Bronchi

Bronchi are large air tubes leading from the trachea, or windpipe, to the lungs. The end of the trachea transitions into two bronchi: the left main bronchus and the right main bronchus. The two main bronchi are asymmetrical, with the right being wider, shorter and more vertical than the left. The main bronchi branch off in much the way a tree's branches spread from large branches near the trunk to multiple smaller branches. The right main bronchus branches into three smaller bronchi, while the left main bronchus divides into two (1).

The bronchi, along with the trachea, are composed of rings of hyaline cartilage (a type of strong, elastic cartilage), fibrous tissue, muscle, mucous membranes, and glands. As the main bronchi branch out into smaller bronchi, the amount of cartilage in the walls decreases and the amount of muscle increases. The branches terminate into bronchioles, which are extremely small in diameter (approximately one millimeter) and do not contain cartilage (2). The bronchioles bring air to the alveoli (the air sacs), where oxygen exchange occurs (3).

When lung cancer stems from the bronchi, it also may also be termed "bronchial cancer." When the cancer arises from epithelial cells - as often is the case with cancer linked to asbestos exposure - it is termed "bronchiolar carcinoma" (4).

'Bronchi' Sources:
  1. Thompson, Brad H., M.D. "Bronchial Anatomy." From the Virtual Hospital website. Available: http://lib.cpums.edu.cn/jiepou/tupu/atlas/www.vh.org/adult/provider/radiology/LungAnatomy/BronchAnatomy/BronchAnat.html (Accessed July 12, 2007).
  2. "Cartilage." From the University of Wester Cape's Department of Biodiversity and Conservation Biology. Available: http://www.botany.uwc.ac.za/sci_ed/grade10/mammal/cart.htm
  3. "Alveoli." From the John Hopkins School of Medicine's Interactive Respiratory Physiology webpage. Available: http://oac.med.jhmi.edu/res_phys/Encyclopedia/Alveoli/Alveoli.HTML (Accesed July 12, 2007).
  4. "Lung Cancer and Bronchial Cancer." From the Orebro University Hospital website. Available: http://www.orebroll.se/huv/HUV_page____5598.aspx (Accessed July 12, 2007).




 

 

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