A. The Tongue
(copied from E.2. The Mouth and the Nose)
1.
The tongue is a skeletal muscle, attached at one end to the bones of the skull.
2.
Its major function is to move the food (= bolus) around the mouth, by the teeth and the inner membranes of the mouth cavity and to mix it with saliva to help the digestive process.
3.
The upper surface of the tongue also has several sensors to detect five types of tastes. They do this by having taste buds imbedded into the surface of the tongue.
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These taste buds have sensory cells that pick up a particular taste with their taste hairs and then deliver action potentials to the nerves that go to the brain.
5.
Because these taste cells don’t live very long, 5-10 days max, they are constantly being replaced by the accompanying base cells.
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These are the five tastes that the tongue can detect. Please note that the tip of the tongue detects the nicest thing in our food: sweet!
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Also note that that the back of the tongue detects what could be most dangerous for us, before swallowing something that is very bitter!
8.
Although you may be familiar with the tastes sweet, salty, sour and bitter, you may not be familiar with the taste ‘Umami” (I wasn’t!).
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Umami as a taste was ‘discovered’ only last century by a Japanese scientist. Umami in Japanese means ‘delicious’. It tastes essentially as yummy, nice flavour in many types of food, in sushi’s, in tomato sauce etc.
10.
A recent article informed me of two new/important facts about these taste bugs:
a) the taste areas depicted in the above figure shows where a particular taste (sweet, or salty, etc) is most sensitive. But other areas in the tongue can also detect sweet, salty or other tastes, only less sensitive. In other words, the taste bugs are located all over the tongue.
11.
b) we also have taste bugs elsewhere in the body! Apparently, taste bugs are also located in the gastrointestinal tract, muscles, brain etc. and ongoing research will discover more locations and what they are doing there!
(for more see: The Textbooks Were Wrong About How Your Tongue Works)
1.
Also, interesting to know that the thresholds for perceiving the different types of taste are not the same.
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In fact, the threshold for bitter is the lowest! This is of course to detect as soon as possible something that might be ‘toxic’ in the food!
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At the other end of the sensitivity scale are “sweet’ and ‘salty’.
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On the other hand, there is also the possibility of ‘taste blindness’; some people cannot taste certain substances.
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And, as you may have experiences, some people have more sensitive tastes than others!
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Taste senses are not only located on the tongue but are also found in the palate, in the epithelium of the roof of the mouth, the soft palate, the throat lining and the epiglottis!
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Moreover, the tongue contains not only taste receptors, but also temperature sensors, pressure sensors, and touch sensors. A very sensitive organ indeed!
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And oh yes, what you taste is also influenced by what you smell, in your nose! How complex can it be, all for the protection of humans?
9.
Finally, the action potentials generated in the afferent nerves must also travel to the brain. The anterior two-thirds of the receptors in the tongue travel via the facial nerve, and the posterior one-third travel via the glossopharyngeal nerve to the brainstem. The back of the mouth is innervated by the vagus nerve.
10.
From the brainstem, the nerve fibres travel to the solitary nucleus in the thalamus, and from there, they ultimately reach the gustatory cortex. Interestingly, the taste nerves, in contrast to the optical nerves do not (partially) cross-over to the other side of the brain! No one knows why or why not 😉
1.
While researching about ‘taste’, I discovered also more interesting info about the tongue, especially as it has multiple functions.
2.
It is basically a striated muscle that is attached on one end (to a bone; os hyoideum) and mobile at the other end.
3.
In addition, at the back there is also the lingual tonsil, a lymphatic organ, part of the immune system.
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The tongue mucosa is a thick layer of squamous epithelium with a rough, sometimes bumpy, surface.
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And of course, you have the taste buds which contain the taste sensors (see above).
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But the tongue has several functions in the mouth.
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It examines the food using touch, taste and temperature sensors.
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It is also important in chewing and mixing the food with saliva.
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The tongue also plays an important role in swallowing food, but also in speaking and it even helps in cleaning the teeth.
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And… oh yes… the tongue also plays an important role in human eroticism; French kissing and licking!!!
