Asthma is a complex problem caused by many factors that may act individually or in combination with others. Our bodies require oxygen from the air we breathe in order for our cells to carry out all of the vital functions of our body. When we breathe in, oxygen-carrying air enters through the mouth or nose, descends through the windpipe, then to tubes called the bronchi. The bronchi branch out into each lung where oxygen is picked up by passing blood, which then carries the oxygen throughout the body.
During an asthma episode is that the bronchial tubes become narrowed, and even blocked. As a result, oxygen and air can't get in or out of the lungs easily, and the asthmatic person, frequently a child, begins to breathe heavily, wheeze or cough.
There are two reasons the bronchi narrow: either because they are squeezed by muscles around them after irritation occurs, or because they are blocked by mucus and swelling within the bronchial tubes themselves.
The condition when bronchi are narrowed by squeezing of the surrounding muscles is called "broncho-constriction." This occurs when muscles, wrapped around the bronchi like a series of elastic bands, tighten and restrict the passage of air. It's normal for these muscles to occasionally close the airway, such as in response to protect the body from dangerous inhalants; however, in asthmatics these muscles sometimes overreact, become spasmodic, and constrict or block the bronchi.
For many years, broncho-constriction was thought to be the main cause of asthma, and treatment was aimed at broncho-dilation, or opening the bronchi to permit the passage of air into the lungs, and oxygen into the blood. More recently, we've become aware of another problem: bronchial inflammation. This occurs when the walls of the bronchi swell up and produce mucus, in reaction to some sort of environmental irritation. This inflammatory response to the environment is often referred to as an allergic reaction.
It's normal for the bronchi to produce mucus in order to trap the breathed-in irritants, and protect the lungs. But some asthmatics can produce an overabundance of mucus, and the bronchi can become chronically inflamed and narrowed, resulting in blocked airways and asthmatic symptoms.
So there are two possible conditions associated with an asthmatic's airways: broncho-constriction and bronchial inflammation. It is widely believed that the more an airway is inflamed, the more likely it is that the bronchial muscles will constrict.
Asthma Risk Factors
Asthma is common respiratory disorder affecting millions of adults and children in the USA and around the world. While a growing number of people are diagnosed with the condition each year, but it isn't clear why. A number of factors are thought to increase the chances of developing asthma. These include:
- A family history of asthma
- Frequent respiratory infections as a child
- Exposure to secondhand smoke
- Living in an urban area, especially if there's a lot of air pollution
- Exposure to occupational triggers, such as chemicals used in farming, hairdressing and manufacturing
- Low birth weight
- Being overweight
1) Mayo Clinic Staff. 2008. Risk factors of asthma. (Online) http://www.mayoclinic.com/health/asthma/ds00021/dsection=risk-factors accessed 01-31-2010
2) Dr. Paul Roumeliotis. 2010. What causes asthma? (Online) http://www.drpaul.com/asthma/asthma-causes.html accessed 01-31-10_