Question

Describe the counter current multiplier system in the loop of henle?

Answer 1

This involves the vasa recta capillaries and the Loop of Henle fluid together, for one purpose.

Explanation:

That purpose is primarily to establish a high osmotic gradient, or high concentration, of salts in the renal (kidney) medulla.
Why is this needed?
High salts sitting in the renal medulla will promote the work of the collecting ducts later on.
A step-wise gradient of salts is 'built' inside the medulla tissue by the Loop of Henle.
The countercurrent multiplier system uses the salt reabsorbed from the ascending limb of the Loop of Henle to 'lay down' salts there.
Active transport of salts occurs.
In the descending limb, only water is reabsorbed into the renal medulla and blood (vasa recta).
The idea is for the vasa recta to keep solutes and water circulating throughout the renal medulla.
It also supplies necessary oxygen and nutrients to it as well.

Overall, the vasa recta keeps the osmotic gradient 'firm' and established.
Remember the gradient was established by the Loop of Henle.