Question

Which one is the first heart sound ?

• A. Lubb sound during closure of semilunar valves
• B. Dupp sound during closure of semilunar valves
• C. Lubb sound during closure of atrioventricular valves
• D. Dupp sound during closure of atrioventricular valves

Answer 1

Answer: (C)

Lubb sound during closure of atrioventricular valves

Answer 2

Two sounds are heard normally through a stethoscope during each cardiac cycle. The first is a low, slightly prolonged "lubb" (first sound), caused by sudden closure of the. mitral and the tricuspid valves (atrioventricular valves) at the? start of ventricular? systole. The second is a shorter, high pitched "dupp" (second sound) caused by. vibrations associated with closure of the aortic and pulmonary valves just after the end of the ventricular systole.The first sound has a duration of 0.15 second and a frequency of 25-45 Hz. The second sound lasts about 0.12 seconds with a frequency of 50 Hz.