Which fibers pull the atrioventricular valves closed when the papillary muscles contract, preventing backflow?

• A. Atria
• B. Chordae Tendinae
• C. Papillary Muscles
• D. Aorta

Answer: (B)

Chordae tendineae are the fibrous cords that anchor the atrioventricular valve leaflets to the papillary muscles inside the ventricle. When the ventricles contract, the papillary muscles also pull, and this tension is transmitted through the chordae tendineae to the valve leaflets. The leaflets are held taut and prevented from bulging back into the atria, so the blood flows forward and regurgitation is avoided. The atria and the aorta don’t provide this pulling action, and the papillary muscles themselves don’t directly close the valve—the cords are the fibers that exert the closing pull.