The Human Digestive System

How do we digest food?

            The human body requires a constant supply of food in order to carry out its numerous activities. The food we consume performs two main functions in our body. First, it supplies proteins for the growth of the body and second, it supplies energy to the tissues for the day to day work.

The Human Digestive System

            The process of digestion is very complex and elaborate. Digestion begins at the mouth. When we chew food, the saliva produced in the mouth moistens it. The saliva contains a substance called ptyalin, which converts the starch of the food into simple sugar. This is the first stage of digestion. Therefore we should swallow the food only after chewing it properly.

            After that, the food material passes through the esophagus to the stomach where the gastric juices get mixed with it. The walls of the stomach secret juices containing an enzyme called pepsin and hydrochloric acid. Pepsin breaks down the molecules of proteins into peptones.

            From stomach, the food then enters the small intestine, where it mixes with three other digestive juices- bile, pancreatic juice and intestinal juice. The liver produces bile. Its main function is to digest the fats. The pancreatic juice is basic in nature and neutralizes the acids. It also digests the proteins. The intestinal juice converts sugar into glucose. Here, many enzymes also mix with the food. The digestion of food mainly takes place here. The digested food is them absorbed by the blood vessels present in the wall of small intestine. The remaining waste of the food now goes to the large intestine and is finally excreted out of the body as faeces through the anus.

Why Some Fruits Sweet While Others is Sour?

            Some fruits like watermelons, guavas, grapes, apples, mangoes, etc. are sweet in taste while lemons, oranges, raw mangoes, etc. are sour. Each fruit has a distinct taste, which differs in some way from the taste of others fruits. The question arises- why does every fruit have a characteristic taste?

Sweet Fruits

Sour Fruits

            In fact, the taste of a fruit depends on the compounds present in it. In general, a fruit contains fructose natural sugar, organic acids, vitamins, starch, proteins, minerals and cellulose. All these are in a mixed state inside the fruit and are found in different proportions. Fruits having more fructose content taste sweeter, while those having more acids, taste sour. Orange is a fruit, which has almost equal quantities of fructose and acids; hence it tastes both sweet and sour.

            In general, raw fruits contain more acids but on ripening, the quantity of acid in them decreases and the amount of sugar increases. Hence raw mangoes are sour, but ripe ones are sweet. Raw bananas contain more of starch, but it gets converted into fructose when the fruit ripens.

            During the process of ripening, chemical changes take place inside the fruit by which the quantity of sugar increases thus adding to the sweetness of the fruit.

            We notice a difference of taste in two fruits of the same kind. Two apples or mangoes do not always taste alike. This is so because there are many varieties of the same fruit and also the variations in the quality of soil, climate, growing technique; manure, water, etc. change the proportion of the compounds inside the fruit resulting in the difference of taste.

            Sour fruits like lemons; do not taste sweet even after they are ripe, because of the presence of excessive amounts of acids.

What is Our Body Made of?

            Our body is made of more than 20 different chemical elements, the greatest part being oxygen. Oxygen combined with hydrogen forms water, and our body contains 65% of water.

The Human Body is composed of many different chemical elements. It may be surprising to discover that 65% of our in water

            A person weighing 100 kilograms contains approximately 65 kilograms of water. Did you know that our body has carbon equal to nearly 13 kilograms of coke? Carbon combined with hydrogen and oxygen make fats and sugars, which produce energy in the body. Our body also contains proteins, which are made of carbon, hydrogen, oxygen and nitrogen. Proteins are used for the growth and repair of the body parts.

            The body also contains calcium and phosphorus-it contains about 1.25 kilograms of calcium and enough phosphorus. Both these elements form essential parts of the bones and teeth. The body also contains sulphur, iron and other metals. But these elements are preset in traces.

How long can Man Survive Without Food?

        Like air and water, food is also essential part for all living beings. From the smallest insects to the biggest animals- all need food for their survival. So much so that even plants cannot live have long without food. Each person requires a certain amount of food daily, depending on his size, weight, age and amount of activity. Most of us feel uncomfortable, if we skip just one meal. Also, if we go without food for 12 hours or more we feel all the more lethargic.

            Energy required to do work is obtained form food we eat. Our cells and tissues suffer damage every day while doing work and need to be repaired and replaced. Food is thus needed for the growth, maintenance and development of our body. In short, we need carbohydrates, proteins, fats, vitamins, minerals and water as food for proper functioning of our body.

            Have you ever given a thought to how long we can survive without food? There are some animals that can store food in their bodies and live on stored food for a long time. It has been observed that smaller and more active animals consume more food than others, in proportion to their body weight. Warm-blooded animals use up the food stored in their body more quickly. A dog can survive without food for 20 days at the most. However, some bugs can survive without food for one full year.

            Man cannot store food in his stomach. If he misses one meal, he feels weak. Food is required to maintain the flow of blood. All constituents of blood are obtained form food. The moment blood runs low on nutritional materials, a signal goes to the brain and we start feeling hungry.

            There are a few examples of people who survived for a very long time without food. Angus Warviern of Scotland survived without food for 382 days, i.e., from June 1965 to July 1966. During this period, he took only coffee, tea, water and soda water. One South African woman survived for 102 days on water and soda water. Stefan Taylor of New Zealand survived for 40 days in 1970 on a daily intake of just one glass of water. There are many such examples. Such people are endowed with exceptional power. A common man can, at the most, survive without food for a week.