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 right bronchus now passes below the artery, and is known as the hyparterial branch which divides into the two lobar bronchi to the middle and lower lobes. The left main bronchus is smaller in caliber but longer than the right, being 5 cm long.It enters the root of the left lung opposite the sixth thoracic vertebra.he right main bronchus subdivides into three secondary bronchi (also known as lobar bronchi), which deliver oxygen to the three lobes of the right lungâthe superior, middle and inferior lobe.