T3 Head and Neck Flashcards
From where does the craniofacial region develop?
prechordal area
What is the dominant part of the future head region?
forebrain
What is the earliest representation of the facial region?
stomodeum
Much of the tissue involved in the formation of the facial area is derived from where?
the neural crest
Early primordia for the facial region are situated around the stomodeum. The frontonasal prominence consists of what?
forebrain neural crest cells and midbrain neural crest cells
Early primordia for the facial region are situated around the stomodeum. The ectodermal nasal placodes form what?
Nasomedial process (from forebrain neural crest) and nasolateral process (from midbrain neural crest).
The maxillary and mandibular processes are filled with what type of cells?
neural crest mesencyme
What is the name for four pairs of lateral endodermal outpockets from the foregut?
pharyngeal pouches
What is the name for the ventral midline endodermal outpocketings from floor of foregut between pharyngeal pouches I and II?
Thyroid diverticulum
What is the name for four pairs of ectodermal inpocketings that lie opposite tot he associated pharyngeal pouches?
pharyngeal grooves
What is the name for five pairs of mesenchymal masses that lie between the pharyngeal pouches and grooves?
Pharyngeal (branchial) arches
What is an aortic arch?
single artery within each pharyngeal arch that connects the ventral aorta to the dorsal aorta
In the neural tube, what is the function of the basic signaling center?
- segmentation of cranial neural tube occurs as a result of Hox gene expression.
- segmentation is carried over into the neural crest cells
What does the neural tube give rise to?
neural crest tissue
In pharyngeal endoderm, patterning is heavily based on what?
exposure to retinoic acid
The first pharyngeal pouch is not dependent on retinoic acid. What IS it dependent on?
Otx2
What pharyngeal pouches are dependent on retinoic acid? how much?
Second pouch, slightly dependent
Third and Fourth pouches, heavily dependent
The pharyngeal endoderm signals the prepatterning of the cranial ectoderm via _____.
FGF8
True/False: Pharyngeal arch patterning is dependent on neural crest.
False
What is the development of the pharyngeal arches dependent on?
signals from pharyngeal pouches
What genes heavily influence dorsoventral patterning in the pharyngeal arches?
DLX genes
Signaling from what center is necessary for the development of the neural crest derivatives involved in lower facial morphogenesis?
cranial ectoderm
Cranial ectoderm is prepatterned by what from where?
by FGF8 from pharyngeal endoderm
Frontonasal ectodermal zone is induced by what from where?
shh from forebrain
What is an ectodermal signaling center involving the establishment of dorsoventral gradient of FGF8 (more dorsal) and shh (more ventral)?
frontonasal ectodermal zone
facial primordia consist of what?
frontonasal prominence, nasomedial processes, and nasolateral processes
Primordia for jaws forms from what number pharyngeal arch?
first
Maxillary processes consists of __________ derived from forebrain and midbrain
neural crest
Mandibular processes consist of neural crest derived from ______ and _______.
midbrain and hindbrain
Subdivision of first arch into upper and lower jaw primordia is dependent on what?
endothelin-1
From where is Meckel’s cartilage derived?
neural crest cells
Around what does the mandible form?
Meckel’s cartilage
What are the derivatives of Meckel’s cartilage?
articular and quadrate
What type of joint is the TMJ?
synovial
Formation of the TMJ involves what transcription factor?
early expression of Barx-1
What comes of the quadrate bone?
moves to middle ear and becomes the incus
What comes of the articular bone?
move to middle ear and becomes the malleus
The stapes is present in lower vertebrates as the only middle ear bone. From where is the stapes derived?
pharyngeal arch II
When does the palate form?
between 6 and 10 weeks of development
What does the palate divide?
the common oronasal cavity into a nasal cavity and an oral cavity. these two cavities remain connected together in the adult as the pharynx (oropharynx and nasopharynx)
What does the median palatine process (unpaired) form?
primary palate = premaxilla
What does the lateral palatine process (paired) form?
secondary palate
What tf nasal placodes require for development
pax6 and retinoid
Where do the nasal placode develop?
they develop from anterolateral edges of neural plate (before closure)
What are nasal pits?
invagination of nasal placodes
What is the source of retinoids that stimulate FGF-8 to stimulate proliferation of mesenchyme in nasomedial and nasolateral processes?
nasal pits
What are nasal pits surrounded by?
nasomedial and nasolateral processes
Where is olfactory epithelium derived?
dorsal epithelium of nasal pits
What TF does olfactory epithelium require?
FGF-8
What does olfactory epithelium form?
bipolar neurons that project to olfactory bulb
What is the dental lamina?
C shaped bands of oral ectoderm overlying neural crest mesenchyme
What is a tooth bud?
epithelial downgrowth overlying neural crest mesenchyme and marking position of a single tooth
What is the cap stage?
Inverted cup-shaped layer of ectoderm capped by stellate reticulum and covering a mass of mesenchyme = the dental papilla
What is the bell stage?
- cone shaped primodium covered by stellate reticulum overlying the enamel organ
- Enamel organ: ameloblasts make up the outermost layer of this two layered covering
- dental papilla: odontoblasts form the outermost layer of the pulpy mass and lie under and adjacent to the layer of ameloblasts.
What is the dental sac?
a condensation of mesenchymal cells around the developing tooth which will form the cementum and periodontal ligament
What does Osr2 do?
inhibit BMP-4. If Osr2 is removed, there will be another row of teeth formed on the lingual side of the normal row
What do salivary glands arise as?
typical epithelial exocrine glands from oral epithelium
What does the development of salivary glands depend on?
interactions between the epithelium and the underlying mesenchyme
Branching pattern of salivary glands depends heavily on what?
shh
For salivary gland development, the signaling between ______ and ______ occurs within the epithelium rather than between the epithelium and mesenchyme as occurs in other types of glandular development.
shh and FGF
