Stomach

Infobox Anatomy
Name = Stomach
Latin = Ventriculus
Greek = Gaster
GraySubject = 247
GrayPage = 1161

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Caption = The location of the stomach in the body.


Caption2=Diagram from [http://training.seer.cancer.gov/ss_module07_ugi/unit02_sec02_anatomy.html 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
Precursor =
System = |pqp35ykyj 4oh
Artery =
Vein =
Nerve = celiac ganglia, vagus [GeorgiaPhysiology|6/6ch2/s6ch2_30]
Lymph = celiac preaortic lymph nodes [NormanAnatomy|stomach]
MeshName = Stomach
MeshNumber = A03.556.875.875
DorlandsPre = g_03
DorlandsSuf = 12386049
In human anatomy, the stomach is a J-shaped hollow muscular organ of the gastrointestinal tract involved in the second phase of digestion, following mastication. The word "stomach" is derived from the Latin "stomachus" ["stomach, throat," also "pride, inclination, indignation" (which were thought to have their origin in that organ) [http://www.etymonline.com/index.php?search=stomach&searchmode=none] Online Etymological Dictionary] , which derives from the Greek word "stomachos" (polytonic|στόμαχος). The words "gastro-" and "gastric" (meaning related to the stomach) are both derived from the Greek word "gaster" (polytonic|γαστήρ).

For information about the stomach of cows, for example, lookup ruminants.

Functions

The stomach is a highly acidic environment due to hydrochloric acid production and secretion which produces a luminal pH range usually between 1 and 2 depending on the species, food intake, time of the day, drug use, and other factors. Combined with digestive enzymes, such an environment is able to break down large molecules (such as from food) to smaller ones so that they can eventually be absorbed from the small intestine. A zymogen called pepsinogen is secreted by chief cells and turns into pepsin under low pH conditions and is a necessity in protein digestion. [cite book
last = Maton
first = Anthea
authorlink =
coauthors = Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright
title = Human Biology and Health
publisher = Prentice Hall
date = 1993
location = Englewood Cliffs, New Jersey, USA
pages =
url =
doi =
id =
isbn = 0-13-981176-1
oclc = 32308337]

The human stomach can produce and secrete about 2.2 to 3 liters of gastric acid per day with basal secretion levels being typically highest in the evening. The stomach can expand to hold between 2-4 liters of food. It is a temporary food storage area, and in the process of digestion, the food goes into the stomach first.

Absorption of vitamin B12 from the small intestine is dependent on conjugation to a glycoprotein called intrinsic factor which is produced by parietal cells of the stomach.

Other functions include absorbing some ions, water, and some lipid soluble compounds such as alcohol, aspirin, and caffeine.

Anatomy of the human stomach

The stomach lies between the esophagus and the duodenum (the first part of the small intestine). It is on the left side of the abdominal cavity. The top of the stomach lies against the diaphragm. Lying beneath the stomach is the pancreas, and the greater omentum which hangs 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 (anterior gastric, posterior, superior and inferior, celiac and myenteric), which regulate both the secretory activity and the motor activity of the muscles.

In humans, the stomach has a relaxed volume of about 45 ml, it generally expands to hold about 1 liter of food, [cite book |author=Sherwood, Lauralee |title=Human physiology: from cells to systems |publisher=Wadsworth Pub. Co |location=Belmont, CA |year=1997 |pages= |isbn=0314092455 |oclc= 35270048|doi=] but can hold as much as 4 liters.

ections

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

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

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:

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.

Diseases of the stomach

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 stomach ulcers, gastritis, and stomach cancer are caused by "Helicobacter pylori" infection.

References

External links

* [http://www.med.uiuc.edu/m1/biochemistry/TA%20reviews/sam/AminoAcids.htm Digestion of proteins in the stomach]
* [http://uk.geocities.com/bacterial_ed/bacteria_and_food.htm Site with details of how ruminants process food]
* [http://www.comedycentral.com/motherload/index.jhtml?ml_video=83957 Interview with Dr. Jerome Groopman, Highlight at 2:30]