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

Development Of The Head And Neck Flashcards

1
Q

The dominant part of the future head region is what?

A

-the forebrain

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2
Q

The earliest representation of the facial region is what?

A

-the stomodeum

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3
Q

Much of the tissue involved in the formation of the facial area is derived from where?

A

Neural crest

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4
Q

What is the frontonasal prominence?

A

-consists of forebrain neural crest cells and midbrain neural crest cells

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5
Q

What will the ectoderm all nasal placodes form?

A

-will form nasomedial (from forebrain neural crest) and nasolateral (from midbrain neural crest) processes

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6
Q

Maxillary and mandibular processes filled with ________ ________ __________.

A

-neural crest mesenchyme

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7
Q

What are the components of the pharyngeal region?

A
  • pharyngeal pouches
  • thyroid diverculum
  • pharyngeal grooves
  • pharyngeal/brachial arches
  • aortic arches
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8
Q

What composes the pharyngeal pouches?

A

-four pairs of lateral endodermal out pockets from the foregut

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9
Q

What composes thyroid diverticulum?

A

-ventral midline endodermal outpocketings from floor of foregut between pharyngeal pouches I and II

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10
Q

What composes the pharyngeal grooves?

A

-four pairs of ectodermal inpocketings that lie opposite. To the associated pharyngeal pouches

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11
Q

What composes the pharyngeal/brachial arches?

A

-five pairs of mesenchymal masses that lie between the pharyngeal pouches and grooves

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12
Q

What composes the aortic arches?

A

-single artery within each pharyngeal arch that connects the ventral aorta to the dorsal aorta

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13
Q

What are some derivatives of pharyngeal tissues?

A
  • pharyngeal arch derived musculature -> mesoderm from somitomeres
  • rest of pharyngeal arch mesenchyme (especially ventral) -> from neural crest
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14
Q

What is the basic signaling center in craniofacial development?

A
  • 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
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15
Q

What is the role of pharyngeal endoderm in craniofacial development?

A
  • 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
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16
Q

The craniofacial region develops mostly from where?

A

Prechordal area

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17
Q

How do pharyngeal arches signal for craniofacial development?

A
  • 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
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18
Q

What does cranial ectoderm do for craniofacial development?

A
  • 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
19
Q

What does the frontonasal ectodermal zone do?

A

-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

20
Q

What is the facial primordia?

A
  • frontonasal prominence
  • nasomedial processes
  • nasolateral processes
21
Q

What is the primordia for the jaws? Where are they derived from?

A
  • maxillary processes -> neural crest derived from forebrain and midbrain
  • mandibular processes -> neural crest from midbrain and hindbrain
  • Meckel’s cartilage -> neural crest
22
Q

Subdivisions of first arch into upper and lower jaw primordia is dependent on __________.

A

Endothelin-1

23
Q

Describe Meckel’s cartilage.

A
  • slender, elongated cartilaginous rod that develops within the first arch
  • the mandible forms around this cartilage
  • derivatives include articular and quadrate
24
Q

Describe the non mammalian temporomandibular joint.

A

-articulation occurs between quadrate bone (upper) and articular bone (lower)

25
Q

Describe the mammalian temporomandibular joint.

A
  • 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
26
Q

How do the palate form?

A
  • 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
27
Q

What is the primordia for the palate?

A
  • median palatine process -> forms primary palate, premaxilla
  • lateral palatine processes (paired) -> secondary palate
28
Q

What is the primordia for the nose?

A
  • nasal placode
  • nasal pits
  • olfactory epithelium
29
Q

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

A
  • requires Pax-6 and retinoids

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

30
Q

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

A

-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
31
Q

What do the olfactory epithelium form? What does it develop from and what is required for it to develop?

A
  • forms bipolar neurons that project to olfactory bulb
  • gives rise to cells that migrate to hypothalamus and synthesize LHRF
  • derived from dorsal epithelium of nasal pits and requires FGF-8
32
Q

What are the stages of tooth development?

A
  • dental lamina
  • tooth bud
  • cap stage

-bell stage
+enamel organ -> ameloblasts
+dental papilla -> odontoblasts

-dental sac

33
Q

Dental lamina stage

A

-C shaped bands of oral ectoderm overlying neural crest mesenchyme

34
Q

Tooth bud stage

A

-epithelial downgrowth overlying neural crest mesenchyme and marking position of a single tooth

35
Q

Cap stage

A

-inverted cup shaped layer of ectoderm (ameloblasts layer) capped by stellate reticulum and covering a mass of mesenchyme -> dental papilla

36
Q

Bell stage

A

-cone shaped primordium covered by stellate reticulum overlying the enamel organ

37
Q

What is the enamel organ?

A

-ameloblasts make up the outermost layer of the two layered covering

38
Q

What is the dental papilla?

A

-odontoblasts form the outermost layer of this pulpy mass and lie under and adjacent to the layer of ameloblasts

39
Q

Dental sac

A

-a condensation of mesenchymal cells around the developing tooth which will form the cementum and periodontal ligament

40
Q

What is necessary for development of the tooth past the bud stage?

A

Pax-9

41
Q

What forms non-tooth forming spaces?

A

BMP-4 inhibits FGF-8, creating non tooth forming spaces

42
Q

How do the salivary glands form?

A
  • arise as typical epithelial exocrine glands from the oral epithelium
  • development depends on interactions between the epithelium and the underlying mesenchyme
43
Q

What does the patterning of the salivary glands depend on?

A
  • Shh
  • signaling between Shh and FGF occurs within the epithelium rather than between the epithelium and mesenchyme as occurs in other types of glandular development

Embryology Exam III (9 decks)

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