PRENATAL GROWTH AND
DEVELOPMENT OF CRANIAL AND
FACIAL REGION
DR. ZUBER AHAMED NAQVI
Preclinical orthodontics
Objectives
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Prenatal growth of cranial base
Chondro-cranial ossification
Prenatal embryology of maxilla
Prenatal embryology of palate
Prenatal embryology of mandible
Prenatal growth of cranial base
• Earliest evidence of
cranial base formation4th -8th week of
intrauterine life.
• A capsule is formed
around the brain called
ectomenix or
ectomeningeal capsule.
• Basal portion of this this
capsule gives rise to
future cranial base.
• 40th day onwards this
ectomeningeal capsule
is converted into
cartilage.
• Chondrofication occurs
in 4 regions.
• Parachordal (4)
• Hypophyseal
• Nasal (1)
• Otic (5)
CHONDRO-CRANIAL OSSIFICTION
• Base of cranial base
undergoes both
endochondral as well as
intramembranous
ossification.
• ENDOCHONDRAL
OSSIFICATION- in this type
of osteogenesis the bone
formation is preceded by
formation of a cartilaginous
model that is subsequently
replaced by bone.
• INTRAMEMBRANOUS
OSSIFICATION- in this
type of ossification, the
formation of bone is not
preceded by formation
of a cartilaginous
model.
• Bone is laid down
directly in a fibrous
membrane.
CHONDRO-CRANIAL OSSIFICTION
ENDOCHONDRAL OSSIFICATION
INTRAMEMBRANOUS OSSIFICATION
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• Occipital bone
• Temporal bone
• Sphenoid bone
Occipital bone
Temporal bone
Ethmoid bone
Sphenoid bone
Prenatal embryology of maxilla
• At 4th week of intrauterine
life , five brachial arches
form in the region of future
head and neck.
• Each of these aches gives
rise to muscles, connective
tissue, vasculature, skeletal
components and neural
components of face.
Mandibular arch
• The first brachial arch is
called the mandibular
arch and plays an
important role in the
development of the
naso-maxillary region.
• Mesoderm covering the developing brain proliferates and
forms a downward projection that overlaps the upper part of
stomatodaeum – frontonasal process.
• Mandiblar arch gives a bud on its dorsal surface – forms the
maxillary process
• The ectoderm overlying the frontonasal process s shows
bilateral localized thickenings – nasal placodes
• Nasal pits divides the frontonasal process into two parts– Medial nasal process
– Lateral nasal process
• The mandibular process
grow medially and fuse to
form the lower lip and
mandible .
• The line of fusion of the
maxillary process and the
medial nasal process
corresponds to the nasolacrimal duct.
DEVELOPMENT OF PALATE
• Palate is formed by the
contributions
of the –
1. Maxillary process
2. Palatal shelves given off by the maxillary process
3. Frontonasal process.
DEVELOPMENT OF PALATE
Fronto-nasal process gives
rise to the premaxilla while
the palatal shelves forms
the secondary palate.
Initially developing palatal
shelves grow vertically
downward towards the floor
of the mouth.
Around 7th week of
intrauterine life they
change growth from vertical
to horizontal.
If fails- cleft lip and palate
Around 8 ½ week of
intrauterine life the two palatal
shelves fuse and form
secondary palate.
OSSIFICATIONFrom 8th week of intrauterine
life.
Intramembranous type .
Most posterior part of palate
does not ossify and forms soft
palate.
Mid palatal suture ossifies by
15 years of age in most cases.
PRENATAL EMBRYOLOGY OF MANDIBLE
• Mandibular arch forms the
lateral wall of stomodaeum.
• Mandibular processes grow
towards and fuse in the
midline.
• They form the midline lower
border of the stomodeum
i.e. the lower lip and the
lower jaw.
Meckel’s cartilage
• It extends from the cartilaginous otic capsule to the midline or
symphysis and provides a template for guiding the growth of the
mandible.
• A major part of the Meckel's cartilage disappears during growth and
the remaining part develops into the following structures which are
called as remnants of Meckel's cartilage1. Anterior ligament of malleus.
2. Mental ossicles.
3. Incus and malleus.
4. Spine of sphenoid bone.
5. Spheno-mandibular ligament.
(A MISS)
Ossification
• A single ossification center
for each half of the
mandible arises in the
region of the bifurcation of
the inferior alveolar nerve
into mental and incisive
branches.
Ossification of mandible
• Ossification spreads
below and around the
inferior alveolar nerve
and its incisive branches
and upwards to form a
trough for
accommodating the
developing tooth buds.
Ossification
• Intramembranous ossification spreads dorsally and ventrally
forms the body and ramus of the mandible.
• Endochondral ossification is seen at 3 regions of mandible1. The condylar process.
2. The coronoid process.
3. The mental region.
References
• Enlow: Handbook of facial growth.
• Graber TM: Orthodontics: Principles and
Practice.