pleural sac

anatomy

Also known as: pleural cavity

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Last updated

July 23, 2026

Quick Summary

The pleural sac, also known as the pleural cavity, is the space between two membranes that surround the lungs. The inner membrane, the visceral pleura, covers the lungs, while the outer membrane, the parietal pleura, lines the thoracic cavity. These two membranes are normally in close contact and are lubricated by a thin fluid that allows the lungs to move smoothly during breathing.123

Disorders of the pleural sac can include inflammation (pleurisy), the accumulation of excess fluid (pleural effusion), pus (empyema), or air (pneumothorax) within the space. These conditions can cause pain, shortness of breath, and fever.123

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human respiratory system
Gross anatomy
The lung surfaces facing these pleural areas are named accordingly, since the shape of the lungs is determined by the shape of the pleural cavities. Because of the presence of pleural recesses, which form a kind of reserve space, the pleural cavity is larger than the lung volume.
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The lung surfaces facing these pleural areas are named accordingly, since the shape of the lungs is determined by the shape of the pleural cavities. Because of the presence of pleural recesses, which form a kind of reserve space, the pleural cavity is larger than the lung volume.
Read More