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Human Growth & Development > Head & Neck Development > Flashcards

Head & Neck Development Flashcards

Dr. Timothy Cox

1
Q

Morphogenesis of the head and neck is a _____ process, NOT a _____ process

A

Generative; descriptive

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2
Q

Encode RNA & proteins:

A

Genes (DNA)

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3
Q

The complement of RNA & proteins produced defines the ______; meaning its appearance and how it behaves

A

Identity of each cell

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4
Q

Provides the blueprint that ensures we all have a maxilla & mandible & an integrated oronasal cavity:

A

Genes (genome)

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5
Q

Gene mutations & differences in non-genetic instructions determines everything about:

A

Phenotype

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6
Q

Cells that are tightly compact, & tightly bound together. often found in sheets within the body & have a very distinct sort of shape; not very mobile:

A

Epithelia

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7
Q

Cells that are loosely connected, surrounded by many types of extracellular matrix so they can move around in the body because they are not attached to anything; they can receive and move towards signals:

A

Mesenchyme

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8
Q

Outer cell layer

A

Ectoderm

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9
Q

Middle cell layer:

A

Mesoderm

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10
Q

Inner cell layer:

A

Endoderm

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11
Q

The terms ecto-, endo- & mesoderm are related to the:

A

Embryonic origin of cells

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12
Q

All aspects of the craniofacial complex are defined by axes: (3)

A
  1. Left-right
  2. Dorsal-ventral
  3. Anterior-posterior
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13
Q

Clinical treatments always consider _____ & ____ because the are critical for function & esthetics

A

Form & Symmetry

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14
Q

Tooth shape, spacing, number & cusp pattern are all examples of:

A

Form

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15
Q

In a clinical aspect, form and symmetry are always considered because:

A

They are critical for function & esthetics

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16
Q

Axis that becomes apparent by the blastocyst stage:

A

Dorsal-ventral axis

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17
Q

When does the dorsal-ventral axis become apparent?

A

Blastocyst stage

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18
Q

At the 4-cell stage of development, what structures do we see?

A

Blastomeres

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19
Q

The 32-cell stage in which we still just see a ball of cells:

A

morula

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20
Q

Once we reach the 32-cell stage and the morula is formed, the cells start to undergo a process called:

A

Compaction

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21
Q

During first three weeks of development the cells within the outer coating (which are called the zona pellucida) undergo some sort of specialization to create an outer lining of cells called the:

A

Ectodermal cell layer

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22
Q

During the first three weeks of development when compaction takes place, the cells of the zona pellucida become the ectodermal cell layer, while the cells in the middle become the:

A

Inner cell mass

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23
Q

During the first three weeks of developement, the cells that comprise the inner cell mass will give rise to the _____

A

Embryo

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24
Q

During the first three weeks of development, the cells that comprise the inner cell mass that go on to become the embryo itself are also referred to as _____ because:

A

Embryonic stem cells; they give rise to every organ & tissue in the human body

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25
Q

Following fertilization, the zygote (single cell) undergoes _____ cell divisions to result in a total of _____ cells just prior to implantation

A

6 cell divisions; 64 cells

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26
Q

During the first three weeks of development, the morula undergoes compaction to form the ectodermal cell layer, & the inner cell mass. What else is formed during this point in development?

A

Left over space to form a cavity

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27
Q

Once the morula undergoes compaction to form an ectodermal cell layer, an inner cell mass and a cavity of space, it is now considered:

A

Blastocyst

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28
Q

With the formation of the blastocyst, we can see that everything practically hatches from the _____ as it passes down the fallopian tubes:

A

Zona pellucida

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29
Q

What process occurs following the formation of a blastocyst?

A

Implantation

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30
Q

Once implantation into the uterus occurs, this sets off a series of:

A

More specialized differentiations

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31
Q

After implantation, around the third week of development, the more specialized differentiations lead to:

A

Specification of the germ layers

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32
Q

What are the germ layers that are formed following implantation, around the third week of development?

A

Ectoderm
Endoderm
Mesoderm

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33
Q

The inner cell mass leads to:

A

Embryonic stem cells

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34
Q

Anterior-posterior axis (head-tail) and left-right axis determined at the start of _____ with the appearance of the _____

A

Week 3; primitive streak

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35
Q

Two-layered epithelial disc; the region between where the ectoderm & endoderm contact:

A

Bilaminar disc

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36
Q

The bilaminar disc is location in which the ________ will form from

A

Embryo proper

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37
Q

Ectodermal layer of the bilaminar disc:

A

Epiblast

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38
Q

Endoderm layer of the bilaminar disc:

A

Hypoblast

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39
Q

Layer of the bilaminar disc that will form the entirety of the embryo:

A

Epiblast

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40
Q

One of the first things we will see on the bilaminar disc is a:

A

Invagination of cells that converge at the midline

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41
Q

What happens to the epiblastic cells at the midline of the bilaminar disc?

A

Converge at midline & ingress

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42
Q

Once the epiblastic cells at the midline of the bilaminar disc converge and ingress this marks:

A

The posterior end

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43
Q

When does the primitive streak start to appear?

A

Around day 15

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44
Q

When is the posterior end of the embryo determined?

A

Around day 15 with the primitive streak formation

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45
Q

Invagination of epiblastic cells that marks the posterior end of the embryo, therefore defining the anterior-posterior axis:

A

Primitive streak

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46
Q

Once the primitive streak is forming, defining the anterior-posterior axis, you essentially will have:

A

A left-right axis

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47
Q

Looking down at the embryo at the bilaminar disc, the endoderm forms the ______ while the ectoderm forms the _______

A

Endoderm= yolk sac
Ectoderm= Amniotic cavity

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48
Q

The furrow of the primitive streak progressively elongates along the midline through the process of:

A

Convergent extension

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49
Q

Describe the path direction of formation of the primitive streak:

A

Starts on posterior end & moves anteriorly

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50
Q

When you have tightly bound epithelial cells on either side of the primitive streak and these cells start to proliferate and grow. As they come together at the midline they have to work out how to deal with these extra cells that are all pushing together. The result is the intertwining of cells.

This process is called:

A

Convergent extension

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51
Q

The process of convergent extension causes the expansion of the _____ length of the embryo:

A

Anterior-posterior

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52
Q

Convergence may also be called _____

A

Intercalation

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53
Q

Convergence/intercalation results in:

A

Embryoelongation (extension)

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54
Q

Cells of the epiblast (layer 1) migrate through the primitive streak to form _____ & _____

A

Mesoderm & embryonic (gut) endoderm

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55
Q

The start to forming the inner tissue of the embryo occurs through the process:

A

Gastrulation

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56
Q

Formation of the second & third germ layer occur through:

A

Gastrulation

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57
Q

Gastrulation occurs through the process of ________ to form mesoderm:

A

Epithelial to mesenchyme transformation (EMT)

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58
Q

During the process of gastrulation, the movement of epiblast (ectoderm) occurs to form _________ (both epithelia)

A

Embryonic endoderm

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59
Q

Describe the growth of the germ layers:

A

Disproportionate growth

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60
Q

The growth of the germ layers can be described as disproportionate, why is this?

A

Greater proliferation of the epiblast (ectoderm) because it also generate all the mesoderm & embryonic endoderm

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61
Q

As the germ layers are being formed, the generated (proliferating) mesoderm migrates:

A

Toward anterior (head) end

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62
Q

When the mesoderm is being driven forward, it receives information that tells it to start forming structures, this is the key process of:

A

Head formation

63
Q

The primitive streak ends in an asymmetric bulge called the:

A

Node

64
Q

The anterior-most end (ventral side) of the primitive streak is unique in both:

A

Appearance & function

65
Q

The node may also be called the:

A

Organizer

66
Q

The node (organizer) is a _______ structure across _____

A

Conserved; all vertebrates

67
Q

Describe what the node is essential for:

A
  1. Patterning & induction of embryonic cells (mesoderm & embryonic endoderm)
  2. Establishment of L-R symmetry of organs
68
Q

Factors secreted by cells of the node induce anteriorly migrating mesoderm to form:

A
  1. The prechordal plate
  2. The notochord
69
Q

Factors secreted by the cells of the nude induce _________ to form the prechordal plate & the notochord

A

Anteriorly migrating mesoderm

70
Q

What forms first, the prechordal plate or the notochord?

A

Prechordal plate

71
Q

Forms from the most anterior region of mesoderm & provides the signals for the induction of head structures:

A

Prechordal plate

72
Q

The prechordal plate provides:

A

The signals for the induction of head structures

73
Q

Transient epithelial-like rod structure along the midline that provides the signals for induction of the neural plate:

A

Notochord

74
Q

Describe the locational relationship between the notochord and prechordal plate:

A

The notochord is just anterior to the prechordal plate

75
Q

The notochord provides:

A

The signals for the induction of the neural plate

76
Q

The neural plate is formed from the ______ and ultimately gives rise to the _____

A

Overlying ectoderm; spinal cord

77
Q

The node induces the _______

A

Body axis

78
Q

Provides signals to specify the fate of the mesoderm passing by the node:

A

The node

79
Q

The node is responsible for inducing & specifying the fate of the ____ as its formed

A

Mesoderm

80
Q

Responsible for the creation of aymmetry in the symmetrical embyro

A

The node

81
Q

Explain how the node is responsible for the creation of asymmetry in the symmetrical embryo:

A

First establishes molecular asymmetric which is converted into asymmetric organogenesis

82
Q

Establishing molecular asymmetry occurs the:

A

Asymmetric expression of morphogenetic factors around the node

83
Q

Give examples of morphogenetic factors are expressed in an asymmetric manner in order to establish molecular asymmetry:

A

-SHH
-BMP4
-FGF8

84
Q

Asymmetric expression of morphogenetic factors around the node initiates a ______ to promote ______

A

Cascade of gene expression; asymmetric specialization/commitment of mesoderm

85
Q

The node generates _____

A

Asymmetry

86
Q

Nodal cells each have:

A

One motile cilium

87
Q

A membrane covered extension fro the cell that has a microtubule cytoskeleton core which helps define its properties

A

Cilium

88
Q

The properties of the cilium may be _____ or _____

A

-Mechanosensory
-Rotational

89
Q

Cilium can be a site where _______ are secreted from

A

Growth factors

90
Q

Describe the properties of the cilium on the cells of the node:

A

Rotational

91
Q

Nodal cilia have a _______ (for a few hours only)

A

Rotational beat

92
Q

The rotational beat of the nodal cilia generates ______

A

Leftward flow

93
Q

The rotational beat of the nodal cilia generates a leftward flow, resulting in:

A

Asymmetric distribution of morphogens/growth factors

94
Q

Describe what is meant by saying the nodal cilia have a rotational beat:

A

They all rotate in the same direction

95
Q

In nearly all internal organs their are __________, that is an evolutionarily conserved mechanism in vertebrates

A

Reproducible morphological & functional asymmetries

96
Q

In mice, there are _____ genes that affect L-R asymmetry

A

27 genes

97
Q

Explain how the 27 genes in mice affect L-R asymmetry:

A

Cilia function affected; gene expression around node changes

98
Q

The normal arrangement of internal organs:

A

Situs solitus

99
Q

Where all organs are on the complete opposite side of the body; however health is normal

A

Situs inversus

100
Q

Partial situs can be ______

A

Deleterious

101
Q

The process of neural tube formation:

A

Neurulation

102
Q

Neurulation is a key aspect of development for setting up the:

A

Head & neck

103
Q

The neural tube is the precursor to the:

A

Brain & spinal cord

104
Q

During gastrulation, you have mesoderm forming between ectoderm & endoderm and the formation of a _______ along the length of the embryo as a result of nodal signaling

A

Notochord

105
Q

Signals from the notocord lead to the cells in the ectoderm to start to thicken, enlarge, & form a slightly different appearace to the regular ectoderm, this is called:

A

The neural plate

106
Q

As the notochord keeps on signaling, the cells closest to the notochord change shape and that allows for:

A

The neural plate to fold

107
Q

When factors from the mesoderm induce thickening of the overlying ectoderm this results in the:

A

Neural plate

108
Q

Signals from the notochord induce a _____ to help drive folding

A

Hinge point

109
Q

As the neural plate continues to get signals for folding this ultimately results in:

A

Formation of the neural tube

110
Q

The morphological difference of the anterior-most region of the neural tube reflects ________ and thus _______

A

Unique underyling cellular identities; different inductive cues

111
Q

Transcription factor expressed in anterior visceral endoderm that contributes to anterior (head) specification:

A

Lim1 gene

112
Q

The advance maturity of the anterior end of the neural plate leads to:

A

Expansion of the neural plate

113
Q

The expanded portion of the neural plate ultimately gives rise to the:

A

Future brain

114
Q

Describe the directionality of the neural tube closure:

A

Closure of the neural tube proceeds anteriorly & posteriorly from mid-region

(posteriorly over the tail)
(anteriorly over the brain)

115
Q

By the end of week 3 the head & neck region comprises around:

A

Half of the embryo

116
Q

-Anencephaly
-Craniorachischisis
-Open spina bifida
-Closed spina bifida
-Encephalocele
-Iniencephaly

What do all of these have in common?

A

Caused by defects in neural tube closure

117
Q

When a small portion of the neural tube doesn’t close off in the spinal cord region, resulting in exposed spinal fluid and leakage:

A

Open spina bifida

118
Q

Caused by a defect in neural tube closure that results in this common, viable condition:

A

Spina bifida

119
Q

Failure of closure of the neural tube at the ____ end often results in more severe defects like an encephalocele:

A

Anterior end

120
Q

The whole process of head formation that occurs while the neural tube is growing & trying to close off:

A

Cephalization

121
Q

At the very anterior end of the neural tube, the midline region where ectodern & endoderm contact eachother directly with no mesoderm in between:

A

Oropharyngeal membrane

122
Q

The orpharyngeal membrane is important for ______ and provides a hingepoint for folding at the anterior end:

A

facial development

123
Q

The mesoderm that is around the oropharyngeal membrane region forms the:

A

Cardiac tissue

124
Q

The oropharyngeal membrane serves as the ______ during cephalization

A

Hinge point

125
Q

Folding of the whole embryo occurs while ____ occurs

A

Cephalization

126
Q

Folding of the whole embryo while cephalization occurs is cocomitant with the formation of:

A

pharyngeal arches

127
Q

The pharyngeal arches give rise to:

A

The face & neck

128
Q

What other type of specialization occurs along with folding of the whole embryo?

A

Foregut & hindgut specialization

129
Q

The process of neural tube developement gives rise to a unique population of pluripotent stem-like cells called:

A

Neural crest cells

130
Q

The unique population of pluripotent stem-like cells that are created during the process of neural tube development originate at:

A

The CREST of the enclosing neural tube

131
Q

Neural crest cells migrate ____ to populate the _____ side of the embryo

A

Ventro-laterally; ventral

132
Q

Neural crest cells differentiate into:

A

A wide variety of cell types/tissues

133
Q

Neural crest cells are generated by a process of _______ that is analogous to that of generating the third germ layer

A

Epithelial-mesenchymal transformation (EMT)

134
Q

During gastrulation the neural cells go from a ________ phenotype to a ______ phenotype

A

Ectodermal —> Mesenchymal

135
Q

Conversion from an epithelial phenotype to a mesenchymal (highly motile) phenotype:

A

EMT

136
Q

Population of neural crest cells that give rise to craniofacial structures, migrate extensively & drive outgrowth of the primitive tissue masses that will form much of the head & neck:

A

Cranial neural crest cells

137
Q

Cranial neural crest cell migration drives outgrowth of the _____ tissue that will form much of the ____ & ____

A

primitive tissue; head & neck

138
Q

Cranial neural crest cells are unique in:

A

Developmental potential

139
Q

Cranial neural crest cell migration driving outgrowth of primitive tissue can be considered:

A

A second wave of development

140
Q

Major contributor to craniofacial structure and specifically to mineralized tissues of the oral region:

A

Cranial neural crest cells

141
Q

Major derivatives of neural crest cells include:

CNCC-Specific tissue contributions include:

A
  1. Sensory nervous system
  2. Autonomic nervous system
  3. Pigment cells
  4. Endocrine & paracrine cells
  5. Mesectodermal cells including
    -skeleton
    -connective tissue
    -mnuscle
142
Q

CNCC fate is determined:

A

Prior to departure from neural tube

143
Q

CNCC have ______ identities

A

Positional

144
Q

We can see multiple visible constrictions in the neural tube called _____

A

Rhobomeres

145
Q

Describe the multiple visible constrictions seen in the neural tube:

A
  • Rhombomeres 1-8
  • the diencephalon
  • the anterior mesencephalon
146
Q

The multiple visible constrictions seen in the neural tube define distinct populations of _____ and their ______ into early facial tissue

A

CNCC; route of migration

147
Q

What is unique to the cranial neural crest cells of each rhombomere on the neural tube?

A

Their patterns of gene expression

148
Q

The directed CNCC migration can be described as _____ paths of migration, defined by _____

A

Reproducible; mesoderm

149
Q

Clusters of mesoderm:

A

Somites

150
Q

Key takeaway from the process of morphogenesis of the head and neck, is that the process is:

A

HIGHLY coordinated

151
Q

Early molecular patterning that occurs during gastrulation enables later:

A

Coordinated tissue morphogenesis

152
Q

Embryogenesis is a _____ process of development, not a ______ process

A

Generative; descriptive

153
Q

_______ & _______ can result from differences in the generative process of embryogenesis:

A

Malformation & Normal phenotypic variation

154
Q
  • Single changes in gene sequence
  • Combination of ‘normal’ gene variants
  • Changes in the ‘environment’ to which cells respond

These are all differences in the generative process of embryogenesis that can result in:

A
  1. Malformation
  2. Normal phenotypic variation

Human Growth & Development (11 decks)

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