What is the role of the chordae tendineae and papillary muscles?

• A. They open AV valves
• B. They prevent AV valve prolapse during systole by tethering leaflets
• C. They anchor semilunar valves
• D. They regulate heart rate

Answer: (B)

The main idea is that these tendon-like structures keep the atrioventricular valves from bulging backward during contraction. The chordae tendineae connect each valve leaflet to papillary muscles inside the ventricle. When the ventricle contracts, the papillary muscles also contract and pull on the chordae, tensing the leaflets so they stay snug shut against the high pressure. This tethering prevents prolapse of the mitral and tricuspid valves and stops blood from flowing backward into the atria. They’re active during systole to maintain valve competence, and they’re relatively slack during diastole to allow the valves to open for ventricular filling. These structures don’t open AV valves, don’t anchor the semilunar valves, and don’t regulate heart rate.