Which of the following is the PRIMARY structural change in the lungs of a patient with emphysema?

Explanation

## Emphysema: Pathological Definition **Key Point:** Emphysema is defined as permanent enlargement of airspaces distal to the terminal bronchiole, accompanied by destruction of alveolar walls and loss of elastic recoil. ### Structural Changes in Emphysema | Feature | Emphysema | Chronic Bronchitis | |---------|-----------|-------------------| | **Primary lesion** | Alveolar wall destruction | Bronchial inflammation & mucus gland hyperplasia | | **Elastic recoil** | Markedly decreased | Preserved initially | | **Airway obstruction** | Loss of radial traction | Mucus plugging & smooth muscle hypertrophy | | **Pathology type** | Obstructive | Obstructive | ### Pathological Mechanism 1. **Oxidative stress** → imbalance of protease-antiprotease system 2. **Neutrophil elastase** and **matrix metalloproteinases** → destruction of elastic fibres and alveolar walls 3. **Loss of elastic recoil** → airway collapse during expiration (air trapping) 4. **Emphysematous spaces** → reduced gas exchange surface area **High-Yield:** The hallmark finding is **alveolar wall destruction**, NOT bronchial changes (which define chronic bronchitis). This is the single most important distinguishing feature on histology. **Clinical Pearl:** Patients with pure emphysema present as "pink puffers" (barrel chest, pursed-lip breathing, preserved oxygenation initially) due to increased work of breathing and preserved gas exchange until late disease. [cite:Robbins 10e Ch 15]