GROWTH AND DEVELOPMENT

Adolescence is influenced by CNS-mediated hormonal ac­tivity. Physical growth occurs simultaneously with sexual maturation. Adolescents typically experience gains of 20% to 25% in linear growth. An adolescent growth spurt last­ing approximately 24 to 36 months accounts for most of this somatic growth. The age at onset, duration, and ex­tent of the growth varies between males and females and among individuals. In females, the growth spurt usually begins around 10 to 14 years of age. It begins earlier in fe­males than in males and ends earlier, with less dramatic changes in weight and height. Females usually gain ap­proximately 5 to 20 cm in height and 7 to 25 kg in weight. Most females have completed their growth spurt by 16 or

ADOLESCENT PERIOD

The adolescent period, which extends from 13 through 19 years of age, is a time of rapid changes in body size and shape, and physical, psychological, and social functioning.

Adolescence is a time when hormones and sexual matura­tion interact with social structures in fostering the transition from childhood to adulthood.

The development tasks of adolescence include achieving independence from parents, adopting peer codes and mak­ing personal lifestyle choices, forming or revising individual body image, and coming to terms with one's body image.

17 years of age. Males begin their growth spurt later, but it usually is more pronounced, with an increase in height of 10 to 30 cm and an increase in weight of 7 to 30 kg. Males may continue to gain in height until 18 to 20 years of age. Increases in height are possible until approximately 25 years of age.³⁴

The changes in physical body size have a characteris­tic pattern. Growth in arms, legs, hands, feet, and neck is followed by increases in hip and chest size and several months later by increases in shoulder width and depth and trunk length. The period of these rapid and dramatic changes may be difficult for the adolescent and parents. Shoe size may change several times over several months. Although brain size is not significantly increased during adolescence, the size and shape of the skull and facial bones change, making the features of the face appear to be out of proportion until full adult growth is attained.⁶,³⁴ Muscle mass and strength also increase during adolescence. Sometimes, there maybe a discrepancy between the growth of bone and muscle mass, creating a temporary dysfunc­tion with slower or less smooth movements resulting from the mismatch of bone and muscle. Body proportions undergo typical changes during adolescence. In males, the thorax becomes broader, and the pelvis remains narrow. In females, the opposite occurs: the thorax remains nar­row, and the pelvis widens.

Organ systems also undergo changes in function, and some have changes in structure. The heart increases in size as the result of increased muscle cell size. Heart rate de­creases to normal adult rates, whereas blood pressure in­creases rapidly to adult rates. Circulating blood volume and hemoglobin concentration increase. Males demonstrate greater changes in blood volume and higher hemoglobin concentrations because of the influence of testosterone and the relatively higher muscle mass.

Skin becomes thicker, and additional hair growth oc­curs in both sexes. Sebaceous and sweat gland activity in­creases. Plugged sebaceous glands frequently result in acne (see Chapter 61). Increased sweat gland activity results in perspiration and body odor. The eyes undergo changes that may contribute to increased myopia. Auditory acuity peaks in adolescence and begins to decline after approxi­mately 13 years of age.

Voice changes are of significant importance during adolescence for both sexes; however, the change is more pronounced in males. The voice change results from the growth of the larynx. There is more growth of the larynx in males than in females. The paranasal sinuses reach adult proportions, which increases the resonance of the voice, adding to the adult sound of the voice.⁶,³⁴

Changes in the endocrine system are of great impor­tance in the initiation and continuation of the adolescent growth spurt. The hormones involved include growth hor­mone (GH), thyroid hormones, adrenal hormones, insulin, and the gonadotropic hormones. GH regulates growth in childhood but is essentially replaced by sex hormones as the primary impetus for growth during adolescence. The exact role of GH in the adolescent growth spurt is unclear. Thyroid hormone, a significant hormone in the regulation of metabolism during childhood, continues to be important during adolescence. The relation of thyroid hormone to the other hormones and its role in the adolescent growth spurt is unclear. The thyroid gland becomes larger during adolescence, and it is believed that production of thyroid hormones is increased during this period. Insulin is nec­essary for appropriate growth at all stages, including ado­lescence. Insulin must be present for GH to be effective. The pancreatic islets of Langerhans increase in size during adolescence.⁶,³⁴

The anterior pituitary gland produces the gonado­tropic hormones, follicle-stimulating hormone, and lu-teinizing hormone. These hormones influence target organs to secrete sex hormones. The ovaries respond by secreting estrogens and progesterone, and the testes re­spond by producing androgens, resulting in the matura­tion of the primary sex characteristics and the appearance of secondary sex characteristics. Primary sex characteristics are those involved in reproductive function (i.e., internal and external genitalia). The secondary sex characteristics are the physical signs that signal the presence of sexual maturity but are not directly involved in reproduction (i.e., pubic and axillary hair). Androgens initiate the be­ginning of the growth spurt. Sex hormones, including an­drogens, also conclude height growth by causing bone maturity, epiphyseal closure of bones, and discontinua­tion of skeletal growth.

The dramatic and extensive physical changes that occur during the transition from child to adult are matched only by the psychosocial changes that occur during the adolescent period. It is not possible to develop one guide that adequately describes and explains the tremendous changes that occur during adolescence because the experi­ence is unique for each adolescent. There are, fortunately, some commonalities within the process that can be used to facilitate understanding of these changes. The transition from child to adult is not a smooth, continuous, or uniform process. There are frequent periods of rapid change, fol­lowed by brief plateaus. These periods can change with little or no warning, which makes living with an adolescent difficult at times.

One thing that persons who deal with adolescents must remember: no matter how rocky the transition from child to adult, adolescence is not a permanent disability! Eighty percent of adolescents go through adolescence with little or no lasting difficulties. Health care professionals who care for adolescents may need to offer support to wor­ried parents that the difficulties their adolescent is experi­encing, and that the entire family is experiencing as a result, may be normal. The adolescent also may need re­assurance that his or her feelings are not abnormal.^6,34

Common concerns of adolescents include conflicts with parents, conflicts with siblings, concerns about school, and concerns about peers and peer relationships. Personal identity is an overwhelming concern expressed by adoles­cents. Common health problems experienced by adoles­cents include headache, stomachache, and insomnia. These disorders may be psychosomatic in origin. Adolescents also may exhibit situational anxiety and mild depression. The health care worker may need to refer adolescents for spe­cialized counseling or medical care if any of the health care concerns are exaggerated.

Parents of adolescents also may have concerns about their child during the adolescent period. Common concerns related to the adolescent's behavior include rebelliousness, wasting time, risk-taking behaviors, mood swings, drug experimentation, school problems, psychosomatic com­plaints, and sexual activity.³⁴ Adolescence is a period of transition from childhood to adulthood and is often filled with conflicts as the adolescent attempts to take on an adult role. Open communication between the adolescent and family can help make the transition less stressful; how­ever, communication between parents and adolescents is more difficult.

GROWTH AND DEVELOPMENT

Although physical growth is steady throughout the early school years, it is slower than in the previous periods and the adolescent period to follow. During late childhood,

 

MIDDLE CHILDHOOD

>- The middle childhood years (6 to 12 years) are those dur­ing which the child begins school through the beginning of adolescence.

>- Growth during this period averages 3 to 3.5 kg and 6 cm per year, and occurs in approximately three to four bursts per year that last for approximately 8 weeks.

>- Muscular strength, coordination, and stamina increase pro­gressively, as does the ability to perform complex move­ments such as shooting basketballs, playing the piano, and dancing.

>- During this stage, the child develops the cognitive skills that are needed to consider several factors simultane­ously and to evaluate oneself and perceive others' evaluations.

children typically gain approximately 3 to 3.5 kg and grow an average of 6 cm per year.⁵ The average 6-year-old child is 116 cm tall and weighs approximately 21 kg. By 12 years of age, the same child may weigh 40 kg and be 150 cm tall. There is only a slight difference in the body sizes of boys and girls during this period, with boys being only slightly taller and heavier than girls.⁷

During late childhood, a child's legs grow longer, pos­ture improves, and his or her center of gravity descends to a lower point. These changes make children more graceful and help them to be successful at climbing, bike riding, roller skating, and other physical activities. Body fat dis­tribution decreases and, in combination with the length­ening skeleton, gives the child a thinner appearance. As body fat decreases, lean muscle mass increases. By 12 years of age, boys and girls have doubled their body strength and physical capabilities. Although muscular strength in­creases, the muscles are still relatively immature, and in­jury from overstrenuous activities, such as difficult sports, can occur. With the gains in length, the head circumfer­ence decreases in relation to height, waist circumference decreases in relation to height, and leg length increases in relation to height.

Facial proportions change as the face grows faster in relation to the rest of the cranium. The brain and skull grow very little during late childhood. Primary teeth are lost and replaced by permanent teeth. When the perma­nent teeth first appear, they may appear to be too big for the mouth and face. This is a temporary imbalance that is alleviated as the face grows. Caloric requirements usu­ally are lower compared with previous periods and with the adolescent period to follow. Cardiac growth is slow. Heart rate and respiratory rates continue to decrease, and blood pressure gradually rises. Growth of the eye contin­ues, and the normal farsightedness of the preschool child is gradually converted to 20/20 vision by approximately 11 to 12 years. Frequent vision assessment is recom­mended during late childhood as part of normal routine health screenings.⁷

Bone ossification and mineralization continues. Bones cannot resist muscle pressure and pull as well as mature bones. Precautions should be taken to prevent alterations in bone structure, such as providing properly fitting shoes and adequate desks to prevent poor posture. Children should be checked routinely and often for scoliosis (see Chapter 58) during this period.

Toward the end of late childhood, the physical differ­ences between the two sexes become apparent. Females usually enter pubescence approximately 2 years before males, resulting in noticeable differences in height, weight, and development of secondary sex characteristics. There is much individual variation among children of the same sex. These differences can be extremely difficult for chil­dren to cope with.

Entry into the school setting has a major impact on the psychosocial development of the child at this age. The child begins to develop relationships with other chil­dren, forming groups. Peers become more important as the child moves out of the security of the family and into the bigger world. Usually during this period, children begin to form closer bonds with individual "best friends." However, the best-friend relationships may frequently change. The personality of the child begins to appear. Although the personality is still developing, the basic tem­perament and approach to life become apparent. Although changes in personality occur with maturity, the basic ele­ments may not change. The major task of this stage, as identified by Erikson, is the development of industry or ac­complishment.¹⁷ Failure to meet this task results in a sense of inferiority or incompetence, which can impede further progress.

GROWTH AND DEVELOPMENT

Early childhood is a period of continued physical growth and maturation. Compared with infancy, physical growth is not as dramatic. Weight gain during the toddler stage is 1.8 to 2.7 kg per year (an average of 2.3 kg per year). At 2 years, the average weight is 12 kg, and by 2.5 years, the birth weight has quadrupled. By the preschool years, growth slows considerably. The average weight gain is ap­proximately 2.3 kg per year, and almost all organ systems

EARLY CHILDHOOD

>- Early childhood, which encompasses the period from 18 months through 5 years of age, is a period of continued growth and development.

>- During this time, the child passes through the stages of toddler (i.e., 18 months to 3 years) and preschooler (i.e., 3 years through 5 years).

>- The major achievements are the development and refine­ment of locomotion and language, which take place as children progress from dependence to independence.

>- During early childhood, the child begins to develop in­dependence. The toddler must acquire a sense of auto­nomy while overcoming a sense of doubt and shame. The preschooler must acquire a sense of initiative and develop a conscience.

>- Learning is ongoing and progressive and includes inter­actions with others, appropriate social behavior, and sex role functions.

-have reached full maturity. At 3 years, the average weight is 14.5 kg, and by 6 years, it has increased to 21 kg. Dur­ing early childhood, height increases an average 7.5 cm per year and comes primarily through an increase in leg length. At 2 years of age, the average height is 86.6 cm, and by 6 years, it has reached 116 cm. In the first 2 years of life, head circumference increases by 2.5 cm per year. After 2 years of age, head circumference growth slows, and by 5 years, the average increase in head circumfer­ence is 1.25 cm per year.⁷

The maturation of organ systems is ongoing during early childhood. The respiratory system continues its growth and maturation, but because of the relative imma­turity of the airway structures, otitis media and respiratory infections are common. The barrel-shaped chest that is characteristic of infancy has begun to change to a more adult shape. The respiratory rate of infancy has slowed and averages 20 to 30 breaths/minute. Respirations remain ab­dominal until 7 years of age.⁷

Neural growth remains rapid during early childhood. Growth is primarily hypertrophic. The brain is 90% of adult size by 2 years of age. The cephalocaudal, proxi-modistal principle is followed as myelinization of the cor­tex, brain stem, and spinal cord is completed. The spinal cord is completely myelinated by 2 years of age. At that time, control of anal and urethral sphincters and the motor skills of locomotion can be achieved and mastered. The continuing maturation of the neuromuscular system is in­creasingly evident as complex gross and fine motor skills are acquired throughout early childhood.

Growth and maturation in the musculoskeletal system continue with ossification of the skeletal system, growth of the legs, and changes in muscle and fat proportions. Legs grow faster than the trunk in early childhood; after the first year of life, approximately two thirds of the increase in

height is leg growth. Muscle growth is balanced by a corre­sponding decrease in adipose tissue accumulation.

During early childhood, many important psychosocial tasks are mastered by the child. Independence begins to develop, and the child is on the way to becoming a social being in control of the environment. Development and re­finement of gross and fine motor abilities allow involve­ment with a potentially infinite number of tasks and activities. Learning is ongoing and progressive and in­cludes interactions with others, appropriate social behav­ior, and sex role functions. Erikson described the tasks that must be accomplished in early childhood. The toddler must acquire a sense of autonomy while overcoming a sense of doubt and shame. The preschooler must acquire a sense of initiative and develop a conscience.¹⁷

GROWTH AND DEVELOPMENT

Physical growth is rapid during infancy. After birth, there is a period of relative starvation as the infant adjusts to en-teral feeding. Typically, infants lose approximately 5% to 10% of their birth weight, but within days, they begin to gain weight, and by 2 weeks, they are back to birth weight. Average birth weight for a term newborn is 3000 to 4000 g, and this weight usually is doubled by 6 months and tripled by approximately 1 year after birth.

The median height at birth is 49.9 cm for girls and 50.5 cm for boys. During the first 6 months, height in­creases by 2.5 cm per month. By 1 year, the increase in length is 50% of the birth length. This increase is primar­ily in trunk growth. Median head circumference at birth is 34.5 cm for girls and 34.8 cm for boys. The skull bones of newborn infants are incomplete and are connected by bands of connective tissue called sutures. At the junction of the sutures are wider spaces of unossified membranous tissue called fontanels. The larger anterior fontanel is pal­pable until about 18 months to 2 years of age; the smaller

INFANCY

>- Infancy, which is the time from birth to 18 months of age, is a period of rapid physical growth and maturation.

>- From an average birth weight of 3000 to 4000 g in the full-term infant and a median height of 49.9 cm for girls and 50.5 cm for boys, the infant manages to triple its weight and increase its length by 50% at 1 year of age.

>- Developmentally, the infant begins life with a number of primitive reflexes and little body control. By 18 months, a child is able to run, grasp and manipulate objects, feed himself/herself, play with toys, and communicate with others.

>■ Basic trust, the first of Erikson's psychosocial stages, devel­ops as infants learn that basic needs are met regularly.

>- At the age of 18 months or the end of the infancy period, the emergence of symbolic thought causes a reorganiza­tion of behaviors with implications for the many develop­mental domains that lie ahead as the child moves to the early childhood stage of development.

Growth and Development

After completing this section of the chapter, you should be able to meet the following objectives:

♦ Characterize the use of percentiles to describe growth
and development during infancy and childhood

♦ Describe the major events that occur during prenatal
development from fertilization to birth

♦ Define the terms low birth weight, small for gestational age,
and large for gestational age

♦ Identify reasons for abnormal intrauterine growth

♦ Describe assessment methods for determination of
gestational age

The phrase growth and development describes a process whereby a fertilized ovum becomes an adult person. Phys­ical growth describes changes in the body as a whole or in its individual parts. Development, on the other hand, em­braces other aspects of differentiation, such as changes in body function and psychosocial behaviors.

Physical growth occurs in a cephalocaudal (head-to-toe) direction. Relative body proportions change over the life span. In early fetal development, the head is the largest part of the body, but proportional size changes as the in­dividual grows (Fig. 2-1).

The average newborn weighs approximately 3000 to 4000 g and is 50 to 53 cm long. The first year is a period of rapid growth demonstrated by lengthening of the trunk and deposition of subcutaneous fat.⁵ After the first year until onset of puberty, the legs grow more rapidly than any other part of the body.

The onset of puberty is marked by significant alter­ations in body proportions because of the effects of the pu-bertal growth spurt. The feet and hands are the first to grow. Because the trunk grows faster than the legs, at ado­lescence a large portion of the increase in height is a result of trunk growth. The brain also undergoes a period of

rapid growth. At birth, the brain is 25% of adult size; at

1 year, it is 50% of adult size; and at 5 years, it is 90% of
adult size. The size of the head reflects brain growth.⁶ Linear
growth is a result of skeletal growth. After maturation of
the skeleton is complete, linear growth is complete. By

2 years of age, the length is 50% of the adult height. Be­
ginning with the third year, the growth rate is 5 to 6 cm
for the next 9 years. A growth spurt during adolescence is
necessary for adult height to be reached. Males add ap­
proximately 20 cm and females 16 cm to height during
this time. Weight is rapidly increased after birth. Generally
by 6 months of age, the birth weight is doubled; by 1 year
of age it is tripled. The average weight increase is 2 to
2.75 kg per year until the adolescent growth spurt begins.⁷

Growth and development encompass a complex in­teraction between genetic and environmental influences. The experience of each child is unique, and the patterns of growth and development may be profoundly different for individual children within the context of what is consid­ered normal. Because of the wide variability, these norms often can be expressed only in statistical terms.

Evaluation of growth and development requires com­parison of an individual's growth and development to a standard. Statistics are calculations derived from measure­ments that are used to describe the sample measured or to make predictions about the rest of the population repre­sented by the sample. Because all individuals grow and de­velop at different rates, the standard must somehow take this individual variation into account. The standard typi­cally is derived from measurements made on a sample of individuals deemed representative of the total population. When multiple measurements of biologic variables such as height, weight, head circumference, and blood pressure are made, most values fall around the center or middle of all the values. Plotting the data on a graph yields a bell-shaped curve, which depicts the normal distribution of these continuously variable values (Fig. 2-2).

The mean and standard deviation are common statis­tics used in describing the characteristics of a population. The mean represents the average of the measurements; it is the sum of the values divided by the number of values. A normal bell-shaped curve is symmetric, with the mean falling in the center of the curve and with one half of the values falling on either side of the mean. The standard de-

viation determines how far a value varies or deviates from the mean. The points 1 standard deviation above and below the mean include 68% of all values, 2 standard de­viations 95% of all values, and 3 standard deviations 99.7% of all values.⁵ If a child's height is within 1 standard devi­ation of the mean, he or she is as tall as 68% of children in the population. If a child's height is greater than 3 stan­dard deviations, he or she is taller than 99.7% of children in the population.

The bell-shaped curve can also be marked by percen-tiles, which are useful for comparison of an individual's val­ues with other values. When quantitative data are arranged in ascending and descending order, a middle value, called the median, can be described with one half (50%) of the val­ues falling on either side. The values can be further divided into percentiles. A percentile is a number that indicates the percentage of values for the population that are equal to or below the number. Percentiles are used most often to com­pare an individual's value with a set of norms. They are used extensively to develop and interpret physical growth charts and measurements of ability and intelligence