|Female external genitalia||Image|
FEMALE EXTERNAL GENITALIA
Female external genitalia consist of vulva (large lip and small lip or labium majus or labium minus, vestibule, bulb of vestibule, the greater vestibular gland, clitoris and the mons pubis. It includes the hymen in the virgin.
While the large lip is a homologue of the male scrotum, the small lip is the homologue of male penile urethra. The structures share the same embryological origin and similar vessels and nerves. The large lips are also called labia majora (plural) or labia majora pudendi. They are hair-bearing and they meet posteriorly at the commissure of labia (or posterior commissure) and anteriorly at the anterior commissure where they are more prominent. They structurally contain fatty tissue mingled with connective tissue and striated muscles resembling those of dartos muscle of the scrotum. The round ligament of uterus is attached to the labium majus. The small lips (or labia minora for plural or labia minora pudendi) are devoid of hair or fat. They are attached to the sides and dorsum of the clitoris forming two folds- the frenulum of clitoris (below the clitoris) and prepuce of clitoris (overhanging the clitoris). In the virgin, a membrane exists between the labia minora, which is just a thin mucous membrane, an extension from the membrane of the lower vagina, known as the hymen. This covers the introitus (opening into vagina) before the first sexual intercourse. The hymen is porous and usually has a small hole that allows the menstrual flow to pass before removal. It may be absent due to congenital or traumatic reasons. Or it may be imperforate in some women, a condition which is called imperforate hymen. Its structure is variable. It may be concave towards the pubes, or semilunar, cribriform, or fringed (forms border around the labia in a fringed manner). It may also be absent. When stretched, it is annular and widest at its posterior aspect. When torn at the first intercourse, rags of its tissue remain even in the multiparous and are called carunculae hymenales (carunculae mytriformes). It guards the opening into the vagina, called introitus.
The mons pubis is the prominent hair-bearing area of the external genitalia. Internally it contains considerable fat of the Camper's fascia. In the female its hairs stops abruptly at the junction between the abdomen and perineum. But in the male it extends convexly to the umbilicus.
This is the homologue of the penis. It is found in the female and it has all the features of the penis except the (penile) urethra. Hence it is provided with the corpus spongiosum, which is inserted into the glans clitoridis, without a urethra. It also has the two corpora cavernosa including all the vessels and nerves, which are the homologues of the male- e.g. deep artery of clitoris and dorsal artery of clitoris, deep dorsal vein of clitoris, crus of the clitoris and its covering ischiocavernosus muscle. The corpora cavernosa are separated by an incomplete septum called the pectiniform septum. The clitoris has suspensory ligament of clitoris. Ordinarily the clitoris is covered by prepuce, just like the uncircumcised penis. When erect, the prepuce retracts, allowing the organ to come out. It then presents with a root, shaft, neck and a very sensitive head called the glans clitoridis whose proximal edge is called the corona glandis. The shaft and neck may be called the body or corpus clitoridis. It is removed in mild female circumcision. In severe female circumcision, the clitoris is removed together with the vulva.
The crus of clitoris extends from the everted edge of the pubic arch at its medial surface and adjacent part of the perineal membrane (inferior fascia of urogenital diaphragm. They form the posterior part of the corpora cavernosa of the clitoris, the erectile tissue of the female. This is because they become the corpora cavernosa anteriorly. They also provide attachments for the Ischiocavernosus of the clitoris.
Function: This organ is specially designed for sexual arousal mechanism in the female. It is therefore the most sensitive part of the female sexual nervous system (but there are exceptions). Also, the glans clitoridis is the most sensitive part of the clitoris. It is removed in minimal female circumcision. In maximal female circumcision, the whole of the labia majora are removed along with the clitoris. It is also responsible for the maximal stimulation of sexual activity as in climax or orgasm. Again there are exceptions. This kind of orgasm is said to be different from the vaginal orgasm and is therefore called clitoral orgasm. Vaginal orgasm is not very common and may be present in less than 35% of women but clitoral orgasm is commoner probably because of masturbative activity of women in their earlier ages or easy manipulation by the male partner. Vaginal orgasm is due to deep pressure stimulation of the uterovaginal plexuses of nerves placed in the walls of the vagina. Clitoral orgasm may result from the excitation of these plexuses via tactile stimulation of the organ. It is a copiously innervated organ for its size.
It is bilateral. It is the homologue of the single bulb of penis in the male, which is the posterior part of the corpus spongiosum. In the female it serves similar function, containing erectile tissue and meeting anteriorly at the commissure of bulbs or commissura bulborum. This commissure is attached to the glans clitoridis. It is placed superficial to the greater vestibular gland. It is connected to the clitoris by strands of erectile tissue and plexus of veins. The corpus spongiosum in the female is therefore represented by the commissure, glans clitoridis, and the strip of erectile tissue, which attaches the bulb to the glans.
This gland is the homologue of the male bulbo-urethral gland. It is bilateral and placed deep to the bulb of vestibule. It opens with a duct between the labium minus and the hymen (carunculae hymenales) and may be responsible for lubricating the lower part of vagina.
Arteries of the female external genitalia
Veins of female external genitalia
Nerve supply of female external genitalia
Clitoris (see above)
Blood and nerve supply