Menstrual cycle is the cycle of natural changes that
occurs in the uterus and ovary as an essential part of
making sexual reproduction possible. Menstrual fluid
cannot easily clot. The end of the cycle of menstruation is
called menopause. During the follicular phase,
gonadotropins (LH and FSH) increase gradually and
stimulate follicular development as well as secretion of
estrogen by growing follicles.