What is the primary characteristic of emphysema?

The primary characteristic of emphysema is the enlargement of air spaces in the lungs, specifically in the alveoli. This condition arises from the destruction of the alveolar walls, leading to a loss of elastic recoil in the lungs. As these small air sacs expand, they become less efficient in gas exchange, resulting in decreased oxygen intake and impaired removal of carbon dioxide.

This enlargement means that the lungs can hold more air, but this excessive air trapping can lead to over-inflation of the lungs and difficulty in breathing, particularly during expiration. Such structural changes are primarily caused by long-term exposure to harmful particulates or irritants, most commonly from cigarette smoke.

While other options mention various lung issues, they do not define emphysema. Increased fibrosis pertains more to conditions like pulmonary fibrosis, mucus production is often associated with chronic bronchitis, and the development of lung tumors relates to neoplastic processes rather than the disease pathology of emphysema. Therefore, the enlargement of air spaces is the hallmark feature that distinguishes this condition.