Blood supply of the Brain

Arterial Blood Supply

• Arterial blood supply of the brain • Brain is supplied by pairs of internal

carotid artery and vetebral artery.

Internal Carotid Artery

• Internal carotid artery: branch off from common carotid artery, enters brain from carotid canal, splits into middle and anterior cerebral artery under the anterior perforated substance

• Before internal carotid artery splits into the terminal branches, it gives off:

Branches from ICA• 1). Hypophysial arteries: further splits into

– anterior hypophysial artery: supply hypothalamus. The anterior hypophysial artery breaks into capillaries forming the hypophyseal portal veins which convey hormones from hypothalamus into anterior pituitary.

– posterior hypophysial artery: supply neural lobe of the pituitary • 2). Ophthalmic artery: supply eyes, paranasal sinuses and

parts of the nose• 3). Posterior communicating artery: runs backward to join

the posterior cerebral artery • 4). Anterior choroidal artery: supply choroid plexus of

temporal horn of lateral ventricles and other areas including optic tract, uncus, hippocampus, lateral geniculate nucleus, etc.

Occlusion of internal carotid artery

• 1. ipsilateral blindness (ophthalmic A) 2. half vision of the contralateral eye (infarction of optic nerve, lateral geniculate body supplied by anterior choroidal A)

Terminal Branches• Middle Cerebral Artery:

– bigger branch of the two terminal branches – It branches off frontal, parietal, and temporal branches supplying

primary motor and premotor cortex, frontal eye field, primary somatosensary area. Left middle cerebral artery supplies language center.

– Occlusion of middle cerebral artery: paralysis of face, arm, aphasia (language center)

• Anterior Cerebral Artery: – meets together to form anterior communicating artery before

they join, gives off recurrent artery of Heubner, also called medial straite artery, supplies corpus striatum.

– It then ascends along the longitudinal fissure then bends backward around the genu of the corpus callosum. It branches into pericallosal artery, along the upper surface of corpus callosum and callosomarginal artery follows the cingulate sulcus, which has three branches (anterior medial frontal, medial frontal medial, and posterior medial frontal)

Vertebrobasilar system • Vertebral artery, branch from the subclavian

artery, joins together to form the basilar artery. The latter artery splits into posterior cerebral arteries.

• Branches off the vertebral artery 1. spinal artery: anterior spinal artery: one formed by branches from each vertebral artery 2. posterior spinal artery: one on each side 3 . posterior inferior cerebellar artery (PICA) largest branch off vertebral artery, supplies cerebellar hemisphere, inferior vermis, etc.

Basilar artery

• Branches off basilar artery • 1. anterior inferior cerebellar artery (AICA)

supplies inferior surface of the cerebellum 2. labyrinthine artery supplies the membranous labyrinth of the internal ear 3. Pontine arteries supply pons and pontine tegmentum 4. superior cerebellar artery supplies pons, superior cerebellar peduncle, and inferior colliculus, etc.

Basilar artery

• Occlusion of basilar artery: basilar artery: coma, die soon, loss control of respiration center labyrinthine artery: deaf, vestibular dysfunction (vertigo, fall)

Posterior cerebral artery

• Posterior cerebral artery gives off– 1. Posterior medial central artery – 2. temporal artery: temporal lobe – 3. calcarine artery: supplies primary and

association cortex for vision – 4. parietooccipital branches: parietal and

occipital lobes – 5. posterior choroidal artery: choroid plexus

located at central part of the lateral ventricle, third ventricle, etc.

Circle of Willis • Consists:

– anterior communicating, anterior cerebral, internal carotid (short segment), posterior communicating, and posterior cerebral arteries. Normally not too much blood flow, could be served as alternative route if one of the artery in occluded.

• Common site for aneurysms, terminal part of internal carotid artery anterior communicating artery proximal of middle cerebral artery

• Groups of arteries arise from the circle – 1. anteromedial group: branch from anterior cerebral and

communicating artery provides blood to hypothalamus – 2. anterolateral group: branch from middle cerebral artery – 3. posteromedial: branches from posterior cerebral and posterior

communicating arteries