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CHAPTER 2

The Vagina

THE VAGINA IS A FIBROMUSCULAR TUBE that connects the vulva with the cervix. I realize this is the least sexy way to describe something that brings so much pleasure. Personally, I’d love to use a different term, as vagina means “sheath” in Latin, and I hate having female anatomy defined in terms of how it fits with a penis. Medically, the vagina starts at the hymen, so just inside the vestibule.

Why Do We Even Have a Hymen?

Evolutionary biologists have not been able to answer this question.

Some experts have postulated that a hymen may once have served to prove to a male mate that he wouldn’t be raising another man’s child, but there are several reasons why that seems improbable and ridiculously patriarchal. The hymen can tear from physical activity, and approximately 50 percent of teens who report sexual activity still have an intact hymen, meaning it is a highly unreliable “virginity indicator.” This “preserving purity” theory also implies that, evolutionarily speaking, only the first child has value, but for most of human history 30–50 percent of newborns did not survive their first year. It makes no sense to invest a supposedly precious biological resource for a sexual encounter that may not provide a child who lives—or even produce a child at all.

Another proposed theory is that the hymen evolved to make first sex painful so women would only have sex with a “bonded” male partner. However, it’s pretty clear that for the majority of women, their sexual debut is not painful enough that they are going to hold out for some hypothetical Mr. Right. If it hurt that much, we wouldn’t have so many teen pregnancies. Also, if the evolutionary goal was to keep the first sex disappointing enough that women wouldn’t bother to look elsewhere and hence stay with their “first man,” it seems counterproductive to have such an amazing organ as the clitoris be fully functional early in the reproductive years.

My theory is the hymen was at one point in human history a physical barrier for protection. Before puberty, the mucosa (skin) of the vagina is very sensitive to irritants. If a prepubertal girl gets even a small amount of dirt in her vagina, the dirt can cause a profuse inflammatory reaction. Estrogen, fat pads in the mons and labia majora, pubic hair, and labia minora—essentially all of the protective mechanisms for the lower vagina—don’t develop until puberty. So I believe the hymen was a prepuberty physical barrier against dirt and debris. As we evolved and began to walk upright, physically taking the vaginal opening farther away from dirt, the need for a physical barrier for the lower vagina lessened, and evolution became less invested in a rigid, physically protective hymen. This would explain why we now have so many variations in hymen shape: it is simply no longer biologically important.

In a fetus, the vagina starts as a solid tube. The cells from the inside gradually disappear—this proceeds from top (the cervix) to bottom. Any remnants that remain at the lower part of the vagina are the hymen, which can be a ring, crescent shaped, have holes, or even be absent altogether. Sometimes larger portions of cells are left behind, which can lead to a band of vaginal tissue that runs horizontally or vertically. This band is called a septum. A septum can be flimsy and break easily with a tampon or penetration during sex, but it can also be very thick; rarely, it can even obstruct the vagina. The presence of a septum should be considered for any teen who has not had a period by the age of sixteen, any women who is unable to insert a tampon, fingers, a penis, or have a speculum exam due to pain, and any woman who has a feeling of an obstruction with vaginal penetration.

Vagina: The Basics

The vagina is lined with specialized skin called mucosa. The mucosa is arranged in accordion-like folds or ridges called rugae—some women may perceive these as “bumps” or a roughness. The best visual for rugae is a king-sized fitted sheet on a queen-sized bed.

The mucosa sits atop a layer of smooth muscle, which is technically the outer wall of the vagina. Smooth muscle is a type of muscle not under voluntary control (your gut is also made of smooth muscle). While not all the functions of the vaginal smooth muscle are well known, it is believed it moves blood and vaginal discharge towards the vaginal opening. If the muscle contractions become uncoordinated or spasm excessively, this can cause pain. There is data that suggests that some women who have painful periods have more spasms or uncoordinated activity of their vaginal smooth muscle.

The rugae and smooth muscle allow the vagina to be collapsed at rest with the walls touching, keeping air out, and then to stretch for penetration or for a vaginal delivery. Everyone (okay, the patriarchy) seems very impressed with the ability of a penis to grow, but the few centimeters of change that a penis can muster up pales in comparison with the vagina’s ability to stretch.

The vaginal smooth muscle is surrounded by a network of blood vessels. The rich blood flow is one of the reasons the vagina typically heals well after injury.

Vaginal length can vary significantly. The back wall (closer to the rectum) is longer and can range from 5.1 to 14.4 cm, and the front wall ranges from 4.4 to 8.4 cm. Your body size and shape are not predictive of your vaginal length. The vagina gets wider as you move from the vaginal opening towards the cervix.

The pelvic floor

The pelvic floor muscles (PFM) are two layers of muscles that wrap around the vagina and the vaginal opening. These muscles provide structural support for organs, assist with continence (bladder and bowel), contract during orgasm, and also help with stability of your core and posture. On average, the pelvic floor muscles contract 3–15 times during an orgasm. We know this because there have been studies where women have stimulated themselves to orgasm in a highly monitored setting. (I always wonder how people get funding for these kinds of studies!)

Image 3: Pelvic floor muscles. ILLUSTRATION BY LISA A. CLARK, MA, CMI.

Image 4: Female pelvic floor (sagittal view). ILLUSTRATION BY LISA A. CLARK, MA, CMI.

The superficial layer is directly beneath the skin of the vulva and is made of three muscles: ischiocavernosus, bulbospongiosus, and superficial transverse perineal. The point where the superficial transverse perineal, bulbospongiosus, and the anal sphincter come together is called the perineal body.

The deeper layer of muscles extends from the pubic bone from front to back, out to the hips, and back to the coccyx (tailbone), like a hammock. There are openings for the urethra, vagina, and rectum. This deeper layer, called the levator ani, is a made up of three muscles: the puborectalis, pubococcygeus, and the iliococcygeus.

The muscles in your pelvic floor are not typically in your conscious control—you don’t think about emptying your bladder or bowel or about having an orgasm, you just do. Once we get enough motor and sensory control, we train the bladder and bowel to work relatively independently, like a computer program that runs in the background. Evolutionarily speaking, these activities were likely off-loaded from the consciousness because if we had to be constantly aware of regulating bladder and bowel function, we would never have crawled out of the swamp!

Weakness or tearing of the pelvic floor, most commonly caused by childbirth, can contribute to incontinence (both bladder and bowel) and pelvic organ prolapse (descending of the pelvic organs and structures). If the pelvic floor becomes too tight, the resulting muscle spasm can lead to pain with sex and pelvic pain.

The vaginal mucosa

The mucosa (skin) of the vagina is about twenty-eight cell layers thick. Like the vulva, there is a layer of basal cells constantly producing new cells. Unlike in the vulva, the cells of the vagina are filled with glycogen, a storage sugar. They also have much less keratin than the vulva cells, making the surface of the vagina slightly less waterproof than the vulva. This allows a small amount of fluid to leave the bloodstream and leak between the cells of the vagina to become part of the vaginal discharge. This fluid is called transudate. The reduced waterproofing also means some substances can be absorbed from the vagina into the bloodstream.

The vaginal mucosa turns over much faster than the vulvar skin—a new layer is produced every ninety-six hours. There are several biological reasons:

• FRICTION: No matter how gentle you are with a finger, toy, tongue, or penis, friction will rub off the top layer of cells, and this needs to be repaired quickly. If heterosexual sex led to prolonged internal injury, that would dramatically affect our ability to procreate.

• NUTRITION FOR THE ECOSYSTEM: The surface layer of cells sheds approximately every four hours for a woman of reproductive age. These dead cells are filled with the storage sugar glycogen (made of thousands of glucose molecules), which feeds the bacteria that keeps the vagina healthy. Up to 3 percent of vaginal secretions are glycogen.

• CONFUSING THE BAD BACTERIA: The dead cells floating in the vagina work like a decoy. They are the first cells encountered by pathogenic (potentially harmful) bacteria. If this bacteria attaches to these free-floating cells, it gets flushed out as part of the vaginal discharge.

Image 5: Hand holding pad with discharge. ILLUSTRATION BY LISA A. CLARK, MA, CMI.

Vaginal ecosystem

The vagina typically produces 1–3 ml of discharge in twenty-four hours, but up to 4 ml has been reported as normal. For perspective, 4 ml is a completely soaked mini pad, and the image below contains a very normal amount—2 ml.

Based on my anecdotal experience, and from what I hear from colleagues around the country, more and more women erroneously believe that any vaginal discharge is abnormal. I don’t know if this is because mainstream porn frequently looks dry, women don’t talk much about their discharge, more women are removing all their pubic hair and so discharge that would normally be trapped now appears on underwear, or the fact that there are shelves of products in drugstores designed to “tame” a healthy, wet vagina.

Vaginal discharge is made of secretions from the cervix, the glands at the vaginal opening (Bartholin’s and Skene’s), various substances made by the healthy bacteria, cells that have been shed from the vaginal surface, and a small amount of transudate (fluid that leaks across from the bloodstream).

One of the most well-known bacteria in the vagina is the Lactobacillus species (spp.), often referred to as lactobacilli. These are healthy bacteria that protect the vagina. The lactobacilli produce lactic acid, which keeps the vaginal pH between 3.5 and 4.5 (acidic), making it harder for many bacteria and viruses to thrive. Lactobacilli also make proteins called bacteriocins that kill or inhibit the growth of pathogenic (harmful) bacteria—think of bacteriocins like homemade antibiotics. Lactobacilli bind to the mucosal (skin) cells in the vagina, preventing other bacteria from binding. Lactobacilli also produce hydrogen peroxide, which we used to believe had a role in vaginal defense mechanisms (that theory has fallen out of favor).

There are many different species of lactobacilli. The four main ones in terms of the vagina are L. crispatus, L. jensenii, L. iners, and L. gasseri. We are now only beginning to understand the full role of the different lactobacilli species, and so what today we think we know could change. For example, when I was in training everyone thought L. acidophilus was most common, but that was because it was one of the only types of lactobacilli that could be grown easily in a lab. With the advent of DNA technology, we have been able to get a better evaluation of the vaginal microbiome because we don’t have to coax bacteria to grow. We currently believe L. iners is the most prevalent species; 84 percent of women have this bacteria, and it dominates the vaginal microbiome for 34 percent of women. Comparatively, L. acidophilus likely has a minor role, if it even has any at all.

Each woman has one of five community states of vaginal bacteria. Four are dominated by Lactobacillus spp. (73 percent of women); the remaining 27 percent have few lactobacilli and instead have a diverse collection of other bacteria. There are many factors that go into the vaginal bacteria communities, and it is likely a complex combination of genetics and environment. White and Asian women are more likely to have lactobacilli-dominant vaginal communities, whereas approximately 40 percent of African American and Hispanic women have other, non-lactobacilli bacterial communities. The more lactobacilli, the more acidic the vaginal pH, so women who have non-lactobacilli-dominant communities may have a slightly elevated vaginal pH (in the 4.7–5.0 range).

This does not mean that those 40 percent of African American and Hispanic women have unhealthy vaginal bacteria; rather, this is a normal variant. We are only beginning to understand the vaginal microbiome, and many factors besides lactobacilli go into vaginal health.

Vaginal pH increases during menses due to the blood itself, which has a pH of 7.35. Blood also binds lactobacilli, so lactobacilli levels are reduced with bleeding. This is one explanation for why women are most susceptible to infections at the end of their menstrual periods, as they have the lowest counts of good bacteria as well as a higher pH. In addition, blood is also a good medium for bacterial growth.

SHOULD I GET MY VAGINAL MICROBIOME TESTED? There is at least one test on the market that allows you to assess some of the bacteria in your microbiome and, given the expansion of the at-home medical-testing market, we can likely expect more. Given what we currently know about the vaginal microbiome, there are a few issues with this testing. The first is that your microbiome can fluctuate from day to day for a variety of reasons—it can even be different in the morning and the evening of one day. A single snapshot, or even three snapshots on different days, is not very helpful. If I took a picture of your hair at 4 P.M. one day, that would not be representative of how your hair looks day to day, nor would it tell me how to wash your hair or what hair-care products to choose.

Another issue with home testing is worry. We know that some women normally have a healthy microbiome with low levels of lactobacilli. A home test evaluating lactobacilli might erroneously identify these women as having an abnormal microbiome and cause worry.

Finally, we have no idea how to use information from home microbiome testing and no way to replace or augment the microbiome. One day these tests may be useful, but as of today, in 2019, they are not.

BOTTOM LINE

• The folds in the vagina are called rugae.

• The length of the vagina is not related to overall size and body shape.

• Vaginal discharge is typically 1–3 ml a day.

• The vagina has a lot of sugar in the form of glycogen to feed the good bacteria (see chapter 7 for more on food and your vagina).

• There are five different communities of vaginal bacteria.