Question

Heart produces two distinct sounds one after the other. The second sound is produced when

• A. vibration of ventricular walls to blood gushing in from atria
• B. semilunar valves close down after the blood flows into the vessels from ventricles
• C. reception of signal by AV node from SA node
• D. opening up of AV valves

Answer 1

The correct option is B semilunar valves close down after the blood flows into the vessels from ventricles

Lubb and dub are the two sounds produced in the heart.

Lubb is produced when the bicuspid and tricuspid valves shut close during a ventricular systole. This is the first sound to be produced.

Dub sound is produced during the ventricular diastole leading to the closure of the valves of the aorta and the pulmonary artery (the semilunar valves). This is the second heart sound.