The tongue is the principal organ of the sense of taste, and an important organ of speech; it also assists in the mastication and deglutition of the food. It is situated in the floor of the mouth, within the curve of the body of the mandible.
Muscles of the Tongue.—The tongue is divided into lateral halves by a median fibrous septum which extends throughout its entire length and is fixed below to the hyoid bone. In either half there are two sets of muscles, extrinsic and intrinsic; the former have their origins outside the tongue, the latter are contained entirely within it.
The extrinsic muscles are:
The intrinsic muscles are:
Nerves.—The muscles of the tongue are supplied by the hypoglossal nerve.
The sensory nerves of the tongue are:
Actions.—The movements of the tongue, although numerous and complicated, may be understood by carefully considering the direction of the fibers of its muscles. The Genioglossi, by means of their posterior fibers, draw the root of the tongue forward, and protrude the apex from the mouth. The anterior fibers draw the tongue back into the mouth. The two muscles acting in their entirety draw the tongue downward, so as to make its superior surface concave from side to side, forming a channel along which fluids may pass toward the pharynx, as in sucking. The Hyoglossi depress the tongue, and draw down its sides. The Styloglossi draw the tongue upward and backward. The Glossopalatini draw the root of the tongue upward. The intrinsic muscles are mainly concerned in altering the shape of the tongue, whereby it becomes shortened, narrowed, or curved in different directions; thus, the Longitudinalis superior and inferior tend to shorten the tongue, but the former, in addition, turn the tip and sides upward so as to render the dorsum concave, while the latter pull the tip downward and render the dorsum convex. The Transversus narrows and elongates the tongue, and the Verticalis flattens and broadens it. The complex arrangement of the muscular fibers of the tongue, and the various directions in which they run, give to this organ the power of assuming the forms necessary for the enunciation of the different consonantal sounds; and Macalister states "there is reason to believe that the musculature of the tongue varies in different races owing to the hereditary practice and habitual use of certain motions required for enunciating the several vernacular languages.
Vessels and Nerves.—The main artery of the tongue is the lingual branch of the external carotid, but the external maxillary and ascending pharyngeal also give branches to it. The veins open into the internal jugular.