Occupational Safety and Health Administration. 1  Department of Labor, Labor Department, DoL, Labor - the federal department responsible for promoting the working conditions of wage earners in the United States; created in 1913.
The oxygen and carbon dioxide exchange take place in the alveoli. Primary bronchi are located on the upper portion of the lungs, secondary bronchi is located at the center of the lungs and tertiary bronchi is located near bottom of the organs above the bronchioles.
A bronchus is either of the two major branches of the trachea that lead to the lungs. The bronchi begin when the trachea divides to form the right and left main bronchi (pleural of bronchus.) These bronchi, in turn, travel to each of the lungs. The bronchi divide first into lobar bronchi and then tertiary bronchi.