Asked by rabin barakat on Jul 07, 2024
Verified
Starting from the collecting duct, indicate the order in which urea molecules move to maintain the medullary concentration gradient.
(1) Ascending limb
(2) Distal convoluted tubule
(3) Interstitial fluid
(4) Collecting duct
(5) Descending limb
A) 2, 5, 1, 4, 3
B) 1, 3, 5, 2, 4
C) 3, 5, 1, 2, 4
D) 4, 2, 1, 3, 5
E) 4, 3, 5, 1, 2
Medullary Concentration Gradient
A gradient of solute concentration in the kidney medulla that facilitates water reabsorption and urine concentration through osmosis.
Urea Molecules
Organic compounds and the main nitrogen-containing substance in the urine of mammals, formed in the liver from ammonia and carbon dioxide.
Ascending Limb
The part of the loop of Henle in the nephron that transports fluid from the lower to the upper parts of the kidney.
- Analyze the contribution of the countercurrent mechanism towards urine concentration and the maintenance of the osmotic gradient within the medulla.
Verified Answer
MR
Michael RinkoJul 10, 2024
Final Answer :
E
Explanation :
Urea moves from the collecting duct (4) into the interstitial fluid (3), then into the descending limb (5) of the loop of Henle. It does not typically move through the ascending limb (1) or the distal convoluted tubule (2) in significant amounts in this context, as these segments are relatively impermeable to urea. The correct sequence emphasizes the role of urea recycling in maintaining the medullary concentration gradient, crucial for the kidney's ability to concentrate urine.
Learning Objectives
- Analyze the contribution of the countercurrent mechanism towards urine concentration and the maintenance of the osmotic gradient within the medulla.