Folds of membranous tissue (peritoneum, mesothelium) attached to the wall of the abdomen and enclosing viscera. Examples include the mesentery for the small intestine; the transverse mesocolon, which attaches the transverse portion of the colon to the back wall of the abdomen; and the mesosigmoid, which enfolds the sigmoid portion of the colon. Cells of the same embryologic origin also surround the other organs of the body such as the lungs (pleura) or the heart (pericardium). [from
HPO]