Pathology-Hemostasis Flashcards
What three main factors affect the formation of a thrombus?
Vascular wall, platelets, coagulation cascade
Describe vasoconstriction during normal hemostasis
Neurologic reflect causes vasoconstriction and is amplified by endothelin
What does endothelin do
increases vasoconstriction
Describe what happens during primary hemostasis
- wall expose so endothelium lays down vWF
- GF1b on platelets binds vWF
- Platelets release ADP and TXA2
- Granules recruit more platelets
What does vWF do
causes platelet adhesion
What does GF1b do
binds vWF
Dense granules
ADP, calcium, serotonin, histamine, epinephrine
Alpha granules
V, VIII, protein s, fibrinogen
What happens during secondary hemostasis?
- Tissue factor is synthesized
- Tissue factor and secreted platelet granules activate coagulation cascade
- Activates thrombin that cleaves fibrinogen to fibrin to form secondary plug
What does fibrinogen do?
Allows platelets to aggregate; forms dimers once cleaved
5 steps of primary hemostasis
- vasoconstriction
- platelet adhesion
- platelet activation and secretion
- platelet aggregation
- primary platelet plug
What types of things activate the endothelium?
Infectious agents, hemodynamic factors, plasma mediators, most importantly cytokines
How do PGI-2 and NO prevent thrombi formation
vasodilation
Anticoagulant effects of endothelium
Heparin like molecules interact with antithrombin III, causing an inactivation of coat factors
Antithrombin III
Inactivates thrombin so it cannot cleave fibrinogen