Blood supply of brain and spinal cord

1. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai
Blood supply of Brain
(Long Question)
Introduction:
 Blood supply of brain and spinal cord is derived from the branches of Internal carotid
and vertebral arteries. Branches of these arteries also form circle of Willis at the base of
brain and supply brain.
(No need to draw this diagram- only for understanding)
Circle of willis

2. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai
Internal carotid artery: (***Important - Viva)
 It is branch of common carotid artery at the level of upper border of thyroid cartilage.
Parts of Internal carotid artery:
1. Cervical part: In neck.
2. Petrous part: In petrous temporal bone
3. Cavernous part: In cavernous sinus
4. Cerebral part: at base of brain supplying brain
Branches of Cerebral part of Internal carotid artery:
 Ophthalmic artery: Supply orbit and eye (Central artery of Retina is End artery and
blockage of this artery leads to blindness)
Middle Cerebral artery: Supply following parts of cerebrum (*****Important - Viva)
1. All superolateral surface up to parietooccipital sulcus except narrow strip along
superomedial border supplied by anterior cerebral artery. ( all motor area
except leg area)
Applied Anatomy:
Middle Cerebral Artery Occlusion (Blocakge):
• Contralateral hemiparesis and hemisensory loss of face and
arm(precentral and postcentral gyri).
• Aphasia if left hemisphere is affected (Broca’s motor area of speech).
• Contralateral homonymous hemianopia (Optic radiation).
• Anosognosia- loss of stereognosis if right hemisphere is affected.

3. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai
 Anterior Cerebral artery: Supply following parts of cerebrum(*****Important - Viva)
1. All medial surface up to parietooccipital sulcus.
2. 1 inch(2.5cm) strip on superolateral surface (leg area of motor area)
Applied Anatomy:
Anterior Cerebral Artery Occlusion (Blockage):
1. Contralateral hemiparesis and hemisensory loss of leg and
foot(paracentral lobule).
2. Inability to identify objects and Personality changes(frontal and parietal
lobes).
 Anterior choroidal artery: Form choroid plexus and help in formation of
cerebraospinal fluid (CSF)
 Posterior communicating artery: Communicates with posterior cerebral artery and
help in formation of circle of WIllis

4. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai
(Draw this diagram- only for long question of Blood supply of brain but important for viva to
know arteries supplying parts of Brain)

5. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai
Verebral artery: (***Important - Viva)
 It is branch of subclavian artery in the neck.
Parts of Vertebral artery:
1. 1st
part: In neck from origin to foramen of 6th
cervical vertebra.
2. 2nd
part: In foramina transversarium of 6th
to 1st
cervical vertebra
3. 3rd
part: on posterior arch of atlas vertebra
4. 4th
part: In cranial cavity
Branches of Cranial part of Vertebral artery: (***Important - Viva)
 Anterior spinal artery: Supply anterior two third of spinal cord
 Posterior inferior cerebellar artery: supply cerebellum, medulla oblongata and give
posterior spinal artery which supply posterior one third of spinal cord
Two vertebral arteries unite at the lower border of pons and form Basilar artery.
Basilar artery is located in basilar sulcus of pons and terminates by dividing in to posterior
cerebral arteries.
Branches of Basilar artery:
 Anterior inferior cerebellar artery: Supply cerebellum
 Pontine arteries: Supply pons
 Labrynthine artery: Supply Internal ear
 Superior cerebellar artery: supply cerebellum
 Posterior cerebral artery: Help in formation of circle of Willis.
Posterior cerebral artery supply: (*****Important - Viva)
1. Inferolateral and medial surface of temporal lobe.
2. Lateral and medial surface of occipital lobe (Visual cortex).
Applied Anatomy:
Posterior Cerebral Artery Occlusion (Blockage):
1. Contralateral homonymous hemianopia (calcarine cortex). Macula is spared-
not affected due to it’s dual blood supply also from middle cerebral artery.
2. Impairment of memory (Medial part of temporal lobe).

6. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai
Circle of Willis (Circulosus arteriosus cerebri):
(***** Very Important Short note)
(Draw this diagram- for short note with labels with Red circles)
 Introduction: Circle of Willis is vascular anastmotic circle formed between branches of
two internal carotid and two vertebral arteries.
 Location: Interpeduncular fossa at the base of brain.
 Arteries contributing formation of circle of Willis:
 Anteriorly: Anterior communicating artery (Branch of Internal carotid artery).
 Anterolateraly: Anterior cerebral artery(Branch of Internal carotid artery).
 Posterolateraly: Posterior communicating artery (Branch of Internal carotid
artery).
 Posteriorly: Posterior cerebral artery (Branch of Basilar artery)

7. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai
 Importance: Circle of Willis is end to end functional anastomosis and allow blood to
supply both cerebral hemisphere in case of blockage of any of the arteries forming
circle.
 Normally streams of all the vessels do not mix. At a point where opposite vessels
meet, the pressure is zero.
 Applied anatomy:
 During blockage of one of the internal carotid or vertebral artery the blood will be
supplied by the circle of Willis.
 Carotid angiography: Radioopaque dye is injected in the common carotid artery will
show blood vessels of one side only (Due to Zero point as At this point pressure is Zero
normally and Blood do not cross to opposite side). If the circle of willis is completely
seen and arteries of opposite side are seen, it indicated blockage in one of the vessels
forming circle of willis:
 Vertebral angiography: Similar like carotid angiography done for vertebral artery.
…………………
Veins of the brain:
 External Cerebral Veins:
 Superior cerebral veins: From lateral surface of cerebrum and drains into superior
sagittal sinus.
 Superficial middle cerebral vein: From lateral surface of cerebrum and drains into
cavernous sinus.
 Deep middle cerebral vein: Drains insula and joined by anterior cerebral and striate
veins to form basal vein. Basal vein joins with great cerebral vein which ultimately
drains into straight sinus.
 Internal Cerebral Veins:
 Two internal cerebral veins: Formed by union of thalamostriate vein and choroid vein.
These veins drain into straight sinus.

8. Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai
(No need to draw this diagram- only for understanding)
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