Which of the following diagrams is correct with regard to the proximal (P) and distal (D) tubule of the Nephron.
- [figure]
- [figure]
- [figure]
- [figure]
Answer
(4) [figure]
Solution
As per NCERT, the proximal convoluted tubule (P) reabsorbs nearly all essential nutrients, 70–80% of electrolytes (NaCl) and water, and HCO3-; it maintains pH by selective secretion of H+ and ammonia (NH3) into the filtrate.
As per NCERT, the distal convoluted tubule (D) conditionally reabsorbs Na+ (NaCl) and water, reabsorbs HCO3-, and secretes H+ and K+.
⇒ Option (1): NaCl is shown secreted into D — wrong.
⇒ Option (2): H2O is shown secreted into both P and D, and NH3 reabsorbed from D — wrong.
⇒ Option (3): H2O is shown secreted into P — wrong.
∴ Only diagram (4) is correct for both tubules.
Answer: (4)