What produces the S1 heart sound?

What produces the S1 heart sound?

• A. Closure of the mitral valve
• B. Closure of the aortic valve
• C. Closure of the tricuspid valve
• D. Closure of the pulmonic valve

Answer: (A)

S1 arises from the closure of the atrioventricular valves as the ventricles begin to contract at the start of systole. The mitral and tricuspid valves close to prevent backflow into the atria, and the mitral valve’s closure is the most audible and typically dominates what clinicians hear as the first heart sound, best at the apex. The timing of this sound aligns with the onset of ventricular systole and the QRS complex on ECG. In contrast, S2 comes from the closure of the semilunar valves (aortic and pulmonic) at the end of systole, so closures of those valves would describe the second heart sound, not the first. The closure of the mitral valve is the best single description for what produces the first heart sound in these options.

S1 arises from the closure of the atrioventricular valves as the ventricles begin to contract at the start of systole. The mitral and tricuspid valves close to prevent backflow into the atria, and the mitral valve’s closure is the most audible and typically dominates what clinicians hear as the first heart sound, best at the apex. The timing of this sound aligns with the onset of ventricular systole and the QRS complex on ECG. In contrast, S2 comes from the closure of the semilunar valves (aortic and pulmonic) at the end of systole, so closures of those valves would describe the second heart sound, not the first. The closure of the mitral valve is the best single description for what produces the first heart sound in these options.