Tongue

At a glance

English

Tongue

Latin (TA2)

Lingua

System

Digestive

Region

Whole body

Side

Single, on the midline

About the tongue

The tongue is a mass of skeletal muscle covered by mucous membrane. It is anchored below to the mandible and hyoid bone and behind to the styloid process and soft palate, but its tip and sides are free. A V-shaped groove on its upper surface, the terminal sulcus, divides it into a front two-thirds (the oral part, lying in the mouth) and a back third (the pharyngeal part, facing the oropharynx). The apex of the V points backwards to a small pit, the foramen caecum, which marks where the thyroid gland began to grow down in the embryo.

The surface differs between the two parts. In front, the dorsum is rough with papillae: many tiny thread-like filiform papillae that give grip, scattered red fungiform papillae, leaf-like foliate folds at the sides, and a row of large vallate papillae just in front of the sulcus, each ringed by a trench lined with taste buds. Behind the sulcus there are no papillae; instead the surface is bumpy with the lymphoid nodules of the lingual tonsil. On the underside a midline fold, the frenulum, tethers the tongue to the oral floor, and the deep lingual veins show through the thin lining on each side.

Two groups of muscles move it. The intrinsic muscles, running lengthways, across and vertically inside the tongue, change its shape: they curl, flatten, narrow and lengthen it. The extrinsic muscles, genioglossus, hyoglossus, styloglossus and palatoglossus, attach it to bone or palate and change its position, pushing it out, drawing it back, lowering or raising it. A midline fibrous septum separates right and left halves.

Nerve supply follows its embryological origin and is a classic examination topic. If the hypoglossal nerve is damaged on one side, the tongue wastes on that side and, when pushed out, deviates towards the weak side. Cancers of the tongue most often arise on its side edges. Because the pharyngeal part slopes towards the airway, a relaxed tongue can fall back and block breathing in an unconscious patient.

Function and supply

Function

Moves food during chewing, forms and pushes the bolus back for swallowing, carries taste buds, and shapes the mouth for speech.

Nerve supply

Motor: hypoglossal nerve to all tongue muscles except palatoglossus (vagus). Front two-thirds: lingual nerve for general sensation, chorda tympani (facial) for taste. Back third: glossopharyngeal nerve for both; internal laryngeal branch of the vagus near the epiglottis.

Blood supply

The lingual artery from the external carotid, with its deep and dorsal lingual branches; veins drain to the internal jugular vein.