biology 141 integumentary system chapter 5. the integument integument: skin – largest body organ ...

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Biology 141 Biology 141 Integumentary System Integumentary System Chapter 5 Chapter 5

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  • Biology 141Integumentary SystemChapter 5

  • The IntegumentIntegument: Skin largest body organIntegumentary System:SkinHairNailsFunction:ProtectionMaintain body temperatureProvide sensory input

    Dermatology: medical specialty dealing with the integumentary system

  • Structure of the SkinCutaneous membrane: skinEpidermis superficial layerDermis deep layer

    Subcutaneous membraneHypodermis fat layer; not technically a part of the skin.

  • Structure of the SkinThe 2 layers of skin; epidermis Multilayered epithelial tissuethinner

    DermisConnective tissuethicker

  • EpidermisCell types found in the epidermis:Keratinocytes: multilayeredProduce keratin protein (tough, water repellant)MelanocytesProduces pigment melanin to protect nuclear DNA in keratinocytesLangerhans cellImmune responseMerkel cellsContact Merkle discs to detect sensations

  • EpidermisTissue Layers

    Composed of different strata (layers)outermost - dead cells Innermost - Cells divideCells die as they are pushed upward Layers originate from the deepest cell layer of columnar cells called the stratum germinativum.

  • Sublayers of the Stratum germinativum

    Stratum basale ("base layer") Cells of stratum basale are closest to the blood supply in the dermis and are thus the healthiest Only these cells can reproduce

    Stratum spinosum ("spiny layer") Cells are pushed from below and become "squished" and look "spiny" on cross sectional view Because the cells are farther away from the dermal blood supply, they are less healthy and thus don't reproduce

  • Basal Cell CarcinomaLow magnification (left) of skin cross-section of shows different layers (epidermis, dermis and subcutaneous tissue), and areas of tumor invasion. Higher magnification (right): tumor cells resemble those in the normal basal cell layer of the epidermis. Tumor cells appear to bud off from the epidermis and grow downward as islands and cords of basophilic cells with hyperchromatic nuclei.

  • Epidermis Tissue Layers (deep to superficial)Stratum germinativum ("growth layer")stratum basal germination basement layerStratum spinosum thorn-like

    Stratum granulosum "grainy layer"

    Stratum lucidum "clear layer"

    Stratum corneum horny layer (top layer)

  • Epidermis: Tissue Layersstratum basal: Single row of cuboidal or columnar keratinocytes.Some are stem cellsContainsMelanocytesLangerhans cellsMerkle cells and discs

  • Epidermis: Tissue Layersstratum basal Damage to this layer damages stem cellsUnable to regenerate skinRequire skin graftsGrafts can be autologous (same individual) or transplanted from a donor.Skin sheets can also be grown in the lab

  • Epidermis: Tissue Layersstratum spinosum multilayered keratinocytesFew Langerhans cells and Melanocytes

  • Epidermis: Tissue Layersstratum granulosumMultilayered, flattened keratinocytesCells undergoing apoptosisSecretes water repellantcells loose nuclei, appear grainy Keratohyalin (a precursor to keratin) forms in granules here

  • Epidermis: Tissue Layersstratum lucidum: Multilayered, dead keratinocyteswith large amount of keratin

    Translucent and flattened

    Found only in thick skin (hairless)FingertipsPalmssoles

  • Epidermis: Tissue Layersstratum corneum: MultilayeredFlat, dead keratinocytesprimarily keratin protein"horny layer" - cells have processes Flattened cells filled with keratin form "keratinized layer" and make this "keratinized stratified squamous epithelium"

    Constant friction results in callus formation

  • DermisDermis: Connective tissueContainsBlood vesselsNervesGlandsHair follicles

  • Dermis2 main regions:

    Papillary: upper layer

    Reticular: deep layer

  • DermisPapillary: upper layerlies next to the epidermiscontains the derma papillae (projections into the upper epidermis) epidermal ridges creat fingerprints, palm prints and footprints.Contain capillariesContain Meisssner corpuscles (tactile receptors)Contain free nerve endingsSenses temperature, pain, itch, tickle

  • DermisReticular: deep layerAttaches to the subcutaneous layerDense irregular connective tissuecontains more collagen fibers increasing the strength of the skin.Contains:Few adipose cellsHair folliclesNerves and Pacinian corpuscles (deep pressure)Sebaceous glands (oil)Sudoriforous glands (sweat)

  • Accessory StructuresReceptors: Meissners corpuscles and Pacinian corpusclesMeissners: located in the papillary layer of dermisproject into the papillae.touch receptorsPacinian: spherical, onion-likeLie deep in the reticular layerpressure

  • Sensory receptors in the DermisMeissners Corpuscle detects light touchPapillary layerPacinian Corpuscle detects deep touch (pressure)Reticular layer

  • DermisTears in the reticular region of the dermis result in stretch marks.

    Incisions against the grain of the collagen fibers = wide scar

    Incisions with the grain = thin scar

  • Structural Basis of Skin ColorSkin color pigments:MelaninHemoglobinCarotene

    Melanin number of melanocytes the same in all peopleAmount of melanin produced variesAccumulation results inAge spotsFrecklesmoles

  • MelaninFunction:Absorbs UV radiationPrevents damage to DNA in epidermal cellsNeutralizes free radicals

  • HemoglobinFound in RBCs

    Skin color depends on amount of oxygen in the blood Blue cyanotic: low oxygenYellow - jaundice: high bilirubinLiver damageRed erythema: engorgement of capillariesInjuryHeatInfectionInflammationAllergic reactionWhite pallor: low number of RBC Shockanemia

  • CaroteneYellow-orange pigment found in egg yolks and orange vegetablesPrecursor to vitamin AExcessive dietary intake results in accumulation in the subcutaneous layer

  • Albinism / VitiligoAlbinism: Inherited inability to synthesize melaninMelanin is not produced in skin, hair, and eyes.

    Vitiligo: partial or complete loss of melanocytes in patches of skinImmune system attacks and destroys melanocytes.

  • Accessory StructuresHair: piliColumns of dead, keratinized cells - compactly cemented shaft portion of the hair that projects above the surface.root portion below the surface extending into the dermis.

  • HairHair shaft and root consist of 3 concentric layers of cells:MedullaCortexCuticle

  • Human HairCuticle showing scalesNo medulla, brown pigment granules in cortexLight medulla

  • HairHair follicle: composed of the root sheath encasement with 2 layers:Internal root sheath produced by matrix, surrounds rootExternal root sheathextension of epidermisThe Dermal root sheath is part of the dermis

  • Hairbulb - enlarged region of the root containing the follicular papilla (involution of loose connective tissue).

  • Hairarrector pili muscle smooth muscle that upon contraction forces the skin into goose bumps.

  • Accessory StructuresGlands: sebaceous and sweat glands

    Sebaceous glands:Usually connected to hair folliclessecretes sebum (oil)Moisturizes hair and skinkeeps hair pliable.Keeps skin softInhibits bacteria

  • Acne: Inflammation of a sebaceous gland.

    Blocked sebaceous glandNormal sebaceous gland

  • Sudoriferous Glands (Sweat glands)2 main types of glands: eccrine and apocrineeccrine: empty directly out through the skin surfacetubular with a coiled basal portion located deep in the dermisRegulates body temperatureapocrine: larger, empty directly into the hair follicle canalsecretory portion located in the subcutaneous layerExcretory duct opens into hair folliclestimuli: psychic factors; emotions, sexual excitement

  • Sudoriferous Glands

  • Accessory structures and location

  • Ceruminous GlandsModified sweat glands in the external ear.Produce ear wax (cerumen)Provides a sticky barrier

  • NailsTightly packed, hard, keratinized epithelial cells.

    Structure:Nail body: visible portionPink due to capillary bedFree edge: part that extends past the digitWhite due to lack of capillariesNail root: portion buried in a fold of skin

  • Nails

  • Types of Skin2 types of skin based on structure:Thin (hairy) skinThick (hairless skin)

  • Functions of the SkinThermoregulation: by sweat and blood flowBlood reservoir8-10% of blood flowProtectionAgainst external assaultCutaneous sensationsTactile, pressure, pain, temperature, tickleExcretion and absorptionExcrete salts, water, and small amounts of CO2 and ureaAbsorbs lipid molecules (vitamins A,D,E and K, drugs, lotions, poisons, heavy metals, steroids)Synthesis of vitamin DUV light activates precursor molecules that can be modified by the liver. Vit. D produces calcitrol which aids in the absorption of calcium in the GI tract.

  • Maintaining Homeostasis: Skin Wound HealingWound healing can occur via 2 routes:Epidermal Wound Healing affects only the epidermis.

    Deep Wound Healing wound extends to dermis and subcutaneous layers

  • Epidermal Wound HealingInjury response:Basal cells detach from the basement membrane.Hormone (epidermal growth factor) stimulates basal stem cells to divide to replace migrating cells.Migrating cells move across woundCells stop migrating upon touching other cells (contact inhibition)

  • Deep Wound Healing

    4 phases:Inflammatory: clot formation closes the wound, WBC kill invadersMigratory:scab formation, epithelial cells migrate, fibroblasts produce fibrin for scar tissueProliferative:Extensive growth of epithelial cells, depositing collagen fibersMaturation:Scab sloughs off, collagen fibers organize

  • Development of the Integumentary SystemEpidermis is derived from the ectodermDermis is derived from the mesoderm

  • Aging and the Integumentary SystemMost changes occur in the dermisCollagen fibers decrease in numberElastic fibers loose elasticityFibroblast (produce collagen and elastin) decrease in numberDecrease number of melanocytes gray hairSubcutaneous adipose tissue is lostHealing is longer

  • Sun DamageUV A rays:Not absorbed by the ozone layerPenetrate deep into skin and absorbed by melanocytesDepress the immune systemDarken the skinUV B rays:Some absorbed by ozonePenetration of skin not as deepCause sunburn

  • Sun DamageSunscreenAbsorb UV B, but allow UV A rays to reach the skinSunblockBlock both UV A and UV B rays

  • Skin CancerBasal cell carcinoma78% of all skin cancersTumors arise from the stratum basaleRarely metastasizeSquamous cell carcinoma20% of all skin cancersArise from squamous cell of epidermismetastasizeMalignant melanoma2% of all skin cancersArise from melanocytesMetastasize rapidly (can kill within months)

  • Skin CancerBasal cell carcinomamelanomasquamous cell carcinoma

  • BurnsBurns are graded by severity:First degree: only epidermis, redSecond degree: all epidermis and part of dermis, blistersThird degree: all epidermis, dermis and subcutaneous layers, blackFourth degree: muscle layers are burned

  • BurnsHalf of all patients with over 70% of the body burned, dies.

    Estimating surface area for burns uses the rule of nines.

  • BurnsHead and neck (front and back)9% Each upper limb (front and back)9% Trunk (front and back)4 x 9% (or 36%)Each lower limb 9% front9% back

    Perineum (anal and urogenital region)1%

  • Pressure UlcersDecubitus ulcers caused by constant deficiency of blood flow from prolonged pressure against an object.

    Occur most often in bedridden patients.