ALIMENTARY CANAL OF PLANARIA

Planaria is a free-living, flat, slender and small worm. The digestive tract consists of a ventrally placed mouth, muscular pharynx and intestine. The pharynx can be protruded from the mouth when attacking a prey.

The pharynx leads into the intestine. The intestine has three main branches, one anterior and two posterior, with each giving rise to extensive lateral diverticula (branches) thus forming a gastrovascular cavity. The gastrovascular cavity (anterior and posterior intestines) is lined with phagocytic cells, glandular storage cells and gland cells.

Planarians are carnivorous in diet, feeding on small animals such as crustaceans, rotifers, nematodes and insects. They capture their prey by entangling them in mucus glands. The entangled prey is then wrapped with the body of the planarian and the pharynx is then protruded from the mouth and sucked in the small bits of the prey into the intestine.

Digestion is mostly intracellular, that is, the phagocytic cells of gastrodermal cells engulf the food and digest it. The digested food is distributed by diffusion to all parts of the body by gastrovascular cavity. The extensive branching of the gastrovascular cavity all over the body gives it a large absorptive surface area.