What are the hearts two atrioventricular valves and two semilunar valves?

Tricuspid valve has three flaps and it is located between the right auricle and right ventricle. It prevents the blood from flowing back into the auricle.

The mitral or bicuspid valve is situated between left auricle and left ventricle. It has two flaps which help in maintaining the blood flow in one direction (from left auricle to left ventricle). Tricuspid and bicuspid valves are together called auriculo-ventriclar valves.

Semilunar valves has flap which resembles half moon. Pulmonary semilunar valve keep the direction of blood flow from right ventricle to lungs and aortic semilunar valve keep the direction of blood flow from left ventricle to aorta.