5a. DSA Renal Blood Flow And GFR Flashcards
3 layers of Glomerular filtration barrier?
Capillary Endothelium
Glomerular basement membrane
Podocyte epithelium
Filtered load of X =
(Plasma concentration of X)(GFR)
Urinary excretion =
Amount filtered - amount reabsorbed + amount secreted
Tubular reabsorption =
Glomerular filtration - urinary excretion + amount secreted
If excretion > filtration, tubular secretion must have occurred
Urine excretion rate =
Urinary concentration of X(Ux)
Urine flow rate (V)
Ux(V)
Renal clearance
Cx =((Ux)(V))/Plasma[x]?
Rate of removal by the kidneys.
Clearance is a flow rate
what can change filtration fraction
changes in gfr or rbf
ff=gfr/rbf
whats filtered/total blood flow to kidney
what is filtered load
a rate in mg/min
GFR(Plasma [X])
amount of substance x that passes through the glomerular capillaries into Bowman’s space
GFR directly proportional to clearance if:
substance is freely filterable in the glomerulus
substance is neither reabsorbed or secreted
substance is not synthesized, broken down, or accumulated by the kidneys
substance is physiologically inert (does not affect kidney function)
what is normal GFR
125 mL/min
Creatinine clearance
freely filtered
creatinine produced is creatinine excreted
useful for long term monitoring of renal funtion
inulin clearance
freely filtered but neither reabsorbed or secreted
inulin filtered is amount secreted
immediate effects of sympathetic stimulation
renin secretion by granular cells
angiotensin II exerts thirst
angiotensin II restores systemic BP by vasoconstriction
angiotensin II preferentially acts on efferent? arteriole
stimulates Na reabsorption in PCT and DCT
GFR is stabilized
systemic BP is raised
eventual effects of sympathetic stimulation
decreased urinary output
decreased urinary Na excretion
increased water intake
if BUN/Cr ratio is >20:1 where is the problem
pre-renal
