Which structure contracts to tense the chordae tendineae during ventricular contraction?

• A. Papillary muscle
• B. Chordae tendinae
• C. Pectinate muscle
• D. Tricuspid

Answer: (A)

When the ventricles contract (systole), the heart must keep the atrioventricular valves from fluttering backward into the atria. The chordae tendineae anchor the valve leaflets to the papillary muscles, which are muscles that project from the ventricular wall. As the ventricles squeeze, the papillary muscles contract and pull on the chordae, tightening them and pulling the valve leaflets closed. This prevents prolapse of the leaflets into the atria and stops backflow. The cords themselves aren’t contractile; they just transmit the tension created by the papillary muscles. The pectinate muscles are located in the atria and don’t participate in this tension mechanism, and the tricuspid structure is the valve itself, not the contracting muscle that tense the cords.