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

Explanation

## Definition and Histology of Contusion **Key Point:** A contusion is a blunt force injury characterized by hemorrhage in the dermis and subcutaneous tissues with the epidermis remaining intact — the hallmark feature that distinguishes it from abrasion. ### Microscopic Features of Contusion 1. **Intact epidermis** — outer skin layer is not breached 2. **Hemorrhage in dermis** — red blood cells extravasate into dermal tissue 3. **Subcutaneous bleeding** — may extend into deeper fat and muscle planes 4. **No loss of skin continuity** — the wound is closed ### Comparison with Abrasion | Feature | Contusion | Abrasion | |---------|-----------|----------| | **Epidermis** | Intact | Lost/denuded | | **Dermis** | Hemorrhage present | Exposed | | **Bleeding** | Present (internal) | Minimal/none | | **Scar formation** | Rare | Common | | **Healing time** | Days to weeks | Hours to days | **High-Yield:** The presence of hemorrhage *without* loss of skin continuity is the defining histological criterion of contusion. This distinguishes it from abrasion (epidermis lost) and laceration (full-thickness wound with irregular margins). **Clinical Pearl:** Contusions appear as bruises or ecchymoses clinically — the color changes (red → purple → yellow) reflect the breakdown of hemoglobin over time. Abrasions, by contrast, appear as raw, bleeding surfaces with loss of the outer skin layer. [cite:Parikh's Textbook of Medical Jurisprudence & Toxicology Ch 5]