Papillary muscles
Musculi papillares
Papillary muscles are cone-shaped projections of ventricular muscle whose tips anchor the chordae tendineae. They contract early in systole so that the AV valve cusps do not turn inside out into the atria.
Overview
Number and position. The right ventricle has three papillary muscles. The anterior is the largest and is connected to the moderator band. The posterior is inferior, and the septal is small and variable. The left ventricle has two, the anterolateral and the posteromedial. They are much larger than those on the right, and each sends chordae to the neighbouring halves of both mitral cusps.
Function. The papillary muscles do not open the valves. The AV valves open and close passively as pressures change. Instead, the papillary muscles contract slightly before the rest of the ventricle, because the Purkinje network reaches them first. This tightens the chordae as ventricular pressure rises, so the cusps meet (coapt) at the correct level and do not prolapse.
- Location
Arise from the inner walls of both ventricles and project into the cavities toward the AV valves.
Anatomy
- Arterial supply
Left ventricle: the anterolateral muscle has a dual supply from LAD diagonals and circumflex marginals. The posteromedial muscle usually has a single supply from the posterior interventricular artery, which comes from the RCA in right-dominant hearts. Right ventricle: branches of the RCA and LAD.
Function
- Tighten the chordae tendineae during systole, preventing prolapse and regurgitation of the AV valves.
- Help maintain the shape of the ventricle.
Clinical significance
Papillary muscle rupture
Papillary muscle rupture typically occurs 2–7 days after myocardial infarction. The posteromedial muscle ruptures much more often than the anterolateral, because it has only one blood supply. Rupture causes sudden severe mitral regurgitation, flash pulmonary oedema and cardiogenic shock, and needs emergency surgery.
Ischaemic (functional) mitral regurgitation
When ischaemia or scarring displaces the papillary muscles, they pull the leaflets apart so that a structurally normal valve cannot close completely.
Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.