[homology-note] "In all vertebrates, the pharyngeal apparatus develops from a series of bulges found on the lateral surface of the head, the pharyngeal arches, which consist of a number of different embryonic cell types. Each arch has an external covering of ectoderm and inner covering of endoderm, and between these a mesenchymal filling of neural crest with a central core of mesoderm.[well established][VHOG]" xsd:string {date_retrieved="2012-09-17", external_class="VHOG:0001102", ontology="VHOG", source="DOI:10.1046/j.1469-7580.2001.19910133.x Graham A. The development and evolution of the pharyngeal arches. J Anat (2001)", source="http://bgee.unil.ch/"}