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.
The human trachea (windpipe) divides into two main bronchi (also called mainstem bronchi), at the anatomical point known as the carina. The right main bronchus is wider and shorter than the left main bronchus. The right main bronchus subdivides into three lobar bronchi and the left main bronchus divides into two.