Nasal Cavity Cancer in Laboratory Animal Bioassays of Environmental Compounds
D. V. M. Gerd Reznik, Sherman F. Stinson in Nasal Tumors in Animals and Man, 2017
The nasal cavity is a complex organ consisting of several different epithelial types organized into varied anatomical structures and regions. For results obtained in an animal system to have relevance in man, some degree of anatomical and physiological comparability should exist. The anatomy and physiology of the nasal cavities in humans and experimental animals have been considered in detail in earlier chapters. Little information is available on the normal morphology and pathology of the nasal cavities of rodents except in rats, mice, and hamsters. Data on some primate species are also known, but these have not been used extensively for carcinogenesis studies due to limitations imposed by size and life span. Although the structural design of the nasal cavities differs between humans and the various laboratory animal species, the organization and epithelial types found are basically similar. Squamous epithelium lines the nares and parts of the extreme posterior regions. Modified respiratory epithelium covers the turbinals and surfaces of the air conducting passages and paranasal sinuses. Submucosal glands are abundant underlying the respiratory epithelium. Rodents lack the profuse submucosal lymphoid accumulations found in the human nasopharynx, although these are present in dogs and nonhuman primates. In the olfactory regions, the epithelium is of neuroepithelial origin. Sensory cells are found and, possibly, neuroendocrine cells are present.
Epithelial Function and Airway Responsiveness
Alastair G. Stewart in AIRWAY WALL REMODELLING in ASTHMA, 2020
Cells in the airway epithelium secrete a diverse array of materials, including mucus, water, and electrolytes,149,150 as part of the complex of defence mechanisms to protect the lungs from harmful substances inhaled from the external environment. The epithelium presents the first barrier to allergens by providing a blanket of mucus over the airway surface which traps allergens for transport back to the pharynx by the beating cilia. The mucus contains proteolytic enzymes which also degrade allergens.151 In healthy airways, the production of mucus is limited to provide an adequate system for airway lubrication and the entrapment of inhaled foreign particles. However, the amount, composition, and viscosity of mucus may be altered in airway diseases, including viral infections, asthma, bronchitis, and cystic fibrosis.1,152,153 In the larger airways, submucosal glands provide the bulk of the material secreted to the airway surface.1,3,6 However, epithelial serous, goblet, and Clara cells also contribute significantly to airway mucus production.154,155
Structure and Function of the Respiratory System
Hans Bisgaard, Chris O’Callaghan, Gerald C. Smaldone in Drug Delivery to the Lung, 2001
The submucosal glands are continuous with the epithelium and are found from the trachea to the end of the small bronchi. A narrow ciliated tract is continuous with a collecting duct that leads into mucous and serous tubules. The submucosal glands are the major source of tracheobronchial mucus and increase in chronic bronchitis and asthma. Glands appear early in gestation; during childhood, the gland area is relatively large in comparison with that in the adult (52). This may have implications for relative hypersecretion in small airways during early life (53). Any airway obstruction as the result of excess secretions or mucus will obviously have a deleterious effect on aerosol delivery to the more distal airways.
The epithelial sodium channel (ENaC) as a therapeutic target for cystic fibrosis lung disease
Published in Expert Opinion on Therapeutic Targets, 2018
Patrick J. Moore, Robert Tarran
Electrolyte transport across pulmonary epithelia, together with accompanying osmotic water flow, regulates ASL volume. In turn, ASL volume has been shown to directly affect mucus rheology and mucus clearance rates [26]. Simply put, the more fluid in the lung, the more quickly mucus is cleared. For example, patients with pseudohypoaldosteronism have reduced ENaC activity, increased airway secretions, and incredibly fast mucus clearance rates [77]. During normal mucus clearance, ASL/mucus moves from the distal to the proximal airways. However, with every successive generation, there is a reduction in pulmonary surface area that leads to an abundance of ASL. Thus, excess ASL needs to be absorbed in a controlled fashion, without causing dehydration, in order to maintain a constant ASL volume and prevent ASL pooling. In normal airways, Cl− secretion via CFTR and Na+ absorption through ENaC are balanced to control ASL volume homeostasis and to achieve this goal. Glands can also secrete additional ASL. However, submucosal glands are most commonly present in large airways (i.e. the first 16–17 generations) and are less common/absent in successive generations [78,79]. In contrast, Na+ absorption has been detected from the nose and trachea, to the alveolar surfaces, which highlights its importance in lung fluid homeostasis [80,81].
Current status and advances in esophageal drug delivery technology: influence of physiological, pathophysiological and pharmaceutical factors
Published in Drug Delivery, 2023
Ai Wei Lim, Nicholas J. Talley, Marjorie M. Walker, Gert Storm, Susan Hua
The esophageal mucus is thought to act as a buffer layer on the surface of the mucosa to neutralize and protect the esophagus from stomach refluxates. It also plays a role in the innate immune system that forms a barrier against pathogens (Sarosiek & McCallum, 2000; Nochi & Kiyono, 2006). Mucus is produced in the esophagus mainly by the esophageal submucosal glands. These glands are connected to the lumen of the esophagus via small ducts that are located between the submucosa and mucosa of the epithelium (Meyer et al., 1986). Esophageal mucus contains a mixture of mucin, proteins (e.g. threonine 16.3%, serine 14.2%, glycine 8.9%, glutamine 8.5%, alanine 8.4%, proline 8.0%, asparagine 7.6%, leucine 6.9%, valine 5.7%, lysine 3.3%, isoleucine 2.8%, histidine 2.6%, arginine 2.6%, phenylalanine 2.6%, and tyrosine 1.1% (Namiot et al., 1994)), polypeptides (e.g. epidermal growth factors, prostaglandin E2, and immunoglobulin A (Sarosiek et al., 1993, 1994)), phospholipids, and bicarbonate ions (Namiot et al., 1994).
Endogenous lung stem cells for lung regeneration
Published in Expert Opinion on Biological Therapy, 2019
Another fail-safe strategy that has been discovered to facilitate epithelial regeneration is the dedifferentiation of mature secretory cells into bona fide self-renewing multipotent basal cells, which occurs after existing basal cells are ablated [65]. Intriguingly, de-differentiation of secretory cells appears to be blocked when basal cells remain in close proximity, suggesting that this is a tightly controlled backup reparative strategy. On a related note, two recent independent studies have uncovered a 'reserve' stem cell role for myoepithelial cells in repairing the luminal epithelium after severe injury [66,67]. Although the existence of myoepithelial cells under the basement membrane of submucosal glands has been well documented, their role in lung homeostasis has remained an enigma until now. Based on the expression of smooth muscle actin (Act2a) or myosin heavy chain 11 (Myh11), lineage tracing studies in multiple injury models has exposed the multipotency of these cells in regeneration of the submucosal gland epithelium and luminal epithelium after severe injury [66,67]. In the steady state, myoepithelial cells give rise to submucosal gland epithelial cells but do not give rise to luminal epithelial cells in the steady state [68]. Collectively, these studies suggest that myoepithelial cells serve as dedicated stem cells of the submucosal glands and ‘reserve’ stem cells for the luminal epithelium. A schematic of airway repair strategies is shown in Figure 2.
Related Knowledge Centers
- Racemic Mixture
- Exocrine Gland
- Mucus
- Smooth Muscle
- Goblet Cell
- Trachea
- Bronchus
- Esophageal Gland
- Brunner'S Glands