Mechanisms for Pumping Blood
Figure shows the three mechanisms for pumping blood. The importance of these three mechanisms in regulating blood flow varies according to the animal. In vertebrates, heart plays a major role in circulation; in arthropods both the movement of limbs and contraction of dorsal hearts are important. In the giant earthworm peristaltic contractions of the dorsal vessel move the blood in the anterior directions and thus fill 5 pairs of lateral hearts.
Figure: Three types of pumps that move the blood in the circulatory system