<Tr> <Td> arteriolar end of capillary </Td> <Td> + 35 </Td> <Td> − 2 </Td> <Td> + 28 </Td> <Td> + 0.1 </Td> </Tr> <Tr> <Td> venular end of capillary </Td> <Td> + 15 </Td> <Td> − 2 </Td> <Td> + 28 </Td> <Td> + 3 </Td> </Tr> <P> It is reasoned that some albumin escapes from the capillaries and enters the interstitial fluid where it would produce a flow of water equivalent to that produced by a hydrostatic pressure of + 3 mmHg . Thus, the difference in protein concentration would produce a flow of fluid into the vessel at the venous end equivalent to 28 − 3 = 25 mmHg of hydrostatic pressure . The total oncotic pressure present at the venous end could be considered as + 25 mmHg . </P> <P> In the beginning (arteriolar end) of a capillary, there is a net driving force ((P c − P i) − σ (π c − π i) (\ displaystyle (P_ (\ mathrm (c)) - P_ (\ mathrm (i))) - \ sigma (\ pi _ (\ mathrm (c)) - \ pi _ (\ mathrm (i))))) outwards from the capillary of + 9 mmHg . In the end (venular end), on the other hand, there is a net driving force of − 8 mmHg . </P>

What two opposing forces determine the direction and rate of fluid flow across capillary walls