The Menstrual Cycle
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In females the menstrual cycle is a self-regulating process during which the body undergoes many physiological and hormonal changes. The menstrual cycle is regulated by two hormones secreted from the pituitary gland, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These control the production of the hormones estrogen and progesterone, which are produced in the ovaries. Females begin their menstrual cycle during puberty at the onset of menarche, their first menstrual period. Females continue to have many menstrual cycles throughout their lives until menopause occurs between ages 40 to 60. The average menstrual cycle lasts about 28 days, but can last anywhere from 24 to 42 days. There are three major phases of the menstrual cycle: the menstrual phase, the proliferate phase, and the secretory phase. |  |
The Menstrual Phase
The menstrual phase is the phase during which the lining of the uterus, called the endometrium, is shed as menstrual flow out of the cervix and vagina. This process is what women experience during their menstrual periods, and the menstrual flow actually consists of blood, mucus, and tissue. The first day of menstrual flow is defined as day number one of the next menstrual cycle. Menstruation lasts for approximately 3 to 7 days, although some women have shorter or longer periods. Menstruation is triggered by reduced levels of the hormones estrogen and progesterone at the end of the previous menstrual cycle. The onset of a new menstrual period indicates that the woman is not pregnant. However, this does not mean that a woman cannot become pregnant during her period; women can get pregnant at any time throughout their menstrual cycle. Also during the menstrual phase, the pituitary gland begins to secrete follicle-stimulating hormone (FSH). Rising levels of FSH trigger the beginning of the next phase, called the proliferative phase.
The Proliferative (Follicular) Phase
Also referred to as the follicular phase, the proliferative phase is the part of the menstrual cycle during which follicles inside the ovaries develop and mature in preparation for ovulation. The levels of FSH increase in the bloodstream during the proliferative phase, stimulating the maturation of follicles. Each follicle contains an ovum, or egg. Although many follicles may grow and increase in size during this phase, only one will reach full growth and release the ovum at the time of ovulation.
Also during the proliferative phase, the ovaries produce estrogen. The rising levels of estrogen cause the lining of the uterus to begin thickening. (The proliferative phase gets its name from the proliferation of the cells in the uterine lining at this time.) Once the levels of estrogen are at their peak, the pituitary gland slows the secretion of FSH, and instead begins to secrete luteinizing hormone (LH). As a result of the increase in LH, the mature follicle ruptures and releases the ovum from inside. Once released from the ovary, the ovum will then travel to the fallopian tubes. The releasing of the mature egg from the follicle is called ovulation. Ovulation occurs 14 days before the beginning of the next menstrual period. Ovulation is the most fertile time during a woman's menstrual cycle.
The Secretory (Luteal) Phase
After ovulation occurs, LH causes the burst follicle to develop into a structure called the corpus luteum. The corpus luteum is a small yellow structure in the ovary that secretes the hormones estrogen and progesterone. The progesterone and the estrogen are at a high level during the secretory phase, and they help prepare the endometrium to secrete nutrients that would nourish a conceptus if a fertilized egg were to implant in it. If conception and implantation do not occur, the pituitary gland will reduce LH and FSH production. Without the presence of LH, the corpus luteum deteriorates and subsequently the estrogen and progesterone levels decrease. The drop in estrogen and progesterone levels triggers the shedding of the endometirum, causing menstruation to begin and the cycle starts over again.
References
Crooks, R., & Baur, K. (2005). Our sexuality. Belmont, CA: Thompson Wadsworth.
Hyde, J.S., & DeLamater, J.D. (2006). Understanding human sexuality. New York: McGraw-Hill.
Menstrual cycle. (n.d.). Retrived February 12, 2007, from http://en.wikipedia.org/wiki/Menstrual_cycle
Frequently Asked Questions About Menstruation
Why Is My Period Late?
First and foremost a late period can signal the onset pregnancy. For some women, this is an exciting time if they've been trying to become pregnant. For others who are not intending pregnancy, a late period is a very stressful time. If a female has engaged in unprotected sex, sex during which the condom broke, activities where sperm have come into contact with her vagina, and her period has not come on its normal date, then there is a chance she may be pregnant. The only sure way to find this out is by taking a pregnancy test, either at home or at the doctor's office. For more information on this topic, please see our Pregnancy Section.
A second cause for a late period could be an STI, such as Pelvic Inflammatory Disease, which can cause such symptoms as "disruptions of menstrual periods." Because of this, it is important to also get tested for STIs. People who are sexually active should get tested after every new partner, unless they used sufficient protection.
Many people want to know just how late a period can be before they should worry, but this is not an easy question to answer, since there is so much variation among women. One suggestion is for females to get in touch with their bodies by keeping track of their menstrual cycle lengths for a long period of time. This involves writing down on a calendar their start and stop dates each month. This way, when the question of a late period arises, women can refer to what their cycles have been like in the past and see if there really is a reason to be concerned.
A final thought to keep in mind is that stress can often delay a period, so stressing out over a late period is a real catch-22. If a woman's period is late, she should calmly consider the fluctuation of her past start dates, what behaviors she has engaged in, and then decide if she needs to take a pregnancy test or get examined for STIs. In either case, these simple tests can be done at a doctor's office, where women can also get more specific information for their personal situations.
Why Is My Period Irregular?
Just like a late period, an irregular period may also be an indicator of an STI, pregnancy, or other changes in a female's body.
One important thing to keep in mind - for young women especially - is that it may take a significant amount of time after menarche (first menstruation) before menstruation is regular. One quote from a female SexInfo reader portrays exactly how erratic and even frustrating this process can be:
"I am 19 years old. When I was 13, I got my first period. Then I did not get another period until I was 15. Then my period was regular until I was 16, when I began to miss it for months at a time. Most recently, I missed it for about a year, but I got it a week ago. I have had at most, 15 periods in my life! The doctors say that there is nothing wrong with me, and that I just need to eat better and exercise. My question is, if there is nothing wrong with me, then why do I miss my period so often?"
Understanding how common this situation is may help some women to quell their own worries. This is an ordinary - granted annoying - aspect of being a woman. However, it must be stated that for sexually active females, an irregular period may not always be ordinary, as this type of change can be an indication of pregnancy or . (See the above section for more details.)
Some women are so bothered by an irregular period that they may consider talking with a doctor about ways to achieve a regular cycle. There are several ways to shorten (or even completely stop) your period. Some women like to have their period every month, as proof that they are not pregnant, but would prefer it to be shorter. In this case, we recommend increasing the amount of aerobic exercise you currently do. Studies have shown that an increased amount of strenuous cardiovascular exercise (such as running or vigorous sports) greatly reduces the length of a woman's period. Also, masturbating during your period can help to make it shorter, while also relieving cramping and discomfort. Most hormonal contraceptive methods, such as birth control pills, will give you a steady cycle, while reducing the amount of time that each period lasts.
If a woman is interested in completely stopping her period, there are several options available. First of all, there are brands of birth control pills that can be taken for months at a time without having a period. The most popular version of this type of pill is Seasonale; but a health care provider will be able to prescribe generic brands as well. Another option is using a low-dose or progestin only birth control method, such as Implanon or Depro-Provera. Although there are no guarantees that your period will disappear completely, menstruation is usually very minimal on this type of birth control, and it often becomes nonexistent. Keep in mind that these methods only temporarily eliminate your period, and once you stop taking the birth control, your cycle will regulate again. We recommend seeing a doctor to go over the various options. This allows each woman to decide which method would be best for her.
How Are Sexual Activity and the Menstrual Cycle Related?
Sometimes people are curious about the ways that menstruation might either inhibit or enhance sexual activity, and/or whether or not sexual activity is possible during menstruation. While some women find that they are more sexually excited during their menstrual periods, this is not true for most women; and in fact there is considerable variability in women's sex drives across the span of the menstrual cycle. The relationship between female sex drive and menstruation is a popular area of research, and yet there have not been conclusive findings about when women are most sexually excited.
Some evidence suggests that women are more sexually excited during the time of ovulation, which is the most fertile phase of the menstrual cycle: It is the time at which the ovary releases an egg - about 14 days before the start of the next menstrual period. At this time, hormone levels of estrogen and testosterone are at their highest peak of the cycle, and it is this surge of hormones that may lead many women to report higher interest in - and frequency of - sexual activity. From an evolutionary standpoint, this finding seems to make sense, since an increased sex drive at the time of ovulation would promote the chances for conception and reproduction.
However, many women feel most sexually excited just before, during, or just after their period, which could possibly be attributed to varying social, cultural, and psychological factors. For some females, menstruation is a time when they may not care to engage in sexual activity for reasons such as cleanliness or discomfort. Consequently, a woman may feel more excited right before her period, in anticipation of the upcoming period of sexual inactivity, or especially interested just after, having not engaged in sexual activity for a time. Along this same line of thought, people have speculated that when women are sexually excited during menstruation, it is because the time of sexual inactivity that often accompanies their period makes them desire or miss being sexually active even more so than normal.
It is still up for debate whether a woman's sexual excitement is most influenced by hormone levels, psychological processes, or other factors. Although there are certain times during the cycle when a woman may be more likely to engage in sexual activity, it is ultimately individual preference that determines when a woman feels most sexually excited. It is crucial to keep in mind that even though pregnancy is least likely to happen when a woman is menstruating, it is still possible; and this is why a form of contraception should always be used. Additional information on this topic can be found by clicking here.
A second issue concerning sexual activity and menstruation is the confusion between menstrual bleeding and bleeding for other reasons, such as rough manual stimulation or intercourse. Sometimes people are puzzled as to which type of bleeding they are experiencing, but there a few things to keep in mind. Bleeding from aggressive sexually excited or vigorous coitus usually occurs either directly or very soon after the episode. For example, it is unlikely that a woman who was roughly stimulated will only begin to see blood 2-3 days later. This type of blood is usually a brighter red, as compared with menstrual blood (which can be darkish red or even brown, depending on the woman and how heavy her flow tends to be). The sooner blood leaves the body, the brighter in color it is. Conversely, blood that stays inside the body longer can become a darker color. To avoid bleeding from sexual activity, women should encourage their partner to be very gentle, use sufficient lubrication, and do any necessary nail trimming to avoid scratching the sensitive vaginal tissue.
How Are Wight and the Menstrual Cycle Related?
Sudden changes in a woman's body, including changes in diet, exercise, weight and stress, may lead to changes in her menstrual cycle. If a woman has a variation in her normal diet and/or exercise, and then added stress on top of that, she might miss her period, get it early, or get it for longer. Typically, weight loss can cause the menstrual flow to lighten; however, fluctuations from cycle to cycle are normal throughout a woman's life. Weight gain is one of the symptoms of Premenstrual Syndrome (PMS) as defined by the Food and Drug Administration. This type of weight gain - sometimes referred to as "bloating" - usually occurs during the second half of the menstrual cycle (14 days or more after the first day of the period), and is absent for about 7 days after a menstrual period ends (during the first half of the menstrual cycle). It is also normal for women to gain a little weight as they grow older, especially after menopause. Maintaining a weight that is within the Body Mass Index (calculate you BMI here) via exercise and proper diet can not only help women maintain a positive body image, but keep her body, mind and menstrual cycle healthy and regular as well.
Related Articles
For information on menstrual difficulties, such as PMS, Click here.
For diagrams and definitions of the female anatomy, Click here.
To look at Questions and Answers about the menstrual cycle, Click here.
References
Food and Drug Administration : MedlinePlus Medical Encyclopedia