The circulatory system transports blood throughout the body using the heart and blood vessels. The heart pumps blood into arteries which branch into smaller arterioles and capillaries where nutrients and oxygen are exchanged, then blood returns to the heart through veins. Blood contains red blood cells, white blood cells, platelets suspended in plasma which carries nutrients, waste, hormones, and antibodies. The circulatory system allows for transportation of these materials to sustain life.