ABSTRACT
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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.
