Which disorder is characterized by increased responsiveness of the trachea and bronchi?

Asthma is characterized by increased responsiveness of the trachea and bronchi, leading to a condition known as airway hyperreactivity. This hyperresponsiveness results in bronchoconstriction in response to various stimuli, such as allergens, respiratory infections, exercise, or environmental factors. In asthma, the airways become inflamed and narrowed, which contributes to symptoms like wheezing, coughing, shortness of breath, and chest tightness.

The key feature of asthma is this exaggerated response, which is not typically seen in chronic bronchitis, pneumonia, or emphysema. While chronic bronchitis involves inflammation and narrowing of the airways, it does not mainly involve the hyperreactivity characteristic of asthma. Pneumonia is an infection of the lungs and does not primarily involve tracheobronchial responsiveness. Emphysema primarily involves destruction of alveolar walls and is focused on airflow obstruction rather than the hyperreactivity of the airways. Thus, asthma uniquely qualifies with its hallmark of increased airway responsiveness.