Head & Neck Development- Cox Flashcards
Morphogenesis of the head and neck is a ____ process, not a ____ process
generative; descriptive
___ encode RNA and Proteins
Genes (DNA)
The complement of RNA & Protein produced defines the ____; meaning its appearance and how it behaves
identity of each cell
provides the blueprint that ensures we have a maxilla and mandible and an integrated oronasal cavity:
genes (genome)
gene mutations and diffrences in non-genetic instructions determines everything about our:
phenotype
Cells that are tightly compact and tightly bound together, often found in sheets within the body and have a very distinct sort of shape; not very mobile
epithelia
Cells that are loosely connected, surrounded by many types of ECM so they can move around in the body because they are not attached to anything; they can receive and move towards signals
mesenchyme
Outer cell layer:
ectoderm
Middle cell layer:
mesoderm
Inner cell layer:
endoderm
The terms ecto, endo and mesoderm are related to:
the embryonic origin of cells
All aspects of the craniofacial complex are defined by axes including:
Left-right
Dorsal-ventral
Anterior-posterior
Clinical treatments always consider:
form & symmetry
Clinical treatments always consider form and symmetry because they are:
critical for function and esthetics
Tooth shape, spacing, number, and cusp pattern are all examples of:
form
Name the lineage of cells prior to implantation:
- zygote
- 2-cell stage
- 4-cell stage
- 8-cell stage
- morula
- blastocyst
- late-hatched blastocyst
Cells that make up the outer coating during the blastocyst stage:
zona pellucida
Where the cells within the zona pellucida undergo some sort of specialization to get the formation into an ectodermal layer
compaction
By week 3 of development (carneigie stage 7-9) the mass of cells now has:
ectoderm, mesoderm, & endoderm
The dorsal-ventral (DV) axis is apparent by the ____ stage
blastocyst
During the first 3 weeks of development, the cells in the inner cell mass give rise to the ____ itself and may be referred to as ___.
embryo; embryonic stem cells
The AP and LR axis are determined at the start of week ___, with the appearance of the ____.
3; primitive streak
By week 3 of development, the ectoderm contains the ___, while the endoderm contains the ___.
epiblast (forms embryo); hypoblast
By week 3 of development, ____ cells converge at the midline and ingress (which marks the ___ end)
ectodermal epiblastic cells; posterior end of embryo
The appearance of a primitive streak defines the ____ axis which ultimately defines the ___ axis.
A-P; L-R
The ____ is a furrow that progressively elongates along the midline:
primitive streak
The primitive streak progressively elongates along the midline through a process of:
convergent extension
Early appearance of a primitive streak starts ___ and moves ___ along the midline through convergent extension
posteriorly; anteriorly
During the formation of the 2nd and 3rd germ layer, cells of the ____ migrate through the primitive streak to form ___ & ___
epiblast (layer 1); mesoderm & embryonic (gut) endoderm
During formation of the 2nd an 3rd germ layers, cells of the epiblast (layer 1) _____ to form mesoderm & embryonic (gut) endoderm
migrate through primitive streak
Formation of 2nd and 3rd germ layers occurs through a process called:
gastrulation
Gastrulation occurs through a process of _____ to form ____.
epithelial to mesenchyme transformation (EMT) ; mesoderm
Gastrulation (formation of 2nd and 3rd germ layers) involves the movement of epiblast (ectoderm) to form _____- both epthelia
embryonic endoderm
Describe the growth of the germ layers:
disproprortionate
There is greater proliferation of ____ because it also generates all ___ and ____
epiblast (ectoderm); mesoderm & embryonic endoderm
During proliferation of germ layers, the generated (proliferating) mesoderm migrates toward ___ end
anterior (head)
The key head-forming events is when ___ is being driven forward
mesoderm
An asymmetric bulge at the end of the primitive streak:
the node
Located at the anterior-most end (ventral side) of primitive streak that is unique in both appearance and function:
the node
The ___ (or organizer) is a conserved structure across all vertebrates
Node
The Node is essential for:
- patterning and induction of embryonic cells (mesoderm and embryonic endoderm)
- establishment of the left-right symmetry
Essential for patterning and induction of embryonic cells (mesoderm and embryonic endoderm) as well as the establishment of left-right symmetry and all the internal organs of the body:
The node
Factors secreted by cells of the node induce anteriorly migrating mesoderm to form:
the prechordal plate & then the notochord
Factors secreted by cells of the node induce ___ to form the prechordal plate & notochord
anteriorly migrating mesoderm
- forms from the most anterior region of mesoderm
- provides the signals for induction of head structures
prechordal plate
- transient epithelial-like rod structures along the midline
- provides the signals for induction of the neural plate
notochord
The prechordal plate forms from the most anterior region of ___.
mesoderm
The prechordal plate provides signals for ___ of ___.
induction of head structures
The notochord is a ___ epithelial-like rod structure along the midline
transient
The notochord provides signals for ___ of ___ from the overlying ectoderm (ultimately giving rise to the spinal cord)
induction of neural plate
The node induces the:
body axis
The node induces and specifies the fate of the ___ as it is formed
mesoderm
The node is responsible for creation of ____ in the ___.
asymmetry in the symmetrical embryo
The node first establishes ____, and then conversion into ___.
molecular asymmetry; asymmetric organogenesis
during the process of establishing molecular asymmetry, there is asymmetric expression of ____ around the node
morphogenic factors
The asymmetric expression of morphogenic factors (such as SHH, BMP4 & FGF8) around the node initiates a cascade of gene expression to promote:
asymmetric specialization/ commitment of mesoderm
Nodal cells each have:
one motile cilia
a membrane covered extension from the cell that has a microtubule cytoskeleton core which helps define the properties of it:
cilium
Cilium can be:
mechanosensory or rotational
Nodal cilia have a ___ beat (for a few hours only)
rotational
The nodal cilia have a rotational beat (for a few hours only) that generate a ____, resulting in asymmetric distribution of morphogens/growth factors
leftward flow
Reproducible morphological & functional asymmetries in nearly all:
internal organs
Organ asymmetry is an evolutionarily ____ in vertebrates
conserved mechanism
In mice, ~ ____ genes affect L-R asymmetry and these genes affect the function of ___.
27; cilia
Normal range of internal organs:
situs solitus
Where all organs are on the complete opposite side of the body, 1-8500: 1-10k individuals experience this and results in NORMAL health
situs inversus
____ can be deleterious such as ___ & ___
partial situs; right & left isomerism
Neural tube formation:
neurulation
The neural tube is the precursor to:
brain & spinal cord
During neurulation, factors from the ___ induce the thickening of the overlying ___.
mesoderm; ectoderm
During neurulation, factors from the mesoderm induce the thickening of the overlying ectoderm leading to the:
neural plate
During neurulation, signals from the ___ induce a “hinge” point (floor plate) to help drive folding
notochord
During neurulation, ___ patterning of ___ begins
D-V patterning of neurons
The morphological difference of the anterior-most region of the neural tube reflects ___ and thus ___
unique underlying cellular identities; different inductive cues
The 3 components that are really defining segments of the future brain that produce different cues (secreted factors)
- notochord
- pre-chordal plate
- anterior visceral endoderm
____ ( transcription factor) is expressed in anterior visceral endoderm and is involved in anterior specification
LIM1 gene
The advanced maturity of the anterior end of the neural tube leads to an ______ and eventually a future brain
expanded neural plate
Closure of the neural tube proceeds ___ and ____ from the mid-region
anteriorly & posteriorly
By the end of week 3, head and neck regions comprise:
nearly half of the embryo
List the disease resulting from defects in neural tube closure towards the posterior end:
- open spina bifida
- closed spina bifida
List the disease resulting from defects in neural tube closure towards the middle/ middle anterior portion:
- craniorachischisis
- encephalocele
List the disease resulting from defects in neural tube closure towards the anterior end:
- anencephaly
- iniencephaly
Head formation =
cephalization
The ____ serves as the hinge point during cephalization
oropharyngeal membrane
At the very anterior end there is a midline region where the ectoderm and endoderm contact each other directly where there is no mesoderm between:
oropharyngeal membrane
folding of the hole embryo occurs while:
cephalization occurs
____ is concomitant with formation of pharyngeal arches (face & neck)
embryonic folding
During embryonic folding ___ & ___ specialization occurs
foregut & hindgut
A unique population of (pluripotent), stem-like cells originating at the “crest” of the enclosing neural tube:
neural crest cells
Where do neural crest cells originate?
At the “crest” of the enclosing neural tube
Neural crest cells migrate ___ to populate the ___ side of the embryo
Ventro-laterally; ventral
Neural crest cells differentiate into a:
wide variety of cell types/tissues
NCC are generated by a process of ___
Epithelial-mesenchymal transformation
NCC are generated by a process of EMT that is analogous to the generation of the:
third germ layer (mesoderm)
Drives the outgrowth of the primitive tissue masses that will form much of the head and neck:
Cranial neural crest cell (CNCC) migration
Describe the potential of cranial neural crest cells (CNCC):
unique in developmental potential (distinct from other neural crest cells)
CNCC can be referred to as a “____” and is vertebrate specific
second wave of development
Major contributor to craniofacial structure, and specifically to mineralized tissues of the oral region
CNCC
- sensory nervous system
- autonomic nervous system
- pigment cells
- endocrine & paraendocrine cells
These are all major derivatives of:
neural crest
- mesectodermal cells
- skeleton
- connective tissue
- muscle
These are all:
CNCC- specific tissue contributions
CNCC fate is determined:
prior to departure from neural tube
CNCC fate is determined prior to departure from the neural tube meaning they have:
positional identities
There are multiple visible constrictions in the neural tube including:
- rhombomeres 1-8
- the diencephalon
- the anterior mesencephalon
Define distinct populations of CNCC and their route of migration into early facial tissue:
The multiple visible constrictions in the neural tube
directed CNCC migration involves ___ paths of migration
reproducible
The directed CNCC migration that involve reproducible paths of migration are defined by:
mesoderm
Pharyngeal arches ___ are populated by NC cells from rhombomeres ___ respectively
1,2,3 & 2,4,6
If r2 cells are transplanted into r4 position, migration still occurs through ___ but cells differentiate into structures characteristic of ___.
arch 2; arch 1
Early molecular patterning established during ___ enables later ___.
gastrulation; coordinated tissue morphogenesis
Embryogenesis is a ____ process (Not ___)
generative; descriptive
____ & ____ can result from:
- single changes in gene sequence
- combinations of normal gene variants
- changes in the environment to which cells respond
malformation & normal phenotypic variation
