1. Wound Healing

 

Wound Healing

This is a perfect first topic because it connects anatomy, physiology, pathology, diabetes, nutrition, infection, surgery, and OSCE.

Why Wound Healing Is High-Yield

Wound healing appears in:

  1. Basic physiology

  2. Pathology

  3. Principles of surgery

  4. Infection

  5. Nutrition

  6. Diabetes and steroids

  7. Sutures and wound complications

  8. OSCE counselling

Wound Healing: Exam-Focused Version

Definition

Wound healing is the biological process by which the body restores tissue integrity after injury.

The key point:

Healing is not just “closure.” It is controlled inflammation, tissue formation, collagen deposition, and remodelling.

The 4 Phases of Wound Healing

1. Haemostasis

Time: immediate

What happens:

  1. Vasoconstriction

  2. Platelet plug formation

  3. Clot formation

  4. Fibrin scaffold formation

Main cells:

  • Platelets

  • Endothelial cells

Important mediators:

  • Thromboxane A2

  • ADP

  • Fibrin

  • Platelet-derived growth factor

Exam point:

Haemostasis provides the temporary matrix for later cell migration.

2. Inflammation

Time: day 0–3

What happens:

  1. Vasodilation

  2. Increased vascular permeability

  3. Neutrophil migration

  4. Macrophage activation

Main cells:

  • Neutrophils early

  • Macrophages later

Key role of macrophages:

Macrophages are the most important regulatory cells in wound healing.

They clear debris, control infection, and release growth factors.

Important mediators:

  • IL-1

  • IL-6

  • TNF-alpha

  • TGF-beta

  • PDGF

MCQ trap:

Neutrophils arrive first, but macrophages coordinate healing.

3. Proliferation

Time: day 3–21

What happens:

  1. Fibroblast proliferation

  2. Collagen type III deposition

  3. Angiogenesis

  4. Granulation tissue formation

  5. Epithelialisation

  6. Wound contraction

Main cells:

  • Fibroblasts

  • Endothelial cells

  • Keratinocytes

  • Myofibroblasts

Key collagen:

Early wound = type III collagen.

Granulation tissue consists of:

  1. New capillaries

  2. Fibroblasts

  3. Loose extracellular matrix

  4. Inflammatory cells

4. Remodelling / Maturation

Time: weeks to months

What happens:

  1. Type III collagen replaced by type I collagen

  2. Collagen cross-linking

  3. Scar strength increases

  4. Vascularity decreases

Important point:

A healed wound never regains 100% of original tensile strength.

At around 3 months, tensile strength reaches roughly 70–80% of normal tissue strength.

MCQ trap:

The scar becomes stronger due to collagen cross-linking and remodelling, not because it returns to normal tissue.

Types of Wound Healing

Primary Intention

Clean surgical incision closed with sutures.

Features:

  • Minimal tissue loss

  • Minimal granulation tissue

  • Small scar

  • Fast healing

Example:

Clean elective hernia incision closed primarily.

Secondary Intention

Wound left open to heal by granulation, contraction, and epithelialisation.

Features:

  • More tissue loss

  • More granulation tissue

  • More contraction

  • Larger scar

  • Slower healing

Example:

Infected abscess cavity after drainage.

Tertiary Intention / Delayed Primary Closure

Wound initially left open, then closed later after infection/contamination risk improves.

Example:

Contaminated traumatic wound cleaned and closed after a few days.

Factors That Impair Wound Healing

Local Factors

  1. Infection

  2. Poor blood supply

  3. Foreign body

  4. Haematoma

  5. Necrotic tissue

  6. Excessive tension

  7. Poor surgical technique

  8. Radiation

Systemic Factors

  1. Diabetes mellitus

  2. Malnutrition

  3. Vitamin C deficiency

  4. Zinc deficiency

  5. Steroids

  6. Smoking

  7. Anaemia

  8. Uraemia

  9. Jaundice

  10. Advanced age

  11. Immunosuppression

High-yield exam memory:

“Infection, ischaemia, diabetes, malnutrition, steroids, smoking” are the big six.

Vitamin and Nutritional Points

Vitamin C

Needed for:

Hydroxylation of proline and lysine during collagen synthesis.

Deficiency causes:

  • Poor collagen formation

  • Weak scar

  • Bleeding tendency

  • Delayed healing

Zinc

Needed for:

  • DNA synthesis

  • Cell proliferation

  • Enzyme function

Protein

Needed for:

  • Fibroblast activity

  • Collagen synthesis

  • Immune function

Wound Complications

1. Wound Infection

Usually presents with:

  • Pain

  • Redness

  • Warmth

  • Swelling

  • Pus

  • Fever

  • Wound breakdown

Management principle:

Open, drain, culture if needed, remove necrotic tissue, antibiotics if cellulitis/systemic features/high-risk patient.

2. Wound Dehiscence

Partial or complete separation of wound layers.

Risk factors:

  • Infection

  • Poor suturing

  • Raised intra-abdominal pressure

  • Malnutrition

  • Steroids

  • Diabetes

  • Obesity

  • Emergency surgery

Important surgical emergency:

Burst abdomen = complete abdominal wound dehiscence.

Management:

  1. Cover with warm saline-soaked sterile packs

  2. Resuscitate

  3. Analgesia

  4. Broad-spectrum antibiotics if indicated

  5. Urgent return to theatre

3. Hypertrophic Scar

Features:

  • Raised scar

  • Confined to wound boundary

  • May regress over time

4. Keloid

Features:

  • Extends beyond original wound boundary

  • Does not regress easily

  • More common in darker skin

  • Common sites: sternum, shoulder, ear lobes

MCQ trap:

Hypertrophic scar stays within wound margin. Keloid grows beyond it.

MCQ Traps to Remember

  1. Macrophages are the key regulatory cells in wound healing.

  2. Type III collagen is laid down first.

  3. Type I collagen dominates mature scar.

  4. Vitamin C is needed for collagen hydroxylation.

  5. Primary intention gives minimal granulation tissue.

  6. Secondary intention gives more contraction and scarring.

  7. Keloid extends beyond the wound margin.

  8. Wounds never regain full original tensile strength.

Mini Practice: Answer These Now

Try these without looking back.

Question 1

The most important cell regulating wound healing is:

A. Neutrophil
B. Macrophage
C. Platelet
D. Keratinocyte
E. Eosinophil

Question 2

The main collagen laid down in the early proliferative phase is:

A. Type I
B. Type II
C. Type III
D. Type IV
E. Type V

Question 3

Vitamin C is important in wound healing because it is required for:

A. Platelet aggregation
B. Collagen hydroxylation
C. Keratinocyte migration
D. Fibrinolysis
E. Angiogenesis only

Question 4

A scar that grows beyond the original wound margin is called:

A. Contracture
B. Hypertrophic scar
C. Keloid
D. Granuloma
E. Sinus

Question 5

A contaminated wound that is cleaned and closed after a few days heals by:

A. Primary intention
B. Secondary intention
C. Tertiary intention
D. Epithelialisation only
E. Fibrosis only

Answers

  1. B — Macrophage

  2. C — Type III

  3. B — Collagen hydroxylation

  4. C — Keloid

  5. C — Tertiary intention / delayed primary closure

Your First Assignment

Before the next session, prepare these three things:

1. One-page summary

Write one page on:

Phases of wound healing and factors delaying wound healing

2. Active recall list

Memorise:

  • 4 phases of wound healing

  • Type III vs Type I collagen

  • Local and systemic factors delaying healing

  • Keloid vs hypertrophic scar

  • Primary vs secondary vs tertiary intention

3. Practice answer

Write a short answer to this OSCE/viva question:

“A 62-year-old diabetic patient develops redness and discharge from an abdominal surgical wound on day 5 after laparotomy. How would you assess and manage this patient?”

Send me your answer, and I’ll mark it like an examiner.


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