Mucus, Goblet Cell, Submucosal Gland
Airway mucus blankets all mucosal surfaces, providing a physicochemical barrier that protects underlying epithelium against bacteria, viruses, and inhaled particles and gases. Mucus maintains airway hydration and plays an important role in the innate immu
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Mucus, Goblet Cell, Submucosal Gland Takeshi Shimizu
Keywords
Mucin • MUC gene • Mucus hypersecretion
Abbreviations Core Messages
AP-1 AR AZM CAM CF CREB CRS cysLTs EGFR EM Foxa2 IL NF-κB RA STAT6 TGF TLR TNF
Activated protein-1 Allergic rhinitis Azithromycin Clarithromycin Cystic fibrosis cAMP response element binding protein Chronic rhinosinusitis Cysteinyl leukotrienes Epidermal growth factor receptor Erythromycin Forkhead box a2 Interleukin Nuclear factor κ-B Retinoic acid Signal transducer and activator of transcription 6 Transforming growth factor Toll-like receptor Tumor necrosis factor
Airway mucus is important for the host defense mechanism, acting as a physicochemical barrier to protect underlying epithelium from pathogens and particles. The major components of mucus are glycoproteins called mucins, which are secreted by epithelial goblet and submucosal gland cells. Mucins are large heterogeneous macromolecules containing hundreds of oligosaccharide chains attached to peptide backbones, which are encoded by several MUC genes. Hypersecretion of mucus is commonly observed in various sinonasal inflammatory conditions such as acute rhinitis, chronic rhinosinusitis, and allergic rhinitis. Mucus hypersecretion, leading to rhinorrhea, contributes significantly to the pathophysiology of these diseases by impairing mucociliary function, resulting in stagnation of pathological mucus that contains various inflammatory mediators and pathogenic microbes.
T. Shimizu, MD Department of Otorhinolaryngology, Shiga University of Medical Science, Seta-Tsukinowa, Otsu, Shiga 520-2192, Japan e-mail: [email protected] T.M. Önerci (ed.), Nasal Physiology and Pathophysiology of Nasal Disorders, DOI 10.1007/978-3-642-37250-6_1, © Springer-Verlag Berlin Heidelberg 2013
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T. Shimizu
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Introduction
Airway mucus blankets all mucosal surfaces, providing a physicochemical barrier that protects underlying epithelium against bacteria, viruses, and inhaled particles and gases. Mucus maintains airway hydration and plays an important role in the innate immune system by trapping foreign and endogenous substances, facilitating clearance by mucociliary activity. Mucus also has antioxidant, antiprotease, and antimicrobial functions. Composed of water, ions, serum protein exudates, epithelial secretions, and glandular and goblet cell products, mucus contains various defensive components such as glycoproteins (mucins), antibodies, defensin, lysozyme, and lactoferrin. The mucous blanket is subdivided into two layers: the outer mucous layer and the periciliary fluid layer. The outer mucous layer is a gel layer, produced mainly by secretions of epithelial goblet cells and submucosal glands. The periciliary fluid, or sol layer is produced by ion transport through the epithelium (Fig. 1.1). Ciliary beating takes place at 10–14 Hz in this periciliary layer,
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Fig. 1.1 Mucous blanket is subdivided into two layers: the outer mucous layer and the periciliary fluid layer. (a) Normal mucous blanket. (b) Pathological mucous bla
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