Cross-section of human heart, displaying heart valves, chordae tendineae, and papillary muscles
Have you ever heard the expression “Tugging on your heart-strings”? Well, it’s not completely metaphorical, at least in terminology. There are literally parts of your heart known colloquially as “heart strings”, which have been described in an anatomical sense as far back as Vesalius.
These “heart strings” are more properly called chordae tendineae. You can see them in the illustration, looking like thin wires or netting within the ventricles. They start at the atrioventricular heart valves (the bicuspid or mitral and the tricuspid), and connect to the papillary muscles near the apex of the heart. The collagenous structure of these strings imparts to them a high level of strength, and the papillary muscles combined with some elastin give a high level of flexibility. they’re what keep your heart valves from everting (prolapsing) when the blood moves from the atria to the ventricles.
See, the valves have no muscular structure of their own, but work because the pressure of the blood pushing against them makes them open and close taut. But if the chordae tendineae weren’t there, that same pressure that makes sure they shut well also means that their fibrous structure would end up simply turning inside-out, and the blood would flow back into the atria, instead of to the lungs or the rest of the body. Insufficiency of the heart strings is one of many possible causes of mitral prolapse and valve insufficiency (leaky valves).
Anatomy: Descriptive and Surgical. Henry Gray, 1900.