DEVELOPMENT OF FACE DUHS

							                    LECTURE OUTLINE
                  DEVELOPMENT OF FACE

                          Learning Objectives
  At the end of this lecture, Students should be able to :-
 Know the Developmental stages of Face
 Discuss the congenital Anomalies of face

                           Development of Face
  The developing face is represented by
 the frontonasal region, and
 the first pharyngeal (branchial, visceral) arch.
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              Branchial Apparatus; Components

1) Branchial arches: 6 paired mesenchyme bars
2) Branchial grooves: 5 ectoderm invaginations
3) Pharyngeal pouches: 5 pairs of outpocketings from pharyngeal
   endoderm
4) Branchial membranes: appositional grooves and pouches
• 1st pair of branchial arches → face
• 2nd, 3rd, 4th, 6th pairs → neck




• 2nd arches grow caudally → overlap 3rd, 4th, 6th arches → fuse
  with epicardial ridge → neck
• Clefts 2,3,4 → cervical sinus → disappear
    The developing face is represented by
•   the frontonasal region, and
•    the first pharyngeal (branchial, visceral) arch.
•   Primordia:
•   5 prominences around stomodeum
•   Single frontonasal prominence
•   Paired maxillary prominences
•   Paired mandibular prominences
    Facial Primordia (5) form in fourth wk surrounding stomodeum
     ( primitive mouth)
   five elevations
   Frontonasal prominence
   Maxillary prominence:
   paired, upper branches of first branchial arch
   Mandibular prominence: paired, lower branches of first branchial
    arch
 Removal of the surface ectoderm (some of which remains here)
  in the cranial and cervical region reveals the underlying
  mesenchyme (loosely organized cell populations.)
 The majority of the mesenchyme immediately subjacent to the
  surface ectoderm is derived from the neural crest. Cells of
  mesodermal origin also contribute to the mesenchyme.
Mandibular prominences → lower jaw and lip
Frontonasal prominence (upper part) → forehead
Frontonasal prominence (lower part)
→ nasal placode → medial nasal prominence,nasal pits
                  lateral nasal prominence
 Development of Medial &
   Lateral Nasal Prominences
 Initially these placodes are convex later on they are stretched to
  produce a flat depression in each placode.
 Mesenchyme in the margin of the placodes proliferate producing
  horseshoe shaped elevations.
 Each elevation has two parts, medial and lateral prominences.
 As a result the placode lies in a depression the Nasal Pit.
 These pits are primordia anterior nares and nasal cavities
 Fusion of three Eminences
 Union of the medial nasal prominence,
 lateral nasal prominence and maxillary prominence is required
  for normal development of the upper lip.

 The medial nasal prominences merge in the midline to smooth
  the median furrow.
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 By the 5th week, right and left mandibular prominences fuse to
  form the lower jaws and lips
 By the 6th week, medial nasal prominence merge to give rise to
  intermaxillary segment, which develops into:-
 median portion of the nose
 Premaxillary part of maxilla and its associated gums
 Primary Palate
 the Middle part of upper lip (philtrum)
                     Development of Mandible

 The mandibular process appears initially as a partially divided
  bilateral structure
 It soon merges at the median line.
 This process will give rise to the mandible,
 the lower part of the face and
 the body of the tongue.
Development Of Nose and Palate

   By the 5th week, the nasal placodes develop bilaterally on the
    lower part of the frontonasal process where they border the oral
    cavity.
   At the margins of the placodes, mesenchyme proliferates and
    produces medial and lateral nasal processes thus transforming the
    placodes into nasal pits(nostrils).
   By the 6th week of IU life, The medial and lateral nasal processes
    appear as horse shoe shaped structures with the open end of the
    slit in contact with the oral cavity.
   The point of contact of the epithelial covered medial nasal and
    maxillary processes is termed the nasal fin.
   This vertically positioned epithelial sheet under each nostril
    separates the medial nasal and maxillary processes; and when
    the fin disappears, the lip will fuse.
   On each side, the lateral nasal process is separated from the
    maxillary process by a groove called the nasolacrimal groove.
   This groove will eventually disappear , but before it disappears,
    the epithelium at its depth will canalise , and form the
    nasolacrimal duct
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     Development Of Upper lip and Maxilla
   During the 6th week, the 2 medial nasal processes merge in the
    midline to form the intermaxillary segment.
   This will give rise to the centre of the upper lip, the primary
    palate, and the part of the alveolar process carrying the incisor
    teeth.
   Each maxillary process grows medially and fuses, first with the
    lateral nasal processes and then with the medial nasal process.
   The medial and lateral nasal processes also fuses with each other;
    thus closing the nasal pits to the stomatodeum.




         Development Of Upper lip and Maxilla
 During the 6th week, the 2 medial nasal processes merge in the
  midline to form the intermaxillary segment.
 This will give rise to the centre of the upper lip, the primary
  palate, and the part of the alveolar process carrying the incisor
  teeth.
 Each maxillary process grows medially and fuses, first with the
  lateral nasal processes and then with the medial nasal process.
 The medial and lateral nasal processes also fuses with each other
  ;thus closing the nasal pits to the stomatodeum.

 The mesoderm of the lateral part of the lip is formed from the
  maxillary process. The overlying skin is derived from ectoderm of
  the same process.
 The failure of fusion of medial nasal process with the lateral nasal
  process leads to the formation of cleft lip.
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  Development of Face
 Neural crest cells form the majority of the facial and cranial
  skeleton.
 However, mesodermal cells also contribute to the cranium.
 Derivatives of Frontonasal Prominence
 By the end of 4th week, bilateral oval thickening of the surface
  ectoderm occur on the inefriolateral parts of frontonasal
  prominence, the Nasal Placodes
 these are the primodia of nose and nasal cavities.
 Formation of Upper Jaw & Nasal Primordium
 Contribution of each of the prominences to the face is illustrated
  here:
                  Congenital Malformations
Cleft lip
   • Division of upper lip, unilateral or bilateral;
   • Failure of maxillary prominence to fuse with medial nasal
      prominence on the same side.




Oblique facial cleft
  • Division extending from the upper lip to medial margin of orbit;
  • Failure of maxillary prominence to fuse with lateral nasal
     prominence on the same side.
Cleft palate

  • Failure of lateral palatine process to fuse with each other or with
    median palatine process.

  • Unilateral or bilateral, complete or incomplete, with or without
    cleft lip.




                                               Cervical cyst and fistula

      Failure of closure of cervical sinus(cyst), may connect to
       surface or pharynx(fistula);

      Cyst on lateral side of neck along anterior border of
       sternocleidomastoid muscle.
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