Figure 2.

Schematic representation of the various barriers separating the CNS from the peripheral tissues (left panel). Permeable membranes are indicated by green arrows, and tight barriers are illustrated by red perpendicular symbols. Schematic representation of the CSF transport within the brain (left panel). CSF is produced by the choroid plexus within the ventricles entering into the subarachnoid space from where it can enter the glymphatic system or exit into the peripheral circulation. CSF egress routes include meningeal lymphatics, perineuronal pathways, parasagittal spaces, arachnoid villi/ granulations, and adventitia of large cerebral vessels. Schematic representation of the various barriers separating the CNS from the peripheral tissues (right panel). Permeable membranes are indicated by green arrows, and tight barriers are illustrated by red perpendicular symbols.