Aged Skin: A Study by Light, Transmission Electron, and Scanning Electron Microscopy.

Abstract

The fine structural organization of the epidermis, dermal/epidermal junction, and dermis from an unexposed site (upper inner arm) of elderly people was compared with the organization of a similar region of young people. Despite an overall thinning of the epidermis and focal areas of cytologic atypia, the characteristic morphological markers associated with the keratinization process are not markedly altered in appearance or amount. A well-formed stratum corneum consisting of flattened, enucleated horny cells enveloped by a thickened membrane, and intracellular spaces filled with electron-dense material provide structural evidence that barrier ability is not compromised in senile skin. The dermal/epidermal changes in aged skin are marked and have significant physiologic implications. The major change is a relatively flat dermal/epidermal junction resulting from the retraction of the epidermal papillae as well as the microprojections of basal cells into the dermis. This flattening results in a more fragile epidermal/dermal interface and, consequently, the epidermis is less resistant to shearing forces. Retraction of the epidermal downgrowths (preferential sites of the putative epidermal stem cell) may also explain the loss in proliferative capacity associated with the aged epidermis. The three-dimensional arrangements of collagen and elastic fibers showed marked alterations with age. Both fibrous components appear more compact because of a decrease in spaces between the fibers. Collagen bundles appear to unravel, and the individual elastic fibers show signs of elastosis. These changes may contribute to the loss of resilience that is one of the salient features of senile skin.

Advances in MR imaging of the skin

“…However, the present work clearly shows that the ADC values in the direction perpendicular to the skin surface in the epidermis and outer dermis are quite similar while the ADC value in the inner dermis is much lower. If the epidermis and outer dermis are rather isotropic tissues, the inner dermis is much more anisotropic, with the predominant direction of collagen fibres being parallel to the skin surface (17,18), thereby implying restricted diffusion in the direction perpendicular to the skin in accordance with the present measurements.…”

The aged epidermal permeability barrier. Structural, functional, and lipid biochemical abnormalities in humans and a senescent murine model.

“…In recent years considerable attention has focused on functional abnormalities of the dermis in intrinsically and photoaged skin. The relative lack of interest in the epidermis of the aged may reflect the reportedly normal thickness of the stratum corneum (1)(2)(3)(4)(5)(6), with an increase in corneocyte surface area the only described structural abnormality (7). Likewise, only minor functional abnormalities have been reported in aged epidermis.…”

Aging Skin: Nourishing from Out-In. Lessons from Wound Healing

“…The quantity of elastin, a determinant of skin elasticity, is fairly constant with age. However, like collagen, elastin in the aged dermis has a disorganized morphology, resulting in decreased skin elasticity [16,17].…”