Describe the steps from ovulation through implantation in the uterine wall. How does hormonal control of these steps occur
After ovulation, the mature egg is released from the ovary and moves into the fallopian tube. If sperm is present and fertilizes the egg, it forms a zygote.
The fertilized egg continues to travel down the fallopian tube towards the uterus. During this time, the zygote undergoes several cell divisions and forms a blastocyst.
The blastocyst reaches the uterus around 5-7 days after ovulation. In order to implant into the uterine wall, the blastocyst first attaches to the endometrium, the inner lining of the uterus.
Hormonal control of these steps is primarily regulated by estrogen and progesterone. After ovulation, the empty follicle in the ovary (the corpus luteum) produces progesterone, which helps thicken the endometrium to prepare for implantation.
If fertilization occurs, the developing embryo signals the corpus luteum to continue producing progesterone to maintain the thickened lining and support pregnancy. The embryo also produces human chorionic gonadotropin (hCG), which signals the corpus luteum to continue producing progesterone.
If fertilization does not occur, the corpus luteum regresses and stops producing progesterone, causing the endometrium to shed during menstruation.