Page 375 - Concise Pathology for Exam Preparation ( PDFDrive )

360 SECTION II Diseases of Organ Systems

Respiratory bronchiole
Terminal bronchiole Alveolar duct

Alveolus
Normal

Alveolus

Respiratory bronchiole
Centriacinar

Respiratory bronchiole Alveolus

Panacinar
Irregular dilatation of respiratory bronchiole

Dilated alveolus

Irregular
FIGURE 13.3. Types of emphysema.

Others Types of Emphysema
Sometimes the term ‘emphysema’ may be applied to certain conditions not conforming
strictly to the definition of emphysema, eg,
1. Compensatory emphysema: Dilatation of alveoli without destruction of septal walls
in response to loss/removal of lung substance elsewhere
2. Obstructive overinflation: Expansion of lung because of air trapped within it. Trapping
of air may be due to
(a) Subtotal obstruction: Air enters in inspiration but cannot exit in expiration (ball
valve mechanism)
(b) Total obstruction: Ventilation through collaterals (pores of Kohn and canals of
Lambert), which bring in air behind the obstruction
3. Bullous emphysema:
(a) A form of emphysema that produces large subpleural bullae (blebs . 1 cm in size),
rupture of which may lead to pneumothorax
(b) Usually a consequence of old tuberculous scarring
4. Interstitial emphysema
(a) Characterized by air entry into connective tissue stroma of lung, mediastinum or
subcutaneous tissue
(b) Causes include an alveolar tear caused by bronchiolar obstruction accompanied by
explosive coughing (whooping cough, bronchitis, etc.) or puncture of the lung due
to a chest wound or a fractured rib
Pathogenesis of Emphysema
• Role of ‘Protease–antiprotease’ mechanism:
• Homozygous patients with a genetic deficiency of protease inhibitor a-1 AT have an
increased tendency to develop emphysema. Smoking exaggerates this tendency.

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