Fig. 1. The load-bearing structures of skin.

(A) The stratum corneum consists of terminally differentiated keratinocytes embedded in a lipid matrix and provides the contact surface for external mechanical loads. (B) In the viable epidermis, mechanical loads are borne directly by keratinocytes. Desmosomes provide mechanical junctions between neighboring cells, while keratin filaments provide the cell’s internal structural support. (C) The epidermal-dermal junction (EDJ) mechanically connects the dermis to the epidermis via the intermediate layer, the lamina densa. Anchoring fibrils connect the keratinocytes of the epidermis to the lamina densa (or basement membrane), and likewise, fibrils loop down from the lamina densa into the extracellular matrix (ECM) of the dermis. (D) Loads in the dermis are borne by extracellular matrix consisting of structural fibers, such as collagen and elastin, embedded in a ground substance consisting of glycosaminoglycans, proteoglycans, and water. Dermal fibroblasts create and maintain this matrix.