What do the heart sounds S1 and S2 indicate?

What do the heart sounds S1 and S2 indicate?

• A. S1 marks the start of systole and S2 marks the start of diastole
• B. S1 marks the end of diastole and S2 marks the end of systole
• C. S1 indicates valve closure of aortic and pulmonic
• D. S2 indicates onset of atrial systole

Answer: (A)

These sounds come from valve closures and tell us where we are in the heartbeat cycle. S1, the “lub,” happens when the mitral and tricuspid valves close at the start of ventricular systole. S2, the “dub,” happens when the aortic and pulmonic valves close, marking the start of diastole. So S1 marks the beginning of systole and S2 marks the beginning of diastole. The other options mix up which valves are closing or when diastole begins, so they don’t fit as well.

These sounds come from valve closures and tell us where we are in the heartbeat cycle. S1, the “lub,” happens when the mitral and tricuspid valves close at the start of ventricular systole. S2, the “dub,” happens when the aortic and pulmonic valves close, marking the start of diastole. So S1 marks the beginning of systole and S2 marks the beginning of diastole. The other options mix up which valves are closing or when diastole begins, so they don’t fit as well.