In your menstrual cycle, the hypothalamus, the anterior
pituitary, and the ovaries interact to result in ovulation. In
general, this process repeats itself approximately every 28 to
30 days in four phases. The first phase of the cycle is the
three to seven days of menstruation. The first day you start
menstruating is the first day of your cycle. When the end of
menstruation is near, one of the ovaries begins to prepare an
egg, also called an ovum, to be released into one of the
fallopian tubes. The lining of the uterus, the endometrium,
begins to thicken in preparation for a fertilized egg. The third
step, called ovulation, happens around day 14 of a 28-day cycle.
A mature egg is released from the ovary and enters the fallopian
tube. The fourth and final phase is marked by the egg's journey
down the fallopian tube. The endometrius continues to thicken.
If the egg isn't fertilized by a sperm cell, it disintegrates.
The thickened lining of the uterus isn't needed, so it's shed by
the body. This is your period,