A review of the types of taste buds, their location on the tongue, and their associated flavors.
The senses refer to the physiological mechanism of sensation and allow us to obtain information about what is happening around us, as well as certain internal states of the body itself. The sense of sight seems the most important of all because, with 130 million photosensitive cells distributed in each eye, these complex devices allow us to locate our figure and actions in 3 dimensions, with all that this entails.
Although smell and taste seem less relevant than sight itself, can you imagine how human beings could have evolved without a sense that warns us that what we are ingesting is dangerous? Disgust is a primal sensation present in many animals, since the regurgitation of a toxic or harmful element, in many cases, can save the life of the individual.
Thus, the taste buds and the sense of taste, in general, play a much more important evolutionary role than might initially be expected. If you want to know everything about the taste buds, read on.
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What are the taste buds?
Taste buds are defined as a set of sensory receptors, specifically referred to as taste receptors. They are found in the language and are the main promoters of taste, which allows us to enjoy food and discriminate those not edible elements. The papilla refers to the cutaneous fold that we have on the tongue, but what really encodes the “understanding” of the taste are the taste buds found in it.
On average, a healthy adult individual has about 10,000 taste buds distributed in taste buds, which regenerate approximately every two weeks. Unfortunately, as time goes by, these structures deteriorate. An elderly person has half as many buttons as a young person, and therefore sometimes it is more difficult for older people to identify certain flavours. Smokers have the same problem, as exposure to tobacco smoke decreases the proportion of these cells.
What are the taste buds?
As we have mentioned in previous lines, the taste buds are the sensory cells present in the papillae in charge of transmitting the signals that are translated into the taste itself. Each taste bud is formed by the association of about 50-100 cells, known as taste receptor cells (TCR). In mammals, the taste buds are widely distributed on the tongue, soft palate, and oropharynx.
These curious buttons have an ovoid shape, between 50 and 60 microns high and 30 to 70 high. In each taste bud, we find three cell types, whose characteristics and functions are different. We present them in the following list:
- Type I: they are thin and dense, with a support function. They also function as glia and present ionic currents involved in salty taste transduction (60% of the total).
- Type II: clear and fine, with small villi at its apical end. They have transduction receptors for sweet, bitter and umami taste (30% of the total).
- Type III: Similar to the previous ones, but they present synaptic vesicles in the central area. They mediate acid taste transduction (10% of the total).
In general, two possible neural models are described to explain the functioning of the taste buds. To keep things simple, we will say that the former postulates that a taste receptor cell itself detects a single basic taste modality and is innervated by individual nerve fibres that transmit the signals of that single modality (this is known as a marked line). Once these cells are stimulated, the information is sent as an action potential to the brain.
In the other model, known as the computational model, individual taste receptor cells detect one or more taste modalities, and the fibres transmit signals from multiple modalities at once. It is, therefore, a more intricate activity complex than the previous case.
Types of taste buds
Once we have explored the world of taste buds, we can go back to the papillae. It is time to clarify that there are four types of them, and we will tell you about them briefly below.
- Fungiform papillae
They are so named because they are shaped like a mushroom, no more, no less. They are rare in many animals and are located on the tip of the tongue. It is interesting to know that they are found in humans and are also present in other mammals. They are much more numerous in carnivores and of reduced appearance in bovids and horses.
Composed of a head and a pedicel, this type of papillae is very visible, due to the blood vessels’ reddish colour that irrigate them. These types of papillae are much more stimulated in old age and the early stages of development, as they are especially specialized in processing the sweet taste. According to various sources, this type is the type of gustatory nature most represented in the human species.
Also known as circumvallate papillae, they are a large and underrepresented type of papilla, but they detect the bitter taste with vital importance. These are found in a number of 11 in a V-arrangement on the back of the tongue, near the tonsils, and can be clearly seen as “bumps” or lumps.
In addition to their detection of bitter flavours, they also have a series of minor salivary glands that aid the digestion process. We say that they are the most important papillae because they detect the bitter taste, which, in many cases, can represent dangerous ingestion. In addition to this, being in the furthest part of the tongue, they contribute to the gag reflex.
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- Filiform papillae
The filiform papillae have a conical/cylindrical shape and end in a crown of filaments, which gives them their characteristic name. They are distributed over the entire surface of the tongue, always arranged in parallel series that go obliquely from the groove in the middle of the tongue to its edges. They are the most abundant type within the tongue but, curiously, their function is not to interpret flavours.
The filiform papillae act as a covering for the tongue. They cause a rough and abrasive structure to be present, which helps us clean our mouths, swallow and speak. Put more simply; they act as physiological “handles” in multiple oral processes. Its thermal and tactile function is stimulated, above all, during the adult period of the individual.
- Foliate papillae
Foliate or foliate papillae appear as short vertical folds, present in parallel on both sides of the back of the tongue. These appear in the form of symmetrical ridges, in the numbering of 4-5 folds, depending on the individual. Its receptors pick up salty flavours.
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An overview of the language
Let’s do a final little review, as we have introduced a lot of terminologies that requires a “mind map”. Imagine your own tongue in the mirror. At the tip, the fungiform papillae are agglutinated, which are responsible for interpreting the sweet flavours.
If you move backwards, near the bell, you will find 11 large papillae arranged in a V shape, which are in charge of processing the bitter taste and promoting vomiting or when the ingested element can be harmful to the body.
On the sides and looking at the base of the tongue, we will find a series of folds, in which the foliate papillae are found. These are responsible for capturing the salty flavours.
Even so, as we have seen previously, each taste bud contains multiple cells in charge of identifying different types of flavours and, according to the computational model, each button would send information from more than one flavour to the relevant nerve ending. In that case, the “taste map” described here would be of little use to us, since it is postulated that each papilla may contain all or some of the cells that interpret certain flavours. Be that as it may, the tongue map helps understand the arrangement of the types of papillae and get a general idea about their function.
As you may have read in these lines, the taste buds world gives a lot to talk about. There are certain discrepancies and debates because the truth is that, even today, we do not know some of the peculiarities of the sense of taste.
Even so, it is clear that this has been essential for the development and permanence of the human species over time. The taste buds have allowed us to discriminate those dangerous foods from the nutritious ones, allowing us to develop on a physical level thanks to an adequate caloric intake. In the human body, every cell counts.