3. Countercurrent Multiplication And Urea Recycling

Question 1

What is the corticopapillary gradient established by?

Answer 1

Urea recycling

Countercurrent multiplication

Question 2

What is corticopapillary gradient maintained by?

Answer 2

Vasa recta

Question 3

What happens in the thin descending limb?

Answer 3

Water, Na+ and Cl- reabsorption

Question 4

What happens in thin ascending limb?

Answer 4

Minimal Na+ and Cl- transport

Impermeable to water

Question 5

What happens in the thick ascending limb?

Answer 5

Impermeable to water
Na+K+2Cl- co transporter apical membrane
Na+K+ATPase on basolateral membrane

Question 6

What does urea recycling help to maintain?

Answer 6

Medullary hypertonicity

Question 7

How much urea is reabsorbed?

Answer 7

50% in PCT with Na+

Question 8

What happens to the tubular conc of urea?

Answer 8

Increases as it diffuses down conc gradient from medulla into lumen

Question 9

What role does ADH have in urea recycling?

Answer 9

Causes increase urea transporter (UT1) on apical surface of medullary collecting tubules, enables urea to flow down conc gradient

Question 10

What happens to the reabsorbed urea?

Answer 10

Secreted ack into Loop of Henle and goes back up to DCT/CD and is recycled

Question 11

What is the maximum osmolality of the interstitium?

Answer 11

1400mosm/kg H2O (hypertonic)

Question 12

What is the osmolality of fluid leaving the LoH?

Answer 12

100mOsm/kg H2O (hypotonic)

Question 13

What is normal plasma osmolality?

Answer 13

300mOsm/kg H2O (isotonic)