Development of Orofacial structures Flashcards
What are the 2 categories of bones in the brain?
Neurocranium and Viscerocranium (facial bones)
What cell type produces the neurocranium and viscerocranium?
Mesenchyme (from NCC)
What are the 2 types of bone formation?
Intramembranous ossificiation (from mesenchyme) and Endochondral ossification (from cartilage)
What bones in the neurocranium are formed via endochondral ossification?
Occipital bone, body of sphenoid, ethmoid and parts of the temporal bone
What bones in the neurocranium are formed via intramembranous ossification?
Frontal and parietal bones
Frontal bone + parietal bones =
Calvaria
What connects bones in the neurocranium that are formed via intramembranous ossification?
SUTURES
What bones in the viscerocranium are formed from endochondral ossification?
PA bones – malleus, incus, stapes, styloid process, lesser and greater horns of hyoid
What bones in viscerocranium are formed from intramembranous ossification?
Within maxillary prominence: Squamous part of temporal, maxilla and zygomatic bones
Within mandibular prominence: mandible
What bones formed from mesenchyme in the viscerocranium becomes part of neurocranium?
Squamous part of temporal bone
Bones in babies skulls join too early; as the brain grows the skull deforms to allow growth in certain areas not fused
Craniosynostosis
What are the types of craniosynostosis?
Scaphocephaly, brachycephaly, plagiocephaly, trigonocephaly
Scaphocephaly
Premature closure of sagittal suture = skull to be long, narrow
Brachycephaly
Premature closure of coronal suture = high, tower like skull
Plagiocephaly
Premature closure of coronal or lambdoid sutures on one side = skull is twisted and asymmetric
Trigonocephaly
Premature closure of metopic (frontal) suture = frontal and occipital bones are malformed
What are the facial primordia and when do they appear?
Frontonasal prominence, 2 maxillary prominences and 2 mandibular prominences that appear during 4th week
Where do the maxillary and mandibular prominences come from?
PA 1
What separates the prominences from the cavity of primordial pharynx?
Oropharyngeal membrane
When does the oropharyngeal membrane rupture?
Day 26
Where do the facial primordia arise?
Around the stomodeum (opening of mouth)
What facial primordia grows first and where are they growing?
Mandibular prominence (MDP), all grow toward midline and towards each other
Bilateral oval thickenings of surface ectoderm on inferolateral portion of FNP
Nasal placodes
What is created when the placodal edges of the nasal placode proliferate?
Medial and lateral nasal prominences
What is formed between the MNP and LNP?
Nasal pit
What does the nasal pit go on to form?
Nostrils and nasal cavities
When do the facial primordia start to move?
End of 4th week, after day 26 when the oropharyngeal membrane ruptures
What separates the maxillary prominence and the lateral nasal prominence?
Nasolacrimal groove
When the MXP grow toward each other what happens?
The medial nasal prominences also grow toward each other with the MXPs
when do the MNPs start to grow toward the midline?
End of 6th week
Once the medial nasal prominences merge with each other, what is formed?
Intermaxillary segment
What does the intermaxillary segment create?
Premaxillary part of maxilla, primary palate, core of philtrum of upper lip
What separates the growing nasal sacs from the oral cavity?
Oronasal membrane that will eventually rupture so the cavities will connect
How is the palate greated?
Primary palate + secondary palate = palate
Primary palate
Median palatine process
Secondary palate
Lateral palatine process or Palatal shelf
What creates the lateral palatine processes?
MXPs
Describe how the palatal shelves/lateral palatine processes grow
They start by extending inferiorly on each side of the tongue, as the mandible grows it pulls the tongue forward and down in the mouth and then the lateral palatine processes flip up horizontally where they fuse
Lack of fusion between lateral palatine processes and nasal septum or median palatine process
Cleft palate
Lack of fusion between the medial nasal prominence and maxillary prominence
Cleft lip
when does the nasal septum fuse with the median and lateral palatine processes?
Weeks 9-12
What arch contributes most to tongue development?
PA 1
Describe PA 1’s contribution to tongue development
One median lingual swelling that gets overgrown by 2 lateral lingual swellings that fuse to create the oral part of the tongue
Oral part of the tongue
Anterior 2/3
What is mostly overgrown but the PA 2 contribute to the tongue
Copulla
What do the PA3 and PA4 contribute to the tongue
Hypopharyngeal eminence
Pharyngeal part of tongue
Posterior 1/3
Line of fusion between anterior and posterior tongue
Terminal sulcus
What nerves supply the anterior tongue?
Lingual (V3), chorda tympani (VII)
What nerves supply the posterior tongue?
IX, X
Incomplete fusion of lateral lingual swellings
Glossoschissis
Frenulum is short and attached to tip of tongue
Ankyloglossia
Excessively large tongue commonly seen in children with down’s syndrome
Macroglossia
Tiny tongue commonly seen with micrognathia
Microglossia
Where does the tongue musculature come from and what nerve supplies them?
Occipital myotomes; CN XII
