Platelets are a source of

Options

A. Fibrinogen
B. Calcium
C. Thromboplastin
D. Haemoglobin.

Answer

**Step-by-Step Text Solution:**

1. **Understanding Platelets**: Platelets, also known as thrombocytes, are small cell fragments in the blood that play a crucial role in the process of blood clotting.

2. **Identifying the Options**: The question asks for what platelets are a source of. The options provided include fibrinogen, calcium, thromboplastin, and hemoglobin.

3. **Analyzing Fibrinogen**: Fibrinogen is a protein produced by the liver that helps in blood clotting by forming fibrin, which is essential for clot formation. However, platelets themselves do not produce fibrinogen, so this option is incorrect.

4. **Analyzing Calcium**: Calcium is an important mineral that is a key component of bones and is involved in various physiological processes, including blood coagulation. However, platelets are not a source of calcium, making this option incorrect as well.

5. **Analyzing Thromboplastin**: Thromboplastin, also known as tissue factor or thrombokinas, is a plasma protein that plays a significant role in blood coagulation. It is found in platelets and helps in the conversion of prothrombin to thrombin, which is essential for blood clotting. Therefore, this option is correct.

6. **Analyzing Hemoglobin**: Hemoglobin is a protein found in red blood cells that is responsible for transporting oxygen and carbon dioxide in the blood. It is not related to platelets, so this option is incorrect.

7. **Conclusion**: The correct answer to the question "Platelets are a source of" is thromboplastin.

**Final Answer**: Platelets are a source of thromboplastin.

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