View of the basal surface of the brain with an axial section of the right temporal lobe at the level of the calcarine fissure. The temporal arteries are cut near their origins. The temporal and occipital horns, atrium, calcar avis, and choroid plexus are shown. The segments of the posterior cerebral artery are numbered. In this specimen the calcarine and parieto-occipital originate at the P4 segment; the posterior pericallosal artery is a branch of the parieto-occipital artery. 1, P1 segment; 2, oculomotor nerve; 3, P2A segment; 4, anterior temporal artery; 5, P2P segment; 6, posterolateral choroidal artery; 7, P3 segment; 8, P4 segment; 9, parieto-occipital artery; 10, calcarine artery; 11, calcar avis; 12, cuneus; 13, posterior pericallosal artery; 14, hippocampus head; 15, dentate gyri; 16, temporal horn; 17, atrium; 18, occipital horn; 19, amygdala. (Image courtesy of E de Oliveira)