Muscles of Facial Expression

The muscles of facial expression are unique among all muscles in the human body in that they are the only muscles that do not insert into hard tissue but rather insert into the connective tissue underlying the skin of the head and neck. This means that when they contract, they do not move a joint, but rather move soft tissue, allowing the large range of facial expressions that our species uses to show emotions. Although they are found throughout the head and neck all of these muscles are innervated by branches of the facial nerve, cranial nerve VII (Appendix G). As these muscles are numerous, we will be ignoring the minor ones and mainly concentrating on the ones the affect the oral cavity in order to keep this section to a manageable amount of material. Other than the orbicularis oris all of these muscles are paired with one on the left and one on the right side.