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The Integumentary System

The Skin and its Appendages

The SkinTwo main components

● Epidermis ● Dermis ●  (Hypodermis)

EpidermisCells of the Epidermis

● Keratinocytes ● Melanocytes ● Dendritic Cells

(Langerhans cells)

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EpidermisLayers of the Epidermis

● Thick Skin ○  Stratum Basale ○  Stratum Spinosum ○  Stratum Granulosum ○  Stratum Lucidum ○  Stratum Corneum

● Thin Skin

○  Absence of Stratum Lucidum

EpidermisLayers of Epidermis

●  Stratum Basale (germinatum)

●  Single row of stem cells

●  10-25% melanocytes

●  very small amount of tactile cells

EpidermisLayers of the Epidermis

●  Stratum Spinosum ○  several cells thick ○  weblike intermediate filament

network ○  melanin granules and dendritic cells

present

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EpidermisLayers of the Epidermis

●  Stratum Granulosum ○  Keratinization Begins ○  Keratohyaline granules ○  Lamellar granules

EpidermisLayers of the Epidermis

●  Stratum Lucidum ○  Only present in thick skin ○  2-3 rows of clear, flat, dead

keratinocytes

EpidermisLayers of the Epidermis

●  Stratum Corneum ○  anucleate ○  20-30 cells thick ○  ¾ of epidermis ○  high keratin content ○  thickened, glycoprotein covered plasma

membranes ○  loses 50k cells/min

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DermisComposition ●  Connective Tissue proper ●  Rich nerve and vascular supply ●  contains hair follicles, glands, and sensory receptors Layers ●  Papillary Layer ●  Reticular Layer

DermisPapillary Layer

●  Thin ●  areolar ●  highly vascularized ●  low density (great for

phagocytes) ●  Dermal papillae (form

friction ridges in thin skin)

DermisReticular layer

●  80% of Dermis ●  dense irregular

connective tissue ●  blood vessel network

(cutaneous plexus) ●  cleaveage and flexure

lines

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Appendages of the Skin

Hair and Hair Follicles

Nails

● Sweat Glands ○ Eccrine Glands Apocrine Glands

Sebaceous (oil) Glands

Appendages of the SkinHair and Hair Follicles

●  Structure of hair ●  Structure of a hair follicle ●  Types and growth of hair ● Hair thinning and baldness

Appendages of the skinStructure of a hair (fig 5.5)

●  Produced by hair follicles ●  Conists primarily of dead keratinized cells ●  cells contain hard keratin Regions

●  Shaft ●  Root Concentric Layers

●  Medulla ●  Cortex ●  Cuticle

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Appendages of the skinStructure of a Hair Follicle (fig 5.5)

●  Epithelium based ●  Hair bulb ●  Hair follicle receptor ●  Hair papillae ●  Peripheral connective tissue sheath ●  Epithelial root sheath

Appendages of the SkinTypes and Growth of Hair ●  Vellus Hair ●  Terminal Hair

Appendages of the SkinHair Thinning and Baldness ●  Alopecia ●  True Baldness (Male Pattern)

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Appendages of the SkinNails (fig 5.6) ●  Scale-like modification of epidermis ●  hard keratin ●  free edge, nail plate, root ●  nail bed ●  nail matrix ●  nail folds and cuticle

Appendages of the SkinSweat (Sudoriferous) Glands

● Eccrine (Merocrine) Sweat Glands ● Apocrine Sweat Glands

Appendages of the SkinSebaceous (Oil) Glands ●  Simple branched alvolar glands ●  secrete sebum ●  holocrine type glands ●  secrete into hair follicles and occasionally pores

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Skin FunctionsProtection

● Chemical Barriers ○  acid mantle

● Physical Barriers ● Biological Barriers

○  dendritic cells, macrophages, DNA

Skin FunctionsBody Temperature Regulation Heat Loss ● Vaodilation ● heat loss through sweat evaporation Heat conservation ● Vasoconstriction

Skin FunctionsCutaneous Sensation

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Skin FunctionsMetabolic Functions ●  Produces vitamin D precursor ●  disarm cancer causing chemicals ●  activate some steroid hormones

Skin FunctionsBlood Resevoir ●  5% of total blood volume

Skin FunctionsExcretion ●  ammonia, uric acid, urea, salt, water.

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Homeostatic Imbalances of SkinSkin Cancer

● Basal Cell Carcinoma ● Squamous Cell Carcinoma ● Melanoma

○  Asymmetry ○  Border Irregularity ○  Color ○  Diameter ○  Elevation

Study GuideWill Post Wednesday