2.  All humans have roughly the same number of melanocytes. Color is based on the activity, not the number.  Increase in Melanin production in those exposed to more UV radiation, decreased Melanin production in those exposed to less UV radiation  Melanin is a “natural suncreen”. Dark skinned people seldom have skin cancer due to its effectiveness, however when they get it, it is more deadly.

3.  Tanning is the body’s built in protective mechanism, it leads to increased melanin production and protection from UV radiation.  Albinos genetically can’t produce melanin and have to be extremely cautious about exposure to the sun.  Skin color is controlled by many factors: ◦ Amounts and kind of pigment present ◦ Amount of carotene present ◦ Amount of oxygen bound to hemoglobin ◦ Emotional stimuli

4.  Cyanosis- when blood is poorly oxygenated and skin appears blue  Redness- can indicate embarrassment, fever, hypertension, inflammation or allergy  Pallor (paleness)-emotional stress(fear, anger), anemia, low blood pressure, impaired blood flow into the area  Jaundice (yellow)-liver disorder  Bruises (black and blue)-blood escapes circulatory system and clots in tissue spaces. ◦ Hematomas-unusual bruising-VitaminC deficiency or hemophilia are common causes

5.  Sebaceous Glands-oil glands, found everywhere but palms of hands and soles of feet ◦ Sebum-mixture of oily substances and fragmented cells, keeps skin soft, prevents brittle hair, kills bacteria. ◦ During adolescence hormones increase amount of oil produces and skin is oilier at that time in life. ◦ Acne is infection of the sebaceous glands ◦ “Cradle cap” is due to overactive sebaceous glands in infants. Yellow brown crust, comes off as dandruff.

6.  2 kinds of sweat glands (Sudoriferous glands) ◦ Eccrine- produces primarily water, it is odorless and actually inhibits bacterial growth. Helps body regulate temperature. You can lose 7L of water on a hot day ◦ Apocrine-produces fatty acids and proteins which provides a food source for bacteria on skin. The by- product of those bacteria is body odor. ◦ Sweat reaches the skin by a duct that opens as a pore.

7.  Functions: ◦ Guards head against bumps ◦ Eyelashes protect the eyes ◦ Keeps foreign particles out of respiratory tract ◦ In the past helped with keeping the body warm.

8.  It is produced by a hair follicle. Root is enclosed in follicle, the shaft is the part projecting from the surface.  Hair is formed by well-nourished stratum basal epithelial cells in the matrix. The farther away they get from the growing region, they become keratinized and die.  Consists of central core (medulla) surrounded by cortex layer, surrounded by a cuticle. ◦ Cuticle provides strength, when it wears away, you get split ends.

9.  Melanocytes determine hair color  Texture is determined by the shape of the hairshaft: ◦ Oval hairshaft – smooth hair ◦ Flat hairshaft- curly, kinky hair ◦ Hair is all over the body with exception of palms of hands, soles of feet, lips ◦ Hormones account for development of hairy regions such as armpits Arrector pili- bands of smooth muscle connect to hair follicle and dermal tissue, when muscles contract they form “goose bumps”

10.  Scalelike modification of epidermis- mostly nonliving material  They have a free edge, a body and a root, border is overlapped by skin folds.  Nails are transparent and nearly colorless but look pink due to rich blood supply in the dermis  White crescent is called LUNULA

11.  Skin can develop more than 1000 disorders with many causes ◦ Athlete’s foot- fungus ◦ Boils- staph infection-bacteria ◦ Cold Sores- virus ◦ Contact Dermatitis- chemicals, allergy ◦ Impetigo- staph infection, very contagious, especially common in children ◦ Psoriasis-unknown cause- red lesions covered with dry, silvery scales, can be disfiguring.

12.  Tissue damage and cell death caused by heat, electricity, UV radiation and some chemicals.  Damages due to burns: ◦ Body loses fluids as they seep from burned surfaces, dehydration and electrolyte imbalance follows. Can lead to kidney shutdown and circulatory shock. ◦ Infection can set in after 24 hours and your immune system is weakened because of the burn.

13.  1 st Degree- only epidermis is damaged. Red and swollen. Usually not that serious.  2 nd Degree- injures epidermis and upper region of dermis. Skin is red and painful, blisters appear. Regrowth of epithelium can occur. Usually no scars.  3 rd Degree- full thickness of skin burns, appears gray-white or blackened. Nerves are destroyed. Regeneration isn’t possible, must have skin graft.  Facial burns are dangerous when Respiratory pathways are effectedsince they can swell and cause suffocation.

14.  Subcutaneous tissue decreases, intolerance to cold  Skin is drier  Skin is thinner- more likely to bruise  Lost elasticity- allows bags under eyes  Hair Loss- by 50, the number of hair follicles has dropped by 1/3 and continues to decline  Male pattern baldness is an obvious baldness that increases as you age

15.  Graying- amount of melanin in hair decreases or becomes entirely absent.  Causes of graying or hair loss: ◦ Anxiety ◦ Protein deficient diet ◦ Chemotherapy ◦ Radiation ◦ Excessive Vitamin A ◦ Fungal disorders This is usually not permanent when it comes to hair loss.