<Tr> <Th> MeSH </Th> <Td> D001812 </Td> </Tr> <Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> <P> The blood--brain barrier (BBB) is a highly selective semipermeable border that separates the circulating blood from the brain and extracellular fluid in the central nervous system (CNS). The blood--brain barrier is formed by endothelial cells of the capillary wall, astrocyte end - feet ensheathing the capillary, and pericytes embedded in the capillary basement membrane . This system allows the passage of water, some gases, and lipid - soluble molecules by passive diffusion, as well as the selective transport of molecules such as glucose and amino acids that are crucial to neural function . Specialized structures participating in sensory and secretory integration within neuronal networks--the circumventricular organs and choroid plexus--do not have a blood--brain barrier . </P> <P> The blood - brain barrier restricts the diffusion of solutes in the blood (e.g., bacteria) and large or hydrophilic molecules into the cerebrospinal fluid (CSF), while allowing the diffusion of hydrophobic molecules (O, CO, hormones) and small polar molecules . Cells of the barrier actively transport metabolic products such as glucose across the barrier using specific transport proteins . </P>

What type of cell contributes to the blood-brain barrier in the central nervous system