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UV rays cause cholesterol-like steroid to change to vitamin D3 Decreased Vitamin D leads to abnormal bone growth Most common cancer Most people survive Treatment = removal of tumor Melanomas—extremely dangerous Usually begin as mole Grow rapidly Spread via lymphatic system Papillary Layer Supports and nourishes epidermis Capillaries and nerves for skin surface are here Reticular Layer Elastic fibers for elasticity Collagen fibers limit elasticity for protection Hair Follicles Sweat Glands Increased adipose cells Decreased heat loss in infants Energy reserve Shock absorber Everywhere except: Sides and soles of feet Palms Sides of fingers/toes Lips Parts of genitalia Hair follicles—where hair is produced Hair papillae—where vessels and nerves are Hair root—anchors hair into skin Hair shaft—what we see Cuticle—surface layer of hair Grows about 0.3 mm/day May become inactive for awhile Round hairs = straight hair Flattened hairs = curly hair Functions Protect from UV rays Cushion light blows Insulate Prevent entry of pathogens Sensory nerve fiber at base Arrector pili—bundle of smooth muscle Causes hair to stand up “Goosebumps” Due to amounts of pigment produced by melanocytes Due to genetics Pigment production decreases with age No pigment = white hair Average about 50 hairs/day More than 100 hairs/day = hair loss Temporarily due to: Drugs Diet Radiation High Fever Stress Pregnancy AKA: Oil Glands Secrete into hair follicle Sometimes onto skin Secreted through arrector pili Sebum—secretion of oil Lubricates hair and skin Inhibits bacteria High amounts at puberty Acne—sebaceous duct blocked Secretions accumulate Causes pimples Apocrine Glands Secrete into armpits, nipples and groin Sticky, cloudy, odorous secretion Starts at puberty Odorous when bacteria feed on sweat