Sun damage is a condition defined by _________.

• A. Heat damage to joint tissue
• B. Bacterial infection of the epidermis
• C. Mechanical trauma to skin
• D. UV damage to the epidermis and dermis

Answer: (D)

Ultraviolet radiation from the sun damages skin cells and their DNA, affecting both the outer layer (epidermis) and the deeper layer (dermis). UVB mainly hits the epidermis, causing sunburn and direct DNA mutations in keratinocytes, while UVA penetrates deeper into the dermis, contributing to photoaging by degrading collagen and elastin. Over time this combined damage leads to pigment changes, wrinkles, and higher skin cancer risk. Hence, sun damage is defined by UV damage to the epidermis and dermis. The other options describe heat injury, infection, or mechanical trauma, which are not how sun damage is defined.