Question

Which is true regarding coronary function?

A) The AV valves open before the semilunar valves close.

B) The semilunar valves close before the AV valves open.

C) When the ventricles are relaxed, the AV valves resist the flow of blood from the atria into the ventricles.

D) When the ventricles contract, the cusps of the AV valves are open.

Answer 1

The true statement about coronary function is that the semilunar valves close before the AV valves open, which occurs during the transition from ventricular contraction (systole) to relaxation (diastole).

Step-by-step explanation:

The statement regarding coronary function that is true is: The semilunar valves close before the AV valves open. During the cardiac cycle, when the ventricles contract in a phase called systole, the atrioventricular (AV) valves are closed to prevent backflow of blood into the atria. At this same time, the semilunar valves are open to allow blood to be ejected into the pulmonary artery and the aorta.

Once the ventricles relax (diastole), the semilunar valves close to prevent the backflow of blood back into the ventricles. Then the AV valves open, allowing blood to flow from the atria into the ventricles. This can be seen in Figure 19.14a where the AV valves are closed and the semilunar valves are open during ventricular contraction, and in Figure 19.13a where the AV valves are open and the semilunar valves are closed when the ventricles are relaxed.