A 35-year-old man undergoes elective abdominal surgery for peptic ulcer perforation repair. On postoperative day 5, the wound shows erythema, induration, and serosanguinous discharge. Histologically, the wound demonstrates prominent fibroblast proliferation, collagen deposition, and neovascularization. Which phase of wound healing is predominantly occurring?

Explanation

## Wound Healing Phases: Timeline and Histology Wound healing progresses through four overlapping phases: | Phase | Timeline | Key Features | Histology | |-------|----------|--------------|----------| | **Hemostasis** | 0–minutes | Platelet aggregation, fibrin clot | Fibrin mesh, platelets | | **Inflammatory** | 0–3 days | Neutrophils, macrophages, cytokine release | Inflammatory cell infiltrate | | **Proliferative** | 3–21 days | Angiogenesis, collagen synthesis, epithelialization | Fibroblasts, new vessels, collagen | | **Remodeling** | 21 days–2 years | Collagen cross-linking, scar maturation | Organized collagen, reduced cellularity | ### Clinical and Histological Clues in This Case: - **Postoperative day 5**: Falls within the proliferative phase (days 3–21) - **Fibroblast proliferation**: Hallmark of proliferation phase - **Collagen deposition**: Active synthesis during proliferation - **Neovascularization**: Angiogenesis is a cardinal feature of proliferation - **Erythema and induration**: Reflect active granulation tissue formation **Key Point:** The proliferative phase is characterized by the transition from inflammation to tissue rebuilding. Fibroblasts migrate into the wound, synthesize collagen (types I and III), and endothelial cells form new blood vessels. This phase peaks around day 5–7 and is clinically the most important for wound strength gain. **Clinical Pearl:** Wound strength increases from ~5% at day 3 to ~20% by day 7 during the proliferative phase due to collagen accumulation.