Anatomical study of arrangement and attachment of the medial pterygoid muscle in Japanese men.

We precisely examined the origin, attachment, manner and insertion of the medial pterygoid muscle to clarify the relationship between muscle morphology and mastication movement. The muscular bundle attachment of the medial pterygoid muscle at the origin could be divided into three types; 1) the muscle was attached to the inner surface of the medial pterygoid plate with a strong tendon, 2) to the posterior maxilla wall with a strong tendon, and 3) directly to the periosteum of the inner surface of the lateral plate without a tendon. Provided that the muscular bundles had a firmly tendinous attachment under strong and significant force during their functioning, significant force would be applied to the medial pterygoid muscle in two directions. Observations of the intersection with the medial pterygoid muscle in the posterior wall of the maxillary bone at the origin revealed intersecting fibers or tendon fusion in all 55 specimens. Since there are different muscular bundle groups within the medial pterygoid muscle, we expect to elucidate more of masticatory function by observing other masticatory muscles as well as the medial pterygoid muscle.