Pleural Membrane Anatomy and Function

Liceth Sosa, John Simmons
  • Author
    Liceth Sosa

    Liceth holds a degree in Pharmacy from the National University of Colombia and postgraduate studies in Epidemiology from the Andes University. She has more than six years of experience in the pharmaceutical industry and has a broad knowledge in several health technologies such medical devices, biologics and small molecules.

  • Instructor
    John Simmons

    John has taught college science courses face-to-face and online since 1994 and has a doctorate in physiology.

Learn about the pleural membrane, its location and function. Also explore the major organs in the pleural cavity. Updated: 10/06/2021

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What is the Pleura or Pleural Membrane?

The pleura (also known as the pleural membrane) is a serous membrane made up of two layers: the outer pleura (called the parietal pleura), and the inner pleura (called the visceral pleura). Both layers are covered by mesothelial cells, which are specialized pavement-like cells found in vital organs.

The parietal pleura is in contact with the inside of the ribcage, the mediastinum, and the superior edge of the diaphragm. The mediastinum is a division of the thoracic cavity where the heart and other vital structures are located. The visceral pleura covers the surface of the lungs.

Located between the parietal and visceral pleura is the pleural cavity. This space is filled with a small amount of pleural fluid, which functions to keep each pleura humid and prevents friction when the lungs move during breathing.

Pleural Fluid

Pleural fluid lubricates the pleural membranes. The fluid is produced by blood vessels of the pleural membranes at a rate of approximately 0.6 mL/hour and is absorbed by the parietal pleural lymphatic system at a similar rate. The lymphatic system is a network of blood vessels through which a fluid containing white blood cells (known as lymph) drains from a tissue to the blood. Disturbances in the balance of pleural fluid production and absorption rates can cause harmful accumulation of pleural fluid.

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Layers of the Pleural Membrane

Let's look at the layers of the pleural membrane.

Parietal Pleura

The parietal pleura is 30 to 40 micrometers thick and is in contact with the inside of the ribcage, the mediastinum and the upper surface of the diaphragm. The parietal pleura receives its blood supply from the intercostal arteries (arteries between the ribs). It is sensitive to pain and is highly involved in the formation of parietal fluid.

One of the remarkable features of parietal pleura is the presence of lymphatic stomata over its surface. Stomata are holes that open into the pleural space and function as the primary site of removal of pleural fluid from the pleural space.

Visceral Pleura

The visceral pleura covers the surface of the lungs. It receives its blood supply from the bronchial (lung) circulation. The thickness of the visceral pleura varies over the surface of the lung, ranging from 20 to 80 micrometers. Due to its lack of sensory innervation, the visceral pleura is not sensitive to pain. The visceral pleural connective tissue dissipates stresses in the lung, and minimizes overexpansion of the lung thereby reducing the risk of pneumothorax.

A pneumothorax is a collapsed lung, and occurs when air enters the space between the chest wall and the lung (the pleural cavity). As air accumulates in this space, it pushes on the lung and causes it to collapse. Treatment involves inserting a needle or chest tube into the pleural cavity to remove the excess air. A pneumothorax can occur after a penetrating chest injury. Patients with pneumothorax feel chest pain and shortness of breath.

Pneumothoraxes are classified according to their cause. A primary spontaneous pneumothorax occurs without an apparent cause and in the absence of significant lung disease. A secondary spontaneous pneumothorax occurs in the presence of existing lung disease (e.g. tuberculosis). A traumatic pneumothorax develops from physical trauma.

Functions of the Pleural Membrane

The main function of the pleura is to provide mechanical protection and a smooth, lubricating elastic surface for the lungs to move during breathing.

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Frequently Asked Questions

What is the role of the pleural membrane?

The pleural membrane provides protection and a smooth, lubricating elastic surface for lung movement when breathing. It also maintains the normal dynamic homeostasis in the pleural space.

What organs are in the pleural cavity?

The organs covered by the pleural membrane are the lungs. The pleural cavity is the space between the visceral and parietal pleura.

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