Which of the following substances, if introdced into the blood system, would cause coagulation of blood at the site of its introduction

Options

A. Thromboplastin
B. Fibrinogen
C. Heparin
D. prothrombin

Answer

To solve the question regarding which substance would cause coagulation of blood at the site of its introduction, we can follow these steps:

### Step 1: Understand the Role of Thromboplastin
Thromboplastin, also known as thrombokinase, is a crucial factor in the blood coagulation process. It is a mixture of phospholipids and tissue factor found in the plasma that initiates the clotting cascade.

**Hint:** Look for substances that initiate the coagulation process.

### Step 2: Examine the Coagulation Process
The coagulation process involves several steps:
- Thromboplastin converts prothrombin (a plasma protein) into thrombin.
- Thrombin then acts on fibrinogen, converting it into fibrin, which forms the mesh that constitutes the blood clot.

**Hint:** Identify the sequence of events in the coagulation pathway.

### Step 3: Analyze the Options
1. **Thromboplastin**: This is essential for initiating coagulation by converting prothrombin to thrombin. Therefore, it would cause coagulation at the site of introduction.

2. **Fibrinogen**: This is converted into fibrin by thrombin, but it does not initiate coagulation itself. Thus, it is not the correct answer.

3. **Heparin**: This is an anticoagulant that prevents blood clotting, so it would not cause coagulation. Hence, it is incorrect.

4. **Prothrombin**: This is a precursor to thrombin but requires thromboplastin for its conversion. Therefore, it cannot cause coagulation on its own.

**Hint:** Evaluate each option based on its role in the coagulation process.

### Step 4: Conclusion
Based on the analysis, the correct answer is **thromboplastin**, as it is the substance that directly initiates the coagulation process when introduced into the blood system.

**Final Answer:** Thromboplastin