Epithelialization

In adults, a few areas may require further study. For example, there is a report of soya consumption causing an increased incidence of hyperplastic epithelial cells in the nipple aspirate fluid of pre- and postmenopausal women.This could constitute a risk factor for breast cancer. Also, the use in herbal medicine of particular plants emphasises that these species have the potential to cause physiological changes. Consequently, the increasing public interest in the use of herbal medicines could lead to unintended (adverse) effects, particularly as most... 

Compounds in animal diets can exert their effects in the gastrointestinal tract or after absorption through the gut epithelial tissue into the bloodstream, or both. On some occasions the administered compounds may be applied topically (Table 1). 

Artifacts introduced through sample preparation are common materials these may be bits of facial tissue, wax, epithelial cells, hair, or dried stain, all inadvertently introduced by the microscopist. Detergent residues on so-called precleaned microscope slides and broken glass are common artifacts, as are knife marks and chatter marks from sectioning with a faulty blade, or scratch marks from grinding and polishing. 

Airway cross-sections have the nominal anatomy shown in Fig. 5.16. Airway surface liquid (AST), primarily composed of mucus gel and water, surrounds the airway lumen with a thickness thought to vary from 5 to 10 mm. AST lies on the apical surface of airway epithelial cells (mostly columnar ciliated epithelium). This layer of cells, roughly two to three cells thick in proximal airways and eventually thinning to a single cell thickness in distal airways, rests along a basement membrane on its basal surface. Connective tissue (collagen fibers, basement membranes, elastin, and water) lies between the basement membrane and airway smooth muscle. Edema occurs when the volume of water within the connective tissue increases considerably. Interspersed within the smooth muscle are respiratory supply vessels (capillaries, arteriovenous anastomoses), nerves, and lymphatic vessels. 

Cilia are thin cylindrical hair-like structures with a cross-sectional radius of 0.1 gm projecting from the apical epithelial surface of ciliated columnar cells. Ciliary length is thought to correspond to periciliary fluid depth and range from approximately 7 gm in proximal airways to roughly 5 gm in more distal airways.- Each ciliated epithelial cell supports approximately 200 cilia at a density of eight cilia/gm. Short microvilli, possibly associated with secretory functions, are interspersed among the cilia. 

Nonciliated cells separate fields of ciliated epithelial cells from each other. Synchronized ciliary movement, with a beat frequency in human proximal airways under normal conditions of 8-15 EIz, propels mucus along the mucociliary escalator at a rate of up to 25 mm/min. Beat frequencies appear to slow to roughly 7 Hz in more distal airways. Cilia move in the same direction and in phase within each field but cilia in adjacent fields move in slightly different directions and are phase shifted. These beat patterns result in metachronal waves that steadily move mucus at higher velocities ( -12-18 mm/min) than would be achievable by summing the motion of individual cilia. 

Mucus gel is propelled toward the epiglottis by a two-phase ciliary beat cycle. Forward mucus movement occurs during the effective or power phase of the cycle, when cilia fully extend and traverse an arc perpendicular to the epithelial surface (Fig. 5.24). Claw-like structures, 25-35 nm long, project from each cilia tip and appear to assist in the mechanical transfer of momentum from cilia to mucus gel. Maximum mucus velocity depends on the extent cilia penetrate the epiphase during the power phase, periciliary and mucus gel viscosity, and cilia density. 

During the recovery or preparatory phase, cilia bend over, swing back to start position generally parallel to the epithelial surface, and stiffen in anticipation of the next power phase. Ciliary bending and axial movement... 

Apical epithelial surface In the airway, surface interfacing with lumen. 

Squamous epithelium Flattened, interlocking, toughened epithelial cells. 

Transepithelial Passing across a layer of epithelial cells. 

Nitric oxide may induce deleterious effects when airway epithelial or immunological cells are exposed to mineral particles (asbestos, quartz). These particles also stimulate cells to produce NO in large quantities, but pulmonary cells are unable to destroy these particles, and a non-physiologically excess production of NO results, perhaps causing tissue damage due to a reaction of NO with cellular macromolecules. 

Marsh, J. P., and Mossman, B. L (1991) Role of asbestos and active oxygen species in. ictiva-rion. and expression of ornirhinc decarboxylase in hamster tracheal epithelial cells. Cancer Ra. 51(1), 167-173. 

FIGURE 24.4 In the small intestine, fatty acids combine with bile salts in mixed micelles, which deliver fatty acids to epithelial cells that cover the intestinal villi. Triacylglycerols are formed within the epithelial cells. 

The keratolytic analogue motretinide (53) is effective in treating acne and the excess epithelial growth characteristic... 

Decken-. overhead, ceiling, roof covering, -gewebe, n. epithelial tissue, -lampe, /. ceiling lamp, dome lamp, -licht, n. skylight. Strich, m. (Leather) daub. 

Epithel, n. epithelium, -zelle, /. epithelial cell. Epizuckersaure, /. episaccharic acid. 

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