Head and neck muscles (chewing, facial, and throat muscles)

Deep part of masseter

Musculus masseter, pars profunda

Origin

Inner surface of the zygomatic arch (full length)

Insertion

Upper half of the ramus of the mandible and the coronoid process

Function

Elevation (closing) of the mandible; stabilizes and slightly retrudes the mandible during chewing

Innervation

Masseteric nerve (branch of CN V3, mandibular nerve)

Movement & chain

Works together with the superficial part of masseter and temporalis in the jaw-closing chain; the deep part mainly provides stability and a slight retrusive component, contrasting with the more protrusive superficial part.

Palpation

Harder to distinguish from the superficial part; the deep part lies beneath the more easily palpable superficial part at the level of the zygomatic arch.

Clinical

Hypertrophy (e.g. with bruxism) can contribute to temporomandibular complaints and a square jawline.

Segmental innervation

Mandibular nerve (V3), motor.

In clinical practice

Masseter as a whole, including this deep part, is a commonly used injection site for botulinum toxin in bruxism and for cosmetic jawline slimming.

Region in the model

Head and neck muscles (chewing, facial, and throat muscles)