Development of Orofacial Structures Flashcards
What does the Neurocranium give rise to
Derived from Mesenchyme
gives rise to bones that enclose the brain
Cartilaginous and membranous components
what does the Viscerocranium give rise to
Derived from mesenchyme
gives rise to bones that comprise the facial skeleton
Cartilaginous and membranous components
What are the Cartilaginous and membranous parts of the Neurocranium
Cartilaginous: Occipital bone Body of sphenoid bone ethmoid bone Petrous and mastoid parts of the temporal bone
Membranous parts:
Calveria
-frontal and parietal bones
What are the Cartilaginous and membranous parts of the viscerocranium
Cartilaginous:
all the PA CT structures
Membranous: Maxillary prominence squamous part of temporal bone Maxilla Zygomatic bone
Craniosynstosis and the 4 types
Premature fusion of cranial structure
Scaphocephaly: sagital suture
head is long, narrow, and wedged shaped cranium
most common
Brachycephaly: Entire coronal suture
High, tower like cranium
Plagiocephaly: one side of coronal suture
twisted and asymetric
Trigoncephaly: Frontal suture
Frontal Nasal prominence derivatives
Forehead
dorsum/apex of nose
rostral boundary of stomodeum
Lateral nasal Prominence derivatives
Alae of nose
Medial Nasal Prominence derivatives
Nasal Septum
Ethmoid bone
Cribiform plate
Maxillary Prominence derivative
Upper check
Upper lip
and secondary palate
Mandibular Prominence derivative
Chin
Lower lip
Cheek
what are the 5 facial primordiaey surround and when do they appear
2 maxilary prominences
2 mandibular prominences
1 frontonasal prominence
surround the stomodeum=face
appear during the 4th week
What are the first parts of the face to form and how? what happens if it is incomplete?
LOwer jaw and the lip are first parts of face to form from the oropharyngeal membrane distenegrates and the 2 mandibular prominences merge together at the medial end
incomplete fusion results in a chin dimple
What invades the maxillary prominences
Primordial lips and cheeks are invaded by mesencyme from PA2 to give rise to the facial muscles
What are the nasal Placodes and where do they rise
Vilateral oval thickenings of surface ectoderm on the inferolateral portion of frontonasal prominence
Proliferation causes horse shoe shaped elevations which gives rise to the medial and lateral nasal prominences
These elevations result in formation of nasal pits and the premordial nares
What happens to the Median Nasal prominences
shifted towards the midline with medial growth of maxillary prominences
- regulated by PDGFRA
- Fusion results in formation of intermaxillary segment (Philtrum)
What happens to the lateral nasal prominences
Seperated from maxillary prominence by nasolacrimal groove
merges with maxillary prominence by end of week 6
What is the Auricular primordia
Six auricular hillocks form around the first pharyngeal groove
development of the mandible pushes ears from neck to side of head at level of the eyes
when does the nose and mandible reach its characteristic form
14 weeks
how does the skull move as the brain forms
the cranial cavity expands bi laterally
orbits will move from the lateral side to forward facing orientaion we are now
How are the nasal cavities formed
Nasal placodes depress and form nasal pits
Mesenchyme from the medial and lateral Nasal prominences induce nasal pits to become deeper
-Primordial nasal sacs
Primordial nasal sacs grow dorsally and ventrally to the forebrain
What separates the primordial sacs
Oronasal membrane seperates the primordial nasal sacs
but this will rupture at the end of week 6
WHat is the primodal choanae
Connection between the nasopharynx and the nasal cavity
What is the Nasal concahe
Superior, middle, and inferior turbinate
inflammed with rhinitis
What is the Olfactory Epithelium
Specializes into olfactory nerve
in parkinson disease is patients lose these cells and smell prior to the onsent of parkinson symptoms
When does the Palate form and what is considered the critical period
two stages that occur between weeks 6-12
Critical period- Endo of week 6, beginning of week 9
How is the primary palate formed
Fusion of the median Nasal prominences forms the median palatine process
- located between maxillary prominences
- forms premaxillary part of maxilla
How is the secondary palate formed
Develops from lateral palatine processes (Palatal shelves)
-Mesenchymal projections extending from internal aspects of maxillary prominences
How is the final Palate formed
Bone extends from the maxillae and palatine bones into the lateral palatine processes to form the hard palate
-posterior portions do not ossify (soft palate and uvula)
-Palatine raphe indicates the line of fusion
Incisive fossa is remnant of nasopalatine canal
How does the nasal septum grow
Downward growth of internal parts of merged medial nasal prominences
fuses with lateral palatine processes
-anterior to posterior
Cleft lip and palate and how is it caused
Most common craniofacial malformation
caused by defects in fusion
can be unilateral or bilateral
-unilateral on the left is the most common
Risk factos:
Genetics:
SATB2, SHH, TGF-alpha, TGF B3, IRF6
Environmental;
Antiepileptic drugs, smoking, binge drinking, folate deficiency, obesity
Choanal Atresia
Associated with bony abnormalities of the pterygoid plates and midfacial growth abnormalities
presents as upper airway obstruction, noisy breathing, or cyanosis that worsens during feeding and improves with crying
How does the oral part of the tongue form
Anterior 2/3 of tongue
Median ingual swelling (median tongue bud) appears at the end of the 4th week
Two lateral tongue swellings (distal tongue buds) develop on either side of the median tongue swelling
-induced by mesencyme from pharyngeal arch 1
Pharyngeal part-
- copula = ventromedial parts of PA2
- Hypopharyngeal eminence = ventromedial parts of PA 3 and 4
Hypopharyngeal eminence over grows copula
-terminal sulcus is where fusion of the oral and pharyngeal parts occur
What is tongue musculature derived from
myoblasts of occipital myotomes
CN XII
What is glossoschissis
bifid tongue, snake tongue
Ankyloglossia
short frenulum
can present with problems breast feeding and speaking
Macroglossia
associated with beckwith wiedmann and down syndromes
mucopolysaccharidosis
big tongue
how does odontogenesis begin
induced by communication between neural crest cells and oral epithelium (ectoderm)
consists of dental laminae
-U shaped bands of oral epithelium that follow the curves of the primitive jaws
What is the Cap stage
the tooth bud becomes cap shaped when invested by mesenchyme
What are the parts of the tooth bud
Enamel organ
Dental papilla
Dental follicle/sac
What makes up the enamel organ
Ectrodermal cells from dental lamina: enamel
Outer cell layer lined by outer enamel epithelium
inner cell layer lines papilla lined by inner enamel epithelium
stellate reticulum
What makes up the dental papilla
Internal part of tooth: dentin and pulp
What makes up the dental follicle/sac
Mesenchyme surrounding dental papilla and enamel organ
cementum
What happens in the bell stage
The enamel organ becomes bell shaped due to differentiation of enamel
Odontoblasts: from dental papilla cells nect to inner enamel epithelium, predentin calcifies to become dentin
Ameloblasts: coming from inner enamel epithelium differentiates in response to dentin production and produces enamel
What happens in root development
Epithelial root sheath: fusion of inner and outer enamel epithelium and production of root dentin
Pulp: central dental papilla
Cementum: inner cells of dental sac from cementoblasts
Peridontal ligament: outer cells of dental sac
Eruption
Root of tooth and crown erupt through oral epithelium
mandibular teeth erupt first
Deciduous root is resorbed by odontoclasts
Permenant tooth development
Permanent dentition consists of 32 teeth
Deciduous permenant teeth appear at 10 weeks
Tooth buds for permanant teeth appear at different times
-mostly during the fetal period
Buds for 2nd/3rd permenant molars develop after birth
