Menstruation is a process in the female reproductive system that occurs in all primates. It is a cyclic process that occurs every 28 days on average, in which the lining of the uterus (the endometrium) is shed and a new one is built up. During this process, bleeding occurs from the vagina, which is a combination of blood and tissue from the endometrium. The purpose of menstruation is to prepare the body for the possibility of pregnancy. During menstruation, the ovaries produce hormones that cause the endometrial lining to thicken, in preparation for a fertilized egg. If a fertilized egg does not implant in the endometrium, the lining is shed, resulting in menstruation. The hormones also regulate the cycle of menstruation, as well as other processes such as ovulation.
Menstruation, ovulation,
female reproductive system