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Neuro > Embryo Orofacial > Flashcards

Embryo Orofacial Flashcards

1
Q

Intramembraneous vs. Endochondral ossification

A
  1. mesenchyme produces osseous tissue w/o cartilage formation
  2. bone formation occurs in preexisting cartilaginous models
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2
Q

Cartilaginous Neurocranium

A
  • Several cartilages fuse, forming base of cranium (endochondral ossification)
  • Defined order: occipital bone (base) → body of sphenoid → ethmoid bone
  • Temporal bone (petrous & mastoid parts)
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3
Q

Membranous Neurocranium

A

• Head mesenchyme at the sides & top of the brain
• Will form calvaria (frontal & parietal bones) via
intramembraneous ossification
• Interconnected via sutures

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4
Q

Cartilaginous Viscerocranium

A

• NCCs form bones & CT of craniofacial structures
• PA1: malleus & incus
• PA2: stapes, styloid process of temporal bone;
lesser horn of the hyoid
• PA3: greater horns of the hyoid bone.
• PA4: cartilages fuse → laryngeal cartilages
(except epiglottis)

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5
Q

What is the temporal unique?

A

formed from two parts
neuro cranial: petrous & mastoid parts
viscerocranial - styloid process

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6
Q

Membranous Viscerocranium

A
  • Intramembranous ossification w/in maxillary prominence: squamous temporal**, maxillary, & zygomatic bones
  • Cells of mandibular prominence form the mandible
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7
Q

Craniosynostosis

A
  • Premature fusion of cranial sutures, often associated with other skeletal defects
  • Cause is unclear
  • More common in boys
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8
Q

Scaphocephaly

A

premature closure of sagittal suture → cranium becomes long, narrow, & wedge shaped
• Accounts for 50% of cases

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9
Q

Brachycephaly

A

premature closure of the coronal suture → a high, tower-like cranium
• Accounts for 30% of cases

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10
Q

Plagiocephaly

A

premature closure of the coronal suture on one side → cranium is twisted & asymmetric

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11
Q

Trigoncephaly

A

premature closure of the frontal (metopic) suture

• Deformities of frontal & orbital bones in addition to other anomalies

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12
Q

What does the facial development depend on?

A

inductive interactions of forebrain, frontonasal region, and developing eye

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13
Q

When do the five facial primordia appear? and where?

A

4th week - prominences around stomodeum

  • Maxillary prominences (2)
  • Mandibular prominences (2)
  • Frontonasal prominence (1)

maxillary and mandibular fuse at front

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14
Q

What separates the facial primordial from the primordial pharynx?

A

bilaminar membrane, oropharyngeal membrane

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15
Q

When does facial development occur? where are the growth factors?

A
  • week 4-8

- mesenchyme

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16
Q

What forms from the frontonasal prominence?

A
  • Frontal portion will form the forehead
  • Nasal portion forms rostral boundary of stomodeum & nose
  • NCC from fore brain & midbrain
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17
Q

What are the first parts of the face to form?

A

lower jaw and lower lip
• Oropharyngeal membrane disintegrates
• Extension & fusion of mandibular prominences toward/at the
midline

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18
Q

When/where doe the nasal placodes form? what are they?

A
  • week 4
  • inferolateral parts of FNP
  • Bilateral oval thickenings of the surface ectoderm that are primordia of the nasal epithelium
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19
Q

What fuses first: maxillary or mandibular?

A

mandibular

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20
Q

What do NP’s edges form?

A
  • medial and lateral nasal prominences as the placode invaginate
  • leaves the nasal pits of the placodes, which form the nostrils and nasal cavities
  • lateral nasal prominences form the alae (sides) of the nose
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21
Q

What does the nasolacrimal groove separate?

A

Lateral nasal prominence from maxillary prominence

*by end of 6th week though they merge at the nasolacrimal groove

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22
Q

When does the medial nasal prominences merge with the maxillary and lateral nasal prominences?

A

b/t weeks 7-10

*results in the continuity of the upper jaw and lip, and separation of nasal pits form the stomodeum

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23
Q

How do we get the inter maxillary segment?

A

Medial nasal prominences form it when they merge

  • Forms deep portion of philtrum of upper lip
  • Premaxillary part of maxilla
  • Primary palate
24
Q

Where does most of the upper lip, maxilla, and secondary palate come from?

A

maxillary prominences

*will merge laterally with mandibular prominences

25
Q

How do we get primordial nasal sacs? what separates it from the oral cavity?

A
  1. expansion of MNP and LNP mesenchyme causes nasal pits to deepen
  2. oronasal membrane (ruptures end of 6 week connecting cavities - why you can water come out of your nose)
26
Q

When does palatogenesis begin?

A

6th week (done by 12)

critical period: 6-9

27
Q

What is included in palatogenesis?

A

Merging of the MNP forms the median palatine process (primary palate)
• Wedge-shaped mass of mesenchyme
• Between the maxillary prominences
• Forms premaxillary part of the maxilla

28
Q

How do we get the second palate?

A
  • early 6th week from lateral palatine processs (palatine shelves)
  • mesenchymal projections project inferomedially on each side of tongue
  • as the jaw elongates it pulls tongue away from its root and moves inferiorly in the mouth
  • processes assume horizon position above tongue in weeks 7-8
29
Q

What does the primary palate contribute to? secondary?

A
  1. hard

2. soft and hard

30
Q

If the tongue doesn’t get out of the way what happens?

A

palatel shelves can’t merge

31
Q

How do we get the hard plate? soft palate?

A
  1. bone extends from maxillae and palatine bones into lateral palatine processes
  2. posterior portions don’t ossify –> extend posteriorly and fuse –> form soft palate and uvula
32
Q

Cleft lip

A

• Often clefting of the nose and/or maxilla
• Maxillary prominence(s) & median nasal
prominence(s)

33
Q

Cleft Palate

A

clefts of secondary palate to incisive fossa
• May involve uvula and/or hard & soft palates
• Lateral palatine processes w/nasal septum
• Lateral palatine processes w/medial palatine process

34
Q

What is the basic reason for cleft?

A

primordia don’t fuse properly

35
Q

How do we get the nasal septum?

A
  • Down growth from internal parts of merged medial nasal prominences
  • Fusion of nasal septum & palatine processes begins anteriorly (9th week) & is completed posteriorly (12th week)
36
Q

What is the first indication of tongue development?

A
  • Median lingual swelling appears end of 4th week

- triangular elevation in floor of primordial pharynx

37
Q

What grows on the sides of the medial lingual swelling?

A
  • lateral lingual swellings (distal tongue buds)

- rapidly proliferate, merge, and overgrow median swelling

38
Q

Where do tongue buds come from?

A

proliferation of mesenchyme in venttomedal parts of PA1

39
Q

What forms the oral part of tongue (ant 2/3)? posterior 1/3?

A
  1. merged lateral lingual swellings
  2. hypo pharyngeal eminence overgrows copula

*where they fuse is terminal sulcus; where circumvalle papilla taste buds form

40
Q

How do we form the pharyngeal part of the tongue?

A

• Ventromedial parts of PA2 fuse, forming the copula
• Ventromedial parts of PA3 & PA4 develop the
hypopharyngeal eminence

41
Q

Where does the muscle of the tongue come from?

A

myoblasts of occipital metopes (XII to innervate)

NOT NC

42
Q

Glossoschissis

A

bifid tongue

*lateral lingual swellings don’t fuse completely

43
Q

Ankyloglossia

A

tongue tied; connection b/t floor of mouth and tongue is too long, and limits tongue movements

44
Q

Macroglossia

A

tongue is too big for mouth

45
Q

Odontogenesis

A

development of teeth

*Teeth develop from reciprocal inductions between neural crest– induced mesenchyme & overlying oral epithelium (ectoderm)

46
Q

What are dental laminae? tooth buds?

A
  1. U-shaped bands of oral epithelium that follow the curves of the primitive jaw
  2. form in each dental laminae during “bud stage”

*anterior mandibular –> anteriorly maxillary –> posteriorly (6th week)

47
Q

Cap Stage

A
  • Tooth bud is invested by mesenchyme & becomes ‘cap shaped’
  • Consists of the enamel organ, dental papilla, & dental sac
48
Q

Enamel organ

A

ectodermal cells from dental lamina → produces enamel
• Outer cell layer = outer enamel epithelium (OEE)
• Inner cell layer lining the papilla = inner enamel epithelium (IEE)
• Stellate reticulum

49
Q

Dental Papilla

A

internal part of each tooth (mesenchyme)→ forms dentin & pulp

50
Q

Dental Follicle/sac

A

mesenchyme surrounding dental papilla & enamel organ → forms the PDL &
cementum (anchors tooth in jaw)

51
Q

Bell Stage

A
  • Differentiation of enamel organ results in a bell shape
  • Dental papilla cells adjacent to IEE form odontoblasts
    Produce predentin → calcifies & become dentin
    • Inner enamel epithelium → differentiates into ameloblasts in response to dentin production → produce enamel
    • Enamel & dentin formation begins at the cusps & progresses toward the future root
52
Q

What is the epithelial root sheath?

A 
• Fusion of IEE & OEE
• Grows into mesenchyme &
initiates root formation
• Odontoblasts produce root
dentin
53
Q

What forms the pulp of the tooth? inner cells of the dental sac? outer cells of the dental sac?

A
  1. central dental papilla
  2. Cementoblasts (they product cementum around roots)
  3. PDL (collagen ligament that anchors tooth to bone)
54
Q

Tooth Eruption

A

Emergence of the tooth from the dental follicle in the jaw & its functional position in the mouth
•Root of the tooth grows & crown gradually erupts through oral epithelium
Mandibular teeth usually erupt before maxillary teeth Gingiva: part of the oral mucosa around the erupted crown
As a permanent tooth grows, the deciduous root is resorbed by osteoclasts (odontoclasts)
• Only crown and uppermost part of the root are shed Permanent teeth usually begin to erupt at 6yrs

55
Q

Permanent Tooth Development

A
  • Permanent dentition consists of 32 teeth • Stages are similar to deciduous teeth
  • Deciduous permanent teeth appear at ~10 weeks
  • Extensions of the dental lamina, lingual to deciduous tooth buds
  • Nondeciduous molars develop as buds from posterior extensions of the dental laminae
  • Tooth buds for permanent teeth appear at different times
  • Mostly during the fetal period
  • Buds for 2nd/3rd permanent molars develop after birth

Neuro (10 decks)

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