5.1 Renal Flashcards
Formation of urine
How much water filtered bowmans a day
GFR is 125ml min = 180l day
4 times larger than TBW
Normal state hydration 99%> reabsorbed
Why is glom filtrate - UF
Doesn’t contain proteins in plasma
How is filtered water handled in kidney
Where reabsorberd?
Prox 65%
Loop Henle 15%
Distal tub varies 8% - Absence ADH
>19% Max ADH
Maj filtered water prox tub
water move - passive - water moves down conc gradient
Osmosis water low solute to high solute
reabsorption solute - changeing osmolality - causes movement water
Most important solute Na+
reabsoprtion - active
NaKAtpse - BL membrane - Prox tubule
Water follows passively down osmotic gradient
15% Filtered load reabsorbed in LOH -
Nearly all from water permeable desc LOG
Occurs - high medullary osmolality
Ascending - water imperm reabsop solute - delivers hypotonic to distal tubule
20% filter wat delivery to distal tubule Amt reabs - depends on ADH level Max = 19% reabs = Urine vol 500mls - <1% filtered volume osm 1200-1400 Reabs water occurs response osmotic gradient
What is nephron mad up of
What size can pass
what is the passage from aff art
what happens in nephritis
Nephron - individual renal tububle + Gloermuls
Afferent arteriole larger efferent
Glom membrane - permits passage of neutral substanc up to 4nm diam
Afferent arterole -> glomerulus -> efferent art -> pertibu caps -> intertublar vasa recta
Efferent art juxtamed glo drain into peritublar network
also into loops dip int o medulla along LOH
Per glom caps x50 skel Neutral sub <4nm free filtered >8 - not sialoprotein on GC wall - charge repel anion more expeceted size alone - albumin
- charge dissipated in neprhtits - predispose to proteinuria
What is the max urine vol in absence ADH
8% filtered load is reabsorbed in distal tubule -
12% original GFR appears urine
Urine vol 22L day - Urine osmalilty reach min val 30-60
What is the obligatory water loss in urine
Min urine vol necc excrete daily solute load
Dep:
1 Daily solute load
2 Max urine osmolality
Daily sol - Typically 700mosm day
max urine osm under extreme cond -~1400mosm/kg
Under condition - excrete sol load
olbigtory water loss day 500 mls (1400/700)
Body total oblig watewr loss high - other insensible loss
What are the major contributor to normal solute load
Na 100-150 mmol day
K 70-100
Cl 150
Urea 400
Urea - major contrib nitrogen waste exretion
Creatine ony 12mmol day
Failure excretion daily urea = azotemia
Excretion electyo vary amount kiney excrete depend daily intake
Intake unreg - kidney major exerting regu control
If daily Na is low - kidney able decrease Na day s -
How much and where + How Na reabs
NaCl - cotport
3% EwnANa coupled to H, Gluc, aA, organic Po4 other
Prox tub - asc lim distal tub collecting duct
Move cotport or exchange from lumen to cell
Gradient maint active Na/ K atpase bl membr
N 60% Filter na reabs PT - Na/H exch
30% asc lib Na 2 Cl K - cotport
DT 7% nAcL Cotport
3% ENac channel in CD - fine tune aldo
Gluc
Glu AA HCO3- reabs w/ Na in early pt
filtered rate 100mg /min - essentaly all reabsorbed
max tport tmg - exceeded - appears urine
375mg min man (300 womin)
Renal threshold
plasma level @ which gluc first appear
actual level less than 375 - ~180mg dl
not all nephorn ident + remove all gluc below
splay - deviation actual curve from ideal
Lum sodium dep gluc tport 2
What is normal gfr
why does UF occur in glom
125mls min
180l day
UF - starlings in glom capillary favours net filtration
tubules carry filtered fluid away keep hydrostatic in bowman’s low
What is UF
All sub cept colloid filterr accross semiperm membrane
Plasma - proteins maj colloids present
Glom cap UF - fluid and solutes filtered w/ exception pl protein
How GFR measure
Clearance certrain tracers - inulin from Ren Plasma Flow
Should be frree filter, neither secret nor reasbo, should be non toxic non metabolised
Amt tracer in urine - equal amt filtered cannot enter tubules other way
Tracer T
amt filter = plasmaa conc x gfr
amt tracer in urine = urine conc x urine vol
Therfore Pt x GFr = Utx V
GFR = Ut x V/Pt
What is clearance
Vol plasma from which tracer is totally cleared per unit time
Effectiveness removal substrance plsama
Cl = Amt removed plasma unit time / pl con
Kidney - amt removed plasma is same as amt in urine
amt urine - urine conc x urine vol
C = UV/P
GFR = UV/P = freel filtered neither reabs GFR = Clearance inulin
GFR = Cin
what is metabolic water production
Water during oxidation food - water prod final rxn etpc
cat cyto oxidase
2H+1.2 O2 = H2O
5mls kg day - 350 400 mls
GFR per neprhon
GFR = Kf {(PgC-Pt)-(NGc-Nt)
Kf - glom UF, Coeff, produt permeabilty - effective filtration surf area
can be alter mesagnial cell - contract = reduced area = rediced Kf
Endothelin, AT II, Vaso, Na contract
ANP DA< PGED2, cAMP = relax
PGC - higher than n caps
affer art short, straigh brance interlob AA
Efferent art - high resistance
Onctic pressure rise along glomerulus fluid leave= net filtration pressure reduction
exchange accross GC - flow lim rather diff lim
Preop test Rfxn - what are they telling us
Fuctions kidney x 5
1 Water balance
2 Electrolyte balance
3 AB balance
4 excretion waste
5 endocrine
Ability kidney excrtete nitrogenous waste prod metab
Why Creatinine so useful
Broad indicator glob renal fxn
all fxn bar endocrine involve change glom filtrate in tubules
Kidney - large number small fxn ‘nephron’
Tot GFR - measure - total amt filtration all nephorn - indirect index function all nephorne
Cr Cl - est gfr(some secr) - endog sub
valu not as acc inulin
12 /24 urine collectin reqd - limit use
However plasma cr level - incersel related creatine clear - used index GFR
Cr level - index GFR - single easy obtain
Juxtaglomerular apparatus
Struct kidney
2 omponenets - situated adjacent each other
JG cell - wall afferent arteriole
Mac densa wall distal tubule
Fxn - pressure regulation
Sensor afferent arteriolar pressure - intra renal barorec
Secretion Renin - activate RAAS
Mac densa:
1 Sens fluid flow rate distal tubule
2 prod local vcon
What is tubuloglomerural feedback
Control GFR - Feedback signal derived tubule
Important mech - autoreg GFR
Rate flow thru DT inc, Glom filt decr nephron vice versa
What are effect Renin
How Ang II prod
Renin - enz secre JG cell
Act plasma prot - angotensionged - prod decapept ANgI - inactive
Term two AA - rxn cat ACR = octapept Ang II
ACe pressent endothelial cell pulm capilary -
addit AA split off prod Ang III some tissue
less potent
What are major actions of AngII
Vasoconstriction
Stim release aldo adrenal - na hco3 reab PT, Na reabs in cell CD - exhcange K/H
Action hypotahlamus - icnrease thirst ADH
Increases activity SNS
Actions hypothal - subfornical organ & organum vasculosum of lamina temrinalis - both access blood born med outside BBB
Net result - actions
renal salt and water rention
increased TPR ,
INcrease CO
Arterial pressure increase
Excretion Bic
How much bic filtered
How much reabs - where
4000-5000mosm /day
Product plasma bic and GFR
eg filt = HCO3 x GFR
24x180
4230
Under normal conditions totally reabsorbed
90% Prox tubule and rest distal
Reabs - crucial main ab balance - loss - acidifying affect
When does bic apparear in urine
Plasma [HCO3} exceed 27-28mmol/l
Renal threshold exceeded + bic appears urine
What is the role of renl bic reabsoprtion in A-B balance body
Major role kidney ab - reabsorp filt bic
fiter daily fixed acid load
Reabs - prox tube - secretion equi amt H by prox tube and reab equiv amt a -
Amt h secreted large - not lead net excretion
Amt H secretion a/w excretion anio fixed acid - smaller
70mmol/day
reporesent net excretion amt H body
