Table 2. Parameters used for the derivation of the model parameters in Table 1.
| Parameter | Equation and nominal value | Ref. |
|---|---|---|
| Pressures gradient | ||
| ISF baseline velocity in the brain grey matter |  |
19 |
| Range of reported ISF velocities |  |
19,20 |
| Vascular dimensions | ||
| Distance between arteriole-venule pair |  |
10 |
| Capillary diameter |  |
35 |
| Capillary volume fraction in the brain |  |
36 |
| Cortical penetrating arteriole diameter |  |
36 |
| Astrocyte dimensions | ||
| AU diameter |  |
10 |
| AU volume |  |
|
| Astrocyte soma diameter |  |
10 |
| Surface area of astrocyte soma |  |
|
| PM to soma surface ratio |  |
10 |
| PM surface area |  |
|
| Astrocyte process diameter |  |
37 |
| Process intracellular space tortuosity assuming cylindrical structures |  |
|
| AQP4 | ||
| Single AQP4 channel water conductivity |  |
38 |
| AQP4 density on EF |  |
27 |
| AQP4 density on PM (except EF) |  |
39 |
| EF length (estimated from the fact that EF fully wraps around capillaries) |  |
17 |
| EF width |  |
17 |
| EF surface area |  |
|
| EF thickness |  |
17 |
| GJ | ||
| Hydraulic diameter of a GJ channel |  |
18 |
| PM thickness |  |
40 |
| Resistance of single GJ channel to water flow |  |
|
| GJ channel density in the contact region between neighbouring astrocytes |  |
41 |
| Surface area of the contact region between neighbouring astrocytes |  |
41 |
| ECS | ||
| ECS thickness |  |
42 |
| Inter-endfeet gap thickness |  |
7,43 |
| ECS volume fraction |  |
5 |
| Width of ECS channel surrounding typical cellular features (processes) |  |
|
| ECS tortuosity assuming cylindrical structures |  |
|
| Resistance of a single ECS pathway for half the length of one AU |  |
|
| Volume of a single ECS pathway for the length of one AU |  |
|
| Total ECS volume in one AU |  |
|
| Number of parallel ECS pathways in one AU |  |
|
| PVS | ||
| Length of PVS segment considered for a penetrating vessel |  |
36 |
| Thickness of PVS channel |  |
44 |
| Hydraulic permeability of PVS |  |
45 |
| Capillary BM | ||
| BM thickness |  |
46 |
| Hydraulic permeability of BM |  |
47 |
| Volume of single capillary with the length of one AU |  |
|
| Number of capillaries in one AU |  |
|
| Cross section area of BM layer |  |
|
| Diffusion | ||
| Diffusion coefficient for natural solutes and tracers in the brain parenchyma |  |
5 |
| Fluid properties | ||
| Dynamic viscosity |  |
|
| Density |  |
|
The most prominent spatial dimensions are illustrated in the Supplementary Fig. S1. Derivations are all documented in details in Supplementary Information S1.