Week 1: intro to renal physiology Flashcards Preview

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Flashcards in Week 1: intro to renal physiology Deck (12):

What are some disturbances of renal function?

-most common causes of renal failure are chronic: diabetic nephropathy, hypertension
-primary inherited renal disease: ADPKD autosomal dominant polycystic kidney disease
-overmedication, CHF, glomerulonephritis, acid base disturbances


Define filtration, reabsorption, secretion, excretion

-filtration: From glomerular capillaries into renal tubular lumen. occurs in glomerulus.
-reabsorption: transport from tubular lumen fluid back into systemic circulation
-secretion: transport from non glomerular capillaries or interstitial fluid into tubular lumen fluid
-excretion: removal of a material from body fluids into urine


What is the equation for excretion of material x?

excretion: amount in urine x urine flow rate
filtration: amount in plasma x plasma filtration rate
secretion: Amt added across tubule/time
reabsorption: Amt removed form tubule/time


What is the glomerular filtration rate (GFR)?

-rate (ml/min) of production of ultra filtrate across glomerular capillaries into Bowman's space
-filtrate if blood and protein free
-sum of filtration across all glomeruli in the two kidneys
-normal: GFR is about 120ml/min=180L/day
-20% of plasma filtered out of the blood while 80% of plasma continues past the capillaries and enters peritubular capillary network


What is the filtration fraction?

RPF: renal plasma flow
in normal: =120/600=.20
20% of plasma filtered out of the blood


What is clearance? renal clearance?

-rate of removal of a substance from a volume of blood or plasma. blood cleared of the substance in volume/time
-renal clearance: rate the blood or plasma is cleared of a substance by excretion into urine over time


How is GFR estimated using inulin?

-Inulin is a polyfructuse that is freely filtered at glomerulus and not reabsorbed, secreted, synthesized, or metabolized.
P(In) X GFR = U(In) x V
plasma [inulin] x GFR=Urine[Inulin] X urine flow rate
-inulin clearance=GFR =(U x V)/P


How is GFR estimated from clinical data, i.e. creatinine?

-creatinine is a by product of skeletal muscle creatine metabolism
-is produced at constant rate and normally excreted in urine at same rate
-P[creatinine] x GRF= U[creatinine] X V
-excretion rate=U x V
-means that P x GRF is a constant
-if GFR falls, P[Cr] rises


What are the limitations of estimating GFR from plasma creatinine?

-Cr levels may be high from high meat diet, low in malnourished patients, high after marathon
-Cr production and GFR may be low in cirrhotic patients


Describe PAH secretion.

-PAH is an organic acid, its excretion is greater than rate of PAH filtration
-PAH enters cell across basolateral membrane by PAH/aketoglutarate anti port mechanism
-aketoglutarate concentrates in the cell, concentration driven by downhill cotransport with Na+


How can renal blood flow be measured by determining the clearance of PAH?

-PAH is infused at low level so that 100% will be removed from renal circulation, urine and plasma concentrations, and urine flow rate are measured
RPF= U[PAH] x V/ Plasma[PAH]
Partery x RPFartery -[Pvein x RPFvein]=U x V
[Pvein x RPFvein]=0
P[PAH]artery x RPFartery=U[PAH] X V
-Renal blood flow=RPF corrected for hematocrit


What is that transport rate?

Transport rate =filtration rate-excretion rate
filtration rate=GFR x P[x]
excretion rate=U[x] x V