The pleura is a double-layered membrane surrounding the lungs and lining the chest cavity. It plays a critical role in protecting the lungs and facilitating smooth respiratory movements. The pleura is divided into two layers:

1. Visceral Pleura: This is the inner layer of the pleura that directly covers the lungs. It adheres closely to the lung tissue and follows the contours of the lungs, including the fissures between the lobes.

2. Parietal Pleura: The outer layer of the pleura lines the chest wall, diaphragm, and the mediastinum (the central compartment of the thoracic cavity). It is more distant from the lungs compared to the visceral pleura.

### Pleural Cavity The space between the visceral and parietal pleurae is called the pleural cavity (or pleural space). This cavity contains a small amount of pleural fluid, which acts as a lubricant to reduce friction between the two layers as the lungs expand and contract during breathing. This allows for smooth movement of the lungs within the chest during respiration.

### Functions of the Pleura - Lubrication: The pleural fluid helps reduce friction between the lungs and chest wall, making breathing easier. - Protection: The pleura helps protect the lungs from external infection and injury. - Pressure regulation: The pleura helps maintain the appropriate pressure within the lungs and the pleural cavity, which is critical for proper lung expansion and respiration.

### Conditions Affecting the Pleura Several medical conditions can affect the pleura, leading to discomfort or respiratory problems: - Pleuritis (Pleurisy): Inflammation of the pleura, often caused by infections or other conditions such as autoimmune diseases, leading to sharp chest pain during breathing. - Pleural Effusion: Accumulation of excess fluid in the pleural cavity, which can lead to difficulty breathing and reduced lung expansion. - Pneumothorax: Presence of air in the pleural cavity, causing the lung to collapse. - Mesothelioma: A rare and aggressive form of cancer that affects the pleura, often linked to asbestos exposure.

Understanding the anatomy and function of the pleura is important in diagnosing and treating various lung and chest conditions.