Definition: Heart valves are the thin membranes connected to the walls of the heart that regulate blood flow in and out of the heart.
Example: There are four types of valves in the heart: the mitral valve, tricuspid valve, aortic valve, and pulmonary valve. The mitral and tricuspid valves control blood flow from the atria to the ventricles. The aortic and pulmonary valves control blood flow out of the ventricles. People who have damaged, congenital heart defects, or non-functioning heart valves may have it replaced with either a tissue based valve replacement or a mechanical heart valve replacement.