The heart has four valves. These valves make that circulation inside the heart goes in only one direction. Blood thus passes from a cavity to another without the possibility of going back.
There are two types of valves in the heart. Two are made up of leaflets and cords. Two others are made of cusps. Those made of three cusps are called ‘’ tricuspid valves”.
The tricuspid valves are the pulmonary and the aortic valve. They are made of three cups attached to a fibrous ring of the cardiac skeleton. They respectively separate the pulmonary artery from the right ventricle and the aorta from the left ventricle.
A cusp is a very flexible, pocket-shaped structure which is folded up against its ring during ejection of blood by the ventricles (right or left).
When the ejection ends, the column of blood tries a return towards the ventricles because of the pressure decrease and the effect of suction due to the ventricle relaxation. This blood backflow makes the cusps reopen, making the valve tight again and preventing blood from going back into the ventricles.