Part 19

Origin.—From the major part of the surface of the palatine bone and the distal head and shaft of the pterygoid and the sphenoidal projection.

Insertion.—By a tendon to the antero-internal part of the articular part of the mandible.

Shape.—Fusiform with a thick fleshy belly.

Relations.—Superiorly with the palatine, the pterygoid, and the sphenoid bones. Inferiorly with the skin.

Action.—It aids in closing the jaw.

=Pterygoideus Externus.= (Synonym.—Pterygoideus lateralis.)

Location.—Supero-external to the pterygoideus internus.

Origin.—From the outer part of the extremity of the orbital process of the quadrate.

Insertion.—The fibers pass downward, outward and forward and are inserted to the inner part of the mandibular ramus.

Shape.—A small round bundle.

Relations.—Inferiorly with the pterygoideus internus. Externally with the inferior maxilla.

Action.—Aids in closing the jaw.

=Digastricus= (Fig. 17, No. B, 16). Location.—Extends from the basi-temporal to the side of the neck.

Origin.—From the external lateral angle of the basi-temporal.

Insertion.—Opposite the angle of the jaw the fibers spread out in fan-like arrangement. The muscle meets its fellow of the opposite side; extends longitudinally over the superior larynx, for some distance down the neck.

Shape.—Thin and ribbon-shaped.

Relations.—Externally to the platysma myoides. The anterior fasciculi blend with those of the mylo-hyoideus; internally with the larynx at the upper part.

Action.—To raise the trachea and hyoid apparatus against the pharynx.

THE MUSCLES OF THE TONGUE

Mylo-hyoideus Stylo-hyoideus Genio-hyoideus Cerato-hyoideus Sterno-hyoideus Depressor-glossus Cerato-glossus Hyoideus transversus

=Mylo-hyoideus.= Location.—The forepart of the inter-ramal space.

Origin.—From the inner side of the lower jaw at a point just above the lower border and the inturned edge of the horny sheath of the beak.

Insertion.—By aponeurosis to the under side of the hyoid, on the median line between the first and the second basi-branchial.

Shape.—Thin, flat, and delicate.

Relations.—Inferiorly with the skin. Thin and rather broad, it meets its fellow of the opposite side. Laterally with the rami of the jaw. Superiorly with the hyoid apparatus.

Action.—Lifts the tongue upward against the roof of the mouth.

=Stylo-hyoideus= (Fig. 17, No. B, 6). Location.—Supero-posterior to the hyoid apparatus.

Origin.—From the outer portion of the articular enlargement of the lower jaw.