BIOLOGY Volume 1 - A Guide to General Biology - 2004

9. UTILIZATION OF ENERGY

9.7. Respiratory diseases

9.7.3. Emphysema

Pulmonary emphysema is associated with the gradual destruction of the delicate walls of the alveoli. As a result, the air-filled space in the Lungs increases (Fig. 9.33), while the surface area available for gas exchange correspondingly decreases. Consequently, the patient begins to experience increasingly severe shortness of breath. In severe cases, even walking across a room becomes an impossible task. Confined to a chair, the patient is often unable to raise an arm without becoming breathless. The lung tissue in such patients loses its elasticity. Exhalation is therefore impaired, and a significant amount of air remains trapped in the lungs upon expiration. This can be easily demonstrated by measuring the forced expiratory volume — the maximum volume of air that can be exhaled in a given time (usually 1 s) following a maximum inhalation. (This volume is also reduced in asthma patients.) Breathing largely loses its involuntary character — the patient must remain conscious of it and make an active effort to breathe. An inflammatory process and narrowing of the small bronchioles are also observed.

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Fig. 9.33. A. Cytology/practical/120.html">Lung of a person suffering from pulmonary emphysema. There are fewer alveoli than normal and the air-filled space is larger (cf. Fig. 9.22). B. The same tissue at high magnification.

The primary cause of emphysema is prolonged irritation of the lungs caused by cigarette smoke, air pollutants, or dust particles. Damage is caused by both chemical and physical factors. For instance, substances contained in cigarette smoke disrupt the normal balance between the breakdown and repair of elastic tissue. They inhibit Enzymes that prevent the degradation of elastic tissue in the alveolar walls and suppress repair processes. In response to increasing stress, leukocytes in the lungs secrete Proteolytic Enzymes, which in turn also contribute to the destruction of the alveolar walls. Physical factors, such as violent coughing caused by Bronchitis (see below), further contribute to alveolar wall damage.

In Great Britain, pulmonary emphysema is very widespread. It affects 1 in 100 people, and is 10 times more common in men than in women.