The muscles of mastication, associated with movements of the jaw, are comprised of four muscles: the Masseter, Temporalis, Medial Pterygoid and Lateral Pterygoid. All of these muscles develop from the first pharyngeal arch and are innervated by a branch of the trigeminal nerve, the mandibular nerve (CN V). In this article, we will explore the anatomy of the muscles of mastication – their attachments, actions, and innervation.
The Masseter muscle is the strongest muscle of mastication. It is quadrangular in shape and composed of two parts – Deep and Surface. It is located deep to the Pterygoid and Temporalis muscles. Its Surface part originates from the maxillary process of the zygomatic bone and attaches to the ramus of the mandible. Similarly, the Deep part originates from the zygomatic arch of the temporal bone and attaches to the ramus of the mandible. It has one action – elevation of the mandible (closing the mouth) – and is innervated by the Mandibular nerve (V3).
The Temporalis muscle originates from the Temporal Fossa, a shallow depression on the lateral aspect of the skull. Temporalis attaches to the Coronoid Process of the mandible and acts on the mandible in order to perform the action of elevation (closing the mouth) as well as retraction of the mandible (moving the jaw posteriorly). It is innervated by the Mandibular nerve (V3).
The Medial Pterygoid muscle is also quadrangular in shape and has two heads – Deep and Surface. It originates from the maxillary tuberosity and the pyramidal process of palatine bone respectively. Both heads attach to the ramus of the mandible near the angle of the mandible. It is innervated by the Mandibular nerve (V3).
The Lateral Pterygoid muscle is triangular in shape with two heads - Superior and Inferior. It originates from the Greater Wing of the Sphenoid and the Lateral Pterygoid Plate of the Sphenoid bone respectively. Both heads converge into a tendon which attaches to the neck of the mandible. The muscle acts on the mandible to perform protraction and depression of the chin bilaterally and mediates 'side-to-side' movement of the jaw unilaterally. It is innervated by the Mandibular nerve (V3).
The Muscles of Mastication are an important part of our anatomy, responsible for the movement and control of the jaw. There are four muscles of mastication: the Masseter, Temporalis, Medial Pterygoid and Lateral Pterygoid. All of these muscles are bilateral structures, originating from the first pharyngeal arch and innervated by a branch of the trigeminal nerve, the mandibular nerve (CN V). Each muscle serves a unique purpose, performing specific actions, and is attached to different parts of the skull.
The Masseter muscle, the most powerful muscle of mastication, is located deep to the Pterygoid and Temporalis muscles. Its two parts originate from the maxillary process of the zygomatic bone and the zygomatic arch of the temporal bone, attaching to the ramus of the mandible. It is innervated by the Mandibular nerve (V3) and is responsible for the elevation of the mandible (closing the mouth).
The Temporalis muscle originates from the Temporal Fossa, a shallow depression on the lateral aspect of the skull. It attaches to the Coronoid Process of the mandible and is responsible for the elevation (closing the mouth) as well as retraction of the mandible (moving the jaw posteriorly). This muscle is innervated by the Mandibular nerve (V3).
The Medial Pterygoid muscle is also quadrangular in shape and composed of two heads – Deep and Surface. It originates from the maxillary tuberosity and the pyramidal process of palatine bone, attaching to the ramus of the mandible near the angle of the mandible. It is innervated by the Mandibular nerve (V3) and is involved in the elevation of the mandible (closing the mouth).
The Lateral Pterygoid muscle originates from the Greater Wing of the Sphenoid and the Lateral Pterygoid Plate of the Sphenoid bone. Its two heads converge into a tendon which attaches to the neck of the mandible and its actions include protraction, depression of the chin bilaterally, and 'side-to-side' movement of the jaw unilaterally. This muscle is innervated by the Mandibular nerve (V3).
An understanding of the anatomy and physiology of the muscles of mastication is essential in order to properly diagnose and treat disorders of the temporomandibular joint. Thus, it is important to become familiar with the anatomy and physiology of these four muscles and the actions they perform.
