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

Squamous Temporal 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 priomordial pharynx?

Answer 11

Oropharyngeal Membane

NOTE: wouldn’t be able to make O shape with mouth if membrane doesn’t go away/

Question 12

In what weeks does facial development occur?

Answer 12

Weeks 4-8

Question 13

What does the frontonasal prominence give rise to?

Answer 13

Fontal portion - Forehead

Nasal portion - rostral boundary of stomodeum and nose

Question 14

What forms the maxillary (MXP) & mandibular (MDP) prominences

Answer 14

Splitting of PA1

Question 15

What does the maxillary prominence form when PA1 splits?

Answer 15

Lateral boundaries of stomodeum

Question 16

What does the Mandibular prominences form when PA1 splits

Answer 16

Caudual boundary of stomodeum

Question 17

How does the mandibular prominece fold?

What can incomplete fusion result in?

Answer 17

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

Incomplete fusion can lead to chin dimple

Question 18

What does the maxillary prominences give rise to?

Answer 18

Upper Lip

Maxilla

Secondary Palate

Question 19

What are the first parts of the face to form

Answer 19

Lower jaw and lower lips

Question 20

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

Answer 20

Nasal placodes

Question 21

What do the edges of the nasal placodes proliferate into.

What is in the middle?

Answer 21

1. Medial nasal prominences (MNP)

Lateral nasal prominences (LNP) - forms alae (sides) of nose

2. Nasal Pit

Question 22

What seapartes lateral nasal prominence from maxillary prominence?

When do they fuse?

Answer 22

Nasolacrimal Groove

Fuses by Week 6

Question 23

What gives rise to the intermaxillary segment?

What does it consist of?

Answer 23

Fusion of Medial Nasal Prominence

Premaxillary part of maxilla, primary palate (median palatine process), core of philtrum of upper lip

(but surface of lip is from maxillary prominence)

Question 24

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

What do they invade into?

Answer 24

2^nd Pharyngeal Arch

Invade primordial lips and cheeks to give facial expression muscles

Question 25

What is the direct embryonic origin of the philtrum?

Answer 25

Fusion of Median Nasal Prominence

Question 26

What pharyngeal arch do the muscles of mastication arise from?

Answer 26

1^st Pharyngeal Arch

Question 27

How do nasal cavities form?

Answer 27

Nasal placodes --\> nasal pits --\> primordial nasal sacs

Question 28

Another name for the primary and secondary palates

Answer 28

Primary palate - Median palatine process (comes from fusion of median nasal prominence) Secondary palate - Lateral palatine process (comes from maxillary prominence which is lateral)

Question 29

What is the critical period for palatogenesis?

Answer 29

End of 6th week ---\> beginning of 9th week

Question 30

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

Answer 30

Primary palate ## Footnote *Fusion of median nasal prominences*

Question 31

What is the embryonic origin of the secondary palate?

Answer 31

Lateral palatine processes (shelves) from the maxillary prominences

Question 32

What is the incsive fossa a remnant of?

Answer 32

Nasopalatine Canal

Question 33

What embryonic structures failed to fuse in cleft lip?

Answer 33

Maxillary prominences and median nasal prominences

Question 34

What structures failed to fuse in a cleft palate?

Answer 34

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

Question 35

How does the nasal septum form?

Answer 35

1. Downward growth of merged medial nasal prominences 2. Fuses with lateral palatine processes (*from maxillary*)

Question 36

How does the anterior ⅔ of the tongue form? What induces the development?

Answer 36

1. Median lingual swelling appears first 2. Two lateral lingual swellings develop on either side ## Footnote *Induced by mesenchyme from Pharyngeal Arch 1*

Question 37

What are the contributions of Pharngyeal Arches 2,3, and 4 to form the posterior ⅓ of the tongue?

Answer 37

* Ventromedial parts of Pharngyeal Arch 2: _Copula_ * Ventromedial parts of Pharngyeal Arch 3 and 4: _Hypopharyngeal Eminence_ Hypopharyngeal eminence overgrows copula to form posterior ⅓ of tongue

Question 38

What embryological structures do tongue muscles arise from?

Answer 38

Myoblasts of occipital myotomes NOT NEURAL CREST CELLS

Question 39

What is glossoschissis?

Answer 39

Bifid tongue (abnormal fusion of lateral lingual swellings)

Question 40

What is ankyloglossia?

Answer 40

Short Frenulum * Attachment between tongue and floor of oral cavity is too short and anchors tongue down, limiting movement * Problems with breastfeeding and speaking

Question 41

What is macroglossia? What is it asscoiated with?

Answer 41

Large Tongue Associated with Beckwith-Wiedemann and Down Syndrome

Question 42

What is Microglossia

Answer 42

Abnormally small tongue (rare)