Countercurrent Multiplication And Urea Cycling

Question 1

What is the corticopapillary gradient?

What is it established and maintained by?

Answer 1

Osmolatility gradient from cortex to renal papilla

Established by;

• Urea recycling
• Countercurrent multiplication

Maintained;
- By vasa Recta

Question 2

Compare the permeability of the 3 parts of LoH

Answer 2

Thin descending;
- Permeable to water, Na, Cl

Thin ascending;

• Impermeable to water
• Minimal Na and Cl transport

Thick ascending;
- Impermeable to water (Na-K-Cl transporter on apical membrane allows Na reabsorption)

Question 3

Describe the permeability of the parts of Vasa Recta

Answer 3

Descending- Absorbs solutes and loses water

Ascending- Loses solutes and reabsorbs water

Question 4

Compare the Osmolality of the Interstitium and Vasa Recta

Answer 4

Equal at all times

Question 5

Urea in the interstitum diffuses into hairpin bend of LoH. Where does this urea come from?

Answer 5

ADH causes release of urea from CD into interstitium, through UT1 transporters