the integumentary system skin and its accessory structures lecture for medical students department...

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The Integumentary System •Skin and its accessory structures Lecture for medical students Department of histology, cytology and embryology KhNMU

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  • The Integumentary SystemSkin and its accessory structuresLecture for medical students Department of histology,cytology and embryology KhNMU

  • 5-*General Functions of the SkinRegulation of body temperatureProtection as physical barrierSensory receptors Excretion and absorptionSynthesis of vitamin D

  • 5-*2 Major layers of skinepidermis is epithelial tissue dermis is layer of connective tissue, nerve & muscleSubcutaneous tissue (hypodermis) is layer of adipose & areolar tissuesubcutaneous injectionintradermal = within the skin layer

  • 5-*Development of the SkinEpidermis develops from ectodermDermis develops from mesoderm

    Slippery coating of oil and sloughed off skin called vernix caseosa is present at birth

  • 5-*Cell types of the Epidermis Keratinocytes--90%produce keratin Melanocytes-----8 %produces melanin pigmentlong cell processesLangerhan cellsfrom bone marrowphagocytes Merkel cellstouch receptor

  • 5-*Layers (Strata) of the Epidermis543



  • 5-*1. Stratum BasaleDeepest single layer of cells Stratum germinativumCombination of merkel cells, melanocytes, keratinocytes & stem cells that divide repeatedly

  • 5-*2. Stratum Spinosum8 to 10 cell layers held together by desmosomesAt slide cells shrink and look spinyMelanin

  • 5-*3. Stratum Granulosum3 - 5 layers of flat dying cellsNuclear degenerationContain dark-staining keratohyalin granules

  • 5-*4. Stratum Lucidum Seen only in thick skin on palms & soles of feetThree to five layers of clear, flat, dead cellsContains precursor of keratin

  • 5-*5. Stratum Corneum25 to 30 layers of flat dead cells filled with keratin Continuously shedBarrier to light, heat, water, chemicals & bacteriaFriction stimulates callus formation

  • 5-*Keratinization & Epidermal GrowthStem cells divide to produce keratinocytesAs keratinocytes are pushed up towards the surface, they fill with keratin

  • 5-*DermisConnective tissue layerContains hair follicles, glands, nerves & blood vesselsMajor layers of dermispapillary reticular

  • 5-*Papillary l.Top 20% of dermisComposed of loose CTFinger like projections called dermal papillaeFunctions:contains capillaries that feed epidermiscontains Meissners corpuscles (touch) & free nerve endings (pain and temperature)

  • 5-* Reticular l.Dense irregular connective tissueCollagen and elastic fibersContains glands & hair folliclesProvides strength, extensibility & elasticity to skinEpidermal ridges conforms to dermal papillae = fingerprints

  • 5-*Types of SkinThin skin - covers most of bodythin epidermis (.1 to .15 mm.) that lacks stratum lucidumlacks epidermal ridges, has fewer sweat glands and sensory receptorsThick skin - only on palms and solesthick epidermis (.6 to 4.5 mm.) with distinct stratum lucidum & thick stratum corneumlacks hair follicles and sebaceous glands-thick hypodermis

  • 5-*Accessory Structures of Skin Epidermal derivativesEpithelium sinks inward during development to form:hairglandsnails

  • 5-* Structure of Hair Shaft -- visiblemedulla, cortex & cuticleRoot -- below the surfaceFollicle surrounds root:external root sheathinternal root sheathbase of follicle is bulbgerminal cell layerC.t.Papilla contains blood vessels

  • 5-*Hair Related Structures Muscle arrector pilismooth muscle in dermis contracts with cold or fear.forms goosebumps as hair is pulled vertically

  • Hair Color and Texture(a) Blond, straight(b) Black, straight(c) Red, wavy(d) Gray, wavyCuticleCortexMedullaEumelaninPheomelaninEumelaninPheomelaninAir spaceCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The McGraw-Hill Companies, Inc./Joe DeGrandis, photographer

  • Glands of the SkinSebaceous Sweat Ceruminous (wax) glandsMammary (milk) glands

  • 5-*Histology of skin glands

  • 5-*Sebaceous (oil) glandsSecretory portion in the dermisMost open onto hair shafts Sebumcombination of cholesterol, proteins, fats & saltskeeps hair and skin from soft & pliableAcnebacterial inflammation of glandssecretions stimulated by hormones at puberty

  • 5-* Sweat glands Eccrine (sweat) glandsmost areas of skinregulate body temperature with perspiration Apocrine (sweat) glandsarmpit and pubic regionduct opens onto hair folliclesecretions more viscous

  • 5-* NailsTightly packed keratinized cellsNail bodyvisible portion pink due to underlying capillariesfree edge appears whiteNail rootburied under skin layerslunula is white due to thickened stratum basaleEponychium (cuticle)stratum corneum layer

  • 6-*Skin Colormelanin most significant factor in skin colorproduced by melanocytesaccumulate in the keratinocytes of stratum basale and stratum spinosumeumelanin brownish blackpheomelanin - a reddish yellow sulfur-containing pigment

    people of different skin colors have the same number of melanocytesdark skinned peopleproduce greater quantities of melaninmelanin granules in keratinocytes more spread out than tightly clumpedmelanin breaks down more slowlymelanized cells seen throughout the epidermislight skinned peoplemelanin clumped near keratinocyte nucleusmelanin breaks down more rapidlylittle seen beyond stratum basale

    amount of melanin also varies with exposure to ultraviolet (UV) rays of sunlight

  • 5-*Thermoregulation Releasing of sweat onto the skinperspiration & its evaporation lowers body temperatureAdjusting flow of blood to the body surfacein moderate exercise, more blood brought to surface helps lower temperaturewith extreme exercise, blood is shunted to muscles and body temperature risesShivering and constriction of surface vesselsraise internal body temperature as needed

  • 5-*ProtectionPhysical, chemical and biological barriertight cell junctions prevent bacterial invasionlipids released retard evaporationpigment protects somewhat against UV lightlangerhans cells alert immune system

  • 5-*Cutaneous SensationsTouch, temperature, pressure, vibration, tickling and some pain sensations arise from the skin.

  • 5-*Excretion and AbsorptionOnly a minor role is played by the skin400 mL of water evaporates from it dailySmall amounts salt, CO2, ammonia and urea are excretedLipid soluble substances can be absorbed through the skinvitamins A, D, E and K, Oxygen and CO2acetone and dry-cleaning fluid, lead, mercury, arsenic, poisons in poison ivy and oak

  • 5-*Synthesis of Vitamin DSunlight activates a precursor to vitamin DEnzymes in the liver and kidneys transform that molecule into calcitriol (most active form of vitamin D)Necessary vitamin for absorption of calcium from food in the gastrointestinal tract

  • 5-*Epidermal Wound HealingAbrasion or minor burnBasal cells migrate across the woundContact inhibition with other cells stops migrationEpidermal growth factor stimulates cell division Full thickness of epidermis results from further cell division

  • 5-* Deep Wound HealingIf an injury reaches dermis, healing occurs in 4 phasesinflammatory phase has clot unite wound edges and WBCs arrive from dilated and more permeable blood vesselsmigratory phase begins the regrowth of epithelial cells and the formation of scar tissue by the fibroblastsproliferative phase is a completion of tissue formationmaturation phase sees the scab fall offScar formationhypertrophic scar remains within the boundaries of the original woundkeloid scar extends into previously normal tissuecollagen fibers are very dense and fewer blood vessels are present so the tissue is lighter in color

  • 5-*Phases of Deep Wound HealingWhich phases have been left out of this illustration?

  • 5-*Development of the SkinEpidermis develops from ectodermal germ layerDermis develops from mesodermal germ layerat 8 weeks, fetal skin is simple cuboidal epitheliumnails begin to form at 10 weeks, but do not reach the fingertip until the 9th monthdermis forms from mesoderm by 11 weeksby 16 weeks, all layers of the epidermis are presentoil and sweat glands form in 4th and 5th monthby 6th months, delicate fetal hair (lanugo) has formedSlippery coating of oil and sloughed off skin called vernix caseosa is present at birth

  • 5-*Skin Cancer1 million cases diagnosed per year3 common forms of skin cancerbasal cell carcinoma (rarely metastasize)squamous cell carcinoma (may metastasize)malignant melanomas (metastasize rapidly) most common cancer in young womenarise from melanocytes ----life threateningkey to treatment is early detection watch for changes in symmetry, border, color and sizerisks factors include-- skin color, sun exposure, family history, age and immunological status