Second largest hollow space of the body, enclosed by the ribs, vertebral column, and breastbone and separated from the abdominal cavity by the diaphragm. It contains the lungs and bronchi, part of the esophagus and trachea, and the heart and major blood vessels. A membrane called the pleura lines the cavity (parietal pleura) and continues over the lung (visceral pleura) and the rest of the cavity's contents, defining a space called the mediastinum. Disorders include blood (hemothorax) or air (pneumothorax, which can lead to atelectasis) in the pleural cavity and inflammation of the pleura (pleurisy).
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It contains three potential spaces lined with mesothelium: the paired pleural cavities and the pericardial cavity. The mediastinum comprises those organs which lie in the centre of the chest between the lungs.