The mitral valve has an anterior and a posterior cusp. The anterior cusp is larger and is attached on the upper right part of the margin of the left AV orifice. The posterior cusp is attached to the lower left part. The anterior cusp intervenes between the Mitral and Aortic orifices. There is, therefore, a forceful blood flow on both surfaces of this cusp. The papillary muscles connected to the cusp of the mitral valve are also called the anterior and posterior. These terms are misleading. The anterior papillary muscle arises from the sterno-costal wall of the ventricle near the lower end. The posterior papillary muscle arises from the diaphragmatic wall near its anterior end. The two muscles run backwards almost parallel to each other and their origins are close together. The chordae tendinae arising from these papillary muscles pass to the adjoining part of the two cusps of the mitral valve.
The mitral valve closes during ventricular contraction (systole) and thus prevents blood from flowing back into the left atrium.The papillary muscles and chordae prevent the valve cusps from prolapsing into the left atrium during systole.All components of the valve apparatus are essential for the proper functioning of the mitral valve.