In this Health Alert and accompanying illustration, Johns Hopkins explains how lung disorders block the airways and cause discomfort -- shortness of breath, coughing, noisy breathing, and chest pain.

The obstructive lung diseases -- asthma and chronic obstructive pulmonary disease (COPD), which includes chronic bronchitis and emphysema -- all interfere with normal breathing by narrowing the airways that deliver air to your lungs.

The airways begin in your nose and mouth. Inhaled air passes down the pharynx (throat), through the larynx (voice box), and into the trachea (windpipe), the body's largest airway. The trachea divides into two airways, the right and left mainstem bronchi, which bring air to the lungs. There the bronchi divide many times before ending in the smallest airways called bronchioles.

The lungs supply oxygen to the blood, which carries it throughout the body. Lungs also remove carbon dioxide (a waste product that accumulates in the blood). This process, called gas exchange, occurs in the alveoli, groups of tiny air sacs clustered at the end of each bronchiole.

In asthma, the bronchial lining swells and the lungs produce too much mucus, which can obstruct the airways. Also, the smooth muscle around the bronchi can constrict. In chronic bronchitis, the bronchial lining is inflamed and there is overproduction of mucus, but the smooth muscle around the bronchioles tightens only in some cases. In emphysema, the lungs lose some of their elasticity. The airways, which are normally held open by the elastic elements in the walls of the alveoli, collapse, obstructing airflow in and out of the lungs.