Question

The “lub” sound (first heart sound) is caused by the

• A. Filling of the ventricles
• B. Ventricular contraction
• C. Closing of the av valves
• D. Closing of semilunar valves

Answer 1

The correct option is C

Closing of the av valves

"Lub" is the sound of the tricuspid and bicuspid valves closing. This occurs during ventricular systole. "dub" is the sound of the semilunar valves closing. Together, they're the sounds of someone's heart doing its job.