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Question: Answered & Verified by Expert
'Lub' sound of Heart is caused by the ______
BiologyBody Fluids and CirculationNEETNEET 2024 (Re-NEET)
Options:
  • A closure of the semilunar valves
  • B opening of tricuspid and bicuspid valves
  • C opening of the semilunar valves
  • D closure of the tricuspid and bicuspid valves
Solution:
1784 Upvotes Verified Answer
The correct answer is: closure of the tricuspid and bicuspid valves
The correct answer is option (4) because LUB is the first heart sound and it is produced by closing of AV valves; (tricuspid valve in between right atrium and right ventricle) and (bicuspid /mitral valve in between left atrium and left ventricle), during ventricular systole.
- Option (1) is incorrect as closure of the semilunar valves produce the second heart sound called 'DUB'.
- Option (2) is incorrect because opening of valves are not responsible for production of heart sounds 'LUB' and 'DUB'.
- Option (3) is incorrect because opening of semilunar valves does not produce only heart sounds.

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