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	The '''bronchioles''' or '''bronchioli''' are the passageways by which air passes through the ] or ] to the ] (air sacs) of the lungs, in which branches no longer contain ] or ]s in their ]. They are branches of the ], and are part of the ] of the ]. The bronchioles divide further into smaller '''terminal''' bronchioles which are still in the conducting zone and these then divide into the smaller '''respiratory''' bronchioles which mark the beginning of the respiratory region.		The '''bronchioles''' or '''bronchioli''' are the passageways by which air passes through the ] or ] to the ] (air sacs) of the lungs, in which branches no longer contain ] or ]s in their ]. They are branches of the ], and are part of the ] of the ]. The bronchioles divide further into smaller '''terminal''' bronchioles which are still in the conducting zone and these then divide into the smaller '''respiratory''' bronchioles which mark the beginning of the respiratory region.

			ako si Edward napat
	== Structure ==
	] showing r. b respiratory bronchiole;al. d ];a. s ];'a' alveolus;]]
	A pulmonary lobule is the portion of the ] ventilated by one bronchiole. Bronchioles are approximately 1mm or less in diameter and their walls consist of ] cuboidal ] and a layer of ].
	Bronchioles divide into even smaller bronchioles, called ''terminal'', which are 0.5mm or less in diameter. Terminal bronchioles in turn divide into smaller respiratory bronchioles which divide into ]. Terminal bronchioles mark the end of the conducting division of air flow in the ] while respiratory bronchioles are the beginning of the respiratory division where actual ] takes place.

	The diameter of the bronchioles plays an important role in air flow. The bronchioles change diameter to either increase or reduce air flow. An increase in diameter is called ] and is stimulated by either ] or ] to increase air flow. A decrease in diameter is called ] and is stimulated by ], ], cold air, chemical irritants and other factors to decrease air flow.

	===Bronchioles===
	]
	The '''primary bronchi''', in each lung, which are the ] and ], give rise to ''']'''. These in turn give rise to ''']''' (tertiary meaning third). The tertiary bronchi subdivide into the '''bronchioles'''. They are histologically distinct from the tertiary bronchi in that their walls do not have ] and they have ]s in their epithelial lining. The ] starts as a ] and changes to ] as the bronchioles decreases in size. The diameter of the 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 ]s attached to the surrounding ] tissue for support. The inner lining (]) of these bronchioles is thin with no glands present, and is surrounded by a layer of ]. As the bronchioles get smaller they divide into '''terminal bronchioles''', these bronchioles mark the end of the ], which covers the first division through the sixteenth division of the ]. ] only become present when the conducting zone changes to the ], from the sixteenth through the twenty-third division of the tract.

	===Terminal bronchioles===
	The terminal bronchiole is the most distal segment of the conducting zone. It branches off the lesser bronchioles. Each of the terminal bronchioles divides to form ]s which contain a small number of alveoli. Terminal bronchioles are lined with simple ] containing ]s. Terminal bronchioles contain a limited number of ciliated cells and no ]s. Club cells are non-ciliated, rounded protein secreting cells. Their secretions are a nonsticky, proteinaceous compound to maintain the airway in the smallest bronchioles. The secretion, called ], reduces ], allowing for bronchioles to expand during inspiration and keeping the bronchioles from collapsing during expiration. Club cells, a ] of the ], produce ]s that detoxify substances dissolved in the respiratory fluid.

	===Respiratory bronchioles===
	The '''respiratory bronchioles''' are the narrowest airways of the ]s, one fiftieth of an inch across.<ref name="Merck">Merck Manual of medical information,home edition, copyright 1997, first printing of pocket books 1999, Pocket Books, a division of Simon and Schuster Inc</ref> The ] divide many times before evolving into the bronchioles.
	The bronchioles deliver air to the exchange surfaces of the lungs.<ref>Human Anatomy by Frederic Martini sixth edition, page 643</ref>
	They are interrupted by ] which are thin walled evaginations. ] are distal continuations of the respiratory bronchioles.

	==Clinical significance==		==Clinical significance==

Revision as of 13:29, 9 June 2014

Bronchiole
Diagram of the alveoli with both cross-section and external view.
Details
Identifiers
Latin	Bronchioli
MeSH	D055745
TA98	A06.5.02.026
TA2	3282
TH	H3.05.02.0.00005
FMA	7410
Anatomical terminology[edit on Wikidata]

The bronchioles or bronchioli are the passageways by which air passes through the nose or mouth to the alveoli (air sacs) of the lungs, in which branches no longer contain cartilage or glands in their submucosa. They are branches of the bronchi, and are part of the conducting zone of the respiratory system. The bronchioles divide further into smaller terminal bronchioles which are still in the conducting zone and these then divide into the smaller respiratory bronchioles which mark the beginning of the respiratory region.

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Clinical significance

Bronchospasm, a potentially life-threatening situation, occurs when the smooth muscular tissue of the bronchioles constricts, severely narrowing their diameter. The most common cause of this is asthma. Bronchospasm is commonly treated by oxygen therapy and bronchodilators.

Diseases of the bronchioles include asthma, bronchiolitis obliterans, respiratory syncytial virus infections, and influenza.