Which statement describes S2 heart sounds?

Which statement describes S2 heart sounds?

• A. AV valves close; ventricular systole
• B. Semilunar valves close; AV valves open
• C. AV valves open; semilunar valves close
• D. Aortic/Pulmonary valves close; sign of ventricular diastole

Answer: (D)

Second heart sound occurs when the semilunar valves (aortic and pulmonary) close at the end of ventricular systole, signaling the start of ventricular diastole. This closure prevents backflow into the ventricles after they’ve finished contracting, and the resulting high-pitched, short “dub” marks the beginning of diastole. The alternative descriptions describe the other phase (S1) or mix events that don’t define S2, so this statement best captures what S2 represents.

Second heart sound occurs when the semilunar valves (aortic and pulmonary) close at the end of ventricular systole, signaling the start of ventricular diastole. This closure prevents backflow into the ventricles after they’ve finished contracting, and the resulting high-pitched, short “dub” marks the beginning of diastole. The alternative descriptions describe the other phase (S1) or mix events that don’t define S2, so this statement best captures what S2 represents.