👉 A menstruum is a type of menstrual cycle where a woman experiences two main phases, usually known as menses. These are the endometrial cycle and the ovarian cycle. The endometrium, which forms during ovulation, can shed its lining through the menstrual period, while the lining of the womb (ovary) continues to produce hormones like estrogen for several months after menstruation is complete. The first phase of a menstruum includes the release of an egg from the ovaries, followed