Cerebrospinal fluid

Introduction

• CSF is clear, colorless and transparent• Circulates through cavity of the:– Brain– Subarachnoid space– Central canal of spinal cord

• Part of Extracellular fluid (ECF)

Properties

• Volume : approximately 150 mL• Rate of formation: approximately 0.3 mL/min• Specific gravity : 1.005• Reaction : Alkaline

Composition Cerebrospinal Fluid

Water - 99.13% Solids - 0.87%

Inorganic substances

1.Sodium

2.Calcium

3.Potassium

4.Magnesium

5.Chlorides

6.Phosphate

7.Bicarbonates

8.Sulfates

Organic substances

1.Proteins

2.Amino acids

3.Sugar

4.Cholesterol

5.Urea

6.Uric acid

7.Creatinine

8.Lactic acid

Lymphocytes in CSF : 6/ cu mm

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• As CSF is part of ECF therefore it contain more amount of Sodium than Potassium.

• Contains some lymphocytes.• CSF secreted by ventricles does not contain

any cell.• The lymphocytes are added when it flows in

the spinal cord.

Formation of CSF

• Site of formation– Formed by the choroid plexus situated within the

ventricles.

– The choroid plexus are tuft of capillary projections present inside ventricles and covered by:• Pia mater • Ependymal covering.

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Mechanism of formation• Formed by process of secretion.

• Does not involve ultrafiltration or dialysis.

• Uses energy.

• Active transport mechanism is involved in secretion.

Circulation of CSF Formation of CSF in lateral ventricles

Foramen of Monro

Third ventricle

Aqueductus Sylvius

Fourth ventricle

Foramen of magendie and foramen of Luschka

Cisterna magna and Cisterna lateralis

Subarachnoid spaces

To cerebral hemispheres To the spinal cord

Absorption of CSF

• Mostly absorbed by the Arachnoid villi into Dural sinuses and Spinal veins.

• Small amount is absorbed along the perineural spaces into cervical lymphatics and in to the perivascular spaces.

• Normally, 500 mL of CSF is formed everyday and equal amount is absorbed.

Pressure exerted by CSF

• Varies in different position: Lateral recumbent position = 10-18 cm of H2O Lying position = 13 cm of H2O Sitting position = 30 cm of H2O

Coughing and crying increases the pressure by decreasing the absorption.

Compression of internal jugular vein also raises the CSF pressure.

Function of CSF

• Protective Function:– Acts as buffer – Protects the brain from shock

• If brain receives severe blow , countercoup injury may take place.

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• Medium of Exchange• CSF is the medium through which substances

like :– Nutritive substances– Waste materials

are exchanged between blood and brain tissues.

CSF disorders

• Hydrocephalus– Abnormal accumulation of CSF in the skull with

enlargement of head.

• 2 types of Hydrocephalus 1. non-communicating 2. communicating

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Non-communicating Hydrocephalus or Internal Hydrocephalus

Due to the obstruction of any of the foramen through which CSF escapes results in dilation of ventricular cavity.

Communicating Hydrocephalus or External Hydrocephalus

Due to blockage of Arachnoid villi.

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Symptoms of Hydrocephalus: Headache Vomiting Atrophy of brain Mental weakness Convulsions