CTB theme 3 Flashcards
What are the steps in the estblishment of a body plan ?
fertilisation cleavage gastrualtion organogenesis larval stage maturity gametogenesis
What happens in gastrualation ?
development of the 3 germ layers
What are the 2 germ layers ?
ectoderm, endoderm and mesoderm
What happens in organogenesis ?
tissue morphogenesis and cell differentiation
formation of body structures and organs
germ layers make derivatives
What are the derivatives of the ectoderm ?
external cells- epidermis and dental epithelium
CNS
craniofacial tissues-cartialge, bone and teeth
What are the derivatives of the mesoderm ?
blood
connective tissue
notochord
bone
What are the derivatives of the endoderm ?
internal cells
stomach cells
thyroid cells
lung alveolar cells
What does susceptibiltiy to teratogens mean ?
human embryo can have developmental birth defects
When is the embryo susceptible to teratogens ?
first trimester- 3/4 weeks to 12 weeks
craniofacial abnormalities important in 4-12 weeks
What are some early head formation defects ?
holoprosencephaly
anencephaly
What is holoprosencephaly ?
facial midline defect due to deficiency in forebrain tissue
not symmetrical face
What causes holoprosencephaly ?
mutation in Shh pathways genes
What is anencephaly ?
abnormal brain development due to failure of neural tube to close
What causes anencephaly ?
teratogens
severe malnutrition
folic acid deficiency
What do high retinoic acid levels interfere with ?
Hox gene expression
What is an important early embryo development stage ?
folding of the early embryo
What are the 3 types of embryo folds ?
head
lateral
tail
What happens at 16 days in the embryo ?
3 germ layers present
ectoderm proliferates to form the neural palte
head fold occurs
What happens at 18 days in the embryo ?
ectoderm proliferates and meets endoderm forming the oropharyngeal membrane
What are the functions of the oropharyngeal membrane ?
separates the future mouth (stromedeum) from the pharynx
acts as a transient signalling centre to pattern the oral cavity
eventually broken down
What is the future mouth called ?
stromedeum
What happens in 22 days in the embryo ?
formation of the stromedeum
heart now located inwards
What happens in 30 days in the embryo ?
rudiments of most organs established
oropharyngeal membrane breaks down
pharyngeal arches broken down- 1, 2 and 3
What are the pharyngeal arches ?
1- mandibular arch
2- maxillary arch
3- third arch
What is present at 4 weeks of development ?
somites
heart
pharyngeal arches
What is the structure of the pharyngeal arches ?
each arch is covered in ectoderm and lined with endoderm
internal mesoderm core infiltrated with CNCs
What does each pharyngeal arch form ?
artery
cartilage
nerve
Why are there CNCs in the mesoderm of the pharyngeal arch ?
CNCs replace the mesoderm as they migrate into the arches
What is the artery and nerve formed in the first pharyngeal arch ?
maxillary artery
trigeminal
What is the artery and nerve formed in the second pharyngeal arch ?
hyoid artery
facial
What is the artery formed in the third pharyngeal arch ?
internal carotid artery
glossopharyngeal
What is the artery and nerve formed by the 4th pharyngeal arch ?
right subclavian
vagus
What are muscles of the 1st pharyngeal arch ?
muscles of mastication anterior belly of digastric tensor tympani mylohyoid tensor veli palatini
What are the muscles of the 2nd pharyngeal arch ?
muscles of facial expression
stapedius
stylohyoid
posterior digastric
What are the muscles of the 3rd pharyngeal arch ?
stylopharyngeus
What are the muscles of the 4th pharyngeal arch ?
muscles of the larynx and pharynx
What are the skeletal derivatives of the 1st arch ?
malleus
incus
meckels
sternothyroid ligament
What are the skeletal derivatives of the 2nd arch ?
stapes
styloid process
stylohyoid ligament
lesser cornu of hyoid
What are the skeletal derivatives of the 3rd arch ?
greater cornu of hyoid
What are the skeletal derivatives of the 4th arch ?
laryngeal cartilages
What is the process of cranial neural crest cell formation ?
- CNCs induced molecularly at the border between neuroectoderm and epidermis
- neural plate invaginates and forms the neural folds- open tube
- neural folds fuse to form the neural tube - CNCs migrate along specific pathways
- migration to predetemined destinations - become specialised cell types
Where are CNCa specified ?
at the border between neuroectoderm and epidermis
What does the border of neuroectoderm and epidemris specify and create ?
specifies CNCs
creates BMP4 and WNT6 signalling proteins
What do BMP4 and WNT6 do ?
indice TFs necesary for CNC migration and specification
What are the gradients of BMP4 and WNT6 ?
overlapping gradients
cells get intermediate signals and migrate to where theyre determined
What do CNC do in migration ?
migrate along specific pathways from the early brain to pharyngeal arches
What determines CNC identity ?
overlapping expression of homoeobox TFs - determine CNC identity
What happens in the development of the face at 4-5 weeks ?
formation and growth of an unpaired frontonasal prominence
formation of nasal placodes (epithelium thickenings)
formation of paired nasomedial/nasolateral processes which form the nasal pit
formation and growth and merger of the mandibular processes
Formation and growth of paired maxillary processes
What does the mandibular arch divide into ?
mandibular and maxillary processes
What happens in the development of the face (5-6 weeks) ?
Recession of the nasolateral prominence due to excessive growth of the nasolateral process
Growth of the nasolateral process which fuses with the maxillary process
What does the fusion of maxillary process and nasolateal process form ?
nasolacrimal duct
cheek
alar base of nose
What happens in the development of the face at 7-8 weeks ?
merger of the nasomedial process
further growth of maxillary processes and fusion with nasomedial process
What does fusion of the maxillary process and nasomedial process lead to ?
central part of nose, upper lip and primary palate
upper lip laterally- maxillary process
upper lip medially- nasomedial process - philtrum
What does the maxillary process form ?
maxilla
lateral part of the upper lip
What does the mandibular process form ?
mandible
upper lip
What does the medial nasal process form ?
medial part of the nose
medial part of the upper lip
primary palate
What does the lateral nasal process form ?
lateral part of the nose
What is median cleft lip ?
single cleft in the midline
failure of medial nasal processes to fuse
What is bilateral cleft lip ?
cleft from nose to upper lip
failure of maxillary and medial nasal processes to fuse
What is an oblique facial cleft ?
persistence of the nasolacrimal groove
failure of maxilllary and lateral nasal process to fuse
What is lateral facial cleft ?
macrostomia
failure of merger between mandibular and maxillary process
cleft from the lip on the cheek
What is the median mandibular cleft ?
from the lower lip to chin
failure of merger of mandibular processes
chin dimple
Why is median cleft lip associated with cleft palate ?
both the upper lip and the palate are due to fusion of mesiolateral processes
What is frontonasal dysplasia ?
various degrees of excessive tissue in frontonasal process
broad nasal bridge
hypertolerism
cleft nose and median cleft
What are the range of clinical presentations of hypertolerism ?
single genetic pathways
What is treacher collins syndrome ?
hypopalsia of mandible and facial bones
macrostomia
cleft palate
eyelid coloboma
What causes treacher collins syndrome ?
mutation in Tcof1 decreased ribosome biogenesis increased p53 cell cycle arrest and apoptosis lost of neural crest cells hypoplasia of facial bones
How can we prevent treacher collins syndrome ?
inject inhibitor of p53- prevent apoptosis
How does the primary palate develop ?
Nasal pits relocated inwards
thin oronasal membrnae separate oral and nasal cavities
primary palate forms from the merger of mesionasal processes that grow inwards into the oral cavtity
How does the primary palate form ?
ingrowth and merger of nasomedial processes
form median palatal process
What does persistence of the oronasal membrane cause ?
choanal artesia
tissue blocks nasal passage
complete or partial
bilateral or unilateral
What does the secondary palate form from ?
lateral outgrowths of maxillary processes
What does the secondary palate close ?
the space between the oral and nasal cavity
How does the secondary palate form ?
lateral palatine processes appear as maxilalry outgrowths - grow downwards
palatal shelves elevate
downgrowth of the nasal septum
fusion of the palatal shelves in the anterior part and the primary palate
Fusion of the palatal shelves in the posterior part and formation of the palatal raphe
What is present at the border of the primary and secondary palate ?
incisive foramen - blood vessels and nerves to the hard palate
How does the uvula form ?
from the medial soft palate
What are the functions of the uvula ?
swallowing
speech
reflex
breathing
What is the proposed mechanism of palatal shelf elevation ?
GAGs at the hinges
GAGs hydrate- causing elevation
How do the palatal shelves meet and fuse ?
meet through the growth of mesenchymal cells
Fusion of the shelves from the Medial epithelial seam
What happens to the medial epithelial seam ?
it is removed apoptolytically
results in continuous secondary palate
What happens in van der woude syddrome ?
fusion of the palatal epithelia with other oral epithelia
Which mutation causes van der Woude syndrome ?
IRF6
What does incomplete removal of epithelial remnanats of MES lead to ?
palatal cysts
What are palatal cysts ?
benign
interfere with denture fitting
What is an early growth or morphogenetic effect in the palate ?
failure of palatal shelf formation due to reduced mesenchymal cell proliferation
What causes premature epithelial fusion ?
epithelium of the palatal shelves fuses with oral epithelia
What is failure of palatal shelf elevation ?
obstruction or abnormal cell differentiation in hinge region of palatal shelves
What is a late growth defect ?
failure of shelves to meet after elevation
reduced mesenchymal cell proliferation
head too wide
What is a unilateral cleft palate ?
from the nose, lip and primary palate
can be bilateral
What are the types of secondary palate clefts ?
unilateral– one palatal shelf fused with the nasal septum
bilateral- both palatal shelves fused with the nasal septum
What are the bones of the hard palate ?
premaxillary part of maxilla (not part of maxilla)
palatine process of maxilla
horizontal plate of palatine bone
What is the premaxilla ?
primary palate
holds the incisors
What does the palatine process of maxilla do ?
fuse with the premaxilla
and then the horizontal process of palatine bone
Which teeth are likely to be missing in the cleft lip area ?
2s and 5s
What is torus platinus ?
late defect
benign outgrowth in midline of hard palate
What are the types of CL/P or CP ?
syndromic or isolated
What are the causes of syndromic CL/P or CP ?
single gene mutation in coding regions
affect gene function more strongly
pleitropic effects in multiple organs
What are the causes of isolated CL/P or CP ?
mutations in gene regulatory DNA regions- effect tissue specific expression
genetic and environmental interactions
What are the environmental risk factors for CL/P and CP ?
deficiencies in maternal diet
excessive or insufficient mineral intake
alcohol, tobacco
teratogens- nitrates
What is the gene mutation in holopresencephaly ?
SHH
GLI2
What is the gene mutation in van der woude syndrome ?
IRF6
What is the gene mutation in crouzon ?
FGFR2
What is the gene mutation in Apert ?
FGFR2
What is the gene mutation in pierre robin ?
SOX9
What is the mutation in di george ?
TBX1
What is the gene mutation in treacher collins syndrome ?
Tcof1
What is the genetic module common to both palate and tooth development ?
Pax9 initiated in mesenchyme
signalling cascade between MSX1 and BMP
Signals back to epithelium to form enamel knot
expression of Shh by enamel knot
How is the anterior tongue formed ?
appearance of 3 swellings on 1st pharyngeal arch- tuberculum impar and 2 lateral lingual swellings
lateral lingual swellings enlarge rapidly and fuse with each other and tuberculum impar
How is the posterior tongue formed ?
hypobachial eminence on PA 3 and 4
overgrows the copula - PA 2
What is at the border between the anterior and posterior tongue ?
teminal sulcus
Where is the anterior tongue derived from ?
ectoderm epithelium
Where is the posterior tongue derived from ?
endoderm epithelium
What is the foramen caecum ?
between copula and tuberculum impar
marks original location of the thyroid primordium
What is the thyroid primordium ?
migrates down towards the 3rd tracheal cartilage
stays connected to the thyroglossal duct during migration
How is the epiglottis formed ?
posterior part of 4th pharyngeal arch
Where do the tongue muscles derive from ?
occipital somites that have migrated forward
What is the innervation of the anterior 2/3 of the tongue ?
lingual nerve and chorda tympani
What is the innervation of the posterior 1/3 of the tongue ?
glossopharyngeal
What is the innervation of the epgiglottis ?
vagus
What is ankyglossia ?
tongue tie
thick lingual frenulum
impaired tongue movement
van der Woude syndrome
What is macroglossia ?
tongue hyperplasia
downs syndrome
due to acromegaly- too much GH
What are developmnetal defects of thyroid migration ?
ectopic thyroid tissue
lingual thyroid
thyroglossal duct sinus
What are the rods of hyaline cartilage that form either side of the jaw in mandible development ?
meckels cartilage
How far does meckels cartilage extend ?
from the optic capsule to the midline of the merged mandiible
What does meckels cartilage do in mandible development ?
forms a framework that the mandible can develop arounf
Where is osteogenesis initiated in the mandible ?
at the branching of the mental and incisive nerve
How does osteogenesis happen in the mandible ?
via lateral mesenchymal cell proliferation
How does the mandible grow ?
it takes the shape of a trough under the incisive nerve
meckels process gets smaller and the alveoalr process grows under the tooth germ
meckels cartilge is resorbed and the nerve is in a bony canal and the alveolar process surrounds the tooth germ
When does the symphysis that joins the 2 mandible bones develop ?
10 weeks
How does the lingula form ?
when mandible diverts from meckels cartilage
Where does the incisive nerve enter the mandible ?
at mandibular foramen
What is attached to the lingula ?
sphenomandibular ligament
What are the attachments of the sphenomandibualr ligament ?
spine of sphenoid to lingula of the mandible
What forms the sphenomandibular ligament ?
perichondrium
What is the fate of meckels cartilage ?
meckels cartilage degrades in the middle- dorsal and ventral remnants remain
space filled with bone
(not endochondral)
What do the dorsal remnants of meckels cartilage form ?
ossfiy to form incus
malleus
spine of spehnoid
What do the ventral remnants of meckels cartilage from ?
lingula
mental ossicles
What type of cartilage is meckels cartilage ?
priamary cartilage
What are secondary cartilages ?
associated with membranous bone
form later in development
larger cells and less ECM
What are the 3 secondary cartilages associated with the mandible ?
condylar cartilage
coronoid cartilage
symphyseal cartilage
What is the condylar cartilage ?
carrot shaped
enters mandible
continue to grow until 16-20 years
grows via the endochondral growth plate
What is the coronoid cartilage ?
transient and ossified fully before birth
What is the symohyseal cartilage ?
forms mental ossicles
ossified at 1/2 years
What is the mandibular symphysis ?
not true symohyseal joint more like a suture
What is a suture ?
bones connected by fibrous tissue that enables growth and stability
When does the mental protuberance form ?
after puberty
What is a fibrous joint ?
two bones connected by fibres
growth still occurs
little movement- provide stability
Give an example of a fibrous joint ?
PDL
mediates tooth attachmnet between cementum and bone
acts as shock absorber and responds to masticatory and intrusive forces
What is a cartilaginous joint ?
bones connected by cartilage
two types- primary and secondary
What is a primary cartilaginous joint ?
bones joined by cartilage only
costochondral joint
What is a secondary cartilaginous joint ?
fibrous portion in the middle
pubic symphysis- stretch in birth
What is a synovial joint ?
2 bones are articular surfaces
covered with hyaline cartilage in a joint cavity filled with synovial fluid
eg. TMJ
How does the articular disc enter the lateral pterygoid ?
via a tendon
What is the articular disc divided into ?
anterior and posterior bands
intermediate zone - thin
Which types of movements can the TMJ carry out ?
Rotational- horizontal
translational
What is the position of the disc in a closed mouth ?
posterior band is situated above the condyle
What is the position of the disc in an open mouth ?
condyle translates forward
intermediate zone is now the articular eminence
What is the position of the disc in a fully open mouth ?
Anterior band is situated above the condyle
What forms the TMJ ?
mesenchymal cells
How is the TMJ formed ?
12 weeks
2 clefts appear in mesenchyme- form the upper and lower cavities
intervening mesenchyme between the clefts becomes the disc
joint capsule forms from the mesenchymal cell condensation around the joint
How does the articular eminence form ?
after tooth eruption
needed functionally in the mouth when there is teeth present
What is the condyle covered with ?
fibrous tissue - contains progenitor cells that contain chondorcytes for endochondral ossification
What is the mandibular fossa of the temporal bone covered in ?
outer fibrous layer- more fibrous for articulation
inner cellular layer
What are the layers of cells on the condyle ?
under the fibrous layer there is the proliferative layer
hypertrophic zone- Large cells due to excess ECM cartilage production
calcified cartilage
What does the proliferative layer of the condyle allow ?
the cells in the proliferative layer can divide into chondrocytes that produce cartilage allowing condylar growth until 16-20 years.
What is the difference between a developing and adult condyle ?
adult condyle has a reduced proliferative layer
adult condyle has calcified cartilage and fibrocartilage zone
What do the cells of the proliferative layer of the condyle do ?
persist throughout life and can respond to fucntional changes like masticatory stress
What is the basis for orthodontic treatment ?
articualr surfaces can be remodelled via the proliferative layer - excess in young
What are the features of the articular eminence ?
no endochonrally ossified cartilage- fibrocartilage isntead
proliferative layer responds to fucntional changes that induce remodelling
thick layer of fibres cover surface for articulation
What is the synovial membrane ?
lines the capsule
bilayered folds that protrude into the cavity and produce synovial fluid
more folds with pathology and age
What is the purpose of the TML ?
prevents posterior, inferior, lateral and medial displacement
How does TMJ dislocation happen ?
in the forward direction
condyle slips over and past the articular eminence
What are the attachment of the temporalis ?
from the temporal fossa to the coronoid process and the ramus of the mandible
What can cause bruxism lead to ?
jaw pain
What can epileptic seizures cause ?
rupture the tendon between temporalis and coronoid
What are the attachments of the masseter ?
from the zygomatic arch to the angle of the mandible and ramus
What are the attachments of medial pterygoid ?
superficial head from maxilalry tuberosity to the ramus
deep head from the spine of sphenoid to ramus
What are the attachments of lateral pterygoid ?
superior head from the GWS to the neck of the condyle and joint capsule
inferior head from lateral pterygoid plate to condylar neck and TMJ capsule
What is the TMJ innervated by ?
CN V
Which nerve types innervate the TMJ ?
free nerve endings
ruffinis corpuscles
golgi tendon organs
pacini
What is the function of the free nerve endings in the TMJ ?
widely distributed to sense pain and allow joint protection
What is the purpose of ruffinis corpuscles ?
encapsualated
joint cpasule
proprioception- joint posture
What is the purpose of golgi tendon organs ?
encapsulated
in joint ligaments
sense extreme joint movements for ligament protection
What are pacicni corpuscles ?
least abundant
encapsualted
associated with joint capsule
sense pressure and vibration
What happens to the mandible in Treacher collins syndrome ?
small mandible - micrognathia
lack of zygoma
What happens to the mandible in pierre robin sequence ?
small mandible
cleft palate
base of tongue too far back
What happens to the mandible in acromegaly ?
large mandible
pituitary tumour- high GH
What is hemifacial microsomia ?
lower half side of face is underdeveloped
facial assymetry
What happens in TMJ disorder ?
pain
dysfucntion
restricted jaw movements
clicking
What are causes of TMJ disorder ?
neurological
musculoskeletal
rhematological
How can facial assymetry be caused ?
ankylosis due to trauma and infection
What is anterior displacement ?
posterior band of disc in front of condyle
bilaminar zone abnormally stretched
What is AP with reduction ?
return to original position leading to popping sound
What is AP without reduction ?
not return to position
grinding sound of AE and condyle
What is eagle stylohyoid ligament ?
elongated styloid process calcified stylohyoid ligament orofacil pain diagnose with CT scan remove styloidectomy
What is endochondral ossification ?
bones are made from a cartilage model
chondorcytes produce cartilage and this is replaced by osteoid from osteoblasts
Where does endochondral ossification take place ?
long bones via the epiphyseal growth plate
mandibular condyle via secondary cartilages
base of the skull- synchondrosis
What is intramembranous ossification ?
bones are made from osteoblasts that have differentiated from mesenchymal stem cells
Where does intramembranous ossification take place ?
facial bones
flat skull bones
mandible
maxilla
What is sutural ossification ?
fibrous tissue between bones that allows stability during skull growth
How do endochondral bones develop ?
Perichondrium made from chondrocytes derived from mesenchymal stem cells
Makes the cartilage model
perichondrium in the diaphysis makes osteoblasts- periosteum
produce a collar of bone - cortical bone
cartilage begins to calcify
blood vessels invade cartilage and introduce osteoblasts and osteoclasts- primary ossification centre
bone trabeculae made link to collar bone
Secondary ossification centres made in diaphysis via blood vessel invasion
How is growth in bone length mediated ?
epiphyseal growth plate
How is growth in bone thickness mediated ?
via the periosteum
What is present between the epiphysis and diaphysis ?
epiphyseal growth plate
a cartilaginous growth plate
What are the cellular layers of the epiphyseal growth plate ?
resting chondorcytes proliferating chondrocytes prehypertrophic chondrocytes hypertrophic chondorcytes calcification zone
What are resting chondorcytes ?
reservoir of chondrocytes to replenish dead chondrocytes
What are proliferating chondrocytes ?
chondrocytes are aligned in columns
secrete cartilage matrix
collagen type II
What are prehypertrophic chondrocytes ?
Chondrocytes begin to swell with the increased production of cartilage
collagen type X
What are hypertrophic chondrocytes ?
fully matured chondrocytes that eventually die via apoptosis
What happens in calcification zone ?
cartilage matrix is replaced by osteoid
What is a sychondroses ?
cartialaginous joints between bones of the cranial base
What are synchondroses like ?
mirror image of the epiphyseal growth plate
What do synchondroses allow ?
growth of the cranial base during puberty in all directions
like between the sphenoid and occipital bones
What is the condylar cartilage ?
associated with the intramembranous bone - mediates growth of the condyle - intramembranous bone
What is epiphyseal cartilage ?
mediates growth of the endochondral bonses
How is cartilage formed in epiphyseal growth plate ?
cartilage formed by chondorcyte proliferation, maturation and hypertrophy
How is cartilage produced in the condyle ?
mesenchymal cells respond to fucntional loading and differentiate into chonrocytes
How are chondorcytes aligned in epiphyseal cartilage ?
in columns - allows growth lengthwise in long bones
How are chondrocytes aligned in condylar cartilage ?
randomly- allows growth in a multi dimensional capacity.
What is a suture ?
fibrous joint between 2 skull bones that enables a response to mechanical stress and allows bone growth in response to brain growth
What are the 2 layers of a suture ?
cambrian layer- cellular layer that contians osteoblasts that allow bone growth
capsular layer- more fibrous and contains fibroblasts that provide stabilty
What are the bones of the cranial base ?
ethmoid sphenoid petrous part of temporal basiocciput exoccipital
What are the bones of the face ?
mandible
maxilla
zygomatic
nasal bones
What are the bones of the cranial vault ?
frontal
parietal
temporal
occipital
What is the neurocranium ?
cranial vault and cranial base
surrounds the brain
What is the viscerocranium ?
facial skeleton
surrounds the oral cavity
pharynx and upper respiratory tract
How is the skull base mainly formed ?
endochondral
How are flat bones mainly formed ?
intramembranous
What is the endochondral neurocranium ?
occipital body of sphenoid ethmoid petrous mastoid process
What is the intramembranous neurocranium ?
interparietal part of occipital bone
parietal part of temporal
frontal bone
squamous part of temporal bone
What is the membranous viscerocranium ?
maxillary process squamous part of temporal zygomatic maxilla premaxilla mandible tympanic ring
Which germ layer forms the anterior bones ?
neural crest
Which germ layer forms the posterior bones ?
mesoderm
How is the cranial vault formed ?
5 weeks IU
intramembranous ossification
What are the bones of the cranial vault ?
frontal
parietal
squamous temporal
squamous occipital
How does intramembranous ossification progress in cranial vault ?
ossification progresses until the bones meet at sutures or frontanelles
7 months IU
What are sutures ?
coordinate skull growth in response to brain growth
close in adulthood
What are fontanelles ?
enlarged sutures where 3 or more bones meet
needed for flexibility to pass down the birth canal
variable postnatal closure
What does premature fusion of the sutures lead to ?
craniosynostosis
What is the mechanism of craniosynostosis ?
FGFR2 mutation
premature closure of sagittal or coronal suture
What does premature closing of the sagittal suture lead to ?
scaphcephaly
long narrow skull
cant grow sideways
What does premature closure of the coronal suture lead to ?
bracycephaly
short skull
What is plagiocephaly ?
closure of the coronal suture on one side
How does the cranial base develop ?
endochondral ossification
Describe the development of the cranial base ?
cartilages extend fro the cranial end of the notochord to the nasal capsule
cartilages grow towards each other and fuse at 8 weeks IU to form endochondral bones
What do the occipital scleretomes and parachordial cartialges form ?
basilar part of occipital
condylar part of occipital
What do the hypophyseal and trabecular cartilages form ?
body of sphenoid
What do the trabecular and nasal cartialges form ?
perpendicular plate of ethmoid
crista galli of ethmoid
What do the ala orbitalis and ala temporalis form ?
lesser and greater wings of sphenoid
What does the otic capsule and lateral part of the parachordial cartilage form ?
petrous part and mastoid process of temporal bone
What do the paired nasal cartilages and prechordal cartilages form ?
nasal cavity
What is a synchondroses ?
cartilaginous joint that acts as a growth centre
What is the purpose of synchondroses ?
development and growth influences structure and dimensions of craniofacial skeleton
What are the 3 types of synchondroses in the cranial vault ?
inter sphenoidal synchondroses
spehno-ethmoidal synchondoroses
sphenooccipital synchondroses
When does the intersphenoidal synchondrosis ossify ?
7 months IU
When does the sphenoethmnoidal synchondrosis form ?
7 years
When does sphenoccipital synchondrosis form ?
13-17 years at age
Where does ossification start in the mandible and maxilla at 7 weeks IU ?
mandible- branching of the mental and incisive nerve
maxilla- primary canine
ossification spreads rapidly
meckels cartilage starts getting resorbed
What are simple bones ?
formed from ossification of one element
eg. endochondral bone ossifies at malleus
What is a compound bone ?
formed from the fusion of 2 or more ossifying elements
can be both chondral or both intramembranous or mix
What is an example of a compound bone ?
sphenoid bone
body- 2 parts ossify endochondrally
Lesser wing- ossified endochondrally before birth
GWS and Lpt- starts endochondrally and spreads intramembranously
Mpt- intramembranously
What are the parts of the occipital bone ?
supraoccipital
basiooccipital
exoccipital
interparietal
What is different about a foetal head ?
mandible not fused - visible symphysis
large forehead, small face and large eyes
small face as no need for large masticatory apparatu s
Which bones form the hard palate ?
premaxilla
palatal process of maxilla
horizontal plate of palatine bone
What is the importance of understanding craniofacial growth ?
orthodontic treatment is carried out to modify craniofacial growth
facial growth directly influences skeletal relationship of jaws
How does the mandible grow ?
elongation of condyle and ramus in posterior superior direction
body of mandible lengthens
Which skull components grow as a cartilaginous joint ?
synchondroses and condyle
Which skull components grow at sutures ?
cranial vault
nasomaxilalry complex
Which bones grow via bone remodelling ?
all bones
What is relocation ?
bone deposition and formation on oppsing surface of a bone cause bone to drift into space towards the deposition side
What is displacement ?
external forces generated by growing soft tissues
separate bones from each other allowing compensatory bone growth into space
What does nanci say about remodelling ?
size increase if deposition is greater
What is drift ?
equal bone deposition and resorption on oppsing surfaces allows the bone to move into space
What is displacement ?
growth in one location causes the bone to be pushed away
What is secondary displacement ?
relocation of bones that are not growing themselves
What is rotation ?
result of reversed deposition and rotation fields around the central axis
How does the cranial base grow ?
via synchondroses and remodelling
What is a synchondroses ?
cartilaginous joint that acts as a growth centre
What are the 3 synchondroses ?
sphenoccipital synchondroses
sphenoethmoidal synchondroses
intersehnoidal synchondroses
What is the sphenoccipital synchondroses ?
ossifies at 13-17 years
allows cranial base growth
What is the sphenoethmoidal synchondroses ?
ossfies at 7 years
anterior cranial abse growht
When does the intersphenoidal synchondroses ossify ?
at 7 months
What does growth of the spehnoccipital synchondroses influence ?
affects the angle of cranial base
influences facial form
What is a class I relationship ?
orthognathic
What is a class II relationship ?
retrognathic
What is a class III relationship ?
prognathic
What is enlows hypothesis ?
craniofacial development is integrated
What type of head is associated with class II ?
dociocephalic
What type of face is associated with class II ?
leptoprosopic
What leads to a class II ?
cranial base is obtuse
backwards rotation of the mandible
What is the profile of a class II face ?
long narrow head convex profile glabella and supraorbital ridges sloped forehead long and thin nose
What type of head is associated with class III ?
bracycephalic
How is a class III produced ?
angle of the cranial base is acute
forwards rotation of amndible
What type of face is associated with class III ?
euryprosopic
What is the facial profile of class III ?
round and wide space
forehead upright
glabella and supraorbital ridges inconspicuous
short and wide nose
What causes mandibular rotation ?
growth of cervical region of vertebral region displaces the head from the shoulder girdle
growth stretches muscle groups
descent of mandibular symphysis and hyoid bone leads to increased anterior facial growth
posterior facial height increases due to condyle growth
What leads to mandibular rotation ?
extreme anterior or posterior facial growth
What leads to forward rotation ?
excess posterior facial growth
forward rotation of mandible
deep bite and prognathic mandible
What leads to backward rotation ?
excess anterior facial growth
backwards rotation
open bite
retrognathic mandible
What can restore normal occlusion after mandibular rotation ?
dentoalveoalr compensation
mandibular rotation
What is mandibular compensation ?
obtuse angle- backwards rotation
retrognathism can be repaired by growth of ramus- pushes teeth forward- correct predisposition for malocclusion
What is dentoalveolar compensation ?
backwards rotation can result in anterior open bite
mandibular and maxillary incisors grow to compensate
How does the cranial vault grow ?
displacement- skull growth by periosteal bone deposition on both sides of suture to maintain patency
bone remodelling– depostion and resorption occurs on internal and external surfaces to reduce curvature
How does craniosynostosis occur ?
premature fusion of sutures
brain expansions results in excess bone growth in regions of skull that are parallel to prematurely closed suture
What type of head is in sagittal craniosynostosis ?
long and narrow
What type of head is in coronal craniosynostosis ?
bilateral
increases in width
How do the nasomaxillary complexes grow ?
sutural growth
How does the maxilla increase in height ?
due to downwards growth
bone deposition in zygoamtic and frontal sutures
remodelling at alveolar processes
remodelling at hard palate- deposition on internal hard palate and resorption on external palate
How does the maxilla grow in width ?
lateral growth
growth at midpalatal suture
What causes the increase in maxillary length ?
forward growth in maxilla
How does maxillary length increase ?
growth at posterior surface of maxillary tuberosities
backwards growth causes forward displacement
remodelling in area above incisors
What are the characteristics of a newborn mandible ?
smaller and narrower mandible
obtuse mandible angle
no erupted teeth
symphysis still visible
How does the mandible grow ?
forward and downward displacement of mandible
growth of condylar cartilage
bone remodelling of ramus - deposition of posterior ramus margin, resorption on anterior ramus margin
backward and upward growth of mandible
How does the mandible grow laterally ?
lateral growth occurs in complex bone remodelling along lateral and lingual surfaces of condyle, coronoid, ramus and mandible
What are the differences between neonatal and adult skull ?
neonatal face is smaller, large cranial vault and orbits
smaller bones
6 fontanells- close at 18 months
metopic suture still opne
symphyseal suture open - closes at 1/2 yeard
sphenoccipital synchomdroses
What is a female facial profile ?
facial growth stops after puberty flatter and more delicate face overhang of supra orbital ridges prominent zygoamtic bone thinner and less prominent nose
What is a male facial profile ?
facial growth continues into 20s
bulky face wider and longer airwayd
roman nose and greek nose
What is the gonial angle ?
angle of the mandible
What are the 5 parts of the occipital bone ?
supraoccipital
basioccipital
interparietal
exoccipital x 2
What are the feature of cleidocranial dysplasia ?
Malformed tooth roots Hyperdontia Hypertelorism Short cranial base Bracycephalic bulldog Class III no shoulder blades
What causes craniosynostosis ?
FGFR2 mutation
Why is there an increased intercranial pressure in craniosynostosis ?
brain grows and there is not enough space for brain to grow into
impairs mental development
Why is their proptosis in craniosynostosis ?
underdeveloped orbits
shallower orbits
popping eyes
What causes crouzons syndrome ?
FGFR2 mutation
What are the features of crouzons syndrome ?
bicoronal and sagittal synostosis Bracycpehalic short head and short cranial base increase in intracranial pressure Hypoplastic maxilla
What causes aperts syndrome ?
FGFR2 mutation on chromosome 7
What is aperts syndrome ?
crouzons with clawe digits - syndactyly
What is the mutation in Treacher collins syndrome ?
TCOF1
mutation in treacle gene
What are the features of treacher collins syndrome ?
small mandile- class II cleft palate downwards sloping eyes coloboma learning difficulties hearing diffculties
Why are there hearing difficulties in treacher collins ?
first arch structures are affected- malleus and incus
What is hemifacial microsomi ?
underdeveloped side of the mandible
What are the features of hemifacial microsomia ?
small mandible on one side
small ears
narrow eyes
flat maxilla
What are the causes of CL/P ?
classic eratogens
anti epileptics
diazepam
corticosteroids
Which teeth are most likely missing in cleft lip/palate ?
2 and 5
What are dental abnormalities in cleidocranial dysplasia ?
abnormal roots
delayed tooth eruption
What can cleft lip palate surgery lead to ?
severe class III
What is the nasion ?
Where the frontal and nasal bones meet
What is the menton ?
lowest point of mandibular symphysis
What is the gonion ?
the most posterior inferior part of the angle of the mandible
What is the maxillary plane ?
from the ANS to the PNS
What is the mandibular plane ?
from the metnon to the gonion
What is the anterior cranial base ?
from the nasion to the sellla turcica
Which angles of the cephalometrry can be used to estimate skeletal relationships ?
SNB - 78
SNA- 81
ANB - 3
What is the ANB in class I ?
2-4
What is the ANB in class II ?
bigger than 4
What is the ANB in class III ?
less than 2
What is the developmental relationship between mylohyoid and meckels cartilage ?
mylohyoid develops with meckels cartilage
mylohyoid joins mandible to hyoid bone
when meckels cartilage is resorbed it must be transferred to the mandible via the perichondrium
What is the consequence of incomplete removal of MES ?
leads to palatal cysts
reinduced by signals
What happens at 16-20 years to the condylar cartilage ?
converted to fibrocartilage
What is the structure of a synchondroses ?
bilateral epiphyseal growth plate
allows growth in 2 directions
resting chondrocytes in the midline
What does the intersphenoidal synchomndroses connect ?
connects the basisphenoid and the the presphenoid
What does the sphenoccipital synchondroses connect ?
connects the basispehnoid with the basiocciput
What does the sphenoethmoidal synchondroses connect ?
presphenoid and the ethmoid
How does the maxilla grow in width ?
deposition at the mid-palatal suture
Is the maxilla a compound or simple bone ?
it is a compound bone- fusion of premaxill and maxilla
both formed from intramembranous
