Mylohyoid muscle

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Mylohyoid muscle
Mylohyoid muscle.PNG
Muscles of the neck. Anterior view. Mylohyoid muscle colored in bright red.
Gray1195.png
Surface anatomy of neck, anterior view (Mylohyoid muscle labeled at right, second from top).
Latin musculus mylohyoideus
Gray's p.393
Origin Mylohyoid line (mandible)
Insertion body of hyoid bone and median raphe
Artery mylohyoid branch of inferior alveolar artery
Nerve mylohyoid nerve, from inferior alveolar branch of mandibular nerve [V3]
Actions Raises oral cavity floor, elevates hyoid, elevates tongue, depresses mandible
Anatomical terms of muscle

The mylohyoid muscle is a paired muscle running from the mandible to the hyoid bone, forming the floor of the oral cavity (the mouth).[1] :987 It is named after its two attachments near the molar teeth ("mylo" comes from the Greek word for "molar").[2] These muscles are mesodermal in embryologic origin. The mylohyoid muscle is derived from the first pharyngeal arch.

Structure[edit]

The mylohyoid muscle is flat and triangular, and is situated immediately superior to the anterior belly of the digastric muscle. It is classified as an anterior suprahyoid muscle.[clarification needed] Together, the paired mylohyoid muscles form a muscular floor (diaphragm) for the oral cavity (the mouth).[3] :212

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 two muscles intermesh). [1] :987-8

The mylohyoid muscle separates the sublingual space from the submandibular space, which communicate in a lateral gap between the mylohyoid and geniohyoid muscles. [4] The submandibular gland wraps around the edges of the mylohyoid, and is divided into superficial and deep lobes above and below the muscle.[1] :997

Innervation[edit]

The mylohyoid muscle is innervated by a branch of the mandibular nerve, the inferior alveolar nerve. A specific branch of this nerve, the mylohyoid nerve, emerges to give motor supply to the muscle.[1] :987

Variations[edit]

The mylohyoid 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.[citation needed]

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[edit]

The mylohyoid elevates the hyoid and the tongue. This is particularly important during swallowing and speaking. Alternatively, if other muscles are used to keep the position of the hyoid fixed, then the mylohoid depresses the mandible. [1] :987 It also functions as reinforcing the floor of mouth.[1] :987

Clinical relevance[edit]

The mylohyoid 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 mylohoid, these spaces communicate. Infections, especially odontogenic infections can spread from one space to the other via this communication, or alternatively penetrate the mylohyoid which is a poor barrier to the spread of infection. Due to the fact that the attachment of mylohyoid (the mylohoid line) becomes more superior towards the posterior of the mandible, posterior infected teeth are more likely to drain into the mandibular 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).

Additional images[edit]

References[edit]

  1. ^ a b c d e f Drake, Richard L.; Vogl, Wayne; Tibbitts, Adam W.M. Mitchell; illustrations by Richard; Richardson, Paul (2005). Gray's anatomy for students (Pbk. ed.). Philadelphia: Elsevier/Churchill Livingstone. ISBN 978-0-443-06612-2. 
  2. ^ http://www.anatomy.usyd.edu.au/glossary/glossary.cgi?page=m
  3. ^ Herring, Margaret J. Fehrenbach, Susan W. Illustrated anatomy of the head and neck (4th ed.). St. Louis, Mo.: Elsevier/Saunders. ISBN 978-1437724196. 
  4. ^ a b c Otonari-Yamamoto, Mika; Nakajima, Koh; Tsuji, Yuriko; Otonari, Takamichi; Curtin, Hugh D.; Okano, Tomohiro; Sano, Tsukasa (1 May 2010). "Imaging of the Mylohyoid Muscle: Separation of Submandibular and Sublingual Spaces". American Journal of Roentgenology 194 (5): W431–W438. doi:10.2214/AJR.09.3516. PMID 20410390. 

External links[edit]

This article incorporates text from a public domain edition of Gray's Anatomy.