Which valves are the atrioventricular valves?

• A. Tricuspid and mitral (bicuspid) valves
• B. Aortic and pulmonary valves
• C. Semilunar valves
• D. Mitral and aortic valves

Answer: (A)

Atrioventricular valves are the valves between the atria and the ventricles. The two are the tricuspid valve on the right and the mitral (bicuspid) valve on the left. They differ from the semilunar valves, which are the aortic valve and the pulmonary valve at the exits of the ventricles.

The AV valves have chordae tendineae attached to papillary muscles, which help prevent the valve cusps from flipping back into the atria when the ventricles contract. They open during atrial diastole to allow blood to move from the atria into the ventricles, and they close during ventricular systole to stop backflow into the atria. Semilunar valves operate at the outflow tracts and open when ventricular pressure is high enough, then close during relaxation.

So, the valves between the atria and ventricles are the tricuspid and mitral valves.