This document summarizes the arterial supply and venous drainage of the brain and spinal cord. It discusses how the brain receives blood from the internal carotid and vertebral arteries, which connect at the circle of Willis to provide an interconnected blood supply. It describes the branches of these arteries and their territories. It also outlines the venous drainage pathways and discusses the blood-brain barrier. For the spinal cord, it explains that the anterior and posterior spinal arteries are the main arterial supply, along with segmental arteries.

1. Dr. Ajaya Jang Kunwar

2. Blood supply of Brain
 If blood supply stops - 10 sec – Unconscious
 If it continue to cease – irreversible damage
 starts at 4 min – completes in 10 min
 Brain consists of 2% of total body but
 Receives 20% cardiac output
 20% total O2

3. Arterial supply of brain
 Brain is supplied by 2 sets of arteries
 A pair of Vertebral arteries
 A pair of Internal carotid arteries

9. Circle of Willis (Circulus arteriosus)
 Anteriorly:
 Anterior communicating & anterior cerebral arteries
 Posteriorly:
 Basilar artery dividing into 2 posterior cerebral arteries
 Laterally on either side:
 Posterior communicating artery connecting internal
carotid with Posterior cerebral artery

11. Circle of Willis
lies around the
interpeduncular
fossa

12.  Equalizes blood flow to different parts of the brain.
 Little interchange of blood across right and left half due to
equality of blood pressure.
 In case of occlusion, circle of willis acts as principal collateral
channel.
Functional
Significance of
Circle of Willis

13. Branches of cranial part of vertebral artery
1. Anterior spinal artery
2. Posterior spinal
3. Posterior inferior cerebellar
 (Largest branch)
4. Meningeal arteries
 Supplies the dura matter of
posterior cranial fossa
5. Medullary arteries
 Supplies medulla oblongata

14. Branches of Basilar artery
1. Pontine arteries
2. Anterior inferior cerebellar
artery
3. Labyrinthine artery
4. Superior cerebellar artery
5. Posterior cerebral artery
 Anterior temporal
 Posterior temporal
 Parieto-occipital
 Calcarine artery

15. Branches of Internal carotid artery
1. Ophthalmic artery
2. Posterior
communicating
3. Anterior choroidal
 Supplies choroid plexus
of interior horn of Lateral
ventricle (artery of
cerebral thrombosis)
4. Anterior cerebral artery
5. Middle cerebral artery
 Carries 30% of carotid blood
6. Hypophyseal arteries

16. Branching pattern of cerebral arteries
 Cortical branches
 Central branches (Perforating arteries)
 Choroidal arteries

17. Cortical branches
 Supplies outer portion of cerebrum.
 Derived from ant, middle & post cerebral arteries.
 Ramify in the piamater & form freely anastomosing
superficial plexuses.
 Two set of br’s
 Short - Supplies cortical grey matter
 Long - Supplies white matter
End arteries: do not anastomose with other arteries.

18. Central branches (Striate arteries)
 Derived from circle of willis
 Penetrate the base of the brain
 Supplies:
 Diencephalon, Basal nuclei, Internal capsule
 4 groups
 Anteromedial: From Ant. Cerebral & Ant. Com. Art.
 Anterolateral: From mid. Cerebral
 Posteromedial: From Post. Cerebral & Post. Com. Art.
 Posterolateral: Posterior cerebral
 Central br’s are end arteries

19. Choroidal Arteries
 Anterior choroidal artery
 From Int. Carotid art: choroid plexus of Inf. Horn of
Lateral ventricle
 Posterior choroidal artery
 From Post. Cerebral art: choroid plexus of 3rd and lateral
ventricle.

21. Superolateral
surface
1. Most of surface (2/3) –
• Middle cerebral artery
2. A small strip c. 2.5 cm along
superomedial border upto parieto-
occipital sulcus –
• Anterior cerebral artery
3. Occipital lobe + inferior part of
temporal lobe (excluding – temporal
pole –
• Posterior cerebral artery

23. Occlusion of middle cerebral artery may
lead to
 Contralateral hemiplegia, hemianaesthesia (mainly
face & arm) – due to invl. Of most of primary motor and
sensory areas
 Apasia (Loss of speech) – if dominant hemisphere
involved due to inv. of motor & sensory speech area
 Contralateral homonymous hemianopia (right or left
half of vision both sides lost) – invl. of optic radiation

24. Motor
Homunculus

25. Sensory
Homunculus

26. Medial Surface
1. Most of med. surface upto parieto-
occipital sulcus (2/3)
• Anterior cerebral artery
2. Temporal pole
• Middle cerebral artery
3. Rest of temporal lobe + Occipital lobe
• Posterior cerebral artery

29. Occlusion of anterior cerebral
artery leads to
 Contralateral hemiparesis, hemianaesthia (mainly
leg & foot)
 Due to Invol. of upper part of prim. motor and prim.
sensory areas and paracentral lobule
 Inability to identify object correctly
 Due to invl. of superior parietal lobule
 Apathy and personality changes
 Invl. of part of frontal lobe

30. Inferior surface
1. Most of inferior surface except
temporal pole
• Posterior cerebral artery
2. Temporal pole + lateral part of
orbital surface of frontal lobe
• Middle cerebral artery
3. Medial part of orbital surface of
frontal lobe
• Anterior cerebral artery

32. Occlusion of posterior cerebral
may lead to
 Contralateral homonymous hemianopia: –
 inv. Of visual cortex with some degree of macular
sparing (Since occipital pole also has alternative supply
from middle cerebral artery)

33.  Corpus striatum and
internal capsule:
 By medial and lateral striate
central branch of middle
cerebral artery.
 Thalamus:
 By br of post communicating,
basilar and post cerebral
arteries.
 Midbrain:
 By post cerebral, superior
cerebellar and basilar arteries.
Blood supply of other parts of Brain

34.  Pons:
 By pontine br. Of basilar
and ant. inf. and sup
cerebellar arteries.
 Medulla:
 By vertebral, ant and post
spinal, post inferior
cerebellar and basilar
arteries.
N.B. The brain stem, cerebellum and occipital lobe are
supplied by the vertebrobasilar system.

35. Cerebellum
1. Superior cerebellar artery
2. Anterior inferior cerebellar
3. Posterior inferior cerebellar

36. Venous drainage of brain
 Thin walled. Absence of muscular layer
 No valves
 Venous return of brain doesn’t follow the arterial
pattern.
 Veins of brain are
 Cerebral (Superficial or external and Deep veins)
 Cerebellar
 Veins of brainstem

37. External cerebral veins.
 Superior cerebral veins.
 Middle cerebral vein.
 Superficial and Deep
 Inferior cerebral veins
 Other veins
 Deep cerebral, Anterior
cerebral and Striate veins
form the basal vein.

40. Inferior cerebral and other veins in
base of brain

41. Internal cerebral veins
 2 int. cerebral veins on
either side of midline
in tela choroidea of 3rd
ventricle
 Formed by the union
of
 Septal
 Thalamostriate
 Choroidal vein at the
interventricular
foramen
 Joins to form great
cerebral vein (of
Galen) - Empties into
straight sinus.

42. Veins of midbrain
&
cerebellum also join
the great cerebreal
vein (of Galen)

45. Blood brain barrier
1. Tight junction between the
endothelial cells
2. Basement membrane of
endothelial cells
3. Foot process of Astrocytes

46. Arterial supply
of spinal cord
1. Anterior spinal artery.
2. Two posterior spinal
arteries.
3. Radicular or segmental
arteries.

48. 2/3
1/3

49.  A single Y - shaped artery.
 Arises from :Vertebral artery at the level of the
medulla.
 Supplies the cord at the Cervical Level.
 It is most vulnerable in the anterior part of the cord
particularly in the Thoracic Segment.

50.  Two arteries.
 Arise from
 Vertebral Or
 Posterior Inferior Cerebellar arteries.
 Spinal Arteries (Anterior &Posterior) are
Insufficient alone to supply the cord Below the
Cervical Level.

51.  Origin from following arteries :
 1. Deep cervical
 2. Ascending cervical
 3. Intercostal.
 4. Lumbar.
 They share in the arterial supply
of the cord Below the Cervical
Level.
 They Anastomose freely with the
Spinal Arteries.

52.  Artery of Adamkiewicz.
 It may arise from: Intercostal
or Lumbar arteries (usually T1
or T11).
 It supplies
 Lower half of the spinal cord
(T8 –L3).
 These are Vulnerable Segments.
 Occlusion of the artery may
cause Muscle weakness and
Paralysis.

53. Venous drainage of spinal cord
 4 channels drain into
vertebral, posterior
intercostal, lumbar
and lateral sacral
veins.