Meninges and physiology of csf

1. Meninges
Dr Zaid Azhar

2. Protection of Brain
• Bone
• Water (CSF)
• Packaging material (Membranes) concentric
membranous coverings limit the excessive
movements of brain within skull

3. Need for protection
• CSF gives buoyancy to brain and protect the brain
from mechanical forces applied to skull.
• Sudden halt of a moving head. Movement of brain
relative to skull and septa leads to injury to cranial
nerves and delicate and fragile veins.

4. Meninges
• The brain and spinal cord
are surrounded by three
connective tissue
membranes, the meninges
(singular, meninx):
1. Dura mater (tough mother)-
outermost, tough
membrane
2. Arachnoid mater (spider
mother) - spider web
filamentous layer
3. Pia mater (gentle mother) -
thin vascular layer adherent
to contours of brain.

5. Layers
• OUTSIDE to INSIDE: DAP
• Outer tough dense connective tissue layer DURA
(attached to skull).
• Middle one delicate impermeable ARACHNOID
(covers the brain)
• Innermost is PIA (invests the brain).

6. Meninges

7. Meninges

8. Function of meninges
• Cover and protect the CNS.
• Protect blood vessels and enclose venous sinuses.
• Contain cerebrospinal fluid (CSF).
• Form partitions in the skull.

9. Dura Mater
• Outermost sheet, tough,
strongest of the meninges.
• Composed of two layers:
1. Endosteal layer, outer
layer - attached to inside
of skull – fused to
periosteum, present in
skull only
2. Meningeal layer, inner
layer - true external
covering, extends
downwards and
surrounds spinal cord to
form the dural sheath of
the spinal cord in the
vertebral canal.

10. Dura Mater
• Dural sinuses
Two layers are fused except to enclose the dural
venous sinuses
• Meningeal layer of cranial dura gives rise to dural
septa which divide the cranial cavity into
compartments.

11. Cranial dural septa
The inner layer of dura matter is folded and modified into:
1. Falx cerebri
2. Tentorium cerebelli
3. Falx cerebelli
4. Diaphragma selli
The dural septa extend
inward & limit excessive
movement of the brain.

12. • Sickle-like form that dips into
the longitudinal fissure.
• Separates 2 cerebral
hemispheres above the
corpus callosum.
• Upper border enclose the
superior saggital sinus,
lower margin is free and
concave and contains the
inferiorsagittal sinus
Falx cerebri

13. • Shape: tent- shaped
• It separates the temporal &
occipital lobes of the cerebral
hemispheres from the
cerebellum & infratentorial
brainstem.
Intercavernous
circular sulcus
Tentorium
cerebelli
Tentorium cerebelli

14. • Small sickle-shaped fold of
dura mater
• Continuation of falx
cerebri, partly separating
the two cerebellar
hemispheres.
• It’s post. fixed margin
encloses occipital sinus.
Falx cerebelli
Occipital sinus
Falx cerebelli

15. • Circular fold of dura mater that
forms the roof for the sella
turcica of the sphenoid bone
• A small opening in the center
allows passage of the stalk of the
pituitary gland.
• It encloses the anterior and
posterior intercavernous
sinuses.
Diaphragma sellae
Dorsum sellae
Diaphragma sellae/ sellar diaphragm

16. Arachnoid Mater
• A delicate, impermeable
membrane that covers the
brain.
• Located beneath the dura
mater.
• CSF lie in subarachnoid
space.
• Subdural space, between
meningeal dura mater &
arachnoid mater

17. Subarachnoid Space (SAS)
• Space between arachnoid
mater & pia mater
• SAS surrounds each cranial
nerve for a short distance at
its foramen. Around the optic
nerve the space reaches as far
as the eyeball; the central
retinal artery & vein cross it.
Increased intracranial
pressure may compress the
vein causing edema of the
optic disc, papilloedema.

18. Arachnoid villi
• Projections from the
arachnoid protrude
through the dura mater
into the dural sinuses.
• Transport the one-way
flow of CSF from the
subarachnoid space to
the dural sinuses.
• Aggregations of
arachnoid villi are called
arachnoid granulation.

19. Pia Mater
• It is a delicate highly vascular
connective tissue layer.
• Closely applied to the outer
surface of the brain and spinal
cord, follows the contours of
gyri & sulci the cortex.
• Connected to arachnoid by
trabeculae.
• Carries the blood vessels into
the brain.
• Forms [with the ependymal
cells of the brain and the blood
vessels] the choroid plexus.

20. Meninges around spinal cord