Lecture 13: Development of Orofacial Structures

Question 1

What does the viscerocranium become?

What is its embryological origin?

Answer 1

Facial skeleton

Mesenchyme

Question 2

What does the neurocranium become?

What is its embryological origin?

Answer 2

Bones that enclose the brain

Mesenchyme

Question 3

What bones form from the cartilagenous neurocranium?

Answer 3

1. Occipital Bone
2. Body of Sphenoid Bone
3. Ethmoid Bone
4. Petrous and mastoid parts of Temporal Bone

Question 4

What bones arise from the membranous neurocranium?

Answer 4

Frontal and Parietal Bones

Question 5

What bone initially begins as part of the viscerocranium and then migrates to become part of neurocranium?

Answer 5

Frontal Bone

Question 6

Male newborn patient presents with a long, narrow, wedge-shaped head.

What is the most likely diagnosis? This most likely results from premature closure of what suture?

Answer 6

Scaphocephaly

Sagittal suture

Question 7

Male infant that has a high, tower-like head may have what disorder? From premature closure of what suture?

Answer 7

Brachycephaly

Coronal suture

Question 8

An infant presenting with a twisted, asymmetric head may have what disorder? Due to premature closure of what suture?

Answer 8

Plagiocephaly

Coronal suture

Question 9

A premature closure of the frontal (metopic) suture may result in what disorder? What bones does this affect?

Answer 9

Trigonocephaly

Frontal and Orbital bones

Question 10

What is the facial primordia?

What makes up the facial primordia?

Answer 10

Tissue that surrounds stromodeum (primitive mouth)

• 2 Maxillary Prominences
• 2 Mandibular Prominences
• 1 Frontonasal Prominence

Question 11

What separates the the facial primordia from the pharyngeal pharynx?

Answer 11

Oropharyngeal Membane

Question 12

In what weeks does facial development occur?

Answer 12

Weeks 4-8

Question 13

How does the mandibular prominece fold?

What can incomplete fusion result in?

Answer 13

1. Oropharyngeal membrane disintegrates
2. Medial ends of both prominences merge

Incomplete fusion can lead to chin dimple

Question 14

What does the maxillary prominences give rise to?

Answer 14

Upper Lip

Maxilla

Secondary Palate

Question 15

What pharyngeal arch do the muscles of facial expression come from?

What do they invade into?

Answer 15

2^nd Pharyngeal Arch

Invade primordial lips and cheeks to give facial expression muscles

Question 16

What does the frontonasal prominence give rise to?

Answer 16

Forehead

Caudal boundary of stomodeum and nose

Question 17

At the end of the 4th week, what forms on the inferolateral parts of the frontal nasal prominence?

Answer 17

Nasal placodes

Question 18

What is the direct embryonic origin of the philtrum?

Answer 18

Fusion of Median Nasal Prominence

Question 19

What seapartes lateral nasal prominence from maxillary prominence?

When do they fuse?

Answer 19

Nasolacrimal Groove

Fuses by Week 6

Question 20

How does the auricle develop?

Answer 20

Six hillocks surround Pharyngeal Arch 1 and is pushed from the neck to side of the head when the mandible develops

Question 21

What pharyngeal arch do the muscles of mastication arise from?

Answer 21

1^st Pharyngeal Arch

Question 22

What is the critical period for palatogenesis?

Answer 22

Weeks 6-9 (finishes development at 12)

Question 23

What gives rise to the intermaxillary segment?

Answer 23

Medial Nasal Prominence

Question 24

What part of the palate does the intermaxillary segment give rise to?

Answer 24

Primary palate

Question 25

What is the embryonic origin of the secondary palate?

Answer 25

Lateral palatine processes (shelves) from the maxillary prominences

Question 26

How do nasal cavities form?

Answer 26

1. Nasal Placodes (thickened ectoderm) depress and form nasal pits (eventual nostrils) 2. Primitve oronasal membrane is formed and disintegrates giving nasal sacs

Question 28

What embryonic structures failed to fuse in cleft lip?

Answer 28

Maxillary prominences and median nasal prominences

Question 29

What structures failed to fuse in a cleft palate?

Answer 29

Lateral palatine process w/ nasal septum and/or medial palatine process

Question 30

When is the period of development of the nasal septum?

Answer 30

Weeks 9-12

Question 31

Merged lateral lingual swellings form what part of the tongue?

Answer 31

Anterior 2/3

Question 32

What pharyngeal arch does the anterior tongue arise from?

Answer 32

1^st Pharyngeal Arch

Question 33

What are the contributions of PAs 2,3, and 4 to form the posterior 1/3 of the tongue?

Answer 33

PA2 (ventromedial) - Copula PA 3/4 (ventromedial) - hypopharyngeal eminence Hypopharyngeal eminence overgrows copula to form posterior 1/3 of tongue

Question 34

What embryological structures do tongue muscles arise from?

Answer 34

Myoblasts of occipital myotomes NOT NCC

Question 35

What is glossoschissis?

Answer 35

Bifid tongue (abnormal fusion of lateral lingual swellings)

Question 36

What is ankyloglossia?

Answer 36

Attachment between tongue and floor of oral cavity is too long and anchors tongue down, limiting movement

Question 37

What is the order of tooth bud formation? In what week?

Answer 37

Anterior mandibular =\> anterior maxillary =\> posterior Week 6

Question 38

What cells produce dentin?

Answer 38

Odontoblasts from dental papilla cells

Question 39

What cells produce enamel?

Answer 39

Ameloblasts from inner enamel epithelium

Question 40

What stage of odontogenesis are inner enamel and outer enamel epithelium formed?

Answer 40

Cap stage

Question 41

What stage of odontogenesis are dentin and enamel formed?

Answer 41

Bell stage

Question 42

What forms from fusino of the IEE and OEE?

Answer 42

Epithelial root sheath =\> dental root/dental sac

Question 43

What forms the collagen ligament that anchors tooth to bone?

Answer 43

Outer cells of the dental sac

Question 44

What cells are responsible for degenerating roots of baby teeth to make room for permanent teeth?

Answer 44

Osteoclasts