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Stomach
	The location of the stomach in the human body.
	Diagram from cancer.gov:; * 1. Body of stomach; * 2. Fundus; * 3. Anterior wall; * 4. Greater curvature; * 5. Lesser curvature; * 6. Cardia; * 9. Pyloric sphincter; * 10. Pyloric antrum; * 11. Pyloric canal; * 12. Angular notch; * 13. Gastric canal; * 14. Rugal folds; ; Work of the United States Government
Latin	Ventriculus
Gray's	subject #247 1161
Nerve	celiac ganglia, vagus
Lymph	celiac preaortic lymph nodes
MeSH	Stomach
Dorlands/Elsevier	Stomach

In most mammals, the stomach is a hollow, muscular organ of the gastrointestinal tract (digestive system), between the esophagus and the small intestine. It is involved in the second phase of digestion, following mastication (chewing). The word stomach is derived from the Latin stomachus which is derived from the Greek word stomachos which is derived from the word gastro- and gastric (meaning related to the stomach) are both derived from the Greek word gaster (γαστήρ). The stomach churns food before it moves on to the rest of the body.

This article is primarily about the human stomach, though the information about its processes are directly applicable to most mammals.^[3] A notable exception to this is cows. For information about the stomach of cows, buffalo and similar mammals, see ruminants.

[edit] Anatomy of the Stomach

The stomach lies between the esophagus (food and liquid throat tube) and the duodenum (the first part of the small intestine). It is on the left upper part of the abdominal cavity. The top of the stomach lies against the diaphragm. Lying behind the stomach is the pancreas. The greater omentum hangs down from the greater curvature.

Two smooth muscle valves, or sphincters, keep the contents of the stomach contained. They are the esophageal sphincter (found in the cardiac region) dividing the tract above, and the Pyloric sphincter dividing the stomach from the small intestine.

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

In humans, the stomach has a relaxed, near empty volume of about 45 ml. It normally expands to hold about 1 litre of food,^[4] but will hold as much as 1.5 litres.

In the fundus, an interesting phenomenon occurs during digestion. The food will loop around in the fundus after entering the stomach. This occurence is also known as the "Magical Looping". This only occurs at times when the parasympathic nervous system takes over control of the GI-tract.

[edit] Sections

The stomach is divided into four sections, each of which has different cells and functions. The sections are:

Cardia	Where the contents of the esophagus empty into the stomach.
Fundus	Formed by the upper curvature of the organ.
Corpus Body	The main, central region.
Pylorus or antrum	The lower section of the organ that facilitates emptying the contents into the small intestine.

[edit] Blood supply

Blood supply to the stomach: left and right gastric artery, left and right gastro-omental artery and short gastric artery.^[5]

The lesser curvature of the 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, are supplied by the short gastric artery.

Like the other parts of the gastrointestinal tract, the stomach walls are made of the following layers, from inside to outside:

mucosa	The first main layer. This consists of an epithelium, the lamina propria composed of loose connective tissue and which has gastric glands in it underneath, and a thin layer of smooth muscle called the muscularis mucosae.
submucosa	This layer lies over the mucosa and consists of fibrous connective tissue, separating the mucosa from the next layer. The Meissner's plexus is in this layer.
muscularis externa	Over the submucosa, the muscularis externa in the stomach differs from that of other GI organs in that it has three layers of smooth muscle instead of two. 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. 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. outer longitudinal layer: Auerbach's plexus is found between this layer and the middle circular layer.
serosa	This layer is over the muscularis externa, consisting of layers of connective tissue continuous with the peritoneum.

Cross section of stomach wall.

Microscopic cross section of the pyloric part of the stomach wall.

[edit] Glands

The epithelium of the stomach forms deep pits. The glands at these locations are named for the corresponding part of the stomach:

Cardiac glands (at cardia)	Pyloric glands (at pylorus)	Fundic glands (at fundus)

Different types of cells are found at the different layers of these glands:

Layer of stomach	Name	Secretion	Region of stomach	Staining
Isthmus of gland	mucous cells	mucus gel layer	Fundic, cardiac, pyloric	Clear
Body of gland	parietal (oxyntic) cells	gastric acid and intrinsic factor	Fundic, cardiac, pyloric	Acidophilic
Base of gland	chief (zymogenic) cells	pepsinogen, rennin	Fundic only	Basophilic
Base of gland	enteroendocrine (APUD) cells	hormones gastrin, histamine, endorphins, serotonin, cholecystokinin and somatostatin	Fundic, cardiac, pyloric	-

[edit] Control of secretion and motility

The movement and the flow of chemicals into the stomach are controlled by both the autonomic nervous system and by the various digestive system hormones:

Gastrin	The hormone gastrin causes an increase in the secretion of HCl, pepsinogen and intrinsic factor from parietal cells in the stomach. It also causes increased motility in the stomach. Gastrin is released by G-cells in the stomach in response to distenstion 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.
Secretin	In a different and rare manner, secretin, produced in the small intestine, has most effects on the pancreas, but will also diminish acid secretion in the stomach.
Gastric inhibitory peptide	Gastric inhibitory peptide (GIP) decreases both gastric acid and motility.
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 only to push food into the small intestine when the intestine is not busy. While the intestine is full and still digesting food, the stomach acts as storage for food.

[edit] EGF in gastric defence

Epidermal growth factor or EGF results in cellular proliferation, differentiation, and survival.^[6] EGF is a low-molecular-weight polypeptide first purified from the mouse submandibular gland, but since then found in many human tissues including submandibular gland, parotid gland. Salivary EGF, which seems also regulated by dietary inorganic iodine, plays also 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 as well as mucosal protection from intraluminal injurious factors such as gastric acid, bile acids, pepsin, and trypsin and to physical, chemical and bacterial agents.^[7]

[edit] Diseases of the stomach

Main article: Stomach disease

Historically, it was widely believed that the highly acidic environment of the stomach would keep the stomach immune from infection. However, a large number of studies have indicated that most cases of peptic ulcers, gastritis, and stomach cancer are caused by Helicobacter pylori infection.

[edit] In other animals

Although the precise shape and size of the stomach varies widely between 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, chimaeras, lungfishes, and some teleost fish have no stomach at all, with the oesophagus opening directly into the intestine. These animals all consume diets that either require little storage of food, or no pre-digestion with gastric juices, or both.^[8]

The gastric lining is usually divided into two regions, an anterior portion lined by fundic glands, and a posterior 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 man. 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.^[8]

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.^[8]

[edit] Pictures

An endoscopy of a normal stomach of a healthy 65-year old woman.

[edit] See also

Borborygmus, growling of stomach

[edit] References

^ Physiology at MCG 6/6ch2/s6ch2_30
^ stomach at The Anatomy Lesson by Wesley Norman (Georgetown University)
^ http://www.britannica.com/EBchecked/topic/275485/human-body
^ Sherwood, Lauralee (1997). Human physiology: from cells to systems. Belmont, CA: Wadsworth Pub. Co. ISBN 0314092455. OCLC 35270048.
^ Anne M. R. Agur; Moore, Keith L. (2007). Essential Clinical Anatomy (Point (Lippincott Williams & Wilkins)). Hagerstown, MD: Lippincott Williams & Wilkins. ISBN 078176274X. OCLC 172964542. ; p. 150
^ Herbst RS (2004). "Review of epidermal growth factor receptor biology". International Journal of Radiation Oncology, Biology, Physics 59 (2 Suppl): 21–6. doi:10.1016/j.ijrobp.2003.11.041. PMID 15142631.
^ Venturi S.; Venturi M. (2009). "Iodine in evolution of salivary glands and in oral health". Nutrition and Health 20: 119–134.
^ ^a ^b ^c Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 345-349. ISBN 0-03-910284-X.

[edit] External links

Look up stomach in Wiktionary, the free dictionary.

[0] Physiology at MCG 6/6ch2/s6ch2_30

[1] stomach at The Anatomy Lesson by Wesley Norman (Georgetown University)

[2] ttp://www.britannica.com/EBchecked/topic/275485/human-body

[3] Sherwood, Lauralee (1997). Human physiology: from cells to systems. Belmont, CA: Wadsworth Pub. Co. ISBN 0314092455. OCLC 35270048.

[Moore150-4] Anne M. R. Agur; Moore, Keith L. (2007). Essential Clinical Anatomy (Point (Lippincott Williams & Wilkins)). Hagerstown, MD: Lippincott Williams & Wilkins. ISBN 078176274X. OCLC 172964542. ; p. 150

[Herbst-5] Herbst RS (2004). "Review of epidermal growth factor receptor biology". International Journal of Radiation Oncology, Biology, Physics 59 (2 Suppl): 21–6. doi:10.1016/j.ijrobp.2003.11.041. PMID 15142631.

[6] Venturi S.; Venturi M. (2009). "Iodine in evolution of salivary glands and in oral health". Nutrition and Health 20: 119–134.

[VB-7] Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 345-349. ISBN 0-03-910284-X.

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