As the glomerular filtrate moves down the descending limb of the loop of Henle, its osmolarity increases. Which specific property of this segment is responsible for concentrating the filtrate?

Step-by-step solution

The descending limb of the loop of Henle is permeable to water but almost impermeable to electrolytes. As the glomerular filtrate moves down this segment, water moves out of the tubule into the hyperosmotic medullary interstitium due to osmosis. This loss of water concentrates the filtrate, increasing its osmolarity from about 300 mOsmol/L in the cortex to about 1200 mOsmol/L in the inner medulla. The ascending limb, on the other hand, is impermeable to water but allows the transport of electrolytes, which dilutes