CEREBROSPINAL FLUID (CSF)

CEREBROSPINAL FLUID

The Cerebrospinal fluid is a modified tissue fluid.It is contained in the ventricular system of  the brain and in the subarachonoid space aroundthe brain and spinal chord. CSF replaces lymph in the CNS

CSF 

The cerebrospinal fluid fill the space between the arachnoid and the pia mater (subarachnoid space) and acts as a water cushion . 

The brain almost float in the cerebrospinal fluid without puting "its weight" onthe neck. The CSF forms watery cushions around the blood vessels to give them shock free enviornment.

Formation 

1. The bulk of CSF is formed by the choroid plexuses of the lateral ventricales and lesser amount by the choroid plexus of the third and forth ventricles. 
2. Possily, it is also formed by the capillaries on the surface of the brain and spinal cord.    

The brain produces roughly 500 mL of cerebrospinal fluid per day, at a rate of about 25 mL an hour.

Circulation

1. CSF passes from each lateral ventrical to the third ventricle through the intervetricular foramen of Monro. From third ventricle,it passes to the fourth ventrical the cerebral aqueduct . From the forth ventrical,the CSF passes to the subarachnoid spaces of the cerebrum and the vertebral canal through the median and lateral apertures of the fourth ventricle .
2. Some of it passes down the central canal of the spinal chord. 

Absorption

1. CSF is absorbed chiefly through the arachnoid villi and granulations, and is thus drain into cranial venous sinuses.
2. It also absorbed partly by the perinural lymphatics around the first, secondand eighth cranial nerves.
3. It is also absorbed by veins related to spinal nerves.

Functions CSF 

1. CSF decreases the sudden pressure or forces on delicate nervous tissue.
2. CSF nourishes nervous tissue. Only CSF comes in contact with neurons . Even blood cannot directly comes in contact with neurons. It provides nourishment and returns products ofmetabolism to the venous sinuses.
3. Pineal gland secretions reach pituitary gland via CSF. 
4. Neurons cannot lives without glucose and oxygen for more than 3 to 5 minutes. These are constantly provided by CSF .
5. There is no CSF bain barrir, so drugs can rach the neurons through CSF
6. There is blood CSF barrier. There are no antibodies in CNS, making infections of brain very seriou entity.

  
Clinical anatomy 

1. Drainage of CSF at regular intervals is of therepeutic values in meningitis. certain intractable headaches of unknown  aetiology are also know to have been cured by a mere lumbar puncture with drainage of CSF.
2. Obstractin in  the vertribal canal produces Froin's syndrome or loculation syndrome . This is characterized by yellowish discolouration of CSF. 
3. Hydrocephalus : It is the dilatation of the ventricular system. and occurs due to obstruction of CSF circulation.