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Chapter 5

Integumentary System

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Integumentary System• Consists of:

– Skin

– Hair

– Nails

– Glands

• Functions– Protection

– Sensation

– Temperature regulation

– Vitamin D production

– Excretion

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Hypodermis• Skin rests on this,

but not a part• Consists of loose

connective tissue• Types of cells

– Fibroblasts

– Adipose cells

– Macrophages

• Also called– Subcutaneous tissue

– Superficial fascia

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Skin

• Dermis– Structural strength– Cleavage lines– Two layers

• Reticular• Papillary

• Epidermis– Avascular– Cells– Layers or strata

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Cleavage or Tension Lines

• Elastin and collagen fibers oriented in some directions more than others

• Important in surgery– If incision parallel

to lines there is less gapping, faster healing, less scar tissue

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Dermis and Epidermis

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Epidermal Cells• Cell types

– Keratinocytes: Produce keratin for strength– Melanocytes: Contribute to skin color– Langerhans’ cells: Part of the immune system– Merkel’s cells: Detect light touch and pressure

• Desquamate: Older cells slough off

• Keratinization: Cells die and produce outer layer that resists abrasion and forms permeability layer

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Epidermal Strata• Stratum Basale

– Deepest portion of epidermis and single layer– High mitotic activity and cells become keratinized

• Stratum Spinosum– Limited cell division

• Stratum Granulosum– In superficial layers nucleus and other organelles

degenerate and cell dies

• Stratum Lucidum– Thin, clear zone

• Stratum Corneum– Most superficial and consists of cornified cells

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Epidermal Layers and Keratinization

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Thick and Thin Skin

• Thick skin– Has all 5 epithelial strata– Found in areas subject to pressure or friction

• Palms of hands, fingertips, soles of feet

• Thin skin– More flexible than thick skin– Covers rest of body

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Skin Color

• Determined by 3 factors– Pigments

• Melanin: Provides for protection against UV light• Albinism: Deficiency or absence of pigment• Carotene: Yellow pigment

– Blood circulating through the skin• Imparts reddish hue and increases during blushing,

anger, inflammation• Cyanosis: Blue color caused by decrease in blood

oxygen content

– Thickness of stratum corneum

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Accessory Skin Structures

• Hair– Found everywhere on human body except palms, soles,

lips, nipples, parts of external genitalia, and distal segments of fingers and toes

• Glands– Sebaceous or oil glands

– Sudoriferous or sweat glands

– Ceruminous glands

– Mammary glands

• Nails

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Hair Structure

• Composed of shaft and root– Shaft protrudes

above skin surface– Root located below

surface and base forms the hair bulb

• Has 3 concentric layers– Medulla: Central axis– Cortex: Forms bulk

of hair– Cuticle: Forms hair

surface

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Hair Growth, Color, and Muscles

• Hair Growth– Cycles

• Growth and resting

– Permanent hair loss• Pattern balding most common

• Hair Color– Caused by varying amounts and types of melanin

• Muscles– Arrector pili: Muscle contraction causes hair to “stand

on end”

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Oil and Sweat Glands• Sebaceous glands

– Produce sebum

– Oils hair and skin surface

• Sudoriferous glands– Merocrine or eccrine

• Most common

• Numerous in palms and soles

– Apocrine• Found in axillae,

genitalia, around anus

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Nails

• Anatomy– Nail root

proximally

– Nail body distally: Eponychium or cuticle

• Growth– Grow continuously

unlike hair

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Burns• Classifications

– First-degree

– Second-degree

– Third-degree

• Skin Grafts– Split skin

– Artificial skin

– Cadavers or pigs

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The Rule of Nines

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Aging Effects

• Skin more easily damaged

• Skin becomes drier

• Functioning melanocytes decrease or increase as with age spots

• Sunlight ages skin more rapidly

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Clinical Disorders

• Bacterial infections– Acne

• Viral Infections– Chicken pox, German measles, cold sores

• Decubitus ulcers or bedsores– Ischemia and necrosis

• Cancer– Basal cell carcinoma

– Squamous cell carcinoma

– Malignant melanoma

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