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The Integumentary SystemThe Integumentary System

Functions of the skin and subcutaneous tissueFunctions of the skin and subcutaneous tissue epidermis and dermisepidermis and dermis hypodermishypodermis thick and thin skinthick and thin skin skin colorskin color skin markingsskin markings

Hair and nailsHair and nails Cutaneous glandsCutaneous glands Skin disordersSkin disorders

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OverviewOverview

Largest organ (15% of body weight)Largest organ (15% of body weight) EpidermisEpidermis

keratinized stratified squamous epitheliumkeratinized stratified squamous epithelium DermisDermis

connective tissue layerconnective tissue layer HypodermisHypodermis Thickness variable, normally 1-2 mmThickness variable, normally 1-2 mm

dermis may thicken, up to 6 mmdermis may thicken, up to 6 mm stratum corneum layer increasedstratum corneum layer increased

• calluses on hands and feetcalluses on hands and feet

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Structure of the SkinStructure of the Skin

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Functions of the SkinFunctions of the Skin Resistance to trauma and infectionResistance to trauma and infection

packed with keratin and linked by desmosomespacked with keratin and linked by desmosomes acid mantle (pH 4-6)acid mantle (pH 4-6)

Barrier to ultraviolet lightBarrier to ultraviolet light Vitamin D synthesisVitamin D synthesis Sensory receptorsSensory receptors Thermoreceptors through sweatingThermoreceptors through sweating Nonverbal communicationNonverbal communication

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Cells of the EpidermisCells of the Epidermis

Stem cellsStem cells undifferentiated cells in deepest layersundifferentiated cells in deepest layers

Keratinocytes – most of the skin cellsKeratinocytes – most of the skin cells MelanocytesMelanocytes

synthesize pigment that shield UVsynthesize pigment that shield UV Tactile (merkel) cellsTactile (merkel) cells

receptor cells associated with nerve fibersreceptor cells associated with nerve fibers Dendritic (langerhans) cellsDendritic (langerhans) cells

macrophages guard against pathogensmacrophages guard against pathogens

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Cell and Layers of the EpidermisCell and Layers of the Epidermis

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Stratum BasaleStratum Basale

Single layer cells on basement membraneSingle layer cells on basement membrane Cell types in this layerCell types in this layer

keratinocyteskeratinocytes• undergo mitosis to replace epidermisundergo mitosis to replace epidermis

melanocytes melanocytes • distribute melanin through cell processesdistribute melanin through cell processes• melanin picked up by keratinocytes melanin picked up by keratinocytes

merkel cells are touch receptors merkel cells are touch receptors • form Merkel discform Merkel disc

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Stratum SpinosumStratum Spinosum

Several layers of keratinocytesSeveral layers of keratinocytes appear spiny due to shrinkageappear spiny due to shrinkage

during histological preparationduring histological preparation Contains dendritic (Langerhans)Contains dendritic (Langerhans)

cellscells macrophages from bone marrowmacrophages from bone marrow

that migrate to the epidermisthat migrate to the epidermis help protect body against pathogens by help protect body against pathogens by

“presenting” them to the immune system“presenting” them to the immune system

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Stratum GranulosumStratum Granulosum

3 to 5 layers Flat keratinocytes3 to 5 layers Flat keratinocytes Contain keratinohyalin granulesContain keratinohyalin granules

combine with filaments of cytoskeleton combine with filaments of cytoskeleton to form keratinto form keratin

Produces lipid-filled vesicles thatProduces lipid-filled vesicles thatrelease a glycolipid by exocytosisrelease a glycolipid by exocytosisto waterproof the skinto waterproof the skin forms a barrier between surface cellsforms a barrier between surface cells

and deeper layers of the epidermisand deeper layers of the epidermis cuts off surface strata from nutrient supplycuts off surface strata from nutrient supply

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Stratum LucidumStratum Lucidum

Thin translucent zone seen only in thick skinThin translucent zone seen only in thick skin Keratinocytes are packed with eleidin, a Keratinocytes are packed with eleidin, a

precursor to keratinprecursor to keratin does not stain welldoes not stain well

Cells have no nucleus or organellesCells have no nucleus or organelles

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Stratum CorneumStratum Corneum

Up to 30 layers of dead, scaly,Up to 30 layers of dead, scaly,keratinized cellskeratinized cells surface cells flake off (exfoliate)surface cells flake off (exfoliate)

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Life History of KeratinocytesLife History of Keratinocytes

Produced by stem cells in stratum basaleProduced by stem cells in stratum basale New cells push others toward surfaceNew cells push others toward surface

cells grow flat and fill with vesiclescells grow flat and fill with vesicles Cells filled with keratin Cells filled with keratin

forms water barrierforms water barrier Cells die and exfoliateCells die and exfoliate

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DermisDermis

CompositionComposition collagen, elastic and reticular fibers, fibroblastscollagen, elastic and reticular fibers, fibroblasts

Dermal papillae - extensions of the dermis Dermal papillae - extensions of the dermis into the epidermisinto the epidermis forming the ridges of the fingerprintsforming the ridges of the fingerprints

LayersLayers papillary layerpapillary layer reticular layer is deeper part of dermisreticular layer is deeper part of dermis

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HypodermisHypodermis

Subcutaneous tissue/ superficial Subcutaneous tissue/ superficial fasciafascia

Mostly adiposeMostly adipose FunctionsFunctions

energy reservoirenergy reservoir thermal insulationthermal insulation

Hypodermic injections (subQ)Hypodermic injections (subQ) highly vascular highly vascular

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Skin Colors (Pigmentation)Skin Colors (Pigmentation)

Hemoglobin = red pigment of red blood cellsHemoglobin = red pigment of red blood cells Carotene = yellow pigment Carotene = yellow pigment

concentrates in stratum corneum and fatconcentrates in stratum corneum and fat Melanin = yellow, brown, and black hues Melanin = yellow, brown, and black hues

pigment synthesis stimulated by UV radiationpigment synthesis stimulated by UV radiation

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Abnormal Skin Colors 1Abnormal Skin Colors 1

Cyanosis = blueness from deficiency of Cyanosis = blueness from deficiency of oxygen in the circulating blood (cold oxygen in the circulating blood (cold weather)weather)

Erythema = redness due to dilated Erythema = redness due to dilated cutaneous vessels (anger, sunburn, cutaneous vessels (anger, sunburn, embarrassment)embarrassment)

Jaundice = yellowing of skin and sclera due Jaundice = yellowing of skin and sclera due to excess of bilirubin in blood (liver disease)to excess of bilirubin in blood (liver disease)

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Abnormal Skin Colors 2Abnormal Skin Colors 2

Bronzing = golden-brown color of Addison Bronzing = golden-brown color of Addison disease (deficiency of glucocorticoid disease (deficiency of glucocorticoid hormone)hormone)

Pallor = pale color from lack of blood flowPallor = pale color from lack of blood flow Albinism = a genetic lack of melaninAlbinism = a genetic lack of melanin Hematoma = a bruise (visible clotted Hematoma = a bruise (visible clotted

blood)blood)

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Skin MarkingsSkin Markings Hemangiomas (birthmarks)Hemangiomas (birthmarks)

discolored skin caused by benign tumors of dermal blood discolored skin caused by benign tumors of dermal blood capillaries (strawberry birthmarks disappear in childhood -- capillaries (strawberry birthmarks disappear in childhood -- port wine birthmarks last for life)port wine birthmarks last for life)

Freckles and moles = aggregations of melanocytesFreckles and moles = aggregations of melanocytes freckles are flat; moles are elevatedfreckles are flat; moles are elevated

Friction ridges leave oily fingerprints on touched Friction ridges leave oily fingerprints on touched surfacessurfaces unique pattern formed during fetal developmentunique pattern formed during fetal development

Flexion creases form after birth by repeated closing Flexion creases form after birth by repeated closing of the handof the hand

Flexion lines form in wrist and elbow areasFlexion lines form in wrist and elbow areas

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Characteristics of Human HairCharacteristics of Human Hair Hair (composed of hard keratin)Hair (composed of hard keratin)

disulfide bridges between moleculesdisulfide bridges between molecules Hair found almost everywhereHair found almost everywhere

differences between sexes or individuals is differences between sexes or individuals is difference in texture and color of hairdifference in texture and color of hair

3 different body hair types3 different body hair types lanugo -- fine, unpigmented fetal hairlanugo -- fine, unpigmented fetal hair vellus -- fine, unpigmented hair of children and vellus -- fine, unpigmented hair of children and

womenwomen terminal hair -- coarse, long, pigmented hair of terminal hair -- coarse, long, pigmented hair of

scalpscalp

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Structure of Hair and FollicleStructure of Hair and Follicle Hair is filament of keratinized cellsHair is filament of keratinized cells

shaft = above skin; root = within follicleshaft = above skin; root = within follicle in cross section: medulla, cortex and cuticle in cross section: medulla, cortex and cuticle

Follicle is oblique tube within the skinFollicle is oblique tube within the skin bulb is where hair originatesbulb is where hair originates vascular tissue (papilla) in bulb provides nutrientsvascular tissue (papilla) in bulb provides nutrients

Texture and shape of hairTexture and shape of hair straight hair = round, wavy = oval straight hair = round, wavy = oval

Hair color = pigment in cells of cortexHair color = pigment in cells of cortex

2121Eumelanin pigment colors brown and black hair.

Hair Color and Texture, Hair Color and Texture, BrunetteBrunette

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Blond hair contain pheomelanin pigment, but little eumelanin.

Hair Color and Texture, BlondeHair Color and Texture, Blonde

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Red hair contains little eumelanin but lots of pheomelanin.

Hair Color and Texture, RedHair Color and Texture, Red

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White hair = air in medulla and lack of pigment in cortex. Gray hair is a mixture of white and pigmented hairs.

Hair Color and Texture, Gray and Hair Color and Texture, Gray and WhiteWhite

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Structure of Hair FollicleStructure of Hair Follicle

Epithelial root sheathEpithelial root sheath Connective tissue Connective tissue

root sheathroot sheath Hair receptors Hair receptors

entwine each follicleentwine each follicle Piloerector musclePiloerector muscle

goose bumpsgoose bumps

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Hair Growth and LossHair Growth and Loss Hair cycle = 3 repeating cyclesHair cycle = 3 repeating cycles

anagen is growth stage (90% of scalp follicles)anagen is growth stage (90% of scalp follicles)• lasts 6-8 years in young adult lasts 6-8 years in young adult

catagen is shrinking follicle (lasts 2-3 weeks)catagen is shrinking follicle (lasts 2-3 weeks) telogen is resting stage (lasts 1-3 months)telogen is resting stage (lasts 1-3 months)

Thinning or baldness = alopeciaThinning or baldness = alopecia Pattern baldness = genetic and hormonalPattern baldness = genetic and hormonal

sex-influenced trait(dominant in males, recessive in sex-influenced trait(dominant in males, recessive in females); expressed only with high testosterone levelsfemales); expressed only with high testosterone levels

Hirsutism = excessive hair growthHirsutism = excessive hair growth hormone imbalance (ovary or adrenal cortex problem)hormone imbalance (ovary or adrenal cortex problem)

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Functions of HairFunctions of Hair Body hair (too thin to provide warmth)Body hair (too thin to provide warmth)

alert us to parasites crawling on skinalert us to parasites crawling on skin Scalp hair Scalp hair

heat retention and sunburn coverheat retention and sunburn cover Beard, pubic and axillary hair indicate sexual Beard, pubic and axillary hair indicate sexual

maturity and help distribute sexual scentsmaturity and help distribute sexual scents Guard hairs and eyelashes Guard hairs and eyelashes

prevent foreign objects from getting into nostrils, prevent foreign objects from getting into nostrils, ear canals or eyesear canals or eyes

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Fingernail StructureFingernail Structure

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NailsNails

Derivative of stratum corneumDerivative of stratum corneum densely packed cells filled with hard keratindensely packed cells filled with hard keratin

Flat nails allow for fleshy, sensitive fingertipsFlat nails allow for fleshy, sensitive fingertips Growth rate is 1 mm per weekGrowth rate is 1 mm per week

new cells added by mitosis in the nail matrixnew cells added by mitosis in the nail matrix nail plate is visible part of nailnail plate is visible part of nail

• medical diagnosis of iron deficiency = concave nailsmedical diagnosis of iron deficiency = concave nails

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Cutaneous GlandsCutaneous Glands

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Sweat GlandsSweat Glands

Filtrate of plasma and some waste productsFiltrate of plasma and some waste products 500 ml of insensible perspiration/day500 ml of insensible perspiration/day sweating with visible wetness is diaphoresis sweating with visible wetness is diaphoresis

Merocrine glands is simple tubular gland Merocrine glands is simple tubular gland millions of them help cool the bodymillions of them help cool the body

Apocrine glands produce sweat containing fatty Apocrine glands produce sweat containing fatty acidsacids found only near hair follicles and respond to stress and found only near hair follicles and respond to stress and

sexsex bromhidrosis is body odor produced by bacterial action bromhidrosis is body odor produced by bacterial action

on fatty acidson fatty acids

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Sebaceous GlandsSebaceous Glands

Oily secretion called sebum that contains Oily secretion called sebum that contains broken-down cellsbroken-down cells lanolin in skin creams is sheep sebumlanolin in skin creams is sheep sebum

Flask-shaped gland with duct that opens into hair Flask-shaped gland with duct that opens into hair folliclefollicle

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Ceruminous GlandsCeruminous Glands

Found only in external ear canalFound only in external ear canal Their secretion combines with sebum to Their secretion combines with sebum to

produce earwaxproduce earwax waterproof keeps eardrum flexiblewaterproof keeps eardrum flexible bitterness repel mites and other pestsbitterness repel mites and other pests

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Mammary GlandsMammary Glands Breasts of both sexes rarely contain glandsBreasts of both sexes rarely contain glands

secondary sexual characteristic of femalessecondary sexual characteristic of females• found only during lactation and pregnancyfound only during lactation and pregnancy

modified apocrine sweat glandmodified apocrine sweat gland thicker secretion released by ducts open on the nipplethicker secretion released by ducts open on the nipple

Mammary ridges or milk linesMammary ridges or milk lines 2 rows of mammary glands in most mammals2 rows of mammary glands in most mammals primates kept only anteriormost glandsprimates kept only anteriormost glands

Additional nipples (polythelia) Additional nipples (polythelia) may develop along milk linemay develop along milk line

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BurnsBurns Hot water, sunlight, radiation, electric shock or Hot water, sunlight, radiation, electric shock or

acids and basesacids and bases Death from fluid loss and infectionDeath from fluid loss and infection Degrees of burnsDegrees of burns

1st-degree = only the epidermis (red, painful and edema)1st-degree = only the epidermis (red, painful and edema) 2nd-degree = epidermis and part of dermis (blistered)2nd-degree = epidermis and part of dermis (blistered)

• epidermis regenerates from hair follicles and sweat glandsepidermis regenerates from hair follicles and sweat glands 3rd-degree = epidermis, dermis and more is destroyed3rd-degree = epidermis, dermis and more is destroyed

• often requires grafts or fibrosis and disfigurement may occuroften requires grafts or fibrosis and disfigurement may occur Treatment – IV nutrition and fluid replacement, Treatment – IV nutrition and fluid replacement,

debridement and infection controldebridement and infection control