Ridley's The Vulva. Группа авторов

Figure 2.8 Histology of vestibular papillomatosis. Low power showing papillary projections with normal epithelium each arising from individual base.

Hymen

The hymen is a thin membrane of connective tissue surrounding the inner edge of the vestibule and the opening of the vagina. The appearance is again varied and can be a ring or semi‐circular fold. Once ruptured, an irregular ragged edge is left around the vaginal opening, and these small elevations are termed hymenal remnants (Fig 2.9). Rupture can occur with exercise, tampon use, or sexual intercourse. It is clear that hymenal examination does not predict virginity status accurately or reliably and should never be performed for this purpose [24]. Developmental anomalies of the hymen are discussed in Chapter 1.

Figure 2.9 Hymenal remnants and tags.

The external urethral meatus and urethra

The female urethra is about 4 cm long and runs from the bladder downwards and forwards, embedded in the anterior wall of the vagina behind the symphysis pubis. The length can vary, and in a large study of 927 Caucasian women, the length was increased in the obese but reduced in those with a history of vaginal delivery [25]. After passing through the pelvic floor and perineal membrane, it ends at the external urethral orifice. The urethra is fixed at its origin by the pubovesical ligaments, throughout its length by the anterior wall of the vagina, and as it enters the perineum by the urogenital diaphragm. The external urethral orifice lies in the midline of the vestibule between the vagina and the clitoris. The orifice is easily seen, and on occasions there may be bright red projections of prolapsed urethral mucosa herniating out. These urethral caruncles are most commonly seen in post‐menopausal women and are thought to be due to reduced oestrogen (Figure 2.10).

Figure 2.10 Urethral caruncle in a patient with lichen sclerosus.

      Skene’s glands (paraurethral glands) are paired glands with their ducts opening on each side of the urethral orifice. Evidence suggests that they are analogous to the male prostate gland [26].

Associated structures

      The vagina

      The vagina is a fibromuscular tube about 7–10 cm long. It opens on the vulval vestibule and extends upwards and backwards, to be attached just above the lower margin of the uterine cervix. As the long axis of the vagina forms a right angle with the long axis of the normal anteverted uterus, the cervix projects downwards and backwards into the upper vagina. The vaginal fold around the periphery of the cervix is divided into anterior, posterior, and lateral fornices. The posterior wall of the vagina is about 2 cm longer than the anterior wall, but they are in contact with each other in the un‐distended vagina. This gives the vagina a crescentic or H‐shaped appearance in cross‐section. The outer wall of the vagina contains its vascular, lymphatic, and nerve supply.

The vagina is related anteriorly to the base of the bladder and to the urethra, which is embedded in its anterior wall. Posteriorly, the upper part of the vaginal wall is covered with peritoneum, and below the rectouterine pouch it is directly related to the ampulla of the rectum. In the perineum, it is separated from the anal canal by the perineal body (Figure 2.11). The upper vagina gives attachment to the uterosacral ligaments posteriorly, the cardinal or transverse ligaments laterally, and the base of the bladder anteriorly, which itself is supported by the pubovesical ligaments. As the vagina passes through the pelvic floor, the most medial fibres of the pubococcygeus blend with its walls to form a supporting muscular sling. Below the pelvic floor the vagina is supported by the urogenital diaphragm, the perineal body, and the perineal musculature. Thus, the vagina has three compartments:

Figure 2.11 Midline section through pelvis and perineum.

       upper, above the pelvic floor and related to the rectum

       middle, which traverses the pelvic floor and urogenital diaphragm

       lower in the perineum.

The perineum

      The perineum is the outer diamond‐shaped area inferior to the sheet of muscle forming the pelvic floor, and is bounded by the symphysis pubis anteriorly, the ischial tuberosities laterally, and the coccyx posteriorly. It is an embryological junctional zone derived from the body wall ectoderm, hindgut endoderm, and the intervening mesoderm that surrounded the original cloacal membrane. It is further divided into an anterior urogenital triangle and posterior anal triangle. The vulva lies mainly within the anterior urogenital triangle but then extends anteriorly to the pubic symphysis. The anal canal and ischiorectal fossa occupy the posterior anal triangle. The perineal body is a fibromuscular mass lying between the upper half of the anterior anal wall and the entire posterior portion of the vagina. It is the central point where muscles attach to the ischial tuberosities.

The urogenital triangle

      The urogenital triangle is contained within the subpubic arch and is divided into superficial and deep perineal pouches by the urogenital diaphragm.

       The urogenital diaphragm

The urogenital diaphragm (also known as perineal membrane or triangular ligament) is a tough fibrous membrane attached to the pubic rami (Figure 2.12). It has three midline breaks, one at the apex of the triangle just below the pubic symphysis where the clitoral vessels and nerves pass from the deep to the superficial perineal pouch, and two more posteriorly for the entrances of the urethra and vagina.

       Deep perineal pouch

      The deep perineal pouch is limited above by the pelvic floor and pubovesical ligaments and below by the urogenital diaphragm. It is continuous with the ischiorectal fossae posteriorly. The urethra and vagina pass through the deep perineal pouch in the midline. Vessels and nerves run alongside the urethra and vagina, and their clitoral branches ascend through the apical opening in the urogenital diaphragm. The deep pouch also contains voluntary muscle fibres, some of which surround the urethra and vagina while others run transversely into the perineal body behind the vagina.

       Superficial perineal pouch

This lies below the urogenital triangle and contains the structural elements of the female external genitalia, which, with