E, The medial part of the left parahippocampal gyrus has been removed to expose the lateral posterior choroidal arteries arising from the P2 and passing through the choroidal fissure located between the fimbria and thalamus to reach the choroid plexus in the temporal horn. Perforating branches like the thalamogeniculate arteries also arise from the P2 and ascend to penetrate the lower surface of the thalamus in the region of the geniculate bodies. F, Enlarged view with the lower part of the hippocampal gyrus removed while preserving the fimbria. The P2 has been retracted medially to expose the lateral posterior choroidal arteries passing through the choroidal fissure located between the fimbria and thalamus to enter the choroid plexus in the temporal horn. The anterior choroidal artery is also seen passing through the fissure. G, Another specimen. The M1 and P1 and P2 give rise to a series of perforating branches that enter the basal surface of the brain. The P2 has been retracted to expose the lateral posterior choroidal branches passing laterally through the choroidal fissure to reach the choroid plexus in the temporal horn and atrium. The parahippocampal gyrus has been removed. The fimbria and thalamus border the choroidal fissure. The lateral geniculate body protrudes from the lower margin of the thalamus. H, Enlarged view. The lateral posterior choroidal artery passes laterally through the choroidal fissure to reach the choroid plexus. The medial posterior choroidal encircles the brainstem. (Images courtesy of AL Rhoton, Jr.)