THE HUMAN TONGUE

A Labelled Diagram of The Human Tongue

When we talk about the tongue, what comes to your mind? Is it just an ordinary muscular taste organ or is there more to the usage of the tongue other than taste?

The tongue is a muscular HYDROSTAT in the mouth; it is covered with pink moist tissue called MUCOSA. Its rough texture is a result of tiny bumps called PAPILLAE which is sensitive and kept moist by saliva and is richly supplied with nerves and blood vessels.
Thousands of taste buds cover the surface of the papillae. These taste buds are collections of nerve-like cells that connect to nerves running into the brain.

The tongue is attached to the mouth by webs of tough tissues and mucosa. In the front of the mouth, the tongue is held down by a tether called FRENUM while at the back of the mouth, the tongue is anchored into the HYOID bone.

The primary function of the tongue is to aid GUSTATION. The four common tastes are SWEET, SOUR, BITTER and SALTY. A fifth taste called UMAMI results from tasting glutamate (present in MSG). The nerves in the tongue help detect and transmit taste signals to the brain. All parts of the tongue can detect different tastes.

In humans, a secondary function of the tongue is phone articulation. It is responsible for speech, sounds and accents. The tongue also serves as a natural means of cleaning one's teeth.

Structure of The Human Tongue

STRUCTURE

The tongue is a muscular structure that forms part of the floor of the oral cavity. The human tongue is divided into anterior and posterior parts. The anterior part is the visible part situated at the front, and roughly two-thirds the length of the tongue. The posterior part is the part closest to the throat, and roughly one-third of length. These parts differ in terms of their EMBRYOLOGICAL development and nerve supply. The two parts of the tongue are divided by the terminal sulcus.

                                                    

The left and right sides of the tongue are separated by the lingual SEPTUM.

The anterior tongue is, at its apex, thin and narrow, it is directed forward against the lingual surfaces of the lower incisor teeth. The posterior part is, at its root, directed backward, and connected with the hyoid bone by the hyoglossi and genioglossi muscles and the hyoglossal membrane; with the epiglottis by three folds (glossoepiglottic) of mucous membrane; with the soft palate by the glossopalatine arches; and with the pharynx by the constrictores pharyngis superiores and the mucous membrane.

In phonetics and phonology, a distinction is made between the tip of the tongue and the blade (the portion just behind the tip). Sounds made with the tongue tip are said to be apical, while those made with the tongue blade are said to be laminal.

LENGTH

The average length of the human tongue from the OROPHARYNX to the tip is 10 cm (4in)

INNERVATION

Nerves which supply the sensation and taste of the tongue differ between the anterior and posterior parts.

Anteriorly, the sensation of taste is passed along the chorda tympani, a branch of the facial nerve. Sensation is passed along the lingual nerve, a branch of the trigeminal nerve.

Posteriorly, both taste and sensation are passed along the glossopharyngeal nerve.

All intrinsic and extrinsic muscles of the tongue are supplied by the hypoglossal nerve, with the exception of the palatoglossus. The palatoglossus is innervated by the vagus nerve.

BLOOD SUPPLY

The tongue receives its blood supply primarily from the lingual artery, a branch of the external carotid artery. Veins of the tongue, the lingual veins, drain into internal jugular vein. The floor of mouth also receives its blood supply from the lingual artery. There is also secondary blood supply to the tongue from the tonsillar branch of the facial artery and the ascending pharyngeal artery.

The triangle formed by the intermediate tendon of the digastric muscle, the posterior border of the mylohyoid muscle, and the hypoglossal nerve is sometimes called Pirogov's, Pirogoff's, or Pirogov-Belclard's triangle.The lingual artery is a good place to stop severe hemorrage from the tongue.

DEVELOPMENT

The anterior tongue is derived primarily from the first pharyngeal arch. The posterior tongue is derived primarily from the third pharyngeal arch. The second arch however has a substantial contribution during fetal development, but this later atrophies. The fourth arch may also contribute, depending upon how the boundaries of the tongue are defined.

The terminal sulcus, which separates the anterior and posterior tongue, is shaped like a V, with the tip of the V situated posteriorly. At the apex is the foramen caecum, which is the point where the embryological thyroid begins to descend

From the facts above you will see that the human tongue plays more role in the mouth other than taste.

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HYDROSTAT - An electrical device for detecting the presence of water, as from overflow or leakage. (In this case, the tongue is not an electric device).

MUCOSA - Another name for mucus membrane.

PAPILLAE - Any small, nipple-like process or projection.

FRENUM -  A fold of membrane that checks or restrains the motion of a part.

HYOID - Also, hyoidal, hyoidean. noting or pertaining to a U shaped.

GUSTATION - The act of tasting.

SWEET - Having the taste or flavour characteristic of sugar, honey, etc. 

SOUR - Having an acid taste, resembling that of vinegar, lemon juice, etc.

BITTER - Having a harsh, disagreeably acrid taste, like that of aspirin, quinine, wormwood, or aloes. 

SALTY - Tasting of or containing salt; saline. E.g. Sea water. 

UMAMI  - A strong meaty taste imparted by glutamate and certain other amino acids.

EMBRYOLOGICAL - The origin, growth, and development of an embryo.

SEPTUM - A dividing wall, membrane or the like 

OROPHARYNX - The part of the PHARYNX between the soft palate and the upper edge of the epiglottis (PHARYNX - The tube or cavity, with its surrounding membrane and muscles, that connects the mouth and nasal passages with the esophagus).

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