Hemostasis

1. General Characteristics
   

1. Vascular spasms (vasoconstriction at injured site)
2. Platelet plug formation (plugging the hole)
3. Coagulation (blood clotting - complex mechanism)
   

1. Vascular Spasms
   

1. First response to vascular injury - VASOCONSTRICTION is stimulated by:
   

1. compression of vessel by escaping blood
2. injury "chemicals" released by injured cells
3. reflexes from adjacent pain receptors
   

2. Formation of a Platelet Plug
   

1. damage to endothelium of vessel
2. platelets become spiky and sticky in response
3. platelets attach to damaged vessel wall to plug it
4. platelets produce thromboxane A2 - granule release
5. serotonin release enhances vascular spasm
6. ADP - attracts and stimulates platelets at site
7. prostacylin - inhibits aggregation at other sites

Category: Pathology Notes