Science Sunday

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

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Mindy is an attorney and Managing Editor of Teen Skepchick. She hates the law and loves stars. You can follow her on Twitter and on Google+.


  1. March 5, 2012 at 5:31 pm —

    Thank you! The ignorance around this subject by *national media figures* is appalling.

    • March 13, 2012 at 7:37 pm —

      @ auroravesper: I know, right?! It's unacceptable. This is 5th grade biology stuff.

  2. March 12, 2012 at 11:52 pm —

    Is it possible, simply possible, that during the time between conception and implantion (whether it's 1 second or one hour or one day) you're already pregnant?
    And, to push your incredulity a little farther, that anything introduced into a woman's body during that time which ultimately prevents implantation is causing an abortion?  You've conveniently defined pregnancy as beginning at implantation which, while serving your premise well, ignores any other legitimate concept.
    I personally couldn't care less what decisions you make about your own body, but chastising others about their sincerely held beliefs while dismissing the basis of their argument, is not-so-subtly dishonest.

    • March 13, 2012 at 12:47 am —

      Mindy hasn't 'conveniently defined' anything. Implantation is, medically speaking, the point at which a pregnancy begins. 

      I personally couldn't care less what decisions you make about your own body.

      Great! Awesome!

      … but chastising others about their sincerely held beliefs while dismissing the basis of their argument, is not-so-subtly dishonest.

      Unfortunately, the people who hold these beliefs so sincerely as they do are also trying their darndest to rob people of basic health care and the right to bodily autonomy. They also hold these beliefs because they are woefully ignorant of science and medicine. Standing back and not criticising somebodies beliefs when they are not only wrong but actively causing harm and injustice is only enabling them.
      If you wish to correct any of the science in this post, feel free to do so. If you wish to correct a definition used in this post, feel free to do so. We welcome it! However, ignoring all of the information in the post and resorting to special pleading to make your (unsubstantiated) case is not. 

  3. March 13, 2012 at 7:56 am —

    Fine. We'll do it your way.
    Case substantiated: "Human development begins at fertilization, the process during which a male gamete or sperm (spermatozoo developmentn) unites with a female gamete or oocyte (ovum) to form a single cell called a zygote. This highly specialized, totipotent cell marked the beginning of each of us as a unique individual." Keith L. Moore, The Developing Human: Clinically Oriented Embryology, 7th edition. Philadelphia, PA: Saunders, 2003. pp. 16, 2.
    What I'm asking, despite your rhetoric, is whether there is any room in your carefully framed argument for a logical opposition.  Not a 'woefully ignorant' medieval belief, not an 'unsubstantiated' opinion.  I'm not offering a direct denial or a special pleading, just asking if your carefully framed argument might have some reasonable, coherent, logical opposition.
    Painting your oppnents as ignorant, backward, harmful deniers of 'justice' makes you seem like a zealot.  Especially when your facts and definitions are so easily disputed.

    • March 13, 2012 at 12:10 pm —

      I would be careful who you quote in these issues. As I think one of the main points of this post was, there is a lot of bad information about reproduction out there being spread by people with ideological agendas. Case and point is Keith L. Moore, the person you quoted above. He has been heavily criticized for twisting his own reasoning to prove the Qur’an. Also I don't see how anyone is opposing "reasonable, coherent, logical opposition." From what I was reading that is encouraged. If you have any such argument please lay it out. Otherwise let the science be the science.

      There are people who are rejecting reality and imposing their ideological views on others causing direct and measurable harm. This is a problem that must be opposed.

      “If anyone can show me, and prove to me, that I am wrong in thought or deed, I will gladly change. I seek the truth, which never yet hurt anybody. It is only persistence in self-delusion and ignorance which does harm.”- Marcus Aurelius

      • March 13, 2012 at 6:41 pm —

        I just picked a random textbook from Amazon to quote.  I couldn't care less what other ideas, whacko or not, the good professor might have.  A stopped clock is correct twice a day, too.
        If you can't see how calling anyone who might oppose your viewpoint "ignorant", "retrograde","misinformed" and "highly offensive" isn't framing your opposition as everything except "reasonable, coherent and logical" then the matriarchal othodoxy has already won the argument.
        "…Rejecting reality"?  Who's rejecting reality?  Now, don't get me wrong, I'm as pro-abortion as the next person, and the last time I checked, abortion on demand is still the law of the land.  In the good ol' US of A a woman can get an abortion anywhere, anytime for any reason – or no reason at all.  No scarlet letter.  No public shaming.  Just get your boyfriend to stop playin' X-Box for five damn minutes, make him take you the ATM and go get it done.  Bing, bang, boom.  On with life.  C'est la vie.  We be 'bortin dem chillens so fas' det it make yer head jest a spinnin'.

        • March 13, 2012 at 6:56 pm —

          @ heywoodjabuzzoff

          A a woman can get an abortion anywhere, anytime for any reason – or no reason at all.

          Not really. Over 80% of counties in the US don't have an abortion provider, which is a real problem because several states have waiting periods and bans on late abortions. Your statement is simply untrue. In addition, abortions dont' come all that cheap, especially if insurance doesn't cover it. Birth control is a much more cost effective way of dealing with unwanted pregnancies. Which, btw, is what this post is about.
          In addition, we should not conflate development with pregnancy. They are two distict phenomenons. For example, we can fertilize ova outside of a uterus, but that is meaningless unless that embryo becomes implanted. It has no hope otherwise. Implantation, or pregnancy, is the significant moment. Birth control does not cause abortion because it does not terminate a pregnancy. It prevents a pregnancy from beginning. I'm not pulling these terms out of thin air. There is no controversy here. A woman does not become pregnant until the embryo implants, which it fails to do much of the time.
          @ carvert: I'm glad you understood the point of the post, which was to provide acctuate information about female reproduction. I find that people, even women, don't really know what's going on. Women aren't supposed to have a sexuality of any kind, and recognizing that we do is important.

          • March 13, 2012 at 7:03 pm

            Mindy misdirects the readers with: "Not really. Over 80% of counties in the US don't have an abortion provider, which is a real problem because several states have waiting periods and bans on late abortions. Your statement is simply untrue.
            According to the Guttmacher Policy Review: "From a medical point of view, however, this reliance on specialist providers has worked out well. Abortion in the United States has an exemplary safety record and involves far less risk than carrying a pregnancy to term. Moreover, the way abortions are provided mirrors the rise of outpatient surgery and the preponderance of specialists, from cardiologists to podiatrists, throughout the U.S. health care system."
            Having an abortion clinic on every corner isn't required in order to provide reasonable, competent, safe abortions to any woman who wants one.  How she funds is her own problem.

  4. March 13, 2012 at 7:13 pm —

    Well, my post was about menstruation and birth control, so the whole abortion convo is entirely off topic. But while abortion in the US is very safe (I never said it wasn't), the fact remains that it is functionally not available to all women all the time. I never said that abortion clinics need to be on every street corner. But driving several hours to an abortion provider, then waiting 3 days (because of mandatory waiting periods) and driving back to have the actual procedure done prohibits many women from getting an abortion they may otherwise desire. It may not be a big problem for middle income people, but for those in the lower income brackets, it is a real problem.
    Now, does anyone have anything to say about the actual post?

  5. March 13, 2012 at 7:17 pm —

    @ Heywood  I don't think she misdirected at all. Infact she answered your statement directly and then moved the conversation back to it's original topic.
    Your first comment was basically, "why don't you accept fertilization as the beginning of pregnancy?" And when you were answered you quoted an author known to misinterpret data. And when you were called on that you changed topic to abortion access.
    Then when Mindy corrected you and steered the talk back to the beginning you acuse HER of misdirecting! Hilarious!

  6. March 13, 2012 at 7:50 pm —

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