Digestion of food occurs in following ways in:
(i) Mouth (Buccal cavity) The mouth contains teeth, which crushes the food into small particles. Salivary glands present in the mouth secretes saliva which moistens the food. It also contains enzyme salivary amylase, that acts as
(ii) Stomach Gastric glands are present in the wall of the stomach which releases the following secretions:
(a) Hydrochloric acid To make the medium acidic for the action of enzyme pepsin.
(b) Mucus To protect the inner lining of the stomach from the action of acid.
(c) Pepsin A protein digesting enzyme.
(iii) Small intestine It is the site of complete digestion of carbohydrates, proteins and fats.
It receives secretions from liver and pancreas.
(a) Bile juice It is secreted by liver and performs the following functions :
It makes the medium alkaline for the pancreatic enzymes to act and also breaks down large fat globules into smaller globules.
(b) Pancreatic juice It is secreted by pancreas. Contains enzymes like amylase for digesting starch, trypsin for digesting proteins and lipase for breaking down emulsified fats.
(c) Intestinal juice It is secreted by the walls of small intestine. Contains a number of enzymes such as maltase, lipase etc., for complete digestion.