Anatomical study of the conjoint tendon of the temporalis and bucinator in Japanese cadavers

A processing model in which each stage of mastication and deglutition overlaps has recently been proposed, suggesting coordinated activity of the bucinator, pharyngeal muscles, and masticatory muscles. However, there is little anatomical evidence demonstrating structural continuity among these components. Since functional integration among these muscles likely depends on connective tissue interfaces, this study aimed to examine the distribution of the dense connective tissue layer covering bucinator and temporalis tendons and its relationship with the surrounding muscles. Twelve halves of nine adult Japanese cadaveric heads were examined: five halves were observed macroscopically and seven histologically. A dense connective tissue layer was identified between the bucinator, deep temporalis tendon, and superficial temporalis tendon. This layer was formed by the fusion of the temporal fascia and buccopharyngeal fascia, was continuous with the masseteric fascia, and received partial attachment from the medial pterygoid muscle. In addition, loose connective tissue was observed in the space between the superficial and deep temporalis tendons. The fibre orientation of the dense connective tissue layer and bucinator was consistent with that of the tendon. This dense layer formed a capsule-like structure enclosing loose connective tissue and neurovascular bundles, and was centrally located among the bucinator, temporalis, masseter, medial pterygoid muscle, and superior constrictor of the pharynx. These findings suggest that this structure may contribute to coordinated muscle activity and efficient force transmission during mastication and deglutition, providing a structural basis for future functional and imaging studies.