A muscular organ which plays an important role in mastication, speech, swallowing, cleansing, taste, suckling, and exploring. The lower surface is covered by a thin non-keratinized layer of mucosal epithelium, which is continuous with the floor of the mouth. The tongue is anchored anteriorly by the lingual fraenum (frenulum linguae), either side of which lie the fimbriated (frilly) folds of tissue. The upper surface of the tongue (dorsum) is divided into an anterior two thirds within the oral cavity and a posterior third that faces the pharynx separated by a V-shaped groove (sulcus terminalis) at the apex of which is a small depression (foramen caecum). The tongue is divided into two halves mesio-distally by a fibrous septum. The anterior two thirds of the tongue are covered by a specialized keratinized mucosa containing the circumvallate, filiform, fungiform, and foliate papillae in which (except for the filiform) are embedded taste buds.
The tongue consists of intrinsic muscles, which alter the shape of the tongue, and extrinsic muscles which alter its position to facilitate speech, swallowing, and eating. Because the tongue is divided into two halves by the median septum, all the intrinsic muscles are paired and consist of superior and inferior longitudinal, transverse, and vertical fibre bundles. The extrinsic muscles of the tongue (hyoglossus, styloglossus, palatoglossus, genioglossus) arise from structures outside the tongue and insert into it. The primary blood supply is from the lingual artery and venous drainage is via the lingual or facial veins. The nerve supply consists of motor innervation from the hypoglossal nerve (except for the palatoglossal muscle, which is supplied by the pharyngeal branch of the vagus nerve) and sensory innervation of the oral anterior two thirds of the tongue via the lingual nerve. The tongue may become enlarged in conditions such as Down's syndrome (Down syndrome), myxoedema, and acromegaly.