Flaps of skin on either side of the vaginal opening in the vulva
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 inner vaginal and urethral openings to encompass the vestibule.[2] At the glans clitoridis, each labium splits, above forming the clitoral hood, and below the frenulum of the clitoris. At the bottom, the labia meet at the labial commissure. The labia minora vary widely in size, color and shape from individual to individual.
The labia minora are situated between the labia majora and together form the labia. The labia minora are homologous to the penile raphe and ventral penile skin 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 clitoris (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 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 during clitoral erection or be gently pulled back to increase 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
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]
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