Doctors use stethoscope to hear the sounds produced during each cardiac cycle. The first sound is heard when:
A
Ventricular walls vibrate due to pushing in of blood from atria
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B
Semilunar valves are closed
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C
AV node receives signal from SA node
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D
The tricuspid and bicuspid valves are closed
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Solution
The correct option is D The tricuspid and bicuspid valves are closed During each cardiac cycle two prominent sounds are produced which can be heard by stethoscope. The first heart sound (lub) is associated with the closure of bicuspid and tricuspid valves while the second heart sound (dub) is associated with a closure of the semilunar valves.