GFR & RBF Flashcards
Define PGC
Hydrostatic pressure within the glomerular capillary
Favors filtration
Define PBC
Hydrostatic pressure within Bowman’s capsule
Favors absorption
Define (Pi)GC
Oncotic (colloid osmotic) pressure within the glomerular capillary
Favors absorption
Define (Pi)BC
Oncotic (colloid osmotic) pressure within Bowman’s Capsule
Favors filtration
What is the equation for Net Filtration
Net filtration = PGC - PBC - (pi)GC
What three factors contribute to GFR
Hydraulic conductivity (the permeability of the endothelium) (Lp)
Surface area for filtration (Sf)
Capillary ultrafiltration pressure (PUF)
What is an equation for GFR
GFR = Kf x PUF
Where Kf = (Lp) x (Sf)
Is the permeability or the surface area is increased, what happens to the GFR
It increases
What is the equation for PUF
PUF = PGC - PBC - (Pi)GC
What can alter the PUF
CHANGING glomerular capillary pressure (PGC)
What determines PGC
Renal arterial BP
Afferent and Efferent arteriolar resistance
What within the glomerulus can change surface area and what does this cause
The mesangial cells can contract which decreases surface area and thus Kf and thus GFR
Where is the first drop in hydrostatic pressure within the renal system
At the afferent arteriole
How does (Pi)GC changes as the blood moves through the capillary
On the afferent side, it is low and filtration is high, however towards the efferent side, it rises and levels out, causing less filtration because more fluid is removed and thus more proteins are present, limiting the filtration
Where does most filtration take place in the capillary? What about least
Most @ afferent arteriole
Least @ efferent arteriole
