| Labia minora | |
|---|---|
 Hairless human vulva with labia minora encircled between the rounded thicker outerlabia majora. | |
| Details | |
| Precursor | Urogenital folds |
| Part of | Vulva |
| Identifiers | |
| Latin | labium minus pudendi |
| TA98 | A09.2.01.007 |
| TA2 | 3553 |
| FMA | 20374 |
| Anatomical terminology | |
Thelabia minora (Latin for 'smaller lips',sg.:labium minus), also known as theinner labia,inner lips, ornymphae,[1] are two flaps ofskin that are part of theprimatevulva, extending outwards from the innervaginal andurethral openings to encompass thevestibule.[2] At theglans clitoridis, each labium splits, above forming theclitoral hood, and below thefrenulum of the clitoris. At the bottom, the labia meet at thelabial commissure. The labia minora vary widely in size, color and shape from individual to individual.
The labia minora are situated between thelabia majora and together form thelabia. The labia minora arehomologous to thepenile raphe and ventral penile skin in males.[3][4]
The labia minora extend from theclitoris obliquely downward, laterally, and backward on either side of thevulval vestibule, ending between the bottom of the vulval vestibule and the labia majora. Theposterior ends (bottom) of the labia minora are usually joined across the middle line by a flap of skin, named thefrenulum 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 theglans clitoris (clitoral tip or head); this fold is named theclitoral 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, thefrenulum clitoridis.[5]
The clitoral hood typically covers the shaft and sometimes the glans — which is highly sensitive to touch — helping protect the clitoris from mechanical irritation and dryness. However, the hood is movable and can slide duringclitoral erection or be gently pulled back to increase exposure of the clitoris tosexual stimulation.
On the opposed surfaces of the labia minora are numeroussebaceous glands not associated with hair follicles.[5] They are lined bystratified 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.
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 thepudendal cleft and making the termminora (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 tourethra (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 oflabiaplasty, surgery to alter the labia—usually, to make them smaller.[9][10][11] On the other hand, there is an opposite movement oflabia 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]
The inner lips serve to protect from mechanical irritation, dryness and infections of the highly sensitive area of thevulval 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 thefemale external urethral opening (meatus) is also situated between labia minora, they may play a role in guiding the stream of the urine duringfemale urination.
Being very sensitive by their structure to any irritation, and situated in the excretion area where traces of urine,vaginal discharge,smegma and evenfeces may be present, the inner lips may be susceptible to inflammatory infections of the vulva such asvulvitis.
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, frommons pubis to theperineum andanus. Apart from water and special liquid cleansing agents (lotions), there are commercially availablewet 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 ofestrogen in their bodies, may lead to the mostly pediatric condition known aslabial 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); whileG-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.
The labia minora in non-primateplacentalmammals (namelyEuungulata andCarnivora) are a sole pair of small labia that protect theinternal vestibule and are rather called thelabia vulvae or simplylabia. In primates, they are calledlabia minora to differentiate them from thelabia majora, the latter of which are a feature only present in the Primates order.[15][16]
When the labia vulvae are closed together, they form a pudendal cleft. The joining of the labia vulvae top and bottom are respectively referred to as the anterior and posterior commissures.
One or more of the preceding sentences incorporates text in thepublic domain frompage 1265–1266 of the 20th edition ofGray's Anatomy (1918)
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