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The Human Body in Health and Illness

Chapter 7: Skin and Appendages1Lesson 7-1 ObjectivesList six functions of the skin.Define stratum germinativum and stratum corneum.Describe the two layers of the skinepidermis and dermis.List the two major functions of the subcutaneous layer.22IntroductionSkin (integument) is bodys largest organIntegumentary system describes the skin and its appendagesthe hair, nails, and skin glandsYou shed about 1.5 lbs per year

33Skin Perspective On average, 1 cm2 of skin contains:3,000,000 cells10 hairs15 sebaceous glands3 feet of blood vessels700 sweat glands

3000 sensory cells at nerve endings12 feet of nerves200 pain receptors2 cold receptors12 sensors for heat

4Functions of the SkinServes as mechanical barrierProtects internal structures Participates in the immune responseActs as a gland for vitamin D synthesisPerforms excretory functionPerforms sensory roleHelps regulate body temperature55The skin, the accessory structures, and the subcutaneous tissue form the integumentary system .Structure of the SkinLayersEpidermis(lays upon dermis)Dermis (skin)Subcutaneousa.k.a: Hypodermis Accessory structuresHair, nails, glands..etc.

66Oxygen and nutrients diffuse into the lower epidermis from the richly nourished dermis.In which layers are the blood vessels found?The blood vessels are found in the dermis and subcutaneous.Where are the statum germinativum and stratum corneum found? Both are layers of epidermis; the statrum germinativum is the deeper of the two.

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7Overview Structure of the SkinSkin classified as cutaneous membraneTwo primary layersepidermis and dermis; joined by dermoepidermal junctionHypodermis lies beneath dermisThin and thick skin (Figure 7-3)Thin skin covers most of body surface (1 to 3 mm thick); has hair and smooth surfaceThick skinsoles and palms (4 to 5 mm thick); ridged surface with no hair

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10Layers of EpidermisFrom deep to Superfical: Stratum BasaleA.k.a Stratum Germinativum Stratum SpinosumStratum GranulosumStratum LucidumStratum Corneum2. **3. 4.

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Layers uncovered

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13Epidermis: Outer Layer continuedLayers of the epidermisStratum corneum (surface layer); composed of dead, flattened cells that slough off , our hornsStratum germinativum (deepest), a.k.a. stratum basale: cells continuously dividing and moving toward surfaceKeratinization: The protein keratin makes skin cells hard, flat, and water resistant.(Keratinocytescells that actually produce protein) 1414As the cells of the stratum germinativum divide, they push the older cells toward the surface of the epithelium.To what do the terms exfoliation and desquamation refer?These terms describe the sloughing off of the stratum corneum.What are dander and dandruff?Individual dead cells are called dander; when clumped together by oil, they are dandruff. Epidermal growth and repairShortened turnover time increase thickness of the stratum corneum; results in callus formationNormally 10% to 12% of all cells in stratum basale enter mitosis daily

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Structure of the SkinDermopidermal junction (DEJ)A basement membrane Polysaccharide gel serve to glue the epidermis to the dermis belowPartial barrier to the passage of some cells and large molecules1616Dermis Our hide, strong and stretchytrue skinLies under and supports the epidermisGives strengthSits on the subcutaneous layer or hypodermisEmbedded with accessory structuresIncludes blood vessels that nourish epidermisReservoir storage for water and electrolytes1717What role do the collagen and elastin fibers of the dermis play?These fibers make the dermis stretchable and strong.What accessory structures are embedded in the dermis?The hair, nails, and certain glands are embedded in the dermis.The sensory receptors that detect pain, temperature, pressure, and touch are also located in the dermis.Dermis continued2 major regions:Papillary: upper/superficial dermal layer Pain receptors (free nerve endings)Touch receptors: Meissners corpusclesAllow for gripGenetically unique= fingerprintsArrector pili (goose bumps)Reticular: Deepest of skin layerBlood vessel, sweat glands, oil glandsPacinian corpuscles: Deep pressure receptorsLast line of defenseLeather

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19Dermis (cont)During wound healingfibroblasts begin forming an unusually dense mass of new connective fibersif not replaced by normal tissue, this mass remains a scarCleavage lines (Figure 7-7)patterns formed by the collagenous fibers of the reticular layer of the dermisalso called Langers lines

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Langers lines21Scar formationCleavage lines - patterns formed by the collagenous fibers of the reticular layer also22

Subcutaneous Layer: HypodermisA.k.a = subcutaneous layerConnection point to tissue that lies beneath skinHighly vascularizedTwo main roles:Its fat insulates body from extreme temperature changes. Its connective tissue anchors the skin to underlying structures.NOT PART OF THE SKIN2323Is the subcutaneous layer considered to be part of the skin?No, it is not.Why are many drugs injected subcutaneously (SC)?The hypodermis has a rich supply of blood vessels. The blood vessels absorb the drug and distribute it throughout the body.

ProblemsDecubitus ulcers; Bed soresBlood supply is cut offBedridden patients who are not regularly movedPressure of bone on skin eventually cuts off supply line

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Real life

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Skin ColorDetermined by: genes, physiology, and sometimes pathologyDark pigment: MelaninEumelanin-dark brown-blackPheomelanin-red-brownMelanocyte= Make melanin in epidermis(St.Basale)Melanocyte malfunctions: Albinism (defect in melanin)Vitiligo (loss of brown pigment)26

What is the physiological basis of the summer tan?UV radiation boosts melanin production, beginning with a tan, and potentially leading to permanent damage.Moles are abnormal but harmless concentrations of melanin.What are signs that a mole may be becoming a melanoma? Signs of possible melanoma are asymmetrical shape, irregular borders, change in color, and diameter larger than a pencil eraser. Skin color continuedBeta-carotene: Orange-yellow (some veggies)Presence of melanin overshadows carotenes tint in most peopleLipofuscin: brown-yellow age spotsHemoglobinRed coloring from blood cells in dermis capillariesOxygen content determines the extent of red coloring

27Skin Color (contd.)Physiological changes:Blushing: Blood vessel dilation Pallor: Blood vessel constriction Pathological changes:Cyanosis or bluish tint: Poor oxygenation Jaundice or yellowing: Bilirubin deposition (Bile and Liver products)Bronzing: Melanin overproductionEcchymosis: Black and blue bruising28

Jaundice can be a sign of liver disease; the liver is unable to excrete bilirubin, so it is deposited in the skin. In light-skinned people, bronze skin can signal poor adrenal function. A bruise, or ecchymosis, is clotted blood under the skin.Fear can make a person look white as a sheet. Physiologically, what is going on?Vasoconstriction is part of the fear response. 29

29Accessory Structures: HairFunctions: Detect insects, protect eyes, keep dust out of lungsHormones affect growth.Melanin influences color.Hair arises in epidermis.Cosmetic role

3030What role do the arrector pili muscles play?When the arrector pili muscles contract, they cause the hair to stand up on end.The hair follicle is surrounded by epidermal tissue.Distinguish between hirsuitism and alopecia. The former can be caused by steroid therapy and the latter can be caused by cancer or chemotherapy.

Developmental of HairDistribution-over entire bodyExcept palms and soles of feetLanugo: fine and soft hair before birthVellus Hair: fine, barely noticeable hair, childhoodBody HairHead hairAndrogenic Hair: Coarse body hairTerminal Hair: coarse pubic hair and axillary hair

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Make up of hairPapillacluster of capillaries under germinal matrix; feed follicleRoot(hair follicle): part of hair embedded in follicle in dermis but hair develops from epidermisShaftvisible part of hairMedullainner core of hairCortexouter portionWhat conditioner works onGrowth is erratic

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33Accessory Structures: NailsProtect tips of fingers and toes from injuryCondition affected by oxygenation of blood supply, trauma, and nutritional deficiencies

3434Nails are thin plates of stratified squamous epithelial cells. They contain a very hard form of keratin and slide over a layer called the nail bed, which is part of the epidermis.Clubbing is an indication chronic lung or heart disease; it results from chronically poor oxygenation of the nail and fingertip. NailsConsist of epidermal cells converted to hard keratinNail bodyvisible part of each nailIt is what you trimRootpart of nail in groove hidden by fold of skin, the cuticleLunulamoon-shaped white area nearest root

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36Nails continuedNail bedlayer of epithelium under nail body; contains abundant blood vesselsAppears pink under translucent nailsNails may have pigmented streaksGrowthnails grow by mitosis of cells in statum basale beneath the lunulaAverage growth about 0.5 mm per week, or slightly over 1 inch per year

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Accessory Structures: Glands Sebaceous glands:Oil glands Secrete sebum and in fetus vernix caseosa SudoriferousSweat glands

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38What is the role of the vernix caseosa?This cream cheeselike covering found on the fetus protects it from maceration.What happens when the sebaceous glands become blocked?When accumulated sebum blocks a sebaceous gland and is exposed to air and dries out, it turns black and forms a blackhead. If it becomes infected with staphylococci, it becomes a pustule, or pimple. Sudoriferous GlandsApocrine glands: Found with hair follicles; more active at pubertyAxillary and Genital RegionsEcc

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