Internal Structures

Here we are focusing on Learning Objective 7.

Describe the location, arrangement and function of the chordae tendinae and the papillary muscles.

Chordae Tendinae

The chordae tendinae are known as the 'heart strings' and found on the interior ventricle surface. They are tendons composed mainly of collagen that attach the papillary muscles to the atrioventricular valves. They act to anchor the bicuspid and tricuspid valves to the papillary muscles.

Papillary Muscles

Papillary muscles are located on the interior surface of the ventricles and attach to the atrioventricular valves via the chordinae tendineae we have seen above. The papillary muscles receive their blood supply from the coronary circulation. 3 papillary muscles are located in the right ventricle while 2 are located in the left ventricle.

Papillary muscles in both ventricles contract shortly before ventricular systole and maintain tension on the chordinae tendineae throughout the isovolumetric and ejection phases. By bracing the AV valves against the change in pressure they prevent backflow of blood to the atria.

Cadaver heart dissected to show chordae tendineae, papilary muscles and trabeculae carneae.

Dissection of heart showing chordae tendineae, papillary muscles and trabeculae carnea.

Tip: Trabeculae carneae are rounded irregular muscles projecting from the inner surface of ventricles. To avoid confusing the papillary muscles with trabeculae carnae look for chordinae tendineae attachments!

Clinic Corner

Rupture of the chordae tendineae or damage to the papillary muscles results in acute mitral regurgitation where blood reenters the left atrium during ventricular systole. This can lead to congestive heart failure as the atrium is overloaded with blood from pulmonary veins and the ventricle which raises diastolic pressure. Rupture of these structures can be caused by include endocarditis (inflammation of the hearts inner lining) and rheumatic fever.

Diagram showing how rupture of the chordae tendineae can cause mitral valve prolapse.

Comparison of normal and prolapsed mitral valves.

Image Credits: National Institutes of Health (USA) 2017, E.Faccio & P.Saccheri 2007, OpenStax College 2013, National Heart Lung and Blood Institute 2013 - All Image Usage Complies with CC BY-SA 3.0

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