Atrioventricular orifice and tricuspid valve

The tricuspid valve occupies the right atrioventricular orifice, located at the level of the right atrium floor, which connects right atrium and right ventricle. It is formed by three flaps, also called cusps. Each flap consists of a fibrous lamina coated with endocardium.

The valve is characterized by two faces: the face facing upwards, looking towards the atrium, is called axial , while the face facing downwards, looking towards the ventricle, is called parietal.

Each cusp has a free margin, facing the center of the orifice, and a fixed margin that surrounds the orifice itself. The free margin, in its parietal face, attaches to the tendon ropes that extend from the apex of the papillary muscles. The papillary muscles are trabeculae of I order with base localized in the wall of the ventricle and apex which from start to the aforementioned tendon cords.

During ventricular systole , the pressure generated by the contraction of the myocardium causes the blood to push on the cusps making it rise and close. The approach of the cusps is almost perfect and takes place along a closing line.

But what is the function of papillary muscles?

During the ventricular systole (with slight delay) the papillary muscles contract and tension the tendon cords. This means that the valve cusps, already raised, are better able to withstand the pressure exerted by the blood.