Clinical Anatomy 28:355–362 (2015)
REVIEW
Self-Assessment of Anatomy, Sexual Sensitivity, and Function of the Labia and Vagina JUSTINE M. SCHOBER,1,2* NIEVES MARTIN ALGUACIL,2,3 R. SCOTT COOPER,4 DONALD W. PFAFF,2 AND HEINO F.L. MEYER-BAHLBURG5 1
Pediatric Urology, UPMC Hamot, Erie, Pennsylvania Pfaff Laboratory of Neurobiology and Behavior, Rockefeller University, New York, New York 3 Department of Anatomy and Embryology, School of Veterinary Medicine, Universidad Complutense de Madrid, Spain 4 Lake Erie College of Osteopathic Medicine, Erie, Pennsylvania 5 NYS Psychiatric Institute/Department of Psychiatry, College of Physicians and Surgeons of Columbia University, New York, New York 2
Patient perceptions of genital esthetics are motivating requests for plastic surgeries that could change sexual sensitivity. There is little information about the sensitivities of labial and introital sites. The aim of this study is to assess the relationship between sexual sensitivity and self-reported sizes of labial and introital sites. Sixty-two healthy, sexually active, adult women (mean age 37.9, range 21–60) with no history of genital or vaginal surgery gave written consent to participate in this study. A modified version of Self-Assessment of Genital Anatomy and Sexual Function (L-SAGASF-F) was used to assess labial and introital size. Site-specific sensation was rated on Likert scales of 1–5. Anatomical locations were compared for ratings. Of 62 responders, 84% (52) described their labia as “average-sized,” 11% (7) described their labia minora and 13% (8) their labia majora as “large”, and 3% (2) and 5% (3) as “small”. Sexual pleasure ratings were “moderate” (median value: 3.0 for external genitalia and vaginal lumen) or “strong” (median value: 4.0 for the interior vagina). Significantly higher rankings related to the vaginal opening (P 5 0.007). Orgasm intensity for stimulation of the external genitalia progressively increased toward the vaginal opening, from 1.0 to 3.0 (P 5 0.001); vaginal ratings showed a similar progression, from 2.0 at the external luminal margin to 3.0 in the deep interior (P < 0.0001). Orgasm effort scores were intermediate (median: 3.0), uniform throughout the external and internal areas (P 5 0.626). Ratings for labial and introital sensitivity, regardless of self-reported size, were very similar to those at other genital sites for sexual pleasure. Surgical excision of labial and introital structures could modify sexual sensation. Clin. Anat. 28:355–362, 2015. VC 2015 Wiley Periodicals, Inc. Key words: genital and sexual sensitivity; genital anatomy; sexual function; labia; vagina
INTRODUCTION The relationship between vaginal anatomy, sexual sensitivity (the ability of a stimulus to contribute to arousal and/or orgasm), and function are poorly understood by both practitioners and patients. Vaginal anatomy and sexual function have been examined
C V
2015 Wiley Periodicals, Inc.
*Correspondence to: Justine Schober, 333 State Street, Suite 201, Erie, Pennsylvania 16507. E-mail: [email protected] Received 14 November 2014; Accepted 11 December 2014 Published online 12 February 2015 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/ca.22503
27% (17) 11% 62% (39) (7) 5% (3) 90% (54) 2% (1) 3% (2) 95% (41) 5% (2)
Other
using a variety of criteria but correlations with the anatomical features of introital caliber, length, and vulvovaginal atrophy are poor (Weber et al., 1995). The distance between the clitoris and the urethral meatus (CUMD) was measured in an attempt to correlate genital anatomy with orgasm. Bonaparte (1933) and Landis et al. (1940) noted that the shorter the CUMD, the more likely women were to achieve orgasm. Lack of statistical analysis was a criticism until Wallen and Lloyd (2011) analyzed the raw data from both studies and demonstrated a strong inverse relationship between the CUMD and orgasm during intercourse. A lack of personal awareness of the diversity of female genital appearances could underlie choices for cosmetic genital surgery that risk sensory damage (Lloyd et al., 2005). Outcomes of sexual function and satisfaction in adult women can be influenced by the variability of genital structures, the coital capacity of the vagina, pain or sensitivity during sexual activity, aspects of women’s perception of genital cosmesis, and emotional and cultural factors. General cutaneous sensitivity, erotic sensitivity, and orgasmic capacity have important implications for women’s quality of life. In the past, cosmetic genitoplasty has been criticized and debated because it can result in impaired sexual function (Chase, 1996; Diamond and Sigmundson, 1997; Schober, 1998). The nerve density, epithelial qualities, and vascular compartments of the labia minora that contribute to sexual arousal and orgasm are poorly defined. Surgical procedure development, and counseling about surgical risks related to labioplasty, may be based on inadequate information. Data about healthy women and their perceptions of vaginal appearance, coupled with genital-site-specific sensory data, are also sparse. Outcome data after genital cosmetic procedures in adult women who do not have genital development disorders suggest patient satisfaction (Goodman et al., 2010; Iglesia et al., 2013). However, surgeries such as vaginoplasty, labiaplasty, and labia majora augmentation are not without complications, and lack quality studies with long term follow-up (Iglesia et al., 2013). To achieve an objective assessment of the risks and benefits of genitoplasty, a comprehensive and systematic battery of tools is needed to characterize the pre- and postsurgical genitalia. Aspects should include: observable anatomy and perception by the patient, sensory response to systematic tactile and erotic stimulation, and the patient’s sexual experience in real-life erotic situations. The empirical basis for such a battery of assessment tools is incomplete. The present study represents a first step towards these assessments by asking healthy women to rate the sizes of their labia and introitus, and to rate the intensity and effort required to achieve orgasm in terms of stimulation of these sentinel structures.
MATERIALS AND METHODS 38.1 (21–60)
Sep/Div/ Cohabit. Wid Single Graduate Deg Married College*
Marital status (n 5 62) Education (n 5 60) Race (n 5 60) Ethnicity (n 5 43)
Mean age, yrs African (range) Hispanic NonHisp Asian Am White Other HS
50% (31) 15% (9) 10% (6) 24% (15) 2% (1)
Schober et al.
TABLE 1. Respondent Demographics
356
Sample The goal was to recruit a diverse sample of healthy women to establish baseline information on genital
Self-Assessment of Anatomy
357
TABLE 2. Size Perceptions, External Genitalia Area
Indeterminant (“1”)
Small (“2”)
Average (“3”)
Large (“4”)
Very Large (“5”)
Median rating
Total responses
0 0
3% (2) 5% (3)
84% (52) 84% (53)
11% (7) 10% (6)
2% (1) 2% (1)
3.0 3.0
62 63
Labia majora Labia minora
sensitivity. The target population for our convenience sample comprised employees in one department of a community-based teaching hospital in northwestern Pennsylvania. Criteria for inclusion in the study were adult women between the ages of 18 and 60 who were sexually active. Women with a history of genital feminizing surgery or genital/vaginal excision surgery, degenerative neuromuscular pathologies or congenital abnormalities were excluded. No exclusions were made for parity status, sexual orientation, or marital status. All eligible women invited agreed to participate; they constituted a sample of 63 healthy, sexually active, adult women (mean age 38.1, range 21– 60 years) (Table 1). Most were non-Hispanic Caucasians and had one or more years of college education; half were married. The study was approved by the IRB of the study hospital. An instructional cover sheet advised respondents that completion and return of the survey tacitly provided informed consent.
Assessment Several standardized self-reporting questionnaires are currently in use for patient-report-based assessment of sexual function in anatomically normal women (Fisher et al., 2011). Self-Assessment of Genital Anatomy and Sexual Functioning for Females (SAGASF-F), a tool specifically designed to assess patient-perceived outcome of feminizing genitoplasty in terms of appearance, sensitivity, and sexual function, has been piloted (Schober et al., 2004) and its reliability has been established (Meyer-Bahlburg et al., 2006; Schober et al., 2009). All women in the present study were given a slightly shortened version of the SAGASF-F (Schober et al., 2004) to complete at home and to deposit in a box at the hospital, without identifying information. This questionnaire examines many aspects of female genital anatomy, sensitivity, pain/ discomfort, and sexual function. It also includes information on the respondents’ demographics and their reproductive, medical, and sexual history. It includes anatomical graphs that provide a basis for selfassessment including examples of appearance, size, and position of the labia and vagina. In the sections of the SAGASF-F that are pertinent to the present report, the participant reads an introduction designed to help her understand the rating tasks. Thereafter, responses are prompted to assess sexual pleasure, orgasm TABLE 3. Self-Perceptions of the Vagina Size of opening (n 5 62)
Location of opening (n 5 52)
Small: 3% (2) Adequate: 92% (57) Large: 5% (3)
Mid-position: 94% (49) Anal bias: 6% (3)
intensity, and the effort required to achieve orgasm using 5-point Likert scales. For sexual pleasure (and, analogously, for orgasm intensity), respondents were given this prompt: “Sexual touch/stimulation of this area by a partner or yourself. . . has produced (rate 1 through 5): Sexual pleasure—1/none, 2/mild, 3/moderate, 4/strong, 5/very strong.” For orgasm effort, the query was: “If orgasm was achieved, please describe the effort required,” followed by a line with the anchors: 1/very strong, 2/strong, 3/moderate, 4/little, 5/very little.
Data Analysis Statistical analysis utilized SPSS for Windows version 12.0. Based on the outcome of Shapiro-Wilk and Kolmogorov-Smirnov Tests, data were analyzed using nonparametric methods. Friedman Tests and the Mann-Whitney U Test were used to examine differences in ratings for each functional category across anatomical areas. When the outcome reached significance (alpha 5 0.05), Bonferroni-corrected Wilcoxon Rank Sum Tests were used to compare areas pairwise to identify specific areas of differential function/sensitivity. Sample sizes differed among items because not every participant answered all items, and
Fig. 1. Ratings of the intensity of sexual pleasure, from “None” (1) to “Intense/Very Strong” (5). Black horizontal bars represent median values, boxes depict 25th through 75th percentiles, circles denote outliers. Numbers in parenthesis accompanying the axis labels denote mean rank established by the Friedman Test (P < 0.0001). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
358
Schober et al.
Fig. 2. Ratings of the intensity of orgasm, from None (1) to Intense/Very Strong (5). Black horizontal bars represent median values, boxes depict 25th through 75th percentiles, circles denote outliers. Numbers accompanying the axis labels denote mean ranks derived from the Friedman Test (P < 0.0001). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
we did not make estimates when no answer was provided.
lia to the perivaginal area, with no intensity (median value: 1.0) at the labia majora to moderate intensity around the vaginal opening (median value: 3.0). This increase in intensity was also reflected within the vagina, proceeding from mild intensity (median value: 2.0) about the superficial regions to moderate (median value: 3.0) within the deep interior. These global differences were significant (P < 0.0001) with mean ranks increasing in a concentric (peripheral to central) manner (Fig. 2). Posthoc comparisons demonstrated significantly greater intensity for the perivaginal area than the labia minora (P 5 0.004), the shallow vaginal interior than the inner rim (P < 0.0001), and the deep vagina than the perivaginal opening (P 5 0.005). The effort to achieve orgasm (Fig. 3) was perceived as moderate (median value: 3.0) throughout the external genitalia and vagina. For the former, a limited number of individuals rated the effort at the extremes, either “very strong” (1.0) or “very little” (5.0). The Friedman rank test revealed no significant difference in ratings among these areas (P 5 0.626).
Size Effects, External Genitalia The labia minora and labia majora were rated as large or very large by seven (11%) and eight (13%) women, respectively. In order to check whether perceived large labia size was associated with increased erotic sensitivity, we compared these women’s ratings of sexual pleasure and orgasm intensity to those by women with small or averaged-sized labia. The
RESULTS Genital Anatomy Most respondents rated their labia majora and minora as “average-sized” (84% each), 3% and 5%, respectively, as “small,” and 13% and 12% as “large” or “very large” (Table 2), with 98% (60/61) describing the location as “usual.” Of 52 respondents, 94% (49) rated the location of their vaginal opening as “in midposition,” with the remainder noting a location “near the anus (far back).” Ninety-two percent (57/62) indicated that their vaginal openings were “adequate for sexual penetration” (Table 3).
Sexual Pleasure, Orgasm Intensity, and Effort Median ratings for sexual pleasure were “moderate” (3.0) for all areas except the deep interior of the vagina (median rating: 4.0, “strong”; Fig. 1). Mean ranks established by the Friedman Test showed a generalized increase concentrically from the labia majora to the perivaginal opening (P < 0.001; Fig. 1). Posthoc testing revealed that the perivaginal opening was significantly more pleasure-sensitive than the labia majora (P 5 0.007); other areas of the external genitalia were equivalent, as were all regions of the vagina proper. Ratings for orgasm (Fig. 2) demonstrated increasing intensity from the periphery of the external genita-
Fig. 3. Ratings of the effort to attain orgasm, from Very Strong (1) to Very Little (5). Black horizontal bars represent median values, boxes depict 25th through 75th percentiles, circles denote outliers, asterisks indicate extremes. Numbers accompanying the axis labels denote mean ranks derived from the Friedman Test (P 5 0.626). *denotes number of responses. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Self-Assessment of Anatomy
359
TABLE 4. Differences in Median Ratings of Pleasure and Orgasm Intensity Between Women with Large or Very Large Labia and Women with Small or Average-sized Labia Pleasure
Orgasm intensity
Rating category Area
Labia majora
Labia minora
Perivaginal opening
Labia majora Labia minora
20.5 21.0
0 11.0
10.5 12.0
differences were small for the labia majora (Table 4). However, women with (self-reported) large labia minora gave median ratings of sexual pleasure in this area up to 2.0 units higher than the rest of the sample population, and they rated the intensity in the area of the perivaginal opening as either strong or very strong. Because of the small sample size, none of these differences attained conventional significance (P 0.068).
DISCUSSION Authors have listed many sites in the female genitalia as the most sensitive in regard to sexual function. These sites include a controversial neurovascular € fenberg, bundle on the anterior vaginal wall (Gra 1950) [the existence of which was recently corroborated by hematoxylin and eosin staining (Ostrzenski et al., 2014)], the clitoris and labia minora (Kinsey et al., 1953), and the area superior to and directly on the clitoris (Schober et al., 2004, Woodhouse, in
Fig. 4. A: Combined image for color overlays including the ratings for orgasm and sexual sensitivity for the SAGASF F tool as published separately in Schober (2009) (color densities are mathematical conversions of the Likert scale means). B: Color image gradient depiction of
Labia majora 0 0
Labia minora
Perivaginal opening
20.5 21.0
11.0 11.0
press) (Fig. 4A). In addition to direct stimulation of the previously-listed structures, indirect stimulation of genital structures by forces transmitted through the vaginal wall could contribute to orgasm. Wallen and Lloyd proposed that less androgen stimulation in utero resulted in the bulb and the body of the clitoris being packed into a smaller space, pressing them closer to the anterior vaginal wall, allowing for increased capacity for orgasm. MRI studies show that the penis takes on a boomerang shape in “missionary position” (Schultz et al., 1999), possibly to increase contact with the anterior vaginal wall. Studies of orgasm by Singer revealed multiple sites of sexual sensation that differed in the kinds of orgasm they produce (Singer and Singer, 1972). Given the great diversity of findings, there may be an ordered series of stimulus presentations culminating in orgasm. In terms of sexual pleasure and orgasmic sensitivity, two findings emerged from our study. First, there were no significant differences in mean ratings between external genital and internal vaginal sites for any category of sexual sensitivity (sexual pleasure,
sexual pleasure ratings and orgasm intensity ratings, indicating an increase from lateral genital areas to medial vaginal opening. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
360
Schober et al.
orgasmic sensitivity and orgasm effort). Second, the vaginal introitus (the area around the opening of the vagina) was rated as the area requiring the least amount of effort for stimulation to orgasm. The choice of this distal vaginal site might corroborate the locus € fenberg and by of erogenous activity noted by Gra Wallen and Lloyd. It is unclear whether the method of assessment (global self-reporting) in this study, compared to responses to specific experimental stimula€ fenberg, 1950) or self-stimulation (Singer tion (Gra and Singer, 1972), explains why our findings differ from others. Much is known about the differential anatomy of the genitalia, physiological changes in the body related to sexual arousal and orgasm, and sexual behaviors and dysfunctions (Goldstein and Berman, 1998; Heiman, 1998). There are published measurements of the length and transverse diameter of the glans clitoris, the widths of the labia majora and labium minora, and perineal and vaginal lengths in premenopausal and postmenopausal women (Verkauf et al., 1992; Basaran et al., 2008). A wide range of sizes is noted for each measurement, but no statistically significant association has been noted with age, parity, ethnicity, hormone use, or history of sexual activity. In this self-reported study, most women judged their own labia minora, labia majora, and vaginal opening to be average-sized. It is noteworthy that 11% indicated that their labia minora were large or very large, and 13% indicated that their labia majora were large or very large. Their sexual pleasure ratings were higher than those of women who reported average-sized or small labia. This could indicate that women with labial sizes outside the range that could be judged “typical” suffer no adverse effect on sexuality in consequence, but rather increased sensitivity, perhaps because the surface area for contact is larger. Labioplasty typically involves excising, and thus reducing, sexually sensitive labial tissue. It can alter the dermatome. Surgery on any genital structure could modify sensation in that structure by undercutting or excising genital epithelium, which provides terminal innervation. Information about the relationship of female genital sensation to its underlying innervation remains incomplete. Human clitoral innervation has been elucidated in fetal studies (Baskin et al., 1999). Recent studies of the labia minora indicate a higher density of innervation on the introital side (Schober et al., 2010). This study also shows that orgasm intensity increased progressively, from 1.0 to 3.0, as stimulation of the external genitalia proceeded from lateral areas toward the more median vaginal opening (P 5 0.001) (Fig. 4B). Studies from the vertebrate literature form an important basis for understanding human genital sensitivity. In rats, the genital skin stimulation required for lordosis (the reflexive copulatory posture of the female rat) has been mapped in great detail (Kow et al., 1979). Pressure on crucial skin areas initiates the chain of events leading to intromission. Summation of stimuli to a wide area of peri-vaginal skin around the introitus initiates lordosis. Non-cutaneous
stimuli are insufficient: lordosis is never displayed before cutaneous contact (Kow, 1976). Experiments in which somatosensory stimuli were applied to the female skin locations contacted by the male rat revealed a minimally adequate combination that involved flank stimulation followed by pressure on the posterior rump, tail base, and perineum. Here, estradiol significantly facilitated the appearance of the reflex response (Kow and Pfaff, 1973–1974; Pfaff et al., 1977), and progesterone given after estrogen treatment had a significant synergistic effect (Kow et al., 1974). The order of stimulus application was also important. Flank stimulation had to precede (or at least accompany) stimulation of the rump and perineum, followed quickly by perineal pressure. The best response was elicited by quick changes in pressure during the application of this combination of stimuli (Kow, 1976). Gradual applications of pressure were often less effective for eliciting lordosis than rapid fluctuations. Within effective locations on the skin of a female rat, lordosis can be enhanced by increasing any of three factors: stimulus pressure, total area stimulated, and the amount of estrogen (Kow and Pfaff, 1973–1974). As with other vertebrates, these three factors are also likely to be involved in the human sexual response (although the lordosis reflex in the female rat is certainly not a direct homologue of the arousal and orgasm responses in the human female). In human genital sensitivity the tactile response is similar, but not equivalent, to the sexual response. The sensitivity of human genitalia to vibratory and hot/cold sensory inputs has been studied, but never specifically for sexual stimulation (Vardi et al., 2000). € fenberg (1950) suggested an area of Studies by Gra increased sensitivity over the urethra (G-spot) on the anterior vaginal wall. Kinsey et al. (1953) concluded from studies of masturbation that areas of the clitoris and labia minora are most sensitive. Studies of orgasm by Singer and Singer (1972) indicated multiple sites of sexual sensation differing in the kinds of orgasm they produce. Schober et al. (2004) studied healthy adult females with no history of genital surgery, and found less sexual sensitivity in the vagina than the external genitalia, the clitoral area exhibiting the highest sensitivity scores. The sexual sensation values of various genital sites have been considered in different ways (Woodhouse, in press) (Fig.4A). Ultimately, there may be an ordered series of stimulus presentations related to initiation of the arousal circuit. Hence, the external genitalia could make an important contribution to arousal in preparation for penetrative intercourse. The lordosis reflex is the reflexive copulatory posture of the female rat initiated by pressure on perineal skin (Kow et al., 1979). The threshold (milligrams of force) for the pudenal nerve response of the perineal region in female rats was electrically recorded. An ordered path of cutaneous sensitivity was reported, with the most sensitive points in the middle of the receptive field. This study shows that the mean score on each sensitivity indicator (sexual pleasure, orgasm intensity, and orgasm effort) was higher for the labia minora than the labia majora (3.0, 2.13, 3.0) vs. (2.85, 1.95,
Self-Assessment of Anatomy 2.97) (Fig.4B). The similarity in average ratings across the epithelial area tested has neurophysiological implications. All the areas are innervated by the pudendal nerve. Therefore, either the density of innervation must be similar across these areas or, if some of these sub-regions are much more densely innervated than others, the synaptic impact of the more sparsely innervated subregions on the dorsal horn of the lumbar spinal cord must be more powerful than that of the more densely innervated subregions, ensuring the equipotency of stimuli across the pudendal field for enhancing arousal. The location of highsensitivity responses indicated by this survey appears consistent with previous studies of sexual sensitivity in the vertebrate perineum. The distribution of sensitivity responses in our study may correspond to the dermatome that the nerve bundles supply. Because the human sexual response is multifactorial, including a strong cognitive element, sexual stimulation and its resultant response may be very individualized. Observational studies are not impossible and have been documented by Kinsey et al. (1953) and by Masters and Johnson (1966). However, a natural sexual response generally requires a degree of privacy during stimulation, and many individuals and couples are likely to refuse functional evaluation by direct observation. Even if this is not the case, natural observation requires patients’ subjective reports to be incorporated with sensory experiences and feelings, especially in women for whom discrepancies between physiological and subjective erotic responses are well documented (Laan and Everaerd, 1995). Thus, a tool for systematic self-reporting, which is more easily accepted by more people and poses less of a logistical problem than direct testing, is essential for further understanding of the human sexual response. In this respect, a woman’s judgment of her own sensation is the critical variable. Even this is limited by recall bias, particularly in subjects with limited sexual experience. Future studies are needed to elucidate women’s ratings of genital size, their preference for genital appearance, and whether self- perception of atypical genitalia affects sexual functioning adversely. Comparative assessment, if not direct measurement, of genital anatomy by a urologist or gynecologist could be of value.
CONCLUSIONS Evidence-based practice guidelines have not yet been established for labioplasty (Mirzabeigi et al., 2012). Our preliminary findings could have important implications for genitoplastic surgery. First, healthy women who rated their vaginal openings as large or very large did not differ in their ratings of sexual pleasure for this area. This suggests that women may accept a larger vaginal size than is commonly believed, which would facilitate more conservative management of introital tightening. Second, healthy women regard both the labia and the introitus as important for sexual sensation. This provides a strong case against surgical excision of the labia and introital structures and for preserving the important sites for
361
sexual sensation. The diversity of labioplasty techniques complicates outcome studies. However, additional large-sample studies of patients are needed to understand the risks of cosmetic genital surgery.
ACKNOWLEDGMENT The authors have no conflicts of interest or monetary support from any institution or industry to declare.
REFERENCES Basaran M, Kosif R, Bayar U, Civelek B. 2008. Characteristics of external genitalia in pre- and postmenopausal women. Climacteric 11:416–421. Baskin LS, Erol A, Li YW, Liu WH, Kurzrock E, Cunha GR. 1999. Anatomical studies of the human clitoris. J Urol 162:1015–1020. s de la femme. Bulletin de la Bonaparte M. 1933. Les deuxfrigidite te de Sexologie 5:161–170. Socie Chase C. 1996. Re: Measurement of pudendal evoked potentials during feminizing genitoplasty: Technique and applications. J Urol 156:1139–1140. Diamond M, Sigmundson HK. 1997. Sex reassignment at birth. Long-term review and clinical implications. Arch Pediatr Adolesc Med 151:298–304. Fisher TD, Davis CM, Yarber WL, Davis SL. 2011. Handbook of Sexuality-Related Measures. 3rd Ed. New York: Routledge (Taylor and Francis Group). Goldstein I, Berman JR. 1998. Vasculogenic female sexual dysfunction: Vaginal engorgement and clitoral erectile insufficiency syndromes. Int J Impot Res 10(Suppl 2):S84–S90; discussion S98S101. Goodman MP, Placik OJ, Benson RH III, Miklos JR, Moore RD, Jason RA, Matlock DL, Simopoulos AF, Stern BH, Stanton RA, Kolb SE, Gonzalez F. 2010. A large multicenter outcome study of female genital plastic surgery. J Sex Med 7:1565–1577. € fenberg E. 1950. The role of the urethra in female orgasm. Int J Gra Sexol 3:145–148. Heiman JR. 1998. Psychophysiological models of female sexual response. Int J Impot Res 10(Suppl 2):S94–S97; discussion S98-S101. Iglesia CB, Yurteri-Kaplan L, Alinsod R. 2013. Female genital cosmetic surgery: A review of techniques and outcomes. Int Urogynecol J 24:1997–2009. Kinsey AC, Pomeroy WB, Martin CE, Gebhard PH. 1953. Sexual Behavior in the Human Female. Philadelphia, PA: WB Saunders Co. Kow LM, Pfaff DW. 1973–1974. Effects of estrogen treatment on the size of receptive field and response threshold of pudendal nerve in the female rat. Neuroendocrinology 13:299–313. Kow LM, Malsbury C, Pfaff DW. 1974. Effects of progesterone on female reproductive behavior in rats: Possible modes of action and role in behavioral sex differences. In: Montagna W, Sadler W, editors. Reproductive Behavior. New York: Plenum. p 179–210. Kow LM. 1976. Sensory requirements for the lordosis reflex in female rats. Brain Res 101:47–66. Kow LM, Montgomery MO, Pfaff DW. 1979. Triggering of lordosis reflex in female rats with somatosensory stimulation: Quantitative determination of stimulus parameters. J Neurophysiol l42: 195–202. Laan E, Everaerd W. 1995. Determinants of female sexual arousal: Psychophysiological theory and data. Annu Rev Sex Res 6:32–76. Landis C, Landis A, Bowles M. 1940.Sex in Development. New York: P.B. Hoeber Inc. Lloyd J, Crouch NS, Minto CL, Liao LM, Creighton SM. 2005. Female genital appearance: "Normality" unfolds. BJOG 112:643–646. Masters WH, Johnson VE. 1966. In: Human Sexual Response. Boston: Little, Brown and Company.
362
Schober et al.
Meyer-Bahlburg HFL, Dolezal C, Schober JM. 2006. Self-Assessment of Genital Anatomy and Sexual Function – Female (SAGASF-F): Retest reliability in a sample of women without genital surgery (Poster). In: International Academy of Sex Research, 32nd Annual Meeting, Amsterdam, The Netherlands, July 12–15, 2006. BOOK OF ABSTRACTS, p 51. Mirzabeigi MN, Moore JH Jr, Mericli AF, Bucciarelli P, Jandali S, Valerio IL, Stofman GM. 2012. Current trends in vaginal labioplasty: A survey of plastic surgeons. Ann Plast Surg 68:125–134. Ostrzenski A, Krajewski P, Ganjei-Azar P, Wasiutynski A, Scheinberg M, Tarka S, Fudalej M. 2014. Verification of the anatomy and newly discovered histology of the G-spot complex. BJOG 121: 1333–1342. Pfaff D, Montgomery M, Lewis C. 1977. Somatosensory determinants of lordosis in female rats: Behavioral definition of the estrogen effect. J Comp Physiol Psychol 91:134–145. Schober JM. 1998. Feminizing genitoplasty for intersex. In: Stringer MD, Oldham KT, Mouriquand PDE, Howard ER, editors. Pediatric Surgery and Urology: Long-Term Outcomes. London: W.B. Saunders Co., 1st Ed. Ch. 44. p 549–558. Schober JM, Meyer-Bahlburg HF, Ransley PG. 2004. Self-assessment of genital anatomy, sexual sensitivity and function in women: Implications for genitoplasty. BJU Int 94:589–594.
Schober JM, Meyer-Bahlburg HF, Dolezal C. 2009. Self-ratings of genital anatomy, sexual sensitivity and function in men using the ’Self-Assessment of Genital Anatomy and Sexual Function, Male’ questionnaire. BJU Int 103:1096–1103. Schober J, Cooney T, Pfaff D, Mayoglou L, Martin-Alguacil N. 2010. Innervation of the labia minora of prepubertal girls. J Pediatr Adolesc Gynecol 23:352–357. Schultz WW, van Andel P, Sabelis I, Mooyaart E. 1999. Magnetic resonance imaging of male and female genitals during coitus and female sexual arousal. BMJ 319:1596–600. Singer J, Singer I. 1972. Types of female orgasm. J Sex Res 8:255–267. Vardi Y, Gruenwald I, Sprecher E, Gertman I, Yartnitsky D. 2000. Normative values for female genital sensation. Urology 56: 1035–1040. Verkauf BS, Von Thron J, O’Brien WF. 1992. Clitoral size in normal women. Obstet Gynecol 80:41–44. Weber AM, Walters MD, Schover LR, Mitchinson A. 1995. Vaginal anatomy and sexual function. Obstet Gynecol 86:946–949. Wallen K, Lloyd EA. 2011. Female sexual arousal: Genital anatomy and orgasm in intercourse. Horm Behav 59:780–792. Woodhouse C. (ed.). 2015. Adolescent Urology and Long-Term Outcomes. Wiley Blackwell: London, UK, ISBN 978-1-118–84481-6, in press.
REVIEW
Self-Assessment of Anatomy, Sexual Sensitivity, and Function of the Labia and Vagina JUSTINE M. SCHOBER,1,2* NIEVES MARTIN ALGUACIL,2,3 R. SCOTT COOPER,4 DONALD W. PFAFF,2 AND HEINO F.L. MEYER-BAHLBURG5 1
Pediatric Urology, UPMC Hamot, Erie, Pennsylvania Pfaff Laboratory of Neurobiology and Behavior, Rockefeller University, New York, New York 3 Department of Anatomy and Embryology, School of Veterinary Medicine, Universidad Complutense de Madrid, Spain 4 Lake Erie College of Osteopathic Medicine, Erie, Pennsylvania 5 NYS Psychiatric Institute/Department of Psychiatry, College of Physicians and Surgeons of Columbia University, New York, New York 2
Patient perceptions of genital esthetics are motivating requests for plastic surgeries that could change sexual sensitivity. There is little information about the sensitivities of labial and introital sites. The aim of this study is to assess the relationship between sexual sensitivity and self-reported sizes of labial and introital sites. Sixty-two healthy, sexually active, adult women (mean age 37.9, range 21–60) with no history of genital or vaginal surgery gave written consent to participate in this study. A modified version of Self-Assessment of Genital Anatomy and Sexual Function (L-SAGASF-F) was used to assess labial and introital size. Site-specific sensation was rated on Likert scales of 1–5. Anatomical locations were compared for ratings. Of 62 responders, 84% (52) described their labia as “average-sized,” 11% (7) described their labia minora and 13% (8) their labia majora as “large”, and 3% (2) and 5% (3) as “small”. Sexual pleasure ratings were “moderate” (median value: 3.0 for external genitalia and vaginal lumen) or “strong” (median value: 4.0 for the interior vagina). Significantly higher rankings related to the vaginal opening (P 5 0.007). Orgasm intensity for stimulation of the external genitalia progressively increased toward the vaginal opening, from 1.0 to 3.0 (P 5 0.001); vaginal ratings showed a similar progression, from 2.0 at the external luminal margin to 3.0 in the deep interior (P < 0.0001). Orgasm effort scores were intermediate (median: 3.0), uniform throughout the external and internal areas (P 5 0.626). Ratings for labial and introital sensitivity, regardless of self-reported size, were very similar to those at other genital sites for sexual pleasure. Surgical excision of labial and introital structures could modify sexual sensation. Clin. Anat. 28:355–362, 2015. VC 2015 Wiley Periodicals, Inc. Key words: genital and sexual sensitivity; genital anatomy; sexual function; labia; vagina
INTRODUCTION The relationship between vaginal anatomy, sexual sensitivity (the ability of a stimulus to contribute to arousal and/or orgasm), and function are poorly understood by both practitioners and patients. Vaginal anatomy and sexual function have been examined
C V
2015 Wiley Periodicals, Inc.
*Correspondence to: Justine Schober, 333 State Street, Suite 201, Erie, Pennsylvania 16507. E-mail: [email protected] Received 14 November 2014; Accepted 11 December 2014 Published online 12 February 2015 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/ca.22503
27% (17) 11% 62% (39) (7) 5% (3) 90% (54) 2% (1) 3% (2) 95% (41) 5% (2)
Other
using a variety of criteria but correlations with the anatomical features of introital caliber, length, and vulvovaginal atrophy are poor (Weber et al., 1995). The distance between the clitoris and the urethral meatus (CUMD) was measured in an attempt to correlate genital anatomy with orgasm. Bonaparte (1933) and Landis et al. (1940) noted that the shorter the CUMD, the more likely women were to achieve orgasm. Lack of statistical analysis was a criticism until Wallen and Lloyd (2011) analyzed the raw data from both studies and demonstrated a strong inverse relationship between the CUMD and orgasm during intercourse. A lack of personal awareness of the diversity of female genital appearances could underlie choices for cosmetic genital surgery that risk sensory damage (Lloyd et al., 2005). Outcomes of sexual function and satisfaction in adult women can be influenced by the variability of genital structures, the coital capacity of the vagina, pain or sensitivity during sexual activity, aspects of women’s perception of genital cosmesis, and emotional and cultural factors. General cutaneous sensitivity, erotic sensitivity, and orgasmic capacity have important implications for women’s quality of life. In the past, cosmetic genitoplasty has been criticized and debated because it can result in impaired sexual function (Chase, 1996; Diamond and Sigmundson, 1997; Schober, 1998). The nerve density, epithelial qualities, and vascular compartments of the labia minora that contribute to sexual arousal and orgasm are poorly defined. Surgical procedure development, and counseling about surgical risks related to labioplasty, may be based on inadequate information. Data about healthy women and their perceptions of vaginal appearance, coupled with genital-site-specific sensory data, are also sparse. Outcome data after genital cosmetic procedures in adult women who do not have genital development disorders suggest patient satisfaction (Goodman et al., 2010; Iglesia et al., 2013). However, surgeries such as vaginoplasty, labiaplasty, and labia majora augmentation are not without complications, and lack quality studies with long term follow-up (Iglesia et al., 2013). To achieve an objective assessment of the risks and benefits of genitoplasty, a comprehensive and systematic battery of tools is needed to characterize the pre- and postsurgical genitalia. Aspects should include: observable anatomy and perception by the patient, sensory response to systematic tactile and erotic stimulation, and the patient’s sexual experience in real-life erotic situations. The empirical basis for such a battery of assessment tools is incomplete. The present study represents a first step towards these assessments by asking healthy women to rate the sizes of their labia and introitus, and to rate the intensity and effort required to achieve orgasm in terms of stimulation of these sentinel structures.
MATERIALS AND METHODS 38.1 (21–60)
Sep/Div/ Cohabit. Wid Single Graduate Deg Married College*
Marital status (n 5 62) Education (n 5 60) Race (n 5 60) Ethnicity (n 5 43)
Mean age, yrs African (range) Hispanic NonHisp Asian Am White Other HS
50% (31) 15% (9) 10% (6) 24% (15) 2% (1)
Schober et al.
TABLE 1. Respondent Demographics
356
Sample The goal was to recruit a diverse sample of healthy women to establish baseline information on genital
Self-Assessment of Anatomy
357
TABLE 2. Size Perceptions, External Genitalia Area
Indeterminant (“1”)
Small (“2”)
Average (“3”)
Large (“4”)
Very Large (“5”)
Median rating
Total responses
0 0
3% (2) 5% (3)
84% (52) 84% (53)
11% (7) 10% (6)
2% (1) 2% (1)
3.0 3.0
62 63
Labia majora Labia minora
sensitivity. The target population for our convenience sample comprised employees in one department of a community-based teaching hospital in northwestern Pennsylvania. Criteria for inclusion in the study were adult women between the ages of 18 and 60 who were sexually active. Women with a history of genital feminizing surgery or genital/vaginal excision surgery, degenerative neuromuscular pathologies or congenital abnormalities were excluded. No exclusions were made for parity status, sexual orientation, or marital status. All eligible women invited agreed to participate; they constituted a sample of 63 healthy, sexually active, adult women (mean age 38.1, range 21– 60 years) (Table 1). Most were non-Hispanic Caucasians and had one or more years of college education; half were married. The study was approved by the IRB of the study hospital. An instructional cover sheet advised respondents that completion and return of the survey tacitly provided informed consent.
Assessment Several standardized self-reporting questionnaires are currently in use for patient-report-based assessment of sexual function in anatomically normal women (Fisher et al., 2011). Self-Assessment of Genital Anatomy and Sexual Functioning for Females (SAGASF-F), a tool specifically designed to assess patient-perceived outcome of feminizing genitoplasty in terms of appearance, sensitivity, and sexual function, has been piloted (Schober et al., 2004) and its reliability has been established (Meyer-Bahlburg et al., 2006; Schober et al., 2009). All women in the present study were given a slightly shortened version of the SAGASF-F (Schober et al., 2004) to complete at home and to deposit in a box at the hospital, without identifying information. This questionnaire examines many aspects of female genital anatomy, sensitivity, pain/ discomfort, and sexual function. It also includes information on the respondents’ demographics and their reproductive, medical, and sexual history. It includes anatomical graphs that provide a basis for selfassessment including examples of appearance, size, and position of the labia and vagina. In the sections of the SAGASF-F that are pertinent to the present report, the participant reads an introduction designed to help her understand the rating tasks. Thereafter, responses are prompted to assess sexual pleasure, orgasm TABLE 3. Self-Perceptions of the Vagina Size of opening (n 5 62)
Location of opening (n 5 52)
Small: 3% (2) Adequate: 92% (57) Large: 5% (3)
Mid-position: 94% (49) Anal bias: 6% (3)
intensity, and the effort required to achieve orgasm using 5-point Likert scales. For sexual pleasure (and, analogously, for orgasm intensity), respondents were given this prompt: “Sexual touch/stimulation of this area by a partner or yourself. . . has produced (rate 1 through 5): Sexual pleasure—1/none, 2/mild, 3/moderate, 4/strong, 5/very strong.” For orgasm effort, the query was: “If orgasm was achieved, please describe the effort required,” followed by a line with the anchors: 1/very strong, 2/strong, 3/moderate, 4/little, 5/very little.
Data Analysis Statistical analysis utilized SPSS for Windows version 12.0. Based on the outcome of Shapiro-Wilk and Kolmogorov-Smirnov Tests, data were analyzed using nonparametric methods. Friedman Tests and the Mann-Whitney U Test were used to examine differences in ratings for each functional category across anatomical areas. When the outcome reached significance (alpha 5 0.05), Bonferroni-corrected Wilcoxon Rank Sum Tests were used to compare areas pairwise to identify specific areas of differential function/sensitivity. Sample sizes differed among items because not every participant answered all items, and
Fig. 1. Ratings of the intensity of sexual pleasure, from “None” (1) to “Intense/Very Strong” (5). Black horizontal bars represent median values, boxes depict 25th through 75th percentiles, circles denote outliers. Numbers in parenthesis accompanying the axis labels denote mean rank established by the Friedman Test (P < 0.0001). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
358
Schober et al.
Fig. 2. Ratings of the intensity of orgasm, from None (1) to Intense/Very Strong (5). Black horizontal bars represent median values, boxes depict 25th through 75th percentiles, circles denote outliers. Numbers accompanying the axis labels denote mean ranks derived from the Friedman Test (P < 0.0001). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
we did not make estimates when no answer was provided.
lia to the perivaginal area, with no intensity (median value: 1.0) at the labia majora to moderate intensity around the vaginal opening (median value: 3.0). This increase in intensity was also reflected within the vagina, proceeding from mild intensity (median value: 2.0) about the superficial regions to moderate (median value: 3.0) within the deep interior. These global differences were significant (P < 0.0001) with mean ranks increasing in a concentric (peripheral to central) manner (Fig. 2). Posthoc comparisons demonstrated significantly greater intensity for the perivaginal area than the labia minora (P 5 0.004), the shallow vaginal interior than the inner rim (P < 0.0001), and the deep vagina than the perivaginal opening (P 5 0.005). The effort to achieve orgasm (Fig. 3) was perceived as moderate (median value: 3.0) throughout the external genitalia and vagina. For the former, a limited number of individuals rated the effort at the extremes, either “very strong” (1.0) or “very little” (5.0). The Friedman rank test revealed no significant difference in ratings among these areas (P 5 0.626).
Size Effects, External Genitalia The labia minora and labia majora were rated as large or very large by seven (11%) and eight (13%) women, respectively. In order to check whether perceived large labia size was associated with increased erotic sensitivity, we compared these women’s ratings of sexual pleasure and orgasm intensity to those by women with small or averaged-sized labia. The
RESULTS Genital Anatomy Most respondents rated their labia majora and minora as “average-sized” (84% each), 3% and 5%, respectively, as “small,” and 13% and 12% as “large” or “very large” (Table 2), with 98% (60/61) describing the location as “usual.” Of 52 respondents, 94% (49) rated the location of their vaginal opening as “in midposition,” with the remainder noting a location “near the anus (far back).” Ninety-two percent (57/62) indicated that their vaginal openings were “adequate for sexual penetration” (Table 3).
Sexual Pleasure, Orgasm Intensity, and Effort Median ratings for sexual pleasure were “moderate” (3.0) for all areas except the deep interior of the vagina (median rating: 4.0, “strong”; Fig. 1). Mean ranks established by the Friedman Test showed a generalized increase concentrically from the labia majora to the perivaginal opening (P < 0.001; Fig. 1). Posthoc testing revealed that the perivaginal opening was significantly more pleasure-sensitive than the labia majora (P 5 0.007); other areas of the external genitalia were equivalent, as were all regions of the vagina proper. Ratings for orgasm (Fig. 2) demonstrated increasing intensity from the periphery of the external genita-
Fig. 3. Ratings of the effort to attain orgasm, from Very Strong (1) to Very Little (5). Black horizontal bars represent median values, boxes depict 25th through 75th percentiles, circles denote outliers, asterisks indicate extremes. Numbers accompanying the axis labels denote mean ranks derived from the Friedman Test (P 5 0.626). *denotes number of responses. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Self-Assessment of Anatomy
359
TABLE 4. Differences in Median Ratings of Pleasure and Orgasm Intensity Between Women with Large or Very Large Labia and Women with Small or Average-sized Labia Pleasure
Orgasm intensity
Rating category Area
Labia majora
Labia minora
Perivaginal opening
Labia majora Labia minora
20.5 21.0
0 11.0
10.5 12.0
differences were small for the labia majora (Table 4). However, women with (self-reported) large labia minora gave median ratings of sexual pleasure in this area up to 2.0 units higher than the rest of the sample population, and they rated the intensity in the area of the perivaginal opening as either strong or very strong. Because of the small sample size, none of these differences attained conventional significance (P 0.068).
DISCUSSION Authors have listed many sites in the female genitalia as the most sensitive in regard to sexual function. These sites include a controversial neurovascular € fenberg, bundle on the anterior vaginal wall (Gra 1950) [the existence of which was recently corroborated by hematoxylin and eosin staining (Ostrzenski et al., 2014)], the clitoris and labia minora (Kinsey et al., 1953), and the area superior to and directly on the clitoris (Schober et al., 2004, Woodhouse, in
Fig. 4. A: Combined image for color overlays including the ratings for orgasm and sexual sensitivity for the SAGASF F tool as published separately in Schober (2009) (color densities are mathematical conversions of the Likert scale means). B: Color image gradient depiction of
Labia majora 0 0
Labia minora
Perivaginal opening
20.5 21.0
11.0 11.0
press) (Fig. 4A). In addition to direct stimulation of the previously-listed structures, indirect stimulation of genital structures by forces transmitted through the vaginal wall could contribute to orgasm. Wallen and Lloyd proposed that less androgen stimulation in utero resulted in the bulb and the body of the clitoris being packed into a smaller space, pressing them closer to the anterior vaginal wall, allowing for increased capacity for orgasm. MRI studies show that the penis takes on a boomerang shape in “missionary position” (Schultz et al., 1999), possibly to increase contact with the anterior vaginal wall. Studies of orgasm by Singer revealed multiple sites of sexual sensation that differed in the kinds of orgasm they produce (Singer and Singer, 1972). Given the great diversity of findings, there may be an ordered series of stimulus presentations culminating in orgasm. In terms of sexual pleasure and orgasmic sensitivity, two findings emerged from our study. First, there were no significant differences in mean ratings between external genital and internal vaginal sites for any category of sexual sensitivity (sexual pleasure,
sexual pleasure ratings and orgasm intensity ratings, indicating an increase from lateral genital areas to medial vaginal opening. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
360
Schober et al.
orgasmic sensitivity and orgasm effort). Second, the vaginal introitus (the area around the opening of the vagina) was rated as the area requiring the least amount of effort for stimulation to orgasm. The choice of this distal vaginal site might corroborate the locus € fenberg and by of erogenous activity noted by Gra Wallen and Lloyd. It is unclear whether the method of assessment (global self-reporting) in this study, compared to responses to specific experimental stimula€ fenberg, 1950) or self-stimulation (Singer tion (Gra and Singer, 1972), explains why our findings differ from others. Much is known about the differential anatomy of the genitalia, physiological changes in the body related to sexual arousal and orgasm, and sexual behaviors and dysfunctions (Goldstein and Berman, 1998; Heiman, 1998). There are published measurements of the length and transverse diameter of the glans clitoris, the widths of the labia majora and labium minora, and perineal and vaginal lengths in premenopausal and postmenopausal women (Verkauf et al., 1992; Basaran et al., 2008). A wide range of sizes is noted for each measurement, but no statistically significant association has been noted with age, parity, ethnicity, hormone use, or history of sexual activity. In this self-reported study, most women judged their own labia minora, labia majora, and vaginal opening to be average-sized. It is noteworthy that 11% indicated that their labia minora were large or very large, and 13% indicated that their labia majora were large or very large. Their sexual pleasure ratings were higher than those of women who reported average-sized or small labia. This could indicate that women with labial sizes outside the range that could be judged “typical” suffer no adverse effect on sexuality in consequence, but rather increased sensitivity, perhaps because the surface area for contact is larger. Labioplasty typically involves excising, and thus reducing, sexually sensitive labial tissue. It can alter the dermatome. Surgery on any genital structure could modify sensation in that structure by undercutting or excising genital epithelium, which provides terminal innervation. Information about the relationship of female genital sensation to its underlying innervation remains incomplete. Human clitoral innervation has been elucidated in fetal studies (Baskin et al., 1999). Recent studies of the labia minora indicate a higher density of innervation on the introital side (Schober et al., 2010). This study also shows that orgasm intensity increased progressively, from 1.0 to 3.0, as stimulation of the external genitalia proceeded from lateral areas toward the more median vaginal opening (P 5 0.001) (Fig. 4B). Studies from the vertebrate literature form an important basis for understanding human genital sensitivity. In rats, the genital skin stimulation required for lordosis (the reflexive copulatory posture of the female rat) has been mapped in great detail (Kow et al., 1979). Pressure on crucial skin areas initiates the chain of events leading to intromission. Summation of stimuli to a wide area of peri-vaginal skin around the introitus initiates lordosis. Non-cutaneous
stimuli are insufficient: lordosis is never displayed before cutaneous contact (Kow, 1976). Experiments in which somatosensory stimuli were applied to the female skin locations contacted by the male rat revealed a minimally adequate combination that involved flank stimulation followed by pressure on the posterior rump, tail base, and perineum. Here, estradiol significantly facilitated the appearance of the reflex response (Kow and Pfaff, 1973–1974; Pfaff et al., 1977), and progesterone given after estrogen treatment had a significant synergistic effect (Kow et al., 1974). The order of stimulus application was also important. Flank stimulation had to precede (or at least accompany) stimulation of the rump and perineum, followed quickly by perineal pressure. The best response was elicited by quick changes in pressure during the application of this combination of stimuli (Kow, 1976). Gradual applications of pressure were often less effective for eliciting lordosis than rapid fluctuations. Within effective locations on the skin of a female rat, lordosis can be enhanced by increasing any of three factors: stimulus pressure, total area stimulated, and the amount of estrogen (Kow and Pfaff, 1973–1974). As with other vertebrates, these three factors are also likely to be involved in the human sexual response (although the lordosis reflex in the female rat is certainly not a direct homologue of the arousal and orgasm responses in the human female). In human genital sensitivity the tactile response is similar, but not equivalent, to the sexual response. The sensitivity of human genitalia to vibratory and hot/cold sensory inputs has been studied, but never specifically for sexual stimulation (Vardi et al., 2000). € fenberg (1950) suggested an area of Studies by Gra increased sensitivity over the urethra (G-spot) on the anterior vaginal wall. Kinsey et al. (1953) concluded from studies of masturbation that areas of the clitoris and labia minora are most sensitive. Studies of orgasm by Singer and Singer (1972) indicated multiple sites of sexual sensation differing in the kinds of orgasm they produce. Schober et al. (2004) studied healthy adult females with no history of genital surgery, and found less sexual sensitivity in the vagina than the external genitalia, the clitoral area exhibiting the highest sensitivity scores. The sexual sensation values of various genital sites have been considered in different ways (Woodhouse, in press) (Fig.4A). Ultimately, there may be an ordered series of stimulus presentations related to initiation of the arousal circuit. Hence, the external genitalia could make an important contribution to arousal in preparation for penetrative intercourse. The lordosis reflex is the reflexive copulatory posture of the female rat initiated by pressure on perineal skin (Kow et al., 1979). The threshold (milligrams of force) for the pudenal nerve response of the perineal region in female rats was electrically recorded. An ordered path of cutaneous sensitivity was reported, with the most sensitive points in the middle of the receptive field. This study shows that the mean score on each sensitivity indicator (sexual pleasure, orgasm intensity, and orgasm effort) was higher for the labia minora than the labia majora (3.0, 2.13, 3.0) vs. (2.85, 1.95,
Self-Assessment of Anatomy 2.97) (Fig.4B). The similarity in average ratings across the epithelial area tested has neurophysiological implications. All the areas are innervated by the pudendal nerve. Therefore, either the density of innervation must be similar across these areas or, if some of these sub-regions are much more densely innervated than others, the synaptic impact of the more sparsely innervated subregions on the dorsal horn of the lumbar spinal cord must be more powerful than that of the more densely innervated subregions, ensuring the equipotency of stimuli across the pudendal field for enhancing arousal. The location of highsensitivity responses indicated by this survey appears consistent with previous studies of sexual sensitivity in the vertebrate perineum. The distribution of sensitivity responses in our study may correspond to the dermatome that the nerve bundles supply. Because the human sexual response is multifactorial, including a strong cognitive element, sexual stimulation and its resultant response may be very individualized. Observational studies are not impossible and have been documented by Kinsey et al. (1953) and by Masters and Johnson (1966). However, a natural sexual response generally requires a degree of privacy during stimulation, and many individuals and couples are likely to refuse functional evaluation by direct observation. Even if this is not the case, natural observation requires patients’ subjective reports to be incorporated with sensory experiences and feelings, especially in women for whom discrepancies between physiological and subjective erotic responses are well documented (Laan and Everaerd, 1995). Thus, a tool for systematic self-reporting, which is more easily accepted by more people and poses less of a logistical problem than direct testing, is essential for further understanding of the human sexual response. In this respect, a woman’s judgment of her own sensation is the critical variable. Even this is limited by recall bias, particularly in subjects with limited sexual experience. Future studies are needed to elucidate women’s ratings of genital size, their preference for genital appearance, and whether self- perception of atypical genitalia affects sexual functioning adversely. Comparative assessment, if not direct measurement, of genital anatomy by a urologist or gynecologist could be of value.
CONCLUSIONS Evidence-based practice guidelines have not yet been established for labioplasty (Mirzabeigi et al., 2012). Our preliminary findings could have important implications for genitoplastic surgery. First, healthy women who rated their vaginal openings as large or very large did not differ in their ratings of sexual pleasure for this area. This suggests that women may accept a larger vaginal size than is commonly believed, which would facilitate more conservative management of introital tightening. Second, healthy women regard both the labia and the introitus as important for sexual sensation. This provides a strong case against surgical excision of the labia and introital structures and for preserving the important sites for
361
sexual sensation. The diversity of labioplasty techniques complicates outcome studies. However, additional large-sample studies of patients are needed to understand the risks of cosmetic genital surgery.
ACKNOWLEDGMENT The authors have no conflicts of interest or monetary support from any institution or industry to declare.
REFERENCES Basaran M, Kosif R, Bayar U, Civelek B. 2008. Characteristics of external genitalia in pre- and postmenopausal women. Climacteric 11:416–421. Baskin LS, Erol A, Li YW, Liu WH, Kurzrock E, Cunha GR. 1999. Anatomical studies of the human clitoris. J Urol 162:1015–1020. s de la femme. Bulletin de la Bonaparte M. 1933. Les deuxfrigidite te de Sexologie 5:161–170. Socie Chase C. 1996. Re: Measurement of pudendal evoked potentials during feminizing genitoplasty: Technique and applications. J Urol 156:1139–1140. Diamond M, Sigmundson HK. 1997. Sex reassignment at birth. Long-term review and clinical implications. Arch Pediatr Adolesc Med 151:298–304. Fisher TD, Davis CM, Yarber WL, Davis SL. 2011. Handbook of Sexuality-Related Measures. 3rd Ed. New York: Routledge (Taylor and Francis Group). Goldstein I, Berman JR. 1998. Vasculogenic female sexual dysfunction: Vaginal engorgement and clitoral erectile insufficiency syndromes. Int J Impot Res 10(Suppl 2):S84–S90; discussion S98S101. Goodman MP, Placik OJ, Benson RH III, Miklos JR, Moore RD, Jason RA, Matlock DL, Simopoulos AF, Stern BH, Stanton RA, Kolb SE, Gonzalez F. 2010. A large multicenter outcome study of female genital plastic surgery. J Sex Med 7:1565–1577. € fenberg E. 1950. The role of the urethra in female orgasm. Int J Gra Sexol 3:145–148. Heiman JR. 1998. Psychophysiological models of female sexual response. Int J Impot Res 10(Suppl 2):S94–S97; discussion S98-S101. Iglesia CB, Yurteri-Kaplan L, Alinsod R. 2013. Female genital cosmetic surgery: A review of techniques and outcomes. Int Urogynecol J 24:1997–2009. Kinsey AC, Pomeroy WB, Martin CE, Gebhard PH. 1953. Sexual Behavior in the Human Female. Philadelphia, PA: WB Saunders Co. Kow LM, Pfaff DW. 1973–1974. Effects of estrogen treatment on the size of receptive field and response threshold of pudendal nerve in the female rat. Neuroendocrinology 13:299–313. Kow LM, Malsbury C, Pfaff DW. 1974. Effects of progesterone on female reproductive behavior in rats: Possible modes of action and role in behavioral sex differences. In: Montagna W, Sadler W, editors. Reproductive Behavior. New York: Plenum. p 179–210. Kow LM. 1976. Sensory requirements for the lordosis reflex in female rats. Brain Res 101:47–66. Kow LM, Montgomery MO, Pfaff DW. 1979. Triggering of lordosis reflex in female rats with somatosensory stimulation: Quantitative determination of stimulus parameters. J Neurophysiol l42: 195–202. Laan E, Everaerd W. 1995. Determinants of female sexual arousal: Psychophysiological theory and data. Annu Rev Sex Res 6:32–76. Landis C, Landis A, Bowles M. 1940.Sex in Development. New York: P.B. Hoeber Inc. Lloyd J, Crouch NS, Minto CL, Liao LM, Creighton SM. 2005. Female genital appearance: "Normality" unfolds. BJOG 112:643–646. Masters WH, Johnson VE. 1966. In: Human Sexual Response. Boston: Little, Brown and Company.
362
Schober et al.
Meyer-Bahlburg HFL, Dolezal C, Schober JM. 2006. Self-Assessment of Genital Anatomy and Sexual Function – Female (SAGASF-F): Retest reliability in a sample of women without genital surgery (Poster). In: International Academy of Sex Research, 32nd Annual Meeting, Amsterdam, The Netherlands, July 12–15, 2006. BOOK OF ABSTRACTS, p 51. Mirzabeigi MN, Moore JH Jr, Mericli AF, Bucciarelli P, Jandali S, Valerio IL, Stofman GM. 2012. Current trends in vaginal labioplasty: A survey of plastic surgeons. Ann Plast Surg 68:125–134. Ostrzenski A, Krajewski P, Ganjei-Azar P, Wasiutynski A, Scheinberg M, Tarka S, Fudalej M. 2014. Verification of the anatomy and newly discovered histology of the G-spot complex. BJOG 121: 1333–1342. Pfaff D, Montgomery M, Lewis C. 1977. Somatosensory determinants of lordosis in female rats: Behavioral definition of the estrogen effect. J Comp Physiol Psychol 91:134–145. Schober JM. 1998. Feminizing genitoplasty for intersex. In: Stringer MD, Oldham KT, Mouriquand PDE, Howard ER, editors. Pediatric Surgery and Urology: Long-Term Outcomes. London: W.B. Saunders Co., 1st Ed. Ch. 44. p 549–558. Schober JM, Meyer-Bahlburg HF, Ransley PG. 2004. Self-assessment of genital anatomy, sexual sensitivity and function in women: Implications for genitoplasty. BJU Int 94:589–594.
Schober JM, Meyer-Bahlburg HF, Dolezal C. 2009. Self-ratings of genital anatomy, sexual sensitivity and function in men using the ’Self-Assessment of Genital Anatomy and Sexual Function, Male’ questionnaire. BJU Int 103:1096–1103. Schober J, Cooney T, Pfaff D, Mayoglou L, Martin-Alguacil N. 2010. Innervation of the labia minora of prepubertal girls. J Pediatr Adolesc Gynecol 23:352–357. Schultz WW, van Andel P, Sabelis I, Mooyaart E. 1999. Magnetic resonance imaging of male and female genitals during coitus and female sexual arousal. BMJ 319:1596–600. Singer J, Singer I. 1972. Types of female orgasm. J Sex Res 8:255–267. Vardi Y, Gruenwald I, Sprecher E, Gertman I, Yartnitsky D. 2000. Normative values for female genital sensation. Urology 56: 1035–1040. Verkauf BS, Von Thron J, O’Brien WF. 1992. Clitoral size in normal women. Obstet Gynecol 80:41–44. Weber AM, Walters MD, Schover LR, Mitchinson A. 1995. Vaginal anatomy and sexual function. Obstet Gynecol 86:946–949. Wallen K, Lloyd EA. 2011. Female sexual arousal: Genital anatomy and orgasm in intercourse. Horm Behav 59:780–792. Woodhouse C. (ed.). 2015. Adolescent Urology and Long-Term Outcomes. Wiley Blackwell: London, UK, ISBN 978-1-118–84481-6, in press.
