Pleura: Understanding the Lung Covering - Definition & Function

The pleura is a double-layered serous membrane enclosing each lung and lining the thoracic cavity.

Layers

• Visceral Pleura: Adherent to lung surface; follows fissures. Insensitive to pain.
• Parietal Pleura: Lines thoracic wall, diaphragm, mediastinum. Somatic innervation (pain-sensitive).

Pleural Cavity

Potential space between layers containing 5–15 mL pleural fluid (transudate). Functions:

• Lubrication: Frictionless sliding during respiration.
• Surface Tension: Couples lung to chest wall (transmits expansion).
• Pressure Gradient: Negative intrapleural pressure (-5 cmH₂O at rest) keeps lungs inflated.

Clinical Relevance

• Pleuritis: Inflamed pleura → sharp pleuritic pain.
• Pleural Effusion: Fluid accumulation → dyspnea, dullness.
• Pneumothorax: Air entry → lung collapse.