How does digestion take place in the stomach

The stomach stores the food for 4-5 hours.

- The food mixes thoroughly with the acidic gastric juice of the stomach by the

churning movements of its muscular wall and is called the chyme.

- The gastric juice is a mixture of mucus, hydrochloric acid and protein digesting

enzymes (Pepsinogen and pro-rennin).

- Hydrochloric acid carries out the following functions:

(i) It activates the pepsinogen into its active form pepsin and thus initiates

protein digestion.

(ii) It provides the acidic medium necessary for the action of enzymes in the

gastric juice.

- The mucus and the bicarbonates in the gastric juice protect the gastric mucosa

from the excoriation by the hydrochloric acid.

- Pepsin converts the proteins into proteoses and peptones.

- Rennin is a proteolytic enzyme present in the gastric juice of human adults and

calves; it acts on the milk proteins.

- Trace amounts of lipases are also present in the gastric juice.