Heart Valves

The heart valves regulate the direction of blood flow.

The atrioventricular (AV) valves open to allow blood flow from the atria to the ventricles; when the ventricles contract, the AV valves close to prevent backflow. The tricuspid and mitral valves are the atrioventricular valves.

Simultaneously, ventricular contraction forces the semilunar valves open, allowing for blood ejection. When contraction finishes, the semilunar valves shut to prevent backflow from the arteries. The semilunar valves are the pulmonic and the aortic valves.