There are two papillary muscles associated with the mitral valve (Fig. 3) When looking from the atrial side, the anterolateral is to the left and the posteromedial is to the right. The muscles are located under their respective commissures. They originate from the lower third of the left ventricular free wall. The papillary muscles are extensions of the ventricular muscle from which they originate. The chords originate from the fibrous tips of these muscles, extending to insert on the mitral leaflets. The blood supply of the anterolateral papillary muscle derives from the left circumflex and/or diagonal systems. The blood supply.