Menstrual Cycle

The menstrual cycle is a regular physiological process in females that occurs as part of the reproductive system. It is typically 28 days long and is necessary for the release of an egg to be fertilized and for pregnancy to occur. A woman's hormones, specifically progesterone and estrogen, fluctuate during the cycle, producing a variety of symptoms such as bloating, breast tenderness, headaches, and mood swings. The hormones also cause the endometrium, the lining of the uterus, to thicken in preparation for implantation of the fertilized egg. If the egg is not fertilized, the endometrium is shed and expelled as menstrual flow, starting the cycle anew. As such, the menstrual cycle is an essential part of the body's reproductive system and is necessary for normal sexual and reproductive functioning.