blood-cerebrospinal fluid (CSF) barrier

blood-ce·re·bro·spi·nal flu·id (CSF) bar·ri·er

(blŭd-ser'ă-brō-spī'năl flū'id bar'ē-ĕr)
A barrier located at the tight junctions that surround and connect the cuboidal epithelial cells on the surface of the choroid plexus; capillaries and connective tissue stroma of the choroid do not represent a barrier to protein tracers or dyes.