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1. The Cerebrospinal Fluid
Dr.Sahar Aldisi

2. The cerebrospinal Fluid [CSF] is a clear, colorless
transparent, tissue fluid present in the cerebral
ventricles, spinal canal, and subarachnoid
spaces.

3. The Capacity of the cerebral cavity is 1600-1700
ml, 150 ml occupied by Cerebrospinal fluid
and the remainder contains the brain and the
spinal cord.

4. Functions of Cerebrospinal Fluid:
1-Cushioning between the brain and cranium
The main function of CSF is cushioning the brain within its solid
vault.
The brain floats in the fluid due to the equal gravity between it
and the CSF .So that any blow to the head (without intensity) will
move the entire brain simultaneously with the skull protecting the
whole brain from being momentarily contorted.

5. A contrecoup is also a characteristic of CSF. It means that when a blow is intense or
severe it may not damage the brain on the side of the head where the blow is
struck but on the opposite side.
The reason behind that is that when the blow is struck, the fluid on that
side is so incompressible making it push the brain at the same time in union with
the skull .While on the opposite side, a sudden movement of the whole skull
causes the skull to pull away from the brain creating a vacuum space in the cranial
vault leading to a sudden vacuum collapse and the brain strikes the inner surface
of the skull when it is no longer accelerated by the blow.

6. 2-Act as a reservoir and regulates the contents of the
cranium
3-Serves as a medium for nutritional exchange in CNS
4-Transport hormones and hormone releasing factors
5-Removes the metabolic waste products through
absorption

7. CSF composition
Proteins 20-40 mg/100 ml
Glucose 50-65 mg/100 ml
Cholesterol 0.2 mg/100 ml
Na+ 147 meq/Kg H2O
Ca+ 2.3 meq/kg H2O
Urea 12.0 mg/100 ml
Creatinine 1.5 mg/100 ml
Lactic acid 18.0 mg/100 ml

8. Sources of CSF secretion
1- Two thirds are secreted from the choroid plexus in
the four ventricles mainly in the two lateral ones.

9. 2-Ependymal surfaces of all ventricles
3- Arachnoidal membranes
4-Perivascular spaces surrounding blood vessels
of the brain.

10. Locations of CSF:
1-In the ventricles of the brain.
2-Cisterns around the outside of the brain.
3-Subarachnoid Space around both the brain and
spinal cord.
All chambers are connected with one another
keeping the pressure in all of them at a constant
level.

11. Passage of CSF
Lateral ventricles  Third ventricle  Aqueduct of
Sylvuis Fourth ventricle
Foramina of Luschka
Foramina of Magendie
Cisterna Magna

12. Cisterna Magma (a space behind the medulla
and beneath cerebellum) and is continuous
with subarachnoid space surrounding the
entire brain and spinal cord and the cerebrum.

13. Secretion depends on active transport of sodium ions
through epithelial cells lining the outside of the plexus.
Sodium ions pulling large amounts of Chloride ions due to
positive charge attraction of negative ions of chloride.
Thereby increasing the osmotically action of NaCl in CSF
causing immediate osmosis of water through the membrane
providing the fluid of secretion.

14. The osmotic pressure and sodium concentration
is equal to that of plasma due to movements of
small amounts of glucose into CSF and potassium
and bicarbonate ions out into the capillaries .
Chloride ion concentration is 15% less than plasma ,
potassuim 40% less , Glucose 30% less.

15. Absorption of CSF occurs through inward finger-like
projections of the arachnoid membrane through the walls and into
venous sinuses called arachnoidal villi which macroscopically cause
arachnoidal granulations protruding into the sinuses
Arachnoidal villi are covered with endothelial cells with
vesicular passages allowing the free flow of:
1- CSF
2-Disolved protein molecules
3-Red and white blood cells

16. The large arteries and veins of the brain lie on
the surface of the brain with their ends penetrating
inwards carrying a layer of pia mater which the
membrane covering the brain. Pia is loosely
adherent to the vessels creating space called
perivascular space between pia and each vessel.

17. A small amount of protein leaks out of the brain
capillaries into interstitial spaces of the brain.
Excess protein leaves the brain tissue flowing with
fluid through perivascular spaces into subarachnoid
spaces where it flows with CSF. This occurs due to
absence of true lymphatics in the brain tissue to be
absorbed through arachnoidal villi into large
cerebral veins.
Perivascular spaces transport fluid and proteins
and extraneous particulate matter out of the brain
.Also, in cases of infection dead white blood cells
and infection debris are transported.

18. Regulation of CSF pressure by Arachoidal Villi
Normally, in cases of CSF pressure increase
1.5 mmHg greater than blood pressure in venous
sinuses, arachnoidal villi act as valves allowing
CSF to flow and its contents into venous sinuses
yet preventing blood flow in the opposite
direction.

19. Further increase in CSF pressure leads to
wider opening of these valves, thereby
preventing any rise in pressure more than few
mmHg.

20. The pressure of CSF is increased in
standing, coughing, sneezing, crying,
compression of internal Jugular vein
(Queckenstedt’s sign)

21. Blood Cerebrospinal Fluid and Blood Brain Barrier
A barrier protects the brain and spinal cord from harmful
substances.

22. Barrier exist both at the choroid plexus and at the
tissue capillary membrane in all areas of the brain
parenchyma except in some areas in the hypothalamus
, pineal gland ,and area postrema , where substances
infuse with greater ease in the tissue . The ease of
diffusion in the areas is important because they have
sensory receptors that respond to specific changes in
the body fluids, such as changes in osmolarity and in
glucose concentration, as well as receptors for peptide
hormones that regulate thirst such as angiotensin  .

23. The blood-brain barrier also has specific
molecules that facilitate transport of
hormones such as leptin, from the blood into
the hypothalamus where it binds to specific
receptor that control other function such as
appetite and sympathetic nervous system
activity.

24. The blood CSF and blood brain barriers are highly
permeable to water , carbon dioxide , oxygen and most lipid-
soluble substances such as alcohol and anesthetics ;slightly
permeable to electrolytes such as sodium , chloride , and
potassium and almost totally impermeable to plasma proteins
and most non-lipid soluble large organic molecules .
Therefore, the blood CSF and blood brain barriers often make
it impossible to achieve effective concentrations of
therapeutic drugs such as protein antibodies and non-lipid
soluble drugs in the CSF or parenchyma of the brain.

25. •The cause of the low permeability of the blood
CSF and blood brain barriers is the manner in
which the endothelial cells of the brain tissue
capillaries are joined to one another. They are
joined by the so-called tight junctions. That is, the
membrane of the adjacent endothelial cells are
tightly fused rather than having large split pores
between them , as is the case for most other
capillaries of the body .

26. Pathological conditions elevating CSF pressure:
1-Haemorrhage or infection in the cranial vault:
Where large numbers of RBCs and WBCs suddenly
appear in the CSF causing serious blockage of small
absorption channels through arachnoid villi
elevating pressure to 400-600 mmHg (four times
normal ).
2-Large brain tumors: elevates CSF pressure by
decreasing reabsorption of CSF back to blood to 500
mmHg.

27. High CSF pressure
pathological effects:
1-Papilledema (Edema of
the optic disc)
When pressure rises in
the cerebrospinal fluid
system, it also rises inside
the optic nerve sheath
.The retinal artery and
vein pierce this sheath a
few millimeters behind
the eye and then pass
alone with the optic nerve
into the eye itself.

28. A-High CSF pressure pushes
fluid first into the optic nerve
sheath and then along the
spaces between the optic
nerve fibers to the interior of
the eyeball.
b-The high pressure decreases
outward fluid flow in the
optic nerves, causing
accumulation of excess fluid
in the optic disc at the center
of the retina
c- The pressure in the sheath
also impedes flow of blood in
the retinal vein, thereby
increasing the retinal capillary
pressure throughout the eye
which results in more retinal
edema.

29. 2-Hydrocephalus (excess water in the cranial vault)

30. There are 2 types of hydrocephalus:
Communicating Hydrocephalus1.
2.Non-Communicating Hydrocephalus

31. 1. Communicating Hydrocephalus:
Where fluid flows readily from ventricular system to
subarachnoid space and blockage of arachnoid villi thereby
blocking the flow of fluid and preventing absorption.
This collection of fluid outside of the brain or inside the
ventricles causing a tremendous swelling of the head in
infancy when the skull can be stretched damaging the brain
at any age.

32. Non-communicating Hydrocephalus:
Flow out of one or more of the ventricles is blocked.
Usually due to a block of aqueduct of Sylvuis due to atresia
(closure) before birth in many babies or in cases of tumors
.This excessive accumulation of fluid in the 3 ventricles will
flatten the brain into a thin shell against the skull leading to
swelling of the whole head in neonates because the skull
bones have not been fused yet.

33. Brain edema:
Occurs due to the solid cranial vault causing extra
accumulation of edema fluid thereby compressing
blood vessels causing serious low blood flow and
destruction of brain tissue.

34. Common causes:
1-Increased capillary pressure
2-Damage to the capillary wall making it leaky to
the fluid
3-Serious blow to the head leading to brain
concussion

35. Effects of brain Edema:
1-Brain Ischemia leading to arterial dilation with
further increase in capillary pressure and edema
fluid thereby worsening the edema.
2-Decrease of blood flow decreasing oxygen delivery
increasing the permeability of capillaries allowing
more fluid leakage and turning off sodium ion
pumps of neuronal tissue cells and swelling even
more .

36. Thanks