What are the Pleura of the Lungs?

Anatomy and Function of the Pleural Membranes

diagram of the pleura in anatomy
What are the pleura?. A.D.A.M. Medical Encyclopedia

Definition: Pleura

The pleura refers to the 2 membranes that cover the lungs and line the chest cavity. The purpose of the pleura is to cushion the lungs during respiration.

The pleural cavity is the space between these 2 membranes and contains pleural fluid.

Structure of the Pleura

The pleura are made up of 2 layers:

  • The visceral pleura is the thin slippery serous membrane that covers the surface of the lungs, dipping into the areas separating the different lobes of the lungs.
  • The parietal pleura is the outer membrane of the pleura which lines the inner chest wall and the diaphragm.

The visceral and parietal pleura join at the hilum of each lung, the area where the major bronchi, as well as pulmonary arteries and veins, enter each lung.

Between the pleura lies the pleural cavity. This space contains around 4 teaspoons of fluid.

Function of the Pleura

The pleura glide past each other via the lubrication of the pleural space, allowing the lungs to actively expand during inspiration and relax during exhalation.

Conditions Involving the Pleura

Pleurisy - Pleurisy refers to an inflammation of the pleural membranes. When these layers become inflamed, the surfaces become rough and sticky. This can lead to sharp pains with breathing.  Pleurisy is most commonly caused by viral infections but can be caused by bacterial infections and autoimmune diseases such as rheumatoid arthritis and lupus.

For example, pleurisy may occur with lupus when antibodies attack the pleura resulting in inflammation.

Pleural Effusion - In a pleural effusion, excess fluid collects in the pleural space. When the amount of fluid accumulates rapidly or is large, breathing can be hampered. Congestive heart failure is the most common cause of a pleural effusion.

Malignant Pleural Effusion - A malignant pleural effusion refers to an effusion in which cancer cells are present.  This can be due to lung cancer or spread (metastases) to the lungs from other cancers.

Mesothelioma - Pleural mesothelioma is the most common type of mesothelioma. This cancer, which arises in the pleura, is most commonly caused by occupational exposure to asbestos.

Pneumothorax - In a pneumothorax, air collects in the pleural cavity. It may be caused by trauma to the chest, chest surgery, and COPD among other causes.

Hemothorax - A hemothorax refers to blood in the pleural cavity which can occur during chest surgery or trauma.

Treatment

Treatment of pleurisy will depend upon the underlying cause. When air (as in a pneumothorax) blood (as in a hemothorax) or fluid (as in a pleural effusion) accumulate in the pleural space, a chest tube is often placed to remove the air, fluid, or blood.

Sources:

Batra, H., and V. Antony. Pleural mesothelial cells in pleural and lung diseases. Journal of Thoracic Disease. 2015. 7(6):964-80.

Bertin, F., and J. Deslauriers. Anatomy of the Pleura: Reflection Lines and Recesses. Thoracic Surgery Clinics. 2011. 21(2):165-171.

National Heart, Lung, and Blood Institute. What are Pleurisy and Other Pleural Disorders? Updated 09/21/11. http://www.nhlbi.nih.gov/health/health-topics/topics/pleurisy

U.S. National Library of Medicine. MedlinePlus. Pleural Disorders. Updated 11/16/16. https://medlineplus.gov/pleuraldisorders.html

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