Which of the following help to maintain a concentration gradient in the medullary interstitium?
(a) The proximity between the Henle’s loop and the vasa recta
(b) The counter-current flow of the filtrate in the two limbs of the Henle’s loop
(c) Renin-angiotensin mechanism
(d) The counter-current flow of blood in the two limbs of the vasa recta
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 the vasa recta is also in a counter-current pattern. The proximity between the Henle’s loop and the vasa recta, as well as the counter-current in them help in maintaining an increasing osmolarity towards the inner medullary interstitium, i.e., from 300 mOsmolL–1 in the cortex to about 1200 mOsmolL–1 in the inner medulla.
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