Question

 Draw a labelled diagram of the human digestive system. With the help of this diagram, describe the process of digestion of food in man (humans).

Answer 1

Following is the process of digestion of food in a human being:

(i) Digestion in mouth: Digestion of food starts in the mouth. Here, the food is cut into small pieces by the teeth. The saliva produced by the salivary glands is mixed with the food by the tongue. The saliva contains the enzyme salivary amylase, which digests the starch and breaks it into sugar.

(ii) Digestion in stomach: The food then passes through the oesophagus and reaches the stomach. The walls of stomach release hydrochloric acid, mucous and the enzyme pepsin. HCl creates an acidic environment in the stomach, pepsin digests proteins and mucous prevents the stomach wall from erosion.

(iii) Digestion in small intestine: The partially digested food enters the small intestine. Small intestine receives secretions from liver and pancreas. Liver secrets bile, which helps in making the food alkaline and also breaks the fats. Pancreas secrete three enzymes, which are trypsin, amylase and lipase. Trypsin digests proteins, amylase digests starch and lipase digests fats.
 The intestinal juice secreted by small intestine completes the digestion of starch into glucose, proteins into amino acids and fats into fatty acid and glycerol.