Development of face скачать в хорошем качестве

Development of face

During week 3 of embryonic development, an oropharyngeal membrane initially appears at the site of the future face. It is comprised of ectoderm and endoderm – externally and internally, respectively. During the 4th week, the oropharyngeal membrane begins to break down in order to become the future oral cavity, and sits at the beginning of the digestive tract. The structures of the external face are derived from two sources: Frontonasal prominence – formed by the proliferation of mesenchymal neural crest cells ventral to the forebrain. Mandibular and maxillary prominences – parts of the 1st pharyngeal arch.A space lies between the maxillary prominences, covered by the oropharyngeal membrane; this is known as the stomatodeum, the precursor to the mouth and pituitary gland. Nasal development is instigated by the appearance of raised bumps called nasal placodes on both sides of the frontonasal prominence. These then invaginate to form nasal pits, with medial and lateral nasal prominences on either side. As the maxillary prominences expand medially, the nasal prominences are ‘pushed’ closer to the midline.  The maxillary prominences then fuse with nasal prominences & thereafter fuse in midline to form a continuous suture.