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The cerebrum III

Veins of the brain
  • No muscular tissue in their thin walls
  • Don’t possess any valves
  • Lie in the subarachnoid space
  • Drain into cranial venous sinuses
External cerebral veins
Internal cerebral veins
  1. Superior cerebral vein                                  : Drain to superior sagittal sinus
  2. Superficial middle cerebral vein              : Drain to cavernous sinus
  3. Deep middle cerebral vein (It’s joined by the anterior cerebral & the striate veins to form the basal vein; basal vein drains to great cerebral vein & it drains to the straight sinus)
  1. 2 internal cerebral veins (Formed by the union of thalamostriate vein & the choroid vein)
  2. 2 veins unite to form the great cerebral vein

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Veins of specific brain areas

  • Midbrain
Drain to basal or great cerebral veins
  • Pons
Drain to basal vein, cerebellar vein & neighboring venous sinuses
  • Medulla oblongata
Drain to spinal veins & neighboring venous sinuses
  • Cerebellum
Drain to great cerebral vein

Cerebral circulation

  • Cerebral blood flow is measured by the intra carotid injection or inhalation of radioactive Krypton or Xenon
  • Normal cerebral blood flow : 50 – 60ml per 100g of brain per minute
  • Right half of the brain is supplied by the vertebral & internal carotid arteries on the right side and vice versa
  • The streams of the vertebral & internal carotid arteries come together in the posterior communicating artery (At that point pressure is equal on both sides & don’t mix)
  • If one of the arteries is occluded, blood moves forward or backward to compensate the reduction
  • If the vertebral or internal carotid artery is occluded on one side, blood can flow across the midline (Via anterior communicating artery)
  • Streams of 2 vertebral arteries remain separate within the basilar artery & don’t mix
  • Cerebral blood flow remain constant despite changes in general blood pressure (Compensatory lowering of cerebral vascular resistance in low blood pressure & vice versa)
Brain capillaries

  • Greater in the grey matter than in white matter
  • Blood brain barrier isolates the brain from the rest of the body
  • BBB is formed by the tight junctions that exist between the endothelial cells in the capillary beds

Nerves of the cerebral arteries

  • Cerebral arteries are supplied by sympathetic post ganglionic fibers (derived from the superior cervical sympathetic ganglion) & cause vasoconstriction
  • Under normal circumstances, the local blood flow is mainly controlled by CO2, H+ & O2 levels
  • Local increase in CO2 & H+ level (Viewing an object will increase O22 tension will result in local increase in blood flow (Vasodilatation) & glucose consumption in the visual cortex of the occipital lobe) or decrease in O2 tension will result in local increase in blood flow (Vasodilatation)

Subdural vs Extradural Hemorrhage

imageSubdural hemorrhage
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Extradural hemorrhage

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The cerebrum III The cerebrum III Reviewed by Radiology Madeeasy on August 10, 2010 Rating: 5
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