Given below are statements: one is labelled as Assertion A and the other is labelled as Reason R.
As

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Question

Given below are statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: Nephrons are of two types: Cortical & Juxta medullary, based on their relative position in cortex and medulla.
Reason R: Juxta medullary nephrons have short loop of Henle whereas, cortical nephrons have longer loop of Henle.
In the light of the above statements, choose the correct answer from the options given below:
(1) Both A and R are true but R is NOT the correct explanation of A.
(2) A is true but R is false.
(3) A is false but R is true.
(4) Both A and R are true and R is the correct explanation of A.

Accepted Answer

Correct Answer: B — A is true but R is false.Step-by-step Solution:Assertion A (True): Nephrons are classified into two types based on the position of the renal corpuscle (Bowman's capsule + glomerulus) in the kidney cortex: (1) Cortical nephrons — renal corpuscle lies in the outer cortex; constitute ~85% of all nephrons. (2) Juxtamedullary nephrons — renal corpuscle lies near the corticomedullary junction (juxta = near); constitute ~15% of nephrons. This classification is correct.Reason R (False): The statement has the relationship reversed. Juxtamedullary nephrons have long loops of Henle that extend deep into the inner medulla, sometimes reaching the tip of the renal papilla. This long loop is essential for producing a concentrated urine (countercurrent multiplier mechanism). Cortical nephrons have short loops of Henle that barely penetrate the medulla or remain entirely within the cortex. The Reason incorrectly states the opposite — attributing short loops to juxtamedullary and long loops to cortical nephrons.Key Concepts:Cortical nephrons (~85%): Short loop of Henle; renal corpuscle in outer cortex; less important for urine concentration.Juxtamedullary nephrons (~15%): Long loop of Henle extending deep into medulla; associated with vasa recta (long peritubular capillaries); critical for countercurrent multiplication and production of hypertonic urine.The longer the loop of Henle, the greater the ability to concentrate urine — desert animals have proportionally more juxtamedullary nephrons.

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