Which of the following is the defining characteristic that distinguishes an abrasion from a contusion?

## Defining Features of Abrasion vs Contusion **Key Point:** The critical distinction lies in the depth of tissue injury and the presence or absence of bleeding. ### Abrasion (Graze) - Superficial injury confined to **epidermis only** (or superficial dermis) - Caused by friction/rubbing against a rough surface - **No bleeding** (capillaries in epidermis are sparse) - Wound edges are **irregular and ill-defined** - Healing without scar formation (if confined to epidermis) - Examples: road rash, friction burns ### Contusion (Bruise) - **Deeper injury** involving dermis, subcutaneous tissue, and sometimes muscle - Caused by blunt force trauma - **Bleeding into tissues** (capillaries ruptured in deeper layers) - Produces discoloration (ecchymosis) that evolves: red → purple → blue → green → yellow - Wound edges are **well-defined** - May heal with scarring if severe **High-Yield:** The **absence of bleeding** in abrasion vs **presence of bleeding** in contusion is the fundamental forensic distinction. **Clinical Pearl:** In autopsy, abrasions appear as drying of the epidermis without hemorrhage, while contusions show hemorrhage in the dermis and subcutaneous layers.