Emphysema involves irreversible enlargement of the air spaces distal to the terminal bronchioles.

• A. True
• B. False
• C. Irreversible enlargement of the air spaces distal to the terminal bronchioles
• D. Enlargement is reversible

Answer: (C)

Emphysema is defined by irreversible enlargement of the air spaces distal to the terminal bronchioles due to destruction of the alveolar walls and loss of elastic recoil. This destruction causes airway collapse on exhalation, air trapping, and hyperinflation with impaired gas exchange. The irreversibility is the key feature—if the enlargement were reversible, it would not be emphysema. The location “distal to the terminal bronchioles” points to the acinar regions (alveoli and small airways) rather than the conducting airways, helping distinguish emphysema from other obstructive processes.