CEREBROSPINAL FLUID AND BLOOD BRAIN BARRIER

Dr. Rati TandonJ.N.M.C.,AMU,

ALIGARH

CEREBROSPINAL FLUID

The cerebrospinal Fluid [CSF] is a clear, colorless

transparent, tissue fluid present in the ventricles,

spinal canal, and subarachnoid spaces.

Cerebrospinal Fluid (CSF)

• Functions– Gives buoyancy to CNS structures• Reduces weight by 97% (1.5 kg to 50gm).

– Protects CNS from blows and other trauma (shock absorber).

– Nourishes brain and carries chemical signals

COMPOSITION

• Clear and colorless.• Specific gravity 1005-1008.• Cell free (0-5 lymphocytes).• Low protein content compared to plasma (25 and

600mg/100ml).• Glucose content half to that of blood (50 and

100mg/100ml).• Chloride content is slightly higher than blood (120

and100mEq/L).

• In bacterial meningitis: cloudy raised protein content increased number of cells

FORMATION OF CSF

Rate of formation:

About 20-25 ml/hour

550 ml/day in adults.

Total quantity: 150 ml:

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].

• Hang from roof of each ventricle; produce CSF at constant rate; keep in motion – Clusters of capillaries enclosed by pia mater and

layer of ependymal cells.

• Cavity of ventricle

Choroid Plexuses

CIRCULATION OF CSF

Lateral ventricle (in cerebral hemispheres)

Foramen of Monro [Interventricular foramen]

Third ventricle (in diencephalon around and between R/L thalamus)

Subarachnoid space of Brain and Spinal cord

Fourth ventricle (between pons/cerebellum)

Cerebral aqueduct

Foramen of magendie and foramen of luschka

Figure 12.24a Formation, location, and circulation of CSF. Slide 1

Superiorsagittal sinus

Choroid plexus

InterventricularforamenThird ventricle

Cerebral aqueductLateral apertureFourth ventricleMedian aperture

Central canalof spinal cord

(a) CSF circulation

1 The choroid plexus of each Ventricle produces CSF.

2 CSF flows through the ventriclesand into the subarachnoid space via the median and lateral apertures.

3 CSF flows through the subarachnoid space over brain and spinal cord.

4 CSF is absorbed into the dural venous sinuses via the arachnoid villi.

Arachnoid villus

Subarachnoid spaceArachnoid materMeningeal dura materPeriosteal dura mater

Right lateral ventricle(deep to cut)

Choroid plexusof fourth ventricle

1

4

2

3

Subarachnoid space – between arachnoid & pia mater; contains cerebrospinal fluid (CSF)

Arachnoid granulations (villi) – projections of arachnoid into dural sinuses for drainage of CSF

LUMBAR PUNCTURE

• A lumbar puncture also called a spinal tap is a procedure where a sample of cerebrospinal fluid is taken for examination.

• CSF is mainly used to diagnose meningitis [an infection of the meninges].

• It is also used to diagnose some other conditions of the brain and spinal cord.

CEREBROSPINAL FLUID

HYDROCEPHALUS

What is the blood brain barrier (BBB)?

•The brain is a privileged site, sheltered from the systemic circulation by the blood-brain barrier (BBB).

. Semipermeable barrier.• Highly specialised brain endothelial structure.• Helps maintain stable environment for brain. • Separates neurons from some blood borne

substances.

• It intervene between the blood in the capillaries and extracellular spaces surrounding neurons.

• Principal components:1. Capillary endothelial cells and tight junctions

between them.2. A basement membrane on which capillary

endothelial cells are arranged.3. Foot process of astrocytes.

MDufilho

Capillary

Neuron

Astrocyte

Astrocytes are the most abundant CNS neuroglia.

MDufilho

Blood Brain Barrier: Functions

• Selective barrier– Allows nutrients to move by facilitated diffusion– Metabolic wastes, proteins, toxins, most drugs, small

nonessential amino acids, K+ denied– Allows any fat-soluble substances to pass, including

alcohol, nicotine, and anesthetics • Absent in some areas, e.g., vomiting center and

hypothalamus, where necessary to monitor chemical composition of blood

• Areas that are devoid of:1. Pineal gland2. Neurohypophysis3. Area postrema (at lower end of floor of

fourth ventricle.4. Wall of supraoptic recess of third ventricle.