• Question: What causes a blood clot?

    Asked by georgina19 to Clare, Mariana, Robert, Susanne on 21 Nov 2012.
    • Photo: Clare Taylor

      Clare Taylor answered on 21 Nov 2012:

      Blood clots form when the lining of a blood vessel becomes damaged. Tiny irregular shaped things called platelets migrate to the injured area to form a plug. These platelets then release chemicals that start the clotting process which involves a series of clotting factors that are produced by the body. The end result is that a protein called fibrin is formed, and the fibrin sticks to itself to form a mesh that makes up the final blood clot and stop your blood from flowing out of the injured vessel. This all happens very quickly!

    • Photo: Robert Insall

      Robert Insall answered on 21 Nov 2012:

      Hello Georgina. I like your profile page. Practical work is truly the way to succeed in science.

      Blood clots get caused by damae to blood vessels. The first thing that happens is small, round white blood cells called platelets get “activated”. Activated means they go from a round plate shape (that’s why they’re called platelets) to great big hairy sticky things that glom together and start a clot.

      They also secrete a protein called thrombin that starts a whole load of other reactions that make long fibres. But it’s the platelets that start it all.

    • Photo: Susanne Muekusch

      Susanne Muekusch answered on 21 Nov 2012:

      Hi Georgina,

      The cascade of signals that send the message “damaged vessel -> form a blood clot!” is really complicated. Since Clare and Robert covered already what happens, I will tell you a bit about what can go wrong.

      Some individuals lack a part of the signalling cascade- the message stops somewhere along the way and never gets to the “form a blood clot!” point. Blood clotting is very inefficient and as a consequence the patients bleed much longer than healthy people. The disorder is called bleeding disorder or hemophilia. It is inherited and was very common in european dynasties.

      Some drugs like Aspirin inhibit the ability to form blood clots. My brother cut himself a little bit when he was ill and had taken some Aspirin. It continued to bleed for two hours!!! Normally, it would have stopped after two minutes. Aspirin is used as a prophylactic treatment in patients at a high risk of stroke or heart attack- both can be caused by blood clots. Aspirin lowers the risk of blood clots forming.

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