A reconstruction of the duct system and secretory tubules of the human bronchial submucosal gland

Abstract

A graphic reconstruction has been made of a submucosal gland from a normal human main bronchus, revealing a collecting duct not previously described. Ciliated respiratory epithelium dips into the gland opening to line the first part of the duct, the ciliated duct, and then gives way, in the collecting duct, to an epithelium composed of tall, columnar, eosinophilic cells containing numerous large mitochondria. This cell structure suggests that the collecting duct controls ionic and water concentration. From the collecting duct arise secretory tubules lined by mucous cells-mucous tubules. Tubules lined by serous cells serous tubules-arise from mucous tubules either terminally or laterally.Submucosal glands are found in the normal human bronchial tree in those airways with cartilage in the wall. The glands lie between the epithelium and plates of cartilage and between, and occasionally external to, the plates of cartilage (Miller, 1947;Reid, 1968). They have been variously described as compound tubular, tubuloacinar, and racemose structures. Fuchs-Wolfring (1898) described two cell types-the mucous, and the serous or albuminous-and reported that sometimes the mucous cells were in continuity with high columnar epithelium.Recent electron microscopic studies have revealed in the bronchial glands a cell type not previously reported at this site (Meyrick and Reid, 1969). It is filled with numerous large mitochondria ( Fig. 1) and has a well-developed Golgi apparatus. Dense granules lie near the cell apex and lateral edges, and most cells include lipochondria. The plasma membrane of the base is flat and uncomplicated but the lateral surfaces interdigitate with adjacent cells. These cells are found next to mucous cells and are arranged as a tube. Myoepithelial cells are found in association with them as well as with the secretory cells.The present paper describes an extension of this study to light microscopy, which has revealed a central duct system in the bronchial gland lined with these cells. A description is also given of a reconstruction of the duct system and of the mucous and serous secretory tubules. MATERIALS AND METHODSPREPARATION OF TISSUES FOR LIGHT MICROSCOPY Specimens of bronchus were obtained at neoropsy and from surgical resection. The cases studied were either 'normal' or had a history of 'simple bronchitis'.Bronchial rings were examined from 20 cases, 17 men and 3 women, with an age range from 16 to 65 years. Fifteen of the specimens were obtained at resection and five at necropsy: of the latter, one was from a woman and four were from men. Resection specimens were from patients with carcinoma save for one who suffered from bronchiectasis: ,these specimens included main and lobar bronchi. The necropsy lungs were considered normal: these specimens included trachea and main bronchus. In total, there were three specimens of trachea, 13 of main bronchus, and four of lobar bronchus. The specimen used for the gland reconstruction was from a man, 63 years of age, who died from a dissecting aneurysm of the aort...

The Glandular Stem/Progenitor Cell Niche in Airway Development and Repair

“…Distal regions of this tubular network comprise serous acini and tubules. Secretory products move vectorially from the distal serous tubules, through mucous tubules, and then accumulate in collecting ducts, which, together with ciliated ducts, connect each glandular network to the airway lumen (2). Each of these spatially distinct SMG regions has specific cell types that control both the content/viscosity of secretory products and the timing of the expulsion of secretions in response to airway irritation and infection (2)(3)(4)(5).…”

Parasympathetic control of airway submucosal glands: Central reflexes and the airway intrinsic nervous system

“…(Meyrick, Sturgess et al 1969;Meyrick and Reid 1970). The original abstract can't be beat for conciseness: "A graphic reconstruction has been made of a submucosal gland from a normal human main bronchus, revealing a collecting duct not previously described.…”

“…Tubules lined by serous cells-serous tubules-arise from mucous tubules either terminally or laterally." (Meyrick, Sturgess et al 1969), (italics added). The existence of four distinct epithelial compartments within a single gland means that the mucus emanating from the duct orifice is a complex product of multiple cell types; the spatial separation of the cell types is interesting and not yet explained.…”

MDR1-Pgp 170 expression in human bronchus

“…After immunodetection of MDR1 Pgp 170 using the C494 MoAb on tissue sections after paraffin embedding, similar results were observed in the five samples tested. Staining was observed at the apical part of ciliated epithelial cells either on the surface epithelium or ciliated collecting ducts [30] (fig. 1).…”