The blood-brain barrier (BBB) protects the brain from fluctuations in the blood by only allowing certain substances to pass between the blood and brain tissue. It is formed by tight junctions between endothelial cells in brain capillaries surrounded by astrocyte end-feet and pericytes. The BBB prevents unwanted substances from entering the brain while allowing passage of oxygen, carbon dioxide, hormones and other essential molecules through active or passive transport. Disruption of the BBB is implicated in several neurological disorders.

2. Introduction
-Nowhere in the body is there more need for
homeostasis than in the brain.
-The blood- brain barrier protects the brain
against surging fluctuations in ion concentrations.
-It is a diffusion barrier
-Essential for normal function of central nervous
system(CNS)
-contains a number of key structure that carry its
important function

4. • 1885: Paul Ehrlich: intravenous dyes in experimental
organisms caused staining of all organs except the
brain
• 1913: Edwin Goldmann put forward hypothesis that
the cerebral capillaries provide anatomical basis for a
physiological barrier between brain and the rest of the
body
• 1950s: Electron microscopy demonstrated that the
outermost layers of endothelial cells in brain capillaries
are fused together

5. Function of BBB
Separate circulating blood
from the brain extracellular Allow the diffusion of small
fluid (BECF) in the central hydrophobic molecules (O2,
nervous system (CNS). CO2, hormones)
Restrict the diffusion of
Provide an optimal chemical microscopic objects (e.g.,
environment for cerebral bacteria) and large or
function. hydrophilic molecules into
the cerebrospinal fluid (CSF)

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8. Permeability of BBB

12. • The BBB exists at the level of the
endothelial cells of cerebral
capillaries. The endothelial cells
are joined together by an
extensive network of tight
junctions and surrounded by a
basement membrane, within
which pericytes reside. Astrocytic
processes (so-called end-feet)
surround cerebral capillaries .

14. Astrocytes
 A large, star-shaped cell found in certain tissues of the
nervous system.
 Have many processes
 One of its function is maintenance of the blood–brain
barrier

16.  one of the elongated, contractile cells found
wrapped about precapillary arterioles outside
the basement membrane.
 Responsible for tight junction formation and
vesicle trafficking amongst endothelial cells.
 Open or close a given amount to allow (or
disallow) certain sized particles to flow to the
brain

18. • Prevent the passage of molecules and ions through the
space between cells.
• Materials must actually enter the cells (by diffusion or
active transport) in order to pass through the tissue.
• Provides control over what substances are allowed
through.

19. • Form the walls of capillaries
• The endothelial cells meet each other at what are called
tight junctions
• Materials must actually enter the cells (by diffusion or
active transport) in order to pass through the tissue.
• Provides control over what substances are allowed
through.

20. Without the BBB, undesirable molecules could freely
diffuse from the capillaries to the fluid that surrounds the
brain cells.
• Poisons taken in from the
Toxin
environment
• Upset the delicate electrochemical
Ions
gradients of the cerebral fluid.
Acids and • Might upset the cerebral fluid's
bases delicate pH balance.

21. Diseases Description

22. • 1- Menigitis is an inflammation of the membranes
which surround the brain and spinal cord.
• 2- Epilepsy is a neurological disease characterized by
frequent and often untreatable seizures.
• 3- Multiple sclerosis which is an auto-immune and
neurodegenerative disorder. This causes the immune
system attacks the myelin protecting the neurons in the
central nervous system.
• 4- Neuromyelitis optica will causes these patients have
high levels of antibodies against a protein called
Aquaporin levels, antibodies against a protein called
Aquaporin, a component of the astrocyte foot.

23. • 5- Sleeping sickness a condition in which trypanosoma
protozoa are found in brain tissues. Parasites possibly infect
the brain from the blood.
• 6- Progressive Multifocal Leukoencephalopathy is a
disease in the CNS. It affects immune compromised patients
usually seen with having AIDS.
• 7- De Vivo disease is a condition caused by an inadequate
transport of glucose across the barrier resulting in mental
retardation and other neurological problems.
• 8- Alzheimer's Disease indicate that disruption in the blood
brain barrier will allow blood plasma containing amyloid beta to
enter the brain and adheres preferentially to the surface of
astrocytes.