The glomerular filtrate in the loop of Henle gets concentrated in the descending and then gets diluted in the ascending limbs. Explain.

Explanation

The glomerular filtrate in the loop of Henle gets concentrated in the descending loop and then gets diluted in the ascending limb. The thin wall of descending limb of Henle's loop is permeable to water, but not to the solutes. The isotonic tubular fluid flows down the limb. It gradually looses its water the by exosmosis due to increasing osmolarity of medullary interstitium through which the limb extends.
Thus, the filtrate becomes hypertonic to blood plasma. The ascending limb of loop of Henle is impermeable to water, but permeable to ions like `K^(+),Cl^(-),Na^(+)` and it is partially permeable to urea.
Thus, in the thick ascending limb of the loop of Henle, Na, K, Ca, Mg and Cl are reabsorbed, making the filtrate hypotonic to blood plasma and diluted as compared to descending limb.