Anatomy, Physiology, and Care of the Integumentary System: Wounds and Pressure Injuries

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

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 tissue, and skin appendages (glands, hair, nails), as well as associated blood vessels, nerves, and sensory organs. The skin itself consists of three primary layers:

Epidermis: The outermost layer, composed of stratified epithelial cells that form a protective, waterproof barrier of keratin. It lacks blood vessels and relies on underlying tissues for nourishment and waste removal. The epidermis regenerates rapidly when well-nourished.
Dermis: The middle layer, made of elastic connective tissue (primarily collagen). It contains nerves, hair follicles, glands, immune cells, and blood vessels. Hair shafts project through the dermis, while follicles are embedded within it.
Subcutaneous Tissue (Hypodermis): The deepest layer, consisting of adipose (fat) and connective tissue. It stores energy, insulates the body, and cushions underlying structures. This layer also contains blood and lymph vessels, nerves, and fat cells.

Mucous membranes line body cavities that open to the exterior (e.g., digestive, respiratory, urinary, and reproductive tracts). They secrete mucus, provide protection, and absorb substances.

Functions of the Skin and Mucous Membranes

Protection: Acts as a barrier against water loss, microorganisms, UV radiation, and physical injury.
Temperature Regulation: Perspiration and blood vessel dilation dissipate heat; constriction and piloerection (goosebumps) conserve heat.
Psychosocial: Contributes to appearance, self-esteem, identification, and communication.
Sensation: Contains nerve endings for touch, pain, pressure, and temperature.
Vitamin D Production: UV rays activate skin to produce vitamin D.
Immunologic: Triggers immune responses when the skin is breached.
Absorption: Absorbs substances (e.g., medications) for local/systemic effects.
Elimination: Excretes water, electrolytes, and nitrogenous wastes via sweat.

Factors Affecting Skin Integrity

Integrity: Unbroken, healthy skin and mucous membranes are the first line of defense against pathogens.
Resistance to Injury: Varies with age, tissue amount, comorbidities, nutrition, hydration, and circulation.
Developmental Considerations: Infants have thinner, more fragile skin; older adults have delayed cell maturation, decreased elasticity, and impaired circulation/collagen formation.
State of Health: Malnutrition, dehydration, excessive moisture, jaundice, and skin diseases (e.g., eczema, psoriasis) increase risk for skin breakdown.

Wounds and Pressure Injuries

Wound Classification

A wound is a break in the normal integrity of the skin and tissues. Wounds are classified by etiology, depth, and healing process:

Etiology:
- Surgical: Intentional, controlled, sterile incisions.
- Traumatic: Accidental injuries (e.g., lacerations, abrasions).
- Neuropathic/Vascular: Related to underlying neurologic or circulatory issues (e.g., diabetic ulcers).
- Pressure-related: Due to prolonged pressure, often over bony prominences.
Open vs. Closed:
- Open: Skin surface is broken (e.g., incision, abrasion).
- Closed: Skin intact, but underlying tissue damaged (e.g., contusion, hematoma).
Acute vs. Chronic:
- Acute: Heal within days to weeks, edges well-approximated.
- Chronic: Do not progress through normal healing, remain in inflammatory phase, increased infection risk.

Common Types of Wounds and Causes

Type	Cause
Incision	Sharp instrument; well-approximated edges
Contusion	Blunt force; skin intact, underlying tissue injured
Abrasion	Friction/rubbing; superficial skin loss
Laceration	Tearing with blunt/irregular instrument; often contaminated
Puncture	Penetration by sharp/blunt object
Penetrating	Foreign object lodges in tissue
Avulsion	Tearing from normal position; possible vessel/nerve damage
Chemical	Toxic agents (drugs, acids, etc.)
Thermal	High/low temperatures; burns/frostbite
Irradiation	UV/radiation exposure
Pressure Ulcers	Compromised circulation from pressure/friction
Venous/Arterial/Diabetic Ulcers	Vascular insufficiency, neuropathy

Wound Healing

Wound healing is a complex process involving tissue repair and regeneration. It occurs in several phases:

Hemostasis: Immediate vasoconstriction and clot formation to stop bleeding.
Inflammatory Phase: Lasts 2–3 days; WBCs (leukocytes, macrophages) remove debris and bacteria; growth factors released.
Proliferation/Repair Phase: Lasts several weeks; fibroblasts synthesize collagen, new capillaries form, granulation tissue develops, and epithelialization occurs.
Maturation/Remodeling Phase: Begins ~3 weeks post-injury, may last months/years; collagen reorganizes, scar tissue forms (less elastic, 70–80% strength of normal tissue).

Wounds may heal by:

Primary Intention: Edges well-approximated (e.g., surgical incision).
Secondary Intention: Edges not approximated; more tissue loss, longer healing, more scarring.
Tertiary Intention: Wound left open initially, then closed after infection/edema resolves.

Factors Affecting Wound Healing

Local Factors:
- Pressure, desiccation (drying), maceration (overhydration), trauma, edema, infection, excessive bleeding, necrosis, biofilm formation.
Systemic Factors:
- Age, circulation/oxygenation, nutritional status, wound etiology, general health, immunosuppression, medication use, adherence to treatment.

Wound Complications

Infection: Delays healing, may cause systemic illness (e.g., sepsis, osteomyelitis).
Hemorrhage: May require pressure, fluid replacement, or surgery.
Dehiscence: Partial/total separation of wound layers.
Evisceration: Protrusion of internal organs through wound; medical emergency.
Fistula: Abnormal passage between organs or from organ to skin.

Pressure Injuries (Pressure Ulcers)

Pathophysiology and Risk Factors

Pressure injuries result from prolonged pressure, friction, shear, and microclimate (moisture/temperature) changes, especially over bony prominences. They are common in older adults, immobile patients, and those with chronic illnesses.

Mechanisms:
- External pressure compresses blood vessels, causing ischemia and necrosis.
- Friction damages superficial skin layers.
- Shear forces stretch/tear blood vessels and tissues.
- Microclimate (moisture) reduces skin tolerance to pressure/shear.
Risk Factors:
- Immobility, poor nutrition/hydration, incontinence, altered mental status, advanced age, chronic diseases (e.g., diabetes), poor skin hygiene, sensory deficits, obesity/thinness, smoking, surgery, terminal illness.

Pressure Injury Staging

Stage	Description
Stage 1	Intact skin with nonblanchable erythema (redness); may be painful, firm, soft, warmer/cooler than adjacent tissue.
Stage 2	Partial-thickness loss of dermis; shallow open ulcer or serum-filled blister.
Stage 3	Full-thickness tissue loss; subcutaneous fat may be visible; bone/tendon/muscle not exposed; may have slough/eschar, undermining, or tunneling.
Stage 4	Full-thickness tissue loss with exposed/palpable bone, cartilage, ligament, tendon, fascia, or muscle; often with slough/eschar, undermining, or tunneling.
Unstageable	Full-thickness loss; depth obscured by slough or eschar.
Deep Tissue Pressure Injury (DTPI)	Persistent nonblanchable deep red, maroon, or purple discoloration; may be intact or nonintact skin.

Assessment and Documentation

Skin Assessment: Systematic head-to-toe inspection, focusing on bony prominences and at-risk areas. Frequency depends on care setting (e.g., every shift in acute care).
Wound Assessment: Location, size (length, width, depth), appearance (edges, color, tissue type), drainage (amount, type, odor), presence of drains/tubes, pain, periwound skin condition.
Risk Assessment Tools: Braden Scale (mental status, continence, mobility, activity, nutrition), PUSH Tool (monitors healing), RYB Classification (Red-Yellow-Black).
Laboratory Indicators: Albumin, prealbumin, total lymphocyte count, hemoglobin A1c, glucose.

Wound and Pressure Injury Management

Prevention Strategies

Regular repositioning (e.g., every 2 hours in bed, every hour in chair).
Use of support surfaces (special mattresses, cushions).
Minimize friction and shear (use lifting devices, friction-reducing sheets).
Maintain skin hygiene and moisture balance (barrier creams, moisture-wicking materials).
Optimize nutrition and hydration.
Educate patients and caregivers on risk factors and prevention.

Wound Care Principles

Promote moist wound healing (closed dressings preferred over open air).
Debride necrotic tissue (autolytic, enzymatic, mechanical, or surgical methods).
Choose dressings based on wound characteristics (moisture, exudate, infection risk).
Use aseptic technique for dressing changes; sterile for surgical wounds, clean for pressure injuries.
Manage pain before and during dressing changes.

Types of Dressings

Type	Purpose	Example
Gauze (dry/wet)	Absorb drainage, cover wounds	Closed surgical wounds
Nonadherent	Prevent sticking to wound	Telfa, petrolatum gauze
Transparent films	Occlusive, waterproof, allow visualization	IV sites, noninfected wounds
Hydrocolloids	Maintain moist environment, autolytic debridement	Pressure injuries
Foams, alginates	Absorb heavy exudate	Venous ulcers

Wound Drains

Type	Purpose	Example
Penrose (open)	Passive drainage into dressing	Abscess drainage
Jackson-Pratt (closed)	Active suction drainage	Post-surgical wounds
Hemovac (closed)	Active suction drainage	Orthopedic/abdominal surgery
T-tube	Collects bile	After gallbladder surgery

Advanced Therapies

Negative Pressure Wound Therapy (NPWT): Applies uniform negative pressure to promote healing, remove exudate, and stimulate tissue growth. Not used with active bleeding, exposed vessels/organs, malignancy, or dry/necrotic tissue.
Growth Factors: Recombinant PDGF can promote healing in chronic wounds.
Hyperbaric Oxygen Therapy (HBOT): Patient breathes 100% oxygen in a pressurized chamber to enhance oxygenation, angiogenesis, and immune function in chronic wounds.
Fibrin Sealants: Used intraoperatively to stop bleeding and glue tissues; eventually absorbed by the body.

Heat and Cold Therapy

Heat: Dilates blood vessels, increases metabolism, reduces muscle tension, and relieves pain. Used for infections, wounds, arthritis, and muscle pain. Prolonged application can cause vasoconstriction and tissue damage.
Cold: Constricts blood vessels, reduces edema, muscle spasms, and pain. Used after trauma, for dental pain, and muscle spasms. Prolonged exposure can cause tissue injury.
Rebound Phenomenon: Maximum vasodilation (heat) or vasoconstriction (cold) occurs within 20–30 minutes, after which the opposite effect may occur.

Patient Education and Documentation

Teach patients/caregivers about wound care, infection signs, pain management, and nutrition.
Document wound characteristics, care provided, patient response, and progress toward healing.
Use photographs for objective assessment over time.

Psychological Effects of Wounds and Pressure Injuries

Pain: Both physical and psychological; may be worsened by movement or dressing changes.
Anxiety and Fear: Concerns about wound appearance, healing, and privacy.
Impact on Activities of Daily Living: May limit self-care, work, and social activities.
Body Image Changes: Scarring or disfigurement can affect self-esteem and social relationships.

Summary Table: Wound Healing Phases

Phase	Key Events	Time Frame
Hemostasis	Vasoconstriction, platelet aggregation, clot formation	Immediate
Inflammatory	WBC infiltration, debris removal, growth factor release	2–3 days
Proliferation	Fibroblast activity, collagen synthesis, granulation tissue, epithelialization	Several weeks
Maturation	Collagen remodeling, scar formation	3 weeks to years

Additional info: This summary expands on the original notes with definitions, examples, and context for wound types, healing phases, and care strategies, as would be expected in a college-level Personal Health course.