Development
The development of pubic hair can be assessed using the Tanner scale. Before the onset of puberty, the genital area of both boys and girls has very fine vellus hair, referred to as Tanner stage 1 hair. As puberty begins, the body produces rising levels of the sex hormones known as androgens, and in response the skin of the genital area begins to produce thicker and rougher, often curlier, hair with a faster growth rate. The onset of pubic hair development is termed pubarche. The change for each hair follicle is relatively abrupt, but the extent of skin which grows androgenic hair gradually increases over several years.
In males, the first pubic hair appears as a few sparse hairs on the scrotum or at the upper base of the penis (stage 2). Within a year, hairs around the base of the penis are numerous (stage 3). Within 3 to 4 years, hair fills the pubic area (stage 4) and becomes much thicker and darker, and by 5 years extends to the near thighs and upwards on the abdomen toward the umbilicus (stage 5).
Other areas of the skin are similarly, though slightly less, sensitive to androgens and androgenic hair typically appears somewhat later. In rough sequence of sensitivity to androgens and appearance of androgenic hair, are the armpits (axillae), perianal area, upper lip, preauricular areas (sideburns), periareolar areas (nipples), middle of the chest, neck under the chin, remainder of chest and beard area, limbs and shoulders, back, and buttocks.
Although generally considered part of the process of puberty, pubarche is distinct and independent of the process of maturation of the gonads that leads to sexual maturation and fertility. Pubic hair can develop from adrenal androgens alone, and can develop even when the ovaries or testes are defective and nonfunctional. See puberty for details.
There is little if any difference in the capacity of male and female bodies to grow hair in response to androgens. The obvious sex-dimorphic difference in hair distribution in men and women is primarily a result of differences in the levels of androgen reached as maturity occurs.
Pubic hair and axillary (armpit) hair can vary in color considerably from the hair of the scalp. In most people it is darker, although it can also be lighter. In most cases it is most similar in color to the eyebrows of the individual. On some individuals, pubic hair is thick and/or coarse; on others it may be sparse and/or fine; these varieties may appear in either sex. Hair texture varies from tightly curled to entirely straight. Pubic hair patterns can also vary by race and ethnicity.
Patterns of pubic hair, known as the escutcheon, vary between sexes. On most women, the pubic patch is triangular and lies over the mons pubis. On many men, the pubic patch tapers upwards to a line of hair pointing towards the navel (see abdominal hair), roughly a more upward-pointing triangle. As with axillary (armpit) hair, pubic hair is associated with a concentration of sebaceous glands in the area.
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