55. Development of The Palate

  1. The palate: development begins during week 5, but fusion of its component parts is not complete until week 12. The palate forms from 2 major parts: the primary and secondary palates
    1. THE PRIMARY PALATE OR MEDIAN PALATINE PROCESS develops from the innermost or ventral portion of the intermaxillary segment of the upper jaw at the end of week 5. The segment is covered with ectoderm
      1. The intermaxillary segment is formed by merging of the medial nasal prominences
      2. The segment forms a wedge-shaped mesodermal mass between the maxillary prominences of the developing upper jaw
    2. THE SECONDARY PALATE develops from 2 horizontal mesodermal projections called the lateral palatine processes or palatine shelves, formed on the inner surfaces of the maxillary prominences which appear in week 6
      1. They project obliquely downward on each side of the tongue, but as the jaw develops, the tongue moves down and the lateral palatine processes grow toward each other and fuse
        1. They also fuse with the primary palate and the nasal septum, the latter developing as a downward growth from the merged medial nasal prominences
      2. Fusion begins anteriorly in week 9 and is completed posteriorly by week 12
    3. MEMBRANE BONE develops in the primary palate, forming the premaxillary part of the upper jaw and carrying the incisor teeth
      1. At the same time, bone extends into the lateral palatine processes to form the hard palate
      2. The posterior portions of the lateral palatine processes do not become ossified, but extend past the nasal septum and fuse to form the soft palate and uvula. This is the last portion of the palate to form
        1. The palatine raphe indicates the line of fusion of the lateral palatine processes
      3. The nasopalatine canal persists in the palatine midline between the premaxillary portion of the maxilla and the palatine processes of the maxilla Most of it is obliterated except for the incisive foramen

development of the palate: image #1