The mesothelium is a membrane that forms the lining of several body cavities: the pleura (thoracal cavity), peritoneum (abdominal cavity) and pericardium (heart sac). Mesothelial tissue also surrounds the male internal reproductive organs (the tunica vaginalis testis ) and the tunica serosa uteri covers the internal reproductive organs in women.

Origin

Mesothelium derives from the embryonic mesoderm cell layer, that lines the coelom (body cavity) in the embryo. It develops into the layer of cells that covers and protects most of the internal organs of the body. It is composed of two layers of cells:

• One layer that immediately surrounds the organ (visceral);
• A sac around the cavity (parietal).

Function

The mesothelium produces a lubricating fluid that is released between these layers, allowing moving organs (such as the beating heart, the expanding and contracting lungs, and peristaltically active intestine) to glide easily against adjacent structures.

Role in disease

Mesothelioma (cancer of the mesothelium) is a disease in which cells of the mesothelium become abnormal and divide without control or order. They can invade and damage nearby tissues and organs. Cancer cells can also metastasize (spread) from their original site to other parts of the body. Most cases of mesothelioma begin in the pleura or peritoneum. It is linked with asbestos exposure and smoking.

As mesothelium lacks tight junctions , an ultrastructure that closely links cells together (as seen in epithelia), it is prone to shedding during surgery. When this happens, the exposed surface can form adhesions with other surfaces, leading to intraabdominal (or rarely intrathoracal) adhesions.

Sources

• Mesothelioma: Questions and Answers (National Cancer Institute).