Biology 141Biology 141

Integumentary SystemIntegumentary System

Chapter 5Chapter 5

The IntegumentThe Integument IntegumentIntegument: Skin – largest body organ: Skin – largest body organ Integumentary System:Integumentary System:

– SkinSkin– HairHair– NailsNails

Function:Function:– ProtectionProtection– Maintain body temperatureMaintain body temperature– Provide sensory inputProvide sensory input

Dermatology: medical specialty dealing with the Dermatology: medical specialty dealing with the integumentary systemintegumentary system

Structure of the SkinStructure of the Skin

Cutaneous membrane: skinCutaneous membrane: skin– Epidermis – superficial layerEpidermis – superficial layer– Dermis – deep layerDermis – deep layer

Subcutaneous membraneSubcutaneous membrane– Hypodermis – fat layer; not technically a Hypodermis – fat layer; not technically a

part of the skin.part of the skin.

Structure of the SkinStructure of the Skin

The 2 layers of The 2 layers of skin; skin; – epidermis epidermis

Multilayered Multilayered epithelial tissueepithelial tissue

thinner thinner

– DermisDermisConnective tissueConnective tissuethickerthicker

EpidermisEpidermis

Cell types found in the epidermis:Cell types found in the epidermis:– Keratinocytes:Keratinocytes:

multilayeredmultilayered Produce keratin protein (tough, water repellant)Produce keratin protein (tough, water repellant)

– MelanocytesMelanocytes Produces pigment melanin to protect nuclear DNA in Produces pigment melanin to protect nuclear DNA in

keratinocyteskeratinocytes

– Langerhans cellLangerhans cell Immune responseImmune response

– Merkel cellsMerkel cells Contact Merkle discs to detect sensationsContact Merkle discs to detect sensations

EpidermisEpidermis

Tissue Layers Tissue Layers

Composed of different strata (layers)Composed of different strata (layers)– outermost - dead cells outermost - dead cells – Innermost - Cells divideInnermost - Cells divide

Cells die as they are pushed upward Cells die as they are pushed upward Layers originate from the deepest Layers originate from the deepest

cell layer of columnar cells called the cell layer of columnar cells called the stratum germinativumstratum germinativum..

Sublayers of the Sublayers of the Stratum Stratum germinativumgerminativum

Stratum basale ("base layer") Stratum basale ("base layer") – Cells of stratum basale are closest to the blood supply in Cells of stratum basale are closest to the blood supply in

the dermis and are thus the healthiest  the dermis and are thus the healthiest  – Only these cells can reproduceOnly these cells can reproduce

Stratum spinosum ("spiny layer") Stratum spinosum ("spiny layer") – Cells are pushed from below and become "squished" Cells are pushed from below and become "squished"

and look "spiny" on cross sectional view and look "spiny" on cross sectional view – Because the cells are farther away from the dermal Because the cells are farther away from the dermal

blood supply, they are less healthy and thus don't blood supply, they are less healthy and thus don't reproduce reproduce

Basal Cell CarcinomaBasal Cell Carcinoma Low magnification (left) of skin cross-section of shows Low magnification (left) of skin cross-section of shows

different layers (epidermis, dermis and subcutaneous different layers (epidermis, dermis and subcutaneous tissue), and tissue), and

areas of tumor invasion.  areas of tumor invasion.  Higher magnification (right): tumor cells resemble those in Higher magnification (right): tumor cells resemble those in

the normal basal cell layer of the epidermis.  the normal basal cell layer of the epidermis.  Tumor cells appear to bud off from the epidermis and grow Tumor cells appear to bud off from the epidermis and grow

downward as islands and cords of basophilic cells with downward as islands and cords of basophilic cells with hyperchromatic nuclei. hyperchromatic nuclei. 

Epidermis Tissue Layers Epidermis Tissue Layers (deep to superficial)(deep to superficial)  

Stratum germinativum ("growth layer")Stratum germinativum ("growth layer")– stratum basal – germination basement layerstratum basal – germination basement layer– Stratum spinosum – “thorn-like”Stratum spinosum – “thorn-like”

Stratum granulosum "grainy layer" Stratum granulosum "grainy layer"

Stratum lucidum "clear layer" Stratum lucidum "clear layer"

Stratum corneum “horny layer” (top layer)Stratum corneum “horny layer” (top layer)

Epidermis: Tissue LayersEpidermis: Tissue Layers

stratum basal: stratum basal: – Single row of cuboidal or columnar Single row of cuboidal or columnar

keratinocytes.keratinocytes.– Some are stem cellsSome are stem cells– ContainsContains

MelanocytesMelanocytesLangerhans cellsLangerhans cellsMerkle cells and discsMerkle cells and discs

Epidermis: Tissue LayersEpidermis: Tissue Layers

stratum basal –stratum basal –– Damage to this layer damages stem Damage to this layer damages stem

cellscellsUnable to regenerate skinUnable to regenerate skinRequire skin graftsRequire skin graftsGrafts can be autologous (same individual) Grafts can be autologous (same individual)

or transplanted from a donor.or transplanted from a donor.– Skin sheets can also be grown in the lab Skin sheets can also be grown in the lab

Epidermis: Tissue LayersEpidermis: Tissue Layers

stratum spinosum stratum spinosum – multilayered keratinocytesmultilayered keratinocytes– Few Langerhans cells and MelanocytesFew Langerhans cells and Melanocytes

Epidermis: Tissue LayersEpidermis: Tissue Layers

stratum granulosumstratum granulosum– Multilayered, flattened keratinocytesMultilayered, flattened keratinocytes– Cells undergoing apoptosisCells undergoing apoptosis– Secretes water repellantSecretes water repellant– cells loose nuclei, appear grainy cells loose nuclei, appear grainy – Keratohyalin (a precursor to keratin) Keratohyalin (a precursor to keratin)

forms in granules here forms in granules here

Epidermis: Tissue LayersEpidermis: Tissue Layers stratum lucidum: stratum lucidum:

– Multilayered, dead Multilayered, dead keratinocyteskeratinocytes

with large amount of with large amount of keratin keratin

– Translucent and Translucent and flattened flattened

– Found only in thick skin Found only in thick skin (hairless)(hairless)

FingertipsFingertips PalmsPalms solessoles

Epidermis: Tissue LayersEpidermis: Tissue Layers

stratum corneum: stratum corneum: – MultilayeredMultilayered– Flat, dead keratinocytesFlat, dead keratinocytes– primarily keratin proteinprimarily keratin protein– "horny layer" - cells have processes "horny layer" - cells have processes – Flattened cells filled with keratin form Flattened cells filled with keratin form

"keratinized layer" and make this "keratinized "keratinized layer" and make this "keratinized stratified squamous epithelium"stratified squamous epithelium"

– Constant friction results in callus formationConstant friction results in callus formation

DermisDermis

DermisDermis: : – Connective tissueConnective tissue– ContainsContains

Blood vesselsBlood vesselsNervesNervesGlandsGlandsHair folliclesHair follicles

DermisDermis

2 main regions: 2 main regions:

Papillary: upper layerPapillary: upper layer

Reticular: deep layerReticular: deep layer

DermisDermis

PapillaryPapillary: upper layer: upper layer lies next to the epidermislies next to the epidermiscontains the derma papillae (projections into contains the derma papillae (projections into

the upper epidermis)the upper epidermis)– epidermal ridges creat fingerprints, palm prints epidermal ridges creat fingerprints, palm prints

and footprints.and footprints.– Contain capillariesContain capillaries– Contain Meisssner corpuscles (tactile receptors)Contain Meisssner corpuscles (tactile receptors)– Contain free nerve endingsContain free nerve endings

Senses temperature, pain, itch, tickleSenses temperature, pain, itch, tickle

DermisDermis

Reticular: deep layerReticular: deep layerAttaches to the subcutaneous layerAttaches to the subcutaneous layerDense irregular connective tissueDense irregular connective tissuecontains more collagen fibers contains more collagen fibers

– increasing the strength of the skin.increasing the strength of the skin.Contains:Contains:

– Few adipose cellsFew adipose cells– Hair folliclesHair follicles– Nerves and Pacinian corpuscles (deep pressure)Nerves and Pacinian corpuscles (deep pressure)– Sebaceous glands (oil)Sebaceous glands (oil)– Sudoriforous glands (sweat)Sudoriforous glands (sweat)

Accessory StructuresAccessory Structures

Receptors:Receptors: Meissner’s corpuscles Meissner’s corpuscles and Pacinian corpusclesand Pacinian corpuscles

Meissner’s: located in the papillary Meissner’s: located in the papillary layer of dermislayer of dermis– project into the papillae.project into the papillae.– touch receptorstouch receptors

Pacinian: spherical, onion-likePacinian: spherical, onion-like– Lie deep in the reticular layerLie deep in the reticular layer– pressurepressure

Sensory receptors in the DermisSensory receptors in the Dermis

Meissner’s Meissner’s Corpuscle detects Corpuscle detects light touchlight touch

Papillary layerPapillary layer

Pacinian Corpuscle Pacinian Corpuscle detects deep touch detects deep touch (pressure)(pressure)

Reticular layerReticular layer

DermisDermis

Tears in the reticular region of the Tears in the reticular region of the dermis result in stretch marks.dermis result in stretch marks.

Incisions against the grain of the Incisions against the grain of the collagen fibers = wide scarcollagen fibers = wide scar

Incisions with the grain = thin scarIncisions with the grain = thin scar

Structural Basis of Skin ColorStructural Basis of Skin Color Skin color pigments:Skin color pigments:

– MelaninMelanin– HemoglobinHemoglobin– CaroteneCarotene

Melanin – number of melanocytes the Melanin – number of melanocytes the same in all peoplesame in all people– Amount of melanin produced variesAmount of melanin produced varies– Accumulation results inAccumulation results in

Age spotsAge spots FrecklesFreckles molesmoles

MelaninMelanin

Function:Function:– Absorbs UV radiationAbsorbs UV radiation– Prevents damage to DNA in epidermal Prevents damage to DNA in epidermal

cellscells– Neutralizes free radicalsNeutralizes free radicals

HemoglobinHemoglobin

Found in RBCsFound in RBCs

Skin color depends Skin color depends on amount of on amount of oxygen in the oxygen in the blood blood – Blue – cyanotic: low Blue – cyanotic: low

oxygenoxygen– Yellow - jaundice: Yellow - jaundice:

high bilirubinhigh bilirubin Liver damageLiver damage

– Red – erythema: Red – erythema: engorgement of engorgement of capillariescapillaries

InjuryInjury HeatHeat InfectionInfection InflammationInflammation Allergic reactionAllergic reaction

– White – pallor: low White – pallor: low number of RBC number of RBC

ShockShock anemiaanemia

CaroteneCarotene

Yellow-orange pigment found in egg Yellow-orange pigment found in egg yolks and orange vegetablesyolks and orange vegetables– Precursor to vitamin APrecursor to vitamin A– Excessive dietary intake results in Excessive dietary intake results in

accumulation in the subcutaneous layeraccumulation in the subcutaneous layer

Albinism / VitiligoAlbinism / Vitiligo

Albinism: Inherited inability to Albinism: Inherited inability to synthesize melaninsynthesize melanin– Melanin is not produced in skin, hair, Melanin is not produced in skin, hair,

and eyes.and eyes.

Vitiligo: partial or complete loss of Vitiligo: partial or complete loss of melanocytes in patches of skinmelanocytes in patches of skin– Immune system attacks and destroys Immune system attacks and destroys

melanocytes.melanocytes.

Accessory StructuresAccessory Structures

Hair: piliHair: pili Columns of dead, keratinized cells - Columns of dead, keratinized cells -

compactly cemented together.compactly cemented together. hair shaft – portion of the hair that hair shaft – portion of the hair that

projects above the surface.projects above the surface. root – portion below the surface root – portion below the surface

extending into the dermis.extending into the dermis.

HairHair

Hair shaft and root consist of 3 Hair shaft and root consist of 3 concentric layers of cells:concentric layers of cells:– MedullaMedulla– CortexCortex– CuticleCuticle

Human HairHuman Hair Cuticle showing scalesCuticle showing scales No medulla, brown No medulla, brown

pigment granules in cortexpigment granules in cortex

Light medullaLight medulla

HairHair

Hair follicle: Hair follicle: composed of the composed of the root sheath – root sheath – encasement with 2 encasement with 2 layers:layers:– Internal root sheathInternal root sheath

produced by matrix, produced by matrix, surrounds rootsurrounds root

– External root External root sheathsheath

extension of extension of epidermisepidermis

The Dermal root The Dermal root sheath is part of the sheath is part of the dermisdermis

HairHair

bulb - enlarged bulb - enlarged region of the root region of the root containing the containing the follicular papilla follicular papilla (involution of (involution of loose connective loose connective tissue).tissue).

HairHair

arrector pili arrector pili muscle – smooth muscle – smooth muscle that muscle that upon upon contraction contraction forces the skin forces the skin into goose into goose bumps. bumps.

Accessory StructuresAccessory Structures

GlandsGlands: sebaceous and sweat glands: sebaceous and sweat glands

Sebaceous glandsSebaceous glands:: Usually connected to hair folliclesUsually connected to hair follicles secretes sebum (oil)secretes sebum (oil) Moisturizes hair and skinMoisturizes hair and skin

– keeps hair pliable.keeps hair pliable.– Keeps skin softKeeps skin soft– Inhibits bacteriaInhibits bacteria

Acne: Acne: Inflammation of a sebaceous gland.Inflammation of a sebaceous gland.

Blocked sebaceous glandBlocked sebaceous gland Normal sebaceous glandNormal sebaceous gland

Sudoriferous Glands Sudoriferous Glands (Sweat glands)(Sweat glands)

2 main types of glands: eccrine and apocrine2 main types of glands: eccrine and apocrine eccrine: eccrine:

– empty directly out through the skin surfaceempty directly out through the skin surface– tubular with a coiled basal portion located deep in the tubular with a coiled basal portion located deep in the

dermisdermis– Regulates body temperatureRegulates body temperature

apocrine: apocrine: – larger, empty directly into the hair follicle canallarger, empty directly into the hair follicle canal– secretory portion located in the subcutaneous layersecretory portion located in the subcutaneous layer– Excretory duct opens into hair follicleExcretory duct opens into hair follicle– stimuli: psychic factors; emotions, sexual excitementstimuli: psychic factors; emotions, sexual excitement

Sudoriferous GlandsSudoriferous Glands

Accessory structures and locationAccessory structures and location

Ceruminous GlandsCeruminous Glands

Modified sweat glands in the external Modified sweat glands in the external ear.ear.– Produce ear wax (cerumen)Produce ear wax (cerumen)– Provides a sticky barrierProvides a sticky barrier

NailsNails

Tightly packed, hard, keratinized epithelial Tightly packed, hard, keratinized epithelial cells.cells.

Structure:Structure:– Nail body: visible portionNail body: visible portion

Pink due to capillary bedPink due to capillary bed

– Free edge: part that extends past the digitFree edge: part that extends past the digit White due to lack of capillariesWhite due to lack of capillaries

– Nail root: portion buried in a fold of skinNail root: portion buried in a fold of skin

NailsNails

Types of SkinTypes of Skin

2 types of skin based on structure:2 types of skin based on structure:– Thin (hairy) skinThin (hairy) skin– Thick (hairless skin)Thick (hairless skin)

Functions of the SkinFunctions of the Skin Thermoregulation: Thermoregulation:

– by sweat and blood flowby sweat and blood flow Blood reservoirBlood reservoir

– 8-10% of blood flow8-10% of blood flow ProtectionProtection

– Against external assaultAgainst external assault Cutaneous sensationsCutaneous sensations

– Tactile, pressure, pain, Tactile, pressure, pain, temperature, tickletemperature, tickle

Excretion and absorptionExcretion and absorption– Excrete salts, water, and Excrete salts, water, and

small amounts of CO2 and small amounts of CO2 and ureaurea

– Absorbs lipid molecules Absorbs lipid molecules (vitamins A,D,E and K, (vitamins A,D,E and K, drugs, lotions, poisons, drugs, lotions, poisons, heavy metals, steroids)heavy metals, steroids)

Synthesis of vitamin DSynthesis of vitamin D– UV light activates UV light activates

precursor molecules that precursor molecules that can be modified by the can be modified by the liver. Vit. D produces liver. Vit. D produces calcitrol which aids in the calcitrol which aids in the absorption of calcium in absorption of calcium in the GI tract.the GI tract.

Maintaining Homeostasis: Skin Maintaining Homeostasis: Skin Wound HealingWound Healing

Wound healing can occur via 2 Wound healing can occur via 2 routes:routes:– Epidermal Wound Healing – affects only Epidermal Wound Healing – affects only

the epidermis.the epidermis.

– Deep Wound Healing – wound extends Deep Wound Healing – wound extends to dermis and subcutaneous layersto dermis and subcutaneous layers

Epidermal Wound HealingEpidermal Wound Healing

Injury response:Injury response:– Basal cells detach from the basement Basal cells detach from the basement

membrane.membrane.– Hormone (epidermal growth factor) Hormone (epidermal growth factor)

stimulates basal stem cells to divide to stimulates basal stem cells to divide to replace migrating cells.replace migrating cells.

– Migrating cells move across woundMigrating cells move across wound– Cells stop migrating upon touching other Cells stop migrating upon touching other

cells (contact inhibition) cells (contact inhibition)

Deep Wound HealingDeep Wound Healing

4 phases:4 phases:– Inflammatory: Inflammatory:

clot formation closes the wound, WBC kill invadersclot formation closes the wound, WBC kill invaders

– Migratory:Migratory: scab formation, epithelial cells migrate, fibroblasts scab formation, epithelial cells migrate, fibroblasts

produce fibrin for scar tissueproduce fibrin for scar tissue

– Proliferative:Proliferative: Extensive growth of epithelial cells, depositing Extensive growth of epithelial cells, depositing

collagen fiberscollagen fibers

– Maturation:Maturation: Scab sloughs off, collagen fibers organizeScab sloughs off, collagen fibers organize

Development of the Integumentary Development of the Integumentary SystemSystem

Epidermis is derived from the Epidermis is derived from the ectodermectoderm

Dermis is derived from the Dermis is derived from the mesodermmesoderm

Aging and the Integumentary Aging and the Integumentary SystemSystem

Most changes occur in the dermisMost changes occur in the dermis– Collagen fibers decrease in numberCollagen fibers decrease in number– Elastic fibers loose elasticityElastic fibers loose elasticity– Fibroblast (produce collagen and elastin) Fibroblast (produce collagen and elastin)

decrease in numberdecrease in number– Decrease number of melanocytes – gray Decrease number of melanocytes – gray

hairhair– Subcutaneous adipose tissue is lostSubcutaneous adipose tissue is lost– Healing is longerHealing is longer

Sun DamageSun Damage

UV A rays:UV A rays:– Not absorbed by the ozone layerNot absorbed by the ozone layer– Penetrate deep into skin and absorbed by Penetrate deep into skin and absorbed by

melanocytesmelanocytes– Depress the immune systemDepress the immune system– Darken the skinDarken the skin

UV B rays:UV B rays:– Some absorbed by ozoneSome absorbed by ozone– Penetration of skin not as deepPenetration of skin not as deep– Cause sunburnCause sunburn

Sun DamageSun Damage

SunscreenSunscreen– Absorb UV B, but allow UV A rays to Absorb UV B, but allow UV A rays to

reach the skinreach the skin SunblockSunblock

– Block both UV A and UV B raysBlock both UV A and UV B rays

Skin CancerSkin Cancer Basal cell carcinomaBasal cell carcinoma

– 78% of all skin cancers78% of all skin cancers– Tumors arise from the stratum basaleTumors arise from the stratum basale– Rarely metastasizeRarely metastasize

Squamous cell carcinomaSquamous cell carcinoma– 20% of all skin cancers20% of all skin cancers– Arise from squamous cell of epidermisArise from squamous cell of epidermis– metastasizemetastasize

Malignant melanomaMalignant melanoma– 2% of all skin cancers2% of all skin cancers– Arise from melanocytesArise from melanocytes– Metastasize rapidly (can kill within months)Metastasize rapidly (can kill within months)

Skin CancerSkin Cancer Basal cell Basal cell

carcinomacarcinoma melanomamelanoma squamous cell squamous cell

carcinomacarcinoma

BurnsBurns

Burns are graded by severity:Burns are graded by severity:– First degree: only epidermis, redFirst degree: only epidermis, red– Second degree: all epidermis and part of Second degree: all epidermis and part of

dermis, blistersdermis, blisters– Third degree: all epidermis, dermis and Third degree: all epidermis, dermis and

subcutaneous layers, blacksubcutaneous layers, black– Fourth degree: muscle layers are burnedFourth degree: muscle layers are burned

BurnsBurns

Half of all patients with over 70% of Half of all patients with over 70% of the body burned, dies.the body burned, dies.

Estimating surface area for burns Estimating surface area for burns uses the rule of nines.uses the rule of nines.

BurnsBurns Head and neck (front and back)Head and neck (front and back)

– 9% 9% Each upper limb (front and back)Each upper limb (front and back)

– 9% 9% Trunk (front and back)Trunk (front and back)

– 4 x 9% (or 36%)4 x 9% (or 36%) Each lower limb Each lower limb

– 9% front9% front– 9% back9% back

Perineum (anal and urogenital region)Perineum (anal and urogenital region)– 1%1%

Pressure UlcersPressure Ulcers

Decubitus ulcers caused by constant Decubitus ulcers caused by constant deficiency of blood flow from deficiency of blood flow from prolonged pressure against an prolonged pressure against an object.object.

Occur most often in bedridden Occur most often in bedridden patients.patients.