Diagram of the alveoli with both cross-section and external view.
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| colspan="2" |Schematic longitudinal section of a primary lobule of the lung (anatomical unit); r. b., respiratory bronchiole; al. d., alveolar duct; at., atria; a. s., alveolar sac; a, alveolus or air cell; p. a.: pulmonary artery: p. v., pulmonary vein; l., lymphatic; l. n., lymph node.
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|Latin
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|colspan="2"|[subject #240 ]
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|System
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|Precursor
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|MeSH
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|Dorlands/Elsevier
|colspan="2"|[Bronchioles/A04.411.125]
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The bronchioles are the first airway branches that no longer contain cartilage. They are branches of the bronchi, and are smaller than one millimetre in diameter.
There are no glands or cartilage in any of the bronchioles, and the epithelial cells become more cuboidal in shape.
Bronchioles divide until they become terminal bronchioles. After these the respiratory bronchioles have sporadic alveoli on their walls. Eventually the respiratory tract branches into alveolar ducts, then alveolar sacs.
Pathology
Bronchospasm, a life-threatening situation, occurs when the smooth muscular tissue of the bronchioles constricts, severely narrowing their diameter. Bronchospasm is commonly treated by oxygen therapy and bronchodilators.
