CROSS MY BORDER

The concept of the brain being a 'privileged' organ arose from experiments demonstrated that dyes injected into bloodstream stained organs strongly except the brain (Erlich P, 1885).

This observation came from a special barrier that did not allow penetration of hydrophilic molecules from blood to brain, and was shown to be at the level of the microvascular endothelium of the brain (Reese and Karnovsky, 1967). 
This is the foundation of the concept know as the blood-brain-barrier (BBB).


BBB contains microvascular endothellial cells connected through tight junctions,
the perivascular space and the glia limitans. The perivascular space is filled with
lymphatic fluid draining from the brains parenchyma and perivascular cells.

The glia limitans is formed by astrocyte endfeet which separate the vasculature from
the brain parenchyma.
The glia limitans, or glial limiting membrane, is the outermost layer of proper
nervous tissue of the brain and spinal cord, lying directly under the pia mater.


The BBB limits ionic and fluid movements between the brain and the
 bloodstream.
 It provides the brain with nutrients and is involved in the removal
of waste products; it creates a stable microenvironment for the
brain that is not subject to the strong fluctuations in ionic content
that can occur in the blood stream.

My blood for TBV: