The first heart sound (S1) is produced by the closure of which valves?

The first heart sound (S1) is produced by the closure of which valves?

• A. Aortic and pulmonic valves
• B. Mitral and tricuspid valves
• C. Both sets
• D. None of the above

Answer: (B)

The first heart sound comes from the closing of the atrioventricular valves—the mitral and tricuspid valves—as the ventricles begin to contract. This marks the start of systole. It’s typically heard best at the apex and is louder when the AV valves close forcefully. In contrast, the semilunar valves (aortic and pulmonic) close later, producing the second heart sound at the end of systole. So naming the mitral and tricuspid valves correctly identifies the cause of the first heart sound.

The first heart sound comes from the closing of the atrioventricular valves—the mitral and tricuspid valves—as the ventricles begin to contract. This marks the start of systole. It’s typically heard best at the apex and is louder when the AV valves close forcefully. In contrast, the semilunar valves (aortic and pulmonic) close later, producing the second heart sound at the end of systole. So naming the mitral and tricuspid valves correctly identifies the cause of the first heart sound.