Pleural Cavity

The lungs occupy the right and left pleural cavities in the thoracic cavity. The left and right pleural cavities are divided into outer and inner layers.

1. The outer parietal layer lines the inner surface of the thoracic wall, the thoracic surface of the diaphragm, and the medial wall of the mediastinum.

2. The inner visceral layer closely covers all surfaces of the lungs.

The pleural cavity is a potential space that separates the different layers of pleura from each other. In reality, this potential space is not in fact an actual space. This potential space is lined with pleural fluid that separates the visceral pleura and parietal pleura. The pleural fluid also functions to:

1. Lubricate movement of the lungs.

2. Adhere the two pleural layers to each other, thus maintaining the inflation of the lungs.

3. Pleural effusion is when there is an excess of pleural fluid in this space.

Pleural Recesses:

The right and left costodiaphragmatic recesses are spaces between the costal and diaphragmatic parietal pleura.

During inspiration, the lungs descend into the right and left costodiaphragmatic recesses.During expiration, the lungs ascend so that the costal and diaphragmatic parietal pleura come together.