Masseter Muscle: Location and Actions

The masseter is a jaw muscle that gets its name from the Greek work “to chew”. It is the major muscle of mastication (chewing) of the human jaw and serves primarily to elevate the mandible (lower jaw) while the deep tissues help to protrude (protract) it forward. Although we rarely think of it, the mandible is the only bone of the skull that is actually moveable. The upper jaw is fixed. There is a lot of moving for the mandible to do, therefore, and the masseter is the primary worker. Located on each side of the face in the parotid (near or below the ear) region at the back of the jaw, these muscles are easily visible or palpable when you clench your jaw, as they contract strongly just in front of the lower ears.

superficial and deep masster muscle

Note: Other muscles of mastication besides the masseter are the temporalis (elevates and retracts the mandible), the medial pterygoid (elevates mandible and protrudes jaw with l. pterygoid) and lateral pterygoid (protrudes mandible). The medial and lateral pterygoids together on one side move the lower jaw to the opposite side.

The masseter muscle covers the side of the jaw nearest the ear and for its size, it is one of the strongest muscles and some physiologists believe it to be the strongest muscle of all but this is hard to determine with complete accuracy. The masseter’s closest competitors are the gluteus maximus and the rectus femoris. The tongue is sometimes also claimed to be the strongest but since the tongue is actually eight muscles, four intrinsic and four extrinsic, this is clearly debatable.

See Masseter Trigger Points

Masseter muscle
mage by Rob Swatski

The average human can bite down with a force of 150 pounds and bites of over 250 pounds are within the norm. In fact the world record bite recorded by the 1992 Guinness Book of Records records the strongest human bite at an astounding 4,337 N or 975 foot pounds for 2 seconds. The masseter achieves these seemingly impossible forces because of its mechanical advantage as it its lever arm is much shorter than most muscles. 1“The “strongest” human muscle | Guinness World Record 2009-2010 – Athletics, Human Body, Swimming, Animal, Olympics.” http://www.worldrecordsnews.com/2009/08/strongest-human-muscle.html.

Masseter Muscle Origin, Insertion, and Actions

Origin: The larger superficial layer originates on the zygomatic process of the maxilla and the lower border of the zygomatic arch. The smaller deep portion originates on the zygomatic arch.

Insertion: The superficial portion inserts on the ramus of the mandible and the deep portion inserts on the upper half of the ramus and the lateral surface of the coronoid process of the mandible. 2“masseter (anatomy) – General Practice Notebook.” http://www.gpnotebook.co.uk/simplepage.cfm?ID=-100270003.

Actions:  Elevates the mandible (lower jaw) while the deep tissues help to protrude (protract) it forward. The main chewing muscle.

See Masseter Trigger Points and Referred Pain Patterns

 

Sources   [ + ]

1. “The “strongest” human muscle | Guinness World Record 2009-2010 – Athletics, Human Body, Swimming, Animal, Olympics.” http://www.worldrecordsnews.com/2009/08/strongest-human-muscle.html.
2. “masseter (anatomy) – General Practice Notebook.” http://www.gpnotebook.co.uk/simplepage.cfm?ID=-100270003.