Fabiana's Wound Healing Matcher

Reference Material

Phases of Wound Healing

Phase	Timing	Key Cells	Major Events & Mediators
1. Hemostasis & Inflammation	Immediate – 3 Days	• Platelets • Neutrophils (arrive w/in 24h) • Macrophages (arrive 2–3 days)	Hemostasis: Platelet aggregation and clot formation (fibrin). Inflammation: • Platelets release PDGF and TGF-β (chemotaxis). • Neutrophils: Clear bacteria/debris. • Macrophages: Phagocytose debris and secrete growth factors.
2. Proliferation	Day 3 – Weeks	• Fibroblasts • Myofibroblasts • Endothelial cells • Keratinocytes	Granulation Tissue Formation: • Fibroblasts synthesize Collagen Type III and fibronectin. • Angiogenesis: Stimulated by VEGF and FGF. • Wound Contraction: Mediated by myofibroblasts. • Epithelialization: Keratinocytes migrate.
3. Remodeling (Maturation)	1 Week – 6+ Months	• Fibroblasts	Collagen Swapping: • Collagen Type III is replaced by Collagen Type I. • Mediated by Collagenases (Matrix Metalloproteinases), require Zinc. Outcome: • Tensile strength increases. • Scar tissue is avascular/acellular.

High-Yield USMLE Step 1 Notes

• Deficiency Checks: Delayed wound healing is often a Step 1 question hook.
  • Vitamin C deficiency (Scurvy): Impairs hydroxylation of proline/lysine; creates weak collagen.
  • Zinc deficiency: Impairs collagenase activity (delayed remodeling).
  • Copper deficiency: Impairs lysyl oxidase (cross-linking).
• Keloids vs. Hypertrophic Scars:
  • Hypertrophic: Parallel collagen arrangement, confined to wound borders.
  • Keloid: Disorganized collagen (Type I & III), extends beyond wound borders, high recurrence.
• Dehiscence: Rupture of a wound; most common in abdominal surgery due to increased abdominal pressure.

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