Which statement describes S1 heart sounds?

Which statement describes S1 heart sounds?

• A. AV valves close; semilunar valves open
• B. Semilunar valves close; AV valves open
• C. AV valves open; semilunar valves close
• D. Both sets of valves open

Answer: (A)

The main idea is that the first heart sound (S1) is produced when the atrioventricular valves close at the start of ventricular systole. As the ventricles contract, their pressure rises and the mitral and tricuspid valves snap shut to prevent backflow into the atria. That closure creates the lub sound. Soon after, the ventricles generate enough pressure to open the semilunar valves (aortic and pulmonary), allowing blood to be ejected. So describing S1 as AV valves closing and the semilunar valves opening matches the sequence of events at the beginning of systole.

The main idea is that the first heart sound (S1) is produced when the atrioventricular valves close at the start of ventricular systole. As the ventricles contract, their pressure rises and the mitral and tricuspid valves snap shut to prevent backflow into the atria. That closure creates the lub sound. Soon after, the ventricles generate enough pressure to open the semilunar valves (aortic and pulmonary), allowing blood to be ejected. So describing S1 as AV valves closing and the semilunar valves opening matches the sequence of events at the beginning of systole.