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The blood does not clot inside the body due to anti-coagulants. Why does it clot outside the body? For example; when the blood is taken in a tube, it clots after some time, why?

Yes, a deficiency of anti-coagulants can be the reason. But what actually happens outside the body to clot the blood because there is no specific mechanism which can be found inside the body to clot the blood on injured parts?

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closed as too broad by MattDMo, Satwik Pasani, fileunderwater, kmm Nov 14 '13 at 13:40

There are either too many possible answers, or good answers would be too long for this format. Please add details to narrow the answer set or to isolate an issue that can be answered in a few paragraphs.If this question can be reworded to fit the rules in the help center, please edit the question.

    
Please read the Coagulation article on Wikipedia and let us know if you have any more specific questions. As it currently stands, this question is very broad, and there exist many excellent resources online regarding this subject. –  MattDMo Nov 14 '13 at 1:05
    
Blood also clots inside the body (If I am not mistaken) in certain circumstances such as injured endothelial lining, atherosclerotic plaque etc. –  Satwik Pasani Nov 14 '13 at 2:35
    
There are different factors that cause the blood to clot at the point of injury. By outside, i mean in a tube. When blood is taken in a tube, after some time it clots. Why does this happen because there is no mechanism outside the body to control it. Let me edit my question –  Rafique Nov 14 '13 at 16:49

1 Answer 1

From Guyton and Hall :

Glass containers allow contact activation of the platelets and Factor XII with rapid development of clots.

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this does not explain why this is and so it is not an answer –  caters Aug 10 at 4:51

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