Session 3- Countercurrent multiplication and urea recycling Flashcards
What are cortical nephrons
Short loop of henle that status in the cortex
Juxtamedullary nephrons
Long LoH extends into the medulla - 15% of nephrons are like this
What is teh vasa recta
Capillaries that wrap around the loop of Henle- allow reabsorption of water
How is corticopapillary gradient established
Urea recycling
Countercurrent multiplication
What maintains the corticopapillary gradient
Vasa recta
What is Normal plasma osmolality
300mOsm/kg - isotonic
What is maximum osmolality of interstitium
1400mOsm/kg hypertonic
What happens in the descend of teh vasa recta
Absorb solutes such as na+ Cl- and urea and water is lost
what happens in the ascend of the vasa recta
Reabsorb water and lots o solutes
why does blood move slowly through the vasa recta
To equilibrate at each stratification level - minimises washout
Function of urea in medulla
Helps to maintain medullary hyper tonicity
How is urea recycled
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
what does the descending limb reabsorb
water
impermeable to ions
what do the thick and thin ascending limb reabsorb
ions- sodium chloride and potassium
impermeable to water
what causes water to be reabsorbed passively
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.
what is the key role of th Juxtoglomerular apparatus
control blood pressure
why do we reabsorb urea into the interstitium
maintain osmolarity of the medulla which drives the reabsorbtion of water in loop of Henle
what are the peritubular capillaries derivative of
efferent arteriole
peritubular capillaries then converge and drain into the venous system
what does the apical surface face
tubular lume
what does the basolateral surface face
peritubular capillaries which alongside the nephron
how does osmolarity chnage as you move down in the medulla
increases- a part of the corticopapillary gradient
how does the tonicity of the interstium compare to that of the tubule
interstitium is hypertonic relative to the tubule
how is the corticopapillary system established
urea recycling
countercurrent multiplication
what areas of the nephron are impermeable to urea
early DCT
thick ascending limb
also impermeable to water
how much urea is reabsorbed in the PCT
50%
hoe much urea is reabsorbed in the glomerulus
100%
at the bottom of the loop of henle what is the {urea}
110%
how much is urea is reabsorbed at the late DCT
110%
