Posterior leaflet of left atrioventricular valve

At a glance

English

Posterior leaflet of left atrioventricular valve

Latin (TA2)

Cuspis posterior valvae atrioventricularis sinistrae

System

Heart

Region

Trunk

Side

Single, on the midline

About the posterior leaflet of left atrioventricular valve

The left atrioventricular valve, the mitral valve, has two leaflets, anterior and posterior, that guard the opening from the left atrium into the left ventricle. The posterior leaflet hangs from the posterior and lateral part of the fibrous ring and wraps around roughly two-thirds of its circumference, while the anterior leaflet takes the remaining third next to the aortic valve.

Although its base is long, the posterior leaflet is short from base to free edge, so the two leaflets cover a similar area. Its edge usually carries two small clefts that divide it into three scallops, named P1, P2 and P3 from the lateral (anterolateral) end to the medial (posteromedial) end; the matching opposite zones of the anterior leaflet are A1 to A3. The two leaflets meet at the anterolateral and posteromedial commissures. The surface facing the atrium is smooth; the ventricular surface and the free margin receive chordae tendineae, as does a rough zone near the edge where the leaflets meet.

The cords come from the two papillary muscles of the left ventricle. The anterolateral muscle sends cords to the lateral halves of both leaflets and the posteromedial muscle to the medial halves. When the ventricle contracts the papillary muscles tighten the cords, so the leaflets meet firmly and are not pushed back into the atrium.

The posterior leaflet is the part most often affected in mitral valve prolapse, usually at the middle scallop, P2, where a cord may lengthen or tear and let the leaflet flail into the atrium. It is also the leaflet most often repaired, by cutting out the loose segment and reshaping the ring. Calcium deposits in the ring commonly build up beneath this leaflet in older people. The circumflex artery and coronary sinus run close to its base.

Function and supply

Begins at

The posterior and lateral part of the left fibrous ring of the mitral orifice.

Ends at

Its free edge and ventricular surface are held by chordae tendineae from the anterolateral and posteromedial papillary muscles of the left ventricle.

Function

Meets the anterior leaflet during systole to stop blood flowing back into the left atrium; opens in diastole to let the left ventricle fill.