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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 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.

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.

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.

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