The external genital organs of the female are collectively known as the vulva (also called the pudendum). Its functions are threefold:
- To act as sensory tissue during sexual intercourse
- To assist in micturition, by directing the flow of urine
- Defend the internal female reproductive tract from infection.
In this article, we shall look at the anatomy of the vulva – its structure, blood supply and innervation.
Structures of the Vulva
The vulva is comprised of many different anatomical structures, the most important of which are mentioned below:
- Mons pubis: A fat pad at the anterior of the vulva, which is covered in pubic hair.
- Labia majora: Two hair-bearing external folds, embryologically derived from labioscrotal swellings. They fuse posteriorly and extend anteriorly to the mons pubis.
- Labia minora: Two hairless folds of skin, embryologically derived from urethral folds. They lie within the labia majora. They fuse anteriorly to form the prepuce (hood) of the clitoris and extend posteriorly either side of the vaginal opening. They fuse again posterior to the vestibule, creating a fold of skin called the fourchette.
- Vestibule: The area between and surrounding the labia. The external vaginal orifice (vaginal opening) and urethra open into the vestibule.
- Bartholin’s Glands: Located either side of the vaginal orifice, these glands secrete lubricating mucus from small ducts during sexual arousion.
- Clitoris: Located under the prepuce and embryologically derived from the genital tubercle. The clitoris is formed of erectile corpora cavernosa tissue, which becomes engorged with blood during sexual stimulation.
Clinical Relevance: Infection of Bartholin’s Glands
The Bartholin’s glands (also known as the greater vestibular nerves) can become easily infected, and inflamed as a consequence. When this occurs, it is known as bartholinitis.
Bartholinitis is treated with a suitable antibiotic to clear the infection.
In some cases, the glands can become blocked, without infection, and fill with fluid. This is known as a Bartholin’s cyst.
Vascular Supply and Lymphatics
Blood supply to the external genitalia is delivered by the paired pudendal arteries, with the internal branch contributing mostly.
The veins of the vulva are the pudendal veins, with the smaller labial veins as tributaries. During sexual activity, these veins become engorged, increasing the size of the clitoris.
Lymphatic drainage is to the superficial inguinal lymph nodes.
The external female genitalia receives sensory and parasympathetic nervous supply.
With regards to sensory innervation, the vulva can be split into anterior and posterior sections:
- The anterior portion of the vulva is supplied by the ilioinguinal nerve, and the genital branch of the genitofemoral nerve
- The posterior portion of the vulva is supplied by the pudendal nerve, and by the posterior cutaneous nerve of the thigh.
The clitoris and the vestibule also receive parasympathetic innervation from the cavernous nerves, derived from the uterovaginal plexus.
Clinical Relevance: Sexually Transmitted Infections
Herpes simplex is most commonly caused by the Herpes simplex Type II virus. Symptoms include localised itching and burning, with formation of painful red vesicles ~3 days after infection. These may ulcerate and last up to 2 weeks, sometimes with recurrent attacks.
Genital warts are benign growths of epithelium caused by HPV. Infection can spread to the vagina and cervix, and is readily transmitted via sexual activity. Certain strains of HPV may predispose affected individuals to dysplastic changes in the cervix, vagina and/or anus which can potentially lead to carcinoma.