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The human heart is enclosed in a double-walled sac containing a lubricating fluid that reduces friction during heartbeat. This protective sac is called what?
AMyocardium
BEndocardium
CPericardium
DDiaphragm
Answer & Solution
Correct answer: C. Pericardium
1. The structure is a double-walled sac around the heart with lubricating fluid.
2. Myocardium is the cardiac muscle layer, not the outer sac, so option A is wrong.
3. The diaphragm lies below the heart and endocardium lines the chambers, ruling out options B and D.
4. The double-walled protective sac is the pericardium, option C.
_Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 14 Transportation in Plants and Circulation in Animals "Structure of Human Heart", p.214_
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