Cerebrospinal fluid is found on the subarachnoid space, which is the space between the arachnoid mater and the pia mater. The arachnoid mater is the middle layer of the brain covering while the pia mater is the layer of meninges or brain covering nearest the brain. CSF is also called Liquor cerebrospinalis because it actually constitutes all the fluid in the spaces in the brain and spinal cord aside from blood.
Functions of the Cerebrospinal Fluid
CSF acts in many ways such as:
- It acts as a buffer or cushion for the cerebral cortex or the brain tissue. It minimizes any effects of head injuries because it absorbs the any shock to the cranium.
- It auto regulates the cerebral blood flood flow. The flow of CSF in the brain prevents excessive blood volume to circulate in the brain tissues because of the mechanism that nothing in excess should be present in the brain.
- It acts as an immunological protection of the brain and the spinal cord. CSF contains immunologic chemicals such as white blood cells, proteins and inflammatory cells to protect the CNS from infections.
- It maintains the density of the brain. The bran weighs about 1400 grams, but its weight is never acted against the brain cells because of the presence of CSF that maintains buoyancy. Without CSF, the weight of the brain may be acted on itself causing death of cells and impairment in blood circulation because of pressure in certain parts of the organ.
- Maintains intracranial pressure
The presence of CSF maintains normal intracranial pressure in the brain, which is 7-15 mmHg.
Production and Circulation of Cerebrospinal Fluid
About 50 to 70% of cerebrospinal fluid is produced in the brain in the choroid plexus. The remaining is produced in the ventricular walls around the blood vessels. Cerebrospinal fluid circulates along the ventricles and in the subarachnoid space in the brain and spinal cord. It circulates in a pulsatile manner continuously. CSF is constantly produced in the choroid plexus, but excessive CSF is prevented by its reabsorption in the venous sinus blood for elimination when the blood circulates in the kidneys. In this way, CSF is constantly renewed and eliminated from the system.
Components of Cerebrospinal Fluid
CSF contains plasma proteins such as globular proteins and albumin. It also contains ions and metals such as sodium, potassium, chloride, calcium, magnesium, and iron. It also contains glucose, lactase, creatinine, phosphorus, urea and carbon dioxide. CSF may contain traces of white blood cells, but the presence of elevated WBC count in the CSF may mean CNS infection. There should also be no red blood cells in the CSF because any presence of which may indicate cerebral hemorrhage. Cerebrospinal fluid is normally neutral with a pH of 7.28 to 7.32.
Uses of CSF Studies
Certain conditions or diseases can be diagnosed through the use of the CSF. CSF is studied under the microscope to detect presence of abnormal cells in the fluid. The physical appearance of the fluid may also be used to detect any abnormalities. CSF is aspirated from the lumbar spine in order to be examined. This process is known as lumbar puncture, where a physician uses a thin needle to aspirate CSF from the lumbar spine.
The presence of cloudy CSF may indicate infection; however, viral infections of the CNS may still present a clear CSF. The presence of markedly increased proteins may indicate inflammatory condition while a markedly increased WBC may indicate ongoing CNS infection.
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