Sequential Pattern in Female Reproductive Cycle
Menstruation is the actual blood flow from the sloughing off of the uterine endothelium. The actual blood loss is due to progesterone withdrawal that occurs in the latter part of menstruation. The female reproductive cycle involves a sequential pattern of changes in the tropic hormones (hormones that stimulates an organ) which will cause a cyclic change in the female gonads (ovaries). Average cycle varies from woman to woman but it usually is 28, ranging from 20-45 days. The female reproductive cycle is further divided into two cycles that considers the changes in the uterus and ovaries.
In obstetric nursing it is important to fully understand and if possible, memorize the menstrual cycle as it is the backbone of OB learning. However, before proceeding to the cycle stages, it is important to note that all the phases in a reproductive cycle is influenced by the functioning of four organs, namely:
- Anterior pituitary gland
It is very essential to chronologically memorize these body organs to easily remember the sequence of changes that occurs recurrently in a woman’s body each month. Again, remembering these body parts in order would help one to fully understand the processes involve in a menstrual cycle. Now let’s start.
- Approximately three days after menstruation (actual blood flow), a dramatic decrease estrogen level would be noted. Extreme reduction of its level will stimulate the hypothalamus to produce Follicle Stimulating Hormone Releasing Factor (FSHRF), a tropic hormone indirectly related in estrogen production.
- FSHRF then triggers the Anterior Pituitary Gland to produce Follicle Stimulating Hormone (FSH).
- In response FSH goes to the ovaries and would cause release of the first ovarian hormone, estrogen.
- With the influence of estrogen, primordial follicles (immature cells incapable of fertilization located at the cortex of the ovaries) are now called Graafian follicles.
- Estrogen in higher amount would cause rapid growth of the uterine lining (proliferation). Therefore, this phase is called a Proliferative phase because of the rapid growth of uterine lining. It is also termed as Estrogenic phase due to increase estrogen production and Follicular phase because of the presence of graafian follicle. Because this event occurs after the actual menstruation it is also called a Postmenstrual Phase and since ovulation has not occurred yet it can also be termed as Preovulatory phase (before ovulation).
- Estrogen increases fat deposition causing a woman to feel bloated.
- A significant decline of progesterone will stimulate the hypothalamus to stimulate to release of Luteinizing Hormone Releasing Factor.
- LHRF sets off the production of luteinizing hormone (LH) in the anterior pituitary gland.
- LH makes it way to the ovaries which in turn produces the second ovarian hormone, progesterone.
- High levels of estrogen and progesterone would then cause the release of the mature ovum. This phenomenon known as ovulation exactly occurs 14 days before the next menstrual period. Meaning to say, in a 30 day cycle, ovulation occurs on the 16th day. In a 28 day cycle it is on the 14th day. The technique here is just to subtract 14 from the number of cycle the woman has. (E.g. 30 days – 14 = 16th day)
- During ovulation the woman may feel pain in either right or left lower abdominal quadrant due to the pressure in the release of the ovum. This is called mittelschmerz.
- Right after ovulation, Graafian follicle (a body containing high amounts of estrogen) with the influence of the escalating progesterone level will change its color to yellow and is now called corpus luteum.
- Corpus luteum has a life span of about 8-10. Because follicles develop to corpus luteum (a body containing high amounts of progesterone), this stage is termed Luteal Phase and as the changes occurred after ovulation it is also called Postovulatory phase. Menses is expected in a fixed date (if no fertilization will occur) therefore it is also a premenstrual phase.
- Progesterone causes increase blood supply, thickening and vascularity of the uterus. Capillaries are pooling down the uterine portions in preparation for possible implantation of zygote (the result of the fusion of DNA from sperm and egg). This is the reason why progesterone is called the hormone of pregnancy. However, if no fertilization would occur on the 8th to the 10th of corpus luteum’s lifespan, progesterone level starts to drop.
- Progesterone diminution will cause alteration in corpus luteum’s color. Thus, it will turn white for the succeeding 3-4 days and is called corpus albicans.
- Withdrawal of the progesterone hormone (on the 4th day of corpus albicans) would cause the sloughing off and rupture of capillaries in the uterus. Thus, actual blood flow then takes place.