Heart Valve States During Ventricular Systole

Steps:

• Ventricular contraction increases pressure in the ventricles above atrial pressure.
• This pressure closes the atrioventricular valve (X) to block backflow into the atria.
• Simultaneously, ventricular pressure exceeds arterial pressure, opening the semilunar valve (Y) for blood ejection.
• Result: valve X closed, valve Y open.

Why B is correct:

• In cardiac systole, atrioventricular valves close while semilunar valves open to direct blood flow unidirectionally, per the physiology of the cardiac cycle.

Why the others are wrong:

• A: Both closed blocks outflow to arteries, halting circulation.
• C: Both open permits regurgitation into atria, disrupting pressure gradients.
• D: X open allows backflow to atria, causing inefficient pumping.

Final answer: B