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