The Blood Supply of the Brain and
Spinal Cord
Dr. Nimir
Dr. Safaa
• Objectives
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Describe the four arteries supplying the CNS.
Follow up each artery to its destination.
Describe the circle of Willis and its branches.
Discuss the principle of end artery type of
circulation.
• Describe venous drainage of the brain.
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Blood Supply of the Brain
The brain is supplied by:
Two internal carotid arteries
Two vertebral arteries.
They lie within subarachnoid space
Their branches anastomose on inferior surface of brain to form
Circle of Willis.
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 Internal Carotid Artery
It begins at the bifurcation of
the common carotid artery,
where it has the carotid sinus.
It ascends by passing through
the carotid canal of the
temporal bone.
Then pass through cavernous
sinus and perforates the dura
mater and enters the
subarachnoid space .
At the medial end of the lateral
cerebral sulcus it divides into :
Anterior cerebral artery
Middle cerebral artery
Branches of internal
carotid artery
 Ophthalmic artery
supplies:
• The eye
• Frontal area of scalp
• Ethmoid and frontal
sinuses
• Dorsum of nose.
 Posterior
communicating
artery join the
posterior cerebral
artery, forming part of
circle of Willis.
 Choroidal artery
• Enters inferior
horn of lateral
ventricle to form
choroid plexus.
• It gives branches
to:
• Crus cerebri
• Lateral
geniculate body
• Optic tract
• Internal capsule.
 Anterior cerebral artery
• It enters longitudinal
fissure of the cerebrum
where it joins artery of
opposite side by anterior
communicating artery.
 Cortical branches supply:
• All the medial surface of
the cerebrum till parietooccipital sulcus
• 1 inch of lateral surface
(leg area).
 Central branches supply:
• Parts of lentiform
• Caudate nuclei
• Internal capsule.
 Middle cerebral artery
• It is largest branch of
internal carotid, runs in
lateral cerebral sulcus.
 Its cortical branches supply:
• Entire lateral & orbital
surfaces of cortex
• Except:
• 1 inch of lateral supplied by
anterior cerebral artery
• Occipital pole and
inferolateral surface of
hemisphere supplied by
posterior cerebral artery
• Thus supplies all body
except the (leg area).
 Central branches enter the anterior perforated substance
and supply the:
• Lentiform and caudate nuclei
• Internal capsule
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Vertebral Artery:
Branch of the first part
of subclavian artery
Passes through
foramina transverseria
of the upper six cervical
vertebrae
Enters skull through
foramen magnum.
At the lower border of
the pons, it joins the
vessel of the opposite
side to form the basilar
artery.
• Branches of vertebral
artery:
• Meningeal branches supply
bone and dura in posterior
cranial fossa.
• Posterior spinal artery.
• Anterior spinal artery.
• Posterior inferior cerebellar
artery largest branch of
vertebral which supplies:
• Cerebellum
• Medulla oblongata
• Choroid plexus of fourth
ventricle.
• Medullary arteries to
medulla oblongata.
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Basilar Artery
It is formed by union of
the two vertebral arteries
at the pons.
Its branches are:
Pontine arteries to pons.
Labyrinthine artery to
internal ear.
Anterior inferior
cerebellar artery(AICA)
for cerebellum,pons &
upper medulla.
Superior cerebellar artery
for cerebellum,pons &
pineal gland.
• Posterior cerebral artery
is joined by posterior
communicating branch
of internal carotid.
 Its cortical branches
supply:
• Inferolateral & medial
surfaces of temporal
lobe
• lateral & medial surfaces
of occipital lobe (visual
cortex).
 Its central branches
supply:
 Thalamus
 Lentiform nucleus
 Midbrain
 Pineal gland
 Medial geniculate
bodies.
 Choroidal branch for
choroid plexus of
lateral & third
ventricles.
• Circle of Willis:
• It lies in the
interpeduncular fossa
at the base of the
brain.
• It is formed by the
anastomosis between
the two internal
carotid arteries and
the two vertebral
arteries.
• It allows blood that
enters by either
internal carotid or
vertebral arteries to
be distributed to any
part of both cerebral
hemispheres.
• Arteries to specific brain
areas:
• Corpus striatum and
internal capsule supplied
mainly by medial and
lateral striate central
branches of middle
cerebral artery plus central
branches of anterior
cerebral artery.
• Thalamus is supplied
mainly by posterior
communicating, basilar,
and posterior cerebral
arteries.
• Midbrain is supplied by
posterior cerebral, superior
cerebellar, and basilar
arteries.
• Pons is supplied by basilar
and anterior, inferior, and
superior cerebellar
arteries.
• Medulla oblongata is
supplied by vertebral,
anterior and posterior
spinal, posterior inferior
cerebellar, and basilar
arteries.
• Cerebellum is supplied by
superior cerebellar,
anterior inferior
cerebellar, and posterior
inferior cerebellar arteries.
• End arteries (terminal):
• Anatomic (True) End
Artery: No anastomoses.
• Functional End Artery:
Ineffectual anastomoses.
• An example of a true
terminal arteries is that
which supplies the retina.
• Functional end arteries
supply segments of the
brain.
Veins of the Brain
• They have no muscular tissue in their walls, and they have no
valves. They lie in subarachnoid space. They drain into the
cranial (dural) venous sinuses.
• Emissary veins connect the dural venous sinuses with the
diploic veins of the skull and with the veins of the scalp
• Cerebral veins divided
into:
 External Cerebral Veins:
• Superior cerebral veins
drains superolateral &
medial surfaces and empty
into the superior sagittal
sinus.
• Superficial middle cerebral
vein drains the lateral
surface of the cerebral
hemisphere & empties
into the cavernous sinus.
• Deep middle cerebral
vein drains insula and
is joined by anterior
cerebral and striate
veins to form the
basal vein.
• Basal vein joins the
great cerebral vein,
which in turn drains
into straight sinus .
 Internal Cerebral Veins
• There are two internal
cerebral veins.
• They are formed by union
of the thalamostriate vein
and choroid vein
• The two unite to form the
great cerebral vein, which
is joined with basal veins
& empties into the
straight sinus.
Veins of specific brain areas:
• Midbrain is drained by
veins that open into the
basal or great cerebral
veins.
• Pons is drained by veins
that open into basal vein,
cerebellar veins.
• Medulla oblongata is
drained by veins that open
into spinal veins.
• Cerebellum is drained by
veins that empty into
great cerebral vein or
adjacent venous sinuses.
Dural venous sinuses
• The dural venous sinuses are endothelial-lined spaces
between the outer periosteal and the inner meningeal
layers of the dura mater
• They finally drain into internal jugular veins
• Emptying into the dural venous sinuses are diploic vein and
emissary veins.
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The dural venous sinuses
Superior sagittal sinus
Inferior sagittal sinus
Straight sinus
Transverse sinuses
Sigmoid sinuses
Occipital sinuses
Confluence of sinuses
Superior petrosal
Inferior petrosal
Cavernous sinuses
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The superior sagittal sinus
Deviates ,usually the right
& becomes continuous
with the right transverse
sinus.
It communicates with
venous lacunae on each
side.
Numerous arachnoid villi
and granulations project
into the lacunae
It usually becomes
continuous with the right
transverse sinus.
• At the internal occipital
protuberance, it is dilated
to form the confluence of
the sinuses
• It receives :
• The superior cerebral
veins
• The occipital sinus
• Diploic & emissary veins
• CSF(through arachnoid
granulations)
The inferior sagittal
sinus
• Joins the great
cerebral vein to
form the straight
sinus
• It receives a few
cerebral veins from
the medial surface
of the cerebral
hemispheres.
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The straight sinus
Is formed by the union of
the inferior sagittal sinus
with the great cerebral
vein.
It ends by turning to the
left (sometimes to the
right) to form the
transverse sinus.
It receives:
Inferior sagittal sinus
Great cerebral vein,
posterior cerebral veins
Superior cerebellar veins
Veins from the falx
cerebri
• The transverse sinuses
• Are paired structures that
begins at the internal
occipital protuberance
• The right sinus is usually
continuous with the
superior sagittal sinus, and
the left is continuous with
the straight sinus.
• The transverse sinuses
receive the:
• Superior petrosal sinuses
• Inferior cerebral
• Cerebellar veins
• Diploic veins.
• They end by turning
downward as the sigmoid
sinuses .
• The sigmoid sinuses
• Are a direct continuation of
the transverse sinuses.
• The sinus then reaches the
posterior part of the jugular
foramen to become
continuous with the
superior bulb of the internal
jugular vein.
• The occipital sinus
• Is a small sinus occupying
the attached margin of the
falx cerebelli.
• It communicates with the
internal vertebral venous
plexus
• Drains into the confluence
of sinuses.
The cavernous sinuses
• Are situated in the
middle cranial fossa on
each side of the body
of the sphenoid bone
• The two sinuses
communicate with
each other by anterior
and posterior
intercavernous sinuses
cerebri .
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The cavernous sinus receives:
Cerebral and ophthalmic veins
Emissary veins from pterygoid plexus of veins
Sphenoparietal sinuses
It has important communication with the facial vein through the
superior ophthalmic vein. (This is a route by which infection can
travel from the facial skin to the cavernous sinus.)
 Structures passing
through each
cavernous sinus are:
• The internal carotid
artery;
• The abducent nerve
[VI].
 Structures in the
lateral wall of
cavernous sinus are the
:
• Oculomotor nerve [III];
• Trochlear nerve [IV];
• Ophthalmic nerve [V1];
• Maxillary nerve [V2].
• The superior and
inferior petrosal sinuses
• Are small sinuses
situated on the superior
and inferior borders of
the petrous part of the
temporal bone .
• Superior sinuses drain
the cavernous sinus into
the transverse sinus.
• Inferior sinuses drains
the cavernous sinus into
the internal jugular
vein.
 Blood Supply of the
Spinal Cord
• It is supplied by three
arteries:
• Two posterior spinal
arteries from vertebral
arteries.
• Anterior spinal artery
from union of two
arteries from vertebral
artery .
• Spinal arteries are
reinforced by segmental
arteries that arise from
arteries outside the
vertebral column.
• Each segmental spinal
artery gives rise to
anterior and posterior
radicular arteries
• The great anterior
medullary artery of
Adamkiewicz , that
arise from the aorta,
enters the vertebral
canal and
anastomoses with the
anterior and posterior
spinal arteries.
Veins of the Spinal Cord
• The veins of the spinal cord drain into six
tortuous longitudinal channels that
communicate within the skull with the veins
of the brain and the venous sinuses.
• They drain mainly into the internal vertebral
venous plexus.