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The stomach is a muscular, hollow organ in the
gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...
of humans and many other animals, including several
invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chorda ...
s. The stomach has a dilated structure and functions as a vital organ in the
digestive system The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller compone ...
. The stomach is involved in the gastric phase of digestion, following chewing. It performs a chemical breakdown by means of enzymes and hydrochloric acid. In humans and many other animals, the stomach is located between the
oesophagus The esophagus ( American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to ...
and the
small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...
. The stomach secretes digestive enzymes and
gastric acid Gastric acid, gastric juice, or stomach acid is a digestive fluid formed within the stomach lining. With a pH between 1 and 3, gastric acid plays a key role in digestion of proteins by activating digestive enzymes, which together break down the ...
to aid in food digestion. The pyloric sphincter controls the passage of partially digested food (
chyme Chyme or chymus (; from Greek χυμός ''khymos'', "juice") is the semi-fluid mass of partly digested food that is expelled by a person's stomach, through the pyloric valve, into the duodenumduodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...
, where
peristalsis Peristalsis ( , ) is a radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. Peristalsis is progression of coordinated contraction of involuntary circular muscles, whi ...
takes over to move this through the rest of intestines.


Structure

In the human digestive system, the stomach lies between the
oesophagus The esophagus ( American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to ...
and the
duodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...
(the first part of the
small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...
). It is in the
left upper quadrant The human abdomen is divided into quadrants and regions by anatomists and physicians for the purposes of study, diagnosis, and treatment. The division into four quadrants allows the localisation of pain and tenderness, scars, lumps, and other ...
of the
abdominal cavity The abdominal cavity is a large body cavity in humans and many other animals that contains many organs. It is a part of the abdominopelvic cavity. It is located below the thoracic cavity, and above the pelvic cavity. Its dome-shaped roof is th ...
. The top of the stomach lies against the
diaphragm Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...
. Lying behind the stomach is the
pancreas The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e. it has both an ...
. A large double fold of visceral
peritoneum The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mes ...
called the greater omentum hangs down from the greater curvature of the stomach. Two sphincters keep the contents of the stomach contained; the lower oesophageal sphincter (found in the cardiac region), at the junction of the oesophagus and stomach, and the pyloric sphincter at the junction of the stomach with the duodenum. The stomach is surrounded by
parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of ...
(stimulant) and sympathetic (inhibitor) plexuses (networks of
blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide awa ...
s and
nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the ...
s in the
anterior Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Th ...
gastric, posterior,
superior Superior may refer to: *Superior (hierarchy), something which is higher in a hierarchical structure of any kind Places *Superior (proposed U.S. state), an unsuccessful proposal for the Upper Peninsula of Michigan to form a separate state *Lake ...
and inferior, 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. 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.


Sections

In classical anatomy the human stomach is divided into four sections, beginning at the cardia. * The ''cardia'' is where the contents of the oesophagus empty into the stomach. * The ''fundus'' () is formed in the upper curved part. * The ''body'' is the main, central region of the stomach. * The '' pylorus'' () is the lower section of the stomach that empties contents into the
duodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...
. The cardia is defined as the region following the "z-line" of the gastroesophageal junction, the point at which the
epithelium Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...
changes from stratified squamous to columnar. Near the cardia is the lower oesophageal sphincter. Research has shown that the cardia is not an anatomically distinct region of the stomach but a region of the oesophageal lining damaged by reflux.


Anatomical proximity

The stomach bed refers to the structures upon which the stomach rests in mammals. These include the tail of the pancreas, splenic artery, left
kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blo ...
, left
suprarenal gland The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex which ...
, transverse colon and its
mesocolon The mesentery is an organ that attaches the intestines to the posterior abdominal wall in humans and is formed by the double fold of peritoneum. It helps in storing fat and allowing blood vessels, lymphatics, and nerves to supply the intestin ...
, and the
left crus of diaphragm The crus of diaphragm (pl. crura), refers to one of two tendinous structures that extends below the diaphragm to the vertebral column. There is a right crus and a left crus, which together form a tether for muscular contraction. They take their ...
, and the
left colic flexure In the anatomy of the human digestive tract, there are two colic flexures, or curvatures in the transverse colon. The right colic flexure is also known as the hepatic flexure, and the left colic flexure is also known as the splenic flexure. Note ...
. 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.


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
mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It i ...
,
submucosa The submucosa (or tela submucosa) is a thin layer of tissue in various organs of the gastrointestinal, respiratory, and genitourinary tracts. It is the layer of dense irregular connective tissue that supports the mucosa (mucous membrane) and j ...
, muscularis externa,
subserosa The subserosa or tela subserosa, is a thin layer of tissue in the walls of various organs. It is a layer of connective tissue (usually of the areolar type) between the muscular layer (muscularis externa) and the serosa ( serous membrane). The ...
and serosa. The inner part of the lining of the stomach, the
gastric mucosa The gastric mucosa is the mucous membrane layer of the stomach, which contains the glands and the gastric pits. In humans, it is about 1 mm thick, and its surface is smooth, soft, and velvety. It consists of simple columnar epithelium, lamin ...
, consists of an outer layer of column-shaped cells, a
lamina propria The lamina propria is a thin layer of connective tissue that forms part of the moist linings known as mucous membranes or mucosae, which line various tubes in the body, such as the respiratory tract, the gastrointestinal tract, and the urogenit ...
, and a thin layer of
smooth muscle Smooth muscle is an involuntary non- striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit ...
called the muscularis mucosa. Beneath the mucosa lies the
submucosa The submucosa (or tela submucosa) is a thin layer of tissue in various organs of the gastrointestinal, respiratory, and genitourinary tracts. It is the layer of dense irregular connective tissue that supports the mucosa (mucous membrane) and j ...
, consisting of
fibrous connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tissue is ...
.
Meissner's plexus The submucosal plexus (Meissner's plexus, plexus of the submucosa, plexus submucosus) lies in the submucosa of the intestinal wall. The nerves of this plexus are derived from the myenteric plexus which itself is derived from the plexuses of parasy ...
is in this layer interior to the oblique muscle layer. Outside of the submucosa lies another muscular layer, the muscularis externa. 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. The presence of the inner oblique layer is distinct from other parts of the gastrointestinal tract, which do not possess this layer. Stomach contains the thickest muscularis 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 human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller compone ...
. 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 Chyme or chymus (; from Greek χυμός ''khymos'', "juice") is the semi-fluid mass of partly digested food that is expelled by a person's stomach, through the pyloric valve, into the duodenumduodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...
. This layer is concentric to the longitudinal axis of the stomach. *
Auerbach's plexus The myenteric plexus (or Auerbach's plexus) provides motor innervation to both layers of the muscular layer of the gut, having both parasympathetic and sympathetic input (although present ganglion cell bodies belong to parasympathetic innervation ...
(myenteric plexus) is found between the outer longitudinal and the middle circular layer and is responsible for the innervation of both (causing
peristalsis Peristalsis ( , ) is a radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. Peristalsis is progression of coordinated contraction of involuntary circular muscles, whi ...
and 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 serosa, consisting of layers of connective tissue continuous with the
peritoneum The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mes ...
.


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. Gastric juice is an acidic fluid containing
hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the dige ...
and the digestive enzyme pepsin. The glands contains a number of cells, with the function of the glands changing depending on their position within the stomach. 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 Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It ...
and
bicarbonate In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial biochemi ...
. Additional cells present include parietal cells that secrete hydrochloric acid and intrinsic factor, chief cells that secrete
pepsinogen Pepsin is an endopeptidase that breaks down proteins into smaller peptides. It is produced in the gastric chief cells of the stomach lining and is one of the main digestive enzymes in the digestive systems of humans and many other animals, ...
(this is a precursor to pepsin- the highly acidic environment converts the pepsinogen to pepsin), and neuroendocrine cells that secrete
serotonin Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and va ...
. Glands differ where the stomach meets the esophagus and near the pylorus. Near the junction between the stomach and the oesophagus lie ''cardiac glands'', which primarily secrete mucus. 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 with short ducts or compound racemose resembling the duodenal Brunner's glands. Near the pylorus lie ''pyloric glands'' located in the antrum of the pylorus. They secrete mucus, as well as
gastrin Gastrin is a peptide hormone that stimulates secretion of gastric acid (HCl) by the parietal cells of the stomach and aids in gastric motility. It is released by G cells in the pyloric antrum of the stomach, duodenum, and the pancreas. Gast ...
produced by their G cells.


Gene and protein expression

About 20,000
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
coding genes are expressed in human cells and nearly 70% of these genes are expressed in the normal stomach. 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 GKN1, expressed in the mucosa; pepsinogen PGC and the lipase LIPF, expressed in chief cells; and gastric ATPase ATP4A and gastric intrinsic factor GIF, expressed in parietal cells.


Development

In early human embryogenesis, the ventral part of the
embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
abuts the
yolk sac The yolk sac is a membranous wikt:sac, sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac' ...
. During the third week of development, as the embryo grows, it begins to surround parts of the sac. The enveloped portions form the basis for the adult gastrointestinal tract. 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 In human anatomy, the inferior mesenteric artery, often abbreviated as IMA, is the third main branch of the abdominal aorta and arises at the level of L3, supplying the large intestine from the distal transverse colon to the upper part of the a ...
. The areas supplied by these arteries are used to define the
foregut The foregut is the anterior part of the alimentary canal, from the mouth to the duodenum at the entrance of the bile duct. Beyond the stomach, the foregut is attached to the abdominal walls by mesentery. The foregut arises from the endoderm, devel ...
, midgut, and
hindgut The hindgut (or epigaster) is the posterior ( caudal) part of the alimentary canal. In mammals, it includes the distal one third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon and up to the ano-rectal ju ...
. 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.


Function


Digestion

In the human digestive system, a bolus (a small rounded mass of chewed up food) enters the stomach through the
esophagus The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to t ...
via the lower esophageal sphincter. The stomach releases proteases (protein-digesting
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
s such as pepsin) and
hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the dige ...
, which kills or inhibits
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
and provides the acidic pH of 2 for the
protease A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the ...
s to work. Food is churned by the stomach through muscular contractions of the wall called
peristalsis Peristalsis ( , ) is a radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. Peristalsis is progression of coordinated contraction of involuntary circular muscles, whi ...
– reducing the volume of the bolus, before looping around the fundus and the body of stomach as the boluses are converted into
chyme Chyme or chymus (; from Greek χυμός ''khymos'', "juice") is the semi-fluid mass of partly digested food that is expelled by a person's stomach, through the pyloric valve, into the duodenumpyloric sphincter and into the
duodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...
of the
small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...
, where the extraction of nutrients begins. Gastric juice in the stomach also contains
pepsinogen Pepsin is an endopeptidase that breaks down proteins into smaller peptides. It is produced in the gastric chief cells of the stomach lining and is one of the main digestive enzymes in the digestive systems of humans and many other animals, ...
.
Hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the dige ...
activates this inactive form of enzyme into the active form, pepsin. Pepsin breaks down proteins into polypeptides.


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 Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat inc ...
*
Amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...
* 10–20% of ingested
ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...
(e.g. from alcoholic beverages) *
Caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine chemical classification, class. It is mainly recreational drug use, used recreationally as a Nootropic, cognitive enhancer, increasing alertness and attentional perfor ...
* To a small extent water-soluble
vitamin A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrie ...
s (most are absorbed in the small intestine) 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 cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "hol ...
s, and the functioning of the
nervous system In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes ...
.


Control of secretion and motility

Chyme from the stomach is slowly released into the
duodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...
through coordinated
peristalsis Peristalsis ( , ) is a radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. Peristalsis is progression of coordinated contraction of involuntary circular muscles, whi ...
and opening of the pyloric sphincter. The movement and the flow of chemicals into the stomach are controlled by both the
autonomic nervous system The autonomic nervous system (ANS), formerly referred to as the vegetative nervous system, is a division of the peripheral nervous system that supplies internal organs, smooth muscle and glands. The autonomic nervous system is a control system t ...
and by the various digestive hormones of the digestive system: Other than gastrin, these hormones all act to turn off the stomach action. This is in response to food products in the
liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it i ...
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 Epidermal growth factor (EGF) is a protein that stimulates cell growth and differentiation by binding to its receptor, EGFR. Human EGF is 6-k Da and has 53 amino acid residues and three intramolecular disulfide bonds. EGF was originally de ...
(EGF) results in cellular proliferation, differentiation, and survival. 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 The paired submandibular glands (historically known as submaxillary glands) are major salivary glands located beneath the floor of the mouth. They each weigh about 15 grams and contribute some 60–67% of unstimulated saliva secretion; on stimul ...
, and the parotid gland. Salivary EGF, which also seems to be regulated by dietary inorganic
iodine Iodine is a chemical element with the Symbol (chemistry), symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , ...
, also plays an important physiological role in the maintenance of oro-oesophageal 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. ;Stomach as nutrition sensor The human stomach can "taste"
sodium glutamate Monosodium glutamate (MSG), also known as sodium glutamate, is the sodium salt of glutamic acid. MSG is found naturally in some foods including tomatoes and cheese in this glutamic acid form. MSG is used in cooking as a flavor enhancer w ...
using glutamate receptors and this information is passed to the lateral hypothalamus and
limbic system The limbic system, also known as the paleomammalian cortex, is a set of brain structures located on both sides of the thalamus, immediately beneath the medial temporal lobe of the cerebrum primarily in the forebrain.Schacter, Daniel L. 2012. ''P ...
in the
brain A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...
as a
palatability Palatability (or palatableness) is the hedonic reward (i.e., pleasure Pleasure refers to experience that feels good, that involves the enjoyment of something. It contrasts with pain or suffering, which are forms of feeling bad. It is closely ...
signal through the
vagus nerve The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and righ ...
. The stomach can also sense, independently of tongue and oral taste receptors,
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
,
carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may o ...
s,
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
s, and fats. This allows the brain to link
nutritional Nutrition is the biochemical and physiological process by which an organism uses food to support its life. It provides organisms with nutrients, which can be metabolized to create energy and chemical structures. Failure to obtain sufficient nu ...
value of foods to their tastes. ;Thyrogastric syndrome This syndrome defines the association between thyroid disease and chronic gastritis, which was first described in the 1960s. 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. In 1993, a more complete investigation on the stomach and thyroid was published, 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.


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 An upper gastrointestinal series, also called a barium swallow, barium study, or barium meal, is a series of radiographs used to examine the gastrointestinal tract for abnormalities. A contrast medium, usually a radiocontrast agent such as bar ...
. Another method of examination of the stomach, is the use of an
endoscope An endoscope is an inspection instrument composed of image sensor, optical lens, light source and mechanical device, which is used to look deep into the body by way of openings such as the mouth or anus. A typical endoscope applies several modern t ...
. A
gastric emptying scan A gastric emptying scan is a nuclear medicine study which provides an assessment of the stomach's ability to empty. It may be used if there are complications after gastric surgery, for gastric reflux, or suspected gastroparesis amongst other indic ...
is considered the gold standard to assess gastric emptying rate. 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 Stomach cancer, also known as gastric cancer, is a cancer that develops from the lining of the stomach. Most cases of stomach cancers are gastric carcinomas, which can be divided into a number of subtypes, including gastric adenocarcinomas. Ly ...
. A stomach rumble is actually noise from the intestines.


Surgery

In humans, many
bariatric surgery Bariatric surgery (or weight loss surgery) includes a variety of procedures performed on people who are obese. Long term weight loss through the standard of care procedures ( Roux en-Y bypass, sleeve gastrectomy, and biliopancreatic diversio ...
procedures involve the stomach, in order to lose weight. A
gastric band A laparoscopic adjustable gastric band, commonly called a lap-band, A band, or LAGB, is an inflatable silicone device placed around the top portion of the stomach to treat obesity, intended to decrease food consumption. Adjustable 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 A gastrectomy is a partial or total surgical removal of the stomach. Indications Gastrectomies are performed to treat stomach cancer and perforations of the stomach wall. In severe duodenal ulcers it may be necessary to remove the lower porti ...
, 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 The heart is a muscular Organ (biology), organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as ca ...
. 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).


History

There were previously conflicting statements in the academic anatomy community over whether the cardia is part of the stomach, part of the oesophagus 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."Barrett KE (2006
"Chapter 7. Esophageal Motility"
in ''Gastrointestinal Physiology''. Lange Medical Books/McGraw-Hill.


Etymology

The word ''stomach'' is derived from the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
' which has roots from the Greek word ''stomachos'' (), ultimately from ''stoma'' (), "mouth". ''Gastro-'' and ''gastric'' (meaning "related to the stomach") are both derived from the Greek word ''gaster'' (, meaning "belly").


Other animals

Although the precise shape and size of the stomach varies widely among different vertebrates, the relative positions of the oesophageal 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,
chimaera Chimaeras are cartilaginous fish in the order Chimaeriformes , known informally as ghost sharks, rat fish, spookfish, or rabbit fish; the last three names are not to be confused with rattails, Opisthoproctidae, or Siganidae, respectively. At ...
s,
lungfish Lungfish are freshwater vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, i ...
es, and some
teleost Teleostei (; Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts ), is, by far, the largest infraclass in the class Actinopterygii, the ray-finned fishes, containing 96% of all extant species of fish. Tele ...
fish have no stomach at all, with the oesophagus opening directly into the intestine. These animals all consume diets that require little storage of food, no predigestion with gastric juices, or both. 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
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...
s, 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 oesophagus. Ruminants, in particular, have a complex stomach, the first three chambers of which are all lined with oesophageal mucosa. In
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s and
crocodilian Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period (Cenomanian stage) and are the closest livin ...
s, 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 A crop is a plant that can be grown and harvested extensively for profit or subsistence. When the plants of the same kind are cultivated at one place on a large scale, it is called a crop. Most crops are cultivated in agriculture or hydropon ...
. 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. In
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
s there is also a crop. The insect stomach is called the midgut. Information about the stomach in
echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the ...
s or
mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000  extant species of molluscs are recognized. The number of fossil species is est ...
s can be found under the respective articles.


Additional images

File:Greater omentum 2.jpg, Greater omentum and stomach of humans Image:Gray532.png, 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. File:An open stomach.jpg, An autopsy of a human stomach, showing the many folds () of the stomach. 2012 Instituto Nacional de Cardiología File:Slide15ffff.JPG, Human stomach File:3D Medical Animation Stomach Structure.jpg, High-quality image of the stomach


See also

* Gastroesophageal reflux disease * Human gastrointestinal microbiota * Proton-pump inhibitor


References


External links


Stomach at the Human Protein Atlas

"Stomach" article from the Encyclopedia of Nursing & Allied Health, from enotes.com






{{Authority control Abdomen Digestive system Organs (anatomy)