Helping Teens Answer the Question "Who Am I?": Physical Development (page 2)

By — University of Florida IFAS Extension
Updated on Jan 2, 2009


Puberty also has many effects on adolescents. Puberty is the time of development when youth become physically mature and capable of reproduction. These changes in the body are controlled by the endocrine glands. These glands manufacture hormones that are released by the pituitary gland, which is located at the base of the brain. These changes are quite different for girls and boys, so it is important to examine these changes individually for each sex.

By knowing what to expect during these critical years of physical development, parents will not be surprised if their child is on the early or late side of what we know to be the age range when these signs of puberty usually occur. Keep in mind that these ages are only an estimate and not every child fits within this range. Also, over time, we are seeing youth develop earlier, so this may be expected in future generations of teens.


For girls, on average, puberty takes about 3-4 years for completion, but may take less than a year and a half to as many as 5 years. The first sign of puberty for girls is the budding of breasts and a height spurt at the average age of 10. But it may range anywhere from ages 8-13. Some other signs of puberty include: the first appearance of pubic hair at around age 10 ½, but again, it could be as early as 8 years old and as late as 14 years old for some girls. The first menstruation usually takes place around age 12 ½ but some girls start as early as 10 ½ or as late as 15 ½, so don't be alarmed. If you have any concerns about this, however, contact your pediatrician. The first appearance of underarm hair usually occurs around age 13. Most girls have their breast growth completed at around age 14 and pubic hair growth at around age 14 ½.


For boys, the first puberty milestone is when the testes begin to enlarge at around 11 ½ years old. But remember, it may occur earlier or later so this could be anytime between the ages of 9 ½ to 13 ½ years old. Some other signs of puberty include: the first signs of pubic hair at around age 12 (or between ages 10-15); the penis begins to enlarge at about age 12 (or between ages 10 ½ to about 14 ½); a height spurt at around age 12 ½; the first ejaculation occurs (usually in their sleep) at about age 13; facial and body hair begin to grow at around age 14; voices begin to deepen at about age 14; penis growth is usually completed at around age 14 ½; and pubic hair growth is completed at around age 15 ½.

Late Adolescence, ages 15-18 years

Late adolescence is the second phase of physical growth for adolescents and leads them into emerging adulthood. As we have seen, many of the most rapid physical changes have already occurred. During this stage, the body begins to fill out and complete the process. As the adolescent body approaches its adult size, growth changes decrease quickly.

Height changes are nearly completed by around age 16 for girls and around age 17 for boys (Tanner, 1990). Muscle continues to develop at a more dramatic rate and in a much different pattern than fat during adolescence. Boys develop larger skeletal muscles, and greater heart and lung capacity. Boys also have an increase in red blood cells that allows them to carry more oxygen from the lungs to the muscles than those of girls, which helps them gain more muscle strength. It also explains gender differences in motor development throughout the teenage years.

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