Embryogenesis of the Face and Oral Cavity

Question 1

List basic mechanisms of facial organ formation

Answer 1

• Epithelia-to-mesenchymal transition (EMT)

- Arborization

Question 2

Describe Arborization

Answer 2

• Glandular organs branch out (like tree)

- E.g. liver, lungs, and salivary glands

Question 3

Describe ‘epithelia-to-mesenchymal transition (EMT)’

Answer 3

• Epithelial cells lose polarity and cell-cell adhesion and gain migratory and invasive properties
• Essential for forming:
  1) Mesoderm
  2) Neural crest cells
  3) Palate and lip fusion

Question 4

Oral cavity is formed from?

Answer 4

• Frontonasal prominence
• 1st pharyngeal arches
• 2nd pharyngeal arches

Question 5

____ and ____ are part of 1st pharyngeal arch

Answer 5

Maxillary and mandibular processes

Question 6

Nose is formed from?

Answer 6

Formed from:

• Medial nasal process
• Lateral nasal process

Opening between in nostril

Question 7

Describe development of upper lip

Answer 7

• 4-8 weeks

- Formed from: medial nasal process (fuse), lateral nasal process, and maxillary prominence

Question 8

How does cleft lip form?

Answer 8

• Cleft of upper lip: failure to fuse of three prominences on one side
• Midline cleft: failure for medial nasal prominence to fuse
• Male > Female (more males have this than female)
• 1:700 children (this is rate of occurrence)

Question 9

Describe development of palate

Answer 9

• 6-9 weeks
• Formed from: Medial nasal process, maxillary prominence
• Primary palate = fusion of medial nasal prominence at anterior palate (Forms maxillary incisors)
• Secondary palate = fusion of lateral palatine shelves (maxillary process)
• Cleft palate: Females have more than men (opposite cleft lip), 1 in 700 children get this

Question 10

Describe development of maxilla

Answer 10

• 6-7 weeks
• Ossifications starts in maxillary process of 1st arch
• Intramembranous ossification
• Ossification spreads to palatine process

Question 11

Describe Mandible development

Answer 11

• 6-7 weeks
• Meckel’s cartilage = cartilage template for mandible; degrades to form inferior alveolar canal: does NOT contribute to ossification of mandible, some remains as sphenomandibular ligament, rest degrades
• Mandibular process (1st arch) mesoderm cells condensate at mental foramen
• Intramembranous ossification starts at mental foramen and spreads around cartialge
• Condylar cartilage: develops as independent secondary cartilage, very separated from mandible body, fuses with ramus later in development
• Mandible forms as 4 separate segments that fuse

Question 12

Describe Tongue development

Answer 12

• 4-7 weeks
• Formed from: 1st arch = anterior tongue, 2nd and 3rd arch = posterior tongue, 4th arch = epiglottis
• Sulcus terminalis = fusion of 1st and 2nd arch of tongue
• Foramen caecum = thyroid gland origin

Question 13

Describe salivary glands

Answer 13

• Formed from: Parotid gland = ectoderm (4-6 week), submandibular and sublingual and endoderm (6-8 weeks)
• Glandular masses produce arborization inward