Fig. 7

Schematic diagram of a cross section of the theoretical array of parenchymal blood vessels in the model used by Ray et al. [193]. In this model the vessel array is approximated by a regular repeating pattern of arterioles (red circles) and venules (blue circles) running perpendicular to the cortical surface. Streamlines (thin black lines) connect arterioles the sources of flow, and venules,- the sinks. Conveniently for the calculation of flow from the flow velocity the midplanes between the planes of arterioles and venules separate the sources from the sinks and the direction of flow is perpendicular to the midplanes (see footnote 26). Note that the cross-sectional area available for perivascular flow along the arterioles and venules is much smaller than the area available for flow through the interstitium. Thus, with the same flow inwards along periarterial spaces, through the interstitium and outwards along perivenous spaces, the flow velocity would be much higher in the perivascular spaces than in the interstitium