Head & Neck Development Flashcards
Dr. Timothy Cox (154 cards)
1
Q
Morphogenesis of the head and neck is a _____ process, NOT a _____ process
A
Generative; descriptive
2
Q
Encode RNA & proteins:
A
Genes (DNA)
3
Q
The complement of RNA & proteins produced defines the ______; meaning its appearance and how it behaves
A
Identity of each cell
4
Q
Provides the blueprint that ensures we all have a maxilla & mandible & an integrated oronasal cavity:
A
Genes (genome)
5
Q
Gene mutations & differences in non-genetic instructions determines everything about:
A
Phenotype
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
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
8
Q
Outer cell layer
A
Ectoderm
9
Q
Middle cell layer:
A
Mesoderm
10
Q
Inner cell layer:
A
Endoderm
11
Q
The terms ecto-, endo- & mesoderm are related to the:
A
Embryonic origin of cells
12
Q
All aspects of the craniofacial complex are defined by axes: (3)
A
- Left-right
- Dorsal-ventral
- Anterior-posterior
13
Q
Clinical treatments always consider _____ & ____ because the are critical for function & esthetics
A
Form & Symmetry
14
Q
Tooth shape, spacing, number & cusp pattern are all examples of:
A
Form
15
Q
In a clinical aspect, form and symmetry are always considered because:
A
They are critical for function & esthetics
16
Q
Axis that becomes apparent by the blastocyst stage:
A
Dorsal-ventral axis
17
Q
When does the dorsal-ventral axis become apparent?
A
Blastocyst stage
18
Q
At the 4-cell stage of development, what structures do we see?
A
Blastomeres
19
Q
The 32-cell stage in which we still just see a ball of cells:
A
morula
20
Q
Once we reach the 32-cell stage and the morula is formed, the cells start to undergo a process called:
A
Compaction
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
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
23
Q
During the first three weeks of developement, the cells that comprise the inner cell mass will give rise to the _____
A
Embryo
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
25
Following fertilization, the zygote (single cell) undergoes _____ cell divisions to result in a total of _____ cells just prior to implantation
6 cell divisions; 64 cells
26
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?
Left over space to form a cavity
27
Once the morula undergoes compaction to form an ectodermal cell layer, an inner cell mass and a cavity of space, it is now considered:
Blastocyst
28
With the formation of the blastocyst, we can see that everything practically hatches from the _____ as it passes down the fallopian tubes:
Zona pellucida
29
What process occurs following the formation of a blastocyst?
Implantation
30
Once implantation into the uterus occurs, this sets off a series of:
More specialized differentiations
31
After implantation, around the third week of development, the more specialized differentiations lead to:
Specification of the germ layers
32
What are the germ layers that are formed following implantation, around the third week of development?
Ectoderm
Endoderm
Mesoderm
33
The inner cell mass leads to:
Embryonic stem cells
34
Anterior-posterior axis (head-tail) and left-right axis determined at the start of _____ with the appearance of the _____
Week 3; primitive streak
35
Two-layered epithelial disc; the region between where the ectoderm & endoderm contact:
Bilaminar disc
36
The bilaminar disc is location in which the ________ will form from
Embryo proper
37
Ectodermal layer of the bilaminar disc:
Epiblast
38
Endoderm layer of the bilaminar disc:
Hypoblast
39
Layer of the bilaminar disc that will form the entirety of the embryo:
Epiblast
40
One of the first things we will see on the bilaminar disc is a:
Invagination of cells that converge at the midline
41
What happens to the epiblastic cells at the midline of the bilaminar disc?
Converge at midline & ingress
42
Once the epiblastic cells at the midline of the bilaminar disc converge and ingress this marks:
The posterior end
43
When does the primitive streak start to appear?
Around day 15
44
When is the posterior end of the embryo determined?
Around day 15 with the primitive streak formation
45
Invagination of epiblastic cells that marks the posterior end of the embryo, therefore defining the anterior-posterior axis:
Primitive streak
46
Once the primitive streak is forming, defining the anterior-posterior axis, you essentially will have:
A left-right axis
47
Looking down at the embryo at the bilaminar disc, the endoderm forms the ______ while the ectoderm forms the _______
Endoderm= yolk sac
Ectoderm= Amniotic cavity
48
The furrow of the primitive streak progressively elongates along the midline through the process of:
Convergent extension
49
Describe the path direction of formation of the primitive streak:
Starts on posterior end & moves anteriorly
50
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:
Convergent extension
51
The process of convergent extension causes the expansion of the _____ length of the embryo:
Anterior-posterior
52
Convergence may also be called _____
Intercalation
53
Convergence/intercalation results in:
Embryoelongation (extension)
54
Cells of the epiblast (layer 1) migrate through the primitive streak to form _____ & _____
Mesoderm & embryonic (gut) endoderm
55
The start to forming the inner tissue of the embryo occurs through the process:
Gastrulation
56
Formation of the second & third germ layer occur through:
Gastrulation
57
Gastrulation occurs through the process of ________ to form mesoderm:
Epithelial to mesenchyme transformation (EMT)
58
During the process of gastrulation, the movement of epiblast (ectoderm) occurs to form _________ (both epithelia)
Embryonic endoderm
59
Describe the growth of the germ layers:
Disproportionate growth
60
The growth of the germ layers can be described as disproportionate, why is this?
Greater proliferation of the epiblast (ectoderm) because it also generate all the mesoderm & embryonic endoderm
61
As the germ layers are being formed, the generated (proliferating) mesoderm migrates:
Toward anterior (head) end
62
When the mesoderm is being driven forward, it receives information that tells it to start forming structures, this is the key process of:
Head formation
63
The primitive streak ends in an asymmetric bulge called the:
Node
64
The anterior-most end (ventral side) of the primitive streak is unique in both:
Appearance & function
65
The node may also be called the:
Organizer
66
The node (organizer) is a _______ structure across _____
Conserved; all vertebrates
67
Describe what the node is essential for:
1. Patterning & induction of embryonic cells (mesoderm & embryonic endoderm)
2. Establishment of L-R symmetry of organs
68
Factors secreted by cells of the node induce anteriorly migrating mesoderm to form:
1. The prechordal plate
2. The notochord
69
Factors secreted by the cells of the nude induce _________ to form the prechordal plate & the notochord
Anteriorly migrating mesoderm
70
What forms first, the prechordal plate or the notochord?
Prechordal plate
71
Forms from the most anterior region of mesoderm & provides the signals for the induction of head structures:
Prechordal plate
72
The prechordal plate provides:
The signals for the induction of head structures
73
Transient epithelial-like rod structure along the midline that provides the signals for induction of the neural plate:
Notochord
74
Describe the locational relationship between the notochord and prechordal plate:
The notochord is just anterior to the prechordal plate
75
The notochord provides:
The signals for the induction of the neural plate
76
The neural plate is formed from the ______ and ultimately gives rise to the _____
Overlying ectoderm; spinal cord
77
The node induces the _______
Body axis
78
Provides signals to specify the fate of the mesoderm passing by the node:
The node
79
The node is responsible for inducing & specifying the fate of the ____ as its formed
Mesoderm
80
Responsible for the creation of aymmetry in the symmetrical embyro
The node
81
Explain how the node is responsible for the creation of asymmetry in the symmetrical embryo:
First establishes molecular asymmetric which is converted into asymmetric organogenesis
82
Establishing molecular asymmetry occurs the:
Asymmetric expression of morphogenetic factors around the node
83
Give examples of morphogenetic factors are expressed in an asymmetric manner in order to establish molecular asymmetry:
-SHH
-BMP4
-FGF8
84
Asymmetric expression of morphogenetic factors around the node initiates a ______ to promote ______
Cascade of gene expression; asymmetric specialization/commitment of mesoderm
85
The node generates _____
Asymmetry
86
Nodal cells each have:
One motile cilium
87
A membrane covered extension fro the cell that has a microtubule cytoskeleton core which helps define its properties
Cilium
88
The properties of the cilium may be _____ or _____
-Mechanosensory
-Rotational
89
Cilium can be a site where _______ are secreted from
Growth factors
90
Describe the properties of the cilium on the cells of the node:
Rotational
91
Nodal cilia have a _______ (for a few hours only)
Rotational beat
92
The rotational beat of the nodal cilia generates ______
Leftward flow
93
The rotational beat of the nodal cilia generates a leftward flow, resulting in:
Asymmetric distribution of morphogens/growth factors
94
Describe what is meant by saying the nodal cilia have a rotational beat:
They all rotate in the same direction
95
In nearly all internal organs their are __________, that is an evolutionarily conserved mechanism in vertebrates
Reproducible morphological & functional asymmetries
96
In mice, there are _____ genes that affect L-R asymmetry
27 genes
97
Explain how the 27 genes in mice affect L-R asymmetry:
Cilia function affected; gene expression around node changes
98
The normal arrangement of internal organs:
Situs solitus
99
Where all organs are on the complete opposite side of the body; however health is normal
Situs inversus
100
Partial situs can be ______
Deleterious
101
The process of neural tube formation:
Neurulation
102
Neurulation is a key aspect of development for setting up the:
Head & neck
103
The neural tube is the precursor to the:
Brain & spinal cord
104
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
Notochord
105
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:
The neural plate
106
As the notochord keeps on signaling, the cells closest to the notochord change shape and that allows for:
The neural plate to fold
107
When factors from the mesoderm induce thickening of the overlying ectoderm this results in the:
Neural plate
108
Signals from the notochord induce a _____ to help drive folding
Hinge point
109
As the neural plate continues to get signals for folding this ultimately results in:
Formation of the neural tube
110
The morphological difference of the anterior-most region of the neural tube reflects ________ and thus _______
Unique underyling cellular identities; different inductive cues
111
Transcription factor expressed in anterior visceral endoderm that contributes to anterior (head) specification:
Lim1 gene
112
The advance maturity of the anterior end of the neural plate leads to:
Expansion of the neural plate
113
The expanded portion of the neural plate ultimately gives rise to the:
Future brain
114
Describe the directionality of the neural tube closure:
Closure of the neural tube proceeds anteriorly & posteriorly from mid-region
(posteriorly over the tail)
(anteriorly over the brain)
115
By the end of week 3 the head & neck region comprises around:
Half of the embryo
116
-Anencephaly
-Craniorachischisis
-Open spina bifida
-Closed spina bifida
-Encephalocele
-Iniencephaly
What do all of these have in common?
Caused by defects in neural tube closure
117
When a small portion of the neural tube doesn't close off in the spinal cord region, resulting in exposed spinal fluid and leakage:
Open spina bifida
118
Caused by a defect in neural tube closure that results in this common, viable condition:
Spina bifida
119
Failure of closure of the neural tube at the ____ end often results in more severe defects like an encephalocele:
Anterior end
120
The whole process of head formation that occurs while the neural tube is growing & trying to close off:
Cephalization
121
At the very anterior end of the neural tube, the midline region where ectodern & endoderm contact eachother directly with no mesoderm in between:
Oropharyngeal membrane
122
The orpharyngeal membrane is important for ______ and provides a hingepoint for folding at the anterior end:
facial development
123
The mesoderm that is around the oropharyngeal membrane region forms the:
Cardiac tissue
124
The oropharyngeal membrane serves as the ______ during cephalization
Hinge point
125
Folding of the whole embryo occurs while ____ occurs
Cephalization
126
Folding of the whole embryo while cephalization occurs is cocomitant with the formation of:
pharyngeal arches
127
The pharyngeal arches give rise to:
The face & neck
128
What other type of specialization occurs along with folding of the whole embryo?
Foregut & hindgut specialization
129
The process of neural tube developement gives rise to a unique population of pluripotent stem-like cells called:
Neural crest cells
130
The unique population of pluripotent stem-like cells that are created during the process of neural tube development originate at:
The CREST of the enclosing neural tube
131
Neural crest cells migrate ____ to populate the _____ side of the embryo
Ventro-laterally; ventral
132
Neural crest cells differentiate into:
A wide variety of cell types/tissues
133
Neural crest cells are generated by a process of _______ that is analogous to that of generating the third germ layer
Epithelial-mesenchymal transformation (EMT)
134
During gastrulation the neural cells go from a ________ phenotype to a ______ phenotype
Ectodermal ---> Mesenchymal
135
Conversion from an epithelial phenotype to a mesenchymal (highly motile) phenotype:
EMT
136
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:
Cranial neural crest cells
137
Cranial neural crest cell migration drives outgrowth of the _____ tissue that will form much of the ____ & ____
primitive tissue; head & neck
138
Cranial neural crest cells are unique in:
Developmental potential
139
Cranial neural crest cell migration driving outgrowth of primitive tissue can be considered:
A second wave of development
140
Major contributor to craniofacial structure and specifically to mineralized tissues of the oral region:
Cranial neural crest cells
141
Major derivatives of neural crest cells include:
CNCC-Specific tissue contributions include:
1. Sensory nervous system
2. Autonomic nervous system
3. Pigment cells
4. Endocrine & paracrine cells
1. Mesectodermal cells including
-skeleton
-connective tissue
-mnuscle
142
CNCC fate is determined:
Prior to departure from neural tube
143
CNCC have ______ identities
Positional
144
We can see multiple visible constrictions in the neural tube called _____
Rhobomeres
145
Describe the multiple visible constrictions seen in the neural tube:
- Rhombomeres 1-8
- the diencephalon
- the anterior mesencephalon
146
The multiple visible constrictions seen in the neural tube define distinct populations of _____ and their ______ into early facial tissue
CNCC; route of migration
147
What is unique to the cranial neural crest cells of each rhombomere on the neural tube?
Their patterns of gene expression
148
The directed CNCC migration can be described as _____ paths of migration, defined by _____
Reproducible; mesoderm
149
Clusters of mesoderm:
Somites
150
Key takeaway from the process of morphogenesis of the head and neck, is that the process is:
HIGHLY coordinated
151
Early molecular patterning that occurs during gastrulation enables later:
Coordinated tissue morphogenesis
152
Embryogenesis is a _____ process of development, not a ______ process
Generative; descriptive
153
_______ & _______ can result from differences in the generative process of embryogenesis:
Malformation & Normal phenotypic variation
154
- 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:
1. Malformation
2. Normal phenotypic variation
