Development Of The Head And Neck Flashcards Preview

Embryology Exam III > Development Of The Head And Neck > Flashcards

Flashcards in Development Of The Head And Neck Deck (43)
Loading 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 __________.



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)


Describe the mammalian temporomandibular joint.

-synovial joint with an articular disc

-formations involves early expression of Barx-1

-articular surfaces are the temporal bone and the mandibular condyle

-quadrate bone moves into middle ear -> incus

-articular bone moves into middle ear -> malleus


How do the palate form?

-forms between 6-10 weeks and divides the common oronasal cavity into a nasal and oral cavity

-two cavities remain connected in the adult as the pharynx


What is the primordia for the palate?

-median palatine process -> forms primary palate, premaxilla

-lateral palatine processes (paired) -> secondary palate


What is the primordia for the nose?

-nasal placode

-nasal pits

-olfactory epithelium


What is required for the development of the nasal placodes? Where does it develop from?

-requires Pax-6 and retinoids

-develop from anterolateral edges of neural plate (before closure)


Explain where the nasal pits come from and how they develop.

-invaginations of nasal placodes

-surrounded by nasomedial and nasolateral processes
+nasomedial processes form tip and crest of nose + septum
+nasolateral processes form nasal alae

-source of retinoids that stimulate FGF-8 to stimulate proliferation of mesenchyme in nasomedial and nasolateral processes

-deepen to form cavities that eventually become continuous with oral cavity via choanae

-medial areas of nasal capsule gives rise to nasal septum and ethmoid bones

-lateral wall of nasal capsule forms nasal conchae