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Atrioventricular Valves

The atrioventricular (AV) valves separate the atria from the ventricles. They prevent blood from flowing backward into the atria when the ventricles contract. The right atrioventricular valve is the tricuspid valve, while the left atrioventricular valve is the mitral, or bicuspid, valve.

The cusps of the AV valves are attached to strong strands of connective tissue called the chordae tendineae. These tendinous cords connect the valve cusps to the papillary muscles, which project from the walls of the ventricles. The chordae tendineae consist mainly of collagen fibers with smaller amounts of elastic tissue and are covered by endocardium.

When the ventricles contract, pressure within the chambers rises sharply. At the same time, the papillary muscles also contract, tightening the chordae tendineae and preventing the valve cusps from being pushed back into the atria. This mechanism prevents regurgitation of blood during ventricular contraction.

The tricuspid valve is located between the right atrium and the right ventricle. It consists of three cusps and allows deoxygenated blood to pass from the right atrium into the right ventricle.

The cusps are connected to the papillary muscles of the right ventricle by the chordae tendineae. During ventricular contraction, these muscles stabilize the valve and prevent blood from flowing backward into the right atrium.

The mitral valve lies between the left atrium and the left ventricle. Unlike the tricuspid valve, it possesses only two cusps and is therefore also known as the bicuspid valve.

The cusps are anchored by chordae tendineae to two papillary muscles, the anterior and posterior papillary muscles of the left ventricle. Because the left ventricle generates much greater pressure than the right ventricle, the mitral valve and its supporting structures must withstand stronger forces during ventricular contraction.