Blastotsüst
Blastotsüst, commonly known in English as the blastocyst, is a stage of early mammalian embryonic development. It typically forms about five to six days after fertilization in humans and other primates, and serves as a key transitional structure before implantation. The blastocyst is a hollow sphere composed of three parts: an outer layer of trophoblast cells, a fluid-filled cavity called the blastocoel, and an inner cell mass that will give rise to the embryo proper. The trophoblast ultimately contributes to the placenta and supporting tissues, while the inner cell mass differentiates into the embryo’s tissues.
Formation begins as the earlier morula develops a fluid-filled cavity, resulting in the blastocoel. The outer
Clinical relevance is notable in assisted reproduction. Culturing embryos to the blastocyst stage allows for more
Etymology derives from Greek roots meaning “bud” and “sac,” reflecting its vesicular nature. In some languages,