During injury mast cells secrete

Options

A. Histamine
B. Heparin
C. Prothrombin
D. Antibodies

Answer

**Step-by-Step Solution:**

1. **Understanding Mast Cells:**
- Mast cells are a type of white blood cell that play a crucial role in the immune system, particularly in allergic reactions and inflammation. They are primarily found in connective tissues and mucosal areas.

2. **Role of Mast Cells During Injury:**
- When an injury occurs, mast cells respond quickly due to their proximity to the site of injury. They release various substances that help mediate the inflammatory response.

3. **Inflammatory Mediators:**
- The substances released by mast cells during injury are called inflammatory mediators. These mediators are responsible for the symptoms of inflammation, such as redness, swelling, and warmth.

4. **Key Substance Released: Histamine:**
- One of the primary substances released by mast cells is histamine. Histamine is a chemical that causes blood vessels to dilate and increases their permeability, leading to the classic signs of inflammation.

5. **Effects of Histamine:**
- The release of histamine results in:
- Dilation of blood vessels, which increases blood flow to the area (causing redness).
- Increased permeability of blood vessels, allowing fluids and immune cells to enter the tissue (causing swelling).
- Activation of endothelial cells, which further promotes the inflammatory response.

6. **Evaluating the Options:**
- The options provided are:
- Histamine
- Heparin
- Prothrombin
- Antibodies
- Histamine is the correct answer as it is the primary mediator released by mast cells during an injury. Heparin, while also released, is primarily an anticoagulant and not directly involved in the inflammatory response. Prothrombin is related to blood clotting, and antibodies are produced by B cells, not mast cells.

7. **Conclusion:**
- Therefore, the correct answer is that during injury, mast cells secrete histamine.

---