The heart has four separate chambers that pump blood: the right atrium, right ventricle, left atrium and left ventricle. As blood leaves each chamber, it passes through a valve, which prevents the backward flow of blood. These valves are thin membranes attached to the heart wall, which open and close as the heart muscle contracts and relaxes, allowing blood to flow through the heart. This opening and closing is what causes the heartbeat sound.
The four valves of the heart, in order of circulation, are: Tricuspid, Pulmonary, Mitral and Aortic.
Here is a step-by-step description of how the valves function normally:
- When the left ventricle relaxes, the aortic valve closes and the mitral valve opens, to allow blood to flow from the left atrium into the left ventricle.
- The left atrium contracts, allowing even more blood to flow into the left ventricle.
- When the left ventricle contracts again, the mitral valve closes and the aortic valve opens, so blood flows into the aorta.
A normal, healthy heart valve lets blood flow smoothly and freely in one direction. It closes completely and doesn't allow any blood to flow back through the valve.