Development of Orofacial Strucutes Flashcards
What is neurocranium derived from? What does it give rise to?
Mesenchyme, cartilaginous and membranous components
Bones that enclose the brain: frontal, parietal, occipital, petrous part of temporal
What is viscerocranium derived from? What does it give rise to?
Mesenchyme
Facial skeleton: nasal, lacrimal, zygomatic, maxilla, incisive, mandible, sphenoid, squamous part of temporal
What do the cartilaginous parts of neurocranium give rise to? Membranous parts?
Occipital bone, body of sphenoid, ethmoid bone, petrous and mastoid parts of temporal bone
Calvaria= frontal and parietal bones
What do the cartilaginous parts of viscerocranium give rise to? Membranous parts?
NCC –> bones and connective tissue
Maxillary prominence, squamous part of temporal, maxilla, zygomatic bone
What is scaphocephaly?
Premature fusion of sagittal suture
Long narrow wedge shaped cranium
What is brachycephaly?
Premature fusion of entire coronal suture
High tower like cranium
What is plagiocephaly?
Premature fusion of one side of coronal suture
Twisted and asymmetric
What is trigonocephaly?
premature fusion of frontal suture
What is derived from the frontal nasal prominence?
Forehead
Dorsum/apex of nose
Rostal boundary of stomodeum
What is derived from the lateral nasal prominence? What separates it from the maxillary prominence? When does it merge with the maxillary?
Alae of nose (nasal flaring)
nasolacrimal groove
End of week 6
What is derived from the medial nasal prominence? What regulates its growth?
Nasal septum
Ethmoid bone
Cribiform plate
PDGFRA, shifted towards midline with medial growth of maxillary prominence
What is derived from the maxillary prominence? What is the process?
Upper cheek
Upper Lip
Maxillary prominence grows medially and merges laterally with mandibular prominence
Invaded by mesenchyme from PA2 –> facial muscles
What is derived from the mandibular prominence? What is the process? What happens if there is incomplete fusion?
Chin
Lower lip
Cheek
Caused when oropharnygeal membrane disintegrates and medial ends of mandibular prominence merge
chin dimple.
When does the facial primordia appear? What is its structure?
week 4
Surrounds stomodeum= primitive oral cavity
Separated from primordial pharynx by oropharyngeal membrane which ruptures day 26
How are the medial and lateral prominences formed?
Nasal placodes (thickened surface ectoderm) on inferolateral portion of the frontonasal prominence proliferate causing horse shoe shaped elevations –> medial and lateral nasal prominences –> primordial nasal snares
How is the philtrum/intermaxillary segment formed?
Fusion of median nasal prominence and maxillary
Above midline of upper lip
What signaling molecule responsible for development of mandibular process?
BMP
How are nasal cavities formed?
Nasal placodes (ectoderm) depress and form nasal pits Mesenchyme from medial and lateral proinences induce pits to become deeper --> primordial nasal sacs which grow dorsally and ventrally to forebrain, separated by oronasal membrane which ruptures end of week 6
What is the primordial choanae?
Connection between nasopharynx and nasal cavity
What is the nasal conchae?
Superior middle and inferior turbinate
Can become inflamed with allergies (rhinitis)
What does olfactory epithelium become?
Olfactory n.
In Parkinson’s symptom is losing sense of smell prior to onset of normal symptoms
What are the 2 stages of platogenesis? When do they occur? What is the critical period?
Primary= fusion of median nasal prominences forms median palatine process –> premaxillary part of mazilla
Secondary= develop from lateral palatine processes (palatal shelves) which are mesenchymal projections extending from internal aspects of maxillary prominence
Weeks 6-12
critical= end of week 6-beginning of week 9
How do we get our final palate?
Bone extends from maxillae and palatine bones into lateral palatine processes to form hard palate
- posterior portions do not ossify –> soft palate and uvula
What is the palatine raphe?
Line of fusion
What is the incisive fossa?
Remnant of nasopalatine canal
How do we get the nasal septum?
Downward growth of internal parts of merged medial nasal prominences
Fuses with lateral palatine processes anterior to posterior
What causes cleft lip and/or palate? What are risk factors?
Defects in fusion
Genetics: SATB2, SHH, TGF-alpha, TGF-B3, IRF6
antiepileptic drugs, smoking binge drinking, folate deficiency, obesity
What is choanal atresia? How does it present?
bony abnormalities of pterygoid plates and midfacial growth abnormalities?
upper airway obstruction, noisy breathing, cyanosis that worsens during feeding and improves with crying
Connected to Treacher-collins (arch 1) CHARGE, Kallman, or VACTERL syndromes
How does the oral part (anterior 2/3) of the tongue develop?
Median tongue bud appears at end of 4th week and then two lateral swelling develop on either side
Induced by PA 1
How does the pharyngeal part (post 2/3) of tongue develop?
Copula= PA2
hypopharyngeal eminence= PA3 and 4, eventually overgrows copula and fusion at terminal sulcus of oral and pharyngeal parts
What innervates the mucosa, taste, taste buds, and musculature of the anterior 2/3 of the tongue?
mucosa= Lingual branch of V3
taste= Chorda Tympani (CN VII)
taste buds= CN IX
musculature= CN XII
What innervates the mucosa, taste, taste buds, and musculature of the posterior 1/3 of the tongue?
Mucosa and taste= CN IX
Musculature= CN XII
Sensation to pharynx= CN X
Palatogglossus m.= CN X
What is clossochissis?
Bifid tongue
What is ankyloglossia?
Short frenulum (attaches inferior tongue to oral cavity Can present with problems breastfeeding and speaking
What is macroglossia?
Big tongue
Associated with downs, beckwith-wiedemann, muscopolysaccharidoses
What induces odontogenesis?
Communication between NCCs and oral epithelium (ectoderm)
What is the cap stage of odontogenesis?
Tooth bud becomes cap shaped when invested by mesenchyme
What does the tooth bud consist of?
Enamel organ= ectodermal cells from dental lamina –> enamel
Dental papilla= internal part of tooth –> dentin and pulp
Dental follicle/sac= mesenchyme surrounding papilla and enamel organ – >cementum
What is the bell stage of odontogenesis?
Enamel organ becomes bell shaped due to differentiation of enamel
What do odontoblasts give rise to?
Predentin calcified to give dentin
Comes from dental papilla cells next to inner enamel epithelium
What do ameoblasts give rise to?
Enamel
Inner enamel epithelium differentiates in response to dentin production
How does the root of the tooth form?
Epithelial root sheath= fusion of outer and inner enamel
Pulp= central dental papilla
Cementum= inner cells of dental sac from cementoblasts
Periodontal ligament= outer cells of dental sac
What erupts through epithelium when your tooth erupts?
Root of tooth and crown
Mandibular teeth erupt first
Deciduous root resorbed by odontoclasts and crown and upper root are shed
When do the buds for our 2nd and 3rd permanent molars develop?
After birth
Why you have to get your wisdom teeth out
When do deciduous permanent teeth appear?
10 weeks
extension of dental lamina, lingual to deciduous tooth buds
What is the epithelium covering the posterior 1/3 of the tongue derive from?
Endoderm
What is the hypobranchial eminence derived from?
PA 3 and 4
What is derived from the dental lamina?
enamel organ
What tissue gives rise to the dental sac?
Head mesenchyme
What is the philtrum of the upper lip derived from?
medial nasal prominence
