Mesothelium - Definition, Structure, and Function

What is the Mesothelium and Why is it Important?

book with name mesothelioma and stethoscope
What is the mesothelium?. Photo©designer491

Definition: Mesothelium

The mesothelium is the layer of tissues (membranes) that surround and protect organs of the chest, abdominal cavity, and pelvis.

Structure of the Mesothelium 

The mesothelium is divided into three primary regions:

  • The pleura - The pleura are the two membranes which form a lining around the lungs. This, in turn, is divided into the visceral pleura which lies directly over the lungs, and the parietal pleura, which is the outer layer of the lung lining.
  • The pericardium - The pericardium refers the mesothelium that forms a lining around the heart and the mediastinum.
  • The peritoneum - The lining peritoneum is the layers of mesothelium lining the abdominal cavity. This region is also divided into two layers. The visceral peritoneum lines the internal organs, and the parietal peritoneum, which lines the abdominal and pelvic walls.

Function of the Mesothelium

It was once thought that the only purpose of the mesothelium was to provide a slippery, non-sticky surface in order to protect the organs of the chest and abdominal cavity during movement. We are now learning, that similar to the tonsils and appendix, the mesothelium has other important functions as well. These include:

  • The transport and movement of fluids and matter across the membrane from the outer aspects of the chest and abdominal cavities to the internal organs.
  • Coagulation (blood clotting)
  • Healing
  • Immune function in that it appears to have a protective role both against infection as well as the spread of tumors.

Medical Conditions Involving the Mesothelium

Mesothelioma is a type of cancer that begins in the mesothelium (in any region where mesothelium is present.) This cancer is most common in people who have been exposed to asbestos (see asbestos dangers,) and continues to increase in incidence worldwide.

Symptoms of mesothelioma may include a cough, difficulty swallowing, abdominal pain and bloating, and other symptoms depending upon the location of the tumor. A surgical procedure called pleurodesis (removal of the pleura) is sometimes performed to remove the tumor, though the prognosis is usually poor by the time this cancer is diagnosed.

Adhesions are a common complication after abdominal surgery. Scar tissue involving the mesothelioma in the abdominal cavity may create bands of tissue, which in turn can trap the bowel and cause obstruction. Symptoms of adhesions are often abdominal pain, cramping, and bloating. When adhesions are mild (not causing a complete obstruction) people may suffer from chronic intermittent episodes of abdominal pain, especially after eating large meals.


American Cancer Society. What is Malignant Mesothelioma? Updated 02/17/16.

Canadian Cancer Society. Anatomy and Physiology of the Mesothelium. Accessed 10/30/15.

Mutsaers, S. Mesothelial cells: their structure, function and role in serosal repair. Respirology. 2002. 7(3):171-91.

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