ABSTRACT
In vertebrates, including humans, all vital organs are located within the body cavity, which is surrounded and protected by a body wall formed by ribs, vertebrae, and layers of thick muscle. The body cavity is divided into thoracic, cardiac, and abdominal compartments. The thoracic cage is constructed like a vertical cone-shaped bellows, with the diaphragm as the moving part in the lowermost and widest end for the best protection and function of the lung. Within the limited protected cavity space, the lung moves and changes volume constantly.
