What is meant by the counterflow of fluid through the limbs of the loop of Henle, and what is its role in the normal function of a human kidney?

Concepts to Consider: The filtrate passing down through the descending limb of the loop is flowing in an opposite direction to the filtrate moving upward through the ascending limb. This countercurrent mechanism helps maintain a high salt concentration in the interstitial fluid of the medulla that draws water osmotically from the filtrate in the collecting ducts, thus preventing dehydration and excessive water loss.