Question

Which feature enables the mammalian kidney to concentrate urine in the medullary region ?

• A. Maintaining a high osmotic pressure in the tissues between the tubules.
• B. Rapid removal of sodium ions from medullary tissue.
• C. High oxidative metabolism of medullary cells
• D. Rapid flow of blood through the medulla

Answer 1

The correct option is A Maintaining a high osmotic pressure in the tissues between the tubules.

The flow of filtrate in the two limbs of Henle’s loop is in opposite directions and thus forms a counter current. The flow of blood through the two limbs of vasa recta is
also in a counter current pattern. The proximity between the Henle’s loop and vasa recta, as well as the counter current in them help in maintaining an increasing osmolarity towards the inner medullary interstitium.