What is Respiratory System? How are the parts of the Respiratory System arranged? Information on Respiratory System.
Respiratory System; Like all other living things, you must have air, water, and food to stay alive. You know that water has many important uses in your body. In fact, about two thirds of your weight is water. Food provides the materials that your body needs to grow, repair itself, and keep working properly. Food also provides the energy that your body needs to carry on all of its activities. To get energy from food, your body must use oxygen. This oxygen is taken into the blood from the air and carried to the cells, where it is used.
You might live for a month without eating, because some food is always stored in your cells. Without water, you would probably die in three or four days. But if you did not get oxygen from the air, you could not live for more than seven minutes! So you can understand why your body needs another important system, or special set of organs, to keep it supplied with oxygen. This is the breathing system, or respiratory system, that helps your body use food.
When you breathe air in, it first goes into your nose. The nasal passages from your nostrils to your throat are quite narrow and irregular, partly because of the turbinate bones. The walls of these passages are moist and warm, too. So if the air is not clean, much of the dust is caught in the moisture on the walls of the nasal passages. The air is also warmed as it passes from the nose back to the throat. Here the air goes down across the food tube and into the glottis, the opening to the voice box. Just above the glottis is a little flap called the epiglottis. When you swallow, this covers the glottis so that no food or water can pass through it.
The air next goes into the voice box, or larynx. You have probably heard the front of the larynx called the Adam’s apple. In the larynx, the air passes through a narrow slit between two bands of muscle tissue. These are the vocal cords that vibrate to make the sounds of the voice. From the larynx, the air goes down through a rather large tube known as the windpipe, or trachea. About 6 inches below the larynx, the trachea divides into two parts called bronchial tubes. Air goes through the right bronchial tube into the right lung and through the left bronchial tube into the left lung,
The lungs are the main organs of the respiratory system. They let oxygen from the air into the blood and let out carbon dioxide. Except for the parts taken up by the heart and the windpipe, the lungs fill almost the entire chest cavity. Inside each lung, the bronchial tubes fork like the branches of a tree. That is, they divide and subdivide to form smaller and smaller tubes until they reach every part of the lungs. The linings of all these air passages are covered with tiny living hairs, called cilia, that move back and forth. The movements of the cilia sweep dust and other unwanted materials up and out of all the air passages.
At the ends of the very smallest bronchial tubes, the air goes into many tiny cup-shaped parts, These are the air sacs, or alveoli, which are arranged around the tubes somewhat like a bunch of grapes on a stem. Scientists have estimated that a person’s lungs contain about 600 million air sacs. If the linings of all these sacs formed a single sheet, it would cover the walls of a room 20 feet long, 15 feet wide, and 10 feet high. The lungs are very light, spongy organs because they contain so many bronchial tubes and air sacs.
Blood vessels running all through the lungs carry blood to each air sac, or alveolus, and then back again to the heart. Only the thin wall of the air sac and the thin wall of a capillary are between the air and the blood. So oxygen easily diffuses from the air sacs through the walls into the blood, while carbon dioxide easily diffuses from the blood through the walls into the air sacs.
When blood is sent to the lungs by the heart, it has come back from the cells in the rest of the body. So the blood that goes into the wall of an air sac contains much dissolved carbon dioxide but very little oxygen. At the same time, the air that goes into the air sac contains much oxygen but very little carbon dioxide. You have learned that dissolved materials always diffuse from where there is more of them to where there is less. Oxygen from the air dissolves in the moisture on the lining of the air sac and diffuses through the lining into the blood. Meanwhile, carbon dioxide diffuses from the blood into the air sac. The blood then flows from the lungs back to the heart, which sends it out to all other parts of the body.
Soon after air goes into an air sac, it gives up some of its oxygen and takes in some carbon dioxide from the blood. To keep diffusion going as it should, this carbon dioxide must be gotten out of the air sacs and more oxygen gotten in. Breathing, which is caused by movements of the chest, forces the used air out of the air sacs in your lungs and brings in fresh air. The breathing muscles are controlled automatically so that you breathe at the proper rate to keep your air sacs supplied with fresh air. Ordinarily, you breathe about twenty-two times a minute. Of course, you breathe faster when you are exercising and slower when you are resting. Fresh air is brought into your lungs when you breathe in, or inhale, while used air is forced out of your lungs when you breathe out, or exhale.
Some people think that all the oxygen is taken out of the air in the lungs and that what we breathe out is pure carbon dioxide. Air is a mixture of gases that is mostly nitrogen. This gas is not used in the body. So the amount of nitrogen does not change as air is breathed in and out. But while air is in the lungs, it is changed in three ways: (1) About one fifth of the oxygen in the air goes into the blood. (2) An almost equal amount of carbon dioxide comes out of the blood into the air. (3) Moisture from the linings of the air passages and air sacs evaporates until the air is almost saturated with water vapor.