How Blood Clots
The cascade, in order.
A cut stops bleeding within minutes. Put the steps of clotting in the order they happen.
Tap the card that comes next
Two things are needed at the prothrombin step and are commonly asked: calcium ions, and vitamin K. Haemophilia is a failure somewhere in this cascade, which is why the blood does not clot.
Free play — put the stages in order yourself, then play the whole thing through as one continuous process. Switch to when you're ready to test yourself.
What this lesson covers
Challenges to clear
- Put the whole cascade in order.
- Lay thromboplastin in its correct place — before thrombin, not after.
The task
A cut stops bleeding within minutes. Put the steps of clotting in the order they happen.
What this lesson covers
- Injury — A blood vessel is cut and blood begins to escape.
- Platelets accumulate and rupture — Platelets collect at the injured site, stick to the rough surface and disintegrate.
- Thromboplastin released — The broken platelets and damaged tissue release the enzyme thromboplastin.
- Prothrombin → thrombin — Thromboplastin converts the inactive plasma protein prothrombin into active thrombin. This step needs calcium ions, and prothrombin itself needs vitamin K to be made in the liver.
- Fibrinogen → fibrin — Thrombin converts the soluble plasma protein fibrinogen into insoluble threads of fibrin.
- A mesh traps blood cells — The fibrin threads form a network across the wound, trapping red blood cells.
- The clot forms and hardens — The trapped mass dries and hardens into a clot, sealing the wound and preventing further loss of blood and entry of germs.
Hint
Two things are needed at the prothrombin step and are commonly asked: calcium ions, and vitamin K. Haemophilia is a failure somewhere in this cascade, which is why the blood does not clot.