Glomerular Filtration Rate - Determinants
Glomerular Filtration Rate - Arteriole Regulation
Glomerular filtration rate
The volume of ultrafiltrate formed by all of the nephrons of the kidneys per minute;
Units = mL/min.
Typical healthy GFR is between 110-130 mL/min; it varies based on sex, body composition, age, and other factors.
GFR is directly proportional to:
Filtration membrane permeability.
Surface area available for filtration.
Net filtration pressure is largely influenced by hydrostatic glomerular capillary pressure (PGC), which is easily adjusted by altering blood flow through the glomerulus.
Of the three variables that determine GFR, net filtration pressure is the easiest to manipulate.
Arteriole Regulation
Baseline:
Constant supply of renal blood flows through the afferent arteriole, glomerulus, and efferent arteriole.
Constant hydrostatic capillary pressure.
Constant GFR.
Afferent Arteriole Constriction:
Reduces renal blood flow.
Reduces hydrostatic capillary pressure.
Reduces GFR.
Afferent Arteriole Dilation:
Increases renal blood flow.
Increases hydrostatic capillary pressure.
Increases GFR.
Efferent Arteriole Mild Constriction:
Decreases renal blood flow.
Increases hydrostatic capillary pressure.
Increases GFR.
Efferent Arteriole Extreme Constriction:
Decreases renal blood flow.
Increases capillary oncotic forces.
Decreases GFR.
Efferent Arteriole Dilation:
Increases renal blood flow.
Decreases hydrostatic capillary pressure.
Decreases GFR.
Clinical Correlations:
GFR is clinically measured to evaluate kidney functioning.
GFR can be altered by medications that cause vasoconstriction or vasodilation.