Development Of The Head And Neck Flashcards
The dominant part of the future head region is what?
-the forebrain
The earliest representation of the facial region is what?
-the stomodeum
Much of the tissue involved in the formation of the facial area is derived from where?
Neural crest
What is the frontonasal prominence?
-consists of forebrain neural crest cells and midbrain neural crest cells
What will the ectoderm all nasal placodes form?
-will form nasomedial (from forebrain neural crest) and nasolateral (from midbrain neural crest) processes
Maxillary and mandibular processes filled with ________ ________ __________.
-neural crest mesenchyme
What are the components of the pharyngeal region?
- pharyngeal pouches
- thyroid diverculum
- pharyngeal grooves
- pharyngeal/brachial arches
- aortic arches
What composes the pharyngeal pouches?
-four pairs of lateral endodermal out pockets from the foregut
What composes thyroid diverticulum?
-ventral midline endodermal outpocketings from floor of foregut between pharyngeal pouches I and II
What composes the pharyngeal grooves?
-four pairs of ectodermal inpocketings that lie opposite. To the associated pharyngeal pouches
What composes the pharyngeal/brachial arches?
-five pairs of mesenchymal masses that lie between the pharyngeal pouches and grooves
What composes the aortic arches?
-single artery within each pharyngeal arch that connects the ventral aorta to the dorsal aorta
What are some derivatives of pharyngeal tissues?
- pharyngeal arch derived musculature -> mesoderm from somitomeres
- rest of pharyngeal arch mesenchyme (especially ventral) -> from neural crest
What is the basic signaling center in craniofacial development?
- neural tube and paraxial mesoderm
- segmentation of cranial neural tube occurs as a result of Hox gene expression
- segmentation is carried over onto the neural crest cells
- gives rise to neural crest tissue
What is the role of pharyngeal endoderm in craniofacial development?
- patterning is heavily based on exposure to RA
- first pouch is not dependent on RA but is dependent on Otx2
- second pouch is somewhat dependent on RA
- pouches 3 and 4 are heavily dependent on RA
- pharyngeal arch patterning is not dependent on neural crest
- signals the pre patterning of the cranial ectoderm via FGF-8
The craniofacial region develops mostly from where?
Prechordal area
How do pharyngeal arches signal for craniofacial development?
- depends on signals from pharyngeal pouches
- not depend on neural crest
- Dlx genes heavily influence dorsoventral patterning
- Arch 1 ectoderm uses Edn-1 to signal migrating neural crest cells and influences development of arch 1
What does cranial ectoderm do for craniofacial development?
- signaling from this center is necessary for the development of neural crest derivatives involved in lower face morphogenesis
- ectoderm is pre patterned by FGF-8 signals from pharyngeal endoderm
What does the frontonasal ectodermal zone do?
-induced by Shh from forebrain
-is an ectodermal signal center involving establishment of a dorsoventral gradient of FGF-8 (dorsal) and Shh (ventral)
+involved in shaping tip of snout
What is the facial primordia?
- frontonasal prominence
- nasomedial processes
- nasolateral processes
What is the primordia for the jaws? Where are they derived from?
- maxillary processes -> neural crest derived from forebrain and midbrain
- mandibular processes -> neural crest from midbrain and hindbrain
- Meckel’s cartilage -> neural crest
Subdivisions of first arch into upper and lower jaw primordia is dependent on __________.
Endothelin-1
Describe Meckel’s cartilage.
- slender, elongated cartilaginous rod that develops within the first arch
- the mandible forms around this cartilage
- derivatives include articular and quadrate
Describe the non mammalian temporomandibular joint.
-articulation occurs between quadrate bone (upper) and articular bone (lower)
