ch 5: the integumentary system. general info –integumentary system – skin, sweat and oil glands,...

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Ch 5: The Integumentary System

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  • Ch 5: The Integumentary System

  • General infoIntegumentary system skin, sweat and oil glands, hairs and nailsSkin Weighs: 9-12 pounds7% of total body weightIntegument = covering Composed of:EpidermisEpithelial cells (relies on dermis below for nutrients)Outermost protectionDermisMost of the skinTough layerFibrous connective tissueHypodermisDeep to the skin Adipose & areolar tissue grows with weight gain Anchors the underlying tissue

  • Figure 5.1EpidermisDermisHypodermis(superficialfascia)Hair rootHair shaftPoreDermal papillae (papillary layer of dermis)Meissner's corpuscleFree nerve endingReticular layer of dermis Sebaceous (oil) glandArrector pili muscleSensory nerve fiberEccrine sweat glandPacinian corpuscleArteryVeinAdipose tissueHair follicle receptor(root hair plexus)Hair follicleEccrine sweatgland

  • EpidermisMade of: Keratinized stratified squamous epithelium consisting of four distinct cell types and four/five distinct layersCells:KeratinocytesMajority of epidermal cells, produce a fibrous protein keratin protection Arise in the deepest part of the epidermis (stratum basale) undergoes continuous mitosisAs they are pushed up they produce keratinWhen they reach the surface they are dead and scale like keratin filled plasma membranesNew epidermis every 25 45 daysFriction can cause a thickening of the epidermis = a callus

  • Cells cont.Melanocytes Spider shaped epithelial cells that synthesize the pigment melaninProduction and movement Melanin is moved to the melanocytes processes to be periodically transferred to keratinocytesAccumulate on the superficial side of keratinocytes nucleus Forms a pigment shield that protects the nucleus from UV radiation

  • Cells cont. Langerhans cells Epidermal dendritic (projections) cellsProcesses extend around the keratinocytes to form a continuous networkArise from bone marrow migrate to epidermis Composed of macrophages that help activate the immune system

  • Cells cont. Merkel cells Present at epidermal-dermal junctionsShape = spiky hemisphereClosely associated with sensory nerve endingsSensory nerve endings + Merkel cells = Merkel discs = sensory receptors for touch

  • Layers general infoEpidermis - five layers or strata - bed sheetsDeep to superficial the layers (for thick skin) are:Stratum basaleStratum spinosumStratum granulosumStratum lucidum (absent in thin skin)Stratum corneumThick skin covers the palms, fingertips, and soles of the feet.

  • Layers of EpidermisStratum Basale Basal layer deepest epidermal layer, site of mitosis (renews the cell population)Firmly attached to dermis wavy borderlineSingle row of cells = youngest keratinocytesAlternative name = stratum germinativum (germinating layer)10-25% of cells are melanocytes branches will stretch into the more superficial stratum spinosum layer

  • Layers of the Epidermis cont. Stratum Spinosum Prickly layerMultiple cell layers thick Contains:Keratinocytesmelanin granuleshighest concentration of Langerhans cellsKeratinocytes Irregular giving the layer its prickly appearanceOccurs when the cells shrink but the desmosomes hold tightMelanin granules and Langerhans cells scattered among the keratinocytes

  • Layers cont. Stratum Granulosum 3-5 cell layers Granular layer Help to form keratin Keratinocytes undergo a great deal of physical changes turn them into the tough outer cells of the epidermisThickens because cytosol proteins bind to inner membrane face & lamellated granules coat the outer surfacesLamellated granules Contain a waterproofing glycolipid Slows water loss across the epidermis

  • Layers cont. Stratum lucidum Clear layerFound only in thick skin and is composed of dead keratinocytesClear, flat, dead keratinocytes w/ no distinct boundaries

  • Layers cont. Stratum corneum Horny layerOutermost protective layer composed of a thick layer of dead keratinocytes of the epidermal thickness Keratin & thickened plasma membranes protect the skin against abrasions Glycolipids between the cells waterproofs the layerDandruff from scalp & dry skin slough off shed 40 lbs of dead flakes in lifetime

  • Dermis2nd major skin layer Composed of:Connective tissue proper Fibroblasts, macrophages, mast cells, white blood cells Matrix embedded w/ collagen, elastin & reticular fibersSupplied w/ nerve fibers, blood vessels, & lymphatic vesselsHair follicles, oil, & sweat glands reside in the dermis

  • Dermal layers 2 layers Papillary & ReticularPapillary Superficial layerHighly vascularized areolar connective tissue Containing a woven mat of collagen and elastin fibersDermal papillae Superior surfaceIndent the overlying epidermis Hands & feet lie atop larger mounds dermal ridges elevate the overlying epidermis epidermal ridges increase friction & enhance gripping ability of hands and feet Genetically determined ridges Fingerprints the identifying film that is left from the sweat that seeps from the pores along the crestsMeissners corpuscles nervous pain receptors

  • Dermal layers Reticular layers 80% of the thickness of the dermis Dense irregular connective tissue Matrix Thick bundles of interlacing collagen fibers most run parallel to skin surfaceLines of cleavage or tension lines Run longitudinallyExternally invisible Important for surgery skin gapes less when incisions are made parallel to the lines Flexure lines Dermal folds that occur at or near joints where the dermis is secured to deeper structuresAccommodates joint movementDeep creases in the palms

  • Cleavage LinesFlexure Lines

  • Skin PigmentsSkin color is determine by three pigments:Melanin Only pigment (of the three) made in the skinA polymer tyrosine amino acidColor = yellow blackProcess-Melanocytes synthesize tyrosinase Increased activity when exposed to UV radiationMelanin build up (a tan) helps protect our DNA absorbs the light and dissipates the energy as heatSkin color determined by the kind and amount of melanin made and retainedFreckles = accumulations of melanin

  • Skin pigments Hemoglobin Fair skinned people Color = provides a pinkish hue due to oxygenated bloodCommon in Caucasians small amounts of melanin epidermis is almost transparent allows hemoglobins color to show through CaroteneColor = yellow orange Accumulates in the stratum corneum & fatty tissue of hypodermisObvious: palms and soles of the feet where corneum is the thickest & when carotene rich foods (carrots) are eaten in large amounts

  • Discolorations of the skinErythema:Skin reddening Blood vessels of the dermis dilatePallor/blanching:Paling of the skin due to stress, fear, low bp, or anemiaJaundice:Can indicate a liver disorderYellow bile pigments accumulate in the blood deposited in tissues

  • Discolorations of the skin cont. Bronzing:Addisons disease metallic appearance of the skinIncreased production and functions of the adrenal cortexBruises:Blood escaping from circulation and accumulating beneath the skinClotted blood = hematoma blood swelling

  • Appendages of the skin Appendages = hair & hair follicles, nails, sweat glands, & oil glands Sweat glands/sudoriferous glands -Sudor = sweatDistributed over entire body except nipples & external genitalia~ 2.5 million sweat glands per personTwo types:Eccrine & Apocrine

  • Glands Eccrine sweat glands AKA merocrine sweat glandsProduce true sweatMost numerous of the sweat glandsAbundant on palms of hands, soles of the feet and the foreheadSimple, coiled, tubular glandDuct extends to the open, skin surface, through a funnel pore Sweat is released by exocytosis 99% waterSalts, antibodies, dermicidin, metabolic wastes, vit C, lactic acid (attracts mosquitoes)Components depend on heredity and dietControlled by sympathetic nervous system no controlPrevents over heating of the body begins on forehead & spreads inferiorlyAnxiety sweat begins on palms, soles of feet and armpits then spreads

  • GlandsApocrine sweat glands Confined to the armpits & genital areas Produce true sweat with the addition of fatty substances & proteins Larger than eccrine glandsDucts empty into the hair follicles Very viscous & can appear milky or yellowSecretion is odorless organic molecules are decomposed by bacteria on the skin = odor Induced by androgens (hormones)

  • GlandsCeruminous glands Modified sweat glands Lines the ear canal secretes sticky, bitter substance ear = cerumen Thought to deter insects and block foreign materials Mammary glands Modified sweat glandsFound in breastsProduce milk

  • Sebaceous GlandsSimple branched alveolar glands - found everywhere except palms of hands and soles of feetSecrete:Sebum (oily secretion lipids and cell fragments)Secreted into hair follicle occasionally to a pore on the skins surfaceSoften and lubricates the skin & hair Slows water loss from the skin when external humidity is lowKills bacteriaStimulated by hormones androgensActive during puberty

  • HairHair is found everywhere exceptPalms, soles of our feet, lips, nipples, and parts of our external genitaliaMain functions: sensing, sunlight protection, heat loss, filters, & shields

  • Hairs contHairs, or pili, are flexible strands produced by hair follicles that consist of dead, hard, keratinized cellsBenefits of hard keratinTough and durableIndividual cells dont slough offRegions of the hair:2 main regionsShaftProjects from the skinRound shaft/pore = straight Oval shaft/pore = silky & wavyFlat shaft/pore = kinky Root Embedded in the skinArea where hair develops & grows

  • Hair contThree concentric layers of keratinized cells:Medulla:Inner coreConsists of large cells & air spacesAbsent in fine hairsCortex: Middle layerBulky layer surrounding the medullaSeveral layers of flattened cellsCuticle: Outer layerHeavily keratinized Single layer of cells that overlap one anotherArrangement helps keep hair apartProvides strength

  • Hair

  • Hair contSplit ends =When cuticle wears away & allows the cortex & medulla to frizz outHair pigments (melanin of different colors) are made by melanocytes at the base of the hair follicleMelanin colors combine to produce the hair colorGrey or white hair is due to decreased melanin production & melanin granules being replaced by air bubbles in the hair shaftMelanocytes

  • Structure of hair Hair follicles reside in the dermisFold down from the epidermis into the dermis & occasionally into the hypodermisDeep end of the hair follicle is expanded, forms hair bulb -surrounded by a knot of sensory nerve endings = root hair plexus (hair follicle receptor) enables the hair to be a sense receptorHair papilla Hair matrix = actively dividing area of the hair bulb = produces hair Supplies nutrients to the growing hair Wall of hair follicle:Outer thick connective tissue root sheath derived from dermis Inner epithelial root sheath derived from epidermis

  • Structure of hair cont. Arrector pili raiser of hairSmooth muscle cells associated with each hair folliclePulls hair into an upright position Dimples the skin in response to cold or fearUsed for heat retention

  • Types of hairHair classified as vellus or terminalVellus:Vell wool or fleeceWomen & children (peach fuzz) Pale, soft hairStomach & face Terminal:CoarserLonger & darker than vellus hairEyebrows, scalp, axillary, & pubic regions in both sexesFace & chest of malesGrowth due to androgens (in males testosterone)

  • Homeostatic imbalancesHair growth influenced by nutrition & hormonesPoor nutrition = poor hair growthRate of hair growth influenced by sex & age - varies from one body region to another (about 2 mm a week)Growth cycles includes an active phase & resting phaseFollicles can become inactive for months at a timeCan lose up to 90 scalp hairs a dayEyebrows = active for 3-4 months inhibits long eyebrow hairsEyelashes = slowest growing cycle

  • Homeostatic imbalancesBaldness/hair thinning due to.After 40, hairs are not replaced as fast, longer resting phaseAlopecia = hair thinningTerminal hair is replaced by vellus hairGenetics = true or frank baldnessMale pattern baldness - sex-influenced traitGene is turned on during adulthood - inhibits hair follicles response to testosterone shortens hair growth cyclesHomeostatic imbalancesEmotional trauma, fever, surgery, protein-deficient diets, & lactationCan be reversed if imbalances are correctedSevere burns & radiation hair loss is permanent because the follicle was eliminated

  • NailsScale-like modification of the epidermis that forms a clear, protective coveringContain: hard keratin, a free edge, body (visible attached portion) & proximal root (embedded in skin) Nail bed deeper epidermal layer that extends beneath the nailNail itself corresponds to the superficial keratinized layers Nail matrix nail bed responsible for nail growthAppear pink due to rich blood supply of capillaries underlying the dermisLunula little moon lies over thick nail matrix appears whiteNail folds overlap of skin folds on the proximal and lateral bordersCuticle nail fold that projects onto the nail body

  • Nails

  • Functions Functions of Integumentary system - ProtectionChemical barrierSkin secretions & melaninLow pH of skin secretions inhibits skin bacteria from multiplying out of controlAntibacterial substances in sebum that kill bacteriaPhysical/mechanical barrierContinuity of skinWaterproofing glycolipids block diffusion of H2O & H2O soluble substancesLipid soluble substances (O2, CO2, & fat soluble vitamins) will penetrate in small amountsBiological barriersLangerhans cells epidermis Macrophages dermis dispose of viruses & bacteria that may have penetrated the epidermis

  • Functions cont.Body temp regulation sweat glands to cool the bodyconstriction or dilation of capillariesCutaneous sensation Cutaneous sensory receptors part of the nervous systemRespond to stimuli outside the bodyMeisners corpuscles, Merkel discs, Pacinian receptors, & root hair plexuses Vit D production Occurs when skin is exposed to sunlight Needed for calcium absorption Blood reservoir Holds around 5% of the bodys bloodMay be diverted to other areas when needed Nervous system constricts dermal vessels when other areas need bloodNitrogenous waste Skin excretes limited amounts of nitrogenous waste Ammonia, urea, & uric acid

  • Homeostatic imbalances Skin cancers:Basal cell -Most common skin cancer sun exposure 30% of all Caucasians in their lifetime Cells in the stratum basale layer invade the dermis & epidermis Shiny, dome shaped nodules that develop a central ulcerMetastasis seldom occurs Squamous cell -Grow rapidly will metastasize if not treated Arise from keratinocytes in the stratum spinosum Scaly reddened elevated lesion Melanoma -Most dangerous Highly metastatic & resistant to chemotherapy Cancer of melanocytes Develop from preexisting moles or areas w/ high pigment Spreading brown/black patch - will spread to surrounding lymph & blood vessels

  • A: basal cell, B: Squamous cell, C: Melanoma

  • BurnsA burn is:Tissue damage inflicted by intense heat, electricity, radiation, or certain chemicals, all of which denature cell proteins and cause cell death to infected areasThreats to patients:Most immediate threat = dehydration & electrolyte imbalance due to fluid lossRenal failure and circulatory shock can occurInfection becomes threat Burned skin is sterile for 24 hours Bacteria, viruses, & fungi invade the area and thrive in the dead tissueRule of nine = body divided into 11 areas - each account for about 9% of the bodys total area method for determining how much of the body surface has been burned

  • Rule of Nines

  • Burns cont.First degree Damage only to the epidermis Redness, swelling, & painHeal w/in 2-3 daysSunburn partial thickness burnSecond degree Injure epidermis & upper regions of the dermisSymptoms similar to 1st degree, include blisters Heal w/in 3-4 weeks w/ little or no scaringNeed to be mindful of the possibility of infectionsPartial thickness burnThird degree Involve entire thickness of skinGrey-white, cherry red, or blackenedInitially no edema Not painful nerve endings have been destroyed Skin grafting is usually necessary

  • B: First degree

    C: Second degree

    D: Third degree

  • Developmental aspectsEpidermis develops from:Embryonic ectodermDermis & hypodermis develop from:MesodermDevelopment:4th month - skin is well formedDuring adolescence, skin & hair become oilier as sebaceous glands are activatedOptimal skin appearance 20s & 30sApproach of old age:Epidermal cell replacement slowsAdipose tissue diminishesElastic fibers clump Collagen fibers stiffen Wrinkles = loss of subcutaneous tissue (adipose tissue) & decrease in elasticitySkin thinsBecomes more prone to bruising & other injuriesHair thins due to inactive hair follicles & activation of genes responsible for balding