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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


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
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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