Rag worms have a closed circulatory system. They are able to circulate the required nutrients, blood, and gases, through a series of closed vessels (dorsal and ventral vessels). The dorsal vessel allows blood to circulate to the front sections of the creature's body. The ventral blood vessel allows the blood to circulate behind the back of the body. The body supplies the body wall and the intestine with blood. The ventral vessel consists of several branches. The branches split into capillary beds to receive and release the nutrients and oxygen supplied through the vessels.