Platelets are a source of

Options

A. Fibrinoge
B. Calcium
C. Thromboplastin
D. Hemoglobin

Answer

**Step-by-Step 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 (coagulation).

2. **Role in Blood Clotting:**
- When there is an injury to a blood vessel, platelets aggregate at the site and release various substances that help in the clotting process.

3. **Conversion of Prothrombin to Thrombin:**
- One of the key functions of platelets is to facilitate the conversion of prothrombin (a plasma protein) into thrombin. This conversion is essential for the clotting process.

4. **Thromboplastin:**
- The substance that catalyzes the conversion of prothrombin to thrombin is known as thromboplastin. Thromboplastin is a complex enzyme that is found in platelets and is crucial for blood coagulation.

5. **Identifying the Correct Answer:**
- The question asks what platelets are a source of among the options: fibrinogen, calcium, thromboplastin, and hemoglobin.
- Since platelets are involved in the clotting process primarily through the release of thromboplastin, the correct answer is **option C: thromboplastin**.

6. **Conclusion:**
- Therefore, platelets are a source of thromboplastin, which plays a vital role in the blood coagulation process.

**Final Answer:**
- Platelets are a source of **thromboplastin** (Option C).

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