Distribution of macromolecular components in the muscle-bone junction of human masticatory muscles

At the muscle-bone junction, the attachment is composed of macromolecular components that differ from those in masticatory muscles. In the temporal and lateral pterygoid muscles, numerous fine fibers form complex arrangements between collagenous bundles and the tendon-bone junctions. Collagenous bundles are directly inserted into the bone tissue at the site of the adhesive attachment. Reticular fibers are arranged irregularly and cover the collagenous bundles as a network. Numerous collagenous fibers are also tightly connected with the bundles that are found near the muscle-bone junction of the lateral pterygoid muscle. Strong or moderate staining for collagen types I, III, and V, tenascin, laminin, and fibronectin was observed in close association with the border of the bone matrix. Different distributions of these macromolecular components were found in each masticatory muscle. The results suggest that the morphological properties of the muscle-bone junction of each muscle reflect the tension or the stretch applied to a mandible bone. The distribution of macromolecular components in each muscle also reflects the form and calcification of the mandibular bone during aging.