CIRCLE OF WILLIS

SUMMARY

FORM
1. Arterial polygon formed by the anterior (ICA) & posterior circulation (vertebral a.) which anastamose around the optic chiasm and pituitary stalk in the supracellar cistern.

FUNCTIONS
2. Allows equalization of blood flow & anastomotic circulation should a part become occluded.

STRUCTURE
3. Anterior circulation: bilateral ICA, bilateral A1 segment of ACA, single ACOM
4. Posterior circulation: bilateralPCOM, bilateral P1 segment of PCA, single basilar a.




Image: Circle of Willis. Netter. (2014). Atlas of Human Anatomy, Sixth Edition. 6th ed. Elsevier.

Reference(s)

R.M.H McMinn (1998). Last’s anatomy: regional and applied. Edinburgh: Churchill Livingstone. Get it on Amazon.
Drake, Richard L., et al. Gray's Anatomy for Students. Elsevier, 2023. Get it on Amazon.