The Female Reproductive System : -
- The female reproductive system consists of internal organs, including the ovaries, oviducts, uterus and vagina; external genital structures, and the breasts.
- Menarche, the beginning of menstruation in females after puberty, occurs at about age 15.
- In the reproductive phase of female life, the menstrual cycle, takes place between each menses (the start of bleeding), lasts about 28 days.
- Menopause occurs when this cycle eventually ceases, between the ages of 45 and 55.
The menstrual cycle is under the control of the hormone system and is necessary for reproduction. It may be divided into several phases: menstruation, the follicular phase, and the luteal phase.
Stimulated by gradually increasing amounts of estrogen in the follicular phase, the lining of the uterus thickens. Follicles in the ovary begin developing under the influence of a complex interplay of hormones, and after several days one or occasionally two become dominant. The dominant follicle releases an ovum, or egg, in an event called ovulation. After ovulation, the remains of the dominant follicle in the ovary become a corpus luteum; this body has a primary function of producing large amounts of progesterone. Under the influence of progesterone, the endometrium (uterine lining) changes to prepare for potential implantation of an embryo to establish a pregnancy. If implantation does not occur within approximately two weeks, the corpus luteum will involutes, causing sharp drops in levels of both progesterone and estrogen. These hormone drops cause the uterus to shed its lining in a process termed menstruation.