The
coelom ( , plural
coeloms or
coelomata ) (Greek
koiloma, hollow, cavity) refers to the main
body cavity in most multicellular animals and is positioned inside the body to surround and contain the
digestive tract and other organs. In developed
animals, it is lined with a mesodermal
epithelium. In other animals, such as
molluscs, it remains undifferentiated.