Write names of different parts of human digestive system and explain functions of any three parts.
(1) The digestive system of human beings consists of an alimentary canal and the associated digestive glands.
Alimentary canal: The human alimentary canal begins with the mouth and ends in the anus. It is a long muscular tube of varying diameter consisting of oesophagus, stomach, small intestine and large intestine. Associated digestive glands: The digestive glands associated with the alimentary canal are salivary glands and gastric glands.
(1) Mouth: In the mouth, there are teeth which masticate the food and convert the larger particles of food into smaller ones. The tongue helps in tasting the food and rolling it into a soft ball. There are salivary glands in the mouth which secrete saliva.
(2) Oesophagus: The oesophagus is a narrow tube carrying food to the stomach. Due to peristalsis, the food is pushed forward in the alimentary canal.
(3) Stomach: The stomach is a J-shaped muscular organ situated on the left side of the abdomen. Muscles of the stomach also undergo peristalsis and push the food forward. In the stomach, the food is mixed thoroughly with the gastric juice secreted by the gastric glands present in the stomach wall. There is a sphincter muscle at the lower end of the stomach. This sphincter muscle releases the partially digested food into the small intestine.