The mitral is a dual-flap valve in the heart that lies between the left atrium (LA) and the left ventricle (LV). During diastole, a normally-functioning mitral valve opens as a result of increased pressure from the left atrium as it fills with blood. As atrial pressure increases above that of the left ventricle, the mitral valve opens. Opening facilitates the passive flow of blood into the left ventricle. Diastole ends with atrial contraction. The mitral valve closes at the end of atrial contraction to prevent a reversal of blood flow.
The mitral valve has two cusps, or leaflets, that guard the opening. The opening is surrounded by a fibrous ring known as the mitral valve annulus. The orientation of the two leaflets resembles a bishop‘s miter, whence the valve receives its name. These valve leaflets are prevented from prolapsing into the left atrium by the action of tendons attached to the posterior surface of the valve, chordae tendineae.
The inelastic chordae tendineae are attached at one end to the papillary muscles and the other to the valve cusps. Papillary muscles are fingerlike projections from the wall of the left ventricle. Chordae tendineae from each muscle are attached to both leaflets of the mitral valve. Thus, when the left ventricle contracts, the intraventricular pressure forces the valve to close, while the tendons keep the leaflets coapting together and prevent the valve from opening in the wrong direction, thus preventing blood to flow back to the left atrium.