What is the X in X-mas?
branchial arch n.
Any of usually six embryonic arches that give rise to specialized structures in the head and neck in the higher vertebrates. Also called gill arch, pharyngeal arch, visceral arch.
one of the bony or cartilaginous curved bars on either side of the pharynx (throat) that support the gills of fishes and amphibians; also, a corresponding rudimentary ridge in the embryo of higher vertebrates, which in some species may form real but transitory gill slits. In the human embryo, the branchial arches give rise to such structures as the mandible, hyoid bone, and larynx.