1. Blood clotting

3. Vasoconstriction of damaged blood vessel Triggers
Direct injury to vascular smooth muscle
Chemicals released by endothelial cells and platelets
Pain reflexes
Most effective in smaller blood vessels

4. Positive Feedback cycle
Damaged endothelium exposes collagen fibers
Platelets stick to collagen fibers
Swell, become spiked and sticky, and release chemical messengers

5. Reinforces platelet plug with fibrin threads
Blood transformed from liquid to gel
Series of reactions using clotting factors
Vitamin K needed to synthesize 4 of them

8. Clot Retraction Stabilizes clot
Actin and myosin in platelets CONTRACT within 30–60 minutes
Contraction pulls on fibrin strands, squeezing serum from clot
Draws ruptured blood vessel edges together