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Adolescence comprises a period in the life cycle between childhood
and adulthood. Biological, psychological, social, environmental, and
legal changes influence the definitive onset and termination of
adolescence. Pubescence is often described as the onset of adolescence;
however, the mean age of onset of puberty in girls in the United States
varies by race and is earlier than in previous generations. The
mean age of onset for white girls is 9.7 years with a range of onset
from 7.8 to 11.6 years; and for black girls, 8.1 years with a range
of onset from 6.1 to 10.1 years. In boys, the onset of puberty has remained
stable at 11.4 years of age with a range of 9.5 to 13.51-6 (see Chapter 540). For purposes of discussion in
this section, adolescence in chronologic years is defined as the period
from 10 to 21 years.
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All bodily tissues are affected by the biological changes of
puberty. Growth of the reproductive, cardiovascular, and musculoskeletal
systems is closely correlated during this period. The major biological changes
occurring during puberty can be classified into 6 groups: skeletal
growth, alterations in body composition, cardiorespiratory changes,
hematologic development, neuroendocrine development, and reproductive
maturation. Chronologic age does not always correlate with biological
maturity. Sexual maturation rating (SMR) stages, as originally described
by Tanner and Marshall, provide a more accurate assessment of the
biological developmental stage of the adolescent (see Chapter 540).7,8
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The secondary growth spurt at pubescence accounts for approximately
25% of final adult height.9 As outlined
in Table 63-1,10 the growth spurt
for girls occurs at an earlier sexual maturity rating (SMR 2–3)
than for boys (SMR 4). Girls reach a final mean adult height of
163.8 cm at a mean age of 16 years compared with 176.8 cm for boys
at a mean age of 18 years. Assessment of skeletal growth during
adolescence is done through the use of a height-velocity curve with
consideration of the gender-specific sexual maturity rating. Bone
age can be determined through the use of a hand roentgenogram.11
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