Pleural Cavity – Functions, Diseases

Pleural cavity surrounds the lungs. Pleura is a serous membrane that folds back to form 2 layered structure. The space between the 2 pleural layers is called

pleural cavity

. It contains pleural fluid. Outer pleura called

parietal pleura

is appended to chest wall. Inner pleura called

visceral pleura

covers lungs and the adjoining structures, like bronchi, nerves and blood vessels.

Outer layer is very sensitive to pain while inner layer is not. This is due to absence of sensory innervation.


Pleural cavity with pleurae aids in the functioning of lungs while respiring. Pleural fluid in the pleural cavity helps pleurae to slide against each other easily during exhalation. Surface tension of pleural fluid helps to increase the thickness of cell wall of lungs with chest wall. This relationship helps in inflation of alveoli during breathing. During heavy breathing, chest wall movements are transmitted to lungs by pleural cavity. This is because closely opposed chest wall transmit pressures to inner surface and then to lung itself.


Pleural diseases include:

  • Pleural effusion:

    Fluid accumulation in the pleural space. This abnormal collection of fluid is due to excess volumes of fluid (that is, renal failure and intravenous fluids), decrease in fluid protein ( for example, proteinuria, cirrhosis), bleeding (hemothorax), heart failure, inflammation, perforation or malignancies of thoracic organs (that is, esophageal rupture, chylothorax), infections (like pleural empyema, parapneumonic effusions).

  • Pneumothorax:

    This refers to accumulation of air in the pleural cavity either arising from the lung or outside. Pneumothoraces might be iatrogenic, spontaneous or traumatic.

  • Tension Pneumothorax:

    This is a condition where the air enters on inspiration but do not exit on expiration. Each breath collects more air in chest cavity that leads to lung compression.

  • Pleural Tumors:

    This is a condition where pleurae grows abnormally. This can be malignant or benign in nature.

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