01 - Growth and Development During the Preschool Years

Introduction

Introduction

This is the first of several programs that focus on specific features of human growth and development. Before viewing this program, you should have looked at the introductory programs in this series that deal with general principles in growth and the elements that control it.

This module is divided into three sections:

• Section 1 describes and sets limits on normal growth variation.
• Section 2 points out important factors that affect growth and cause variation.
• Section 3 provides details of craniofacial growth during the preschool (primary dentition) years.

Be sure you do the reading (pages 66-72 in the 5th ed or pages 72-86 in the 4th ed of Contemporary Orthodonticsand the appropriate section in your embryology text) as well as viewing this program.

Learning Objectives

The learning objectives for this module are to:

• identify the embryologic source of the facial tissues
• relate the most frequent types of facial congenital deformity to the time in embryologic development when they arose
• describe the process of fusion of the upper lip and palate, and identify the facial processes whose failure to fuse results in a cleft of the lip
• describe the changes in facial proportions from birth to early adolescence
• use percentiles to select children who need evaluation to rule out pathologic effects on growth
• describe gender differences in the rate and timing of growth
• describe the effect on growth of low birth weight, acute and chronic illness, emotional deprivation, and malnutrition
• discuss secular trends in growth and indicate their effect on the accuracy of growth charts.

Normal Growth Variations

What is Normal?

The brothers shown here are about the same size, but one is 6 years old and the other is 9. Can you tell which is the 9 year old? It’s the one on the right, who is slightly shorter than his brother, weighs considerably less and is slow in erupting his permanent teeth.

Do you think this represents normal variation? It will be very important in professional practice for you to know whether you are dealing with a child who is just small for his age, or one who is suffering from some condition that would influence the kind of treatment he should receive.

What is Normal? (cont.)

The children pictured here are siblings, but only a year apart in age. The girl is shorter and less mature looking than her brother. The same question as with the last picture: given the age difference, is this normal variation, or could one or both be abnormally adanced or delayed in their growth?

How could you determine that? The best way would be to see where each of them would fit on a growth chart that shows the range of normal variation.

Normal Variation: Populations

The normal bell-shaped curve of variability in populations, which you are familiar with by now, expresses very well the differences in physical growth of a group of children of the same age and gender. The important question in examining any child patient is whether differences from the mean of the normal curve represent just normal variation, or whether there is an indication of abnormality in growth and development.

Normal Variation: Birth Length and Weight

Do you recognize that this graph of variation in birth length and weight, and subsequent growth, is another version of a normal distribution? If the data were plotted as numbers of children with a given birth length or weight at any specific time, a bell-shaped curve would have been generated. You would get another normal distribution if you took any other point in time. This plot shows you the percentage of children with birth length or weight above or below a certain amount and the percentage distributions at other points in time in early life.

Normal birth weights can range from 2000 grams or about 4 ½ pounds to 4000 grams or nearly 9 pounds. Birth weights outside this range would be considered at least suggestive of abnormality. In fact, it is common today to speak in terms of birth weight instead of prematurity when discussing newborns who are at risk because of their immaturity at birth. But how was that normal range established?

The Limits of Normal Variation

The normal range for physical characteristics typically extends from the 3rd to the 97th percentiles, which are outside the colored area of a chart like this.

As a general guideline, children above the 97th or below the 3rd percentile are considered possibly abnormal and in need of special investigation. It is possible that these children are simply very small or very large normals, but there is also a significant chance of an abnormality affecting growth. This is true at all stages of growth, from infancy through adolescence.

Note that the percentile lines form channels. A normal child tends to stay in the same channel. In other words, a child who starts out at the 60th percentile tends to stay there during growth. So does a child who starts out at the 20th percentile. A major change in the percentile rank suggests a deviation from the normal growth pattern and a possible abnormality.

Factors Affecting Growth

Important Factors That Influence Growth

Let’s look now in more detail at important factors that influence growth. Don’t forget that normal variation should go at the top of the list.

FACTORS INFLUENCING GROWTH

• Normal variation
• Heredity / genetic traits
• Changes in body proportions
• Gender
• Low birth weight
• Chronic disease
• Psychologic / emotional factors
• Nutrition
• Ethnic / cultural background
• Urban / rural environment
• Socio-economic status / family size
• Secular trends

Heredity

Heredity is an obviously important factor. The boy on the left, the youngest but tallest of this group, has the tallest father, and that isn’t coincidence. Generally speaking, large children have large parents. It is not uncommon, however, to see a small or large child in a family that has a tendency toward the opposite trait.

For all human populations, there is a modest but not perfect correlation between the size of the parents and the size of the children. The correlation coefficient (r) is 0.5 or less. R², the coefficient of determination, expresses the amount of the total variation accounted for by the factor being examined. If the correlation between parent and child size is 0.5, (0.5)² = 0.25, so heredity explains not more than 25% of the variation in size.

The bottom line: heredity is an important factor in determining how tall you are, but it’s far from the only thing.

Cephalocaudal Growth Gradient

Another factor that must be considered in growth variations is changes in body proportions and changes in tissue systems during growth. Facial proportions, as you know, reflect the cephalocaudal gradient of growth (image 1). That’s another way of saying that generally structures close to the brain grow faster sooner and slower later than those further away.

Have you ever considered that you’re used to looking at differences in facial proportions as you evaluate how old a child is? You might well make the judgment “big for his age” based on that.

Proportions & Systems

To a major extent, the changes in body proportions with age reflect different growth rates for different tissue systems. Classically, four major tissue systems are distinguished, and a display like this of their growth pattern is called “Scammon’s curves” after the anthropologist who first published them.

The curves show the early growth of the nervous tissues (and the neurocranium), the tremendous proliferation of lymphoid tissue early in life and its “negative growth” later, and the initially slow and then very rapid growth of sexual tissues. The adolescent growth spurt, and all the things that contribute to that, will be emphasized when we study adolescence in more detail.

You need to be able to draw these curves from memory, so look at them carefully and be sure you understand what is happening during growth of each of the tissue systems.

Proportions & Systems (cont.)

The change in facial proportions with growth reflects an interaction between the neural and general body growth curves.

As you have already learned in a different context, the growth of the maxilla is influenced to some degree by growth of the cranial base, which in turn has to grow in about the same way as the brain. Although mandibular growth is closer to the general body curve, it too is somewhat influenced by growth of the neural structures above. We can plot curves for the maxilla and mandible like the ones Scammon plotted, making this relationship clearer and clarifying why you should expect the mandible to be underdeveloped relative to the maxilla in early childhood and why it would catch up later.

Gender

Another important factor in growth variation is gender. That’s more important in adolescence and adulthood than childhood, however. Boys are a little larger than girls at early ages, but at ages between 10 and 12 girls are likely to be larger, and the adult size differential isn’t there until the males have their later and more intense growth spurt. Note the similar growth velocities for boys and girls up to puberty.

Low Birth Weight

Low birth weight, which primarily indicates premature birth, is an important factor in growth variation early in life. Immaturity of the child’s organs, especially the respiratory tract, can greatly complicate the early weeks of life after premature birth. Perhaps it will surprise you to learn, however, that the vast majority of low birth weight children catch up and eventually grow quite normally.

This graph illustrates catch-up growth in two low birth weight groups, twins who were small for gestational age (SGA), which twins usually are because of intra-uterine competition for resources, and twins with birth weight less than 1750 grams (born quite prematurely). Note that by age 6 both groups were nearly to the norm. Low birth weight has a long-term residual effect on some children, but for most it isn’t a factor after childhood.

Chronic Disease

Chronic illness such as congenital heart disease or an endocrine dysfunction can lead to sustained deficiencies in growth. This usually affects both height and weight, with about the same impact on all tissue systems.

This graph shows the growth of a boy with growth hormone deficiency. Note that he was below the normal range in infancy, and that his lack of growth moved him further from the normal.

But if chronic problems are corrected, catch-up growth usually occurs. Note that when injections of human growth hormone (HGH) began at age 6, this boy grew faster than normal, and almost made it to the 3rd percentile at age 14.

Successful repair of a congenital heart defect might have the same effect. Such a child probably would never get back to the mean, but might pull into the normal range.

Short-term Illness

Short-term illness (severe influenza leading to pneumonia, for instance) causes fluctuations in growth rates, but has little long-term impact. Even more chronic but still transient illness (mononucleosis, for example) usually is followed by catch-up growth that takes a child back to the channel he was in before getting sick. One way to look at it is that absence of catch-up growth indicates a medical problem that hasn’t been corrected.

Psychologic/Emotional

Psychologic and emotional factors also can affect growth. This graph shows the result of changing the social environment of two children who had fallen outside the normal range. Neither child had an identifiable organic cause for the growth problem. When each was removed from a very poor home environment and placed in a special boarding school where presumably emotional stress was reduced, the catch-up growth response was dramatic.

It takes severe levels of emotional distress to depress growth, but there’s no doubt this can occur. The mechanism is thought to be induction of a reversible growth hormone deficiency.

Nutrition

The role of nutrition in growth is probably understood best from examining a chart of this type, which shows a partitioning of energy requirements. When nutrition is inadequate, the partitioning reflects physiologic priorities. Growth is, so to speak, taken off the top. If nutrition is barely adequate, generalized growth will be depressed. But if it’s adequate, better nutrition doesn’t lead to much if any increase in growth.

Nutrition (cont.)

Another way to consider nutrition and growth is to look at the amount of energy needed for growth as a percent of intake. An infant needs to devote a considerable proportion of the total toward growth, and this need is particularly acute for a premature infant. After that, the proportion devoted to growth decreases rapidly. So from a growth perspective, malnutrition at an early age would be particularly significant.

Ethnic/Culture

The ethnic and cultural background of an individual isn’t really a factor in growth, but it can greatly affect how growth is perceived, because the standards one is judged against can make a big difference.

For example, note the 50th percentile points for Dutch boys (blue lines) and 50th percentile points for boys from an American city (red lines), placed on this typical growth chart. At age 10, the average Dutch boy is 140 cm tall, while the American boys average 135 cm. Five cm is nearly two inches, not a trivial difference. When growth charts are used, you have to be careful about the source of the data that was used to construct them and how well the individual who is being charted fits the reference group.

City/Rural

Still another potentially important variable is whether you live in the city or a rural area. This graph (image 1) shows the height of 7 year old boys in several countries, developed and underdeveloped, as of 1970. Note that the city children were consistently bigger at the same age. More recent data (image 2) shows the same trend.

The US population shows the same effect. The difference isn’t nutrition (although the vast difference for Poland may reflect a nutrition component). More services and goods—health care, sanitation, welfare—are available in the city, and that seems to overshadow any detrimental effects of city noise and pollution.

Image 1, height of urban vs. rural children, 1970: Children who live in cities have an advantage in terms of access to services that promote health and growth.	Image 2, height of urban vs. rural children, 21st century: The same trend holds true for more modern data – urban children have an advantage.

Socioeconomic Status

Socioeconomic status (SES) and family size also can affect growth. This graph plots the height of 7 year old boys by social class and by the number of children in the family. SES is determined by the head of the household’s employment and educational status. Note that as SES declines, so does the height of the children. As the number of children in the family increases, height declines within the same SES. These differences are attributed to the amount of resources available to the individual family members.

Secular Trends

There has been a strong trend over the past few hundred years for humans to become larger, reach an equivalent size at an earlier age, and reach developmental milestones earlier. This has occurred throughout the world, even where nutritional status didn’t change. These changes are termed the secular trend in growth.

Menarche is a dramatic developmental milestone that tends to get recorded, and so there are particularly good data for this. It’s interesting that there has been a steady decline for at least 150 years in the age of first menstruation in girls. To some extent this probably reflects earlier acquisition of a critical body mass. All other things being equal, sexual maturation in girls and menarche occur when a critical mass of about 46-48 kg (100-105 pounds) is reached. Why the faster growth to that body mass occurs now, however, isn’t totally clear. Nutrition is a part of it but apparently not the whole story.

Secular Trends (cont.)

Whatever the reason for it, the secular trend needs to be taken into account when growth charts and percentile levels are used. Growth charts often are plots of data from 30 to 50 or more years ago. Plotting typical American children of the early 21st century on growth charts from 1940s puts you pretty close to the mythical city of Lake Wobegon, where all the children are above average. People like to hear that their child is above average, which may account for the popularity of old growth charts.

Development Indicators

Earlier growth implies earlier physical maturation, and it is accompanied by quicker social and mental development too. Various biologic ages can be calculated, using developmental milestones, and it’s interesting to plot various indicators of a child’s physical and behavioral development on the same chart.

In this graph, various development indicators are plotted together for one particular girl. Like most people who are advanced (or a bit behind) in one characteristic, she was advanced in all of them.

On this chart, dental (the yellow line) represents dental age, calculated from the stage of dental development. Interestingly, dental age shows the poorest correlation with the other developmental scales of any of the biologic ages. A child who is advanced in everything else probably is advanced dentally too, but the dentist needs to remember that dental age doesn’t track very tightly with the other developmental ages.

Preschool Craniofacial Growth

Cephalometric Overview of Craniofacial Changes

Now let’s focus more closely on craniofacial changes in the preschool years. These cephalometric tracings of the same child at age 2 (red) and age 6 (blue) are superimposed on the back end of the cranial base, at sella turcica (the cavity in the sphenoid bone that houses the pituitary gland).

Note that during this time the brain mass increased and the brain case expanded. The cranial base lengthened, and that pushed the maxilla and midface forward. The mandible moved downward and forward, and the face grew more than the cranium—all of which you would have expected from what you already know about facial growth.

Growth of Lymphoid Tissues

Scammon’s growth curves show a great deal of growth of lymphoid tissue in childhood. Most of this lymphoid growth occurs in areas you can’t see, but dentists get a good look at tonsils.

You’d expect the tonsils to be large in childhood and indeed they are (though usually not so large as these). Scammon’s curve predicts that they’ll normally shrink later, so large tonsils at age 6 or so often is a self-correcting condition.

Image 1, Scammon’s curves: Growth of lymphoid tissue peaks and then retracts.	Image 2, view of the tonsils: Tonsils are often enlarged near age six but then shrink.

Growth of Sex Organs and Sexual Maturation

Growth of the sex organs and sexual maturation in preschool children isn’t expected. If it occurs, which occasionally happens, something is wrong. The most likely cause is some sort of endocrine-secreting tumor, so a very sexually precocious child needs medical attention. As a dentist who treats children, you might be the first to note that your patient looked a lot more mature than one would expect at that age.

Decline in Velocity of Craniofacial Growth

A plot of growth velocity shows that the rate of growth declines sharply from infancy to childhood. If Johnny isn’t growing as fast any more when he’s about to start to school, he’s probably perfectly normal. But notice that he’s still growing at a rate that requires new clothes and shoes every year. The rate of growth typically drops to its lowest level just before the onset of puberty and the adolescent growth.

Cephalocaudal Gradient of Craniofacial Growth - Newborn

In this view of the skull of a newborn, the relative underdevelopment of the mandible is apparent. The ramus is very short. The maxilla isn’t well developed either compared to the cranium, but it’s ahead of the mandible. That’s another reflection of the cephalocaudal gradient of growth.

Cephalocaudal Gradient of Craniofacial Growth - Age 4

In this 4-year-old, the cranium still is large compared to the face, but the face has developed vertically as well as anteroposteriorly. The floor of the nose has descended from its earlier position just below the orbits. The maxilla and mandible have expanded laterally.

Note that the 4-year-old’s mandible has a more acute gonial angle than previously. The downward and forward growth of both jaws is evident.

Cephalocaudal Gradient of Craniofacial Growth - Age 6

This skull from a 6 year old child, just prior to eruption of permanent incisors, shows how the face has continued to grow faster than the cranium. The floor of the nose is now well below the orbits, and the alveolar processes of both maxilla and mandible have developed considerably.

The face still has a long way to go to catch up with the cranium, which at age 6 has reached essentially its adult size. By the time you’re six or seven, you need as large a cap as you’ll ever require, because by then brain growth is complete and the cranial vault is through expanding. In contrast, the adult mandible is twice as large as the six year old’s.

Growth Beyond Age 6

Of course it is as important to understand growth beyond age 6 as it is to understand what happens in the pre-school years. We’ll continue into that time, with emphasis on the adolescent growth spurt and its implications for orthodontic treatment, in the next program.

Before you move on to the next module, be sure you have done the reading (pages 66-72 in the 5th ed or pages 72-86 in the 4th ed of Contemporary Orthodontics) and have used the self-test to confirm your understanding of this important information.

Self-Test

Introduction

Remember that you are being tested on the first section of Chapter 3 in Contemporary Orthodontics, the material on embryonic development of the face, as well as the content of the computer teaching program. This is pages 72-78 of the text in the 4th edition, as well as the pictures on pages 79-81. Read this carefully. It’s not covered in any of the computer teaching programs.

Question 1

1. ectoderm ✓
2. mesoderm
3. endoderm
4. all three are equally important

Correct

That’s correct. In the formation of the face almost all the tissue, including muscle and bone that elsewhere is derived from mesoderm, is of ectodermal origin.

Incorrect

No, that’s incorrect. In the formation of the face almost all the tissue, including muscle and bone that elsewhere is derived from mesoderm, is of ectodermal origin.

Question 2

Hemifacial microsomia and related congenital syndromes arise at which of the stages of craniofacial development?

1. germ layer formation and initial organization of structures
2. neural tube formation
3. origin, migration and interaction of cell populations ✓
4. formation of organ systems
5. final differentiation of tissues

Correct

That’s right. Hemifacial microsomia is an example of a problem arising early in development from loss of neural crest cells before they migrate into the developing fact. Thalidomide and isotretnoin (Accutane) are drugs that create malformations by this mechanism.

Incorrect

No, that’s wrong. Hemifacial microsomia is an example of a problem arising early in embryologic development from loss of neural crest cells before they migrate into the developing face, so it arises at the stage of origin, migration and interaction of cell populations. Thalidomide and isotretenoin (Accutane) are drugs that create malformations by this mechanism.

Question 3

Cleft lip and palate arise at which of the stages of craniofacial development?

1. germ layer formation and initial organization of structures
2. neural tube formation
3. origin, migration and interaction of cell populations
4. formation of organ systems ✓
5. final differentiation of tissues

Correct

That’s right. Cleft lip and palate arise after the cell populations are in place, at the stage in the second month of embryonic life when organ systems are being formed.

Incorrect

No, you’re wrong. Cleft lip and palate arise after the cell populations are in place, at the stage in the second month of embryonic life when organ systems are being formed.

Question 4

The upper lip in an adult is derived from which of the facial processes?

1. median and lateral nasal
2. lateral nasal and maxillary
3. median nasal and maxillary ✓
4. median nasal, lateral nasal and maxillary

Correct

That’s right. The upper lip is derived from the median nasal and maxillary processes. Although failure of fusion between the median and lateral nasal processes results in a cleft lip, the lateral nasal process forms the outer parts of the nose and contributes little or nothing to the ultimate upper lip.

Incorrect

No, that’s wrong. The upper lip is derived from the median nasal and maxillary processes. Although failure of fusion between the median and lateral nasal processes results in a cleft lip, the lateral nasal process forms the outer parts of the nose and contributes little or nothing to the ultimate upper lip. The correct answer is (3) median nasal and maxillary.

Question 5

Crouzon’s syndrome and the other malformations due to early closure of craniofacial sutures arise at which of the stages of craniofacial development?

1. germ layer formation and initial organization of structures
2. neural tube formation
3. origin, migration and interaction of cell populations
4. formation of organ systems
5. final differentiation of tissues ✓

Correct

That’s right. The characteristic hypertelorism and midface deficiency of Crouzon’s syndrome are due to prenatal fusion of the superior and posterior sutures of the maxilla, along the wall of the orbit. This occurs in fetal life, during the final differentiation of tissues, considerably later than the embryologic origin of clefts and related problems.

Incorrect

No, that’s wrong. The characteristic hypertelorism and midface deficiency of Crouzon’s syndrome are due to prenatal fusion of the superior and posterior sutures of the maxilla, along the wall of the orbit. This occurs in fetal life, during the final differentiation of tissues, considerably later than the embryologic origin of clefts and related problems.

Question 6

(A) In normal human infants, the mandible is prominent at birth because (B) like all the structures of the head and face, a high percentage of mandibular growth is completed before birth.

1. A true, B true, A and B related
2. A true, B true, A and B not related
3. A true, B false
4. A false, B true
5. A and B false ✓

Correct

That’s correct, both statements are false. Human newborns have an underdeveloped mandible relative to the rest of the head and face, for which their mothers should be grateful because this facilitates the head’s passage through the birth canal. The mandible grows more than other facial structures in postnatal life and eventually catches up.

Incorrect

That’s wrong. Both statements are false. Human newborns have an underdeveloped mandible relative to the rest of the head and face, for which their mothers should be grateful because this facilitates the head’s passage through the birth canal. The mandible grows more than other facial structures in postnatal life and eventually catches up.

Question 7

At what degree of deviation from the normal height-weight standards is special investigation of a child’s status indicated?

1. <10 percentile or >90 percentile
2. <5 percentile or >95 percentile
3. <3 percentile or >97 percentile ✓
4. <1 percentile or >99 percentile

Correct

That’s right, the general guideline is that children who are below the 3rd or above the 97th percentile should be examined carefully to be sure they represent only normal variation rather than some abnormal condition. Such a child would plot outside the colored area of a chart like the one shown here.

Incorrect

No, that’s wrong. The general guideline is that a child who is below the 3rd or above the 97th percentile should be examined carefully to be sure they represent only normal variation rather than some abnormal condition. Such a child would plot outside the colored area of a chart like the one shown here.

Question 8

How well can you predict the size a child will attain from examining her parents?

1. 90% accuracy
2. 67% accuracy
3. 50% accuracy
4. 25% accuracy ✓
5. <10% accuracy, almost unpredictable

Correct

That’s right, there is a correlation between the size of parents and their children, but genetic / hereditary factors explain only about 25% of the variation, so 25% accuracy is about all you could hope for.

Incorrect

No, that’s incorrect. There is a correlation between the size of parents and their children, so knowing the size of parents has some predictive value. But genetic / hereditary factors explain only about 25% of the variation, so 25% accuracy is about all you could hope for.

Question 9

Compared to an eight-year-old, a normal four-year-old child has a:

(1) relatively larger cranium

(2) relatively longer lower face

(3) more prominent mandible.

1. 1 only ✓
2. 1 and 2
3. 2 and 3
4. 1 and 3
5. all of the above

Correct

That’s right, compared to an eight-year-old, the four year old has a relatively larger cranium, but the face is shorter and the mandible less prominent, because the face grows faster than the cranium between ages four and eight.

Incorrect

No, that’s wrong. Compared to an eight-year-old, the four year old has a relatively larger cranium, but the face is shorter and the mandible less prominent, because the face grows faster than the cranium between ages four and eight.

Question 10

(A) The growth curve for the mandible follows the neural growth curve because (B) all the facial structures are close enough to the brain to be influenced by its growth curve.

1. A true, B true, A and B related
2. A true, B true, A and B not related
3. A true, B false
4. A false, B true ✓
5. A and B false

Correct

That’s correct. The mandible doesn’t follow the neural growth curve, so the first statement is false, but it’s true that the facial structures are close enough to the brain to be influenced by its growth curve. In fact, the growth curves for the maxilla and mandible fall in between the neural and general body curves.

Incorrect

No, that’s wrong. The mandible doesn’t follow the neural growth curve, so the first statement if false, but it’s true that the facial structures are close enough to the brain to be influenced by its growth curve. In fact, the growth curves for the maxilla and mandible fall in between. The correct answer is (4) A false, B true.

Question 11

At age 12, girls are typically:

1. smaller and less developed than boys
2. smaller but more developed than boys
3. larger but less developed than boys
4. larger and more developed than boys ✓

Correct

That’s right. Girls reach their adolescent growth spurt earlier than boys, and at age 12 they’re typically both bigger and more developed. The males end up bigger because they continue growing for a longer time.

Incorrect

That’s wrong. Girls reach their adolescent growth spurt earlier than boys, and at age 12 they’re typically both bigger and more developed. The males catch up and ultimately are bigger because they continue growing for a longer time.

Question 12

Complete recovery from low birth weight, so that the individual ends up close to the mean for the population in height and weight as an adult, is:

1. quite likely ✓
2. often happens but frequently does not
3. possible but unlikely
4. quite unlikely, growth deficit usually persists

Correct

That’s correct. In the absence of other problems, it’s quite likely that a child who was born prematurely and therefore has a low birth weight will ultimately completely catch up with his or her peers.

Incorrect

No, that’s wrong. In the absence of other problems, it’s quite likely that a child who was born prematurely and therefore has a low birth weight will ultimately completely catch up with his or her peers.

Question 13

Complete recovery from a growth deficit caused by chronic illness such as growth hormone deficiency, so that the individual ends up close to the mean for the population in height and weight as an adult, is:

1. quite likely
2. often happens but frequently does not
3. possible but unlikely
4. quite unlikely, growth deficit usually persists ✓

Correct

That’s right. A child who is successfully treated for a chronic growth-inhibiting condition usually moves closer to the growth norms, but the growth deficit usually persists. The longer the problem was present, the less the chance that the child will achieve normal height and weight.

Incorrect

No, that’s incorrect. A child who is successfully treated for a chronic growth-inhibiting condition usually moves close to the growth norms, but the growth deficit usually persists. It’s quite unlikely that he or she will be at the median for the population, and the longer the problem was present, the less the chance that the child will achieve normal height and weight.

Question 14

(A) Severe acute illness affects a child’s growth status only temporarily because (B) rapid catch-up growth usually occurs after the illness.

1. A true, B true, A and B related ✓
2. A true, B true, A and B not related
3. A true, B false
4. A false, B true
5. A and B false

Correct

That’s right, both statements are true and they’re related. Even though growth stops during the acute illness, a subsequent period of rapid catch-up growth usually brings the child back to his or her previous status.

Incorrect

No, that’s wrong. Both statements are true, and they’re related. Even though growth stops during the acute illness, a subsequent period of rapid catch-up growth usually brings the child back to his or her previous status.

Question 15

Severe growth inhibition due to a highly stressful social environment is:

1. frequently observed
2. unusual but not uncommon
3. rare but possible ✓
4. never happens directly, effect secondary to malnutrition

Correct

That’s correct, psychologic and emotional factors can affect growth, but severe growth inhibition (fortunately) is rare even though it is possible. Subtle effects may be relatively common.

Incorrect

No, that’s wrong. Psychologic and emotional factors can affect growth, but severe growth inhibition (fortunately) is rare even though it is possible. Subtle effects may be relatively common.

Question 16

(A) Chronic malnutrition does not affect growth in the same way as chronic illness because (B) the energy available to an individual is preferentially directed toward growth.

1. A true, B true, A and B related
2. A true, B true, A and B not relanted
3. A true, B false
4. A false, B true
5. A and B false ✓

Correct

That’s right, both statements are false. Chronic malnutrition affects growth remarkably similarly to chronic illness. Energy is available for growth only after the organism’s other needs for survival have been met.

Incorrect

No, that’s incorrect. Both statements are false. Chronic malnutrition affects growth remarkably similarly to chronic illness. Energy is available for growth only after the organism’s other needs for survival have been met.

Question 17

Influences on the ultimate height of an individual include:

(1) racial/ethnic origin

(2) rural vs urban setting

(3) number of children in the family

1. 1 only
2. 1 and 2
3. 1 and 3
4. 2 and 3
5. 1, 2 and 3 ✓

Correct

That’s correct, not only racial/ethnic origin but also rural vs urban setting and number of children in the family are influences on an individual’s ultimate height. Urban children and members of smaller families tend to be bigger, perhaps because more resources are available to them.

Incorrect

No, that’s wrong, all three of these factors can affect growth. Not only racial/ethnic origin but also rural vs urban setting and number of children in the family are influences on the individual’s ultimate height. Urban children and members of smaller families tend to be bigger, perhaps because more resources are available to them.

Question 18

The term “secular trend” in growth and development refers to:

1. the world-wide trend toward earlier development ✓
2. the unpredictability of changes over time
3. the increase in the age at menarche observed in many countries
4. the way growth charts quickly go out of date

Correct

That’s correct, a secular trend is one that is related strongly to time. In growth and development, there has been a strong world-wide trend toward earlier development. Earlier (not later) sexual maturation is only one example of this.

Incorrect

No, that’s wrong. A secular trend is any of a number of changes that are related strongly to time. In growth and development, there has been a strong world-wide trend toward earlier development. Earlier (not later) sexual maturation is only one example of this.

Question 19

An average child from your practice in some future year, whose growth is plotted on a growth chart based on 1965 data, is likely to appear:

1. advanced ✓
2. average
3. retarded
4. no way to predict because of the secular trend

Correct

That’s correct, the average child now is bigger at the same age than the average child of the 1960s and this trend toward faster growth and development seems to be continuing, so the old growth chart would make an average child look advanced. Most people are pleased to be told their child is above average, which perhaps accounts for the popularity of old growth charts.

Incorrect

No, that’s wrong. The average child now is bigger than the average child of 50 years ago and this trend toward faster growth and development seems to be continuing, so the old growth chart would make an average child look advanced. Most people are pleased to be told their child is above average, which perhaps accounts for the popularity of old growth charts.

Question 20

Which of the following is not typical of physical growth in the preschool years?

1. cranial growth is well advanced
2. lymphoid tissue is beginning to shrink ✓
3. mandibular deficiency is decreasing
4. sexual development is very slow

Correct

That’s correct, lymphoid tissue tends to grow very rapidly during the preschool years. It doesn’t begin to shrink until sexual development starts at the beginning of adolescence.

Incorrect

No, that’s wrong. During the preschool years, neural and cranial growth is nearly completed, and there is very slow sexual development. But lymphoid tissue tends to grow very rapidly. It doesn’t begin to shrink until sexual development starts at the beginning of adolescence.