Gastric acid and pepsin secretion

Gastric juice contains a very high concentration of hydrochloric acid (pH 1) and pepsin. The physiological role of gastric acid is probably to facilitate digestion by reducing the size of certain food particles and also to prevent gastric colonization by micro-organisms. Acid secretion takes place in the parietal cells located in the deep part of the gastric glands in the body and the fundus of the stomach. Pepsin is secreted by the chief cells located in the same area. Acid secretion is regulated by nervous (vagal) and humoral (gastrin) mechanisms (O„lbe.§nd...H.§g.!yDd 1986). Pepsin secretion is less well studied than acid secretion. However, both seem to be regulated by very similar mechanisms. Gastrin is produced by the G cells in the gastric antrum. There are gastrins of different sizes: G17 (containing 17 amino acids) is dominant in the gastric mucosa while G34 predominates in serum. Gastrin secretion is reduced when the antral mucosa becomes acidic and is stimulated by a neutral antral environment. The expectation and swallowing of food and the presence of food in the stomach constitute the strongest biological stimulating mechanisms for acid and pepsin secretion. There is a very complex interaction between stimulating and inhibiting nervous and humoral factors regulating acid secretion.

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