|Class 11 Biology Excretory Products Elimination||Concentration of Urine|
Concentration of Urine
Removal of water makes the Urine/ filtrate more concentrated. Counter current mechanism plays the important role here.
Counter current mechanism
Filtrate flows in opposite direction through the Henle’s loop and therefore forms a counter current. The descending limb is permeable to water, and the ascending limb is impermeable to water, but permeable to electrolytes. The proximity between the Henle’s loop & vasa recta, as well as the counter current in them help in maintaining an increasing osmolarity towards the inner medullary interstitium.
Cause of the gradient:
with the descending limb of vasa recta. NaCl is returned to the interstitium by the ascending portion of vasa recta.
This transport of substances facilitated by the arrangementof Henle’s loop & vasa recta is called the counter current mechanism
The overall process of urine formation:
amount of excess water in the body