Question

Semilunar valves closes when
1) ventricular pressure rises
2) Atrial pressure rises
3) ventricular pressure falls
4) Atrial pressure falls

Answer 1

The valve between the left ventricle and the aorta is the aortic semilunar valve. When the ventricles contract, atrioventricular valves close to prevent blood from flowing back into the atria. When the ventricles relax, semilunar valves close to prevent blood from flowing back into the ventricles.

Answer 2

due to the pressure in the atria