Organ system: The digestive system
The stomach is an organ of digestion in the gastrointestinal tract.
Acid production
Specialised cells known as parietal cells are able to actively transport protons from the cell cytoplasm out into canaliculi to form a strong acid. This diffuses into the gastric lumen. These cells can produce an acid with a pH as low as 0.8, but this is diluted to reach a normal pH of between 1.0 and 3.0. Acid has two major functions in the stomach:- Denaturation of proteins
- Destruction of any swallowed pathogens or toxins
Enzyme production
Gastric chief cells produce a pro-enzyme called pepsinogen. This is a precursor to a powerful protease enzyme called pepsin. Pepsinogen is activated by the highly acidic environment in the gastric lumen. It is capable of catalysing the breakdown of proteins (long chains of amino acids) into peptides (short chains of amino acids).Intrinsic factor production
Parietal cells also produce a glycoprotein called intrinsic factor. This binds to vitamin B12 to facilitate absorption into the body. The IF-B12 complex is absorbed by cells in the ileum later in the gastrointestinal tract. B12 is an essential nutrient which allows DNA synthesis. Blood cells are rapidly produced in the body and so these cell lines require a rapid rate of DNA synthesis. B12 deficiency is often detected as impaired production of new functional blood cells. |
| Simplified representation of the stomach |
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