Asthma

Asthma is a chronic inflammatory disease of the airways in the human body. An asthma attack affects the bronchi and bronchioles in the lungs. The bronchi and bronchioles are tiny tubes through which air passes in and out of the body. In people with asthma, certain materials, such as dust, fumes, and pollen, can irritate these tubes. By contrast, people without asthma are unaffected by these materials.

As these tubes become irritated, they swell and give off mucus. The liquid fills air spaces in the bronchi and bronchioles. Both swelling and mucus narrow the tubes, making it more difficult for air to get in and out of the lungs. As a result, an asthmatic person has to make a much greater effort to breathe in air and to expel it.

Some children are thought to develop asthma for genetic reasons. Their bodies are especially sensitive to materials in the environment that have little or no effect on other people. These materials are known as allergens.

When children with this condition are exposed to dust mites, fungi, and other allergens, their bodies produce chemicals known as antibodies. The function of these antibodies is to fight off the invasion of materials from the environment. However, the release of antibodies also inflames the bronchi and bronchioles. The more often an asthmatic child is exposed to allergens, the more serious the response becomes. This condition, known as atopy, is thought to occur in anywhere from 30 to 50 percent of the general population.

Category:     Health
Source:        Adapted from: Sick! Diseases And Disorders, Injuries And Infections,
                    published by U.X.L, 2000
Words         250

哮喘

哮喘是人体呼吸道的一种慢性炎症。哮喘发生时，肺里的支气管和细支气管会受到影响。支气管和细支气管是指空气进出人体所经过的细小管道。有些物质，如尘埃、烟雾和花粉，会刺激哮喘患者身体里的这些细管。相反，不患哮喘病的人就不受这些物质的影响。

 这些细管受到刺激时就会肿胀并产生粘液。这种粘液挤满支气管和细支气管中的空气空隙。由于肿胀和粘液都使细管变窄，空气就更难进出肺部。结果是，哮喘病人得更加费力地进行呼吸。

 据认为，有些儿童是由于遗传原因而患哮喘病的。他们的身体对于环境里的某些物质特别敏感，而这些物质对其他人的影响并不大或者根本没有。这些物质被称为变应原。

 当有这类情况的儿童接触到尘粒、真菌和其它变应原时，他们的身体会产生被称为抗体的化学物质。这些抗体的作用是击退来自周围环境的物质对人体的侵袭。然而，抗体的产生也会引起支气管和细支气管炎。患哮喘病的儿童接触变应原的机会越多，所产生的反应就越严重。据认为，有这种被称为特应性现象的人占总人口的百分之三十至五十。

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