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Dentistry Module 4 > Craniofacial Biology > Flashcards

Craniofacial Biology Flashcards

1
Q

What is the incidence of treacher Collins syndrome?

A

1:50,000 live births

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2
Q

What causes TCS?

A

Abnormal formation of the first and second branchial arches during the 5th to 8th weeks of human fetal development

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3
Q

What are the main characteristics of TCS?

A
  • Facial dysmorphism (particularly of the cheek bones, eye sockets and jaw)
  • absent, small or unusually formed ears
  • potential loss of vision and hearing
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4
Q

What type of gene and mutation is most commonly the cause of TCS?

A

Gene: TCOF1
Mutation: loss of function mutation

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5
Q

What protein does the gene, TCOF1 encode?

A

Treacle

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6
Q

Aside from TCOF1, what are the other genes, which mutations cause TCS?

A

POLR1D and POLR1C

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7
Q

What is the main concern in a newborn with TCS?

A

Respiratory failure due to narrowing of airway from Craniofacial malformation

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8
Q

Mutation of which gene accounts for 70-93% of TCS individuals?

A

TCOF1

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9
Q

Mutation of which genes account for 11-23% of TCS individuals?

A

POLR1D and POLR1C

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10
Q

What type of mutations are the majority of TCOF1 mutations?

A

Deletions

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11
Q

What effect does mutation of TCOF1 have on treacle protein?

A

Results in truncated treacle protein which is small and non-functional

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12
Q

What protein is active during early embryonic development in structures that become bones and other tissues in the face?

A

Treacle

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13
Q

What is the key role of treacle?

A

Pre-ribosomal processing and making of ribosome

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14
Q

The study of the processes by which organs grow and develop

A

Developmental biology

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15
Q

The process by which a single parent cell divides to make two new daughter cells ( total number of chromosomes maintained)

A

Mitosis

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16
Q

A special form of cell division involving two rounds of division that result in four cells with only one copy of each chromosome

A

Meiosis

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17
Q

The process by which an undifferentiated cell is instructed by specific organisers to produce a morphogenic effect

A

Induction

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18
Q

An organiser is part of an embryo, what does it influence?

A

Influences another part of the embryo to direct histological and morphological differentiation

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19
Q

What is ‘patterning’ and when does it occur?

A

Patterning is certain physiologic processes or spatial and temporal events which are key to further development. Occurs during the embryonic period from the 2nd to 8th week of parental development.

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20
Q

The development of different cell types

A

Cytodifferentiation

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21
Q

The development of different histologic tissue types within a structure

A

Histodifferentiation

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22
Q

The development of differing morphology, which makes up its structure or shape, for each organ or system.

A

Morphodifferentiation

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23
Q

During the second week of prenatal development, what develops from the blastocyst, appearing as a three-dimensional but flattened, essentially circulate plate of bilateral cells.

A

A bilaminar embryonic disc

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24
Q

What general types of phenomena are tissue interactions associated with?

A
  • instructive
  • permissive
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25
Q

The ability of one tissue to determine specific patterns of morphogenesis and differentiation that will develop in an associated tissue

A

Instructive tissue interactions

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26
Q

The ability of an interacting tissue to provide certain conditions that is necessary for its committed partner tissue to progress to full expression of its pre-determined phenotype

A

Permissive tissue interactions

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27
Q

What protein is very important for fusion of palatal shelves during development?

A

Hyluronase synthase

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28
Q

What virus has been known to lead to craniofacial development issues in newborns?

A

Zika virus

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29
Q

What are common symptoms of Zika virus?

A

Fever, rash, conjunctivitis, muscle and joint pain, malaise and headache

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30
Q

What congenital abnormality in regards to craniofacial development is a risk if pregnant woman contracts Zika virus?

A

Virus can cause microcephaly (baby’s head is much smaller than expected)

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31
Q

What four aspects make up the craniofacial complex?

A
  • cranial vault
  • cranial base
  • nasomaxillary complex
  • mandible
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32
Q

What are the main sutures important for normal fetal development?

A
  • coronal
  • sagittal
  • lambdoid
  • parietal
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33
Q

What is craniosynostosis?

A

A birth defect in which the bones in a baby’s skull join together too early

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34
Q

What craniosynostosis is this:

A genetic disorder characterised by the premature fusion of certain skull bones

A

Crouzon syndrome

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35
Q

What craniosynostosis is this:

A type of disorder where the head appears tall with some length and width

A

Turricephaly

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36
Q

What craniosynostosis is this:

The head is flattened on one side, causing it to look asymmetrical

A

Plagiocephaly

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37
Q

What craniosynostosis is this:

A condition where the baby’s skull has fused together before birth causing a triangular shape or ridge on the forehead

A

Trigonocephaly

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38
Q

A cartilaginous joint where bones are joined together by hyaline cartilage, or where a bone is attached to hyaline cartilage

A

Synchondrosis

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39
Q

Type of ossification where cartilage grows rapidly and is replaced by bone

A

Endochondral ossification

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40
Q

What is a homeobox gene?

A

A DNA sequence that regulates large scale anatomical features in the early stages of embryonic development

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41
Q

What two factors are homeobox genes responsible for?

A
  • craniofacial shape and patterning
  • patterning of the dentition
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42
Q

How are homeobox genes important in regards to tooth development?

A

MSX1 &2 in the initiation, developmental position and morphodifferentiation of tooth buds

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43
Q

Condition caused by the disruption of development due to artery bursting

A

Hemifacial microsomia

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44
Q

When right and left palatal shelves fail to meet and fuse with the nasal septum, what can be the result?

A

Cleft palate

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45
Q

What plays an important role in the site-specific nature of cell differentiation and proliferation?

A

Cell-cell interactions

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46
Q

What type of interactions occur between cytokines and matrix macromolecules to mediate cell-cell interactions?

A

Dynamic and reciprocal

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47
Q

What are the four primary germ layers?

A
  1. Ectoderm
  2. Mesoderm
  3. Endoderm
  4. Neural crest/ectoderm-mesenchyme
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48
Q

What germ layer comes from the epiblast layer?

A

Ectoderm

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49
Q

What germ layer comes from the migratory cells of the epiblast layer?

A

Mesoderm

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50
Q

What germ layer comes from the hypoblast layer?

A

Endoderm

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51
Q

What germ layer comes from the ectoderm that migrates into mesoderm to form structures in the head and neck?

A

Neural crest/ ecto-mesenchyme

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52
Q

At what post-ovulatory age (days) does the branchial arches start to form?

A

Days 24/25

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53
Q

What cranio-facial structures do the branchial arches develop to form?

A

Face, pharynx, larynx, naso-cavities, mouth and neck

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54
Q

What happens in the stomatodeum just before 28 days of foetal development?

A

Group of cells across this area undergo apoptosis allowing growth factors to seep in

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55
Q

What is the stomatodeum?

A

Developing oral cavity in a foetus

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56
Q

When do pharyngeal arches start to appear?

A

In 4th and 5th week as neural crest cells migrate into the head and neck region

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57
Q

A typical pharyngeal arch contains?

A
  • artery
  • cartilage
  • muscle
  • nerve
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58
Q

What genes control type of neural crest cell that develops?

A

Homeobox genes

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59
Q

What 4 components make up the branchial arch system?

A
  1. Arches
  2. Clefts
  3. Grooves
  4. Pouches
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60
Q

Which branchial arch disappears very early in development?

A

5

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61
Q

Which pharyngeal arch is a continuation of the endoderm?

A

1st arch

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62
Q

Which pharyngeal arch lays the framework for the development of the mandible and maxilla through meckle’s cartilage?

A

1st arch ( mandibular arch)

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63
Q

what muscles are associated with the 1st pharyngeal arch?

A

-Muscles of mastication
-anterior belly of digastric
-mylohyoid
-tensor tympani
-tensor veli palatini

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64
Q

what cranial nerve is associated with 1st pharyngeal branch?

A

Trigeminal nerve ( CN V)

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65
Q

Which arteries does the 1st pharyngeal branch give rise to?

A

Maxillary artery
Internal carotid arteries

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66
Q

What cartilage is associated with 1st pharyngeal arch?

A

Meckle’s cartilage

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67
Q

What two bones does meckel’s cartilage give rise to?

A
  • Incus body
  • malleus
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68
Q

What two ligaments does meckel’s cartilage give rise to?

A
  • sphenomandibular
  • sphenomalleolar
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69
Q

What syndrome is a result of the failure of neural crest cell migration during development of pharyngeal arch 1?

A

Treacher- Collins Syndrome

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70
Q

What is another name given to the 2nd pharyngeal arch?

A

Hyoid arch

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71
Q

What cartilage is associated with 2nd pharyngeal arch?

A

Reichert’s cartilage

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72
Q

What structures does reichert’s cartilage form?

A
  • stapes
  • lesser horn and superior hyoid body
  • styloid process, stylohyoid ligament
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73
Q

what muscles are associated with the 2nd pharyngeal arch?

A

Muscles of facial expression
Stapedius
Stylohyoid
Posterior belly of digastric

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74
Q

What nerve is associated with 2nd pharyngeal branch?

A

Facial nerve (VII)

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75
Q

What artery is derived from 3rd pharyngeal branch?

A

Internal carotid artery

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76
Q

What nerve is associated with the 3rd pharyngeal branch?

A

Glossopharyngeal nerve (IX)

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77
Q

What muscles are associated with the 3rd pharyngeal branch?

A

Stylopharyngeus

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78
Q

What are the skeletal derivates associated with the 3rd pharyngeal branch?

A

Greater horn of hyoid
Inferior hyoid body

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79
Q

Which pharyngeal arch forms the root of the tongue?

A

3rd arch

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80
Q

Which pharyngeal arch forms the thyroid gland and tonsil?

A

2nd arch

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81
Q

Which arteries are given off from the 4th pharyngeal branch?

A

Right subclavian artery
Aorta

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82
Q

Which cranial nerve is associated with the 4th pharyngeal arch?

A

Vagus nerve (CN X)

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83
Q

What muscles are associated with pharyngeal arch 4?

A

Pharyngeal constrictor
Soft palate

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84
Q

What cartilage does the 4th pharyngeal arch form?

A

Thyroid cartilage

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85
Q

Which pharyngeal arch forms the pharynx and epiglottis?

A

4th arch

86
Q

What cartilage is associated with pharyngeal arch 6?

A

Cricoid and arytenoid cartilages

87
Q

Which pharyngeal arch forms the larynx?

A

Arch 6

88
Q

What muscles are associated with pharyngeal arch 6?

A

Muscles of larynx

89
Q

What cranial nerve is associated with 6th pharyngeal arch?

A

Vagus nerve (CN X)

90
Q

Which clefts are obliterated by the proliferation of 2nd pharyngeal arch, which grows over the top of them?

A

2nd-6th clefts

91
Q

What structure is found between each arch?

A

Pouches

92
Q

What does the 1st pouch form?

A

Middle ear and auditory tube?

93
Q

What does the 2nd pouch form?

A

Tonsillar fossa ( palatine tonsil)

94
Q

What does the 3rd pouch form?

A

Inferior parathyroid gland
Thymus

95
Q

What does the 4th pouch form?

A

Superior parathyroid gland
Post-branchial body

96
Q

What does pharyngeal groove/cleft 1 form?

A

External auditory meatus

97
Q

As the neck develops, what happens to all grooves/clefts, except the first?

A

They are obliterated by cervical sinus development

98
Q

Where are pharyngeal membranes found?

A

In the floor of the pharyngeal grooves

99
Q

Which pharyngeal membrane becomes the tympanic membrane, while the others are obliterated?

A

1st pharyngeal membrane

100
Q

What is the consequence of the 2nd pharyngeal arch failing to enlarge over the 2nd -4th clefts?

A

Branchial fistula/cyst

101
Q

Which pharyngeal arch has very little homeobox gene expression?

A

1st pharyngeal arch

102
Q

Define the term used for: the prominence in the upper facial area at the most cephalic end of an embryo

A

Fronto-nasal process

103
Q

Define the term used for: relating to the head or the head end of a structure

A

Cephalic end

104
Q

Define the term used for: the processes of first branchial arch that fuse at the midline to form mandibular arch

A

Mandibular processes

105
Q

Define the term used for: lower dental arch with mandibular teeth or the 1st branchial/pharyngeal arch inferior to the stomodeum in the embryo

A

Mandibular arch

106
Q

Define the term used for: the prominence from mandibular arch that grows superiorly and anteriorly on each side of the stomodeum of the embryo

A

Maxillary processes

107
Q

Define the term used for: upper dental arch in which the maxillary teeth form

A

Maxillary arch

108
Q

Define the term used for: placodes that develop into olfactory organ for the sensation of smell located in the mature nose

A

Nasal placode

109
Q

Define the term used for: area of ectoderm found at the location of the developing special sense organs on the embryo

A

Placode

110
Q

The development and joining of what structures establishes the basic morphology of the face between weeks 4-10?

A

The five prominences

111
Q

What are the five prominences that make up the formation of the face?

A
  1. Frontonasal prominence
  2. Maxillary prominences x2
  3. Mandibular prominences x2
112
Q

What are the two types of fusion that can occur between prominences?

A
  1. “ fusion”- between prominences by elimination of furrow
  2. True fusion- of separate processes
113
Q

What forms from the stomodeum, specifically the fused nasal prominence?

A

Primary palate

114
Q

At 27 days of development, what starts to form from the nasal placode?

A

Nasal pit

115
Q

At 34 days of development what starts to form from the developing otic placode?

A

The eyes

116
Q

Where is the nasolacrimal groove/nasal optic furrow found in the developing skull?

A

Between the lateral nasal prominence and the maxillary prominence

117
Q

During the 7th week of development, what tubular structures does the nasolacrimal groove form?

A

Nasolacrimal sac and duct

118
Q

What is the function of the developed nasolacrimal duct after birth?

A

It drains excess tears from the conjunctiva of the eye into the nasal cavity

119
Q

At 6 weeks, what structure does the left and right medial prominences join to form?

A

The basic structure of the nose ( primordial of bridge and septum)

120
Q

How is the intermaxillary segment formed in the 7th week of development?

A

The inferior tips of the medial nasal processes expand laterally and inferiorly to join with the intermaxillary process

121
Q

what does the intermaxillary process give rise to?

A
  • filtrum
  • primary palate
122
Q

By what week of development is the structure of the face fairly recognisable?

A

10 weeks

123
Q

In what week of development is the mouth reduced to it’s final width?

A

Weeks 7-8

124
Q

Define macrostomia

A

An enlargement of the mouth at the oral commissure (too little fusion)

125
Q

Define microstomia

A

A small sized mouth due to too much fusion during Craniofacial-facial development

126
Q

mesenchyme associated with the frontonasal prominence, is from what part of the brain?

A

Forebrain and midbrain

127
Q

What part of the brain is mesenchyme associated with the maxillary and mandibular processes from?

A

Midbrain and hindbrain

128
Q

At what week in Craniofacial development is the first sign of tooth development, with formation of the primary epithelial band?

A

Week 6

129
Q

During what week of Craniofacial development does ossification of the mandible occur?

A

6-7th week

130
Q

During what week of Craniofacial development does ossification of the maxilla occur?

A

8th week

131
Q

During what week of Craniofacial development does ossification of the primary palate and capsule occur?

A

8th week

132
Q

What are the two methods of osteogenesis?

A
  • intramembranous
  • endochondral
133
Q

In intramembranous ossification what do mesenchymal cells differentiate into?

A

Osteoblasts

134
Q

What is the major controlling element of pattern formation during development?

A

Retinoic acids

135
Q

What are the five growth factor families implicated in facial development? And what do they do?

A
  1. BMP
  2. FGF
  3. Shh
  4. Wnt
  5. Endothelins

Control proliferation, survival and apoptosis

136
Q

What controls patterning of the facial primordia?

A

Neural crest cells

137
Q

What is the prevalence of cleft lip?

A

1:1000 births

138
Q

What is the ‘mandibular process’ and what does it give rise to?

A

An embryological structure which gives rise to the mandible

139
Q

What cells make up cartilage?

A

Chondroblasts and chondrocytes

140
Q

What are the three types of cartilage?

A
  1. Hyaline
  2. Fibrocartilage
  3. Elastic cartilage
141
Q

what is the most common type of cartilage?

A

Hyaline

142
Q

What are the three functions of cartilage?

A
  1. supporting framework of some organs, preventing collapse
  2. articulating surface of bones
  3. template for the growth and development of long bones
143
Q

What do chondroblasts mature into?

A

Chondrocytes

144
Q

What is perichondrium?

A

A dense, irregular layer of fibrous connective tissue that covers the surface of most cartilage in the body

145
Q

What does the outer layer of cartilage contain?

A

fibroblasts that produce collagen

146
Q

What does the inner layer of cartilage contain?

A

Chondroblasts

147
Q

What are the two mechanisms of cartilage growth?

A
  1. Interstitial growth
  2. Appositional growth
148
Q

What is interstitial growth of cartilage?

A

Chondrocytes grow, divide and lay down more matrix inside the existing cartilage

149
Q

What is appositional growth of cartilage?

A

New surface layers of matrix are added to the pre-existing matrix by new chondrobalsts from the perichondrium

150
Q

What is the main cartilage of the 1st pharyngeal arch?

A

Meckel’s cartilage

151
Q

What is the fate of meckel’s cartilage, summarised?

A

Transforms to sphenomandibular ligament or disappears, absorbed by the growing mandibular bone

152
Q

What is the full name for the growth factor, CCN2?

A

Connective tissue growth factor

153
Q

What is the growth factor CCN2 required for in meckel’s cartilage development?

A

Accelerates adhesion and aggregation of 1st arch cells, as well as having a significant contribution to mandibular morphogenesis and tooth development

154
Q

What is the fundamental role of growth factor, CCN2, in ossification?

A

Acts as a messenger from chondrocytes to osteoblasts, guiding ossification

155
Q

What two types of ossification are involved in formation of the mandible and identify which is primary and secondary

A
  1. Intramembranous (primary)
  2. Endochondral (secondary)
156
Q

The process of laying down new bone material by osteoblasts

A

Osteogenesis

157
Q

when does initial formation of the mandible occur?

A

10 weeks in utero

158
Q

What are the three mandibular secondary cartilages?

A
  1. Condylar
  2. Coronoid
  3. Symphyseal
159
Q

What mandibular secondary cartilage is of most importance, disappearing at 20 years of age?

A

Condylar cartilage

160
Q

Which mandibular secondary cartilage disappears before birth?

A

Coronoid cartilage

161
Q

Which mandibular secondary cartilage disappears before the 1st year after birth?

A

Symphyseal cartilage

162
Q

what type of cartilage are secondary growth cartilages?

A

Fibrocartilage

163
Q

what type of cartilage growth do secondary cartilages undergo?

A

Apppositional growth

164
Q

what type of ossification do secondary growth cartilages undergo?

A

Endochondral ossification

165
Q

When does formation of the palate start and end?

A

Starts at week 6 i.u. And ends at week 12 i.u.

166
Q

What is the function of the primary palate?

A

Demarcates oral vs nasal components

167
Q

Where is the primary palate derived from?

A

From fused medial nasal prominences

168
Q

When does ossification of the primary palate occur?

A

Week 8 i.u.

169
Q

What is the role of the definitive (secondary) palate?

A

Separates the nasal airway + oral cavity

170
Q

What is formation of the definitive (secondary) palate important for?

A
  • mastication : bolus formation
  • sensation : taste and texture
  • speech
171
Q

Where do the palatal shelves initial migrate to?

A

Grow down the sides of the tongue

172
Q

At what week does the tongue withdraw downwards, allowing space for the palatal shelves to flip and elevate?

A

Week 8

173
Q

At what stage in palatal shelve elevation does hyaluronan accumulate?

A

Prior to elevation

174
Q

At what week do the lateral palatal shelves contact each other at the midline to form the definitive or secondary palate?

A

End of week 8

175
Q

what direction does fusion of the palate occur? Front to back OR back to front?

A

Front to back

176
Q

At what week is the secondary palate completely fused?

A

Week 12

177
Q

What group of cells are found at the midline once two separate structures make contact in true fusion?

A

Epithelial cells

178
Q

What molecules of high specificity are involved in epithelial adhesion?

A

Sticky surface glycoproteins

179
Q

To achieve true fusion, what must happen to the midline epithelial cells?

A

Disintegration

180
Q

what are the three theories of midline epithelial cell disintegration?

A
  1. Epithelial-mesenchymal transition
  2. Apoptosis of epithelial cells
  3. Migration to the nasal or oral edge
181
Q

What are Mesenchymal cells role in the formation of the palate?

A

Make the matrix of the upper palate

182
Q

What are the risk factors for cleft palate?

A
  • smoking
  • alcohol abuse
  • drugs
  • viruses
  • excess vitamin A
  • deficiencies in folic acid
183
Q

How many hyaluronan enzymes are there? And what are they called?

A

3
HA synthase 1,2 and 3

184
Q

Which HN enzyme is mostly expressed during development of the head and neck?

A

HN2

185
Q

What is the purpose of the knockout mouse experiment?

A

To silence the gene of interest to see what effect this has on development

186
Q

What gene, if ‘knocked out’ will result in cleft palate formation?

A

TGF beta 3

187
Q

What two roles do homeobox genes play in Craniofacial development?

A
  1. Craniofacial shape and patterning
  2. Patterning of the dentition
188
Q

What genes direct migration of neural crest cells into first branchial arch to become ectomesenchyme?

A

Homeobox genes

189
Q

What two homeobox genes are involved in the initiation , patterning and morphodifferentiation of tooth buds?

A

MSX1 and MSX2

190
Q

What are the different types of single gene mutations?

A
  • autosomal dominant
  • autosomal recessive
  • x-linked recessive
191
Q

give an example of a condition that is autosomal dominant in inheritance

A

Osteogenesis imperfecta

192
Q

give an example of a condition that is autosomal recessive in inheritance

A

Cystic fibrosis

193
Q

give an example of a condition that is x-linked in inheritance

A

Amelogenesis imperfecta

194
Q

what is an example of a Craniofacial condition that is autosomal dominant?

A

Crouzon syndrome

195
Q

What is the diagnostic feature of van der woude syndrome, commonly mistaken as cleft palate?

A

Lower lip pits

196
Q

What are the two clinical symptoms of dentinogenesis imperfecta?

A
  • opalescent dentine that is easily worn
  • blue sclerae of eye
197
Q

Define penetrance

A

The probability that presence of disease genotype will cause disease

198
Q

define expressivity

A

The variation in the severity of expression of a particular gene. Refers to the components of the phenotype that are exhibited in an individual.

199
Q

Give an example of a condition with variable expressivity

A

Myotonic muscular dystrophy- inability to quickly relax a muscle after sustained contraction

200
Q

If an individual is described as having complete penetrance, how will their condition present?

A

They will express full phenotypic features of a condition

201
Q

What is required for autosomal recessive inheritance to cause disease?

A

Two faulty copies of a gene

202
Q

In an x-linked recessive inheritance, which offspring sex can only be affected if the mother is a carrier?

A

Male

203
Q

In x-linked recessive inheritance, female offspring can only be carriers of a disease. True of false?

A

True

204
Q

What form of cleft lip has a major manifestation, meaning it’s more likely to cause cleft lip in future offspring?

A

Bilateral cleft lip

205
Q

What is the role of folic acid as a dietary supplement regarding neural tube defects?

A

Has been found to reduce the risk of neural tube defects by 70%

206
Q

In autosomal recessive inheritance, are the parents of affected individuals typically affected themselves or just gene carriers?

A

Gene carriers

207
Q

In autosomal recessive inheritance what are the chances of offspring inheriting two copies of the disease allele?

A

1 in 4 (25%)

208
Q

What causes complex multi factorial disorders?

A

The interactions of variations in multiple genes and environmental factors

209
Q

Define ‘anticipation’ in terms of genetic disease

A

Term used to describe genetic disease that increases in severity or is marked by an earlier age of onset with each successive generation

210
Q

When viewings sections through an embryonic head, what does it mean if meckels cartilage appears close together? And what does it mean when it appears far apart?

A

meckel’s cartilage is close together at the front of the head, and further apart at the back.

Dentistry Module 4 (20 decks)

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