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Anatomia, histologia, embryologia2024; 53(6); e70000; doi: 10.1111/ahe.70000

Gross Anatomy of the Equine Masseter Muscle: Lamination and Intramuscular Course of the N. Massetericus.

Abstract: The masticatory muscles of the horse are arranged in an asymmetrical pattern. Four individual muscles on the medial side of the mandible are opposed by one muscle (M. masseter) on the lateral side. However, recent studies on various herbivorous mammals indicate that the masseter muscle features a complex stratigraphic structure that might account for a functional diversity resembling an arrangement of several individual muscles. The functional consideration of the multidirectional equine masticatory movements leads to a similar hypothesis. In order to elucidate the detailed anatomy of the equine masseter muscle, eight cadaveric equine heads were dissected. Additional 29 skull specimens were assessed with regard to the masseteric attachment within the Fossa masseterica. A constant arrangement of nine individual muscular layers within the masseteric muscle was determined. The individual layers were clearly separated by tendon plates and their attachment areas at the masseteric fossa of the mandible were arranged in a constant pattern of bony ridges. With similar consistency, the main trunk of the masseteric nerve was found to run from dorsocaudal to ventrorostral: On that course, the nerve penetrated between the muscular layers from medial to lateral at constant positions. The findings of this study serve as a basis for further studies with the aim of developing biomechanical concepts of equine masticatory movement.
© 2024 The Author(s). Anatomia, Histologia, Embryologia published by Wiley‐VCH GmbH.
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Publication Date: 2024-10-27 PubMed ID: 39462227DOI: 10.1111/ahe.70000Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The researchers of this study dissected eight horse heads and examined 29 horse skulls in order to further understand the complex structure of the horse’s masseter muscle, a muscle involved in their chewing mechanism. They found a consistent pattern of nine individual muscular layers within the masseter muscle, separated by tendon plates, as well as identified a specific course followed by the main masseteric nerve.

Objective of the Study

  • The main objective of this study was to explore the detailed anatomy of the equine masseter muscle due to its potential role in functional diversity concerning chewing movements in horses. The researchers hypothesized that the horse’s masticatory movements could be multidirectional, which led to this detailed study of the masseter muscle’s structure.

Methodology

  • The researchers dissected eight cadaveric horse heads and examined 29 skull specimens. These examinations aimed to find the precise features and arrangement of the masseter muscle, particularly its attachment within the Masseteric Fossa, a depression on the outer surface of the mandible where the masseter muscle attaches.

Findings

  • The study determined a consistent arrangement of nine individual muscular layers within the masseter muscle, which could indicate a complex and highly specialized muscular structure.
  • These individual layers were found to be separated by tendon plates, suggesting a firm but flexible composition that might be suitable for performing diverse, multi-directional movements.
  • The research also found consistent patterns of bony ridges at the masseteric fossa, where the muscle layers attach. This could further emphasize the complexity and structural specialization of the horse’s masseter muscle.
  • The researchers also discovered a consistent path followed by the main trunk of the masseteric nerve running from the back upper part to the lower front part of the muscle. It was noted that this nerve penetrated the muscular layers from the inside nearest the mandible, to the outside furthest from the mandible.

Conclusions

  • The findings of this research provide a better and more detailed understanding of the horse’s masseter muscle. This could form the basis for further studies, particularly in developing biomechanical concepts of equine masticatory movements.

Cite This Article

APA
Süß F, Guth S, Müller-Ehrenberg H, Röcken M, Staszyk C. (2024). Gross Anatomy of the Equine Masseter Muscle: Lamination and Intramuscular Course of the N. Massetericus. Anat Histol Embryol, 53(6), e70000. https://doi.org/10.1111/ahe.70000

Publication

Anatomia, histologia, embryologia
ISSN: 1439-0264
NlmUniqueID: 7704218
Country: Germany
Language: English
Volume: 53
Issue: 6
Pages: e70000

Researcher Affiliations

Süß, Franziska
  • Faculty of Veterinary Medicine, Institute of Veterinary-Anatomy, -Histology and -Embryology, Justus-Liebig-University Giessen, Giessen, Germany.
Guth, Sinja
  • Veterinary Practice Dr. Guth, Aschaffenburg, Germany.
Müller-Ehrenberg, Hannes
  • Orthopaedic Specialist, Münster, Germany.
Röcken, Michael
  • Clinic for Horses (Surgery, Orthopedics), Faculty of Veterinary Medicine, Justus-Liebig-University Giessen, Giessen, Germany.
Staszyk, Carsten
  • Faculty of Veterinary Medicine, Institute of Veterinary-Anatomy, -Histology and -Embryology, Justus-Liebig-University Giessen, Giessen, Germany.

MeSH Terms

  • Animals
  • Horses / anatomy & histology
  • Masseter Muscle / anatomy & histology
  • Mandible / anatomy & histology
  • Cadaver

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Citations

This article has been cited 1 times.
  1. Gobbo E, Topal O, Novalija I, Mladenić D, Zupan Šemrov M. An iterative approach to identify key predictive features of fear reactivity and fearfulness in horses (Equus caballus). Sci Rep 2025 Jul 9;15(1):24590.
    doi: 10.1038/s41598-025-10725-4pubmed: 40628935google scholar: lookup
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