Glomerular Filtration Flashcards
Where does filtration occur?
At the interface between vascular and epithelial structures
What determines permeability across the GF barrier?
- Size
- Charge
- Shape
What is SNGFR?
Single nephron glomerular filtration rate
What forces govern intravascular and transcellular fluid movements?
Starling forces
When do you find proteins/osmolytes in the primary ultrafiltrate?
Defective filtration
What is glomerulonephritis?
Bacterial infection causing injury to the glomerulus
What is Goodpasture’s syndrome?
Antibodies attack the basement membrane
What is Alport Syndrome?
Collagen IV defect so bm splits
What is the result of High dose lithium treatment?
GSK inhibition which leads to impaired filtration barrier
Why does net ultrafiltration pressure decrease at the efferent end?
Capillary oncotic pressure builds up as filtration proceeds
Why does net ultrafiltration pressure decrease at the efferent end?
Capillary oncotic pressure builds up as filtration proceeds
What regulates glomerular filtration?
- Hormonal
- Autoregulation
- Tubuloglomerular feedback
What hormone regulates GF?
RAAs system
What provides tubuloglomerular feedback?
JG apparatus
Describe tubuloglomerular feedback?
When there is high flow rates there is inefficient removal of NaCl this is sensed by macula densa cells. These release ATP and adenosine to increase glomerular mesangial cell constriction and decrease glomerular capillary filtration area
How can you measure GFR non invasively?
Clearance of special substances.
What is inulin?
Used for clearance because it is freely filtered, non toxic, not secreted, not absorbed, and not metabolized. The amount that filtered should be the amount secreted
What are GFR and inulin clearance not dependent on?
[Pin]
What is creatinine?
Product of protein metabolism that can be measured to measure GFR
What is a pro to using creatinine measurements over inulin?
No need for infusion and can collect samples over a longer period of time
What is the pros of using inulin over creatinine?
It gives you a more accurate GFR
What amount of cardiac output is delivered to the kidney?
1/5 (20%)
50% of this is plasma
What percentage of plasma crosses into the bowman’s capsule?
20-30%
How much of the filtered plasma is actually excreted?
<1%
How many layers are in the basement membrane?
3
What charge of molecules do not cross the basement membrane?
Negatively charged molecules because the bm is negatively charged itself
What is the lumenal oncotic pressure in a healthy individual?
- No big molecules should be in the ultrafiltrate
Why does oncotic pressure in the efferent capillary increase?
You are taking away your solvent and you have more solutes at the end of the glomerulus
At what renal blood flow is oncotic pressure the highest?
Low blood flow
When is the net Puf the lowest?
At low flow
What happens to GFR if there is a drop in PA (arterial pressure)?
Decreases rapidly after 100mmHg without any signals (autoregulation)
What is the autoregulatory range?
This is the range of PA that the GFR and RBF are maintained at constant values without any signals from other systems (80mmHg-200mmHg)
