Development of face and palate

1. DEVELOPMENT
OF
FACE AND
PALATE
DeepashreePaul
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DEEPASHREE PAUL

2. Introduction
Embryology
Theories of Development of face
Development of face
Development of palate
Developmental Anomalies
How did the face evolve?

3. INTRODUCTION
Adequate information is required on
general embryology to explain the
development of the head, particularly the
structures in & around the mouth. It builds
the background for understanding the
origins of the tissues associated with facial
& dental development.
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4. BLASTOCYST
“after 4-5
days of
fertilization”
EMBRYOBLAST
.
AMNIOTIC CAVITY FORMATION
on 9th
day of fertilization
Primitive Yolk Sac
Blastocysts
Inner Layer Outer Layer 2
layer embryo (trophoblast)
a) ecto
b) endo

5. Primitive streak
+ Germ layer
Notocord

6. The most typical feature in the development of the head & neck is
formed by the branchial or pharyngeal arches. These arches appear
in the 4th
& 5th
weeks of development & contribute greatly to the
characteristic external appearance of the embryo.Initially they consist
of bars of mesenchymal tissue separated by deep clefts (pharyngeal
clefts).
Pharyngeal arches contribute to the formation of face . At the end of
4th
week , the center of the face is formed by the stomodeum ,
surrounded by the first pair of pharyngeal arches.
(LANGMAN’S MEDICAL EMBRYOLOGY)

7. • Oral development in embryo is demarcated extremely early
in life by the appearance of the prechordal plate (14th
day)
Endodermal Thickening
Oropharyngeal Membrane
• Facial development occurs mainly between the fourth and
eighth weeks.
• After 5th
week of development proliferetion of FNP slows
down & maxillary, mandibular,lateral nasal process start
growing rapidly
• By the end of the embryonic period, (8th
week) the face has an
unquestionable human appearance!
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8. Primitive node
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9. Formation of frontonasal process
• Embryonic disc undergoes folding at the cranial (head fold)
and caudal (tail fold) ends.
• Then the gut is closed cranially by prochordal plate which is
called buccopharyngeal membrane.
• The stomatodaeum (future mouth) is a depression bounded
cranially by forebrain bulging and caudally by pericardial
cavity.
• The mesoderm covering the developing forebrain
proliferates, and forms a downward projection overlapping
the upper part of stomatodaeum. This projection is called
frontonasal process.
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11. THEORIES OF DEVELOPMENT
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Theory of His (Dursey & His)
Fusion of facial processes
Central region of face is site of
union of the processes
Once epithelial contact is
established, penetration by
mesoderm occurs to complete
fusion
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Theory of mesodermal penetration/
Stark Theory
Free end facial processes do not exist
Central face composed of bilamellar membrane of ectoderm
(primary plate/epithelial wall) into which mesenchyme migrates
Caudal to stomodeum (lower face & neck), branchial arches (ecto,
meso & endoderm)
Craniofacial mesoderm later augmented by neuroectoderm
brought in by migrating neural crest cells
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Neural crest cell theory (Johnston)
Cells arise from dorsolateral surface of neural tube & migrate
beneath ectoderm to form a continuous layer that supplements
underlying mesoderm
Facial skeleton derived from NC cells
Failure of penetration by neuroectoderm  epithelial wall breaks 
facial cleft
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Developmental field reassignment
theory/Neuromeric theory
Neural tube conceived as a series of developmental zones or
neuromeres
Each of these neuromeres are defined by a unique overlap of
genetic coding called unique “barcode” to form the
mesoderm & endoderm of the embryo
The migrating neural crest cells then instruct to differentiate
into the appropriate facial tissues by genetically determined
“fields” with defined cellular content and a fixed position.
This system permits the “mapping” of the face into
developmental zones with distinct spatial origins in their
precursor tissue units
Tessier’s classification based on this map.
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16. The genetic control of the early
development of the face guided by some
sequential events…..
Ectodermal cells covering forebrain
Synthesis of retinoic acid
Maintain signals of FGF-8 & shh Neural crest cells
Frontonasal
process
+ (Migration by WNT gene)

17. ORGANIZING CENTRES
• Development of the face depends upon
inductive activities of 2 organizing centers
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-- Prosencephalic
-- Rhombencephalic

18. ORGANIZING CENTERS
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19. Prosencephalic organizing center
-- Derived from prechordal mesoderm
that migrates from the primitive streak.
-- Situated at the rostral end of the
notochord below the fore brain.
Induces the formation of :
 Visual apparatus
 Inner ear apparatus
 Upper third of face
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20. Rhombencephalic organizing center
• -- Caudal in relation to the Prosencephalic
centre.
Induces the formation of:
-- Middle and lower third of the face.
-- Middle and external ears.
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21. BRANCHIAL ARCHES
The tissues bordering
the oral pit inferiorly
and laterally develop
into five or six pairs of
bars which form the
lower part of the face
and neck. These bars are
termed branchial
arches.

22. The first four branchial arches are well developed in humans.
Only the first and second arches extend to the midline, and each
arch is progressively smaller from first to the last.
The mandibular branchial arch is the first to develop. It is
located just below the stomodeum.
The hyoid is the second arch to develop.
The IIIrd, IVth and Vth arches consist of paired bars of
epithelium covered mesoderm which are divided in the midline
by the developing heart.

23. SL.N
o
Pharyngeal
arch
Nerve Muscles Skeleton
1. I Mandibular
arch
Mandibular
N.
Tensor tympani,
tensor palati,
muscles of
mastication,
mylohyoid,
anterior belly of
diagastric
MAXILLA,
MANDIBLE,
zygoma,
temporal bone,
part,MECKEL’s
cartilage,
sphenomandibul
ar lig.,ant.lig.of
malleus
2. II Hyoid arch Facial N. facial
muscles,auricular
muscle,platysma,
posterior belly of
diagastric,
stylohyoid,
Stapes,
styloid process,
stylohyoid lig.,
lesser horn &
upper body of
hyoid

24. Sl.no. Pharyngeal
arch
Nerve Muscles Skeleton
3. IIIrd arch Glossopharyngeal N. Stylopharyn
geus
Greater
horn &lower
body of
hyoid
4.
IV th arch Superior laryngeal Muscles of
pharynx
Laryngeal
cartilages
5 VI th arch Recurrent laryngeal Soft

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26. 3rd
week: oropharyngeal membrane
End of 4th
week: nasal placodes, maxillary and mandibular
processes
5th
week: lateral & medial nasal process
6th
week: primitive palate, primitive skull
7th
week: Upper lip, philtrum, tip of nose, primitive
cheeks, eyelids
6-8 week: secondary palate
CALENDER OF DEVELOPMENT OF
FACE

27. DEVELOPMENT THE OF FACE
• The facial primordia appear
early in the fourth week
around the primordial
stomodeum
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28. Five facial primordia
appear as prominences
around the stomodeum
• The single frontonasal
prominence
• Paired maxillary
prominences
• Paired mandibular
prominences
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FNP

29. • TheThe Nasal placodesNasal placodes::
• Two bilateral oval thickenings
in the surface ectoderm, of the
frontonasal prominence,
appear, by the end of the
fourth week.
• Nasal placodesNasal placodes are the
primordia of the nose and nasal
cavities.
Initially these placodes are
convex.
• Later, they are stretched to
produce a flat depression.
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31. 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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32. • 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 (future anterior nares)
from the stomodeum.
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33. • 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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34. • Each lateral nasalEach lateral nasal
prominence isprominence is
separated fromseparated from
the maxillarythe maxillary
prominence by aprominence by a
cleft calledcleft called
nasolacrimalnasolacrimal
groovegroove
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35. • 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
• By the late fetal period, the nasolacrimal duct drains into
the inferior meatus in the lateral wall of the nasal cavity
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36. FORMATION OF UPPER & LOWER
LIP
• The maxillary process grows medially and approaches the
lateral and medial nasal processes but remains separated
from them by distinct grooves(the naso-optic groove and the
bucco-nasal groove).
• The medial growth of the maxillary process pushes the medial
nasal process toward the midline, where it merges with its
anatomic counterpart from the opposite side.

37. • In this way the upper lip is formed from the maxillary
process of each side and the medial nasal process with
fusion occuring between the forward extend of the
maxillary process (globulomaxillary process).
• The lower lip is formed by merging of the two streams
of ectomesenchyme of the mandibular processes.

38. DEVELOPMENT OF EYE
• The eyes develop during the 5th
week.
• The first external sign of eye development is the
appearance of the lens placodes between the maxillary
and frontonasal processes at the lateral sides of the face.

39. • The lens placode sinks below the surface and is eventually
cut off from the surface ectoderm.
• The developing eyeball now presents as a bulge facing
laterally. With the narrowing of the frontonasal process,
they come to face forwards.
• The eyelids are derived from folds of ectoderm that are
formed above and below the eyes, and by mesoderm
enclosed within the folds.

40. 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.
• Initially the ear located in the
neck.
• As the mandible develops the ears
ascend to the level of the eye.
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41. Development of Palate
The palate develops from two stages:
• Primary palate
• Secondary palate
• 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 endend of the sixth week until the beginningbeginning of ninth
week (6- 9)
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42. Primary Palate
• Early in the sixth week the primary palate or median
palatine process begins to develop from the
intermaxillary segment of the maxilla
• The primary palate forms the premaxillary part of
the maxilla
• It represents only a small part of the adult hard
palate
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43. 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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44. •Initially the lateral
palatine processes or
palatal shelves project
inferomedially on
each side of the
developing tongue
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45. • 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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46. • 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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48. •Palatal shelves move medially and
fuse with the nasal septum.
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50. DEVELOPMENTAL ANOMALIS
CRANIOFACIAL ANOMALIES-
• Cleftslips& palate
• Obliquefacial cleft
• Median cleft lip
• Microstomia
• Macrostomia
• Mandibular cleft

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52. Evolution of face
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54. THANK YOU
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