menstrual cycle

Menstrual cycle is the reproductive cycle in females that lasts on an average for 28 days. It starts from the development of follicles in the ovary. This is called the follicular phase, and takes place as an effect of FSH (follicle stimulating hormone) from the pituitary. The follicles release estrogen. During the follicular phase, the endometrium (inner layer) of the uterus starts acquiring more tissue and blood vessels, to prepare for the attachment of the embryo. Then the follicles develop and rupture, releasing the ovum, as the result of an increased secretion of LH (luteinizing hormone) from the pituitary. This is called ovulation. The ruptured ovarian follicles convert to a structure callled corpus luteum, which secretes progesterone, that is responsible for further growth of the endometrium. If the ovum is not fertilized by a sperm, the developing lining of the uterus is shed along with blood and mucus, and this process is called menstruation. After menstruation is complete, the cycle starts all over again.