1. Menstruation is the stage of the menstrual cycle usually lasting from three to five days. 2. The menstrual flow occurs when the egg is not fertilized by a sperm. 3. At the age between 45 to 55 years of age menopausal stage occur. 4. The entire cycle is divided into five phases. 5. Menstruation is important to female for the continuity of human race. 6. Menstrual flow usually lasts for 10 to 15 days.​