Mylohyoid muscle

At a glance

English

Mylohyoid muscle

Latin (TA2)

Musculus mylohyoideus

System

Muscle

Region

Neck

Side

Paired, left and right

About the mylohyoid muscle

The paired mylohyoids together make a muscular sling between the halves of the mandible, the floor on which the tongue rests; for this reason they are also called the diaphragm of the mouth. The name refers to the line on the inner mandible near the molar teeth where the muscle starts, and to the hyoid bone where it ends. Mylohyoid is one of the suprahyoid muscles and develops from the first pharyngeal arch.

Each muscle arises along the mylohyoid line, a ridge on the inner surface of the mandible that runs from near the symphysis in front to the region of the last molar behind. The front and middle fibres run inwards to meet those of the other side in a midline seam, the mylohyoid raphe, which stretches from the chin to the hyoid. The rearmost fibres pass down to the front of the body of the hyoid. The anterior belly of digastric lies directly below the muscle, and geniohyoid and the tongue lie above.

Mylohyoid raises the floor of the mouth, and with it the hyoid and tongue, at the start of swallowing, pressing the tongue up against the palate to push food back. It also tenses the floor of the mouth for speech. When the hyoid is held still by the muscles below, it helps lower the mandible. It is supplied by the nerve to mylohyoid, itself from the inferior alveolar nerve of the mandibular division, and blood comes from the mylohyoid branch of the inferior alveolar artery, the submental artery and the sublingual artery.

The muscle separates the sublingual space above from the submandibular space below; the two connect around its free back edge, where the submandibular gland folds over it. Infections from teeth can spread between them there or straight through the muscle. Because the mylohyoid line climbs towards the back, the roots of the back molars lie below it and usually drain into the submandibular space, while front teeth drain into the sublingual space. Gaps in the muscle through which gland tissue or fat bulges are common. The seam may be missing, and the muscle may be replaced in part by the anterior digastric.

Attachments, action and supply

Origin

Mylohyoid line of the mandible.

Insertion

Midline mylohyoid raphe and the front of the hyoid body.

Action

Raises the floor of the mouth, hyoid and tongue in swallowing and speech; helps depress the mandible.

Nerve supply

Nerve to mylohyoid, from the inferior alveolar nerve (CN V3).

Blood supply

Mylohyoid branch of the inferior alveolar artery, submental and sublingual arteries.