Pleural Cavity and Membranes - Anatomy & Physiology
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Introduction
The surface of the inner wall of all of the body cavities are lined by a serous membrane which consists of a single layer of flat epithelium with a thin underlying propria (connective tissue). Within the thoracic cavity, this is known as the Pleura.
Structure of the Pleural Membranes
- Each lung is placed within a separatte layer of membrane, thus there are two pleural sacs.
- The space between the two sacs is known as the Mediastinum.
- The pleura covering the surface of the lung is known as Pulmonary Pleura or Visceral Pleura. This becomes continuous with the Mediastinal Pleura as it wraps around the lung.
- The Diaphragmatic and Costal Pleura are continuous with the Mediastinal Pleura. Together, these three membranes are the Parietal Pleura.
- Between the Parietal and Visceral Pleura is the Pleural Cavity. This contains a small amount of serous fluid which establishes adhesion between the layers and allows smooth movement.
- The Heart is invested in a Parietal and Visceral layer of Pericardium with the Pericardial Space separating the two membranes.
- Cranially the Costal and Mediastinal Pleura adjoin to form a 'dome' of pleura which extends cranially to the thoracic inlet. This is known as the Cupulae Pleurae. This region is only protected by soft tissue, and thus is vulnerable to injury.