Question

Which of the following statements is/are true?
(a) Urine is hypertonic in the distal convoluted tubule.
(b) When the urine passes into the collecting tubule. It becomes hypotonic.
(c) Urine is isotonic in the proximal convoluted tubule.
(d) Urine becomes more and more hypotonic as it passes through the Henle's loop.

• A. a and d only
• B. a and c only
• C. b-and c only
• D. c only

Answer 1

The correct option is D c only

The nephron is the structural and functional unit of the kidney. Its body is divided into renal corpuscle, proximal convoluted tubule, Henle's loop and distal convoluted tubule (DCT).

• PCT is lined with cuboidal epithelium with brush border. It increases the surface area for absorption. Almost all essential nutrients and 70-80 % of electrolytes and water are reabsorbed by PCT with small changes in luminal osmolarity. Hence urine is isotonic in the proximal convoluted tubule.
  
• The ascending limb of Henle's loop is impermeable to water and permeable to electrolytes. The ascending limb of the loop of Henle passes filtrate into DCT. hence urine is hypotonic to DCT.
  
• So, the correct answer is 'a and c only'.