Ovulation is part of the menstrual cycle, which occurs each month in a sexually mature female. Another part of the cycle is menstruation. Menstruation is the process in which blood and other tissues are shed from the uterus and leave the body through the vagina. It is also called a menstrual period or menses. The menstrual cycle is sometimes divided into two cycles, called the ovarian cycle and the uterine cycle. The ovarian cycle includes the events that occur in the ovary. The uterine cycle refer to the events that occur in the uterus. The two cycles are closely related, so here they are described together and referred to jointly as the menstrual cycle.