How does the tongue work?

The tongue is an extremely movable group of muscles, which is well-supplied with blood and has many nerves. It has an oblong shape and is covered with a dense layer of connective tissue. Above this layer, a special kind of mucous membrane makes up the surface of the tongue. The root of the tongue is firmly anchored to the floor of the mouth. The other parts of the tongue can move freely. A strip of tissue called the lingual frenulum connects the underside of the tongue to the floor of the mouth. When you close your mouth, the tongue almost fills up the entire cavity of your mouth. Various muscles keep the tongue “suspended” in the throat: Muscles and ligaments connect the tongue to the hyoid bone (or lingual bone) in the upper part of the throat and to the voice box. The lingual frenulum connects the tongue to the lower jaw. Some muscles even connect the tongue to the base of the skull.

The tongue can be divided into different sections:

• Tip and sides of the tongue: These areas are parts of the movable section of the tongue. They are very flexible and can perform complex movements.
• Dorsum: The upper surface of the tongue is called the dorsum. It has many sensory cells for our senses of taste and touch.
• Root of the tongue: The root of the tongue can’t move freely and is connected to the floor of the mouth. It can’t be seen from outside the mouth.

If you look at your tongue in the mirror, you usually see a slightly white, matt, velvety surface. The upper surface is slightly curved, and in the middle it falls towards the groove that divides the tongue in half lengthwise.

The rough surface of the tongue is due to a special feature of the mucous membrane: the papillae, which appear as many small bumps on the tongue. They are formed by (groups of) cells bulging up from underneath. These papillae have different jobs to do:

• Mechanical papillae: These papillae anchor the mucous membrane firmly to the tongue. They also sense touch, allowing us to feel the form and texture of food in our mouth.
• Taste papillae: Taste papillae have a lot of sensory cells in them. The papillae make the surface of the tongue much larger, exposing many more sensory cells to the food you eat, which helps you to recognize the different tastes better.
  

Saliva and bits of food may get stuck in the grooves between the papillae, especially on the last third of the tongue at the back of the mouth. Decay-causing (putrefactive) bacteria can grow there. Then a whitish film covers the tongue, which also causes bad breath. These bacteria mainly live on remains of protein-rich food like fish, cheese or milk.

If you stick out the tip of your tongue and move it upwards, you can see the shiny surface underneath: The most noticeable part of it is the band of tissue (lingual frenulum) in the middle and a vein on either side of it, which can be seen as bluish strings underneath the mucous membrane. Where the tongue meets the floor of the mouth, you can see two salivary glands (submandibular glands) to the left and right of the lingual frenulum.

The mucous membrane lining the mouth can absorb some substances – for example, medications that need to act quickly. The tablet, fluid or spray is put underneath the tongue, but is not meant to be swallowed. This is called sublingual administration (from the Latin word “lingua”, meaning “tongue” or “language”). One example is nitroglycerin spray used for sudden chest pain caused by reduced blood flow through the coronary arteries. This spray acts very quickly because it enters the bloodstream directly.

The tongue has a great ability to move in all directions. The reason for this is the way the muscle fibers are arranged, which is unique in our body. They run in all three directions: from front to back, from the sides to the middle and from top to bottom. This allows the tongue to make the following movements:

• Getting longer and shorter: The tongue is the only muscle in your body that you can actively make longer, not just shorter. When the vertical and horizontal fibers contract at the same time, the tongue becomes narrower and longer. Then you can stick our tongue out.
• Raising and lowering
• Bending backwards
• Pushing forward and pulling back
• Rounding or hollowing
• Making grooves
• Changing its position: Additional muscles can change the position of the tongue: They pull into the tongue from the front (from the lower jaw), from below and behind (from the hyoid bone) and from above and behind (from the base of the skull).

The tongue is a bit like a piston, with the cavity of the mouth being the cylinder: When then tongue moves backward in the closed mouth it produces low pressure, which sucks in fluid and chewed or soft food so you can swallow it.

When we chew, the tongue and the cheeks work together to constantly place the food between the teeth so that it can be chewed. The tongue presses the crushed food against the roof of the mouth and moves it along to the throat when it’s ready to be swallowed. The movements of the tongue also massage small glands directly underneath it, squeezing out saliva. This starts pre-digestion of the food, and the chewed food can move through the food pipe more easily.

The tongue presses the chewed food into the throat, which starts the process of swallowing.

The mucous membrane covering the tongue contains many taste receptors to ‘test’ the things we eat and drink. These receptors are found in the taste buds, where the sensory cells are arranged like orange sections around a fluid-filled funnel. The chemical substances responsible for taste arrive here and are recognized by the sensory cells.

Our sense of taste used to be vital to our survival because it was the only way to test food and tell the difference between good food and poisonous or rotten food. Many tastes automatically trigger the increased production of saliva and stomach acid too, in order to get your digestion going.

The tip of the tongue is the part of the body that is most sensitive to touch. This fine sensitivity to touch mainly allows you to do two things: On the one hand, you can test the mechanical characteristics of food. Because the tongue is so sensitive to touch, small pieces of grit, bone fragments or fish bones feel much larger than they really are. So this “magnifying” effect of the tongue protects us. The tongue also searches the entire mouth for remaining bits of food after you have swallowed the main bit.

In humans, the flexibility of the tongue is important for speaking too. Only when the tongue, lips and teeth work together do sounds from the throat turn into understandable letters and words. The tongue is extremely agile and quick: It can produce more than 90 words per minute, using more than 20 different movements. The tongue is essential for pronouncing the consonants “t,” “d,” “l” or the rolling “r.” When pronouncing the letter “k”, for example, the tongue is narrower at the back. And when we say “s”, the tip of the tongue moves backwards. If the tip of the tongue remains between the teeth, we hear a typical lisp.

The fact that the tongue is essential for speaking can also be seen in the ability of parrots to imitate human language: Although they only have a very simple vocal organ with fewer muscle groups than humans do, they have an extraordinarily thick tongue. This helps them to produce many sounds that sound like human language.

All of the immune system cells on the tongue are collectively called the lingual tonsil. The lingual tonsil is found in the back of the mouth, at the base of the tongue, and is part of the tonsillar (lymphatic) ring. Together with the palatine tonsils and the adenoids, the lingual tonsil is responsible for fighting germs that come in through the mouth.