The labia are part of the female
genitalia; they are the major externally visible portions of the
vulva
The vulva (plural: vulvas or vulvae; derived from Latin for wrapper or covering) consists of the external female sex organs. The vulva includes the mons pubis (or mons veneris), labia majora, labia minora, clitoris, vestibular bulbs, v ...
. In humans, there are two pairs of labia: the ''
labia majora'' (or the outer labia) are larger and thicker, while the ''
labia minora'' are folds of skin between the outer labia. The labia surround and protect the
clitoris
The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora (inner lips), above the o ...
and the openings of the
vagina
In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hy ...
and the
urethra
The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra c ...
.
Etymology
''Labium'' (plural ''labia'') is a
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...
-derived term meaning "
lip". ''Labium'' and its derivatives (including labial, labrum) are used to describe any lip-like structure, but in the English language, ''labium'' often specifically refers to parts of the
vulva
The vulva (plural: vulvas or vulvae; derived from Latin for wrapper or covering) consists of the external female sex organs. The vulva includes the mons pubis (or mons veneris), labia majora, labia minora, clitoris, vestibular bulbs, v ...
.
Anatomy
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
The vulva (plural: vulvas or vulvae; derived from Latin for wrapper or covering) consists of the external female sex organs. The vulva includes the mons pubis (or mons veneris), labia majora, labia minora, clitoris, vestibular bulbs, v ...
to form the
pudendal cleft
The vulva (plural: vulvas or vulvae; derived from Latin for wrapper or covering) consists of the external female sex organs. The vulva includes the mons pubis (or mons veneris), labia majora, labia minora, clitoris, vestibular bulbs, v ...
through the middle. The labia majora often have a plump appearance, and are thicker towards the anterior.
The anterior junction of the labia majora is called the
anterior commissure, which is below the
mons pubis and above the clitoris. To the posterior, the labia majora join at the
posterior commissure, which is above the
perineum
The perineum in humans is the space between the anus and scrotum in the male, or between the anus and the vulva in the female. The perineum is the region of the body between the pubic symphysis (pubic arch) and the coccyx (tail bone), inclu ...
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: nymphae), also called inner labia or inner lips, are two soft folds of fat-free, hairless skin between the labia majora. 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.
When standing or with the legs together, the labia majora usually entirely or partially cover the moist, sensitive inner surfaces of the
vulva
The vulva (plural: vulvas or vulvae; derived from Latin for wrapper or covering) consists of the external female sex organs. The vulva includes the mons pubis (or mons veneris), labia majora, labia minora, clitoris, vestibular bulbs, v ...
, which indirectly protects the vagina and urethra,
much like the lips protect the mouth. 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
An apocrine sweat gland (; from Greek ''apo'' 'away' and ''krinein'' 'to separate') is composed of a coiled secretory portion located at the junction of the dermis and subcutaneous fat, from which a straight portion inserts and secretes into the ...
, and
eccrine sweat glands. The labia majora have fewer superficial nerve endings than the rest of the vulva, but the skin is highly vascularized.
The internal surface of the labia minora is a thin moist skin, with the appearance of a mucous membrane. 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.
Diversity
The color, size, length and shape of the inner labia can vary extensively from woman to woman.
In some women the ''labia minora'' are almost non-existent, and in others they can be fleshy and protuberant. They can range in color from a light pink to brownish black,
and texturally can vary between smooth and very rugose.
Embryonic development and homology
The biological sex of an individual is determined at
conception, which is the moment a
sperm fertilizes an
ovum
The egg cell, or ovum (plural ova), is the female reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete i ...
,
creating a
zygote
A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism.
In multicell ...
.
The chromosome type contained in the sperm determines the sex of the zygote. A
Y chromosome
The Y chromosome is one of two sex chromosomes ( allosomes) in therian mammals, including humans, and many other animals. The other is the X chromosome. Y is normally the sex-determining chromosome in many species, since it is the presence or a ...
results in a male, and an
X chromosome
The X chromosome is one of the two sex-determining chromosomes ( allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO se ...
results in a female. A male zygote will later grow into an
embryo
An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...
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
Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during preg ...
.
Initially, the external genitals develop the same way regardless of the sex of the embryo, and this period of development is called the ''sexually indifferent'' stage.
The embryo develops three distinct external genital structures: a
genital tubercle; two
urogenital folds, one on either side of the tubercle; and two
labioscrotal swellings, each bounding one of the urogenital folds.
Sexual differentiation starts on the internal sex organs at about 5 weeks of gestation, resulting in the formation of either testes in males, or ovaries in females. If testes are formed, they begin to secrete androgens that affect the external genital development at about week 8 or 9 of gestation.
The urogenital folds form the labia minora in females, or penile shaft in males. The labioscrotal swellings become the labia majora in females, or they fuse to become the scrotum in males. Because the male and female parts develop from the same tissues, this makes them
homologous
Homology may refer to:
Sciences
Biology
*Homology (biology), any characteristic of biological organisms that is derived from a common ancestor
*Sequence homology, biological homology between DNA, RNA, or protein sequences
* Homologous chrom ...
(different versions of the same structure). Sexual differentiation is complete at around 12 weeks of gestation.
Changes over time
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 adhesion
Labial fusion is a medical condition of the female genital anatomy where the labia minora become fused together. It is generally a pediatric condition.
Presentation
Labial fusion is rarely present at birth, but rather acquired later in infancy, s ...
s 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.
During early childhood, the labia majora look flat and smooth because of decreasing levels of body fat, and the diminished effects of maternal hormones. The labia minora become less prominent.
During
puberty
Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a b ...
, 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.
By adulthood, the outer surface of the labia majora may be darker than the surrounding skin, and may have wrinkles similar to those on a male's scrotum. During the reproductive years, if a woman delivers a child, the fourchette will flatten. Pregnancy may cause the labia minora to darken in color.
Later in life, the labia majora once again gradually lose fat, becoming flatter and more wrinkled, and pubic hair turns grey. 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.
Sexual arousal and response
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
Oral sex, sometimes referred to as oral intercourse, is sexual activity involving the stimulation of the genitalia of a person by another person using the mouth (including the lips, tongue, or teeth) and the throat. Cunnilingus is oral sex p ...
. Moving the labia minora can also stimulate the extremely sensitive clitoris.
During
sexual arousal, the labia majora swell due to increased
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in th ...
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.
Because pregnancy and childbirth increase genital vascularity, the inner and outer labia will engorge faster in women who have had children.
After a period of sexual stimulation, the labia minora will become further engorged with blood approximately 30 seconds to 3 minutes before orgasm,
causing them to redden further.
In women who have had children, the labia majora may also swell significantly during this period, becoming dark red. 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.
The labia minora return to their original color within 2 minutes, and engorgement dissipates in about 5 to 10 minutes.
The labia majora return to their pre-arousal state in approximately 1 hour.
Society and culture
In many cultures and locations all over the world, the labia, as part of the
genitalia, are considered private, or
intimate parts, whose exposure (especially in
public
In public relations and communication science, publics are groups of individual people, and the public (a.k.a. the general public) is the totality of such groupings. This is a different concept to the sociological concept of the ''Öffentlichk ...
) is governed by fairly strict socio-cultural
mores. In many cases,
public exposure is limited, and often prohibited by law.
Views on pubic hair differ between people and between cultures. 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
Sugaring is a food preservation method similar to pickling. Sugaring is the process of desiccating a food by first dehydrating it, then packing it with pure sugar. This sugar can be crystalline in the form of table or raw sugar, or it can be de ...
and
depilatory products while permanent hair removal can be accomplished using
electrolysis or
laser hair removal.
In Korea, pubic hair is considered a sign of fertility, leading some women to have pubic hair transplants.
Some women are self-conscious about the size, color or asymmetry of their labia. Viewing
pornography may influence a woman's view of her genitals.
Models in pornography frequently have small or non-existent labia minora, and images are often airbrushed,
so pornographic images do not depict the full range of natural variations of the vulva. 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.
Developing an awareness for how much the labia truly differ between individuals may help to overcome this self-consciousness.
In several countries in Africa and Asia, the external female genitals are routinely altered or removed for reasons related to ideas about tradition, purity, hygiene and aesthetics. 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. FGM is mostly outlawed around the world, even in countries where the practice is widespread.
Labiaplasty is a controversial
plastic surgery procedure that involves the creation or reshaping of the labia.
The Centrefold Project
/ref> Labia piercing is a cosmetic piercing, usually with a special needle under sterile conditions, of the inner or outer labia. Jewelry is worn in the resulting opening.
Additional images
File:Clitoris_outer_anatomy.gif, Outer anatomy of clitoris.
File:Illu repdt female.jpg, Organs of the female reproductive system.
File:Gray1230.png, Median sagittal section of female pelvis.
File: Hairy vulva of a young woman 2.jpg, Labia majora with pubic hair.
See also
* '' Femalia''
* Labia pride
* Labia stretching
* Labiaplasty
References
External links
*
{{Authority control
*
Mammal female reproductive system