Blood supply
Vascular Supply
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About 18% of the total blood volume in the body circulates in the
brain, which accounts for about 2% of the body weight.
The blood transports oxygen, nutrients, and other substances
necessary for proper functioning of the brain tissues and carries
away metabolites.
Loss of consciousness occurs in less than 15 seconds after blood
flow to the brain has stopped, and irreparable damage to the
brain tissue occurs within 5 minutes.
Cerebrovascular disease, or stroke, occurs as a result of
vascular compromise or hemorrhage and is one of the most
frequent sources of neurologic disability.
Nearly half of the admissions to many busy neurologic services
are because of strokes.
Cerebrovascular disease is the third most common cause of death
in industrialized societies.
BLOOD SUPPLY TO THE BRAIN
• High demand for oxygen and nutrients
• Arterial blood through: internal carotid and
vertebral arteries
• Venous blood from brain in the internal
jugular veins
• Cerebrovascular accidents (CVA): stroke,
shutting off blood supply to brain
Arterial supply
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The circle of Willis (after the English
neuroanatomist Sir Thomas Willis) is a
confluence of vessels that gives rise to all of
the major cerebral arteries.
Supplied by the paired internal carotid
arteries and the basilar artery.
Contains a paired posterior communicating
artery and an unpaired anterior
communicating artery.
The circle of Willis shows many variations
among individuals.
Occlusion of major cerebral arteries
produces a characteristic clinical picture.
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Why do individual differences in
vascular supply matter?
What might they achieve?
What problems might they give?
How might they assist after damage?
VENOUS DRAINAGE
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The venous drainage of the brain and
coverings includes:
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the veins of the brain itself,
the dural venous sinuses,
the dura's meningeal veins,
and the diploic veins between the tables
of the skull.