mosby items and derived items © 2007, 2003 by mosby, inc.slide 1 chapter 6 skin and its appendages

Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 1

Chapter 6Chapter 6Skin and Its AppendagesSkin and Its Appendages

Mosby items and derived items © 2007, 2003 by Mosby, Inc.

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IntroductionIntroduction

• Skin (integument) - body’s largest organSkin (integument) - body’s largest organ

• Approximately 1.6 to 1.9 mApproximately 1.6 to 1.9 m22 in in average-sized adultaverage-sized adult

• Integumentary system -skin and its Integumentary system -skin and its appendages—the hair, nails, and appendages—the hair, nails, and skin glandsskin glands

Structure of the SkinStructure of the Skin

• Cutaneous membraneCutaneous membrane

• Two primary layers—epidermis and dermis; Two primary layers—epidermis and dermis; joined by dermal-epidermal junction joined by dermal-epidermal junction

• Hypodermis beneath dermisHypodermis beneath dermis


• Thin and thick skinThin and thick skin

““Thin skin”—covers most of body surface Thin skin”—covers most of body surface (1 to 3 mm thick)(1 to 3 mm thick)

““Thick skin”—soles and palms Thick skin”—soles and palms (4 to 5 mm thick)(4 to 5 mm thick)


• EpidermisEpidermis

Cell typesCell types

• KeratinocytesKeratinocytes

• MelanocytesMelanocytes

• Langerhans cellsLangerhans cells


Epidermis - made of 5 layers (strata) from inside Epidermis - made of 5 layers (strata) from inside out:out:

• Stratum germinativum (growth layer)—Made of Stratum germinativum (growth layer)—Made of stratum basale and stratum spinosumstratum basale and stratum spinosum

Stratum basale (base layer)—single layer of Stratum basale (base layer)—single layer of columnar cells - divide mitoticallycolumnar cells - divide mitotically

Stratum spinosum (spiny layer)—Stratum spinosum (spiny layer)—

– supportsupport


Epidermis layersEpidermis layers

• Stratum granulosumStratum granulosum

lysosomallysosomal

• Stratum lucidumStratum lucidum

cells filled with what will become keratincells filled with what will become keratin

• Stratum corneumStratum corneum

most superficial layer; most superficial layer;

dead cells filled with keratin (barrier area)dead cells filled with keratin (barrier area)

Epidermal growth and Epidermal growth and repairrepair

• regeneration time - every 35 days regeneration time - every 35 days

• -callus formation - formed when an -callus formation - formed when an area receives a lot of frictionarea receives a lot of friction

• - -mitosis - 10% of cells in stratum - -mitosis - 10% of cells in stratum basale enter mitosis on a daily basale enter mitosis on a daily basis.basis.


• Dermal-epidermal junctionDermal-epidermal junction

the epidermis glued to dermis belowthe epidermis glued to dermis below

partial barrierpartial barrier


• DermisDermis

““true skin”—thicker than epidermis true skin”—thicker than epidermis

Storage of water and electrolytesStorage of water and electrolytes

StructuresStructures

• Arrector pili muscles/hair folliclesArrector pili muscles/hair follicles

• Sensory receptorsSensory receptors

• Sweat/sebaceous glandsSweat/sebaceous glands

• Blood vesselsBlood vessels


• Dermis LayersDermis Layers

• Papillary layerPapillary layer

Composed of dermal papillae Composed of dermal papillae

Contains collagenous and elastic fibersContains collagenous and elastic fibers

Contains dermal-epidermal junction Contains dermal-epidermal junction

Forms fingerprintsForms fingerprints

• Reticular layerReticular layer

Contains collagenous fibers , elastic fibers - makes skin Contains collagenous fibers , elastic fibers - makes skin tough but stretchable. tough but stretchable.

DermisDermis

• Dermal growth and repairDermal growth and repair

• Dermis does not shed constantlyDermis does not shed constantly

• During wound healing fibroblasts form scarsDuring wound healing fibroblasts form scars

Hypodermis Hypodermis ((Subcutaneous layer)Subcutaneous layer)

Deep to the dermisDeep to the dermis

between the skin and other structuresbetween the skin and other structures

Not actually part of the skinNot actually part of the skin

Skin ColorSkin Color

• MelaninMelanin

Responsible for skin color - quantity, type, and Responsible for skin color - quantity, type, and distribution of melanindistribution of melanin

Produced by melanocytesProduced by melanocytes

Albinism—absence of melaninAlbinism—absence of melanin

Process regulated by Process regulated by enzymesenzymes, exposure to sunlight (UV , exposure to sunlight (UV radiation), certain hormones radiation), certain hormones

Skin ColorSkin Color

• Other pigmentsOther pigments

Beta carotene Beta carotene

HemoglobinHemoglobin

• Redder skin color when blood flow to skin increasesRedder skin color when blood flow to skin increases

• Cyanosis - bluish color caused by loss of oxygenCyanosis - bluish color caused by loss of oxygen

• Bruising - internal bleedingBruising - internal bleeding

Functions of the Skin Functions of the Skin

• Protection Protection Surface film Surface film

• Protective barrier -mixing of sweat and oil with epithelial Protective barrier -mixing of sweat and oil with epithelial cells from skin surfacecells from skin surface

Physical barrier to microorganismsPhysical barrier to microorganisms

Barrier to chemical hazardsBarrier to chemical hazards

Reduces potential for mechanical traumaReduces potential for mechanical trauma

Prevents dehydrationPrevents dehydration

Protects (via melanin) excess UV exposureProtects (via melanin) excess UV exposure

Functions of the SkinFunctions of the Skin

• SensationSensation

Somatic (skin) sensory receptors detect Somatic (skin) sensory receptors detect

• Pressure - Paccinian corpuscles Pressure - Paccinian corpuscles

• Touch - Meissner’s corpusclesTouch - Meissner’s corpuscles

• Temperature - Organs of Ruffini and Krause bulbsTemperature - Organs of Ruffini and Krause bulbs

• Pain - nerve endings.Pain - nerve endings.


• FlexibilityFlexibility

Skin is supple and elastic, thus permitting Skin is supple and elastic, thus permitting change in body contours without injurychange in body contours without injury

• ExcretionExcretion

WaterWater

Urea/ammonia/uricUrea/ammonia/uric acid acid


• Hormone (Vitamin D) production Hormone (Vitamin D) production

Exposure of skin to UV light converts Exposure of skin to UV light converts chemicals to chemicals to precursor to vitamin D precursor to vitamin D

Blood transports precursor to liver Blood transports precursor to liver and kidneys, where vitamin D is and kidneys, where vitamin D is producedproduced


• ImmunityImmunity

Phagocytic cells destroy bacteriaPhagocytic cells destroy bacteria

Langerhans cells trigger helpful immune Langerhans cells trigger helpful immune reaction working with “helper T cells”reaction working with “helper T cells”


• Homeostasis of body temperaturesHomeostasis of body temperatures

heat production must equal heat loss; skin plays heat production must equal heat loss; skin plays a critical role in this processa critical role in this process

Heat productionHeat production

• By metabolism of foods in skeletal muscles and liverBy metabolism of foods in skeletal muscles and liver

• Chief determinant of heat production is the amount of Chief determinant of heat production is the amount of muscular work being performedmuscular work being performed


Homeostatic regulation of heat lossHomeostatic regulation of heat loss

• negative feedback loopnegative feedback loop

• Receptors in the hypothalamus monitor the Receptors in the hypothalamus monitor the body’s internal temperaturebody’s internal temperature

• If the body temperature is increased, the If the body temperature is increased, the hypothalamus sends a nervous signal to the hypothalamus sends a nervous signal to the sweat glands and blood vessels of the skinsweat glands and blood vessels of the skin

• The hypothalamus continues to act until the The hypothalamus continues to act until the body’s temperature returns to normalbody’s temperature returns to normal

Appendages of the SkinAppendages of the Skin

• HairHair Development of hairDevelopment of hair

• DistributionDistribution

• lanugolanugo

• terminal hairterminal hair

Development of hairDevelopment of hair

• Hair follicles and hair develop from epidermisHair follicles and hair develop from epidermis

• PapillaPapilla

• RootRoot

• ShaftShaft

• MedullaMedulla


Appearance of hairAppearance of hair

• ColorColor

• GrowthGrowth

• Sebaceous glandsSebaceous glands

• Male pattern baldness -genetic tendency and male sex Male pattern baldness -genetic tendency and male sex hormones hormones


• Nails (Figure 6-17)Nails (Figure 6-17) Consist of epidermal cells converted to hard keratinConsist of epidermal cells converted to hard keratin Nail body—visible part of each nailNail body—visible part of each nail Root—part of nail in groove hidden by fold of skin, the Root—part of nail in groove hidden by fold of skin, the

cuticlecuticle Lunula—moon-shaped white area nearest rootLunula—moon-shaped white area nearest root Nail bedNail bed

• Appears pinkAppears pink

• onycholysisonycholysis GrowthGrowth


• Skin glands (Figure 6-20)Skin glands (Figure 6-20)

Two types of sweat glands:Two types of sweat glands:

• Eccrine glandsEccrine glands

• Apocrine glandsApocrine glands


• Skin glands (cont.)Skin glands (cont.)

Sebaceous glandsSebaceous glands

• Secrete sebumSecrete sebum

• antifungal activityantifungal activity

• Found in dermis except in palms and solesFound in dermis except in palms and soles

• Secretion increases in adolescence; may lead to Secretion increases in adolescence; may lead to formation of pimples and blackheadsformation of pimples and blackheads


• Skin glands (cont.)Skin glands (cont.)

Ceruminous glandsCeruminous glands

• Modified apocrine sweat glandsModified apocrine sweat glands

• cerumen (wax)cerumen (wax)

• Function of cerumen Function of cerumen

protect area from dehydration; excess secretion can cause protect area from dehydration; excess secretion can cause blockage of ear canal and loss of hearingblockage of ear canal and loss of hearing

Cycle of Life: SkinCycle of Life: Skin

• ChildrenChildren

Skin is smooth, unwrinkled, and characterized Skin is smooth, unwrinkled, and characterized by elasticity and flexibilityby elasticity and flexibility

Few sweat glandsFew sweat glands

Rapid healingRapid healing


• AdultsAdults

Development and activation of sebaceous Development and activation of sebaceous and sweat glandsand sweat glands

Increased sweat productionIncreased sweat production

• Body odorBody odor

Increased sebum productionIncreased sebum production

• AcneAcne


• Old ageOld age

Decreased sebaceous and sweat gland activityDecreased sebaceous and sweat gland activity

• Wrinkling (Figure 6-21)Wrinkling (Figure 6-21)

• Decrease of body’s ability to cool itselfDecrease of body’s ability to cool itself

mosby items and derived items © 2007, 2003 by mosby, inc.slide 1 chapter 6 skin and its appendages

Documents

skin glandsslide

skin colormelaninresponsible

skin tough

skin surfacephysical

skin color quantity

epidermal growth

epithelial cells

certain hormones slide