The three membranes that surround the brain and spinal cord are the dura mater, arachnoid mater, and pia mater. The dura mater forms partitions that divide the cranial cavity and dural venous sinuses. The arachnoid mater separates the subdural space from the subarachnoid space filled with cerebrospinal fluid (CSF). The pia mater closely invests the brain and spinal cord. CSF is produced by the choroid plexus and absorbed through arachnoid villi into venous sinuses, with the CSF circulating through the ventricles and subarachnoid space.

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

5. Dura mater
and its
processes
exposed by
removing part
of the right
half of the
skull, and the
brain

7. Tentorium
cerebelli from
above.

8. Dural venous sinuses
 Blood-filled spaces situated between
layers of dura mater:
 Superior & inferior, straight, transverse,
sigmoid, and occipital sinuses
- Confluens of sinuses
- Cavernous sinuses
- Superior and inferior petrosal sinuses

10. Oblique section through the cavernous sinus

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

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

14. Subarachnoid space red spinal cord & roots white

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

16. Brain’s cavities
 Lateral ventricles (right & left)
 Third ventricle
 Aqueduct
 Fourth ventricles

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

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.

25. CSF Circulation
Pathway:
Lateral ventricles  interventricular foramen
Third ventricle  Cerebral aqueduct  Fourth
ventricle  Foramina of Magendie & Luschka 
Subarachnoid space  arachnoid granulations 
venous sinus of dura (superior sagittal sinus)

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.