2.3. The Loop of Henle - The Vasa Recta

Question 1

What are the Vasa Recta?

Answer 1

A specialist arrangement of the peritubular capillaries of the juxtamedullary nephrons

Question 2

What do the Vasa Recta act as?

Answer 2

counter-current exchangers in the counter-current mechanism

Question 3

What would happen if the medullary capillaries drained straight through?

Answer 3

They would instantly remove the NaCl, abolishing the interstitial gradient

Question 4

Why are the medullary capillaries not able to drain the NaCl instantly?

Answer 4

Due to the arrangement in “Hairpin Loops” so they do not interfere with the interstitium and the gradient

Question 5

Is the Vasa Recta freely permeable to H2O and solutes?

Answer 5

Yes

Question 6

What results from the Vasa Recta being freely permeable to H2O and solutes?

Answer 6

This will then equilibrate with the medullary interstitial gradient

Question 7

What are the functions fo the Vasa Recta?

Answer 7

1. T provide O2 for the medulla, whilst not disturbing the interstitial gradient
2. To remove volume from the interstitium

Question 8

What do the balance of forces in the Vasa Recta favour?

Answer 8

Reabsorption

Question 9

Why is reabsorption favoured?

Answer 9

1. Due to the high oncotic pressure

2. Due to the high tissue pressure

Question 10

Why is there a high oncotic and tissue pressure?

Answer 10

Due to the renal capsule driving fluid into the capillaries

Question 11

Is the flow rate through the Vasa Recta low or high?

Answer 11

Low

Question 12

What is the benefit of a low flow rate through the Vasa Recta?

Answer 12

There is time for the equilibration to occur within the interstitium - so the gradient is not disturbed