The root of the lung

Lung

The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

 is covered in front, above, and behind by pleura; at its inferior border, the investing layers come into contact. Here they form a sort of mesenteric fold, the pulmonary ligament, which extends between the inferior part of the mediastinal surface of the lung and the pericardium

Pericardium

The pericardium is a double-walled sac that contains the heart and the roots of the great vessels.-Layers:...

. The pulmonary ligament droops down from the hilum of the lung

Hilum of lung

Above and behind the cardiac impression is a triangular depression named the hilum, where the structures which form the root of the lung enter and leave the viscus. These include the pulmonary artery, superiormost on the left lung, the superior and inferior pulmonary veins, lymphatic vessels and...

.

Just above the diaphragm the ligament ends in a free falciform border. It serves to retain the inferior part of the lung in position.