Why does menstruation occur?

Explanation

Since the ovary of a woman releases one egg (or ovum) every month, therefore, the uterus also prepares itself every month every month to receive a fertilised a egg(if formed). In this process, the inner lining of the uterus becomes thick and soft which lots of blood capillaries (blood vessels). In, it. This preparation in uterus is necessary because in case the egg is fertilised by a sperm, then the uterus has to keep this fertilised egg and nourish it to develo it into a baby. If, however, the egg released by the ovary is not fertilised, then the thick lining of the uterus is not needed. So, the uterus lining breaks down and comes out through the vagina in the form of blood and mucous. This is called menstruation.