cycle, menstrual

cycle, menstrual The monthly progression of changes in the endometrium (the lining of the uterus), which includes the shedding of part of the endometrium and menstruation (monthly vaginal bleeding). This cycle is governed by a complex sequence of hormones that influence fertility and may affect mood and a variety of physical functions. By convention, the menstrual cycle is considered to begin on the first day of menstrual bleeding. See also menstruation.