A pharyngeal arch is a structure that forms during the early development of vertebrate embryos. These arches are a series of paired structures that appear in the region of the pharynx, contributing to the formation of various anatomical features. Each arch contains a core of mesoderm, which is surrounded by ectoderm and endoderm, and is associated with specific nerves, blood vessels, and cartilage. In humans, there are typically five pairs of pharyngeal arches, numbered one to six, although the fifth arch usually disappears. These arches give rise to important structures, including parts of the jaw, ear, and throat. The development of pharyngeal arches is crucial for proper formation of the head and neck regions.