This document discusses the structure and function of the integumentary system. It describes the three layers of the skin - epidermis, dermis and hypodermis - and their components. Specific conditions that can affect the skin like pressure ulcers, keloids, pruritus, inflammatory disorders, papulosquamous disorders, and vesiculobullous disorders are examined in detail, outlining their signs, symptoms and pathogenesis. Diagrams supplement the textual descriptions of various skin diseases and disorders.

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Structure, Function, and Disorders
of the Integument

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Layers of the Skin
 Epidermis
 Dermis
 Hypodermis

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Layers of the Skin (cont’d)

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Layers of the Skin (cont’d)
 Dermal appendages:
 Nails
 Hair
 Sebaceous glands
 Eccrine and apocrine sweat glands
 Blood supply
 Papillary capillaries

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Nails

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Aging and Skin Integrity
 The integumentary system reflects
numerous changes from genetic and
environmental factors
 The skin becomes thinner, drier, wrinkled, and
demonstrates a change in pigmentation
 Shortening and decrease in the number of
capillary loops
 Fewer melanocytes and Langerhans cells

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Aging and Skin Integrity (cont’d)
 The integumentary system reflects
numerous changes from genetic and
environmental factors (cont’d)
 Atrophy of the 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
 Macule
 Papule
 Patch
 Plaque
 Wheal
 Nodule
 Tumor
 Vesicle
 Bulla
 Pustule
 Cyst
 Telangiectasia
 Scale
 Lichenification
 Keloid
 Scar
 Excoriation
 Fissure
 Erosion
 Ulcer
 Atrophy

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Pressure Ulcers
 Pressure ulcers result from any unrelieved
pressure on the skin, causing underlying
tissue damage
 Pressure
 Shearing forces
 Friction
 Moisture

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Pressure Ulcers (cont’d)

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Pressure Ulcers (cont’d)
 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

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Keloids
 Elevated, rounded, and firm
 Clawlike 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 (cont’d)

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Pruritus
 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
 The CNS can modulate the itch response

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Pruritus (cont’d)
 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
 Inflammatory disorders
 The most common inflammatory disorders of
the skin are dermatitis or eczema
 There are various types of dermatitis
 The disorders are generally characterized by:
• Pruritus
• Lesions with indistinct borders
• Epidermal changes

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Inflammatory Disorders
 Allergic contact dermatitis
 Caused by a hypersensitivity type IV reaction
 The allergen comes in contact with the skin,
binds to a carrier protein to form a sensitizing
antigen; Langerhans cells process the antigen
and carry it to T cells, which become sensitized
to the antigen
 Manifestations:
• Erythema
• Swelling
• Pruritus
• Vesicular lesions

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Allergic Contact Dermatitis

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Inflammatory Disorders
 Atopic dermatitis
 Type I hypersensitivity: activation of mast cells,
eosinophils, T-lymphocytes, and other
inflammatory cells
 Causes red, weeping crusts and chronic
inflammation, lichenification

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Inflammatory Disorders (cont’d)
 Irritant contact dermatitis
 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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Inflammatory Disorders (cont’d)
 Stasis dermatitis
 Occurs in the legs as a result of venous stasis,
edema, and vascular trauma
 Sequence of events:
• Erythema
• Pruritus
• Scaling
• Petechiae
• Ulcerations

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Inflammatory Disorders (cont’d)
 Seborrheic dermatitis
 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
 Psoriasis
 Chronic, relapsing, proliferative skin disorder
 T cell immune- mediated skin disease
 Scaly, thick, silvery, elevated lesions, usually
on the scalp, elbows, or knees caused by a
high rate of mitosis in the basale layer

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Papulosquamous Disorders
(cont’d)
 Psoriasis (cont’d)
 Shows evidence of dermal and epidermal
thickening
 Epidermal turnover goes from 26 to 30 days to
3 to 4 days
 Cells do not have time to mature or adequately
keratinize

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Psoriasis

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Papulosquamous Disorders
 Psoriasis (cont’d)
 Plaque psoriasis
 Inverse psoriasis
 Guttate psoriasis
 Pustular psoriasis
 Erythrodermic psoriasis

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Papulosquamous Disorders
(cont’d)

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Papulosquamous Disorders
(cont’d)
 Pityriasis rosea
 Benign, self-limiting inflammatory disorder
 Usually occurs during the winter months
 Herald patch
• Circular, demarcated, salmon-pink, 3- to 4-cm lesion

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Papulosquamous Disorders
(cont’d)

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Papulosquamous Disorders
(cont’d)
 Lichen planus
 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
 Acne vulgaris
 Inflammatory disease of the pilosebaceous
follicles
 Acne rosacea
 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
(cont’d)
 Lupus erythematosus
 Inflammatory, autoimmune disease with
cutaneous manifestations
 Discoid lupus erythematosus
• Restricted to the skin
• Photosensitivity
• Butterfly pattern over the nose and cheeks
 Systemic lupus erythematosus

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Discoid Lupus Erythematosus

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Vesiculobullous Disorders
 Pemphigus
 Rare, chronic, blister-forming disease of the
skin and oral mucous membranes
 Blisters form in the 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 (cont’d)
 Pemphigus (cont’d)
 Tissue biopsies demonstrate autoantibody
presence
 Types:
• Pemphigus vulgaris (severe)
• Pemphigus foliaceus
• Pemphigus erythematosus

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Vesiculobullous Disorders (cont’d)
 Bullous pemphigoid
 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
 Erythema multiforme
 Acute, recurring disorder of the 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

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Vesiculobullous Disorders (cont’d)
 Erythema multiforme (cont’d)
 “Bull’s-eye” or target lesion
• Erythematous regions surrounded by rings of
alternating edema and inflammation
 Bullous lesions form erosions and crusts when
they rupture
 Affects the mouth, air passages, esophagus,
urethra, and conjunctiva
 Severe forms:
• Stevens-Johnson syndrome (bullous form)
• Toxic epidermal necrolysis

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Infections
 Bacterial infections:
 Folliculitis
 Furuncles
 Carbuncles
 Cellulitis
 Erysipelas
 Impetigo

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Furuncle

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Infections
 Viral infections
 Herpes zoster and varicella

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Herpes Simplex Virus

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Warts
 Benign lesions caused by the human
papillomavirus (HPV)
 Diagnosed by visualization
 Condylomata acuminata
 Venereal warts

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Fungal Infections
 Fungi causing superficial skin lesions are
called dermatophytes
 Fungal disorders are called mycoses;
mycoses caused by dermatophytes are
termed tinea
 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
 Candidiasis
 Caused by Candida albicans
 Normally found on the skin, in the GI tract, and in the
vagina
 Candida 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
• Neoplastic diseases

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Vascular Disorders
 Cutaneous vasculitis
 Results from immune complexes in the small
blood vessels
• Develops from drugs, bacterial infections, viral
infections, or allergens
 Lesions
• Palpable purpura progressing to hemorrhagic bullae
with necrosis and ulceration

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Vascular Disorders (cont’d)
 Urticaria
 Caused by 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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Vascular Disorders (cont’d)
 Scleroderma
 Sclerosis of the skin that can progress to the
internal organs
 The disease is 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 (cont’d)
 Scleroderma (cont’d)
 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
 Bees
 Mosquitoes
 Flies

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Benign Tumors
 Seborrheic keratosis
 Keratoacanthoma
 Actinic keratosis
 Nevi (moles)

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Seborrheic Keratosis

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Cancer
 Basal cell carcinoma
 Squamous cell carcinoma
 Malignant melanoma
 Kaposi sarcoma

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Basal Cell Carcinoma

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Squamous Cell Carcinoma

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Malignant Melanoma

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Kaposi Sarcoma

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Burns
 Partial-thickness burns
 First degree
 Superficial and deep partial
 Second degree
 Full-thickness burns
 Third degree
 “Rule of nines”

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Superficial Partial-Thickness Burn

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Axillary Burn Scar Contracture

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Deep Partial-Thickness Burn

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Full-Thickness Burn

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Estimating Burn Injury

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Burns

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Hypertrophic Scarring

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Cultured Epithelial Autograft

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Frostbite
 Skin injury caused by exposure to extreme
cold
 Usually affects fingers, toes, ears, nose,
and cheeks
 The “burning reaction” is caused by
alternating cycles of vasoconstriction and
vasodilation
 Inflammation and reperfusion are both part
of the pathophysiology

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Disorders of the Hair
 Male-pattern alopecia
 Genetically predisposed response to
androgens
 Androgen-sensitive and androgen-insensitive
follicles

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Disorders of the Hair (cont’d)
 Female-pattern alopecia
 Associated with 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 (cont’d)
 Alopecia areata
 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
 Paronychia
 Acute or chronic infection of the cuticle
 Onychomycosis
 Fungal or dermatophyte infection of the nail
plate