The flaps of tricuspid valves are attached to muscular extension of of right ventricle known as :

Explanation

The flaps of the tricuspid valve are attached to muscular extensions of the right ventricle known as papillary muscles. The papillary muscles are located on the walls of the right ventricle and are connected to the flaps of the tricuspid valve by thin cords called chordae tendineae. When the right ventricle contracts, the papillary muscles contract as well. This pulls on the chordae tendineae, which prevents the flaps of the tricuspid valve from prolapsing into the right atrium. This ensures that blood flows only in one direction, from the right atrium to the right ventricle. The papillary muscles and chordae tendineae are important for the proper functioning of the tricuspid valve. If the papillary muscles are damaged or the chordae tendineae are too weak, the flaps of the tricuspid valve may not close properly, which can lead to regurgitation of blood back into the right atrium.