What is peristalsis ? How does it help in digestion. 

Peristalsis is the travelling wave of alternate contraction and relaxation which pass from anterior end of alimentary up to posterior end of alimantary.

Peristalsis is produced by involuntary contraction of circular muscles which is preceded by a simultaneous contraction of longitudinal muscles and relaxation of circular muscles present in gut wall.

These waves of contraction and relaxation help in properly mixing up of food with digestive enzymes for proper digestion and the movement of the food thhroguh the alimentary canal.