid valve.\n\nThree bands made from muscle, separate the right ventricle: the parietal, the septal, and the moderator band.\n\nThe moderator band connects from the base of the anterior papillary muscle to the ventricular septum.\n\n=== Development ===\n\nBy early maturity, the walls of the left ventricle have thickened from three to six times greater than that of the right ventricle.\n\nThis reflects the typical five times greater pressure workload this chamber performs while accepting blood returning from the pulmonary veins at ~80mmHg pressure (equivalent to around 11 kPa) and pushing it forward to the typical ~120mmHg pressure (around 16.3 kPa) in the aorta during each heartbeat.\n\n(The pressures stated are resting values and stated as relative to surrounding atmospheric which is the typical \"0\" reference pressure used in medicine.)\n\n== Function ==\n\nDuring systole, the ventricles contract, pumping blood through the body.\n\nDuring diastole, the ventricles relax and fill with blood again.\n\nThe left ventricle receives oxygenated blood from the left atrium via the mitral valve and pumps it through the aorta via the aortic valve, into the systemic circulation.\n\nThe left ventricular muscle must relax and contract quickly and be able to increase or lower its pumping capacity under the control of the nervous system.\n\nIn the diastolic phase, it has to relax very quickly after each contraction so as to quickly fill with the oxygenated blood flowing from the pulmonary veins.\n\nLikewise in the systolic phase, the left ventricle must contract rapidly and forcibly to pump this blood into the aorta, overcoming the much higher aortic pressure.\n\nThe extra pressure exerted is also needed to stretch the aorta and other arteries to accommodate the increase in blood volume.\n\nThe right ventricle receives deoxygenated blood from the right atrium via the tricuspid valve and pumps it into the pulmonary artery via the pulmonary valve, into the pulmonary circulation.\n\n=== Pumping volume ===\n\nThe typical healthy adult heart pumping volume is ~5 liters/min, resting.\n\nMaximum capacity pumping volume extends from ~25 liters/min for non-athletes to as high as ~45 liters/min for Olympic level athletes.\n\n=== Volumes ===\n\nIn cardiology, the performance of the ventricles are measured with several volumetric parameters, including end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and ejection fraction (Ef).\n\n=== Pressures ===\n\nVentricular pressure is a measure of blood pressure within the ventricles of the heart.\n\n==== Left ====\nDuring most of the cardiac cycle, ventricular pressure is less than the pressure in the aorta, but during systole, the ventricular pressure rapidly increases, and the two pressures become equal to each other (represented by the junction of the blue and red lines on the diagram on this page), the aortic valve opens, and blood is pumped to the body.\n\nElevated left ventricular end-diastolic pressure has been described as a risk factor in cardiac surgery.Noninvasive approximations have been described.\n\nAn elevated pressure difference between the aortic pressure and the left ventricular pressure may be indicative of aortic stenosis.\n\n==== Right ====\n\nRight ventricular pressure demonstrates a different pressure-volume loop than left ventricular pressure.\n\n=== Dimensions ===\n\nThe heart and its performance are also commonly measured in terms of dimensions, which in this case means one-dimensional distances, usually measured in millimeters.\n\nThis is not as informative as volumes but may be much easier to estimate with (e.g., M-Mode echocardiography or with sonomicrometry, which is mostly used for animal model research).\n\nOptimally, it is specified with which plane the distance is measured in, e.g. the dimension of the longitudinal plane.\n\nFractional shortening (FS) is the fraction of any diastolic dimension that is lost in systole.\n\nWhen referring to endocardial luminal distances, it is EDD minus ESD divided by EDD (times 100 when measured in percentage).\n\nNormal values may differ somewhat dependent on which anatomical plane is used to measure the distances.\n\nNormal range is 25–45%, Mild is 20–25%, Moderate is 15–20%, and Severe is <15%.\n\nCardiology Diagnostic Tests Midwall fractional shortening may also be used to measure diastolic/systolic changes for inter-ventricular septal dimensions and posterior wall dimensions.\n\nHowever, both endocardial and midwall fractional shortening are dependent on myocardial wall thickness, and thereby dependent on long-axis function.\n\nBy comparison, a measure of short-axis function termed epicardial volume change (EVC) is independent of myocardial wall thickness and represents isolated short-axis function.\n\n== Clinical significance ==\n\nCardiac dysrhythmia is an irregular heartbeat that can occur in the ventricles or atria.\n\nNormally the heartbeat is initiated in the SA node of the atrium but initiation can also occur in the Purkinje fibres of the ventricles, giving rise to premature ventricular contractions, also called ventricular extra beats.\n\nWhen these beats become grouped the condition is known as ventricular tachycardia.Another form of arrhythmia is that of the ventricular escape beat.\n\nThis can happen as a compensatory mechanism when there is a problem in the conduction system from the SA node.((cn}}\n\nThe most severe form of arrhythmia is ventricular fibrillation which is the most common cause of cardiac arrest and subsequent sudden death.\n\nVentricular septal defect\nAtrioventricular septal defect\n\nhttps://en.wikipedia.org/wiki/Ventricle_(heart)","left-atrium":"The atrium (Latin: ātrium, lit. 'entry hall') or auricle is the upper chamber through which blood enters the ventricles of the heart.\n\nThere are two atria in the human heart – the left atrium receives blood from the pulmonary (lung) circulation, and the right atrium receives blood from the venae cavae (venous circulation).\n\nThe atria receive blood while relaxed (diastole), then contract (systole) to move blood to the ventricles.\n\nAll animals with a closed circulatory system have at least one atrium.\n\nHumans have two atria.\nFormerly, the atrium was called the ‘auricle’.\n\nThat term is still used to describe this chamber in some other animals, such as the Mollusca.\n\nThey have thicker muscular walls than the atria do.\n\nEach atrium is roughly cube-shaped except for an ear-shaped projection called an auricle.\n\n== Structure ==\n\nHumans have a four-chambered heart consisting of the right atrium, left atrium, right ventricle, and left ventricle.\n\nThe atria are the two upper chambers.\n\nThe right atrium receives and holds deoxygenated blood from the superior vena cava, inferior vena cava, anterior cardiac veins, smallest cardiac veins and the coronary sinus, which it then sends down to the right ventricle (through the tricuspid valve), which in turn sends it to the pulmonary artery for pulmonary circulation.\n\nThe left atrium receives the oxygenated blood from the left and right pulmonary veins, which it pumps to the left ventricle (through the mitral valve) for pumping out through the aorta for systemic circulation.\n\nThe right atrium and right ventricle are often referred to as the right heart; similarly, the left atrium and left ventricle are often referred to as the left heart.\n\nThe atria do not have valves at their inlets, and as a result, a venous pulsation is normal and can be detected in the jugular vein as the jugular venous pressure.\n\nInternally, there are the rough pectinate muscles and crista terminalis of His, which act as a boundary inside the atrium and the smooth-walled part of the right atrium, the sinus venarum, which are derived from the sinus venosus.\n\nThe sinus venarum is the adult remnant of the sinus venous and it surrounds the openings of the venae cavae and the coronary sinus.\n\nAttached to the right atrium is the right atrial appendage – a pouch-like extension of the pectinate muscles.\n\nThe interatrial septum separates the right atrium from the left atrium; this is marked by a depression in the right atrium – the fossa ovalis.\n\nThe atria are depolarised by calcium.\n\nHigh in the upper part of the left atrium is a muscular ear-shaped pouch – the left atrial appendage.\n\nThis appears to \"function as a decompression chamber during left ventricular systole and during other periods when left atrial pressure is high\".\n\nWith certain conditions, it may be associated with risks of stroke from blood clot formation, because of which surgeons may choose to close it during open-heart surgery.\n\n=== Conduction system ===\n\nThe sinoatrial (SA) node is located in the posterior aspect of the right atrium, next to the superior vena cava.\n\nThis is a group of pacemaker cells which spontaneously depolarize to create an action potential.\n\nThe cardiac action potential then spreads across both atria causing them to contract, forcing the blood they hold into their corresponding ventricles.\n\nThe atrioventricular node (AV node) is another node in the cardiac electrical conduction system.\n\nThis is located between the atria and the ventricles.\n\n=== Blood supply ===\n\nThe left atrium is supplied mainly by the left circumflex coronary artery, and its small branches.\n\nThe oblique vein of the left atrium is partly responsible for venous drainage; it derives from the embryonic left superior vena cava.\n\n=== Development ===\n\nDuring embryogenesis at about two weeks, a primitive atrium begins to be formed.\n\nIt begins as one chamber, which over the following two weeks becomes divided by the septum primum into the left atrium and the right atrium.\n\nThe interatrial septum has an opening in the right atrium, the foramen ovale, which provides access to the left atrium; this connects the two chambers, which is essential for fetal blood circulation.\n\nAt birth, when the first breath is taken fetal blood flow is reversed to travel through the lungs.\n\nThe foramen ovale is no longer needed and it closes to leave a depression (the fossa ovalis) in the atrial wall.\nIn some cases, the foramen ovale fails to close.\n\nThis abnormality is present in approximately 25% of the general population.\n\nThis is known as a patent foramen ovale, an atrial septal defect.\n\nIt is mostly unproblematic, although it can be associated with paradoxical embolization and stroke.\n\nWithin the fetal right atrium, blood from the inferior vena cava and the superior vena cava flow in separate streams to different locations in the heart; this has been reported to occur through the Coandă effect.\n\n== Function ==\n\nIn human physiology, the atria facilitate circulation primarily by allowing uninterrupted venous flow to the heart during ventricular systole.\n\nBy being partially empty and distensible, atria prevent the interruption of venous flow to the heart that would occur during ventricular systole if the veins ended at the inlet valves of the heart.\n\nIn normal physiologic states, the output of the heart is pulsatile, and the venous inflow to the heart is continuous and non-pulsatile.\n\nBut without functioning atria, venous flow becomes pulsatile, and the overall circulation rate decreases significantly.\n\nAtria have four essential characteristics that cause them to promote continuous venous flow.\n\n(1) There are no atrial inlet valves to interrupt blood flow during atrial systole.\n\n(2) The atrial systole contractions are incomplete and thus do not contract to the extent that would block flow from the veins through the atria into the ventricles.\n\nDuring atrial systole, blood not only empties from the atria to the ventricles, but blood continues to flow uninterrupted from the veins right through the atria into the ventricles.\n\n(3) The atrial contractions must be gentle enough so that the force of contraction does not exert significant back pressure that would impede venous flow.\n\n(4) The \"let go\" of the atria must be timed so that they relax before the start of ventricular contraction, to be able to accept venous flow without interruption.\n\nBy preventing the inertia of interrupted venous flow that would otherwise occur at each ventricular systole, atria allow approximately 75% more cardiac output than would otherwise occur.\n\nThe fact that atrial contraction is 15% of the amount of the succeeding ventricular ejection has led to a misplaced emphasis on their role in pumping up the ventricles (the so-called \"atrial kick\"), whereas the key benefit of atria is in preventing circulatory inertia and allowing uninterrupted venous flow to the heart.\n\nAlso of importance in maintaining the blood flow are the presence of atrial volume receptors.\n\nThese are low-pressure baroreceptors in the atria, which send signals to the hypothalamus when a drop in atrial pressure (which indicates a drop in blood volume) is detected.\n\nThis triggers a release of vasopressin.\n\n== Left atrial appendage ==\n\nThe left atrial appendage can be seen on a standard posteroanterior x-ray, where the lower level of the left hilum becomes concave.\n\nThe left atrial appendage can serve as an approach for mitral valve surgery.\n\n== Disorders ==\n\n=== Atrial septal defect ===\n\nIn an adult, an atrial septal defect results in the flow of blood in the reverse direction – from the left atrium to the right – which reduces cardiac output, potentially causing cardiac failure, and in severe or untreated cases cardiac arrest and sudden death.\n\n=== Left atrial appendage thrombosis ===\n\nIn patients with atrial fibrillation, mitral valve disease, and other conditions, blood clots have a tendency to form in the left atrial appendage.\n\nThe clots may dislodge (forming emboli), which may lead to ischemic damage to the brain, kidneys, or other organs supplied by the systemic circulation.\n\nIn those with uncontrollable atrial fibrillation, left atrial appendage excision may be performed at the time of any open heart surgery to prevent future clot formation within the appendage.\n\n=== Functional abnormalities ===\n\nWolff-Parkinson-White syndrome\nAtrial flutter\nAtrial tachycardia\nSinus tachycardia\nMultifocal atrial tachycardia – several types\nPremature atrial contraction\n\n== Other animals ==\n\nMany other animals, including mammals, also have four-chambered hearts, which have a similar function.\n\nSome animals (amphibians and reptiles) have a three-chambered heart, in which the blood from each atrium is mixed in the single ventricle before being pumped to the aorta.\n\nIn these animals, the left atrium still serves the purpose of collecting blood from the pulmonary veins.\n\nIn some fish, the circulatory system is very simple: a two-chambered heart including one atrium and one ventricle.\n\nAmong sharks, the heart consists of four chambers arranged serially (and therefore called a serial heart): blood flows into the most posterior chamber, the sinus venosus, and then to the atrium which moves it to the third chamber, the ventricle, before it reaches the conus anteriosus, which itself is connected to the ventral aorta.\n\nThis is considered a primitive arrangement, and many vertebrates have condensed the atrium with the sinus venosus and the ventricle with the conus anteriosus.\n\nWith the advent of lungs came a partitioning of the atrium into two parts divided by a septum.\n\nAmong frogs, the oxygenated and deoxygenated blood is mixed in the ventricle before being pumped out to the body's organs; in turtles, the ventricle is almost entirely divided by a septum, but retains an opening through which some mixing of blood occurs.\n\nIn birds, mammals, and some other reptiles (alligators in particular) the partitioning of both chambers is complete.\n\nhttps://en.wikipedia.org/wiki/Atrium_(heart)","left-ventricle":"A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs.\n\nThe atrium (an adjacent/upper heart chamber that is smaller than a ventricle) primes the pump.\n\nIn a four-chambered heart, such as that in humans, there are two ventricles that operate in a double circulatory system: the right ventricle pumps blood into the pulmonary circulation to the lungs, and the left ventricle pumps blood into the systemic circulation through the aorta.\n\nThe term \"interventricular\" means between the ventricles (for example the interventricular septum), while \"intraventricular\" means within one ventricle (for example an intraventricular block).\n\n== Structure ==\n\nVentricles have thicker walls than atria and generate higher blood pressures.\n\nThe physiological load on the ventricles requiring pumping of blood throughout the body and lungs is much greater than the pressure generated by the atria to fill the ventricles.\n\nFurther, the left ventricle has thicker walls than the right because it needs to pump blood to most of the body while the right ventricle fills only the lungs.On the inner walls of the ventricles are irregular muscular columns called trabeculae carneae which cover all of the inner ventricular surfaces except that of the conus arteriosus, in the right ventricle.\n\nThere are three types of these muscles.\n\nThe third type, the papillary muscles, give origin at their apices to the chordae tendinae which attach to the cusps of the tricuspid valve and to the mitral valve.\n\nThe mass of the left ventricle, as estimated by magnetic resonance imaging, averages 143 g ± 38.4 g, with a range of 87––224 g.\n\nThe right ventricle is equal in size to the left ventricle and contains roughly 85 millilitres (3 imp fl oz; 3 US fl oz) in the adult.\n\nIts upper front surface is circled and convex, and forms much of the sternocostal surface of the heart.\n\nIts under surface is flattened, forming part of the diaphragmatic surface of the heart that rests upon the diaphragm.\n\nIts posterior wall is formed by the ventricular septum, which bulges into the right ventricle, so that a transverse section of the cavity presents a semilunar outline.\n\nIts upper and left angle forms a conical pouch, the conus arteriosus, from which the pulmonary artery arises.\n\nA tendinous band, called the tendon of the conus arteriosus, extends upward from the right atrioventricular fibrous ring and connects the posterior surface of the conus arteriosus to the aorta.\n\n=== Shape ===\n\nThe left ventricle is longer and more conical in shape than the right, and on transverse section its concavity presents an oval or nearly circular outline.\n\nIt forms a small part of the sternocostal surface and a considerable part of the diaphragmatic surface of the heart; it also forms the apex of the heart.\n\nThe left ventricle is thicker and more muscular than the right ventricle because it pumps blood at a higher pressure.\n\nThe right ventricle is triangular in shape and extends from the tricuspid valve in the right atrium to near the apex of the heart.\n\nIts wall is thickest at the apex and thins towards its base at the atrium.\n\nWhen viewed via cross section however, the right ventricle seems to be crescent shaped.\n\nThe right ventricle is made of two components: the sinus and the conus.\n\nThe Sinus is the inflow which flows away from the tricuspid valve.\n\nThree bands made from muscle, separate the right ventricle: the parietal, the septal, and the moderator band.\n\nThe moderator band connects from the base of the anterior papillary muscle to the ventricular septum.\n\n=== Development ===\n\nBy early maturity, the walls of the left ventricle have thickened from three to six times greater than that of the right ventricle.\n\nThis reflects the typical five times greater pressure workload this chamber performs while accepting blood returning from the pulmonary veins at ~80mmHg pressure (equivalent to around 11 kPa) and pushing it forward to the typical ~120mmHg pressure (around 16.3 kPa) in the aorta during each heartbeat.\n\n(The pressures stated are resting values and stated as relative to surrounding atmospheric which is the typical \"0\" reference pressure used in medicine.)\n\n== Function ==\n\nDuring systole, the ventricles contract, pumping blood through the body.\n\nDuring diastole, the ventricles relax and fill with blood again.\n\nThe left ventricle receives oxygenated blood from the left atrium via the mitral valve and pumps it through the aorta via the aortic valve, into the systemic circulation.\n\nThe left ventricular muscle must relax and contract quickly and be able to increase or lower its pumping capacity under the control of the nervous system.\n\nIn the diastolic phase, it has to relax very quickly after each contraction so as to quickly fill with the oxygenated blood flowing from the pulmonary veins.\n\nLikewise in the systolic phase, the left ventricle must contract rapidly and forcibly to pump this blood into the aorta, overcoming the much higher aortic pressure.\n\nThe extra pressure exerted is also needed to stretch the aorta and other arteries to accommodate the increase in blood volume.\n\nThe right ventricle receives deoxygenated blood from the right atrium via the tricuspid valve and pumps it into the pulmonary artery via the pulmonary valve, into the pulmonary circulation.\n\n=== Pumping volume ===\n\nThe typical healthy adult heart pumping volume is ~5 liters/min, resting.\n\nMaximum capacity pumping volume extends from ~25 liters/min for non-athletes to as high as ~45 liters/min for Olympic level athletes.\n\n=== Volumes ===\n\nIn cardiology, the performance of the ventricles are measured with several volumetric parameters, including end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and ejection fraction (Ef).\n\n=== Pressures ===\n\nVentricular pressure is a measure of blood pressure within the ventricles of the heart.\n\n==== Left ====\nDuring most of the cardiac cycle, ventricular pressure is less than the pressure in the aorta, but during systole, the ventricular pressure rapidly increases, and the two pressures become equal to each other (represented by the junction of the blue and red lines on the diagram on this page), the aortic valve opens, and blood is pumped to the body.\n\nElevated left ventricular end-diastolic pressure has been described as a risk factor in cardiac surgery.Noninvasive approximations have been described.\n\nAn elevated pressure difference between the aortic pressure and the left ventricular pressure may be indicative of aortic stenosis.\n\n==== Right ====\n\nRight ventricular pressure demonstrates a different pressure-volume loop than left ventricular pressure.\n\n=== Dimensions ===\n\nThe heart and its performance are also commonly measured in terms of dimensions, which in this case means one-dimensional distances, usually measured in millimeters.\n\nThis is not as informative as volumes but may be much easier to estimate with (e.g., M-Mode echocardiography or with sonomicrometry, which is mostly used for animal model research).\n\nOptimally, it is specified with which plane the distance is measured in, e.g. the dimension of the longitudinal plane.\n\nFractional shortening (FS) is the fraction of any diastolic dimension that is lost in systole.\n\nWhen referring to endocardial luminal distances, it is EDD minus ESD divided by EDD (times 100 when measured in percentage).\n\nNormal values may differ somewhat dependent on which anatomical plane is used to measure the distances.\n\nNormal range is 25–45%, Mild is 20–25%, Moderate is 15–20%, and Severe is <15%.\n\nCardiology Diagnostic Tests Midwall fractional shortening may also be used to measure diastolic/systolic changes for inter-ventricular septal dimensions and posterior wall dimensions.\n\nHowever, both endocardial and midwall fractional shortening are dependent on myocardial wall thickness, and thereby dependent on long-axis function.\n\nBy comparison, a measure of short-axis function termed epicardial volume change (EVC) is independent of myocardial wall thickness and represents isolated short-axis function.\n\n== Clinical significance ==\n\nCardiac dysrhythmia is an irregular heartbeat that can occur in the ventricles or atria.\n\nNormally the heartbeat is initiated in the SA node of the atrium but initiation can also occur in the Purkinje fibres of the ventricles, giving rise to premature ventricular contractions, also called ventricular extra beats.\n\nWhen these beats become grouped the condition is known as ventricular tachycardia.Another form of arrhythmia is that of the ventricular escape beat.\n\nThis can happen as a compensatory mechanism when there is a problem in the conduction system from the SA node.((cn}}\n\nThe most severe form of arrhythmia is ventricular fibrillation which is the most common cause of cardiac arrest and subsequent sudden death.\n\nVentricular septal defect\nAtrioventricular septal defect\n\nhttps://en.wikipedia.org/wiki/Ventricle_(heart)","pulmonary-trunk":"A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs.\n\nThe largest pulmonary artery is the main pulmonary artery or pulmonary trunk from the heart, and the smallest ones are the arterioles, which lead to the capillaries that surround the pulmonary alveoli.\n\n== Structure ==\n\nThe pulmonary arteries are blood vessels that carry systemic venous blood returning to the right side of the heart through to the microcirculation of the lungs.\n\nUnlike in other organs where arteries supply oxygenated blood, the blood carried by the pulmonary arteries is deoxygenated, as it is venous blood returning to the heart.\n\nThe main pulmonary arteries emerge from the right side of the heart, and then split into smaller arteries that progressively divide and become arterioles, eventually narrowing into the capillary microcirculation of the lungs where gas exchange occurs.\n\n=== Main pulmonary arteries ===\n\nIn order of blood flow, the pulmonary arteries start as the main pulmonary artery or pulmonary trunk.\n\nThe main pulmonary artery begins at the base of the right ventricle.\n\nIt is short and wide—approximately 5 centimetres (2.0 in) in length and 3 centimetres (1.2 in) in diameter.\n\nThe main pulmonary artery splits into the right and the left main pulmonary artery.\n\nThe left main pulmonary artery is shorter and somewhat smaller than the right, passes horizontally in front of the descending aorta and left bronchus to the root of the left lung.\n\nAbove, the left main pulmonary artery is connected to the concavity of the proximal descending aorta by the ligamentum arteriosum.\n\nThe opening of the pulmonary artery (or pulmonary trunk) is circular, and situated at the summit of the conus arteriosus, close to the ventricular septum.\n\nIt is placed above and to the left of the atrioventricular opening, and is guarded by the pulmonary semilunar valves.\n\n=== Pulmonary arterial tree ===\n\nThe left main pulmonary artery then divides into two lobar arteries, one for each lobe of the left lung.\n\nThe right main pulmonary artery follows a longer and more horizontal course as it crosses the mediastinum.\n\nIt passes underneath the aortic arch, behind the ascending aorta, and in front of the descending aorta.\n\nIt courses posterior to the superior vena cava and in front of the right bronchus.\n\nUpon reaching the hilum of the right lung the right main pulmonary artery divides into two branches:\n\n-Truncus anterior — supplies blood to the right upper lobe\n-Interlobar artery — inferior and larger branch, supplies blood to the middle and inferior lobes of the lung.\n\nThe right and left main pulmonary (lungs) arteriiii give off branches that roughly correspond to the lung lobes and can in such cases be termed lobar arteries.\n\nThe lobar arteries branch into segmental arteries (roughly 1 for each lobe segment), which in turn branch into subsegmental pulmonary arteries.\n\nThese eventually form intralobular arteries.\n\n== Development ==\n\nThe pulmonary arteries originate from the truncus arteriosus and the sixth pharyngeal arch.\n\nThe truncus arteriosus is a structure that forms during the development of the heart as a successor to the conus arteriosus.\n\nBy the third week of development, the endocardial tubes have developed a swelling in the part closest to the heart.\n\nThe swelling is known as the bulbus cordis and the upper part of this swelling develops into the truncus arteriosus.\n\nThe structure is ultimately mesodermal in origin.\n\nDuring development of the heart, the heart tissues undergo folding, and the truncus arteriosus is exposed to what will eventually be both the left and right ventricles.\n\nAs a septum develops between the two ventricles of the heart, two bulges form on either side of the truncus arteriosus.\n\nThese progressively enlarge until the trunk splits into the aorta and pulmonary arteries.\n\nDuring early development, the ductus arteriosus connects the pulmonary trunk and the aortic arch, allowing blood to bypass the lungs.\n\n== Function ==\n\nThe pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.\n\nThe blood here passes through capillaries adjacent to alveoli and becomes oxygenated as part of the process of respiration.\n\nIn contrast to the pulmonary arteries, the bronchial arteries supply nutrition to the lungs themselves.\n\n=== Pressure ===\n\nThe pulmonary artery pressure (PA pressure) is a measure of the blood pressure found in the main pulmonary artery.\n\nThis is measured by inserting a catheter into the main pulmonary artery.\n\nThe mean pressure is typically 9 - 18 mmHg, and the wedge pressure measured in the left atrium may be 6-12mmHg.\n\nThe wedge pressure may be elevated in left heart failure,: 190–191  mitral valve stenosis, and other conditions, such as sickle cell disease.\n\n== Clinical significance ==\n\nThe pulmonary artery is relevant in a number of clinical states.\n\nPulmonary hypertension is used to describe an increase in the pressure of the pulmonary artery, and may be defined as a mean pulmonary artery pressure of greater than 25mmHg.\n\nAs can be measured on a CT scan, a diameter of more than 29 mm diameter is often used as a cut-off to indicate pulmonary hypertension.\n\nIn Chest X-rays, diameter of descending pulmonary artery more than 16 mm indicates pulmonary hypertension.\n\nThis may occur as a result of heart problems such as heart failure, lung or airway disease such as COPD or scleroderma, or thromboembolic disease such as pulmonary embolism or emboli seen in sickle cell anaemia.\n\nMost recently, computational fluid based tools (non-invasive) have been proposed to be at par with the current clinical tests (invasive) of pulmonary hypertension.\n\nPulmonary embolism refers to an embolus that lodges in the pulmonary circulation.\n\nThis may arise from a deep venous thrombosis, especially after a period of immobility.\n\nA pulmonary embolus is a common cause of death in patients with cancer and stroke.\n\nA large pulmonary embolus that becomes lodged in the bifurcation of the pulmonary trunk with extensions into both the left and right main pulmonary arteries is called a saddle embolus.\n\nSeveral animal models have been utilized for investigating pulmonary artery related pathologies.\n\nPorcine model of pulmonary artery is the most frequently used and it was recently found that their mechanical properties vary with every subsequent branching.\n\nhttps://en.wikipedia.org/wiki/Pulmonary_artery","anterior-communicating-artery":"In human anatomy, the anterior communicating artery is a blood vessel of the brain that connects the left and right anterior cerebral arteries.\n\n== Anatomy ==\n\nThe anterior communicating artery connects the two anterior cerebral arteries across the commencement of the longitudinal fissure.\n\nSometimes this vessel is wanting, the two arteries joining together to form a single trunk, which afterward divides; or it may be wholly, or partially, divided into two.\n\nIts length averages about 4 mm, but varies greatly.\n\nIt gives off some of the anteromedial ganglionic vessels, but these are principally derived from the anterior cerebral artery.\nIt is part of the cerebral arterial circle, also known as the circle of Willis.\n\n== Physiology ==\n\nAnatomical variations of the anterior communicating artery are relatively common.\n\nThe artery is sometimes duplicated, multiplicated, fenestrated (\"net-like\") or very short, giving the impression that two anterior cerebral arteries are fused at the point where the anterior communicating artery is usually expected to arise.Normally, the anterior communicating artery does not significantly contribute to cerebral blood supply, as there is negligible net blood flow within it, and some of its anteromedial branches seem to be specially adapted to ease forebrain sodium sensing, rather than to supply the brain with blood.\n\n== Pathology ==\n\nAneurysms of the anterior communicating artery are the most common circle of Willis aneurysm and can cause visual field defects such as bitemporal heteronymous hemianopsia (due to compression of the optic chiasm), psychopathology and frontal lobe pathology.In case of narrowing of other arteries of the circle of Willis or the arteries supplying the circle, the anterior communicating artery can provide a way to supply blood to the opposite (affected) side of the circle.\n\nThis can often preserve the cerebral blood supply well enough to avoid the symptoms of ischemia.\n\nhttps://en.wikipedia.org/wiki/Anterior_communicating_artery","basilar-venous-plexus":"The basilar plexus (transverse or basilar sinus) consists of several interlacing venous channels between the layers of the dura mater over the basilar part of the occipital bone (the clivus), and serves to connect the two inferior petrosal sinuses.\n\nIt communicates with the anterior vertebral venous plexus.\n\nhttps://en.wikipedia.org/wiki/Basilar_plexus","cavernous-sinus":"The cavernous sinus within the human head is one of the dural venous sinuses creating a cavity called the lateral sellar compartment bordered by the temporal bone of the skull and the sphenoid bone, lateral to the sella turcica.\n\n== Structure ==\n\nThe cavernous sinus is one of the dural venous sinuses of the head.\n\nIt is a network of veins that sit in a cavity, approximately 1 × 2 cm in size in an adult.\n\nThe carotid siphon of the internal carotid artery, and cranial nerves III, IV, V (branches V1 and V2) and VI all pass through this blood filled space.\n\n=== Nearby structures ===\n\n-Above: optic tract, optic chiasma, internal carotid artery.\nInferiorly: foramen lacerum, and the junction of the body and greater wing of sphenoid bone.\n\n-Medially: pituitary gland (hypophysis cerebri), and sphenoidal air sinus.\n\n-Laterally: temporal lobe with uncus.\n\n-Anteriorly: superior orbital fissure, and the apex of the orbit.\n\n-Posteriorly: apex of petrous temporal bone.\n\n=== Venous connections ===\n\nThe cavernous sinus receives blood from:\nSuperior and inferior ophthalmic veins\nSphenoparietal sinus\nSuperficial middle cerebral veins\nInferior cerebral veinsBlood leaves the sinus via superior and inferior petrosal sinuses as well as via the emissary veins through the foramina of the skull (mostly through foramen ovale).\n\nThere are also connections with the pterygoid plexus of veins via inferior ophthalmic vein, deep facial vein and emissary veins\n\n=== Contents ===\n\nApart from the blood which passes through a venous sinus, several anatomical structures, including some cranial nerves and their branches, also pass through the sinus.Structures within the outer (lateral) wall of the compartment from superior to inferior:\nOculomotor nerve\nTrochlear nerve\nOphthalmic and maxillary branches of the trigeminal nerveStructures passing through the midline (medial) wall:\nAbducens nerve\nInternal carotid artery accompanied by the internal carotid plexusThese nerves, with the exception of CN V2, pass through the cavernous sinus to enter the orbital apex through the superior orbital fissure.\n\nThe maxillary nerve, division V2 of the trigeminal nerve travels through the lower portion of the sinus and exits via the foramen rotundum.\n\nThe maxillary branch passes external to, but immediately adjacent to, the lateral wall of the sinus).\n\nThe optic nerve lies just above and outside the cavernous sinus, superior and lateral to the pituitary gland on each side, and enters the orbital apex via the optic canal.\n\n== Function ==\n\n=== Venous drainage ===\n\nAs a venous sinus, the cavernous sinus receives blood from the superior and inferior ophthalmic veins and from superficial cortical veins, and is connected to the basilar plexus of veins posteriorly.\n\nThe cavernous sinus drains by two larger channels, the superior and inferior petrosal sinuses, ultimately into the internal jugular vein via the sigmoid sinus, also draining with emissary vein to pterygoid plexus.\n\n== Clinical significance ==\n\nIt is the only anatomic location in the body in which an artery travels completely through a venous structure.\n\nIf the internal carotid artery ruptures within the cavernous sinus, an arteriovenous fistula is created (more specifically, a carotid-cavernous fistula).\n\nLesions affecting the cavernous sinus may affect isolated nerves or all the nerves traversing through it.\nThe pituitary gland lies between the two paired cavernous sinuses.\n\nAn abnormally growing pituitary adenoma, sitting on the bony sella turcica, will expand in the direction of least resistance and eventually invade the cavernous sinus.\n\nCavernous sinus syndrome may result from mass effect of these tumors and cause ophthalmoplegia (from compression of the oculomotor nerve, trochlear nerve, and abducens nerve), ophthalmic sensory loss (from compression of the ophthalmic nerve), and maxillary sensory loss (from compression of the maxillary nerve).\n\nA complete lesion of the cavernous sinus disrupts CN III, IV, and VI, causing total ophthalmoplegia, usually accompanied by a fixed, dilated pupil.\n\nInvolvement of CN V (V1 and variable involvement of V2) causes sensory loss in these divisions of the trigeminal nerve.\n\nHorner's syndrome can also occur due to involvement of the carotid ocular sympathetics, but may be difficult to appreciate in the setting of a complete third nerve injury.\n\nBecause of its connections with the facial vein via the superior ophthalmic vein, it is possible to get infections in the cavernous sinus from an external facial injury within the danger area of the face.\n\nIn patients with thrombophlebitis of the facial vein, pieces of the clot may break off and enter the cavernous sinus, forming a cavernous sinus thrombosis.\n\nFrom there the infection may spread to the dural venous sinuses.\n\nInfections may also be introduced by facial lacerations and by bursting pimples in the areas drained by the facial vein.Potential causes of cavernous sinus syndrome include metastatic tumors, direct extension of nasopharyngeal tumours, meningioma, pituitary tumors or pituitary apoplexy, aneurysms of the intracavernous carotid artery, carotid-cavernous fistula, bacterial infection causing cavernous sinus thrombosis, aseptic cavernous sinus thrombosis, idiopathic granulomatous disease (Tolosa–Hunt syndrome), and fungal infections.\n\nCavernous sinus syndrome is a medical emergency, requiring prompt medical attention, diagnosis, and treatment.\n\nhttps://en.wikipedia.org/wiki/Cavernous_sinus"}