[PHYSIO] URINE CONCENTRATION Flashcards
counter current multiplier system found in
loop of henle
role of counter-current multiplier
builds up osmolarity in medullary interstitium by throwing NaCl into the interstitium
counter current multiplier system: active or passive?
active
counter current exchanger system found in
vasa recta
counter current exchanger system role
1-maintains osmolarity of medullary interstitium by trapping salts
2-remove water from interstitium
establishes osmotic equilibrium b/w tubular fluid & medullary interstitium
MCD
MCD depends on
ADH & urea reabsorption
counter current exchanger system: active or passive?
passive
thin ascending limb of LH receives hypertonic fluid due to
H2O reabsorption in descending limb
urea enters descending limb
role of thin ascending limb of LH in counter current multiplier system
passively diffuses NaCl to interstitium
role of thick ascending limb of LH in counter current multiplier system
ACTIVELY pumps out NaCl via Na-K ATPase
NaCl is pumped inside thick ascending limb of LH via
Na-K/2Cl cotransporter
counter current exchanger system prevents removal of ___by blood
NaCl & urea
urine concentration depends on
high interstitial osmolarity
high interstitial osmolarity depends on
NaCl & urea salts
vasa recta is permeable to
water & solutes
sources of water in interstitial space
1-descending limb of LH
2-DCT & CD
3-descending limb of VR
water handling of descending limb of VR
transports water into interstitium
water handling of ascending limb of VR
absorbs water from interstitium and transports it back to circulation
site of urea trapping
inner MCD
permeability of MCD to urea depends on
ADH
urea trapping contributes to interstitial osmolarity by
600 mOsm/L
outer cortical portion of MCD permeability
permeable to H20
impermeable to urea
(in presence of ADH)
inner medullary portion of MCD permeability
permeable to both H20 & Urea
(in presence of ADH)
inner medullary portion of MCD permeability
permeable to both H20 & Urea
(in presence of ADH)
effect of high protein diet on urine concentration
↑urea production
↑H2O reabsorption
↑osmolarity
↑urine concentration
effect of high protein diet on urine concentration
↑urea production
↑H2O reabsorption
↑osmolarity
↑urine concentration
passive reabsorption of urea occurs in?
under effect of?
-inner MCD
-ADH
steps of urea cycle
1-passively diffuses from MCD to MI
2-passively enters descending limb of VR
-⤷ exits thru ascending limb
of VR
2- and passively enters descending limb of LH
⤷exits thru MCD
why does drinking excess H20 cause loss of urea in urine
↓blood osmolarity
↓ADH
↓H2O reabsorption
↓MCD permeability to urea
↓passive urea reabsorp from MCD
role of ADH in urine concentration
↑DCT &CD H2O permeability
↑ inner MCD urea permeability
VC efferent arteriole
⤷↓VR BF & ↓wash out of solutes
⤷↑Na reaching LH so ↑Na
reabsorption
urine concentration can fail due to
1- diabetes insipidus
2-CRF
3-excessive medullary BF
4-diuretics
5-osmotic diuresis
