an embryo attaches to the uterus during prenatal development.
an embryo attaches to the uterus during prenatal development.
when does an embryo attach to the uterus?
prenatal development
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the syncytiotrophoblast implants the blastocyst in the decidual epithelium by projections of chorionic villi, forming the embryonic part of the placenta. the placenta develops once the blastocyst is implanted, connecting the embryo to the uterine wall. the decidua here is termed the decidua basalis; it lies between the blastocyst and the myometrium and forms the maternal part of the placenta. the implantation is assisted by hydrolytic enzymes that erode the epithelium. the syncytiotrophoblast also produces human chorionic gonadotropin, a hormone that stimulates the release of progesterone from the corpus luteum. progesterone enriches the uterus with a thick lining of blood vessels and capillaries so that it can oxygenate and sustain the developing embryo. the uterus liberates sugar from stored glycogen from its cells to nourish the embryo. the villi begin to branch and contain blood vessels of the embryo. other villi, called terminal or free villi, exchange nutrients. the embryo is joined to the trophoblastic shell by a narrow connecting stalk that develops into the umbilical cord to attach the placenta to the embryo.
human embryonic development