Human Pump

Blood is the essential transport system of the body. It carries oxygen from the lungs to the cells and takes away carbon dioxide, it supplies food to all parts of the body and takes away waste for excretion by the kidneys; it transports the chemical messengers, our hormones, and the body's defender, the white blood cells and the antibodies. Pumping the blood round this system in less than a minute, is the work of the heart. The heart is a special kind of muscle, unique in the body. Tough fibers and flaps within the heart make valves, which ensure the blood never flows backwards against the immense pressures the heart creates.