RE Glomerular Filtration
Terms
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copy deck
- three levels of filtration
-
fenestrated capillary
-70,000 kDa (albumin 65,000)
-keeps blood cells in
basement membrane
-lamina rara interna (neg)
-lamina densa
-lamina rara externa (neg- b/c type IV collagen & hep sulphate)
(loses charge w/glycation)
podocytes - normal renal bloodflow
- 600 ml/minute
- normal clearance
-
120 ml/minute
(amount of filtered plasma at bowmans capsule)
99% is reabsorbed - osmotic pressure in BC
- 0 (shouldn't be any protein in there)
- use for permeability constant
-
index of kidney health
Kf= GFR/ (Pgc-Pbc-oncPgc) - GFR affected by
-
blood pressure affects acute change
Kf affects chronic change - Kf affected by
-
hormones, disease
contraction of mesangial cells - Normal Starling Forces
-
Pgc = 45mmHg
Pbc = 10 mmHg
oncPgc = 19 mmHg - modification of filtration pressure
-
-contract afferents
-dilate afferents
-contract effs
-dilate effs
-dilate both
-obstruct urinary flow
-change protein concentration - contract afferents
-
decrease flow, decrease filtration
(sympathetic stim, AT II) - dilate afferents
- increase pressure & GFR
- constrict efferents
-
increase pressure & GFR
low levels of GFR - dilate efferents
- decrease pressure & GFR
- constrict afferents & efferents
- decrease flow, no change hydrostatic, increase oncotic pressure, decrease GFR
- change protein concentration affect on GFR
-
increase prot - decrease GFR
(& vice versa) - Calculate GFR
-
creatinine clearance
GFR= UV/P - normal clearance of creatinine
-
male 92-110 ml/min
female 74-110 ml/min - normal creatinine levels
- 0.8 - 1.2 mg/dl
- problem with creatinine clearance to calculate GFR
-
can be secreted into tubule
saturatable - estimation of RBF
-
calculate RPF (renal plasma flow)
* RPF = [U]/[RA]
* (ignores [RV])
estimate RBF
* RBF = RPF/1-Hct - PAH
-
organic acid used to calculate RPF
not synthesized/metabolized
amount back to RV is minimal - metabolism of creatinine
-
creatine to phosphocreatine via creatine kinase
spontaneous to creatinine from either
byproduct of muscles - causes of decreased Kf
-
(permeability constant)
Renal dz, DM, HTN - causes of increased P (BC)
- urinary tract obstruction
- causes of increased glomerular oncotic pressure with decreased glomerular pressure
-
decreased renal blood flow
increased plasma protein conc - causes of decreased resistance at efferents & glomerular pressure
- decreased AT II
- causes of increased R (A) & decreased glomerular pressure
-
sympathetic stim
vasoconstrictor autocoids - causes of incrased GFR
- pregnancy