Lec 14 Blood Supply

7/27/2019 Lec 14 Blood Supply

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Blood SupplyBrain

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Introduction One of the most metabolically active systems

Normal cerebral blood flow is about 50 mL/100 g of brain tissue/min

◦ Thus, a brain of average weight (1400 - 1500 g) has a

normal blood flow of 700 - 750 mL/min

A blood flow of 25 mL/100 g of brain tissue/min

constitutes ischemic penumbra (a dangerously

deficient blood supply leading to loss of brain cells)

A blood flow of 8 mL/100 g of brain tissue/min leadsto an almost complete loss of functional neurons

Consciousness is lost within 10 seconds of the

cessation of blood supply to the brain

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Arterial Supply of the Brain

Derived from two arteries: (1) the

internal carotid artery and (2) the

vertebral artery

These arteries and their branches arise inpairs that supply blood to both sides of

the brain

Basilar artery◦ Is a single artery

◦ But its braches are always in pairs

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Internal Carotid Artery - Branches

Ophthalmic artery

Posterior communicating artery

◦ Also supplies blood to the hypophysis, infundibulum,

parts of the hypothalamus, thalamus, and hippocampus Choroidal artery

◦ Choroidal plexus of lateral ventircle

◦ Also supplies crus cerebri, lateral geniculate body,

optic tract, & internal capsule Anterior cerebral artery

Middle cerebral artery

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Vertebro-Basilar Circulation

System includes the two vertebral arteries,the basilar artery (which is formed by the

union of the two vertebral arteries), and

their branches

Supplies the medulla, pons, mesencephalon,

and cerebellum

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Vertebral artery - Branches

Meningeal branches◦ Bone & dura in posterior cranial fossa

Posterior spinal artery

Anterior spinal artery◦ Contributing branches from each vertebral A.

Posterior inferior cerebellar artery◦

Choroidal plexus of 4

th

ventricle, vermis, centralnucleus, & undersuface of cerebellum, & medullaoblongata

Medullary arteries

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Anterior Spinal Artery

Formed by union of two small arisingfrom each vertebral artery

Supplies the medial structures of the

medulla, which include the pyramids,medial lemniscus, medial longitudinal

fasciculus, hypoglossal nucleus, and the

inferior olivary nucleus Also Anterior 2/3rd of Spinal cord

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Posterior Inferior Cerebellar

Artery (PICA) Supplies the regions of the lateral medulla that include the

spinothalamic tract, dorsal and ventral spinocerebellar

tracts, descending sympathetic tract, descending tract of

cranial nerve V, and nucleus ambiguus

Also supplies the vermal region and inferior-lateral surfaceof the cerebellar hemisphere

Wallenberg's syndrome

◦ Damage to the lateral medulla esp. N. ambiguss

◦ Presents as lack of coordination in speech

(dysphonia), disturbance in articulation (dysarthria),and dysphagia (difficulty in swallowing)

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Posterior Spinal Artery (PSA)

Majority of cases it arises from PICA

Supplies the fasciculus gracilis and

cuneatus as well as the gracile and

cuneate nuclei, spinal trigeminal nucleus,dorsal and caudal portions of the inferior

cerebellar peduncle, and portions of the

solitary tract and dorsal motor nucleus of the vagus nerve

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Basilar artery - Branches

Pontine arteries

Labyrinthine artery

Anterior inferior cerebellar artery

Superior cerebellar artery

Posterior cerebral arteries

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Pontine Arteries

Several pairs of pontine arteries arise from thebasilar artery

Paramedian arteries

◦ Supply the medial portion of the lower and upperpons

Include pontine nuclei, corticopontine fibers, the corticospinal

and corticobulbar tracts, and portions of the ventral pontine

tegmentum, and medial lemniscus

Short circumferential arteries◦ Supply substantia nigra and lateral portions of the

midbrain tegmentum

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Labyrinthine (Internal

Auditory) Artery

Supplies the cochlea and labyrinth

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Anterior Inferior Cerebellar

Artery (AICA)

Supplies the ventral and inferior surface

of the cerebellum and lateral parts of the

pons

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Superior Cerebellar Artery

Supplies the rostral level of the pons,caudal part of the midbrain, and superior

surface of the cerebellum

◦ Includes portions of the superior and middlecerebellar peduncles, the medial and laterallemniscus, part of the spinal trigeminal nucleus

and tract, the spinothalamic tract, and

superior cerebellar peduncle

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25Circulation at the base of the brain



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Major Cerebral Blood Vessels

1. Anterior cerebral artery

2. Middle cerebral artery

3. Posterior cerebral artery

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Anterior cerebral artery

Anterior communicating artery

◦ Also supplies anterior hypothalamus, including preoptic and

suprachiasmatic areas

Cortical branches

◦ Oribtal branches – Orbital & Medial surface of Frontal lobe

◦ Frontopolar branches - Medial portions of the frontal lobe and lateralparts of the convexity of the hemisphere

◦ Callosomarginal artery - Paracentral lobule and portions of thecingulate gyrus

◦ Pericallosal artery - Precuneus

Central branches

◦ Medial striate artery (Recurrent artery of Heubner)

Supplies anteromedial part of the head of the caudate nucleus and

parts of the internal capsule, putamen, and septal nuclei

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Middle Cerebral Artery

Cortical branches

Central branches

◦ Lenticulostriate arteries

◦ Lateral striate branches

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Middle Cerebral Artery – Branches

The lenticulostriate branches◦ Supply the putamen, caudate nucleus, and anterior

limb of the internal capsule

Orbitofrontal artery

◦ Parts of the frontal lobe

Precentral (pre-Rolandic) and central (Rolandic)

branches

◦ Supply different regions of the frontal lobe

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Middle Cerebral Artery – Branches

Anterior and posterior parietal arteries◦ Supply different regions of the parietal lobe

Angular branch

◦ Supplies angular gyrus

Anterior, middle, and posterior temporal

arteries

◦ Different regions of temporal lobe◦ Branches of the posterior temporal artery

also supply the lateral portions of the occipitallobe

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Posterior Cerebral Artery

Cortical branches Central branches

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Posterior Cerebral Arteries

Supply most of the midbrain, thalamus,and subthalamic nucleus

Anterior and posterior temporal andparieto-occipital branches

◦ Supply the temporal lobes and medial and

inferior occipital lobes of the cerebral cortex Calcarine artery

◦ Supplies the primary visual cortex

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Arteries of Specific brain areas

Corpus striatum & Internal capsule Thalamus

Midbrain

Pons

Medulla Oblongata

Cerebellum

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V i f B i



Veins of Brain External Cerebral Veins

◦ Superior cerebral veins◦ Superficial middle cerebral veins

◦ Deep middle cerebral veins

◦ Inferior cerebral veins

◦ Anterior cerebral veins

◦ Striate veins

◦ Basal vein

Internal Cerebral Veins

◦ Thalamostriate veins

◦ Choroid veins

◦ Great Cerebral vein 55



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