The cells in the mucosa layer of the stomach that secrete digestive juices are called gastric glands. There are three types of gastric glands. Fundic gland, cardiac gland and pyloric gland. 500-1000 ml of gastric juice is secreted from the stomach every time we eat. Gastric glands are:
(i) Peptic or chief cells: pepsinogen, renin, gelatinase, lipase etc. are secreted from peptic or chief cells.
(ii) Parietal or oxyntic cells: Parietal or oxyntic cells secrete intrinsic factor and HCl.
(iii) Mucous Glands: Mucin is secreted from mucous glands.
(iv) G-cells or Gastrin cells: G-cells secrete gastrin juice.
(v) Gastric gland: Gastric gland secretes gastrin juice.
(vi) Argentaphin cells: It secretes hormones and absorbs vitamin B12. It releases serotonin.
(vii) Mucous Cell or Goblet Cell: It secretes mucus.
Gastric juice
The juice secreted from G-cells, peptic cells, goblet cells, parietal cells, mucous cells etc. of stomach is called gastric juice. Deficiency of vitamin E12 in gastric juice is called pernicious anemia.
Three stages of gastric juice secretion
1. Cephalic stage: This stage begins before the food enters the stomach. At this stage, 20 percent of gastric juice is secreted.
2. Gastric phase: The gastric phase is the time when food settles in the stomach. At this stage, 70 percent of gastric juice is secreted for digestion.
3. Intestinal Phase: When food enters the small intestine from the stomach, the intestinal phase begins. At this stage very little amount of gastric juice is secreted.
Constituents of gastric juice
(i) Water: Gastric juice contains 99.45% water.
(ii) Organic components: Gastric juice contains pepsin, renin, lipase, mucin, intrinsic factor etc.
(iii) Inorganic components: Gastric juice contains sodium chloride, potassium chloride, calcium chloride, calcium phosphate, magnesium phosphate etc.