Figure 2.

Choroid plexus epithelial cells and ventricular ependymal cells. A. General sketch of CSF flow within the human brain with magnification of the choroid plexus and ventricular ependymal cells in B. The choroid plexus is composed of modified ependymal cells with tight junctions and a stromal layer with fenestrated capillaries. This layer is continuous the ependymal cells lining the ventricle, which are connected via gap junctions. The apical membrane of choroid plexus epithelium faces the internal CSF compartment. C. Important channels in the apical and basolateral membranes of choroid plexus epithelial cells. NKCC1 is predominantly located on the apical membrane, where it plays an important role in the production of CSF through the activation of aquaporin-1 channels, which have been found both on apical and basolateral membranes but predominantly on the apical side of CPECs.