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Mitral valve

From Academic Kids

The mitral valve is a valve in the heart that lies between the left atrium (LA) and the left ventricle (LV). The mitral valve and the tricuspid valve are known as the atrioventricular valves, because they lie between the atria and the ventricles of the heart.

Contents

Overview

A normally functioning mitral valve allows blood to flow into the left ventricle during ventricular diastole, and prevent blood from going retrograde from the ventricle to the left atrium during systole.

Anatomy

The mitral valve is made up of two valve leaflets (the anteromedial leaflet and the posterolateral leaflet) and a ring around the valve, known as the mitral valve annulus. (The orientation of the two leaflets resembles a bishop's miter, which is where the valve receives its name.) These valve leaflets are prevented from prolapsing into the left atrium by the subvalvular aparatus.

The subvalvular aparatus, which lies completely in the LV, is made up of the papillary muscles and the chordae tendineae. The anteromedial papillary muscle and the posteromedial papillary muscle each attach to the walls of the LV. They are attached to their respective leaflets of the mitral valve by the chordae tendineae.

Normal physiology

During left ventricular diastole, after the pressure drops in the left ventricle due to relaxation of the ventricular myocardium, the mitral valve opens, and blood travels from the left atrium to the left ventricle. About 70-80% of the blood that travels across the mitral valve occurs during the early filling phase of the left ventricle. This early filling phase is due to active relaxation of the ventricular myocardium, causing a pressure gradient that allows a rapid flow of blood from the left atrium, across the mitral valve. This early filling across the mitral valve is seen on doppler echocardiography of the mitral valve as the E wave.

After the E wave, there is a period of slow filling of the ventricle.

Left atrial contraction (left atrial systole) (during left ventricular diastole) causes added blood to flow across the mitral valve immediately before left ventricular systole. This late flow across the open mitral valve is seen on doppler echocardiography of the mitral valve as the A wave. The late filling of the LV contributes about 20% to the volume in the left ventricle prior to ventricular systole, and is known as the atrial kick.

Related topics

External links


Cardiovascular system - Heart Edit (http://en.wikipedia.org/w/wiki.phtml?title=MediaWiki:Heart&action=edit)

Pericardium - Epicardium - Myocardium - Endocardium - Cardiac pacemaker - Sinoatrial node - Atrioventricular node - Bundle of His - Purkinje fibers - Heart valves

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