Breathing is the process of taking air into the lungs and forcing it out again. When a person takes air into the lungs, he is said to inhale, and when he forces it out, he is said to exhale. The first of these processes is also known as inspiration, and the second as expiration. Together they are known as respiration. Breathing is a part of the house cleaning and heating systems of the body. It has nothing to do with feeding the body, but helps to get rid of waste materials and to supply heat. In other words, it takes the place of the vacuum cleaner and the drafts on the stove or furnace in a house.
How breathing is done.
In breathing most of the air enters the body through the nose. This organ is especially suited to receive the air for several reasons. First, it takes the chill off the air. Second, it strains out particles of dust. The straining is done by tiny hairs that project from the lining. Third, by detecting odors, it helps to tell whether air is fit for breathing. Air may also be taken into the body through the mouth, but the mouth is not an organ for breathing. It warms the air somewhat but does little to remove impurities.
From the nose the air passes through the back part of the throat to the windpipe, or trachea, which leads to the lungs. The trachea splits into two parts known as bronchi, one of which leads to each lung. The bronchi further divide like the branches of a tree, forming what is known as the bronchial tubes. The lungs are two large organs in the upper part of the trunk. They are made up of the bronchial tubes and countless tiny pockets, the walls of which are filled with blood vessels. When the air is inhaled, the pockets fill with fresh air, and some of the oxygen passes into the blood. At the same time carbon dioxide, a waste material which the blood has brought from the cells of the body, passes out of the blood into the air pockets. When a person exhales, the carbon dioxide is carried from the body.
Breathing is carried on by a broad, flat muscle just below the lungs, known as the diaphragm, and by other muscles attached to the ribs. The diaphragm bows up slightly in the center between the lungs. When it contracts, the part that was bowed upward straightens out, giving the lungs more room. At the same time the muscles raise the ribs and give the lungs still more room. Thus the space in the chest is increased, and the air flows in just as water runs through a hole into a pipe. This explains what happens when a person inhales.
When the air is exhaled, the muscles of the ribs expand and the diaphragm bows upward again in the center. These movements make the chest smaller, and the air is forced out. The whole process is like the working of a bellows used to supply air for the fire in an old-fashioned blacksmith shop.
What the air does for the body.
Breathing supplies the body with oxygen, making it possible for oxidation to take place in the cells. Were it not for oxygen, the body could not use food. Both food and oxygen, as you have already learned, are necessary for oxidation. It is by oxidation that the body grows, renews its cells, and gets heat and energy.
Breathing also helps to control the temperature of the body. If the body becomes too warm, less oxygen is taken into the blood and less oxidation takes place. On the other hand, if the body becomes too cold, more oxygen is sent to the cells and greater oxidation takes place. The lungs and sweat glands perhaps do more to keep the temperature of the body at 98.6 degrees than do any other organs. They act as regulators.
In addition, breathing helps to clean the body. It removes the carbon dioxide which is formed during oxidation and carried to the lungs by the blood. The carbon dioxide must be removed, for it is a poison. Moreover it does not burn and would soon stop oxidation. Thus you may think of breathing as a process that supplies oxygen for oxidation and at the same time removes one of the chief waste materials formed.
Breathing controlled by body needs.
Most people, except small children, breathe about eighteen times a minute. People who are sick, excited, or working very hard often breathe faster. The number of times a person breathes is regulated according to the needs of his body. By thinking about it, he may breathe somewhat faster or more slowly than usual, but such breathing does very little good. Of course, a person never entirely empties his lungs when he exhales. The more deeply he breathes, however, the more air he drives out. This fact some people to believe that we should practice deep breathing to remove stale air from the lower part of the lungs. Science has shown, though, that deep breathing exercises are unnecessary and do little good.
If a person works hard or plays hard, he naturally breathes more deeply and more rapidly, because the cells of the body need more oxygen. Thus more oxygen passes into the blood. The circulation of the blood increases sufficiently to carry the added oxygen to the cells. In this way faster and deeper breathing and increased circulation of the blood take care of the needs of the cells. When a person is resting, the cells do not need so much oxygen, and slower breathing is sufficient. In fact, it has been proved that forced breathing does little to help more oxygen reach the cells. The air merely passes in and out of the lungs without change.
Choosing good air.
If air is to meet the needs of the body, it must be fresh and pure. It should be as free from dust as possible. The air in the country is usually much cleaner than the air in cities, as fewer tiny particles of soot and dust are floating about. Sunlight has a great effect on the condition of the air, as it kills disease germs. Air in well-lighted places, therefore, is better for breathing than air in dark places. The movement of air is also important. It keeps stale air from settling in one place and brings in fresh air. The need for movement explains why school buildings and other public buildings are often supplied with ventilating systems to keep the air moving. Of course a person should get plenty of fresh air as he sleeps. The window in the bedroom should always be open, but he should not sleep in a draft.
The temperature of air is also important. It should be neither too hot nor too cold. The body is most comfortable when the temperature of the air is from 68 to 70 degrees. Warm air tends to make the body too warm and colder air, too cold. In extremely cold weather, a person should always be careful to breathe in through the nose so that the air may be partly warmed before it reaches the delicate membranes of the lungs.