This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidneys and Body Fluids, Subject name: Physiology
Countercurrent mechanism in the kidney is responsible for 
Select and explain. 
A. Absorption of glucose, B. Maintenance of blood flow, C. Osmotic gradient in medulla, D. Secretion of uric acid
C: Osmotic gradient in medulla
Answer: C: Osmotic gradient in medulla 
Explanation: Ans. (c) Osmotic gradient in medulla(Ref: Ganong, 25th ed/p.685)Loop of Henle plays an important role in concentration of urine by creating medullary hyperosmolarity through countercurrent mechanism