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Anatomy of the Heart: Valves

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What are heart valves?

Valves are flap-like structures that allow blood to flow in one direction. The heart has two kinds of valves, atrioventricular and semilunar valves.

Atrioventricular Valves

The atrioventricular valves are thin structures that are composed of endocardium and connective tissue. They are located between the atria and the ventricles.

Semilunar Valves

The semilunar valves are flaps of endocardium and connective tissue reinforced by fibers which prevent the valves from turning inside out. They are shaped like a half moon, hence the name semilunar (semi-, -lunar).

The semilunar valves are located between the aorta and the left ventricle and between the pulmonary artery and the right ventricle.

Heart Sounds

The audible sounds that can be heard from the heart are made by the closing of the heart valves. These sounds are referred to as the "lub-dupp" sounds. The "lub" sound is made by the contraction of the ventricles and the closing of the atrioventricular valves. The "dupp" sound is made by the semilunar valves closing.

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