Facial development Flashcards
What are the 2 life in utero phase
Embryonic 8wks
Foetal 8+wks
When does ossification of the face occur
7-8wks
What is very important in the development of the face
Neural crest cell migration
What in the neural plate
A thickened portion of ectoderm along the midline of the embryo
What happens in neural crest cell migration
On the neural plate formation of the neural groove which then leads to formation of the neural tube
Masses of cells detach from the lateral side of the neural plate and form the neural crest
During the folding of the neural plate, cells develop from the ectoderm along the edge of the groove, termed neural crest cells which undergo migration within embryo and differentiate into many cell types e.g. spinal ganglia, Schwann cells
This neural crest derived ectomesenchyme contributes to branchial arch cartilage, bone and connective tissue proper, as well as dental tissues - pulp,dentine, cementum and periodontal
ligament
When and how neural tube formed
3 weeks and by the migration of the neural folds which fuse and form it
What does the neural tube form into
Forms into brain and spinal cord
What does failure of the neural folds fusing cause
Spina bifida
What does failure of the neural tube devlopment lead to
Anencephaly (cerbral hemispheres and cranial vault missing)
What happens at week 4
Neural crest cells form the fronto nasal process and laterally the pharyngeal arches
How many pharyngeal arches are there
6
Talk about the 1st pharyngeal arch
Appears about the 28th day
2 parts
maxillary prominence- becomes future maxilla, zygomatic bone and part of temporal bone
Mandibular prominence- Becomes mandible and gives rise to MOM,mylohyoid,ant. belly diagastric
The assoc. artery is thet Maxillary artery and the assoc. nerve is the trigminal nerve
Talk about the 2nd pharyngeal arch
Approx 28th day
2 assoc. arteries- Stapedial and hyoid
Assoc. nerve is the Facial nerve and muscles are the facial expression,stylohyoid, post. belly of diagastric muscle
Talk about the 3rd pharyngeal arch
30th day and assoc. artery becomes common carotid and proximal portion of the interanl carotid artery
Gives rise to lower body and greater horn of hyoid
Assoc. nerve glossopharyngeal
Talk about the 4th 5th and 6th pharyngeal arch
4th= 32nd day and assoc. nerve superior laryngeal branch of the vagus nerve
5th= spawns in and dissapears
6th=33rd day and assoc nerve recurrent laryngeal branch of the vagus nerve
When does formation of face occur and what does most of it
first 8 weeks
Migrating neural crest cells
-Either in fronto nasal process or pharyngeal arches
What are defects of the face closely related to
defects of the ant. brain
What may lead to cleft formation
Failure of fusion between the various facial processes or between the palatine
processes
Why can cleft lip and
alveolus can occur independently of cleft palate
The upper lip and anterior part of the palate have different embryological origins
from the posterior palate and they fuse at different times
What happens week 5-7
Fusion of facial process’s
What are the 2 types of bone formation
Intramembranous
Endochondral
How does intramembranous bone formation occur and what bones
Bone is directly deposited inot primitive mesenchmyal tissue
Neural crest dervied mesenchymal cells differentiate to osteoblasts
OB’s become entrapped by osteiod and they secrete and transform to O-cytes
Trabecular bone and periosteum form
Corticol bone forms superficially to trabecular bone
Blood vessels form red marrow
Includes vaults of skull, maxilla and most of mandible
How doe esndochondral bone formation occur and what bones
Bone precedded by a hylaine cartlidge model
several centres of ossification occur which then fuse
Forms base of skull
When does base of skull ossification start
It starts as a series of cartlidges which undergo endochondral ossification from multiple centres, starting with the basi-occiput at 10-12 weeks
When does vault of skull ossification start
Begins 3rd month in several centres
Fusion is incomplete at birth, leaving widenings known as fontanelles to allow flexibility in the
skull during birth
Anterior fontanelle closes at 2 years the posterior at about 1 year
Growth of the skull continues until 7
What are the facial cartlidges
Nasal capsule and meckels
Though mandible&maxilla form intramem. they devlop next to these pre-exsisting cartlingous skeletons which support it
WHat do nasal capsule and meckels help with
NC= primary skeleton in the upper face
M= preceeds the mandible
How does the mandible develop
As several units all responding to different stimuli
What are the different mandible units and how do they form
Condylar unit which forms the articulation and contains largest secondary
cartilage formation
Angular unit which forms in response to the lateral pterygoid and masseter muscles
Coronoid unit which responds to temporalis muscle development
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 sites of secondary cartlidge formation in the mandible
All 12-14wks I.U
Condylar- Growth until 20yrs
Coronoid- Dissapears long before birth
Symphyseal- Disaspears afer birth
External enviroment influnces what in early stages of pregnancy
cranio-facial abnormalities
What is a primary problem
Defect in the structure of a organ or part of an organ that can be traced back to an anomlt in development
What is a secondary problem
Interuption in the normal development of organ traced back to other influences
What is the defintion of:
Deformation
Agensia
Sequence
syndrome
Deformation- Anomly occur due to outer mechanical effects on exsisting structures
Agensia- Abscence of organ cause of failed devlopment during embryonic period
Sequence- Single factor results in numerous secondary effects (Pierre Robin)
Syndrome- Group of anomalies traced to a common origin
What facial syndromes cause maxillary hypoplasia
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*
*=Can be associated with clefts
What facial syndromes can cause mandibular problems
Treacher Collin’s Syndrome* (mandibulofacial dysostosis)
Pierre-Robin*
Stickler’s Syndrome*
Van der Woude Syndrome*
Turner’s Syndrome
Hemifacial Microsomia*
What syndromes can arrise in early development (1-8wks) and are they multifactorial or enviromental
Foetal alcohol- Enviromental
Hemifacia lmicrosomia- Multifactorial
Treacher collins- Multifactorial
Cleft lip/palate- Multifactorial
What is asooc. with foetal alcohol syndrome and what causes it
High maternal alcohol intake in early development (17 days)
microcephaly (small head)
short palpebral fissures
short nose
long upper lip with deficient
philtrum
small midface
small mandible
What is assoc. with hemifacial microsomia and when does it occur
Neural crest cell migration (day 19-28)
Unilateral mandibular hypolasia, zygomatic arch hypoplasia, high arched palate, malformed pinna
What is treacher collins assoc. with and when does it hapen
Deformity of 1st and 2nd branchial arches, (day 19-28)
slant palpebral fissures, Hypoplastic or missing zygomatic arches, Hypoplastic mandible with antigonial notch
