Physical Changes of Puberty

In females, secondary sexual characteristic development is a result of estrogens from the ovaries. Breast budding is generally the first sexual characteristic to appear, and is most commonly classified by Marshall and Tanner's (1969) 5 stages of development, as illustrated in Table 16.1. Breast development begins in the United States between ages 8 and 13, with a mean age of 9.96 for White girls and a mean age of 8.87 for African American girls (Herman-Giddens et al., 1997). The process of developing mature breasts from breast budding takes approximately 4.5 years, regardless of whether or not girls enter puberty earlier or later than average (Brooks-Gunn & Reiter, 1990). Pubic hair development typically begins shortly after breast budding; however approximately 20 percent of girls experience pubic hair development prior to breast budding.

Pubic hair development begins in the United States between the ages of 8 and 13 years, with a mean age 10.5 years in White girls and 8.8 years for African American girls (Herman-Giddens et al., 1997). Table 16.1 illustrates the 5 stages of pubertal hair development in girls. Menarche is a late sign of pubertal development in girls and occurs following the peak in height velocity and during the rapid increase in weight and body fat (Tanner, 1978). The mean age of menarche in North America is 12.88 years for White girls and 12.16 years for African American girls (Herman-Giddens et al., 1997).

In males, secondary sexual characteristic development is a result of testosterone from the testes. The onset of testicular growth is the initial sign of pubertal development, which occurs on average

Table 16.1

The Five Pubertal Stages for Breast and Pubic Hair Growth in Girls

Stage Pubic Hair Development Breast Development

Table 16.1

The Five Pubertal Stages for Breast and Pubic Hair Growth in Girls

Stage Pubic Hair Development Breast Development

1.

No pubic hair

No breast development

2.

There is a small amount of long pubic hair chiefly along vaginal lips.

The first sign of breast development has appeared. This stage is sometimes referred to as the breast budding stage. Some palpable breast tissue under the nipple, the flat area of the nipple (areola) may be somewhat enlarged.

3.

Hair is darker, coarser, and curlier and spreads sparsely over skin around vaginal lips.

The breast is more distinct although there is no separation between contours of the two breasts.

4.

Hair is adult in type, but area covered is smaller than in most adults. There is no pubic hair on the inside of the thighs.

The breast is further enlarged and there is greater contour distinction. The nipple including the areola forms a secondary mound on the breast.

5.

Hair is adult in type, distributed as an inverse triangle. There may be hair on the inside of the thighs.

Mature stage size may vary in the mature stage. The breast is fully developed. The contours are distinct and the areola has receded into the general contour of the breast.

Source-. Table adapted and reproduced from W.A. Marshall and J.M. Tanner, Variations in the pattern of pubertal changes in girls, Archives of Disease in Childhood, 44 [1969], pp. 291-303. Copyright 1969 by BMJ Publishing Group.

Source-. Table adapted and reproduced from W.A. Marshall and J.M. Tanner, Variations in the pattern of pubertal changes in girls, Archives of Disease in Childhood, 44 [1969], pp. 291-303. Copyright 1969 by BMJ Publishing Group.

between ages 11 and 11.5, but can begin as early as age 9.5 (Brooks-Gunn & Reiter, 1990). Similar to girls, the most common classification of testicular and pubic hair development in males is Tanner's 5 stages of development (Marshall & Tanner, 1969), as illustrated in Table 16.2. Pubic hair growth begins on average at about age 12, however, 41% of boys are in Tanner Stage 4 of testicular growth when initial pubic hair growth begins. The average length of time between initial genital growth and

TABLE 16.2

The Five Pubertal Stages for Penile and Pubic Hair Growth in Boys

Stage Pubic Hair Development

Penile Development

1. There is no pubic hair, although there may be a fine velus over the pubes similar to that over other parts of the abdomen.

2. Sparse growth of lightly pigmented hair, which is usually straight or only slightly curled. This usually begins at either side of the base of the penis.

3. The hair spreads over the pubic symphysis and is considerably darker and courser and usually more curled.

4. The hair is adult in character but covers an area considerably smaller than in most adults. There is no spread to the medial surface of the thighs.

5. The hair is distributed in an inverse triangle as in the female. It has spread to the medial surface of the thighs but not up the linea alba or elsewhere above the base of the triangle.

The infantile state that persists from birth until puberty begins. During this time the genitalia increase slightly in overall size but there is little change in general appearance.

The scrotum has begun to enlarge, and there is some reddening and change in texture of the scrotal skin.

The penis has increased in length and there is smaller increase in breadth. There has been further growth of the scrotum.

The length and breadth of the penis have increased further and the glans has developed. The scrotum is further enlarged and the scrotal skin has become darker.

The genitalia are adult in size and shape. The appearance of the genitalia may satisfy criteria for one of these stages for a considerable time before the penis and scrotum are sufficiently developed to be classified as belonging to the next stage.

Source: Table adapted and reproduced from N.M. Morris and J.R. Udry, Validation of a self-administered instrument to assess stage of adolescent development, Journal of Youth and Adolescence, 9 [1980], pp. 275-276. Reprinted with kind permission of Springer Science and Business Media.

the development of mature genitalia in boys is 3 years (Brooks-Gunn & Reiter, 1990). Spermarche, or first ejaculation, usually occurs between 13 and 14 years of age. More noticeable physical changes in boys include voice changing and the development of facial hair, which occur predominantly in early adolescence (Brooks-Gunn & Reiter, 1990).

Compared to girls, not as many studies have been conducted with boys that compare timing of pubertal onset across ethnic groups. Based on data from the Third National Health and Nutrition Examination Survey (NHANES III), conducted between 1988 and 1994, African American boys had earlier median and mean ages for Tanner stages than the White and Mexican American boys (Sun et al., 2002). These findings parallel the findings that African American girls begin puberty earlier than White girls (Herman-Giddens et al., 1997).

Gender Differences in Physical Change

The developmental course of physical changes during puberty for girls and boys is demonstrated in Figures 16.1 and 16.2, respectively. Boys typically begin pubertal development about a year later than girls. Gender differences are also evident in regards to the alterations in linear growth, body composition, and the regional distribution of body fat during puberty. The pubertal growth spurt begins about 2 years earlier for females compared to males, and it also occurs at an earlier stage in puberty in girls than it does it boys (Fechner, 2003). Girls average a peak height velocity of 9 cm/yr at Tanner stage 2, and a total height gain of 25 cm during pubertal growth (Marshall & Tanner, 1969). Boys attain a mean peak height velocity of 10.3 cm/yr during Tanner stage 4 and gain 28 cm in height total (Marshall & Tanner, 1970). Increases and/or redistribution of body fat also occur in girls and boys during puberty. Prepubertally, lean body mass, bone mass, and body fat are about equal in boys and girls. However, postpubertal boys have 1.5 times the lean body mass and bone mass of postpubertal girls, and post-pubertal girls have twice as much body fat as postpubertal boys (Grumbach & Styne, 1998).

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