K Fourchette The labia majora , also commonly called outer labia or outer lips, are lip-like structures consisting mostly of skin and adipose fatty tissue, which extend on either side of the vulva to form the pudendal cleft through the middle. The labia majora often have a plump appearance, and are thicker towards the anterior. To the posterior, the labia majora join at the posterior commissure , which is above the perineum and below the frenulum of the labia minora.
The grooves between the labia majora and labia minora are known as the interlabial sulci or interlabial folds. The labia minora obsolete: They enclose and protect the vulvar vestibule, urethra and vagina. The upper portion of each labium minora splits to join with both the clitoral glans , and the clitoral hood.
The labia minora meet posterially at the frenulum of the labia minora also known as the fourchette , which is a fold of skin below the vaginal orifice. The fourchette is more prominent in younger women, and often recedes after sexual activity  and childbirth. The outer surface of the labia majora is pigmented skin, and develops pubic hair during puberty.
The inner surface of the labia majora is smooth, hairless skin, which resembles a mucous membrane, and is only visible when the labia majora and labia minora are drawn apart. Both the inner and outer surfaces of the labia majora contain sebaceous glands oil glands , apocrine sweat glands , and eccrine sweat glands. The labia majora have fewer superficial nerve endings than the rest of the vulva, but the skin is highly vascularized. They contain many sebaceous glands, and occasionally have eccrine sweat glands.
The labia minora have many sensory nerve endings, and have a core of erectile tissue. They can range in color from a light pink to brownish black,  and texturally can vary between smooth and very rugose.
A Y chromosome results in a male, and an X chromosome results in a female. A male zygote will later grow into an embryo and form testes , which produce androgens primarily male hormones , usually causing male genitals to be formed. Female genitals will usually be formed in the absence of significant androgen exposure.
The genitals begin to develop after approximately 4 to 6 weeks of gestation. If testes are formed, they begin to secrete androgens that affect the external genital development at about week 8 or 9 of gestation. The labioscrotal swellings become the labia majora and mons pubis in females, or fuse to become the scrotum in males. Because the male and female parts develop from the same tissues, this makes them homologous different versions of the same structure.
Sexual differentiation is complete at around 12 weeks of gestation. Progression of pubic hair growth can be seen on the right. The genital tissues are greatly influenced by natural fluctuations in hormone levels, which lead to changes in labia size, appearance, and elasticity at various life stages. At birth, the labia minora are well-developed, and the labia majora appear plump due to being exposed to maternal hormones in the womb. The labia majora have the same color as the surrounding skin.
Labial adhesions can occur between the ages of 3 months and 2 years, and may make the vulva look flat. These adhesions are not usually a cause for concern, and usually disappear without treatment.
Treatment options may include estrogen cream, manual separation with local anesthesia, or surgical separation under sedation. The labia minora become less prominent. During puberty , increased hormone levels often significantly change the appearance of the labia.
The labia minora become more elastic, prominent, and wrinkled. The labia majora regain fat, and begin growing pubic hair close to the pudendal cleft. Hair is initially sparse and straight, but gradually becomes darker, denser, and curlier as growth spreads outward and upward toward the thighs and mons pubis.
At the end of puberty, pubic hair will be coarse, curly, and fairly thick. The patch of pubic hair covering the genitals will eventually often form a triangle shape.
During the reproductive years, if a woman delivers a child, the fourchette will flatten. Pregnancy may cause the labia minora to darken in color. Following menopause, falling hormone levels cause further changes to the labia. The labia minora atrophy, making them become less elastic, and pubic hair on the labia majora becomes more sparse.
A vulva in the resting, unaroused state. The woman is sexually aroused, causing the inner and outer labia to swell, the labia majora to recede slightly, and the vulva to become lubricated. The labia are one of a woman's erogenous zones. The labia minora are sexually responsive,  and sensitivity varies greatly between women. In some women, they are so sensitive that anything other than light touch may be uncomfortable, whereas stimulation may elicit no sexual response in others.
The labia may be sexually stimulated as part of masturbation or with a sex partner , such as by fingering or oral sex. Moving the labia minora can also stimulate the extremely sensitive clitoris. During sexual arousal , the labia majora swell due to increased blood flow to the region,  and draw back,  opening the vulva slightly.
The labia minora become engorged with blood, causing them to expand in diameter by two to three times, and darken or redden in color. Continued stimulation can result in an orgasm, and the orgasmic contractions help remove blood trapped in the inner and outer labia, as well as the clitoris and other parts of the vulva, which causes pleasurable orgasmic sensations.
Following orgasm or when a woman is no longer sexually aroused, the labia gradually return to their unaroused state. In many cases, public exposure is limited, and often prohibited by law.
Some women prefer the look or feel of pubic hair, while others may choose to remove some or all of it. Temporary methods of removal include shaving , trimming, waxing , sugaring and depilatory products while permanent hair removal can be accomplished using electrolysis or laser hair removal.
Viewing pornography may influence a woman's view of her genitals. This can lead viewers of pornography to have unrealistic expectations about how the labia should look. Similar to how some women develop self-esteem issues from comparing their faces and bodies to airbrushed models in magazines, women who compare their vulvas to idealized pornographic images may believe their own labia are abnormal.
This can have a negative impact on a woman's life, since genital self-consciousness makes it more difficult to enjoy sexual activity, see a gynecologist, or perform a genital self-examination. Known as female genital mutilation , the procedures include clitoridectomy and so-called " pharaonic circumcision ," whereby the inner and outer labia are removed and the vulva is sewn shut.
Jewelry is worn in the resulting opening.