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Ch6 Skin - The Skin HP 320 The Integumentary System(The...

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1/24/2008 1 HP 320 The Integumentary System (The Skin) The Skin square6 Largest body organ in mass & surface area square6 Protects internal organs square6 Acts as a barrier against bacterial invasion square6 Necessary for survival square6 if 60% of the skin is destroyed death is likely to occur square6 Epidermis - outermost layer square6 composed of epithelial cells square6 avascular square6 subdivided into strata square6 Dermis/Corium - True skin square6 a framework of connective tissue, with blood vessels, nerve endings and glands Structure of Skin Epidermal Layers From uppermost to deepest square6 Stratum corneum square6 Stratum lucidum square6 Stratum granulosum square6 Stratum spinosum square6 Stratum basale /germinativum Stratum Basale/Germinativum square6 Deepest layer square6 Undergoes constant mitosis to replace cells exfoliated from the skin's surface square6 Cells are pushed up, and die as they move upwards square6 due to lack of blood supply square6 Cytoplasm is replaced by keratin (a protein) square6 thickens and protects the skin square6 Keratinized cells reach outermost layer and become hard & flattened square6 Produce the cornified (horny) uppermost layer of the epidermis, the stratum corneum Melanin square6 Melanocytes : cells in the basal layer which produce a dark pigment, melanin square6 Melanin is responsible for skin, eyes & hair color square6 color ranges from yellow to brown to black square6 helps protect the deeper layers of the skin from the harmful effects of the sun
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1/24/2008 2 Melanin square6 Patches of melanin in the skin c3right birthmarks, freckles & age spots square6 Malignant melanocytes melanoma square6 Amount of melanin produced depends upon genetics & exposure to sunlight square6 sun exposure causes melanocytes to increase production of melanin in order to protect the skin from damaging ultraviolet (UV) rays, producing a suntan Stratum Corneum square6 Outermost layer exposed to the air square6 Protective layer square6 Exfoliation: keratinized cells constantly flaking off square6 continuously replaced by cells from the lower strata square6 Keratinized cells are responsible for: square6 waterproofing of the skin square6 protection against infection square6 resistance against wear and tear Dermis (Corium) square6 True skin square6 Elastic connective tissue square6 Has blood vessels & capillaries for respiration square6 Has nerve ending for touch, pressure, heat, cold & pain square6 Appendages include: square6 skin glands square6 hair square6 nails Hypodermis (Sub Hypodermis (Sub-Cutaneous Layer) Cutaneous Layer) square6 Below the dermis: no clear boundary square6 Composed mostly of adipose tissue square6 insulation & energy source square6 Anchors skin to underlying organs square6 Connects skin to surface muscles square6 Sebaceous (oil) & sudoriferous (sweat) glands may extend into the hypodermis square6 Rich in nerves & blood vessels Skin Accessories: Sebaceous (Oil) Glands square6 Sac-like structures found everywhere on the skin except on the palms, soles & back of feet square6
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