Quartz 4

Unit Self-Test

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Level I Growth and Development — Unit A Self-Test

Module 1: The Study of Physical Growth

Question 1

(A) Anthropometric data are preferred over craniometric data in the study of growth because (B) soft tissue rather than hard tissue landmarks are used in craniometric studies.

  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, anthropometric data are preferred over craniometric data in growth studies, not because soft tissue landmarks are used in anthropometry, but because they are (or can be) longitudinal rather than cross-sectional. Craniometric data, which are obtained from skulls (no soft tissue available), always are cross-sectional. The soft tissue landmarks are a disadvantage of anthropometry for studies of skeletal growth.

Question 2

In fetal and postnatal growth, what is meant by the “cephalocaudal gradient of growth?”

  1. head grows faster than trunk and limbs
  2. trunk and limbs grow faster than head ✓
  3. cephalic structures are more important for growth
  4. caudal structures are more important for growth

Correct

That’s right. In very early (embryonic) development, the cranium represents 25% of the whole individual, and the head about half. From then on, the trunk and limbs grow faster than the head, and the face more than the cranium.

Question 3

How would you establish a child’s reading age?

  1. compare against standards for social development
  2. compare against standards for reading development ✓
  3. evaluate with scores of standard IQ tests
  4. not possible, developmental ages relate to physical characteristics only

Correct

That’s right, there are standards for reading development just as there are standards for development on other physical and social-psychological scales. A child can be advanced or slow in reading just as he or she could be in physical development. It’s interesting that the different types of development are highly correlated.

Question 4

Which of the following is the most appropriate description of the concept of pattern in growth?

  1. proportional size relationships
  2. changes in proportions over time ✓
  3. conservation of proportions as size increases
  4. changes in proportions as size increases

Correct

That’s right. Pattern in growth refers to the way in which proportional relationships change (or are maintained) as the individual changes over time (whether or not he gets bigger). The changing proportions of the face describe its growth pattern.

Question 5

On growth charts with 6-month data plots, what is the significance of a child “crossing the percentiles” downward?

  1. indicates growth disturbance, perhaps chronic illness or chronic problem ✓
  2. Indicates increasingly active growth, perhaps tumor
  3. no significance over this period of time, quick changes more important
  4. no significance, changes in channels typically occur during normal growth

Correct

That’s right, a downward movement across the percentile channels over a 6 month period indicates a growth disturbance and raises the question of some chronic illness or other chronic problem. A normal child usually stays within his or her channel.

Question 6

(A) Girls grow earlier than boys at adolescence because (B) girls mature sexually earlier than boys.

  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. As a group, girls grow earlier than boys at adolescence, and the reason is their earlier sexual maturation. In an important sense, adolescence and adolescent growth is a sexual phenomenon.

Question 7

Which of the following is not appropriately described as growth?

  1. increase in size
  2. increase in number
  3. increase in complexity
  4. increase in specialization ✓

Correct

That is correct. Growth refers to an increase in size, number or occasionally complexity, but not to increased specialization. The term “development” often is used to describe an increase in specialization of biologic functions, but sometimes it is used to describe an increase in complexity—so sometimes there is an overlap with growth, sometimes there isn’t.

Question 8

The value of implants, such as metallic pins placed in the jaws, in radiographic studies of growth is that:

  1. the implants mark areas of bone that are growing
  2. the implants mark areas of bone that are remodeling
  3. the implants mark areas of bone that are not growing or remodeling ✓
  4. the implants outline areas of bone of particular interest so they can be evaluated

Correct

That’s correct, the implants mark areas that are not growing or remodeling. This provides stable areas for superimposition of longitudinal x-rays, and then you can see which other areas are changing and how much, and which areas are not changing. As this superimposition on implants in the mandible shows, implant studies are an excellent way to determine the changing proportions that define the growth pattern.

Question 9

What percentage of a normally distributed population is within two standard deviations of the mean?

  1. 50%
  2. 66%
  3. 78%
  4. 87%
  5. 95% ✓

Correct

That’s right, 95% of the population are within two standard deviations of the mean, and 99% are within three standard deviations. But when you’re treating patients with problems, you’re likely to encounter individuals who are at the extremes of the normal distribution.

Question 10

How do vital stains contribute to the study of growth?

  1. stain everything that was present when they were administered
  2. stain everything that was growing when they were administered
  3. stain everything that grew after they were administered
  4. stain specific things that were growing at the time they were administered ✓

Correct

That’s correct. A vital stain marks specific things that were growing when it was administered, for instance, the bone that was being laid down at that time. Different vital stains are used for different tissues. If it stained everything, you couldn’t distinguish one structure from another.

Question 11

Within the face, the postnatal cephalocaudal gradient of growth predicts that:

  1. the face grows faster than the cranium
  2. the mandible grows faster than the maxilla
  3. the maxilla grows faster than the cranium
  4. all of the above ✓
  5. none of the above

Correct

That’s right. The cephalocaudal gradient of growth predicts (correctly) that a structure further away from the cranium grow faster than one closer to it. So in postnatal life both jaws grow faster than the cranium and the mandible grows faster than the maxilla.

Question 12

If a girl’s bone age is 12, what is her chronologic age most likely to be?

  1. 10
  2. 11
  3. 12 ✓
  4. 13

Correct

That’s right, the greatest probability is that the developmental age matches the chronologic age. That’s how the developmental age was established. But for any individual, the chronologic and developmental ages may or may not coincide.

Question 13

Which of the following is the major disadvantage of cephalometric radiography in the study of growth?

  1. requires damaging x-rays
  2. requires complex head positioning equipment
  3. makes it difficult to see soft tissue landmarks
  4. offers a two-dimensional view of three-dimensional objects ✓

Correct

That’s right. All of the responses are disadvantages to some extent, but the biggest disadvantage is the two-dimensional view that the radiograph provides. Changes in distances between points that are not in the same plane will be distorted. The compensating advantage is that longitudinal data for skeletal dimensions can be obtained by superimposing tracings of serial cephalometric radiographs.

Question 14

The difference between a growth distance curve and a growth velocity curve is that:

  1. distance curve plots total achieved, velocity curve plots increment ✓
  2. distance curve plots increment, velocity curve plots total achieved
  3. both curves plot increment, but velocity curve magnifies it
  4. both curves plot total achieved, but distance curve magnifies it

Correct

That’s right. Distance curves plot the total growth achieved, velocity curves plot the growth increment since the last measurement. Both types of plots are valuable, depending on what you’re trying to observe—but velocity plots make it easier to appreciate the changes that are occurring, as at adolescence.

Question 15

(A) Longitudinal growth data are quite inefficient in terms of the amount of information obtained from each subject because (B) the longitudinal data highlight individual variations.

  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. Longitudinal data are very efficient, not inefficient, for growth studies, so the first statement is false. It’s true that the longitudinal data highlight individual variations, so the second statement is true. That’s another advantage of longitudinal versus cross-sectional data.

Question 16

What does it mean to say that a child is in the 95% percentile for height?

  1. she’s in the shortest 5% of the population her age
  2. she’s in the tallest 5% of the population her age ✓
  3. she’s more than two standard deviations below the mean
  4. she’s more than two standard deviations above the mean

Correct

That’s correct, she’s in the tallest 5%, taller than 95% of her age group. But that puts her within two standard deviations of the mean, in her case, exactly two above.

Module 2: The Nature of Craniofacial Growth

Question 1

In growth of the craniofacial skeleton, which of the following cellular activities is most active?

  1. Hyperplasia
  2. Hypertrophy
  3. Secretion of extracellular material ✓
  4. All are equally important

Correct

That is correct. Although all the cellular processes are important, secretion of extracullar material is particularly important in growth of the skeletal system, in which the extracellular material later calcifies into bone. Cartilage cells mature and secrete extracellular matrix that becomes calcified; osteoblasts also later form new bone by secreting extracellular matrix that calcifies.

Question 2

In growth of the cranial and facial soft tissues, which of the following cellular activities is the least important?

  1. Hyperplasia
  2. Hypertrophy
  3. Secretion of extracellular material ✓
  4. All are equally important

Correct

That’s right. Secretion of extracellular material can occur as soft tissues are formed, but this is not an important characteristic of growth of the craniofacial soft tissues.

Question 3

(A) Interstitial growth does not occur in the growth of calcified tissues because (B) the rigid calcified tissue mass cannot expand internally.

  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. Calcified tissues don’t grow by interstitial growth that leads to external expansion, because it’s physically impossible. So these statements are both true and they’re related.

Question 4

Which of the following statements best describes the growth of a long bone of the limbs?

  1. The bone is formed in cartilage and replaced by endochondral ossification
  2. Cartilage does all the growing, then is replaced by bone
  3. A little cartilage is present originally, but most of the growth is bone apposition
  4. Both replacement of cartilage and direct apposition of bone are major contributors to the growth ✓
  5. None of the above, there’s no role for cartilage except in facial growth

Correct

That’s right. Replacement of cartilage that grows at the epiphyseal plates is very important, but so is direct apposition of bone at the periosteum.

Question 5

(A) Significant interstitial remodeling of long bones occurs around Haversian systems because (B) the final increments of bone growth are obtained in this manner.

  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. It’s true that long bones remodel internally around their Haversian systems, but this has almost nothing to do with growth, so the first statement is true but the second is false.

Question 6

(A) Formation of bone always requires the intermediate step of cartilage formation because (B) osteoblasts must secrete their matrix on a framework of calcified cartilage.

  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. Bone can be (and often is) formed without an intermediate cartilage step, because osteoclasts can secrete their matrix directly in connective tissue.

Question 7

Growth of the cranial vault involves which of the following processes?

(1) endochondral ossification at multiple growth centers

(2) apposition of new bone at sutures

(3) apposition of new bone on external surfaces

(4) apposition of new bone on internal surfaces

  1. 1 and 2
  2. 2 and 3 ✓
  3. 2, 4 and 4
  4. All of the above

Correct

That’s right, the cranial vault grows primarily by apposition of new bone at the sutures, and to a smaller extent by adding new bone on the outer surfaces, so the second and third statements are correct. There aren’t any growth centers in the cranium and no endochondral ossification, and bone is removed rather than added on the internal surfaces, so the first and last statements are incorrect.

Question 8

Which of the following types of growth is most important in the cranial base?

  1. endochondral ossification at multiple growth centers ✓
  2. apposition of new bone along suture lines
  3. apposition of new bone on external surfaces
  4. removal of bone from internal surfaces

Correct

That’s right, all of these processes are involved to some extent in growth of the cranial base—but cartilage growth and endochondral replacement of bone at the midline synchondroses are particularly important in lengthening the cranial base and projecting the midface forward.

Question 9

Growth of the maxilla involves which of the following processes?

(1) endochondral ossification at multiple growth centers

(2) apposition of new bone along suture lines

(3) apposition of new bone on external surfaces

(4) removal of bone from external or internal surfaces

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

Correct

That’s right, there’s no direct endochondral ossification and no cartilaginous growth centers in maxillary growth, and both growth at sutures and surface remodeling are important. Compared to the cranium, the maxilla has less sutural growth and more remodeling partly because it’s pushed forward by growth of the cranial base behind it and remodeling occurs in response to that.

Question 10

What is the major area for addition of new bone to the surface of the maxilla during growth?

  1. tuberosity ✓
  2. upper anterior surface
  3. lower anterior surface
  4. paranasal areas
  5. all of the above, bone is added to all surfaces about equally

Correct

That’s right, the main area of the maxilla where bone is added during growth is the tuberosity. Formation of new bone here allows the dental arch to become longer during growth and provides space of the molar teeth as they erupt. Most of the anterior surfaces, in contrast, are resorbed rather than added to during growth.

Question 11

Which of the following mechanisms move the roof of the mouth downward during growth?

(1) endochondral ossification at the back of the maxilla

(2) displacement of the maxillary core from the cranium and cranial base

(3) apposition of bone on the inferior surface of the palatal bone

(4) resorption of bone on the nasal surface of the palatal bone

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

Correct

That’s right. No endochondral ossification is involved in downward movement of the roof of the mouth, but displacement of the core of the maxilla and remodeling of the bony surfaces are important. In some instances, with the roof of the mouth being an excellent example, the direction of remodeling is the same as the direction of displacement.

Question 12

(A) Most aspects of mandibular growth can be explained by endochondral ossification because (B) a cartilaginous model of the mandible forms early in embryonic life and then resorbs.

  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 first statement (A) is false, but the second statement (B) is true. Mandibular growth is mostly a surface phenomenon, and endochondral ossification at the condyle plays a smaller role, so the first statement is false. It’s true that a cartilaginous model of the mandible forms early in life and then resorbs, although the new, primarily membranous mandible forms alongside it without really replacing it in the classic form of endochondral bone growth.

Question 13

Which of the following is the best illustration of remodeling resorption?

  1. backward movement of the mandibular ramus ✓
  2. forward movement of the chin
  3. lateral movement of the mandibular alveolar process
  4. backward movement of the maxillary tuberosity

Correct

That’s correct. The ramus moves backward as bone is removed from its front surface and added to the back. There’s so much remodeling that in a young child, what at one time was the back surface eventually becomes the front surface and then is resorbed away.

Question 14

Which of the following is not an area of significant bone apposition during mandibular growth?

  1. posterior border of ramus
  2. superior border of ramus
  3. alveolar process
  4. chin ✓

Correct

That’s right. Little or no bone is added at the chin during mandibular growth, and the area immediately above the chin prominence usually is resorptive. In contrast, there is major apposition of bone in the other areas.

Question 15

After it first comes into occlusal contact with its antagonists at about age 6, how much further does a typical permanent first molar erupt?

  1. stops after coming into occlusion
  2. 1-2 mm
  3. 3-5 mm
  4. 10 mm or more ✓

Correct

That’s correct, after it comes into occlusion a typical first molar has to erupt a centimeter or more. The mandible grows away from the maxilla, creating a space into which the teeth have to erupt to stay in occlusion, and there’s a lot of vertical growth after age 6.

Question 16

Which of the following is a site of interstitial growth?

  1. synchondrosis of cranial base ✓
  2. roof of the mouth
  3. ramus of the mandible
  4. maxillary tuberosity
  5. none of the above

Correct

That’s right, the synchondrosis contains cartilage that can and does grow interstitially, but the other bony areas can’t grow interstitially.

Module 3: Theories of Craniofacial Growth

Question 1

Which of the following is not the focus of a major theory of craniofacial growth?

  1. nervous system ✓
  2. bone
  3. cartilage
  4. soft tissue matrix

Correct

That is correct. There have been no serious efforts to explain craniofacial growth as determined by the nervous system, but major theories have been build around bone as the primary determinant of its own growth, cartilage as the primary determinant with bone as a follower, and the soft tissue matrix as the primary determinant with cartilage and bone as secondary followers.

Question 2

Which of the following can be considered evidence that the sutures between craniofacial bones are sites but not centers of growth?

  1. failure of suture growth on transplantation
  2. increased growth when sutures are mechanically pulled apart
  3. decreased growth when sutures are mechanically compressed.
  4. 1 only
  5. 1 and 2
  6. 1, 2 and 3 ✓
  7. none of the above

Correct

That’s right, all three are correct. Both the failure of sutures to grow when they are transplanted and their response to outside influences suggest that sutures react to other influences and are not the primary determinant of their own growth.

Question 3

(A) The epiphyseal plates of long bones and the synchondroses of the cranial base can be considered centers of growth because (B) these areas are capable of growing independently of local environment influences.

  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. The epiphyseal plates certainly, and the synchondroses almost certainly, can grow independently. That’s the definition of a growth center. The independence of growth distinguishes a growth center from a growth site.

Question 4

Cartilage whose growth could potentially pull the maxilla away from the cranium and cranial base, putting tension on sutures, is found in the:

  1. maxillary tuberosity
  2. synchondroses of the cranial base
  3. mandibular condyle
  4. nasal septum ✓
  5. all of the above

Correct

That’s right. The cartilage of the nasal septum is located so that its growth could pull the maxilla forward, separating the sutures and leading to growth at those sites.

Question 5

What happens when the cartilage of the nasal septum is surgically removed at an early age?

  1. the prominence of the midface is greatly reduced ✓
  2. the prominence of the midface is slightly reduced
  3. there is essentially no effect on the prominence of the midface
  4. the midface isn’t affected but mandibular growth is stimulated

Correct

That’s right, surgical removal of the septum at an early age greatly reduces the prominence of the midface. That isn’t controversial, but why it happens is. Proponents of the cartilage theory say it’s just what you’d expect if a growth center were removed. Functional matrix proponents say it’s just the effect of the surgery and collapse of structures afterward, and the loss of the cartilage wasn’t what made the difference. It’s hard to be absolutely certain, but the septal cartilage seems to behave as if it had at least some characteristics of a growth center.

Question 6

What happens when the mandibular condyle is transplanted to a different location?

  1. grows exuberantly, more than normal
  2. grows normally
  3. grows noticeably but perhaps less than normal
  4. grows poorly, almost not at all ✓

Correct

That’s correct, condylar cartilage grows very poorly when transplanted, almost not at all. This is evidence that it is different from the primary growth cartilages and lacks the potential to grow independently.

Question 7

(A) Fracture of the condylar process of the mandible in a growing child is a devastating injury because (B) the fractured condyle is displaced, resorbs and is lost.

  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, the first statement is false even thought the second is true. Early condylar fracture usually does not lead to long term growth problems. The fractured condyle is displaced, resorbs and is lost, but a new condylar process (complete with a cartilage cap) usually regenerates and often normal growth occurs.

Question 8

What is the chance in humans that essentially normal growth will be observed after the mandibular condyle, and its presumed growth center, are lost?

  1. less than 15%
  2. 15 – 40%
  3. 40 – 75%
  4. 65 – 85% ✓
  5. greater than 85%

Correct

That’s right. The chance of essentially normal growth is about 75% after a condylar fracture that leads to resorption of the original condyle and regeneration of a new one. But keep in mind that although most of the children do well, about 1 in 4, at least of those who were diagnosed, has a growth problem long-term.

Question 9

What is the usual determinant of growth of the cranial vault (brain case)?

  1. mechanical pressure from growth of the brain ✓
  2. neurotrophic growth factors released by the growing brain
  3. higher pressure in the cerebrospinal fluid as life stresses increase with age
  4. cartilage proliferation at the synchondroses of the cranial base

Correct

That’s right, under normal conditions the size of the cranial vault reflects the size of the brain beneath it because mechanical pressure form the growing brain separates the sutures. Neurotrophic growth factors and cranial base growth have little or nothing to do with the bone growth in the cranial vault, and cerebrospinal fluid pressure doesn’t increase during normal growth (although if it does increase, as in hydrocephaly, brain growth is inhibited while the cranial vault expands).

Question 10

(A) Ankylosis of the mandible leads to growth failure because (B) displacement of the mandible away from the skull as its soft tissue matrix grows is the normal determinant of mandibular growth.

  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 very much related. Ankylosis that prevents mandibular displacement impedes growth because the mandible has to be displaced from the skull in order to grow. That doesn’t mean there are no limits on the mandible’s growth, just that the limits are in the soft tissue, not in the bone itself.

Question 11

Lengthening of the cranial base occurs primarily because of:

  1. pressure created by the growing brain above it
  2. cartilage growth at the synchondroses ✓
  3. bony remodeling at the anterior and posterior sutures
  4. forward displacement of the anterior cranial base due to jaw function

Correct

That’s right. The cranial base lengthens primarily as a result of growth at the synchondroses, which seems rather independent of the growth of the brain above it (though some influence cannot be totally ruled out). Remodeling at the sutures and jaw function are not determinants of this growth.

Question 12

The maxilla grows forward because it is:

  1. wedged forward by growth at the sutures
  2. pulled from in front by the soft tissues and nasal septum
  3. pushed from behind by the lengthening cranial base
  4. 1 only
  5. 2 only
  6. 3 only
  7. 1 and 2
  8. 2 and 3 ✓

Correct

That’s right, the maxilla grows forward for two reasons. It’s both pushed forward by the cranial base, and pulled forward by the soft tissue matrix in which it’s embedded. But growth at the sutures is a reaction to the pull of the soft tissues, not a reason for the growth.

Question 13

The mandible grows forward because it is:

  1. pushed forward by growth at the condyles
  2. pulled forward by growth of the soft tissues in which it is embedded
  3. pushed from behind by the lengthening cranial base
  4. 1 only
  5. 2 only ✓
  6. 3 only
  7. 1 and 2
  8. 2 and 3
  9. all the above

Correct

That’s right. The mandible grows because it is pulled forward by the soft tissue matrix. Condylar growth is reactive, and the cranial base growth is largely irrelevant to forward movement of the mandible.

Question 14

How does the body of the mandible become longer during growth?

  1. cartilage growth and endochondral ossification at the anterior growth center
  2. remodeling of the ramus
  3. addition of bone at the chin
  4. 1 only
  5. 2 only ✓
  6. 1 and 2
  7. 2 and 3
  8. 1 and 3
  9. all the above

Correct

That’s correct. The body of the mandible gets longer as the ramus is remodeled, with bone added to the posterior surface and removed from the anterior surface. The remodeling is part of the response to growth of the soft tissue matrix around the mandible.

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