Final answer:
Glomerular capillary hydrostatic pressure is the Starling force responsible for driving fluid out of the glomerulus into Bowman's capsule, and is high due to efferent arteriole resistance.
Step-by-step explanation:
The Starling force that drives fluid out of the glomerulus is the glomerular capillary hydrostatic pressure, which is relatively high (60 mm Hg) because of the resistance in the efferent arterioles. This pressure is opposed by the osmotic pressure, which is typically higher in the glomerular capillary due to the retention of cells and large proteins that cannot pass through the filtration membrane, creating a colloid osmotic pressure of about 30 mm Hg within the capillary. On the other hand, the absence of proteins in Bowman's space leads to an osmotic pressure near zero, making hydrostatic pressure the primary force for pushing water across the membrane, despite the osmotic pressure working against it. The sum of all these pressures results in a net filtration pressure (NFP) of approximately 10 mm Hg.