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Cerebrospinal Fluid (CSF)

The cerebrospinal fluid [CSF] is a clear, colorless transparent, tissue fluid that is present in the cerebral ventricles, spinal canal and subarachnoid spaces. It is an ultrafiltrate of blood plasma, normally CSF doesnot contain red blood cells and at most 4 white blood cells/┬Ál may be present.

What are the  functions of CSF
CSF has both physical and metabolic function
It is   
A shock absorber
A mechanical buffer
Act as cushion between the brain and cranium
Act as a reservoir and regulates the contents of the cranium
Serves as a medium for nutritional exchange in CNS
Transport hormones and hormone releasing factors
Removes the metabolic waste products through absorption

The total CSF volume 
The total CSF volume in the adult is 150ml
Rate of formation of CSF 
20-25 ml/hour 
550 ml/day in adults.   Turns over 3.7 times a day
30-40 ml within the ventricles
About 110-120 ml in the subarachnoid space, of which 75-80 ml in spinal part and 25-30 ml in the cranial part.

Composition of CSF
Proteins = 20-40 mg/100 ml
Glucose = 50-65 mg/100 ml
Cholesterol = 0.2 mg/100 ml
Na+ = 147 meq/Kg  H2O
Ca+ = 2.3 meq/kg H2O
Urea = 12.0 mg/100 ml
Creatinine = 1.5 mg/100 ml
Lactic acid = 18.0 mg/100 ml

Characteristics of  CSF 
Colour = Clear, transparent fluid
Specific gravity = 1.004-1.007
Reaction = Alkaline 
Cells = 0-3/ cmm
Pressure = 60-150 mm of H2O 

The pressure of CSF is increased in standing, coughing, sneezing, crying, compression of internal Jugular vein which is called Queckenstedt’s sign.