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Phys3 Clear & Transp

Clearance Volume of plasma cleared of a substance per unit time
What does clearance asses 1.Filtration. 2.reabsorption. 3.secretion. **The amount cleared equals the amount in the urine at that time.
What does a difference b/w GFR and the clearance of a substance indicate? NET secretion or reabsorption
Cx X Px = Ux X V 1.Cx: volume of plasma cleared per unit time. 2.Px: Plasma concentration of x. 3.Ux: [x] in urine. 4.V: volume of urine per time.
Clearance equation Cx = (Ux X V)/Px **Measured in ml/min, measure the VOLUME of plasma cleared per unit TIME
If a substance is filtered and COMPLETELY reabsorbed, what is the clearance of that substance? O
What does it mean to be freely filtered and what are some examples of freely filtered substances? Concentrations in Bowman's capsule equal that in the BL plasma. 1.Univalent electrolytes. 2.Urea. 3.Glucose. 4.aa's. **GFR=(Ux X V)/Px
What are some examples of solutes that are not freely filtered? those bound to proteins: 1.Ca2+. 2.Phosphate. 3.Magnesium.
Why is inulin a good indicator of GFR 1.Freely filtered. 2.Not reabsorbed. 3.Not secreted. 4.Not Metabolized. **C(inulin) will equal GFR
Can a substance have a clearance that is greater than GFR? YES, if the substance is freely filtered AND is excreted.
Can the clearance of a substance be used to measure RBF? YES, if it is secreted and NONE appears in the renal vein. **RBF = (U(PAH) X V)/P(PAH)
substance with a clearance = RBF PAH (b/c it can be removed in a single pass).
If GFR=Clearance NO net reabsorption or secretion.
If GFR < Clearance Net SECRETION
If GFR > Clearance Net Reabsorption
Practical method of measuring GFR Creatinine clearance. It is endogenous and is exported into the BL continuously by skeletal muscle. **It is freely filtered and not reabsorbed (very little is secreted so it could overestimate GFR).
Method for measuring creatine clearance 1.24 hr patient urine. 2.BL sample during collection time. 3.[creatinine] in both BL & urine. 4.Use clearance formlua.
Can C(creatinine) levels give inaccurate GFR? YES: 1.Dec muscle mass (elderly and children will appear to have dec GFR). 2.Ingestion of large amount of meat (Inc [creatinine] which will make GFR appear high).
What happens to teh GFR with aging? It DECREASES with every DECADE
normal plasma value of creatinine? 1mg/dl
relationship b/w plasma creatinine and GFR? INVERSELY related. **If GFR dramatically decreases, plasma [creatinine] Inc (GFR < 40ml/min)
How will renal disease cause Inc in BUN? Low GFR leads to low urine flow, which Inc urea retention and INCREASES BUN. **Fast flow rates will lead to decreased BUN
using BUN to determine dehydration High BUN confirms dehydration. The volume depletion causes low GFR and very low urea excretion. **Problematic b/c High protein diet causes Inc BUN while low protein diet causes dec BUN.
what happens to the BUN/Creatine ratio with vloume depletion? INCREASES b/c of the flow dependence of urea excretion but NOT creatinine.
How does an Inc FF affect π(PTC) INCREASES it
How does a Ded FF affect π(PTC) DECREASES it
Created by: WeeG