Anatomy, Head and Neck: Facial Muscles

Excerpt

The human face possesses around 30 muscles on each side, depending on how they are counted. The facial muscles are striated muscles that link the facial skin to the skull bone to perform important daily life functions, such as mastication and emotion expression. The facial muscles produce various movements but are often categorized into facial expression (mimetic) and mastication muscles. The facial nerve (cranial nerve or CN VII) innervates the facial expression muscles, while the trigeminal nerve's mandibular division (CN V3) innervates the muscles of mastication. Distinguishing these groups based on innervation makes categorization largely dependent on embryonic origin, which does not always precisely correlate with function. Nevertheless, this method is commonly used when describing these muscles.

Despite different innervations and functions, the facial muscles, by and large, act synchronously. For example, during chewing, the orbicularis oris and buccinator retain food inside the mouth, while the masseter and temporalis move the mandible when chewing food. The pterygoid muscles move the mandible when the latter needs anteroposterior or lateral and medial adjustment.

CNs VII and V3 control other muscles besides these groups, making their dysfunction debilitating. Functional impairment of these nerves reduces quality of life (See Image. Muscular and Fibrous Structures of the Head, Face, and Neck).