part_of part of part of has part has part has_part only in taxon develops from existence starts and ends during Theria <mammals> morula inner cell mass trophoblast blastula stage blastula blastocyst https://upload.wikimedia.org/wikipedia/commons/7/72/Blastocyst_English.svg Gilbert fig11.32 has blastocyst has giving rise to ICM and trophoblast (which in this source is a synonym for trophectoderm) embryonic structure