Puberty, Health and Biological Processes
for Middle Childhood through Adolescence

School of Family and Consumer Sciences 400.404/504    Instructor: D. Witt

On Biological and Physical Development in Middle Childhood.

Development occurs most in the first three years of life than any other period throughout development.
During middle childhood, it becomes slow and quite irregular. At age 6, children generally weigh 45 pounds and are 3.5 feet tall. Children continue to grow about 2 to 3 inches in height and 5 pounds in weight each year on average, however such growth tends to occur in spurts that happen at slightly different ages for boy and girls.

For Girls at ages 4.5, 6.5, 8.5, and 10            For Boys at ages 4.5, 7.0, 9.0 and 10.5
  • During infancy and early childhood, children grow from head to toe (cephalocaudally). However, during middle childhood, we reverse in development—we grow from bottom to top.
  • In the early periods of development, we also grow from center outward (proximodistally).  This development reverses during middle childhood, with limbs growing faster than the trunk of the body.
  • Also Females accumulate more body fat (start getting "curves" after the age of 8 and continues throughout adolescence.
The Nature vs. Nurture Arguments:
  • NATURE - Good genes are passed thru next generation.  Bad genes are not passed
  • NURTURE - Nutrition, Health, Disease control, Family Resources play as big a part.
  • SECULAR TRENDS - Changes in growth or body size from one generation to another generation. Onset of menarche - Menstruation has begun at slightly earlier ages for girls with each passing century.

  • SKELETAL DEVELOPMENT DURING MIDDLE CHILDHOOD
    • Bones grow longer and broader
    • Replacement of primary (baby) teeth with permanent teeth (around ages 6-7 - Between ages 6 and 12, all 20 primary teeth are replaced
    •     Children lose their 1st at the end of early childhood.  Girls lose their teeth earlier than boys
    • The 1st teeth to go are central incisors (lower and upper front teeth). - In 14% of cases, serious difficulties in chewing and biting may result
    • Malocclusion are generally caused by thumb sucking after permanent teeth start coming in or are crowded.

  • BRAIN DEVELOPMENT
    • The frontal lobe increases in size and maturity.  Responsible for development of more complex thought and end of self-consciousness. Prefrontal cortex continues to grow throughout adolescence.
    • Brain development is highly attributed to neurotransmitters—chemicals that allow communication between neurons through synapses.  Over time, they become more selective and efficient
    • When neurotransmitters are not balanced, predisposed to epilepsy, ADHD, and emotional disturbances - this is not the norm for the vast majority of children.

  • HEALTH RELATED PROBLEMS
    • Infections/diseases are less prevalent in middle childhood, unless diet and home discipline is poor - related to poverty.
    • Some 25% are affected with myopia (nearsightedness)
    • 27% of children suffer from obesity (leading to HB pressure, cholesterol, diabetes, respiratory abnormalities, heart disease.
    • There are some known factors associated with childhood obesity, including heredity, social class, early growth patterns (early developers), family dietary habits, responsiveness to food ques, level of physical activity, television viewing (by the time a child reach high school, he or she has spent 25,000 hours watching TV), traumatic events.

The Onset of Rapid Biologically Induced Change
Defined as a biological phenomenon in which the human body becomes capable of fertility. But it's about much more than reproduction. Puberty is an awkward time in the lives of Western adolescents.
The IMMINENT BIOLOGICAL TRANSITION must be integrated with the social norms providing for its acceptance. That means, depending on the particular social environment of the individual, puberty can be easily accomplished or may be met with resistance, conflicts and disagreements as to its MEANING.

Genetic Influences on Adolescent Development
Genes and Genetic Principles Individuals carry the combined genetic code of their biological parents through 23 pairs of chromosomes. Except for the general "humanness" of the general genetic code for human beings, each person's genetic code makes them unique. "Every person is like every other, and at once, like no other."
The General Hereditary Code provides human commonalities, such as:

    • physical similarities (anatomy, brain structure, size, type-placement-number of internal organs, skeletal form and function, number of eyes, senses, orifices.
    • psychological similarities (allowing for the diagnosis of mental illness or the assessment of mental health, similarities in cognitive processes).
Genotype is the special arrangement of chromosomes & genes that individualizes each person (genes for eye color, voice timbre, height, weight, maybe even temperament). The

Phenotype
is the sum of all of a person's physical and psychological features that can be observed and measured.
Genotype is potential outcome - Phenotype is actual outcome. Any one phenotypical characteristic can be the result of any genotypical arrangement, or due to Environmental Interruptions, can be changed dramatically.

So Genetic Heredity plays a part, but only a part in the final outcome of any given characteristic. Biological determinants can be mitigated by social or other environmental conditions.
Here's another example:: A genotype likely to produce average intelligence could be interrupted by super diet and strong family attitudes toward the value of education - producing a "smarter than genetically predictable child".

Polygentic Inheritance refers to the principle that explains the importance of "interaction between genetic effects" - as potential characteristics combine in effect, the outcome is said to fall into a "reaction range" of phenotypes. This suggests that environmental events can alter the outcome phenotype. The extent to which heredity determines the development of the person often depends on the extent to which the social/environmental conditions are CONDUCIVE to the person's biology.

For example, society has often run in opposition to biology: Chinese foot binding, scarification rituals of circumcision, Anti-intellectualism in the Western World. In other instances, genetic potential stubbornly has its way in spite of environmental interruptions.

Canalization refers to the narrow path of development of some human characteristics - mainly the general physical traits, but some psychological ones adhere to natural human development over environment:

    For example, while some abused children will learn to emulate the behaviors they experience from abusive are givers, MOST do not grow up to become abusers themselves. Similarly, severely deprived children tend to rapidly catch up on develop after deprivation is discontinued.

    This is true generally, however environmental intrusion into normal development can trump nature if the intrusion is powerful enough and more constant. This is known as the continuum of indirectness - that the more influence the environment may exert on a particular trait, the less direct the influence of natural heredity.

    Generally, physical characteristics are more directly influenced by genes (barring such events as cosmetic surgery, famine, war, accidents) while psychological "tendencies" such as the susceptibility to disease, native intelligence, emotional traits, are less directly controlled by genes.

The Heritability Quotient is a mathematical equation for estimating how much more alike identical twins are than fraternal twins - but it is useful in this discussion as well. It states that biological heredity declines in effect from most influential to least influential in the following order:

Heredity/Biology is most important for physical attributes, temperament, development of psychosis, and risk of mental retardation.  Environment is most important development of cognitive curiosity, development of interests and intelligence. 

Biological Processes, Puberty, and Physical Development for Teenagers
General Features of Physical Growth & Development

    All human beings follow the same 4 growth curves from conception through the end of adolescence.

    Growth Curves show the relative increases or decreases in four areas of growth as the child ages and matures. The more constant the slope of the curve, the more continuous the pattern of development.

    Dramatic increases in growth define a "spurt" in that area.

    1. Skeletal growth - follows the General and most continuous s curve. Included here is organ development (kidneys, liver, etc.). The curve tends to "spurt" during adolescence.
    2. Reproductive organ growth curve - dormant until adolescence with rapid increases around 14 years of age. Reasons for such dramatic increases: pituitary and thyroid glands responsible for muscular and skeletal growth are not the same ones that regulate reproductive functions. Reproductive development is sex hormones (produced in the gonads - androgen, estrogen, testosterone).
    3. Brain and head development starts rapidly and begins to slow after adolescence (eyes, brain, ears, skull). Head is usually the most developed part of the body through age twenty.
    4. Lymphoid system and tissue development - tonsils, adenoids, lymph nodes
Factors influencing growth curves are the regulatory principles of development
  • Target Seeking/self stabilizing - interruptions of normal development may retard normal growth until crisis subsides. Then the individual tends to "catch up" to normal growth..
  • Maturity gradients - in different regions of the body.
  • Cephalocaudal Development - development from the head down.
  • Proximodistal Development - development from the chest out
  • Feedback regulation - the teenage nose - growth producing hormones from pituitary gland influence secretions from gonads, hypothalamus until their optimum levels are reached. Then pituitary gland shuts down production for a while. No gland overproduces.
  • Body Mass - the attainment of appropriate level of body mass (usually at adolescence ages) - triggers the beginning of puberty. For girls - 106+3 lbs.
Puberty - Instead of a single life event, puberty is a process of development.
Beginning about age 11 or 12 for girls and 13 or 14 for boys, and continuing into the middle teens. Maturation of sex organs and height and weight gain. The biological meaning of puberty is that children are now able to reproduce.

The simple biological truth.is that individuals are now able to reproduce
The complex sociological problem.
  • The endocrine systems effects - the hormonal system that stimulates these physical changes secretes hormones through the blood stream, where exocrine glands (saliva, sweat, and milk glands are carried through independent duct systems.
  • Endocrine gland secretions (hormones) are powerful biochemicals that stimulate other organs to growth. 6 The hypothalamus-pituitary-gonadal axis - in adolescence, the pituitary gland is the main hormone producer (the "master" gland). Located at the base of the brain, the Pituitary regulates all other organs during puberty.It stimulates the gonads (testes in males and ovaries in females) to produce Androgens (primarily in males) and Estrogens (primarily in females).
  • The hypothalamus, located higher in the brain, monitors the interaction n between pituitary gland and gonads, regulating the optimal hormonal levels - and optimal growth.
  • More precisely, testosterone is an androgen that is increasingly produced throughout t puberty in males. This is linked to development of secondary sex characteristics (external genitals, increased height, weight, and voice development, upper body strength, pubic hair growth, etc.)
  • Estradiol, is an estrogen that increases during puberty for females. As increases occur, breast and uterine development begin, menstrual cycles begin and stabilize, and height, weight gains, etc. occur.
  • Finally, the thyroid gland interacts with this whole process to aid in development of skeletal maturation.

Physical Changes - height and weigh growth is achieved two years earlier for girls than boys on the average. Making for tenuous peer relations (tall girls, short boys).
    Individual Variation in Puberty
    • For boys, puberty may being as early as age 10 and as late as 14.
    • For girls, puberty may begin as early as age 10 and as late as 16.
    • The pubertal process described in the text is based on average results and the standard distribution. Variations are more the rule.
Psychological Adaptation to Changes in Physical Development in Adolescence
 Body Image - Adolescents show a great deal of interest in their bodies.
Development of a poor body image may be the root cause of eating disorders (anorexia, bulimia, overeating) especially in young girls.
Sensitivity and dissatisfaction with body is more likely in early adolescence than in late teens.
Generally, early developing girls and boys had higher satisfaction with their bodies than late developers.

Early Maturation and late maturation
  • Self Esteem -for early maturing boys, higher self-esteem in sixth grade but differences disappear by 9th grade -for girls, no difference in self-esteem
  • Body Image -Early maturing boys and girls were less satisfied with body (most probably their extra weight) in sixth and seventh grades. -Early maturing girls begin less satisfied, but by 9th grade, early maturing girls were the most satisfied of all groups of girls.
  • Opposite Sex Popularity -early maturing girls were more popular and dated more from the sixth grade on through high school. -Early Maturing boys were more popular as well, but uninterested in girls so much as muscle sports.
  • Academic Behavior -early girls score lower on achievement tests, and many will drop out of high school or miss college the first time.
  • Independence - -early girls are more independent, enjoy more freedom from parental control, more likely to be left alone at home.
Menarche and the Menstrual Cycle - Range of reactions of young girls to Menarche - most found it a wonderment, a little upsetting, somewhat annoying later. But most really found it a sign of maturity - a positive experience. Only a minority of girls found periods to be debilitating g, or to be associated with mood or emotion swings.
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