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OCB02 > Mechanisms of Post-Natal Growth > Flashcards

Mechanisms of Post-Natal Growth Flashcards

1
Q

How many fontanelles are present at birth?

A

6

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2
Q

What is the cranial vault to face ratio in newborns compared to adults?

A

8:1 in newborns vs 3:1 in adults

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3
Q

What parts of the skull follow a neural growth pattern?

A

Cranial vault and structures associated with sense organs

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4
Q

Why does the cranial vault follow a neural growth pattern?

A

Grows in response to developing brain

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5
Q

Which of the neural or somatic growth patterns is faster?

A

Neural

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6
Q

By 10yo how much of the brain is developed?

A

95%

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7
Q

What growth pattern does the face follow?

A

Somatic

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8
Q

When is face growth complete?

A

With eruption of third molars (18-25yo)

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9
Q

What growth pattern does the cranial base have?

A

Intermediate - early is neural then later childhood is somatic

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10
Q

What areas in the head have endochondral origin? (3)

A

Cranial base

Pharyngeal arch cartilages

Otic and nasal capsule

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11
Q

What is the main difference between endochondral and intramembraneous ossification?

A

Endochondral has a hyaline cartilage precursor

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12
Q

Why does secondary cartilage form?

A

In response to pressure/force

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13
Q

What are the three embryonic origins of the bones in the head?

A

Neural crest cells - most skeletal structures

Unsegmented paraxial cranial mesoderm - back of cranial vault and back of cranial base

Segmented paraxial cranial mesoderm - occipital bone

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14
Q

What are the remnants of Meckel’s cartilage?

A

Incus and malleus in the inner ear

Perichondrium of sphenomandibular and sphenomalleolar ligaments

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15
Q

How do neural crest cells form?

A

Epithelial to mesenchymal transformation

Lose adherens junctions and become migratory

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16
Q

What is the function of Meckel’s cartilage? (2)

A

Act as a support on which the mandible is formed

Required for downward growth of mandible

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17
Q

Where is primary cartilage found in the head?

A

Growth plates of cranial base

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18
Q

What type of growth occurs in growth plates?

A

Interstitial

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19
Q

How can ossified primary cartilage be remodelled?

A

Appositional growth

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20
Q

What is an example of secondary cartilage in the head?

A

Condylar cartilage

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21
Q

Why is the cranial vault remodelled?

A

Reduce weight

Flatten

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22
Q

Give two conditions where brain defects have affected skull growth.

A

Microcephaly (eg. zika virus) - underdeveloped skull

Macrocephaly (eg. hydrocephaly) - enlarged skull

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23
Q

What three cartilages form the cranial base?

A

Prechordal - ethmoid

Hypophyseal - sphenoid

Parachordal - occipital

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24
Q

Which cartilages are associated with sense organs?

A

Greater and lesser wings of sphenoid

Periotic capsule (temporal)

25
Q

Name the synchondroses of the cranial base.

A

Spheno-ethmoidal (ethmoid and presphenoid)

Intersphenoid (presphenoid and basi-sphenoid)

Spheno-occipital (basi-sphenoid and basi-occipital)

26
Q

When are each of the synchondroses of the cranial base fused?

A

Intersphenoid - at birth

Spheno-ethmoidal - 3-5yo

Spheno-occipital - 12-16yo

27
Q

How could achondroplasia affect occlusion? (3)

A

Defects in cranial base development

Cranial base linked to maxilla

No space for third molars, class III occlusion

28
Q

How does the mandible change from birth to adulthood? (3)

A

Increases in width, length, height

Angle decreases from 140° to 115°/120°

Relative sizes of condylar and coronoid processes change from even to a dominating condylar

29
Q

Which pharyngeal arch is the mandible derived from?

A

First

30
Q

What are features of the Pierre Robin Sequence?

A

Micrognathia

Glossoptosis

Airway obstruction

31
Q

How might defects in Meckel’s cartilage cause Pierre Robin Sequence?

A

No lowering of lower jaw

32
Q

By when is the lower jaw ossified?

A

10 weeks i.u.

33
Q

When and where does ossification of the lower jaw begin?

A

6 weeks i.u.

At incisive and mental branch tributary (from inferior alveolar nerve)

34
Q

When does the mandibular secondary cartilages start to form?

A

10 weeks - condylar

11 weeks - coronoid

12 weeks - symphysial

35
Q

Where do the cells giving rise to chondrocytes for secondary cartilage come from?

A

Periosteum

36
Q

When does the symphysial cartilage ossify and why is this important?

A

By the end of year 1

Limits growth in width of mandible

37
Q

When does the condylar cartilage stop growing?

A

20yo

38
Q

Which mandibular secondary cartilage disappears by birth?

A

Coronoid cartilage

39
Q

What is the result of mandibular remodelling from child to adult? (3)

A

Lengthen body

Strengthen chin

Widen mandible at back

40
Q

Why does loss of dentition result in a thinner mandible?

A

Loss of alveolar bone

41
Q

How is room made for the permanent mandibular dentition? (3)

A

Remodelling

Size difference between deciduous molars and their successors

Forward movement of lower teeth through alveolar bone

42
Q

What parts of the upper jaw are endochondral?

A

Nasal capsule and septum

43
Q

Describe the upper jaw at birth. (3)

A

Large frontal process

No alveolar bone

No anterior nasal spine

44
Q

What occurs during the growth of the upper jaw? (3)

A

Displacement at sutures

Dentition and alveolar bone develop

Remodelling forms maxillary sinuses and makes room for third molars

45
Q

Which sutures are growing post-natally in the palatal shelves and until when?

A

Intermaxillary/median palatine - increase width up to 2 yo

Palatomaxillary/transverse palatine suture - increase length up to 7yo

46
Q

What causes displacement at the sutures for upper jaw growth? (3)

A

Expanding brain

Expanding sense organs

Muscle forces

47
Q

When is the septal cartilage ossified?

A

7yo

48
Q

How does the septal cartilage help upper jaw growth?

A

Pushes down on palatal shelves causing a forward and downward movement to develop the arched shape

49
Q

What region of the skull is the septal cartilage a part of?

A

Cranial base

50
Q

When does the cartilage between the greater wings and body of sphenoid ossify?

A

By the end of year 1

51
Q

What region of the skull are the greater wings and body of sphenoid part of?

A

Cranial base

52
Q

When is the cribriform plate of the ethmoid ossified?

A

By the end of year 3

53
Q

When is the midline of the face completely fused?

A

By the end of year 3

54
Q

By when are all the upper jaw sutures fused?

A

10yo

55
Q

By when is all the upper jaw endochondral growth complete?

A

7yo

56
Q

At birth, what percentage of the final width, height and depth is the face?

A

60% width

45% height

35% depth

57
Q

When is the metopic suture fused?

A

By the end of year 1

58
Q

Why is there less growth in the width of the face than height and depth?

A

Midline is fused by 3yo

OCB02 (19 decks)

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