Morphological Characteristics and Notes of the Skin in Preclinical Toxicity Assessment

This review outlines the histological structures of the skin, including the epidermis, dermis, subcutaneous tissue, and associated adnexa, which are essential for toxicological assessments. It highlights the complexity of the skin's structure, such as the variation in epidermal thickness across species and body sites, and the influence of tissue preparation on toxicity assessments. The review emphasizes the role of bulge stem cells in the formation of sebaceous glands, the epidermal basal layer, and hair follicles, noting that these cells and their appendages can be targets of toxicity. It also discusses the primary adverse reactions to topical applications, namely irritant and allergic contact dermatitis, detailing their mechanisms and histological presentations. Additionally, the review mentions the variability in dermal absorption due to regional and species differences, particularly the thickness of the stratum corneum. Understanding these skin structures, functions, and potential artifacts is crucial for evaluating skin toxicity from both topical and systemic exposures.