Facial growth 1 Flashcards
LIfe in utero consists of what 2 phases
embryonic – 1-8 weeks
foetal – 8 weeks to term
What has formed in first 2 months of pregnancy
All of the limbs and organs including the face
External enviroment influnces what in early stages of pregnancy
cranio-facial abnormalities
What is a very important stage in development of the face in embryology
Neural crest migration
what happens near the end of week 3 of embryology
The neural folds fuse to form the neural tube
What does failure in the formation of the nueral tube lead to
Spina Bifida
What does the neural tube develop into
Brain and spinal cord
what does failed development of the neural tube lead to
anencephaly
What happens in the folding of the neural plate
cells develop from the ectoderm along the edge
of the groove, termed neural crest cells
What happens to neural crest cells
undergo extensive migration within the developing embryo and ultimately
differentiate into many cell types e.g. spinal and autonomic ganglia; Schwann cells, adrenal medulla, meninges of the brain
What do nueral crest dervided ectomesenchyme contribute to
branchial arch cartilage, bone and connective tissue
proper, as well as dental tissues - pulp, dentine, cementum and periodontal
ligament
What day does the maxilla nd mandible start to form
46th
When does ossification of the face and skull start
7-8 weeks
During formation of face what may lead to significant malformations during this early period
Environmental factors
Defects of the face, particularly in the midline, may be closely related to what
defects of the anterior parts of the brain
What is most of the face formed by
Migrating neural crest cells
What causes major facial deformaties
Interference with neural crest cell migration
What leads to cleft formation
Failure of fusion between the various facial processes or between the palatine
processes
What has different embryological origins
The upper lip and anterior part of the palate
and
the posterior palate
What does the different embryological origins and different fuse times of the upper lip and anterior part of the palate and the posterior palate mean?
cleft lip and alveolus can occur independently of cleft palate
What happens week 4
Migrating neural crest cells form the frontonasal
process and laterally the branchial arches
What happens week 5-7
extension and fusion of the facial processes
The skull can be divided into what two parts
Neurocranium and viscerocranium
What is the neurocranium
Part of the skull that which forms a protective
case around the brain
What is the viscerocranium
Part of the skull which forms the skeleton of the face
How is intramembranous bone formed
Bone is deposited directly into primitive mesenchymal tissue
Needle-like bone spicules form, which progressively radiate from the primary
ossification centres to the periphery. Progressive bone formation results in the
fusion of adjacent bony centres
What is made of intramembraneous bone
vault of the skull, the maxilla and most of the mandible
How is endochondral bone formed
bones are preceded by a hyaline cartilage ‘model’
Several centres of ossification which eventually fuse
What does endochondral bone form
base of the skull
How is base of skull made
series of cartilages forms the base of skull.
They undergo endochondral
ossification from multiple
centres, starting with the
basi-occiput at 10-12
weeks.
At birth cartilagenous
growth centres remain
between the sphenoid and
occipital bones and in the
nasal septum.
The neurocranium can be divided into what
flat bones of the vault which develop intramembranously and the endochondral elements of the base of the skull
What age does skull stop growing
7
What occurs at the 3 month in vault of the skull
Intramembranous ossification of the vault in several centres
When do fontanelles close
anterior fontanelle closes at about 2 years of age
the posterior at about 1 year
how does the maxilla and mandible form
intramembranously
What do the mandible and maxilla develop adjacen to
pre-existing cartilaginous
skeletons - the nasal
capsule and Meckel’s
cartilage
How does the different parts of the mandible form
They form as several units all responding to different growth stimulate
A condylar unit which forms the articulation
and contains the largest secondary
cartilage formation.
An angular unit which forms in response to
the lateral pterygoid and masseter muscles;
A coronoid unit which responds to
temporalis muscle development (muscular processes).
An alveolar unit which forms only if teeth
are developing.
The body of the mandible forms in
response to the inferior dental nerve
what are the 3 main sites secondary cartlidge formation of the mandible
the condylar cartilage, the coronoid cartilage and at the symphyseal end of
each half of the bony mandible. The cartilages appear between 12 and 14
weeks I.U.
When do the cartilidges dissapear of the mandible
coronoid cartilage disappears long before birth and the symphyseal just
after birth. Growth continues at the condylar cartilage until about 20 years of age.
What precedes the growth of the mandible
Meckels cartiliage
What is the primary skeleton of the upper face
Nasal capsule
What does primary abnormality mean and give examples
Defect in the structure of an organ or part of an organ that can be traced back to an anomaly in it’s development
spina bifida, cleft lip, CHD
What does secondary abnormality mean and give examples
Interruption of the normal development of an organ that can be traced back to other influences
Teratogenic agents; infection (rubella virus), chemical
(thalidomide), chemical (lithium)
Trauma; amniotic bands
What does deformation mean
Anomalies that occur due to outer mechanical effects on
existing structures
What does Agenesia mean
Absence of an organ due to failed development during
embryonic period
What does Sequence mean
Single factor results in numerous secondary effects (PierreRobin)
What does Syndrome mean
Group of anomalies that can be traced to a common origin (Trisomy 21 in Down’s Syndrome)
Give examples of some maxillary hypoplasia facial syndromes
-Apert’s Syndrome (acrosyndactyly)
-Crouzon’s Syndrome(craniofacial dysostosis)
-Oral-Facial Digital Syndrome
-Binder’s Syndrome
- Achondroplasia
-Down’s Syndrome
-Cleidocranial dysostosis
-Foetal Alcohol Syndrome
-Cleft lip/palate
Give examples of some maxillary hypoplasia facial syndromes
Treacher Collin’s Syndrome
(mandibulofacial dysostosis)
Pierre-Robin
Stickler’s Syndrome
Van der Woude Syndrome
Turner’s Syndrome
Hemifacial Microsomia
Give examples of facial syndromes arrising from early problems with facial development
Enviromental- Foetal Alcohol Syndrome
genetic
Mulitifactorial-
Hemifacial microsomia
Treacher Collins syndrome (mandibulofacial dysostosis)
Clefts of lip and palate
What day can foetal syndrome ocur
17 days+
What are signs of foetal alcohol syndrome
microcephaly (small head)
typical faces having:
short palpebral fissures,
short nose,
long upper lip with deficient
philtrum,
small midface
small mandible.
What is the possible cause and signs of hemifacial microsomia
Neural crest migration disrupted (days 19-28)
Unilateral mandibular hypolasia, zygomatic arch
hypoplasia, high arched palate, malformed pinna
1:3500 Live births
Causes of mandibulofacial dysostosis and signs
Deformity of 1st and 2nd branchial arches
-Anti-mongoloid slant palpebral fissures
-Colomboma of lower lid outer 1/3rd
-Hypoplastic or missing zygomatic arches
-Hypoplastic mandible with antigonial notch
-Deformed pinna, conductive deafness
1;10,000 Live births
What is the Aetiology of Cleft lip and palate
Genetic:
Monozygotic twins
Syndromes
Familial pattern
Enviroment
Social deprivation
Smoking (2.5x)
Alcohol
Anti-epileptics
Multivitamins (25% down)
Dental features of cleft lip and palate
Impacted Teeth
Crowding
Hypodontia
Supernumeraries
Hypoplastic teeth
Caries
Achondroplasia cause and effects
Problem with endochondrial ossification
Defects in base of the skull, retrusive
middle third of the face, frontal bossing,
depressed nasal bridge
Crouzon’s (craniofacial dysostosis) cause and effects
Premature closure of cranial sutures (esp coronal and lamdoid)
Proptosis (shallow orbits), orbital dystopia, mild hypertelorism
Retusion and vertical shortening of midface
Prominent nose
Class III malocclusion
Narrow spaced teeth
