human lower-left jawbone showing the jaw's basic structure
A human lower-left jawbone showing the jaw's basic structure

The human jaw is any opposable articulated structure at the entrance of people’s mouths, typically used for grasping and manipulating food.

The term “jaws” is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of most animals. A person’s jawbone connects to the skull at the temporomandibular joints, better known as the TMJs, on either side of your head in front of your ears.

In the human anatomy, the mandible, lower jaw, or jawbone is the largest, strongest, and is the lower positioned bone in our facial skeleton. Its min function is to shape the lower jaw and hold a person’s lower teeth in place. The mandible is positioned beneath the maxilla. It is the only movable bone within a person’s skull (discounting the ossicles of the middle ear). It is connected to the temporal bones by the temporomandibular joints which show its relationship to an individual’s ability to chew, yawn, and other mouth-opening functions.

The power within a person’s jaw is remarkable. For an easy analogy, a person’s jaws seem to be created on the principle of a pair of tongs. The power is applied near the jaw joint, while the work is performed at the opposite extremity of the jaw levers in order for the jaw to function properly.

How the Human Jaw Bone is Formed

The bone is formed as the human fetus miraculously develops a fusion of the left and right mandibular prominences, and the point where these sides join, the mandibular symphysis, is still visible as a faint ridge in the midline. Similar to other symphyses in the human body, this is a midline articulation where the bones are joined by fibrocartilage, however, this articulation becomes fused together in early childhood.

In the human fetus and during the first few months of infancy, both the upper and lower jaws have two halves; these fuse at the midline a few months after birth.

Nerves That Impact the Jaw

Panoramic radiograph lets orofacial pain specialists view the mandible, including the heads and necks of the mandibular condyles, the coronoid processes of the mandible, in addition to the nasal antrum and the maxillary sinuses.
The inferior alveolar nerve, a branch of the mandibular nerve, (also, a chief division of the trigeminal nerve), enters the mandibular foramen and runs towards the front in the mandibular canal; thus supplying nerve sensation to the teeth. At the mental foramen, the nerve breaks into two terminal branches known as incisive and mental nerves. The incisive nerve runs forward in the mandible and supplies a person’s anterior teeth. The mental nerve exits the mental foramen and supplies sensation to a human’s lower lip.

How is a Person’s Jaw the same as the Mandible?

The mandible is part of the jaw. It forms as a bone (ossifies) over time from both a left and right piece of cartilage, called Meckel’s cartilage. In stressful times, or after jaw injury, a higher rate of jaw pain is seen in patients.

These cartilages form the cartilaginous bar of the mandibular arch. Near the head, they are connected with the ear capsules, and they meet at the lower end at the mandibular symphysis, a fusion point between the two bones, by mesodermal tissue. They run forward immediately below the condyles and then, bending downward, lie in a groove near the lower border of the bone; in front of the canine tooth they incline upward to the symphysis. From the proximal end of each cartilage the malleus and incus, two of the bones of the middle ear, are developed; the next succeeding portion, as far as the lingula, is replaced by fibrous tissue, which persists to form the sphenomandibular ligament.” – Wikipedia

The mandible consists of a horizontal arch, which holds the teeth and contains blood vessels and nerves that support a person’s jaw health. Two vertical portions form movable hinge joints that help the jaw perform its many tasks.

Commonality of Jaw Injuries

Injuries to the jaw may commonly cause a jaw bone break, fracture, or dislocation. Other typical causes of jaw dislocation include dental procedures or excessive yawning. A broken jaw (or mandibular fracture) is a common facial injury -second only to a broken nose. This creates a need for temporary anterior bite planes that dentists can use for patient treatment or people may purchase directly.

Temporomandibular joint and muscle disorders, most widely recognized as “TMJ,” are a group of complicated conditions that cause soreness and jaw strain, and dysfunction in the jaw joint as well as the muscles that control jaw movement. We don’t know for certain how many people have TMJ disorders, but some NIH estimates suggest that over 10 million Americans are affected.