NEETZoologyExcretory Products and their Elimination
How does the counter current mechanism help in concentrating the filtrate (urine)?
Options
- ABy maintaining a concentration gradient in the medullary interstitium
- BBy transporting NaCl and urea
- CBy allowing the easy passage of water from the collecting tubule
- DBy producing a dilute urine
Correct answer
C. By allowing the easy passage of water from the collecting tubule
Step-by-step solution
NaCl is transported by the ascending limb of Henle’s loop which is exchanged with the descending limb of vasa recta. NaCl is returned to the interstitium by the ascending portion of vasa recta. Similarly, small amounts of urea enter the thin segment of the ascending limb of Henle’s loop which is transported back to the interstitium by the collecting tubule. The above described transport of substances facilitated by the special arrangement of Henle’s loop and vasa recta is called the counter current mechanism.This m