Abdulelah NuqaliIntern

What is the Blood Brain Barrier?

Structural and functionalFormed by brain microvascular endothelial cells

(BMEC), astrocyte end feet and pericytesEssential for normal function of CNSResponsible for metabolic activities such as the

metabolism of L-dopa to regulate its concentration in the brain.

Properties of the BBBGeneral Properties of the BBB

1. Large molecules do not pass through the BBB easily.

2. Low lipid (fat) soluble molecules do not penetrate into the brain. However, lipid soluble molecules rapidly cross the BBB into the brain.

3. Molecules that have a high electrical charge to them are slowed.

Integrity of BBBTight JunctionsAdherens JunctionsPericytesAstrocyte end feet

Structure of Blood Brain Barrier

Differences between BMEC and normal endothelial cellsStructural differences:

Absence of fenestrationsMore extensive tight junctions (TJ)

Regions of brain not enclosed by BBBCircumventricular organs

area postrema, median eminence, neurohypophysis, pineal gland, subfornical organ and lamina terminalisThese are regions which need to respond to

factors present in systemic circulation

Circumventricular organ functions:

Pineal gland - secretes melatonin and is associated with circadian rhythms

Subfornical organ - regulates body fluids, fluid and electrolyte imbalance

Organum vasculosum of the lamina terminalis – detects peptides

Choroid PlexusArea Postrema - the “vomiting centre” of the

brainMedian eminence - regulates the anterior

pituitary through the release of neurohormonesNeurohypophysis - detects levels of oxytocin and

ADH in the blood

Opening of the BBB 1 – Physiological2 – pathological :

i. Traumatic brain injuryii. Ischaemic strokeiii. Septic encephalopathyiv. Tumour

Increase BBB premeability cerebral edema

Transport of drugs across the BBBLipophilicityMolecular weight

ReferenceK. Lawther, Sajith Kumar, Hari Krovvidi , Blood–brain barrier,

Continuing Education in Anaesthesia, Critical Care & Pain | Volume 11 Number 4, 2011

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