Head & Neck Development Flashcards

(56 cards)

1
Q

Genes (DNA) encode (2)

A

RNA and proteins.

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2
Q

The complement of RNA & protein produced defines the

A

identity of each cell – its appearance and how it behaves.

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3
Q

Cells receive and process information from their surroundings – (6)

A

extracellular matrix, secreted molecules (growth factors) from other cells, hormones, contact with other cells (tension), nutrients, oxygen levels, etc.

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4
Q

Cells receive and process information from their surroundings – extracellular matrix, secreted molecules (growth factors) from other cells, hormones, contact with other cells (tension), nutrients, oxygen levels, etc.
•These in turn modify the genes expressed, thus allowing the cell to

A

adapt to its situation and take on new properties / behaviors

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5
Q

Genes (genome) provide the blueprint that ensures we all have a maxilla and mandible and an integrated oronasal cavity, etc. But gene mutation and differences in these non-genetic ‘instructions’ determines everything about our —.

A

phenotype

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6
Q

All aspects of the craniofacial complex are defined by

axes: (3)

A
  • Left-right
  • Dorsal-ventral
  • Anterior-posterior
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7
Q

Clinical treatments always consider: (2)

A
  • form (eg. tooth shape, spacing, number, cusp pattern), and

* symmetry because they are critical for function and esthetics.

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8
Q

Dorsal-ventral axis

•apparent by — stage

A

blastocyst

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9
Q

Is the D-V axis established as a consequence of cavitation and
formation of inner cell mass (ICM) or is it determined earlier?

A
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10
Q

Anterior-posterior (A-P) axis [head-tail] and left-
right (L-R) axis determined at start of week 3, with
appearance of the

A

primitive streak

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11
Q

Epiblastic cells converge at midline and ingress

marks — end

A

posterior

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12
Q
The Primitive Streak
Appearance defines (2) axes
A

A-P and L-R

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13
Q

Furrow progressively elongates along midline

•through process of

A

convergent extension

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14
Q

Cells of the epiblast (layer 1) migrate through primitive

streak to form (2)

A

mesoderm & embryonic (gut) endoderm

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15
Q
•through process of 
epithelial to 
mesenchyme 
transformation (EMT) 
to form ---
A

mesoderm

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16
Q

Movement of
epiblast (ectoderm)
to form —- – both
epithelia

A

embryonic

endoderm

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17
Q

Disproportionate — of the germ layers

A

growth

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18
Q

Greater proliferation of
epiblast (ectoderm) because it
also generates all (2)

A

mesoderm

and embryonic endoderm.

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19
Q

Anterior-most end (ventral side) of primitive streak is

unique in both

A

appearance and function

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20
Q

The — (or Organizer) is a
conserved structure across all
vertebrates

A

Node

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21
Q

the node is essential for (2)

A

•patterning and induction of embryonic cells
(mesoderm and embryonic endoderm)
•establishment of the left-right symmetry

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22
Q

Factors secreted by cells of the Node induce

anteriorly migrating mesoderm to form: (2)

A
  • the prechordal plate

* the notochord

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23
Q

the prechordal plate (2)

A
  • most anterior region of mesoderm

* provides the signals for induction of head structures

24
Q

the notochord (2)

A
  • transient epithelial-like rod structure along the midline.

* provides the signals for induction of the neural plate

25
The Node induces the
body axis
26
The Node induces the body axis > Induce and specify the fate of the ---- as it is formed
mesoderm
27
Creation of asymmetry in symmetrical embryo (2)
* First establishes molecular asymmetry | * Conversion into asymmetric organogenesis
28
Establishing Molecular Asymmetry
``` Asymmetric expression of morphogenetic factors (eg. SHH, BMP4 & FGF8) around Node > initiates cascade of gene expression to promote asymmetric specialisation / commitment of mesoderm ```
29
Nodal cells each have one
motile cilium
30
A cilium is a membrane covered extension from the cell that has a microtubule cytoskeleton core which helps define the properties of the cilium: (2)
* mechanosensory, or | * rotational
31
Nodal cilia have a rotational beat (for a few hours only) | •generates leftward flow, resulting in
asymmetric distribution of | morphogens / growth factors
32
Reproducible morphological & functional asymmetries in | nearly all
internal organs. | >> Evolutionarily conserved mechanism in vertebrates
33
In mice, ~-- genes affect L-R asymmetry
27 | >> cilia function affected; gene expression around Node changes
34
Organ asymmetry 1 in --- people with situs inversus (normal health) > cf. partial situs which can be deleterious
8500-10000
35
Factors from the mesoderm induce thickening of overlying ectoderm >>
neural plate
36
``` Neurulation [Neural Tube Formation] precursor to (2) ```
brain | spinal cord
37
Signals from notochord induce a ‘hinge’ point (floor plate) to help drive ---
folding
38
The morphological difference of the anterior-most region of | the neural tube reflects
unique underlying cellular identities | and thus different inductive cues (secreted factors)
39
Advanced maturity of anterior end > expanded neural plate | >>
future brain
40
Closure of neural tube | proceeds
anteriorly and posteriorly from mid-region
41
By end of week ---, head & neck region comprises ~half of embryo.
3
42
The --- membrane serves as the hinge point during cephalization
oropharyngeal
43
Embryonic Folding
Folding of whole embryo while | cephalization occurs
44
``` Folding of whole embryo while cephalization occurs (2) ```
•Concomitant with formation of pharyngeal arches (> face & neck) •Foregut and hindgut specialization
45
Neural Crest Cells
a unique population of (pluripotent) stem-like cells originating at the ‘crest’ of the enclosing neural tube. •Migrate ‘ventro-laterally’ to populate the ventral side of the embryo •Differentiate into a wide variety of cell types / tissues
46
NCC generated by
process of epithelial-mesenchymal transformation (EMT) that is analogous to that generating the third germ layer (mesoderm)
47
CNCC migration drives outgrowth of the primitive tissue | masses that will form much of the
head and neck
48
Cranial Neural Crest Cells Unique in --- potential (distinct from other neural crest cells)
developmental
49
Major contributor to craniofacial structure, and | specifically to
mineralized tissues of the oral region
50
Rhombomeres & Cranial Patterning
CNCC fate determined prior to departure from neural tube | > ie. they have “positional identities”
51
Multiple visible constrictions in neural tube (2)
•rhombomeres 1 - 8, the diencephalon and anterior mesencephalon •define distinct populations of CNCC and their route of migration into early facial tissue.
52
Reproducible paths of migration | > defined by ---
mesoderm
53
``` Directed CNCC Migration experiment: Pharyngeal arches 1, 2 & 3 are populated by NC cells from rhombomeres 2, 4 & 6, respectively. >> If r2 cells transplanted to r4 position, ```
migration still occurs through arch 2 - but cells differentiate into structures characteristic of arch 1!
54
Early molecular patterning (est. during gastrulation) | enables later coordinated tissue ---.
morphogenesis
55
Embryogenesis is a ‘---’ process | not descriptive
generative
56
Malformation and normal phenotypic variation can result | from: (3)
* single changes in gene sequence * combinations of ‘normal’ gene variants, or * changes in the ‘environment’ to which cells respond