Muscles of mastication
The four classical muscles of mastication elevate the mandible and move it forward/backward and laterally, facilitating biting and chewing. Other muscles are responsible for opening the jaw, namely the geniohyoid, mylohyoid, and digastric muscles.
Structure
The muscles are:- The masseter
- The temporalis
- The medial pterygoid
- The lateral pterygoid
Each of these primary muscles of mastication is paired, with each side of the mandible possessing one of the four.
Innervation
Unlike most of the other facial muscles, which are innervated by the facial nerve, the muscles of mastication are innervated by the trigeminal nerve. More specifically, they are innervated by the mandibular branch, or V3. The mandibular nerve is both sensory and motor.Development
Embryologically, the muscles of mastication are all derived from the first pharyngeal arch.The muscles of facial expression, on the other hand, are derived from the second pharyngeal arch.
Function
The mandible is the only bone that moves during mastication and other activities, such as talking.While these four muscles are the primary participants in mastication, other muscles help with the process, such as those of the tongue and the cheeks.
| Prime mover | Movement | Origin | Insertion |
| Masseter | Elevates mandible | Zygomatic arch | Mandible |
| Temporalis | Elevates and retracts mandible | Temporal bone | Mandible |
| Lateral pterygoid | Depresses, protracts, laterally moves mandible | Superior head: infratemporal surface of greater wing of sphenoid bone Inferior head: lateral pterygoid plate of sphenoid bone | Mandible; temporo-mandibular joint |
| Medial pterygoid | Elevates, protracts, laterally moves mandible | Deep head: medial surface of lateral pterygoid plate and palatine bone Superficial head: tuberosity of maxilla | Mandible |