Question

Assertion :In the descending limb of the loop of Henle, the uring is hypertonic, while in ascending limb of the loop of Henle, the urine is hypotonic. Reason: Descending limb is impermeable to Na, while ascending limb is impermeable to $H_{2}O$

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

• Henle's loop is a U-shaped tube that plays a significant role in maintaining the osmolarity of medullary interstitial fluid.
• It is divisible into three regions- descending limb, ascending limb and the main loop.
• The descending limb is impermeable to electrolytes and permeable to water.
• Therefore, the filtrate moving down the limb becomes concentrated i.e. hypertonic.
• The ascending loop is impermeable to water and permeable to electrolytes.
• Therefore, the filtrate becomes dilute i.e. hypotonic, when it passes through the ascending loop.
• So, the correct answer is 'Both Assertion and Reason are correct and Reason is the correct explanation for Assertion'.