Comparative study of formation of circle of Willis in human and sheep brain

Introduction: Brain is one of the most metabolically active organs of the mammalian body receiving adequate blood supply, which is essential to maintain the glucose and oxygen levels. This demand is derived from circle of Willis (CoW) and its arterial anastomosis at the base of the brain. To describe the arteries contributing to the formation of CW in sheep brain and to compare it with that of human. Sheep circle of Willis forms an animal model for undertaking further studies on blood supply of certain cranial nerves. Materials and methods: In present study, 20 formalin fixed human brains from the Department of Anatomy, Mamata Medical College and 20 fresh sheep brains from local slaughterhouse were obtained. Sheep brain was removed as per the human brain removal procedure, and circle of Willis was studied by Radiological study. Results: In sheep a well-developed four-sided arterial rete called 'Rete Mirabile cerebri' (RMC) was noted at the base of the brain in inter-peduncular fossa. Internal carotid arteries were either vestigial or absent in sheep. Two emergent arteries arising from steady pool of blood from RMC entered the interpeduncular fossa. These arteries ascended on either side of infundibulum of pituitary gland and then diverged in cranial and caudal directions to form the Circle of Willis. (C) 2016 Published by Elsevier, a division of RELX India, Pvt. Ltd on behalf of Anatomical Society of India.