Question

In the thick segment of the nephron loop ascending limb, approximately how much percent of filtered NaCl is reabsorbed?

1) 10%
2) 20%
3) 30%
4) 40%

Answer 1

Approximately 25-30% of filtered NaCl is reabsorbed in the thick segment of the nephron loop ascending limb, contributing to urine concentration.

Step-by-step explanation:

In the thick segment of the nephron loop ascending limb, approximately 25% to 30% of the filtered NaCl (sodium chloride) is reabsorbed. This region of the nephron is imperative for the concentration of urine and plays a crucial role in maintaining body fluid balance.

The ascending loop's thick portion is lined with cells that are impermeable to water due to the absence of aquaporin proteins, but are efficient in actively reabsorbing ions, particularly Na+ and Cl-, by a cotransport system.

The removal of NaCl from the filtrate while retaining water contributes to hypoosmotic urine by the time it reaches the distal convoluted tubule (DCT), and the pumped NaCl into the interstitial space helps maintain the hyperosmotic environment crucial for water reabsorption in the kidney medulla.