Chapter 1 You: Growing and Changing
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People grow in six different areas. The rate of growth varies from area to
area as well as from person to person.
Physical growth is the easiest to observe. For instance, by age three,
children are twice as tall and four times as heavy as they were at birth.
This rate of growth slows down and then remains steady until about the
age of ten.
At puberty, the growth rates of boys and girls begin to differ.
Puberty is the time when the body fi rst becomes capable of reproducing
sexually. The body changes from that of a boy or girl to that of a man or
woman. This sudden growth and change is triggered by the pituitary
gland at the base of the brain. This gland secretes hormones that affect
other parts of the body. At puberty, hormones from the pituitary gland
stimulate the reproductive glands. The reproductive glands then
produce other hormones that cause changes in boys’ and girls’ bodies.
The age at which puberty begins varies. Most girls reach puberty at
about age 12. Most boys reach puberty two years later, at about age 14.
At puberty, a girl grows rapidly in height and weight. Her hips widen,
her breasts enlarge, and she begins her menstrual cycle. Hair appears in
the pubic region, under the armpits, and on the legs.