1. The Biological and Physical Changes of Adolescence
Chapter Three
The Biological and Physical Changes of Adolescence
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Chapter Objectives
To understand the role of hormones and initiating the stages of puberty and the feedback system regulating these
To look at the biological and physical changes that take place during puberty
To consider the psychological changes that accompany puberty and the social implications of pubertal changes
To know what factors contribute to health in adolescents and what might be cone to improve the well-being of all adolescents
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The Endocrine System
Consists of glands with the body that produce hormones and structures in the central nervous system
Hormones: chemical messengers, androgens in males and estrogens in females increase during puberty
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Hormonal Activity
Testosterone: male sex hormone associated with development of the genitals, skeletal growth and face hair
Estradiol: female sex hormone associated with breast development, distribution of body fat and in conjunction with progesterone, regulation of the menstrual cycle.
The production of hormones change with time of day, month, with stress, diet, weight, exercise, and medications.
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5. Puberty: A Two-Step Process
Pre-puberty: Adrenarche
Adrenal glands, located above the kidneys increase production of androgens between 6-8 years in both sexes.
Continue to rise through adolescence
Peak at the age of 20
Associated with skeletal growth, growth of pubic and underarm hair, oil and sweat glands and the external genitals in males
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6. Puberty: A Two-Step Process
Gonadarche
Hypothalamus: the body’s master clock, plays a central role in regulating the vents of puberty
Secrets a hormone gonadotropin-releasing hormone (GnRH) which act directly on the gonads signaling them to produce sex hormones (see figure 3.2)
Gonads: sex glands, ovaries in the female, testes in the male.
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A Feedback System
Gonadotropin hormones (LH & FSH) circulate in bloodstream, more frequently during sleeping than waking hours at the beginning of puberty
Gonadostat is located in hypothalamus and senses levels of circulating hormones.
Hypothalamus will signal to increase production of sex hormones if levels drop too low and decrease if levels are too high.
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8. The Physical Changes of Puberty
Primary sex characteristics include growth of the ovaries in females and testes in the males
Secondary sex characteristics includes the growth of pubic hair, breast development in females and facial hair in males
Timing varies more than sequence
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Growth Spurt
Regulated by the growth hormone
Growth hormone serves as a “gate crasher” for amino acids, the body’s building blocks and cell multipliers.
Growth hormone also affects changes in bones during puberty
Approximately 1/3 of minerals deposited in bones is during puberty
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10. The Growth Spurt in Females
1 ½ years before growth spurt, legs start to grow faster than body
Rapid growth in height about 11 yrs. old
Last for about 2 years, grow 8-10 inches
Shoulders widen
Later hips widen
Have 50% more body fat than males
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11. The Growth Spurt in Males
Begins anywhere between 10 ½ to 16 years
Boys grow for a longer time than girls
Reach their peak rate in growth 2 years later than girls
Will have 1 ½ times more muscle mass than female
Develop larger hearts, lungs, have higher systolic blood pressure and carry more oxygen in blood than girls.
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12. The Reproductive System of Females
Ovaries grow in size and increase their production of sex hormones at 9 or 10 years old
The uterus double in size, and vagina grows to 4-6 inches
Hymen, referred to as “cherry” is a delicate fold of skin at the opening of the vagina, frequently torn or stretched in childhood
Clitoris is the primary source of sexual stimulation, similar to penis in that it has glans, shaft and prepuce
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13. The Reproductive System of Males
Testes begin to develop around 11 years of age
Sex hormones stimulate the testes to produce sperm
Scrotal sac protects the testes from harm
Penis grows 3-4 inches and doubles in thickness during puberty
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Menarche
Term for girl’s first menstrual period
Average age for menarche is 12 ½ years
The menstrual cycle is regulated by the ovaries, the pituitary gland and the hypothalamus
The shedding of the lining of the uterus is the menstrual flow.
Anovulatory: cycles that occur without the release of an ovum
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Menarche conintued
Impossible to be certain when a female will ovulate, usually 14 days before the next period starts
Body fat is critical for menarche to occur: plays a role in converting androgens into estrogens, produces energy and is necessary for pregnancy
Girls are more likely to have positive experience when prepared for menarche, family important.
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Spermarche
A boy’s first ejaculation of seminal fluid, usually occurs about years of age
Nocturnal emission also know as wet dream
Little discussion or preparation with boys, books, peers or magazines are primary source of information
Not likely to discuss with anyone
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The Secular Trend
Begins earlier today than in the past
Age at menarche dropped by about 3-4 months every 10 years
19th century adolescents reached adult height in their 20’s, now reach adult height in late teens, early 20’s
½ inch taller and 2 pounds heavier than in the past
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18. Heightened Emotionality
Tensions are greatest in early adolescence, about years of age
Adolescents report more extreme states of emotions than their parents report (Larson and Richards, 1994)
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19. Relationships with Parents
Good relationships with parents can provide a powerful buffer against the stresses of adolescence
Adolescents begin to make more decisions, have more freedom and require less supervision
Increased tension and conflict, but most end successfully
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20. Early and Late Maturation
Asynchrony: differences in the timing of pubertal change from one adolescent to the next or within any adolescent
Can affect how they feel and think about themselves
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21. Early and Late Maturing Boys
Advantage for boys to mature earlier
Early maturing boys are self-confident, popular and achieve more recognition
Risk: more likely to engage in smoking or drinking and delinquent behavior, earlier sexual behavior
New research found early maturing boys may experience more adjustment problems than late maturing males.
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22. Early and Late Maturing Girls
Early maturation provides initial advantages and a number of problems
Many are self-conscious, lower self-esteem and lack poise of late maturing girls
Risks: associate with older peers, may engage in drinking and smoking, more likely to experience negative moods and depression, earlier sexual behavior
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23. Maturation and Parents
Who is talking to adolescents about their issues during puberty?
58% of adolescents had personal concerns they did not want to discuss with parents
69% had concerns they would not discuss with friends
82% were concerned about confidentiality
20% have used the Internet for information
Most concerns are common, but enormous issues for adolescents
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24. Body Image and Self-Esteem
How satisfied adolescents are with their bodies depends on how others react to them
How satisfied they are with their bodies predict their level of self-esteem, particularly in girls
Boys have a more positive body image than girls
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Health and Well-Being
Adolescents are at their peak of fitness and health
Muscles have increased 14 fold in boys and 10 fold in girls
Cardiovascular and respiratory systems reach adult level of efficiency
Chronic diseases are rare
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Nutrition
Adolescents have increased nutritional needs, yet eat erratically
Nearly ½ of all the meals eaten in the U.S. are in restaurants
Fail to get the necessary nutrients, but do get excess fats, sugars and salt and calories
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27. Physical Activity How active are adolescents?
2/3 of high-school students say they engage in physical activity for at least 20 minutes, 3 days a week
72% of 9th graders indicate being active as opposed to 52% of 12th graders
Boys (70%) are more active than girls (55%)
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28. Factors That Limit Physical Activity
Fewer high-schools offer physical education
Low-income
High crime neighborhoods
Inadequate transportation
Presence of gangs
Creating safe recreational centers in communities needs to be a priority
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Overweight
Adolescents who are overweight has tripled since the 1970’s
16% of year olds are overweight
Another 15% are at risk
Weight problems cause health risks
Overweight adolescents are less active than peers of average weight
Success of weight loss programs depend on integrating the family.
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Health Care
9 million children and adolescents do not have health insurance, yet 5.8 million could receive free insurance through Medicaid
Adolescents and young adults experience poorer access to health care
Adolescents report difficulty knowing where to go, finding transportation, anxiety as to what might be done, not wanting their parents to know and not having insurance coverage
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Poverty
Adolescents live in conditions they have not control over, yet they constitute risks to their well-being
20% of U.S. adolescents live in poor families
12% live in low-income families
Conditions of poverty are related to stress and elevated risk of injury
Health concerns:
Exposure to toxins, air pollution, inferior drinking water, noise pollution, poor housing, hazardous neighborhoods
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