How does our tongue tell the taste?

What do you use your tongue for? We use it to taste food, speak and even stick it out to tease our friend, don’t we? Man has five sense organs of perception; they are skin, ears, eyes, nose and tongue. The tongue tells us the taste of the food, and without it we would not be able to speak, either. The tongue, which is located inside the mouth, is an important muscle and does not have any bones. It is reddish-pink in colour. If you examine it minutely, you will see granular projections on its upper surface, sides and the underside. These are called papillae. These papillae contain the taste buds (chemo-receptors), and are composed of cells. These are the buds that allow you to taste the food; it enables you to make out if the food is too salty or sweet or bitter. Very small fibre-like projections emerge on 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 four main tastes are — sweet, salty, sour and bitter. All other tastes are a combination of two or more of these. These four tastes are felt by different portions of our tongue. For example, the tip of our tongue senses salt and sweet. Similarly, the buds at the sides of the tongue detect the sour taste. The rear portion of the tongue has buds to detect the bitter taste. The tongue is also sensitive to irritants such as pepper. When we chew our food, a portion of it dissolves in the saliva. This dissolved part of the food comes in contact with the taste buds and generates nerve impulses. The nerve fibres carry these messages to the ‘taste centre’ in the brain. The brain then perceives the taste. The taste of food is known only when it is in the liquid state. In addition to the tongue, our nose, which smells the food, also helps in perceiving the total taste of the food. Smell is also a part of taste. In case of wine, cocoa and fruit juices, it is the smell that helps in the realisation of the real taste. When liquids are sipped, the tongue experiences the taste while their smell enters the nose and, through the ‘smell nerves’, it reaches the brain. This is how the total pleasure of taste is derived. When we suffer from cold, fever, or even constipation/indigestion, the taste buds get covered by impurities and are not fully activated. Heat of the body (in fever) and even hot food deactivates the taste buds, hence, we do not realise the real taste under such adverse conditions. There are about 3,000 taste buds on the tongue of an adult person, which is much more than that of a child. As we grow older, the taste buds start losing their vitality and finally become inactive, besides 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 being constantly replaced. About half of the taste buds are replaced every ten days.