The document discusses the physiology of menstruation, including: 1. The hypothalamus and pituitary gland regulate the menstrual cycle by releasing hormones like FSH and LH that cause egg maturation and ovulation. 2. During ovulation, a follicle ruptures and releases an egg, leaving behind the corpus luteum which produces progesterone. 3. In the absence of fertilization, progesterone levels drop and the thickened uterine lining breaks down and is shed during menstruation.