When a person puts food in his mouth, then teeth cut it into small pieces, chew and grind it. The glands A in the mouth secrete a substance B which is mixed with the food by tongue. The substance B contains an enzyme C which starts the digestion of food in the mouth. The slightly digested food from the mouth goes down a tube D. The special type of movements E in the walls of tube D push the food into stomach for further digestion. The stomach wall secretes gastric juice containing three substance F, G and H. One of the functions of F is to kill bacteria which may enter the stomach with food. The substance G protects the inside layer of stomach from the damaging effect of substance F whereas substance H is an enzyme for digestion. The partially digested food then enters into small intestine for further digestion.
(a) What is (i) gland A
(ii) substance B, and (iii) enzyme C?
(b) Name the tube D.
(c) What is the movement E known as?
(d) What are (i) F (ii) G, and (iii) H?
(a) (i) Salivary glands (A) present in the mouth and secrete saliva.
(ii) Salivary glands(A) secrete saliva (B) which contains an enzyme called salivary amylase (C).
(b) D is Oesophagus. Oesophagus is a long, thin and muscular tube that connects the throat (pharynx) to the stomach.
(c) Peristaltic movement (E) is a wave of contraction and expansion which occurs in the alimentary canal and helps to push the food forward.
(d) (i) Hydrochloric acid (ii) Mucus (iii) Enzyme pepsin
The stomach wall secretes gastric juice which contains three substances: Hydrochloric acid (F), the enzyme pepsin (G) and mucus (H).