126: Overview of Benign Pleural Conditions: Anatomy and Physiology of Pleura

Introduction

The pleural space represents one of the body's potential spaces and can be affected pathologically by liquid, gas, or solid components, all of which can alter respiratory function. These processes may result from benign or malignant conditions, including infectious, inflammatory, or traumatic benign etiologies, as well as primary and secondary malignancies. This chapter provides a brief overview of the clinical presentation, diagnosis, etiology, and treatment of pleural conditions.

Anatomy and Physiology

The pleural space lies within the layer of pleura that covers the lung and the pleural layer that lines the chest wall, diaphragm, and mediastinum. The pleural layers are composed of a monolayer of mesothelial cells supported by a thin membrane of collagen and elastin connective tissue.¹ The pleural surfaces are categorized as the visceral and parietal pleurae. The interior surface, termed the visceral pleura, covers the lung. The exterior surface, denoted by the parietal pleura, lines the chest wall, mediastinum, and diaphragm (Fig. 126-1). An analogous representation of this configuration can be created by invaginating an inflated balloon with one's fist (Fig. 126-2). The portion of the balloon that covers the hand is analogous to the visceral pleural surface, and the exterior surface of the balloon represents the parietal pleural surface. The transition from visceral to parietal pleura occurs at the hilum of the lung. Inferior to the hilum, the anterior and posterior leaves of the visceral pleura fuse together at the inferior pulmonary ligament and anchor the medial aspect of the lower lobe to the mediastinum. The sulci, or sinuses, of the pleural space are defined by various structures: the upward bowing of the diaphragm into the hemithorax, the costophrenic sinus, the costomediastinal sinuses anteriorly and posteriorly, and the mediastinophrenic sinus medially. As the diaphragm descends with inspiration, these sinuses are occupied with inflated lung.

The pleural space develops between the fourth and seventh weeks of gestation. The lateral plate of the embryologic mesoderm differentiates into the splanchnopleure, which give rise to the parietal pleura and the somatopleure, which become the visceral pleura. At ...