Counter current Mechanism.
The Henle’s loop and vasa recta play a significant role in this. The flow of filtrate in the two limbs of Henle’s loop is in opposite directions and thus forms a countercurrent.
The flow of blood through the two limbs of vasa recta is also in a countercurrent 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 in terstitium, i.e., from 300 mOsmolL-1 in the cortex to about 1200 mOsmolL-1 in the inner medulla.
This gradient is mainly caused by NaCI and urea. NaCI is transported by the ascending limb of Henle’s loop which is exchanged with the descending limb of vasa recta. NaCI is returned to the intestitium by the ascending portion of vasa recta.
