Labeled image of a vulva, showing external and internal views
The main structures of the vulva are: the mons pubis, the labia majora and labia minora, the external parts of the clitoris – the clitoral hood and the glans, the urinary meatus, the vaginal opening and hymen, and Bartholin's and Skene's vestibular glands. Other features include the pudendal cleft, pubic hair, sebaceous glands, the vulval vestibule, and the urogenital triangle.
The mons pubis is the soft mound of fatty tissue at the front of the vulva, in the pubic region covering the pubic bone. Mons pubis is Latin for "pubic mound" and is present in both sexes to act as a cushion during sexual intercourse, and is more pronounced in the female. The variant term mons veneris ('mound of Venus') is used specifically for females. The lower part of the mons pubis is divided by a fissure – the pudendal cleft – which separates the mons pubis into the labia majora. After puberty, the clitoral hood and the labia minora can protrude into the pudendal cleft in a variable degree. The mons and labia majora become covered in pubic hair at puberty.
The labia majora and the labia minora cover the vulval vestibule. The outer pair of folds, divided by the pudendal cleft, are the labia majora (New Latin for "larger lips"). They contain and protect the other structures of the vulva. The labia majora meet at the front at the mons pubis, and meet posteriorly at the urogenital triangle (the anterior part of the perineum) between the pudendal cleft and the anus. The labia minora are often pink or brownish black, relevant to the person's skin color.
The grooves between the labia majora and labia minora are called the interlabial sulci, or interlabial folds. The labia minora (smaller lips) are the inner two soft folds, within the labia majora. They have more color than the labia majora and contain numerous sebaceous glands. They meet posteriorly at the frenulum of the labia minora, a fold of restrictive tissue. The labia minora meet again at the front of the vulva to form the clitoral hood, also known as the prepuce.
The visible portion of the clitoris is the clitoral glans. Typically, this is roughly the size and shape of a pea, and can vary in size from about 6 mm to 25 mm. The size can also vary when it is erect. The clitoral glans contains as many nerve endings as the much larger homologous glans penis in the male, which makes it highly sensitive. The only known function of the clitoris is to focus sexual feelings. The clitoral hood is a protective fold of skin which varies in shape and size, and it may partially or completely cover the clitoris. The clitoris is the homologue of the penis, and the clitoral hood is the female equivalent of the male foreskin, and may be partially or completely hidden within the pudendal cleft.
There is a great deal of variation in the appearance of female genitals. Much of this variation lies in the significant differences in the size, shape, and colour of the labia minora. Though called the smaller lips they can often be of considerable size and may protrude outside the vagina or labia majora. This variation has also been evidenced in a large display of 400 vulval casts called the Great Wall of Vagina created by Jamie McCartney to fill the lack of information of what a normal vulva looks like. The casts taken from a large and varied group of women showed clearly that there is much variation. Pubic hair also varies in its colour, texture, and amount of curl.
The area between the labia minora where the vaginal opening and the urinary meatus are located is called the vulval vestibule, or vestibule of the vagina. The urinary meatus is below the clitoris and just in front of the vaginal opening which is near to the perineum. The term introitus is more technically correct than "opening", since the vagina is usually collapsed, with the opening closed. The introitus is sometimes partly covered by a membrane called the hymen. The hymen will usually rupture during the first episode of vigorous sex, and the blood produced by this rupture has been seen to signify virginity. However, the hymen may also rupture spontaneously during exercise or be stretched by normal activities such as the use of tampons and menstrual cups, or be so minor as to be unnoticeable, or be absent. In some rare cases, the hymen may completely cover the vaginal opening, requiring a surgical procedure called a hymenotomy. On either side of the back part of the vaginal opening are the two greater vestibular glands known as Bartholin's glands. These glands secrete mucus and a vaginal and vulval lubricant. They are homologous to the bulbourethral glands in the male. The lesser vestibular glands known as Skene's glands, are found on the anterior wall of the vagina. They are homologues of the male prostate gland and are also referred to as the female prostate.
Muscles underlying the vulva and perineum
Pelvic floor muscles help to support the vulvar structures. The voluntary, pubococcygeus muscle, part of the levator ani muscle partially constricts the vaginal opening. Other muscles of the urogenital triangle support the vulvar area and they include the transverse perineal muscles, the bulbospongiosus, and the ischiocavernosus muscles. The bulbospongiosus muscle decreases the vaginal opening. Their contractions play a role in the vaginal contractions of orgasm by causing the vestibular bulbs to contract.
Blood, lymph and nerve supply
The tissues of the vulva are highly vascularised and blood supply is provided by the three pudendal arteries. Venous return is via the external and internal pudendal veins.
The organs and tissues of the vulva are drained by a chain of superficial inguinal lymph nodes located along the blood vessels.
The ilioinguinal nerve originates from the first lumbar nerve and gives branches that include the anterior labial nerves which supply the skin of the mons pubis and the labia majora. The perineal nerve is one of the terminal branches of the pudendal nerve and this branches into the posterior labial nerves to supply the labia. The pudendal nerve branches include the dorsal nerve of clitoris which gives sensation to the clitoris. The clitoral glans is seen to be populated by a large number of small nerves, a number that decreases as the tissue changes towards the urether. The density of nerves at the glans indicates that it is the center of heightened sensation. Cavernous nerves from the uterovaginal plexus supply the erectile tissue of the clitoris. These are joined underneath the pubic arch by the dorsal nerve of the clitoris.
The pudendal nerve enters the pelvis through the lesser sciatic foramen and continues medial to the internal pudendal artery. The point where the nerve circles the ischial spine is the location where a pudendal block of local anesthetic can be administered to inhibit sensation to the vulva. A number of smaller nerves split off from the pudendal nerve. The deep branch of the perineal nerve supplies the muscles of the perineum and a branch of this supplies the bulb of the vestibule.