Counter Current Mechanism in Kidneys — NEET Biology
✅ Asked in NEET 2024Statement I: Concentrated urine is formed due to counter current mechanism in nephron. Statement II: Counter current mechanism helps maintain osmotic gradient in the medullary interstitium. Choose the correct option:
Statement I: Concentrated urine is formed due to counter current mechanism in nephron. Statement II: Counter current mechanism helps maintain osmotic gradient in the medullary interstitium. Choose the correct option:
Answer & NCERT explanation
Correct answer: C — Both I and II correct
Both statements are correct. Concentrated urine formation depends on the counter-current mechanism in nephron, specifically between loop of Henle and vasa recta. This mechanism maintains a hyperosmotic gradient in medullary interstitium, allowing maximum water reabsorption from collecting duct under ADH influence, producing concentrated urine.
Read more NCERT concept on the PYQ
Mammals have the ability to produce a concentrated urine. The Henle's loop and vasa recta play a significant role in this. The flow of filtrate in the two limbs of Henle's loop is in opposite directions and thus forms a counter current. The flow of blood through the two limbs of vasa recta is
The counter current mechanism involves opposite directional flow of filtrate through Henle's loop and blood through vasa recta, which multiplies solute concentration and enables production of concentrated urine. Many students incorrectly assume both Henle's loop and vasa recta have parallel flows or identical mechanisms—this is wrong. The key is that Henle's loop creates osmotic gradients while vasa recta acts as a counter current multiplier that preserves these gradients without dissipating them. Remember: opposite flow directions in both structures allow maximum reabsorption of water, essential for water conservation in mammals. This mechanism is tested because it directly explains how mammals concentrate urine more than blood plasma.
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