A guide to understanding the envelopes of the brain

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3.  3 Meninges:
A. Dura Mater
B. Arachnoid Mater
C. Pia Mater

4.  Conventionally described as 2 layers
A. ENDOSTEAL LAYER
- is nothing more than the
periosteum covering the inner surface of
the skull bones
B. MENINGEAL LAYER
-dura mater proper
- a dense strong fibrous membrane
covering the brain and is continuous thru
the foramen magnum with the dura of
the spinal cord

5. - endosteal and meningeal layers closely
united except along certain lines where they
separate to form venous sinuses
- the meningeal layer sends inward four
septa which divides the cranial cavity into
freely communicating spaces that lodge the
subdivisions of the brain
- the function of these septa is to
restrict the displacement of the brain
associated with acceleration and
deceleration when the head is moved

6.  Defined as:
-sickle shaped fold of dura mater that
lies in the midline between the two cerebral
hemispheres

7. -Crescent shaped fold of dura mater that
roofs over the posterior cranial fossa. Covers
the upper surface of the Cerebellum and
supports the occipital lobes of the cerebral
hemispheres.
- The Falx Cerebelli are attached to the
upper and lower surfaces of the tentorium
respectively. The straight sinus runs along its
attachment to the falx cerebri, the superior
petrosal sinus along its attachment to the
petros bone and the transverse sinus along
its attachment to the occipital bone.

8.  Is a small, circular fold of dura mater that
forms the roof for the sella turcica. A small
opening in its center allows passage of the
stalk of the hypophysis cerebri.

9.  Branches of the trigeminal, vagus, and the
first three cervical spinal nerves and
branches from the sympathetic trunk pass to
the dura.

10.  Numerous arteries supply the dura mater from
the:
A. Internal Carotid –surrounded by its
sympathetic nerve plexus; runs forward through
the sinus
B. Maxillary –runs forward in the lateral wall of
the sinus
C. Ascending Pharyngeal
D. Occipital and Vertebral Arteries
Note: From the clinical standpoint the most
important is the middle meningeal artery, which
can be damaged in head injuries

11. MAXILLARY ARTERY
TEMPORAL BONE
MIDDLE MENINGEAL ARTERY
FORAMEN SPINOSUM

12.  Lie in the endosteal layer of dura
 The middle meningeal vein follows the
branches of the middle meningeal artery and
drains into the pterygoid venous plexus or
the sphenoparietal sinus.
 The veins lie lateral to the arteries.

13.  Situated between the layers of the dura mater.
 Main Function: receive blood from the brain and
the CSF from the subarachnoid space through the
Arachnoid Villi.
 Emissary Veins- also valveless, connect the dural
venous sinuses with the diploic veins of the skull
and with the veins of the skull
 Superior Sagittal Sinus – occupies the upper fixed
border of the falx cerebri; begins anteriorly at
the foramen cecum;continuous with
corresponding transverse sinus

14.  Inferior Sagittal Sinus – occupies the free lower
margin of the falx cerebri
 Straight Sinus – occupies the line of junction of
the falx cerebri with the tentorium cerebelli
(formed from the union of the inferior sagittal
sinus with the great cerebral vein; ends by
turning to the left to from the transverse sinus)
 Transverse Sinus – Paired structures and they
begin at the internal occipital protruberance
(receive the superior petrosal sinuses, inferior
cerebral and cerebellar veins and the diploic
veins). End by turning downward as the
sigmoid sinuses.

15.  Sigmoid Sinus – Direct continuation of the
transverse sinus. Each sinus trurns downward
and medially and grooves the mastoid part of
the temporal bone. (Superior Bulb of the
Internal Jugular Vein)
 Occipital Sinus- is a small sinus occupying t
he attached margin of the falx cerebelli and
commences near the foramen magnum where
it communicated with the vertebral vein and
drains into the confluence of sinuses.
 Cavernous Sinus- middle cranial fossa on
each side of the body of the sphenoid bone

16.  Superior and Inferior Petrosal Sinus-
communicate with each other by means of
the anterior and posterior intercavernous
sinuses which run in the diaphragma sellae
anterior and posterior to the stalk of the
hypophysis cerebri.

18.  Is a delicate, impermeable membrane
covering the brain and lying between the pia
mater and the dura mater externally.
 Separated from the dura by a potential space
the SUBDURAL SPACE.
 Separated from the pia by the
SUBARACHNOID SPACE.
 Outer and Inner covered by flattened
mesothelial cells.

19.  Cisterna Cerebellomedularis – inf. Surface of
cerebellum and roof of fourth ventricle
 Cisterna Interpeduncularis – 2 cerebral
peduncles
 Arachnoid Villi – most numerous along the
sup. Sagittal sinus (ARACHNOID
GRANULATIONS)
 CSF- produced by the choroid plexuses within
the lateral third and fourth ventricles of the
brain

21.  Is a vascular membrane covered by flattened
mesothelial cells. It closely invests the brain,
covering the gyri and descending into the
deepest sulci.
 The pia mater forms the tela choroidea of
the roof of the third and fourth ventricles of
the brain, and it fuses with the ependyma to
form the choroid plexus in the lateral, third,
and fourth ventricles of the brain.

22.  Emissary veins which are valveless, connect
the dural venous sinuses with the diploic
veins of the skull and with the veins of the
scalp.

23. Coronal Section through the body of the sphenoid bone

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