Papillary muscles

The papillary muscles are thick bands and ridges of endocardial-lined myocardium that project into the lumen of the cardiac ventricles. They essentially represent dominant ventricular trabeculae which attach to the cusps of the atrioventricular valves via the chordae tendineae. During systole, they contract to close atrioventricular valves and prevent the valves from prolapsing.

The right ventricle has 3 papillary muscles that attach to the cusps of the tricuspid valve:

• the anterior papillary muscle attaches to the chordae tendineae of the anterior and posterior cusps
• the posterior papillary muscle attaches to the chordae tendineae of the posterior and septal cusps
• the septal papillary muscle attaches to the chordae tendineae of the anterior and septal cusps

Within the anterior papillary muscle, there is a prominent band that extends from the interventricular septum that contains the right bundle branch, known as the septomarginal trabecula or moderator band.

The left ventricle has 2 papillary muscles that attach to the cusps of the mitral valve:

• anterior papillary muscle attaches to the chordae tendineae of the anterior and posterior cusps
• posterior papillary muscle attaches to the chordae tendineae of the anterior and posterior cusps

Related pathology

• papillary muscle calcification