Mylohyoid muscle

Origin and insertion

Mylohyoid is a sheet like muscle, originating from the entire length of the mylohyoid line on the inner surface of mandible. It courses inferomedially, with its fibers inserting onto the mylohyoid raphe (median fibrous raphe) and superior aspect of body of hyoid bone. The anterior fibers insert into the mylohyoid raphe forming a connection in the midsagittal plane, while the posterior fibers insert to the hyoid bone only.

The mylohyoid raphe extends from the symphysis menti of mandible to the body of hyoid bone. It might be absent in some individuals. In that case the mylohyoid muscle fibers either blend with the anterior belly of digastric muscle, or the left and right mylohyoid muscles fuse with each other.

Relations

Forming the floor of the mouth, the superior surface of mylohyoid muscle is related to the structures of the oral cavity; it lies directly beneath the geniohyoid, hyoglossus and styloglossus muscles, hypoglossal (CN XII) and lingual nerves, submandibular ganglion, sublingual and submandibular glands, and the lingual artery and vein.

The inferior surface of the muscle relates to the structures of the anterior neck triangle; platysma, anterior belly of digastric muscle, submandibular gland, mylohyoid nerve and artery, and the facial and submental arteries and veins.

Innervation

Mylohyoid innervation is supplied by the nerve to mylohyoid muscle. This nerve is a branch of the inferior alveolar nerve, which in turn comes from the mandibular nerve. Thus the main source for mylohyoid innervation is the mandibular nerve (CN V3).

Blood supply

Arterial supply to mylohyoid muscle comes from three sources;

• Sublingual branch of the lingual artery
• Inferior alveolar artery (a branch of maxillary artery)
• Submental artery (a branch of the facial artery)

Function

Attaching between the mandible and hyoid bone, the mylohyoid muscle has the following actions; 

• Like all the other suprahyoid muscles, it elevates both the hyoid bone and floor of mouth, when the mandibular attachment is fixed 
• It depresses mandible with the hyoid attachment fixed.

With its elevating actions on hyoid and floor of the mouth, the mylohyoid muscle aids deglutition by pressing the tongue against the hard palate, thus pushing the bolus towards the pharynx. Along with digastric and geniohyoid muscles, the mylohyoid can depress the mandible against resistance, separating teeth that may be held together by food and facilitating chewing.

Learn more about the suprahyoid muscles, including the mylohyoid and other important muscles of the ventral neck.