Question

Doctors use stethoscope to hear the sounds produced during each cardiac cycle. The second sound in heard when :

• A. AV valves open up
• B. Ventricular walls vibrate due to gushing in of blood from artia.
• C. Semilunar valves close down after the blood flows into vessels from ventricles.
• D. AV node recives signal from SA node.

Answer 1

The correct option is C Semilunar valves close down after the blood flows into vessels from ventricles.

During each cardiac cycle, two prominent sounds are produced which can be easily heard through a stethoscope. The first sound (lub) is associated with the closure of the tricuspid and bicuspid valves during ventricular systole to prevent the backflow of blood to atria. The second sound (dub) is associated with the closure of semilunar valves during ventricular diastole to prevent the backflow of blood to ventricles.