NCIt definition : One of a series of paired mesodermal tissue bands located on either side of the embryonic
pharyngeal foregut, composed of an ectodermal covering, and endodermal lining, and
a mesenchymal core, that contains an arch artery, a cranial nerve, a cartilaginous
rod and a muscular component. Each arch differentiates to form different components
of the head and neck.;