| THE
CEREBROSPINAL FLUID & ITS PATHWAY |
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| General organization of the ventricular system |
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 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
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| Functions
of the CSF: |
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- 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.
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| CSF composition |
- Contains less cells, protein, K+ , Ca++
- Contains more Na+, Cl-, Mg++
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Note
- 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.
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| CSF formation |
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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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