Valve States During Ventricular Systole

Steps:

• Examine pressure diagram: at X, left ventricular pressure exceeds atrial pressure and aortic pressure rises.
• Identify phase: high ventricular pressure indicates systole, closing atrioventricular valves.
• Check bicuspid (mitral) valve: closes when ventricular pressure > atrial pressure to prevent backflow.
• Check semi-lunar (aortic) valve: opens when ventricular pressure > aortic pressure to eject blood.

Why A is correct:

• During systole, bicuspid closes (ventricular pressure > atrial) and semi-lunar opens (ventricular pressure > aortic), per pressure gradient rules for unidirectional flow.

Why the others are wrong:

• B: Describes diastole, when bicuspid opens for filling and semi-lunar closes; mismatches high ventricular pressure at X.
• C and D: Not enough information on options.

Final answer: A