Vertebrobasilar System Quiz

Vertebrobasilar System

• The vertebral arteries (4th part) enter the skull through the foramen magnum and merge at the pons' lower border to form the basilar artery.
• The basilar artery travels along the pons' ventral surface and splits into right and left posterior cerebral arteries at its upper border.

Vertebral Artery Branches

• Two posterior spinal arteries
• Anterior spinal artery: Two branches from each vertebral artery, joining to form a single artery.
• Posterior inferior cerebellar artery
• Meningeal branches: Supply the dura mater in the posterior cranial fossa.
• Medullary arteries: Supply the medulla oblongata.

Basilar Artery Branches

• Pontine branches: Supply the pons.
• Anterior inferior cerebellar artery: Supplies the anterior portion of the cerebellum's inferior surface.
• Internal auditory (Labyrinthine) artery: Enters the internal auditory meatus to supply the inner ear.
• Superior cerebellar artery: Supplies the cerebellum's superior surface.
• Posterior cerebral artery: Curves around the cerebral peduncle, supplying the cerebrum's inferior surface. It passes through the precalcarine sulcus.

Internal Carotid Artery (Cerebral Part)

• Enters the cranial cavity via the carotid canal.
• Travels through the cavernous sinus.
• Ends at the anterior perforated substance, splitting into the middle cerebral artery and anterior cerebral artery.

Internal Carotid Artery Branches

• Opthalmic artery: Supplies orbital structures, including the eyeball.
• Posterior communicating artery: Runs backward and connects (anastomoses) with the posterior cerebral artery.
• Anterior choroidal artery: Forms the choroid plexus of the lateral ventricle.
• Anterior cerebral artery: Runs forward above the optic nerve, communicates with its partner via the anterior communicating artery, and supplies the cerebrum's medial surface.
• Middle cerebral artery: Courses laterally through the lateral sulcus, then upward in the posterior ramus, supplying the cerebrum's superolateral surface.

Circle of Willis (Circulus Arteriosus)

• A network of anastomoses (connections) between branches of the basilar, internal carotid, and vertebral arteries.
• Location: Interpeduncular fossa.
• Formation: Formed by the anterior communicating artery and anterior cerebral arteries anteriorly; the basilar artery splitting into two posterior cerebral arteries posteriorly; and the posterior communicating artery on each side.
• Significance: Provides a backup blood supply in case one major artery is blocked.

Arterial Supply of the Brainstem, Cerebellum, and Cerebrum

• Medulla: Supplied by two vertebral arteries, anterior and posterior spinal arteries, anterior and posterior inferior cerebellar arteries, and the basilar artery.
• Pons: Supplied by numerous branches from the basilar artery and the anterior inferior cerebellar artery.
• Midbrain: Supplied by posterior cerebral artery, superior cerebellar artery, direct branches from the basilar artery, posterior communicating artery, and anterior choroidal artery.
• Cerebellum: Superior surface: superior cerebellar artery; Inferior surface: anterior part by anterior inferior cerebellar artery, posterior part by posterior inferior cerebellar artery.
• Cerebrum:
  • Superolateral surface: Primarily supplied by the middle cerebral artery, except for a narrow strip adjacent to the superomedial border (anterior cerebral artery) and a narrow strip along the lower temporal and occipital border (posterior cerebral artery). Temporal pole is supplied by middle cerebral artery.
  • Medial surface: Primarily supplied by the anterior cerebral artery, except for the temporal pole (middle cerebral artery) and the occipital lobe (posterior cerebral artery).
  • Inferior surface: Primarily supplied by the posterior cerebral artery, except for the lateral orbital surface of the frontal lobe, and the temporal pole (middle cerebral artery) and the medial part of the frontal lobe orbital surface (anterior cerebral artery).

Cerebral Artery Branches

• Cortical branches: Supply the outer portion of the cerebrum.
• Central branches: Supply internal structures (e.g., corpus callosum, internal capsule).
• Choroidal branches: Supply choroid plexuses within the ventricles.

Applied Anatomy (Motor and Sensory Areas)

• Motor area (4):
  • Upper third: Anterior cerebral artery.
  • Lower two-thirds: Middle cerebral artery.
  • Implications of occlusion: Anterior cerebral artery – lower limb/perineal movement issues; Middle cerebral artery – head, neck, arm movement issues.
• Sensory area (3,1,2):
  • Upper third: Anterior cerebral artery.
  • Lower two-thirds: Middle cerebral artery.
  • Implications of occlusion: Anterior cerebral artery – lower limb/perineal sensation issues; Middle cerebral artery – head, neck, arm sensation issues.