## Distinguishing Abrasion from Contusion **Key Point:** Abrasion and contusion are both blunt force injuries but differ fundamentally in depth of tissue involvement. ### Abrasion (Graze) - Superficial injury affecting **epidermis only** (or epidermis + superficial dermis) - Results from tangential scraping or friction against a rough surface - **No hemorrhage** in the wound itself (bleeding is absent because vessels are in deeper layers) - Healing occurs through epithelialization; minimal scarring - Edges are **not sharply demarcated** ### Contusion (Bruise) - Blunt force injury affecting **dermis and subcutaneous tissue** (deeper than abrasion) - Caused by blunt impact without breaking the skin - **Hemorrhage** into tissue planes (extravasation of blood) - Skin remains intact; discoloration develops over time (red → blue → green → yellow) - Can occur in the absence of visible external injury ### Comparison Table | Feature | Abrasion | Contusion | | --- | --- | --- | | **Depth** | Epidermis only | Dermis + subcutaneous | | **Bleeding** | None (superficial) | Present (tissue hemorrhage) | | **Skin integrity** | Broken | Intact | | **Mechanism** | Friction/scraping | Blunt impact | | **Healing** | Fast (days) | Slow (weeks) | **High-Yield:** The **absence of bleeding in an abrasion** is a key distinguishing feature — abrasions do not bleed because the injury is too superficial to reach blood vessels. Contusions, by contrast, always involve hemorrhage into tissue planes. **Clinical Pearl:** In forensic investigation, abrasions are useful for determining the **direction of force** (the abraded tissue points in the direction of movement), while contusions help establish the **site and severity of blunt trauma**.
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