Anat Cell Biol.  2021 Sep;54(3):308-314. 10.5115/acb.21.074.

Morphology of the temporalis muscle focusing on the tendinous attachment onto the coronoid process

• Yu SK
• Kim TH
• Yang KY
• Bae CJ
• Kim HJ

• KMID: 2521043
• DOI: http://doi.org/10.5115/acb.21.074

Abstract

The temporalis muscle is usually described as a single layer originating at the temporal line, converging to a tendon, and inserting onto a narrow site of the coronoid process. However, recent studies have shown that the temporalis muscle can be divided into two or three separate segments and the distal attachment continues inferiorly beyond the coronoid process. Therefore, the aims of this study were to analyze the morphology of the temporalis muscle focusing on the tendinous attachment onto the coronoid process and to provide educational values. The temporalis muscle was carefully dissected in 26 cadavers and classified based on the muscle fascicle direction. Each divided part was sketched and measured based on bony landmarks to elucidate its tendinous insertion site onto the coronoid process, and the results obtained were reviewed through the literature. The temporalis muscle ends at two distinct terminal tendons with wider insertion sites than usually presented in textbooks and atlases and separates into two parts that combine to act as a single structural unit. The superficial part is a large fan-shaped muscle commonly recognized as the temporalis muscle. This converges infero-medially to form the superficial tendon and the lateral boundary of the retromolar triangle. Meanwhile, the deep part is a narrow vertically oriented rectangular muscle that converges postero-laterally to form the deep tendon and the medial boundary of the retromolar triangle. These results indicate that understanding the temporalis muscle’s insertion site onto the coronoid process will be useful clinically with educational values during surgical procedures.

Keyword

Temporalis muscle; Coronoid process; Superficial temporalis tendon; Deep temporalis tendon; Retromolar region

Figure

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  Fig. 1 Diagram showing the dimensions measured the two separate parts of the temporalis muscle attached onto the coronoid process based on the bony landmarks. ①, height of the ending point of the superficial part of the temporalis muscle (TMs) from the inferior border of the mandible; ②, height of the ending point of the deep part of the temporalis muscle (TMd) from the inferior border of the mandible; ③, height of the separating point of the two parts from the inferior border of the mandible; ④, height of the lingula from the inferior border of the mandible; ⑤, width of the TMd from the anterior border of the mandibular ramus; ⑥, width of the lingula from the anterior border of the mandibular ramus; ⑦, distance of the end point of the posterior border of the TMs based on the mandibular notch.

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  Fig. 2 Photograph (A) and schematic (B) illustrating the two distinct terminal tendons of the temporalis muscle that formed the boundary on both sides of the retromolar triangle. The blue and green colors indicate the dimensions of the TMs and TMd onto the coronoid process, respectively. TMs, superficial part of the temporalis muscle; TMd, deep part of the temporalis muscle.

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  Fig. 3 Photograph (A) and schematic (B) showing the dimensions of the TMs attached onto the coronoid process on the lateral side of the mandible. TMs, superficial part of the temporalis muscle.

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  Fig. 4 Photographs (A–C) and schematic (D) showing the dimensions of the TMs and TMd attached onto the coronoid process on the medial side of the mandible. The dotted arrows indicated that the muscle fibers of two separate parts of the temporalis muscle were intermingled in the posterior side. TMs, superficial part of the temporalis muscle; TMd, deep part of the temporalis muscle.

Reference

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