The<unk>  <unk>  is a membranic structure that acts primarily to protect the<unk>  from chemicals in the<unk> , while still allowing essential metabolic function. It is composed of endothelial cells, which are packed very tightly in<unk>  capillaries. This higher density restricts passage of substances from the<unk> stream much more than endothelial cells in capillaries elsewhere in the body. Astrocyte cells called astrocytic feet surround the endothelial cells of the<unk> , providing biochemical support to those cells. The<unk>  is distinct from the similar<unk> -cerebrospinal fluid barrier, a function of the choroid plexus.
Blood-brain barrier
Alveolar-capillary barrier
Circulatory system
Subarachnoid space
Cerebral circulation
Autonomic nervous system
Growth cone
Sympathetic nervous system