WordNet

any of the smallest bronchial ducts; ending in alveoli
of or relating to or involving bronchioles

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/10/31 19:25:44」(JST)

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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.

Structure

A lobule of the lung showing r. b respiratory bronchiole;al. d alveolar duct;a. s alveolar sac;'a' alveolus;

A pulmonary lobule is the portion of the lung ventilated by one bronchiole. Bronchioles are approximately 1mm or less in diameter and their walls consist of ciliated cuboidal epithelium and a layer of smooth muscle. 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 alveolar ducts. Terminal bronchioles mark the end of the conducting division of air flow in the respiratory system while respiratory bronchioles are the beginning of the respiratory division where actual gas exchange 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 bronchodilation and is stimulated by either epinephrine or sympathetic nerves to increase air flow. A decrease in diameter is called bronchoconstriction and is stimulated by histamine, parasympathetic nerves, cold air, chemical irritants and other factors to decrease air flow.

Bronchioles

The primary bronchi, in each lung, which are the left and right bronchus, give rise to secondary bronchi. These in turn give rise to tertiary bronchi (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 hyaline cartilage and they have club cells in their epithelial lining. The epithelium starts as a simple ciliated columnar epithelium and changes to simple ciliated cuboidal epithelium 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 elastic fibers attached to the surrounding 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 bronchioles get smaller they divide into terminal bronchioles, these bronchioles mark the end of the conducting zone, which covers the first division through the sixteenth division of the respiratory tract. Alveoli only become present when the conducting zone changes to the respiratory zone, 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 respiratory bronchioles which contain a small number of alveoli. Terminal bronchioles are lined with simple cuboidal epithelium containing club cells. Terminal bronchioles contain a limited number of ciliated cells and no goblet cells. 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 surfactant, reduces surface tension, allowing for bronchioles to expand during inspiration and keeping the bronchioles from collapsing during expiration. Club cells, a stem cell of the respiratory system, produce enzymes that detoxify substances dissolved in the respiratory fluid.

Respiratory bronchioles

The respiratory bronchioles are the narrowest airways of the lungs, one fiftieth of an inch across.^[1] The bronchi divide many times before evolving into the bronchioles. The bronchioles deliver air to the exchange surfaces of the lungs.^[2] They are interrupted by alveoli which are thin walled evaginations. Alveolar ducts are distal continuations of the respiratory bronchioles.

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.

Inflammation

The medical condition of inflammation of the bronchioles is termed bronchiolitis.

Additional images

Cross sectional cut of primary bronchiole
1. Trachea
2. Mainstem bronchus
3. Lobar bronchus
4. Segmental bronchus
5. Bronchiole
6. Alveolar duct
7. Alveolus

References

^ Merck Manual of medical information,home edition, copyright 1997, first printing of pocket books 1999, Pocket Books, a division of Simon and Schuster Inc
^ Human Anatomy by Frederic Martini sixth edition, page 643

External links

Histology image: 13607loa - Histology Learning System at Boston University
Terminal+bronchiole at eMedicine Dictionary
Diagram at davidson.edu
Histology at umdnj.edu
Respiratory+bronchioles at eMedicine Dictionary
Histology image: 13606loa - Histology Learning System at Boston University

UpToDate Contents

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1. 幼児および小児における細気管支炎：治療、転帰および予防 bronchiolitis in infants and children treatment outcome and prevention
2. 幼児および小児における細気管支炎：臨床的特徴および診断 bronchiolitis in infants and children clinical features and diagnosis
3. 成人における細気管支炎 bronchiolitis in adults
4. 慢性肺移植拒絶反応：閉塞性細気管支炎 chronic lung transplant rejection bronchiolitis obliterans
5. 呼吸細気管支炎関連間質性肺疾患 respiratory bronchiolitis associated interstitial lung disease

English Journal

Species of Angiostrongylus (Nematoda: Metastrongyloidea) in wildlife: A review.

Spratt DM1.
International journal for parasitology. Parasites and wildlife.Int J Parasitol Parasites Wildl.2015 Mar 9;4(2):178-89. doi: 10.1016/j.ijppaw.2015.02.006. eCollection 2015.
Twenty-one species of Angiostrongylus plus Angiostrongylus sp. (Nematoda: Metastrongyloidea) are known currently in wildlife. These occur naturally in rodents, tupaiids, mephitids, mustelids, procyonids, felids, and canids, and aberrantly in a range of avian, marsupial and eutherian hosts including
PMID 25853051

Local origin of mesenchymal cells in a murine orthotopic lung transplantation model of bronchiolitis obliterans.

Mimura T1, Walker N1, Aoki Y1, Manning CM1, Murdock BJ1, Myers JL2, Lagstein A2, Osterholzer JJ1, Lama VN3.
The American journal of pathology.Am J Pathol.2015 Jun;185(6):1564-74. doi: 10.1016/j.ajpath.2015.03.002. Epub 2015 Apr 4.
Bronchiolitis obliterans is the leading cause of chronic graft failure and long-term mortality in lung transplant recipients. Here, we used a novel murine model to characterize allograft fibrogenesis within a whole-lung microenvironment. Unilateral left lung transplantation was performed in mice acr
PMID 25848843

Bilateral spontaneous pneumothorax secondary to aspiration pneumonia induced by a wristwatch lodged at the pharyngoesophageal junction.

Kawai C1, Miyao M, Kotani H, Tamaki K.
Forensic science, medicine, and pathology.Forensic Sci Med Pathol.2015 Jun;11(2):249-54. doi: 10.1007/s12024-015-9663-y. Epub 2015 Feb 28.
Bilateral spontaneous pneumothorax secondary to disease is rare and seldom encountered in forensic autopsies; however, traumatic bilateral pneumothorax occurs often. Herein, we present a forensic case involving a 50-year-old woman who died 4 days after ingesting a wristwatch. Postmortem computed to
PMID 25724839

Japanese Journal

TBLBで診断した肺MALTリンパ腫の1例

気管支学 : 日本気管支研究会雑誌 37(3), 303-307, 2015-05-25
NAID 110009970294

An improved dispersion method of multi-wall carbon nanotube for inhalation toxicity studies of experimental animals

Journal of toxicological sciences 38(4), 619-628, 2013-08-01
NAID 10031178704

柔軟壁の呼吸器系に組み込まれた閉鎖細気管支の開通に関する計算

日本肺サーファクタント・界面医学会雑誌 = Journal of Japanese Medical Society for Lung Surfactant and Biological Interface 43, 19-27, 2012-10-15
NAID 10031123265

Related Pictures

Bronchioles and alveoli in the lungs - Mayo Clinic Bronchioles - Definition, Location, Size, Function, Pictures Bronchioles Definition, Location, Anatomy, Function, Diagram Bronchioles and alveoli - Mayo Clinic Bronchioles | www.pixshark.com - Images Galleries With A Bite! Bronchiole - YouTube Bronchiole - Wikipedia

★リンクテーブル★

リンク元	「細気管支」「bronchiolar」「気管支梢」「bronchiolus」

「細気管支」

Bronchiole
	Diagram of the alveoli with both cross-section and external view.
Details
Latin	Bronchioli
Identifiers
Gray's	p.1098
Code	TH H3.05.02.0.00005
TA	A06.5.02.026
FMA	FMA:76497
	Anatomical terminology

　　[★]

英: bronchiole n. / -s pl.
ラ: bronchiolus
関: 気管支の分岐、クララ細胞、肺小葉

直径1mm以下の細気管支では軟骨が消失 (SP.629)
分泌腺と平滑筋がない (SP.629)
線毛立方上皮細胞、クララ細胞(細気管支、終末細気管支、呼吸細気管支に存在) (SP.629)

臨床関連

肺の末梢気道、特に細気管支領域は解剖学的に気道と肺胞の接点に位置し、喫煙や大気汚染物質により早期から障害を生じると考えられてきた。特に内径2mm以下の末梢気道の病変は呼吸生理学的にsmall airway diseaseと呼ばれ、進行すれば肺気腫などの慢性閉塞性疾患の発生につながるものとして喫煙などとの関連で論じられてきた。 (講義録呼吸器学 p.79)