The tongue and its importance

FORKED tongue, tongue-lashing, tongue twister …Even the English language recognizes that importance of the tongue, without which we would not be able to speak, swallow, or taste.

This important part of our body can even tell us, in a general way, the state of our health. And what more graphic way to express disgust than by sticking out your tongue?

The tongue is a mass of ‘voluntary’ muscles called intrinsic and extrinsic muscles. The intrinsic muscles allow the tongue to change size and shape quickly. The flexible extrinsic muscles allow the tongue to rapidly change position. The bottom is attached to the floor of the mouth. This is where the salivary glands are located. Many nerves are situated in the tongue and floor of the mouth. If a person becomes unconscious, the tongue tends to fall back into the airway, causing suffocation. It is, therefore, necessary to look in the person’s mouth and clear the airway before commencing CPR (cardio-pulmonary resuscitation).

The tongue is not the lively red colour of the gums; rather, it has a grayish coat on the surface, caused by the specialized cells of which it is made. The muscle is covered with a mucous membrane formed into nipple-like elevations called papillae.

Papillae roughen the tongue’s surface to help it guide foods during chewing and swallowing. Papillae also contain nerves for touch sensations, and most contain taste buds. Examination of the tongue with a mirror reveals a row of v-shaped, rounded, raised areas toward the back of the tongue where the taste buds responding to bitterness are located.

In front of this row are tall, thin, cone-shaped raised areas that respond to sweet, sour, or salty substances. At the sides of the tongue are taste buds that react to acidic ingredients.

The tongue has several functions. It is involved in speech, manipulation and positioning of food, tasting, and swallowing. The tongue aids chewing by crushing food against the roof of the mouth (the palate), and by rolling the food between the teeth. Swallowing is accomplished as the tongue presses the food against the palate and pushes it backward into the oropharynx (entrance into the digestive and respiratory systems).

The act of chewing involves coordinated movements of certain muscles that close the mouth and raise and lower the mandible, causing the teeth to grind and crush the food. The smell and taste of food cause saliva to be secreted immediately, which helps dissolve, dilute, and lubricate chewed food. The cheeks become tense and the tongue moves the food between the teeth and backwards towards the stomach. If disease necessitates surgical removal of the tongue, or it is missing at birth due to genetic disturbances, chewing is assisted by the cheeks and the floor of the mouth.

The tongue is, of course, very active in speech. If the tongue is incorrectly attached to the floor of the mouth from birth, speech is impeded and a ‘lisp’ develops. The tongue must be placed near or against the upper front teeth to form the consonants ‘D’ and ‘T’. Producing the sound made by the letter ‘L’ also requires the interplay of tongue and teeth.

The tongue’s appearance is often used as an aid in the diagnosis of various diseases and conditions. We know, for instance, that during illness, some of the papillae become engorged and change colour, becoming strawberry in appearance. When people have pernicious anemia, their tongue may be sore, appear beefy-red, and have white patchy white spots on the surface. An enlarged tongue is a sign of hypothyroidism.

According to Chinese medical science, the tongue is divided into certain sections, with each part pertaining to an organ. In this approach to the diagnosis and treatment of disease, the tip of the tongue represents the heart and lung; the central part represents the spleen and stomach; the root of the tongue represents the kidneys; and the sides of the tongue represent the liver and gall bladder.

Colour, texture, size, and shape of the tongue are taken into consideration as a diagnostic tool to help determine the organ to be treated. So, although self-diagnosis by using the tongue is certainly not practical, understanding what a healthy tongue looks like may give you clues about your general health.

Any variation in colour (too red or pale), texture (thickly coated), size (enlarged or swollen), or shape (scalloped border) may indicate an unhealthy condition.

Cleansing of the teeth and mouth as well as good digestion depend a great deal upon the salivary glands. A number of these glands secrete saliva in the mouth. Saliva – which contains water, salts, enzymes, and mucus – moistens and softens foods for ease in swallowing, and cleanses the teeth and mouth.

The function of the salivary glands is affected by hormones produced by the pancreas, testes, ovaries, and the thyroid and pituitary glands. The nature and quantity of saliva is affected by reflexes for which the taste buds act as receptors. The presences of soft moist foods in the mouth will, for instance, stimulate less secretion of the lubricating component of saliva. Salivation or watering of the mouth can also be a conditioned reflex, as when we think about certain food or hear the mention of a particular food.

There are a few minor salivary glands situated around the lips, inside cheeks, in the palate, and on the tongue. There are also three major pairs of salivary glands. On each side of the face, just in front of the ears, are the parotid glands, the largest of the salivary glands.

The duct for each parotid gland, called Stenson’s duct, opens into the mouth from each cheek opposite the upper second molar. The parotid glands produce a clear watery secretion that functions as a cleansing, dissolving, and digestive agent. The saliva produced by the parotid gland contains a substance called ptyalin, a salivary enzyme that breaks down starch. When a sour food, such as a lemon, is introduced into the mouth, it stimulates the parotid glands.

The sublingual glands are located in the floor of the mouth, under the tongue.
The duct for these glands, called Rivinus’ duct, opens into the mouth from the floor of the mouth directly behind the lower front teeth. The saliva secreted by this gland is thicker and ropey compared with the secretion from the parotid. Sublingual-gland secretions serve as lubricating agents; bland substances such as milk and bread stimulate its production.

The sub-mandibular glands are located in the floor of the mouth, under the base of the tongue and more to the side of the lower jaw. These glands secrete a mixed type of saliva that is thin at first and becomes thicker. This secretion is also used for lubricative and digestive purposes.

Next week, I will deal with other structures which also play an integral role in the dental-oral complex.