- Comprises of 3 cellular layers and a basement membrane
- Together these form a barrier virtually impenetrable barrier to lipophobic molecules
Capillary Endothelium
- Interconnected by tight junctions (50-100x 'tighter' than peripheral capillaries) restricting the passage of substances from the capillaries to the brain ECF
- Differ from extracerebral capillaries in having a high density of mitochondria
- Have a relative paucity of pinocytic vesicles for vesicular transport
Basement Memebrane
- Surrounds the endothelium
- 40-50nm thick
- Rich in proteoglycans, heparin sulphate, collagen type IV and laminin
Pericytes
- Reside next to capillaries
- Possesses smooth muscle like action
Astrocytes
- A type of supportive glial cell
- Projections called foot processes ensheath >95% of vessel surface
- Secrete chemicals that reduce the permeability of the capillary endothelial cells