The mesothelium is a membrane that covers and keeps most of the important organs of the body protected. This material contains of a couple different types of cells.  This membrane also helps organ to move easily around.  It is an extremely vital membrane in the body. The mesothelium lines the chest, lungs, and abdominal area. When mesothelioma affects someone, it begins to progress and spread into these areas as the cancer progresses into the latter stages.

This is about the majority of the mesothelium.  The peritoneum is what covers most of the organs in the abdominal area, the pleura surrounds the lungs and chest cavity, and the pericardium protects the heart.