Pleural

Pleural refers to the pleura, the pair of serous membranes that surround the lungs and line the chest cavity. The pleura consist of a visceral layer that covers the lungs and a parietal layer that lines the thoracic wall, diaphragm, and mediastinum. The space between these layers, the pleural cavity, contains a small amount of lubricating pleural fluid.

The principal function of the pleura is to allow smooth expansion and recoil of the lungs during breathing. Negative intrapleural pressure helps keep the lungs inflated, and the serous fluid reduces friction between the moving surfaces. The transpulmonary pressure, the difference between intrapulmonary and intrapleural pressures, helps maintain lung inflation.

Innervation and circulation differ between the layers. The parietal pleura is somatically innervated by intercostal and phrenic nerves and is sensitive to pain. The visceral pleura is innervated by autonomic nerves and is not well localized for pain. Blood supply to the visceral pleura comes mainly from the bronchial arteries, while the parietal pleura receives blood from intercostal and internal thoracic arteries. Lymphatic drainage primarily targets mediastinal and diaphragmatic nodes.

Pathology involving the pleura includes pleural effusion, the accumulation of fluid in the pleural space; pneumothorax, air entering the space causing partial or complete lung collapse; and pleuritis (pleurisy), inflammation of the pleura that can cause chest pain. Chronic asbestos exposure can lead to pleural plaques and, more rarely, mesothelioma, a cancer of the pleura.

In medical usage, pleural commonly appears in terms describing the pleura or pleural space, and radiographic or ultrasound evaluation often focuses on detecting fluid, air, or thickening of the pleural membranes.