Branchial arches are structures that develop in the embryo and are crucial for the formation of various anatomical features in the head and neck. They arise from mesoderm and neural crest cells and are numbered from one to six. Each arch contains a cartilaginous rod, muscle, nerve, and blood vessel, contributing to the development of structures such as the jaw, ears, and throat. In humans, the first two branchial arches are particularly significant. The first arch forms the mandible and maxilla, while the second arch contributes to the hyoid bone and muscles of facial expression. The remaining arches contribute to structures in the pharynx and larynx.