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Distribution and numbers of mucous glands in the horse trachea.
Abstract: Horses commonly suffer from respiratory diseases associated with excess secretions in the airway lumen, some of which are presumably derived from airway mucous glands. However, these structures have been little investigated in the horse. Accordingly, we describe here the number, distribution and size of equine tracheal mucous glands, and compare the data with similar information for other mammalian species. Two types of gland acini were present. In the thick connective tissue, up to 400 microm beneath the epithelium, gland acini were grouped in thin sheets that, in cross-section, averaged 20 microm thick and were up to 4.0 mm in length. However, it is probable that most sheets had maximal diameters much less than 4.0 mm. Between 400 to 900 microm below the epithelium, the connective tissue was much more diffuse, and glands were larger and more globular. Gland volume in the ventral portion was approximately 1.7 microl/cm2 of mucosal surface, and approximately 1.1 microl/cm2 in the dorsal portion. Glands were somewhat more abundant between, rather than over, the cartilaginous rings, but the difference between the 2 locations was not marked. Mucous gland openings were small (20 microm diameter) and very unevenly distributed, generally occurring about 100 microm apart in longitudinal rows of about 5. Average frequency of openings in the ventral portions of 3 tracheas was approximately 1.0/mm2 of mucosal surface. The volume of individual glands was therefore approximately 17 nl. Although the frequency of gland openings in the horse trachea is similar to that for the tracheas of other large mammalian species, horse tracheal gland volume was only about 15% that of the other species. Therefore, the excess 'mucous' secretions seen in equine recurrent airway obstruction and other respiratory diseases are unlikely to be caused by comparatively high levels of airway mucous gland secretion. Instead, they may be caused mainly by hyperplasia of the mucus-producing cells of the surface epithelium or by vascular transudation.
Publication Date: 2002-10-03 PubMed ID: 12358006DOI: 10.2746/042516402776180151Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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The researchers of this article investigated the number, distribution, and size of the mucous glands in the horse’s trachea in order to understand their role in horse respiratory diseases associated with excessive secretions. They found that while the glands in the horse’s trachea are similar to other mammals in terms of their distribution, they have smaller volumes, therefore, the increased mucus in diseased horses are unlikely to be a result of these glands’ secretion.
Analysis of Gland Types and Distribution
- In the horse trachea, researchers identified two types of gland structures, commonly referred to as gland acini. Some of these are located up to 400 micrometers deep within the epithelium, or surface tissue, of the trachea. These acini form thin sheets that measure around 20 micrometers in thickness and up to 4 millimeters in length.
- Other gland acini are found deeper within the trachea, between 400 to 900 micrometers below the surface epithelium. Here, the connective tissue is sparse and the glands are generally bigger in size and rounder in shape.
Comparison Between Ventral and Dorsal Portion
- Examination also revealed that gland volumes differed depending on the tracheal location. In the ventral, or front, part of the trachea, gland volume was approximately 1.7 microliters per square cm of mucosal surface compared to 1.1 microliters in the dorsal, or rear, part of the trachea.
- Additionally, the glands were found to be slightly more abundant in the spaces between the cartilaginous rings of the trachea rather than directly over these structures.
Size and Distribution of Gland Openings
- Researchers also studied the glands’ openings and found them to be small—around 20 micrometers in diameter—and their distribution to be highly irregular over the trachea’s surface.
- Despite the irregular distribution, the researchers found these openings occur at an average frequency of about one per square millimeter of mucosal surface. From this data, they determined the volume of individual glands to be around 17 nanoliters.
Comparative Analysis with Other Species
- While the frequency of gland openings in a horse’s trachea is similar to that of other large mammals, the tracheal gland volume in horses is only about 15% of other species. This suggests that the increase in ‘mucous’ secretions often seen in horses suffering from recurrent airway obstruction and other respiratory diseases may not be due to an increased level of secretion from these glands.
- Instead, the source of this excess mucus may be hyperplasia (or excess growth) of the mucus-producing cells on the trachea’s surface or increased secretion from the blood vessels (vascular transudation).</li
Cite This Article
APA
Widdicombe JH, Pecson IS.
(2002).
Distribution and numbers of mucous glands in the horse trachea.
Equine Vet J, 34(6), 630-633.
https://doi.org/10.2746/042516402776180151 Publication
Researcher Affiliations
- Department of Human Physiology, University of California-Davis, 95616, USA.
MeSH Terms
- Animals
- Exocrine Glands / anatomy & histology
- Exocrine Glands / ultrastructure
- Horses / anatomy & histology
- Microscopy, Electron, Scanning / methods
- Microscopy, Electron, Scanning / veterinary
- Mucus / metabolism
- Trachea / anatomy & histology
- Trachea / ultrastructure
Grant Funding
- HL60288 / NHLBI NIH HHS
Citations
This article has been cited 5 times.- Ostedgaard LS, Price MP, Whitworth KM, Abou Alaiwa MH, Fischer AJ, Warrier A, Samuel M, Spate LD, Allen PD, Hilkin BM, Romano Ibarra GS, Ortiz Bezara ME, Goodell BJ, Mather SE, Powers LS, Stroik MR, Gansemer ND, Hippee CE, Zarei K, Goeken JA, Businga TR, Hoffman EA, Meyerholz DK, Prather RS, Stoltz DA, Welsh MJ. Lack of airway submucosal glands impairs respiratory host defenses. Elife 2020 Oct 7;9.
- Hajighasemi-Ossareh M, Borthwell RM, Lachowicz-Scroggins M, Stevens JE, Finkbeiner WE, Widdicombe JH. Distribution and size of mucous glands in the ferret tracheobronchial tree. Anat Rec (Hoboken) 2013 Nov;296(11):1768-74.
- Cho HJ, Joo NS, Wine JJ. Defective fluid secretion from submucosal glands of nasal turbinates from CFTR-/- and CFTR (ΔF508/ΔF508) pigs. PLoS One 2011;6(8):e24424.
- Widdicombe JH. Transgenic animals may help resolve a sticky situation in cystic fibrosis. J Clin Invest 2010 Sep;120(9):3093-6.
- Wine JJ. Parasympathetic control of airway submucosal glands: central reflexes and the airway intrinsic nervous system. Auton Neurosci 2007 Apr 30;133(1):35-54.
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