An anatomical study of muscle-bone junction in human masticatory muscles —Macroscopic, immunohistochemical and scanning electron microscopic analyses—

Abstract

In this study, seventy adult humans were selected at autopsy from donations at Nippon Dental University for macroscopic, histochemical, and scanning microscopic analyses of the muscle-bone junction in mandible. The following results were obtained. 1) Macroscopic analysis at human muscle-bone junction in mandible showed that various attachments were found in each masticatory muscle, however there were no strong correlations between measurments values and aging and sex. 2) Immunohistochemical analysis also revealed that anti PCNA (cyclin proliferating cell nuclear antigen) positive cells were observed predominatly at the muscle-bone junction, and the percentage of these cells in pterygoid muscles was higher than in other muscles. Different distributions of the ECMs (ectracellular matrices) were found in each masticatory muscle. The intense stanings for collagen types III and V and tenascin were found at the medial portion of the lateral surface of the body in the mandible. The moderate stainings for collagen types I and III, and lamine were mainly found in the other lateral surface of the body in the mandible. The intense stainings for collagen type I, and lamine were found at the attachment of the top of the coronoid process in the mandible. The moderate stainings for collagen types III and V, and lamine were mainly found on the posterior surface of the coronoid process. The strong stainings for collagen types I, III and V, lamine and tenascin were found at the attachment of the inner inferior border of ramus. The strong stainings for collagen types I, III and V, and lamine, fibronectin and tenascin were found throughout the whole attachment of the border in the pterygoid fovea. 3) With scanning electron microscopic analysis, complex arrangements of numerous fine fibers were found between collagenous bundles and the tendon-bone junctions. There were various structual features at these sites; masseter muscle (root-like structure), temporal muscle (complex tight junction), medial pterygoid muscle (round-like structure) and lateral pterygoid muscle (bundlelike structure).