View of the medial surface of the left hemisphere. The proximal third of the calcarine fissure is retracted with two spatulas exposing the calcarine artery originating from P3. 1, P2A segment; 2, P2P segment; 3, thalamogeniculate artery; 4, P3 segment; 5, posteromedial choroid artery; 6, calcarine artery; 7, calcarine fissure; 8, velum interpositum cistern; 9, splenium of the corpus callosum; 10, cingulate gyrus. (Image courtesy of E de Oliveira)