The flow of blood through the heart is directed by one-way valves. The atrioventricular valves prevent blood flowing back from the ventricles into the atria. The semilunar valves prevent blood flowing back into the ventricles from the arteries.

The atrioventricular valve in the RIght side of the heart is the tRIcuspid valve.

The atrioventricular valve in the Left side of the heart is mitraL or bicuspid valve.

The semilunar valve at the entrance of the aorta is the aortic valve. The semi-lunar valve at the entrance of the pulmonary artery is the pulmonary valve.