ABSTRACT
The anatomic facets of skin are infinite, making a complete review of age-related changes in skin structure problematic. This overview, therefore, focuses on certain readily quantifiable aspects of the skin: protein, glycosaminoglycan (GAG), water, and lipid content and structure. Where possible, we address differences between intrinsic aging, physiologic aging, and extrinsic aging due to photoexposure, wind, relative humidity, and other environmental factors, although we acknowledge that this distinction is not always easily made. Ultimately, we hope to unify each topic and the general understanding of skin structure with respect to aging. This chapter reviews each category of structure and function in turn, beginning with a brief description of commonly used quantitative methods of study. Each section includes a table presenting research data, a discussion of the experimental outcomes and, wherever possible, an evidence-based summary of the effect of age on the parameter discussed.
