mesothelium

n. membranous tissue which originated in the embryonic mesoderm and covers internal and external organs (Anatomy); membranous lining of the embryonic body cavity (Embryology)

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 covers the internal reproductive organs of women (the tunica serosa uteri). Mesothelium that covers the internal organs is called visceral mesothelium, while the layer that covers the body walls is called the parietal mesothelium.
See more at Wikipedia.org...

Mesothelium /meso·the·li·um/ the layer of cells, derived from mesoderm, lining the body cavity of the embryo; in the adult, it forms the simple [more]Mesothelium - Community and Resources

Noun
1. epithelium originating in the embryonic mesoderm; lines the primordial body cavity
(hypernym) epithelium, epithelial tissue

n. mesothelium, membranous tissue which originated in the embryonic mesoderm and covers internal and external organs (Anatomy)