The net force determining the local rate of ultrafiltration of fluid across
the glomerular capillary wall (PuF), as across capillaries generally, is given
by the difference between the transcapillary hydraulic pressure (AP),
which favors filtration, and the corresponding difference in colloid osmotic
pressure (AII), which opposes it. At any point along the glomerular
capillary network, the local rate of ultrafiltration is equal to the product
of the local effective hydraulic permeability of the capillary wall (k) and
the local net driving pressure (PtJF). T