The right side of the heart contains the right atrium and right ventricle . This side pumps blood to the lungs to be refreshed with oxygen. The left side of the heart contains the left atrium and left ventricle . This side pumps oxygen-rich blood to the body. The right and left sides of the heart are divided by a wall called the septum .
Blood is pumped through the chambers with the help of four heart valves.
The valves open and close to let the blood flow in only one direction. The mitral valve has two flaps. All the others have three flaps. This diagram shows the four heart valves in a closed position. Click here to continue.