Chapter 44
Structure, Function, and Disorders of
the Integument
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Integument: Overview
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Skin is the largest organ; covers the entire body
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Accessory structures of hair, nails, and glands
Primary function is to protect the body
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Accounts for approximately 20% of the body’s weight
Barrier against microorganisms, ultraviolet radiation,
loss of body fluids, and the stress of mechanical
forces
Regulates body temperature
Involved in the production of vitamin D
Touch and pressure receptors provide important
protective functions and pleasurable sensations
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Layers of the Skin
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Epidermis
Dermis
Subcutaneous
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Layers of the Skin
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Layers of the Skin
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Epidermis
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Stratum basale
Stratum germinativum
Stratum spinosum
Stratum lucidum
Stratum corneum
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Layers of the Skin
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Epidermis
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Keratinocytes
• Keratin
Melanocytes
Langerhans cells
Merkel cells
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Layers of the Skin
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Dermis
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Collagen, elastin, reticulum, and a gel-like ground
substance
 Hair follicles, sebaceous glands, sweat glands,
blood vessels, lymphatic vessels, nerves
 Fibroblasts, mast cells, macrophages
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Subcutaneous layer
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Adipocytes
Dermal, subcutaneous collagen continuous
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Layers of the Skin
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Dermal appendages
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Nails
Hair
Sebaceous glands
Eccrine and apocrine sweat glands
Blood supply
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Papillary capillaries
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Nails
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Aging and Skin Integrity
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Integumentary system reflects changes from
genetic and environmental factors
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The skin becomes thinner, drier, wrinkled, and
demonstrates changes in pigmentation
 Shortening and decrease in number of capillary loops
 Fewer melanocytes and Langerhans cells
 Atrophy of sebaceous, eccrine, and apocrine glands
 Changes in hair color
 Fewer hair follicles and growth of thinner hair
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Clinical Manifestations of
Skin Dysfunction
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Macule
Papule
Patch
Plaque
Wheal
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Clinical Manifestations of
Skin Dysfunction
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Nodule
Tumor
Vesicle
Bulla
Pustule
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Clinical Manifestations of
Skin Dysfunction
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Cyst
Telangiectasia
Scale
Lichenification
Keloid
Scar
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Clinical Manifestations of
Skin Dysfunction
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Excoriation
Fissure
Erosion
Ulcer
Atrophy
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Clinical Manifestations of
Skin Dysfunction
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Pressure ulcers
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Pressure ulcers result from any unrelieved
pressure on the skin, causing underlying tissue
damage
• Pressure
• Shearing forces
• Friction
• Moisture
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Clinical Manifestations of
Skin Dysfunction
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Pressure ulcers: risk factors
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Older adults in hospitals and nursing homes
Neurologic disorders that result in loss of mobility
and/or sensation (spinal cord injuries, dementia, or
cerebrovascular disease)
Immobilization
Incontinence
Debilitation
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Clinical Manifestations of
Skin Dysfunction
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Pressure ulcers: risk factors
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Lying in bed without changing position or relieving
pressure over an extended period
Lying for hours on hard imaging and operating
tables
Chronic diseases accompanied by anemia,
edema, renal failure, malnutrition, sepsis, and
urinary or fecal incontinence
Coarse bed sheets used for turning by dragging,
which produces a shearing force
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Clinical Manifestations of
Skin Dysfunction
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Pressure ulcers: risk factors for the critically ill
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Norepinephrine infusion
 APACHE II score
 Fecal incontinence
 Anemia
 Age greater than 60 years
 Renal insufficiency
 Length of hospital stay
 Individuals with darkly pigmented skin because early
signs of skin damage may not be clearly visible
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Clinical Manifestations of
Skin Dysfunction
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Pressure ulcers
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Stages
• I. Nonblanchable erythema of intact skin
• II. Partial-thickness skin loss involving epidermis or
dermis
• III. Full-thickness skin loss involving damage or loss of
subcutaneous tissue
• IV. Full-thickness skin loss with damage to muscle, bone,
or supporting structures
• Unstageable if wound bed covered with eschar
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Clinical Manifestations of
Skin Dysfunction
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Keloids
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Elevated, rounded, and firm
Claw-like margins that extend beyond the original
site of injury
Excessive collagen formation during dermal
connective tissue repair
Common in darkly pigmented skin types and burn
scars
Type III collagen is increased
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Keloids
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Clinical Manifestations of
Skin Dysfunction
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Pruritus
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Itching
Most common symptom of primary skin disorders
Itch is carried by specific unmyelinated C-nerve
fibers and is triggered by a number of itch
mediators
CNS can modulate the itch response
Pain stimuli at lower intensities can induce itching
Chronic itching can result in infections and
scarring due to persistent scratching
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Disorders of the Skin
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Inflammatory disorders
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Dermatitis or eczema most common
Various types of dermatitis
Generally characterized by pruritus, lesions with
indistinct borders, and epidermal changes
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Inflammatory Disorders
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Allergic contact dermatitis
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Caused by a hypersensitivity type IV reaction
Allergen comes into contact with skin, binds to
carrier protein to form sensitizing antigen;
Langerhans cells process antigen, carry it to T
cells, which become sensitized to antigen
Manifestations
• Erythema, swelling, pruritus, vesicular lesions
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Allergic Contact Dermatitis
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Inflammatory Disorders
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Atopic dermatitis
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Type I hypersensitivity—activation of mast cells,
eosinophils, T lymphocytes, other inflammatory
cells
Causes red, weeping crusts and chronic
inflammation, lichenification
Irritant contact dermatitis
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Nonimmunologic inflammation of the skin
 Chemical irritation from acids or prolonged
exposure to irritating substances
 Symptoms similar to allergic contact dermatitis
 Treatment—remove stimulus
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Atopic Dermatitis
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Inflammatory Disorders
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Stasis dermatitis
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Occurs in the legs as a result of venous stasis,
edema, and vascular trauma
Sequence of events: erythema, pruritus, scaling,
petechiae, ulcerations
Seborrheic dermatitis
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Inflammation of the skin involving the scalp,
eyebrows, eyelids, nasolabial folds, and ear
canals
Scaly, white, or yellowish plaques
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Stasis and Seborrheic Dermatitis
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Papulosquamous Disorders
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Psoriasis
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Chronic, relapsing, proliferative skin disorder
 T-cell immune-mediated skin disease
 Scaly, thick, silvery, elevated lesions, usually on
scalp, elbows, or knees caused by a high rate of
mitosis in the basal layer
 Shows evidence of dermal and epidermal
thickening
 Epidermal turnover goes from 26-30 days to 3-4
days
 Cells do not have time to mature or keratinize
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Psoriasis
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Papulosquamous Disorders
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Psoriasis
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Plaque psoriasis
Inverse psoriasis
Guttate psoriasis
Pustular psoriasis
Erythrodermic psoriasis
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Papulosquamous Disorders
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Pityriasis rosea
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Benign, self-limiting inflammatory disorder
Usually occurs during winter months
Herald patch
• Circular, demarcated, salmon-pink, 3- to 4-cm lesion
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Pityriasis Rosea Herald Patch
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Papulosquamous Disorders
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Lichen planus
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Benign, inflammatory disorder of the skin and
mucous membranes
Unknown origin, but T cells, adhesion molecules,
inflammatory cytokines, and antigen presenting
cells are involved
Nonscaling violet-colored, 2- to 4-mm lesions
Wrists, ankles, lower legs, genitalia
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Lichen Planus
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Papulosquamous Disorders
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Acne vulgaris
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Inflammatory disease of the pilosebaceous
follicles
Acne rosacea
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Inflammation of the skin that develops in
adulthood
 Lesions
• Erythematotelangiectatic, papulopustular, phymatous,
and ocular
• Associated with chronic, inappropriate vasodilation
resulting in flushing and sensitivity to the sun
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Papulosquamous Disorders
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Lupus erythematosus
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Inflammatory, autoimmune disease with cutaneous
manifestations
Thought to be an altered immune response to an
unknown antigen or response to UV wavelengths
with the development of self-reactive T and B
cells, decreased number of regulatory T cells, and
increased proinflammatory cytokines
Autoantibodies and immune complexes cause
tissue damage
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Papulosquamous Disorders
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Discoid lupus erythematosus
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Restricted to the skin
Photosensitivity
Butterfly pattern over the nose and cheeks
Subtype of systemic lupus erythematosus (SLE)
Leads to SLE in approximately 5% of cases
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Discoid Lupus Erythematosus
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Vesiculobullous Disorders
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Diseases that have different causes and
clinical courses but share the common
characteristic of vesicle, or blister, formation
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Pemphigus
Erythema multiforme
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Vesiculobullous Disorders
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Pemphigus
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Rare, chronic, blister-forming disease of the skin
and oral mucous membranes
Blisters form in deep or superficial epidermis
Autoimmune disease caused by circulating IgG
autoantibodies
• The antibodies are against the cell surface adhesion
molecule, desmoglein in the suprabasal layer of the
epidermis
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Vesiculobullous Disorders
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Pemphigus
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Tissue biopsies demonstrate autoantibody
presence
Types
• Pemphigus vulgaris (severe)
• Pemphigus foliaceus
• Pemphigus erythematosus
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Vesiculobullous Disorders
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Bullous pemphigoid
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More benign disease than pemphigus vulgaris
Bound IgG and blistering of the subepidermal skin
layer
Subepidermal blistering and eosinophils
distinguish pemphigoid from pemphigus
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Bullous Pemphigoid
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Vesiculobullous Disorders
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Erythema multiforme
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Acute recurring disorder of skin and mucous
membranes
Associated with allergic or toxic reactions to drugs
or microorganisms
Caused by immune complexes formed and
deposited around dermal blood vessels, basement
membranes, and keratinocytes
“Bull’s-eye” or target lesion
• Erythematous regions surrounded by rings of alternating
edema and inflammation
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Vesiculobullous Disorders
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Erythema multiforme
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Bullous lesions form erosions and crusts when
they rupture
Affects the mouth, air passages, esophagus,
urethra, and conjunctivae
Severe forms
• Stevens-Johnson syndrome (bullous form)
• Toxic epidermal necrolysis
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Erythema Multiforme
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Infections
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Bacterial infections
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Folliculitis
• Infection of hair follicles
• Staphylococcus aureus common cause
Furuncles
• “Boils” are an inflammation of the hair follicles
• Develop from preceding folliculitis; spread through
follicular wall into the surrounding dermis
• S. aureus common causative organism
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Furuncle
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Infections
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Bacterial infections
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Carbuncles
• Collection of infected hair follicles
• Erythematous, painful, swollen mass that drains through
many openings
• Abscesses may develop
• Chills, fever, malaise: systemic symptoms that occur
during early stages of lesion development
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Infections
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Bacterial infections
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Cellulitis
• Infection of the dermis and subcutaneous tissue
• Usually caused by Staphylococcus or group B streptococci
Erysipelas
• An acute superficial infection of the upper dermis (a
superficial form of cellulitis)
• Most often caused by group A streptococci
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Impetigo
• A superficial lesion of the skin
• Caused by coagulase-positive Staphylococcus or αhemolytic streptococci
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Infections
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Viral infections
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Herpes simplex virus (HSV)
• Eight types
• DNA virus
• HSV-1 usually causes infection of the cornea (herpes
keratitis), mouth (gingivostomatitis), and labia (labialis)
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
Contact with infected saliva
“Cold sore” or “fever blister” the most common manifestation
• HSV-2 causes genital infections
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Skin-to-skin mucous membrane contact during viral shedding
Vertical transmission from mother to neonate is associated with
significant neonatal morbidity and mortality
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Infections
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Viral infections
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Herpes zoster (shingles)/varicella (chickenpox)
• Caused by herpes varicella-zoster virus (VZV)
Initial infection with varicella followed years later
by herpes zoster
• Pain and paresthesia localized to the affected
dermatome (cutaneous area innervated by a single
spinal nerve) followed by vesicular eruptions along a
facial, cervical, or thoracic lumbar dermatome
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Herpes Simplex Virus
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Warts
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Benign lesions caused by human
papillomavirus (HPV)
Diagnosed by visualization
Condylomata acuminata
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Venereal warts
Highly contagious, sexually transmitted
Cauliflower-like lesions occur in moist areas, along
the glans of the penis, vulva, and anus
Oncogenic HPV a primary cause of cervical
cancer
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Fungal Infections
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Fungi causing superficial skin lesions are
called dermatophytes
Fungal disorders called mycoses; mycoses
caused by dermatophytes are termed tinea
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Tinea capitis (scalp)
Tinea pedis (athlete’s foot)
Tinea corporis (ringworm)
Tinea cruris (groin, jock itch)
Tinea unguium (nails) or onychomycosis
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Tinea Pedis
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Fungal Infections
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Candidiasis
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Caused by Candida albicans
Normally found on skin, in GI tract, and in vagina
C. albicans can change from a commensal
organism to a pathogen
• Local environment of moisture and warmth, systemic
administration of antibiotics, pregnancy, diabetes
mellitus, Cushing disease, debilitated states, age
younger than 6 months, immunosuppression, and
neoplastic diseases
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Vascular Disorders
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Cutaneous vasculitis
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Results from immune complexes in the small
blood vessels
• Develops from drugs, bacterial infections, viral infections,
or allergens
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Lesions
• Palpable purpura progressing to hemorrhagic bullae with
necrosis and ulceration
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Cutaneous Vasculitis
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Vascular Disorders
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Urticaria
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Due to type I hypersensitivity reactions to
allergens
Histamine release causes endothelial cells of the
skin to contract
• Causes leakage of fluid from the vessels
Treatment
• Antihistamines and steroids
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Urticaria
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Vascular Disorders
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Scleroderma
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Sclerosis of the skin that can progress to internal
organs
 Associated with several antibodies
 Lesions exhibit massive deposits of collagen with
inflammation, vascular changes, and capillary
dilation
 Skin is hard, hypopigmented, taut, and tightly
connected to underlying tissue
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Vascular Disorders
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Scleroderma
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Facial skin becomes very tight
Fingers become tapered and flexed; nails and
fingertips can be lost from atrophy
Mouth may not open completely
50% of patients die within 5 years
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Scleroderma
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Insect Bites
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Ticks
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Mosquitoes
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
Lyme disease, Rocky Mountain spotted fever
Malaria, yellow fever, dengue fever, filariasis, St.
Louis encephalitis
Flies
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Painful bites
Urticaria, mild bleeding
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Benign Tumors
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Seborrheic keratosis
Keratoacanthoma
Actinic keratosis
Nevi (moles)
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Cancer
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Basal cell carcinoma
Squamous cell carcinoma
Malignant melanoma
Kaposi sarcoma
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Frostbite
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Skin injury from exposure to extreme cold
Affects fingers, toes, ears, nose, cheeks
“Burning reaction” is caused by alternating
cycles of vasoconstriction and vasodilation
Inflammation and reperfusion part of the
pathophysiology
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Disorders of the Hair
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Male-pattern alopecia
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Genetically predisposed response to androgens
Androgen-sensitive and androgen-insensitive
follicles
Female-pattern alopecia
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
Elevated levels of the serum adrenal androgen
dehydroepiandrosterone sulfate
No loss of hair along the frontal hairline
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Disorders of the Hair
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Alopecia areata
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Autoimmune T-cell–mediated inflammatory
disease against hair follicles that results in
baldness
Hirsutism

Androgen-sensitive areas
• Abnormal growth and distribution of hair on the face,
body, and pubic area in a male pattern that occurs in
women
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Disorders of the Nail
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Paronychia
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
Acute or chronic infection of the cuticle
Onychomycosis

Fungal or dermatophyte infection of the nail plate
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