Blastocyst
For the specific, non-species developmental stage, see Blastula. For the single-celled parasite, see Blastocystis. Blastocyst Blastocyst just before implantation A human blastocyst, with inner cell mass at upper right Details Carnegie stage 3 Days 5–9 Gives rise to Gastrula Identifiers Latin Blastocystis MeSH D001755 TE E2.0.1.2.0.0.12 FMA 83041 Anatomical terminology [edit on Wikidata] The blastocyst is a structure formed in the early development of mammals. It possesses an inner cell mass (ICM) which subsequently forms the embryo. The outer layer of the blastocyst consists of cells collectively called the trophoblast. This layer surrounds the inner cell mass and a fluid-filled cavity known as the blastocoel. The trophoblast gives rise to the placenta. The name "blastocyst" arises from the Greek βλαστός blastos ("a sprout") and κύστις kystis ("bladder, capsule"). In humans, blastocyst formation begins a...