Development of Orofacial Structures Flashcards
What embryological layer is the neurocranium derived from?
Mesenchyme
What does the neurocranium give rise to?
Bones that enclose the brain and cartilaginous/membranous components
What embryological layer does the viscerocranium give rise to?
Mesenchyme
What does the viscerocranium give rise to?
Bones that comprise the facial skeleton and cartilaginous/membranous components
Describe intramembranous ossification
Mesenchymal origin without cartilage formation; neovascularization occurs; osteoblasts deposit osteoid (to form bone and osteocytes)
Describe endochondral ossification
Preexisting cartilaginous model (long bones); primary ossification centers appear in diaphysis; chondrocytes hypertrophy and matrix calcifies
What are the cartilaginous parts of the neurocranium?
Occipital bone, body of sphenoid bone, ethmoid bone, and petrous and mastoid parts of temporal bone
What are the membranous parts of the neurocranium?
Calvaria (frontal and parietal bones)
What are the cartilaginous parts of the viscerocranium?
Neural crest cells give rise to bones and connective tissue
What are the membranous parts of the viscerocranium?
Maxillary prominence, squamous part of temporal bone, maxilla, and zygomatic bone
What skeletal structures come from the 1st pharyngeal arch?
Malleus and incus
What skeletal structures come from the 2nd pharyngeal arch?
Stapes, styloid process of temporal bone, and lesser horn of hyoid
What skeletal structures come from the 3rd pharyngeal arch?
Greater horn of hyoid
What skeletal structures come from the 4th pharyngeal arch?
Laryngeal cartilage (except epiglottis)
What is craniosynostosis?
Premature fusion of cranial sutures
What is scaphocephaly and what is it characterized by?
Premature fusion of the sagittal suture; characterized by long, narrow, wedge shaped cranium; most common
What is brachycephaly and what is it characterized by?
Premature fusion of entire coronal suture; characterized by high, tower-like cranium
What is plagiocephaly and what is it characterized by?
Premature fusion of one side of coronal suture; characterized by twisted and asymmetric skull
What is trigonocephaly and what is it characterized by?
Premature fusion of frontal (metopic) suture
What is derived from the frontal nasal prominence?
Forehead and dorsum/apex of the nose
What is derived from the lateral nasal prominence?
Alae of nose
What is derived from the medial nasal prominence?
Nasal septum, ethmoid bone, and cribriform plate
What is derived from the maxillary prominence?
Upper cheek and upper lip
What is derived from the mandibular prominence?
Chin, lower lip, and cheek
What are the 5 facial primordia? When do they appear? What do they do?
2 maxillary prominences, 2 mandibular prominences, and 1 frontonasal prominence; appear during week 4; surround stomodeum
The 5 facial primordia are separated from the primordial pharynx by the oropharyngeal membrane. When does this rupture?
Around day 26
Describe the mandibular prominences
Lower jaw and lip are the first parts of the face to form; oropharyngeal membrane disintegrates and the medial ends of the mandibular prominences merge; incomplete fusion results in chin dimple
Describe maxillary prominences
Gives rise to upper lip, maxilla, and secondary palate; grow medially and merge laterally with mandibular prominences; the primordial lips and cheeks are invaded by mesenchyme from PA2 and this gives rise to facial muscles
Describe the frontonasal prominence
Surrounds ventrolateral part of forebrain and gives rise to forehead, rostral boundary of stomodeum and nose
What are nasal placodes?
Bilateral oval thickenings of surface ectoderm on the inferolateral portion of frontonasal prominence; proliferation causes horse-shoe shaped elevations called medial and lateral nasal prominences; these elevations result in formation of nasal pits (primordial nares)
Describe the median nasal prominence
Shifted towards midline with medial growth of maxillary prominences; regulated by PDGFRA; fusion results in formation of inter maxillary segment (philtrum)
Describe the lateral nasal prominence
Separated from maxillary prominence by nasolacrimal groove; merges with maxillary prominence by end of week 6
What is the auricular primordia?
6 auricular hillocks form around the 1st pharyngeal groove; development of the mandible pushes ears from neck to side of the head at the level of the eyes
While on your NICU rotation, you are called to the delivery room to evaluate a newborn who is in respiratory distress. Upon arriving to the delivery room, you notice that the baby is using accessory muscles in order to breathe. In addition, you notice that the baby demonstrates nasal flaring. From which structure did the flaring part of the baby’s nose develop?
Lateral nasal prominence
Which signaling molecule is responsible for development of both mandibular processes and removing webbing from the hands/feet?
BMP
Mesenchyme from medial and lateral nasal prominences induce nasal pits to become deeper. These are called what?
Primordial nasal sacs
What is the primordial choanae?
Connection between nasopharynx and nasal cavity
What is the nasal conchae?
Divided into superior, middle, and inferior turbinate; these become inflamed with rhinitis
What is the olfactory epithelium?
Specializes into olfactory nerve; loss of smell can occur about 10 years prior to the onset of symptoms of Parkinson’s disease
Palatogenesis occurs in 2 stages. Between what week does this occur and when is the critical period?
Occurs between weeks 6-12; critical period is end of week 6 to the beginning of week 9
What is the primary palate?
Fusion of medial nasal prominences to form the median palatine process; located between maxillary prominences; forms premaxillary part of maxilla
What is the secondary palate?
Develops from lateral palatine processes (palatal shelves); mesenchymal projections extending from internal aspects of maxillary prominences
What is the final palate?
Bone extends from the maxillae and palatine bones into lateral palatine processes to form the hard palate; posterior portions don’t ossify (becomes soft palate and uvula)
What is the palatine raphe?
Line of fusion in final palate
What is the incisive fossa in the hard palate a remnant of?
Nasopalatine canal
What is the nasal septum?
Downward growth of internal parts of merged medial nasal prominences; fuses with lateral palatine processes anterior to posterior
What is the most common craniofacial malformation?
Cleft lip and palate
What causes cleft lip and palate?
Defects in fusion; can be unilateral or bilateral, but unilateral cleft lip on the left is most common
What environmental factors can cause cleft lip and palate?
Antiepileptic drugs, smoking, binge drinking, folate deficiency, and obesity
What is 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
Choanal atresia can also be part of what other syndromes?
Treacher-Collins, CHARGE, Kallman, or VACTERL syndromes
What part of the tongue is called the oral part?
Anterior 2/3
Describe oral part of tongue development
Medial lingual swelling (median tongue bud) appears at the end of 4th week; 2 lateral tongue swellings (distal tongue buds) develop on either side of medial lingual swelling; induced by mesenchyme from PA1
Where does the copula of the pharyngeal part of the tongue come from?
Ventromedial part of PA2
Where does the hypopharyngeal eminence of the pharyngeal part of the tongue come from?
Ventromedial part of PA3 and PA4
this eminence overgrown the copula
What happens at the terminal sulcus?
Fusion of oral and pharyngeal parts of the tongue
What innervates the mucosa of the anterior 2/3 of the tongue?
Lingual branch of V3
What innervates the taste of the anterior 2/3 of the tongue?
Chorda tympani (VII)
What innervates the taste buds of the anterior 2/3 of the tongue?
IX
What innervates the musculature of the anterior 2/3 of the tongue?
XII
What innervates the mucosa and taste of the posterior 1/3 of the tongue?
IX
What innervates the musculature of the posterior 1/3 of the tongue?
XII
What innervates the sensation to the pharynx?
X
What innervates the palatogglossus muscle?
X
What is glossoschissis?
Bifid tongue
What is ankyloglossia?
Short frenulum; can present with problems breastfeeding and speaking
What is macroglossia?
Associated with Beckwith-Wiedemann and Down Syndromes mucopolysaccharidoses
What is the dental laminae?
U-shaped bands of oral epithelium that follow the curves of the primitive jaws
How many different tooth buds are there?
10
Odontogenesis is induced by what?
Communication between neural crest cells and oral epithelium
What is the cap stage?
Tooth bud becomes cap shaped when invested by mesenchyme
What does a tooth bud consist of?
Enamel organ, dental papilla, and dental follicle/sac
What do extodermal cells from the dental lamina give rise to?
Enamel
The outer cell layer of the enamel organ is lined by what?
Outer enamel epithelium
The inner cell layer of the enamel organ that lines the papilla is lined by what?
Inner enamel epithelium
What makes up the internal part of the tooth (the dental papilla)?
Dentin and pulp
What is the dental follicle/sac?
Mesenchyme surrounding dental papilla and enamel organ; also cementum
What is the bell stage?
Enamel organ becomes bell shaped due to differentiation of enamel
What are odontoblasts?
From dental papilla cells next to inner enamel; predentin calcifies to become dentin
What are ameloblasts?
Inner enamel epithelium that differentiates in response to dentin production; produces enamel
What is the epithelial root sheath?
Fusion of inner and outer enamel epithelium; root dentin produced by odontoblasts
What is the pulp?
Central dental papilla
What is the cementum?
Inner cells of dental sac that form cementoblasts
What is the periodontal ligament?
Outer cells from the dental sac
What is tooth eruption?
Root of tooth and crown erupt through the oral epithelium; mandibular teeth erupt first; the deciduous root is resorbed by odontoclasts (osteoclasts); the crown and upper root are shed
When do deciduous permanent teeth appear?
About 10 weeks
When do tooth buds for permanent teeth mostly appear?
Fetal period
How many teeth make up the permanent dentition?
32
