Part of: Reproductive System
What Happens During Menstruation?
During the monthly hormone cycle the mucous membranes lining the inside of the uterus prepare for the possibility that an egg might be fertilized and settle in the uterus. The mucous membranes supply nutrients to the embryo if the woman gets pregnant. If the egg cell is not fertilized, it dies.
At the end of the cycle some blood vessels in the mucous membranes of the uterus open up for some time, and the uppermost mucous layer together with the egg cell and some blood is shed through the vagina. This is the monthly period, also called menstruation. As long as a woman is not pregnant and does not use hormonal contraceptives, the period usually is a sign that one menstrual cycle has finished and the next one has started. In most women, the period lasts 3 to 5 days.