Breathing might seem like the easiest and most natural thing in the world, but it actually involves complex processes. Air enters the nose and mouth and moves down through the pharynx. The pharynx, or throat, splits into two tubes: the esophagus which carries food, and the trachea, or windpipe, which carries air. When eating, the epiglottis, a flap of tissue that covers the larynx, helps keep food out of the windpipe. The trachea leads into the chest and divides into two branches, which extend to the lungs.
Lungs are a key part of the respiratory system. Lungs have a lot of airways called bronchi. ”Bronchiole are tiny bronchi and these airways get smaller and smaller, like branches on a tree. At the end of these branches are alveoli, which are no wider than a hair. Alveoli are like tiny clustered bags of air, and there are around 300 million of them in a single set of human lungs. Oxygen passes through the thin walls of alveoli and the surrounding capillaries into the blood.
Inhalation occurs when the trachea carries air into the lungs. When this happens, muscles contract to raise the rib cage up. The lungs expand, sucking in air, while the diaphragm contracts and pulls down. During exhalation, air comes out through the nose or lips, and the rib cage moves down and inward. The lungs shrink and cause air to go out, while the diaphragm relaxes and moves up.
Cilia, which line inside the nose, are an important feature in the respiratory system. They clean, moisten, and warm the air for the lungs. Another vital part of the pharynx is the larynx, or vocal cords, which are made up of two flaps of tissue. When they are open, air passes through, but when closed, air causes the cords to vibrate and make sound. The tighter they are closed, the higher the pitch will be.
Clearly, breathing is more complicated than it seems!