Transcript 04-face,nose, palate..

DEVELOPMENT
OF
FACE , NOSE
AND
PALATE
By
Prof.
Saeed Abuel Makarem
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Development The of Face

The facial
primordia appear
early in the fourth
week around the
primordial
stomodeum
FN
MX
md
MX
md
S
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Five facial primordia
appear as prominences
around the stomodeum

The single frontonasal
prominence

The paired maxillary
prominences

The paired mandibular
prominences
FNP
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
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
The paired facial
prominences are derivatives
of the first pair of
pharyngeal arches
The prominences are
produced mainly by the
proliferation of neural
crest cells.
These cells migrate
from the
Mesencephalon and &
Rhombencephalon
regions of the neural
folds into the arches
during the fourth week
1st
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
The Nasal placodes:

Two bilateral oval thickenings
in the surface ectoderm, of
the frontonasal prominence,
appear, by the end of the
fourth week.

Nasal placodes are the
primordia of the nose and
nasal cavities.
Initially these placodes are
convex.
Later, they are stretched to
produce a flat depression in
each placode.

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
Mesenchyme in the
margins of the placodes
proliferate, producing
horse shoe shaped
elevations called medial
and lateral nasal
prominences

Now the nasal placodes lie
in depression called nasal
pits

These pits are the
primordia of the anterior
nares (nostrils) and nasal
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Mesenchymal cells are the major source of
the connective tissue components, including
muscles, cartilage, bone, and
ligaments in the facial and in the oral
regions.
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The frontonasal prominence
(FNP) is formed of 2 parts:

1- Frontal part: forms the forehead

2- Nasal part: forms the rostral boundary of the
stomodeum.

The paired maxillary prominences form the
lateral boundaries of the stomodeum

The paired mandibular prominences constitute
the caudal boundary of the primitive mouth
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
Facial development occurs mainly between
the fourth and eighth weeks.

By the end of the embryonic period, (8th week)
the face has an unquestionabl human
appearance.
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
Between the 7th and 8th weeks, the two medial
nasal prominences merge with each other and
with the maxillary and lateral nasal prominences
Merging of the medial nasal and maxillary
prominences results in continuity of the upper
jaw and upper lip and separation of the nasal
pits from the stomodeum
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
The lower jaw and lower
lips are the first parts of
the face to form

They result from
merging of the medial
ends of the mandibular
prominences in the
median plane

Median cleft lower lip is
a very rare condition
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
Each lateral nasal
prominence is
separated from
the maxillary
prominence by a
cleft called
nasolacrimal
groove
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
The nasolacrimal duct develops from a
rodlike thickening of ectoderm in the floor
of the nasolacrimal groove

This thickening gives rise to a solid epithelial
cord that separates from the ectoderm and
sinks into the mesenchyme

As a result of cell degeneration, this epithelial
cord canalizes to form the nasolacrimal duct
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
The cranial end of this duct
expands to form the lacrimal
sac

By the late fetal period, the
nasolacrimal duct drains into
the inferior meatus in the
lateral wall of the nasal cavity

The duct usually becomes
completely patent only
after birth

Occasionally, part of the duct
fails to canalize causing
atresia of the nasolacrimal
duct.
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Development of the External Ear

By the end of the fifth week, the
primordia of the auricles of the ears have
begun to develop

Six auricular hillocks form around the
first pharyngeal groove (cleft).

Three on each side of the 1st pharyngeal
groove (cleft).

These are the primordia of the auricle
and external acoustic meatus.
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Initially the ear located in the neck.
As the mandible develops the ears ascend
to the level of the eye.

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Development of The Palate
As the medial nasal prominences merge, they
form an intermaxillary segment
The intermaxillary segment gives rise to:
1- The Philtrum (median part of the upper lip).
2- The Premaxillary part of the maxilla and
associated gingiva (gum).
3- The primary palate.
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Development of Palate
The palate develops from two stages:
Primary palate
 Secondary palate
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Palatogenesis begins at the end of the fifth week and
is completed at twelfth week (5------12 )
The critical period of the palate development is from
the end of the sixth week until the beginning of ninth
week (6 ------ 9)
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Primary Palate

Early in the sixth week the primary palate or median
palatine process begins to develop from the
intermaxillary segment of the maxilla

Initially this segment is formed by merging of the
medial nasal prominences

The primary palate forms the premaxillary part of
the maxilla
It represents only a small part of the adult hard
palate
 (2 Medial nasal prominences >>>>intermaxillary
segment .>>>>>>>>>-primary palate).

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Secondary Palate

The secondary palate is the
primordium of the hard and
soft palate

It begins to develop early in
the sixth week from two
mesenchymal projections
that extend from the internal
aspects of the maxillary
prominences
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 Initially
the lateral
palatine processes or
palatal shelves project
inferomedially on each
side of the developing
tongue
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
As the jaws develop, the
tongue becomes relatively
smaller and moves inferiorly

During the 7th & 8th weeks,
the lateral palatine processes
elongate and ascend to a
horizontal position superior
to the tongue

Gradually these processes
approach each other and
fuse in the median plane
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
Palatine processes also
fuse with the nasal septum
and the posterior part of
the primary palate

The nasal septum develops
as a downgrowth from
internal parts of the
merged medial nasal
prominences

The fusion between the
nasal septum and the
palatine processes begins
anteriorly during the ninth
week and is completed
posteriorly by the twelfth
week
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 Palatal
shelves move medially and
fuse with the nasal septum.
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
Bone gradually develops in the
primary palate, forming the
premaxillary part of the maxilla,
which lodges the incisor teeth
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Concurrently bone extends from
the maxillae and palatine bones
into the lateral palatine
processes to form the hard
palate

The posterior part of these
processes do not ossified.
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They extend posteriorly
beyond the nasal septum
and fuse to form the soft
palate.
 Its soft conical projection
is called uvula
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The median palatine raphe
indicates the line of fusion
of the lateral palatine
processes
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Cleft Lip and Palate

The defect is usually classified according to
developmental criteria
There are two major groups of cleft lip
and palate:

Clefts involving the upper lip and anterior
part of the maxilla

Clefts involving the hard and soft regions of
the palate
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