During ventricular relaxation, which valves close?

During ventricular relaxation, which valves close?

• A. Pulmonary and Aortic valves
• B. AV valves
• C. Tricuspid valve and Mitral valve
• D. Aortic valve only

Answer: (A)

During ventricular relaxation (diastole), the ventricles' pressure falls below the pressure in the aorta and pulmonary artery. This pressure difference makes the semilunar valves—the pulmonary valve and the aortic valve—snap shut to prevent blood from flowing back into the ventricles. The closing of these valves is what produces the second heart sound. In this phase, the atrioventricular valves (tricuspid and mitral) are open, allowing blood to flow from the atria into the ventricles, so they are not closed during ventricular relaxation.

During ventricular relaxation (diastole), the ventricles' pressure falls below the pressure in the aorta and pulmonary artery. This pressure difference makes the semilunar valves—the pulmonary valve and the aortic valve—snap shut to prevent blood from flowing back into the ventricles. The closing of these valves is what produces the second heart sound. In this phase, the atrioventricular valves (tricuspid and mitral) are open, allowing blood to flow from the atria into the ventricles, so they are not closed during ventricular relaxation.