The mitral valve is a one-way piston valve between the left atrium and the left ventricle. Generally, once the ventricle completes a contraction and ejects blood, it immediately begins to relax, at which time the mitral valve opens to allow blood from the atrium into the left ventricle. When the mitral valve is severely narrowed, the blood from the atrium cannot pass through the mitral valve into the left ventricle in a timely manner. At this time, the blood flow speed at the mitral orifice increases, forming turbulence, which results in the appearance of diastolic murmurs.