Development of Orofacial Structures Dennis Flashcards
What is Intramembranous ossification
Mesenchyme produces osseous tissue without the use of cartilage formation. The mesenchyme will condense and become vascular and differentiate into osteoblasts and deposit osteoid. Osteoblasts become trapped in lacunae and become osteocytes.
What is endochondral ossification?
Bone formation occurs using the cartilage model. Primary ossification centers first appear in the diaphysis and then chondrocytes become hypertrophic and eventually calcify. Meaning the chondrocytes die and then replaced by bone
What is the order of cartilaginous neurocranium formation?
Occipital bone, body of sphenoid and finally ethmoid bone
what makes up the membranous neurocranium?
Calvaria frontal and parietal bones which form through intramembranous ossification and are connected by sutures
What is the viscerocranium?
Bones that make up the face
What portions of temporal bone form cartilaginous
Petrous and mastoid part
Relate cartilaginous viscerocranium to the PA’s.
PA1: malleus and incus
PA2: stapes styloid process and lesser horn hyoid
PA3: greater hyoid horn
PA4: cartilages fuse to form laryngeal cartilages
What is Scaphocephaly?
Premature closure of sagittal suture and cranium becomes long narrow and wedge shape. Type of craniosynostosis
What is Brachycephaly?
Premature closure of the coronal suture, creates a high tower like cranium
What is Plagiocephaly?
One side of the coronal suture closes prematurely so the cranium is asymmetric
What is trigonocephaly?
Premature closure of frontal suture which will cause malformation of frontal and orbital bones
When does the facial primordia appear?
4th week
What arches are the maxillary and mandibular prominences from?
1st arch
The facial primorida is separated from cavity of primordial pharynx by _____.
bilaminar membrane- Oropharyngeal membrane
When does the oropharyngeal membrane rupture?
26 days
What are the derivitives of the FNP and what cells make it up?
Frontal portion of the forehead
Nasal portion forms the rostral boundary of the stomodeum and nose tip
NCC from forebrain and midbrain
What cells populate the MXP and MDP?
NCC from midbrain and hindbrain
What are the first parts of the face to form?
The lower components such as the lower jaw and lip
What are nasal placodes and when are they formed by?
Formed by end of fourth week on the inferolateral parts of the FNP
They are bilateral oval thickenings of the surface ectoderm & are primordia of the nasal epithelium
When the placodal edges proliferate what do they produce?
Medial and lateral nasal prominences
The placodes are now in depressions called nasal pits