Structure and function of the integument

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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