Cardiovascular system of the earthworm
Earthworms have a closed circulatory system, in which blood is transported through a closed network of blood vessels. The three major parts of the earthworm's circulatory system include the ventral blood vessel, the dorsal blood vessel, and five pairs of aortic arches. The ventral blood vessel takes blood from the front of the worm to back, while the dorsal blood vessel takes blood from the back of the worm to the front. The aortic arches act as a kind of heart for the worm. The aortic arches are responsible for moving blood from one portion of a worm's body to another. The aortic arches connect the dorsal and ventral blood vessels. In terms of actual pumping of blood, both the dorsal blood vessel and the aortic arches pump blood. The dorsal blood vessel contracts to pump blood to the front of the worm's body. From the dorsal blood vessel, the aortic arches then pump that blood into the ventral blood vessel where it continues along to the rest of the worm's body.