What is "pharyngeal arch"

The pharyngeal arches are structures seen in the development of vertebrates, are recognisable precursors for numerous structures. The arches develop into the branchial arches or gill arches in fish.

In the human embryo, the arches are first seen during the fourth week of development. They appear as a series of outpouchings of mesoderm on both sides of the developing pharynx. The vasculature of the pharyngeal arches is also known as the aortic arches.

In fish, the branchial arches support the gills.