The pulmonary ligament is a thin, triangular-shaped sheet of tissue that helps to anchor the lungs to the mediastinum, the central compartment of the chest that contains the heart, major blood vessels, and trachea. It's not a true ligament made of connective tissue, but rather a reflection of the mediastinal parietal pleura, the membrane lining the chest cavity, which folds over and fuses with the visceral pleura, the membrane covering the lungs.
The pulmonary ligament extends from the hilum of the lung, where the bronchus, blood vessels, and nerves enter the lung, down to the diaphragm. It also stretches from the medial surface of the lower lobe of the lung to the mediastinum. This structure forms a barrier between the anterior and posterior parts of the mediastinal portion of the pleural cavity below the root of the lung.
Though not readily visible on a standard chest X-ray, the pulmonary ligament can be identified on computed tomography (CT) scans. It's often used as a landmark in thoracic surgery, particularly during upper lobectomy. It can also be a site of granulomatous lymphadenitis, a condition that can mimic other lung diseases on CT scans.
