There are four valves in the heart :
(1) Between left ventricle and auricle : Mitral Valve
(2) Between left ventricle and artery carrying pure blood (Aorta) : Aortic Valve
(3) Between right ventricle and auricle : Tricuspid valve
(4) Between right ventricle and artery carrying impure blood to the lungs (pulmonary artery) : Pulmonary Valve
During every heartbeat, each valve opens and closes at different times. The main function of the valve is to maintain unidirectional flow of blood. This is the same as the valve in the tyre of our vehicle, which permits the air to go in but does not allow it to come out !