Temporomandibular Joints

The major components of the temporomandibular joints are the cranial base, the mandible, and the muscles of mastication with their innervation and vascular supply. Each joint can be described as gin-glymoarthrodial, meaning that it is capable of both a hinging and a gliding articulation. An articular disk separates the mandibular fossa and articular tubercle of the temporal bone from the condylar process of the mandible.

The articulating surfaces of the condylar processes and fossae are covered with avascular fibrous tissue (in contrast to most other joints, which have hyaline cartilage). The articular disk consists of dense connective tissue; it also is avascular and devoid of nerves in the area where articulation normally occurs. Posteriorly it is attached to loose vas-cularized connective tissue, the retrodiscal pad or bilaminar zone*, which connects to the posterior wall of the articular capsule surrounding the joint (Fig. 4-1). Medially and laterally the disk is attached firmly to the poles of the condylar process. Anteriorly it fuses with the capsule and with the superior lateral pterygoid muscle. Superior and inferior to the articular disk are two spaces, the superior and inferior synovial cavities. These are bordered peripherally by the capsule and the synovial membranes and are filled with synovial fluid. Because of its firm attachment to the poles of each condylar process, the disk follows condylar movement during both hinging and translation, which is made possible by the loose attachment of the posterior connective tissues.

*Called bilaminar because it consists of two layers: an elastic superior layer and a collagenous inelastic inferior layer.

Bilaminar Zone

Fig. 4-1. Temporomandibular joint (lateral section). The mandible is open.

Fig. 4-1. Temporomandibular joint (lateral section). The mandible is open.

Mandibular

Ligaments

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