Science Sunday: This is for all the peeps who failed human biology 101
If you live in the United States, I’m sure you are aware of the highly offensive and retrograde debate on contraception. You are also probably heard about how asshat Rush Limbaugh called Sandra Fluke, a Georgetown law student, a slut for daring to voice favorable opinions about birth control. As pointed out by Rachel Maddow (relevant video beings around 7:00 minutes), Limbaugh seems to think that a woman must use contraception every time she has sex.
Uh…I think there might be some misinformation here.
So I thought it might be a good idea to write a little primer on women’s reproduction and how contraception works.
Female Human Reproductive Biology 101
First, let’s start out with some definitions.
- ovary: produces egg cells
- uterus: organ in a female where the baby grows
- cervix: the narrow lower or outer end of the uterus
- fallopian tubes: carries the ova to the uterus
- ova: female egg cell
- ovulation: the egg is released from the ovary
- conception: when egg is fertilized by the sperm
- pregnancy: begins when the fertilized egg implants in the uterine wall
- menstruation: periodic shedding of the uterine lining
- embryo: fertilized egg
How’re we doing so far? Keeping up? Good. Let’s move on.
You know about a period, right? You’ve probably used it to dismiss some skirt you slapped on the bottom. But did you know that a period is part of a woman’s menstrual cycle? It is! You see, each month a woman’s body prepares to be pregnant by going through a cycle of hormonal activity. Menstruation is just the most visible part of this cycle, but there are three distinct parts: the follicular phase, the ovulatory phase, and the luteal phase. Let’s take them one by one.
The Follicular Phase
This phase is starts on the first day of the cycle and typically lasts about two weeks. During this phase, a follicle stimulating hormone (FSH) and a luteinizing hormone (LH) travel from the brain to the ovaries and cause the growth of 15 to 20 eggs in the ovaries, each one in its own follicle. These hormones also trigger the body to produce more estrogen, and, as estrogen levels rise, it stops production of the FSH. Eventually, one follicle will become dominant and mature, which will result in the suppression and death of the other follicles. Estrogen will continue to be produced by the dominant follicle.
The Ovulatory Phase
Remember all that estrogen being produced by that dominant follicle? Well, the rise in estrogen causes a surge in luteinizing hormone, which in turn cases the egg to be released from the ovary. (Remember “ovulation” from our definitions?) This egg is then snatched up by finger-like projections at the end of the fallopian tube. Elsewhere in the female reproductive system, the cervix is getting all covered in mucus. If a lady has sex with a guy at this point in the cycle, the mucus will capture the sperm, nourish it, and help it on its way.
The Luteal Phase
This phase starts right after ovulation. The follicle (Remember, where the egg came from?), newly empty, develops into something new: the corpus luteum. The corpus luteum secretes progesterone, which prepares the uterus to be a cushy place for a fertilized egg to settle. If sex occurs and the egg is fertilized, the embryo will travel through the fallopian tube, divide into a ball of cells, and implant in the uterus, and a pregnancy begins. It usually takes about 3-4 days for the embryo to reach the uterus, and it floats around the uterus for an additional 2-3 days. But not all embryos implant. Up to half may not. (Do you see now why “personhood” laws are so scientifically unsound?)
If the egg is not fertilized, it won’t implant and it will pass right on through. The lining of the uterus will then break down and shed. (You know. That time of the month. Amirite?) Then the cycle beings again.
It’s pretty simple, right? Twenty-eight days. One egg. And it’s all controlled by hormones. But with the human-made miracle of modern medicine, we can now control our own fertility.
Hormonal birth control prevents pregnancy by harnessing the power of hormones, specifically estrogen and progestin. These hormones prevent the ovaries from releasing eggs, by thickening the cervical mucus so much that sperm can’t get through, and by thinning the uterine lining. The latter is thought to prevent pregnancy by keeping a fertilized egg from implanting.
Inter-uterine devices, or IUDs, work differently. These affect the way the sperm move and prevent sperm and egg from meeting. Some IUDs use progestin, which prevents ovulation and thickens cervical mucus.
For either IUDs or hormonal birth control, you don’t need to use one every time you have sex. IUDs can be used for 10 years, and birth control pills only require that you take one a day. It doesn’t matter how often you have sex. Just the one will do.
One thing you should know about birth control, as opposed to RU-486, does not terminate a pregnancy. Pregnancy, as you will remember from our definitions section, is when the embryo implants in the uterine wall. Contraception, as the name suggests, prevents a pregnancy from even happening. Contraception, either hormonal or not, are not abortifacients. They do not cause an abortion, and lumping them together is not scientifically accurate.
Almost every single woman of child-bearing age in the United States has used some form of birth control. And, of course, there are a million different health reasons why a woman would want to regulate her cycle, but those are out of the scope of this post. Suffice it to say that this is an issue that I am certain almost all of us will have to deal with at some point, and it’s something we all need to understand, regardless of whether or not you have a uterus.
Featured image credit: Wikipedia