Blood supply of brain (Circle of Willis)

2. M.B.B.S {GMC, AMBEDKARNAGAR}
DR. RAHUL SINGH
THAKUR

3. SOME BASIC TERMS
• GREY MATTER: COLLECTION OF CELL BODIES WITHIN CNS
• WHITE MATTER: BUNDLES OF AXONS
• CEPHALIC – UPWARDS
• CAUDIALLY – DOWNWARDS
• ASCENDING TRACT- UPWARDS
• DESCENDING TRACTS- DOWNWARDS
• R TO L FIBRES: COMMISURE FIBRE
E.G CORPUS CALLOSUM
PEDUNCLES : BUNDLE OF NERVE FIBRE

4. WHAT’S VERY BASIC FUNCTION OF CNS?
• RECEIVE ALL SENSORY INPUT
• PROCESS
• COMPARE
• INTEGRATION
• DECISION MAKING
• SOME MOTOR RESPONSE
{ LOCOMOTOR, GIMOTILITY}

5. DESCRIBE BLOOD SUPPLY OF BRAIN AND CIRCLE OF WILLIS IN DETAILS. 10
MARKS (2011 SUPPLY , 2012 MAIN)
SHORTE NOTE ON CRICLE OF WILLIS. 2013 MAIN, 2014 MAIN,2014 SUPPLY , 2015
MAIN, 2017 MAIN
EVERY SECOND TERMINAL

7. INTRODUCTION
• PROPER BLOOD SUPPLY OF BRAIN IS MOST ESSENTIAL BECAUSE:
IT LEADS TO UNCONSCIOUSNESS AFTER CESATION OF BLOOD SUPPLY FOR 10
SECONDS.
AND IF IT CONTINUES FOR 4 MINS, AN IRREVERSIBLE BRAIN DAMAGE STARTS
AND IS COMPLETED AFTER 10 MINS.

8. FORMATION ANDLOCATION:
• A} pair of vertebral arteries
• B} pair of internal carotid arteries.
• They get anastomose at interpeduncular fossa (base of brain.)
• Two vertebral artery unite at lower border of pons & form BASILAR ARTERY .
• A} Right and Left post cerebral artery

9. FORMATION
CIRCLE OF WILLIS :
A} INTERNAL CAROTID ARTERY
B} BASILAR ARTERY
• BLOOD SUPPLY OF BRAIN: A+ B+ VERTEBRALARTERY

14. • NORMALLY THERE IS NO MIXING OF BLOOD STREAMS:
• A} TWO VERETEBRAL ARTERIES IN THE BASILAR
• B} TWO ANT CEREBRAL ARTERIES IN THE ANT COMMUNICATING
• C} INTERNAL CAROTID AND POST CERBRAL ARTERIES IN POST COMM ARTERY
• THEREFORE RT IS SUPP BY RT VERTEBRAL AND RT INT CAROTID ARTERIES
AND LT BT LT.

15. • HOWEVER, IF ONE OF MAJOR ARTERIES FORMING CIRCLE OF
WILLIS IS BLOCKED, .THEN IT PROVIDES VARIOUS ALTERNATIVE
ROOT FOR COLLATERAL CIRCULATION LIKE AN ARTERIAL TRAFIC
CIRCLE.

16. BRANCH OF VERTEBRAL ARTERIES:
• MEDULLARY AND MENINGEAL ARTERY
• ANTERIOR SPINAL ARTERY
• POSTERIOR INFERIOR CEREBELLAR ARTERY
(PICA)
• POSTERIOR SPINAL ARTERY

18. COMMON CAROTID A} EXTERNAL CAROTID ( HEAD, NECK , FACE)
B} INTERNAL CAROTID ( BRAIN)
CERVICAL PART
PETROUS PART OF TEMPORAL BONE
CAVERNOUS PART
CEREBRAL PART

19. BRANCHES OF CEREBRAL PART OF
INTERNAL CAROTID ARTERY
• POST COMMUNICATING BRANCH
• OPTHALMIC ARTERY
• ANTERIOR CEREBRAL
• ANTERIOR CHOROIDAL ARTERY
MIDDLE CEREBRAL ARTERY

20. BRANCH OF BASILAR ARTERY
• SUPERIOR CEREBELLAR ARTERIES
• LABYRINTHINE ARTERIES
• ANT INF CEREBELLAR ARTERIES ( AICA)
• PONTINE BRANCH
• SUP CEREBELLAR ARTERIES

23. APPLIED ANATOMY
• 2 ARTERIES UNITE TO FORM CIRCLE OF WILLIS
• IF DILATE
• THEN, BERRY SHAPE DILATION (BERRY ANEURYSM)
• LEADS TO SAH
• NOTE: ANEURYSM: EXCESSIVE LOCALISED SWELLING OF THE WALLOF AN ARTERY