Question

The AV valves close when __________.

a) pressure in the ventricles decreases
b) pressure in the atria increases
c) pressure in the ventricles increases
d) pressure in the aorta increases

Answer 1

The atrioventricular valves close when the pressure in the ventricles increases during ventricular systole, preventing the backflow of blood into the atria.

Step-by-step explanation:

The atrioventricular (AV) valves close when pressure in the ventricles increases. This happens during the ventricular systole phase of the cardiac cycle, where the ventricles contract to pump blood out of the heart.

The increased pressure in the ventricles pushes against the AV valves (the tricuspid and the mitral valves), causing them to close. This prevents the backflow of blood into the atria. The AV valve closure occurs simultaneously with the opening of the semilunar valves, which allows blood to flow into the pulmonary artery and aorta.