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How do platelets and fibrin help stop bleeding after a wound occurs?

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Close-up of a person holding a child's hand with scabs on the fingers, gently cleaning the wounds with gauze. — wound Injuries that break skin can be painfully memorable.

When a blood vessel is injured, the body initiates a two-stage process to stop bleeding, known as hemostasis.

Platelet Aggregation

The first stage, primary hemostasis, involves platelets. Upon injury, platelets adhere to the damaged site, change shape, and release chemical signals that recruit more platelets. These platelets clump together to form a "platelet plug," which provides an initial, temporary barrier to blood loss.123

Fibrin Mesh Formation

The second stage, secondary hemostasis, involves the coagulation system. This process triggers the production of an enzyme called thrombin, which converts the soluble plasma protein fibrinogen into long, sticky threads of insoluble fibrin.

These fibrin threads create a structural mesh that entangles platelets and blood cells, reinforcing the initial plug. This meshwork eventually contracts to form a resilient, stable blood clot that effectively seals the wound while healing occurs.24