Part 62

Blood-supply.—External carotid artery.

Nerve-supply.—Facial nerve (stylo-hyoid branch).

3. =Occipito-hyoideus= (M. jugulo-hyoideus; occipito-styloideus).—This is a small triangular muscle, which lies in the space between the paramastoid process and the great cornu of the hyoid bone.

Origin.—The paramastoid (styloid) process of the occipital bone.

Insertion.—The proximal extremity and ventral edge of the great cornu of the hyoid bone.

Action.—It carries the distal extremity of the great cornu backward and upward. Acting with the genio-hyoideus and digastricus, it raises the hyoid bone and the larynx.

Structure.—The muscle is somewhat triangular, its fibers being longer as the ventral border is approached. It blends with the posterior belly of the digastricus.

Relations.—Superficially, the parotid gland; deeply, the guttural pouch.

Blood-supply.—Occipital artery.

Nerve-supply.—Facial nerve.

4. =Genio-hyoideus.=—This is a long, spindle-shaped muscle, which lies under the tongue in contact with its fellow of the opposite side (Fig. 243).

Origin.—The angle of union of the rami of the mandible.

Insertion.—The extremity of the lingual process of the hyoid bone.

Action.—It draws the hyoid bone and tongue forward.

Structure.—The muscle arises by a short tendon, which is succeeded by the belly, composed of long bundles of parallel fibers.

Relations.—Below, the mylo-hyoideus; above, the hyo-glossus, stylo-glossus, genio-glossus, the sublingual gland, submaxillary duct, and the lingual nerve.

Blood-supply.—Sublingual artery.

Nerve-supply.—Hypoglossal nerve.

5. =Kerato-hyoideus.=—This small triangular muscle lies in the space between the thyroid and small cornu, under cover of the hyo-glossus (Fig. 243).

Origin.—The posterior edge of the small cornu and the adjacent part of the ventral border of the great cornu.

Insertion.—The dorsal edge of the thyroid cornu.

Action.—It raises the thyroid cornu and the larynx.

Relations.—The muscle is crossed outwardly by the lingual artery.

Blood-supply.—Lingual artery.

Nerve-supply.—Glosso-pharyngeal nerve.

6. =Hyoideus Transversus.=—This is a thin, unpaired muscle, which extends transversely between the two small cornua of the hyoid bone.

Attachments.—The small cornua close to the junction with the great cornua.

Action.—When relaxed, its upper surface is concave; when it contracts, it elevates the root of the tongue.