Stomach Anatomy Of The Human Stomach Histology Of The Human

In ruminants, the stomach is a large multichambered organ that hosts symbiotic bacteria which produce enzymes required for the digestion of cellulose from plantGreen algae land plants (embryophytes non-vascular embryophytes Hepatophyta liverworts Anthocerophyta hornworts Bryophyta mosses vascular plants (tracheophytes seedless vascular plants Lycopodiophyta clubmosses Equisetophyta horsetails Pteridophyta "true" matter. The partially digested plant matter passes through each of the stomach's chambers in sequence, being regurgitated and rechewed at least once in the process.

1 Anatomy of the human stomach

The stomach lies between the esophagusThe esophagus oe/oesophagus , or gullet is the muscular tube in vertebrates through which ingested food passes from the mouth area to the stomach. Food is passed through the esophagus by using the process of peristalsis. Specifically, in mammals, it conne and the first part of the small intestineIn biology the small intestine is the part of the gastrointestinal tract between the stomach and the large intestine. In humans over 5 years old it is about 7m long. It is divided into three structural parts: duodenum, jejunum and ileum . Food from the st (the duodenumIn anatomy of the digestive system, the duodenum is a hollow jointed tube that connects the stomach to the jejunum. It is the first part of the small intestine, and is about 18 cm (7 in) long. It starts with the duodenal bulb and ends at the ligament of T). It is on the left side of the abdominal cavityThe abdominal cavity is the cavity of the human body (and other animal bodies) that holds the bulk of the viscera and which is located below (or posterior to) the thoracic cavity. Organs of the abdominal cavity include the liver, gallbladder, spleen, panc, the fundus of the stomach lying against the diaphragmIn the anatomy of mammals, the diaphragm is a shelf of muscle extending across the bottom of the ribcage. Its latin name is the transversus thoracis''. It separates the thoracic cavity (with lung and heart) from the abdominal cavity (with liver, stomach,. Lying beneath the stomach is the pancreasThe pancreas is a retroperitoneal organ that serves two functions: exocrine it produces pancreatic juice containing digestive enzymes endocrine it produces several important hormones Anatomy The pancreas is a retroperitoneal organ located posterior to the, and the greater omentum hangs from the greater curvature.

It is divided into five sections, each of which have different cells and functions...

2 Histology of the human stomach

Like the other parts of the gastrointestinal system, the stomach walls are made of a number of layers.

Starting inside the stomach (the lumen) going out, the first main layer is the mucosa. This consists of an epithelium, the lamina propria underneath, and a thin bit of smooth muscle called the muscularis mucosa.

The submucosa lies under this and consists of fibrous connective tissue, it separates the mucosa from the next layer, the muscularis externa. The muscularis in the stomach differs from other GI organs in that it has three layers of muscle instead of two. Under these muscle layers is the adventitia, layers of connective tissue continuous with the omenta.

The epithelium of the stomach forms deep pits. Different types of cells are at different locations down the pits. The cells at the base of these pits are chief cell s, responsible for production of pepsinogen, an inactive precursor for pepsin, which degrades proteins. The secretion of pepsinogen prevents self-digestion of the stomach cells.

Further up the pits, parietal cells produce hydrochloric acid (HCl), which kills most of the bacteria in food, stimulates hunger, and activates pepsinogen into pepsin. Near the top of the pits, closest to the contents of the stomach, there are mucus producing cells that help protect the stomach from self-digestion.

The muscularis externa, as previously mentioned, is made up of three layers of smooth muscle. The innermost layer is obliquely orientated, this is not seen in other parts of the digestive system, this layer is responsible for creating the motion that churns and physically breaks down the food. The next muscle layers are the circular and then the longituditinal, which are present as in other parts of the GI tract. The antrum has thicker muscle in its walls and performs more forceful contractions than the fundus. 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.

3 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 various digestive system hormones.

The hormone gastrin causes increased 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 to distenstion of the antrum, and digestive products. It is inhibited by a low pH (high acid), as well as the hormone somatostatin.

Cholecystokinin (CCK) has most effect on the gall bladder, but it also decreases gastric emptying. Similarly secretin, produced in the small intestine, has most effects on the pancreas, but will also diminish acid secretion in the stomach. Gastric inhibitory peptide (GIP) and enteroglucagon decrease 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 intestines, which have not yet been absorbed. The stomach only needs to push food into the small intestine when the intestine isn't busy. While the intestine is full and still digesting food, the stomach acts as a storage hopper for food.

This pattern is also present in the nervous control of the stomach.

4 diseases

5 See also

Digestive system

Mouth - Pharynx - Esophagus - Stomach - Pancreas - Gallbladder - Liver - Small intestine ( duodenum, jejunum, ileum) - Colon - Cecum - Rectum - Anus

Digestive system

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