Platelets are tiny fragments of cells in the blood. These help blood to clot. They have no nucleus and are made in bone marrow.

Blood clotting[edit | edit source]

When the skin is cut deep enough to break blood vessels, platelets bunch together to seal the wound - this is called blood clotting. For this to work, clotting factors such as the protein fibrin are used.

Clotting is needed to prevent blood loss via the cut and to stop pathogens from entering the body.

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