Anterior communicating aeries in the circle of Willis is derived from ?: (A) Basilar aery, (B) Veebral aery, (C) Internal carotid aery, (D) Anterior cerebral aery
Answer is D. The circulus aeriosus (circle of Willis) is a large aerial anastomosis which unites the internal carotid and veebrobasilar systems. Anteriorly, the anterior cerebral aeries, which are derived from the internal carotid aeries, are joined by the small anterior communicating aery. Posteriorly, the two posterior cerebral aeries, which are formed by the division of the basilar aery, are joined to the ipsilateral internal carotid aery by a posterior communicating aery.