title: [The muscular atrioventricular septum].
abstract: On the left ventricle septal wall, the tricuspid valve ring attachment is displaced forward, towards the cardiac apex. To this trapezoïdal area between the two atrio-ventricular annuli, the medial wall of the right atrium is attached (laminar attachment), resulting in a atrio-ventricular septum which is: --membranous at its superior extremity (membranous atrio-ventricular septum well described in all classical anatomy textbooks); --and muscular at its inferior extremity. Located in the inferior anterior portion of the Koch triangle, the muscular atrio-ventricular septum is roughly triangular in shape. Its superior and anterior borders are well delineated and represented by: --the pars muscularis crest, at its junction with the membranous atrio-ventricular septum; --and the insertion of the tricuspid septal leaflet on this pars muscularis of the inter-ventricular septum. On the contrary, its third border, the posterior inferior left, is not well defined and varies greatly with the amount of fat filling the crux of the heart. The atrio-ventricular septum separates the right atrium from the base of the left ventricle outflow tract. It shares the important relationship of the "carrefour" of the four cardiac chambers (7 - 8) and first of all the conduction system and its vascular supply. The concept of an atrio-ventricular septum, both muscular and membranous, is to be kept in mind for the good understanding and the surgical correction of different types of "common atrio-ventricular canal" (2 - 10).
mesh_terms: D006346:Heart Septum / Q000033:anatomy & histology*; D006351:Heart Valves / Q000033:anatomy & histology; D006352:Heart Ventricles / Q000033:anatomy & histology; D006801:Humans; D012850:Sinus of Valsalva / Q000033:anatomy & histology
vernacular_title: Le septum atrio-ventriculaire musculaire (pars muscularis septi atrioventricularis).