• CSF is clear, colorless and transparent
• Circulates through cavity of the:
– Subarachnoid space
– Central canal of spinal cord
• Part of Extracellular fluid (ECF)
• Volume : approximately 150 mL
• Rate of formation: approximately 0.3 mL/min
• Specific gravity : 1.005
• Reaction : Alkaline
Water - 99.13% Solids - 0.87%
Lymphocytes in CSF : 6/ cu mm
• As CSF is part of ECF therefore it contain more
amount of Sodium than Potassium.
• Contains some lymphocytes.
• CSF secreted by ventricles does not contain
• The lymphocytes are added when it flows in
the spinal cord.
Formation of CSF
• Site of formation
– Formed by the choroid plexus situated within the
– The choroid plexus are tuft of capillary projections present
inside ventricles and covered by:
• Pia mater
• Ependymal covering.
Mechanism of formation
• Formed by process of secretion.
• Does not involve ultrafiltration or dialysis.
• Uses energy.
• Active transport mechanism is involved in secretion.
Circulation of CSF
Formation of CSF in lateral ventricles
Foramen of Monro
Foramen of magendie and foramen of
Cisterna magna and Cisterna lateralis
To cerebral hemispheresTo the spinal cord
Absorption of CSF
• Mostly absorbed by the Arachnoid villi into
Dural sinuses and Spinal veins.
• Small amount is absorbed along the
perineural spaces into cervical lymphatics and
in to the perivascular spaces.
• Normally, 500 mL of CSF is formed everyday
and equal amount is absorbed.
Pressure exerted by CSF
• Varies in different position:
Lateral recumbent position = 10-18 cm of H2O
Lying position = 13 cm of H2O
Sitting position = 30 cm of H2O
Coughing and crying increases the pressure by
decreasing the absorption.
Compression of internal jugular vein also raises
the CSF pressure.
Function of CSF
• Protective Function:
– Acts as buffer
– Protects the brain from shock
• If brain receives severe blow , countercoup
injury may take place.
• Medium of Exchange
• CSF is the medium through which substances
– Nutritive substances
– Waste materials
are exchanged between blood and brain tissues.
– Abnormal accumulation of CSF in the skull with
enlargement of head.
• 2 types of Hydrocephalus
Non-communicating Hydrocephalus or
Due to the obstruction of any of the foramen through
which CSF escapes results in dilation of ventricular
Communicating Hydrocephalus or External
Due to blockage of Arachnoid villi.
Symptoms of Hydrocephalus:
Atrophy of brain