(iii) Renin: It converts casein of milk into paracasein (a protien)

Paracasein is further digested by pepsin.

This partial digestion of food in the stomach reduces food to a paste-like consistency, called chyme. As the acidity level of food reaches a certain level, the pyloric sphincter opens and chyme passes at intervals in brief squirts into the duodenum.

Digestion in the intestine : Here food mixes with bile, pancreatic juice and intestinal juice. In the intestine, the food is digested and absorbed completely. The acidity of food stimulates the mucosa of the duodenum to secrete the hormones secretin, pancreozymin and cholecystokinin and enterokinin. The first two activate the pancreas to secrete pancreatic juice and the third causes the gall bladder to eject bile into the intestine. Enterokinin stimulates the intestine to secrete its own intestinal juice.

Thus in the duodenum, the food is simultaneously acted upon by bile, the pancreatic and intestinal juices. Since these secretions arelkaline, the acidity of chyme is neutralized, and pepsin is inactivated.

(A) Action of bile : Bile is devoid of enzymes. It contains bile pigments and bile salts. The latter help in breaking down oil droplets into small globules, forming a milky emulsion (emulsification) to facilitate further digestion of fats.

(B) Action of pancreatic juice : Here food mixes with the following enzymes:

(i) Trypsin : It is a pancreatic protease, formed from trypsinogen. Trypsin is a pancreatic protease which acts as follows.

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