Anatomy and Physiology of the Integumentary System

Structure of the Skin

The integumentary system is the body's largest organ system, comprising the skin, subcutaneous layer, and skin appendages (glands, hair, nails). It is essential for life, providing protection and multiple physiological functions.

• Epidermis: Outermost layer, composed of stratified epithelial cells fused to form a protective, waterproof layer of keratin. Lacks blood vessels; relies on underlying tissues for nourishment.

• Dermis: Middle layer, made of elastic connective tissue (mainly collagen). Contains nerves, hair follicles, glands, immune cells, and blood vessels.

• Subcutaneous Tissue: Deepest layer, anchors skin to underlying tissues. Composed of adipose (fat) and connective tissue, stores energy, insulates, and cushions.

Example: The skin's layered structure allows for both protection and sensation, with the epidermis acting as a barrier and the dermis housing sensory nerves.

Functions of the Skin and Mucous Membranes

The skin and mucous membranes perform several vital functions:

• Protection: Barrier against water, microorganisms, UV rays, infection, and injury; prevents moisture loss.

• Temperature Regulation: Perspiration and blood vessel dilation dissipate heat; constriction conserves heat; pilomotor muscle contraction creates insulation (goosebumps).

• Psychosocial: Contributes to appearance, self-esteem, identification, and communication.

• Sensation: Millions of nerve endings provide touch, pain, pressure, and temperature perception.

• Vitamin D Production: UV rays activate skin to produce vitamin D.

• Immunologic: Triggers immune responses when skin is broken.

• Absorption: Absorbs substances (e.g., medications) for local/systemic effects.

• Elimination: Excretes water, electrolytes, and nitrogenous wastes via sweat.

Example: Mucous membranes in the respiratory tract trigger sneezing to expel irritants.

Factors Affecting Skin Integrity

Basic Principles

• Healthy, unbroken skin and mucous membranes are the first line of defense against harmful agents.

• Resistance to injury varies by age, tissue amount, comorbidities, nutrition, hydration, and circulation.

• Impaired circulation leads to poor nourishment and waste removal, increasing injury risk.

Developmental Considerations

• Infants (<2 years): Skin is thinner, weaker, easily injured, and prone to infection.

• Children: Skin becomes more resistant with age.

• Older Adults: Delayed epidermal cell maturation, thin skin, impaired circulation/collagen, decreased elasticity, increased risk for tissue damage.

State of Health

• Thin/obese individuals are more susceptible to skin injury.

• Fluid loss (fever, vomiting, diarrhea) causes dehydration, making skin loose/flabby.

• Excessive moisture (perspiration, incontinence) predisposes to skin breakdown.

• Jaundice causes yellowish, itchy, dry skin, increasing risk for lesions and infection.

• Skin diseases (eczema, psoriasis) may be genetic and require special care.

Wounds and Pressure Injuries

Wound Classification

Wounds are breaks in skin/tissue integrity and are classified by cause, openness, and healing process.

• Surgical: Intentional, controlled, sterile.

• Traumatic: Unintentional, may require additional intervention.

• Neuropathic/Vascular: Related to underlying neurologic/circulatory issues.

• Pressure-related: Caused by compromised circulation.

• Open Wounds: Skin surface broken; risk for infection (e.g., incisions, abrasions).

• Closed Wounds: Skin intact; internal injury/hemorrhage possible (e.g., contusions, hematomas).

• Acute Wounds: Heal within days/weeks; edges well-approximated; low infection risk.

• Chronic Wounds: Do not heal normally; edges not approximated; high infection risk; remain in inflammatory phase.

Types of Wounds and Causes

Wound Healing

Wound healing is a physiological process restoring tissue integrity via regeneration and scar formation. It occurs by primary, secondary, or tertiary intention.

• Primary Intention: Edges well-approximated; minimal tissue loss (e.g., surgical incision).

• Secondary Intention: Edges not approximated; large, open wounds; more scar tissue.

• Tertiary Intention: Wounds left open for days to resolve infection/edema, then closed.

Phases of Wound Healing

1. Hemostasis: Immediate; blood vessels constrict, clotting begins, fibrin clot forms.

2. Inflammatory: 2-3 days; WBCs (leukocytes, macrophages) ingest debris, release growth factors, acute inflammation (pain, heat, redness, swelling).

3. Proliferation/Repair: Several weeks; fibroblasts build new tissue (collagen, granulation tissue), capillaries grow, wound sealed.

4. Maturation/Remodeling: Begins ~3 weeks post-injury; collagen remodeled, scar forms, strength increases (but never fully restored).

Example: Surgical wounds typically heal by primary intention, progressing through all four phases.

Factors Affecting Wound Healing

Local Factors

• Pressure: Disrupts blood supply, delays healing.

• Desiccation: Drying out; cell death, crust formation, delayed healing.

• Maceration: Overhydration; tissue erosion, impaired integrity.

• Trauma: Repeated injury delays healing.

• Edema: Interferes with blood supply, oxygen/nutrient delivery.

• Infection: Increases energy demand, toxins interfere with healing.

• Excessive Bleeding: Large clots impede healing, promote infection.

• Necrosis: Dead tissue (slough/eschar) must be removed for healing.

• Biofilm: Bacterial clumps in protective matrix; antibiotic resistance, chronic inflammation.

Systemic Factors

• Age: Infants/children heal faster; older adults have diminished fibroblastic activity/circulation.

• Circulation/Oxygenation: Adequate blood flow and oxygen essential; impaired in vascular/cardiovascular disorders, anemia, obesity.

• Nutritional Status: Proteins, carbs, fats, vitamins (A, C), minerals (zinc) required; malnutrition slows healing.

• Wound Etiology: Cause affects assessment/treatment; systemic issues may recur.

• Medications/Therapies: Corticosteroids, radiation, chemotherapy, prolonged antibiotics delay healing.

• Immunosuppression/Proinflammatory Conditions: Disease, medication, age-related changes delay healing.

• Adherence to Treatment: Nonadherence negatively impacts healing.

Wound Complications

Types of Complications

• Infection: Failure to control microorganism growth; symptoms include purulent drainage, pain, redness, swelling, fever, elevated WBC.

• Hemorrhage: Excessive bleeding; may require pressure dressings, fluid replacement, surgery.

• Dehiscence: Partial/total separation of wound layers; risk factors include obesity, malnutrition, infection, stress.

• Evisceration: Protrusion of internal organs through wound; medical emergency.

• Fistula: Abnormal passage between organs or to outside.

Pressure Injuries

Pathogenesis and Mechanisms

Pressure injuries result from blood vessel collapse due to pressure, friction, shear, and microclimate (temperature/moisture).

• External Pressure: Compresses blood vessels, especially over bony prominences (sacrum, coccyx, hip, heel).

• Friction: Rubbing damages superficial blood vessels.

• Shear: Tissue layers slide, stretching/tearing vessels.

• Microclimate: Moist skin is more susceptible to injury.

Risk Factors for Pressure Injury Development

• Immobility, poor nutrition/hydration, skin moisture, altered mental status, advanced age.

• Other risks: poor hygiene, diabetes, diminished sensory perception, fractures, corticosteroid therapy, immunosuppression, incontinence, obesity/thinness, smoking, surgery, terminal illness.

Pressure Injury Staging

Psychological Effects of Wounds and Pressure Injuries

• Pain: Physical and psychological; worsened by movement, dressing changes.

• Anxiety/Fear: Concerns about wound opening, privacy, appearance, smell.

• Activities of Daily Living: Wounds may limit self-care, work, leisure.

• Body Image: Visible wounds/scars affect self-worth, sexuality, social relationships.

Assessment and Diagnosis

Nursing History and Skin Assessment

• Include questions about skin appearance, activities, risk factors, recent changes, skin care regimens, activity, nutrition, elimination, cognition.

• Inspect skin head-to-toe, including bony prominences, on admission and at regular intervals.

• Early detection and intervention are key to prevention.

Wound Assessment

• Appearance: Location, size (length, width, depth), edge approximation, color, presence of drains/tubes/staples/sutures.

• Drainage: Type (serous, sanguineous, serosanguineous, purulent), amount, color, odor, consistency.

• Example: Serous drainage is clear/watery; sanguineous is bloody; purulent is thick, foul-smelling, yellow/green.

Types of Wound Drains

Sutures and Staples

• Sutures (absorbable/nonabsorbable) hold tissue together; removed when wound strength sufficient.

• Staples may reduce OR time; adhesive strips may be applied after removal for support.

Chronic Wound Assessment (ABCESS Framework)

• A: All of the patient—history, physical, overview

• B: Wound bed management—bioload, biofilm, biomarkers, biopsy

• C: Circulation—arterial, venous, lymphatic

• E: Edema, exudate, erythema management

• S: Skin protection/treatment

• S: Social, societal, spiritual factors

Pressure Injury Assessment

• Use risk assessment tools (e.g., Braden Scale: mental status, continence, mobility, activity, nutrition).

• Assess mobility, nutritional status (albumin, prealbumin, lymphocyte count, HbA1c, glucose), moisture/incontinence, appearance of existing injury (location, stage, size, tissue type, drainage, odor, granulation, epithelialization, periwound skin).

Wound Care and Management

Preventing Pressure Injuries

• Implement turning/positioning schedules (bed-bound: every 2 hours; chair-bound: every hour).

• Use support surfaces (air, gel, water mattresses/cushions) to redistribute pressure.

• Positioning devices (pillows, foam wedges, boots) keep weight off bony prominences.

• Minimize friction/shear; use lifting devices, friction-reducing sheets.

Wound Care Principles

• Closed wound care (moist dressings) promotes healing; open wounds heal slower.

• Ideal dressing: maintains moisture, absorbs exudate, insulates, acts as bacterial barrier, reduces pain, allows pain-free removal.

• Types: dry gauze, nonadherent gauze, transparent films, hydrocolloids, absorbent pads.

• Debridement: autolytic (occlusive dressings), enzymatic (commercial enzymes), mechanical (irrigation, whirlpool, ultrasound, surgical).

Advanced Wound Therapies

• Fibrin Sealants: Fibrinogen + thrombin applied to tissues; stops bleeding, glues surfaces, minimal scarring.

• Negative Pressure Wound Therapy (NPWT): Uniform negative pressure stimulates healing, removes fluid, maintains moist environment.

• Growth Factors: Recombinant PDGF promotes immune cell/fibroblast activity, extracellular matrix formation.

• Hyperbaric Oxygen Therapy (HBOT): Pressurized chamber, 100% oxygen, increases tissue oxygenation, promotes healing.

• Heat and Cold Therapy: Heat dilates vessels, increases metabolism, reduces muscle tension; cold constricts vessels, reduces spasms, promotes comfort.

Changing Dressings and Cleaning Wounds

• Explain procedure, provide privacy, administer analgesics if needed.

• Use aseptic technique; hand hygiene before/after.

• Remove dressings in direction of hair growth; use adhesive remover if needed.

• Clean wounds with normal saline or antimicrobial solutions; sterile technique for open wounds.

Caring for Wound Drains

• Open drains (Penrose): passive drainage into dressings.

• Closed drains (JP, Hemovac): suction, accurate measurement, prevent contamination.

• Drains removed when output decreases or color lightens.

Collecting Wound Cultures

• Culture wounds if infection suspected; allows identification of organisms and targeted intervention.

Removing Sutures or Staples

• Remove when wound strength sufficient; use suture removal set or staple remover.

• Apply adhesive strips for support after removal.

Patient Education and Documentation

Teaching Wound Care

• Teach patients/caregivers about wound care, infection prevention, signs/symptoms, nutrition, pain management, hand hygiene.

• Provide illustrated instructions, involve patient/caregivers in care plan.

Documentation

• Document changes in wound status, characteristics, care, nutrition, support surfaces, reassessment schedule.

• Use photographs for objective evaluation.

Heat and Cold Therapy

Physiological Effects

• Heat: Vasodilation, increased metabolism, reduced blood viscosity, increased capillary permeability, reduced muscle tension, pain relief.

• Cold: Vasoconstriction, reduced blood flow, decreased pain-producing substances, reduced edema/inflammation, reduced muscle spasm, numbness, comfort.

Rebound Phenomenon: Maximum vasodilation (heat) in 20-30 min; prolonged application causes vasoconstriction. Maximum vasoconstriction (cold) at 60°F (15°C); then vasodilation begins.

Example: Heat is used for infections, wounds, arthritis; cold for trauma, dental pain, sprains.

Summary Table: Types of Wound Dressings

Additional info: These notes expand on the original content with definitions, examples, and structured tables for clarity. All key concepts are explained for self-contained study.