Morphology of Cerebral Endothelium and Astrocytes as Determinants of the Neuronal Microenvironment

Abstract
Homeostasis of the neuronal microenvironment is brought about by the selective permeability of the cerebral endothelium. The endothelium is able, in part, to transport certain substrates while excluding other molecules because it comprises a continuous barrier that cannot be bypassed extra-cellularly. Each endothelial cell is joined to its neighbor by belts of tight junctions which occlude the intercellular clefts between them. In this way, the extracellular fluid (ECF) of the central nervous system (CNS) is isolated from the blood (33,4).