Circle of Willis /Anatomy / Simplified- Blood supply to brain / Circulus Arteriosus
@Smart Med Learn Dr. Ankit Jain #circleofwillis #anatomyofcircleofwillis #circulusarteriosus #circleofwillisanatomy #neuroanatomy #anatomy #marrow #usmlestep1 #smartmedlearn
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Circle of Willis
Pair of vertebral artery; enter the skull through foramen magnum. They run upward on the anterolateral aspect of the medulla and merge with each other, at the lower border of the pons to form basilar artery.
Basilar artery runs upward in the midline on the anterior surface of the pons and reaches its upper border. Here basilar artery terminates by divide into right and left posterior cerebral artery.
Spinal branch arises from each vertebral artery at the upper part of the medulla. These spinal branches join with each other to form a single anterior spinal artery, which runs downward along the anterior median longitudinal fissure of the spinal cord. Anterior spinal artery supplies the central part of the medulla and anterior 2/3rd of the spinal cord.
Near the lower end of olive, Posterior inferior cerebellar artery arises from the vertebral artery that wind around the medulla and supply the dorsolateral part of the medulla and cerebellum.
Posterior spinal artery arises from the posterior inferior cerebellar artery. The two posterior spinal arteries together supply the posterior 1/3rd of the spinal cord.
Several small meningeal and medullary branches arise from the cranial part of the vertebral artery. Meningeal branches supply the durameter of posterior cranial fossa, while the medullary branches supply the medulla.
Anterior inferior cerebellar artery arises close to the lower border of the pons. It runs backward and supplies the anterolateral portion of the inferior surface of the cerebellum.
Labyrinthine artery after arising from the basilar artery runs alongwith 8th cranial nerve and enters the internal acoustic meatus to supply the internal ear.
Close to superior border of pons, superior cerebellar artery coming out from the basilar artery. It supplies the superior surface of the cerebellum.
Numerous short slender pontine branches emerge from the basilar artery, which pierce the pons and supply it.
Apart from vertebral artery, another major artery which supplies the brain is ICA. ICA enters the skull through carotid canal and after traverse a short course, it finally comes to lie lateral to the optic chaisma. Here, ICA terminates by dividing into larger middle cerebral artery and smaller anterior cerebral artery.
Anterior cerebral artery runs forward and medially above the optic nerve and comes very close to its fellow. Right and left anterior cerebral artery gets connected with each other with a short transverse anterior communicating artery.
Posterior communicating artery arises from ICA close to its termination. It runs backward and connects the ICA with the posterior cerebral artery.
Around the interpeduncular fossa, a hexagonal arterial circle at the base of the brain, is known as Circle of willis or circulus arteriosus.
Obviously, branches of vertebral artery and ICA take part in the formation of circle of willis.
Circle of willis is formed, anteriorly by the anterior communicating artery. Anteriolaterally, it is formed by the anterior cerebral artery. Posterolaterlly, it is formed by the posterior communicating artery and posteriorly it is formed by the posterior cerebral artery.
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Dr. Ankit Jain
MBBS, MS