The menstrual cycle ?

The menstrual cycle is the monthly series of changes a woman's body goes through in preparation for a possible pregnancy. It involves the shedding of the uterine lining (menstruation), the release of an egg from the ovaries (ovulation), and the thickening of the uterine lining in case of fertilization. The average menstrual cycle is around 28 days, but it can vary from woman to woman. Hormones such as estrogen and progesterone play a key role in regulating the menstrual cycle.