PHYSL212 Study Guide - Von Willebrand Factor, Hemostasis, Coagulation
13 Oct 2014
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Both factors work together to keep system at balance. Mechanisms of hemostasis: key features: vasoconstriction, primary hemostasis or platelet plug formation ( white thrombus , secondary hemostasis or blood clotting or blood coagulation ( red thrombus ) Stem cells (cid:0) megakaryocytes (multiple nuclei) (in bone marrow) (cid:0) platelets (in blood stream) Substances present in platelets: alpha granules: contain relatively large molecules: Adhesion molecules such as von willebrand factor (vwf) Cytokines: dense granules: contain relatively small molecules: Via the use of: thromboxane, fibrinogen (and fibrinogen receptors), vwf receptors (vwf factor) Txa2 (which causes): vasoconstriction and further platelet aggregation. Pl (which causes): thombin, which causes: further platelet aggregation. Disturbance in cell membrane (cid:0) membrane phospholipids (cid:0) arachidonic acid (has 2 pathways: lipoxygenase pathway (cid:0) leukotrienes, cyclooxygenase pathway (cid:0) prostaglandins. Signaling mediates responses to damage in blood vessel: adjacent endothelial cells are a source of signals that influence platelet aggregation and alter blood flow and clot formation at the affected site.
