Tertiary bronchus
Encyclopedia
The tertiary bronchi arise from the secondary bronchi
Secondary bronchus
Secondary bronchi arise from the primary bronchi, with each one serving as the airway to a specific lobe of the lung.-Structure:...

. The respiratory epithelium
Respiratory epithelium
Respiratory epithelium is a type of epithelium found lining the respiratory tract, where it serves to moisten and protect the airways. It also functions as a barrier to potential pathogens and foreign particles, preventing infection and tissue injury by action of the mucociliary escalator.-...

 lining their lumen is surrounded by a layer of smooth muscle
Smooth muscle
Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...

. This layer is composed of two ribbons of smooth muscle that spiral in opposite directions. The smooth muscle layer is surrounded by irregular plates of hyaline cartilage
Hyaline cartilage
Hyaline cartilage consists of a slimy mass, pearly bluish in colour with firm consistency and considerable collagen. It contains no nerves or blood vessels, and its structure is relatively simple....

 which help maintain the patency of the airway.

Each of the tertiary bronchi serves a specific bronchopulmonary segment
Bronchopulmonary segment
Each of the tertiary bronchi serves a specific bronchopulmonary segment. These segments each have their own artery. Thus, each bronchopulmonary segment is supplied by a bronchus, and two arteries, a pulmonary artery and a bronchial artery which run together through the center of the segment...

. There are 10 tertiary bronchi in the right lung, and eight in the left.

The tertiary bronchi get smaller and divide into primary bronchiole
Primary bronchiole
The primary bronchioles arise from the tertiary bronchi. They are histologically distinct from the tertiary bronchi in that their walls do not have hyaline cartilage and they have Clara cells in their epithelial lining. The epithelium starts as a simple ciliated columnar epithelium and changes to...

s.

External links

- "Pleural Cavities and Lungs: The Bronchi and Their Divisions" (1/2) - "Pleural Cavities and Lungs: The Bronchi and Their Divisions" (2/2)
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