Renal Clearance, GFR And Ultrafiltration Flashcards
State the mechanisms of urine formation.
Glomelular filtration, reabsorption and secretion
What determines the ultrafiltrate composition?
The glomerular filtration barrier.
What is the function of the glomerular filtration barrier?
The barrier restricts the filtration of molecules based on their size and electrical charge.
State the clinical importance of the negative charges on the filtration barrier.
- If the - charges is removed, proteins are filtered primarily on their size.
- Between sizes 20-40 A, polyanionic proteins are filtered better than at the normal state.
If there is a loss of negative charge on the barrier, the more freely proteins or molecules can pass through.
How is the ultrafiltration coefficient, Kf, affected by diseases?
If a disease occurs, it reduces the amount of glomerular capillaries therefore reduces the filtration rate and
It increases the thickness of the capillary membrane and reduces the permeability of the membrane.
Describe the changes in Pgc during constriction of the afferent and efferent arteriole.
In constriction of the afferent arteriole, as renal plasma flow increase, Pgc and GFR increases.
In constriction of efferent arteriole, as the renal plasma flow decreases, Pgc and GFR increases.
In dynamics of ultrafiltration, State the what occurs when their is a change in #gc,
An increase in plasma protein, an increase #gc and a decreased GFR
An decrease in plasma protein, decrease in #gc and a increase GFR
In dynamics of ultrafiltration, State the what occurs when their is a change in Pbs.
An increase is PBS leads to a decrease in GFR
A decrease in PBS leads to an increase GFR
State the clinical important of the GFR.
—It is typically the first only sign of kidney disease.
—If the GFR continues to decrease, the disease is progressing.
— An increase in GFR, recuperation occurs.
Why can insulin be used in the estimation of GFR?
Inulin is:
1. freely filtered across the glomerulus
2. It is neither reabsorbed or secreted in the nephrons
3. It is not produced or metabolized by the kidneys
4. It does not alter GFR.
State the composition of the glomerular filtrate.
Plasma ultrafiltrate
No cellular elements
Nearly protein free
Salts and organic molecules.
Describe the filtration membrane in Type 2 DM.
- Reduced glycocalyx
- Reduced endothelial fenestrations
- Thickened glomerular basement membrane
- Increased foot process width w/ decreases filtration slit frequency.
State the equations for Clearance and GFR
Clearance/ GFR = UxV/ P
Why is the use of creatinine preferred over insulin in the estimation of GFR?
- Creatine is freely available in the blood
- Only one sample is needed and can be taken at any time.
- Can be used only to follow changes in GFR in patients with chronic renal disease.
