Blood supply

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Blood supply
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Vascular Supply

• 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.

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Arterial supply

• The circle of Willis (named after the English
  neuroanatomist Sir Thomas Willis) is a confluence
  of vessels that gives rise to all of the major
  cerebral arteries.
• It is fed by the paired internal carotid arteries
  and the basilar artery.
• When the circle is complete, it contains a
  posterior communicating artery on each side and
  an anterior communicating artery.
• The circle of Willis shows many variations among
  individuals.
• Despite these variations, occlusion of each of
  the major cerebral arteries usually 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?

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VENOUS DRAINAGE

• The venous drainage of the brain and coverings
  includes
• 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.

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