Question

Given below are two statements:
Statements I: Concentrated urine is formed due to counter current mechanism in nephron.
Statement II: Counter current mechanism helps to maintain osmotic gradient in the medullary interstitium.
In the light of the above statements, choose the most appropriate answer from the options given below.

• A. Statement I is correct but Statement II is incorrect.
• B. Statement I is incorrect but Statement II is correct.
• C. Both Statement I and Statement II are correct.
• D. Both Statement I and Statement II are incorrect.

Answer 1

The Correct Option is C

To solve this question, we need to understand the role of the counter current mechanism in the nephron and its effect on urine concentration.

1. Statement I: Concentrated urine is formed due to the counter current mechanism in the nephron.
   • The nephron is the functional unit of the kidney, and it plays a crucial role in maintaining fluid and electrolyte balance in the body.
   • The counter current mechanism in the nephron involves the loop of Henle, a structure that creates a difference in the concentration of solutes between the cortex and the medulla of the kidney.
   • This mechanism helps in creating a concentrated urine by allowing water reabsorption from the collecting ducts under the influence of antidiuretic hormone (ADH). 
   • Therefore, Statement I is correct because the counter current mechanism indeed contributes to producing concentrated urine by enhancing water reabsorption.
2. Statement II: Counter current mechanism helps to maintain osmotic gradient in the medullary interstitium.
   • The counter current mechanism also establishes and maintains an osmotic gradient in the renal medulla.
   • This gradient is critical for concentrating urine as it allows the kidneys to excrete urine that is more concentrated than the blood plasma.
   • Thus, Statement II is correct because the countercurrent multiplier, which is part of this mechanism, effectively creates an osmotic gradient in the medullary interstitium, facilitating the kidney's ability to concentrate urine.

Conclusion: Both statements are scientifically accurate. The counter current mechanism is vital in aiding the formation of concentrated urine and maintaining the osmotic gradient in the medullary interstitium. Therefore, the correct answer is: Both Statement I and Statement II are correct.