2. Describe the formation, circulation and
absorption and functions of CSF
Define lumbar puncture
Define hydrocephalus
Discuss blood brain barrier
Dr.Sabiha M. Haq
3. CSF is a fluid produced by the choroid
plexuses within the lateral, third and fourth
ventricles of the brain.
Dr.Sabiha M. Haq
4. Ventricles contain capillaries which are
derived from internal carotid and posterior
cerebral arteries.
A choroid plexus is essentially a tuft of such
capillaries projecting in the cavity of the
ventricles
Dr.Sabiha M. Haq
7. Lateral ventricles communicate with the third
ventricle by a foramen called FORAMEN OF
MONRO.
Third ventricle communicates with the fourth
ventricle by Aqueduct of sylvius.
Dr.Sabiha M. Haq
9. From the fourth ventricle through Foramen
of Magendi (midline) and Foramen of
Luschka (lateral) CSF escapes to the
subarachnoid space and is distributed all over
the brain.
Dr.Sabiha M. Haq
10. Formation of CSF includes both filtration and
secretion
Choroid plexus is the site of formation
Also contains tissue fluid from brain
parenchyma
Dr.Sabiha M. Haq
11. Layer of cuboidal epithelial cells surrounding
a core of capillaries and loose connective
tissue
The Choroid plexus epithelial layer is
continuous with the ependymal cell layer that
lines the ventricles
This double ependymal layer in each ventricle
is calledTela chorodea
Dr.Sabiha M. Haq
14. But unlike the ependyma the CP epithelial
layer has tight junctions in between the cells
on the side facing the ventricle (apical
surface).
These tight junctions prevent the majority of
substances from crossing the cell layer into
the CSF; thus creating a blood-CSF barrier
Dr.Sabiha M. Haq
15. At the sup. sagittal sinus,finger like
projections called arachinoid villi,are seen to
project from the arachnoid mater
Arachnoid villi come in contact with the
venous blood of the sagital sinus
Dr.Sabiha M. Haq
17. The membranous structure which separates
CSF within the arachnoid villi and the venous
blood of sagital sinus, is thin
The epithelium of the membrane shows
pores
When CSF pressure is high ,pores open up
and fluid escapes into the venous blood
Dr.Sabiha M. Haq
18. Venous blood cannot enter the villi
A part of CSF is also absorbed into venous
blood through similar arachnoid villi
projecting into other venous sinuses as well
as into veins of spinal cord.
Dr.Sabiha M. Haq
20. Colour : clear as water
On microscopical examination
Cells - nil to 5/cmm(lymphocytes)
On chemical examination
Glucose – 50-80 mg/100ml
Chloride – 720-750 mg/100 ml
Protein – 20-90 mg/100ml
Dr.Sabiha M. Haq
21. Forms a sort of cushion around the brain
It may carry nutrients to the brain
Distributes neuro endocrine factors
Prevents brain ischemia during variations in
blood pressure
Dr.Sabiha M. Haq
25. Accumulation of CSF in the lateral and
third ventricles due to blocked
Aqueduct of Sylvius
Fails to appear in the 4th ventricle and
onwards
Dr.Sabiha M. Haq
28. The BBB is formed by a single layer of
endothelial cells that line the inner surfaces of
capillaries in the brain
Dr.Sabiha M. Haq
29. It is a semi-permeable
capillary membrane, it allows
some materials to cross, but
prevents others from
crossing
In most parts of the body the
capillaries, are lined with
fenestrated endothelial cells
Dr.Sabiha M. Haq
30. In the brain, the endothelial cells fit tightly
together and substances cannot pass out of
the bloodstream
Some molecules, such as glucose, are
transported out of the blood by active
transport
Dr.Sabiha M. Haq
31. The BBB has several important
functions:
1. Protects the brain from "foreign
substances" in the blood that may injure
the brain.
2. Protects the brain from hormones and
neurotransmitters in the rest of the body.
3. Maintains a constant environment for the
brain. Dr.Sabiha M. Haq
32. 1.Large molecules do not pass through the
BBB easily.
2.Low lipid (fat) soluble molecules do not
penetrate into the brain. However, lipid
soluble molecules rapidly cross the BBB into
the brain.
3.Molecules that have a high electrical charge
on them are slowed down.
Dr.Sabiha M. Haq
33. Therefore:
The BBB is selectively permeable to
:Oxygen, Carbon dioxide and glucose
Readily permeable to small/ lipid
soluble molecules
Not permeable to
hydrogen ions
Dr.Sabiha M. Haq
