Breathing is essential for all living beings. Men, animals, birds, insects and plants – all need oxygen which they get from the air through respiration. However, different creatures breathe differently. Some breathe through lungs, while some others breathe through skin. For example, the earthworm breathes through its skin. Do you know how man breathes and what happens in the body during the process of respiration?
Man inhales air through the nose or mouth. The nose and mouth are joined in the back of the mouth in an area called pharynx. The air inhaled goes to the lungs through the wind pipe. There are two lungs in our body – one each on the left and right of our chest. They are made up of tissues shaped like soft bags. Each lung has millions of air sacs which get filled and enlarged when air is inhaled. When it is exhaled they contract.
The energy-releasing process which utilizes the oxygen and produce carbon-dioxide is termed as ‘tissue respiration’ or external respiration. In man, external respiration is the process whereby air is breathed from the environment into the lungs to provide internal respiration.
The oxygen which is inhaled is circulated throughout the body by the blood. It oxidizes the food materials. During this process of oxidation, carbon-dioxide, water and other substances are produced. The same carbon-dioxide comes out when we breathe out. When we do some physical work or exercise, we need more energy. For the production of more energy we need more oxygen. That is why, the rate of breathing becomes fast when we do any hard work or physical exercise.
Normally, a newly born child breathes 60 times per minute. A 15 year old child breathes 20 times a minute and an adult 16 to 18 times. The rate of breathing is faster in adults than in old people. The process of breathing is controlled by the respiratory centre in the brain. This centre is sensitive to the amount of carbon dioxide in the blood. If there is an increase in carbon dioxide such as during exercise, this centre sends signals to control breathing. As a result the person breathes faster.