“Human Sexual Response” Summary - Female External Genital Response
Welcome to the third installment of Human Sexual Response summaries. I read this book years ago and have gone back to it many times since. However, I have never written in detail about it for the blog, which is a shame because this is a fundamental work of physiological orgasm research. Plus, I think summarizing these helps me understand and retain the research information better.
When I go beyond a basic summary and express my personal opinions or information outside the text, I will note that specifically, often in brackets like these [ME: …].
Masters, William and Virginia Johnson. Human Sexual Response. Little, Brown, and Company, 1966.
SECTION 2 - FEMALE SEXUAL REPSONSE
CHAPTER 4 -FEMALE EXTERNAL GENITALIA: Anatomy and Physiology
This will be a discussion of how physical sexual arousal and orgasm affect the labia majora (outer lips - aka the flesh mounds covering the genitals that have the pubic hair on the outside), the labia minora (inner lips - aka the fleshy, not hairy sensitive tissue between the outer lips that can be quite varied in color, shape, and symmetry amongst women), and Bartholin’s Gland (2 glands that sit on either side of the vaginal hole, towards the butt - if you look close, it might look like a tiny hole or dent, but most people wouldn’t even notice them there.)
[ME: I want to note that M&J’s descriptions of color changes in their work are biased towards white people (as most but not all their participants were white - for instance only 11 black couples were included in this study). So, when they are using specific colors to describe changes, keep that bias in mind and try to focus on the change of color and not necessarily the specific colors they describe, as there could be subtle differences amongst different skin tones]
Figure 4-1 from Human Sexual Response (1966) By William H. Masters and Virginia E. Johnson
Labia Majora (outer lips)
When unstimulated the 2 outer lips often meet in the middle of the body and totally or partially cover the vaginal hole, pee hole, and inner lips - providing “positive protection” (p38) for those inner structures. There is variety, though, and there is also some overall differences in how the inner and outer lips react sexually amongst women who have vs. women who have not given birth. So, M&J will consider women that have not given birth (nulliparous) and also women that have given birth to more than 1 baby (multiparous) when discussing changes in labia during the sexual response cycle.
In women that have not given birth
In the Excitement phase, the outer lips thin out and flatten, in a somewhat upward and outward direction that sort of opens them up. This is usually completed in late Excitement or early Plateau phase
M&J say this outward flattening could be a result of the rapid swelling of the inner lips and lower part of the vaginal canal. However, they also ponder if it may be “an involuntary neurophysiological attempt to remove any exterior impediment to the anticipated mounting process.” (p39) [ME: aka they are saying that this labia opening effect has evolved this way as a means to making sure the dick finds the hole with no barriers. I mean, maybe in a way, but how much barriers is this process really even eliminating? Generally, one should be careful with putting meaning onto how/why the body does what it does. One might let their bias get too involved, and M&J are pretty biased and a bit obsessed with connecting arousal to reproductive intercourse, and that might not be the best way to scientifically investigate this]
There aren’t really any changes in the late plateau or orgasm phases
The labia majora will return to pre arousal conditions during the resolutions phase. This will likely happen rapidly if an orgasm occurred and more slowly if there were plateau level arousal but no orgasm.
If in excitement or plateau for long periods of time, the labia majora may become “severely engorged with venous blood and sometimes even develop edema” (p40) [Me: Edema is basically kinda nastier swelling - and I’m gonna say, just for fun and because I like flipping the script, it’s kind like lady-blue-balls; or one might say blue lips]
In women after more than one birth (particularly ones with labial varicosities - aka varicose veins in the labia that can be common during pregnancies)
Instead of flattening, it may become markedly swollen with venous blood. “Occasionally, during an extended plateau phase, a two- to threefold increase in labial diameter has been demonstrated.” (p40)
If this type of swelling occurs, there is no flattening or elevation of the labia. “They hang pendulous and swollen as a partial curtain to the vaginal outlet.” (p40) There is, however, a slight lateral movement away from the midline so it doesn’t obstruct entrance to the vaginal hole. [ME: Which they phrase as it does not “interfere with the normal mounting process.” (p40)]
“In fact, a restricted but discernible mounting invitation still occurs as an involuntary response to effective sexual stimulation regardless of the degree of multiparity of the individual.” (p40) [ME: AKA no matter how many kids a person birthed, the vulva still opens up a bit when they become physically aroused. Also, I know ‘mounting invitation’ is a phrase used in the sciences related to mating, but I’m not sure the slight spreading of the aroused human vulva could be categorized as a ‘mounting invitation’ in quite the same way a female baboon’s genital changes might be categorized as ‘mounting invitation’…and even how exactly the female baboon’s genital changes are involved in the ‘mounting invitation’ is probably more complicated than we might realize.]
If there is plateau level arousal with no orgasm, the swelling could stick around for up to 3 hours. The more history of varicose veins in the labia majora, the longer it might be. If an orgasm occurs, it will go back to pre-excitement levels much quicker.
Labia Minora (inner lips)
“Aside from changes in the clitoris, the most definitive changes that develop in the external genitalia during a complete cycle of sexual response appear in the labia minora.” (p40)
Excitement Phase
In both females that have and have not birthed children, the inner lips will increase markedly in size (at least 2x sometime up to 3x in diameter by the time plateau phase is reached) and deepen slightly in color.
This inner lip swelling might be part of the reason that the outer lips spread more open
The swelling also “adds at least 1 cm. of the clinical length to the vaginal barrel” (p41) on all sides of the vagina except the vaginal wall in the back (the wall towards the butt).
Plateau Phase - Vivid inner lip color change - “one of the most unique but specific physiologic reactions occurring in the human female during the cycle of sexual response.” (p41)
The change in color of the inner lips at plateau level arousal tends to be different for those who have and have not given birth.
For those who haven’t given birth - the color change “ranges from a pink to a bright red color.” (p41)
For those that have given birth - the color “varies from a bright red to a deep wine color” (p41)
As a rule the more varicosity (or varicose veins) in the pelvic area the darker the color change
They say this color change is so specific that the inner lips have been termed the ‘sex skin’ of the sexually responding women…but the term 'sex skin’ shouldn’t be confused with the ‘sex skin’ term referring to the genital changes in rhesus monkeys and apes.
“No premenopausal woman has been observed to reach plateau-phase levels of sexual tension, develop the ‘sex skin’ changes, and then not experience orgasm.” (p41)
This is, of course, assuming that the stimulation that led up to the color change was not abruptly stopped. They have certainly observed many women that have gotten to Plateau levels of arousal but stimulation was stopped and the orgasm did not happen
“Generally, the more brilliant and definitive the color change, the more intense the individual’s response to the particular means of sexual stimulation. It should be emphasized that the development of the sex skin reaction is clinically pathognomonic of impending orgasmic-phase expression. No woman ever has been observed to attain orgasmic release of sexual tensions without first demonstrating the specific minor-labial color changes.” (p.42) [ME: in other words, M&J are being very bold and clear about saying that this distinct color change of the inner lips in the plateau phase of physical sexual arousal is a clear sign/symptom of impending orgasmic release of sexual tension. Although, one couldn’t say it is a marker of orgasm itself, because immediately stopping the stimulation that initiated the color change could stop the orgasmic release…and thus the color change does not necessarily always mean an orgasm occurred as well.]
Resolution Phase
If orgasm happens, the inner lip color change will revert back rapidly “generally within 10 to 15 seconds” (p42)- long before the swelling decreases.
The second stage of color loss (from the slight deepening of color that happened during the excitation phase to the fully unaroused color) is also relatively rapid, but does not occur with uniform regularity and can go through a sort of blotchy appearance.
Bartholin’s Glands (generally unnoticeable glands in the inner lips located at either side of the vaginal hole towards the bottom)
These glands secrete a mucous-y material, and for many years were assumed to be responsible for producing vaginal lubrication, but that is not true. The mucous from Bartholin’s glands is both too small of an amount and also does not secrete until later in the sexual response cycle.
These glands secrete either late in the excitation phase or early in the plateau phase.
For those who have not give birth, there is generally only about 1 drop of mucous secreted. For those who have given birth, it could occasionally be up to 3 drops.
“Under observation, however, there never has been sufficient secretory material produced to accomplish more than minimal lubrication of the vaginal introitus” (p44) [ME: introitus = opening].
“Basic vaginal lubrication develops in a transudation-like reaction through the walls of the vagina. This lubricating material appears early in the excitement phase, a matter of seconds after the onset of any form of sexual stimualtion. This material normally is produced in such copious quantity that the vaginal barrel and outlet are quickly and effectively lubricated” (p42) [ME: they go into more detail about this later in the book, and really identified this ‘origin of lubrication’ clearly and thoroughly for the first time in this study]
Bartholin’s gland activity is most effectively stimulated during long-continued penile-vaginal intercourse, particularly if the female partner maintains late excitement phase or early plateau phase levels of arousal. The secretions stimulated by the penile movement helps lubricate just the entrance of the vaginal opening but does not contribute to the lubrication inside the vagina.
During masturbation, “there frequently is no evidence of Bartholin’s gland secretory activity.” (p44)
In the past, some have thought secretion from Bartholin’s gland reduced acidity in the vagina to promote greater sperm longevity, but there is so little secretion compared to the vaginal lubrications that this theory is “mechanically and chemically impossible.” (p44) There is actually a reduction of vaginal acidity during long periods of sexual stimulation, but it is the result of the vaginal lubrication not Bartholin’s gland secretion.
