Of all the theories related to the mechanical excitation of cellular activities, the alleged effect of the fluid flow occurring in the lacunar-canalicular pore network on osteocytes is probably the most widely accepted. However, direct experimental verification of the actual occurrence of fluid flow (in response to macroscopically applied mechanical loading of physiologically reasonable magnitude) in these pores has never been obtained. In this work, a multiscale modeling strategy is presented, inspired by the well-established concept of continuum micromechanics, allowing for upscaling (or homogenization) of the fluid flow contributions in the canalicular, lacunar, and vascular pores in terms of a corresponding macroscopic permeability of bone tissue. The same model also allows for proceeding the opposite way, namely for downscaling macroscopically acting pressure gradients to the pore levels. Thus, physiologically relevant, macroscopic pressure gradients can be related straightforwardly to the correspondingly arising canalicular pressure gradients, and, through considering the resulting pressure gradients in suitable transport laws (as for instance the classical Poiseuille law on the canalicular level), also to related fluid velocities. When comparing the such computed fluid velocities (for cortical bone) with the fluid velocities that were shown to efficiently excite bone cells , it turns out that the fluid velocities according to the here presented computations are actually much lower. This implies that, based on the multiscale model, pressure-driven fluid flow in the canalicular pores is not likely to be a potent mechanical stimulus for osteocytes (whereas fluid flow in the vascular pores may indeed reach the required fluid velocities and hence excite the therein residing cells). In conclusion, the work presented in this thesis provides important, unprecedented insights as to the observation scale-specific cellular mechanosensation in bone.