Respiratory Diseases Asthma Asthma is a respiratory disease in which spasm and constriction of the bronchial passages and swelling of their mucous lining cause obstruction of breathing. It is often due to allergy, particularly to dust, animal fur or feathers, moulds, and pollen. Asthma in adults is less likely to be caused by allergy, and more likely to be associated with respiratory infections and emotional upsets. Many people with allergic asthma also suffer from hay fever. Treatments? Emphysema, A progressive respiratory disease characterized by coughing, shortness of breath, and wheezing, developing into extreme difficulty in breathing, and sometimes resulting in disability and death. Although the exact cause is unknown, bronchial spasm, infection, irritation, or a combination of the three seem to be contributory. The highest degree of occurrence is among heavy cigarette smokers, especially those exposed to polluted air. Children who suffer from bronchitis or asthma are also susceptible. In recent years emphysema has become a serious public-health problem. Lung Cancer Growth of malignant cells affecting, initially, the lung. Cancer forms when a lung cell undergoes alterations to its DNA, leading to uncontrolled cell growth. Growth continues until a tumour forms. Martin Rotker/Phototake NYC Cancerous Human Lung This section of human lung tissue shows light-coloured cancerous tissue in the centre of the photograph. At bottom centre lies the heart. While normal lung tissue is light pink, the tissue surrounding the cancer is black and starved of oxygen, the result of a tar-like residue left by cigarette smoke. Most lung cancer begins in the cells lining the main air passages, or bronchi. In their cancerous state, these cells lack the cilia that normally catch and eliminate foreign particles inhaled into the lung. Mucus ordinarily cleared by bronchial cilia becomes trapped, blocking air passages. Cigarette smoking is directly responsible for 90 per cent of cases of lung cancer. Microsoft ® Encarta ® Reference Library 2002. © 1993-2001 Microsoft Corporation. All rights reserved. The process of metastasis (spread) takes place when cells break off from the tumour and travel via the blood or lymphatic system, lodging in other organs. There they begin to multiply, forming other tumours.