In human anatomy, the
masseter is one of the
muscles of mastication-Muscles:*The masseter*The temporalis *The medial pterygoid*The lateral pterygoid...
.
In human anatomy, the
masseter is one of the
muscles of mastication-Muscles:*The masseter*The temporalis *The medial pterygoid*The lateral pterygoid...
.
In the animal kingdom, it is particularly powerful in herbivores to facilitate chewing of plant matter.
Origin and insertion of the two heads
The masseter is a thick, somewhat quadrilateral muscle, consisting of two portions, superficial and deep.
The fibers of the two portions are continuous at their insertion. The masseter muscle is sometimes the target of plastic
jaw reductionJaw reduction is a type of aesthetic plastic surgery in which the objective of treatment is to narrow the lower one-third of the face—particularly the contribution from the mandible and its muscular attachments. There are several techniques for treatment—including surgical and non surgical methods...
surgery.
Superficial
The
superficial portion, the larger, arises by a thick, tendinous
aponeurosisAponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, and are histologically similar to tendons, but are very sparingly supplied with blood vessels and nerves. When dissected, aponeuroses are papery, and peel off by sections...
from the
zygomatic processZygomatic process is a protrusion from the rest of the skull, like the bumper of a car. Most of it belongs to the zygomatic bone, and could therefore be called the zygomatic process of the zygomatic bone...
of the
maxillaThe maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes , the maxilla is sometimes called "upper maxilla", with the mandible being the "lower maxilla"...
, and from the anterior two-thirds of the lower border of the
zygomatic archThe zygomatic arch or cheek bone is formed by the zygomatic process of temporal bone and the temporal process of the zygomatic bone , the two being united by an oblique suture; the tendon of the Temporalis passes medial to the arch to gain insertion into the coronoid process...
.
Its fibers pass downward and backward, to be inserted into the angle and lower half of the lateral surface of the ramus mandibulæ.
Deep
The
deep portion is much smaller, and more muscular in texture.
It arises from the posterior third of the lower border and from the whole of the medial surface of the zygomatic arch
Its fibers pass downward and forward, to be inserted into the upper half of the ramus and the lateral surface of the
coronoid processThe Coronoid process can refer to:* The coronoid process of the mandible, part of the ramus mandibulae of the mandible* The coronoid process of the ulna...
of the mandible.
The deep portion of the muscle is partly concealed, in front, by the superficial portion; behind, it is covered by the
parotid glandThe parotid gland is the largest of the salivary glands. It is found wrapped around the mandibular ramus, and it secretes saliva through Stensen's duct into the oral cavity, to facilitate mastication and swallowing.-Location:...
.
Innervation
Along with the other three muscles of mastication (temporalis,
medial pterygoidThe medial pterygoid , is a thick, quadrilateral muscle of mastication.The mandibular branch of the fifth cranial nerve, the trigeminal nerve, innervates the medial pterygoid muscle.-Origin and insertion:...
and lateral pterygoid), the masseter is innervated by the
mandibular divisionThe mandibular nerve is the largest of the three branches of the trigeminal nerve.-Roots:It is made up of two roots:* a large sensory root proceeding from the inferior angle of the trigeminal ganglion....
of the
trigeminal nerveThe trigeminal nerve is responsible for sensation in the face. Sensory information from the face and body is processed by parallel pathways in the central nervous system....
.