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Unformatted text preview: 1/24/2008 1 HP 320 HP 320 The Integumentary The Integumentary System System (The Skin) (The Skin) The Skin The Skin s Largest body organ in mass & surface area s Protects internal organs s Acts as a barrier against bacterial invasion s Necessary for survival s if 60% of the skin is destroyed death is likely to occur s Epidermis - outermost layer s composed of epithelial cells s avascular s subdivided into strata s Dermis/Corium - True skin s a framework of connective tissue, with blood vessels, nerve endings and glands Structure of Skin Structure of Skin Epidermal Layers Epidermal Layers From uppermost to deepest s Stratum corneum s Stratum lucidum s Stratum granulosum s Stratum spinosum s Stratum basale /germinativum Stratum Basale/Germinativum Stratum Basale/Germinativum s Deepest layer s Undergoes constant mitosis to replace cells exfoliated from the skin's surface s Cells are pushed up, and die as they move upwards s due to lack of blood supply s Cytoplasm is replaced by keratin (a protein) s thickens and protects the skin s Keratinized cells reach outermost layer and become hard & flattened s Produce the cornified (horny) uppermost layer of the epidermis, the stratum corneum Melanin Melanin s Melanocytes : cells in the basal layer which produce a dark pigment, melanin s Melanin is responsible for skin, eyes & hair color s color ranges from yellow to brown to black s helps protect the deeper layers of the skin from the harmful effects of the sun 1/24/2008 2 Melanin Melanin s Patches of melanin in the skin c birthmarks, freckles & age spots s Malignant melanocytes → melanoma s Amount of melanin produced depends upon genetics & exposure to sunlight s 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 Stratum Corneum s Outermost layer exposed to the air s Protective layer s Exfoliation: keratinized cells constantly flaking off s continuously replaced by cells from the lower strata s Keratinized cells are responsible for: s waterproofing of the skin s protection against infection s resistance against wear and tear Dermis (Corium) Dermis (Corium) s True skin s Elastic connective tissue s Has blood vessels & capillaries for respiration s Has nerve ending for touch, pressure, heat, cold & pain s Appendages include: s skin glands s hair s nails Hypodermis (Sub Hypodermis (Sub-Cutaneous Layer) Cutaneous Layer) s Below the dermis: no clear boundary s Composed mostly of adipose tissue s insulation & energy source s Anchors skin to underlying organs s Connects skin to surface muscles s Sebaceous (oil) & sudoriferous (sweat) glands may extend into the hypodermis s Rich in nerves & blood vessels Skin Accessories: Skin Accessories: Sebaceous (Oil) Glands Sebaceous (Oil) Glands s Sac-like structures found everywhere on the skin except on the palms, soles & back of feet s Secret sebum (oil), which lubricates & prevents drying of the skin & hair...
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- Spring '08