Alimentary Canals of Earthworm

 In the earthworm and most other animals, the alimentary canal is a tube with two openings: the mouth through which food enters and the anus through which undigested food leaves the body. With food moving only in one direction, it is possible for different parts of the alimentary canal to become specialized and do different functions in succession.

     The alimentary canal of the earthworm is a long straight tube with the following parts

 • A mouth and a thin walled buccal cavity for food to be ingested;

 • A muscular thick walled pharynx which secretes mucus to lubricate food particles; 

• A narrow tubular thin walled oesophagus;

 • A thin walled crop for storing food;

 • A thick walled muscular gizzard where food is ground against the small stones to break it up; and

 • A long straight intestine in which extracellular digestion occurs.

    An earthworm feeds mainly on the vegetable matter found in the soil it swallows as it burrows. The divested food diffuses through the intestinal wall into the surrounding blood capillaries. The blood then transports the food to all parts of the body.