Menstrual Cycle

The menstrual cycle is a recurring cycle of changes that occurs in the reproductive organs of females. The menstrual cycle is under the control of the hormone system and is necessary for reproduction. Menstrual cycles are counted from the first day of menstrual bleeding, because the onset of menstruation corresponds closely with the hormonal cycle. Menstrual bleeding occurs once every month, at a frequency of every 28 to 32 days.