Lecture 13: Development of Orofacial Structures Flashcards
What does the viscerocranium become?
What is its embryological origin?
Facial skeleton
Mesenchyme
What does the neurocranium become?
What is its embryological origin?
Bones that enclose the brain
Mesenchyme
What bones form from the cartilagenous neurocranium?
- Occipital Bone
- Body of Sphenoid Bone
- Ethmoid Bone
- Petrous and mastoid parts of Temporal Bone
What bones arise from the membranous neurocranium?
Frontal and Parietal Bones
What bone initially begins as part of the viscerocranium and then migrates to become part of neurocranium?
Squamous Temporal bone
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?
Scaphocephaly
Sagittal suture
Male infant that has a high, tower-like head may have what disorder? From premature closure of what suture?
Brachycephaly
Coronal suture
An infant presenting with a twisted, asymmetric head may have what disorder? Due to premature closure of what suture?
Plagiocephaly
Coronal suture
A premature closure of the frontal (metopic) suture may result in what disorder? What bones does this affect?
Trigonocephaly
Frontal and Orbital bones
What is the facial primordia?
What makes up the facial primordia?
Tissue that surrounds stromodeum (primitive mouth)
- 2 Maxillary Prominences
- 2 Mandibular Prominences
- 1 Frontonasal Prominence
What separates the the facial primordia from the priomordial pharynx?
Oropharyngeal Membane
NOTE: wouldn’t be able to make O shape with mouth if membrane doesn’t go away/
In what weeks does facial development occur?
Weeks 4-8
What does the frontonasal prominence give rise to?
Fontal portion - Forehead
Nasal portion - rostral boundary of stomodeum and nose
What forms the maxillary (MXP) & mandibular (MDP) prominences
Splitting of PA1
What does the maxillary prominence form when PA1 splits?
Lateral boundaries of stomodeum
What does the Mandibular prominences form when PA1 splits
Caudual boundary of stomodeum
How does the mandibular prominece fold?
What can incomplete fusion result in?
- Oropharyngeal membrane disintegrates
- Medial ends of both prominences merge
Incomplete fusion can lead to chin dimple
What does the maxillary prominences give rise to?
Upper Lip
Maxilla
Secondary Palate
What are the first parts of the face to form
Lower jaw and lower lips
At the end of the 4th week, what forms on the inferolateral parts of the frontal nasal prominence?
Nasal placodes
What do the edges of the nasal placodes proliferate into.
What is in the middle?
- Medial nasal prominences (MNP)
Lateral nasal prominences (LNP) - forms alae (sides) of nose
- Nasal Pit
What seapartes lateral nasal prominence from maxillary prominence?
When do they fuse?
Nasolacrimal Groove
Fuses by Week 6
What gives rise to the intermaxillary segment?
What does it consist of?
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)
What pharyngeal arch do the muscles of facial expression come from?
What do they invade into?
2nd Pharyngeal Arch
Invade primordial lips and cheeks to give facial expression muscles
What is the direct embryonic origin of the philtrum?
Fusion of Median Nasal Prominence
What pharyngeal arch do the muscles of mastication arise from?
1st Pharyngeal Arch
How do nasal cavities form?
Nasal placodes –> nasal pits –> primordial nasal sacs
Another name for the primary and secondary palates
Primary palate - Median palatine process (comes from fusion of median nasal prominence)
Secondary palate - Lateral palatine process (comes from maxillary prominence which is lateral)
What is the critical period for palatogenesis?
End of 6th week —> beginning of 9th week
What part of the palate does the intermaxillary segment give rise to?
Primary palate
Fusion of median nasal prominences
What is the embryonic origin of the secondary palate?
Lateral palatine processes (shelves) from the maxillary prominences
What is the incsive fossa a remnant of?
Nasopalatine Canal
What embryonic structures failed to fuse in cleft lip?
Maxillary prominences and median nasal prominences
What structures failed to fuse in a cleft palate?
Lateral palatine process w/ nasal septum and/or medial palatine process
How does the nasal septum form?
- Downward growth of merged medial nasal prominences
- Fuses with lateral palatine processes (from maxillary)
How does the anterior ⅔ of the tongue form?
What induces the development?
- Median lingual swelling appears first
- Two lateral lingual swellings develop on either side
Induced by mesenchyme from Pharyngeal Arch 1
What are the contributions of Pharngyeal Arches 2,3, and 4 to form the posterior ⅓ of the tongue?
- 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
What embryological structures do tongue muscles arise from?
Myoblasts of occipital myotomes
NOT NEURAL CREST CELLS
What is glossoschissis?
Bifid tongue (abnormal fusion of lateral lingual swellings)
What is ankyloglossia?
Short Frenulum
- Attachment between tongue and floor of oral cavity is too short and anchors tongue down, limiting movement
- Problems with breastfeeding and speaking
What is macroglossia?
What is it asscoiated with?
Large Tongue
Associated with Beckwith-Wiedemann and Down Syndrome
What is Microglossia
Abnormally small tongue (rare)
