II. Anatomy: Background

  1. Circle of Willis forms a collateral communication between the Anterior Circulation and the Posterior Circulation
  2. Anterior segment of Circle of Willis
    1. Middle Cerebral Artery (bilateral)
    2. Anterior Cerebral Artery (bilateral)
    3. Anterior Communicating Artery (single, midline)
      1. Connects anterior cerebral arteries together
  3. Posterior segment of Circle of Willis
    1. Posterior Cerebral Artery (bilateral)
    2. Basilar Artery (single, midline)
  4. Interconnection between anterior and posterior segments
    1. Posterior communicating arteries (bilateral)
      1. Connects each Internal Carotid Artery to Basilar Artery
  5. Function
    1. Not all patients have a complete Circle of Willis
    2. Redundant Blood Flow in case of cerebral Occlusion
    3. Normal conditions (no Occlusion)
      1. Anterior and posterior communicating arteries typically carry little flow
    4. Arterial Occlusion (Cerebrovascular Accident)
      1. Arterial pressure falls in the occluded circulation
      2. Pressure gradient favors collateral flow across the communicating arteries

III. Anatomy: Goldberg's Circle of Willis Analogy to a Cartoon Spider

  1. Background
    1. Stephen Goldberg , MD describes a brilliant memory aid for the Circle of Willis
    2. Cartoon Spider (named Willis) represents the cerebral Vascular Anatomy
    3. Anatomy is as if viewed from below
      1. Looking up at the inferior brain surface (Brainstem, pons and Optic Chiasm)
  2. Top of Willis head
    1. Anterior Cerebral Artery
    2. Anterior Communicating Artery
  3. Willis Face
    1. Optic Chiasm (eye brows)
    2. Internal Carotid Artery (eyes)
    3. Middle Cerebral Artery (?antenna)
    4. Pituitary Gland (nose)
    5. Mammilary Body (mouth)
    6. Posterior Communicating Artery (jaw line)
  4. Willis Arms
    1. Posterior Cerebral Artery
    2. Cranial Nerve 3 (axilla)
    3. Superior Cerebellar Artery
  5. Willis Body
    1. Pons (trunk)
    2. Basilar Artery (spine)
  6. Willis Legs
    1. Anterior Inferior Cerebellar Artery
    2. Vertebral Artery
    3. Posterior Inferior Cerebellar Artery
  7. Willis Genitalia
    1. Anterior Spinal Artery (penis)
  8. Images
    1. http://lifeinthefastlane.com/a-spider-called-willis/
  9. References
    1. Goldberg (2014) Clinical Neuroanatomy, Medmaster, p. 6-15

IV. Anatomy: Images Circle of Willis

  1. neuroCvCircleWillisGrayBB516.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  2. neuroCvCircleWillisGrayBB519.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)

V. References

  1. Gilman (1989) Manter and Gatz Essentials of Neuroanatomy and Neurophysiology, Davis, p. 216-21
  2. Goldberg (2014) Clinical Neuroanatomy, Medmaster, p. 6-15
  3. Netter (1997) Atlas Human Anatomy, ICON Learning, p. 130-9

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Related Studies

Ontology: Circle of Willis (C0008812)

Definition (MSH) A polygonal anastomosis at the base of the brain formed by the internal carotid (CAROTID ARTERY, INTERNAL), proximal parts of the anterior, middle, and posterior cerebral arteries (ANTERIOR CEREBRAL ARTERY; MIDDLE CEREBRAL ARTERY; POSTERIOR CEREBRAL ARTERY), the anterior communicating artery and the posterior communicating arteries.
Concepts Body Part, Organ, or Organ Component (T023)
MSH D002941
SnomedCT 11279006
LNC LP33689-8, MTHU016971
English Circle, Willis', Willis Circle, Willis' Circle, Cerebral arterial circle, Circulus arteriosus cerebri, Arterial Circle, Cerebral, Cerebral Arterial Circle, circle of willis, circle willies, circle willis, willis circle, circle of Willis, Structure of circle of Willis (body structure), Structure of circle of Willis, Circle of Willis, NOS, Circle of Willis
Spanish estructura del círculo de Willis, Círculo Arterial del Cerebro, Polígono de Willis, Círculo Arterial Cerebral, Circulus Arteriosus Cerebri, Círculo de Willis, círculo arterial del cerebro, círculo de Willis, estructura del círculo de Willis (estructura corporal), polígono de Willis, estructura del polígono de Willis (estructura corporal), estructura del polígono de Willis
Czech circulus arteriosus cerebri, circulus arteriosus Willisi, Willisův tepenný okruh, Willisův circulus arteriosus
Portuguese Círculo Arterial Cerebral, Circulus Arteriosus Cerebri, Polígono de Willis, Círculo Arterial do Cérebro, Círculo de Willis
Finnish Aivojen valtimokehä
Japanese Willis動脈輪, ウィリス動脈輪, ウィリス輪, 大脳動脈輪
Italian Circolo arterioso cerebrale, Circolo di Willis
Swedish Willis ring
Polish Koło tętnicze mózgu
Norwegian Circulus arteriosus Willisi, Circulus arteriosus cerebri
German Circulus arteriosus Willisii, Circulus arteriosus cerebri
Dutch Circulus arteriosus cerebri, Cirkel van Willis, Willis, cirkel van
French Cercle artériel du cerveau, Polygone artériel de Willis, Polygone de Willis