Question

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

Answer 1

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 loses its water the by exosmosis due to increasing osmolarity of medullary interstitium which the limb extends.
Thus, the filtrate becomes hypertonic to blood plasma. The ascending limb of the loop of Henle is impermeable to water. but permeable to ions like $K^{+},C{l}^{-}.N{a}^{+}$ and Cl are reabsorbed, making the filtrate hypotonic to blood plasma and diluted as compared to descending limb.