Solved UPSC CDS/OTA Question
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Q · Circulatory Systemmedium · 45s
What causes the “lub-dub” heart sounds?
TopicCirculatory System
Question Typemultiple choice
Difficultymedium
Marking+1 / −0.33
Test Duration30 min
Step-by-Step Solution
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The first sound (“lub”) follows atrioventricular valve (mitral/tricuspid) closure at systole onset; the second (“dub”) follows semilunar valve (aortic/pulmonary) closure at diastole onset. Abnormal sounds (murmurs) indicate valvular pathology.
Final Answer: Option B - Valve closure