Question

$1^{st}$ heart sound is due to

• A. 'Lubb' at the end of systole
• B. 'Dubb' at the end of systole
• C. 'Lubb' at the begining of ventricular systole
• D. 'Dubb' at the begining of ventricular systole

Answer 1

The correct option is C 'Lubb' at the begining of ventricular systole

During each cardiac cycle two prominent sounds are produced, which can be easily heard through a stethoscope. The first heart sound (lubb) is associated with the closure of the tricuspid and bicuspid valves, at the beginning of ventricle systole.

The second heart sound (dubb) is associated with the closure of the semilunar valves, at the end of ventricle systole. These sounds are of clinical diagnostic significance.