Integumentary system and skin Lecture 2
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Transcript of Integumentary system and skin Lecture 2
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INTEGUMENTARY SYSTEM AND SKIN
LECTURE 2Thermoregulation, Healing and
Aging
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Regulation of Body Temperature Slight shifts in temperature can disrupt
metabolic rates Stable temperature is a balance
between heat lost and heat producedCellular metabolism produces heat
○ Skeletal and cardiac muscle and liver cells are very active
Skin is key to thermoregulation
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Rise in Body Temperature Nervous system signals organs to release heat
Blood is warmed and reaches the brain Signal sent to dermal blood vessels to relax
(vasodilation)Vessels dilate Heat from blood escapes to outside
Deeper blood vessels signaled to contract (vasoconstriction)Blood diverted to surfaceSkin reddens
Heart stimulated to beat faster and move more blood out of deeper regions
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Radiation- heat radiates from warmer surfaces to cooler surroundings
Conduction- heat moves from body to a cooler object in contact
Convection- heated air moves way from body and is replaced with cooler air moving toward the body (circulates)
Evaporation- sweat is released onto skin surface and evaporates, carrying heat away
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Drop in Body Temperature Walls of dermal blood vessels contract
(vasoconstriction)Flow of heat-carrying blood is decreasedReduces heat loss by radiation, conduction and
convection Sweat glands remain inactive Muscles cells in skeletal muscles may
begin to contractIncreases cellular respiration and releases heatRhythmic, strong contractions cause shivering
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Problems in Regulation High humidity
limits or represses evaporationSweating is ineffective
High air temperatureDecreases heat loss by radiationCan also cause heat gain from surroundings
Hyperthermia- body temperature exceeds 106FWeak, dizzy, nauseous, headacheRapid, irregular pulseDry, hot, flushed skin
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Hypothermia- lowered body temperatureBegins with shiveringMental confusion, lethargy, loss of reflexes, loss of
consciousnessOrgans shut down
Core can only withstand a drop of a few degrees
Extremities can withstand drops of 20-30F below normal
Must warm gradually to avoid disrupting respiratory and cardiovascular functioning
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Wound Healing Inflammation is a response to injury or
stressBlood vessels dilate and become permeable
○ Fluids leak into damaged tissue○ Tissue gets more nutrients and oxygen
Skin becomes reddened, swollen, warm and painful
Shallow cutsEpithelial cells divide more rapidly Newly formed cells fill gap
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Deep cutsBlood vessels break and form clotsTissue fluids seep in and dryClotted blot and dried fluids for a scab to protect woundEpithelial cells bridge the wound and fibroblasts
secrete fibers to bind the woundBlood vessels extend beneath scab
○ Phagocytes remove deal cells○ Damaged tissues replace○ Scab falls off
Scars form if excess collagenous fibers formed above the normal epidermal surface
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Burns 1st degree (superficial partial-thickness)
burnOnly affects epidermisSkin becomes warm and reddenedMild edemaTenderSurface layer may peelNo scarring
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2nd degree (deep partial-thickness) burnDestroys epidermis and some underlying dermisFluid accumulates beneath epidermal cells to
form blistersAreas becomes moist and firmColor varies from dark red to waxy whiteExposure to hot objects, liquids, flames, clothesStem cells divide and differentiate during healingLow risk of scarring
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3rd degree (full-thickness) burnDestroys epidermis, dermis and accessory
structures of skinSkin is dry and leatheryRed to black to white in colorResults from immersion in hot liquids, prolonged
exposure to hot objects, flames or chemicalsSpontaneous healing of epithelial cells inward
from burn marginsMay need grafting or temporary membrane coversExtensive scarring
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Aging Aging affects:
skin appearancetemperature regulationvitamin D formation
Epidermis thins over timeCell cycle slowsCells grow larger, more irregular in shape and fewer
Scaly skin results from changes in chemical bonding
Age spots result from oxidation of fats in apocrine and eccrine glands
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Wrinkling and sagging of skinDermis reduces and shrinksFat loss from subcutaneous layer
Wound healing is delayedFewer fibroblasts
Drier skinDecreased oil from sebaceous glands
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Whitening/graying of hairSlowed melanin production
Thinning hair Slower hair growthDecrease in hair follicles
Hard, dull nailsDecreased blood supply to nail bed
Decrease in pain and pressure sensitivity
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Decreased ability to control temperatureNumber of sweat glands decreasesAbility to shiver declinesBlood vessels in deeper layers decreaseDecreased ability to direct blood flow to interior
Paler complexionFewer vessels in skin
Pressure SoresLess blood vessels, different distributionDecreased circulation
Decreased absorption of calciumLess vitamin D production
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