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Meninges, Brain’s cavities, and Cerebrospinal fluid_dr. Djoko P. oK.ppt
1. Meninges, Brain’s cavities, and
Cerebrospinal fluid
Djoko Prakosa
Dept. of Anatomy, Embryology &
Anthropology
2. Meninges
Three layers of membranes that surround
the brain as well as the spinal cord
1. Dura mater
2. Arachnoid mater
3. Pia mater
3. Dura mater
It consists of:
1. Endosteal layer
2. Meningeal layer
The two layers are closely united except along
certain lines, where they separate to form
venous sinuses.
Giving rise to the formation of:
- Dural partitions
- Dural venous sinuses
4. Dural Partitions
Septa form by meningeal layer divide
cranial cavity into freely communicating
spaces lodging subdivisions of the brain
1. Falx Cerebri
2. Tentorium cerebelli
3. Falx cerebelli
4. Diaphragma sellae
11. Blood supply & innervation
Blood Supply
anterior, middle & posterior meningeal arteries
Innervation
meningeal branches of the ophthalmic, maxillary,
mandibular, vagus nerves and from the 1st, 2nd & 3rd
cervical
- sensitive to stretching headache
- referred pain: depend on the stimulus location
12.
13. Arachnoid mater
Delicate, impermeable
Separated from dura by subdural space
Separated from pia by subarachnoid space &
cisternae filled with csf
Project into sinuses arachnoid villi &
granulations
Arteries, veins, nerves pass through it.
Forms a sheath for n. II & fuses with the sclera
15. Pia mater
Vascular membrane, closely invests the brain
Extends over cranial nerves and fuses with
epineurium
Arteries when enter the brain carry a sheath of
pia mater
19. Cerebral Ventricles
The wall:
- lined with:
- a layer of ependymal cells
- subependymal layer of glial fibers & cells
Exchange between ventricular fluid and
subependymal extracellular fluid occurs.
Content:
- Cerebrospinal fluid = Ventricular fluid
20. Fluid compartments & fluid balance in
the CNS
Extracellular fluid in the CNS :
1. CSF
2. Interstitial fluid (15 - 20% brain volume)
- connected and derived from the blood.
- differ in functions & drainage
21.
22. CSF secretion
CSF is produced mainly by the choroid plexus of the
lateral,
third and & fourth ventricles.
Some 11% of CSF comes from extrachoroidal source
The rate of CSF formation in man 0.35 ml/minute.
Intracranial CSF volume + 123 ml
- 25 ml in the ventricles
- 98 ml in the subarachnoid space
50% of CSF is replaced in 5 - 6 hours
CSF is produced by ultrafiltration and by active transport
mechanisms.
23. CSF Composition
The CSF is a watery, clear and colorless fluid.
csf protein < blood plasma
electrolyte content differ from blood plasma
Plasma is 93% water, CSF 99%
vitamins, nucleosides, purines, glucose and amino acids
essential for brain development and metabolism transported
into CSF, whereas toxic metabolites are cleared from CSF
to plasma.
neuroendocrine substances & neurotransmitters
Osmolality CSF = plasma
cells (mostly lymphocytes, 0 - 3 cells/μl)
24. Absorption
In the equilibrium state the rate of absorption of CSF
equals its rate of formation. The arachnoid villi are the major
place for CSF absorption. The mechanism for the bulk flow
reabsorption into the venous system depends upon the
hydrostatic pressure within the subarachnoidal space.
Other sites are the choroid plexus, diffusion into brain and
capillaries, veins and lymphatics placed around spinal nerve
roots.
26. CSF Function
The CSF has several functions:
physical support, excretory function, intracerebral transport
and control of the chemical environment of the central
nervous system (CNS).
The CSF helps in the protection of the brain from
acute blood pressure changes and, therefore, in the
regulation of intracranial pressure.
Since the CSF is considered to be an intracerebral transport
medium, the fluid is also useful for clinical research.
27. CSF Tap
In clinics the CSF is analyzed for its cellular and chemical
constituents.
CSF is obtained by cisternal puncture or lumbar
puncture
Cerebrospinal fluid pressure in the subarachnoid space can
be measured after the puncture. Values of both the
cervical and lumbar spines are affected by changes in body
position.
28. Intracranial Pressure (ICP)
Three components important for intracranial pressure:
Brain, CSF, and blood.
Blood and CSF volumes vary reciprocally --> maintain
intracranial pressure within normal limits.
Causes for an elevated CSF pressure:
space-occupying lesions (e.g., tumors)
cerebral edema (usually associated with brain injury,
hydrocephalus and inflammatory lesions)
29. Hydrocephalus
Non-Communicating:
Obstruction to CSF flow within ventricular system or
at outlet foramina.
Sites of narrowing are commonly obstructed, e.g.
aqueductal stenosis, Tumor of pineal gland
Communicating:
Obstruction to CSF flow in the subarachnoid
space after exit from fourth ventricle.
Causes include leptomeningitis (fibrosis seals
subarachnoid space and obstructs CSF flow) and
subarachnoid hemorrhage.