Facial Growth II Flashcards
majority of the face derived from
neural crest cells
ectomesenchyme
what regions of the embryo make up the skeleton which the face will develop from
frontonasal process and the maxillary and mandibular processes of the first brachial arch
maxilla and mandible form
intramembranously
2 pre-existing carilaginous skeletons of face
- nasal capsule for the maxilla
- Meckel’s cartilage for the mandible
little remanence by birth
secondary cartilages begin to form in utero (3)
neo natal face Vs adult
not miniature version
infant face is:
- small compared to a large cranium
- face 1/2 heigh of skull, in adults 3/4
- change in length due to height of maxilla
- face 1/2 heigh of skull, in adults 3/4
- eyes are large
- ears are low set
- forehead upright and bulbous
- face appears broad
- nasal region is vertically shallow - nasal floor close to the infraorbital rim

3 sites of facial growth
sutures
synchondroses
surface deposition
sutures
Specialised fibrous joints situated between intramembranous bone
- Each suture is a band of connective tissue which has osteogenic cells in the centre and the most peripheral of these cells provide new bone growth
-
bone deposition at periphery
*
-
bone deposition at periphery

growth at sutures
Growth at the sutures occurs in response to growing structures separating the bone
- e.g. growth of the calvarium in response to development of the brain. Where the bones are pushed apart new bone forms in the suture. In the suture growth occurs in areas of tension.
When facial growth is complete the sutures fuse and become inactive

synchondroses found
found in midline (midsagittal plane)
- exist between the ethmoid, sphenoid and occipital bones

synchondroses growth
A cartilage – based growth centre with growth occurring in both directions. The bones on either side of the synchondrosis are moved apart as growth takes place.
- Cartilaginous growth plate with growth at either end of the plates
New cartilage is formed in the centre of a synchondrosis as cartilage at the periphery is transformed into bone
- bones pushed apart, cartilage is laid down in centre of synchondroses, ossified at its edges

surface deposition growth
New bone is deposited beneath the periosteum over the surfaces of the bother the cranial and facial bones
- In order for bones to maintain their shape as they grow, resorption is also taking place
- This process of deposition and resorption is known as remodelling
The change in position of a bone due to remodelling is known as ‘drift’ (cortical drift)

cranial vault comprised of (4)
frontal
temporal
occipital
parietal
2 ways of growth in cranial vault
- Bone growth at the sutures
- External and internal surfaces are remodelled through surface deposition and resorption to displace the bones radially
- Resorption internal calvarium
- Deposition external

why does the forehead continue to grow after neural growth ceases
to accomondate exapanding air sinuses (pneumatisation)
generally more pronounced in males
when does neural growth cease
7 years
fontanelles exist
where more than 2 bones meet
how mant fotanelles are present at birth
- 6 fontanelles are present at birth and these close by age 18 months.
- Allow skull bones to move slightly in relation to each during childbirth
when do sutures fuse
when facial growth is complete
how does the cranial base grown
synchondroses growth
cranial base composed of (5)
frontal
ethmoid
sphenoid
temporal
occipital

what synchondroses has the most effect on post natal fatal growth
spheno occipital synchondroses
as open for longest time

how does growth occur at synchondroses (2 ways)
endochondral ossification
surface remodelling
timeline for cranial base growth
Half the growth in this area is completed by age 3 years
- spheno-ethmoidal synchondrosis fuses at around 7 years
- spheno-occipital synchondrosis closes at around 13 -15 years in females and 15-17 years in males
- The spheno-occipital synchondroses fuses at around 20 years

what is the relevance of growth of the cranial base
Growth between the ages of 4 to 20 years causes an overall increase in length of the cranial base.
- However, the anterior cranial base is relatively stable after the age of 4 years and so has been used for superimposition in cephalometric analysis.
- This allows the orthodontist to assess skeletal changes due to growth and /or treatment.
- Superimpose sequential lat cephs to see change































