Aging of epidermis. I. Morphological changes and their quantitative analysis

Morphological changes in the epidermis caused by aging and sun exposure were studied by light microscopy and micrometric techniques. The following findings were obtained. 1. Corneocytes of the sun exposed skin of young healthy subjects were smaller than those of aged persons. 2. The epidermal rete ridges of the sun-exposed skin of old subjects disappeared and flattened. 3. The thinning and flattening of the epidermis of old subjects were more prominent in sun exposed skin than in sun protected skin. These data suggest that sun exposure accelerates some morphological changes of epidermis considered due to aging.