Question

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

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

Answer 1

The correct option is D

Semilunar valves close down after the blood flows into vessels from ventricles.

The “ lub” is the first heart sound, commonly termed S1, and is caused by turbulence caused by the closure of mitral and tricuspid valves at the start of systole.

The second sound,” dub” or S2, is caused by the closure of aortic and pulmonic valves, marking the end of systole. The pulmonary valve is the semilunar valve of the heart that lies between the right ventricle and the pulmonary artery and has three cusps.