Fig. 3

The choroid plexus with protected regions between its folds. a 3D schematic representation of the ChP with a section plane. b Cross-section of the ChP (from panel a). Capillary blood vessels, stroma, and the layer of epithelial cells forming the interface to ventricular CSF are shown. The blue dashed line delineates the boundary between protected regions and bulk CSF. The protected lengths (\({l}_{\text{prot}}\)) at three exemplary locations are indicated with black arrows. c Magnified view of a protected region and the neighboring ChP epithelium. The intermicrovillar spaces (dark blue) and their segments of the protected region (PR, in blue) are shown. d Laser scanning confocal microscopy image of a rat lateral ventricular ChP section. The white dashed line delineates the border between protected regions and bulk CSF. The blue points mark three exemplary positions on the epithelium at different distances from the outer surface of the ChP. The blue lines indicate the paths (\(\psi\)) along which the protected length for each position is determined. Scale bar: 75 µm