Head & Neck Development Flashcards
- These encode RNA and proteins
Genes
- What defines the identity of each cell?
a. Complement of RNA and protein produced
- Ectoderm =
Outer
- Mesoderm =
Middle
- Endoderm =
Inner
- Clinical treatments always consider what?
a. Form
b. Symmetry
- The dorsal-ventral axis is apparent by what stage?
a. Blastocyst stage
- During what weeks is the dorsal-ventral axis apparent?
a. First 3 weeks
- When does implantation occur?
a. Prior to the formation of 3 germ layers
- The A-P axis and L-R axis are determined when?
a. Start of week 3 with the appearance of the primitive streak
- The A-P axis and L-R axis are determined at the start of week 3 with the appearance of what?
a. Primitive streak (NOT NODE)
- The primitive streak furrows progressively elongate along the midline through the process of what?
a. Convergent extension
- How does the 2nd and 3rd germ layer form?
a. Cells of the epiblast migrate through the primitive streak to form mesoderm and embryonic endoderm
- Is the primitive streak formed by the mesoderm?
No
- What processes form the mesoderm? (think about what this is analogous to)
epithelial mesenchyme transformation (EMT)
- Do you have proportional or disproportionate growth of the germ layers?
a. Disproportionate
- Why do you have disproportionate growth of germ layers?
a. Epiblast (ectoderm) is greater because it forms the mesoderm and endoderm
- This is a conserved structure across all vertebrates
The node
- This is the anterior-most end of the primitive streak
Node
- The node is essential for establishing what?
a. L-R symmetry
b. Patterning and induction of embryonic cells
- Factors secreted by cells of the Node induce anteriorly migrating mesoderm to form what?
a. Prechordal plate
b. Notochord
- What germ layer forms the prechorcal plate and notochord?
Mesoderm
- This is the most anterior region of the mesoderm
Prechordal plate
- This provides signals for the induction of head structures
Prechordal plate
- This is a transient epithelial-like rode structure along the midline
Notochord
- This provides signals for the induction of the neural plate
Notochord
- This induces and specifies the fate of the mesoderm as it is formed
Node
- How do you create asymmetry in a symmetrical embryo?
a. Establish molecular symmetry
b. Conversion into asymmetric organogenesis
- Nodal cells each have how many cilia?
1 motile cilium
- A cilium is a membrane that helps define what property of the cilium?
a. Mechanosensory
b. Rotational
- Nodal cilia have a _______ beat
Rotational beat
- What helps create asymmetry because of an asymmetric distribution of morphogens?
Nodal cilia
- Reproducible morphological and functional asymmetries are in nearly __________
All internal organs
- This is the precursor (process) to the brain and spinal cord
Neurulation
- Factors from the mesoderm induce the thickening of overlying ectoderm to form what?
a. Neural plate
- Signals from the notochord induce a hinge point that helps drive
Folding
- Describe the process of neural tube closure
a. Advanced maturity of anterior end → expanded neural plate → Future brain
- How does neural tube closure proceed?
a. Closes anterior and posterior from the mid-region
- By the end of week 3, the head and neck comprise _______ of the embryo
1/2
- A defect in neural tube closure causes
Spina bifida
- Cephalization =
a. Head formation
- What serves as a hinge point during cephalization?
a. Oropharyngeal membrane
- What 2 things are very important for the formation of the head?
a. Prechordal plate
b. Oropharyngeal membrane
- Foregut and hindgut specialization occur when?
a. Folding of the entire embryo during cephalization
- This is a population of “pluripotent”, stemlike cells that originate at the crest of the enclosing neural tube
a. Neural crest cells
- How do NCC cells migrate?
a. Ventro-laterally
- NCCs are generated by what process? This is also analogous to what?
a. EMT
b. Formation of 3rd germ layer (mesoderm)
- This migrates outgrowth of the primitive tissue masses that will form much of the head and neck
CNCC
- This is a major contributor to craniofacial structures and to mineralized tissues of the oral region
CNCC
- (T/F) CNCCs fate is NOT determined prior to departure from the neural tube
a. False, is determined
- CNCC migration pathway is reproducible? (what is this defined by)
a. Yes
b. Mesoderm
- Is embryogenesis a “generative” process?
No
- How can malformations and normal phenotypic variation result?
a. Single changes in gene sequence
b. Combinations of normal gene variants
c. Changes in the environment to which cells respond
