# Describe the role of platelets and fibrin in blood clotting.

> Cambridge International IGCSE Biology (0610) — 9.4 Blood · Describe · 4 marks

## Mark scheme (4 marks)

1. Platelets stick to the broken vessel wall and clump together, blocking the cut.
2. Fibrinogen is converted to fibrin.
3. Fibrin forms a mesh across the wound.
4. Blood clotting prevents excessive blood loss and/or prevents entry of pathogens / microorganisms into the body.

## Key terms

- [platelets](https://www.gradenine.co.uk/glossary/platelets)
- [fibrin](https://www.gradenine.co.uk/glossary/fibrin)
- [blood clotting](https://www.gradenine.co.uk/glossary/blood-clotting)

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