PHS 4300 Lecture Notes - Lecture 2: Blood Film, Warfarin, Fibrinogen
22 Jan 2018
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Document Summary
Hemostasis: defense system preventing spontaneous bleeding, arrests hemorrhages in case of vascular wall injury. Three phases: vascular spasms immediate constriction in response to the injury, platelet plug formation, coagulation (blood clotting) limitation of clot formation to prevent restriction in airways and bloodstream. Disorders of platelets, hemostasis and coagulation: blood coagulation (clotting) Platelet plugs are stabilized by a meshwork of fibrin fibers. If absent = no clotting: derived from inactive precursor prothrombin, two pathways that lead to conversion to thrombin. Intrinsic pathway: clots formed by stasis of blood, turbulent flow or endothelial injury, triggered by elements within the blood. Extrinsic pathway: clots formed by external trauma to blood vessels, triggered by tissue damage outside of the blood to stimulate the activation of tissue thromboplastin. Three substances that act to decrease clot formation and dissolve clots: plasmin, plasminogen (plg, tissue plasminogen activator (tpa) Evidence of clotting problem: deep venous thrombosis (dvt, myocardial infarction (mi, pulmonary embolism (pe)
