1 and 2: Pair of Maxillary prominences (right and left) à forms cheek (under eyes and side of nose) = area innervated by Maxillary division of Trigeminal (CN V)
3 and 4: Pair of Mandibular prominences (R +L) à lower lip, lower jaw, ear = areas innervated by Mandibular division of Trigeminal (CN V)
•In 4th week, a thickening of the mesenchyme occurs on the side of the embryo in the frontonasal prominence = lens placode =area where eyes develop that begins on the sides of the head(eyes will rotate to front eventually)
•maxillary prominence is paired but unlike the mandibular prominence, is not fused. (Eventually they fuse with medial nasal prominence. If this doesn’t happenàcleft lip)
§This groove deepens and approaches the front of the digestive tract, since at this point there is no connection between the front of the digestive tract and outside world §The deepening of the stomodeum continues until only a thin film remains between the outside world and the digestive tract = oropharyngeal membrane §Eventually the oropharyngeal membrane will rupture and create an opening between the maxillary prominences = primitive mouth (allows the pharynx to communicate with amniotic cavity= “outside world”)
§The oronasal membrane eventually ruptures so the nasal cavity is almost completely confluent with the oral cavity. A small piece of intermaxillary segment at the very front of the developing mouth remains as the only separation between them.
§The nasal septum forms from a fold/sheet that begins at the top of the nasal cavity (in the midline) and grows down to divide the nasal cavity into left and right halves §Lateral palatine processes are horizontal folds (also running front to back) that develop from the sides and grow medially. They meet and fuse at the midline along with the nasal septum.
These defects can lead to changes in appearance—are repaired surgically, and can also lead to changes in speech, and affect breathing and eating.
These defects can also lead to serious problems with development of teeth (missing or extra teeth) since they affect tooth bearing parts of the upper jaw.