Cardiac Cycle Valve Sequence

Steps:

• Identify point 1 as end of diastole: atrioventricular (AV) valves close to start ventricular contraction.
• Identify point 2 as start of ejection: semilunar valves open as ventricular pressure exceeds arterial pressure.
• Identify point 3 as end of systole: semilunar valves close during isovolumetric relaxation.
• Identify point 4 as diastole: AV valves open for ventricular filling.

Why D is correct:

• Aligns with standard cardiac cycle where AV closure initiates systole (point 1), semilunar opening enables ejection (point 2), semilunar closure ends systole (point 3), and AV opening allows filling (point 4).

Why the others are wrong:

• A: Reverses AV and semilunar timings, placing AV open during systole onset.
• B: Swaps opening points, opening semilunar during filling phase.
• C: Misplaces AV closure at diastole and semilunar opening too early.

Final answer: D