单词	trophoblast
释义	trophoblast /ˈtrɒfə(ʊ)blast / /ˈtrəʊfə(ʊ)blast/ noun Embryology A layer of tissue on the outside of a mammalian blastula, supplying the embryo with nourishment and later forming the major part of the placenta.The trophoblast eventually forms the placenta, through which the embryo proper receives dissolved nutrients and is cleansed of waste.... When the developing, fertilized egg at the ‘blastocyst’ stage becomes implanted in the lining of the uterus, it develops ‘villi’ - fine, frond-like cellular projections from its outermost layer, the trophoblast. The placenta derives from embryonic cells called trophoblasts, which form a ball around the cells that ultimately develop into the fetus. Derivatives trophoblastic adjective ... Multiple gestation, gestational trophoblastic disease, triploidy, trisomy 21 syndrome, and hydrops fetalis have been associated with an increased incidence of hyperemesis gravidarum. Nevertheless, one version of this suggestion, the ovarian time bomb hypothesis, explicitly envisages an individual-level cost of parthenogenesis, namely ovarian trophoblastic disease. The vascular endothelium was destroyed by villous proliferation and trophoblastic invasion in this vessel.
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