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The muscles of mastication are a group of muscles responsible for chewing (i.e. movement of the mandible at the temporomandibular joint). These muscles originate from the surface of the skull and insert onto the mandible.¹
There are four muscles that comprise the muscles of mastication, including masseter, temporalis, lateral pterygoid and medial pterygoid.¹
This article will explore the origin, insertion, action, innervation and blood supply of the masticatory muscles. Certain pathologies associated with particular muscles of mastication will also be discussed.¹
This muscle composes of two main parts: the deep and superficial heads.¹
This muscle is only found in mammals.
The masseter originates at the zygomatic arch and maxillary process of the zygomatic bone.
The insertion site is located at the lateral surface of the ramus and angle of the mandible.¹
Bilateral contraction will protrude and elevate the mandible.¹
Unilateral contraction will cause a small amount of side-to-side movement (lateral deviation).
Limitation of jaw opening (also known as trismus) sometimes occurs as a result of radiotherapy in the treatment of head and neck cancers.
This occurs due to fibrosis of the pterygo-masseteric sling.
This muscle lies mostly superficial to the medial pterygoid and comprises of superior and inferior sections.¹
The superior head originates from the infratemporal surface of the greater wing of the sphenoid, whilst the inferior head originates from the lateral surface of the lateral pterygoid plate of the sphenoid.
The fibres from both heads converge to attach to the pterygoid fovea on the neck of the mandible.
A portion of the superior head attaches to the capsule and articular disc of the temporomandibular joint.¹
Bilateral contraction pulls the mandibular condyle and articular disc anteriorly (i.e. protrusion). This movement is thought to be integral to the opening of the jaw.
Unilateral contraction will deviate the mandible to the contralateral side.