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
How is renal bic excertion affect in metabolic alkalosis
In acute met alk - iv admin bic renal threhold exceeded - bic rapidly excreted in urine
acute met alk reapidly corrected by kidney - large capacity excrete
Chronic met alk - must mech interfere kidney abil excrete bic
Second mech - different mech responsible gen disorder in first place
Major factors - interfer - reduced GFR Cl depletion K depletion ECF vol depeletion
Recover chronic met alk - correction prim cauuse
Renal clearance
Amt palsma / blood can cosnidered cleared of sub per unit time
GFR
RBF- PAH
What is free water &* free water cleraance
Non osmotically obligated water
Amt water present in excess req prod solution same osm as plasma
Solution high osmolality than plasma
free water is negative - amt water added to soln - reduce osmolality to plasma
Eg 1l urine 140 collect when pl osm 280
urine - prod 500 mls w/ osm 2800 added to pure water
Litre of urine 500mls pure water in excess - amt reqd prod urine same osm of plasma
How is free water clerance measured
calc urine vol osm and plasma osmolaitly
What happens free water in DI
Increased markedly
Absence ADH - water reeabs CD low -
large vol dilute urine produced
has low osmolality - free water clerance high
squaporin 1 - pt lum and basolat surf
ADG increase perm CD wate r- insert aqua 2 paical membrane pricnipel cells
Countercurrent - concentrating mech - main grad increase mech along medullary pyramid
prod LOH & VR
Endocrine functions kidney
Hormones prod kidney
Hormon prod - enzymes release
Hormones have site action kidney
Hormones prod kidney
1-25 Dihydroxycholalciferol - calcitrio - active form vit d - prod vit precurose
EPO
PG
Enzyme rel kidney - initiate rxn leading prod / hormones
Secretion renin - initiate rxn - prod ang II - from anggen
release aldo
Secretion killikrein - lead prod bradykinin
Hormones have site action kidney
ADH Aldo Calcitriol PTH ANP
What is EPO
Glycoprot - most prod reponse to hypmoaxamei
site - edno cell of pertibular cap - release circ from cells
85% kid 15% liver
sercr fac alkalosis at high altitiude
EPO receptor - Has TK activity - half life 5 hours
inactivated b liver
Where is calcitriol prod
1 25 dihydxycholecalc -
final step in prod active form -
1a hydoxy reaction - cells prox tubule - reaction catlasyed mito enzy 1 a hydroxy lase
What is ANP - (ANF)
Peptide RA
natiruretic effect
Increase BV increase
- CVP rise - RA muscle release ANP - Stretch
Excretion Na kidney
Mech - not full det
prob increase GFR
or inhib DCT Na reabs (on exam explan)
Have GC act - act bind ANP
act - rec glom mesangial - relax cell increase GFR
dilate aff art
Other actions Inhib ADH Decrease release Aldo inhib angII - vcon inhib renin release
ANP - opposite AngII
What effect immersion in water ANP secrtion
Water up to neck - removes effect gravity - periph circluation
increase effect blood vol - rise cvp
release anp increase - increase right strech
increase RAP - stim low press barorecp – decrease ADH
What affect IPPV on ANP
Decreased - decreased atrail distenion - a/w IPPV - increase pressure reduce tmural stech on wall
Red stretch on vol rec - interp hypovol - ADH risis
Renal Na water decrease - net patient
Renin
Angiogen
Renin: Aspartyl protesase - synth prohorm active renin 1* prod from pronenin in kidney
Made liver
increase g/cort, throid and at 2
ace - split histidyl leucine from at 1->at2
inact BK
AT II metab
1/2 1-2 min
Art constrict - BP inc, Potent vasocon, decrease in Na delpleted + cirrohosis
Inc Aldo - rel adreanl - facil NA action, Inc Na reabs - drop gfr - mesangeial contracition
Inc ADh ACTH
Renin increased
drop bp JG cell
Drop NaCl - reach mac densa - SNS activity
Inc cateholamines
Renin Decr - NaCl at MD - Inc Afferetn art bp
Excretion of Urea
Where is urea produced
Major nitrogenous waste - req excretion body
Prod liver Excr by kidney
Deamination gluatamate - production ammonium - fairly toxic CNS - am conv carbomyl phos liver -
cycle reactions - less toxic urea prod
Less toxic urea produce
Whats the effect of high protein diet on urea production
Excess AA _ not store any form
increase degradation liver
Increased Urea prods - renal excr
inc urea conc renal medualla - conc ability increase
1000 mol urea blood pump out LV
how manby appear in urine - without return cientral bv
9-23 assum no recirc 1-2%
Calc - % CO - going kidney 25%
% RBF -> cortex - assum all glomeruli 93% RBF
Filtr fraction 0.17-.2
% filt load urea excrete 20-50% depend hydration
250 reach - 46 filtered
final excre 9-23
What is the filtration fraction
- GFR divided RPF
GFR - glom filt rate RPF - Renal plasma flow
Typically .17-.2
Rises w/ drop sys bp - arteriole constriction
