Any women who is not pregnant, has to suffer monthly cycles due to changes that takes place in ovaries and uterus of their body. Therefore these cycles are called ovarian cycle that is process that goes during and after the maturation of oocyte and uterine cycle is the series of changes that prepares uterus for the preparation of fertilized ovum respectively.
Steps in the reproductive cycle:
Several steps are involved in the reproductive cycle:
Menstrual phase: It last for 5 days, in the ovaries primordial follicle develops into primary and then the secondary follicle due to the influence of FSH whereas in the uterus, declining level of estrogen and progesterone sloughs the stratum functionalis. Thus, making the endometrium thin.
Preovulatory phase: it occurs at the end of menstruation and beginning of ovulation lasting from 6 to 13 days. In the ovaries, only one secondary follicle that develops to particular size secretes estrogen and inhibin making other follicle to degenerate, thus it increases in size forming mature follicle. In the uterus endometrium thickens forming new stratum functional.
Ovulation: it occurs in day 14 when rupture of mature follicle takes place thus releasing the secondary oocyte. It takes place under the influence of FSH and LH.
Postovulatory phase: it occurs between the time of ovulation and next menstruation, thus lasting for 14 days. In the ovary, after ovulation when mature follicle collapse forming corpus hemorrhagium, theca interna cells mix with granulose cell forming corpus luteum. It soon degenerate forming corpus albicans and this takes place under the influence of all the hormones involved in female reproductive system. In the uterus, progesterone and estrogen thickens the endometrium. Thus, in case again when no fertilized ovum is received then level of these hormones decline causing menstruation again.
GnRH release FSH and LH. FSH and LH secrete estrogen. FSH stimulates follicular growth, LH stimulated development of ovarian follicles and theca cell to produce androgen that is made up by granulose cell, thus converted to estrogen. LH also triggers ovulation and forms corpus luteum. Finally corpus luteum produces different hormones involved in female reproductive cycle such as : inhibin, relaxin, progesterone, estrogen.
This, way the coordination of different reproductive organs and hormones helps to complete the cycle in proper and effective way.