Mention briefly about the circulatory system of earthworm

Earthworm exhibits a closed type of blood vascular system. This type of blood vascular system consists of blood vessels, capillaries and heart. Due to closed circulatory system, blood is confined to the heart and blood vessels. Contractions of the body keep blood circulating in one direction. Smaller blood vessels supply the gut, nerve cord, and the body wall. Blood glands are present on the4th, 5th and 6th segments. They produce blood cells and haemoglobin, which is dissolved in blood plasma. Blood cells are phagocytic in nature. Earthworms lack specialised breathing devices. Respiratory exchange occurs through the moist body surface directly into the blood stream.