Above and behind the cardiac impression is a triangular depression named the<unk> , 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, and the bronchus, with bronchial vessels surrounding it.
These structures are invested by pleura, which, below the<unk>  and behind the pericardial impression, forms the pulmonary ligament.
Hilum of lung
Mediastinal pleura
Inferior border of lung
Costomediastinal recess
Mediastinum
Mediastinal surface of lung
Thoracic cavity
Subcostal plane