Body Cavity(redirected from Acoelomates)
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body cavity[′bäd·ē ‚kav·əd·ē]
in animals and man, the space bounded by the internal surface of the body wall. The internal organs are distributed in the body cavity. The primary body cavity does not have a wall, whereas the secondary body cavity, or coelom, is lined with sheets of epithelial mesodermal cells. In vertebrates the secondary body cavity is divided into the pericardial cavity and the abdominal cavity. In mammals, including man, the abdominal cavity is divided by the diaphragm into the thoracic cavity, which is lined with the pleura and contains the lungs, and the abdominal cavity proper, which is lined with the peritoneum and contains the digestive, excretory, and sex organs.