ICSE Class X Biology 2017 Solved Papers

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The diagram given below represents a section of the human heart. Answer the questions that follow:
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Question : 79
Total: 101
What causes the heart sounds 'LUBB' and 'DUP'?
Solution:  
LUBB - Lubb sound is produced due to partial closure of bicuspid and tricuspid valves (auriculo-ventricular values).
DUP - Sound is caused when the two semilunar values shut.
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