The Cycles of the Reproductive System The

The Cycles of the Reproductive System

The Female Reproductive System Functions: Produce fertilizable ova House and nourish a baby There are two cycles (ovarian and menstrual) that occur simultaneously, working together, over a duration of 21 to 40 days (28 days on average)

The Cycles Ovarian Cycle Responsible for: Maturation and release of the oocyte Evolution of the support system of the oocyte Menstrual Cycle Responsible for: The process of the degeneration and renewal of the endometrium – the inner lining of the uterus – the tissue that sustains a fertilized ovum

The Preovulatory Phase (starts at Day 1) Ovarian Cycle The pituitary gland secretes FSH and LH. FSH stimulates follicle development. More than one develop, but only one reaches maturity. The follicle develops and begins to secrete estrogen. The increase in estrogen stimulates the uterus to thicken the endometrium. High amounts of estrogen informs the pituitary gland to reduce FSH secretion and increase LH secretion. Menstrual Cycle The endometrium desquamates (breaks off in layers). This process can take 2 -6 days in duration. A new endometrium begins to develop due to the estrogen secreted by the mature follicle.

The Ovulatory Phase – Ovarian Cycle At the end of the preovulatory phase there was an increase in LH secretion, this causes the rupture of the follicle and the release of it from the ovary. The follicle is picked up by the infundibulum of the fallopian tubes. around 14 days before menstrual flow Menstrual Cycle The new endometrium that was developed at the end of the preovulatory phase remains and is unchanged.

The Postovulatory Phase – takes 14 daysç Ovarian Cycle Estrogen production is reduced, briefly (because of follicle rupture). The ruptured follicle becomes the corpus luteum and secretes progesterone and estrogen production increases again. Due to the high levels of estrogen and progesterone, FSH and LH secretion is inhibited and other oocytes are stopped midproduction. Menstrual Cycle The endometrium thickens because of the estrogen and progesterone production by the corpus luteum.

The Postovulatory Phase – takes 14 daysç Ovarian Cycle Fertilized ovum The corpus luteum continues to produce estrogen and progesterone Non-fertilized ovum The corpus luteum breaks down and hormone production is halted The cycle begins again Menstrual Cycle Fertilized ovum The endometrium remains throughout pregnancy Non-fertilized ovum The uterus is no longer stimulated by the hormones from the corpus luteum. As a result, the endometrium is shed. The cycle begins anew.