Describe the fibrinolytic pathway and identify areas of interaction with the coagulation pathway (80% of marks).
List two anti-fibrinolytic agents and state their specific mechanism of action (20% of marks).
The fibrinolytic pathway is a cascade largely made up of proteolytic enzmes and other factors synthesized in the liver that circulate in inactive precursor forms. Marks were awarded for description of the principal members of the cascade and the pathway relations between them. Endothelium is also important in the fibrinolytic pathway.
Regulation of the pathway to localise the site and size of clot as well as delayed onset of action of fibrinolysis is central to any description. Regulation of fibrinolysis by the coagulation cascade and a description of this area of interaction were expected. Many candidates provided a reasonable description of the fibrinolytic cascade. Marks were not awarded for description of the coagulation cascade that did not have relevance to fibrinolysis. Understanding of regulation of fibrinolysis and it’s interaction with coagulation was poorly answered. Most candidates were able to name two antifibrinolytic agents. Few were able to describe
mechanism of action.
Antifibrinolytic agents? One could list several, but the best known ones are:
The mechanism of action for aprotinin is actually rather complicated, so it would be better to just go with the other two, considering this is only worth 20%. In short:
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Ezihe-Ejiofor, J. Adanma, and Nevil Hutchinson. "Anticlotting mechanisms 2: pharmacology and clinical implications." Continuing Education in Anaesthesia, Critical Care & Pain 13.3 (2013): 93-97.
Chapin, John C., and Katherine A. Hajjar. "Fibrinolysis and the control of blood coagulation." Blood reviews 29.1 (2015): 17-24.