What is emphysema?

Emphysema is a progressive lung disease that primarily affects the alveoli, which are the small air sacs in the lungs responsible for gas exchange. In emphysema, the walls of these air sacs are damaged, leading to a loss of elasticity and a reduction in the surface area available for oxygen intake. This loss of elasticity makes it difficult for the lungs to expel air fully, resulting in airflow obstruction and difficulty in breathing.

In contrast, the other choices provided refer to different conditions: an infection in the lungs typically describes pneumonia or bronchitis, which involve inflammation and infection rather than tissue elasticity; a type of cancer pertains to malignancies affecting the lung tissue but does not involve the characteristic changes seen in emphysema; and a lung condition causing excess mucus production relates more to chronic bronchitis, which is often associated with inflammation and mucus buildup rather than the structural changes of emphysema. Therefore, the defining characteristic of emphysema is its impact on lung tissue elasticity, making the first choice the accurate description of the disease.