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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.