mons pubis (mons) in the adult female is a prominent pad of hair‐bearing skin and subcutaneous fat overlying the pubic symphysis. It forms an inverted triangle with the base being the anterior horizontal line of pubic hair growth. The average length of the base is 16 cm, and the height about 13 cm [12].
The character of pubic hair varies with ethnic background, as it is generally thicker in type 5 and 6 skin types. The normal hair density is 6–31 hairs/cm2, but this, together with the rate of hair growth, reduces with age. About a third of women over the age of 60 have progressive loss of pubic hair [13]. There is no change in the thickness of the hair with age. In contrast to hair growth in the axillae and on the scalp, pubic hair growth is not altered during pregnancy [14].
Labia majora
The labia majora are two cutaneous folds that form the lateral boundaries of the pudendal cleft. They originate from the mons pubis anteriorly and merge with the perineal body posteriorly (the posterior labial commissure). The subcutaneous fat is mainly deposited in the medial aspects, and so they tend to flatten out as they reach the perineal body. The lateral surfaces of the labia majora are adjacent to the medial surfaces of the thighs and are separated from them by a deep groove, the genitocrural or inguinal fold. The medial surfaces may be in contact with each other, but may be separated by the labia minora if they are large. The size of the labia majora varies considerably. The length of the labia majora and introitus has been shown to be positively correlated with body mass index but inversely correlated with age [5].
Table 2.1 Normal measurements of vulval structures
| Mean (mm) | Range (mm) | |
|---|---|---|
| Clitoris | ||
| Width | 4.7 | 1–22 |
| Length | 10.0 | 5–35 |
| Clitoris to urethra | 25.0 | 3–65 |
| Labia majora | ||
| Length | 8.3 | 12–180 |
| Labia minora | ||
| Length | 50.0 | 5–100 |
| Width | 28.6 | 1–61 |
| Perineum | 25.7 | 3–55 |
| Urethra | ||
| Length | 40.0 | 19–45 |
Labia minora
The labia minora are two thin folds of keratinised skin that lie medial to the labia majora and lateral to the vestibule. They are separated from the labia majora by interlabial folds (sulci) in which the normal secretions from the adjacent skin surfaces may accumulate. Anteriorly, the labia minora divide into lateral and medial parts. The lateral parts join in a fold of skin over the glans to form the prepuce or hood of the clitoris, and the medial parts join under the clitoris to form its frenulum. Posteriorly, the labia minora fuse to form a transverse fold behind the vaginal opening, the fourchette.
There is great variation in the size and symmetry of the labia minora (Figure 2.2a–d). In a study of 319 women, the length of the labia minora was associated with height and weight, and 23.8% of women had a 30% difference in the width of the labia minora on each side, confirming the asymmetry seen [7]. In 44 adolescents between the ages of 10 and 19, variation in length and width was again confirmed, with 43% showing asymmetry [10]. They can sometimes be bifid in their anterior insertion (Figure 2.2d).
There is also wide variation in the texture of the labia minora. In a study of 50 women, the rims of the labia minora were smooth in 14, moderately rugose in 34, and markedly rugose in 2 [6]. Pigmentation of the rims is very common and was confirmed in 41 of the 50 patients.
Sebaceous glands (Fordyce spots)
The whole of the inner surface of the labia minora may be covered with small sebaceous papules. These are a normal finding on the vulva, and the term Fordyce spots, which is often used, is not accurate as this refers to ectopic sebaceous glands, as found on the buccal mucosa. On the vulva, they are not ectopic but a part of the normal anatomy. They are very prominent in some women but can be seen more clearly if the labia are stretched (Figure 2.3).
The clitoris
The clitoris is a complex structure, and our understanding of the anatomy has been helped by the use of MRI studies [15,16].
The clitoris has a wishbone like structure with the arms being the crura extending forwards as the corpora cavernosa and meeting in the midline to form the body of the clitoris (Figure 2.4). The tip of the body then bends anteriorly to form the glans clitoris, which is the only visible part, and is non‐erectile. The glans is covered by the clitoral hood, formed by the anterior fusion of the labia minora. The crura are attached to the pubic rami and covered by the ischiocavernosus muscle, and the clitoral body is attached to the pubic symphysis by a suspensory ligament. The clitoral bulbs lie between the crura and the urethra against the vaginal wall. They are covered by the bulbospongiosus muscles, which extend from the perineal body, around the vagina and urethra, to the glans clitoris. The whole of the clitoris is composed of similar erectile tissue with the exception of the glans [16].
Figure 2.2 Variation in appearance of normal labia minora. (a) Symmetrical labia minora with pigmentation on rim. (b) Labia minora protruding outside labia majora in a patient with lichen sclerosus.
