The Integumentary System VNSG 1420 Anatomy & Physiology Chapter 5.

The Integumentary System

VNSG 1420 Anatomy & PhysiologyChapter 5

Integumentary System

Skin & appendagesGlands, hair & nails

Blood vessels, nerves & sensory organsIntegument means coveringCutaneous refers to the skin as a wholeSkin is largest organ of the body

Structure of the SkinTwo layersEpidermis -- outermost portion with thin layer

subdivisions called strata Composed entirely of epithelial cells,

contains no blood vesselsDermis – true skin – framework of connective

tissueContains blood vessels, nerve endings &

glands

Epidermis

Surface layer of the skinStratum basale – deepest layer has the only living cells in the epidermisNew cells multiply (grow in number) by

dividing & accumulate keratin, thicken & die as they push up to the surface

Only layer of cells that reproduces

Epidermis

Contain melanin pigmentProtects cells from harmful ultraviolet

radiationStratum corneum – thick, uppermost, outer layer of epidermis

DermisDeeper layer of skin (also called corium or true skin) with a framework of elastic connective tissue with blood vessels, nerves endings, hair follicles & glands Dermal papillae – extensions form a distinct pattern of ridges on thick skin (fingerprints & footprints)Thickness of dermis varies in areasThin eyelids, thick soles & palms

Subcutaneous Layer

Known as hypodermis/superficial fasciaConsists of loose connective & adipose (fat) tissues, blood vessels & nerve endingsFat serves as insulation & reserve energy supplyDermis rests on subcutaneous tissue that connects the skin to superficial muscles, no clear boundary between dermis & subcutaneous layer

Accessory Structures of the Skin

Sweat glandsSebaceous glandsHairNails

Sebaceous Glands

Lubricate skin & hair, prevent dryingSac-like structures with sebum - oily secretion, ducts open into hair folliclesVernix caseosa --cheese-like covering produced by sebaceous glands before birthBlackheads & pimples form from sebum & keratin blocking glandsCysts - sac of sebum blocking gland

Sweat Glands

Sudoriferous glands - coiled, tubular in dermis & subcutaneous tissueExcretory tube extends to skin surface & opens at a poreRegulate body temperature through sweat evaporation from body surfaceWater, mineral salts & other wastes make up sweat

More on Sweat Glands

Sweat glands in axilla (armpits) & groin release their secretions through hair follicles in response to emotional stress & sexual stimulation (apocrine glands)Their secretions contain cellular matter broken down by bacteria & produce body odor

Modified Sweat Glands

Ceruminous glandsProduce cerumen (ear wax) in ear

canalsCiliary glands Located at edge of eyelids

Mammary glands

Hair

Composed mainly of keratin & is not livingServes as insulationDevelops in sheath called follicle from cells at bottom of follicleGrows from follicular cells at follicle baseArrector pili muscle (involuntary) is attached to most hair follicles -- causes goose bumps when muscle contacts

Nails

Made of keratin, originate in outer layer of epidermisProduced by epidermal cells at proximal end of nail called nail rootChanges in nail signal changes in health status & occur in chronic diseaseColor, thickness, shape & texture

Functions of the Skin

Four major functionsProtection against infectionProtection against dehydrationRegulation of body temperatureCollection of sensory information

Protection Against Infection

Intact skin is primary barrier against infectionMain defense against pathogens

Constant shedding of surface cells --mechanical removal of pathogensProtects body from harmful chemicals & toxins in environmentNon intact skin invites infection of deeper tissues

Protection Against Dehydration

Preventing water loss maintains the wet environment needed by all cellsKeratin & sebum act as lubricants for skin Waterproof & prevent fluid loss by

evaporation

Regulation of Body TemperatureAllows loss of excess heat & protects from cold environment (thermoregulation)Skin blood supply size changes are involved in temperature regulationBlood vessels dilate (widen) for heat to

dissipate & coolConstrict (narrow) to diminish heat loss in cold

conditionsPerspiration from sweat (eccrine) glands cools

Collection of Sensory Information

Free nerve endings & special receptors for touch, pain, pressure & temperature are located in dermisSkin is chief sensory organ of bodySkin sensory reflexes work with brain & spinal cord for adjustment to the environment

Collection of Sensory InformationFree nerve endings & special receptors for touch, pain, pressure & temperature are located in dermisSkin is chief sensory organ of bodySkin sensory reflexes work with brain & spinal cord for adjustment to the environment

Other Activities of Skin

Absorption of medications -- topical creams & patches & subcutaneous injectionsExcretion of water & electrolyte salts in perspiration & nitrogen-containing wastesManufacture of Vitamin D from ultra-violet sunlight rays No breathing or gas exchange occurs

Observation of the Skin

Color, texture & condition should be observedAmount of pigment melanin in epidermis, hair & iris of eyeSurface blood supply quantity & compositionOxygen, hemoglobin, presence of bile or

other chemicals Melanin protects from sun damage

Effects of Aging

Skin changes occur from loss of collagen & fat in tissues, becomes thinner & loses elasticityPigments with age in skin & hairMore sensitivity to cold due to fat & poor circulationHair & skin dry from lack of sebumNails become brittle, flake, thicken or discolor

Care of the Skin

Ensure good general health & prevent diseaseProper nutritionAdequate circulationRegular cleansing & good hand washing

Protection from sunlight exposureSunscreens and sunblockProtective clothing & hats