Kidney: Clearance Flashcards
the amount of a substance that is filtered out of the blood by the kidneys
Renal clearance
Excretion = ______ – Reabsorption + ______
Filtration
Secretion
Measurement of Renal Function is:
Renal Mass Balance
Renal Mass Balance
Cra = Crv + Cu
renal artery= renal vein + urine/ureter
Cra = Crv if _____ ______
completely reabsorbed
Cra = Cu if _____ ____
completely secreted
For substances that are not synthesized or metabolized by renal tissue, the amount entering the kidney (via the renal _____) equals the amount leaving the kidney (via the renal _____ and the ____)
artery
vein
ureter
the amount of substance entering the nephrons by filtration and/or secretion equals the amount leaving by _____ and/or ______
reabsorption
excretion
the use of ______ _______ provides the means for indirectly measuring renal blood flow, glomerular filtration rate, and the rates of tubular reabsorption and secretion of various substances.
mass balance
flow can be determined by measuring the mass balance of a substance that is not synthesized or metabolized by the kidney.
Renal plasma flow
The difficulty of obtaining renal venous plasma samples limits the usefulness of mass balance approach to measuring RPF so we measure excretion of something “______” cleared from blood
completely
the tubular secretory system for ________ is so efficient that at low plasma concentrations it removes 90% or more of the ____ from the plasma as it flows through the kidney, the
para-aminohippurate (PAH)
PAH
The total plasma volume filtered by the glomeruli per unit time (GFR) can be measured using a substance that is _____ filtered but is not reabsorbed or secreted, so that the amount excreted equals the amount filtered, such as inulin
freely
____ is a fructose polysaccharide (molecular weight ~ 5000)
The amount of ____ filtered per unit time by the glomeruli equals the volume of plasma filtered/time (GFR) times the plasma concentration (Pin)
inulin
inulin
Since the ______ cells do not add or remove inulin from the filtrate, the amount entering the nephrons equals the amount exiting by excretion
tubular
GFR = Cu x Volume of urine / Cra
if substance is _____ only
filtered
GFR = Excretion rate of _____ = clearance of inulin
inulin
a waste product of amino acid metabolism
Urea
Clearance of Urea is to the ___ of the Inulin curve for renal clearance
right
Clearance for Urea is to the ____ of Inulin-clearance curve because it is cleared at a slower rate.
This tells us that since the same amounts of inulin and urea were filtered, some urea was ______
right
reabsorbed
If the curve of substance ‘X’ was to the left of the Inulin-clearance curve:
What does that tell you about substance ‘X’?
It secreted! Ex. Penicillin
at very low urine floe rates, about 40% of filtered urea is _____
excreted
as urine flow rises to 2 ml/min, fractional urea excretion _______ rapidly
increases
urea is reabsorbed by a _____ process that depends on water reabsorption to establish a chemical gradient across the tubular wall. Thus when water reabsorption is reduced, urea reabsorption ____
passive
falls
all filtered glucose is reabsorbed at plasma concentrations below ____mg/dl
the reabsorption mechanism becomes saturated at plasma concentrations above ____mg/dl
250
350
the clearance of glucose is 0 when the plasma concentration is below ____mg/dl, because no glucose is excluded.
Above that concentration, glucose concentration ____ and begins to approach the clearance of inulin
250
rises
for a substance that is filtered only, the clearance _____
does not change
for a substance that is reabsorbed, the clearance tends to _____
rise
for a substance that is secreted, the clearance tends to ____
fall
The _____ _____ expresses the excretion of a solute as a percentage of the filtered load
Fractional Excretion (FE)
