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Stomach
Stomach
Stomach
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Stomach
Sections of the human stomach
Scheme of digestive tract, with stomach in red
Details
PrecursorForegut
SystemDigestive system
ArteryRight gastric artery, left gastric artery, right gastro-omental artery, left gastro-omental artery, short gastric arteries
VeinRight gastric vein, left gastric vein, right gastroepiploic vein, left gastroepiploic vein, short gastric veins
NerveCeliac ganglia, vagus nerve[1]
LymphCeliac lymph nodes[2]
Identifiers
Latinventriculus, stomachus
Greekστόμαχος
MeSHD013270
TA98A05.5.01.001
TA22901
FMA7148
Anatomical terminology
Major parts of the
Gastrointestinal tract
Upper gastrointestinal tract
Lower gastrointestinal tract
See also

The stomach is a muscular, hollow organ in the upper gastrointestinal tract of humans and many other animals, including several invertebrates. The Ancient Greek name for the stomach is gaster which is used as gastric in medical terms related to the stomach.[3] The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach is involved in the gastric phase of digestion, following the cephalic phase in which the sight and smell of food and the act of chewing are stimuli. In the stomach a chemical breakdown of food takes place by means of secreted digestive enzymes and gastric acid. It also plays a role in regulating gut microbiota, influencing digestion and overall health.[4]

The stomach is located between the esophagus and the small intestine. The pyloric sphincter controls the passage of partially digested food (chyme) from the stomach into the duodenum, the first and shortest part of the small intestine, where peristalsis takes over to move this through the rest of the intestines.

Structure

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In the human digestive system, the stomach lies between the esophagus and the duodenum (the first part of the small intestine). It is in the left upper quadrant of the abdominal cavity. The top of the stomach lies against the diaphragm. Lying behind the stomach is the pancreas. A large double fold of visceral peritoneum called the greater omentum hangs down from the greater curvature of the stomach. Two sphincters keep the contents of the stomach contained; the lower esophageal sphincter (found in the cardiac region), at the junction of the esophagus and stomach, and the pyloric sphincter at the junction of the stomach with the duodenum.

The stomach is surrounded by parasympathetic (inhibitor) and sympathetic (stimulant) plexuses (networks of blood vessels and nerves in the anterior gastric, posterior, superior and inferior, celiac and myenteric), which regulate both the secretory activity of the stomach and the motor (motion) activity of its muscles.

The stomach is distensible, and can normally expand to hold about one litre of food.[5] The shape of the stomach depends upon the degree of its distension and that of surrounding viscera, e.g. the colon.[4] When empty, the stomach is somewhat J-shaped; when partially distended, it becomes pyriform in shape. In obese persons, it is more horizontal.[4] In a newborn human baby the stomach will only be able to hold about 30 millilitres. The maximum stomach volume in adults is between 2 and 4 litres,[6][7] although volumes of up to 15 litres have been observed in extreme circumstances.[8]

Sections

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"Cardia" redirects here. For the ancient Greek colony, see Cardia (Thrace).
Diagram showing parts of the stomach

The human stomach can be divided into four sections, beginning at the cardia followed by the fundus, the body and the pylorus.[9][10]

  • The gastric cardia is where the contents of the esophagus empty from the gastroesophageal sphincter into the cardiac orifice, the opening into the gastric cardia.[11][10] A cardiac notch at the left of the cardiac orifice, marks the beginning of the greater curvature of the stomach. A horizontal line across from the cardiac notch gives the dome-shaped region called the fundus.[10] The cardia is a very small region of the stomach that surrounds the esophageal opening.[10]
  • The fundus (from Latin 'bottom') is formed in the upper curved part.[12]
  • The body or corpus is the main, central region of the stomach.[12]
  • The pylorus (from Greek 'gatekeeper') connects the stomach to the duodenum at the pyloric sphincter. The pyloric antrum opens to the body of the stomach.[12]

The cardia is defined as the region following the "z-line" of the gastroesophageal junction, the point at which the epithelium changes from stratified squamous to columnar. Near the cardia is the lower esophageal sphincter.[11]

Anatomical proximity

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The stomach bed refers to the structures upon which the stomach rests in mammals.[13][14] These include the tail of the pancreas, splenic artery, left kidney, left suprarenal gland, transverse colon and its mesocolon, and the left crus of diaphragm, and the left colic flexure. The term was introduced around 1896 by Philip Polson of the Catholic University School of Medicine, Dublin. However this was brought into disrepute by surgeon anatomist J Massey.[15][16][17]

Blood supply

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Schematic image of the blood supply to the human stomach: left and right gastric artery, left and right gastroepiploic artery and short gastric arteries[18]

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 5-7 short gastric arteries, which arise from the splenic artery.[4]

Lymphatic drainage

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The two sets of gastric lymph nodes drain the stomach's tissue fluid into the lymphatic system through the intestinal lymph trunk, to the cisterna chyli.[4]

Microanatomy

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Wall

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Main article: Gastrointestinal wall
The gastrointestinal wall of the human stomach
Layers of the gastrointestinal wall of which the stomach is a dilated part

Like the other parts of the gastrointestinal wall, the human stomach wall from inner to outer, consists of a mucosa, submucosa, muscular layer, subserosa and serosa.[19]

The inner part of the stomach wall is the gastric mucosa a mucous membrane that forms the lining of the stomach. The membrane consists of an outer layer of columnar epithelium, a lamina propria, and a thin layer of smooth muscle called the muscularis mucosa. Beneath the mucosa lies the submucosa, consisting of fibrous connective tissue.[20] Meissner's plexus is in this layer interior to the oblique muscle layer.[21]

Outside of the submucosa lies the muscular layer. It consists of three layers of muscular fibres, with fibres lying at angles to each other. These are the inner oblique, middle circular, and outer longitudinal layers.[22] The presence of the inner oblique layer is distinct from other parts of the gastrointestinal tract, which do not possess this layer.[23] The stomach contains the thickest muscular layer consisting of three layers, thus maximum peristalsis occurs here.

  • 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 axis of the stomach.
  • The myenteric plexus (Auerbach's plexus) is found between the outer longitudinal and the middle circular layer and is responsible for the innervation of both (causing peristalsis and mixing).

The outer longitudinal layer is responsible for moving the semi-digested food towards the pylorus of the stomach through muscular shortening.

To the outside of the muscular layer lies a serosa, consisting of layers of connective tissue continuous with the peritoneum.

Smooth mucosa along the inside of the lesser curvature forms a passageway - the gastric canal that fast-tracks liquids entering the stomach, to the pylorus.[10]

Glands

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Main article: Gastric glands
Diagram showing gastric pits (13) gastric glands (12) lamina propria (10) epithelium (11)
Histology of normal fundic mucosa. Fundic glands are simple, branched tubular glands that extend from the bottom of the gastric pits to the muscularis mucosae; the more distinctive cells are parietal cells. H&E stain.
Histology of normal antral mucosa. Antral mucosa is formed by branched coiled tubular glands lined by secretory cells similar in appearance to the surface mucous cells. H&E stain.

The mucosa lining the stomach is lined with gastric 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 digestive enzymes.[24] 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 mucus and bicarbonate. Additional cells present include parietal cells that secrete hydrochloric acid and intrinsic factor, chief cells that secrete pepsinogen (this is a precursor to pepsin- the highly acidic environment converts the pepsinogen to pepsin), and neuroendocrine cells that secrete serotonin.[25][citation needed]

Glands differ where the stomach meets the esophagus and near the pylorus.[26] Near the gastroesophageal junction lie cardiac glands, which primarily secrete mucus.[25] They are fewer in number than the other gastric glands and are more shallowly positioned in the mucosa. There are two kinds - either simple tubular glands with short ducts or compound racemose resembling the duodenal Brunner's glands.[citation needed] Near the pylorus lie pyloric glands located in the antrum of the pylorus. They secrete mucus, as well as gastrin produced by their G cells.[27][citation needed]

Gene and protein expression

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Further information: Bioinformatics § Gene and protein expression

About 20,000 protein-coding genes are expressed in human cells and nearly 70% of these genes are expressed in the normal stomach.[28][29] Just over 150 of these genes are more specifically expressed in the stomach compared to other organs, with only some 20 genes being highly specific. The corresponding specific proteins expressed in stomach are mainly involved in creating a suitable environment for handling the digestion of food for uptake of nutrients. Highly stomach-specific proteins include gastrokine-1 expressed in the mucosa; pepsinogen and gastric lipase, expressed in gastric chief cells; and a gastric ATPase and gastric intrinsic factor, expressed in parietal cells.[30]

Development

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In the early part of the development of the human embryo, the ventral part of the embryo abuts the yolk sac. During the third week of development, as the embryo grows, it begins to surround parts of the yolk sac. The enveloped portions form the basis for the adult gastrointestinal tract.[31] The sac is surrounded by a network of vitelline arteries and veins. Over time, these arteries consolidate into the three main arteries that supply the developing gastrointestinal tract: the celiac artery, superior mesenteric artery, and inferior mesenteric artery. The areas supplied by these arteries are used to define the foregut, midgut, and hindgut.[31] The surrounded sac becomes the primitive gut. Sections of this gut begin to differentiate into the organs of the gastrointestinal tract, and the esophagus, and stomach form from the foregut.[31]

As the stomach rotates during early development, the dorsal and ventral mesentery rotate with it; this rotation produces a space anterior to the expanding stomach called the greater sac, and a space posterior to the stomach called the lesser sac. After this rotation the dorsal mesentery thins and forms the greater omentum, which is attached to the greater curvature of the stomach. The ventral mesentery forms the lesser omentum, and is attached to the developing liver. In the adult, these connective structures of omentum and mesentery form the peritoneum, and act as an insulating and protective layer while also supplying organs with blood and lymph vessels as well as nerves.[32] Arterial supply to all these structures is from the celiac trunk, and venous drainage is by the portal venous system. Lymph from these organs is drained to the prevertebral celiac nodes at the origin of the celiac artery from the aorta.

Function

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Digestion

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Further information: Human digestive system
See also: Gastric acid

In the human digestive system, a bolus (a small rounded mass of chewed up food) enters the stomach through the esophagus via the lower esophageal sphincter. The stomach releases proteases (protein-digesting enzymes such as pepsin), and hydrochloric acid, which kills or inhibits bacteria and provides the acidic pH of 2 for the proteases to work. Food is churned by the stomach through peristaltic muscular contractions of the wall – reducing the volume of the bolus, before looping around the fundus[33] and the body of stomach as the boluses are converted into chyme (partially digested food). Chyme slowly passes through the pyloric sphincter and into the duodenum of the small intestine, where the extraction of nutrients begins.

Gastric juice in the stomach contains pepsinogen and gastric acid, (hydrochloric acid) which activates this inactive form of enzyme into the active form, pepsin. Pepsin breaks down proteins into polypeptides.

Mechanical digestion

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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 pyloric sphincter. In a process called gastric emptying, rhythmic mixing waves force about 3 mL of chyme at a time through the pyloric sphincter and into the duodenum. Release of a greater amount of chyme at one time would overwhelm the capacity of the small intestine to handle it. The rest of the chyme is pushed back into the body of the stomach, where it continues mixing. This process is repeated when the next mixing waves force more chyme into the duodenum.

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.[34]

Chemical digestion

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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 salivary amylase continue until the food begins mixing with the acidic chyme. Ultimately, mixing waves incorporate this food with the chyme, the acidity of which inactivates salivary amylase and activates lingual lipase. Lingual lipase then begins breaking down triglycerides into free fatty acids, and mono- and diglycerides.

The breakdown of protein begins in the stomach through the actions of hydrochloric acid, and the enzyme pepsin.

The stomach can also produce gastric lipase, which can help digesting fat.

The contents of the stomach are completely emptied into the duodenum within two to four 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.[34]

Absorption

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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:

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

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Emptying of stomach chyme into the duodenum through the pyloric sphincter

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 polypeptide Gastric inhibitory polypeptide (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

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Effects of EGF

Epidermal growth factor (EGF) results in cellular proliferation, differentiation, and survival.[39] 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.[40]

Stomach as nutrition sensor

The human stomach has receptors responsive to sodium glutamate[41] and this information is passed to the lateral hypothalamus and limbic system in the brain as a palatability signal through the vagus nerve.[42] The stomach can also sense, independently of tongue and oral taste receptors, glucose,[43] carbohydrates,[44] proteins,[44] and fats.[45] This allows the brain to link nutritional value of foods to their tastes.[43]

Thyrogastric syndrome

This syndrome defines the association between thyroid disease and chronic gastritis, which was first described in the 1960s.[46] 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.[47] In 1993, a more complete investigation on the stomach and thyroid was published,[48] 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.[49]

Clinical significance

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An endoscopy of a normal stomach of a healthy 65-year-old woman
Endoscopic image of a fundic gland polyp

Diseases

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Main article: Stomach disease

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.[50]

A large number of studies have indicated that most cases of peptic ulcers, and gastritis, in humans are caused by Helicobacter pylori infection, and an association has been seen with the development of stomach cancer.[51]

A stomach rumble is actually noise from the intestines.

Surgery

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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.[52][53][54] 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).[55]

Etymology

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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

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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]

Comparison of stomach glandular regions from several mammalian species. Frequency of glands may vary more smoothly between regions than is diagrammed here. Asterisk (ruminant) represents the omasum, which is absent in Tylopoda (Tylopoda also have some cardiac glands opening onto ventral reticulum and rumen[61]) Many other variations exist among the mammals.[62][63]
Yellow
Esophagus
Green
Esophageal (nonglandular) region.[64]
Purple
Cardiac gland region.[64]
Red
Fundic gland region.[64]
Blue
Pyloric gland region.[64]
Dark blue
Duodenum

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 four-chambered stomach. The first three chambers (rumen, reticulum, and omasum) are all lined with esophageal mucosa,[60] while the final chamber functions like a monogastric stomach, which is called the abomasum.

In birds and crocodilians, the stomach is divided into two regions. Anteriorly is a narrow tubular region, the proventriculus, lined by fundic glands, and connecting the true stomach to the crop. Beyond lies the powerful muscular gizzard, lined by pyloric glands, and, in some species, containing stones that the animal swallows to help grind up food.[60]

In insects, there is also a crop. The insect stomach is called the midgut.

Information about the stomach in echinoderms or molluscs can be found under the respective articles.

Additional images

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  • Image showing the celiac artery and its branches
    Image showing the celiac artery and its branches
  • A human stomach at autopsy showing the many folds (rugae)
    A human stomach at autopsy showing the many folds (rugae)
  • High-quality image of the stomach
    High-quality image of the stomach

See also

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Wikimedia Commons has media related to Stomach.

References

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Stomach

View on Grokipedia
from Grokipedia
The stomach is a J-shaped, hollow, muscular organ located in the upper left quadrant of the , positioned between the superiorly and the inferiorly, serving as a central component of the digestive system responsible for temporarily storing ingested , mechanically churning it, and initiating chemical through the secretion of gastric juices to form a semi-liquid mixture known as . Anatomically, the stomach is divided into four main regions: the cardia near the , the fundus above the cardia, the body as the largest central portion, and the leading to the , with an overall capacity to hold approximately 2 to 3 liters of food while its inner surface features —folds that allow expansion—and four tissue layers including the mucosa for , submucosa for support, a thick muscularis externa with three muscle layers for mixing, and an outer serosa. Its intraperitoneal position relates it to adjacent organs such as the liver, , , and diaphragm, and it is innervated primarily by the alongside the for coordinated and . Physiologically, the stomach performs mechanical digestion via churning motions that break down food particles and chemical digestion through secretions from specialized cells: parietal cells produce hydrochloric acid (HCl) to create an acidic environment (pH ~1.0) for protein denaturation and microbial killing, chief cells release pepsinogen (activated to for protein breakdown), and mucous cells secrete a protective mucus-bicarbonate barrier against self-digestion. Additionally, it secretes from parietal cells essential for absorption in the , regulates gastric emptying via the pyloric sphincter to control release (typically over 2 to 4 hours, varying by food type such as faster for carbohydrates than ), and plays a minor role in absorption while primarily acting as a and initial processor in the .

Anatomy

Gross anatomy

The stomach is a J-shaped, hollow, muscular organ situated in the upper , primarily on the left side of the midline, extending from the cardia at its junction with the to the connecting to the . It serves as a for ingested and facilitates initial mechanical through its distensible walls. The organ's overall dimensions in adults average approximately 25 cm in length and 10 to 12 cm in width, though these vary with body size and nutritional status. The stomach is anatomically divided into five principal regions based on their positions and functions: the cardia, fundus, body, antrum, and . The cardia, the most proximal region, surrounds the esophageal opening and is a short conical area about 3 cm in diameter, positioned immediately below the diaphragm. Adjacent and superior to it is the fundus, a dome-shaped expansion that projects upward and to the left, often reaching the level of the fifth , and comprising roughly 10-15% of the stomach's volume. The body, or corpus, forms the largest central portion, occupying about 50-60% of the total length, with a relatively uniform cylindrical shape that tapers distally. The antrum, distal to the body, is a funnel-shaped expansion of the pyloric region, measuring around 7-10 cm in length and serving as a mixing chamber; it transitions into the narrower , a 2-3 cm tubular segment ending at the pyloric . These regions vary in relative size, with the body being the most expansive and the pylorus the most constricted. Surface features of the stomach include the greater and lesser curvatures, which define its convex and concave borders, respectively. The greater curvature, the longer outer convex margin (about 40 cm), arches from the cardia along the left inferior aspect to the , while the shorter lesser curvature (about 30 cm) forms the concave right medial border. Internally, the mucosa features prominent longitudinal folds known as gastric , which are most evident in the empty state and allow the organ to expand; these folds are deepest in the body and fundus, diminishing toward the . The stomach's wall thickness varies regionally, averaging 2-3 mm in the body and fundus but increasing to 5-7 mm in the antrum and due to thicker muscle layers. In its empty state, the stomach has a contracted capacity of about 50 , roughly the size of a , but it can distend to a typical resting volume of 1-1.5 liters and up to 4 liters when fully expanded during a meal, accommodating large boluses through relaxation of its muscular walls. The stomach is positioned beneath the liver and adjacent to the on its superior and left aspects, respectively.

Location and relations

The stomach is situated in the left upper quadrant of the , primarily within the epigastric and left hypochondriac regions, extending from the vertebral levels of T11 to L1 below the diaphragm. It occupies a central position in the superior , lying between the superiorly and the inferiorly, with its J-shaped configuration allowing it to span from the midline toward the left side. As an intraperitoneal organ, the stomach is fully enveloped by the , which provides it with significant mobility within the due to its attachments. The , a double-layered peritoneal fold, hangs from the greater curvature of the stomach and extends inferiorly to attach to the , acting as an apron-like structure. Along the lesser curvature, the connects the stomach to the liver, forming the gastrohepatic ligament, while the links the greater curvature to the , further anchoring the organ while permitting flexibility. This peritoneal investment allows the stomach to shift position with changes in body posture or during , without fixed adhesions to surrounding structures. Anteriorly, the stomach relates to the diaphragm, the left lobe of the liver, and the , with the also contributing to this surface. Posteriorly, it is in close contact with several structures within the bed of the stomach, including the , the left and , the , the via the transverse mesocolon, and the left dome of the diaphragm. These relations position the fundus and body of the stomach against the , while the pylorus approaches the midline.

Blood and lymphatic supply

The arterial supply of the stomach originates from the celiac trunk, which branches into the , , and at the level of the T12 vertebra. The ascends along the lesser curvature, providing branches to both anterior and posterior gastric walls. The , coursing along the superior border of the , gives rise to 3–5 that supply the fundus and upper greater curvature, as well as the left gastroepiploic (gastroomental) artery that runs along the greater curvature within the . Meanwhile, the provides the right gastric artery, which descends along the lesser curvature to anastomose with the , and through its gastroduodenal branch, the , which supplies the and lower greater curvature. These vessels interconnect via extensive anastomoses along both curvatures, forming arterial arcades that ensure redundant blood flow and resilience against occlusion. Venous drainage from the stomach mirrors the arterial pattern and ultimately contributes to the . The left and right gastric veins drain directly into the , while the short gastric veins and left gastroepiploic vein empty into the , which then joins the to form the . The right gastroepiploic vein drains into the , facilitating efficient return of nutrient-rich blood from the stomach to the liver. This parallel venous architecture supports the organ's role in processing absorbed substances before hepatic . Lymphatic drainage follows pathways aligned with the vascular supply, directing fluid from the stomach mucosa and to regional lymph nodes before converging on the . Primary drainage occurs via gastric nodes along the lesser curvature, gastroepiploic nodes along the greater curvature, and pyloric nodes near the , with additional contributions from pancreaticosplenic nodes adjacent to the and subpyloric nodes inferior to the . The stomach is divided into four lymphatic zones: zone 1 (cardia and upper right two-thirds) drains to left gastric nodes; zone 2 ( and lower right two-thirds) to suprapyloric nodes; zone 3 (fundus and upper left one-third) to pancreaticosplenic nodes; and zone 4 (lower left one-third) to infrapyloric nodes. These routes form a hierarchical system that empties into celiac and intestinal trunk nodes, ultimately reaching . The rich lymphatic network aids in immune surveillance and within the gastric wall.

Innervation

The stomach receives dual autonomic innervation from the parasympathetic and sympathetic nervous systems, supplemented by the intrinsic and sensory afferents that coordinate its functions in . The parasympathetic supply primarily arises from the (cranial nerve X), which originates in the dorsal motor nucleus and nucleus tractus solitarius in the . The divides into anterior and posterior trunks as it enters the through the , providing efferent fibers that stimulate gastric of , enzymes, and , as well as for mixing and propulsion of contents. These trunks give rise to branches targeting specific regions: gastric branches to the cardia and fundus, crow's foot branches to the and antrum, and intermediate branches to the body and greater curvature, enabling regional control of and glandular activity. Sympathetic innervation to the stomach derives from the greater, lesser, and least (T5–T12), which in the and superior mesenteric ganglia before forming the around the . These noradrenergic fibers primarily inhibit , promote of gastric vessels to regulate blood flow during stress, and transmit signals via referral to thoracic dermatomes (e.g., epigastric region). The plexus distributes along arterial branches to innervate the muscularis externa, mucosa, and , counterbalancing parasympathetic effects to maintain . The , often called the "second ," comprises an intrinsic network of approximately 100 million neurons embedded in the stomach wall, enabling local reflex control independent of central input. It includes the myenteric (Auerbach's) plexus, located between the longitudinal and circular muscle layers, which coordinates through excitatory and inhibitory nitrergic neurons that drive peristaltic waves and accommodation. The submucosal (Meissner's) plexus, situated in the (though sparser in the stomach compared to the intestine), regulates glandular secretion, mucosal blood flow, and transport via secretomotor neurons, integrating sensory inputs for adaptive responses to luminal contents. These plexuses form interconnected circuits that process local stimuli, such as distension or changes, to sustain gastric function. Sensory innervation involves visceral afferents from both vagal (about 40%) and spinal (60%) pathways, with cell bodies in the nodose ganglion and thoracic dorsal root ganglia (T4–L2, peaking at T10–T11), respectively. Vagal afferents, forming intramuscular arrays and intraganglionic laminar endings, detect mechanical distension and chemical stimuli (e.g., low or nutrients) to initiate reflexes for and secretion, projecting to the nucleus tractus solitarius. Spinal afferents, often peptidergic (expressing CGRP and ), sense noxious distension, , or ischemia, transmitting pain via the to the and higher centers, often resulting in poorly localized epigastric discomfort. These pathways ensure protective feedback, with vagal fibers handling physiological sensations and spinal fibers mediating .

Histology

The stomach wall consists of four principal layers: the mucosa, , muscularis externa, and serosa. The innermost mucosa comprises a , a of rich in blood vessels and lymphoid tissue, and a thin of that allows for localized movements of the mucosal surface. The , composed of , contains larger blood vessels, lymphatics, and nerves, contributing to the stomach's ability to expand via folds. The muscularis externa features three layers—an inner oblique layer unique to the stomach for enhanced mixing, a middle circular layer that thickens at the to form the pyloric sphincter, and an outer longitudinal layer—enabling and churning. The outermost serosa is a layer of visceral covering most of the stomach, providing lubrication and attachment. The mucosa exhibits distinct regional variations corresponding to the cardia, fundus/body, and pylorus. In the cardia, near the esophagus, the mucosa contains short cardiac glands lined primarily by mucus-secreting cells, forming a protective zone. The fundus and body, the main secretory regions, feature deeper leading to long, branched fundic glands that extend through the to the , populated by a mix of cell types. The pylorus, transitioning to the , has shallower pits and predominantly pyloric glands rich in mucus-secreting cells and G-cells, with a thickened muscularis externa. Key cellular components include surface mucous cells that line the luminal surface and , providing a continuous epithelial barrier; mucous neck cells located in the upper portions of glands; chief cells in the deeper gland bases, characterized by basophilic cytoplasm; parietal cells scattered throughout the glands, with eosinophilic features; and enteroendocrine cells dispersed at gland bases, including G-cells in the . serve as openings for coiled or tubular glands that penetrate the mucosa, differing from the by lacking villi and instead relying on these invaginations for surface area. Gene expression profiles, such as those involving transcription factors like in stem cells, help delineate these specialized cell lineages within the gastric .

Molecular biology

The molecular biology of the stomach encompasses distinct and protein expression profiles that underpin the functional specialization of its epithelial cells. Proteomic analyses of stomach mucosa have identified over 14,000 proteins expressed across various regions, with a significant emphasis on such as pepsinogens and transporters like pumps essential for secretion and nutrient processing. These expression patterns exhibit regional specificity, with the fundus and corpus predominantly featuring proteins involved in production, while the antrum expresses mucins and hormones for mucosal protection and motility regulation. In parietal cells, primarily located in the fundus and body regions, the ATP4A and ATP4B genes encode the alpha and beta subunits of the H+/K+-ATPase , which is crucial for secretion. These genes are highly expressed in differentiated parietal cells, serving as markers of their maturation and functional identity during epithelial differentiation. Similarly, the gene, encoding , shows elevated expression in these cells, facilitating absorption and contributing to the differentiated state of parietal lineages. Chief cells, also concentrated in the fundus and corpus, exhibit high expression of the PGA3, PGA4, and PGA5 genes, which code for pepsinogen A precursors that activate into pepsins for protein digestion. According to data from the Human Protein Atlas, these pepsinogen genes demonstrate some of the highest transcript levels in chief cells (e.g., PGA3 at over 86,000 nTPM), underscoring their role as key indicators of chief cell differentiation and secretory function. In the antrum, the GAST is prominently expressed in enteroendocrine G cells, producing to stimulate acid and gastric motility, with transcript levels exceeding 9,000 nTPM as per Human Protein Atlas profiling. proteins, such as MUC5AC and MUC6, show regional enrichment in antral mucous cells, forming a protective barrier; MUC5AC is secreted by surface throughout the stomach but peaks in antral regions, while MUC6 predominates in glandular mucins of the antrum. These patterns highlight how molecular expression drives cell-type specific functions and regional adaptations in the .

Development

Embryonic origins

The stomach originates from the three primary germ layers formed during in the early embryonic period. The contributes to the epithelial lining of the stomach and its associated glands, providing the foundational mucosal surface for . The differentiates into the connective tissues, including the , , muscularis externa, and serosa, which form the structural framework of the organ. Additionally, neural crest-derived gives rise to the , enabling neural coordination of gastrointestinal functions. As a derivative of the , the stomach begins to form during the fourth week of embryonic development from a dilation of the caudal portion of the primitive gut tube, which is a hollow cylinder composed of endodermal cells surrounded by splanchnic . By the fifth week, this dilation elongates and starts to exhibit regional distinctions, marking the initial of the stomach within the foregut segment that extends from the to the . Initially positioned in the midline of the , the primitive stomach remains attached to the body wall via a dorsal mesentery, which provides vascular and supportive connections. During this early phase, the stomach undergoes a 90-degree rotation around its longitudinal axis, shifting its position to the left side of the and establishing the orientation of its curvatures, with the lesser curvature facing medially. This , occurring primarily in the fourth week, also contributes to the formation of the lesser peritoneal sac and repositions the cranial (cardiac) end downward to the left and the caudal (pyloric) end upward to the right. Key to these developmental processes is signaling via Sonic hedgehog (SHH), a protein secreted by the endodermal starting around embryonic day 8.5 in mammals; SHH acts in a paracrine manner to drive epithelial-mesenchymal interactions, promoting proliferation of mesenchymal progenitors, expansion of the , and differentiation of layers essential for stomach wall integrity.

Morphogenesis

The morphogenesis of the stomach involves dynamic shaping processes that transform the primitive into its characteristic adult form, originating from the layer during early embryonic development. Between weeks 5 and 8 of , the foregut undergoes elongation and differential dilation, particularly along its dorsal aspect, expanding into a (spindle-shaped) structure that establishes the greater while the ventral side forms the lesser curvature. This period also features a 90-degree around the stomach's longitudinal axis, reorienting the organ so that its original left surface faces anteriorly and the right surface posteriorly, with the left positioning anteriorly and the right posteriorly. These changes occur concurrently with the growth of the dorsal mesogastrium, which elongates to form the future , and the ventral mesogastrium, which contributes to the . Vascular development supports this morphogenesis, with the emerging as the primary arterial supply to the derivatives, including the stomach, around weeks 5 to 6 as branches from the organize to perfuse the expanding organ. The omental development integrates with this, as the derives from the dorsal and facilitates vascular connections, while venous drainage establishes via the portal system during the same timeframe. Glandular differentiation follows, with the beginning to invaginate by week 8 to form primitive pits and glands. By week 12, parietal cells (responsible for acid secretion) and chief cells (pepsinogen producers) onset in the fundic and body regions, marking the start of specialized cell lineages, though full maturation continues into later . Functional secretion of gastric juices becomes operational by birth, enabling the newborn stomach to process . Positional shifts accompany these internal changes, with the stomach initially forming in a superior midline position within the coelomic cavity and gradually descending from a more thoracic level to its final abdominal location in the upper left quadrant by weeks 8 to 10, driven by overall embryonic and diaphragm partitioning. Fixation occurs via peritoneal ligaments, including the gastrosplenic and splenorenal ligaments from the and the from the , stabilizing the organ relative to adjacent structures like the , liver, and diaphragm.

Congenital anomalies

Congenital anomalies of the stomach encompass a range of developmental abnormalities arising during embryogenesis, primarily affecting the organ's structure, position, or function. These conditions deviate from normal gastric morphogenesis, where the stomach forms from the around weeks 4-7 of , leading to potential obstructions, malpositions, or ectopic tissues. While most are rare, they can manifest in neonates with gastrointestinal symptoms, necessitating early diagnostic evaluation. The most common congenital anomaly is infantile hypertrophic pyloric stenosis (IHPS), characterized by thickening of the pyloric muscle, resulting in . Its incidence is approximately 1.3 to 3 per 1,000 live births, with higher rates in males (male-to-female ratio of 4:1 to 5:1) and first-born infants. involves multifactorial and environmental factors, such as early exposure to erythromycin or maternal during . Clinically, it presents in infants aged 2-8 weeks with progressive, projectile non-bilious , leading to and if untreated; diagnosis is confirmed via showing pyloric muscle thickness exceeding 3-4 mm. Gastric duplication cysts represent another frequent anomaly, comprising 2-9% of all gastrointestinal duplications, with an overall incidence of about 1 in 4,500 live births. These spherical or tubular cysts arise from aberrant budding and share a muscular wall with the stomach, potentially communicating with the lumen. They often remain but can cause vomiting, abdominal pain, or bleeding due to ectopic within the cyst; prenatal or postnatal imaging like MRI aids . Heterotopia, particularly pancreatic rests (ectopic pancreatic tissue), occurs in the stomach in up to 25-30% of cases, though symptomatic forms are rare, with an prevalence of 0.6-13.7% across gastrointestinal sites. This congenital malformation results from aberrant migration of pancreatic primordia during weeks 4-6 of development, lacking connection to the native . It typically presents incidentally during as submucosal nodules in the antrum, but may cause dyspepsia, , or obstruction; endoscopic confirms acinar and ductal elements. Rarer anomalies include congenital microgastria, a hypoplastic tubular stomach with reduced capacity, reported in fewer than 30 cases worldwide, often associated with or limb defects. Gastric atresia, usually pyloric, has an incidence of 1 in 100,000 births and stems from failed recanalization or vascular insult in utero, presenting with immediate postnatal non-bilious vomiting and antenatally; upper GI series delineates the obstruction. affects gastric position in mirror-image reversal as part of totalis (incidence 1 in 10,000), linked to genes disrupting left-right asymmetry, and may lead to midgut malrotation with risk, diagnosed via imaging. Genetic factors, such as FOXF1 mutations, contribute to some anomalies like or malrotation impacting gastric function, occurring in contexts like alveolar dysplasia.

Physiology

Motility

The motility of the stomach encompasses a series of coordinated mechanical actions that mix, grind, and propel ingested food toward the small intestine. These movements are generated by the smooth muscle layers within the muscularis externa and are synchronized by electrical slow waves originating from interstitial cells of Cajal in the pacemaker region along the greater curvature. Peristaltic contractions initiate in the body of the stomach and propagate toward the pylorus, facilitating the distal movement of gastric contents. Mixing waves, arising from rhythmic segmentation-like contractions, promote thorough blending of the food bolus with gastric secretions throughout the corpus and antrum. In the antrum, retropulsion occurs as forceful peristaltic waves drive chyme against the tonically closed pyloric sphincter, redirecting larger particles proximally for additional fragmentation and enhancing overall mixing efficiency. Gastric motility proceeds through distinct phases to optimize processing. Receptive relaxation, vagally mediated via inhibitory neurons releasing and , relaxes the proximal stomach (fundus and upper body) to accommodate up to 1-2 liters of food with minimal pressure rise. This phase transitions to storage, where the fundus maintains low basal tone to retain the bolus without active . Grinding then dominates in the distal stomach, characterized by high-amplitude contractions occurring at a of approximately 3 per minute, which reduce solid particles through shear forces and . The unique arrangement of the stomach's three smooth muscle layers underpins these motility patterns. The innermost oblique layer generates torque-like churning actions critical for grinding and mixing in the body and antrum. The middle circular layer produces constrictions that narrow the lumen, enabling peristaltic and pyloric to control outflow. The outermost longitudinal layer shortens the stomach during waves, contributing to overall from the body to the antrum. Following grinding, gastric emptying ensues, with the stomach typically clearing a over 2-4 hours, though the half-emptying time varies by content type. Liquids empty more rapidly via pressure gradients, while solids exhibit a lag phase before exponential emptying, influenced heavily by —only particles smaller than 1-2 mm pass the , necessitating prior size reduction. Neural control of these processes is primarily exerted through the , integrating sensory feedback to modulate contraction strength and relaxation. A commonly reported sensation of an unsettled or "jiggly" stomach often occurs after consuming a heavy breakfast early in the morning following overnight fasting. The stomach, relatively empty after prolonged fasting, undergoes rapid distension upon ingestion of a large volume of food and secretions. This distension activates stretch receptors in the gastric wall, eliciting vigorous churning and mixing contractions to blend the contents with digestive juices. The semi-liquid gastric contents then slosh mechanically within the distended stomach, particularly during body movements, producing the perceived jiggly or unsettled feeling. High-fat or excessively large meals can delay gastric emptying, prolonging the distension and associated contractions, thereby extending the duration of the sensation.

Secretion

The stomach secretes gastric juice, a complex fluid essential for digestion, consisting primarily of hydrochloric acid (HCl), pepsinogen, mucus, intrinsic factor, and bicarbonate. This secretion occurs from specialized cells in the gastric glands located in the mucosa. Hydrochloric acid, secreted by parietal cells, maintains the gastric lumen at a highly acidic pH of 1.5 to 3.5 and is produced via the H+/K+-ATPase proton pump on the apical membrane of these cells, which exchanges intracellular H+ for extracellular K+. Pepsinogen, the inactive precursor to the protease pepsin, is released by chief cells and activated in the acidic environment. Mucus and bicarbonate are produced by surface mucous cells, forming a protective gel layer. Intrinsic factor, also from parietal cells, binds vitamin B12 to facilitate its absorption later in the intestine. The stomach produces approximately 2 to 3 liters of gastric juice daily in adults, with a low basal secretion rate during that increases to peaks under , such as from meals. This output supports digestive processes while balancing acidity.30287-1/pdf) To prevent self-digestion by the acidic and enzymatic contents, the relies on a pre-epithelial protective barrier formed by and secreted by surface epithelial cells, which traps to neutralize acid at the mucosal surface. This - layer maintains a near-neutral gradient adjacent to the despite the luminal acidity. Gastric secretion is regulated in part by the hormone gastrin, released from G cells in the antrum, which stimulates parietal cell acid production.

Digestion

The stomach initiates the chemical digestion of proteins through the activation of pepsin, the primary proteolytic enzyme in gastric juice. Hydrochloric acid secreted by parietal cells reduces the intragastric pH to approximately 1.5–2, converting inactive pepsinogen—produced by chief cells—into active pepsin. At this optimal pH of around 2, pepsin catalyzes the hydrolysis of internal peptide bonds in proteins, preferentially cleaving those adjacent to aromatic amino acids such as phenylalanine and tyrosine, thereby denaturing proteins and breaking them into smaller polypeptides and oligopeptides. This process marks the beginning of protein degradation, preparing them for further enzymatic action in the small intestine. In contrast, digestion of carbohydrates and lipids is limited in the stomach. Salivary , which begins breakdown in the , becomes inactivated upon exposure to the acidic gastric environment, halting until pancreatic acts in the . Similarly, digestion proceeds minimally via gastric , secreted by chief cells, which hydrolyzes a small portion of triglycerides into diglycerides and free fatty acids, primarily affecting short- and medium-chain fats; the majority of breakdown occurs later in the . Beyond nutrient breakdown, the stomach's acidic milieu provides a critical defense against pathogens. The low of gastric juice, typically below 3, kills or inhibits the growth of many ingested and microbes, serving as a first line of protection against foodborne infections by disrupting microbial cell membranes and metabolic processes. Through these chemical processes, aided briefly by mechanical mixing, the stomach transforms the ingested bolus into —a viscous, semi-liquid of partially digested particles suspended in gastric secretions. This is then released incrementally through the pyloric into the for continued and absorption.

Absorption

The stomach plays a limited role in and substance absorption, functioning primarily as a reservoir and initial processing site rather than a major uptake organ, with the handling the bulk of absorption. The gastric , characterized by its tight junctions and coating, serves as a selective barrier that permits only passive of certain small, lipophilic molecules while preventing broader permeation to maintain mucosal integrity against the acidic lumen. Among the primary absorptions in the stomach is (alcohol), which undergoes passive across the mucosa into the portal bloodstream, accounting for approximately 20-30% of ingested alcohol before the remainder passes to the for faster uptake. This gastric absorption is enhanced on an empty stomach but slowed by , which delays emptying and reduces exposure. Similarly, aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) are rapidly absorbed via passive in the acidic gastric environment, where their non-ionized form predominates, facilitating quick systemic effects but risking local irritation. Minor passive of and electrolytes also occurs, though it represents a negligible fraction of total balance compared to intestinal reabsorption. The stomach absorbs limited from partial lipid breakdown by gastric , but long-chain require further processing downstream. The stomach contributes indirectly to vitamin B12 absorption by secreting from parietal cells, a that binds dietary B12 in the acidic lumen, protecting it from degradation and enabling ileal uptake via ; deficiency in , as in , severely impairs B12 absorption. In contrast, there is no significant gastric absorption of carbohydrates or proteins, as these require enzymatic breakdown into absorbable monomers primarily in the . The emphasis on barrier function underscores the stomach's protective role, with bicarbonate-rich preventing back-diffusion of protons and luminal contents while limiting entry.

Regulation

The regulation of stomach functions, including , , and emptying, is primarily governed by neural and hormonal mechanisms that integrate sensory inputs from the , local enteric reflexes, and enteroendocrine signaling. Neural control operates through three main phases: the cephalic phase, initiated by the sight, smell, or thought of food via vagal efferents that stimulate ; the gastric phase, involving local reflexes triggered by stomach distension and chemical stimuli; and the intestinal phase, featuring enterogastric inhibition to prevent overload of the . These neural pathways ensure coordinated responses, with the playing a central role in transmitting cephalic signals and modulating local reflexes through the . Hormonal regulation complements neural inputs, with key peptides released from enteroendocrine cells in the stomach and . , secreted by G cells in the gastric antrum in response to protein breakdown products and distension, potently stimulates from parietal cells and enhances gastric motility. In contrast, from D cells inhibits release and acid , acting as a paracrine . , produced by P cells in the gastric fundus, promotes hunger signaling and stimulates acid and gastric emptying via vagal pathways. Cholecystokinin (CCK), released by duodenal I cells in response to fats, inhibits gastric emptying by relaxing the proximal stomach and contracting the , thereby slowing nutrient delivery to the intestine. Delayed gastric emptying, such as that induced by high-fat or large-volume meals through mechanisms like CCK, can prolong gastric distension and vigorous mixing contractions, potentially leading to prolonged sensations of an unsettled or jiggly stomach due to mechanical sloshing of semi-liquid gastric contents, particularly after a heavy breakfast following overnight fasting. Gastric secretion occurs in overlapping phases that contribute variably to total acid output: the cephalic phase accounts for approximately 20-30%, driven by anticipatory vagal ; the gastric phase contributes 60-70%, via direct luminal and distension stimuli; and the intestinal phase adds about 10%, primarily through modulatory hormones like CCK and . Feedback loops maintain , with distension receptors in the gastric wall detecting food volume to trigger local reflexes and release, promoting further and . pH-sensing mechanisms in the antrum and activate somatostatin release when acidity rises, inhibiting further acid production to protect the mucosa. These loops, integrated via neural and hormonal signals, prevent excessive and coordinate with downstream intestinal capacity.

Clinical aspects

Disorders

The stomach is susceptible to a range of disorders, broadly categorized into inflammatory, neoplastic, and functional conditions, each with distinct etiologies and clinical implications. Inflammatory disorders, such as gastritis and peptic ulcers, represent the most common pathologies affecting gastric mucosa integrity. Gastritis involves inflammation of the stomach lining and can be acute or chronic; chronic gastritis is frequently associated with Helicobacter pylori infection, which has a global prevalence of approximately 43% in adults based on recent meta-analyses. H. pylori-related gastritis often leads to atrophic changes over time, increasing susceptibility to further complications. Peptic ulcer disease, encompassing both gastric and duodenal ulcers, is predominantly linked to H. pylori infection and nonsteroidal anti-inflammatory drug (NSAID) use; globally, its prevalence reached about 8 million cases in 2019, with a noted increase from prior decades. Recent advancements include FDA-approved vonoprazan-based regimens in 2024 for H. pylori eradication, offering higher success rates in bismuth quadruple therapy. These ulcers result from an imbalance between protective mucosal factors and aggressive elements like acid and pepsin, often manifesting as abdominal pain, bleeding, or perforation. Neoplastic disorders of the stomach primarily include gastric adenocarcinoma and lymphomas, posing significant burdens. Gastric adenocarcinoma, the predominant form of , accounted for 968,784 new cases worldwide in 2022 (GLOBOCAN estimates), with key risk factors including H. pylori , dietary habits high in salted or smoked foods, and . Recent advances include the 2024 approval of for CLDN18.2-positive advanced cases, enhancing targeted treatment options. This malignancy typically arises from chronic progressing through , , and invasive , exhibiting geographic variations with higher incidence in and . Gastric lymphomas, particularly mucosa-associated lymphoid tissue (MALT) lymphomas, constitute about 5% of all gastric neoplasms and are the most common extranodal lymphomas in the stomach; many are H. pylori-associated, where drives lymphoproliferation. Functional disorders, such as dyspepsia and , involve impaired gastric function without structural abnormalities. Functional dyspepsia, characterized by epigastric pain or discomfort without evidence of organic disease, has a global prevalence of approximately 7% according to recent studies using Rome IV criteria, varying by region and diagnostic standards. refers to delayed gastric emptying due to dysfunction, often linked to diabetes mellitus; in diabetic patients, its prevalence is estimated at 9.3%, with higher rates in due to affecting gastric nerves. The 2025 AGA guideline recommends erythromycin and metoclopramide for symptom management, with emerging therapies like relamorelin under investigation. These conditions contribute to symptoms like , , and early , impacting . Recent epidemiological shifts highlight rising cases of non-H. pylori gastritis attributed to NSAIDs, which induce reactive changes in the independently of , with studies noting an increase in such NSAID-associated lesions amid widespread use. Furthermore, post-2020 research has elucidated the gut microbiome's role in gastric cancer , where —beyond H. pylori—promotes , immune evasion, and oncogenesis through microbial metabolites and interactions with host cells. For severe cases of these disorders, such as advanced ulcers or neoplasms, surgical interventions like partial may be considered to alleviate complications.

Surgical procedures

Surgical procedures on the stomach are primarily indicated for treating benign and malignant conditions, such as peptic ulcers and gastric cancer, as well as severe . These interventions aim to remove diseased tissue, restore gastrointestinal continuity, or alter stomach anatomy to improve function and alleviate symptoms. Common approaches include open, laparoscopic, or robotic techniques, with the choice depending on the extent of disease and patient factors. Gastrectomy involves partial or total removal of the stomach. Partial , often performed for distal gastric tumors or complicated ulcers, excises the affected portion while preserving proximal stomach function. Reconstruction typically follows via (gastroduodenostomy, reconnecting the stomach remnant to the ) or (gastrojejunostomy, connecting to the ), with preferred when feasible to maintain physiologic flow and reduce reflux risks. Total gastrectomy is reserved for diffuse gastric cancer or extensive disease requiring complete stomach removal, followed by esophageal-jejunal anastomosis to restore continuity; it carries higher risks of nutritional deficiencies but offers curative potential in advanced cases. Bariatric surgeries modify stomach anatomy to promote in morbid . removes approximately 80% of the stomach along the greater curvature, creating a tubular remnant that limits capacity and reduces production, leading to sustained appetite suppression and 50-70% excess . Roux-en-Y gastric bypass creates a small proximal gastric pouch (20-30 mL) and reroutes the to bypass the distal stomach and proximal , restricting intake and while achieving 60-70% excess and high rates of remission. Pyloroplasty widens the pyloric sphincter to enhance gastric emptying in cases of stenosis or obstruction. The Heineke-Mikulicz technique involves a longitudinal incision through the closed transversely, increasing outlet diameter; it is often combined with for ulcer disease and achieves approximately 90% success in symptom resolution. In refractory , laparoscopic pyloroplasty improves gastric retention scores and normalizes emptying in over 60% of patients. Endoscopic procedures offer minimally invasive options for early gastric lesions. Polypectomy removes benign polyps via snare techniques, while endoscopic mucosal resection (EMR) or submucosal dissection (ESD) targets superficial cancers, achieving en bloc resection rates of 92% for lesions up to 20 mm with EMR and higher for ESD in larger ones. Ablation methods, such as argon plasma coagulation, eradicate intramucosal lesions in unfit patients, often in 1-2 sessions. Complications from these surgeries include , affecting 20-50% of patients post-gastrectomy or bypass, characterized by early (10-30 minutes post-meal) vasomotor symptoms from rapid transit and late (1-3 hours) hypoglycemic episodes. (1-5%) and (5-10%) are notable risks in endoscopic resections, managed endoscopically in most cases.

Diagnostic approaches

Upper gastrointestinal (GI) endoscopy, also known as esophagogastroduodenoscopy (EGD), is a primary diagnostic method for evaluating the stomach, allowing direct visualization of the mucosal lining and enabling biopsy collection for histopathological analysis. This procedure is particularly effective for detecting conditions such as peptic ulcers and Helicobacter pylori infection, where biopsies can confirm the presence of the bacterium through histological examination or rapid urease testing. Performed under sedation, EGD involves inserting a flexible endoscope through the mouth to examine the esophagus, stomach, and duodenum, providing real-time imaging and therapeutic capabilities if needed. Imaging techniques complement endoscopy by offering non-invasive assessment of stomach structure and function. A barium swallow, or upper series, involves ingesting a contrast solution followed by to outline the , stomach, and , helping identify abnormalities like strictures or issues. Computed tomography (CT) and (MRI) are utilized for detecting masses, tumors, or perforations in the stomach, with CT providing detailed cross-sectional views enhanced by contrast agents to evaluate wall thickness and surrounding tissues. serves as an initial screening tool for assessing gastric and wall abnormalities, particularly in cases of suspected , though it is limited by operator dependence and acoustic shadowing from air. Laboratory and functional tests provide targeted evaluation of specific stomach pathologies. The is a non-invasive method to detect H. pylori , involving ingestion of labeled with or ; the bacterium's enzyme breaks it down, releasing detectable labeled in exhaled breath, with exceeding 95%. analysis, performed via nasogastric aspiration, measures basal and stimulated acid secretion to diagnose conditions like Zollinger-Ellison syndrome or , involving collection of gastric juice over an hour after or pentagastrin stimulation. Manometry assesses gastric emptying and motility by recording intraluminal pressure changes via a , aiding in the of delayed emptying disorders like . Recent advancements have enhanced diagnostic precision and accessibility. Capsule endoscopy employs a swallowable camera-equipped pill to capture images of the stomach and , useful for patients unable to undergo traditional , though it is less effective for therapeutic interventions. (AI)-assisted , with developments since 2022, improves detection accuracy for gastric lesions and H. pylori-related changes by analyzing endoscopic images in real-time; recent 2024 meta-analyses show pooled sensitivity of 89-94% and specificity of 92% for early gastric cancer identification. These AI systems reduce interobserver variability and increase adenoma detection rates by up to 30% in clinical trials.

Etymology and comparative anatomy

Etymology

The word stomach derives from the late 14th century stomak, borrowed from estomac, which in turn comes from Latin stomachus meaning ", , or ." This Latin term originated from stómachos (στόμαχος), denoting "" or "," ultimately tracing back to stóma (στόμα), meaning "." The application to the digestive organ reflects its conceptual link to the mouth as the entry point for food, emphasizing the organ's role in initial processing. A related Greek term, gastḗr (γαστήρ), meaning "belly" or "paunch," forms the basis for modern anatomical adjectives like gastric, coined in the 1650s from Modern Latin gastricus. This root, distinct from stómachos but equally tied to abdominal concepts, influenced scientific nomenclature for stomach-related structures and functions, such as gastritis or gastroenterology, highlighting the belly as a site of nourishment and digestion. In , the stomach's naming and conceptualization evolved from metaphorical views, with Hippocratic texts and later portraying it as a "cooking vessel" where ingested food is heated and "concocted" into by innate bodily warmth, akin to boiling in a pot. This analogy underscored the organ's transformative role, bridging early physiological ideas to more precise anatomical descriptions by the , when standardized terminology solidified without major alterations. The English adoption via retained this core meaning through the medieval period, stabilizing post-19th century amid advances in medical anatomy.

Variations in other animals

In vertebrates, the stomach originates from a simple primitive gut tube during embryonic development, which undergoes regionalization to form distinct digestive compartments adapted to dietary needs. This foundational structure evolves into more complex forms in advanced lineages, with increased compartmentalization in mammals to facilitate specialized digestion of plant-based or protein-rich diets. Among mammals, ruminants such as and sheep possess a four-chambered stomach consisting of the , , , and , enabling of fibrous plant material by symbiotic microbes. The and serve as fermentation vats where and break down into volatile fatty acids, while the absorbs water and electrolytes, and the functions as the glandular "true" stomach secreting acid and enzymes. This multi-compartmented design is a key in herbivores, allowing efficient nutrient extraction from recalcitrant vegetation; for instance, non-ruminant herbivores like horses rely on hindgut fermentation but exhibit simpler foregut structures. In contrast, carnivores like cats and dogs have a simple, single-chambered stomach that is highly acidic ( 1-2) to rapidly lyse proteins in meat-based diets and minimize survival. Cetaceans, such as whales, display a multi-chambered stomach inherited from their ancestors, with three to four compartments including a muscular forestomach for initial storage and grinding, followed by glandular regions for enzymatic . This configuration prolongs digesta retention, enhancing microbial and enzymatic breakdown of large, infrequent meals, and supports adaptations for by allowing prey storage during prolonged submergence. In non-mammalian vertebrates, stomach morphology diverges further from the mammalian model. Birds have a specialized two-part stomach consisting of the proventriculus, a glandular anterior chamber that secretes and pepsinogen for chemical , and the (ventriculus), a muscular posterior organ that grinds food mechanically using ingested grit. This division optimizes processing of , , and other varied diets in a lightweight, flight-adapted body. In , the stomach is often simple and J-shaped or absent in some , integrated with a short intestine that may include a valvular spiral structure to increase absorptive surface area without elongating the gut. Carnivorous , for example, have extensible stomachs for bolus prey, while herbivorous or omnivorous emphasize intestinal valves for nutrient uptake from or . Recent metagenomic studies have illuminated the microbiome's role in stomach chambers, revealing distinct microbial communities across compartments that drive efficiency. In yaks, for instance, metagenomes show enriched fiber-degrading like Fibrobacter under high-forage diets, influencing host and growth. Similarly, analyses of buffalo digestive tracts highlight spatial variations in and between and , with protozoal populations modulating production and nutrient flow post-2020. These findings underscore evolutionary fine-tuning of microbial ecosystems for dietary adaptation in multi-chambered stomachs.

References

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