INTEGUMENTARY SYSTEM AND SKIN

LECTURE 2Thermoregulation, Healing and

Aging

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

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

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

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

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

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

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

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

Burns

1st degree (superficial partial-thickness) burnOnly affects epidermisSkin becomes warm and reddenedMild edemaTenderSurface layer may peelNo scarring

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

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

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

Wrinkling and sagging of skinDermis reduces and shrinksFat loss from subcutaneous layer

Wound healing is delayedFewer fibroblasts

Drier skinDecreased oil from sebaceous glands

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

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