During which phase are the AV valves open to allow ventricular filling?

During which phase are the AV valves open to allow ventricular filling?

• A. Ventricular relaxation.
• B. Ventricular contraction.
• C. Atrial systole.
• D. Isovolumetric contraction.

Answer: (A)

AV valves open when the ventricles are filling, which happens during ventricular relaxation (diastole). As the ventricles relax, their pressure falls below the atria, causing the mitral and tricuspid valves to open and blood to flow from the atria into the ventricles. This is the rapid filling phase, and atrial systole later contributes additional blood, but the crucial point is that the valves are open during ventricular relaxation. During ventricular contraction, those valves are closed to prevent backflow, and during isovolumetric contraction all valves are closed, so no filling occurs.

AV valves open when the ventricles are filling, which happens during ventricular relaxation (diastole). As the ventricles relax, their pressure falls below the atria, causing the mitral and tricuspid valves to open and blood to flow from the atria into the ventricles. This is the rapid filling phase, and atrial systole later contributes additional blood, but the crucial point is that the valves are open during ventricular relaxation. During ventricular contraction, those valves are closed to prevent backflow, and during isovolumetric contraction all valves are closed, so no filling occurs.