6. Development of face and assoc. structures

Osteoclasts

resorb bone, leaving a space which is filled by trailing osteoblasts

Osteoblasts

create a cement line (non collagenous proteins) and lay new bone onto it

Gradual replacement of bone

allows for it to be structurally functional and growin at the same time

Cutting cone vs filling cone

refers to the process in bone remodeling where the cutting cone encompasses osteoclast activity to resorb old bone, while the filling cone is associated with osteoblast activity to deposit new bone.

facial development begins from the

outgrowth of the frontonasal prominence

which arches are primarily involved in development of the face

first, second, and third

Palatine fusion

epithelial layers fuse and breaks up the BM so mesenchymal tissues of each begin to grow together

What happens to the stranded like epithelial cells that get trapped inside growing mesenchyme during fusion

they turn into fibroblast like cells (rare transition from epithelial to mesenchymal)

Central face development is going to begin at

week 4-5 (after pharyngeal arches appear)

Nasal (olfactory) placodes

develop through a thickening of the ectoderm at the ‘front’ of the frontonasal process that turn into the nasal pits and subsequently the nasal cavities.

Proliferation of ectomesenchyme on both sides of each nasal placode

results the development of both a medial nasal process and a lateral nasal process which swell outwards

The maxillary process grows

medially to approach both nasal processes

Maxillary process is separated from med/lat nasal processes by what

1)naso-optic groove (lateral)

2)bucconasal groove (medial)

naso-optic groove

is a depression that separates the maxillary process from the lateral nasal process during facial development.

bucconasal groove

is a depression that separates the maxillary process from the medial nasal process during facial development.

Both the naso-optic groove (lateral) bucconasal groove (medial) end up

fusing as they merge with the maxillary process

Lower lip forms through

mesenchymal expansion

intermaxillary process

The lower part of the medial nasal process is called

philtrum

Both halves of the median nasal process are going to merge and create the groove on the upper lip

Primary (where incisors are) palate

formed from merging of arch 1 and median nasal process

what forms the nasolacrimal duct

epithelium along the floor of the naso-optic groove detaches and forms a ‘cord’ which is surrounded by mesenchymal tissue as the groove is obliterated

Which groove contributes to the nasolacrimal duct

the naso-optic groove

Cleft lip is commonly caused by which groove

bucconasal groove

During early development of the upper face, what structures will eventually give rise to the teeth

two ‘primary epithelial bands (odontogenic)

Pre-maxilla is another phrase for

primary palate

the superior epithelium forms the future

nasal epithelium

the inferior epithelium forms future

oral epithelium

Fully fused palate is called

definitive palate

The secondary palate

forms behind the primary palate

90% of the definitive palate is formed from the

secondary palate

The formation of the secondary palate starts around

7-8 weeks and continues until around 12 weeks.

2 main contributers of secondary palate formation

nasal septum
both palatine shelves

How does separation of the oral cavity occur

the nasal septum fuses with the palatine shelves at the midline and then continuing posteriorly

Cleft lip occurs around

7-10 per 10,000 births

Cleft lip is from defective fusion of

the medial nasal process with the maxillary process

80% of cleft lip cases are

unilateral

cleft lip repair ruke of thumb

rule of 10: 10 weeks, 10 lbs, 10 gm %HM

cleft lip is more common in

males

Cleft palate occurs in

5-6 per 10,000 births

cleft palate occurs from failure of fusion of

palatal shelves to fuse

minimal manifestation of cleft palate is

bifid uvula

Cleft palate alone is more common in

females

Cleft palate repair

around 1.5 yrs because it is extremely invasive

What percent of clefting cases are both lip and palate

45% more common in males

Syndromic cleft cases

are associated with additional congenital abnormalities

Non syndromic clefting: environmental

maternal alcohol/cigs
Folic acid def
Corticosteroid use
Anticonvulsant therapy

____ of pts with CL + CP have an associated syndrome of some kind

30%

_____of pts with cleft palate only (CPO) have an associated syndrome

50%

Lateral facial cleft

Lack of fusion of the maxillary and mandibular processes resulting in a cleft extending from the mouth into the cheek region.

Most common facial cleft

lateral facial cleft

Oblique facial cleft

Failure of fusion of the lateral nasal processes with maxillary process resulting in a cleft that extends from the upper lip, through the nose, to the eye

Oblique facial cleft is almost always associated with

CP

Median cleft of the upper lip

A rare type of facial cleft resulting from the failure of fusion of the medial nasal processes, typically characterized by a cleft extending through the middle of the upper lip.

Rarest facial cleft

median cleft of upper lip

•One of the most common major congenital defects

clefting

clefting prevalence

more common in native americans and asians

CL + CP is more common in

males

submucous palatal cleft

Surface is intact, but defect exists in the underlying musculature of the soft palate

Neurocranium

The Brain Pan (basically the bones encasing the brain)

Calvaria

What we might call the ‘top’ or ‘skull cap’

Origin of calvaria

paraxial mesoderm and neural crest in origin

Another name for calvaria

desmocranium

Cranial base

The base of the skull

Cranial base is derived from

special sense organ capsular tissues

Cranial base tissue origin

•Endochondral bone, primarily neural crest

Early form of cranial base

chondrocranium

Facial Skeleton

viscerocranium

viscerocranium

Pharyngeal arch derived, consists of what we consider the face (anterior, lower skill)

Maxilla proper

intramembranous ossification of mesenchyme, forms from Maxillary prominence/process

intramembranous ossification

a process by which bone develops directly from mesenchymal tissue, no cartilage first

Premaxilla

intramembranous ossification of mesenchyme, forms from frontonasal process, forms primary palate, fuses early with maxilla proper

Since the maxilla doesn’t have meckel’s cartilage (like mandible) what does it use to get the condensation signals

cartilage of the nasal capsule provides much of the signal for the condensation of the mesenchyme and development of bone

Primary displacement of maxilla

maxilla itself is growing and pushing outward

Secondary displacement of maxilla

zygomatic and nasal septum cartilage grows which pushes to maxilla outwards

Maxilla formation uccurs along the path of

the anterosuperior dental nerve as it branch from the inferior orbital nerve, ultimately forming the canal the nerve sits in

anterosuperior dental nerve

branch from the inferior orbital nerve that supplies sensation to the upper teeth and maxilla.

The alveolar plates form from the

maxilla and the junction of the palatal process to house the tooth germs

Most of the hard palate is formed from

Ossification from the developing maxilla also spreads to the palatine process

Is maxillary growth terminated after birth

no a lot of post natal development occurs

Mandible forms

by intramembranous ossification lateral to meckel’s cartilage

Ossification of the mandible spreads

posteriorly to form body and ramus

What happens to meckel’s cartilage

largely disappears anteriorly

Secondary / accessory cartilages

condylar, coronoid and symphyseal

Secondary / accessory cartilages form from

Meckel’s cartilage at ~ 10-14 weeks of development.

Condylar cartilage is important for what

it expands into a cone running along the ramus and ossifies through endochondral ossification.

Condylar cartilage remains at the

articular ends on the head

the mandible is both

membranous and endochondral in nature

so does the mandible endochondrally develop from meckels cartilage

No, it endochondrally develops through condylar cartilage which is a derivative of meckel’s cartilage

coronoid cartilage disappears

pre-birth

symphyseal cartilages (2) disappear

in the first year of birth

Condyle cartilage is an important growth center for the

ramus, driving intramembranous ossification, and then ossifies itself through endochondral ossification

Condyle cartilage functions both in

articulation at TMJ and in growth