During ventricular contraction, what happens to the AV valves?

• A. They open to allow blood into the atria.
• B. They close to prevent backflow of blood into the atria.
• C. They detach from the valve annulus.
• D. They become stiff, stopping all flow.

Answer: (B)

During ventricular contraction, the pressure inside the ventricles rises quickly. When ventricular pressure becomes higher than atrial pressure, the atrioventricular valves (the mitral and tricuspid valves) shut to prevent blood from flowing backward into the atria. This closure helps ensure blood moves forward into the arterial system once the semilunar valves open. They don’t open to move blood into the atria during contraction, they don’t detach, and they don’t become stiff and stop all flow in normal physiology.