Integumentary System

Chapter

6

6-1

Chapter 6Integumentary System

(Skin and accessory organs)• Composed of several tissues• Maintains homeostasis• Protective covering• Retards water loss• Regulates body temperature• Houses sensory receptors• Contains immune system cells• Synthesizes chemicals• Excretes small amounts of waste

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Layers of Skin

• Epidermis• Dermis• Subcutaneous layer

or hypodermis

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Epidermis

• lacks blood vessels• keratinized• thickest on palms and soles, thinnest on eyelid (0.8-1.4mm)• melanocytes provide melanin• rests on basement membrane• stratified squamous

6-4

Epidermis

Layers of Epidermis• stratum corneum

•fully keratinized• stratum lucidum

•only in palms and soles• stratum granulosum

•granular layer• stratum spinosum

•thick layer• stratum basale

•deepest layer, can reproduce

6-5

Dermis

• dermal papillae

• binds epidermis to underlying tissues• irregular dense connective tissue

• on average 1.0-2.0mm thick

• muscle cells

• nerve cell processes

• blood vessels

• hair follicles

• glands

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Subcutaneous Layer(hypodermis)

• loose connective tissue

• adipose tissue

• insulates

• major blood vessels

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Hair Follicles

• epidermal cells

• tube-like depression

• extends into dermis

• hair root•reproductive cells

• hair shaft

• hair papilla•contains blood vessels

• dead epidermal cells

• melanin, trichosiderin• arrector pili muscle

6-8

Nails

• protective coverings*

• nail plate•keratinized epithelial cells

• nail bed•surface of skin

• lunula•most active growing region

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Glands

• usually associated with hair follicles

• secrete sebum•fatty material and cellular debris•keeps hair and skin soft, pliable, waterproof

• absent on palms and soles

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•Sebaceous Glands

Glands• sudoriferous glands (sweat)• widespread in skin• deeper dermis or hypodermis

• eccrine glands•most numerous•respond to temp elevation•duct opens superficially at pore•forehead, neck, back

• apocrine glands•develop a scent•duct opens into hair follicle•active at puberty•respond to emotion, pain, arousal•axilla, groin, areola

• ceruminous glands•ear wax

• mammary glands•milk

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Regulation of Body Temperature

6-12

Problems in Temperature Regulation

Hyperthermia – abnormally high body temperature

Hypothermia – abnormally low body temperature

6-13

Skin Color

Genetic Factors• varying amounts of melanin• varying size of melanin granules• albinos lack melanin

Environmental Factors• sunlight• UV light from sunlamps• X rays

Physiological Factors• dilation of dermal blood vessels• constriction of dermal blood vessels• carotene• jaundice

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Healing Cuts

• Shallow cuts– Epithelial cells around margin stimulated to undergo mitosis faster than

normal• Deep cuts

– Escaping blood forms a clot• Mainly fibrin (fibrous protein), blood cells, platelets• Tissue fluids seep into clot and dry: scab

– Fibroblasts migrate to injury and form collagenous fibers that bind the edges of wound

– Connective tissue releases growth factors to stimulate growth.– Blood vessels extend into wound.– Phagocytic cells remove dead cells– Scab falls off– The larger and deeper the injury, the more connective tissue is formed, the

more likely scar tissue will be visible

Healing of Cuts

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Healing of Burns

First degree burn – superficial partial-thicknessepidermis only

Second degree burn – deep partial-thicknessepidermis and some dermisskin grows from surviving accessory organs’ epithelial cells

Third degree burn – full-thicknessskin must grow from margin of burn •autograft• homograft• various skin substitutes• extensive scars

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Second Degree Burn

• Fluid escapes from damaged dermal capillaries forming blister

• Healing occurs from the epithelial cells of surviving accessory organs.

• Cells divide and grow out to surface of dermis, spread over it, and forms new epidermis.

• Eventually skin completely covers area.• No scar tissue should form.

Third Degree Burn

• Injured skin becomes dry and leathery• Healing can only occur from the surviving

epithelial cells growing inward from the margin of the wound.

• Auto graft: moving your skin from undamaged area to damaged area.

• Homograft: using cadaver skin to temporarily cover wound to prevent infection.

• Various skin substitutes: cultured skin from lab• Scar tissue will form

Rule of Nines

6-17

Life Span Changes

•Sebaceous glands secrete less oil•Scaly skin•Wrinkles• Sagging• Melanin production slows•Age spots

• Dermis becomes reduced• Loss of fat•Inability to control body temperature• Hair thins• Number of hair follicles decrease• Impaired nail growth• Sensory receptors decline• Less vitamin D production

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