renal dr; bashardoust. glomerular filtration renal blood flow = 1.2 l/min renal plasma flow = 700...
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RENALDr;
bashardoust
Glomerular Filtration
• Renal blood flow = 1.2 L/min• Renal plasma flow = 700 ml/min (60 % of RBF)• GFR = 125 ml/min = 180 L/day filtered plasma
– Filtered fraction = GFR RPF = 125 700 = 20%
• Urine output = 1 ml/min or 1500 ml/day = 1% of filtered plasma
Renal Anatomy• Functional unit is the nephron
– Approximately 1.25 million/kidney– 80% are cortical – short loop of Henle– 20% are juxtamedullary – loop of Henle projects
into medulla– Cortical nephrons only dilute urine– Juxtamedullary nephrons dilute and concentrate
urine
• Functions of nephron– Glomerular filtration– Tubular reabsorption– Tubular secretion
Filtration, Reabsorption, Secretion
A: filtered, no reabsorption or secretion - inulin, creatinine
B: filtered, some reabsorption - electrolytes
C: filtered, complete reabsorption - glucose, amino acids
D: filtered, plus additional secretion - K+, H+
Anatomy:
J.G.App.
Afferent Arteriole Efferent
Cap. loops
DCT
Glomerular Filtration:
L.R.IL.D.L.R.E
Foot Process
Podocyte
(Visceral epithelium)
GBMGBM
Glomerular Capillary LumenGlomerular Capillary Lumen
Bowman’s Capsule SpaceBowman’s Capsule Space
+
Collagen IVLamininFibronectinEntactinetc.
BLOODBLOOD
ProteinsProteins3.6nm/3.6nm/70,000MW70,000MW
Plasma - Plasma - ProteinsProteins
FILTRATEFILTRATE
Table 47-2. Laboratory Findings in Acute Renal Failure
Index PrerenalAzotemia
Oliguric AcuteRenal Failure
BUN/PCr Ratio >20:1 10-15:1
Urine sodium (UNa), meq/L <20 >40
Urine osmolality, mosmol/L H2O >500 <350
Fractional excretion of sodium <1% >2%
FENa = UNa * PCr * 100
PNa * UCr
Urine/plasma creatinine (UCr/PCr) >40 <20
NOTE: BUN, Blood urea nitrogen; PCr, plasma creatinine; UNa, urine sodium concentration; PNa, plasma sodium concentration; UCr, urine creatinine concentration.