should have two fallopian tubes, one near each ovary. Tubes are kind of like a pickup bar — a place where sperm and egg should meet and, it is hoped, go on to create something bigger and better: a baby! When an egg is released from the ovary, little projections called fimbriae on the end of the tube move back and forth to “entice” the egg into the tube. Once in the fallopian tube, the egg needs a few days to shimmy down to the uterus. One hopes along the way it meets Mr. Sperm and fertilizes, thereby transforming into an embryo by the time it reaches the uterus. Damaged tubes, usually damaged from infection but sometimes from endometriosis or surgery, are a very common cause of infertility. We talk about this in depth in Chapter 11.
The breasts
Breasts aren’t necessary for getting pregnant; women who have had breasts removed can get pregnant. The normal number of breasts, of course, is two. Nipples are a different matter. As many as 1 in 20 people have more than two nipples. The extras may be nothing more than reddish brown, rough pieces of skin, often found in line with the main nipples. Check yourself out!
Controlling your hormones
You can have all the reproductive organs you need, all in perfect order, and still have no chance of getting pregnant. You can’t get pregnant unless your organs are all synchronized to produce an egg and prepare a proper “landing spot” for it in the uterus at the proper time. What you need to orchestrate the process are hormones, which are chemical substances released from one part of the body that cause a reaction in another part of the body.
The three female hormone-control systems that work together to orchestrate your menstrual cycle are
The hypothalamus: The small structure in the middle of the brain that regulates the nervous and endocrine systems, as well as body weight and temperature.
The pituitary: An endocrine gland at the base of the brain below the hypothalamus that secretes several hormones, including follicle stimulating hormone (FSH) and luteinizing hormone (LH), which are critical for reproduction. The pituitary gland used to be called the “master gland” as it plays a large role in controlling functions of the endocrine systems, adrenal glands, ovaries, and testes.
The ovary: The female reproductive organ that produces estrogen, progesterone, and eggs.
These three hormone systems work together in a feedback system called the hypothalamus-pituitary-ovarian axis, which simply means that they function together to produce a seamless masterpiece — your menstrual cycle.
The main female hormones are:
Estrogen (E2)
Luteinizing hormone (LH)
Follicle-stimulating hormone (FSH)
Progesterone (P4)
In Sync: How Female Reproductive Parts Work Together
All the components of your reproductive tract — the vagina, uterus, ovaries, fallopian tubes, and the glands that orchestrate your hormones — have to work together perfectly for you to be able to get pregnant. (Yes, you need sperm, too, but we get to that in a later section, “Hanging Out with the Guys.”)
Although your menstrual cycle seems simple enough, a lot of things, unfortunately, can go wrong. We not only address how your cycle works but also how it may not work in the next few sections.
Taking a spin on the menstrual cycle
The hormone-secreting systems work to create your menstrual cycle like this:
1 Menstrual Phase: During menstruation, the old uterine lining breaks down and passes through the vagina as menstrual flow. This process takes three to seven days and is commonly called a “period.”
2 Follicular/Proliferative Phase: On Day 1 of bleeding, the pituitary gland, under influence from the hypothalamus, releases follicle-stimulating hormone (FSH). The rising FSH levels cause the ovaries to rescue the 10 to 20 remaining follicles, called antral follicles, which begin to grow. The cells surrounding each egg secrete a liquid, forming a follicle, a fluid-filled sac. Each follicle contains one immature egg. During the follicular phase, one follicle continues to develop, and the others die. In the ovary, the one egg-containing follicle is growing (in response to FSH and luteinizing hormone (LH), which is also produced by the pituitary), and this growing follicle begins producing estrogen. The estrogen produced by the ovary causes the uterine lining to thicken or proliferate. This is called the proliferative phase of the uterus. The follicular phase and the proliferative phase occur in the first half of the menstrual cycle. One refers to what’s happening in the ovary (follicular phase), and the other refers to what’s happening in the uterus (proliferative phase).One follicle becomes dominant, growing faster than the others. As the dominant follicle grows, it produces more estrogen, which also increases the lining of the uterus. The amount of FSH released decreases, and the smaller follicles stop growing and are reabsorbed.A large amount of LH, called an LH surge, is released from the pituitary gland as the estrogen rises. This makes the egg inside the dominant follicle mature.
3 Ovulation: The follicleopens; the egg is released (ovulation) and is picked up by one of the fallopian tubes. If the egg is joined by sperm, it will continue to travel through the fallopian tube to the uterus. The uterine lining has now developed enough to support embryo implantation, and the endometrial glands of the uterine lining secrete proteins that help guide the embryo to the correct spot.
4 Luteal phase: The leftover part of the follicle, now called the corpus luteum, produces progesterone and some estrogen, which help an embryo implant. If you are not pregnant, the corpus luteum collapses, progesterone and estrogen levels decline, the uterine lining begins to break down, and menstruation begins roughly two weeks after ovulation.
Recognizing the importance of regular periods
Do your periods always come every 28 days like clockwork? If they do, you’re a rarity; only one in ten women fall into what we’ve been conditioned to think of as a “normal” menstrual pattern. Most women have cycles 25 to 31 days apart.
When your doctor asks you how long your cycles are, he’s asking how many days are between Day 1 of one period and Day 1 of the next period. When he asks how long your period is, he’s asking how many days you bleed. Day 1 of your period is the first day of normal (for you) flow, not the day when you have light or irregular spotting before your period starts.
