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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