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Growth and Development > Head & Neck Development > Flashcards

Head & Neck Development Flashcards

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
Q

The Node induces the

A

body axis

26
Q

The Node induces the body axis
> Induce and specify the
fate of the —- as
it is formed

A

mesoderm

27
Q

Creation of asymmetry in symmetrical embryo (2)

A
  • First establishes molecular asymmetry

* Conversion into asymmetric organogenesis

28
Q

Establishing Molecular Asymmetry

A 
Asymmetric expression of 
morphogenetic factors (eg. SHH, 
BMP4 & FGF8) around Node
> initiates cascade of gene expression 
to promote asymmetric specialisation / 
commitment of mesoderm
29
Q

Nodal cells each have one

A

motile cilium

30
Q

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)

A
  • mechanosensory, or

* rotational

31
Q

Nodal cilia have a rotational beat (for a few hours only)

•generates leftward flow, resulting in

A

asymmetric distribution of

morphogens / growth factors

32
Q

Reproducible morphological & functional asymmetries in

nearly all

A

internal organs.

|&raquo_space; Evolutionarily conserved mechanism in vertebrates

33
Q

In mice, ~– genes affect L-R asymmetry

A

27

|&raquo_space; cilia function affected; gene expression around Node changes

34
Q

Organ asymmetry
1 in — people with situs inversus (normal health)
> cf. partial situs which can be deleterious

A

8500-10000

35
Q

Factors from the mesoderm
induce thickening of overlying
ectoderm&raquo_space;

A

neural plate

36
Q 
Neurulation [Neural Tube Formation] 
precursor to (2)
A

brain

spinal cord

37
Q

Signals from notochord induce a
‘hinge’ point (floor plate) to help
drive —

A

folding

38
Q

The morphological difference of the anterior-most region of

the neural tube reflects

A

unique underlying cellular identities

and thus different inductive cues (secreted factors)

39
Q

Advanced maturity of anterior end > expanded neural plate

|&raquo_space;

A

future brain

40
Q

Closure of neural tube

proceeds

A

anteriorly
and posteriorly from
mid-region

41
Q

By end of week —, head & neck
region comprises ~half of
embryo.

A

3

42
Q

The — membrane serves as the hinge point during cephalization

A

oropharyngeal

43
Q

Embryonic Folding

A

Folding of whole embryo while

cephalization occurs

44
Q 
Folding of whole embryo while 
cephalization occurs  (2)
A

•Concomitant with formation of
pharyngeal arches (> face & neck)
•Foregut and hindgut specialization

45
Q

Neural Crest Cells

A

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
Q

NCC generated by

A

process of epithelial-mesenchymal
transformation (EMT) that is analogous to that generating the
third germ layer (mesoderm)

47
Q

CNCC migration drives outgrowth of the primitive tissue

masses that will form much of the

A

head and neck

48
Q

Cranial Neural Crest Cells
Unique in — potential (distinct from other
neural crest cells)

A

developmental

49
Q

Major contributor to craniofacial structure, and

specifically to

A

mineralized tissues of the oral region

50
Q

Rhombomeres & Cranial Patterning

A

CNCC fate determined prior to departure from neural tube

> ie. they have “positional identities”

51
Q

Multiple visible constrictions in neural tube (2)

A

•rhombomeres 1 - 8, the diencephalon and anterior mesencephalon
•define distinct populations of CNCC and their route of migration
into early facial tissue.

52
Q

Reproducible paths of migration

> defined by —

A

mesoderm

53
Q 
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,
A

migration still occurs through arch 2
- but cells differentiate into structures
characteristic of arch 1!

54
Q

Early molecular patterning (est. during gastrulation)

enables later coordinated tissue —.

A

morphogenesis

55
Q

Embryogenesis is a ‘—’ process

not descriptive

A

generative

56
Q

Malformation and normal phenotypic variation can result

from: (3)

A
  • single changes in gene sequence
  • combinations of ‘normal’ gene variants, or
  • changes in the ‘environment’ to which cells respond

Growth and Development (15 decks)

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