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. Closure of atrioventricular valves
• B. Closure of semilunar valves
• C. Opening of atrioventricular valves
• D. Opening of semilunar valves

Answer: (A)

S1 marks the start of ventricular systole and is produced when the ventricles contract and the atrioventricular valves (mitral and tricuspid) snap shut. This closure creates the familiar “lub” sound as it prevents backflow into the atria. Opening of these valves is a silent event that occurs during filling, not during the sound we hear as S1. The semilunar valves close later, at the end of systole, producing the second sound “dub.” So the first heart sound comes from the closure of the atrioventricular valves.

S1 marks the start of ventricular systole and is produced when the ventricles contract and the atrioventricular valves (mitral and tricuspid) snap shut. This closure creates the familiar “lub” sound as it prevents backflow into the atria. Opening of these valves is a silent event that occurs during filling, not during the sound we hear as S1. The semilunar valves close later, at the end of systole, producing the second sound “dub.” So the first heart sound comes from the closure of the atrioventricular valves.