On the right lung,, immediately above the hilus, is an arched furrow which accommodates the azygos vein (Groove for azygos vein); while running upward, and then arching lateralward some little distance below the apex, is a wide groove for the superior vena cava (Groove for superior vena cava) and right innominate vein (Groove for brachiocephalic vein); behind this, and nearer the apex, is a furrow for the innominate artery. Behind the hilus and the attachment of the pulmonary ligament is a vertical groove for the esophagus (Groove for esophagus); this groove becomes less distinct below, owing to the inclination of the lower part of the esophagus to the left of the middle line. In front and to the right of the lower part of the esophageal groove is a deep concavity for the extrapericardiac portion of the thoracic part of the inferior vena cava (Groove for inferior vena cava).
On the left lung, immediately above the hilus, is a well-marked curved furrow produced by the aortic arch (Groove for aortic arch), and running upward from this toward the apex is a groove accommodating the left subclavian artery; a slight impression in front of the latter and close to the margin of the lung lodges the left innominate vein (Groove for brachiocephalic vein). Behind the hilus and pulmonary ligament is a vertical furrow produced by the descending aorta, and in front of this, near the base of the lung, the lower part of the esophagus causes a shallow impression.