After ovulation occurs, the cervical mucus changes dramatically. It becomes thick, cloudy, and sticky, just about impenetrable to sperm trying to pass through the os, or opening of the cervix.
Making the cervical mucus impenetrable to sperm is one of the ways that the birth control pill prevents pregnancy. In addition, those practicing natural family planning can test the quality of the mucus as an indicator of fertility (see Chapter 7 for more information on this technique).
The uterus: It stretches, and stretches, and stretches
The uterus is about the size of a pear, approximately 3 inches long. A muscular organ, the uterus collapses when empty. Its inner cavity is lined by a tissue called the endometrium, which develops and sheds regularly as part of the menstrual cycle. Menstruation occurs in response to ovarian hormones. The uterus is where the baby develops, and one look at a very pregnant woman tells you that the uterus has the ability to stretch incredibly. Luckily for us women, the uterus also goes back to its regular size after the baby has gone out into the big, wide world — or we’d be big and wide forever.
The ovaries and fallopian tubes
Leading into the ovaries are the fallopian tubes, each about 4 inches long (see Figure 3-4). The entrance to these tubes, near the ovary, is fairly large and lined with tiny “fingers,” called fimbria, which help to guide the eggs released by the ovary into one of the tubes.
Illustration by Kathryn Born
FIGURE 3-4: The ovaries and fallopian tubes: Where it all starts.
A woman has two ovaries, each about 1⁄2 to 1 inch long. The woman’s eggs are stored within the ovaries and then released, usually one at a time each month, at a signal given by the pituitary gland. A woman is born with 200,000 eggs, but by the time she reaches puberty, that number has dwindled to 400 or so.
The ovaries also release the female sex hormones, estrogen and progesterone. These hormones trigger the processes needed to create a baby.
As far as the role that estrogen and progesterone play in a woman’s sexual desire, the evidence seems to tilt away from their having much of a role. Women also produce the male sex hormone, testosterone, and this may play somewhat of a role, but the evidence is not conclusive.
The “Men” Words: Menstruation and Menopause
I don’t know why the two biggest female “problems” start with the prefix “men” — probably a Freudian slip on somebody’s part somewhere along the line.
Some women would disagree with my putting the word “problem” in quotes because they really do think of menstruation and menopause as problems. Because I’m basically an optimist, I refuse to categorize them as such.
Menstruation — “Your monthly visitor”
Females, from about the age of 12 to 50, release an egg every 28 days (or thereabouts because not every woman’s cycle is regular). If the egg meets a sperm that was among the 50 million or so placed there by a man during intercourse, a pregnancy begins. This process is called fertilization. A fertilized egg needs an inviting home where it can divide and subdivide until it becomes a baby. The designated nesting area is called the uterus. (Sometimes a fertilized egg winds up someplace else, which can cause serious complications.)
Although the egg doesn’t need much in terms of decorations on the walls, it does need a blood supply. So at the time of the month when a fertilized egg may mosey on by and attach itself, the uterus dolls itself up with plenty of blood in its lining that an egg would find quite dandy. But if no fertilized egg comes along and implants itself in the walls of the uterus, the uterus doesn’t need all that blood, and it sheds it through menstruation.
The advantages of having your period
What can be good about having blood come out of your vagina once a month, you ask?
First, because menstruation is part of the process of making babies — and I love babies — the ability to have a child is definitely worth such a small inconvenience.
Second, ask any woman who has problems with her menstruation, such as irregular bleeding, and you suddenly discover how nice it is to be able to know approximately when “your friend” will next pay a visit so you can prepare yourself.
Third, disruptions in a woman’s cycle can serve as an early warning signal of possible health problems, so be aware of your body’s regular functioning.
The hormones in birth control pills would stop a woman from having her periods, but because the makers of the Pill thought women would find it strange not to have periods, they put placebos in the cycle so women on the Pill do have their periods. However, the FDA has approved a drug, called Seasonale, that continues the estrogen treatment for longer time frames. Women taking these pills have only four periods a year. The FDA also approved the use of continuous progestin that stops a woman’s periods completely, marketed as Lybrel. And Implanon, which is implanted under the skin on the inside of a woman’s upper arm and can be effective for up to three years, will also stop a woman’s periods.
The IUD and DepoProvera shot may also stop your period after a time, though probably not for several months. As far as doctors know, there is no downside to not having your period. When you’re on these birth control medications, you’re not going to get pregnant, so the lining of your uterus doesn’t have to be prepared with an extra blood supply. Because the world of medicine changes regularly, and because you need a prescription for any of these medications, talk to your doctor and see what might be right for you.
PMS
I suppose that I can’t address the topic of menstruation without also addressing premenstrual syndrome (PMS). Does the onset of menstruation affect women in various physical and psychological ways? Yes. The most recent statistic shows that three out of four women have some sort of PMS symptoms. The medical profession has associated many symptoms with PMS, including irritation, depression, changes in appetite, abdominal bloating, breast tenderness, poor concentration, insomnia, crying spells, and swelling of the extremities.