Heart Valve Closure Due to Pressure Gradient

Steps:

• Identify the right atrioventricular (tricuspid) valve separates the right atrium and right ventricle.
• During ventricular systole, contraction increases right ventricular pressure above right atrial pressure.
• This pressure reversal closes the tricuspid valve to prevent backflow into the atrium.
• Confirm no involvement of semilunar or left-side valves in this right-heart event.

Why D is correct:

• Atrioventricular valves close when ventricular pressure exceeds atrial pressure, per the principle of unidirectional blood flow in cardiac cycle.

Why the others are wrong:

• A: Aortic semilunar valve is on the left side, unaffected by right heart pressures.
• B: Pulmonary semilunar valve closes when right ventricular pressure drops below pulmonary artery pressure, not atrial.
• C: Left atrioventricular (mitral) valve operates on the left side, independent of right heart dynamics.

Final answer: D