Head and Neck Development Flashcards
______ encode RNA and proteins.
Genes (DNA)
Genes (DNA) encode ____ and ____
RNA and proteins
The complement of _____ and _____ produced defines the identity of each cell–its appearance and how it behaves.
RNA & protein
T/F: 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 adapt to its situation and take on new properties / behaviors.
True
_______ 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 phenotype.
Genes (genome)
_____: tightly adherent and tightly compact
Epithelia
_____: loosely connected; migrating
Mesenchyme
All aspects of the craniofacial complex are defined by what 3 axes?
- Left-right
- Dorsal-ventral
- Anterior-posterior
Clinical treatments always consider what 2 things?
- form
* symmetry
____ axis is apparent by blastocyst stage
Dorsal-ventral axis
cells derived from one of two-cell embryos almost always contribute primarily to _____ tissue
embryonic (ICM) tissue
descendants of the other blastomere are primarily _____ -embryonic
extra-embryonic
Anterior-posterior (A-P) axis [head-tail] and left-right (L-R) axis determined at start of week ___, with appearance of the primitive streak
week 3
Anterior-posterior (A-P) axis [head-tail] and left-right (L-R) axis determined at start of week 3, with appearance of the _____
primitive streak
The ______ appearance definesA-P and L-Raxes
primitive streak
The primitive streak appearance defines ___ and ____ axes
A-P and L-R axes
Furrow of primitive streak progressively elongates along midline•through process of ______
convergent extension
Cells of the _____ migrate through primitive streak to form mesoderm & embryonic (gut) endoderm
epiblast (layer 1)
Cells of the epiblast(layer 1) migrate through primitive streak to form ____ and ________
mesoderm & embryonic (gut) endoderm
The Epiblast layer, through process of epithelial to mesenchyme transformation (EMT), forms _____
mesoderm
The Epiblast layer, through process of _______, forms mesoderm
epithelial to mesenchyme transformation (EMT)
Movement of epiblast (ectoderm) to form ________ –both epithelia
embryonic endoderm
Greater proliferation of ______ which germ layer because it also generates all mesoderm and embryonic endoderm.
epiblast (ectoderm)
______: Anterior-most end (ventral side) of primitive streak is unique in both appearance and function; conserved structure across all vertebrates
Node
_____ is Essential for:
•patterning and induction of embryonic cells (mesoderm and embryonic endoderm)
•establishment of the left-right symmetry
Node
______
•most anterior region of mesoderm
•provides the signals for induction of head structures
prechordal plate
______
•transient epithelial-like rod structure along the midline.
•provides the signals for induction of the neural plate
notochord
The _____ Induces and specifies the fate of the mesoderm as it is formed
node
The _____:
Creation of asymmetry in symmetrical embryo
•First establishes molecular asymmetry
•Conversion into asymmetric organogenesis
node
Nodal cells each have _____ mobile cilium
one motile cilium
A ____ is a membrane covered extension from the cell that has a microtubule cytoskeleton core which helps define the properties of the cilium; can be mechanosensory or rotational
cilium
Nodal cilia have a _______ (for a few hours only)
•generates leftward flow
•thought to result in asymmetric distribution of morphogens
rotational beat
T/F: Asymmetric expression of morphogenetic factors (eg.SHH, BMP4 & FGF8) around Node initiates cascade of gene expression to promote asymmetric specialisation / commitment of mesoderm
True
T/F: Reproducible morphological & functional asymmetries in nearly all internal organs.
True
Is Embryogenesis a generative process or descriptive?
Generative
______ and ______ can result from:
* single changes in gene sequence
* combinations of ‘normal’ gene variants, or
•changes in the cellular ‘environment’ [epigenetic effects]
Malformation and normal phenotypic variation
Factors from the mesoderm induce thickening of overlying ectoderm»_space; ______
neural plate
Signals from notochord induce a _____ point (floor plate) to help drive folding
‘hinge’ point
T/F: The morphological difference of the anterior-most region of the neural tube reflects unique underlying cellular identities and thus different inductive cues (secreted factors)
True
Closure of neural tube proceeds ____ and ____ from mid-region (directions_
anteriorly and posteriorly
By end of week ____, head & neck region comprises ~half of embryo.
3
By end of week 3, head & neck region comprises ~ _____
half of embryo
The ______ membrane serves as the hinge point during cephalization
oropharyngeal
T/F: Folding of whole embryo while cephalization occurs •Concomitant with formation of pharyngeal arches (> face & neck)
•Foregut and hindgut specialization
True
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
Neural crest cells
____ generated by process of epithelial-mesenchymal transformation (EMT)that is analogous to that generating the third germ layer (mesoderm)
NCC
NCC generated by process of _______ that is analogous to that generating the third germ layer (mesoderm)
epithelial-mesenchymal transformation (EMT)
______ migration drives outgrowth of the primitive tissue masses that will form much of the head and neck; Unique in developmental potential (distinct from other neural crest cells)“second wave” of development(vertebrate-specific)> Major contributor to craniofacial structure, and specifically to mineralized tissues of the oral region
CNCC
____ fate determined prior to departure from neural tube
CNCC
