Muscles of Mastication

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

Masseter

• This muscle composes of two main parts: the deep and superficial heads.¹
• This muscle is only found in mammals.

Origin

• The masseter originates at the zygomatic arch and maxillary process of the zygomatic bone.

Insertion

• The insertion site is located at the lateral surface of the ramus and angle of the mandible.¹

Action

• Bilateral contraction will protrude and elevate the mandible.¹
• Unilateral contraction will cause a small amount of side-to-side movement (lateral deviation).

Innervation

• The mandibular division of the trigeminal nerve (V3).¹

Blood supply

• The masseteric artery (a branch of the second part of the maxillary artery),¹ facial artery and the transverse facial branch of the superficial temporal artery.

Temporalis

• This large, fan-shaped muscle is located on the lateral aspect of the skull.
• It occupies the temporal fossa.

Origin

• The temporalis originates at the temporal fossa up to the inferior temporal line and the zygomatic bone.

Insertion

• The coronoid process and ramus of the mandible.¹

Action

• Bilateral contraction of the temporalis muscle contributes to retraction and elevation of the mandible.
• Unilateral contraction will cause a small amount of side-to-side movement (lateral deviation).¹

Innervation

• The mandibular division of the trigeminal nerve (V3).¹

Blood supply

• The deep temporal arteries, which are branches of the second part of the maxillary artery.¹

Medial pterygoid

• This muscle is separated into deep and superficial sections.¹

Origin

• • • The deep head originates from the medial aspect of the lateral pterygoid plate of the sphenoid.
    • The superficial head originates from the pyramidal process of the palatine bone and maxillary tuberosity.¹

   

  Insertion

  • • • Both the deep and superficial heads insert onto the medial surface of the ramus and angle of the mandible.
      • The insertion of the medial pterygoid forms a tendinous band with the insertion of the masseter called the pterygo-masseteric sling.¹

   

  Action

  • • • Bilateral contraction of this muscle elevates and protrudes the jaw.
      • Unilateral contraction will deviate the mandible to the contralateral side.

   

  Innervation

  • • • The mandibular division of the trigeminal nerve (V3).¹

   

  Blood supply

  • • • The pterygoid branches of the maxillary artery

   

  Clinical relevance

  • 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.

   

  

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  Lateral pterygoid

  • • • This muscle lies mostly superficial to the medial pterygoid and comprises of superior and inferior sections.¹

  Origin

  • • • 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.

   

  Insertion

  • • • 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

   

  Action

  • • • 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.

   

  Innervation

  • • • The mandibular division of trigeminal nerve (V3).¹

   

  Blood supply

  • • • The pterygoid branches of the maxillary artery.¹

   

  

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  Reviewer

  Dr James Nott

  Anatomy Lecturer & Anatomy Lead at Geeky Medics

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  References

  • • 1. Drake, R. L., Wayne Vogl, A., Mitchell, A. (2009). Gray’s anatomy for students second edition. Elsevier health sciences.

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