What part of the lungs does asthma affect?
Asthma is a disease that affects the airways. To understand asthma and its treatment it is important to have a basic understanding of the anatomy and physiology of the lung and of the abnormalities that occur in the airways of asthmatics. Normal lung anatomy: The structure of the lung can be compared to the structure of a tree. The wind-pipe, medically known as the trachea, is equivalent to the trunk of a tree. Like a tree trunk, the trachea divides into ever-smaller branches called bronchial tubes or airways, which are tubular structures surrounded by concentric bands of muscle (Figure 1). The muscle layer surrounding the airways is not under voluntary control, and its function is unknown. Unlike muscle in the gut, which is important for the propulsive movement of food and digested food, the movement of air in the airways is not dependent on the muscle surrounding the airways but on the rhythmic negative and positive pressure cycles generated by the movement of the diaphragm. Figure 1
