papillary muscle

The papillary muscles are small muscular pillars that rise from the inner walls of the ventricles. Picture them as anchors at the bottom of a tent: the ropes (chordae tendineae) run up from these anchors to keep the valve flaps from blowing inward.

Each papillary muscle gives rise to the chordae tendineae that attach to the leaflets of the atrioventricular valves. During systole — when the ventricle contracts — the papillary muscles contract too, tightening the cords just as the chamber pressure surges, so the valve leaflets stay sealed and do not prolapse back into the atrium.

Papillary muscles depend on a good blood supply from the coronary arteries. In a heart attack, an ischemic papillary muscle can weaken or, rarely, rupture; this causes the supporting cords to fail and the valve to leak severely. The left ventricle typically has two papillary muscle groups, anchoring the mitral valve.