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, and forms to connect the embryo to the uterine wall. The decidua here is termed the decidua basalis and 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.