Histology epidermis

All humans experience intrinsic aging. Typically, it is characterized by smooth, relatively atrophic, finely wrinkled or lax skin. Histologically, the stratum corneum is normal. However, the epidermis is atrophic and there is flattening of the dermo-epidermal junction. Dermal features include decreased thickness, loss of elastic fibers, and a decrease in the biosynthetic capacity of fibroblasts [i, 2] (Table 15.1). 

First, consider the transepidermal route. The fractional area of this route is virtually 1.0, meaning the route constitutes the bulk of the area available for transport. Molecules passing through this route encounter the stratum corneum and then the viable tissues located above the capillary bed. As a practical matter, the total stratum corneum is considered a singular diffusional resistance. Because the histologically definable layers of the viable tissues are also physicochemically indistinct, the set of strata represented by viable epidermis and dermis is handled comparably and treated as a second diffusional resistance in series. 

Histological changes included disorganization of the eells, cytolysis, and enlarged intercellular spaces in the stratum comeum and spinous eells of the epidermis (Lupuleseu and Birmingham 1976). Effects had subsided within 72 hours in some individuals (Lupulescu et al. 1973). These studies are limited because each tested only one dose. 

Histological analyses were done on the skin samples taken by biopsy694). Histological sections of animals fed on the 1 -(chloromethyl)silatrane-containing diet showed no sharply-defined morphological changes in the epidermis. 

Microscopically, the skin is a multilayered organ composed of many histological layers. It is generally subdivided into three layers the epidermis, the dermis, and the hypodermis [1]. The uppermost nonviable layer of the epidermis, the stratum corneum, has been demonstrated to constitute the principal barrier to percutaneous penetration [2,3]. The excellent barrier properties of the stratum corneum can be ascribed to its unique structure and composition. The viable epidermis is situated beneath the stratum corneum and responsible for the generation of the stratum corneum. The dermis is directly adjacent to the epidermis and composed of a matrix of connective tissue, which renders the skin its elasticity and resistance to deformation. The blood vessels that are present in the dermis provide the skin with nutrients and oxygen [1]. The hypodermis or subcutaneous fat tissue is the lowermost layer of the skin. It supports the dermis and epidermis and provides thermal isolation and mechanical protection of the body. 

Histologically, the disease is characterized by a loss of adhesion between suprabasal keratinocytes (acantholysis) and abnormal keratinisation (dyskeratosis) of the epidermis. In HHD, acantholysis is the most prominent histological feature while in the clinically related Darier disease (OMIM 124200), dyskeratosis is much more apparent. Ultrastructural analysis of acantholytic cells reveals perinuclear aggregates of keratin filaments that have retracted from desmosomes (Harada et al., 1994 Hashimoto et al., 1995 Metze et al., 1996). 

Figure 8.15 Histological demonstration of dermal powder injection in the pig. The stratum corneum (SC), dermis (D), and particles delivered to the epidermis (ED) are clearly shown. The particles consist of swellable, slowly soluble polysaccharide microspheres (50 pm diameter when dry). [With modifications from Hickey (2001). Reproduced with permission from Euromed Communications.]...

Fig. 12.3. Epidermal measurements, mitotic figures, and apoptotic keratinocytes in a chronic proliferative dermatitis mutant (Sharplncpdm/Sharplncpdm) mouse. Routine hematoxylin- and eosin-stained paraffin histologic sections can be used to determine proliferation rates based on mitotic index (number of mitotic figures, circled in the figure, in the stratum basale per 1000 cells) or the presence and numbers of apoptotic epidermal keratinocytes (dotted arrows) when present. Epidermal thickness can be measured at high dry magnification (40x) to include the malpigian, living cell, layer (M), the stratum corneum thickness (SC), or the full thickness of the epidermis (M+SC).

Figure 6. Imaging of a mouse ear left) HE histology of a mouse ear, the image size is (0.93x0.7) mm2 right) Longitudinal image of a mouse ear. Image size (1.2x0.5) mm2. E epidermis, sc stratum corneum, D dermis, cc conjunctive capsule, C cartilage.

Histologically, elderly xerotic skin showed an atrophic nucleated epidermis and a threefold increase in corneocyte size. This was accompanied by an approximately 50% increase in the number of... 

Topical applications of retinoic acid derivatives reduce the visible signs of aging and of photodamage,266 though there is little correlation between the histologic changes and the clinical appearance of the skin. Initial improvement in fine wrinkling and skin texture correlates with the deposition of HA in the epidermis. 

Microscopically the skin is a multilayered organ composed of, anatomically, many histological layers, but it is generally described in terms of three tissue layers the epidermis, the dermis, and the subcutaneous fat tissue. 

Little information is available regarding the toxieokineties of lewisite. Lewisite is readily absorbed by mueous membranes and, beeause of its lipophilicity, dermal absorption is signitieant (HSDB, 2004). Dermal absorption is reportedly more rapid than for sulfur mustard (Hurst and Smith, 2008). Axehod and Hamilton (1947) reported that radiolabeled ( " As) lewisite applied to a 0.4S em area of human skin was primarily fixed on the epidermis and that very little was found in the dermis most was detected in hair and hair follicles. In experiments with guinea pigs, histological examination revealed that lewisite applied to skin entered epidermis within 2 min and penetrated into the dermis within 10 min (Ferguson and Silver, 1947). Only trace amounts were detectable in the dermis at 24 h post-application. 

An 86-year-old Japanese man received a pacemaker for atrioventricular block, and 2 months later developed a scaly erythema over the implantation site and later widespread nummular eczema. Histologically, the lesions showed slight spongiosis, intracellular edema, moderate acanthosis in the epidermis, and perivascular infiltration with thickened capillary walls in the dermis. The pacemaker contained titanium and a variety of other metals, but patch tests were all negative. However, titanium sensitivity was demonstrated by intracutaneous and lymphocyte stimulation tests. 

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