Earth wormI (Megascolex )-DIGESTIVE SYSTEM

Digestive System The digestive system is formed of alimentary canal and digestive glands. Alimentary Canal The alimentary canal is a straight tube. It starts from the mouth. The mouth is located at the anterior end of the peristomium. It leads into the buccal cavity. The buccal cavity is located in the first two segments. The buccal cavity leads into a thick walled muscular chamber called pharynx. It lies in the segments three and four. The pharynx leads into a short tube called oesophagus. It lies in the 5"' segment. The oesophagus leads into a hard thick walled muscular sac called gizzard. It is located in the e segment. The gizzard is followed by the intes-tine. It is long and straight and it extends upto the anal segment. The dorsal wall of the intestine has a fold which projects into the lumen of the intestine. It is called typhlosole. It increases the area of absorption. The intestine opens to the outside by the anus located at the posterior end of the anal segment. Digestive Glands Earthworm has two types of digestive glands. They are the following:

1. Pharyngeal gland : It lies around the pharynx and it opens into the pharynx by small ducts. It secretes a proteolytie enzyme.

2. Intestinal gland : These are found in the wall of the intestine. They secrete proteolytic, lipolytic and amylolytic enzymes. Feeding Earthworm feeds on the dead organic mat-ter ofthe soil. It swallows large amount of soil. Digestion Digestion in earthworm is intercellular and intracellular. Intercellular digestion takes place in the intestine. Intracellular digestion takes place in the epithelial cells of the intestine. Absorption Absorption takes place in the posterior part of the intestine. The typhlosole increases the area of absorption.

Feeding Earthworm is a detritus feeder. Earth-worm feeds on the dead organic matter of the soil. It swallows large amount of soil. Digestion Digestion in earthworm is intercellular and intracellular. Intercellular digestion takes place in the intestine. Intracellular digestion takes place in the epithelial cells of the intestine. Absorption Absorption takes place in the posterior part of the intestine. The typhlosole increases the area of absorption. Egestion The undigested material and the soil are collected at the posterior part of the intestine. They are passed out through the anus in the form of worm castings.

Egestion The undigested material and the soil are collected at the posterior part of the intestine. They are passed out through the anus in the form of worm castings.