ABSTRACT
The bony thoracic cage and its associated muscles form an airtight container that protects the heart and lungs, although the main purpose of the ribs is to assist with respiration. In normal quiet respiration, the principal muscle involved is the diaphragm, the muscular and tendinous partition separating the thorax and abdomen. The skeleton of the thorax is covered superficially by the muscles joining the upper limb to the chest wall, with the overlying breasts on the anterior chest wall. Needles or drainage tubes are inserted through the chest wall immediately above a rib, to keep away from the main intercostal vessels and nerves. If the negative pressure in the pleural cavity is destroyed, the lung collapses. If breathing is compromised, a tube may need to be inserted. Inflammation or cancer may cause fluid to collect in the pleural space, compressing the lung and causing difficulty in breathing.
