How does the filtrate get concentrated in the excretory system?

How does the filtrate get concentrated in the excretory system?
  1. Through reabsorption
  2. Through secretion
  3. Through a counter current mechanism
  4. Through osmotic pressure

Solution

The filtrate gets concentrated as it moves down the descending limb of the Loop of Henle and is diluted by the ascending limb, through the operation of a counter current mechanism.

Asked in: NCERT

Practice more Excretory Products and their Elimination questions on Aicharya