Melanocytes – produce melanin; irregularly shaped cells; s. basale INTEGUMENTARY SYSTEM § It consists of the skin, and accessory structures such as hair, glands, and nails. Functions of the Integumentary S. (PSVTE) 1. Protection 2. Sensation 3. Vitamin D production 4. Temperature regulation 5. Excretion Cyanosis - bluish skin color; decreased blood O2 Carotene – yellow pigment in plants (squash, carrots); source of vitamin A Keratinization – cells change shape and chemical composition; cells become filed with the protein keratin (hard) – transformation of the living cells of the stratum basale into the dead squamous cells of the stratum corneum Stratum basale – deepest; cuboidal & columnar cells, undergo mitosis every 19 days Stratum corneum – most superficial stratum; dead squamous cells filled with keratin (structural strength); lipids (prevent fluid loss); joined by desmosomes Callus – thickened area Corn – bony prominence, thickened corn shaped structure Dermis § Dense collagenous connective tissue, contains fibroblasts, adipocytes, macrophages § Nerves, hair follicles, smooth muscles, glands, lymphatic vessels Collagen (resist stretching) & elastic fibers – structural strength Cleavage lines/Tension lines – collagen fibers are oriented in some directions; skin is most resistant to stretch along these lines Stretch marks – skin is overstretched, leaving lines that are visible Dermal papillae – contain blood vessels that supply the epidermis with nutrients, remove waste products, and regulate body temperature Skin Color Melanin – pigments responsible for skin, hair, eye color yellow (Caucasian), Factors of Melanin Production a. Genetic factors b. Exposure to UV light c. Hormones Albinism - recessive genetic trait that causes deficiency / absence of melanin Skin Epidermis § Most superficial layer § Stratified squamous epithelium § In deepest layers, mitosis occurs Melanin pigments – (Asians), black (African) Melanosomes – vesicles derived from GA where melanin is produced brown Birthmarks – congenital disorder of the capillaries in the dermis Subcutaneous Tissue § Attaches the skin to underlying bones § Also called the hypodermis § Loose connective tissue § Storage of our body’s fat (padding, insulation) Accessory Skin Structure Hair § Columns of dead, keratinized epithelial cells § Produced in the hair bulb Hair follicle – where each hair rises Shaft – above the skin Root – below the skin Hair bulb – site of hair cell formation Cortex – hard keratin Medulla – soft central core Cuticle – single layer of overlapping cells that holds the hair in the hair follicle Growth Stage § Hair is formed by epithelial cells within the hair bulb § Divide and undergo keratinization § Hair root + shaft = columns of dead keratinized epithelial cells Resting Stage § Growth stops § Hair is held in the hair follicle Next growth stage § A new hair is formed § The old hair falls out Eyelashes – grow for about 30 days; rest for 105 days Scalp hairs – grow for 3 years; rest for 1 – 2 years Arrector Pili – smooth muscles; contraction = hair to stand on end; produces goose bumps M o r a n o , M . A . Glands I. Sebaceous Glands § Simple, branched acinar glands § Connected by a duct to the superficial part of the hair follicle § Sebum – oily, white substance rich in lipids; released by holocrine secretion; lubricates the hair/surface of the skin (prevents drying and protects against bacteria) II. 3. § § § § Sweat Glands a. Eccrine Sweat Glands Ø Simple, coiled, tubular glands Ø Release sweat by melocrine secretion Ø Numerous in the palms and soles b. Apocrine Sweat Glands Ø Simple, coiled, tubular glands Ø Produce a think secretion rich in organic substances Ø Released primary by melocrine secretion; some glands demonstrate holocrine secretion Ø Open into hair follicles, in armpits and genitalia Ø Become active at puberty III. 4. § § § § § § Other Glands a. Ceruminous glands – cerumen (earwax) b. Mammary glands – milk Nails § § Dead stratum corneum cells Contain a very hard type of keratin Nail body – visible part of the nail Nail root – part of the nail covered by skin Cuticle – eponychium; s. corneum that extends onto the nail body Nail matrix – produces the nail Nail bed – contributes to nail formation Lunula – white, crescent-shaped area; part of the nail matrix visible through the nail body Physiology of the Integumentary S. 1. Protection § Reducing water loss § Prevents microorganisms from entering the body § Protects underlying structures against abrasion § Hair on head = insulator § Eyebrows = keep sweat out of the eyes § Eyelashes = protects the eyes from foreign objects § Hair in the nose, ears = prevents the entry of dust § Nails = protect the ends of the fingers, toes from damage; can be used in defense 2. § 5. § § Sensation Sensory receptors for pain, touch, hot, cold, pressure Vitamin D Production Skin exposed to UV light produces cholecalciferol (modified in the liver, then in the kidneys to produce active vitamin D) Best sources of Vit. D = fatty fish, vit. D fortified milk Small amounts of Vit D = eggs, butter, liver Active Vit. D stimulates the small intestine to absorb calcium and phosphate (normal bone growth, normal muscle function) Temperature Regulation Normal body temp. = 37oC (98.6 oF) Rate of chemical rxns within the body can increased of decreased based on the body temp. Factors that raise body temperature Ø Exercise Ø Fever Ø Increase in environmental temperature The skin controls heat loss from the body through dilation and constriction of blood vessels Sweat glands produce sweat, which evaporates and lowers body temperature Heat is lost by radiation (infrared energy), convection (air movement), conduction (direct contact) Excretion Skin glands remove water and salt Also removes small amounts of urea, uric acid, ammonia Integumentary S. as a Diagnostic Aid Cyanosis – bluish color to the skin caused by decreased blod O2 content Jaundice – yellowish skin color caused by liver damage (viral hepatitis) Rashes & lesions - symptoms of problems elsewhere; e.g. Scarlet fever causes reddish rash, allergic reaction to food or drugs can develop rashes Vitamin A Deficiency – excess keratin; sandpaper texture characteristic Iron Deficiency Anemia – nails become flat or concave Lead Poisoning – high levels of lead in the hair Burns Burn – injury to a tissue caused by heat, cold, friction, chemicals, electricity, and radiation I. § § Partial-thickness Burns S. basale remains viable; Regeneration of the epidermis occurs within the burn area M o r a n o , M . A . a. First-degree burns Ø Epidermis Ø Red and painful Ø Slight edema (swelling) b. Second-degree burns Ø Epidermis, dermis Ø Epidermis regenerates from the epithelial tissue Ø Dermal damage is minimal; v Redness, pain, edema, blisters v Healing = 2 weeks v No scarring Ø Deep into the dermis v Red, tan, or white v Takes several months to heal v Might scar II. Full-thickness Burns a. Third-degree burns Ø Epidermis, dermis, and underlying tissues are completely destroyed Ø Recovery occurs from the edges of the burn wound Ø Region of the 3rd degree burn is painless (sensory receptors have been destroyed) Ø White, tan, brown, black, deep cherry red Ø Take a long time to heal Ø Form scar tissue Ø Skin grafts are used to prevent complications and to speed healing Skin Cancer § Most common type of cancer § Exposure to UV light from the sun § Usually on face, neck, hands § Most like to have skin cancer = fair skinned or older than 50 § Limiting exposure to sun, using sunscreen; reduces the likelihood of developing skin cancer § Ultraviolet light Ø UVA v Longer wavelength v Causes most tanning of the skin v Development of malignant melanoma Ø I. § § § § II. § § § III. § § § § § Squamous cell carcinoma Immediately superficial to the s. basale Cells continue to divide as they produce keratin = nodular, keratinized tumor confined to the epidermis Can invade the dermis, metastasize, and cause death Malignant melanoma Rare form of skin cancer that arises from melanocytes; usually from a pre-existing mole Mole – an aggregation or nest of melanocytes Large, flat, spreading lesion or deeply pigmented nodule Metastasis is common Often fatal FX of Aging on the Integumentary S. § Epidermis thins § Amount of collagen in the dermis decreases § Skin infections are most likely § Repair of skin occurs slower § Decrease no. of elastic fibers in the dermis and loss of fat (sagging of skin, wrinkles) § Decrease of activity of sweat glands = reduced ability to regulate body temp. § Decrease sebaceous gland activity = skin becomes drier § Decrease no. of melanocytes § Some areas, the no. of melanocytes increase = age spots § Increased melanin production = freckles; also, gray/white hair § Skin that is exposed to sunlight = shows signs of aging more rapidly UVB v Most burning of the skin v Development of basal cell and squamous cell carcinoma Basal cell carcinoma Most frequent type S. basale and extends into the dermis to produce an open ulcer Cure; surgical removal or radiation therapy Little danger of cancer to spread, metastasize M o r a n o , M . 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