The illustration contains four parts:

1. The breaking of capillary walls: The diagram is captioned ‘Capillary wall breaks. The text below it reads ‘A blood vessel is injured by a cut or scrape’.
2. Reaction of platelets: The diagram is captioned ‘Platelets Take Action’. The text below it reads ‘Platelets clump at the site and release the clotting factor thromboplastin, which triggers a series of reactions. Thromboplastin converts the protein prothrombin into the enzyme thrombin’.
3. Formation of clot: The diagram is captioned ‘Clot Forms’. The text below it reads ‘Thrombin converts the soluble plasma protein fibrinogen into insoluble, sticky fibrin filaments, which form the clot. The clot seals the damaged area and prevents further loss of blood’.
4. On the top right, a micrograph of a clot indicating fibrin net preventing blood loss.