The Menstrual period 🩸🏃‍♀️👧 The menstrual cycle is a natural process regulated by hormones produced by the hypothalamus, pituitary gland, and ovaries. It is divided into phases that repeat whether or not a woman is sexually active. Follicular Phase: This phase begins on the first day of menstrual bleeding (Day 1 of the cycle). Hormones (FSH and estrogen) cause follicles to grow in the ovaries, and one dominant follicle matures an egg while the uterine lining thickens. Ovulatory Phase: Around