Chordae tendinae are extension of:

Explanation

Option D is correct.The chordae tendinae of the heart are extensions of atrioventricular valves of the papillary muscles. The papillary muscles are small, cone-shaped muscles that project into the ventricles from the inner wall of the heart. The chordae tendinae attach to the papillary muscles at one end and to the leaflets of the atrioventricular valves at the other end. The chordae tendinae serve to keep the leaflets of the atrioventricular valves in place during ventricular contraction. When the ventricles contract, the papillary muscles contract as well. This pulls on the chordae tendinae, which in turn prevents the leaflets of the valves from flapping back into the atria. This ensures that blood flows in the correct direction through the heart. If the chordae tendinae are damaged, the leaflets of the atrioventricular valves may not be able to close properly. This can lead to regurgitation of blood back into the atria, which can cause heart failure.