There are four classical muscles of mastication. During
mastication, three
muscles of mastication (
musculi masticatorii) are responsible for
adduction of the jaw, and one (the
lateral pterygoid) helps to
abduct it. All four move the jaw laterally. Other muscles, usually associated with the
hyoid such as the sternohyomastoid, are responsible for opening the jaw in addition to the
lateral pterygoid.