The relationships of the mediastinal structures to the medial surface of the right lung are shown. Note the groove made by the azygous vein posterior to the inferior pulmonary ligament, and arching over the right main bronchus proximal to the take-off of the right upper lobe bronchus. Note the impression of the right side of the heart on the right middle lobe and medial basal segment of the lower lobe, and the impressions of trachea, esophagus, arch vessels and right brachiocephalic vein above the hilum (see bronchopulmonary segments and tracheobronchial relationships ).