The taste buds Are small sensory organs located in the epithelial tissue of the tongue of vertebrate terrestrial animals. They fulfill the function of sending signals to the brain On stimuli that reach the interior of the oral cavity, which translate into flavors such as sweet, salty, acidic, bitter and umami (Bernays & Chapman, 2016).
The taste buds may have a conical, cylindrical or fungus shape depending on their size and function. Different types of papillae are located in different parts of the tongue, making sensibility more predominant to one taste than another depending on the area of the tongue to which the stimulus arrives.
A human has on average 10,000 taste buds on the tongue, which regenerate every two weeks. To the extent that a human being ages, the number of functional taste buds can be reduced to 5,000. For this reason, some foods have a stronger taste for children than for adults. (Dowshen, 2013)
The functioning of the taste buds depends to a large extent on smell. The majority of flavors are perceived thanks to the joint function exerted by both the taste receptor cells on the taste buds and the receptor organs located inside the nose.
Historically, five different flavors have been classified that can be identified by the taste buds of the human being. However, it has today been called the fat or oleogustus flavor as the sixth flavor that can be identified by the sensory receptors located in the taste buds.
From a biological point of view, the existence of taste buds is attributed to the survival of the species. Bitter and acidic flavors are associated with poisonous or spoiled foods, while sweet and salty flavors represent the intake of energy and nutrients necessary for the proper functioning of the body.
Location
The papillae are located mainly on the tongue and soft palate. Most papillae found on the tongue are not tied to the sense of taste and have a rounded shape giving the tongue a velvety appearance. These papillae, in general, do not have the necessary structure to perceive the flavor and are used only to perceive tactile stimuli.
The taste buds have a structure similar to that of an onion. Each papilla contains between 50 and 100 taste cells that have finger-shaped projections called microvilli.
These microvilli appear through the opening in the upper part of the papilla called the taste bud or taste nerve where they receive the chemicals from the food dissolved in the saliva. (Smith & Margolskee, 2001)
The taste cells, located inside each papilla, are supported by support cells that bend slightly over them.
Structure of a taste bud (Health, 2016)
Fungiform papillae
The fungiform or fungus-shaped papillae are found on the front of the tongue and are the easiest to differentiate from the rest of the papillae.
These papillae have a characteristic pinkish color, a bulky head and are distributed throughout the surface of the tongue, mainly in front of the goblet papillae. This type of papillae is usually used to perceive the sweet taste.
Foliated Papillae
The foliate or filiform papillae are conical in shape, similar to that of a flask. In addition to being receptors of salty and acidic flavors, they exert a tactile and thermal function on the whole surface of the tongue.
Circular Papillae
The circumvallate or goblet papillae are located in the back of the tongue, where the throat begins. Each person has between 7 and 12 circumferential papillae of large size, responsible for perceiving the bitter taste.
These papillae are distributed near the base of the tongue in the shape of an inverted"V".
Likewise, taste buds that are less sensitive to bitter taste can be found in small lateral ditches on the back of the tongue. (Health, 2016)
Distribution and types of papillae (Smith & Margolskee, 2001)
Reception of the flavor
When a stimulus enters the oral cavity, it can affect receptors located on the membrane of taste cells, pass through specific channels or activate ion channels. Any of these processes generate a reaction in taste cells, causing them to release neurotransmitters and send a signal to the brain.
At present, the way in which each different type of stimulus generates a response in the taste organs is not fully understood. The sweet and bitter tastes are perceived thanks to receptors linked to protein G, T1R and T2R. There are different points and sets of taste cells that perceive the sweet and bitter tastes on the tongue.
However, it has been shown that not all recipients perceive the flavors with the same intensity.
Some studies on salty taste reception have indicated the presence of ion channels as responsible for depolarizing the taste cells so that they release neurotransmitters.
The reception of the acidic taste was initially linked to the concentration of hydrogen ions. However, it has been shown that there is no direct relationship between pH, free acidity and acid taste, since different solutions of organic acids with the same pH level have indicated dissimilar gustatory responses. (Roper, 2007)
Types of papillae according to taste receptors
It is estimated that the sense of taste developed in vertebrate animals 500 million years ago, once creatures acquired the ability to perceive their prey in the ocean by locating it around them, devouring it and appreciating its flavor.
At present, five basic tastes have been identified by the taste buds: sweet, bitter, salty, acid and umami.
Each papilla is able to recognize a different type of flavor with greater intensity than the others thanks to the proteins that are in its interior, denominated cells of the taste.
These cells identify the molecules that make up the drinks and foods that enter as stimuli in the oral cavity. Upon receiving a taste, the cells are responsible for sending signals to the brain that subsequently produces the sensation of pleasure or displeasure.
Localization of taste receptors. From left to right: sweet, bitter, salty and acid Distribution and types of papillae (Health, 2016)
Sweet
It is the most elemental pleasure-generating taste. The sweet taste indicates the presence of sugars in the food. Currently, the highest percentage of foods consumed are rich in sugars, therefore fungiform taste cells tend to be the most stimulated.
Bitter
It's a warning sign. The bitter taste is associated with dislike for food, and is usually accompanied by a spastic response of the body and disgust. There are hundreds of bitter substances, mainly from plants. Some of these substances in small concentrations are pleasant in certain foods or drinks.
Some of the antioxidant substances that help metabolism work and prevent the formation of tumors are generally found in bitter-tasting foods or drinks such as coffee .
Salty
The human brain is programmed to enjoy the salty flavor in a minimal concentration. However, a high concentration of salt can cause displeasure. This relationship with the salty taste ensures the consumption of salts, which give the body some of the nutrients and substances it needs to function properly.
Salt taste can lead to addiction and taste buds can be adapted to both high and low salt concentrations in foods.
Acid
It is believed that acid taste was previously associated with the state of food decomposition, indicating that an acid-tasting product was not fit to consume as it could be harmful to the body. There is not much scientific information on the biological principles of this flavor.
Umami
It is defined as an intense and pleasant taste produced by certain amino acids present in cured meats, mature cheeses, Green Tea , The soy sauce and the tomatoes Cooked, among other foods.
The word Umami comes from the Japanese term used to describe those delicious flavors. (McQuaid, 2015)
Other Flavors
At present, different types of gustatory cells are being investigated in order to receive gustatory stimuli different from the five already classified. These flavors are grease, metallic, alkaline and water.
- Oleogutus : A research conducted in Indiana by Purdue University indicates that the taste of fat should be classified as a sixth flavor capable of being detected by the taste buds. This new flavor has been called oleogustus. (Patterson Neubert, 2015).
Purdue University argues that the language has a sixth type of flavor receptor capable of detecting foods with a higher concentration of linoleolic fatty acids and that the attraction that humans feel for consuming high-fat foods is not only due to Its texture or smell, but also its taste.
Foods rich in fatty acids usually consist of triglycerides, which are molecules made up of three types of fatty acids. However, triglycerides are not stimulating receptors of taste cells, so it is believed that by entering foods rich in fatty acids in the oral cavity and mixed with saliva, the fatty acids present in the triglycerides are divided, making it possible To the papillae the perception of them.
- Hot spicy : In the case of spicy, there is no evidence of any response by the taste buds at the time of intake. This stimulus activates a group of receptors known as nociceptors, or pain pathways that only activate in the presence of some element that may be harmful to the tissue.
It is believed that the spicy is a taste, because the contact that has with this stimulant occurs in the interior of the oral cavity.
Taste disorders and their factors
The sense of taste is one of the most important senses for humans. Any alteration in the perception of the flavors is of great importance because it directly affects the food habits and the health of the people.
There are some internal and external factors that affect the sense of taste, such as smoking, the intake of certain foods or drinks, the amount of saliva present in the mouth, age, gender and conditions in the nervous or respiratory system.
Cigarette
He Tobacco consumption Can numb the sense of taste, affecting the type of information that taste receptor cells emit to the brain. This is due to the toxic action of the chemicals present in the cigarette at the time of interacting with the tongue.
The taste buds lose their shape and become flat due to a vascularization process. The number of taste buds, however, does not diminish, it just ceases to function properly.
Saliva
Saliva works as a means of propagation for chemicals released by food once they are chewed. Low salivary volume or infection of the salivary glands affects the dispersion of these chemicals, decreasing the likelihood that they will be perceived by the cells receiving the taste.
Age and gender
There are some differences in the perception of flavors depending on gender and age. Men tend to be more sensitive to acid taste and older women tend to retain the perception of acidic and salty flavors to a greater extent than men. It is estimated that people older than 80 years have in most cases disorders in the sense of taste (Delilbasi, 2003).
Nervous system
There are certain disorders of nervous system Which can alter the sense of taste, since they affect the way messages are sent from the receptor cells of the taste to the brain.
Respiratory system
Ailments in the respiratory system can cause disorders in the taste buds. Diseases such as influenza, sinusitis, or a cold can prevent the combined work of olfactory receptors and taste receptors from completing the signals needed to identify a taste.
References
- Bernays, E., & Chapman, R. (22 of 4, 2016). Encyclopedia Britannica. Obtained from Taste Bud.
- Delilbasi, C. (2003). Evaluation of some factors affecting taste perception. Bagdat: Yeditepe University, Faculty of Dentistry, Department of Oral and Maxillofacial Surgery.
- Dowshen, S. (10 of 2013). Kids Health. Retrieved from What Are Taste Buds?.
- Health, I. (17 of 8 of 2016). U.S. National Library of Medicine. Retrieved from"How does our sense of taste work?.
- Mcquaid, J. (15 of 5 of 2015). For the. Retrieved from"Flavor 101: The Five Basic Tastes." Extracted from parade.com.
- Patterson Neubert, A. (23 of 7 of 2015). Purdue. Retrieved from Research confirms fat is sixth taste; Names it oleogustus. Extracted from purdue.edu.
- Roper, S. D. (2007). Signal transduction and information processing in mammalian taste buds. . European Journal of Physiology, 454, 759-776.
- Smith, D. V., & Margolskee, R.F. (2001). Making Sense of Taste. Scientific American, 32-35.