Basic understanding of pelvic anatomy is key to understanding pathologic processes. Pelvic anatomy must be understood as relationships among visceral organs, connective tissues, muscles, and nerves. Conceptualizing the three-dimensional (3D) aspects of these structures is useful when performing reconstructive pelvic surgery.
EXTERNAL GENITALIA (VULVA)
The female external genitalia, or vulva, include the mons pubis, labia majora and minora, clitoris, vestibule, vestibular bulbs, greater (Bartholin) and lesser vestibular glands, Skene glands, and the distal urethral and vaginal openings (Figure 2-1).
External female genitalia.
Mons Pubis and Labia Majora
The skin over the mons pubis and labia majora contains hair, and the subcutaneous layer is similar to that of the anterior abdominal wall. The subcutaneous layer consists of a superficial fatty layer similar to Camper’s fascia, and a deeper membranous layer, Colles’ fascia, which is continuous with Scarpa’s fascia of the anterior abdominal wall (Figure 2-2).
Dissection of labia majora with vestibular bulb (A) and Colles fascia (B) shown.
The firm attachments of Colles’ fascia to the ischiopubic rami laterally and the perineal membrane posteriorly prevent the spread of blood or infection from the superficial perineal space to the thighs or posterior perineal triangle. Anteriorly, the continuity of Colles with Scarpa fascia may allow the spread of blood and infection between these compartments. This continuity may also be apparent when subcutaneous gas is noted in the vulva during laparoscopic cases.
The inguinal canal allows communication between the intra-abdominal cavity and the subcutaneous tissue of the mons and labia majora. The round ligament and obliterated processus vaginalis exit the inguinal canal through the external or superficial inguinal ring and attach to the subcutaneous tissue or skin of the labia majora. An abnormally patent processus vaginalis, also known as the canal of Nuck, can result in hydroceles or inguinal hernias. Therefore, the differential diagnosis of a mass in the labium majus should include a round ligament leiomyoma and an inguinal hernia.
In contrast to the skin that overlies the labia majora, the skin of the labia minora does not contain hair and the subcutaneous tissue consists primarily of loose connective tissue (Figure 2-3). The labia minora lie between the labia majora and contribute to the lateral boundaries of the vestibule as described below. Anteriorly, each labium minus separates to form two folds that surround the glans of the clitoris. The prepuce is the anterior fold that overlies the glans, and the frenulum is the fold that passes below the clitoris. Posteriorly, the labia minora end at the fourchette.