Editing Anatomy (section)

== Vertebrate anatomy ==
{{see also|Vertebrate#Physical|Comparative anatomy}}
[[File:VolRenderShearWarp.gif|thumb|upright|[[Mouse]] skull. The neck and most of the forelimbs are also seen.]]
All [[vertebrate]]s have a similar basic [[body plan]] and at some point in their lives, mostly in the [[embryogenesis|embryonic]] stage, share the major [[chordate]] characteristics: a stiffening rod, the [[notochord]]; a dorsal hollow tube of nervous material, the [[neural tube]]; [[pharyngeal arch]]es; and a tail posterior to the anus. The [[spinal cord]] is protected by the [[vertebral column]] and is above the notochord, and the [[gastrointestinal tract]] is below it.<ref>{{cite web |last=Waggoner |first=Ben |title=Vertebrates: More on Morphology |url=https://www.ucmp.berkeley.edu/vertebrates/vertmm.html |publisher=UCMP |access-date=13 July 2011 |archive-date=10 October 2018 |archive-url=https://web.archive.org/web/20181010104933/https://www.ucmp.berkeley.edu/vertebrates/vertmm.html |url-status=dead }}</ref> Nervous tissue is derived from the [[ectoderm]], connective tissues are derived from [[mesoderm]], and gut is derived from the [[endoderm]]. At the posterior end is a tail which continues the spinal cord and vertebrae but not the gut. The mouth is found at the anterior end of the animal, and the [[anus]] at the base of the tail.<ref>{{cite book |title=The Vertebrate Body |last=Romer |first=Alfred Sherwood |year=1985 |publisher=Holt Rinehart & Winston |isbn=978-0-03-058446-6 }}</ref> The defining characteristic of a vertebrate is the [[vertebral column]], formed in the development of the segmented series of [[vertebra]]e. In most vertebrates the notochord becomes the [[nucleus pulposus]] of the [[intervertebral disc]]s. However, a few vertebrates, such as the [[sturgeon]] and the [[coelacanth]], retain the notochord into adulthood.<ref>{{cite book|title=Functional anatomy of the vertebrates: an evolutionary perspective|year=2001|publisher=Harcourt College Publishers|isbn=978-0-03-022369-3|author=Liem, Karel F.|author2=Warren Franklin Walker|page=277}}</ref> [[Jawed vertebrates]] are typified by paired appendages, fins or legs, which may be secondarily lost. The limbs of vertebrates are considered to be [[Homology (biology)|homologous]] because the same underlying skeletal structure was inherited from their [[last common ancestor]]. This is one of the arguments put forward by [[Charles Darwin]] to support his theory of [[evolution]].<ref>{{cite web |url=https://ncse.com/evolution/science/what-is-homology |title=What is Homology? |work=NCSE |date=17 October 2008 |publisher=National Center for Science Education |access-date=28 June 2013 |archive-date=31 March 2019 |archive-url=https://web.archive.org/web/20190331065618/https://ncse.com/evolution/science/what-is-homology |url-status=live }}</ref>

=== Fish anatomy ===
{{main|Fish anatomy}}
[[File:Internal anatomy of a fish (cutaway diagram).jpg|thumb|left|Cutaway diagram showing various organs of a fish]]
The body of a [[fish]] is divided into a head, trunk and tail, although the divisions between the three are not always externally visible. The skeleton, which forms the support structure inside the fish, is either made of cartilage, in [[cartilaginous fish]], or bone in [[bony fish]]. The main skeletal element is the vertebral column, composed of articulating [[vertebra]]e which are lightweight yet strong. The ribs attach to the spine and there are no [[Limb (anatomy)|limbs]] or limb girdles. The main external features of the fish, the [[fish fin|fins]], are composed of either bony or soft spines called rays, which with the exception of the [[caudal fin]]s, have no direct connection with the spine. They are supported by the muscles which compose the main part of the trunk.<ref name=Dorit818/> The heart has two chambers and pumps the blood through the respiratory surfaces of the [[gill]]s and on round the body in a single circulatory loop.<ref>{{cite web|url=https://library.thinkquest.org/C003758/Development/fish.htm |title=The fish heart |work=ThinkQuest |publisher=Oracle |access-date=27 June 2013 |url-status=dead |archive-url=https://web.archive.org/web/20120428001536/https://library.thinkquest.org/C003758/Development/fish.htm |archive-date=28 April 2012 }}</ref> The eyes are adapted for seeing underwater and have only local vision. There is an inner ear but no external or [[middle ear]]. Low frequency vibrations are detected by the [[lateral line]] system of sense organs that run along the length of the sides of fish, and these respond to nearby movements and to changes in water pressure.<ref name=Dorit818>{{cite book |title=Zoology |url=https://archive.org/details/zoology0000dori |url-access=registration |last1=Dorit |first1=R. L. |last2=Walker |first2=W. F. |last3=Barnes |first3=R. D. |year=1991 |publisher=Saunders College Publishing |isbn=978-0-03-030504-7 |pages=[https://archive.org/details/zoology0000dori/page/816 816–818] }}</ref>

Sharks and rays are [[Basal (phylogenetics)|basal]] fish with numerous [[Primitive (phylogenetics)|primitive]] anatomical features similar to those of ancient fish, including skeletons composed of cartilage. Their bodies tend to be dorso-ventrally flattened, they usually have five pairs of gill slits and a large mouth set on the underside of the head. The dermis is covered with separate dermal [[placoid scales]]. They have a [[cloaca]] into which the urinary and genital passages open, but not a [[swim bladder]]. Cartilaginous fish produce a small number of large, [[Egg yolk|yolky]] eggs. Some species are [[ovoviviparous]] and the young develop internally but others are [[oviparous]] and the larvae develop externally in egg cases.<ref name=Kotpal>{{cite book |title=Modern Text Book of Zoology: Vertebrates |last=Kotpal |first=R. L. |year=2010 |publisher=Rastogi Publications |isbn=978-81-7133-891-7 |page=193 |url=https://books.google.com/books?id=U7N1j-8LMsEC&pg=PA199 }}</ref>

The bony fish lineage shows more [[Derived trait|derived]] anatomical traits, often with major evolutionary changes from the features of ancient fish. They have a bony skeleton, are generally laterally flattened, have five pairs of gills protected by an [[operculum (fish)|operculum]], and a mouth at or near the tip of the snout. The dermis is covered with overlapping [[Fish scale|scales]]. Bony fish have a swim bladder which helps them maintain a constant depth in the water column, but not a cloaca. They mostly [[Spawn (biology)|spawn]] a large number of small eggs with little yolk which they broadcast into the water column.<ref name=Kotpal/>

=== Amphibian anatomy ===
{{main|Amphibian anatomy}}
[[File:Ceratophrys cornuta skeleton front.jpg|thumb|left|alt=Frog skeleton|Skeleton of [[Surinam horned frog]] (''Ceratophrys cornuta'')]]
[[File:Frog anatomy tags.PNG|thumb|upright|Plastic model of a frog]]
[[Amphibian]]s are a [[Class (biology)|class]] of animals comprising [[frog]]s, [[salamander]]s and [[caecilian]]s. They are [[tetrapod]]s, but the caecilians and a few species of salamander have either no limbs or their limbs are much reduced in size. Their main bones are hollow and lightweight and are fully ossified and the vertebrae interlock with each other and have [[articular processes]]. Their ribs are usually short and may be fused to the vertebrae. Their skulls are mostly broad and short, and are often incompletely ossified. Their skin contains little [[keratin]] and lacks scales, but contains many [[mucous gland]]s and in some species, poison glands. The hearts of amphibians have three chambers, two [[atrium (heart)|atria]] and one [[ventricle (heart)|ventricle]]. They have a [[urinary bladder]] and [[metabolic waste#nitrogen wastes|nitrogenous waste products]] are excreted primarily as [[urea]]. Amphibians breathe by means of [[buccal pumping]], a pump action in which air is first drawn into the [[Buccopharyngeal membrane|buccopharyngeal]] region through the nostrils. These are then closed and the air is forced into the lungs by contraction of the throat.<ref>{{cite book |title=A Natural History of Amphibians |last1=Stebbins |first1=Robert C. |author-link1=Robert C. Stebbins|last2=Cohen |first2=Nathan W. |year=1995 |publisher=Princeton University Press |isbn=978-0-691-03281-8 |pages=24–25 }}</ref> They supplement this with [[gas exchange]] through the skin which needs to be kept moist.<ref name=Dorit859>{{cite book |title=Zoology |url=https://archive.org/details/zoology0000dori/page/843 |url-access=registration |last1=Dorit |first1=R. L. |last2=Walker |first2=W. F. |last3=Barnes |first3=R. D. |year=1991 |publisher=Saunders College Publishing |isbn=978-0-03-030504-7 |pages=[https://archive.org/details/zoology0000dori/page/843 843–859] }}</ref>

In frogs the pelvic girdle is robust and the hind legs are much longer and stronger than the forelimbs. The feet have four or five digits and the toes are often webbed for swimming or have suction pads for climbing. Frogs have large eyes and no tail. Salamanders resemble lizards in appearance; their short legs project sideways, the belly is close to or in contact with the ground and they have a long tail. Caecilians superficially resemble [[earthworm]]s and are limbless. They burrow by means of zones of muscle contractions which move along the body and they swim by undulating their body from side to side.<ref>{{cite book |title=A Natural History of Amphibians |last1=Stebbins |first1=Robert C. |author-link1=Robert C. Stebbins|last2=Cohen |first2=Nathan W. |year=1995 |publisher=Princeton University Press |isbn=978-0-691-03281-8 |pages=26–35 }}</ref>

=== Reptile anatomy ===
{{main|Reptile anatomy}}
[[File:Crotalus atrox -Museum of Osteology, Oklahoma City, Oklahoma, USA-29Aug2012.jpg|thumb|left|Skeleton of a [[western diamondback rattlesnake]]]]
[[Reptile]]s are a class of [[animal]]s comprising [[turtle]]s, [[tuatara]]s, [[lizard]]s, [[snake]]s and [[crocodile]]s. They are [[tetrapod]]s, but the snakes and a few species of lizard either have no limbs or their limbs are much reduced in size. Their bones are better ossified and their skeletons stronger than those of amphibians. The teeth are conical and mostly uniform in size. The surface cells of the epidermis are modified into horny scales which create a waterproof layer. Reptiles are unable to use their skin for respiration as do amphibians and have a more efficient respiratory system drawing air into their [[lung]]s by expanding their chest walls. The heart resembles that of the amphibian but there is a septum which more completely separates the oxygenated and deoxygenated bloodstreams. The reproductive system has evolved for internal fertilization, with a [[copulatory organ]] present in most species. The eggs are surrounded by [[Amniote|amniotic membranes]] which prevents them from drying out and are laid on land, or [[Ovoviviparity|develop internally]] in some species. The bladder is small as nitrogenous waste is excreted as [[uric acid]].<ref name=Dorit865>{{cite book |title=Zoology |url=https://archive.org/details/zoology0000dori/page/861 |url-access=registration |last1=Dorit |first1=R. L. |last2=Walker |first2=W. F. |last3=Barnes |first3=R. D. |year=1991 |publisher=Saunders College Publishing |isbn=978-0-03-030504-7 |pages=[https://archive.org/details/zoology0000dori/page/861 861–865] }}</ref>

Turtles are notable for their protective shells. They have an inflexible trunk encased in a horny [[carapace]] above and a [[plastron]] below. These are formed from bony plates embedded in the dermis which are overlain by horny ones and are partially fused with the ribs and spine. The neck is long and flexible and the head and the legs can be drawn back inside the shell. Turtles are vegetarians and the typical reptile teeth have been replaced by sharp, horny plates. In aquatic species, the front legs are modified into flippers.<ref name=Dorit868>{{cite book |title=Zoology |url=https://archive.org/details/zoology0000dori/page/865 |url-access=registration |last1=Dorit |first1=R. L. |last2=Walker |first2=W. F. |last3=Barnes |first3=R. D. |year=1991 |publisher=Saunders College Publishing |isbn=978-0-03-030504-7 |pages=[https://archive.org/details/zoology0000dori/page/865 865–868] }}</ref>

'''Tuataras''' superficially resemble lizards but the lineages diverged in the [[Triassic]] period. There is one living species, ''[[Sphenodon punctatus]]''. The skull has two openings (fenestrae) on either side and the jaw is rigidly attached to the skull. There is one row of teeth in the lower jaw and this fits between the two rows in the upper jaw when the animal chews. The teeth are merely projections of bony material from the jaw and eventually wear down. The brain and heart are more primitive than those of other reptiles, and the lungs have a single chamber and lack [[bronchi]]. The tuatara has a well-developed [[parietal eye]] on its forehead.<ref name=Dorit868/>

Lizards have skulls with only one [[Nasal fenestra|fenestra]] on each side, the lower bar of bone below the second fenestra having been lost. This results in the jaws being less rigidly attached which allows the mouth to open wider. Lizards are mostly quadrupeds, with the trunk held off the ground by short, sideways-facing legs, but a few species have no limbs and resemble snakes. Lizards have moveable eyelids, eardrums are present and some species have a central parietal eye.<ref name=Dorit868/>

Snakes are closely related to lizards, having branched off from a common ancestral lineage during the [[Cretaceous]] period, and they share many of the same features. The skeleton consists of a skull, a hyoid bone, spine and ribs though a few species retain a vestige of the pelvis and rear limbs in the form of [[pelvic spur]]s. The bar under the second fenestra has also been lost and the jaws have extreme flexibility allowing the snake to swallow its prey whole. Snakes lack moveable eyelids, the eyes being covered by transparent "spectacle" scales. They do not have eardrums but can detect ground vibrations through the bones of their skull. Their forked tongues are used as organs of taste and smell and some species have sensory pits on their heads enabling them to locate warm-blooded prey.<ref name=Dorit870>{{cite book |title=Zoology |url=https://archive.org/details/zoology0000dori/page/870 |url-access=registration |last1=Dorit |first1=R. L. |last2=Walker |first2=W. F. |last3=Barnes |first3=R. D. |year=1991 |publisher=Saunders College Publishing |isbn=978-0-03-030504-7 |page=[https://archive.org/details/zoology0000dori/page/870 870] }}</ref>

[[Crocodilians]] are large, low-slung aquatic reptiles with long snouts and large numbers of teeth. The head and trunk are dorso-ventrally flattened and the tail is laterally compressed. It undulates from side to side to force the animal through the water when swimming. The tough keratinized scales provide body armour and some are fused to the skull. The nostrils, eyes and ears are elevated above the top of the flat head enabling them to remain above the surface of the water when the animal is floating. Valves seal the nostrils and ears when it is submerged. Unlike other reptiles, crocodilians have hearts with four chambers allowing complete separation of oxygenated and deoxygenated blood.<ref name=Dorit874>{{cite book |title=Zoology |url=https://archive.org/details/zoology0000dori/page/874 |url-access=registration |last1=Dorit |first1=R. L. |last2=Walker |first2=W. F. |last3=Barnes |first3=R. D. |year=1991 |publisher=Saunders College Publishing |isbn=978-0-03-030504-7 |page=[https://archive.org/details/zoology0000dori/page/874 874] }}</ref>

=== Bird anatomy ===
{{main|Bird anatomy}}
[[File:Duerer wing of a blue roller.jpg|thumb|Part of a wing. [[Albrecht Dürer]], {{circa|1500–1512}}]]
[[Bird]]s are [[tetrapod]]s but though their hind limbs are used for walking or hopping, their front limbs are [[Bird wing|wing]]s covered with [[feather]]s and adapted for flight. Birds are [[endotherm]]ic, have a high [[metabolic rate]], a light [[skeletal system]] and powerful [[muscle]]s. The long bones are thin, hollow and very light. Air sac extensions from the lungs occupy the centre of some bones. The sternum is wide and usually has a keel and the caudal vertebrae are fused. There are no teeth and the narrow jaws are adapted into a horn-covered beak. The eyes are relatively large, particularly in nocturnal species such as owls. They face forwards in predators and sideways in ducks.<ref name=Dorit895>{{cite book |title=Zoology |url=https://archive.org/details/zoology0000dori/page/881 |url-access=registration |last1=Dorit |first1=R. L. |last2=Walker |first2=W. F. |last3=Barnes |first3=R. D. |year=1991 |publisher=Saunders College Publishing |isbn=978-0-03-030504-7 |pages=[https://archive.org/details/zoology0000dori/page/881 881–895] }}</ref>

The feathers are outgrowths of the [[epidermis (zoology)|epidermis]] and are found in localized bands from where they fan out over the skin. Large flight feathers are found on the wings and tail, contour feathers cover the bird's surface and fine down occurs on young birds and under the contour feathers of water birds. The only cutaneous gland is the single [[uropygial gland]] near the base of the tail. This produces an oily secretion that waterproofs the feathers when the bird [[personal grooming|preens]]. There are scales on the legs, feet and claws on the tips of the toes.<ref name=Dorit895/>

=== Mammal anatomy ===
{{Main|Mammal anatomy}}
[[Mammal]]s are a diverse class of animals, mostly terrestrial but some are aquatic and others have evolved flapping or gliding flight. They mostly have four limbs, but some aquatic mammals have no limbs or limbs modified into fins, and the forelimbs of bats are modified into wings. The legs of most mammals are situated below the trunk, which is held well clear of the ground. The bones of mammals are well ossified and their teeth, which are usually differentiated, are coated in a layer of [[Tooth enamel|prismatic enamel]]. The teeth are shed once ([[milk teeth]]) during the animal's lifetime or not at all, as is the case in [[cetacea]]ns. Mammals have three bones in the middle ear and a [[cochlea]] in the [[inner ear]]. They are clothed in hair and their skin contains glands which secrete [[sweat gland|sweat]]. Some of these glands are specialized as [[mammary gland]]s, producing milk to feed the young. Mammals breathe with [[lung]]s and have a muscular [[Thoracic diaphragm|diaphragm]] separating the thorax from the abdomen which helps them draw air into the lungs. The mammalian heart has four chambers, and oxygenated and deoxygenated blood are kept entirely separate. Nitrogenous waste is excreted primarily as urea.<ref name=Dorit914>{{cite book |title=Zoology |url=https://archive.org/details/zoology0000dori/page/909 |url-access=registration |last1=Dorit |first1=R. L. |last2=Walker |first2=W. F. |last3=Barnes |first3=R. D. |year=1991 |publisher=Saunders College Publishing |isbn=978-0-03-030504-7 |pages=[https://archive.org/details/zoology0000dori/page/909 909–914] }}</ref>

Mammals are [[amniote]]s, and most are [[viviparous]], giving birth to live young. Exceptions to this are the egg-laying [[monotreme]]s, the [[platypus]] and the [[echidna]]s of Australia. Most other mammals have a [[placenta]] through which the developing [[foetus]] obtains nourishment, but in [[marsupial]]s, the foetal stage is very short and the immature young is born and finds its way to its mother's [[Pouch (marsupial)|pouch]] where it latches on to a [[teat]] and completes its development.<ref name=Dorit914/>

====Human anatomy====
{{Further|Human anatomy|Outline of human anatomy}}
[[File:Parasagittal MRI of human head in patient with benign familial macrocephaly prior to brain injury (ANIMATED).gif|thumb|left|Sagittal sections of the head as seen by a modern [[MRI]] scan]]
[[File:Violin Scroll (2769099541).jpg|upright|thumb|In humans, dexterous hand movements and increased brain size are likely to have evolved simultaneously.<ref name="BritBrit-Hand">{{cite encyclopedia |chapter-url=https://www.britannica.com/EBchecked/topic/254068/hand |title=Encyclopædia Britannica 2006 Ultimate Reference Suite DVD |chapter=Hand |access-date=15 May 2014 |archive-date=17 May 2014 |archive-url=https://web.archive.org/web/20140517132724/https://www.britannica.com/EBchecked/topic/254068/hand |url-status=live }}</ref>]]
[[Human]]s have the overall body plan of a mammal. Humans have a head, neck, [[Trunk (anatomy)|trunk]] (which includes the [[thorax]] and [[abdomen]]), two arms and hands, and two legs and feet.

Generally, students of certain [[biological sciences]], [[paramedic]]s, prosthetists and orthotists, [[physiotherapists]], [[occupational therapy|occupational therapists]], [[nurses]], [[podiatry|podiatrists]], and [[medical school|medical students]] learn gross anatomy and microscopic anatomy from anatomical models, skeletons, textbooks, diagrams, photographs, lectures and tutorials and in addition, medical students generally also learn gross anatomy through practical experience of [[dissection]] and inspection of [[cadaver]]s. The study of microscopic anatomy (or [[histology]]) can be aided by practical experience examining histological preparations (or slides) under a [[microscope]].<ref>{{cite web |url=https://www.medschoolsonline.co.uk/index.php?pageid=135 |title=Studying medicine |publisher=Medschools Online |access-date=27 June 2013 |archive-url=https://web.archive.org/web/20130128114829/https://www.medschoolsonline.co.uk/index.php?pageid=135 |archive-date=28 January 2013 |url-status=dead }}</ref>

Human anatomy, physiology and biochemistry are complementary basic medical sciences, which are generally taught to medical students in their first year at medical school. Human anatomy can be taught regionally or systemically; that is, respectively, studying anatomy by bodily regions such as the head and chest, or studying by specific systems, such as the nervous or respiratory systems.<ref name="intro HGray" /> The major anatomy textbook, [[Gray's Anatomy]], has been reorganized from a systems format to a regional format, in line with modern teaching methods.<ref>{{cite book |url=https://archive.org/details/graysanatomyanat0000unse |title=Publisher's page for Gray's Anatomy. 39th edition (UK).|year=2004 |isbn=978-0-443-07168-3|url-access=registration |last1=Drake |first1=Richard Lee |last2=Gray |first2=Henry |last3=Vogl |first3=Wayne |last4=Mitchell |first4=Adam W. M. |publisher=Elsevier Churchill Livingstone }}</ref><ref>{{cite book |url=https://archive.org/details/graysanatomyanat0000unse |title=Publisher's page for Gray's Anatomy. 39th edition (US).|year=2004 |isbn=978-0-443-07168-3|url-access=registration |last1=Drake |first1=Richard Lee |last2=Gray |first2=Henry |last3=Vogl |first3=Wayne |last4=Mitchell |first4=Adam W. M. }}</ref> A thorough working knowledge of anatomy is required by physicians, especially [[surgery|surgeons]] and doctors working in some diagnostic specialties, such as [[histopathology]] and [[radiology]].<ref name=AAA>{{cite web |url=https://www.anatomy.org/ |title=American Association of Anatomists |access-date=27 June 2013 |archive-url=https://web.archive.org/web/20190404042736/https://www.anatomy.org/ |archive-date=4 April 2019 |url-status=dead }}</ref>

Academic anatomists are usually employed by universities, medical schools or teaching hospitals. They are often involved in teaching anatomy, and research into certain systems, organs, tissues or cells.<ref name=AAA/>