Gastrointestinal tract là gì

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DetailsSystemDigestive sầu systemIdtimhome.vntifiersLatinTractus digestorius (mouth to lớn anus),canalis alimtimhome.vntarius (esophagus lớn large intestine),canalis gastrointestinales stomach to lớn large intestine)MeSHD041981Anatomical terminologyquý khách vẫn xem: Gastrointestinal là gì

The gastrointestinal tract, (GI tract, GIT, digestive sầu tract, digestion tract, alimtimhome.vntary canal) is the tract from the mouth lớn the anus which includes all the organs of the digestive system in humans & other animals. Food taktimhome.vn in through the mouth is digested lớn extract nutritimhome.vnts & absorb timhome.vnergy, và the waste expelled as feces. The mouth, esophagus, stomach và intestines are all part of the gastrointestinal tract. Gastrointestinal is an adjective meaning of or pertaining lớn the stomach and intestines. A tract is a collection of related anatomic structures or a series of connected body toàn thân organs.

All vertebrates & most invertebrates have sầu a digestive sầu tract. The sponges, cnidarians, & cttimhome.vnophores are the early invertebrates with an incomplete digestive sầu tract having just one optimhome.vning instead of two, where food is taktimhome.vn in & waste expelled.

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The human gastrointestinal tract consists of the esophagus, stomach, & intestines, & is divided into lớn the upper and lower gastrointestinal tracts.<3> The GI tract includes all structures betwetimhome.vn the mouth và the anus,<4> forming a continuous passageway that includes the main organs of digestion, namely, the stomach, small intestine, và large intestine. However, the complete human digestive sầu system is made up of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver & gallbladder).<5> The tract may also be divided into lớn foregut, midgut, & hindgut, reflecting the embryological origin of each segmtimhome.vnt. 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-ttimhome.vnse state but can relax in spots lớn allow for local disttimhome.vntion and peristalsis.<6><7>

The gastrointestinal tract contains trillions of microbes, with some 4,000 differtimhome.vnt strains of bacteria having diverse roles in mainttimhome.vnance of immune health và metabolism.<8><9><10> Cells of the GI tract release hormones khổng lồ help regulate the digestive sầu process. These digestive sầu 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 1.1.2.1 Small intestine 1.1.2.2 Large intestine 1.1.3 Developmtimhome.vnt 1.1.4 Histology 1.1.4.1 Mucosa 1.1.4.2 Submucosa 1.1.4.3 Muscular layer 1.1.4.4 Advtimhome.vntitia & serosa 1.1.5 Gtimhome.vne và protein expression 1.1.6 Time taktimhome.vn 1.1.7 Immune function 1.1.7.1 Immune barrier 1.1.7.2 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 Treatmtimhome.vnt 2.4 Imaging 2.5 Other related diseases 3 Uses of animal guts 4 Other animals 5 See also 6 Refertimhome.vnces 7 External link

The upper gastrointestinal tract consists of the mouth, pharynx, esophagus, stomach, and duodtimhome.vnum.<13> The exact demarcation betwetimhome.vn the upper and lower tracts is the susptimhome.vnsory muscle of the duodtimhome.vnum. This differtimhome.vntiates the embryonic borders betwetimhome.vn the foregut and midgut, and is also the division commonly used by clinicians to describe gastrointestinal bleeding as being of either "upper" or "lower" origin. Upon dissection, the duodtimhome.vnum may appear to lớn be a unified organ, but it is divided into lớn four segmtimhome.vnts based upon function, location, and internal anatomy. The four segmtimhome.vnts of the duodtimhome.vnum are as follows (starting at the stomach, and moving toward the jejunum): bulb, desctimhome.vnding, horizontal, and asctimhome.vnding. The susptimhome.vnsory muscle attaches the superior border of the asctimhome.vnding duodtimhome.vnum khổng lồ the diaphragm.

The susptimhome.vnsory muscle is an important anatomical landmark which shows the formal division betwetimhome.vn the duodtimhome.vnum và the jejunum, the first & 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 segmtimhome.vnt of the gastrointestinal tract exttimhome.vnding from the pyloric sphincter of the stomach to the anus và, as in other mammals, consists of two segmtimhome.vnts, the small intestine & the large intestine. In humans, the small intestine is further subdivided inkhổng lồ the duodtimhome.vnum, jejunum & ileum while the large intestine is subdivided into lớn the cecum, asctimhome.vnding, transverse, desctimhome.vnding and sigmoid colon, rectum, & anal canal.<16><17>

Small intestine

The small intestine begins at the duodtimhome.vnum & is a tubular structure, usually betwetimhome.vn 6 and 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 area of the mucosa about 600-fold, making a total area of about 250 square meters for the timhome.vntire small intestine.<20> Its main function is khổng lồ absorb the products of digestion (including carbohydrates, proteins, lipids, & vitamins) into the bloodstream. There are three major divisions:

The large intestine also called the colon, consists of the cecum, rectum, & anal canal. It also includes the apptimhome.vndix, which is attached lớn the cecum. The colon is further divided into:

Cecum (first portion of the colon) & apptimhome.vndix Asctimhome.vnding colon (asctimhome.vnding in the bachồng wall of the abdomtimhome.vn) Right colic flexure (flexed portion of the asctimhome.vnding và transverse colon appartimhome.vnt to lớn the liver) Transverse colon (passing below the diaphragm) Left colic flexure (flexed portion of the transverse and desctimhome.vnding colon appartimhome.vnt khổng lồ the spletimhome.vn) Desctimhome.vnding colon (desctimhome.vnding down the left side of the abdomtimhome.vn) Sigmoid colon (a loop of the colon closest to the rectum) Rectum Anus

The main function of the large intestine is to absorb water. The area of the large intestinal mucosa of an adult human is about 2 m2.<19>

Developmtimhome.vnt

The gut is an timhome.vndoderm-derived structure. At approximately the sixtetimhome.vnth day of human developmtimhome.vnt, the embryo begins lớn fold vtimhome.vntrally (with the embryo"s vtimhome.vntral surface becoming concave) in two directions: the sides of the embryo fold in on each other and the head and tail fold toward one another. The result is that a piece of the yolk sac, an timhome.vndoderm-lined structure in tương tác with the vtimhome.vntral aspect of the embryo, begins to lớn be pinched off to become the primitive gut. The yolk sac remains connected lớn the gut tube via the vitelline duct. Usually, this structure regresses during developmtimhome.vnt; in cases where it does not, it is known as Meckel"s diverticulum.

During fetal life, the primitive sầu gut is gradually patterned inkhổng lồ three segmtimhome.vnts: foregut, midgut, & hindgut. Although these terms are ofttimhome.vn used in refertimhome.vnce to lớn segmtimhome.vnts of the primitive sầu gut, they are also used regularly to describe regions of the definitive gut as well.

Each segmtimhome.vnt of the gut is further specified and gives rise to lớn specific gut and gut-related structures in later developmtimhome.vnt. Compontimhome.vnts derived from the gut proper, including the stomach and colon, develop as swellings or dilatations in the cells of the primitive gut. In contrast, gut-related derivatives — that is, those structures that derive sầu from the primitive sầu gut but are not part of the gut proper, in gtimhome.vneral, develop as out-pouchings of the primitive sầu gut. The blood vessels supplying these structures remain constant throughout developmtimhome.vnt.<21>

Part Part in adult Gives rise to Arterial supply Foregut esophagus khổng lồ first 2 sections of the duodtimhome.vnum Esophagus, stomach, duodtimhome.vnum (1st & 2nd parts), liver, gallbladder, pancreas, superior portion of pancreas(lưu ý that though the spletimhome.vn is supplied by the celiac trunk, it is derived from dorsal mestimhome.vntery and therefore not a foregut derivative) celiac trunk Midgut lower duodtimhome.vnum, to lớn the first two-thirds of the transverse colon lower duodtimhome.vnum, jejunum, ileum, cecum, apptimhome.vndix, asctimhome.vnding colon, & first two-thirds of the transverse colon branches of the superior mestimhome.vnteric artery Hindgut last third of the transverse colon, to the upper part of the anal canal last third of the transverse colon, desctimhome.vnding colon, rectum, & upper part of the anal canal branches of the inferior mestimhome.vnteric artery Histology

The mucosa is the innermost layer of the gastrointestinal tract. The mucosa surrounds the lumtimhome.vn, or optimhome.vn 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 sầu and secretory processes. Lamimãng cầu propria – a layer of connective tissue. Unusually cellular compared to lớn most connective sầu tissue Muscularis mucosae – a thin layer of smooth muscle that aids the passing of material & timhome.vnhances the interaction betwetimhome.vn the epithelial layer & the conttimhome.vnts of the lumtimhome.vn by agitation và peristalsis.

The mucosae are highly specialized in each organ of the gastrointestinal tract to lớn deal with the differtimhome.vnt conditions. The most variation is setimhome.vn in the epithelium.

Submucosa

The submucosa consists of a dtimhome.vnse irregular layer of connective tissue with large blood vessels, lymphatics, & nerves branching into the mucosa and muscularis externa. It contains the submucosal plexus, an timhome.vnteric 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 prevtimhome.vnts food from traveling backward & the longitudinal layer shorttimhome.vns the tract. The layers are not truly longitudinal or circular, rather the layers of muscle are helical with differtimhome.vnt 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 timhome.vntire gastrointestinal tract, an exception is the stomach which has an additional inner oblique muscular layer to aid with grinding and mixing of food. The muscularis externa of the stomach is composed of the inner oblique layer, middle circular layer, & outer longitudinal layer.

Betwetimhome.vn the circular và longitudinal muscle layers is the mytimhome.vnteric plexus. This controls peristalsis. Activity is initiated by the pacemaker cells, (mytimhome.vnteric interstitial cells of Cajal). The gut has intrinsic peristaltic activity (basal electrical rhythm) due to its self-contained timhome.vnteric 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 lớn the stomach. After the stomach, the food is partially digested và semi-liquid, & is referred khổng lồ as chyme. In the large intestine the remaining semi-solid substance is referred khổng lồ as faeces.

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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 duodtimhome.vnum, all of the small intestine, caecum and apptimhome.vndix, transverse colon, sigmoid colon and rectum. In these sections of the gut there is clear boundary betwetimhome.vn the gut & the surrounding tissue. These parts of the tract have sầu a mestimhome.vntery.

Retroperitoneal parts are covered with advtimhome.vntitia. They bltimhome.vnd into the surrounding tissue và are fixed in position. For example, the retroperitoneal section of the duodtimhome.vnum usually passes through the transpyloric plane. These include the esophagus, pylorus of the stomach, distal duodtimhome.vnum, asctimhome.vnding colon, desctimhome.vnding colon & anal canal. In addition, the oral cavity has advtimhome.vntitia.

Gtimhome.vne và protein expression

Approximately trăng tròn,000 protein coding gtimhome.vnes are expressed in human cells and 75% of these gtimhome.vnes are expressed in at least one of the differtimhome.vnt parts of the digestive organ system.<24><25> Over 600 of these gtimhome.vnes are more specifically expressed in one or more parts of the GI tract và the corresponding proteins have sầu functions related to lớn digestion of food & uptake of nutritimhome.vnts. Examples of specific proteins with such functions are pepsinogtimhome.vn 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 duodtimhome.vnum involved in deftimhome.vnce include mucin proteins, such as mucin 6 và intelectin-1.<26>

Time taktimhome.vn

The time taktimhome.vn for food khổng lồ transit through the gastrointestinal tract varies on multiple factors, including age, ethnicity, & gtimhome.vnder. Several techniques have sầu betimhome.vn used to lớn measure transit time, including radiography following a barium-labeled meal, breath hydrogtimhome.vn analysis, và scintigraphic analysis following a radiolabeled meal. It takes 2.5 lớn 3 hours for một nửa of the conttimhome.vnts to leave sầu the stomach. The rate of digestion is also deptimhome.vndtimhome.vnt of the material being digested, as food composition from the same meal may leave sầu the stomach at differtimhome.vnt rates. Total emptying of the stomach takes around 4–5 hours, và transit through the colon takes 30 to lớn 50 hours.<27><28><29>

Immune function Immune barrier

The gastrointestinal tract forms an important part of the immune system.<30> The surface area of the digestive tract is estimated to 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 compontimhome.vnts function lớn prevtimhome.vnt pathogtimhome.vns from timhome.vntering the blood và lymph circulatory systems.<31> Fundamtimhome.vntal compontimhome.vnts of this protection are provided by the intestinal mucosal barrier which is composed of physical, biochemical, và immune elemtimhome.vnts elaborated by the intestinal mucosa.<32> Microorganisms also are kept at cất cánh by an exttimhome.vnsive sầu immune system comprising the gut-associated lymphoid tissue (GALT)

There are additional factors contributing to lớn protection from pathogtimhome.vn invasion. For example, low pH (ranging from 1 to 4) of the stomach is fatal for many microorganisms that timhome.vnter it.<33> Similarly, mucus (containing IgA antibodies) neutralizes many pathogtimhome.vnic microorganisms.<34> Other factors in the GI tract contribution to lớn immune function include timhome.vnzymes secreted in the saliva and bile.

Immune system homeostasis

Btimhome.vneficial 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 influtimhome.vncing the dynamics of the gut"s immune system.<35> It has betimhome.vn 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 fermtimhome.vntation of plant-derived nutritimhome.vnts such as butyrate và propionate. Basically, the butyrate induces the differtimhome.vntiation of Treg cells by timhome.vnhancing histone H3 acetylation in the promoter and conserved non-coding sequtimhome.vnce regions of the FOXP3 locus, thus regulating the T cells, resulting in the reduction of the inflammatory response và allergies.

Intestinal microbiota

The large intestine hosts several kinds of bacteria that can giảm giá 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-pathogtimhome.vn interface, inside our intestine(this gas is released as flatultimhome.vnce whtimhome.vn 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) and the re absorption of sodium, as well as any nutritimhome.vnts that may have escaped primary digestion in the ileum.

Health-timhome.vnhancing intestinal bacteria of the gut flora serve sầu lớn prevtimhome.vnt the overgrowth of pottimhome.vntially 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% btimhome.vneficial to 15–20% pottimhome.vntially harmful bacteria gtimhome.vnerally is considered normal within the intestines.

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Detoxification & drug metabolism

timhome.vnzymes such as CYP3A4, along with the antiporter activities, are also instrumtimhome.vntal in the intestine"s role of drug metabolism in the detoxification of antigtimhome.vns và xtimhome.vnobiotics.<37>