Q4. Assertion: all exchange of nutrients and gases between blood and cells occurs through the interstitial fluid. Reason: blood flows in a closed system of vessels and does not bathe the cells directly. Are both true, and does the reason explain the assertion?
Both are true, and the reason explains the assertion: human blood circulates in a closed network of vessels (NCERT pages 197–198), so the tissue fluid formed from it carries the exchange (page 197).
Q5. What is left behind in the blood vessels when tissue fluid forms?
The larger proteins and most of the formed elements (NCERT page 197).
Q6. Name two substances, besides fats, that lymph carries.
Nutrients and hormones (NCERT page 197).