Stomach
Stomach | |
---|---|
left gastro-omental artery, short gastric arteries | |
Vein | Right gastric vein, left gastric vein, right gastroepiploic vein, left gastroepiploic vein, short gastric veins |
Nerve | Celiac ganglia, vagus nerve[1] |
Lymph | Celiac lymph nodes[2] |
Identifiers | |
Latin | ventriculus |
Greek | gaster |
MeSH | D013270 |
TA98 | A05.5.01.001 |
TA2 | 2901 |
FMA | 7148 |
Anatomical terminology] |
Major parts of the |
Gastrointestinal tract |
---|
The stomach is a muscular,
The stomach is located between the
Structure
In the
The stomach is surrounded by
, celiac and myenteric), which regulate both the secretory activity of the stomach and the motor (motion) activity of its muscles.Because it is a distensible organ, it normally expands to hold about one litre of food.[3] The stomach of a newborn human baby will only be able to retain about 30 millilitres. The maximum stomach volume in adults is between 2 and 4 litres.[4][5] Although volumes of up to 15 L have been observed in extreme circumstances.[6]
Sections
In classical anatomy the human stomach is divided into four sections, beginning at the cardia.[7]
- The cardia is where the contents of the esophagus empty into the stomach.[8]
- The fundus (from Latin'bottom') is formed in the upper curved part.
- The body or corpus is the main, central region of the stomach.
- The pyloric sphincter.
The cardia is defined as the region following the "z-line" of the
Anatomical proximity
The stomach bed refers to the structures upon which the stomach rests in mammals.
Blood supply
The lesser curvature of the human stomach is supplied by the right gastric artery inferiorly and the left gastric artery superiorly, which also supplies the cardiac region. The greater curvature is supplied by the right gastroepiploic artery inferiorly and the left gastroepiploic artery superiorly. The fundus of the stomach, and also the upper portion of the greater curvature, is supplied by the short gastric arteries, which arise from the splenic artery.
Microanatomy
Wall
Like the other parts of the gastrointestinal tract, the human stomach walls consist of a
The inner part of the lining of the stomach, the
Outside of the submucosa lies another muscular layer, the
- The inner oblique layer: This layer is responsible for creating the motion that churns and physically breaks down the food. It is the only layer of the three which is not seen in other parts of the digestive system. The antrum has thicker skin cells in its walls and performs more forceful contractions than the fundus.
- The middle circular layer: At this layer, the pylorus is surrounded by a thick circular muscular wall, which is normally tonically constricted, forming a functional (if not anatomically discrete) pyloric sphincter, which controls the movement of chyme into the duodenum. This layer is concentric to the longitudinal axisof the stomach.
- Auerbach's plexus (myenteric plexus) is found between the outer longitudinal and the middle circular layer and is responsible for the innervation of both (causing peristalsisand mixing).
The outer longitudinal layer is responsible for moving the bolus towards the pylorus of the stomach through muscular shortening.
To the outside of the muscularis externa lies a
Glands
The mucosa lining the stomach is lined with a number of these pits, which receive gastric juice, secreted by between 2 and 7 gastric glands.[citation needed] Gastric juice is an acidic fluid containing hydrochloric acid and the digestive enzyme pepsin.[citation needed] The glands contains a number of cells, with the function of the glands changing depending on their position within the stomach.[citation needed]
Within the body and fundus of the stomach lie the fundic glands. In general, these glands are lined by column-shaped cells that secrete a protective layer of
Glands differ where the stomach meets the esophagus and near the pylorus.
Gene and protein expression
About 20,000
Development
In early
Function
Digestion
In the
Gastric juice in the stomach also contains
Mechanical digestion
Within a few moments after food enters the stomach, mixing waves begin to occur at intervals of approximately 20 seconds. A mixing wave is a unique type of peristalsis that mixes and softens the food with gastric juices to create chyme. The initial mixing waves are relatively gentle, but these are followed by more intense waves, starting at the body of the stomach and increasing in force as they reach the pylorus.
The pylorus, which holds around 30 mL of chyme, acts as a filter, permitting only liquids and small food particles to pass through the mostly, but not fully, closed
Gastric emptying is regulated by both the stomach and the duodenum. The presence of chyme in the duodenum activates receptors that inhibit gastric secretion. This prevents additional chyme from being released by the stomach before the duodenum is ready to process it.[29]
Chemical digestion
The fundus stores both undigested food and gases that are released during the process of chemical digestion. Food may sit in the fundus of the stomach for a while before being mixed with the chyme. While the food is in the fundus, the digestive activities of
The breakdown of protein begins in the stomach through the actions of HCl and the enzyme pepsin.
The contents of the stomach are completely emptied into the duodenum within 2 to 4 hours after the meal is eaten. Different types of food take different amounts of time to process. Foods heavy in carbohydrates empty fastest, followed by high-protein foods. Meals with a high triglyceride content remain in the stomach the longest. Since enzymes in the small intestine digest fats slowly, food can stay in the stomach for 6 hours or longer when the duodenum is processing fatty chyme. However, this is still a fraction of the 24 to 72 hours that full digestion typically takes from start to finish.[29]
Absorption
Although the absorption in the human digestive system is mainly a function of the small intestine, some absorption of certain small molecules nevertheless does occur in the stomach through its lining. This includes:
- Water, if the body is dehydrated
- Medication, such as aspirin
- Amino acids[30]
- 10–20% of ingested ethanol (e.g. from alcoholic beverages)[31]
- Caffeine[32]
- To a small extent water-soluble vitamins (most are absorbed in the small intestine)[33]
The parietal cells of the human stomach are responsible for producing intrinsic factor, which is necessary for the absorption of vitamin B12. B12 is used in cellular metabolism and is necessary for the production of red blood cells, and the functioning of the nervous system.
Control of secretion and motility
Chyme from the stomach is slowly released into the duodenum through coordinated peristalsis and opening of the pyloric sphincter. The movement and the flow of chemicals into the stomach are controlled by both the autonomic nervous system and by the various digestive hormones of the digestive system:
Gastrin | The hormone gastrin causes an increase in the secretion of HCl from the parietal cells and pepsinogen from chief cells in the stomach. It also causes increased motility in the stomach. Gastrin is released by G cells in the stomach in response to distension of the antrum and digestive products (especially large quantities of incompletely digested proteins). It is inhibited by a pH normally less than 4(high acid), as well as the hormone somatostatin. |
Cholecystokinin | Cholecystokinin (CCK) has most effect on the gall bladder, causing gall bladder contractions, but it also decreases gastric emptying and increases release of pancreatic juice, which is alkaline and neutralizes the chyme. CCK is synthesized by I-cells in the mucosal epithelium of the small intestine.
|
Secretin | In a different and rare manner, secretin, which has the most effects on the pancreas, also diminishes acid secretion in the stomach. Secretin is synthesized by S-cells, which are located in the duodenal mucosa as well as in the jejunal mucosa in smaller numbers. |
Gastric inhibitory peptide |
Gastric inhibitory peptide (GIP) decreases both gastric acid release and motility. GIP is synthesized by K-cells, which are located in the duodenal and jejunal mucosa. |
Enteroglucagon | Enteroglucagon decreases both gastric acid and motility. |
Other than gastrin, these hormones all act to turn off the stomach action. This is in response to food products in the liver and gall bladder, which have not yet been absorbed. The stomach needs to push food into the small intestine only when the intestine is not busy. While the intestine is full and still digesting food, the stomach acts as storage for food.
Other
- Effects of EGF
Epidermal growth factor (EGF) results in cellular proliferation, differentiation, and survival.[34] EGF is a low-molecular-weight polypeptide first purified from the mouse submandibular gland, but since then found in many human tissues including the submandibular gland, and the parotid gland. Salivary EGF, which also seems to be regulated by dietary inorganic iodine, also plays an important physiological role in the maintenance of oro-esophageal and gastric tissue integrity. The biological effects of salivary EGF include healing of oral and gastroesophageal ulcers, inhibition of gastric acid secretion, stimulation of DNA synthesis, and mucosal protection from intraluminal injurious factors such as gastric acid, bile acids, pepsin, and trypsin and from physical, chemical, and bacterial agents.[35]
- Stomach as nutrition sensor
The human stomach has receptors responsive to
- Thyrogastric syndrome
This syndrome defines the association between thyroid disease and chronic gastritis, which was first described in the 1960s.[41] This term was coined also to indicate the presence of thyroid autoantibodies or autoimmune thyroid disease in patients with pernicious anemia, a late clinical stage of atrophic gastritis.[42] In 1993, a more complete investigation on the stomach and thyroid was published,[43] reporting that the thyroid is, embryogenetically and phylogenetically, derived from a primitive stomach, and that the thyroid cells, such as primitive gastroenteric cells, migrated and specialized in uptake of iodide and in storage and elaboration of iodine compounds during vertebrate evolution. In fact, the stomach and thyroid share iodine-concentrating ability and many morphological and functional similarities, such as cell polarity and apical microvilli, similar organ-specific antigens and associated autoimmune diseases, secretion of glycoproteins (thyroglobulin and mucin) and peptide hormones, the digesting and readsorbing ability, and lastly, similar ability to form iodotyrosines by peroxidase activity, where iodide acts as an electron donor in the presence of H2O2. In the following years, many researchers published reviews about this syndrome.[44]
Clinical significance
Diseases
A series of radiographs can be used to examine the stomach for various disorders. This will often include the use of a barium swallow. Another method of examination of the stomach, is the use of an endoscope. A gastric emptying study is considered the gold standard to assess the gastric emptying rate.[45]
A large number of studies have indicated that most cases of
A stomach rumble is actually noise from the intestines.
Surgery
In humans, many bariatric surgery procedures involve the stomach, in order to lose weight. A gastric band may be placed around the cardia area, which can adjust to limit intake. The anatomy of the stomach may be modified, or the stomach may be bypassed entirely.
Surgical removal of the stomach is called a gastrectomy, and removal of the cardia area is a called a cardiectomy. "Cardiectomy" is a term that is also used to describe the removal of the heart.[47][48][49] A gastrectomy may be carried out because of gastric cancer or severe perforation of the stomach wall.
Fundoplication is stomach surgery in which the fundus is wrapped around the lower esophagus and stitched into place. It is used to treat gastroesophageal reflux disease (GERD).[50]
History
There were previously conflicting statements in the academic anatomy community[51][52][53] over whether the cardia is part of the stomach, part of the esophagus or a distinct entity. Modern surgical and medical textbooks have agreed that "the gastric cardia is now clearly considered to be part of the stomach."[54][55]
Etymology
The word stomach is derived from Greek stomachos (στόμαχος), ultimately from stoma (στόμα) 'mouth'.[56] Gastro- and gastric (meaning 'related to the stomach') are both derived from Greek gaster (γαστήρ) 'belly'.[57][58][59]
Other animals
Although the precise shape and size of the stomach varies widely among different vertebrates, the relative positions of the esophageal and duodenal openings remain relatively constant. As a result, the organ always curves somewhat to the left before curving back to meet the pyloric sphincter. However, lampreys, hagfishes, chimaeras, lungfishes, and some teleost fish have no stomach at all, with the esophagus opening directly into the intestine. These animals all consume diets that require little storage of food, no predigestion with gastric juices, or both.[60]
|
The gastric lining is usually divided into two regions, an anterior portion lined by fundic glands and a posterior portion lined with pyloric glands. Cardiac glands are unique to mammals, and even then are absent in a number of species. The distributions of these glands vary between species, and do not always correspond with the same regions as in humans. Furthermore, in many non-human mammals, a portion of the stomach anterior to the cardiac glands is lined with epithelium essentially identical to that of the esophagus. Ruminants, in particular, have a complex stomach, the first three chambers of which are all lined with esophageal mucosa.[60]
In
In insects, there is also a crop. The insect stomach is called the midgut.
Information about the stomach in
Additional images
-
Greater omentum and stomach of humans
-
A more realistic image, showing the celiac artery and its branches in humans; the liver has been raised, and the lesser omentum and anterior layer of the greater omentum removed.
-
An autopsy of a human stomach, showing the many folds (rugae) of the stomach. 2012 Instituto Nacional de Cardiología.
-
Human stomach
-
High-quality image of the stomach
See also
- Gastroesophageal reflux disease
- Human gastrointestinal microbiota
- Proton-pump inhibitor
References
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- ^ Morris D. Kerstein, Barry Goldberg, Barry Panter, M. David Tilson, Howard Spiro, Gastric Infarction, Gastroenterology, Volume 67, Issue 6, 1974, Pages 1238-1239, ISSN 0016-5085, https://doi.org/10.1016/S0016-5085(19)32710-6.
- ^ Anatomy photo:37:06-0103 at the SUNY Downstate Medical Center – "Abdominal Cavity: The Stomach"
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- ^ [1] Habershon, S. H. "Diseases of the Stomach: A Manual for Practitioners and Students,"Chicago Medical Book Company, 1909, page 11.
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- ^ [4] The Lancet, Volume 1, Part 1, 22 February 1902. page 524, "Royal Academy of Medicine in Ireland." Retrieved 28 February 2012
- ^ [5] The Dublin journal of medical science, Volume 114, page 353."Reviews and bibliographical notes." Retrieved 28 February 2012.
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- ^ "University of Rochester medical center". 2020. Archived from the original on 2021-11-19. Retrieved 2021-12-19.
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{{cite journal}}
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External links
- Stomach at the Human Protein Atlas
- Digestion of proteins in the stomach or tiyan (archived 10 March 2007)
- Site with details of how ruminants process food (archived 27 October 2009)
- Control of Gastric Emptying (Archived 2019-11-12 at the Wayback Machine)