The pleura is a thin, double-layered membrane that surrounds the lungs and lines the inner wall of the chest cavity. It provides a protective and lubricating function, allowing the lungs to move smoothly during breathing.
Layers of the Pleura
The pleura consists of two layers:
- Visceral Pleura: This layer directly covers the surface of each lung. It is tightly adhered to the lung tissue and cannot be easily separated.
- Parietal Pleura: This layer lines the inner surface of the chest wall, the diaphragm (the muscle that helps with breathing), and the mediastinum (the space between the lungs).
Pleural Cavity
Between the visceral and parietal pleura is a potential space called the pleural cavity. This cavity normally contains a small amount of pleural fluid (approximately 10-20 ml).
Function of the Pleura
The pleura plays several vital roles in respiratory function:
- Lubrication: The pleural fluid acts as a lubricant, reducing friction between the lungs and the chest wall during breathing. This allows the lungs to expand and contract smoothly.
- Protection: The pleura protects the lungs from injury and infection.
- Pressure Gradient: The pleural space helps to maintain a negative pressure, which is essential for keeping the lungs inflated. This negative pressure is lower than the pressure inside the lungs, preventing them from collapsing.
Clinical Significance
Various conditions can affect the pleura, including:
- Pleurisy (Pleuritis): Inflammation of the pleura, causing sharp chest pain that worsens with breathing.
- Pleural Effusion: An accumulation of excess fluid in the pleural cavity.
- Pneumothorax: Air entering the pleural cavity, causing the lung to collapse.
- Mesothelioma: A rare cancer that affects the lining of the lungs, abdomen, or heart.
