BIOL 271 Lecture Notes - Lecture 2: Prothrombinase, Tissue Plasminogen Activator, Vasospasm
Document Summary
Hemostasis: stoppage of bleeding when blood vessels are damaged must be quick, localized and carefully controlled three mechanisms: vascular spasm platelet plug formation coagulation (clotting) Vascular spasm damage to arteries or arterioles > immediate contraction of smooth muscle in vessel wall reduces blood loss for several minutes to several hours allows time for other hemostatic mechanisms to proceed. 3 step process: platelet adhesion platelet release reaction platelet aggregation. Platelet adhesion platelets stick to collagen exposed when endothelium is damaged. Platelet release reaction adhered platelets extend projections, contact other platelets and degranulate (release of clotting factors) thromboxane a2, adp and serotonin released > constriction of injured vessel, activation of other platelets. Adp activates more platelets that become sticky and form a platelet plug plug reinforced by brin threads formed during clotting process. Clotting factors: chemicals required for clot formation (coagulation) include: inactive enzymes synthesized by liver cells molecules released by platelets or damaged tissues.
