Blood supply of brain
The brain gets a copious arterial supply from a pair of internal carotid and a pair of vertebral arteries. Both arterial systems form a polygonal anastomosis, circle of Willis, at the base of brain around interpeduncular fossa. The internal carotid arteries supply the frontal, parietal and part of temporal lobes, and vertebral arteries (through the basilar artery and its branches) supply the occipital and part of temporal lobes, together with the brain stem and cerebellum.
Internal carotid artery
Cerebral part of ICA gives of in succession the ophthalmic, posterior communicating, anterior choroid and two terminal branches - the anterior and middle cerebral arteries.
It supplies orbital structures. Out of many branches provided by the artery, the central artery of retina deserves special mention. The central artery of retina is an end artery, runs within the optic nerve and reaches the retina at the center of optic disc.
Posterior communicating artery
It provides communication between ICA and posterior cerebral artery, and forms a part of arterial circle of Willis.
Anterior choroid artery
It provides supply to choroid plexus of the inferior horn, optic tract, uncus, amygdala, hippocampus, globus pallidus, lateral geniculate body and the posterior limb and retrolentiform part of the internal capsule.
Anterior cerebral artery
It has following branches:-
- Medial striate artery (recurrent artery of Heubner): It supplies caudate nucleus (ventral part), putamen, and anterior limb and genu of internal capsule.
- Fronto-polar artery: It supplies medial and orbital surfaces of frontal lobe.
- Orbital branches: It supplies medial and orbital surfaces of frontal lobe.
- Calloso-marginal artery: It supplies the paracentral lobule and parts of gyrus cinguli.
- Pericallosal artery: It supplies medial surface of parietal lobe and precuneous.
Middle cerebral artery
It supplies insular and lateral surface of frontal, parietal, temporal and occipital lobes.
Vertebral artery system
Vertebral artery arises from part of subclavian artery. Its course is divided into four parts and at the lower border of pons, both vertebral arteries unite to form the basilar artery (course and branches of vertebral artery have been explained somewhere else in this book). Cranial (intracranial) branches of vertebral artery are:-
- Anterior spinal artery: It supplies 'median zone' of medulla.
- Posterior spinal artery: It supplies 'posterior zone' of lower medulla which includes fasciculi gracilis and cuneatus with their nuclei.
- Posterior inferior cerebellar artery: It is the largest branch and supplies 'lateral zone' of medulla dorsal to inferior olive, posterior part of cerebellum and choroid plexus of the 4th ventricle.
- Medullary branches: They supply medulla.
- Meningeal branches: They supply meninges.
- Basilar artery is single unpaired artery, formed by union of right and left vertebral arteries. It ends at upper border of pons by dividing into right and left posterior cerebral arteries. Its branches are :-
- Pontine branches: They supply pons.
- Anterior inferior cerebellar artery: It supplies cerebellum (anteroinferior part), pons and medulla at pontomedullary junction.
- Superior cerebellar artery: It supplies cerebellum (superior surface), pons, pineal gland and superior medullary velum.
- Labyrinthine artery: It supplies inner ear.
- Posterior cerebral artery: These are paired terminal branches of basilar artery. It gives following branches :-
- Central branches: It supplies Thalamus, lentiform nucleus, geniculate bodies, and midbrain.
- Posterior choroidal artery: It supplies choroid plexus of 3rd and lateral ventricles.
- Cortical branches: It supplies temporal lobe, occipital lobe (visual striate cortex)