Topics

Topic

design image
Masseter muscle (Deep part)

The masseter muscle is a thick, rectangular muscle of mastication located in the lateral aspect of the face. It is divided into superficial and deep parts. The deep part of the masseter muscle is smaller and lies deep to the superficial part. It plays a crucial role in jaw elevation and chewing. The masseter muscle, particularly its deep part, is clinically significant in dentistry, maxillofacial surgery, and imaging, and its pathology may be involved in temporomandibular joint disorders.

Synonyms

  • Deep layer of masseter

  • Deep part of the masseter muscle

  • Musculus masseter pars profunda

Function

  • Elevation of the mandible (jaw closure)

  • Assists in protrusion of the mandible (minor action)

  • Provides force for mastication (chewing)

Origin

  • Deep part: Zygomatic arch (specifically the deep surface and posterior part of the zygomatic arch)

Insertion

  • Upper half of the ramus of the mandible

  • Coronoid process of the mandible

Nerve Supply

  • Masseteric nerve (branch of the anterior division of the mandibular nerve, CN V3)

Artery Supply

  • Masseteric artery (branch of the maxillary artery)

  • Contributions from the facial artery and transverse facial artery

Vein Supply

  • Masseteric veins (drain into the pterygoid venous plexus)

  • Accompanying veins of the masseteric artery

MRI Appearance

  • T1-weighted: Intermediate to low signal intensity (similar to other skeletal muscles)

  • T2-weighted: Normal muscle demonstrates relatively low signal intensity, but increased signal may indicate edema or pathology.

  • STIR (Short Tau Inversion Recovery): Low signal under normal conditions; hyperintensity indicates edema, inflammation, or pathology

CT Appearance

  • The masseter muscle (deep part) appears as a well-defined, homogenous, soft-tissue density structure lateral to the ramus of the mandible.

MRI images

Masseter Muscle (Deep Part) mri axial image -img-00000-00000