11

Accessory Structures of SkinAccessory Structures of Skin

Epidermal derivativesEpidermal derivatives

Cells sink inward Cells sink inward during development to during development to form:form:– hairhair– oil glandsoil glands– sweat glandssweat glands– nailsnails

Fig. 5.1

22

ShaftShaft -- visible -- visible– medulla, cortex & medulla, cortex &

cuticlecuticle– straight hair straight hair X- X-

sec round sec round – wavy hair wavy hair X-sec X-sec

oval oval – curly hair curly hair x-sec x-sec

kidney shapedkidney shaped

RootRoot -- below the -- below the surfacesurface

FollicleFollicle surrounds root surrounds root– external root external root

sheathsheath– internal root sheathinternal root sheath– base of follicle is base of follicle is

bulbbulbblood vesselsblood vesselsgerminal cell germinal cell layerlayerFig. 5.5

Structure & Fxn. of HairStructure & Fxn. of Hair

33

Hair GrowthHair Growth

Growth cycle = growth Growth cycle = growth stage & resting stagestage & resting stage

Growth stage Growth stage – lasts 2 - 6 yrs.lasts 2 - 6 yrs.– matrix cells @ base of matrix cells @ base of

hair root produce hair root produce lengthlength

Resting stageResting stage– lasts 3 mths.lasts 3 mths.– matrix cells inactive & matrix cells inactive &

follicle atrophiesfollicle atrophies

Old hair falls out as growth Old hair falls out as growth stage begins againstage begins again– normal hair loss = 70 - normal hair loss = 70 -

100 hairs/day100 hairs/day

44

Hair Related StructuresHair Related Structures

Arrector pili Arrector pili musclemuscle– smooth smooth

muscle in muscle in dermis dermis contracts w/ contracts w/ cold or fear.cold or fear.

– forms forms goosebumps goosebumps as hair is as hair is pulled pulled verticallyvertically

Hair root plexusHair root plexus– detect hair detect hair

movementmovement

Fig. 5.5

55

Glands of the SkinGlands of the SkinSpecialized exocrine Specialized exocrine glands found in glands found in dermisdermis

Sebaceous (oil)Sebaceous (oil)

Sudiferous (sweat)Sudiferous (sweat)

Ceruminous (wax)Ceruminous (wax)

Mammary (milk)Mammary (milk)

Fig. 5.1

66

Sebaceous (oil) glandsSebaceous (oil) glandsSebumSebum– Comb. of Comb. of

cholesterol, cholesterol, proteins, fats & proteins, fats & saltssalts

– keeps hair & skin keeps hair & skin soft & pliablesoft & pliable

– inhibits growth of inhibits growth of bacteria & fungi bacteria & fungi (ringworm)(ringworm)

AcneAcne– bacterial bacterial

inflammation of inflammation of glandsglands

– secretions secretions stimulated by stimulated by hormones @ hormones @ pubertypuberty

Secretory portion in the Secretory portion in the dermisdermis

Most open onto hair shafts Most open onto hair shafts

Fig. 5.6

77

Sudoriferous (sweat) glandsSudoriferous (sweat) glandsEccrine (sweat) Eccrine (sweat) glandsglands– most areas of most areas of

skinskin– secretory secretory

portion in dermis portion in dermis with duct to with duct to surfacesurface

– regulate body regulate body temperaturetemperature

– HH22O, NaCl, urea, O, NaCl, urea,

uric acid, A.A., uric acid, A.A., glucose, & lactic glucose, & lactic acid acid Apocrine (sweat) glandsApocrine (sweat) glands

– Armpit & pubic regionsArmpit & pubic regions– Also around areolae & bearded regions of adult malesAlso around areolae & bearded regions of adult males– Secretory portion in dermis w/ duct that opens onto hair follicleSecretory portion in dermis w/ duct that opens onto hair follicle– Secretions more viscous & milky (lipids & protein)Secretions more viscous & milky (lipids & protein)

Fig. 5.6

88

Ceruminous glandsCeruminous glands

Modified sweat glands produce Modified sweat glands produce waxy secretion in ear canalwaxy secretion in ear canal

Cerumin contains secretions of Cerumin contains secretions of oil & wax glandsoil & wax glands

Helps form barrier for entrance Helps form barrier for entrance of foreign bodiesof foreign bodies

Impacted cerumen may reduce Impacted cerumen may reduce hearinghearing

Fig. 22.10

99

Structure of NailsStructure of Nails

Nail rootNail root– buried under skin layersburied under skin layers– lunula is white due to lunula is white due to

thickened stratum basalethickened stratum basaleEponychium (cuticle)Eponychium (cuticle)– stratum corneum layerstratum corneum layer

Tightly packed keratinized cellsTightly packed keratinized cells

Nail bodyNail body– visible portion pink due to visible portion pink due to

underlying capillariesunderlying capillaries– free edge appears whitefree edge appears white

Fig. 5.7

1010

Thin Skin vs. Thick SkinThin Skin vs. Thick Skin

Thick skinThick skin

– only on palms and solesonly on palms and soles

– thick epidermis (.6 to 4.5 thick epidermis (.6 to 4.5 mm.) with distinct mm.) with distinct stratum lucidum & thick stratum lucidum & thick stratum corneumstratum corneum

– lacks hair follicles and lacks hair follicles and sebaceous glandssebaceous glands

1111

Thin Skin vs. Thick SkinThin Skin vs. Thick Skin

Thin skinThin skin

– covers most of bodycovers most of body

– thin epidermis (.1 to .15 mm.) thin epidermis (.1 to .15 mm.) that lacks stratum lucidumthat lacks stratum lucidum

– lacks epidermal ridges, has lacks epidermal ridges, has fewer sweat glands & sensory fewer sweat glands & sensory receptorsreceptors

1212

PhotodamagePhotodamageUVA & UVB light can UVA & UVB light can damage skindamage skin

Acute overexposure Acute overexposure causes sunburncauses sunburn

UVA produces UVA produces oxygen free radicals oxygen free radicals that damage collagen that damage collagen & elastic fibers & elastic fibers leads to wrinklingleads to wrinkling

DNA damage in DNA damage in epidermal cells can epidermal cells can lead to skin cancerlead to skin cancer

1313

Skin CancerSkin Cancer

1 million cases diagnosed per 1 million cases diagnosed per yearyear

3 common forms of skin 3 common forms of skin cancercancer– basal cell carcinoma basal cell carcinoma

(rarely metastasize)(rarely metastasize)– squamous cell carcinoma squamous cell carcinoma

(may metastasize)(may metastasize)– malignant melanomas malignant melanomas

(metastasize rapidly) (metastasize rapidly) most common cancer in most common cancer in young womenyoung womenarise from melanocytes arise from melanocytes ----life threatening----life threateningkey to treatment is early key to treatment is early detection watch for detection watch for changes in symmetry, changes in symmetry, border, color and sizeborder, color and sizerisks factors include-- risks factors include-- skin color, sun skin color, sun exposure, family exposure, family history, age & history, age & immunological statusimmunological status

1414

Epidermal Wound HealingEpidermal Wound Healing

Abrasion or minor burnAbrasion or minor burn

Basal cells migrate across the woundBasal cells migrate across the wound

Contact inhibition w/ other cells stops migrationContact inhibition w/ other cells stops migration

Epidermal growth factor stimulates cell division Epidermal growth factor stimulates cell division

Full thickness of epidermis results from further cell divisionFull thickness of epidermis results from further cell division

1515

Deep Wound HealingDeep Wound Healing

Which phases have been left out of this illustration?

4 phases:4 phases:– InflammatoryInflammatory– MigratoryMigratory– ProliferativeProliferative– MaturationMaturation

Scar formationScar formation– HypertrophicHypertrophic– KeloidKeloid

1616

BurnsBurnsTypes of burns:Types of burns:– 11stst

– 22ndnd

– 33rdrd

Problems that resultProblems that result– shock due to water, plasma & plasma shock due to water, plasma & plasma

protein lossprotein loss– circulatory & kidney problems from circulatory & kidney problems from

loss of plasmaloss of plasma– bacterial infectionbacterial infection

Destruction of Destruction of proteins of the skinproteins of the skin– chemicals, chemicals,

electricity, heatelectricity, heat

1717

Skin GraftsSkin GraftsNew skin can not regenerate if New skin can not regenerate if stratum basale and its stem cells stratum basale and its stem cells are destroyedare destroyed

Skin graft is covering of wound Skin graft is covering of wound with piece of healthy skinwith piece of healthy skin

To ensure no tissue rejection To ensure no tissue rejection occurs transplantations are:occurs transplantations are:

– Autografts (from self)Autografts (from self)

– Isografts (from twin)Isografts (from twin)

– Autologous skin usedAutologous skin used

transplantation of patients transplantation of patients skin grown in cultureskin grown in culture

Serial documentation of healing skin graftsfollowing burns in an 18 month old child.Photographer: Gigi William's                        

http://www.nlm.nih.gov/medlineplus/ency/article/002982.htm for more info.

1818

Pressure SoresPressure Sores

Decubitus ulcersDecubitus ulcers

Caused by constant deficiency Caused by constant deficiency of blood flow to tissueof blood flow to tissue

Areas affected is skin over Areas affected is skin over bony prominence in bedridden bony prominence in bedridden patientspatients

Preventable w/ proper carePreventable w/ proper care