Hilum of the lung

The hilum is a triangular area on the mediastinal surface of each lung where the structures that form the root of the lung enter and leave the organ. These include the pulmonary artery, the superior and inferior pulmonary veins, lymphatic vessels and the main bronchus. Small bronchial vessels that supply the lung tissue also enter the lung at the hilum.

The pulmonary ligament droops down from the hilum of the lung and terminates in a free, or falciform, edge.

The rib cage is separated from the lung by a two layered membranous coating, called a pleura. The hilum represents the point where the parietal pleura (covering the rib cage) and the visceral pleura (covering the lung) are continuous (connect).