## Definition and Depth of Abrasion **Key Point:** An abrasion is a superficial mechanical injury that involves only the epidermis (and sometimes the superficial dermis), without penetrating into deeper layers. ### Pathophysiology Abrasions result from friction or scraping against a rough surface. The injury is confined to the outer layers of skin because the mechanical force is applied tangentially rather than perpendicularly. ### Distinguishing Features | Feature | Abrasion | Contusion | Laceration | |---------|----------|-----------|----------| | **Depth** | Epidermis ± superficial dermis | Dermis, subcutaneous tissue, muscle | Full thickness skin + deeper structures | | **Bleeding** | Minimal or absent (capillaries not reached) | Present (tissue damage) | Prominent (vessel disruption) | | **Wound edges** | Irregular, abraded | Intact skin surface | Irregular or clean depending on mechanism | | **Scarring** | Minimal | Possible if deep | Common | **High-Yield:** Abrasions do NOT bleed significantly because the injury does not reach the vascular plexus in the dermis. This is a key differentiator from contusions and lacerations. ### Clinical Significance - Abrasions are often called "graze wounds" or "friction burns" - They may contain embedded foreign material (dirt, gravel) that requires cleaning - Healing occurs without sutures in most cases - Scarring is minimal unless infection occurs **Clinical Pearl:** In forensic examination, abrasions can indicate the direction of force application and are useful in reconstructing the mechanism of injury.
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