[TA] the ventrally placed and larger of the two leaflets that come together during ventricular systole to close the left atrioventricular orifice; it attaches to the septal aspect of the orifice. SYN: cuspis anterior valvae atrioventricularis sinistrae [TA], anterior cusp of left atrioventricular valve*, cuspis anterior valvae mitralis*.