Earthworms have a closed circulatory system. Three main vessels supply the blood to the earthworm’s internal organs. These are the aortic arches, dorsal blood vessels, and ventral blood vessels. There are 5 pairs of aortic arches whose function are similar to that of the human heart. The aortic arches pump blood into the dorsal and ventral blood vessels. The dorsal vessels pump blood towards the front part of the worm’s body whereas the ventral blood vessels carry blood to the back of the earthworm’s body.