Fig. (1).

Components of the BBB and the transport pathways of substances across the BBB. The typical BBB is mainly composed of ECs, tight junctions, a basement membrane, pericytes, and astrocytes. The substances in capillaries are transported into the brain parenchyma through the paracellular pathway (tight junction, adherens junction, and gap junction complexes) and transcellular pathway (transcellular lipophilic pathway, carrier protein-mediated pathway, receptor-mediated endocytosis, adsorptive endocytosis, and active efflux transporters). ZO-1: (zonula occludens-1); JAM: (junctional adhesion molecule); VE-cadherin: (vascular endothelial-cadherin); lgG: (immunoglobulin G). (A higher resolution / colour version of this figure is available in the electronic copy of the article).