One of the large, detailed illustrations in Andreas Vesalius's De humani corporis fabrica, 1543, marking the rebirth of anatomy
The history of anatomy is characterized by a progressive understanding of the functions of the organs and structures of the human body. Methods have also improved dramatically, advancing from the examination of animals by dissection of carcasses and cadavers (corpses) to 20th century medical imaging techniques including X-ray, ultrasound, and magnetic resonance imaging.
First published in 1938, revised editions of Brinton's book were published in 1952, and 1965, and it is still in print.[4]
Brinton summarizes the revolutionary process as moving from "financial breakdown, [to] organization of the discontented to remedy this breakdown ... revolutionary demands on the part of these organized discontented, demands which if granted would mean the virtual abdication of those governing, attempted use of force by the government, its failure, and the attainment of power by the revolutionists. These revolutionists have hitherto been acting as an organized and nearly unanimous group, but with the attainment of power it is clear that they are not united. The group which dominates these first stages we call the moderates .... power passes by violent ... methods from Right to Left." (p. 253)
According to Brinton, while "we must not expect our revolutions to be identical" (p. 226), three of the four (the English, French and Russian) began "in hope and moderation", reached "a crisis in a reign of terror," and ended "in something like dictatorship — Cromwell, Bonaparte, Stalin". The exception is the American Revolution, which "does not quite follow this pattern". (p. 24)
Fall of the old regime[edit]
The revolutions begin with problems in the pre-revolutionary regime. These include problems functioning — "government deficits, more than usual complaints over taxation, conspicuous governmental favoring of one set of economic interests over another, administrative entanglements and confusions". There are also social problems, such as the feeling by some that careers are not "open to talents", and economic power is separated from political power and social distinction. There is a "loss of self-confidence among many members of the ruling class," the "conversion of many members of that class to the belief that their privileges are unjust or harmful to society." (p. 65) "Intellectuals" switch their allegiance away from the government. (p. 251) In short, "the ruling class becomes politically inept." (p. 252)Financial problems play an important role, as "three of our four revolutions started among people who objected to certain taxes, who organized to protest them .... even in Russia in 1917 the financial problems were real and important." (p. 78)
The revolutions' enemies and supporters disagree over whether plots and manipulation by revolutionists, or the corruption and tyranny of the old regime are responsible for the old regime's fall. Brinton argues both are right, as both the right circumstances and active agitation are necessary for the revolution to succeed. (p. 85-6)
At some point in the first stages of the revolutions "there is a point where constituted authority is challenged by illegal acts of revolutionists" and the response of security forces is strikingly unsuccessful. In France in 1789 the "king didn't really try" to subdue riots effectively. In England the king "didn't have enough good soldiers." In Russia "at the critical moment the soldiers refused to march against the people" and instead joined them. (p. 88)
Background of the revolutionaries[edit]
Revolutions "are born of hope" rather than misery. (p. 250) Contrary to the belief that revolutionaries are disproportionately poor or down-and-out, "revolutionists are more or less a cross section of common humanity". While revolutionaries "behave in a way we should not expect such people to behave," this can be explained by the "revolutionary environment" rather than their background. (p. 120) "`Untouchables` very rarely revolt," and successful slave revolutions, like Haiti's, are few in number. (p.250) Revolutionaries are "not unprosperous" but "feel restraint, cramp, ... rather than downright crushing oppression."(p. 250)Revolutionary regimes[edit]
In each revolution a short "honeymoon" period follows the fall of the old regime, lasting until the "contradictory elements" among the victorious revolutionaries assert themselves. (p. 91) Power then has a tendency "to go from Right to Center to Left." (p. 123) In the process, Brinton says, `the revolution, like Saturn, devours its children,` quoting Pierre Victurnien Vergniaud (p. 121)Moderates and dual power[edit]
The revolutions being studied first produce a "legal" moderate government. It vies with a more radical "illegal" government in a process known as "dual power", or as Brinton prefers to call it "dual sovereignty". In England the "Presbyterian moderates in Parliament" were rivals of "the illegal government of the extremist Independents in the New Model Army." (p. 135) In France, the National Assembly was controlled by the "Girondin moderates", while the Montagnard "extremists" controlled "the Jacobin network," "the Paris commune," (p. 136) and the Societies of the Friends of the Constitution. (p. 162) In Russia, the moderate provisional government of the Duma clashed with the radical Bolsheviks whose illegal government was a "network of soviets." (p. 136)The radicals triumph because:
- they are "better organized, better staffed, better obeyed," (p. 134)
- they have "relatively few responsibilities, while the legal government "has to shoulder some of the unpopularity of the government of the old regime" with "the worn-out machinery, the institutions of the old regime." (p. 134)
- the moderates are hindered by their hesitancy to change direction and fight back against the radical revolutionaries, "with whom they recently stood united," in favor of conservatives, "against whom they have so recently risen." (p. 140) They are drawn to the slogan `no enemies to the Left.` (p. 168)
- the moderates are attacked on one side by "disgruntled but not yet silenced conservatives, and the confident, aggressive extremists," on the other. The moderate revolutionary policies can please neither side. An example is the Root and Branch Bill in the English Revolution which abolished the episcopacy, angering conservatives and established institutions without earning the loyalty of radicals. (p. 141-43)
- they are the "poor" leaders of the wars which accompany the revolutions, unable to "provide the discipline, the enthusiasm," needed. (p. 144)
Radicals and "Reigns of Terror and Virtue"[edit]
In contrast to the moderates, the radicals are aided by a fanatical devotion to their cause, discipline and (in recent revolutions) a study of technique of revolutionary action, obedience to their leadership, ability to ignore contradictions between their rhetoric and action, and drive boldly ahead. (p. 155-60) Even their small numbers are an advantage, giving them "the ability to move swiftly, to make clear and final decisions, to push through to a goal without regard for injured human dispositions." (p. 154)The radicals took power in Russia with the October Revolution, in France with the purge of the Girondins, in England "Pride's Purge" (p. 163). The American Revolution never had a radical dictatorship and Reign of Terror, "though in the treatment of Loyalist, in the pressure to support the army, in some of the phases of social life, you can discern .. many of the phenomena of the Terror as it is seen in our three other societies." (p. 254)
The radical reign is one of "Terror and Virtue." Terror steming from the abundance of summary executions, foreign and civil war, struggle for power; virtue in the form of puritanical "organized asceticism" and suppression of vices such as drunkenness, gambling and prostitution. (p. 180) In its ardor, revolutionary "tragicomedy" touches the average citizen, for whom "politics becomes as real, as pressing, as unavoidable ... as food and drink," their "job, and the weather." (p. 177)
On taking power the radicals rule through dictatorship and "rough-and-ready centralization." "The characteristic form of this supreme authority is that of a committee." (p. 171) The Council of State in England, Committee of Public Safety in France.
At some point in these revolutions, the "process of transfer of power from Right to Left ceases," and groups even more radical than those in power are suppressed. (p. 167) (In France, the Hébertists are sent to the guillotine, (p. 168) in Russia the Kronstadt rebellion is crushed.)
At least in France and Russia, the accession of radicals is also accompanied by a decline in political participation measured in votes cast, as "ordinary, peaceful", "humdrum men and women" favoring moderation find no outlet for their political beliefs. (p. 153-4)
Along with centralization, lethal force in suppression of opposition, rule by committee, radical policies include the spreading of "the gospel of their revolution" to other countries. This is found not only in the Russian and French revolutions, but even seventeenth century England, where Edward Sexby "proposed to the French radicals" in Bordeaux "a republican constitution which was to be called `L'Accord du Peuple` — an adaptation of the English Agreement of the People." (p.193) These attempts seldom make a significant impact as the revolutionaries "are usually too poor, and too occupied at home." (p. 213)
"Thermidor"[edit]
The radical reign of terror, or "crisis" period, is fairly soon replaced by Thermidor period, a period of relaxation from revolutionary policies or "convalescence" from the "fever" of radicalism. Thermidor is named for the period following the fall of Maximilien Robespierre in the French Revolution, in Russia the New Economic Policy of 1921 "can be called Russia's Thermidor" (p. 207), and "perhaps the best date" for that period in England is "Cromwell's dissolution of the Rump." (p. 206)The Thermidor is characterized by
- the "establishment of a `tyrant`", i.e. "an unconstitutional ruler brought to power by revolution." (p. 207) The "`silken threads` of habit, tradition, legality" having been broken, "men must be held together in society by the `iron chains` of dictatorship." (p.208)[5]
- restoration of many pre-revolutionary ways. In Russia this meant an abandonment of the Bolshevik's avant-garde stance against the institution of the family — formerly disparaged as "a stuffy little nest breeding selfishness, jealousy, love of property, indifference toward the great needs of society." (p. 224) The Bolshevik regime restored roadblocks to divorce, (p. 225) laws against homosexuality, (p. 226) and moderated its anti-religious, anti-Orthodox Church stance.
- reaction against Puritanism of the revolution. In England, the Restoration comedy that appeared after the revolution is now "a symbol of naughtiness." (p. 220) In France the post-revolutionary Directory era was known as boom time for reopened dance halls and swaggering jeunesse doree. (p. 218) During the New Economic Policy in Soviet Russia advertising began to appear (p. 225), as did a new class of entrepreneurs known as the Nepmen who were reputed to be `exceptionally vulgar, profiteering, crude, and noisy.` (p. 221)
- the replacement of "missionary spirit" to spread revolution by an "aggressive nationalism." (p. 213) In England Cromwell reconquered Ireland and seized Jamaica. In France Napoleon created an empire. (p. 213)
Lasting results[edit]
Brinton finds the lasting results of the revolutions disappointing (his book was written before the fall of communism in the Soviet bloc). In France, the revolution did away with "the old overlapping jurisdictions, the confusions and the compromises inherited from, the thousand-year struggle" between Crown and feudal nobility. Weights and measure "that varied from region to region, indeed from town to town" were replaced with the metric system. Also gone was non-decimal coinage unsuited "for long division."(p. 239) Some antiquated practices were also eliminated in England. (p. 239) In Russia, the Bolsheviks brought industrialization, and eventually the Sputnik space satellite. (p. 240) Confiscated lands stayed in the hands of the new owners for the most part, redistributing land to many "small independent peasants" in France (p. 241-2), and Puritan businessmen and clergymen in England.(p. 242)Remaining essentially "untouched" were day-to-day social relations between husband and wife and children. Attempts at establishing new religions and personal habits come to naught. The revolutions' "results look rather petty as measured by the brotherhood of man and the achievement of justice on this earth. The blood of the martyrs seems hardly necessary to establish decimal coinage." (p. 259)
Comparisons[edit]
Brinton concludes that despite their ambitions, the political revolutions he studied brought much less lasting social changes than the disruptions and changes of "what is loosely called the Industrial Revolution", and the top-down reforms of Mustapha Kemal's reforms in Turkey, and the Meiji Restoration or post-World War II MacArthur era in Japan. (p. 246)Definition[edit]
Derived from the Greek ἀνατέμνω anatemnō "I cut up, cut open" from ἀνά ana "up", and τέμνω temnō "I cut",[5] anatomy is the scientific study of the structure of organisms including their systems, organs and tissues. It includes the appearance and position of the various parts, the materials from which they are composed, their locations and their relationships with other parts. Anatomy is quite distinct from physiology and biochemistry, which deal respectively with the functions of those parts and the chemical processes involved. For example, an anatomist is concerned with the shape, size, position, structure, blood supply and innervation of an organ such as the liver; while a physiologist is interested in the production of bile, the role of the liver in nutrition and the regulation of bodily functions.[6]
The discipline of anatomy can be subdivided into a number of branches including gross or macroscopic anatomy and microscopic anatomy.[7] Gross anatomy is the study of structures large enough to be seen with the naked eye, and also includes superficial anatomy or surface anatomy, the study by sight of the external body features. Microscopic anatomy is the study of structures on a microscopic scale, including histology (the study of tissues), and embryology (the study of an organism in its immature condition).[3]
Anatomy can be studied using both invasive and non-invasive methods with the goal of obtaining information about the structure and organization of organs and systems.[3] Methods used include dissection, in which a body is opened and its organs studied, and endoscopy, in which a video camera-equipped instrument is inserted through a small incision in the body wall and used to explore the internal organs and other structures. Angiography using X-rays or magnetic resonance angiography are methods to visualize blood vessels.[8][9][10][11]
The term "anatomy" is commonly taken to refer to human anatomy. However, substantially the same structures and tissues are found throughout the rest of the animal kingdom and the term also includes the anatomy of other animals. The term zootomy is also sometimes used to specifically refer to animals. The structure and tissues of plants are of a dissimilar nature and they are studied in plant anatomy.[6]
Animal tissues[edit]
The kingdom Animalia, also called Metazoa, contains multicellular organisms that are heterotrophic and motile (although some have secondarily adopted a sessile lifestyle). Most animals have bodies differentiated into separate tissues and these animals are also known as eumetazoans. They have an internal digestive chamber, with one or two openings; the gametes are produced in multicellular sex organs, and the zygotes include a blastula stage in their embryonic development. Metazoans do not include the sponges, which have undifferentiated cells.[12]
Unlike plant cells, animal cells have neither a cell wall nor chloroplasts. Vacuoles, when present, are more in number and much smaller than those in the plant cell. The body tissues are composed of numerous types of cell, including those found in muscles, nerves and skin. Each typically has a cell membrane formed of phospholipids, cytoplasm and a nucleus. All of the different cells of an animal are derived from the embryonic germ layers. Those simpler invertebrates which are formed from two germ layers of ectoderm and endoderm are called diploblastic and the more developed animals whose structures and organs are formed from three germ layers are called triploblastic.[13] All of a triploblastic animal's tissues and organs are derived from the three germ layers of the embryo, the ectoderm, mesoderm and endoderm.
Animal tissues can be grouped into four basic types: connective, epithelial, muscle and nervous tissue.
Connective tissue[edit]
Connective tissues are fibrous and made up of cells scattered among inorganic material called the extracellular matrix. Connective tissue gives shape to organs and holds them in place. The main types are loose connective tissue, adipose tissue, fibrous connective tissue, cartilage and bone. The extracellular matrix contains proteins, the chief and most abundant of which is collagen. Collagen plays a major part in organizing and maintaining tissues. The matrix can be modified to form a skeleton to support or protect the body. An exoskeleton is a thickened, rigid cuticle which is stiffened by mineralisation, as in crustaceans or by the cross-linking of its proteins as in insects. An endoskeleton is internal and present in all developed animals, as well as in many of those less developed.[13]Epithelium[edit]
Muscle tissue[edit]
Nervous tissue[edit]
Nervous tissue is composed of many nerve cells known as neurons which transmit information. In some slow-moving radially symmetrical marine animals such as ctenophores and cnidarians (including sea anemones and jellyfish), the nerves form a nerve net, but in most animals they are organized longitudinally into bundles. In simple animals, receptor neurons in the body wall cause a local reaction to a stimulus. In more complex animals, specialised receptor cells such as chemoreceptors and photoreceptors are found in groups and send messages along neural networks to other parts of the organism. Neurons can be connected together in ganglia.[19] In higher animals, specialized receptors are the basis of sense organs and there is a central nervous system (brain and spinal cord) and a peripheral nervous system. The latter consists of sensory nerves that transmit information from sense organs and motor nerves that influence target organs.[20][21] The peripheral nervous system is divided into the somatic nervous system which conveys sensation and controls voluntary muscle, and the autonomic nervous system which involuntarily controls smooth muscle, certain glands and internal organs, including the stomach.[22]Vertebrate anatomy[edit]
See also: Comparative anatomy
Fish anatomy[edit]
Main article: Fish anatomy
Sharks and rays are basal fish with numerous 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, yolky eggs. Some species are ovoviviparous and the young develop internally but others are oviparous and the larvae develop externally in egg cases.[29]
The bony fish lineage shows more 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, and a mouth at or near the tip of the snout. The dermis is covered with overlapping 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 a large number of small eggs with little yolk which they broadcast into the water column.[29]
Amphibian anatomy[edit]
Main article: Amphibian anatomy
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 earthworms 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.[32]
Reptile anatomy[edit]
Main article: Reptile anatomy
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 is the case in other reptiles and the lungs have a single chamber and lack bronchi. The tuatara has a well-developed parietal eye on its forehead.[34]
Lizards have skulls with only one 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.[34]
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 spurs. 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.[35]
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 keratinised 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.[36]
Bird anatomy[edit]
Main article: Bird anatomy
The feathers are outgrowths of the 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 preens. There are scales on the legs, feet and claws on the tips of the toes.[37]
Mammal anatomy[edit]
Main article: Mammal anatomy
Mammals are amniotes, and most are viviparous, giving birth to live young. The exception to this are the egg-laying monotremes, the platypus and the echidnas of Australia. Most other mammals have a placenta through which the developing foetus obtains nourishment, but in marsupials, the foetal stage is very short and the immature young is born and finds its way to its mother's pouch where it latches on to a nipple and completes its development.[38]
Human anatomy[edit]
Main article: Human anatomy
In the human, the development of skilled hand movements and increased brain size is likely to have evolved simultaneously.[39]
Generally, students of certain biological sciences, paramedics, prosthetists and orthotists, physiotherapists, occupational therapists, nurses, and 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 cadavers. The study of microscopic anatomy (or histology) can be aided by practical experience examining histological preparations (or slides) under a microscope. [40]
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.[3] The major anatomy textbook, Gray's Anatomy, has been reorganized from a systems format to a regional format, in line with modern teaching methods.[41][42] A thorough working knowledge of anatomy is required by physicians, especially surgeons and doctors working in some diagnostic specialties, such as histopathology and radiology. [43]
Academic human 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.[43]
Invertebrate anatomy[edit]
Metazoans are multicellular organism, different groups of cells of which have separate functions. The most basic types of metazoan tissues are epithelium and connective tissue, both of which are present in nearly all invertebrates. The outer surface of the epidermis is normally formed of epithelial cells and secretes an extracellular matrix which provides support to the organism. An endoskeleton derived from the mesoderm is present in echinoderms, sponges and some cephalopods. Exoskeletons are derived from the epidermis and is composed of chitin in arthropods (insects, spiders, ticks, shrimps, crabs, lobsters). Calcium carbonate constitutes the shells of molluscs, brachiopods and some tube-building polychaete worms and silica forms the exoskeleton of the microscopic diatoms and radiolaria.[45] Other invertebrates may have no rigid structures but the epidermis may secrete a variety of surface coatings such as the pinacoderm of sponges, the gelatinous cuticle of cnidarians (polyps, sea anemones, jellyfish) and the collagenous cuticle of annelids. The outer epithelial layer may include cells of several types including sensory cells, gland cells and stinging cells. There may also be protrusions such as microvilli, cilia, bristles, spines and tubercles.[46]
Arthropod anatomy[edit]
Arthropods comprise the largest phylum in the animal kingdom with over a million known invertebrate species.[47]Insects possess segmented bodies supported by a hard-jointed outer covering, the exoskeleton, made mostly of chitin. The segments of the body are organized into three distinct parts, a head, a thorax and an abdomen.[48] The head typically bears a pair of sensory antennae, a pair of compound eyes, one to three simple eyes (ocelli) and three sets of modified appendages that form the mouthparts. The thorax has three pairs of segmented legs, one pair each for the three segments that compose the thorax and one or two pairs of wings. The abdomen is composed of eleven segments, some of which may be fused and houses the digestive, respiratory, excretory and reproductive systems.[49] There is considerable variation between species and many adaptations to the body parts, especially wings, legs, antennae and mouthparts.[50]
Spiders a class of arachnids have four pairs of legs; a body of two segments—a cephalothorax and an abdomen. Spiders have no wings and no antennae. They have mouthparts called chelicerae which are often connected to venom glands as most spiders are venomous. They have a second pair of appendages called pedipalps attached to the cephalothorax. These have the same segmentation as the legs and function as taste and smell organs. At the end of each pedipalp is a spoon-shaped cymbium that acts to support the pedipalp.
Other branches of anatomy[edit]
- Superficial or surface anatomy is important as the study of anatomical landmarks that can be readily seen from the exterior contours of the body.[3] It enables physicians or veterinary surgeons to gauge the position and anatomy of the associated deeper structures. Superficial is a directional term that indicates that structures are located relatively close to the surface of the body.[51]
- Comparative anatomy relates to the comparison of anatomical structures (both gross and microscopic) in different animals.[3]
Artistic anatomy relates to anatomic studies for artistic reasons.
Surface anatomy (also called superficial anatomy and visual anatomy) is the study of the external features of the body.[1] It deals with anatomical features that can be studied by sight, without dissection. As such, it is a branch of gross anatomy, along with endoscopic and radiological anatomy.[2] Surface anatomy is a descriptive science.[citation needed] In particular, in the case of human surface anatomy, these are the form and proportions of the human body and the surface landmarks which correspond to deeper structures hidden from view, both in static pose and in motion.
In addition, the science of surface anatomy includes the theories and systems of body proportions and related artistic canons.[citation needed] The study of surface anatomy is the basis for depicting the human body in classical art.
Some pseudo-sciences such as physiognomy, phrenology and palmistry rely on surface anatomy.
-
Comparative anatomy is the study of similarities and differences in the anatomy of different species. It is closely related to evolutionary biology and phylogeny (the evolution of species).
- Homologous structures - structures (body parts/anatomy) which are similar in different species because the species have common descent. They may or may not perform the same function. An example is the forelimb structure shared by cats and whales.
- Analogous structures - structures similar in different organisms because they evolved in a similar environment, rather than were inherited from a recent common ancestor. They usually serve the same or similar purposes. An example is the streamlined torpedo body shape of porpoises and sharks. So even though they evolved from different ancestors, porpoises and sharks developed analogous structures as a result of their evolution in the same aquatic environment.
Comparative anatomy has long served as evidence for evolution; it indicates that various organisms share a common ancestor. Also, it assists scientists in classifying organisms based on similar characteristics of their anatomical structures. Comparative anatomy supports Darwin's theory of descent with modification, also known as evolution. A common example of comparative anatomy is the similar bone structures in forelimbs of cats, whales, bats, and humans. All of these appendages consist of the same basic parts; yet, they serve completely different functions. The skeletal parts which form a structure used for swimming, such as a fin, would not be ideal to form a wing, which is better-suited for flight. One explanation for the forelimbs' similar composition is descent with modification. Through random mutations and natural selection, each organism's anatomical structures gradually adapted to suit their respective habitats.[1] Two major concepts of comparative anatomy are:
History[edit]
Main article: History of anatomy
Ancient[edit]
In 1600 BCE, the Edwin Smith Papyrus, an Ancient Egyptian medical text, described the heart, its vessels, liver, spleen, kidneys, hypothalamus, uterus and bladder, and showed the blood vessels diverging from the heart. The Ebers Papyrus (c. 1550 BCE) features a "treatise on the heart", with vessels carrying all the body's fluids to or from every member of the body.[52]The anatomy of the muscles and skeleton is described in the Hippocratic Corpus, an Ancient Greek medical work written by unknown authors.[53] Aristotle described vertebrate anatomy based on animal dissection. Praxagoras identified the difference between arteries and veins. Also in the 4th century BCE, Herophilos and Erasistratus produced more accurate anatomical descriptions based on vivisection of criminals in Alexandria during the Ptolemaic dynasty.[54][55]
In the 2nd century, Galen of Pergamum, an anatomist, clinician, writer and philosopher,[56] wrote the final and highly influential anatomy treatise of ancient times.[57] He compiled existing knowledge and studied anatomy through dissection of animals.[56] He was one of the first experimental physiologists through his vivisection experiments on animals.[58] Galen's drawings, based mostly on dog anatomy, became effectively the only anatomical textbook for the next thousand years.[59] His work was known to Renaissance doctors only through Islamic Golden Age medicine until it was translated from the Greek some time in the 15th century.[59]
Medieval to early modern[edit]
Leonardo da Vinci (1452–1519) was trained in anatomy by Andrea del Verrocchio.[59] He made use of his anatomical knowledge in his artwork, making many sketches of skeletal structures, muscles and organs of humans and other vertebrates that he dissected.[59][63]
Andreas Vesalius (1514–1564) (Latinized from Andries van Wezel), professor of anatomy at the University of Padua, is considered the founder of modern human anatomy.[64] Originally from Brabant, Vesalius published the influential book De humani corporis fabrica ("the structure of the human body"), a large format book in seven volumes, in 1543.[65] The accurate and intricately detailed illustrations, often in allegorical poses against Italianate landscapes, are thought to have been made by the artist Jan van Calcar, a pupil of Titian.[66]
In England, anatomy was the subject of the first public lectures given in any science; these were given by the Company of Barbers and Surgeons in the 16th century, joined in 1583 by the Lumleian lectures in surgery at the Royal College of Physicians.[67]
Late modern[edit]
Further information: History of anatomy in the 19th century
In the United States, medical schools began to be set up towards the end of the 18th century. Classes in anatomy needed a continual stream of cadavers for dissection and these were difficult to obtain. Philadelphia, Baltimore and New York were all renowned for body snatching activity as criminals raided graveyards at night, removing newly buried corpses from their coffins.[68] A similar problem existed in Britain where demand for bodies became so great that grave-raiding and even anatomy murder were practised to obtain cadavers.[69] Some graveyards were in consequence protected with watchtowers. The practice was halted in Britain by the Anatomy Act of 1832,[70][71] while in the United States, similar legislation was enacted after the physician William S. Forbes of Jefferson Medical College was found guilty in 1882 of "complicity with resurrectionists in the despoliation of graves in Lebanon Cemetery".[72]The teaching of anatomy in Britain was transformed by Sir John Struthers, Regius Professor of Anatomy at the University of Aberdeen from 1863 to 1889. He was responsible for setting up the system of three years of "pre-clinical" academic teaching in the sciences underlying medicine, including especially anatomy. This system lasted until the reform of medical training in 1993 and 2003. As well as teaching, he collected many vertebrate skeletons for his museum of comparative anatomy, published over 70 research papers, and became famous for his public dissection of the Tay Whale.[73][74] From 1822 the Royal College of Surgeons regulated the teaching of anatomy in medical schools.[75] Medical museums provided examples in comparative anatomy, and were often used in teaching.[76] Ignaz Semmelweis investigated puerperal fever and he discovered how it was caused. He noticed that the frequently fatal fever occurred more often in mothers examined by medical students than by midwives. The students went from the dissecting room to the hospital ward and examined women in childbirth. Semmelweis showed that when the trainees washed their hands in chlorinated lime before each clinical examination, the incidence of puerperal fever among the mothers could be reduced dramatically.[77]
Before the era of modern medical procedures, the main means for studying the internal structure of the body were palpation and dissection. It was the advent of microscopy that opened up an understanding of the building blocks that constituted living tissues. Technical advances in the development of achromatic lenses increased the resolving power of the microscope and around 1839, Matthias Jakob Schleiden and Theodor Schwann identified that cells were the fundamental unit of organization of all living things. Study of small structures involved passing light through them and the microtome was invented to provide sufficiently thin slices of tissue to examine. Staining techniques using artificial dyes were established to help distinguish between different types of tissue. The fields of cytology and histology developed from here in the late 19th century.[78] The invention of the electron microscope brought a great advance in resolution power and allowed research into the ultrastructure of cells and the organelles and other structures within them. About the same time, in the 1950s, the use of X-ray diffraction for studying the crystal structures of proteins, nucleic acids and other biological molecules gave rise to a new field of molecular anatomy.[78]
Short wavelength electromagnetic radiation such as X-rays can be passed through the body and used in medical radiography to view interior structures that have different degrees of opaqueness. Nowadays, modern techniques such as magnetic resonance imaging, computed tomography, fluoroscopy and ultrasound imaging have enabled researchers and practitioners to examine organs, living or dead, in unprecedented detail. They are used for diagnostic and therapeutic purposes and provide information on the internal structures and organs of the body to a degree far beyond the imagination of earlier generations.[79]
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