Posterior Leaflet of the Mitral Valve Transverse Section

Description

Seen in transverse section through the left heart, the mitral valve is opened to expose the smaller, crescent-shaped posterior leaflet (cuspis posterior valvae atrioventricularis sinistrae) along the posteroinferior margin of the left atrioventricular orifice. Anterior to it lies the larger anterior leaflet, forming the complementary semicircle that meets the posterior leaflet at the anterolateral and posteromedial commissures. Chordae tendineae descend from the free edge of the posterior leaflet to the posteromedial and anterolateral papillary muscles of the left ventricle, with the left atrium situated superior to the annulus and the left ventricular cavity inferior to it. Short leaflet. Big consequences. This plane is a workhorse for understanding why posterior leaflet pathology dominates degenerative mitral regurgitation. P2 scallop prolapse or flail from ruptured chordae typically produces an anteriorly directed regurgitant jet on echocardiography, and surgeons often target that segment with quadrangular resection, neochordae, and annuloplasty while preserving leaflet coaptation height. Commissural orientation in cross-section also helps clarify mechanisms of functional MR, where left ventricular remodeling tethers the posterior leaflet apically and restricts systolic closure, a pattern that can be missed when learners only memorize leaflet names without spatial context. Use this illustration in cardiothoracic anatomy teaching, echo correlation figures (TTE/TEE short-axis concepts), and operative planning graphics for mitral valve repair modules in residency curricula and publisher atlases. It also fits patient-education material explaining posterior leaflet prolapse, chordal rupture, and repair strategies in clear anatomic terms. Anatomical accuracy verified by SciePro's Medical Advisory Board.