neuroglia that support neurons and blood vessels are
Neuroglia Microglia are specialized macrophages capable of phagocytosis that protect neurons of the central nervous system.[17] They are derived from the earliest wave of mononuclear cells that originate in yolk sac blood islands early in development, and colonize the brain shortly after the neural precursors begin to differentiate.[18]
Blood–brain barrier The blood–brain barrier (BBB) is a highly selective semipermeable membrane barrier that separates the circulating blood from the brain and extracellular fluid in the central nervous system (CNS). The blood–brain barrier is formed by brain endothelial cells and it 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. Furthermore, it prevents the entry of lipophilic potential neurotoxins by way of an active transport mechanism mediated by P-glycoprotein. Astrocytes have been claimed to be necessary to create the blood–brain barrier. A few regions in the brain, including the circumventricular organs, do not have a blood–brain barrier.