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Secondary bronchus

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Title: Secondary bronchus  
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Subject: Bronchiole, Tertiary bronchus
Publisher: World Heritage Encyclopedia

Secondary bronchus

Secondary bronchus
1. Trachea
2. Mainstem bronchus
3. Lobar bronchus
4. Segmental bronchus
5. Bronchiole
6. Alveolar duct
7. Alveolus
Front view of cartilages of larynx, trachea, and bronchi.
Latin bronchi lobares

Secondary bronchi (also known as lobar bronchi) arise from the primary bronchi, with each one serving as the airway to a specific lobe of the lung.


They have relatively large lumens that are lined by respiratory epithelium. There is a smooth muscle layer below the epithelium arranged as two ribbons of muscle that spiral in opposite directions. This smooth muscle layer contains seromucous glands. Irregularly arranged plates of hyaline cartilage surround the smooth muscle. These plates give structural support to the bronchus and maintain the patency of the lumen.

A bronchus has cartilage plates, smooth muscle, and mucus-secreting gland-cells in its wall. It also has lining cells with cilia departing towards the mouth; this removes dust and other small debris.

Secondary bronchi of right lung

Secondary bronchi of left lung

  • superior lobe bronchus
  • inferior lobe bronchus

Additional images


  • Gartner, Leslie P. and James L. Hiatt. Color Atlas of Histology, 3rd ed. (2000). ISBN 0-7817-3509-2
  • Gartner, Leslie P. and James L. Hiatt. Color Textbook of Histology, 2nd ed. (2001). ISBN 0-7216-8806-3

External links

  • 19:08-03 - "The divisions of the bronchus."
  • GPnotebook
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