Lab 3: Skin Cancer and Protection

Vocabulary practice flashcards covering skin anatomy, UV radiation types, vitamin D, melanocyte physiology, skin cancer pathologies, and sun protection methods.

Skin

The soft outer covering of animals—particularly vertebrates—and the largest organ of the integumentary system; it protects internal organs and tissues from pathogens, prevents water loss, and aids in thermoregulation.

Epidermis

The outermost layer of the skin, comprised predominantly of dead tissue that forms a protective surface barrier.

Dermis

The layer situated beneath the epidermis—also referred to as 'true skin'—consisting of live tissue containing blood vessels, nerves, glands, and hair follicles.

Vitamin D

An essential nutrient synthesized via sunlight exposure; it regulates the body's utilization of calcium, which is required for building and maintaining strong bones.

Rickets

A bone disease resulting from vitamin D deficiency in which the body cannot properly absorb or use calcium, causing the skeleton to soften and break easily.

Harry Steenbock

The researcher who discovered the method of enriching milk with vitamin D in 1923.

Melanin

A pigment produced in the skin whose quantity determines skin color; it serves as a defense mechanism by blocking UV radiation to prevent damage to underlying cellular DNA.

Melanocytes

Specialized cells in the skin that synthesize melanin and distribute it to surrounding skin cells to protect DNA against UV-induced mutations.

UV-B Radiation

A band of ultraviolet radiation that damages DNA and causes sunburn, but is necessary for the biological synthesis of vitamin D.

UV-A Radiation

A band of ultraviolet radiation comprising $95\%$ of terrestrial UV exposure; it does not cause sunburn, penetrates deeper into the dermis to cause wrinkles, increases melanoma risk, and exacerbates the carcinogenic effects of UV-B.

Melanoma

The deadliest type of skin cancer, arising from UV-induced DNA damage to melanocytes; associated with severe childhood sunburns and causing approximately $8{,}000$ deaths per year in the U.S.

Types of Skin Cancer

The three primary malignancies affecting the skin: squamous cell carcinoma, basal cell carcinoma, and malignant melanoma.

Abnormal Mole Warning Signs

Characteristics indicating a mole should be clinically examined: irregular shape, uneven surface, mottled coloration, or a diameter larger than a pencil eraser.

Sun Protection Factor (SPF)

A rating system that measures sunscreen efficacy against UV-B rays only, indicating the relative multiplier of sun exposure required to burn protected skin compared to unprotected skin.

Broad Spectrum Sunscreen

A sunscreen formulation certified to protect against both UV-A and UV-B radiation; required by the FDA alongside SPF 15 or higher to claim reduction of skin cancer and premature skin aging.

Organic (Chemical) Sunscreen

Sunscreen containing active carbon-based chemicals (such as avobenzone) that absorb into the skin to convert UV radiation into heat; takes approximately $15\,\text{minutes}$ to become effective.

Inorganic (Mineral) Sunscreen

Sunscreen containing physical mineral particles (such as zinc oxide or titanium oxide) that sit on the skin surface to reflect or scatter UV radiation immediately upon application.

Ultraviolet Protection Factor (UPF)

A metric that quantifies the fraction of UV radiation that penetrates through textile fabrics (e.g., UPF $50$ allows only $\frac{1}{50}\text{th}$ or $2\%$ of radiation through).

Dihydroxyacetone (DHA)

The active ingredient in topical sunless tanning products that reacts with dead skin cells in the outer epidermis to temporarily darken skin color without UV radiation.