Blood-brain barrier

Consists primarily of specialized tight junctions between cerebral capillary endothelial cells, surrounded by a matrix of basal lamina, astrocyte-end-feet, microglia, and pericytes.

The choroid plexus epithelial layer has tight junctions, between the cells on the side facing the ventricle.

The BBB safeguards the brain from harmful substances, while allowing essential nutrients to pass through.

The BBB is a physical and biochemical boundary between the blood stream and the parenchyma of the CNS.

These tight junctions prevent the majority of substances from crossing the cell layer into the cerebrospinal fluid (CSF); acts as a blood–CSF barrier. 

The BBB is a tightly regulated site that allows only the passive diffusion of small lipophilic molecules such as oxygen, carbon dioxide gases, and active transport of essential nutrients.

The brain is protected by an endothelial layer covered with pericytes with tight junctions, that serves as a semi permeable protective border.

Protects the brain from many toxic chemicals.

It impedes delivery of drugs to the brain.

Not completely formed until 6 months after birth.

Prevents adequate delivery of chemotherapy to brain tumors and only small and lipophilic molecules are able to cross this barrier.

The blood brain barrier prevents access of most molecules larger than 180 Daltons and also prevents passage of those chemicals that are not lipophilic.

The BBB is composed of tightly bound vascular endothelial cells, surrounded by a basement membrane, and supported by astrocytes, pericytes, and microglia.

The BBB helps shield viruses, bacteria, and neurotoxins from the CNS, and controls the movement of ions, molecules, and cells between the blood and the CNS.

The BBB prevents 98% of small molecule drugs and 100% of large molecule drugs from entering the CNS.

Drugs that cross the BBB subject to, reflux by P-glycoprotein and breast cancer resistance proteins.

Contrast enhancement on imaging studies indicate a partial disruption of this barrier.

The BBB may breakdown in patients with brain metastases, allowing drugs that are water soluble to reach the tumor.

The blood brain barrier may be disrupted around brain metastasis, it remains intact for large portions of the brain.

Focused ultrasound  generates a mechanical wave, inducing oscillations in the medium that transitions between compression and rarefaction of blood vessel walls, and can open the blood brain barrier by compromising its integrity.

Focused ultrasound can create openings in the BBB and enhance drug delivery to decrease the load of cerebral amyloid beta.


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