The placenta is a vascular structure that forms at the site of implantation between the cells that surround the embryo and the endometrium of the uterus. Its main functions are the exchange of gases, nutrients, and wastes between the maternal and fetal bloodstreams. In addition, the placenta secretes hormones. There is no actual blood flow between mother and fetus.
The egg is fertilized in the Fallopian tube, then begins cell division even before it is implanted in the uterine wall. Anatomical Chart Co.