Describe the position and role of the valves in the heart?

There are 4 valves in the heart. The first valve though which the blood passes is the tricuspid which is one of the atrioventriculars (between a ventricle and an atrium) and stops backflow of blood from the right ventricle tothe right atrium. The next valve is the pulmonary valve, one of the semilunars, which stops backflow form the pulmonary artery to the right ventricle. The third valve is the mitral or bicuspid which (the other atrioventricular) which stops backflow from the left ventricle to the left atrium. The last valve is the aortic valve (the other semilunar) which stops backflow from the aorta to the left ventricel.