During ventricular filling, what is the status of the AV and semilunar valves?

• A. AV valves open; semilunar valves closed
• B. AV valves closed; semilunar valves open
• C. AV valves closed; semilunar valves closed
• D. AV valves open; semilunar valves open

Answer: (C)

During ventricular filling, the ventricles are relaxed, so their pressure is low. Blood from the atria flows passively into the ventricles because atrial pressure is higher than ventricular pressure. The valves between the atria and ventricles (the AV valves) are open, allowing this flow. At the same time, the semilunar valves (the aortic and pulmonary valves) remain closed because ventricular pressure is still below the pressures in the aorta and pulmonary artery, so there’s no push to open them. This combination—AV valves open and semilunar valves closed—facilitates filling, including the later atrial kick that completes ventricle filling.