Mylohyoid muscle

Mylohyoid muscle
Muscles of the neck seen from the front (mylohyoid muscle colored in bright red)
Surface anatomy of the neck seen from the front (mylohyoid muscle labeled at right, second from top)
Details
OriginMylohyoid line (mandible)
InsertionBody of hyoid bone and median ridge
ArteryMylohyoid branch of inferior alveolar artery and submental artery of facial artery
NerveMylohyoid nerve, from inferior alveolar branch of mandibular nerve
ActionsRaises oral cavity floor, elevates hyoid, elevates tongue, depresses mandible
Identifiers
LatinMusculus mylohyoideus
TA98A04.2.03.006
TA22165
FMA46320
Anatomical terms of muscle

The mylohyoid muscle or diaphragma oris is a paired muscle of the neck. It runs from the mandible to the hyoid bone, forming the floor of the oral cavity of the mouth.[1] It is named after its two attachments near the molar teeth. It forms the floor of the submental triangle. It elevates the hyoid bone and the tongue, important during swallowing and speaking.

Structure

The mylohyoid muscle is flat and triangular, and is situated immediately superior to the anterior belly of the digastric muscle. It is a pharyngeal muscle (derived from the first pharyngeal arch) and classified as one of the suprahyoid muscles. Together, the paired mylohyoid muscles form a muscular floor for the oral cavity of the mouth.[2]

The two mylohyoid muscles arise from the mandible at the mylohyoid line, which extends from the mandibular symphysis in front to the last molar tooth behind. The posterior fibers pass inferomedially and insert at anterior surface of the hyoid bone. The medial fibres of the two mylohyoid muscles unite in a midline raphe (where the two muscles intermesh).[3]

The mylohyoid muscle separates the sublingual space from the submandibular space, which communicate via a lateral gap between the mylohyoid and hyoglossus muscles at the posterior free margin of mylohyoid muscle.[4] The submandibular gland wraps around the edges of the mylohyoid, and is divided into superficial and deep lobes above and below the muscle.[5]

Nerve supply

The mylohyoid muscle is supplied by a branch of the mandibular nerve, the inferior alveolar nerve. The mylohyoid nerve is a branch of the inferior alveolar nerve. The mylohyoid nerve emerges to give motor supply to the mylohyoid muscle.[1]

Development

The mylohyoid muscles are derived from embryonic mesoderm, specifically the first pharyngeal arch.

Variations

The mylohyoid muscle may be united to or replaced by the anterior belly of the digastric muscle; accessory slips to other hyoid muscles are frequent. This median raphé is sometimes absent; the fibers of the two muscles are then continuous. Variations in the mylohyoid muscle itself are not common.[6] Accessory mylohyoid muscles have been seen in some people, which have the same attachments, nerve supply, and function.[6] The mylohyoid muscle may also be split into an anterior portion and a posterior portion, with the sublingual gland occupying the space between these portions.[7]

An area of herniation of the sublingual gland, blood vessels, or fat, may be present, with studies reporting this in 10-50% of people.[4]

Function

The mylohyoid muscle elevates the hyoid bone and the tongue. This is particularly important during swallowing and speaking. Alternatively, if other muscles are used to keep the position of the hyoid bone fixed, then the mylohyoid muscle depresses the mandible.[1] It also functions as reinforcing the floor of mouth.[1]

Clinical significance

The mylohyoid muscle may be imaged by CT or MRI.[4] The mylohyoid separates the submandibular space below from the sublingual space above. Around the posterior border of the mylohoid muscle, these spaces communicate. Infections, especially odontogenic infections can spread from one space to the other via this communication, or alternatively penetrate the mylohyoid muscle, which is a poor barrier to the spread of infection. Because the attachment of the mylohyoid muscle (the mylohoid line of the mandible) becomes more superior towards the posterior of the mandible, posterior infected teeth are more likely to drain into the submandibular space, and infected anterior teeth are more likely to drain into the sublingual space, since the apices of the teeth are more likely to be below and above the mylohoid line respectively (see diagram).

History

The myloyoid muscle may also be known as the diaphragma oris muscle.[8][9] It is named after its two attachments near the molar teeth ("mylo" comes from the Greek word for "molar").[10]

Additional images

Notes

  1. 1 2 3 4 Drake, Vogl & Tibbitts 2005, p. 987.
  2. ↑ Herring & Fehrenbach 2013, p. 212.
  3. ↑ Drake, Vogl & Tibbitts 2005, pp. 987–8.
  4. 1 2 3 Otonari-Yamamoto, Mika; Nakajima, Koh; Tsuji, Yuriko; Otonari, Takamichi; Curtin, Hugh D.; Okano, Tomohiro; Sano, Tsukasa (2010). "Imaging of the Mylohyoid Muscle: Separation of Submandibular and Sublingual Spaces". American Journal of Roentgenology. 194 (5): W431–8. doi:10.2214/AJR.09.3516. PMID 20410390.
  5. ↑ Drake, Vogl & Tibbitts 2005, p. 997.
  6. 1 2 Sehirli, Ü; Çavdar, S. (1996-03-01). "An accessory mylohyoid muscle". Surgical and Radiologic Anatomy. 18 (1): 57–59. doi:10.1007/BF03207764. ISSN 1279-8517. PMID 8685814. S2CID 6393913.
  7. ↑ Malpas, P. (October 1926). "Anomalies of the Mylohyoid Muscle". Journal of Anatomy. 61 (Pt 1): 64–67. ISSN 0021-8782. PMC 1249927. PMID 17104127.
  8. ↑ "Diaphragma oris - definition - Encyclo". www.encyclo.co.uk. Retrieved 2021-02-15.
  9. ↑ Team, Almaany. "Translation and Meaning of diaphragma oris musculus mylohyoideus In Arabic, English Arabic Dictionary of terms Page 1". www.almaany.com. Retrieved 2021-02-15.
  10. ↑ http://www.anatomy.usyd.edu.au/glossary/glossary.cgi?page=m%5B%5D%5B%5D

References

  • Drake, Richard L.; Vogl, Wayne; Tibbitts, Adam W.M. Mitchell (2005). Gray's anatomy for students. Philadelphia: Elsevier/Churchill Livingstone. ISBN 978-0-443-06612-2.
  • Herring, Margaret J.; Fehrenbach, Susan W. (2013). Illustrated anatomy of the head and neck (4th ed.). St. Louis, MO: Elsevier/Saunders. ISBN 978-1-4377-2419-6.
  • Public domain This article incorporates text in the public domain from page 393 of the 20th edition of Gray's Anatomy (1918)
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