Lung bronchi. Three-dimensional computed tomog- raphy (CT) scan of the two bronchi dividing from the trachea. The trachea is the tube which carries air from the nose and mouth to the two bronchi, which each travel to a lung. CT scans use X-rays to take slice images through the body, which are combined to give this 3-D endoscopic effect. This virtual endoscopy allows a view of internal structures without using invasive techniques.