Embryonic development begins while the fertilized egg is still within the fallopian tube. The developing embryo travels down the tube, reaching the uterus in about a week. As a result of repeated mitotic divisions and some migration of cells, a hollow ball of cells is formed called the blastocyst. Approximately one week after fertilization, the blastocyst embeds itself in the endometrium, a process called implantation. With implantation, pregnancy is established.
The blastocyst will develop into the:
- umbilical cord
and secrete the pregnancy hormone human chorionic gonadotropin (hCG).