Lecture notes from Imperial College London, Medical Biosciences BSc, 2nd year, cardiovascular and thoracic biology (CTB) module.
lecture 6 on cell biology of the respiratory tract (airways and lungs): how the tract protects itself from inhaled insult, and is able to control the calibre of the ai...
Cell biology of the respiratory tract
Introduction
- inhale 12,000L of air per day (increases if exercise)
=> O2 but also particles (tobacco, pollen, microbes, pollution...), noxious gases
=> airway protection (+ homeostasis + ‘cleansing’)
The airway epithelium
- continuous from nasal passages to terminal bronchioles
- goblet cells: secrete mucins (high m weight glycoproteins) onto airway surface (small & large)
=> condensed mucin within granules fuse with apical membrane
=> form open pores to leave cell
=> take on water + swell (many hundred-fold)
=> big mucin ‘globule’ quickly released: exocytosis
- submucosal glands: secrete mucins onto airway surface
=> in larger airways (not in distal airways)
=> submucosal: below the epithelium BUT glandular openings via epithelium
=> gland: secretory acini (comprising secretory cells) in the
collecting duct/ ciliated duct ejects mucus (mixture of molecules) out
mucins
-
including
=> mucous cells secrete mucins
=> serous cells secrete anti-bacterial m (lysozyme, lactoferrin) Acini = smallest secreting
=> glands also secrete water + salt (Na+, Cl-) portion of a gland
=> mucus = aqueous electrolyte solution of mucins and other high molecular weight p
=> viscoelastic properties from mucins
=> secreted on airway surface where entrap & transport particules for mucociliary clearance
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