Dr. Nimir
Dr. Safaa
Ojectives
 Describe the arrangement of the
meninges and their relationship to brain
and spinal cord.
 Explain the occurrence of epidural,
subdural and subarachnoid spaces.
 Locate the principal subarachnoid
cisterns, and arachnoid granulations.
Meninges of Brain
 The brain and spinal
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cord are surrounded
by three protective
membranes, or
meninges:
Dura mater.
Arachnoid mater.
Pia mater.
The dura mater of the
brain has two layers:
Endosteal layer.
Meningeal layer .
These are closely
united except along
certain lines, where
they separate to form
venous sinuses.
 Endosteal layer
covers the inner
surface of the skull
bones.
 At the sutures, it is
continuous with the
sutural ligaments.
 At the foramen
magnum, it does not
become continuous
with the dura mater
of the spinal cord.
 The meningeal layer is the
dura mater proper.
 It is a dense fibrous
membrane covering the
brain and is continuous
through the foramen
magnum with the dura
mater of the spinal cord.
 It provides tubular sheaths
for the cranial nerves as
they pass through the
foramina in the skull.
Outside the skull, the
sheaths fuse with the
epineurium of the nerves.
 In vertebral canal there is
an epidural space
containing fat and internal
vertebral venou plexus.
 The meningeal layer
sends inward four
septa(falx cerebri,falx
cerebelli,tentorium
cerebelli &
diaphragma sellae).
 The function of these
septa is to restrict the
displacement of the
brain associated with
acceleration and
deceleration, when the
head is moved.
 The dura is innervated
by trigeminal, vagus,
first three cervical
spinal nerves and
sympathetics.
 The falx cerebri is a sickle-
shaped fold of dura mater
that lies in the midline
between the two cerebral
hemispheres .
 Narrow anterior end is
attached to the internal
frontal crest and the crista
galli.
 Broad posterior part blends
in the midline with the
upper surface of the
tentorium cerebelli.
 The superior sagittal sinus
runs in its upper fixed
margin, the inferior sagittal
sinus runs in its lower
concave free margin, and
the straight sinus runs
along its attachment to the
tentorium cerebelli.
 The tentorium cerebelli is a
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crescent-shaped fold of
dura mater that roofs over
the posterior cranial fossa.
It covers the upper surface
of the cerebellum It has is a
gap, tentorial notch, for the
passage of the midbrain.
The fixed border forms
transverse & superior
petrosal sinuses .
Falx cerebelli is between
the two cerebellar
hemispheres. It contains
the occipital sinus.
Diaphragma sellae roofs
sella turcica.
 Arachnoid mater is a
delicate,
impermeable
membrane covering
the brain and lying
between the pia mater
internally and the
dura mater externally.
 It is separated from
the dura by a
potential subdural
space, filled by a film
of fluid.
 It is separated from
the pia by
subarachnoid space,
which is filled with
cerebrospinal fluid.
 Arachnoid and pia in some
spaces are widely separated
to form the subarachnoid
cisternae.
 Cisterna
cerebellomedullaris lies
between cerebellum and
roof of the fourth ventricle.
 Cisterna interpeduncularis
lies between the two
cerebral peduncles.
 In certain areas, arachnoid
projects into the venous
sinuses to form arachnoid
villi (arachnoid villi )
through which
cerebrospinal fluid diffuses
into the bloodstream.
 Meninges of Spinal Cord
 Dura mater encloses spinal
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cord and the cauda equina
It is continuous above
through the foramen
magnum with meningeal
layer of brain.
Inferiorly, it ends on the
filum terminale at lower
border of S2.
The dura is separated from
vertebral canal by
extradural space which
contains loose areolar
tissue and internal
vertebral venous plexus.
The dura extends along
each nerve root and
becomes continuous with
epineurium.
 Arachnoid covers spinal
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cord and lies between the
pia mater and dura mater.
It is separated from the pia
mater by subarachnoid
space filled with
cerebrospinal fluid.
It ends on the filum
terminale at the level of S2.
Pia mater closely covers
spinal cord and thickened
on either to form
ligamentum denticulatum,
which adheres to arachnoid
and dura.
Prolongation of pia mater,
filum terminale attaches to
posterior surface of coccyx.