Originally, tissues used by the Silurian jawless fishes as part of their feeding and breathing apparatus. Many facial expressions derive from muscles and nerves of the pharyngeal arches. Early in Nonverbal World , pharyngeal arches were programmed to constrict in response to potentially harmful chemical signs detected in seawater.
Pharyngeal arches are visible as swellings in the throat of the human fetus.
Seawater was pumped in and out of the early pharynx through a series of gill slits at the fish's head end. In human beings, the nerves and muscles used to close the mouth derive from the 1st pharyngeal arch, while those which constrict the throat derive from the 3rd and 4th arches.