The lungs have a complex structure. It contains airways, air sacs or alveoli, interstitium (microscopically thin, delicate lining between the lungs' air sacs) and blood vessels. The lungs are covered all around by pleura (a thin lining). Lung diseases can be caused due to problems in any part of the lung. There are many ways to classify the lung disease and broadly it can be categorised according to the disease process and mechanism by which it affects normal lung functioning.
- Obstructive lung diseases: The flow of exhaled air is decreased due to narrowing or blockage of the airways, as in asthma, emphysema, and chronic bronchitis.
- Inflammatory lung diseases: Lung elasticity and gas exchange in the alveoli are affected. Some diseases which cause lung inflammation and affect gas exchange are pneumonias, emphysema sarcoidosis, idiopathic pulmonary fibrosis, and interstitial lung diseases. Long term inflammation can lead to fibrosis/scarring with loss of lung elasticity.
- Infections: Infection can result in inflammation but are often considered separately as the basic cause of inflammation is infection such as pneumonias (bacterial and viral) and tuberculosis.
- Tumours: Lung cancers can block air flow and/or destroy lung tissue.
In most lung diseases, there is often an overlap of disease process such as emphysema involves both airflow obstruction and gas exchange problems. There are several types of lung diseases but the most common ones are:
- Asthma (obstructive lung disease).
- Pneumonia (inflammatory/infectious).
- Acute and chronic bronchitis (inflammatory/infectious).
- Emphysema (inflammatory/fibrosis).
- Lung cancer (tumour).
Several diseases which affect the blood vessels of the lung may also affect lung functioning, but they are mostly categorised under cardiovascular diseases. Lung diseases have become a leading cause of death and disability worldwide. So if you have symptoms suggestive of lung disease, immediately consult your doctor.
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