Menstruation is the shedding of the functional layer (upper two-thirds) of the endometrium after sex steroid withdrawal.
The role of the functional layer is to prepare the uterus for implantation.
The basal endometrial layer (lower one-third) provides tissue for regeneration during the following cycle.
This shedding process, which consists of three phases (menstrual, proliferative, and secretory), is repeated approximately 300–400 times during a woman's reproductive life.
It also occurs in primates and bats.
Menstruation indicates that conception has not occurred.
- Posted using BlogPress from my iPhone