Question

Explain the counter current exchange process done by the vas’s recta and it’s purpose

Answer 1

Counter current means two things flowing in opposite direction.

Loop of henle is considered as counter current multiplier which is needed to create the osmolarity gradient in the medullary interstitium...

• Vasa recta is the counter current exchanger which is actually needed to maintain the osmolarity gradient which is created by the loop of Henle.
• Let's see how it works

The flow in the loop of Henle is from proximal convoluted tubule to descending limb of Loop of henle to ascending limb to the distal convoluted tubule.

The flow in the Vasa recta is opposite to this.

Vasa recta contains blood and it's formed from efferent arterioles

Loop of Henle contains ultra flitrate ( it will form the urine)

• The ascending limb of Loop of Henle is permeabile to salts . These salts can enter the Vasa recta and it is transported deep into the medulla there by increasing the osmolarity there .
• The descending limb of loop of henle is permeabile to water. This Water enters the ascending limb of Vasa recta and is taken away to the systemic circulation. So water is removed from the medullary interstitium and high osmolarity is maintained there.

This high osmolarity gradient is needed for concentration of the urine and Vasa recta plays an important role in that.

* I hope this solves your doubts. In case you need any further assistance, please leave a comment and I will get back to you.