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The circulatory system — Biology STD 10 — Question

ICSE BoardEnglish MediumSTD 10BiologyThe circulatory system1 Mark
MCQ
The heart sound 'Dub' is produced when:
  • A
    Semilunar valves open
  • B
    Atrioventricular valves close
  • ✓
    Semilunar valves close
  • D
    Atrioventricular valves open
✓

Answer

Correct option: C.
Semilunar valves close
(c) Semilunar valves close
Explanation:
The 'Dub' sound, also known as the second heart sound (S2), is produced by the closing of the semilunar valves-the aortic valve and the pulmonary valve-at the end of the systole when the ventricles relax. This sound is associated with the end of the ventricular contraction and marks the beginning of ventricular filling.

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