head and neck development Flashcards
emergence of the 3 body axes=
all aspects of the craniofacial complex are defined by these
D-V
A-P
L-R
____encode RNA and proteins
genes (DNA)
___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)
these are terms related to the embryonic origin of cells
ectoderm
mesoderm
endoderm
epithelia vs. meshenchyme
clinic treatments always consider ___ and ____ because they are critical for function and esthetics
form (tooth shape, spacing number, etc) and symmetry
in the first 3 weeks, these cells give rise to the embryo itself
inner cell mass
this axis is apparent by the blastocyst stage
dorsal-ventral
the A-P axis (head-tail) and L-R axis determined at the start of week 3 with appearance of the
primitive streak
(this is after implantation)
where the embryo proper is going to form from
bilaminar disc AKA epiblast
this forms when epiblast cells start to move towards each other and since they have no where to go, they start to invaginate and go inward
primitive streak
epiblastic cells converge at midline and ingree which marks the
posterior end
the primitive streak furrow progressively elongates along midline through the process of
convergent extension
convergent extension
cells start to push together and extends post and ant then starts to move inward
starts at posterior end
(think about hands interlocking)
the cells of the epiblast (layer 1 aka ectoderm) migrate through primitive streak to form
mesoderm and embryonic gut (endoderm)
what is the process to form mesoderm during gastrulation?
epithelial to mesenchyme transformation (EMT)
what is there a greater proliferation of because it also generates all mesoderm and embryonic endoderm
ectoderm (epiblast)
this is a conserved anterior/ventral structure across all verterbraes and important in forming head structures and rest of body
the node
what is the node essential for
patterning and induction of embryonic cells (mesoderm and embryonic endoderm)
and
establishment of the L-R symmetry
factors secreted by cells of the node induce anteriorly migrating mesoderm to form:
the prechordal plate and notochord
what is the most anterior region of mesoderm
prechordal plate
what does the prechordal plate do
provides signals for induction of head structures
what is transient epithelial like rod structure along the midline
notochord
what does the notochord do
provides signals for induction of neural plate(gives rise to spinal chord and brain structures)
this induces and specify the fate of the mesoderm as it is formed
the node
creates asymmetry in symmetrical embryo
the node
nodal cells each have one ______which is a membrane covered extension from the cell that has a microtubule cytoskeleton core which helps define MECHANOSENSORY AND ROTATIONAL
one motile cilium
nodal cilia have rotational beat that generates leftward flow resulting in
asymmetric distribution of morphogens/growth factors
neural tube formation:
neurulation
what is the precursor to brain and spinal cord
neurulation
during neurulation, factors from the mesoderm induce thickening of overlying ectoderm creating
neural plate
during neurulation, signals from notochord induce a ___ point(floor plate) to help drive folding
hinge point
the morphological difference of the anterior- most region of the neural tube reflects unique underlying cellular identities and thus
different inductive cues (secreted factors)
advanced maturity of anterior end-> expanded neural plate ->
future brain
by the end of week 3, what regions are comprised
head and neck
this membrane serves as the hinge point for folding during cephalization
oropharyngeal membrane
embryonic folding:
folding of whole embryo while cephalization occurs
-concomitant with formation of pharyngeal arches (>face and neck)
-foregut and hindgut specialization
these are a unique population of stem-like cells originating at the ‘crest’ of the enclosing neural tube
neural crest cells
how do neural crest cells migrate
migrate ventro-laterally to populate the ventral side of the embryo
neural crest cells generated by process of ______ that is analogous(similar) to that generating the third germ layer (mesoderm)
EMT- epithelial-mesenchymal transformation (EMT)
kinda like gastrulation
cranial neural crest cells migration drives outgrowth of the primitive tissue masses that will form much of the:
“second wave” of development
head and neck
these are the major contributor to craniofacial structure, and specifically to mineralized tissues of the oral region
cranial neural crest cells
what cells fate are determined prior to departure from neural tube aka they have “positional identities”
CNCC
define distinct populations of CNCC and their route of migration into early facial tissue
rhombomeres 1-8, the diencephalon and anterior mesencephalon
CNCC migration are reproducible paths of migration that are defined by
mesoderm
embryogenesis is a ____process (not descriptive)
gernative
malformation and normal phenotypic variation can result from
single changes in gene seq
combinations of “normal” gene variants
changes in the environment to which cells respond
