Biomedical Engineering Reference
In-Depth Information
Fig. 8 Recovery of the in
vivo electric potential data of
Cochran et al. [ 23 ](crosses)
by our streaming potential
model (reproduced with
permission from Lemaire
et al. [ 77 ])
x 10 −4
4
3
2
1
0
−1
−2
−3
−4
0
0.5
1
1.5
2
2.5
Time (s)
where the electric double layer develops. Interstitial fluid velocity profiles and
shear stress values at the cell membrane have been computed for physiological
parameters values [ 58 ]. The total average fluid velocity in the canaliculus and its
hydraulic, osmotic and electro-osmotic components as expressed by the modified
Darcy law ( 22 ) are provided in Table 3 . The hydraulic component governs the
total fluid flow within the bulk of the canalicular pore space accounting for more
than 95 % of the transport, while the electro-osmotic and osmotic phenomena are
negligible. However, due to the electro-chemical over-velocities that develops in
the double layer in the close proximity of the osteocyte membrane [ 85 , 86 ], the
contribution of the osmotic and electro-osmotic phenomena cannot be neglected.
This is apparent looking at the shear stress on the cell membrane (see Table 3 ).
The major contribution is still due to the hydraulic gradient (52 %), but neither the
electro-osmotic ( 43 %) nor the osmotic contributions ( 5 %) are negligible.
When transferring this results in the context of the cellular mechano-sensitivity
to shear effects, the osteocytes responding to fluid shear stress [ 65 ], the results
reported in Table 3 indicate that the hydraulic and the electro-chemical parts of the
shear stress may cause an annihilation of the total shear stress stimulation felt by
the cell. Thus, chemical fluxes due to calcium deposition and dissolution from the
canalicular walls can be expected to modulate osteocyte mechano-sensitivity both
in the presence of unidirectional flow due to the pressure differential within the
blood circulatory system and oscillatory flow due to physical activity [ 58 ].
4.5 Fifth Question: What is the Ionic Transport Main
Mechanism Within Bone Tissue?
The mass transport mechanism within the lacuno-canalicular network is another
open question in the domain of bone biomechanics. In the viewpoint of bone
remodelling, it is necessary to properly identify how the chemical species can be
 
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