Wound Healing

Wound -

Definition   

  • A wound is a break or disruption in the normal continuity of the skin, mucous membrane, or underlying tissues, caused by physical, chemical, thermal, or biological injury.
  • A wound is defined as a separation or discontinuity of the skin, tissue, mucous membrane caused by physical, chemical or biological insult

Classification of Wound

A wound is defined as a break in the continuity of the skin, mucous membrane, or underlying tissues caused by physical, chemical, thermal, electrical, or biological agents. Wounds may involve damage to the skin, muscles, blood vessels, nerves, bones, or internal organs and vary widely in severity and healing potential.

Classification of Wounds
1. According to Integrity of Skin

A. Open wound

  • The skin surface is broken, exposing underlying tissues.
  • Examples: incision, laceration, abrasion, puncture.

B. Closed wound

  • The skin remains intact, but underlying tissues are damaged.
  • Examples: contusion (bruise), hematoma.

2. According to Cause or Mechanism of Injury

  1. Incised wound – Clean, straight cut caused by a sharp object (knife, scalpel).
  2. Lacerated wound – Irregular tear of tissues caused by blunt trauma.
  3. Abrasion – Superficial injury caused by friction, involving the epidermis.
  4. Puncture wound – Deep narrow wound caused by pointed objects like nails or needles.
  5. Contusion – Injury caused by blunt force, resulting in bruising.
  6. Crush injury – Caused by compression of tissues between hard surfaces.
  7. Gunshot wound – Caused by firearm projectiles.
  8. Burn wound – Caused by heat, chemicals, electricity, radiation, or friction.

3. According to Degree of Contamination

  1. Clean wound – Uninfected wound with no inflammation; usually surgical.
  2. Clean-contaminated wound – Controlled entry into respiratory, gastrointestinal, or genitourinary tract.
  3. Contaminated wound – Open, fresh wounds with major breaks in sterile technique.
  4. Dirty or infected wound – Old traumatic wounds with retained devitalized tissue or existing infection.

4. According to Duration of Healing

  1. Acute wound – Heals in an orderly and timely (with in 21 days no complications) manner (e.g., surgical incision).
  2. Chronic wound – Fails to heal within the expected time frame due to underlying problems (e.g., pressure ulcers, diabetic ulcers).

5. According to Depth of Tissue Involvement

  1. Superficial wound – Involves only the epidermis.
  2. Partial-thickness wound – Involves epidermis and part of dermis.
  3. Full-thickness wound – Include the epidermis, dermis, subcutaneous fat and sometimes the bone.

6. According to Method of Healing

  1. Healing by primary intention-Wound edges are approximated; minimal tissue loss and scarring.
  2. Healing by secondary intention-Wound edges are not approximated; heals by granulation tissue formation.
  3. Healing by tertiary intention (delayed primary closure)-Wound is initially left open due to contamination and closed later.

Types of  Wound healing-

  1. Primary intention
  2. Secondary intention
  3. Tertiary intention

1. Healing by Primary Intention (Primary Union)

Definition:-Healing that occurs when wound edges are clean, smooth, and closely approximated.

Characteristics:

  • Minimal tissue loss
  • No infection or contamination
  • Wound edges are closed by sutures, staples, or adhesive strips

Healing Process:

  • Rapid epithelialization
  • Minimal granulation tissue formation
  • Limited inflammatory response

Time Taken:-Short duration (few days to 1–2 weeks)

Scar Formation:-Minimal and neat scar

Examples:

  1. Surgical incisions
  2. Clean cuts with suturing

2. Healing by Secondary Intention (Secondary Union)

Definition:-Healing that occurs when wound edges cannot be approximated due to extensive tissue loss.

Characteristics:

  • Large tissue destruction
  • Wound left open
  • Often contaminated or infected

Healing Process:

Healing occurs through:

  • Granulation tissue formation
  • Wound contraction
  • Epithelialization

Time Taken:-Long duration (weeks to months)

Scar Formation:-Large, irregular scar

Examples:

  1. Pressure sores
  2. Burns
  3. Traumatic wounds

3. Healing by Tertiary Intention (Delayed Primary Closure)

Definition:-Healing where the wound is initially left open and closed later.

Characteristics:

  1. Used for contaminated or infected wounds
  2. Closure is delayed until infection subsides

Healing Process:

  1. Initial cleaning and drainage
  2. Later surgical closure

Time Taken:-Moderate (longer than primary, shorter than secondary)

Scar Formation:-Moderate scar

Examples:

  1. Contaminated surgical wounds
  2. Abdominal wounds with infection

Phase of Wound Healing/Wound Healing Process

Wound healing is a dynamic and orderly biological process by which the body repairs damaged tissue and restores skin integrity after injury. It occurs through four overlapping phases.

1. Hemostasis Phase (Immediate)

Time: Immediately after injury (minutes to hours)

Process:

  1. Blood vessels constrict to reduce bleeding
  2. Platelets aggregate and form a blood clot
  3. Fibrin mesh acts as a temporary scaffold

Purpose:

  • Stops bleeding
  • Provides a foundation for cell migration

2. Inflammatory Phase

Time: 1–3 days

Process:

  • Vasodilation occurs
  • White blood cells (neutrophils and macrophages) migrate to wound
  • Removal of bacteria, debris, and dead tissue

Signs:

  1. Redness
  2. Heat
  3. Swelling
  4. Pain

Purpose:

  1. Cleans the wound
  2. Prevents infection

3. Proliferative Phase

Time: 3–21 days

Process:

  1. Fibroblasts produce collagen
  2. Formation of granulation tissue
  3. New blood vessels form (angiogenesis)
  4. Epithelial cells migrate to cover the wound surface (epithelialization)

Purpose:

  1. Fills the wound defect
  2. Restores tissue structure

4. Maturation / Remodeling Phase

Time: Weeks to months (sometimes years)

Process:

  1. Collagen fibers reorganize and strengthen
  2. Scar tissue forms
  3. Blood vessels reduce in number

Purpose:

  1. Increases tensile strength of the wound
  2. Final scar formation
     

Different  Between the  first and second Intention of  Healing 

Features Primary Secondary
Cleanliness Clean Not Clean
Infection Not infected  Infected
Margins Surgically clean Irregular
Sutures Used Not used
Healing Small granulation tissue Large granulation tissue
Outcome Linearscar Irregular wound
Complication Not frequent Frequent

 

Factor Affectng Wound Healing 

A. Local Factors (Wound-related factors)

1. Infection

  • Delays healing
  • Causes increased inflammation and tissue damage

2. Poor Blood Supply

  • Reduces oxygen and nutrient delivery
  • Slows granulation and epithelialization

3. Extent and Type of Wound

  • Large, deep, or contaminated wounds heal slowly
  • Clean surgical wounds heal faster

4. Foreign Bodies

  • Sutures, dirt, or necrotic tissue delay healing

5. Edema

  • Increases pressure
  • Reduces blood flow to the wound area

6. Moisture Balance

  • Too dry → delayed epithelialization
  • Too wet → maceration and infection

7. Repeated Trauma or Pressure

  • Disrupts newly formed tissue
  • Common in pressure ulcers

B. Systemic Factors (Patient-related factors)

1. Age

  • Healing is slower in elderly persons and obesity

2. Nutrition

  • Protein deficiency delays tissue repair
  • Vitamins A, C, zinc are essential

3. Oxygenation

  • Adequate oxygen is required for collagen synthesis

4. Chronic Diseases

  • Diabetes mellitus
  • Anemia
  • HIV
  • Jaundice
  • Vascular diseases

5. Medications

  • Steroids delay inflammation and collagen formation
  • Chemotherapy suppresses cell growth

6. Immunity

  • Reduced immunity increases risk of infection

7. Hydration

  • Dehydration reduces blood volume and healing

8. Smoking

  • Nicotine reduces blood flow
  • Delays wound repair

9. Stress

  • Affects immune response
  • Delays healing

C. Environmental & Lifestyle Factors

1. Poor Hygiene

  • Increases infection risk

2. Socio-economic Status

  • Limited access to healthcare and nutrition

3. Compliance with Treatment

  • Improper wound care delays healing

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