Question

Typical lub-dub sounds heard in heartbeat are due to

• A. Closing of bicuspid and tricuspid valves
• B. Closing of semilunar valves
• C. Closure of bicuspid-tricuspid valves followed by semilunar valves
• D. Blood under pressure through aorta

Answer 1

Answer: (C)

Closure of bicuspid-tricuspid valves followed by semilunar valves

Typical 'lub-dub' sounds heard in heartbeat are due to the closure of bicuspid-tricuspid valves followed by semilunar valves.

S1 – The first heart sound (lub) can be heard the loudest at the mitral area. This sound represents the closure of the mitral and tricuspid valves and is a low pitched, dull sound at the beginning of ventricular systole.

S2 – The second heart sound (dub).

The two major heart sounds are 'lub' (from the closure of AV-valves) and 'dub' (from the closure of aortic and pulmonary valves).

The first heart tone "lub," or S1, is caused by the closure of the mitral and tricuspid atrioventricular valves at the beginning of ventricular systole.

The second heart tone "dub," or S2 (a combination of A2 and P2), is caused by the closure of the aortic valve and pulmonic valve at the end of ventricular systole.

So, the correct answer is option C.