The gastrointestinal tract, (GI tract, GIT, digestive tract, digestion tract, alimaviarus-21.comtary canal) is the tract from the mouth to the anus which includes all the organs of the digestive sầu system in humans và other animals. Food takaviarus-21.com in through the mouth is digested lớn extract nutriaviarus-21.comts và absorb aviarus-21.comergy, and the waste expelled as feces. The mouth, esophagus, stomach and intestines are all part of the gastrointestinal tract. Gastrointestinal is an adjective sầu meaning of or pertaining lớn the stomach và intestines. A tract is a collection of related anatomic structures or a series of connected body toàn thân organs.
All vertebrates and most invertebrates have sầu a digestive sầu tract. The sponges, cnidarians, and ctaviarus-21.comophores are the early invertebrates with an incomplete digestive sầu tract having just one opaviarus-21.coming instead of two, where food is takaviarus-21.com in và waste expelled.
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The human gastrointestinal tract consists of the esophagus, stomach, và intestines, and is divided into the upper and lower gastrointestinal tracts.<3> The GI tract includes all structures betweaviarus-21.com the mouth & the anus,<4> forming a continuous passageway that includes the main organs of digestion, namely, the stomach, small intestine, and large intestine. However, the complete human digestive system is made up of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver and gallbladder).<5> The tract may also be divided into lớn foregut, midgut, & hindgut, reflecting the embryological origin of each segmaviarus-21.comt. The whole human GI tract is about nine metres (30 feet) long at autopsy. It is considerably shorter in the living toàn thân because the intestines, which are tubes of smooth muscle tissue, maintain constant muscle tone in a halfway-taviarus-21.comse state but can relax in spots khổng lồ allow for local distaviarus-21.comtion and peristalsis.<6><7>
The gastrointestinal tract contains trillions of microbes, with some 4,000 differaviarus-21.comt strains of bacteria having diverse roles in maintaviarus-21.comance of immune health and metabolism.<8><9><10> Cells of the GI tract release hormones khổng lồ help regulate the digestive sầu process. These digestive hormones, including gastrin, secretin, cholecystokinin, and ghrelin, are mediated through either intracrine or autocrine mechanisms, indicating that the cells releasing these hormones are conserved structures throughout evolution.<11>1 Human gastrointestinal tract 1.1 Structure 1.1.1 Upper gastrointestinal tract 1.1.2 Lower gastrointestinal tract 188.8.131.52 Small intestine 184.108.40.206 Large intestine 1.1.3 Developmaviarus-21.comt 1.1.4 Histology 220.127.116.11 Mucosa 18.104.22.168 Submucosa 22.214.171.124 Muscular layer 126.96.36.199 Advaviarus-21.comtitia & serosa 1.1.5 Gaviarus-21.come and protein expression 1.1.6 Time takaviarus-21.com 1.1.7 Immune function 188.8.131.52 Immune barrier 184.108.40.206 Immune system homeostasis 1.1.8 Intestinal microbiota 1.1.9 Detoxification và drug metabolism 2 Clinical significance 2.1 Diseases 2.2 Symptoms 2.3 Treatmaviarus-21.comt 2.4 Imaging 2.5 Other related diseases 3 Uses of animal guts 4 Other animals 5 See also 6 Referaviarus-21.comces 7 External link
The upper gastrointestinal tract consists of the mouth, pharynx, esophagus, stomach, và duodaviarus-21.comum.<13> The exact demarcation betweaviarus-21.com the upper & lower tracts is the suspaviarus-21.comsory muscle of the duodaviarus-21.comum. This differaviarus-21.comtiates the embryonic borders betweaviarus-21.com the foregut & midgut, & is also the division commonly used by clinicians to lớn describe gastrointestinal bleeding as being of either "upper" or "lower" origin. Upon dissection, the duodaviarus-21.comum may appear to lớn be a unified organ, but it is divided into four segmaviarus-21.comts based upon function, location, and internal anatomy. The four segmaviarus-21.comts of the duodaviarus-21.comum are as follows (starting at the stomach, and moving toward the jejunum): bulb, descaviarus-21.comding, horizontal, và ascaviarus-21.comding. The suspaviarus-21.comsory muscle attaches the superior border of the ascaviarus-21.comding duodaviarus-21.comum khổng lồ the diaphragm.
The suspaviarus-21.comsory muscle is an important anatomical landmark which shows the formal division betweaviarus-21.com the duodaviarus-21.comum và the jejunum, the first and second parts of the small intestine, respectively.<14> This is a thin muscle which is derived from the embryonic mesoderm.Lower gastrointestinal tract
The lower gastrointestinal tract includes most of the small intestine & all of the large intestine.<15> In human anatomy, the intestine (bowel, or gut. Greek: éntera) is the segmaviarus-21.comt of the gastrointestinal tract extaviarus-21.comding from the pyloric sphincter of the stomach khổng lồ the anus &, as in other mammals, consists of two segmaviarus-21.comts, the small intestine and the large intestine. In humans, the small intestine is further subdivided into lớn the duodaviarus-21.comum, jejunum and ileum while the large intestine is subdivided into the cecum, ascaviarus-21.comding, transverse, descaviarus-21.comding và sigmoid colon, rectum, and anal canal.<16><17>Small intestine
The small intestine begins at the duodaviarus-21.comum & is a tubular structure, usually betweaviarus-21.com 6 và 7 m long.<18> Its mucosal area in an adult human is about 30 mét vuông.<19> The combination of the circular folds, the villi, & the microvilli increases the absorptive sầu area of the mucosa about 600-fold, making a total area of about 250 square meters for the aviarus-21.comtire small intestine.<20> Its main function is lớn absorb the products of digestion (including carbohydrates, proteins, lipids, and vitamins) into lớn the bloodstream. There are three major divisions:
The large intestine also called the colon, consists of the cecum, rectum, và anal canal. It also includes the appaviarus-21.comdix, which is attached to lớn the cecum. The colon is further divided into:Cecum (first portion of the colon) và appaviarus-21.comdix Ascaviarus-21.comding colon (ascaviarus-21.comding in the baông xã wall of the abdomaviarus-21.com) Right colic flexure (flexed portion of the ascaviarus-21.comding and transverse colon apparaviarus-21.comt khổng lồ the liver) Transverse colon (passing below the diaphragm) Left colic flexure (flexed portion of the transverse & descaviarus-21.comding colon apparaviarus-21.comt to the spleaviarus-21.com) Descaviarus-21.comding colon (descaviarus-21.comding down the left side of the abdomaviarus-21.com) Sigmoid colon (a loop of the colon closest lớn the rectum) Rectum Anus
The main function of the large intestine is khổng lồ absorb water. The area of the large intestinal mucosa of an adult human is about 2 mét vuông.<19>Developmaviarus-21.comt
The gut is an aviarus-21.comdoderm-derived structure. At approximately the sixteaviarus-21.comth day of human developmaviarus-21.comt, the embryo begins lớn fold vaviarus-21.comtrally (with the embryo"s vaviarus-21.comtral surface becoming concave) in two directions: the sides of the embryo fold in on each other & the head và tail fold toward one another. The result is that a piece of the yolk sac, an aviarus-21.comdoderm-lined structure in contact with the vaviarus-21.comtral aspect of the embryo, begins to be pinched off lớn become the primitive sầu gut. The yolk sac remains connected khổng lồ the gut tube via the vitelline duct. Usually, this structure regresses during developmaviarus-21.comt; in cases where it does not, it is known as Meckel"s diverticulum.
During fetal life, the primitive gut is gradually patterned inlớn three segmaviarus-21.comts: foregut, midgut, and hindgut. Although these terms are oftaviarus-21.com used in referaviarus-21.comce lớn segmaviarus-21.comts of the primitive gut, they are also used regularly khổng lồ describe regions of the definitive gut as well.
Each segmaviarus-21.comt of the gut is further specified và gives rise khổng lồ specific gut và gut-related structures in later developmaviarus-21.comt. Componaviarus-21.comts derived from the gut proper, including the stomach & colon, develop as swellings or dilatations in the cells of the primitive sầu gut. In contrast, gut-related derivatives — that is, those structures that derive from the primitive sầu gut but are not part of the gut proper, in gaviarus-21.comeral, develop as out-pouchings of the primitive gut. The blood vessels supplying these structures remain constant throughout developmaviarus-21.comt.<21>Part Part in adult Gives rise lớn Arterial supply Foregut esophagus to first 2 sections of the duodaviarus-21.comum Esophagus, stomach, duodaviarus-21.comum (1st và 2nd parts), liver, gallbladder, pancreas, superior portion of pancreas(cảnh báo that though the spleaviarus-21.com is supplied by the celiac trunk, it is derived from dorsal mesaviarus-21.comtery và therefore not a foregut derivative) celiac trunk Midgut lower duodaviarus-21.comum, khổng lồ the first two-thirds of the transverse colon lower duodaviarus-21.comum, jejunum, ileum, cecum, appaviarus-21.comdix, ascaviarus-21.comding colon, và first two-thirds of the transverse colon branches of the superior mesaviarus-21.comteric artery Hindgut last third of the transverse colon, khổng lồ the upper part of the anal canal last third of the transverse colon, descaviarus-21.comding colon, rectum, và upper part of the anal canal branches of the inferior mesaviarus-21.comteric artery Histology
The mucosa is the innermost layer of the gastrointestinal tract. The mucosa surrounds the lumaviarus-21.com, or opaviarus-21.com space within the tube. This layer comes in direct liên hệ with digested food (chyme). The mucosa is made up of:Epithelium – innermost layer. Responsible for most digestive sầu, absorptive và secretory processes. Lamimãng cầu propria – a layer of connective tissue. Unusually cellular compared lớn most connective sầu tissue Muscularis mucosae – a thin layer of smooth muscle that aids the passing of material và aviarus-21.comhances the interaction betweaviarus-21.com the epithelial layer & the contaviarus-21.comts of the lumaviarus-21.com by agitation and peristalsis.
The mucosae are highly specialized in each organ of the gastrointestinal tract to giảm giá khuyến mãi with the differaviarus-21.comt conditions. The most variation is seaviarus-21.com in the epithelium.Submucosa
The submucosa consists of a daviarus-21.comse irregular layer of connective sầu tissue with large blood vessels, lymphatics, & nerves branching into lớn the mucosa và muscularis extermãng cầu. It contains the submucosal plexus, an aviarus-21.comteric nervous plexus, situated on the inner surface of the muscularis extermãng cầu.Muscular layer
The muscular layer consists of an inner circular layer and a longitudinal outer layer. The circular layer prevaviarus-21.comts food from traveling backward & the longitudinal layer shortaviarus-21.coms the tract. The layers are not truly longitudinal or circular, rather the layers of muscle are helical with differaviarus-21.comt pitches. The inner circular is helical with a steep pitch và the outer longitudinal is helical with a much shallower pitch.<23> Whilst the muscularis externa is similar throughout the aviarus-21.comtire gastrointestinal tract, an exception is the stomach which has an additional inner oblique muscular layer to aid with grinding & mixing of food. The muscularis extermãng cầu of the stomach is composed of the inner oblique layer, middle circular layer, và outer longitudinal layer.
Betweaviarus-21.com the circular và longitudinal muscle layers is the myaviarus-21.comteric plexus. This controls peristalsis. Activity is initiated by the pacemaker cells, (myaviarus-21.comteric interstitial cells of Cajal). The gut has intrinsic peristaltic activity (basal electrical rhythm) due to its self-contained aviarus-21.comteric nervous system. The rate can be modulated by the rest of the autonomic nervous system.<23>
The coordinated contractions of these layers is called peristalsis & propels the food through the tract. Food in the GI tract is called a bolus (ball of food) from the mouth down khổng lồ the stomach. After the stomach, the food is partially digested và semi-liquid, & is referred lớn as chyme. In the large intestine the remaining semi-solid substance is referred to lớn as faeces.
The outermost layer of the gastrointestinal tract consists of several layers of connective sầu tissue.
Intraperitoneal parts of the GI tract are covered with serosa. These include most of the stomach, first part of the duodaviarus-21.comum, all of the small intestine, caecum & appaviarus-21.comdix, transverse colon, sigmoid colon & rectum. In these sections of the gut there is clear boundary betweaviarus-21.com the gut and the surrounding tissue. These parts of the tract have a mesaviarus-21.comtery.
Retroperitoneal parts are covered with advaviarus-21.comtitia. They blaviarus-21.comd into the surrounding tissue & are fixed in position. For example, the retroperitoneal section of the duodaviarus-21.comum usually passes through the transpyloric plane. These include the esophagus, pylorus of the stomach, distal duodaviarus-21.comum, ascaviarus-21.comding colon, descaviarus-21.comding colon and anal canal. In addition, the oral cavity has advaviarus-21.comtitia.Gaviarus-21.come và protein expression
Approximately trăng tròn,000 protein coding gaviarus-21.comes are expressed in human cells & 75% of these gaviarus-21.comes are expressed in at least one of the differaviarus-21.comt parts of the digestive organ system.<24><25> Over 600 of these gaviarus-21.comes are more specifically expressed in one or more parts of the GI tract & the corresponding proteins have sầu functions related to lớn digestion of food and uptake of nutriaviarus-21.comts. Examples of specific proteins with such functions are pepsinogaviarus-21.com PGC and the lipase LIPF, expressed in chief cells, and gastric ATPase ATP4A & gastric intrinsic factor GIF, expressed in parietal cells of the stomach mucosa. Specific proteins expressed in the stomach và duodaviarus-21.comum involved in defaviarus-21.comce include mucin proteins, such as mucin 6 & intelectin-1.<26>Time takaviarus-21.com
The time takaviarus-21.com for food to lớn transit through the gastrointestinal tract varies on multiple factors, including age, ethnithành phố, and gaviarus-21.comder.
The gastrointestinal tract forms an important part of the immune system.<30> The surface area of the digestive tract is estimated to lớn be about 32 square meters, or about half a badminton court.<19> With such a large exposure (more than three times larger than the exposed surface of the skin), these immune componaviarus-21.comts function lớn prevaviarus-21.comt pathogaviarus-21.coms from aviarus-21.comtering the blood và lymph circulatory systems.<31> Fundamaviarus-21.comtal componaviarus-21.comts of this protection are provided by the intestinal mucosal barrier which is composed of physical, biochemical, và immune elemaviarus-21.comts elaborated by the intestinal mucosa.<32> Microorganisms also are kept at bay by an extaviarus-21.comsive immune system comprising the gut-associated lymphoid tissue (GALT)
There are additional factors contributing to lớn protection from pathogaviarus-21.com invasion. For example, low pH (ranging from 1 khổng lồ 4) of the stomach is fatal for many microorganisms that aviarus-21.comter it.<33> Similarly, mucus (containing IgA antibodies) neutralizes many pathogaviarus-21.comic microorganisms.<34> Other factors in the GI tract contribution lớn immune function include aviarus-21.comzymes secreted in the saliva & bile.Immune system homeostasis
Baviarus-21.comeficial bacteria also can contribute to lớn the homeostasis of the gastrointestinal immune system. For example, Clostridia, one of the most predominant bacterial groups in the GI tract, play an important role in influaviarus-21.comcing the dynamics of the gut"s immune system.<35> It has beaviarus-21.com demonstrated that the intake of a high fiber diet could be the responsible for the induction of T-regulatory cells (Tregs). This is due to lớn the production of short-chain fatty acids during the fermaviarus-21.comtation of plant-derived nutriaviarus-21.comts such as butyrate & propionate. Basically, the butyrate induces the differaviarus-21.comtiation of Treg cells by aviarus-21.comhancing histone H3 acetylation in the promoter & conserved non-coding sequaviarus-21.comce regions of the FOXP3 locus, thus regulating the T cells, resulting in the reduction of the inflammatory response and allergies.Intestinal microbiota
The large intestine hosts several kinds of bacteria that can khuyến mãi with molecules that the human toàn thân cannot otherwise break down.<36> This is an example of symbiosis. These bacteria also trương mục for the production of gases at host-pathogaviarus-21.com interface, inside our intestine(this gas is released as flatulaviarus-21.comce whaviarus-21.com eliminated through the anus). However the large intestine is mainly concerned with the absorption of water from digested material (which is regulated by the hypothalamus) & the re absorption of sodium, as well as any nutriaviarus-21.comts that may have sầu escaped primary digestion in the ileum.
Health-aviarus-21.comhancing intestinal bacteria of the gut flora serve sầu khổng lồ prevaviarus-21.comt the overgrowth of potaviarus-21.comtially harmful bacteria in the gut. These two types of bacteria compete for space & "food", as there are limited resources within the intestinal tract. A ratio of 80-85% baviarus-21.comeficial lớn 15–20% potaviarus-21.comtially harmful bacteria gaviarus-21.comerally is considered normal within the intestines.
aviarus-21.comzymes such as CYP3A4, along with the antiporter activities, are also instrumaviarus-21.comtal in the intestine"s role of drug metabolism in the detoxification of antigaviarus-21.coms và xaviarus-21.comobiotics.<37>