Histology dermis

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. 

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. 

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.]...

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.

Elastin is typically considered as an amorphous protein consisting of random chain sequences connected by a helical regions. The elastin content varies in elastic fibers such as those found in skin. Elastic fibers are termed oxytalan fibers in the upper dermal layer of skin and they are termed elaunin fibers in the deeper dermis where their elastin content is higher. In vessel wall elastic fibers have recently been differentiated based on histological staining patterns suggesting that differences in mechanical properties of different vessel walls may in part be due to differences in elastin... 

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. 

Damage to the nail beds can be induced by 8-methoxypsoralen and sunlight. Histological examination of the nail beds showed that the photosensitizing effect of the drug induced the generation of many multinucleated epithelial cells and fibroblasts in the dermis. 

The histological effects of AHAs also reach the dermis. Moy showed that fibroblast cultures in a glycolic environment produced up to 10 times as much hydroxyproKne (a precursor of collagen) than when cultivated in a normal saline environment. A practical problem is that AHAs do not normally reach the dermis (because, apart from Easy Phytic solution, they are neutralized before they can penetrate that far) and therefore cannot directly stimulate fibroblasts as well as they did in this in vitro study. 

In the long term, the histological changes brought about by TCA are temporary when the TCA penetrates superficially and long lasting when the TCA penetrates to the papillary dermis at least. 

It is commonly acknowledged that the histological changes that take place in the deep dermis should be considered permanent. We can therefore assume that the results achieved are also permanent, and this corresponds to current clinical experience. The first treatments were carried out in 1996, and the results achieved then were still completely stable in 2005. 

Four months after the peel, the histological changes in the dermis, apart from vasodilation, are still visible. The intercellular space has a higher concentration of gly-cosaminoglycans, and there are more collagen and elastic fibers in the dermis. 

Histologically, freckles are characterized by a normal number of melanocytes in the basal layer. The melanocytes are, however, larger and more dendritic , and give up their melanosomes more readily to the keratinocytes. Freckles disappear completely and definitively with phenol. A TCA peel to the papillary dermis will also get rid of freckles. A local phenol peel is contraindicated on light skin phototypes - which in principle are a good indication for phenol - with freckles, as they will disappear where the phenol has been applied and will persist in the surrounding areas. A combination of local Lip Eyelid and Unideep (TCA to the papillary dermis) is suitable to avoid this freckle demarcation Hne. 

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