PSWs Flashcards
What is clearance?
clearance is a RATE of output/input (excretion of substance/plasma conc of substance) so units = mL/min!
= (Ux*V)/Px
= E/Px
= mg/mL
official definition:
volume of plasma (so amount of plasma) that kidney was able to clear of/remove substance from body per unit time
What’s the principle of mass balance for the kidney?
Input = Output!
so
Artery = Vein + Ureter
Pa x RPF = Pv x RPF + U x V
Do we produce inulin in our body?
NO!
that’s why we don’t have transporters for it in our body!
Is inulin reabsorbed secreted, broken down or made by the body? Does it change GFR?
NO!
Inulin is ONLY filtered but NOT reabsorbed, secreted, broken down or made by body so it doesn’t change GFR. That’s why we can use it to estimate GFR!
AMOUNT FILTERED of a substance = ________ _____________?
FILTERED LOAD
Amount of inulin filtered = amt of inulin _________?
EXCRETED
C____ = GFR?
Inulin
C inulin = GFR bec amt of inulin filtered = amt inulin excreted (bec/ inulin isn’t reabsorbed or secreted)
GFR units?
100 -125 mL/min or 180 L/day
C ______ is a slightly greater than GFR bec/ though most of it is FILTERED, a very small amt of it is _______?
C creatinine ia little > GFR bec/ a small amt is SECRETED.
But, C creatinine is a good estimate of GFR bec/ most of it is filtered.
What substances can we use to estimate GFR?
Inulin, Creatinine
What is a byproduct of skeletal muscle metabolism/breakdown? It’s made at a CONSTANT RATE, proportional to muscle mass.
Creatinine
Does creatinine overestimate GFR?
Yes! (slightly, by only 10%)
In the Clearance equation = C = (Ux *V)/Px, what does V stand for?
Volume flow rate = L/day or ml/min
C cr?
Clearance of Creatinine
C in?
Clearance of inulin
Normal range for Plasma creatinine?
0-2 so its usually 1
How can we measure/estimate RPF?
Clearance of PAH
OR
Excretion of substance/ renal arterial - renal venous conc of substance (but can’t get renal venous conc from patient!)
PAH has RENAL VENOUS PLASMA CONC = 0 so that’s why it’s a good estimate for RPF!
What is PAH?
Amino Acid (organic ion)
Is PAH filtered and secreted?
Yes if PAH is at LOW PLASMA CONC!
PAH is filtered in LOW PLASMA CONC at glomerulus and almost ALL of it is secreted.
At _____ plasma conc of PAH, almost all of PAH that doesn’t get filtered is secreted?
LOW
Filtration Fraction = ?
GFR/RPF
=(Uin/Pin)/(UPAH/PPAH)
What’s one way to quantify the kidney’s regulation of ECF osmolarity?
Free Water Clearance!
V = Cosm + CH20
CH20 = V- Cosm
What does free water clearance tell us?
amt of pure water (NO SOLUTE!) to add or remove from urine to make urine ISOOSMOTIC to plasma
If urine is HYPOtonic to plasma, is free water clearance positive?
Yes!
bec/ water is being excreted to form urine less concentrated than plasma
