Blood brain barrier is formed by

(C) Astrocytes # Blood Brain Barrier: Astrocytes form the structural framework for the neurons and control their biochemical environment.> Astrocyte foot processes are closely associated with the blood vessels to form the blood-brain barrier.# Oligodendrocytes are responsible for the formation and maintenance of the myelin sheath, which surrounds axons and is essential for the rapid transmission of action potentials by solitary conduction.> Microglia are blood-derived mononuclear macrophages> Astrocyte foot processes are closely associated with the blood vessels to form the blood - brain barriers oligodendrocytes forms myelin sheath which surrounds axons.> Microglia are blood derived non nuclear macrophages.# Blood-brain barrier (BBB) is a membranic structure that acts primarily to protect the brain from chemicals in the blood, while still allowing essential metabolic function.> BBB is composed of endothelial cells, which are packed very tightly in brain capillaries.> This higher density restricts passage of substances from the bloodstream much more than endothelial cells in capillaries elsewhere in the body.> Astrocyte cell projections called astrocytic feet (also known as "glial limitans") surround the endothelial cells of the BBB, providing biochemical support to those cells.> BBB is distinct from the similar blood-cerebrospinal fluid barrier, a function of the choroidal cells of the choroid plexus.