Temporomandibular Joint (Jaw)

Bones: The temporal bone, mandible, and zygomatic process.

Cartilage: There is a small articular disc that sits at the mandibular condyle between the bones.

Muscles: The diagastric muscle which contracts to open the mouth. The temporalis and masseter muscles which contract to close the jaw.

Ligaments: The temperomandibular ligament along with the capsule is what holds the joint of the jaw in place.

Joint type: Hinge.

Mechanics: Like many have seen in gator shows, the muscles that open the jaw are not as strong as the muscles that close the jaw. Seeing as how the two muscles that close the jaw attach at the back end of the mandible this is where the largest force is applied, and of which due to the leverage length of the jaw and teeth the force diminishes by nearly half from molars to incisors.

Range of motion: The human jaw as allowed for based on the muscular mechanics can on average open close to 55mm or about 2 inches.

Power: Base on studies (cited below) the average male bite force at the incisors is 87 psi and for females 57psi and for a quick reference a crocodile comes in at 3,700 psi. The human bite force however is plenty enough to bite off a finger, an ear, a nose, or a chunk of skin, in self defense of an attacker.

Injury: Any large amount of impact to zygomatic process or around the mandibular condyle that can fracture or break bone will render the joint useless because the attachment points are broken.

Miscellaneous: The fighting style called Rough-and-Tumble or Gouge fighting developed in 1730s in the southern American colonies is known for its aggressiveness, especially stressing gouging out someone's eyes or biting and ripping.

For information on additional joints please refer back to the Joints page.

Reference Sources

1. The Power of the Human Jaw http://www.scientificamerican.com/article/the-power-of-the-human-jaw/ Scientific American added on 05/02/15