Lecture: The Circle of Willis and Its Feeder Pathways

Overview

The lecture focuses on the two main feeder pathways into the Circle of Willis, highlighting the internal carotid artery and vertebral artery, key vessels supplying blood to the Circle of Willis.

Orientation

• Right & Left Cerebral Hemisphere: Understanding the layout and orientation of the diagram.
• Viewpoint: Inferior view of the Circle of Willis.

Main Feeder Pathways

Vertebral Arteries

• Source: Supplied by the subclavian arteries.
• Pathway: Run through transverse foramina of cervical vertebrae.
• Suboccipital Triangle: Passage before entering foramen magnum.
• Branches:
  • Posterior Inferior Cerebellar Artery (PICA): Key branch from vertebral arteries.
  • Posterior Spinal Arteries: Branch from PICA.
  • Anterior Spinal Artery: Formed by fusion of branches from vertebral arteries.
• Fusion: Vertebral arteries fuse to form the basilar artery.

Basilar Artery

• Formation: Fusion of vertebral arteries.
• Important Branches:
  • Anterior Inferior Cerebellar Artery (AICA): Base of basilar artery.
  • Labyrinthine Arteries: Also known as internal acoustic arteries.
  • Pontine Branches: Supply to the pons.
  • Superior Cerebellar Arteries: Supply to the top of the cerebellum.
• Contribution: Feeds into the posterior cerebral artery (PCA), forming the posterior part of the Circle of Willis.

Circle of Willis Connections

• Posterior Cerebral Artery (PCA): Composed of P1 and P2 segments.
• Posterior Communicating Arteries: Connect the posterior and anterior circulation.
• Internal Carotid Artery: Supplies 80% of the blood to the Circle of Willis.
  • Branches:
    • Ophthalmic Artery
    • Middle Cerebral Artery (MCA): Gives off important branches such as:
      • Anterior Choroidal Artery
      • Lenticulostriate Arteries: Supply internal capsule and lentiform nucleus.
    • Anterior Cerebral Artery (ACA): Consists of A1 and A2 segments.
• Anterior Communicating Artery: A critical vessel prone to aneurysms.

Clinical Relevance

• Next Steps: Future video to cover cerebral ischemic strokes related to occlusions or aneurysms in these vessels.
• Call to Action: Encouragement to follow up with additional educational content on social media and support platforms.

Conclusion

The lecture has provided an in-depth overview of the vascular anatomy feeding into the Circle of Willis, highlighting the clinical importance of these structures.