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Biochemistry

Department of Biochemistry and Biophysics

Hou, TY, Barhoumi, R, Fan, YY, Rivera, GM, Hannoush, RN, McMurray, DN et al.. n-3 polyunsaturated fatty acids suppress CD4(+) T cell proliferation by altering phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2] organization. Biochim. Biophys. Acta. 2015; :. doi: 10.1016/j.bbamem.2015.10.009. PubMed PMID:26476105. .

Hong, W, Wang, Y, Chang, Z, Yang, Y, Pu, J, Sun, T et al.. The identification of novel Mycobacterium tuberculosis DHFR inhibitors and the investigation of their binding preferences by using molecular modelling. Sci Rep. 2015;5 :15328. doi: 10.1038/srep15328. PubMed PMID:26471125. .

Yi, G, Wen, Y, Shu, C, Han, Q, Konan, KV, Li, P et al.. The Hepatitis C Virus NS4B Can Suppress STING Accumulation to Evade Innate Immune Responses. J. Virol. 2015; :. doi: 10.1128/JVI.01720-15. PubMed PMID:26468527. .

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Department of Biochemistry and Biophysics

Biochemistry

Hypothetical types of biochemistry – Wikipedia, the free …

Hypothetical types of biochemistry are forms of biochemistry speculated to be scientifically viable but not proven to exist at this time.[2] The kinds of living beings currently known on Earth all use carbon compounds for basic structural and metabolic functions, water as a solvent and DNA or RNA to define and control their form. If life exists on other planets or moons, it may be chemically similar; it is also possible that there are organisms with quite different chemistries[3]for instance involving other classes of carbon compounds, compounds of another element, or another solvent in place of water.

The possibility of life-forms being based on "alternative" biochemistries is the topic of an ongoing scientific discussion, informed by what is known about extraterrestrial environments and about the chemical behaviour of various elements and compounds. It is also a common subject in science fiction.

The element silicon has been much discussed as a hypothetical alternative to carbon. Silicon is in the same group as carbon in the periodic table, and like carbon is tetravalent, although the silicon analogs of organic compounds are generally less stable. Hypothetical alternatives to water include ammonia, which, like water, is a polar molecule, and cosmically abundant; and non-polar hydrocarbon solvents such as methane and ethane, which are known to exist in liquid form on the surface of Titan.

Apart from the prospect of finding different forms of life on other planets or moons, Earth itself has been suggested as a place where a shadow biosphere of biochemically unfamiliar micro-organisms might have lived in the past, or may still exist today.[4][5]

Perhaps the least unusual alternative biochemistry would be one with differing chirality of its biomolecules. In known Earth-based life, amino acids are almost universally of the L form and sugars are of the D form. Molecules of opposite chirality have identical chemical properties to their mirrored forms, so life that used D amino acids or L sugars may be possible; molecules of such a chirality, however, would be incompatible with organisms using the opposing chirality molecules. Amino acids whose chirality is opposite to the norm are found on Earth, and these substances are generally thought to result from decay of organisms of normal chirality. However, physicist Paul Davies speculates that some of them might be products of "anti-chiral" life.[6]

It is questionable, however, whether such a biochemistry would be truly alien. Although it would certainly be an alternative stereochemistry, molecules that are overwhelmingly found in one enantiomer throughout the vast majority of organisms can nonetheless often be found in another enantiomer in different (often basal) organisms such as in comparisons between members of Archea and other domains,[citation needed] making it an open topic whether an alternative stereochemistry is truly novel.

On Earth, all known living things have a carbon-based structure and system. Scientists have speculated about the pros and cons of using atoms other than carbon to form the molecular structures necessary for life, but no one has proposed a theory employing such atoms to form all the necessary structures. However, as Carl Sagan argued, it is very difficult to be certain whether a statement that applies to all life on Earth will turn out to apply to all life throughout the universe.[7] Sagan used the term "carbon chauvinism" for such an assumption.[8] Carl Sagan regarded silicon and germanium as conceivable alternatives to carbon;[8] but, on the other hand, he noted that carbon does seem more chemically versatile and is more abundant in the cosmos.[9]

The silicon atom has been much discussed as the basis for an alternative biochemical system, because silicon has many chemical properties similar to those of carbon and is in the same group of the periodic table, the carbon group. Like carbon, silicon can create molecules that are sufficiently large to carry biological information.[10]

However, silicon has several drawbacks as an alternative to carbon. Silicon, unlike carbon, lacks the ability to form chemical bonds with diverse types of atoms as is necessary for the chemical versatility required for metabolism. Elements creating organic functional groups with carbon include hydrogen, oxygen, nitrogen, phosphorus, sulfur, and metals such as iron, magnesium, and zinc. Silicon, on the other hand, interacts with very few other types of atoms.[10] Moreover, where it does interact with other atoms, silicon creates molecules that have been described as "monotonous compared with the combinatorial universe of organic macromolecules".[10] This is because silicon atoms are much bigger, having a larger mass and atomic radius, and so have difficulty forming double bonds (the double bonded carbon is part of the carbonyl group, a fundamental motif of bio-organic chemistry).

Silanes, which are chemical compounds of hydrogen and silicon that are analogous to the alkane hydrocarbons, are highly reactive with water, and long-chain silanes spontaneously decompose. Molecules incorporating polymers of alternating silicon and oxygen atoms instead of direct bonds between silicon, known collectively as silicones, are much more stable. It has been suggested that silicone-based chemicals would be more stable than equivalent hydrocarbons in a sulfuric-acid-rich environment, as is found in some extraterrestrial locations.[11]

Of the varieties of molecules identified in the interstellar medium as of 1998[update], 84 are based on carbon while only 8 are based on silicon.[12] Moreover, of those 8 compounds, four also include carbon within them. The cosmic abundance of carbon to silicon is roughly 10 to 1. This may suggest a greater variety of complex carbon compounds throughout the cosmos, providing less of a foundation upon which to build silicon-based biologies, at least under the conditions prevalent on the surface of planets. Also, even though Earth and other terrestrial planets are exceptionally silicon-rich and carbon-poor (the relative abundance of silicon to carbon in the Earth's crust is roughly 925:1), terrestrial life is carbon-based. The fact that carbon is used instead of silicon, may be evidence that silicon is poorly suited for biochemistry on Earth-like planets. For example: silicon is less versatile than carbon in forming compounds; the compounds formed by silicon are unstable and it blocks the flow of heat.[13]

Even so, biogenic silica is used by some Earth life, such as the silicate skeletal structure of diatoms. According to the clay hypothesis of A. G. Cairns-Smith, silicate minerals in water played a crucial role in abiogenesis: they replicated their crystal structures, interacted with carbon compounds, and were the precursors of carbon-based life.[14][15]

Silicon compounds may possibly be biologically useful under temperatures or pressures different from the surface of a terrestrial planet, either in conjunction with or in a role less directly analogous to carbon. Polysilanols, the silicon compounds corresponding to sugars, are soluble in liquid nitrogen, suggesting that they could play in role in very low temperature biochemistry.[16][17]

In cinematic and literary science fiction, at a moment when man-made machines cross from nonliving to living, it is often posited, this new form would be the first example of non-carbon-based life. Since the advent of the microprocessor in the late 1960s, these machines are often classed as computers (or computer-guided robots) and filed under "silicon-based life", even though the silicon backing matrix of these processors is not nearly as fundamental to their operation as carbon is for "wet life".

Arsenic, which is chemically similar to phosphorus, while poisonous for most life forms on Earth, is incorporated into the biochemistry of some organisms.[20] Some marine algae incorporate arsenic into complex organic molecules such as arsenosugars and arsenobetaines. Fungi and bacteria can produce volatile methylated arsenic compounds. Arsenate reduction and arsenite oxidation have been observed in microbes (Chrysiogenes arsenatis).[21] Additionally, some prokaryotes can use arsenate as a terminal electron acceptor during anaerobic growth and some can utilize arsenite as an electron donor to generate energy.

It has been speculated that the earliest life forms on Earth may have used arsenic in place of phosphorus in the structure of their DNA.[22] A common objection to this scenario is that arsenate esters are so much less stable to hydrolysis than corresponding phosphate esters that arsenic would not be suitable for this function.[23]

The authors of a 2010 geomicrobiology study, supported in part by NASA, have postulated that a bacterium, named GFAJ-1, collected in the sediments of Mono Lake in eastern California, can employ such 'arsenic DNA' when cultured without phosphorus.[24][25] They proposed that the bacterium may employ high levels of poly--hydroxybutyrate or other means to reduce the effective concentration of water and stabilize its arsenate esters.[25] This claim was heavily criticized almost immediately after publication for the perceived lack of appropriate controls.[26][27] Science writer Carl Zimmer contacted several scientists for an assessment: "I reached out to a dozen experts ... Almost unanimously, they think the NASA scientists have failed to make their case".[28] Other authors were unable to reproduce their results and showed that the NASA scientists had issues with phosphate contamination (3 M), which could sustain extremophile lifeforms.[29]

In addition to carbon compounds, all currently known terrestrial life also requires water as a solvent. This has led to discussions about whether water is the only liquid capable of filling that role. The idea that an extraterrestrial life-form might be based on a solvent other than water has been taken seriously in recent scientific literature by the biochemist Steven Benner,[30] and by the astrobiological committee chaired by John A. Baross.[31] Solvents discussed by the Baross committee include ammonia,[32]sulfuric acid,[33]formamide,[34] hydrocarbons,[34] and (at temperatures much lower than Earth's) liquid nitrogen, or hydrogen in the form of a supercritical fluid.[35]

Carl Sagan once described himself as both a carbon chauvinist and a water chauvinist;[36] however on another occasion he said he was a carbon chauvinist but "not that much of a water chauvinist".[37] He speculated on hydrocarbons,[37]hydrofluoric acid,[38] and ammonia[37][38] as possible alternatives to water.

Some of the properties of water that are important for life processes include a large temperature range over which it is liquid, a high heat capacity (useful for temperature regulation), a large heat of vaporization, and the ability to dissolve a wide variety of compounds. Water is also amphoteric, meaning it can donate and accept an H+ ion, allowing it to act as an acid or a base. This property is crucial in many organic and biochemical reactions, where water serves as a solvent, a reactant, or a product. There are other chemicals with similar properties that have sometimes been proposed as alternatives. Additionally, water has the unusual property of being less dense as a solid (ice) than as a liquid. This is why bodies of water freeze over but do not freeze solid (from the bottom up). If ice were denser than liquid water (as is true for nearly all other compounds), then large bodies of liquid would slowly freeze solid, which would not be conducive to the formation of life. Water as a compound is cosmically abundant, although much of it is in the form of vapour or ice. Subsurface liquid water is considered likely or possible on several of the outer moons: Enceladus (where geysers have been observed), Europa, Titan and Ganymede. Earth is the only world currently known to have stable bodies of liquid water on its surface.

Not all properties of water are necessarily advantageous for life, however.[39] For instance, water ice has a high albedo,[39] meaning that it reflects a significant quantity of light and heat from the Sun. During ice ages, as reflective ice builds up over the surface of the water, the effects of global cooling are increased.[39]

There are some properties that make certain compounds and elements much more favorable than others as solvents in a successful biosphere. The solvent must be able to exist in liquid equilibrium over a range of temperatures the planetary object would normally encounter. Because boiling points vary with the pressure, the question tends not to be does the prospective solvent remain liquid, but at what pressure. For example, hydrogen cyanide has a narrow liquid phase temperature range at 1 atmosphere, but in an atmosphere with the pressure of Venus, with 92 bars (9.2MPa) of pressure, it can indeed exist in liquid form over a wide temperature range.

The ammonia molecule (NH3), like the water molecule, is abundant in the universe, being a compound of hydrogen (the simplest and most common element) with another very common element, nitrogen.[40] The possible role of liquid ammonia as an alternative solvent for life is an idea that goes back at least to 1954, when J.B.S. Haldane raised the topic at a symposium about life's origin.[41]

Numerous chemical reactions are possible in an ammonia solution, and liquid ammonia has chemical similarities with water.[40][42] Ammonia can dissolve most organic molecules at least as well as water does and, in addition, it is capable of dissolving many elemental metals. Haldane made the point that various common water-related organic compounds have ammonia-related analogs; for instance the ammonia-related amine group (-NH2) is analogous to the water-related alcohol group (-OH).[42]

Ammonia, like water, can either accept or donate an H+ ion. When ammonia accepts an H+, it forms the ammonium cation (NH4+), analogous to hydronium (H3O+). When it donates an H+ ion, it forms the amide anion (NH2), analogous to the hydroxide anion (OH).[32] Compared to water, however, ammonia is more inclined to accept an H+ ion, and less inclined to donate one; it is a stronger nucleophile.[32] Ammonia added to water functions as Arrhenius base: it increases the concentration of the anion hydroxide. Conversely, using a solvent system definition of acidity and basicity, water added to liquid ammonia functions as an acid, because it increases the concentration of the cation ammonium.[42] The carbonyl group (C=O), which is much used in terrestrial biochemistry, would not be stable in ammonia solution, but the analogous imine group (C=NH) could be used instead.[32]

However, ammonia has some problems as a basis for life. The hydrogen bonds between ammonia molecules are weaker than those in water, causing ammonia's heat of vaporization to be half that of water, its surface tension to be a third, and reducing its ability to concentrate non-polar molecules through a hydrophobic effect. Gerald Feinberg and Robert Shapiro have questioned whether ammonia could hold prebiotic molecules together well enough to allow the emergence of a self-reproducing system.[43] Ammonia is also flammable in oxygen, and could not exist sustainably in an environment suitable for aerobic metabolism.[44]

A biosphere based on ammonia would likely exist at temperatures or air pressures that are extremely unusual in relation to life on Earth. Life on Earth usually exists within the melting point and boiling point of water at normal pressure, between 0C (273K) and 100C (373K); at normal pressure ammonia's melting and boiling points are between 78C (195K) and 33C (240K). Chemical reactions generally proceed more slowly at a lower temperature. Therefore, ammonia-based life, if it exists, might metabolize more slowly and evolve more slowly than life on Earth.[44] On the other hand, lower temperatures could also enable living systems to use chemical species which at Earth temperatures would be too unstable to be useful.[40]

Ammonia could be a liquid at Earth-like temperatures, but at much higher pressures; for example, at 60 atm, ammonia melts at 77C (196K) and boils at 98C (371K).[32]

Ammonia and ammoniawater mixtures remain liquid at temperatures far below the freezing point of pure water, so such biochemistries might be well suited to planets and moons orbiting outside the water-based habitability zone. Such conditions could exist, for example, under the surface of Saturn's largest moon Titan.[45]

Methane (CH4) is a simple hydrocarbon: that is, a compound of two of the most common elements in the cosmos, hydrogen and carbon. It has a cosmic abundance comparable with ammonia.[40] Hydrocarbons could act as a solvent over a wide range of temperatures, but would lack polarity. Isaac Asimov, the biochemist and science fiction writer, suggested in 1981 that poly-lipids could form a substitute for proteins in a non-polar solvent such as methane.[40] Lakes composed of a mixture of hydrocarbons, including methane and ethane, have been detected on the surface of Titan by the Cassini spacecraft.

There is debate about the effectiveness of methane and other hydrocarbons as a solvent for life compared to water or ammonia.[46][47][48] Water is a stronger solvent than the hydrocarbons, enabling easier transport of substances in a cell.[49] However, water is also more chemically reactive, and can break down large organic molecules through hydrolysis.[46] A life-form whose solvent was a hydrocarbon would not face the threat of its biomolecules being destroyed in this way.[46] Also, the water molecule's tendency to form strong hydrogen bonds can interfere with internal hydrogen bonding in complex organic molecules.[39] Life with a hydrocarbon solvent could make more use of hydrogen bonds within its biomolecules.[46] Moreover, the strength of hydrogen bonds within biomolecules would be appropriate to a low-temperature biochemistry.[46]

Astrobiologist Chris McKay has argued, on thermodynamic grounds, that if life does exist on Titan's surface, using hydrocarbons as a solvent, it is likely also to use the more complex hydrocarbons as an energy source by reacting them with hydrogen, reducing ethane and acetylene to methane.[50] Possible evidence for this form of life on Titan was identified in 2010 by Darrell Strobel of Johns Hopkins University; a greater abundance of molecular hydrogen in the upper atmospheric layers of Titan compared to the lower layers, arguing for a downward diffusion at a rate of roughly 1025 molecules per second and disappearance of hydrogen near Titan's surface. As Strobel noted, his findings were in line with the effects Chris McKay had predicted if methanogenic life-forms were present.[49][50][51] The same year, another study showed low levels of acetylene on Titan's surface, which were interpreted by Chris McKay as consistent with the hypothesis of organisms reducing acetylene to methane.[49] While restating the biological hypothesis, McKay cautioned that other explanations for the hydrogen and acetylene findings are to be considered more likely: the possibilities of yet unidentified physical or chemical processes (e.g. a non-living surface catalyst enabling acetylene to react with hydrogen), or flaws in the current models of material flow.[52] He noted that even a non-biological catalyst effective at 95 K would in itself be a startling discovery.[52]

A hypothetical cell membrane capable of functioning in liquid methane in Titan conditions was computer-modeled in February 2015. Composed of small molecules that contain carbon, hydrogen, and nitrogen, it would have the same stability and flexibility as cell membranes on Earth, which are composed of phospholipids, compounds of carbon, hydrogen, oxygen, and phosphorus. This hypothetical cell membrane was termed an "azotosome", a classical compound made of "azote", French for nitrogen, and "soma", Greek for body, by analogy with "liposome".[53]

Hydrogen fluoride (HF), like water, is a polar molecule, and due to its polarity it can dissolve many ionic compounds. Its melting point is 84C and its boiling point is 19.54C (at atmospheric pressure); the difference between the two is a little more than 100 K. HF also makes hydrogen bonds with its neighbor molecules, as do water and ammonia. It has been considered as a possible solvent for life by scientists such as Peter Sneath[54] and Carl Sagan.[38]

HF is dangerous to the systems of molecules that Earth-life is made of, but certain other organic compounds, such as paraffin waxes, are stable with it.[38] Like water and ammonia, liquid hydrogen fluoride supports an acid-base chemistry. Using a solvent system definition of acidity and basicity, nitric acid functions as a base when it is added to liquid HF.[55]

However, hydrogen fluoride, unlike water, ammonia and methane, is cosmically rare.[56]

Hydrogen sulfide is the closest chemical analog to water,[57] but is less polar and a weaker inorganic solvent.[58] Hydrogen sulfide is quite plentiful on Jupiter's moon Io, and may be in liquid form a short distance below the surface; and astrobiologist Dirk Schulze-Makuch has suggested it as a possible solvent for life there.[59] On a planet with hydrogen-sulfide oceans the source of the hydrogen sulfide could come from volcanos, in which case it could be mixed in with a bit of hydrogen fluoride, which could help dissolve minerals. Hydrogen sulfide life might use a mixture of carbon monoxide and carbon dioxide as their carbon source. They might produce and live off of sulfur monoxide, which is analogous to oxygen (O2). Hydrogen sulfide, like hydrogen cyanide and ammonia, suffers from the small temperature range where it is liquid, though that, like that of hydrogen cyanide and ammonia, increases with increasing pressure.

Silicon dioxide, also known as glass, silica, or quartz, is very abundant in the universe and has a large temperature range where it is liquid. However, its melting point is 1,600 to 1,725C (2,912 to 3,137F), so it would be impossible to make organic compounds in that temperature, because all of them would decompose. Moreover, if the pressure increases, the melting point goes down.[citation needed] Silicates are similar to silicon dioxide and some could have lower boiling points than silica. Gerald Feinberg and Robert Shapiro have suggested that molten silicate rock could serve as a liquid medium for organisms with a chemistry based on silicon, oxygen, and other elements such as aluminum.[60]

Other solvents sometimes proposed:

Sulfuric acid in liquid form is strongly polar. It remains liquid at higher temperatures than water, its liquid range being 10C to 337C at a pressure of 1 atm, although above 300C it will slowly decompose. Sulfuric acid is known to be abundant in the clouds of Venus, in the form of aerosol droplets. In a biochemistry that used sulfuric acid as a solvent, the alkene group (C=C), with two carbon atoms joined by a double bond, could function analogously to the carbonyl group (C=O) in water-based biochemistry.[33]

A proposal has been made that life on Mars may exist and be using a mixture of water and hydrogen peroxide as its solvent.[64] A 61.2% (by weight) mix of water and hydrogen peroxide has a freezing point of 56.5C, and also tends to super-cool rather than crystallize. It is also hygroscopic, an advantage in a water-scarce environment.[65][66]

Supercritical carbon dioxide has been proposed as a candidate for alternative biochemistry due to its ability to selectively dissolve organic compounds and assist the functioning of enzymes and because "super-Earth"- or "super-Venus"-type planets with dense high-pressure atmospheres may be common.[61]

Physicists have noted that, although photosynthesis on Earth generally involves green plants, a variety of other-colored plants could also support photosynthesis, essential for most life on Earth, and that other colors might be preferred in places that receive a different mix of stellar radiation than Earth.[67][68] These studies indicate that, although blue photosynthetic plants would be less likely, yellow or red plants are plausible.[68]

Many Earth plants and animals undergo major biochemical changes during their life cycles as a response to changing environmental conditions, for example, by having a spore or hibernation state that can be sustained for years or even millennia between more active life stages.[69] Thus, it would be biochemically possible to sustain life in environments that are only periodically consistent with life as we know it.

For example, frogs in cold climates can survive for extended periods of time with most of their body water in a frozen state,[69] whereas desert frogs in Australia can become inactive and dehydrate in dry periods, losing up to 75% of their fluids, yet return to life by rapidly rehydrating in wet periods.[70] Either type of frog would appear biochemically inactive (i.e. not living) during dormant periods to anyone lacking a sensitive means of detecting low levels of metabolism.

In 2007, Vadim N. Tsytovich and colleagues proposed that lifelike behaviors could be exhibited by dust particles suspended in a plasma, under conditions that might exist in space.[71][72] Computer models showed that, when the dust became charged, the particles could self-organize into microscopic helical structures capable of replicating themselves, interacting with other neighboring structures, and evolving into more stable forms. Similar forms of life were described in Fred Hoyle's classic novel The Black Cloud.

Scientists who have considered possible alternatives to carbon-water biochemistry include:

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Hypothetical types of biochemistry - Wikipedia, the free ...

Anatomy

Human Anatomy

What is Human Anatomy?

Human anatomy can be precisely defined as a complementary basic medical science, which deals with the scientific study of morphology of human body. In simpler words, human anatomy is the study of structure of human body.

There are two main levels of structure of human body (as well as every other thing): macroscopic level and microscopic level. For each of the two levels. there is a separate subdivision of anatomy. The one dealing with macroscopic level is known as gross anatomy and the other which deals with microscopic level is called microscopic anatomy or histology.

In gross anatomy, structure of human body is studied as seen by naked eye. There are two approaches for gross anatomy: Regional approach and Systemic approach.

Histology or microscopic anatomy is the study of the structure of various organs and tissues of human body under a microscope. The understanding of the ultra-structure helps understand the tissues and organs in a better way.

In addition to the main subdivisions of human anatomy described above, a third branch, called basic anatomy, is considered of significant importance. It explains the basic terms and definitions used in the study of gross as well as microscopic anatomy. Thus it provides an introduction to anatomy and tells how to study it.

MANanatomy.com provides a brief but effective explanation of all concepts of human anatomy. All the topics are explained in such a way that they are quick to learn and easy to remember. You will quickly find that MANanatomy.com is the best place to learn human anatomy online. Have a look at the quick navigation below:

Human Body Systems:

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Human Anatomy

Anatomy

Human Anatomy: Learn All About the Human Body at InnerBody.com

Explore the human body like never before! With hundreds of interactive anatomy pictures and descriptions of thousands of objects in the body, InnerBody.com will help you discover what you want to know about human anatomy, right here at your fingertips.

Join the millions of students, patients and inquisitive visitors start your anatomy exploration by clicking on any of the systems above.

Find out how to get the most out of InnerBody by watching this quick 2 minute intro video!

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Human Anatomy: Learn All About the Human Body at InnerBody.com

Anatomy

Anatomy – definition of anatomy by The Free Dictionary

anatomy (-nt-m) n. pl. anatomies

1. The bodily structure of a plant or an animal or of any of its parts.

2. The science of the shape and structure of organisms and their parts.

3. A treatise on anatomic science.

4. Dissection of a plant or animal to study the structure, position, and interrelation of its various parts.

5. A skeleton.

6. The human body.

7. A detailed examination or analysis: the anatomy of a crime.

1. (Anatomy) the science concerned with the physical structure of animals and plants

2. (Anatomy) the physical structure of an animal or plant or any of its parts

3. (Anatomy) a book or treatise on this subject

4. (Anatomy) dissection of an animal or plant

5. any detailed analysis: the anatomy of a crime.

6. the human body

[C14: from Latin anatomia, from Greek anatom, from anatemnein to cut up, from ana- + temnein to cut]

n., pl. -mies.

1. the science dealing with the structure of animals and plants.

2. the structure of an animal or plant, or of any of its parts.

3. dissection of all or part of an animal or plant in order to study its structure.

4. Informal. the human body.

5. an analysis or minute examination.

1. The structure of an animal or a plant or any of its parts.

2. The scientific study of the shape and structure of living things.

anatomical (n-tm-kl) adjective

the study of the body and its parts. anatomist, n. anatomical, adj.

Obsolete, human anatomy.

the study concerned with the measurements of the proportions, size, and weight of the human body. anthropometrist, n. anthropometric, anthropometrical, adj.

Physiology, Rare. the labeling of the type of body structure by nonanthropometric means.

the anatomy of the human body. anthropotomist, n. anthropotomical, adj.

Physiology. the study of aponeuroses, membranes that can serve as muscle sheaths or as connectors between muscles and tendons.

the scientific description of the arterial system. arteriographic, arteriographical, adj.

a written work on the ligaments of the human body. desmographic, desmographical, adj.

the branch of anatomy and physiology that studies secretions and the secretory glands.

an abnormal physical condition characterized by extensive structural defects of the skeleton and by gross mental deficiency.

the description of the structure and function of the liver. hepatographic, hepatographical, adj.

the description of the structure and function of kidneys. heprographic, heprographical, adj.

a branch of anatomy that deals with the microscopic features of animal and plant tissues. Also called microscopical anatomy. histologist, n. histological, adj.

the scientific description of the larynx. laryngographic, laryngographical, adj.

histology.

the measurement of muscular phenomena, such as the velocity and intensity of muscular contractions. myographic, adj.

1. the branch of anatomy that studies muscles and musculature. 2. the muscular makeup of an animal or anatomical unit. myologic, adj.

the scientific description of the organs of plants and animals. organographist, n. organographic, organographical, adj.

the branch of anatomy that studies the skeleton and bones. osteologist, n. osteologie, osteological, adj.

the study of pelvic structure. pelycologic, pelycological, adj.

the scientific description of the pharynx. pharyngographic, pharyngographical, adj.

1. an account of the structure and function of the lungs. 2. the recording of the activity of the lungs during respiration. pneumograph, n. pneumographic, pneumographical, adj.

1. a person who dissects cadavers for the purpose of anatomical demonstration. 2. a person who performs autopsies. prosectorial, adj.

the branch of anatomy that studies the viscera.

an anatomical treatise on or description of the joints and ligaments of the body.

1. the anatomy of the ligaments of the body. 2. the science or study of ligaments.

the condition of having a series of similar parts with the same spatial orientation, e.g. the ribs. syntropic, adj.

the joining of two or more bones by muscle.

1. the dissection of animals other than man. 2. the anatomy of animals. zootomist, n. zootomic, zootomical, adj.

Study of the structure of organisms.

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Anatomy - definition of anatomy by The Free Dictionary

Anatomy

Anatomy – Wikipedia, the free encyclopedia

Anatomy is the branch of biology concerned with the study of the structure of organisms and their parts.[1] In some of its facets, anatomy is related to embryology and comparative anatomy, which itself is closely related to evolutionary biology and phylogeny.[2]Human anatomy is one of the basic essential sciences of medicine.[3]

The discipline of anatomy is divided into macroscopic and microscopic anatomy. Macroscopic anatomy, or gross anatomy, is the examination of an animals body parts using unaided eyesight. Gross anatomy also includes the branch of superficial anatomy. Microscopic anatomy involves the use of optical instruments in the study of the tissues of various structures, known as histology and also in the study of cells.

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.

Derived from the Greek anatemn "I cut up, cut open" from ana "up", and temn "I cut",[4] 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.[5]

The discipline of anatomy can be subdivided into a number of branches including gross or macroscopic anatomy and microscopic anatomy.[6]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).[2]

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.[2] 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.[7][8][9][10]

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.[5]

The kingdom Animalia or 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.[11]

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.[12] 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 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.[12]

Epithelial tissue is composed of closely packed cells, bound to each other by cell adhesion molecules, with little intercellular space. Epithelial cells can be squamous (flat), cuboidal or columnar and rest on a basal lamina, the upper layer of the basement membrane,[13] the lower layer is the reticular lamina lying next to the connective tissue in the extracellular matrix secreted by the epithelial cells.[14] There are many different types of epithelium, modified to suit a particular function. In the respiratory tract there is a type of ciliated epithelial lining; in the small intestine there are microvilli on the epithelial lining and in the large intestine there are intestinal villi. Skin consists of an outer layer of keratinised stratified squamous epithelium that covers the exterior of the vertebrate body. Keratinocytes make up to 95% of the cells in the skin.[15] The epithelial cells on the external surface of the body typically secrete an extracellular matrix in the form of a cuticle. In simple animals this may just be a coat of glycoproteins.[12] In more advanced animals, many glands are formed of epithelial cells.[16]

Muscle cells (myocytes) form the active contractile tissue of the body. Muscle tissue functions to produce force and cause motion, either locomotion or movement within internal organs. Muscle is formed of contractile filaments and is separated into three main types; smooth muscle, skeletal muscle and cardiac muscle. Smooth muscle has no striations when examined microscopically. It contracts slowly but maintains contractibility over a wide range of stretch lengths. It is found in such organs as sea anemone tentacles and the body wall of sea cucumbers. Skeletal muscle contracts rapidly but has a limited range of extension. It is found in the movement of appendages and jaws. Obliquely striated muscle is intermediate between the other two. The filaments are staggered and this is the type of muscle found in earthworms that can extend slowly or make rapid contractions.[17] In higher animals striated muscles occur in bundles attached to bone to provide movement and are often arranged in antagonistic sets. Smooth muscle is found in the walls of the uterus, bladder, intestines, stomach, esophagus, respiratory airways, and blood vessels. Cardiac muscle is found only in the heart, allowing it to contract and pump blood round the body.

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.[18] 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.[19][20] 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.[21]

All vertebrates have a similar basic body plan and at some point in their lives, (mostly in the embryonic stage), share the major chordate characteristics; a stiffening rod, the notochord; a dorsal hollow tube of nervous material, the neural tube; pharyngeal arches; 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.[22] 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.[23] The defining characteristic of a vertebrate is the vertebral column, formed in the development of the segmented series of vertebrae. In most vertebrates the notochord becomes the nucleus pulposus of the intervertebral discs. However, a few vertebrates, such as the sturgeon and the coelacanth retain the notochord into adulthood.[24]Jawed vertebrates are typified by paired appendages, fins or legs, which may be secondarily lost. The limbs of vertebrates are considered to be 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.[25]

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 vertebrae which are lightweight yet strong. The ribs attach to the spine and there are no limbs or limb girdles. The main external features of the fish, the fins, are composed of either bony or soft spines called rays, which with the exception of the caudal fins, have no direct connection with the spine. They are supported by the muscles which compose the main part of the trunk.[26] The heart has two chambers and pumps the blood through the respiratory surfaces of the gills and on round the body in a single circulatory loop.[27] 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.[26]

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.[28]

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.[28]

Amphibians are a class of animals comprising frogs, salamanders and caecilians. They are tetrapods, 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 glands and in some species, poison glands. The hearts of amphibians have three chambers, two atria and one ventricle. They have a urinary bladder and 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 region through the nostrils. These are then closed and the air is forced into the lungs by contraction of the throat.[29] They supplement this with gas exchange through the skin which needs to be kept moist.[30]

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.[31]

Reptiles are a class of animals comprising turtles, tuataras, lizards, snakes and crocodiles. They are tetrapods, 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 lungs 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 is designed for internal fertilisation, with a copulatory organ present in most species. The eggs are surrounded by amniotic membranes which prevents them from drying out and are laid on land, or develop internally in some species. The bladder is small as nitrogenous waste is excreted as uric acid.[32]

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.[33]

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.[33]

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.[33]

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.[34]

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.[35]

Birds are tetrapods but though their hind limbs are used for walking or hopping, their front limbs are wings covered with feathers and adapted for flight. Birds are endothermic, have a high metabolic rate, a light skeletal system and powerful muscles. 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.[36]

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.[36]

Mammals 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 prismatic enamel. The teeth are shed once (milk teeth) during the animal's lifetime or not at all, as is the case in cetaceans. 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. Some of these glands are specialised as mammary glands, producing milk to feed the young. Mammals breathe with lungs and have a muscular 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.[37]

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.[37]

Humans have the overall body plan of a mammal. Humans have a head, neck, trunk (which includes the thorax and abdomen), two arms and hands and two legs and feet.

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. [39]

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.[2] The major anatomy textbook, Gray's Anatomy, has been reorganized from a systems format to a regional format, in line with modern teaching methods.[40][41] A thorough working knowledge of anatomy is required by physicians, especially surgeons and doctors working in some diagnostic specialties, such as histopathology and radiology. [42]

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.[42]

Invertebrates constitute a vast array of living organisms ranging from the simplest unicellular eukaryotes such as Paramecium to such complex multicellular animals as the octopus, lobster and dragonfly. They constitute about 95% of the animal species. By definition, none of these creatures has a backbone. The cells of single-cell protozoans have the same basic structure as those of multicellular animals but some parts are specialised into the equivalent of tissues and organs. Locomotion is often provided by cilia or flagella or may proceed via the advance of pseudopodia, food may be gathered by phagocytosis, energy needs may be supplied by photosynthesis and the cell may be supported by an endoskeleton or an exoskeleton. Some protozoans can form multicellular colonies.[43]

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.[44] 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.[45]

Marcello Malpighi, the father of microscopical anatomy, discovered that plants had tubules similar to those he saw in insects like the silk worm. He observed that when a ring-like portion of bark was removed on a trunk a swelling occurred in the tissues above the ring, and he unmistakably interpreted this as growth stimulated by food coming down from the leaves, and being captured above the ring.[46]

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 segmentsa 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 similar segmentation to the legs and function as taste and smell organs. At the end of each male pedipalp is a spoon-shaped cymbium that acts to support the copulatory organ.

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]

Anatomy developed little from classical times until the sixteenth century; as the historian Marie Boas writes, "Progress in anatomy before the sixteenth century is as mysteriously slow as its development after 1500 is startlingly rapid".[59]:120121 Between 1275 and 1326, the anatomists Mondino de Luzzi, Alessandro Achillini and Antonio Benivieni at Bologna carried out the first systematic human dissections since ancient times.[60][61][62] Mondino's Anatomy of 1316 was the first textbook in the medieval rediscovery of human anatomy. It describes the body in the order followed in Mondino's dissections, starting with the abdomen, then the thorax, then the head and limbs. It was the standard anatomy textbook for the next century.[59]

Leonardo da Vinci (14521519) 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 (15141564) (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]

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]

Main article: Bibliography of anatomy

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