and abdominopelvic cavities and their subdivisions. The dorsal cavity includes the cranial and spinal cavities. Other animals Organisms can be also classified according to the type of body cavity they possess, such as pseudocoelomates and protostome coelomates. Coelom In amniotes and some invertebrates the coelom is the large cavity lined by mesothelium, an epithelium derived from mesoderm. Organs formed inside the coelom can freely move, grow, and develop independently of the body wall while fluid in the peritoneum cushions and protects them from shocks. Arthropods and most molluscs have a reduced (but still true) coelom, the hemocoel (of an open circulatory system) and the smaller gonocoel (a cavity that contains the gonads). Their hemocoel is often derived from the blastocoel. See also Gastrovascular cavity References This Wikipedia entry incorporates text from the freely licensed Connexions edition of Anatomy & Physiology text-book by OpenStax College'' External links Further discussion Animal anatomy Developmental biology