Morphologic, microscopic, and immunohistochemical investigations into the function of the primate TMJ disc

The distribution and arrangement of extracellular matrix proteins were examined in the primate temporomandibular joint disc and posterior attachment using a combination of light microscopic, immunohistochemical, and biochemical techniques. The band areas of the disc contain a complex collagenous (type I) fiber network consisting of a mediolaterally directed fiber bundle system that interlaces or becomes continuous with an anteroposteriorly directed collagenous fiber array that runs through the intermediate zone. Thin, branching, elastic fibers are a significant component of the disc and are generally oriented parallel to the collagenous fiber network. Interfibrillar spaces in band areas contain numerous chondrocytes encased within a matrix that is rich in a high molecular weight, predominantly chondroitin-sulfate proteoglycan and type II collagen. The intermediate zone appears tendinous in its construction and is composed of anteroposteriorly oriented elastic and collagenous fibers, scattered chondrocytes, and reduced amounts of chondroitin-sulfate proteoglycan and type II collagen. The posterior attachment is composed of fibrocytes, larger caliber elastic fibers, loosely organized type I collagenous fibers, and low molecular weight dermatan-sulfate proteoglycan. These results indicate that the primate temporomandibular joint disc is a microheterogenous tissue with distinct regional specializations.