Session 3- Countercurrent multiplication and urea recycling

Question 1

What are cortical nephrons

Answer 1

Short loop of henle that status in the cortex

Question 2

Juxtamedullary nephrons

Answer 2

Long LoH extends into the medulla - 15% of nephrons are like this

Question 3

What is teh vasa recta

Answer 3

Capillaries that wrap around the loop of Henle- allow reabsorption of water

Question 4

How is corticopapillary gradient established

Answer 4

Urea recycling

Countercurrent multiplication

Question 5

What maintains the corticopapillary gradient

Answer 5

Vasa recta

Question 6

What is Normal plasma osmolality

Answer 6

300mOsm/kg - isotonic

Question 7

What is maximum osmolality of interstitium

Answer 7

1400mOsm/kg hypertonic

Question 8

What happens in the descend of teh vasa recta

Answer 8

Absorb solutes such as na+ Cl- and urea and water is lost

Question 9

what happens in the ascend of the vasa recta

Answer 9

Reabsorb water and lots o solutes

Question 10

why does blood move slowly through the vasa recta

Answer 10

To equilibrate at each stratification level - minimises washout

Question 11

Function of urea in medulla

Answer 11

Helps to maintain medullary hyper tonicity

Question 12

How is urea recycled

Answer 12

Tubular conc of urea increases as it diffuses down concentration gradient from medulla into lumen

Ascending limb and early DCT impermeable to urea so conc increases as solutes and water reabsorbed

ADH causes increase in UT1 on apical surface of medulla collecting tubules- enables urea to flow down concentration gradient

Question 13

what does the descending limb reabsorb

Answer 13

water

impermeable to ions

Question 14

what do the thick and thin ascending limb reabsorb

Answer 14

ions- sodium chloride and potassium

impermeable to water

Question 15

what causes water to be reabsorbed passively

Answer 15

Because the descending and ascending limb go in opposite directions

when the ions are reabsorbed in the interstitium it makes the medulla (interstitium) salty as water isn’t reabsorbed here as it is impermeable. This causes water to be reabsorbed passively into the interstitium.

Question 16

what is the key role of th Juxtoglomerular apparatus

Answer 16

control blood pressure

Question 17

why do we reabsorb urea into the interstitium

Answer 17

maintain osmolarity of the medulla which drives the reabsorbtion of water in loop of Henle

Question 18

what are the peritubular capillaries derivative of

Answer 18

efferent arteriole

peritubular capillaries then converge and drain into the venous system

Question 19

what does the apical surface face

Answer 19

tubular lume

Question 20

what does the basolateral surface face

Answer 20

peritubular capillaries which alongside the nephron

Question 21

how does osmolarity chnage as you move down in the medulla

Answer 21

increases- a part of the corticopapillary gradient

Question 22

how does the tonicity of the interstium compare to that of the tubule

Answer 22

interstitium is hypertonic relative to the tubule

Question 23

how is the corticopapillary system established

Answer 23

urea recycling

countercurrent multiplication

Question 24

what areas of the nephron are impermeable to urea

Answer 24

early DCT
thick ascending limb

also impermeable to water

Question 25

how much urea is reabsorbed in the PCT

Answer 25

50%

Question 26

hoe much urea is reabsorbed in the glomerulus

Answer 26

100%

Question 27

at the bottom of the loop of henle what is the {urea}

Answer 27

110%

Question 28

how much is urea is reabsorbed at the late DCT

Answer 28

110%