Development Of Orofacial Structures Flashcards
What drives the shape and rate of growth of the head?
Brain development
What are the 5 facial primordia?
2 maxillary prominences
2 mandibular Prominences
1 frontonasal Prominences
When does the facial primordia develop?
Week 4
What does the facial primordia surround?
Stomodeum (primitive oral cavity)
How are the facial primordia separated from the primordial pharynx?
When did it rupture?
Oropharyngeal membrane
Ruptured day 26
What is the first part of the face to form and how?
Mandibular prominence (lower jaw and lip)
Oropharyngeal membrane will disintegrate
—> medial ends of mandibular prominence merge
What causes a chin dimple?
Incomplete fusion of the medial ends of the mandibular prominence
What signaling molecule is response for development of both mandibular processes?
BMP
What does the maxillary prominence make?
Upper lip, maxilla, secondary palate
How does the maxillary prominence grow?
Grows medial and merges laterallywith mandibular prominences
What are the primordial lips and cheeks invaded by?
What does this give rise to?
Invaded by Mesenchyme from PA 2
Gives rise to facial muscles
What are the derivatives of the frontal nasal prominence?
Forehead Rostral border of stomodeum and nose Dorsum/apex of nose Nasal placodes Medial and lateral nasal prominences
How are the nasal placodes formed?
What does proliferation of these lead to?
By bilateral oval thickening of surface ectoderm
Horse-shoe shaped elevations called medial and lateral nasal prominences (eventually form nasal pits)
What are the derivatives of the lateral nasal prominence?
Alae of nose
What are the derivatives of the medial nasal prominence?
Nasal septum
Ethmoid bone
Cribriform plate
What do the horse shoe shaped elevations from the proliferation of the nasal placodes form?
Nasal pits
What are nasal pits?
Primordial nares (nostrils)
How does the medial nasal prominence grow and what does it fuse with?
Shifted toward the midline bc of the medial growth of maxillary prominences
Regulated by PDGFRA
Fuses and forms intermaxillary segment (philtrum)
With what and when do the lateral nasal prominences fuse?
Merges with maxillary prominences by end of weak 6
Separated by these prominence by nasolacrimal ducts
When will the face have its characteristic form?
By 14 weeks (3 1/2 months)
What does the small appearance of the face prenatally result from?
Rudimentary upper and lower jaws
Unreported deciduous teeth
Small nasal cavities
Maxillary sinuses
What depresses and forms nasal pits?
Nasal placodes
What induces nasal pits to become deeper?
What does this form?
Mesenchyme from medial and lateral nasal prominences
Primordial nasal sacs
How do primordial nasal sacs grow?
Dorsal and ventrally to the forebrain
What separates the primordial nasal sacs? When does this rupture?
Oronasal membrane
At end of wk. 6
What is the primordial choanae?
Connection b/w nasopharynx and nasal cavity
What are the nasal conchae?
Superior, middle, and inferior turbinate
What can the conchae become inflamed with?
Rhinitis
What does the olfactory epithelium specialize into?
Olfactory n.
What is an early indicator of Parkinson’s disease?
Loss of smell prior to onset of symptoms
How does the nasal septum develop?
Originates from medial nasal prominence
Downward growth of internal parts of merged medial a nasal prominences, fused with lateral palatine process
(Anterior to posterior)
When does Palatogenesis occur? When is the critical period for it?
2 stages be/w weeks 6-12
Critical period: end of wk. 6 - wk. 9
What does the primary palate make?
How?
Hard palate
Fusion of medial nasal prominences form median palatine process
Where is the median palatine process
B/w maxillary prominences
Forms premaxillary part of maxilla
What does the secondary palate make? How?
All of soft, most of hard palate
Bone extends from maxilla and palatine bones to make lateral palatine process (wk. 6)
Eventually these will grow medially and fuse
What are the lateral palatine process?
What else are they known as?
Mesenchymal projection extending from internal aspects of maxillary prominences
Palatal shelves
How is the final palate made?
What indicates the line of fusion between the primary and secondary palates?
Fuses with nasal septum ~ wk 9
Posterior portions do not ossify - making the soft palate and uvula
Anterior portions ossify - hard palate
Palatine raphe
What is the incisive fossa?
Remnant of the nasopalatine canal
Border b/w primary and secondary palate
What serves as the border b/w the hard and soft palate?
Incisive fossa
What is the most common craniofacial malformation?
Cleft lipand palate
How are cleft lips caused?
What is the most common cleft lift seen?
Defects in fusion
Unilateral Left cleft lip
What are the risk factors for cleft lip and palate?
Genetics (SATB2, SHH, TGF-Alpha, TGF-Beta-3, IRF6
Environmental (antiepileptic drugs, smoking, binge drinking, folate deficiency, obesity)
What does a median cleft lip result from?
Failure of the median nasal prominences to fuse and form intermaxillary segments
What does an unilateral cleft lip result from?
Failure of the maxillary prominence to merge with the medial nasal prominence on the affected side
What does a bilateral cleft lip result from?
Failure of maxillary prominences to meet and unite with the medial nasal prominences on both sides
What does an oblique facial cleft result from?
Failure of the maxillary prominence to fuse with lateral nasal prominences
What does a cleft palate result in?
Failure lateral palatal shelves to fuse and form secondary palate
Leaves the nasal and oral cavities still connected
Results in nursing problems for newborns
Can be incomplete, unilateral complete, or bilateral complete
What are neurocranium and viscerocranium both derived from?
Mesenchyme
What bony derivatives does the neurocranium give rise to?
Bones that enclose brain
What bony derivatives does the Viscerocranium give rise to?
Bones comprising the facial skeleton
What kind of ossification does cartilaginous neurocranium use?
What does it give rise to?
Via endochondral ossification, several cartilage fuse and form base of cranium
Occipital bone —> sphenoid body —> ethmoid bone
Also temporal bone (petrous and mastoid parts)
What kind of ossification does membranous neurocranium use?
What does it give rise to?
Intramembranous ossification
Forms calvaria (frontal and parietal bones - connected via sutures)
What kind of ossification does cartilaginous viscerocranium use?
What does it give rise to?
NCC to form bones and CT
Pa 1-4 derivatives Pa 1: malleus, incus, maxilla Pa2: stapes, styloid process, lesser horn of hyoid PA3: greater horn of hyoid Pa 4: laryngeal cartilage
What kind of ossification does membranous viscerocranium use?
What does it give rise to?
Intramembranous ossification w/ maxillary prominence
Zygomatic bone
Squamous part of temporal bone
Maxillary prominence
What causes the squamous part of the temporal bone to become neurocranium and not viscero?
TMJ development
What causes craniosynostosis?
What types are there?
Which one is most common?
Premature fusion of cranial sutures
Scaphocephaly - most common
Brachycephaly
Plagiocephaly
Trigonocephaly
What is scaphocephaly?
Premature fusion of Sagittal Suture
Results in long narrow wedge shaped cranium
What is Brachycephaly?
Premature fusion of coronal suture
Results in high, tower like cranium
What is plagiocephaly?
Premature fusion of one side of coronal suture
Results in head being twisted and asymmetric
What is trigonocephaly?
Premature fusion of frontal (metopic) suture
Result in pointy head
What is Choanal Atresia?
What does is present as?
Bony abnormalities of the pterygoid plates and midfacial growth abnormalities
Presents as:
Upper airway obstruction
Noisy breathing
Cyanosis that worsens during feeding and improves with crying
What other syndromes can Choanal Atresia be a part of?
Treacher Collins
CHARGE
Kallman
VACTERL
What is the boundary between the ectoderm and endoderm within the oral cavity?
When does this break down?
Oropharyngeal arch
Day 26
What are the ectodermal derivatives within the mouth?
Lining of the mouth
Tooth enamel
What are the endodermal derivatives within the mouth?
…..
What comprises the oral part of the tongue?
Anterior 2/3s of the tongue
How does the oral part of the tongue form?
What induces this?
Wk 4, median lingual swelling appear with two lateral tongue swellings developing on either side
Induced by Mesenchyme from PA 1
What makes up the pahryngeal part of the tongue?
Copula
Hypopharyngeal eminence
What forms the copula? What eventually happens to it?
Ventromedial parts of PA 2
Hypopharyngeal eminence overgrows copula
What form the hypopharyngeal eminence?
Ventromedial parts of PA 3 and 4
What indicates the fusion of the oral and pharyngeal parts of the tongue?
Terminal sulcus
What is the musculature of the tongued derived from?
What are they innervated by?
Myoblasts of occipital myotomes
Innervated by CN 12
What is Glossoschissis?
Bifed tongue
What is ankyloglossia?
What can this present with?
Short frenulum
Present w/ problems breastfeeding and speaking
What is macroglossia associated with?
Beckwith- Weidemann
Down Syndrome
Mucopolysaccharidoses
What provides sensation to the pharynx?
CN 10
What innervates palatoglossus m.?
CN 10 (pharyngeal branch)
What is odontogenesis induced by?
Induced by communication between NCC and oral epithelium
how many tooth ups do we have and where are they located?
10
Located in anteiror mandible, anterior maxilla, posteiror maxilla
What is the cap stage?
When the tooth bud becomes cap shapes by the investment of Mesenchyme
What constitutes a tooth bud?
Enamel organ
Dental papilla
Dental follicle/sac
What is the enamel organ of a tooth bud?
What is the outer cell layer lined with?
What does the inner cell layer line?
Ectodermal cells from dental lamina
Outer cell layer line with outer enamel epithelium
Inner cell layer lines papilla and is lined by inner enamel epithelium
What are ameloblasts?
Inner enamel epithelium that differentiates in response to dentin production and makes enamel
What is the dental papilla of a tooth bud?
Internal part of tooth containing dentin and pulp
What is the dental follicle/sac of the tooth bud?
Mesenchyme that surround dental papilla and enamel organ with cementum
What is the dental lamina?
U shaped bands of oral epithelium that follow the curves of the primitive jaws
What are the stages in odontogenesis?
Cap stage Bell stage Root development Eruption Permanent tooth development
What happens during the bell stage of odontogenesis?
- Odontoblasts produce root denting
- Ameloblasts produce enamel in response to odontoblasts
- Enamel organ becomes bell shaped due to differentiation of enamel
What are odontoblasts?
Cells from dental papilla cells next to the inner enamel epithelium that produces root dentin
(Predentin calcifies to become dentin)
What occurs during the root development stage of odontogenesis?
Epithelial root sheath forms, pulp forms, cementum forms and periodontal l. Forms
How does the epithelial root sheath form?
Fusion of the inner and outer enamel epithelium with root dentin being produced by odontoblasts
Where is pulp located?
In the central dental papilla
What is cementum and what produces it?
Inner cells of dental sac
From cementoblasts
What is the periodontal L.?
Outer cells of dental sac
What occurs during the eruption stage of odontogenesis?
Root and crown erupt thru oral epithelium With the mandibular teeth erupting first
Deciduous roots are resorbed by odontoclasts and crown and upper root are ahead
How many permanent teeth do we have?
32
When do deciduous permanent teeth appear?
~10 week
What are deciduous permanent teeth?
Extension of dental lamina
How do non deciduous molars develop?
As buds from posterior extensions of dental laminae
What is the Stellate reticulum?
A tissue layer lying between stratum intermedium and the outer enamel epithelium
Part of enamel organ
Consists of star shaped cells which protect the underlying dental tissues and maintain the shape of the tooth
What is the Stellate Intermedium?
Cell layer between the inner dental epithelium and Stellate reticulum
Has high alkaline phosphate season activity
Assist ameloblasts in forming enamel
