Physiology 3 Clearance

Question 1

Renal Clearance

Answer 1

Provide insight into renal function and how the kidney handles various solutes and water

Question 2

Filtered load equation

Answer 2

(Vp)(Px) This is the rate at which x is being delivered to the glomerular capillaries. Remember Vp= Cx

Question 3

Excreted load equation

Answer 3

(Vu) (Ux) is the rate at which X is leaving the kidney

Question 4

Principle of Mass Balance

Answer 4

The rate at which the solute leaves the plasma must equal the rate at which it enters the urine. Therefore (Vp)(Px)= (Vu)(Ux) or Filtered load = excreted load

Question 5

Vp

Answer 5

the volume of plasma that originally contained the amount of the solute x that appeared in the urine in one minute. VOLUME OF THE PLASMA THAT WAS CLEARED OF SOLUTE X IN ONE MINUTE AKA CLEARANCE

Question 6

100 mg of plasma containing 100 mg of X goes through the glomerular capillaries in a minute, X is freely filtered. What is the clearance of X

Answer 6

Filter = 20 ml/min (20%) filtered load of x = 20 if at steady state (no net reabsorption and secretion) then we can assume the excreted load of x to be 20. The clearance of X would be the volume of plasma that originally contained 20 mg of x = 20 ml

Question 7

clearance equation

Answer 7

Cx= ((Vu)(Ux))/(Px)

Question 8

GFR definition

Answer 8

rate of fluid flow from the glomerular capillaries into bowmans capsile and proximal tunbule.

Question 9

Measurement of GFR requires a solute with the flour following properties

Answer 9

1.) Freely filtered at the glomerulus 2) Not reabsorbed in the tubules 3.) Not secreted in the tubules 4.) Inert (not metabolized by the kidney)

Question 10

Inulin as a measure of GFR

Answer 10

fructose polymer. At steady state the rate of filtration = rate of excretion. Filtered load = (GFR)(Pinulin) Excreted load- (Vu)(Uinulin)

Question 11

Changes in Creatinine and BUN with respect to changes in GFR

Answer 11

Decreased GFR will result in higher convcentrations of Cr and BUN. Plasma creatine (and BUN) is inversely related to GFR

Question 12

BUN: Creat ration

Answer 12

10:1 normally

Question 13

elevated BUN:Creat ratio

Answer 13

Hypovolemia

Question 14

Estimation of renal plasma flow requires what solute

Answer 14

PAH: 1.) Freely filtered at the glomerulus 2.) Not reabsorbed in the tubules 2.) COMPLETELY SECRETED by the tubules

Question 15

Renal Plasma Flow equation

Answer 15

RPF= ((Vu)(Upah))/(Ppah)

Question 16

Estimating renal blood flow

Answer 16

since plasma only accounts for part of the “blood” knowing hematocrit allows estimation of total renal blood flow: RBF= (RPF)/(1-hematocrit)

Question 17

Renal blood flow normally acounts for what percent of the cardiac output

Answer 17

20%

Question 18

Filtration fraction

Answer 18

fraction of the plasma volume entering the glomerulus that is filtered from the glomerular capillaries into bowmans space and enters the proximal tubule. FF=GFR/RPF or FF= Ccr/Cpah

Question 19

Normal Filtration fraction

Answer 19

20%

Question 20

Fractional Excretion

Answer 20

The fraction of the filtered load of a solute that is excreted. Comparing a substances FE to GFR tells you about the net handling of the substance by the kidney. FE= Excreted load/ Filtered load OR FE= Cx/Ccr OR FE= (Ux/Px)/(Ucr/Pcr)

Question 21

FE <1

Answer 21

Substance X is Reabsorbed (excrete less than was filtered)

Question 22

FE>1

Answer 22

Substance X is Secreted (excrete more than what was filtered)

Question 23

FE= 1

Answer 23

Steady state filtration = excretion

Question 24

Fractional Reabsorption

Answer 24

FR=1-FE

Question 25

Fractiona Excretion of water

Answer 25

How much of the filtered water was excreted or how much was the creatine concentrated? FEH2O = Vu/GFR or FEH2O= Pcr/Ucr