How the respiratory system works

Your lungs bring in the fresh oxygen your body needs to power every process in your body. They also remove carbon dioxide and other waste gases your body doesn’t need. Optimal lung function is vital to your health.

The muscles of your rib cage and diaphragm tighten and flatten to draw air into your lungs. When these muscles relax, the air is naturally expelled from your lungs. After the air is inhaled through the mouth and nose, it passes through the throat and into the trachea (windpipe). The trachea divides into the left and right bronchi. Inside the lungs, each bronchus divides, again and again, becoming narrower and narrower.

Your smallest airways end in alveoli, small thin air sacs arranged in clusters like bunches of balloons. When you inhale, the alveoli expand as air rushes in. When they relax, air moves out of the lungs. Tiny blood vessels surround each of the 300 million alveoli in the lungs. Oxygen moves across the walls of the alveoli are picked up by the blood and carried to the rest of the body. Carbon dioxide or waste gas passes into the air sacs from the blood and is breathed out.

If you have a damaged respiratory tract you are more prone to lung diseases such as asthma, bronchitis, pneumonia, emphysema, and Chronic Obstructive Pulmonary Disease (COPD), a long-term disease usually caused by smoking.


If you have asthma, the inside walls of the airways in your lungs are inflamed and swollen. This makes the muscles surrounding your airways very sensitive, so they tighten and constrict spontaneously. To make matters worse, the membranes in your airway linings secrete excess mucus.

Though a healthy body requires some mucus, too much can be uncomfortable. Excess may be caused by:

  • infections, such as the common cold or flu
  • allergies
  • irritation of the nose, throat, or lungs
  • digestive conditions, such as gastroesophageal reflux disease
  • smoking tobacco products
  • lung diseases, such as pneumonia, lung cancer, cystic fibrosis, or chronic obstructive pulmonary disease


The result is narrowed airways and obstructed airflow that typically leads to coughing, wheezing, and shortness of breath.

Asthma can be set off by many things. Each person has their own set of asthma inducers and asthma triggers.

Asthma inducers: When you breathe in something you’re allergic to such as dust or pollen, or if you have a viral infection like a cold or the flu, your airways can become inflamed (red and swollen).

Asthma triggers: The most common Asthma triggers are tobacco smoke, pollen, pet dander, dust mites, mold, air pollution and smoke from fires, or even cold air and physical exercise. When you breathe in an asthma trigger, the muscles around your airways can go into spasm and squeeze together tightly. This leaves less room for air to pass through. Learn what your inducers and triggers are, and avoid them.

Causes of Asthma

There are a few factors that make a person more prone to asthma:

Family History: If other members of your family have allergic diseases like asthma, hay fever (allergic rhinitis), or eczema, there is a higher chance you will have asthma.

Air pollution indoors and outdoors: People who live near major highways and other polluted places are more likely to get asthma. Also, kids who grow up in a home with mold or dust may be more likely to get asthma.

Work-related asthma: People who work in certain types of jobs can get asthma from things they work with, such as smoke, dust, chemicals, and fumes. For example Laboratory workers can get asthma from exposure to proteins from animals, plants, foods, insects, and fish. Spray painters can get asthma from isocyanates; Bakers and Grain handlers can get asthma from grain dust.

Second-hand smoke: Children whose mothers smoked while pregnant or who grew up in a smoky house are all more likely to get asthma.


Smoking damages your lungs’ natural cleaning and repair system and traps cancer-causing chemicals in your lungs. It destroys the tiny hairs that line the upper airways which protect against infections. This puts you at risk for chronic cough, chest infections, lung cancer, and Chronic Obstructive Pulmonary Disease (COPD).

Smoking permanently damages the alveoli in the lungs, making it hard to breathe. Smoke damages your lungs so much that the alveoli become less stretchy. This means it’s harder for your lungs to take in the oxygen you need and harder to get rid of carbon dioxide When the alveoli are damaged like this, you can feel short of breath and tired. Your heart has to pump much harder to give your body the oxygen it needs. Over time this damage can lead to heart disease and COPD.

NOTE: There are approximately 600 ingredients in cigarettes. When burned, cigarettes create more than 7,000 chemicals. At least 69 of these chemicals are known to cause cancer, and many are toxic. Many of these chemicals also are found in consumer products, but these products have warning labels—such as rat poison packaging.