The origin, course, branches, and distribution of internal carotid artery. The origin, course, branches, and distribution of basilar artery. Describe the formation, branches and distribution of circulus arteriosus. Outline the venous drainage of the brain.

1. Blood Supply
of Brain
1

2. Contents
• The origin, course, branches and distribution of internal carotid artery.
• The origin , course , branches and distribution of basilar artery.
• Describe the formation, branches and distribution of circulus
arteriosus.
• Outline the venous drainage of brain.
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3. Blood supply of Brain-Introduction
 The brain is one of the most metabolically active organs of the body
as it depends on aerobic metabolism of glucose.
 Although the brain constitutes only 2% (1/50) of the total body
weight, it receives 20% (1/5) of the total cardiac output and
consumes 20% of the total O2 used by the body.
 The cerebrovascular diseases (thrombosis, embolism, and
hemorrhage) are the third most common cause of death and the
neurological signs depend on the site of lesion.
 An adequate knowledge of the blood supply of the brain is essential
for proper diagnosis and treatment of these diseases.
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4. The brain
The brain
 Composed of three parts:
- Cerebrum
- Cerebellum
- Brainstem
 The cerebrum is
divided into four lobes:
1.Frontal
2.Parietal
3.Temporal
4.Occipital
4

5. Arteries of the brain
Two pairs of arteries, the carotid and
vertebral.
■ The internal carotid
system, 80% of the
brain’s blood supply
(anterior circulation).
■ The vertebral basilar
system from
subclavian artery(20 %)
(posterior circulation)
Anastomose in the arterial circle of
Willis.
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6. Arteries of the brain
Internal carotid artery:
Origin:
■ One of the two terminal
branches of common carotid
artery.
■ Begins in the neck at the upper
border of thyroid cartilage.
6

7. Arteries of the brain
Internal carotid artery: Course in the cranial
cavity-
• Enters the base of skull & passes thro’ the
carotid canal in the petrous portion of the
temporal bone. Its course here is extradural.
• Passes horizontally forward through cavernous
sinus in an S-shaped curve (the carotid
siphon).
• Emerges on medial side of anterior clinoid
process by piercing the dura & arachnoid
mater.
• Enters the subarachnoid space.
• Then it runs upwards to the anterior
perforated substance where it terminates by
dividing into the anterior and middle cerebral
arteries.
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8. Arteries of the brain
Parts of the internal carotid artery:
• Cervical part – neck
• Petrous part – carotid canal
• Cavernous part – cavernous sinus
• Cerebral part – base of the brain
Branches of the cerebral part :
• Ophthalmic
• Posterior communicating
• Anterior choroidal
• Anterior cerebral
• Middle cerebral
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9. 9

10. Anterior cerebral artery
Origin : Smaller terminal branch of the
internal carotid artery
Course : Runs above the optic nerve to
the medial surface of the frontal
lobe of the cerebral hemisphere .
• Communicate with the ACA of
opposite side by the anterior
communicating artery
• Curves round the genu of the corpus
callosum.
• Enters anterior part of median
longitudinal fissure
• Curves backwards above the
corpus callosum.
• It terminates near the splenium by
anastomosing with the posterior
cerebral artery.
10

11. Anterior cerebral artery
Branches:
• Cortical branches
• Central branches
• Recurrent artery of Heubner .
Cortical branches -
▪ Orbital, frontal, parietal
branches
Supply - orbital surface of the frontal
lobe, all medial surface of the
cerebral cortex as far back as the
parieto-occipital sulcus and adjacent
strip of the suprolateral surface of the
cerebral hemisphere.
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12. Anterior cerebral artery
12

13. Anterior cerebral artery : Functional areas supplied:
 Upper part of primary motor
area(4)
 Upper part of somatosensory
area (3,1,2)
 Upper part of premotor area
(6)
 Upper part of prefrontal cortex
(9,10,11,12)
13

14. Anterior cerebral artery :
Central branches:
• Anteromedial group of central
arteries.
• Joins the fellow of the
opposite side by the anterior
communicating artery.
Recurrent artery of Heubner:
• Pierces the anterior perforated
substance.
• Supplies: basal ganglia,
Internal capsule – anterior
limb
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15. Middle cerebral artery
Origin:
Larger terminal branch and main continuation of internal carotid
artery .Together the middle and anterior cerebral arteries are
referred to as the anterior circulation of the brain.
The middle cerebral artery is the artery most often occluded
in stroke.
Course
▪ Runs laterally in the stem of lateral sulcus between the orbital
and tentorial surfaces to the insula
▪ Terminates on the insula by dividing into branches
Branches :
• Cortical branches
• Central branches (anterolateral group)
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16. Middle cerebral artery
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17. Middle cerebral artery
Cortical branches:
• Orbital, frontal, parietal and
temporal branches
Supply the cerebral cortex
Supply:
▪ Most of superolateral surface (except
narrow strip along the
superomedial border from the
frontal pole to parieto-occipital
sulcus, Occipital lobe, Inferior
temporal gyrus) & insular lobe.
▪ Lateral part of orbital surface.
▪ Anterior part of tentorial surface.
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18. Middle cerebral artery
Central branches (lateral striate
/lenticulostriate arteries)
anterolateral group
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19. Middle cerebral artery
• Functional areas supplied:
 Lower parts of
Primary motor area (area 4)
Premotor area (area 6)
Somatosensory area (area 3 1 2)
Prefrontal area (area 9,10,11,12)
 Broca’s motor speech area (45,44)
 Auditory area (41,42)
 Supramarginal gyrus (40)
 Angular gyrus (39)
 Superior temporal gyrus (22)
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20. Middle cerebral artery
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21. Distribution of middle cerebral arteryDistribution of middle cerebral artery
Arteries of the brain

22. Anterior choroidal artery:
Origin : Branch of internal carotid
artery
Course : Passes backward, enters
inferior horn of lateral ventricle,
and ends in choroid plexus.
Distribution: Supplies:
• Choroid plexus of the inferior horn of
the lateral ventricle.
• Lateral geniculate body.
• Posterior limb & retrolentiform part
of internal capsule.
• Middle 3/5 of crus cerebri.
• Basal ganglia – globus pallidus.
22

23. Vertebral artery
It has 4 parts.
Origin - Arise from the I part of subclavian
artery.
Course -
• I Part - Ascends towards the foramen
transversarium of C6 vertebra.
• II Part - Ascend through the transverse
foramen of the upper six cervical vertebrae
(C6-C1).
• III Part - Emerges from the transverse foramen
of the atlas (C1) runs on the groove on the
upper surface of the post arch of the atlas
pierces the atlanto-occipital membrane and
enters the foramen magnum.
• IV Part - Lies within cranium, the two arteries
run on the anterior aspect of the medulla
oblongata then unite at the lower border of
the pons to form the basilar artery.
23

24. Vertebral artery
• Branches of 4th part:
1. Meningeal
2. Medullary
3. Anterior spinal
4. Posterior spinal
5. Posterior inferior cerebellar
24

25. Basilar artery
• It’s formed by the union of 2
vertebral arteries. Ascends in a
groove on the anterior surface of
the pons.
• At the upper border of the pons/
ponto-midbrain junction, divides
into 2 posterior cerebral arteries.
25

26. Basilar artery
Branches from the basilar artery:
1. Anterior inferior cerebellar artery.
2.The labyrinthine artery.
3.The pontine branches (multiple
vessels that penetrate the pons as
paramedian, short circumferential,
and long circumferential arteries).
4.The superior cerebellar arteries.
5. The basilar artery terminates by
dividing into the posterior cerebral
arteries at the upper border of the
pons.
26

27. 27

28. Posterior cerebral artery
Posterior cerebral artery:
Terminal branch of basilar artery.
Course:
• Ascends beside the midbrain to reach the
splenium of the corpus callosum on the
medial side of the cerebral hemisphere and
terminates by dividing into branches
• Connected to the internal carotid artery by
the posterior communicating artery
Branches:
- Cortical
- Central branches
- Posterior choroidal artery
28

29. Posterior cerebral artery
Cortical branches:
▪ Inferior surfaces of temporal
lobe by temporal branches.
▪ Medial surface of the occipital
lobe by calcarine branches.
▪ Medial surface of the post
part of the parietal & part of
the occipital lobes by
parieto occipital branches.
Functional area supplied:
▪ Visual area (17,18,19).
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30. Posterior cerebral artery
Posterior choroidal artery supply
• Choroid plexus of III ventricle.
• Choroid plexus of central part of
lateral ventricle.
• Ventral part of thalamus.
• Fornix and superior colliculus of
midbrain.
• Central branches:
• Posteromedial group, posterolateral
group
• Many small perforating arteries
arise from PCA to supply the
midbrain, thalamus, hypothalamus
and medial and lateral
geniculate bodies.
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31. Circulus arteriosus-Circle of Willis
Location:
• Lies in the interpeduncular fossa at
the base of brain around optic
chiasma, tuber cinereum and
mamillary bodies.
Formation:
Anterior part:
Anterior cerebral arteries (Rt & Lt)
Anterior communicating artery
Posterior part:
Basilar artery
Posterior cerebral arteries (Rt & Lt)
Lateral part:
Internal carotid artery (Rt & Lt)
Posterior communicating arteries (Rt
& Lt)
31

32. Circulus arteriosus-Circle of Willis
32

33. Circulus arteriosus-Circle of Willis
Distribution of central arteries:
• Central arteries, arise from the arterial
circle and proximal portion of the
principal arteries, penetrate the
substance of the brain and supply the
deep structures.
• Branches of the circle of Willis :
• Central arteries 6 groups:
▪ Anteromedial(AM) group
▪ Posteromedial(PM) group
▪ 2 Anterolateral(AL) groups
▪ 2 Posterolateral (PL)groups 33

34. Circulus arteriosus-Circle of Willis
34
Anteromedial group of central arteries:
Collectively they are referred to as the medial striate arteries.The
largest and most lateral of these to enter the brain is the medial
striate or recurrent artery of Huebner which arises from the
anterior cerebral artery.
Origin:
• Anterior cerebral and anterior communicating arteries
Distribution:
• Anterior part of hypothalamus
• Head of caudate and lentiform nuclei
• Anterior limb of the internal capsule.

35. Circulus arteriosus-Circle of Willis
Anterolateral group of central arteries:
They are also called the lateral striate or
lenticulostriate
arteries.
Origin:
• Middle cerebral artery
Distribution:
• Internal capsule ( Genu, anterior & posterior
limbs)
• Caudate and lentiform nuclei
• Lateral hypothalamus
The most common sites of spontaneous
hemorrhage in
individuals with long-standing hypertension and is
termed the
artery of cerebral hemorrhage. 35

36. Circulus arteriosus-Circle of Willis
Posteromedial group of central arteries:
(Thalamoperforate arteries)
Origin-
• Posterior cerebral artery (Thalamoperforate
arterirs)
• Posterior communicating arteries
Distribution-
• midbrain
• Anterior and medial parts of thalamus
• Posterior part of hypothalamus
• Subthalamus
Posterolateral group of central arteries:
(Thalamogeniculate arteries)
Origin-
• Posterior cerebral artery)
Distribution-
• Posterior and lateral parts of thalamus
• Geniculate bodies
• Colliculi of midbrain and pineal gland 36

37. Arteries of the brainstem and cerebellum
• The cerebellum is supplied by
three pairs of cerebellar arteries.
• Superior cerebellar artery:
supplies the superior surface of
the cerebellum.
• Anterior inferior cerebellar and
posterior inferior cerebellar
arteries:
supplies the inferior surface of
the cerebellum.
37

38. Arteries of the brainstem and cerebellum
The medulla is supplied by
• 1. Two vertebral arteries.
• 2. Anterior and posterior spinal arteries.
• 3. Anterior and posterior inferior cerebellar
arteries.
• 4. Basilar artery.
The pons is supplied by
1. Numerous (pontine) branches from the basilar
artery.
2. Anterior inferior cerebellar artery.
The midbrain is supplied by
1. Basilar artery through its posterior cerebral
and superior
cerebellar arteries. Basilar artery also supplies
themidbrain through direct branches.
2. Branches of posterior communicating and
anterior choroidal arteries.
38

39. Arterial supply of the internal capsule
• Anterior limb: lenticulostriate
branches of middle cerebral artery
(superior half) & recurrent artery
of Heubner of the anterior cerebral
artery(inferior half).
• Genu: lenticulostriate branches of
middle cerebral artery
• Posterior limb: lenticulostriate
branches of middle cerebral artery
(superior half) & anterior choroidal
artery off of the internal carotid
artery (inferior half).
• Retrolentiform + sublentiform
parts = supplied by anterior
choroidal. 39

40. Veins of brain
• Veins of the brain have no
muscular tissue in the wall and
no valves.
• Veins – Located in the
subarachnoid space.
• Venous sinuses – located
between 2 layers of the dura
mater.
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41. Veins of brain
Cerebral veins are divided into:
1.Superficial cerebral veins:
• Superior cerebral veins.
• Inferior cerebral veins.
• Superficial middle cerebral
vein.
2. Deep cerebral veins:
• Internal cerebral vein.
• Basal vein (Rosenthal).
• Great cerebral vein (of Galen).
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42. Cerebral veins
• Superior cerebral veins drain the upper
parts of the superolateral and medial
surface and end in the superior sagittal
sinus.
• Inferior cerebral veins drain the lower
part of the hemisphere.
• Superficial middle cerebral vein drains
superolateral surface and posterior end
of this vein is connected to the superior
sagittal sinus by the superior
anastomotic vein and to the transverse
sinus by the inferior anastomotic vein.
superficial middle cerebral vein
terminates in the cavernous sinus.
42

43. Cerebral veins
Internal cerebral vein:
• Situated in the tela choroidea of
third ventricle, in the roof of
third ventricle.
• Formation: At the
interventricular foramen by the
union of thalamostriate vein and
choroidal veins.
• Termination: Below the
splenium two Internal cerebral
vein joins to form the great
cerebral vein.
43

44. Cerebral veins
Great cerebral vein (vein of
Galen):
• Situated below the splenium, in
the cystern of great cerebral
vein.
• Formation: By the union of two
internal cerebral veins.
• Termination: Joins the inferior
sagittal sinus to form straight
sinus.
• Tributaries: Right and left basal
veins.
44

45. Cerebral veins
•Internal cerebral veins joins to form
the great cerebral vein and the two
basal veins.
• The deep cerebral veins drains the
thalamus, hypothalamus, the corpus
striatum, the internal capsule, copus
callosum and the choroid plexuses.
The corpus striatum and internal
capsule are drained by superior
and inferior striate veins.
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46. Veins of cerebellum & brain stem
• The veins from the upper surface of
the cerebellum drain into the
straight, transverse, and superior
petrosal venous sinuses.
• The veins from the lower surface of
cerebellum drain into right and left
sigmoid , inferior petrosal, occipital
and straight sinus.
• The veins of the midbrain drain into
the great cerebral vein. The pons and
medulla drain into the superior and
inferior petrosal sinuses, transverse
and occipital sinuses.
• Inferiorly, the veins of the medulla
are continuous with the veins of the
spinal cord. 46

47. Middle meningeal veins
• These veins accompany the branches
of middle menigeal artery and consist
of :
1.Frontal (Anterior) trunk.
2.Parietal (Posterior) trunk.
• Both trunks communicate above with
superior sagittal sinus through the
venous lacunae.
• The frontal trunk terminates into
pterygoid venous plexus through the
foramen ovale, or into the spheno-
parietal or cavernous sinus.
• The parietal trunk ends in the
pterygoid venous plexus through the
foramen spinosum.
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48. Blood Supply of Brain - Clinical Importance
48

49. Clinical importance
Berry aneurysms(Congenital cerebral
aneurysms):
 A brain aneurysm (AN-yoo-riz-um) is a
bulge or ballooning in a blood vessel in
the brain.
 It often looks like a berry hanging on a
stem.
 These occur mostly at the sites where
two arteries join in the formation of
the circle of Willis.
 The basic abnormality at these points is
the congenital deficiency of the tunica
media (elastic tissue) in the arterial
wall.
 A brain aneurysm can leak or rupture,
causing bleeding into the brain
(hemorrhagic stroke). 49

50. Clinical importance
Subarachnoid hemorrhage:
• A subarachnoid hemorrhage is
bleeding in the subarachnoid space.
• Bleeding usually results from the
rupture of an abnormal bulge in a
blood vessel (aneurysm) in brain.
• Sometimes bleeding is caused by
trauma, an abnormal tangle of blood
vessels in brain (arteriovenous
malformation), or other blood vessel
or health problems.
• The primary symptom is a sudden,
severe headache.
50

51. Clinical importance
Occlusion of middle cerebral artery:
 The occlusion of middle cerebral artery occurs commonly.
 The most common cause of MCA occlusion is embolism.
 Signs and symptoms:
 Contralateral hemiplegia and hemianesthesia involving mainly the face and
arm, due to involvement of most of the primary motor and sensory areas.
 Aphasia, if left dominant hemisphere is involved—due to involvement of
motor and sensory speech areas.
Cerebral thrombosis most commonly affects the middle cerebral artery or its
main branches because it is a direct continuation of the internal carotid
artery.
51

52. Clinical importance
• Subdural hemorrhage:
• It occurs due to rupture of
cerebral veins in the subdural
space.
• The superior cerebral veins are
most commonly torn, where they
enter the superior sagittal sinus.
• The cause is usually a blow on
the front or back of the head,
resulting in excessive
anteroposterior displacement of
the brain within the skull.
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53. Summary
Arteries of the brain
Brain:
Anterior , posterior , middle cerebral arteries and branches of circle of Willis.
Cerebellum:
Superior , anterior inferior and posterior inferior cerebellar arteries.
Medulla:
• Anterior and posterior spinal arteries
• Vertebral arteries
• Posterior inferior cerebellar arteries.
Pons:
• Paramedian branches of basilar artery (pontine arteries)
• Short circumferential branches of basilar artery
• Superior cerebellar artery and anterior inferior cerebellar arteries.
Midbrain:
Branches from basilar a.
• Posterior cerebral artery and superior cerebellar artery (sup. & inf.
colliculi)
• Anterior choroidal a. and Posterior communicating artery.
53

54. Summary
Cerebral veins
1.Superficial cerebral veins: Superior cerebral veins, inferior cerebral
veins and superficial middle cerebral vein.
2. Deep cerebral veins: Internal cerebral vein, basal vein (Rosenthal)
and Great cerebral vein (of Galen).
• Veins draining the brain open into the dural venous sinuses. These are
the superior sagittal , inferior sagittal, straight, transverse, sigmoid,
cavernous, sphenoparietal, petrosal and occipital sinuses.
• The blood from all these sinuses reaches the sigmoid sinus which
becomes continuous with internal jugular vein.
• The intracranial venous sinuses communicate with veins outside the
skull through emissary veins.
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55. Summary
• Veins of cerebellum & brain stem
• The veins from upper surface of the cerebellum drain into the
straight, transverse, and superior petrosal venous sinuses.
• The veins from lower surface of cerebellum drain into right and left
sigmoid , inferior petrosal, occipital and straight sinus.
• The veins of the midbrain drain into the great cerebral vein. The pons
and medulla drain into the superior and inferior petrosal sinuses,
transverse and occipital sinuses.
• Inferiorly, the veins of the medulla are continuous with the veins of
the spinal cord.
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56. THANK YOU
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