Download Development of the Face

Development of face and oral Cavity
Development of the face
Formation of the face
Both the frontonasal process and the branchial
arches play a large
part in the formation
of the face and the
oral cavity.
Frontonasal prominence
Nasal placode
Maxillary process
1. Pharyngeal arch
(mandibular)
2. Pharyngeal arch
(hyoid arch)
3. Pharyngeal arch
4. And 6. Pharyngeal arch
Developing heart
Formation of the face
The face derives from five prominences that surround the
stomodeum.
The prominences are:
•
the single median frontonasal
prominence and
•
the paired maxillary prominences
•
and mandibular prominences;
(derivatives of the first
pharyngeal arch)
Formation of the face
Tissues from the mandibular arches form all the lower
face and most of the midface while the other
pairs of arches, including branchial grooves and
pharyngeal pouches, are involved mainly in the
formation of the neck region.
Formation of the face
The frontonasal prominence is the
largest and is composed of an
upper frontal and a lower nasal
portion.
In the fourth week, within 3 to 4 days,
two oval ectodermal thickenings,
the nasal placodes, appear
bilaterally, located on the nasal
process.
Formation of the face
The mesenchyme beneath the
ectodermal thickenings rapidly
proliferate, causing a tissue
elevation around the placodes.
Each nasal placode possesses an
outer lateral nasal and an inner
medial nasal swelling.
Formation of the face
In the fifth week, the lateral and medial nasal swellings
enlarge rapidly, with the medials advancing toward
one another and eventually fusing.
Formation of the face
The maxillary prominence is dimensionally not
impressive early in development.
With medial growth of its terminals and broadening of
its other borders, the maxillary
prominence presses onto the
nasal swellings forcing their
medial and lateral arms closer
together.
Formation of the face
During the following week, the medial and lateral
nasal swellings unite and merge with the maxillary
process.
The line of fusion of the maxillary
process with the lateral nasal
swelling is marked by a trough,
the nasolacrimal groove.
Formation of the face
The union of the medial nasal swellings
forms the intermaxillary process of
the maxillary arch.
The intermaxillary process produces:
•
the philtrum of the lip,
•
the segment of the maxilla bearing
the incisor teeth, and
•
the primary
palate.
Fused
palatal
process
Formation of the face
The lateral nasal prominences give rise to the wings
or alae of the nose.
The medial nasal processes produce the inferior
segment of the nasal septum.
Formation of the face
By the end of the fourth week, the two mandibular
prominences have grown towards one another and
merged.
The mandible, the lower lip, the lower portion of the
cheek, the chin, and the gingiva take their origins
from the mandibular prominences.
The maxillary process gives rise to the lateral portions
of the upper lip and cheeks, the maxilla, and the
secondary palate with its associated gingiva.
Formation of the face
A = Maxillary process
B = Mandibular process
C = Medial nasal process
D = Lateral nasal process
Development of face and oral Cavity
Development of the palate
Formation of the palate
The formation of primary palate is a contribution of
the fusion of medial nasal processes.
The secondary palate originates
from lateral palatine processes,
a ledge like outgrowths of the
maxillary process
Formation of the palate
These lateral palatine processes make their
appearance in the sixth week of development.
Early in their formation, they are located along the sides
of the developing tongue.
Indication of initiation of tooth development is also
visible (dental lamina).
Formation of the palate


Another view of the same situation.
The lateral palatine processes are situated besides
developing tongue.
Formation of the palate
Later as the tongue takes a deeper position in the
primitive oral cavity, the palatine processes rise and
grow toward each other.
Formation of the palate
By the eighth week, the lateral palatine processes fuse
with each other as well as with the primary palate and
nasal septum.
These fusions complete the
formation of the ceiling of
the oral cavity and the floor
of the nasal cavity.
The nasal septum separates
the right and left passages
of the nose.
Formation of the palate

Fused palatine processes.
Development of face and oral Cavity
Development of the tongue
Formation of the tongue

The tongue is a muscular
organ composed of:
 an anterior movable part,
termed the body, and
 the posterior firmly
attached base/root or
branchial part.
Formation of the tongue


The tongue originates from the first, second, and
third pharyngeal arches and from a migration of
muscles from the occipital somites.
The anterior part arising
from the first arch is formed
from three masses, the two
lateral lingual swellings and
the tuberculum impar.
Formation of the tongue


These lateral lingual swellings rapidly enlarge,
merge with each other, and overgrow the
tuberculum impar to form the oral part of the tongue.
An U-shaped sulcus develops in front of and on
both sides of this oral part, which allows it to be free
and highly mobile, except at the region of the lingual
frenulum where it remains attached to the floor of
the mouth.
Formation of the tongue
The root of the tongue develops mainly from the third
pharyngeal arch.
Initially it is indicated by a midline elevation that appears
behind the tuberculum imper, which is a large
branchial eminence of the third and fourth arches
(hypobranchial eminence).
Later this eminence
overgrows the second
pharyngeal arch, to
become continuous with
the body of the tongue.
Formation of the tongue
The site of union between the base and the body of the
tongue is delineated by a V-shaped groove called the
sulcus terminalis.
Development of face and oral Cavity
Development of the mandible
Development of the mandible
The basic growth pattern of the mandibular body and
condyle appeared in week 7 of fertilization.
Histologically, the embryonic mandible originated in
the lower part of the first branchial arch from primary
intramembranous ossification in the fibrous
mesenchymal tissue around the Meckel's cartilage.
Development of the mandible
Development of the mandible
Before the begin of ossification the mandibular nerve
and its branches are developed and they ensure the
formation of canals around them.
From this initial ossification, the ramifying trabecular
bones developed forward, backward and upward, to
form the symphysis, mandibular body, and coronoid
process, respectively. (following the path way of the
incisive and the inferior alveolar nerve)
Development of the mandible
Development of the mandible
The accessory cartilages are:
• the condylar cartilage
• the coronoid cartilage
• the symphysial cartilage
Development of the mandible
The condylar cartilage is the largest and most
important one. It appears in the 12th week i. u. and is
quickly replaced by enchondral ossification.
A thin layer of cartilage remains in the condylar head
and persists until the 20
years of life providing
a mechanism of mandibular
growth.
Growth of the mandible
The shape and size of the mandible undergo
considerable transformation from embryonic to adult
mandible.
Growth of the mandible
The mandible grows in all directions:
• Anterio-posterior by bone deposition along the
posterior border of the ramus.
• Vertical by growth of the condyle, along the upper
border of the ramus and the formation of the alveolar
process.
‫صورة‬
• Transverse by bone deposition on the external
surface and bone resorption at the inner surface.
Development of the mandible
The alveolar bone formation begins as the teeth
reach the early bell stage.
The bone begins to grow around the tooth germs and
upward in occlusal direction.
Later this area is called alveolar bone and is divided
into alveoli by septa.