Chapter 13: Adolescence – Physical Development
Chapter Objectives
After this chapter, you should be able to:
- Explain the changes in physical growth and brain growth
- Compare and contrast different male and female changes that occur during puberty
- Discuss teenage pregnancy, birth control, and sexual health
- Summarize adolescent health: sleep, diet, and exercise
- Discuss drug and substance abuse
- Explain the prevalence, risk factors, and consequences of adolescent pregnancy and sexual health
- Describe several mental health issues for teens
Introduction
Adolescence is often defined as the period that begins with puberty and ends with the transition to adulthood. The commonly accepted beginning age for this period of development is age 12. When adolescence ends is harder to pin down. When does adulthood truly begin? Are we an adult at 18 years of age? Or 20? Or even older?
Adolescence physical development has evolved historically, with evidence indicating that this stage is lengthening as individuals start puberty earlier and transition to adulthood later than in the past. Puberty today begins, on average, at age 10–11 years for girls and 11–12 years for boys. This average age of onset has decreased gradually over time since the 19th century by 3–4 months per decade, which has been attributed to a range of factors including better nutrition, obesity, increased father absence, and other environmental factors (Steinberg, 2013). Completion of formal education, financial independence from parents, marriage, and parenthood have all been markers of the end of adolescence and beginning of adulthood, and all of these transitions happen, on average, later now than in the past.
Physical Growth
The adolescent growth spurt is a rapid increase in an individual’s height and weight during puberty resulting from the simultaneous release of growth hormones, thyroid hormones, and androgens. Males experience their growth spurt about two years later than females. The accelerated growth in various body parts happens at different times, but for all adolescents it has a fairly regular sequence. The first places to grow are the extremities (head, hands, and feet), followed by the arms and legs, and later the torso and shoulders. This non-uniform growth is one reason why an adolescent body may seem out of proportion. During puberty, bones become harder and more brittle.
Before puberty, there are nearly no differences between males and females in the distribution of fat and muscle. During puberty, males grow muscle much faster than females, and females experience a higher increase in body fat. An adolescent’s heart and lungs increase in both size and capacity during puberty; these changes contribute to increased strength and tolerance for exercise.
|
Figure 13.1 – An adolescent boy1 |
Figure 13.2 – An adolescent girl2 |
Brain Growth
Brain Growth continues into the early 20s. The development of the frontal lobe, in particular, is important during this stage. Adolescen