Human Anatomy Quiz: Cerebral Arteries

Vessels of Central Nervous System

• Brain is 2% of the body weight
• It requires 17% of the cardiac output and 20% of the oxygen utilized by the body
• The brain receives its blood from two pairs of arteries: internal carotid and vertebral
• About 80% of the brain's blood supply comes from the internal carotid, and the remaining 20% from the vertebral.

Arteries of the Brain

• Internal carotid arteries (80%)
• Vertebral arteries (20%)

Internal Carotid

• 4 segments:
  • Cervical
  • Intrapetrosal
  • Intracavernous
  • Cerebral (supraclinoid)
• Intracavernous and cerebral portion are called carotid siphon by neuroradiologists.

Branches of ICA

• Cervical: No branch
• Petrosal and Intracavernous segment: Small branches to tympanic cavity, cavernous and inferior petrosal sinuses, trigeminal ganglion, meninges of middle cranial fossa
• Cerebral segment: Ophthalmic, Posterior communicating, Anterior choroidal, Terminal branches: anterior and middle cerebral arteries

Anterior Cerebral Artery

• Smaller terminal branch
• Runs forward and medially superior to the optic nerve and enters longitudinal fissure
• Joined the anterior cerebral artery of the opposite side by the anterior communicating artery
• Cortical branches: supply all medial surface of the cerebral cortex as far back as the parietooccipital sulcus and superior border of the supralateral surface of the cerebral hemisphere, 2.5cm of strip of cortex on the lateral surface, leg area of the precentral gyrus
• Central branches: supply caudate nucleus, anterior part of lentiform nucleus and anterior limb of internal capsule

Middle Cerebral Artery

• Largest branch, runs in the lateral sulcus
• Cortical branches: supply the entire lateral surface of the hemisphere except the narrow strip supplied anterior cerebral artery, occipital lobe, and the inferolateral surface of the hemisphere which are supplied by posterior cerebral artery. All motor areas except Leg area (supplied by anterior cerebral artery). The occipital pole (macula) is supplied by MCA.
• Central branches: supply caudate nucleus, lentiform and caudate nuclei, genu and posterior limb of internal capsule

Posterior Communicating Artery

• Runs backward and above oculomotor nerve to join posterior cerebral artery.
• Form part of Circle of Willis.

Posterior Inferior Cerebellar Artery (PICA)

• Largest branch of the vertebral, arises at the caudal end of the medulla on each side
• Runs a course winding between the medulla and cerebellum
• Distribution: posterior part of cerebellar hemisphere, inferior vermis, central nuclei of cerebellum, choroid plexus of 4th ventricle, medullary branches to dorsolateral medulla

Anterior Spinal Artery

• Union of 2 small branches from each vertebral artery
• Runs down in the anterior median fissure of the spinal cord
• Anterior 2/3 of the spinal cord

Posterior Spinal Arteries

• Branch directly from vertebral arteries or indirectly from PICA
• Each descends along the dorsolateral surface of the spinal cord close to the posterior nerve roots
• Posterior 1/3 of the spinal cord

Vertebral Arteries

• Branch of 1st part of subclavian artery
• Passes through foramina of transverse processes of upper 6 vertebrae
• Enters skull through foramen magnum
• Pierces dura and enters subarachnoid space
• Passes upward, forward and medially on the medulla oblongata
• Joins the vessel of the opposite side to form basilar artery.

Branches of the Basilar Artery

• Posterior cerebral artery
• Anterior inferior cerebellar arteries (AICA)
• Pontine arteries
• Superior cerebellar arteries

Cerebral Arterial Circle (Circle of Willis)

• Formed by anterior communicating artery, both anterior cerebral arteries, internal carotid arteries, posterior communicating arteries, and posterior cerebral arteries
• Lies on sella turcica surrounding optic chiasma, tuber cinereum and mamillary bodies

Cerebral Veins

• Deep and superficial groups
• No muscle tissue
• No valve

Veins of the Brain

• Superficial cerebral veins: Drain blood from cortex and subcortical medullary substance and empty into adjacent sinuses of dura mater
• Deep cerebral veins: drain deeper parts of hemispheres, basal nuclei, internal capsule, diencephalon and choroid plexus, ultimately form great cerebral vein which enter straight sinus