The bronchial system begins at the division of the trachea into the two primary bronchi. The bronchi will continue to divide into smaller branches until reaching areas where gas exchange (respiration) can take place. Identify on this section of LUNG WITH BRONCHI those portions of the bronchial system that are in bold print below.

• Primary bronchi are similar to the trachea until they enter the lungs where their cartilage rings are replaced by irregular cartilage plates.

• With branching into smaller secondary and tertiary bronchi inside the lung, the cartilage plates become smaller and less numerous, while an inner smooth muscle layer becomes more prevalent. The epithelium is still pseudostratified. One or more examples of a  tertiary bronchus can be seen on this LUNG WITH BRONCHI slide.

• After the tertiary bronchi, the next branchings within the lung that you should identify are the bronchioles. Bronchioles have no cartilage in their walls and fewer goblet cells in their epithelium than do larger air passages. Find an example of a bronchiole on this LUNG WITH BRONCHI slide.
• Click here for a detailed view of a bronchiole.

See this slide with the virtual microscope