Saeed Abuel Makarem

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        Development The of Face
   The facial primordia
    appear early in the
    fourth week around              FN
    primordial stomodeum
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    Five facial primordia
    appear as prominences
    around the stomodeum:

   The single frontonasal           FNP

   The paired maxillary

   The paired mandibular
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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.                       1st
 These cells migrate from
  lower Mesencephalon
  and upper
  regions of the neural folds
  into the arches during the
  fourth week

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     By the end of the fourth week,
    in the frontonasal prominence,
    a bilateral oval thickenings in
    the surface ectoderm, form the
       nasal placodes

  Nasal placodes are the
 primordia of the nose and nasal
 Initially these placodes are
 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

   Now the nasal placodes lie
    in depression called nasal

   These pits are the primordia
    of the anterior nares
    (nostrils) and nasal cavities

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These 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 of the (FNP) forms the forehead

   2- Nasal part of the (FNP) 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 unquestionably human

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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         M

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    Each lateral nasal
    prominence is
    separated from
    the maxillary
    prominence by a
    cleft called

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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

   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

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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.

   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 or 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 primordia:

 The primary palate
 The secondary palate

   Palatogenesis begins at the end of fifth week and is
    completed at twelfth week (5------12 )

The critical period of 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
 (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

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          the lateral
 Initially
 palatine processes or
 palatal shelves project
 inferomedially on each
 side of the developing

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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
 The fusion between the
  nasal septum and the
  palatine processes begins
  anteriorly during the ninth
  week and is completed
  posteriorly by the twelfth

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        shelves move medially and
 Palatal
 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

   Concurrently bone extends from
    the maxillae and palatine bones
    into the lateral palatine
    processes to form the hard

   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

   Its soft conical projection
    is called uvula

   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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