3.1 Countercurrent multiplication

Question 1

what establishes the corticopapillary gradient?

Answer 1

-urea recycling
-countercurrent multiplication

Question 2

where does countercurrent multiplication occur?

Answer 2

loop of henle

Question 3

where is the corticopapillary gradient?

Answer 3

cortex to renal papilla

Question 4

what maintains the corticopapillary gradient?

Answer 4

vasa recta

Question 5

what is absorbed and lost in plasma of descending limb of vasa recta?

Answer 5

absorb NaCl
lose water

Question 6

what is absorbed and lost in plasma of ascending limb of vasa recta?

Answer 6

NaCl back to interstitium
water absorbed

Question 7

why is there slow flow in vasa recta?

Answer 7

allows enough time for solute absorption so can equilibrate, mimosas washout

Question 8

the vasa recta can absorb water released from collecting duct. how can it do this, and what does it achieve?

Answer 8

ADH puts aquaporin channels into collecting duct so water can be released
maintains high osmolality of interstitium

Question 9

where do we find urea in the body?

Answer 9

-nephron
-muscle (breakdown products of amino acids)

Question 10

describe the process of urea recycling

Answer 10

-some urea in blood, some free in intertstitium
-blood urea 50% reabsorbed in PCT
-descending limb of LoH permeable to urea so some enters (down its conc grad)
-highest urea conc at base of LoH
-ascending limb + DCT impermeable, conc increases as water and solutes reabsorbed
-some leaves via urea transporters in collecting duct, goes back into LoH
-40% excreted (ish)

Question 11

what controls the number of urea transporters in collecting duct? what impact does more transporters have?

Answer 11

ADH
more transporters means more urea reabsorbed so osmotic effect so more water reabsorbed to interstitium then vasa recta