hilum

The hilum is the lung’s doorway — the spot on its inner (medial) face where everything that serves the lung enters and leaves: the main bronchus, the pulmonary artery and veins, nerves, and lymphatic vessels, all bundled together. The whole bundle is called the root of the lung.

Because so many structures crowd through this single gateway, the hilum is a busy crossroads and a key landmark. On a chest X-ray the hila appear as shadows mainly created by the large pulmonary vessels and the airways passing through.

Hilar appearances carry diagnostic weight. Enlarged or lumpy hila on imaging may reflect swollen lymph nodes — seen in sarcoidosis, tuberculosis or lung cancer — or enlarged pulmonary arteries in pulmonary hypertension, so a changed hilum is something clinicians look at carefully.