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Other Terms: Lingua, Langue, Zunge, Lengüeta, Linguetta, Dila
The tongue is the principal organ of the sense of taste. It is also an important organ of speech. It assists in the mastication of food. It is situated in the floor of the mouth within the curve of the body of the mandible.
Parts and Relations
Its root is directed backward and connected with the hyoid bone by the hyoglossus and genioglossus muscles and the hyoglossal membrane. It is connected with the epiglottis by three folds of mucous membrane. It is connected with the soft palate by the glossopalatine arches and with the pharynx by the superior pharyngeal constrictor and the mucous membrane. Its apex, thin and narrow, is directed forward against the lingual surfaces of the lower incisor teeth. Its inferior surface is connected with the mandible by the genioglossus. The mucous membrane is reflected from it to the lingual surface of the gum and onto the floor of the mouth. Here, in the middle line, it is elevated into a distinct vertical fold, the frenulum. The apex of the tongue, part of the inferior surface, the sides, and dorsal surface are free. The dorsal surface of the tongue is convex and marked by a median sulcus which divides it into symmetrical halves. This sulcus ends behind the root of the organ in the foramen caecum . From the foramen caecum, the sulcus terminalis runs laterally and forward on either side to the margin of the tongue. The portion of the dorsal surface of the tongue in front of this groove looks upward. This portion is rough and covered with papillae. The posterior third looks posterior and is smoother. The papillae of the tongue are projections of the dorsal surface of the tongue. They are thickly distributed over the anterior two-thirds of the dorsal surface of the tongue which makes it appear rough. The varieties of papillae are the vallate papillae, fungiform papillae, and filiform papillae. The vallate papillae are large and vary from eight to twelve in number. They are situated on the dorsal surface of the tongue, immediately in front of the foramen caecum and sulcus terminalis. They form a row on either side. The two rows run backward and medially and meet in the middle line. They look like the limbs of the letter V inverted. Each papilla consists of a projection of mucous membrane from one to two millimeters wide. These projections are attached to the bottom of a circular depression of the mucous membrane. The margin of the depression is elevated to form the vallum. The papilla is shaped like a truncated cone, the smaller end is directed downward and attached to the tongue. the broader part or base projects a little above the surface of the tongue and is studded with numerous small secondary papillae and covered by stratified squamous epithelium. The fungiform papillae are more numerous than the vallate papillae. They are found primarily at the sides and apex of the tongue. They are scattered irregularly and sparingly over the dorsal surface of the tongue. They are easily recognized, among the other papillae because of their large size, rounded eminence, and deep red color. They are narrow at their attachment to the tongue, but broad and rounded at their free extremities, and covered with secondary papillae. The filiform papillae cover the anterior two-thirds of the dorsal surface of the tongue. They are very minute, filiform in shape, and arranged in lines parallel with the two rows of the vallate papillae, except at the apex of the organ where their direction is transverse. Projecting from their apices are numerous secondary papillae. The secondary papillae are whitish because of the thickness and density of the epithelium of which they are composed. The cells have become cornified and elongated into dense, imbricated, brush-like processes. The filiform papillae contain a number of elastic fiber, which render them firmer and more elastic than the papillae of mucous membrane.
The main artery of the tongue is the lingual branch of the external carotid. The ascending pharyngeal and external maxillary artery also give branches to it.
The tongue is drained by the lingual branch of the internal jugular vein
The muscles of the tongue are supplied by the hypoglossal nerve. The sensory nerves of the tongue are the lingual branch of the mandibular nerve, the chorda tympani branch of the facial nerve, the lingual branch of the glossopharyngeal nerve, and the superior laryngeal. The lingual branch of the mandibular nerve is distributed to the papillae at the forepart and sides of the tongue. The chorda tympani branches of the facial nerve runs in the sheath of the lingual and is usually regarded as the nerve of taste for the anterior two-thirds of the tongue. The lingual branch of the glossopharyngeal is distributed to the mucous membrane at the base and side of the tongue and to the vallate papillae. This branch supplies both gustatory filaments and fibers of general sensation to this region. The superior laryngeal sends some fine branches to the root near the epiglottis.
The lymphatic vessels of the tongue are drained chiefly into the deep cervical glands lying between the posterior belly of the digastricus and the superior belly of the omohyoid. The lymphatic vessels of the tongue can be divided into four groups: apical, lateral , basal, and median.