Primary bronchiole
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Emeraude
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The '''primary bronchioles''' arise from the [[tertiary bronchus|tertiary bronchi]]. They are histologically distinct from the tertiary bronchi in that their walls do not have [[hyaline cartilage]] and they have [[Clara cell]]s in their epithelial lining. The [[epithelium]] starts as a [[simple columnar epithelium|simple ciliated columnar epithelium]] and changes to [[simple cuboidal epithelium|simple ciliated cuboidal epithelium]] as the primary bronchiole decreases in size. The diameter of the primary bronchioles is often said to be less than 1 mm, though this value can actually range from 5 mm to 0.3 mm. As stated, these bronchioles do not have hyaline cartilage to maintain their patency. Instead, they rely on [[elastic fiber]]s attached to the surrounding [[human lung|lung]] tissue for support. The inner lining ([[lamina propria]]) of these bronchioles is thin with no glands present, and is surrounded by a layer of [[smooth muscle]]. As the primary bronchioles get smaller they divide into [[terminal bronchiole]]s.
==References==
* Dudek, Ronald W. ''High-Yield Histology'', 3rd ed. (2004). ISBN 0-7817-4763-5
* 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'' (2001). ISBN 0-7216-8806-3
[[Category:Respiratory system]]
[[Category:Thorax]]