Heart is a pump-four pumps, in fact. Blood from all parts of the body collects in veins and flows to the right atrium and the right ventricle, the two pumps that send blood to the lungs.

Blood passes through the lungs, where it is cleansed of carbon dioxide and takes up life-sustaining oxygen. The blood then flows to the final two pumps, the left atrium and the left ventricle. The left ventricle collects newly oxygenated blood and, with a muscular push, sends it to all parts of the body.