Bronchus. View through a bronchoscope (a type of endoscope) of the interior of a healthy bronchus. A bronchus is one of the two passages (bronchi) that branch from the trachea (windpipe) and each lead to a lung. Inside the lung they divide into smaller passages known as bronchioles, and ultimately end in air sacs known as alveoli. Bronchoscopy is performed for a variety of reasons, including the removal of inhaled foreign objects, collecting mucus samples, taking tissue biopsies and sealing damaged blood vessels. All these tasks are carried out by small tools which can be attached to the bronchoscope.