cerebrospinal fluid
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Cerebrospinal fluid - PowerPoint PPT PresentationTRANSCRIPT
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Cerebrospinal fluid
It is present within the ventricular system and the cranial & 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.
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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 ( It is an enlarged area of the subarachnoid space ) , located between the medulla & 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 hemispheresSmall amount passes to central canal of medulla oblongata. Then to central canal of
spinal cord.
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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.
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So, 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 nervous system from trauma. 2- Provides mechanical support for brain 3- Nourishes the CNS 4- Remove metabolites from the CNS 5- Serves as a pathway for pineal secretions to reach the pituitary
gland
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With age , the arachnoid villi become hypertrophied to form arachnoid
granulations.
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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 ) is seen on ophthalmoscopy.
Decompression of the dilated ventricles is achieved by inserting a shunt connecting the ventricles to the jugular vein .