General organization of the ventricular system





Comprises ependymal-lined cavities of the brain.


  • Lateral ventricles in the cerebrum .

  • The 3 rd ventricle in the diancephalon

  • Cerebral aqueduct in the midbrain.

  • The 4 th ventricle in the hind gut

Functions of the CSF:


  • Cushions the brain and spinal cord against trauma.
  • Supports brain, which weighs 1400g in air but only 50 g in CSF.
  • Transports nutrients, chemical messengers and waste products.
  • Integrates the brain and peripheral endocrine functions.
  • Influences the microenvironment of neurons & neuroglia.
CSF composition
  • Contains less cells, protein, K+ , Ca++
  • Contains more Na+, Cl-, Mg++


  • The CSF rate of formation is 400-500 mls/day.
  • The total volume is 140-150mls (25mls in ventricles, 75mls in subarachnoid space).
  • The CSF total volume is entirely replaced in 8 hours.

CSF formation

Active and passive mechanisms

Formed in choroid plexuses found at the

  • Roof of third ventricle
  • Floor of lateral ventricle
  • Roof of 4 th ventricle then projects between cerebellum and pons

The choroids epithelium:

  • Cuboidal cells
  • Basal infoldings and
  • Apical microvili
  • Tight junctions
  • Fenestrated subepithelial capillaries




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