Learning Objectives
By the end of lecture student should be able to:
◈ Explain properties of CSF
◈ Comment on composition and formation of CSF
◈ Explain the circulation and absorption of CSF
◈ Summarize the functions of CSF
◈ Comment on the importance of lumbar puncture
◈ Cerebrospinal fuid ( CSF) is the clear, colorless and transparent fluid that circulates through ventricles of
brain, sub arachnoid space and central canal of spinal cord.
◈ It is the part of extra cellular fluid (ECF).
Properties
◈ Volume : 150ml
◈ Rate of Reaction : 0.3ml Per Minute
◈ Specific Gravity : 1.005
◈ Reaction : Alkaline
◈ Lymphocytes : 6/Cumm
◈ CSF contains more amount of sodium than potassium.
◈ Lymphocytes are added when CSF flows in the spinal cord.
Formation of CSF
◈ CSF is formed by choroid plexuses, situated with in the ventricles.
◈ Choroid plexuses are tuft of capillaries present inside the ventricles.
◈ A large amount of CSF is formed in the lateral ventricles.
Factors Affecting CSF Formation
◈ Injection of isotonic saline also stimulates CSF formation
◈ Injection of hypotonic saline increases CSF formation
◈ Hypertonic saline decreases CSF formation and CSF pressure.
Circulation of CSF
Absorption of CSF
◈ CSF is mostly produced by the archnoid villi into dural sinuses and spinal veins
◈ Small amount is absorbed along the perineural spaces into cervical lymphatics and into perivascular spaces
◈ Normally, about 500 mL of CSF is formed everyday and an equal amount is absorbed
Functions of CSF
- Protection: CSF protects the brain from damage by “buffering” the brain. CSF acts to cushion a blow to the head and lessen the impact.
- Buoyancy: because the brain is immersed in fluid, the net weight of the brain is reduced from about 1,400 gm to about 50 gm. Therefore, pressure at the base of the brain is reduced.
- Excretion of waste products: the one-way flow from the CSF to the blood takes potentially harmful metabolites, drugs and other substances away from the brain.
Functions of CSF
- Regulation of cranial content volume:
◈ Regulation of this volume is essential, because brain may be affected if volume is increases . It is prevented by greater absorption of CSF to give space for the cranial contents.
Collection of CSF
◈ CSF is collected by Lumbar Puncture
◈ LUMBAR PUNCTURE
In this the needle is introduced into the subarachnoid
space in the lumbar region.
Indications of LP
◈ Diagnostic
Suspected CNS infection
Suspected subarachnoid hemorrhage
Contrast media for spinal cord imaging
◈ Therapeutic
Instillation of chemotherapy
Blood-Cerebrospinal Fluid Barrier
◈ Barrier between the blood and cerebrospinal fluid that exists at the choroid plexus.
◈ Function of this barrier is same as of blood brain barrier.
◈ Does not allow the movement of substances like chemical agents, pathogens, bile pigments etc.
◈ It allows the movement of only Oxygen, Carbon Dioxide, Water.
Hydrocephalus
◈ Abnormal accumulation of CSF in the skull associated with the enlargement of head is called hydrocephalus.
◈ HYDROCEPHALUS along with increase intracranial pressure causes headache and vomiting
◈ Severe conditions leads to atrophy of brain, mental weakness and convulsions.