Download 17. CSF2010-10-01 05:141.2 MB

Cerebrospinal
fluid
- It is present within the ventricular system and
within the cranial and
spinal subarachnoid
spaces.
- It is produced by the choroid plexus of the
lateral , third and fourth
ventricles .
- The choroid plexus is formed by invagination
of the vascular pia mater
into the ventricular
lumen, where it becomes
highly convoluted ,
producing a sponge- like
appearance.
The choroid plexus enters the 3rd & 4th ventricles through their roofs and the lateral ventricle though the choroid fissure , along the line of fimbria and fornix .
Most of the C. S. F. is produced by the
choroid plexus of the lateral ventricle. Then it
flows through the interventricular foramen
( Foramen of Monro ) into the 3rd ventricle .
By way of the cerebral aqueduct to the 4th
ventricle.
CSF leaves the ventricular system though 3
apertures of the 4th ventricle to enter the
subarachnoid space.
Most passes through the median aperture
(of Magendei) to enter the cisterna magna
which is an enlarged area of the
subarachnoid space located between the
medulla and cerebellum.
Lesser amounts flow through the lateral
apertures (of Luschka) to enter the
subarachnoid space in the region of the
cerebellopontine angle.
From these sites , the majority of CSF flows
superiorly , round the cerebral hemispheres.
Small amount passes to central canal of
medulla oblongata, then to central canal of
spinal cord.
CSF is reabsorbed into the
venous system by passing into the
dural venous sinuses , especially
the superior sagittal and transverse
sinuses.
Along the sinuses are located
arachnoid villi which consist of
invaginations of arachnoid mater
through the dural wall and into the
lumen of the sinus.
Reabsorption occurs at these villi
because
1- The hydrostatic pressure (of
ionates ) in the subarachnoid
space is higher than that in the
sinus lumen
2- The greater colloid osmotic
pressure (of albumin , proteinate )
of the venous blood compared
with CSF.
Thus the CSF is produced by an active
secretory process and by passive
diffusion .
CSF is a colourless and clear fluid
containing little protein and few cells,
(lymphocytes ) , glucose ; chloride .
The volume of CSF in the combined
ventricular and subarachnoid spaces is
150 ml . It is in a rate sufficient to fill
these spaces several times each day .
Functions of CSF
1- Protects the central nervou system
from trauma.
2Provides mechanical support for
brain
3Nourishes the CNS
4Remove metabolites from the
CNS
5- Serves as a pathway for pineal
secretions to reach the pituitary
gland
With age , the arachnoid
villi become
hypertrophied to form
arachnoid granulations
.
Hydrocephalus
- Obstruction of the flow of CSF within the ventricular system (by tumors )
Or the subarachnoid space ( by adhesions ) following head injury or
meningitis, lead to a rise in the fluid pressure causing swelling of the
ventricles (Hydrocephalus ). There is headaches , unsteadiness and
mental impairment .
- Swelling of the optic discs ( Papilloedema ) may be present and is seen
on ophthalmoscopy.
- Decompression of the dilated ventricles is achieved by inserting a shunt
connecting the ventricles to the jugular vein .