part of part of develops from develops from adjacent to adjacent to inner cell mass extraembryonic structure trophectoderm polar trophectoderm Trophectoderm that surrounds the inner cell mass (ICM). EHDAA:60 UBERON:0006280 EMAPA:16048 EHDAA2:0001484 polar trophoblast VHOG:0000980 entire extraembryonic component transitional anatomical structure