Epithelial surface

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. 

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. 

Duration ofcontact devices are considered transient if intended for continuous use for less than 60 minutes, short term if intended for continuous use for not more than 30 days, and long term if intended for continuous use for more than 30 days. Devices that are intended to be introduced into the body or to replace an epithelial surface or the surface of the eye by a surgical procedure for more than 30 days are considered as implants. 

Form protective physical barrier on epithelial surfaces, are involved in cell-cell interactions, and may contain or mask certain surface antigens. 

In healthy individuals, the bladder, ureters and urethra are sterile and sterile urine constantly flushes the urinary traet. Organisms invading the urinary traet must avoid being detached Ifom the epithelial surfaces and washed out during urination. In the male, since the urethra is long ica. 20 cm), bacteria must be introduced directly into the bladder, possibly through eatheterization. In the female, the urethra is much shorter... 

In diphtheria, the organism C. diphtheriae eonfmes itself to epithelial surfaces of the nose and throat and produces a powerfiil toxin which affects the elongation factor involved in protein biosynthesis. The heart and peripheral nerves are particularly affected resulhng in myocarditis (inflammation of the myocardium) and neuritis (inflammation of a nerve). Little damage is produeed at the infective site. 

However, in interphase delaminating neuroblasts, which are known to have completed S-phase and are at the G2 stage of the cell cycle, this codependence of Baz/Insc/Pins seen in mitotic neuroblasts does not apply. Delaminating neuroblasts possess an apical membrane stalk which retains contact with the epithelial surface and this is where apical cortical localization of Insc is initially seen (see Fig. 2). This initial localization of Insc to the apical stalk occurs... 

The histological types of lung cancer seen to excess in uranium miners reflect those in the population at large (Masse, 1984). These occur almost entirely in bronchial airways. Approximately 207 are adenocarcinomas which occur in peripheral bronchioles (Spencer, 1977) where there are no basal cells. Squamous cell cancers predominate in miners exposed early in life to relatively low concentrations of radon daughters (Saccomanno et aJL., 1982). These are considered likely to arise from the secretory small mucous granular cells which undergo cell division and extend to the epithelial surface (Masse, personal communication). Division of these cells is accelerated after irritation by toxicants such as cigarette smoke or infectious diseases (Trump et a L., 1978). 

Particle diameter 0.17 pm (AMD) for Attached Daughters Nasal Deposition 1.3% for Attached and 60% for Unattached Daughters Alpha dose to cells at 22 pm depth below epithelial surface Twenty percent alveolar deposition prior to expiration... 

Alpha dose to cells at 22 m depth below epithelial surface... 

Ion transport in very dilute freshwater environments can also be problematic from the perspective of electrochemical theory. For example, electrochemical theory predicts that Na+ entry through epithelial channels will stop when the external Na+ is <0.1 mmol Na+ (typical of many freshwaters), given intracellular Na+ concentrations of 10-20 mmol 1 1 in gill epithelial cells [83], Thus elevation of Na+ concentrations at the epithelial surface (adsorption) becomes critical to ion-channel function and Na+ uptake into the cells [50], Alternatively, we might postulate other transporters coupled to the Na+ channel to drive uptake (e.g. H+ slippage [84] on the H+-ATPase). 

Shephard, K. L. (1989). The effects of mucus and mucilaginous materials on ion-distributions at epithelial surfaces. In Mucus and Related Topics, eds. Chantler, E. and Ratcliffe, N. A., The Company of Biologists, Cambridge, pp. 123-130. 

One approach to examining inflammation is the assay reported by Elgebaly et al. (1987) for the release of chemotactic factors. Earlier work has elegantly shown that neutrophil or macrophage infiltration from either the endothelial or epithelial surface... 

The function of the mucosal pellicle is to serve as a barrier between the oral epithelial surface and the external environment, and so it may also act as a barrier to drug delivery. However, there are limited studies assessing the role of the mucus layer in buccal permeability. In one study, treatment of the oral mucosa with anticholinergic agents resulted in an increased permeability of certain compounds, and it was suggested that the reduced salivary flow may have been responsible for the reduced barrier properties of the tissue [113]. In... 

While all the aforementioned cell types form the epithelial surface of the airways, basal cells reside deep in the tracheo-bronchial epithelium and are not directly in contact with the airway lumen. Basal cells are considered as the stem cell or progenitor cell of the bronchial epithelium and are pyramidal in shape with a low cytoplasmic/nuclear volume ratio [8, 15-17],... 

Microscopically, the cornea shows a rather simple and multilayered structure that can be divided into six layers the epithelium, basement membrane, Bowman s layer, stroma, Descemet s membrane, and endothelium. The corneal tissue consists of three different cell types epithelial cells, keratocytes (corneal fibroblasts), and endothelial cells. The outermost corneal surface is covered with the preocular tear film, which is functionally associated with the cornea. The epithelial surface must be kept moist and smooth, a role played by the tear film in conjunction with a spreading function of the eyelids during blinking motions. Furthermore, the tear film provides a protection against infectious agents that may gain access into the eye. 

Savage, D. C. (1984). Association of indigenous microorganisms with gastrointestinal epithelial surfaces. In "Human Intestinal Microflora in Health and Disease." (D. H. Hentges, ed.), pp. 55-78. Academic Press Inc., New York, NY. 

Gu, J. M., Robinson, J. R., and Leung, S. H. Binding of acrylic polymers to mucin/epithelial surfaces Structure-property relationships. Crit. Rev. Ther. Drug Carrier Syst. 1988, 5(1), 21-67. 

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