vulval anatomy
The vulva consists of seven main parts: the mons pubis, the labia majora and minora, the vestibule of the vagina, the hymen, the clitoris, and the external urethral orifice (Figure 2.1). All of these structures may vary in size and symmetry, but this is a subject that has been rather neglected. In a study of 59 textbooks, very little was included about this topic [1]. Patients often worry about normal variants and the quest for the ‘perfect’ vulva. Indeed, in a study of 33 women seeking labial reduction, all had labia minora within normal limits [2]. This incorrect perception was confirmed in another study of younger adolescent girls presenting for consideration of genital surgery. Again, none had documented abnormality [3]. Patients will also perceive an abnormality if the labia minora are visible, even though they are of normal size [4]. There has been more interest recently in the normal variation in appearance of the vulva in both popular culture and the scientific literature. The artist Jamie McCartney took plaster casts of 400 vulvas to create a sculpture which illustrates the wide range of appearance (www.greatwallofvagina.co.uk), and this has been used as both an artistic and educational resource.
Several studies have addressed the normal vulval appearance in adults [5,6,7], prepubertal girls [8,9], and adolescents [10]. These studies include women of different ethnicities but the measurements are similar, and average measurements of the vulval structures in adults are shown in Table 2.1. It has been shown that genital dimensions have no effect on sexual function [11].
Figure 2.1 Anatomy of the normal vulva.
Mons pubis
The 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