Menstrual Phase

• Days 1-6
• Menses: shedding of the endometrium due to drastic drops in progesterone levers
• Constriction of Blood vessels (depriving the uterine lining of nutrients and oxygen)
• All hormonal levels are low, but by day three FHS and LH begin to rise

Follicular Phase

(Proliferative)

• Days 7-14
• Uterus thickens, ovarian follicules develop
• Follicle Stimulating Hormone(FHS) and Luteinizing Hormone (LH) = ovarian activity and stimulation of ovulation
• Follicles release estrogen which thickens the endometrium, preparing the uterus for the arrival of an embryo

Ovulation

• Day 14
• One follicle becomes dominant; it burst and releases the oocyte
• Dominant follicle becomes corpus luteum (CL)
• Basal temperature increases immediately after ovulation
• Fertility is greatest five days before and 2 days after ovulation
• Only one gamete produced each month (1 diploid sex cell produces 1 haploid)

Luteal Phase

(Secretory)

• Days 14-28
• CL=Temporary endocrine gland that arises from call of dominant ovarian follicle
• CL released progesterone and estradiol-17beta (estrogen)
• Negative feedback on FSH and LH (which cause regression of CL)
• Atrophy of CL (if failed implantation)

Conception and Implantation

• Maintenance of CL=Human Chorionic Gonadotropin (hCG); unique to embryo (hormone that shows up in pregnancy test)
• CL= maintain placenta, inhibit ovulation, prepare for pregnancy
• Placenta takes over progesterone production at about week 3, atrophy of CL