Keratinization epidermal growth stem cells divide to

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Keratinization & Epidermal Growth Stem cells divide to produce keratinocytes As keratinocytes are pushed up towards the surface, they fill with keratin 4 week journey unless outer layers removed in abrasion Hormone EGF (epidermal growth factor) can speed up process Psoriasis - chronic skin disorder cells shed in 7 to 10 days as flaky silvery scales abnormal keratin produced
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Dermis Connective tissue layer composed of collagen & elastic fibers, fibroblasts, macrophages & fat cells Contains hair follicles, glands, nerves & blood vessels Major regions of dermis papillary region reticular region
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Papillary Region Top 20% of dermis Composed of loose CT & elastic fibers Finger like projections called dermal papillae Functions anchors epidermis to dermis contains capillaries that feed epidermis contains Meissner’s corpuscles (touch) & free nerve endings (pain and temperature)
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Papillary Region – cont.’d. Epidermal ridges form in fetus as epidermis conforms to dermal papillae fingerprints are left by sweat glands open on ridges increase grip of hand
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Reticular Region Dense irregular connective tissue Contains interlacing collagen and elastic fibers Packed with oil glands, sweat gland ducts, fat & hair follicles Provides strength, extensibility & elasticity to skin stretch marks are dermal tears from extreme stretching called Straie
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Skin Color Pigments (1 ) Melanin produced in epidermis by melanocytes same number of melanocytes in everyone, but differing amounts of pigment produced results vary from yellow to tan to black color melanocytes convert tyrosine to melanin UV in sunlight increases melanin production Clinical observations freckles or liver spots - melanocytes in a patch albinism - inherited lack of tyrosinase; no pigment
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Skin Color Pigments (2) Carotene in dermis yellow-orange pigment (precursor of vitamin A) found in stratum corneum & dermis Hemoglobin red, oxygen-carrying pigment in blood cells if other pigments are not present, epidermis is translucent so pinkness will be evident
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Accessory Structures of Skin Epidermal derivatives Cells sink inward during development to form: hair oil glands sweat glands nails
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Glands of the Skin
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