There are 4 heart valves that keep the blood flowing in the proper direction through the chambers of the heart.
The valve that separates the Right Atrium from the Right Ventricle has three flaps, or cusps, and is known as the Tricuspid Valve.
The valve that separates the Left Atrium and Left Ventricle has two flaps, or cusps, and is called the Mitral (Bicuspid) Valve.
Both valves are forced shut as the pressure in the ventricles increase, and
prevents the flow of blood back into the Atria when the ventricles are contracting.
Both the Tricuspid and Mitral Valves are commonly called the Atrioventricular
valves. The flaps of these Atrioventricular valves are attached to the papillary
muscles (extensions of the heart muscle) of the ventricles by the chordae
tendineae.
There are two valves that prevent blood returning to the ventricle after they have completed their contractions. These valves are often called semilunar valves (half moon).
These valves are the Pulmonary Valve, which is located at the opening where the Pulmonary Artery leaves the Right ventricle, and the Aortic Valve, which is located at the opening between the Left Ventricle and the Aorta.
Both these valves have 3 cusps and each cusp looks like a shallow cup that has been cut in half vertically. When the ventricles contract the blood pushes the cusps against the vessel (Pulmonary Artery or Aorta) walls. When the ventricle relaxes the blood flows back into the cusps and causes them to meet in the middle, preventing the backflow of blood.
Last Updated: October 2003
Last Reviewed: November 2003
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