Respiratory epithelium
Respiratory epithelium | |
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Details | |
System | Respiratory system |
Identifiers | |
MeSH | D020545 |
TH | H3.05.00.0.00003 |
Anatomical terms of microanatomy |
This article is part of a series on |
Epithelia |
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Squamous epithelial cell |
Columnar epithelial cell |
Cuboidal epithelial cell |
Specialised epithelia |
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Other |
Respiratory epithelium, or airway epithelium,
Structure
The respiratory epithelium lining the upper respiratory airways is classified as
Cells
The cells in the respiratory epithelium are of five main types: a)
Between the ciliated cells are numerous
Function
The respiratory epithelium functions to moisten and protect the airways. It acts as a physical barrier to pathogens, as well as their removal in the mechanism of mucociliary clearance.
The ciliated cells are the primary components in the mucociliary clearance mechanism. Each epithelial cell has around 200
The basal cells are small, nearly cuboidal that differentiate into the other cell types found within the epithelium. Basal cells respond to injury of the airway epithelium, migrating to cover a site denuded of differentiated epithelial cells, and subsequently differentiating to restore a healthy epithelial cell layer. The differentiated epithelial cells can also dedifferentiate into stem cells and contribute to the repairing of the barrier.[15]
Club cells carry out similar functions in the more distal airways.
Certain parts of the respiratory tract, such as the oropharynx, are also subject to the abrasive swallowing of food. To prevent the destruction of the epithelium in these areas, it changes to stratified squamous epithelium, which is better suited to the constant sloughing and abrasion. The squamous layer of the oropharynx is continuous with the esophagus.[citation needed]
The respiratory epithelium has a further role of immunity for the lungs - that of glucose homeostasis.[16] The glucose concentration in the airway surface liquid is held at a level of around 12 times lower than that of the blood sugar concentration.[16] The tight junctions act as a barrier that restricts the passage of glucose across the epithelium into the airway lumen. Some glucose passes through, where it diffuses into the airway surface liquid to be kept at its reduced level by pulmonary glucose transport, and metabolism.[17] However, airway inflammation decreases the effectiveness of the tight junctions making the barrier more permeable to glucose. Higher levels of glucose promote the proliferation of bacteria by providing glucose as a source for carbon for them.[16] Increased levels of glucose in the airway surface liquid is associated with respiratory diseases, and hyperglycemia.[17]
Clinical significance
Long-term irritation of the epithelial cells can cause the overproduction of mucus, known as
Pulmonary neuroendocrine cells have been associated with a range of chronic lung disorders. They are also the originating cells of small-cell lung cancer.[19]
References
- PMID 18757316.
- ^ "Respiratory mucosa". meshb.nlm.nih.gov. Retrieved 26 July 2019.
- ISBN 9780073378251.
- ^ Mescher AL, "Chapter 17. The Respiratory System" (Chapter). Mescher AL: Junqueira's Basic Histology: Text & Atlas, 12e: "AccessMedicine | the Respiratory System: Introduction". Archived from the original on 2013-06-03. Retrieved 2015-02-24..
- ^ "Bronchi, Bronchial Tree & Lungs". nih.gov. Retrieved 17 September 2019.
- ISBN 978-1-26-002618-4.)
{{cite book}}
: CS1 maint: location missing publisher (link - ^ ISBN 9780323523714.
- PMID 27845721.
- ^ PMID 15817800.
- ISBN 0071054480.
- PMID 32294408.
- ISBN 9781416045748.
- PMID 26185361 PMC 4491388
- ^ U.S. EPA. Integrated Science Assessment for Oxides of Nitrogen – Health Criteria (2016 Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-15/068, 2016. Federal Register Notice Jan 28, 2016 Free download available at Report page at EPA website.
- PMID 25700381.
- ^ S2CID 13733461.
- ^ PMID 22878875.
- ^ Global Initiative for Chronic Obstructive Lung Disease - GOLD (PDF). 2018. p. 15. Retrieved 10 November 2019.
- S2CID 73489416.
Additional images
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Cross-section of pseudostratified columnar epithelium
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Second cross-section