CAL

Question 1

Active transport at regions of the loop and multiplication

Answer 1

Active transport out of the ascending limb creates a relatively small gradient at any one level of the loop.
Due to counter-current flow, this effect gets multiplied to result in a large gradient between cortex and inner medulla.

Question 2

What is the importance of the vasa recta?

Answer 2

• Solutes and water are reabsorbed into the interstitium in the collecting ducts but this just can’t happen forever or the kidneys would burst
• This is solved by the vasa recta circulation which carries away the reabsorbed substances

Question 3

What does the descending vasa recta do?

Answer 3

• Increasing NaCl will pass into the vasa recta as the concentration of NaCl increases in the medulla
• More water will be drawn out of the vasa recta as the concentration of NaCl increases in medulla interstitium

Question 4

What does the ascending vasa recta do?

Answer 4

• Opposite of descending (but not all solute reabsorbs back into the ducts)
• Some solute remains in the vasa recta and is removed so higher blood flow rate = more solute removed = lower osmolarity of interstitium in medulla.

Question 5

Why must the vasa recta ascend after descending and not leave kidneys at medulla?

Answer 5

The concentration gradient would disappear