Which is unrelated to blood coagulation ?

Options

A. Fibrinogen
B. Fibrin
C. Bilirubin
D. Calcium

Answer

To determine which option is unrelated to blood coagulation, we will analyze each of the given options: fibrinous, fibrin, bilirubin, and calcium.

### Step-by-Step Solution:

1. **Understanding Blood Coagulation**:
- Blood coagulation is the process by which blood changes from a liquid to a gel, forming a blood clot. This process is essential for stopping bleeding when injuries occur.

2. **Analyzing the Options**:
- **Option 1: Fibrinous**:
- Fibrinous refers to fibrin, which is a protein involved in the clotting process. It is formed from fibrinogen and is crucial for the formation of blood clots. Therefore, this is related to blood coagulation.

- **Option 2: Fibrin**:
- Fibrin is the actual protein that forms the meshwork of the blood clot. It is derived from fibrinogen in the presence of thrombin and is essential for blood coagulation. Thus, this is also related to blood coagulation.

- **Option 3: Bilirubin**:
- Bilirubin is a waste product formed from the breakdown of hemoglobin in old red blood cells. It is not involved in the blood coagulation process. Instead, it is processed by the liver and excreted in bile. Therefore, this is unrelated to blood coagulation.

- **Option 4: Calcium**:
- Calcium ions play a vital role in the coagulation cascade. They are necessary for the conversion of prothrombin to thrombin, which is a key step in the clotting process. Hence, this is related to blood coagulation.

3. **Conclusion**:
- After analyzing all options, it is clear that **bilirubin** is the only component that is unrelated to blood coagulation.

### Final Answer:
- The correct answer is **bilirubin** (Option 3).

---