The papillary muscles are cone-shaped projections of ventricular muscle that anchor the chordae tendineae. The left ventricle has two (anterolateral and posteromedial) and the right ventricle usually three (anterior, posterior and septal). They contract with the ventricle to keep the atrioventricular valves shut.
| Location | Projecting from the inner walls of both ventricles beneath the mitral and tricuspid valves. |
|---|---|
| Parts |
|
| Nerve Supply | Cardiac plexus; Vagus nerves (parasympathetic, slows rate); Sympathetic cardiac nerves from cervical and upper thoracic (T1-T4) ganglia (raise rate and force) |
| Blood Supply | Left anterior descending and left circumflex arteries (anterolateral); Posterior descending artery (posteromedial); Right coronary artery branches (right ventricular papillary muscles) |
Tense the chordae tendineae during systole so that the mitral and tricuspid leaflets close tightly and do not prolapse into the atria.
The posteromedial papillary muscle usually depends on a single artery (the posterior descending artery), while the anterolateral one has a dual supply, so the posteromedial muscle is more likely to rupture after an inferior myocardial infarction. Papillary muscle dysfunction from ischaemia is a common cause of functional mitral regurgitation. Abnormal papillary muscles can also contribute to outflow obstruction in hypertrophic cardiomyopathy.
Tearing of a papillary muscle, usually a few days after myocardial infarction. It causes acute severe mitral regurgitation and needs emergency surgery.
Impaired contraction from ischaemia or scarring. The valve leaflets are pulled poorly and mitral regurgitation results.
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