Man has five senses of perception – skin, ears, eyes, nose and tongue. The tongue tells us the taste of food and drink warns us if food has gone stale or is bad.
The tongue is located inside the mouth and is an important muscle in our body. It is red in colour. If you examine it minutely, you will see granular bumps or projections on its upper surface, sides and back. These are called papillae. These papillae contain groups of contact called taste buds (chemoreceptors). They are composed of cells. Hairs like fibres emerge at the upper side of our tongue. At the lower end of the tongue, they end in nerve fibres of cells. These join the nerves of taste that lead to the brain.
The 4 main tastes are – sweet, salty, sour and bitter. All other tastes are a combination of two or more of these. These 4 main tastes are felt by different portions of our tongue. For example, salty and sweet tastes are felt by the tip of our tongue. Similarly, a sour taste is detected by the buds on the sides of the tongue and bitter taste, by the back portion of the tongue. The tongue is also sensitive to irritants such as pepper.The taste of food is known only when it is in the liquid state. As we chew our food, a portion of it dissolves in the saliva. This dissolved form of the food activates the particular taste buds. These generate nerve impulses and the nerve fibres carry these messages to the “taste centre” in the brain. The brain then perceives the taste.
In addition to the tongue, our nose, which smells the food, also helps in perceiving the total taste of food. Smell is also a part of the taste. In the case of wine, cocoa and fruit juices, it is the smell which helps in the realization of the real taste. When liquids are taken into the mouth, the tongue experiences the taste while their smell enters the nose and through the “smell nerves”, it reaches the brain. In this way is derived the total pleasure of taste.
When we suffer from cold, fever, or even constipation/indigestion, the taste buds get covered by some impurities and do not get properly activated. Heat of the body (in fever) or even hotness of food, also deactivates the taste buds. Hence, we do not perceive the real taste under such unhealthy conditions.
The number of taste buds on the tongue of an adult is about 3000 which is much more than that of a child. As we grow older, the taste buds start losing vitality and, finally, become inactive, thus decreasing in number. In a 70-year-old man, for example, the number of taste buds is only 40. The taste buds, like all skin cells, are constantly being replaced. About half of the taste buds are replaced every ten days.