What are the two main heart sounds and what do they signify?

What are the two main heart sounds and what do they signify?

• A. S1 and S2; S1 signals closure of the semilunar valves and S2 signals closure of the AV valves
• B. S1 and S2; S1 signals closure of the AV valves and S2 signals closure of the semilunar valves
• C. S1 and S2; both indicate valves opening
• D. S1 signals closure of the AV valves and S2 signals opening of the semilunar valves

Answer: (B)

Two main heart sounds come from valve closures. S1 is the sound you hear at the start of ventricular contraction when the atrioventricular valves (mitral and tricuspid) close. S2 occurs at the start of ventricular relaxation when the semilunar valves (aortic and pulmonary) close, producing the familiar “lub-dub” sequence. The option that pairs S1 with AV valve closure and S2 with semilunar valve closure matches this exactly. The other statements mix up which valves close or refer to valve openings, which do not generate the main heart sounds.

Two main heart sounds come from valve closures. S1 is the sound you hear at the start of ventricular contraction when the atrioventricular valves (mitral and tricuspid) close. S2 occurs at the start of ventricular relaxation when the semilunar valves (aortic and pulmonary) close, producing the familiar “lub-dub” sequence. The option that pairs S1 with AV valve closure and S2 with semilunar valve closure matches this exactly. The other statements mix up which valves close or refer to valve openings, which do not generate the main heart sounds.