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The Integumentary System

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Protection Excretion Temperature maintenance Insulation and cushion Vitamin D3 synthesis Sensory detection

Integumentary system functions:

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Cutaneous membraneEpidermisDermis

Accessory structuresSubcutaneous layer

It is not part of the integumentary systemIt separates the integumentary system from

the deep fasciaAlso known as hypodermis and superficial

fascia

The integumentary system consists of

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Integumentary System

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The Epidermis

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Cells of the epidermis

KeratinocytesMost abundantProduce keratin

Fibrous protein that makes the epidermis though and water resistant

MelanocytesSecretes melanin

Protects the cell against UV raysfreckles

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Cells of the epidermis

Langerhan’s cellsCells that belong to the immune system

Merkel cellsMerkel discs = Merkel cell + nerve endingSense of touch

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Stratum germinativum or basaleStratum spinosumStratum granulosumStratum lucidumStratum corneum

Layers of the epidermis:

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Layers of the Epidermis

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Stratum Germinativum (basale)

Single row of cellsForms epidermal ridgesBasal or germinative cellsMerkel cells (touch)Melanocytes

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Stratum Basale

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Stratum Spinosum

Prickle cellsSeveral layers of cellsCells held together by desmosomesPresence of Langerhan’s cellsCells contain pre-keratin

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Stratum Granulosum

3 to 5 layers of keratinocytesNo cell divisionsLamellated granules

Contain a water resistant glycolipid that reaches the extracellular space

Keratohyalin granulesCombine with the intermediate filaments to

form keratin that will make the skin stronger

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Stratum lucidum (clear layer)

Dead keratinocytesFlat cellsIn thick skin

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Stratum corneum

Outmost layer20-30 layers of cellsDead cellsCytoplasm filled with keratinConstantly shedding and replaced

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The Dermis

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Papillary layerContains blood vessels, lymphaticsFree nerve endingsMeissner corpuscles (touch, pressure)Loose areolar connective tissuePresence of dermal papillae

Produce fingerprints• Genetically determined

Dermal layers

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Dermal papilla

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Fingerprints

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Dermal layersReticular Layer

Dense irregular connective tissueFewer cellsContains network of collagen and elastic

fibers to resist tensionSweat and sebaceous glandsRich blood supplyHair folliclesPacinian corpuscles (deep pressure)

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Dermis

Both layers are rich in collagen and elastic fibersNumerous fibroblasts, adipocytes, macrophagesRichly vascularized

Regulation of body temperatureDecubitus ulcers

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Blood supply Carotene

Present in the s.corneum and hipodermisMelanin

Skin color depends on

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FlushedFever, hypertension

PaleJaundiceCyanoses

Abnormal skin color

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Accessory Structures

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Nail body covers the nail bedNail production occurs at the nail matrixEponychium (cuticle) overlies rootFree edge of nail extends over hyponychiumLunulaRootNail folds

Nails

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Nail

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Originate in hair follicleComposed of root and shaftRoot base (hair papilla) surrounded by hair

bulb and root hair plexusCuticle = superficial dead protective layerCortexMedulla

Hairs

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Hair

FollicleEpidermal layer

Internal epithelial root sheathExternal epithelial root sheath

Glassy membraneConnective root sheathPapilla

Blood vessels enter the hair

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Hair

Arrector pili muscleSmooth muscleWhen contracted cause dimpling of the skin

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SebaceousSudoriferous

Cutaneous Glands

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Discharge waxy sebum onto hair follicle or on the skin surface

Not present on palms and solesSebum

Oil + dead cellsKeep skin and hair moistBlack headAcne

Sebaceous glands

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Sebaceous Glands and Follicles

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Apocrine sweat glandsAxilla and genital areasBegin secretion at pubertyProduce odorous secretion rich in protein and

fatMerocrine (eccrine) sweat gland

All over the bodyRegulates body temperatureSweat or perspiration

Water, salt, urea

Sudoriferous glands

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Sweat Glands