Smooth muscle layer surrounding cut immediately contracts, slowing blood flow. Damaged cells and platelets release potent vasoconstrictors such as serotonin and ADP. Endothelial surfaces become sticky and adhere to each other
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During a platelet plug what do they platelets stick to?
Stick to exposed tissue eg. collagen. Stick to each other using von Willebrands factor (vWF) --> plasma protein
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The platelets bound to collagen through vWF release... (and what do they cause?)
ADP, 5HT ad thromboxane A2 which causes surface of nearby platelets to become sticky --> adhere to other platelets
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What is the process of blood clotting?
Fibrinogen --------(thrombin)------> Fibrin monomers -----(XIIIa and Ca2+)------> Fibrin polymer
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What pathways stimulate thrombin?
1) Intrinsic-all necessary factors in blood 2) Extrinsic - initiating factor on plasma membrane of cells outside of endothelial blood cell lining (TISSUE DAMAGE)
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Name the two anti-clotting systems.
1) Anti-thrombin 2) Thrombomodulin, proteins C and 5
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What does the anti-thrombin system do? (anti-clotting)
Inhibits many clotting factors (thrombin) - activity is enhanced by HEPARIN (present in endothelial cells)
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What does the thrombomodulin system do? (anti-clotting)
Binds thrombin, eliminates thrombin's coagulant effects, activates protein C. Protein 5 acts as a co-factor for protein C to inactivate Va and VIIIa
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How is the clot dissolved?
Aggregated platelets secrete platelet derived growth factor beta ---> Recruitment of fibroblasts ---> Form scar tissue ---> Clot dissolves by plasmin
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