Structure of the masseter muscle:
- The masseter muscle is thick and quadrilateral in shape.
- It consists of three heads: superficial, deep, and coronoid.
- The fibers of the superficial and deep heads are continuous at their insertion.
- The superficial head arises from the zygomatic process of the maxilla and the zygomatic bone.
- The deep head arises from the lower border and medial surface of the zygomatic arch.

Superficial head of the masseter muscle:
- The superficial head is larger than the deep head.
- It arises from the zygomatic process of the maxilla and the zygomatic bone.
- Its fibers pass inferior and posterior.
- It is inserted into the angle of the mandible and the lateral surface of the ramus of the mandible.
- The superficial head is responsible for the elevation of the mandible.

Deep head of the masseter muscle:
- The deep head is smaller and more muscular in texture.
- It arises from the lower border and medial surface of the zygomatic arch.
- Its fibers pass downward and forward.
- It is inserted into the upper half of the ramus of the mandible.
- The deep head is partly concealed by the superficial portion and covered by the parotid gland.

Coronoid head of the masseter muscle:
- The coronoid head of the masseter's tendon and muscle fibers run posterolaterally.
- It originates from the coronoid process of the mandible.
- Its function is to retract the mandible and stabilize the mandibular coronoid process.
- The coronoid head plays a role in the closing of the jaws.
- It is believed to contribute to the protrusion of the mandible.

Innervation of the masseter muscle:
- The masseter muscle is innervated by the anterior division of the mandibular division (V3) of the trigeminal nerve.
- The innervation pathway involves the gyrus precentralis, genu capsula interna, nucleus motorius nervi trigemini, nervus trigeminus, nervus mandibularis, and musculus masseter.
- Along with the other muscles of mastication, the masseter receives innervation from the trigeminal nerve.
- The innervation of the masseter allows for its contraction and the elevation of the mandible.
- The trigeminal nerve plays a crucial role in the motor function of the masseter muscle.

Masseter muscle (Wikipedia)

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In anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it is the most superficial and one of the strongest.

Masseter
The left masseter muscle (red highlight), partially covered by superficial muscles such as the platysma muscle (below) and both the zygomaticus major and minor muscles
Details
Origin	zygomatic arch and maxillary process of zygomatic bone
Insertion	Angle surface of ramus of mandible, coronoid process
Artery	masseteric artery
Nerve	mandibular nerve (V3)
Actions	elevation (as in closing of the mouth) and protrusion of mandible
Identifiers
Latin	musculas masseter
MeSH	D008406
TA98	A04.1.04.002
TA2	2105
FMA	48996
Anatomical terms of muscle [edit on Wikidata]