Temporal Muscle : Parts ,Origin and insertion
The temporal muscle is a compartmentalized muscle that arises from the superior and inferior temporal lines of the temporal bone. It inserts on the coronoid process and on the anterior edge of the ascending ramus of the mandible.
Three functional parts can be distinguished:
- The anterior part has muscle fibers that pull upward and serve as elevators (Moller 1966).
- The middle part effects closure of the jaws and, with a posterior vector, retrusion (Blanksma and van Eijden 1990).
Macroscopic anatomical preparation
The pars anterior and pars media of the temporal muscle consist of approximately 47% fatigue-resistant type-l muscle fibers with a low threshold of stimulation (Eriksson and Thornell 1983). The content of thinner type-IIB fibers is about 45%, leading to a higher concentration of fibers in the muscle (Stalberg et al. 1986). Type-IIA muscle fibers are not present at all and those of type IIC and/or IM account for only about 4% (Ringqvist1974).
Schematic drawing of the right temporal muscle
The muscle comprises a pars anterior (1), pars media (2), and pars posterior (3). Although the sarcomere lengths are the same in the various parts, there are significant differences in the lengths of the muscle-fiber bundles (21.7-28.9 mm) which indicates different functional demands (van Eijden et al. 1996).
Insertion of the temporal muscle on the disk-capsule complex
Medial view. Some of the horizontal fibers (arrows) insert onto the middle and lateral third of the disk (Merida Velasco et al. 1993, Bade etal. 1994).
Insertion of the temporal muscle viewed from above. Easily identified is the tendon (*) of the pars posterior, which inserts on the lateral portion of the disk-condyle complex.