immediately deep to immediately superficial to layer of hippocampus hippocampus pyramidal layer hippocampus stratum oriens BIRNLEX:4113 stratum oriens polymorphic layer of hippocampus Layer that is part of the CA fields of the hippocampus consisting of a narrow relatively cell free layer located deep to the pyramidal cell layer extending through areas CA1, CA2 and CA3. (adapted from Paxinos The rat central nervous system, 2nd ed, Academic Press, San Diego, 1995). EMAPA:35412 FMA:83893 MA:0000958 BAMS:Or oriens layer of hippocampus UBERON:0005371 polymorphic layer of the hippocampus oriens layer of the hippocampus hippocampus alveus