Labia minora
Human hairless vulva with labia minora encircled. The labia minora are the vertical folds of skin in the very middle of the photo, between the rounded thicker outer labia majora.
Details
PrecursorUrogenital folds
Identifiers
Latinlabium minus pudendi
TA98A09.2.01.007
TA23553
FMA20374
Anatomical terminology

The labia minora (Latin for 'smaller lips', sg.: labium minus), also known as the inner labia, inner lips, or nymphae,[1] are two flaps of skin that are part of the primate vulva, extending outwards from the vaginal and urethral openings to encompass the vestibule.[2] The labia minora are situated between the labia majora and together form the labia. They vary widely in size, color and shape from individual to individual.

The labia minora are homologous to the penile raphe in males.[3][4]

Structure and functioning

The labia minora extend from the clitoris obliquely downward, laterally, and backward on either side of the vulval vestibule, ending between the bottom of the vulval vestibule and the labia majora. The posterior ends (bottom) of the labia minora are usually joined across the middle line by a flap of skin, named the frenulum of labia minora.[5]

On the front, each lip forks dividing into two portions surrounding the clitoris. The upper part of each lip passes above the clitoris to meet the upper part of the other lip—which will often be a little larger or smaller—forming a fold which overhangs the glans clitoridis (clitoral tip or head); this fold is named the clitoral hood. The lower part passes beneath the glans clitoridis and becomes united to its under surface, forming, with the inner lip of the opposite side, the frenulum clitoridis.[5]

The clitoral hood serves to cover most of the time the shaft and sometimes the glans (which is very sensitive to the touch) to protect the clitoris from mechanical irritation and from dryness. Yet the hood is movable and can slide during clitoral erection or be pulled upwards a little for greater exposure of the clitoris to sexual stimulation.

Histology

On the opposed surfaces of the labia minora are numerous sebaceous glands not associated with hair follicles.[5] They are lined by stratified squamous epithelium on those surfaces.[6][page needed]

Like the whole area of the vulval vestibule, the mucus secreted by those glands protects the labia from dryness and mechanical irritation.

Variation

The individual size, coloration and shapes of the labia minora are subject to significant variability between women. The labia minora are completely covered by the labia majora in some women in a standing posture, while in others they protrude visibly from the pubic cleft.

Being thinner than the outer labia, the inner labia can be also more narrow than the former, or wider than the labia majora, thus protruding in the pudendal cleft and making the term minora (Latin for smaller) essentially inapplicable in these cases. They can also be smooth or frilled, the latter being more typical of longer or wider inner labia.

From 2003 to 2004, researchers from the Department of Gynaecology, Elizabeth Garrett Anderson Hospital in London, measured the labia and other genital structures of 50 women from the age of 18 to 50, with a mean age of 35.6. The study has since been criticized for its "small and homogenous sample group" consisting primarily of white women.[7] The results were:[8]

Measurement Range Mean [SD]
Clitoral length (mm) 5–35 19.1 [8.7]
Clitoral glans width (mm) 3–10 5.5 [1.7]
Clitoris to urethra (mm) 16–45 28.5 [7.1]
Labia majora length (cm) 7.0–12.0 9.3 [1.3]
Labia minora length (mm) 20–100 60.6 [17.2]
Labia minora width (mm) 5–60 21.8 [9.4]
Perineum length (mm) 15–55 31.3 [8.5]
Vaginal length (cm) 6.5–12.5 9.6 [1.5]
Feature Value Frequency
Tanner stage (n) IV 4
V 46
Colour of genital area
compared with surrounding skin (n)
Same 9
Darker 41
Rugosity of labia (n) Smooth 14
Moderate 34
Marked 2

Due to the frequent portrayal of the pudendal cleft without protrusion in art and pornography, there has been a rise in the popularity of labiaplasty, surgery to alter the labia—usually, to make them smaller.[9][10][11] On the other hand, there is an opposite movement of labia stretching. Its proponents stress the beauty of long labia and their positive role in sexual stimulation of both partners.

Labiaplasty is also sometimes sought by women who have asymmetrical labia minora to adjust the shape of the structures towards identical size.[12]

Labia stretching has traditionally been practised in some African nations in the East and South[13] and the South Pacific.[14]

Functioning

The inner lips serve to protect from mechanical irritation, dryness and infections of the highly sensitive area of the vulval vestibule with vaginal and urethral openings in it between them. During vaginal intercourse, they may contribute to stimulation of the whole vestibule area, the clitoris and the vagina of the woman and the penis of her partner. Stimulation of the clitoris may occur through tension of the clitoral hood and its frenulum by the inner labia pulling at them. During sexual arousal, they are lubricated by the mucus secreted in the vagina and around it to make penetration painless and protect them from irritation.

As the female external urethral opening (meatus) is also situated between labia minora, they may play a role in guiding the stream of the urine during female urination.

Medical conditions

Being very sensitive by their structure to any irritation, and situated in the excretion area where traces of urine, vaginal discharge, smegma and even feces may be present, the inner lips may be susceptible to inflammatory infections of the vulva such as vulvitis.

The likelihood of inflammation may be reduced through appropriate regular hygienic cleansing of the whole vulval vestibule, using water and medically tested cleansing agents designed for vulvas. To avoid contamination of the vulva with fecal bacteria, it is recommended that the vulva is washed only from front to back, from mons pubis to the perineum and anus. Apart from water and special liquid cleansing agents (lotions), there are commercially available wet wipes for female intimate hygiene. Some women wipe the vulval vestibule dry with toilet tissue after urination to avoid irritation and infections from residual drops of the urine in the area.

However, incorrect choice of cleansing agents, or their incorrect application, may itself cause labial irritation and require medical attention. Over-vigorous rubbing of the labia of little girls while washing, combined with the lack of estrogen in their bodies, may lead to the mostly pediatric condition known as labial fusion. If fused labia prevent urination, urine may accumulate and cause pain and inflammation.

In adult females, irritation of the area may be caused by wearing too-tight underwear (especially where wider inner labia protrude in the pudendal cleft); while G-strings, which rub against the labia during body movements, may cause irritation or lead to infection from bacteria transferred from either the external environment or the anus.

Other animals

Non-primate mammals usually have just one pair of small labia known as the labia vulvae, which are homologous to that of the labia minora in primates.[15][16]

Additional images

See also

References

  1. ^ nymphae Archived 2008-06-28 at the Wayback Machine. Dictionary.com. Merriam-Webster's Medical Dictionary. Merriam-Webster, Inc. (accessed: November 24, 2007).
  2. ^ Blüm, Volker (2012). Vertebrate Reproduction: A Textbook. Springer Berlin Heidelberg. p. 74. ISBN 978-3-64271-074-2. Retrieved November 19, 2023.
  3. ^ Hodges, Frederick Mansfield S.; Denniston, George C.; Milos, Marilyn Fayre (2007). Male and Female Circumcision: Medical, Legal, and Ethical Considerations in Pediatric Practice. Springer US. p. 10. ISBN 978-0-58539-937-9. Retrieved November 24, 2023.
  4. ^ Martin, Richard J.; Fanaroff, Avory A.; Walsh, Michele C. (2014). Fanaroff and Martin's Neonatal-Perinatal Medicine E-Book: Diseases of the Fetus and Infant. Elsevier Health Sciences. p. 1522. ISBN 978-0-32329-537-6. Retrieved November 24, 2023.
  5. ^ a b c Public domain One or more of the preceding sentences incorporates text in the public domain from page 1265–1266 of  the 20th edition of Gray's Anatomy (1918)
  6. ^ Manual of Obstetrics. (3rd ed.). Elsevier. pp. 1-16. ISBN 9788131225561.
  7. ^ Oeming, Madita (1 January 2018). "In Vulva Vanitas – The Rise of Labiaplasty in the West" (PDF). Gender Forum. 67: 70–91. ISSN 1613-1878. Archived (PDF) from the original on 18 July 2020. Retrieved 8 June 2020.
  8. ^ Lloyd J, et al. (May 2005). "Female genital appearance: 'normality' unfolds" (PDF). British Journal of Obstetrics and Gynaecology. 112 (5): 643–646. doi:10.1111/j.1471-0528.2004.00517.x. PMID 15842291. S2CID 17818072. Archived (PDF) from the original on 2011-10-05. Retrieved 2011-09-19.
  9. ^ Rowenna Davis (27 February 2011). "Labiaplasty surgery increase blamed on pornography". Life and style. Archived from the original on 2014-12-07. Retrieved 2015-04-03.
  10. ^ Özer M, Mortimore I, Jansma EP, Mullender MG (March 2018). "Labiaplasty: motivation, techniques, and ethics". Nat Rev Urol. 15 (3): 175–189. doi:10.1038/nrurol.2018.1. PMID 29405204. S2CID 3560906.
  11. ^ Clerico C, Lari A, Mojallal A, Boucher F (June 2017). "Anatomy and Aesthetics of the Labia Minora: The Ideal Vulva?". Aesthetic Plast Surg. 41 (3): 714–719. doi:10.1007/s00266-017-0831-1. PMID 28314908. S2CID 4738537.
  12. ^ Triana, Lina (2020), "Lazy S Labiaplasty (Edge Labiaplasty)", Aesthetic Vaginal Plastic Surgery, Springer International Publishing, pp. 37–51, doi:10.1007/978-3-030-24819-2_4, ISBN 978-3-030-24818-5, S2CID 203502492
  13. ^ "Sexual health—a new focus for WHO" (PDF). Progress in Reproductive Health Research (67). World Health Organization: 6. 2004. Archived from the original (PDF) on 12 February 2005.
  14. ^ Robert Suggs, Marquesan Sexual Behavior [New York: Harcourt, Brace and World, 1966], pp. 39–42
  15. ^ McEntee, Mark (2012). Reproductive Pathology of Domestic Mammals. Elsevier Science. p. 192. ISBN 978-0-32313-804-8. Retrieved November 19, 2023.
  16. ^ Andrews, Anthony; Boden, Edward (2015). Black's Veterinary Dictionary. Bloomsbury Publishing. p. 484. ISBN 978-1-40814-955-3. Retrieved December 15, 2023.