Which of the following factors is responsible for the formation of concentrated urine?
Answer: (B) Maintaining hyperosmolarity towards inner medullary interstitium in the kidneys.. Answer: (B) Maintaining hyperosmolarity towards inner medullary interstitium.
- A.Low levels of antidiuretic hormone
- B.Maintaining hyperosmolarity towards inner medullary interstitium in the kidneys.✓
- C.Secretion of erythropoietin by Juxtaglomerular complex
- D.Hydrostatic pressure during glomerular filtration
Correct Answer
(B) Maintaining hyperosmolarity towards inner medullary interstitium in the kidneys.
Solution & Explanation
Answer: (B) Maintaining hyperosmolarity towards inner medullary interstitium. Solution: Concentrated urine is produced by the counter current mechanism between Henle's loop and vasa recta, which maintains an increasing osmolarity (300 to 1200 mOsmolL⁻¹) towards the inner medulla. This gradient draws water out of the collecting duct, concentrating the urine. Low ADH causes dilute urine, erythropoietin/JG complex relates to RBCs, and hydrostatic pressure drives filtration — not concentration. NCERT Reference: Ch 16, p.211, lines 03-06 — "the counter current in them help in maintaining an increasing osmolarity towards the inner medullary interstitium, i.e., from 300 mOsmolL–1 in the cortex to about 1200 mOsmolL–1 in the inner medulla."