Role and function of the stomach – the stomach homogenises swallowed food through peristaltic movement, the hydrochloric acid it produces reduces the number of bacteria, and in the acidic environment pepsin begins to digest proteins.
Some nutrients are absorbed as early as in the stomach, before reaching the intestine.
We distinguish the following three phases of digestion:
- cephalic (brain) phase: the sight and taste of food stimulate the vagus nerve, which increases saliva secretion in the mouth and acid secretion in the stomach;
- gastric (stomach) phase: stretching of the stomach and stimulation of the vagus nerve trigger the release of gastrin, which leads to further secretion of stomach acid; this favours the conversion of pepsinogen into pepsin and thus the digestion of protein;
- intestinal (bowel) phase: mainly as a result of hydrochloric acid, hormones formed in the lining of the duodenum and the small intestine (mainly the jejunum) reduce the release of gastrin, thereby reducing acid secretion.
