Your heart is a muscle that works like a pump. The right side receives blood from the body and pumps it to the lungs.The left side receives blood from the lungs and pumps it out to the rest of your body.

A heart is made up of several different parts. There are four chambers — two on each side of the heart. Two chambers, called the left atrium and right atrium, fill with the blood returning to the heart from the body and lungs. The two other chambers, the left ventricle and right ventricle, release blood to the body and lungs.

Valves within the heart make sure blood travels in the right direction. The four valves are called mitral, tricuspid, aortic and pulmonary.

The blood circulating through your body travels through tubes known as arteries and veins, which together are called blood vessels. Arteries carry the blood away from the heart and veins carry blood back to the heart.

It's important that blood circulates through the entire body because it provides oxygen needed for blood cells, which keep us alive.