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MR LEO
Diagram of the alveoli with both cross-section and external view.
Details
System	respiratory system
Identifiers
Latin	ja ba
MeSH	D055745
TA98	A06.5.02.026
TA2	3282
TH	H3.05.02.0.00005
FMA	7410
Anatomical terminology[edit on Wikidata]

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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 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

Terminal bronchioles

Respiratory bronchioles

The bronchioles deliver air to the exchange surfaces of the lungs. 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. Primary bronchus
  3. Lobar bronchus
  4. Segmental bronchus
  5. Bronchiole
  6. Alveolar duct
  7. Alveolus

References

1. Human Anatomy by Frederic Martini sixth edition, page 643

Further reading

• Saladin, Kenneth S. Anatomy & Physiology: the Unity of Form and Function. New York, NY: McGraw-Hill, 2007.
• 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

External links

• Histology image: 13607loa – Histology Learning System at Boston University
• Diagram at davidson.edu
• Histology at umdnj.edu
• Histology image: 13606loa – Histology Learning System at Boston University

• Lung anatomy