Muscles of tongue has use speech
The tongue is a muscular organ in the mouth of a typical tetrapod. It manipulates food for chewing and swallowing as part of the digestive process, and is the primary organ of taste. The tongue's upper surface (dorsum) is covered by taste buds housed in numerous lingual papillae. It is sensitive and kept moist by saliva and is richly supplied with nerves and blood vessels. The tongue also serves as a natural means of cleaning the teeth. A major function of the tongue is the enabling of speech in humans and vocalization in other animals.
The human tongue is divided into two parts, an oral part at the front and a pharyngeal part at the back. The left and right sides are also separated along most of its length by a vertical section of fibrous tissue (the lingual septum) that results in a groove, the median sulcus, on the tongue's surface.
There are two groups of muscles of the tongue. The four intrinsic muscles alter the shape of the tongue and are not attached to bone. The four paired extrinsic muscles change the position of the tongue and are anchored to bone.Intrinsic
Four paired intrinsic muscles of the tongue originate and insert within the tongue, running along its length. They are the superior longitudinal muscle, the inferior longitudinal muscle, the vertical muscle, and the transverse muscle. These muscles alter the shape of the tongue by lengthening and shortening it, curling and uncurling its apex and edges as in tongue rolling, and flattening and rounding its surface. This provides shape and helps facilitate speech, swallowing, and eating.The superior longitudinal muscle runs along the upper surface of the tongue under the mucous membrane, and elevates, assists in retraction of, or deviates the tip of the tongue. It originates near the epiglottis, at the hyoid bone, from the median fibrous septum.
The inferior longitudinal muscle lines the sides of the tongue, and is joined to the styloglossus muscle.
The vertical muscle is located in the middle of the tongue, and joins the superior and inferior longitudinal muscles.
The transverse muscle divides the tongue at the middle, and is attached to the mucous membranes that run along the sides.Speech
The tongue is one of the primary articulators in the production of speech, and this is facilitated by both the extrinsic muscles that move the tongue and the intrinsic muscles that change its shape. Specifically, different vowels are articulated by changing the tongue's height and retraction to alter the resonant properties of the vocal tract. These resonant properties amplify specific harmonic frequencies (formants) that are different for each vowel, while attenuating other harmonics. For example, [a] is produced with the tongue lowered and centered and [i] is produced with the tongue raised and fronted. Consonants are articulated by constricting airflow through the vocal tract, and many consonants feature a constriction between the tongue and some other part of the vocal tract. For example alveolar consonants like [s] and [n] are articulated with the tongue against the alveolar ridge, while velar consonants like [k] and [g] are articulated with the tongue dorsum against the soft palate (velum). Tongue shape is also relevant to speech articulation, for example in retroflex consonants, where the tip of the tongue is curved backward.