Obi Peter Chiagozie
Menstrual cycle refers to the series of hormonal changes that occur in the female reproductive system, while Ovarian cycle involves series of changes that occur in the ovaries alone, that’s is to say, menstrual cycles includes the ovarian cycle.
The phases of the menstrual cycle are usually described by the changes that occur in the ovary (the ovarian cycle) and/or by the changes that occur in the uterus (the endometrial cycle). I will only examine the menstrual cycle according to changes in hormone levels and the consequent changes in the reproductive organs and among the hormones. The phases will be referred to as the:
Relating to Hormones
1) Menstrual Bleeding Phase;
2) Estrogen Phase; and
3) Progesterone Phase.
Phases of Ovarian Cycle:
Phase of Endometrial Cycle:
The following discuss the changes that occur during each phase in the anterior pituitary gland, ovaries, endometrium, cervix, and the resulting influence on the BBT.
- THE MENSTRUAL BLEEDING PHASE (Days 1 to 5)
The Menstrual Bleeding Phase is also known as menstruation, menses or period. Hormone levels are at their lowest point during this phase. The following changes occur during the Menstrual Bleeding Phase:
Hypothalamus and Anterior Pituitary Gland;
The hypothalamus begins to produce GnRF because of the low levels of estrogen and progesterone in the blood. GnRF stimulates the anterior pituitary gland to begin producing, storing and releasing FSH and LH.
Approximately 20 ovarian follicles enlarge during the first week of each menstrual cycle. They produce estrogen and begin to ripen an ovum in response to FSH from the anterior pituitary gland.
The endometrium is the mucus membrane lining the uterus. During the Menstrual Bleeding Phase, the top (superficial) layer of the thick endometrial lining is becoming detached from the uterine wall, resulting in discharge of endometrial tissue, fluid and blood. The bleeding lasts for 3 to 5 days. The average blood loss is about 50 mililiter (ML).
The cervical canal is open slightly to permit menstrual flow to escape. The cervical glands produce very little mucus during these low-estrogen days of the cycle.
Basal Body Temperature (BBT)
The BBT is the temperature of the body at rest. During the menstrual cycle, the BBT rises from a lower level to a higher level. During the Menstrual Bleeding Phase, the BBT is at its lower level due to the decrease in the production of progesterone in the body.
2. THE OESTROGEN PHASE (Days 6 to 14)
The Estrogen Phase begins about Day 6 and lasts until about Day 13 to 14 when ovulation occurs. It is more variable in length than the other phases. The following changes occur during the Estrogen Phase:
Anterior Pituitary Gland;
The anterior pituitary gland continues to increase its production and storage of LH and FSH. Small amounts of LH and FSH are released into the bloodstream.
Around Day 13 (just prior to ovulation), the high level of estrogen in the blood produced by the dominant ovarian follicle triggers a surge of stored LH (from the anterior pituitary gland) into the bloodstream.
By Day 5 to 7, one
ovarian follicle is developing more rapidly than the others. This is the dominant follicle which will go on to ovulation. The other follicles stop growing; most will shrink and disappear into the ovarian tissue. As the dominant follicle cell develops, it releases an increasing amount of estrogen. The dominant follicle breaks open and releases its ovum because of a surge of LH (from the anterior pituitary gland) into the bloodstream. This process is called ovulation. Ovulation occurs about 12 to 16 days BEFORE the beginning of the next menses. Even in shorter menstrual cycles, ovulation rarely occurs before Day 10 of the cycle; ovulation, which may result in pregnancy (“fertile” ovulation), rarely occurs before Day 12.
The endometrium is built up under the influence of estrogen produced by the growing ovarian follicles. The endometrium develops glands, capillaries and general tissue swelling. With this increased blood supply, the endometrium is prepared for a possible implantation of a fertilized ovum.
The cervical canal is closed, except during the time of ovulation. It is then open to permit the
entrance of sperm. Initially in the Estrogen Phase, no mucus loss from the cervix is apparent. A sensation of dryness exists (although the interior of the vagina is always moist). As the blood levels of estrogen increase, the quantity of cervical mucus also steadily increases because glands in the cervical canal are stimulated by the estrogen. The maximum amount of mucus is produced about the time of ovulation. The mucus becomes clear, slippery and stretchy (like uncooked egg white) and can flow out of the vagina. This type of mucus nourishes the sperm and helps it to travel into the uterus.
Basal Body Temperature (BBT)
The BBT remains at its lower level under the influence of estrogen. Just before ovulation, at the start of the LH surge, the BBT may fall a bit more.
The average period of ovulation for a menstrual cycle which last for 28rays is 14 days. Ovulation is otherwise called “the danger period” because, any act of unprotected sex will veritably result to pregnancy.
It is overt and scientifically proven that sperm lasts for 3days(72hours) while ovum/egg lasts for 3days(72hours) as well, therefore, your safe period is 3/4days before ovulation and 3/4days after ovulation( that is to say that, if ones ovulation normally occurs on the 14th day, then her free periods are from day 11, 10, downward and also from day 18 upwards. Having unprotected sex within days excluding the aforementioned days undoubtedly results to pregnancy.
Some find it very arduous and difficult to know their ovulation time/day, while some very effortless. I believe after reading this article, you will be able to know the time and day of your ovulation.
You can do this by knowing your basal body temperature(BBT) and then comparing it to your rectal(rectum) or vaginal temperature. If your rectal or vaginal temperature is lower than your basal body temperature by -3.0 degree centigrade to -5.0 degree centigrade, then ovulation will occur in few hours, but if your rectal or vaginal temperature is higher than your basal body temperature by +3.0 to 5.0 degree centigrade, then ovulation has occurred.
If your basal body temperature ( BBT )is 35degree at the onset of menstruation, and then it becomes 34.5, 34.4 or 34.3degree, then it means that ovulation is around the corner, but if it is higher than 35degree, then it means that ovulation has occurred some hours ago.
- THE PROGESTERONE PHASE(Days 15 to 28)
The Progesterone Phase begins at approximately Day 15 and ends at about Day 28. The length of this phase is predictably 2 weeks long. It does not vary much from month to month or from woman to woman. The following changes occur during the Progesterone Phase:
Anterior Pituitary Gland:
The empty dominant follicle in the ovary changes into a corpus luteum (which produces progesterone and some estrogen) because of stimulation resulting from the high level of LH released by the anterior pituitary gland. If the ovum is not fertilized, the activity of the pituitary is inhibited because of the high level of progesterone in the blood produced by the corpus luteum. The pituitary production of LH is then reduced (an example of negative feedback).
The corpus luteum is a reorganization of the cells from the ruptured egg follicle. The corpus luteum steadily produces and secretes progesterone. The progesterone reaches a maximum amount about 8 days after ovulation. The corpus luteum also produces small amounts of estrogen during this phase.
As progesterone secretion increases, LH secretion decreases (negative feedback). The corpus luteum begins to degenerate by Day 23 to 24 because the LH level is low. Thus, the production of estrogen and progesterone also declines.
From Days 15 to 22, the blood supply to the endometrium continues to increase due to the rising levels of progesterone produced by the corpus luteum of the ovary. The endometrial glands become larger and secrete nutrients into the uterine cavity because of progesterone stimulation. These nutrients can nourish a fertilized ovum until it is implanted.
Progesterone and estrogen in the blood decrease toward the end of this phase because of the degenerating corpus luteum (Days 23 to 28). The blood vessels supplying the endometrium constrict as a result of this lack of stimulation from the ovarian hormones. The endometrial cells cannot receive the oxygen and nutrients that the blood vessels carried, and they begin to die. The Menstrual Phase begins, and menstrual bleeding occurs.
During the progesterone phase, the cervical canal remains closed. The quantity of cervical mucus decreases. A woman may become “dry” again or develop sticky, thick, cloudy discharge. This mucus makes it difficult for sperm to penetrate and travel into the uterus.
Basal Body Temperature (BBT).
Shortly before, during or after ovulation, the BBT rises 0.2 to 0.5 degrees centigrade, due to the increase in progesterone production. The BBT remains elevated until progesterone levels drop and the Menstrual Phase begins. (See Figure 3 on pages 15 and 16 for an example.)
If fertilization of the ovum occurs, the hormone patterns of the last half of the menstrual cycle change. Another hormone, human chorionic gonadotropin (hCG), will be produced by the developing placenta. hCG is the hormone detected by a pregnancy test. Its blood levels peak at 8 to 12 weeks after conception.
The levels of FSH and LH fall greatly, because their production is suppressed (through negative feedback) by the high blood levels of estrogen and progesterone. (Hormonal contraceptives imitate the state of pregnancy. They release high enough levels of estrogen and/or progestin into the blood to convince the anterior pituitary that the woman is already pregnant. Consequently, the anterior pituitary stops producing FSH and LH.)
In early pregnancy, hCG prevents the corpus luteum from degenerating, so it will continue to function and release progesterone and estrogen to support the developing embryo. By 7 to 10 weeks after conception, the placenta is able to provide the high levels of estrogen and progesterone needed in pregnancy.
When the embryo implants, the continued secretion of progesterone causes the endometrial cells to swell even larger and store and provide more nutrients for the growth of the fetus.
The external cervical canal enlarges slightly, bleeds more easily and becomes filled with a thick mucus “plug”, which helps protect the amniotic sac from vaginal microbes.http://Africanatelegraph.com
The BBT remains elevated, as in the progesterone phase of the menstrual cycle.
EFFECTS OF ABORTION (spontaneous or induced) ON THE MENSTRUAL CYCLE
A spontaneous abortion is an unprovoked interruption of a pregnancy before there is a viable fetus. The cause is usually uncertain, but is sometimes linked to conditions such as malnutrition and/or malaria. Induced abortion refers to the use of a procedure to terminate an unwanted pregnancy.
With the loss of the pregnancy, progesterone and estrogen levels fall rapidly, and FSH levels begin to rise within two weeks of a first trimester abortion and within four weeks of a second trimester abortion. Fertility returns almost immediately postabortion (spontaneous or induced): within two weeks for first trimester abortion and within four weeks for second trimester abortion. Within six weeks of abortion, 75% of women have ovulated.
If the abortion was induced under unsafe conditions, bacteria may have entered the uterus, and endometritis (uterine infection) may be present (requiring prompt treatment). If the abortion was performed or occurred under hygienic conditions, the endometrium will rapidly repair, and future fertility will be unaffected. Sharp instruments (curettage) can damage and even severely scar the endometrium.
The cervical mucus will resume its usual fertile mucus cycle with ovulation. The cervix may be damaged by instruments used during induced abortion. (Soft plastic canulas rarely cause cervical damage.)
Basal Body Temperature (BBT)
The BBT falls to pre-ovulatory levels shortly after the abortion.
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