Cells of the inner layer of the walls of the stomach secrete gastric juice, which includes mucus, hydrochloric acid, and enzymes that digest food. Hydrochloric acid kills harmful microorganisms, promotes the digestion process. Under the action of the enzyme of gastric juice (pepsin), protein molecules break down into simpler compounds. The inner wall of the stomach has numerous folds that increase the surface of the mucous membrane secreting gastric juice.
The middle layer of the wall of the stomach is formed by smooth muscle tissue. Co-contracting and relaxing, the muscles mix its contents with gastric juice. This contributes to better digestion of food.
The outer layer consists of the peritoneum – outgrowths of the inner wall of the abdominal cavity, which cover the stomach and fix its position.
Food is in the stomach for 3 to 6 hours. It turns into a semi-liquid gruel, which gradually, in portions, enters the intestines.
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