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MODEL PAPER 3 — BIOLOGY STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceBIOLOGYMODEL PAPER 33 Marks
Question
Give the cause for the Heart sounds.
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Answer

Heart sounds: These are resulted due to sharp closure of heart valves. The first sound 'lub' occurs at the onset of ventricular systole and; is caused due to sharp closure of AV valve and the ejection of blood from the ventricles.
The second heart sound 'dub' occurs at the beginning of ventricular diastole and is caused by sharp closure of the semilunar valves to the aorta and the pulmonary artery.

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