Orthodontics - Facial Growth Flashcards
at how many weeks is the embryo stage?
1-8 weeks
at how many weeks is the foetal stage?
8 weeks onwards
what cell mass forms the foetus and the supporting structures?
the inner cell mass
what is the germ disc composed of?
the ectoderm and the endoderm
what forms the medoderm?
folding of the ectoderm
name the 3 germ layers
ectoderm
mesoderm
endoderm
what cell mass form the germ disc?
the inner cell mass
how are ectomesenchyme cells formed?
the neural folds fuse to form the neural tube.
neural crest cells/ectomesenchyme cells form along the length of the tube
what does the neural tube develop into?
the brain
the spinal chord
what do neural crest cells/ectomesenchme migrate and differentiate into?
- Dental development: pulp, dentine, cementum, PDL
- Spinal cells
- Autonomic ganglia
- Schwann cells
- Adrenal medulla
- Meninges of the brain
- Bone and connective tissue
what is hemifacial microsomia caused by?
Caused by a deficiency in the migration of neural crest cells on one side.
what is spina bifida caused by?
Caused by failure in closure of the neural tube
what is ancephaly?
When the neural tube doesn’t develop properly and leads to absence of the cranial vault
when does facial development occur?
the first 8 weeks
what cells form the face?
neural crest cells
what 5 facial swellings give rise to facial structures?
the frontonasal
2x mandibular
2x maxillary prominences
what does the neurocranium form?
forms the case around the brain
what type of ossification is the neurocranium formed by?
intramembranous ossification
what does the viscerocranium form?
forms the skeleton of the face
what ossifications forms the base of the skull?
endochondral ossification - ossification which has a cartilage precursor which then is replaced by bone.
name the primary facial cartilages.
the nasal capsule - maxilla
meckels cartilage - gives rise to mandible
describe the relationship between the primary cartilages and the bones of the maxilla and the mandible.
The development of the maxilla and mandible are closely related to these cartilages but do not form from them!
Since these bones are formed by intramembranous ossification – no hyaline cartilage precursor
name the units that form the mandible.
- Condylar
- Coronoid
- Alveolar
- Body
- Angular
what makes the units of the mandible grow?
growth stimuli i.e. muscles attached to the unit
if you do not have a medial pterygoid and masseter what unit of the mandible will not form?
angular
if you do not have a temporalis muscle what unit of the mandible will not form?
coronoid
if you do not have a teeth what unit of the mandible will not form?
alveolar
if you do not have an IAN what unit of the mandible will not form?
the body
where are the 3 sites of secondary cartilages?
- Condylar – facilitates growth until 20 years of age
- Coronoid – removed quickly way before birth
- Symphyseal – removed quickly just before birth
what secondary cartilage is responsible for the continuous growth of the mandible up until the age of 20?
condylar cartilage
what maxillary syndromes are associated with clefts?
Apert’s Crouzon’s Oro-facial digital syndrome Cleidocranial dysostosis Cleft lip and palate
what mandibular syndromes are associated with clefts?
Treacher Collin’s : multifactorial Pierre-Robin Sticklers Van der Woude Hemifacial microsomia
when do malformations of the foetus occur in foetal alcohol syndrome?
during day 17 of development
what are the signs of foetal alcohol syndrome?
Flat philtrum Small head Short palpable fissure – eye slits are small Flat midface Thin and long upper lip low bridge of nose Small nose Small lower jaw Possibility of mild mental retardation