Which of the following prevent(s) blood clotting in uninjured blood vessels ?

Options

A. Albumins
B. Histamine
C. Heparin
D. Globulins

Answer

To solve the question "Which of the following prevent(s) blood clotting in uninjured blood vessels?", we will analyze the options provided: albumins, histamine, heparin, and globulins.

### Step-by-Step Solution:

1. **Understanding Blood Clotting**: Blood clotting is a process that prevents excessive bleeding when blood vessels are injured. However, in uninjured blood vessels, we want to prevent unnecessary clotting to maintain normal blood flow.

2. **Analyzing Albumins**: Albumins are plasma proteins that play a significant role in the transportation of nutrients and osmoregulation. They do not have a direct role in preventing blood clotting. Thus, albumins are not the correct answer.

3. **Analyzing Histamine**: Histamine is a molecule secreted by mast cells during allergic responses. It is involved in inflammatory responses but does not play a role in preventing blood clotting. Therefore, histamine is also not the correct answer.

4. **Analyzing Heparin**: Heparin is a glycosaminoglycan that acts as an anticoagulant. It is released by mast cells and prevents blood clotting by inhibiting the activation of prothrombin, which is essential for the conversion of fibrinogen to fibrin. Heparin is widely used in medical settings to prevent blood clots, making it the correct answer.

5. **Analyzing Globulins**: Globulins, also known as immunoglobulins, are plasma proteins that play a crucial role in the immune response by producing antibodies. They do not prevent blood clotting, so globulins are not the correct answer.

### Conclusion:
After analyzing all the options, we conclude that the correct answer is **Heparin (Option C)**, as it is the only substance that prevents blood clotting in uninjured blood vessels.

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