Define and explain “MESOTHELIOMA” based on the etymological roots of the word.
Mesothelioma is a cancer of the mesothelium. The mesothelium is composed of flat, squamous epithelial cells forming a double-layered membrane lining several body cavities. This mesothelium derives from the embryonic mesoderm cell layer which lines the body cavity (coelum) of the embryo. The visceral layer of the mesothelium closely surrounds the organ; the parietal mesothelium forms a protective sac around the organ. The mesothelium secretes a cushioning, lubricating fluid between these two layers so that the organ(s) can slip freely along contiguous viscera. The mesothelium has several different names deriving from the part of the body that it protects: around the heart it is called the pericardium; around the lungs, the pleura; around the abdominal cavity, the peritoneum; around the internal male reproductive organs, the tunica vaginalis testi; around the internal female reproductive organs, the tunica serosa uteri.