All the joints of the head and face, with the exception of the temporo-mandibular, are sutures. These are immovable joints formed by dentated edges fitted together and firmly united by means of cartilage.

Temporo-Mandibular Joint between the condyle of the mandible and the articular hollow at the root of the zygomatic process of the temporal bone.

Fig. 45. - The Temporo-mandibular Joint.

The joint is a very movable one, the condyle being almost cylindrical in shape, with its long axis directed outwards and forwards. The articular or glenoid fossa is saddle-shaped, being concavo-convex from behind forwards. The joint is divided into an upper and lower part by a meniscus of fibro-cartilage, which compensates for the difference in shape of the two surfaces.

Owing to this construction the joint is particularly movable, and the two joints need not always act simultaneously, but can do so alternately, which gives a lateral movement to the jaw. The movements possible areTransverse axis - raising and depressing of mandible.

During depression - protrusion and retraction.

Alternate - lateral motion.

A combination of all these movements produces a rotatory-movement of the jaw.

Ligaments

A capsule surrounds the joint completely, but internally it is very thin; it is attached to the meniscus all round.

Tempore - Mandibular ligament from the outer half of the lower border of the zygoma to the posterior border and lateral surface of the neck of the mandible (the part supporting the condyle).

A synovial membrane lines both compartments of the joint, which may be continuous through a perforation in the cartilage.

Accessory Ligaments: Spheno-mandibular from the spinous process of the great wing of the sphenoid bone to the lingula on the inner surface of the mandible.

Stylo-Mandibular, from the tip of the styloid process of the temporal bone to the posterior border of the angle of the mandible.