Transcript The Meninges and Blood Vessels of Brain and Spinal

The Meninges of
Brain and Spinal Cord
DR. S. H. KHAN
The Meninges of Brain and Spinal Cord
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The spinal cord and brain are
surrounded by three membranes,
the meninges. Named from the
outside~ inward they are the dura
mater, arachnoid, and pia mater.
DURA MATER
SUB-DURAL SPACE (filled with thin film of fluid)
ARACHNOID MATER
SUB-ARACHNOID SPACE (filled with CSF)
PIA MATER
The meninges of spinal cord
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Spinal Dura mater
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Spinal Arachnoid mater
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Spinal Pia mater
Spinal dura mater
Characters
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Dense, strong, fibrous membrane
Encloses the sp. Cord & cauda
equina
Continuous above foramen
magnum with the meningeal layer
of Dura mater of brain
Below, becomes thinner & ends
at lower border of S2
invests filum terminale to attach at
back of coccyx
Epidural space
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Position: lies between spinal dura mater and periosteum & ligaments of
vertebral canal
Contents: loose connective tissue, semi liquid fat, spinal arteries, vertebral
venous plexus, lymphatics and, the spinal nerves on each side pass through the
epidural space which is applicable for block anesthesia
Subdural space: potential space
Spinal arachnoid mater
Characters
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A thin, delicate, tubular
membrane loosely
investing spinal cord
Above, it is continuous
with cerebral arachnoid
mater
Inferiorly extends as
Dura ( lower border of S2)
Subarachnoid space
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Position: lies between pia
and arachnoid maters
containing cerebrospinal
fluid. Extends upto low.
Border of S2
Terminal cistern : the
largest part of subarachnoid
space extending from
termination of spinal cord
(low. Border of L1) to level of
S2, where it is occupied by
nerves of cauda equina, so
it is the best site for a
lumbar puncture
Lumbar puncture (spinal tap)
Bet. L3 & L4 (adult), L4 & L5 (child)
Spinal pia mater
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A delicate vascular membrane
that closely invests the spinal
cord
Denticulate ligament:
consist of 21 pairs triangular
ligaments extending from
spinal cord on each side
between anterior and
posterior roots of spinal
nerves to spinal dura mater;
these ligaments help to fix
position of spinal cord.
Filum terminale: an
extension of pia beyond conus
medullaris
The Meninges of Brain
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Cerebral Dura mater (Pachymeninx)
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Cerebral Arachnoid mater
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Cerebral Pia mater
Leptomeninges
Cerebral Dura mater
Characters
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A thick and dense
inelastic membrane
Composed of two layers,
an inner - meningeal
and outer - endosteal
Cranial venous sinuses
lie between 2 layers
Endosteal layer of Cerebral Dura mater
 Lies just below the skull bone -Epidural Hge
 Continuous outside at sutures & foramina with
the periosteum of skull bones
 Most strongly adherent to the bones over base of
skull
Meningeal layer of Cerebral Dura mater
(Dura mater proper)
 Dense, strong fibrous membrane
 Continuous through the foramina magnum as
Dura mater of Spinal cord
 Forms 4 septa which divide the cranial cavity
Four septa of Dura mater Proper
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Falx cerebri
－ Lies in between the cerebral hemispheres.
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Tentorium cerebri
－ Roof over the posterior cranial fossa.
－ covers the upper surface of cerebellum .
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Falx cerebelli
－ Lies between the cerebellar hemispheres.
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Diaphragma sellae
－ Forms roof of the sellar/ hypophyseal fossa
Dural Artery Supply
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ICA
Vertebral A.
ECA
Maxillary a.
Middle meningeal artery (clinically important -Epidural hge)
Ascending pharyngeal a.
Occipital a.
Venous Sinuses of duramater
Function: To receive blood from brain through cerebral veins
To receive CSF from SA space through Arachnoid villi
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Superior sagittal sinus
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Inferior sagittal sinus
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Straight sinus
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Confluence of sinus
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Transverse sinus
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Sigmoid sinus
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Superior petrosal
sinuses
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inferior petrosal
sinuses
Cavernous sinus
 Position: lies on each side of sella turcica (hypophyseal fossa)
 Relations of cavernous sinus:
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Internal carotid artery and abducent nerve run through the sinus
Oculomotor and trochlear nerves and ophthalmic & maxillary
divisions of trigeminal nerve lie in the lateral wall of the sinus
MCA
Occul n.
Troch n.
Optha n.
Maxil n.
Pituitary gland
ICA
Abducent n.
Sphenoid air sinus
The flowing of the blood in dural sinus
Sup. sagittal sinus
Inf. sagittal sinus
Straight sinus
Confluence of sinus
Transverse sinus
Sup. petrosal sinus
Sigmoid sinus
Cavernous sinus
Inf. petrosal sinus
Internal jugular vein
Cerebral Arachnoid mater
Characters:
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A delicate membrane
covering brain loosely,
Passing over sulci and
entering only cerebral
longitudinal and transverse
fissures.
Separated from Dura by
potential Subdural space
Separated from Pia by the
Subarachnoid space
Arachnoid villi :
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In certain areas arachnoid projects into venous sinuses to form arachnoid villi
Most numerous along the sup. Sagital sinus
serve as sites where CSF diffuses into bloodstream
Aggregations of arachnoid villi called archnoid granulations,
May give rise to Brain tumour (Meningioma)
Cerebral pia mater
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Thin vascular membrane
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Closely invests brain surface,
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Covers the gyri and descends
into the sulci
Folds of Pia mater enclosing
tufts of capillaries form the
Telachoroidea. Such pia mater
lined by secretory ependyma
form the Choroid plexuses
Tela choroidea and choroid plexus
Capillaries
Pia
Ependyma
Sub Arachnoid Space (SAS)
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Interval between Arachnoid & Pia mater
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Contains :
－ CSF, large blood vessels of brain & cranial nerves
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Extension:
－ Along the olfactory n. to the mucoperiosteum of nose
－ Along the cerebral bl. Vessels, till they become an arteriole or venule
－ Beyond the lower end of spinal cord, ends between S2 & S3
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Around the base of the brain the SAS expands to form
SA cisterns
Subarachnoid cisterns
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In certain situations the Arachnoid & Pia are
widely separated to form the SA cisterns
Has free comunication with one another and
with remainder SA Space
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Cerebellomedullary cistern /
Cisterna magna
(Bet. Inf. Surface of cerebellum and the medulla)
Interpeduncular cistern
(contain circle of Willi’s)
Pre Pontine cistern
(contain vert. & basillar a.)
Quadrigaminal cistern / Cisterna ambiens
(contain the great cerebral vein of Galen)
Cerebellomedullary cistern
Cerebrospinal fluid (CSF)
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Clear colorless fluid,
Contained in the ventricular
system & SA space
Replaces lymph in the CNS
Function:
－ Cushions & protects the CNS.
－ Nourishment of CNS.
－ Removes metabolites from
CNS
Production:
－ By the choroids plexuses within
the lateral ventricle mainly and,
third and fourth ventricles also
Absorption: By arachnoid villi
Amount: 150ml
Rate of production: 0.5ml/min
Density of brain is slightly
greater than that of CSF.
Circulation of cerebrospinal fluid
CSF drains from lateral ventricle
mesencephalic aqueduct
interventricular foramina
fourth ventricle
third ventricle
median and two lateral apertures
subarachnoid space arachnoid granulations superior sagittal sinus
vein
Ventricular System
Lateral
(L&R)
Cerebral
Aqueduct
3rd
4th
The Blood vessels of
Brain and Spinal Cord
Arteries of brain
Two sources
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Internal carotid artery:
supplies anterior 2/3 of
cerebral hemisphere and
parts of diencephalon.
Divides into ant. & mid.
Cerebral arteries.
Vertebral artery:
supplies posterior 1/3 of
cerebral hemisphere and
parts of diencephalon,
brain stem and cerebellum
At lower border of pons
two VA join to form the
basilar artery
Internal carotid artery
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Anterior cerebral artery
Middle cerebral artery
Anterior choroidal artery
Posterior communicating
artery
ICA
ACA
MCA
AChA
PComA
Anterior cerebral artery
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Terminal br. Of ICA
Joins the fellow of the
opposite side by the
anterior communicating
artery
supply all medial surface
of the cerebral cortex up to
the parietooccipital sulcus
ACA
Middle cerebral artery
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Largest br. Of ICA
Cortical branches:
supply entire lateral surface
of cerebral hemisphere,
except occipital pole and
inferolateral surface which is
supplied by PCA
Central branches: supply
lentiform and caudate nuclei,
internal capsule
Posterior communicating artery
runs backward to join posterior
cerebral artery
Vertebral artery
Cranial branches
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Anterior and posterior spinal
arteries
Posterior inferior cerebellar
artery
Branches of basilar
artery
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Anterior inferior cerebral
artery
Labyrinthine artery
Pontine arteries
Superior cerebellar artery
Posterior cerebral artery
Posterior cerebral artery
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Cortical branches:
supply medial and
inferolateral surfaces of
temporal lobe and lat. &
medial surfaces of
occipital lobe
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Central branches:
supply dorsal thalamus,
midbrain, medial and
lateral geniculate bodies,
Cerebral arterial circle ( circle of Willis )
Concept:
－ Arterial anastomosis.
－ Distribute blood to any
part of the cerebral
hemisphere.
－ Equalizes pressure in the
arteries of the two sides
of brain.
Position:
－ lies in the
interpeduncular fossa at
the base of the brain.
Formation:
Anteriorly:
－ Ant. communicating artery
Posteriorly:
－ Basilar artery that divides
into posterior cerebral arteries
On each side:
－ Anterior cerebral arteries,
－ Internal carotid arteries,
－ Posterior communicating arts,
－ Posterior cerebral arteries
VENOUS DRAINAGE
－ very thin wall
－ no valves
－ lie in the subarachnoid
space
－ drain into the cranial
venous sinuses
－ ultimately drain into
internal jugular vein
1.External cerebral veins
2.Internal cerebral veins
Veins of brain
External cerebral veins
 Drain blood from cortex
and subcortical medullary
substance and empty
into adjacent sinuses of
dura mater
Veins of brain
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Internal cerebral
veins: Two veins
drain deeper parts of
hemispheres, basal
nuclei, internal capsule,
diencephalon and
choroid plexus,
ultimately two ICV form
great cerebral vein
of Galen which enter
straight sinus
Blood vessels of spinal cord
Arteries of spinal cord
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Two sources
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One Anterior and two
posterior spinal arteries
Branches of segmental
arteries:
ASA
PSA
Blood vessels of spinal cord
Spinal veins: drain into internal vertebral venous plexus
Post. Sp. A.
Segmental sp. A.
Ant. Spinal artery
Optic/visual pathway
Light falling on the cornea.
Traverse the refractive medias of the
eye.
Stimulates the rods and cones of
retina.
Optic nerve ( nasal & temporal fibers)
Optic chaisma ( nasal fibers cross)
Optic tract
Lateral geniculate body
Optic radiation
Visual cortex