Henle's Loop & Osmolarity — NEET Biology
✅ Asked in NEET 2024Henle's Loop: Reabsorption is minimum in its ascending limb. However, this region plays a significant role in the maintenance of high osmolarity of medullary interstitial fluid. The descending limb of loop of Henle is permeable to water but almost impermeable to electrolytes. This concentrates the filtrate as it moves down. The ascending limb is impermeable to water but allows transport of electrolytes actively or passively. Therefore, as the concentrated filtrate pass upward, it gets diluted due to the passage of electrolytes to the medullary fluid.
NTA tests whether students correctly identify the properties of Henle's loop limbs, especially that the descending limb is permeable to water but impermeable to electrolytes, while the ascending limb does the opposite. Students commonly confuse which limb allows what, or forget that the ascending limb actively transports electrolytes to maintain medullary osmolarity. The key to remember: descending limb = water moves out (concentration increases), ascending limb = electrolytes move out (filtrate dilutes). This concept appeared in 2017, 2023, and 2024 NEET papers because it's fundamental to understanding urine concentration and kidney physiology.
This paragraph was tested 4 times in NEET.
Statement I: In the nephron, the descending limb of loop of Henle is impermeable to water and permeable to electrolytes. Statement II: The proximal convoluted tubule is lined by simple columnar brush border epithelium and increases the surface area for reabsorption. Choose the correct option:
Which part of the nephron is impermeable to water?
Assertion (A): Ascending limb of Henle’s loop is impermeable to water and allows electrolyte transport. Reason (R): Dilution of filtrate occurs due to electrolyte efflux into medullary fluid. Choose the correct option:
Which of the following statements is correct?
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