Which phase of wound healing is characterized by the predominance of type III collagen, and approximately how long does this phase typically last?

Explanation

## Phases of Wound Healing and Collagen Deposition **Key Point:** Type III collagen is the predominant collagen during the proliferative phase (3–21 days). It is later replaced by type I collagen during remodelling, resulting in a stronger scar. ### Timeline and Collagen Composition by Phase | Phase | Duration | Collagen Type | Key Events | |---|---|---|---| | Haemostatic | < 1 day | Fibrin clot | Platelet aggregation, coagulation cascade | | Inflammatory | 1–3 days | Minimal collagen | Neutrophil and macrophage infiltration | | Proliferative | 3–21 days | Type III collagen (predominant) | Fibroblast proliferation, angiogenesis, granulation tissue | | Remodelling | 3 weeks–2 years | Type I collagen (replaces type III) | Collagen cross-linking, scar maturation, tensile strength increase | **Mnemonic:** **HAIR** = **H**aemostasis, **A**ngiogenesis/inflammatory, **I**nterstitial (proliferative), **R**emodelling **High-Yield:** Type III collagen is more soluble and labile than type I; the ratio of type I:type III increases from ~1:3 during proliferation to ~4:1 in mature scar. This shift is essential for scar strength. **Clinical Pearl:** Premature wound disruption (e.g., suture removal before 7–10 days) occurs because type III collagen provides insufficient tensile strength early in healing.