PHSI 208 Lecture Notes - Lecture 35: Von Willebrand Factor, Vascular Smooth Muscle, Basal Lamina
Document Summary
Hemostasis the prevention of hemorrhage (bleeding) is achieved through a 3-step process: Hemostasis is a 3 step process: vasoconstriction, platelet plug formation. Releases substances that reinforce vasoconstriction and activate platelets: coagulation (stable clot) Intrinsic pathway (surface contact pathway: factor xii is activated when contacting exposed collagen, activated platelets, final product is factor xa. Extrinsic pathway (cell injury pathway: factor vii (tissue factor) leaves vessel binds to tissue factor receptor and become activated factor viia, final product is factor xa. Common pathway: factor xa from intrinsic and extrinsic is used to create thrombin, which ultimately converts fibrinogen to a stable fibrin clot. Hemophilia = a name given to several diseases in which one of the factors in the coagulation cascade is defective or lacking. Just recently aav treatment increased factor production in clinical trials. Too much coagulation can be a very bad thing (thrombus: stroke, heart attack, pulmonary embolism)
