Development
These grow and join in the ventral midline. The first arch, as the first to form, separates the mouth pit or stomodeum from the pericardium. By differential growth the neck elongates and new arches form, so the pharynx has six arches ultimately.
Each pharyngeal arch has a cartilaginous stick, a muscle component which differentiates from the cartilaginous tissue, an artery, and a cranial nerve. Each of these is surrounded by mesenchyme. Arches do not develop simultaneously, but instead possess a "staggered" development.
Read more about this topic: Pharyngeal Arch
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