Coagulation Flashcards
What is haemostasis
Cessation of blood loss from damages vessel, followed by repair
What 3 phases can haemostasis be broken into
Vascular, platelet and coagulation
What happens I’m primary haemostasis
Platelets immediately form a plug at the site of injury
What happens in secondary haemostasis
Occurs simultaneously with primary haemostasis
Additional coagulation factors beyond factor VII respond in a complex cascade to form fibrin strands, strengthening platelet plug
Stabilising of clot
What happens I’m tertiary haemostasis
Dissolution of fibrin clot
Dependant I’m plasminogen activation
What is coagulation
Process by which blood changes from liquid to gel forming a clot
What are platelets
Disc shaped, anucleate cellular fragments derived from megakaryocytes
What is the pivotal role of platelets
Haemostasis
Forms initial plug
Pivotal role include adhesion, secretion and aggregation
What controls synthesis of platelets
IL-6, IL-3, IL-11 and thrombopoietin
What do platelets do
Secrete factors that activate other platelets, allow adhesion, cause vasoconstriction
Adhere to vessel wall at damaged site
Platelet aggregation builds up the initial plug
What activates platelets
ADP platelet activating factor Adrenaline Collagen Thrombin Immune complexes High physical shear force
What two processes are initiated when blood is exposed to space under endothelium
Changes in platelets, subsequent recruitment of more platelets
The exposure of Subendothelial factors to plasma factor VII, leading to fibrin formation
What do vessels do in coagulation
Damage results in exposure of basement membrane - blood now exposed to collagen
Damage results in exposure of vessel wall - blood is now exposed to platelet activating factor
The damage results in exposure
Smooth muscle cells in vessel wall respond to damage by contracting
What is factor I and it’d molecular weight
Fibrinogen
340000
Factor II
Prothrombin
Factor III
Tissue factor
Factor IV
Calcium ion
Factor V
Proaccelerin
Factor VII
Serum prothrombin conversion accelerator (SPCA)
Factor VIII
Antihemophillic factor (AHF)
Factor IX
Christmas factor
Factor X
Stuart-Prower factor
Factor XI
Plasma thromboplastin antecedent (PTA)
Factor XII
Hageman factor
Factor XIII
Fibrin-stabilisation factor (FSF)
Role of vitamin k in clotting
Some clotting factors need post-translational modification
This PTM requires vitamin k
What do PTMs do
Involved the addition of a COO- to certain Glu residues in clotting factor
Results in the formation of several y-carboxy glutamates = Gla
What factors need PTM
II, VII, IX, X, Proteins C and S
How is thrombin formed in the coagulation cascade
Protrombin is proteolytically cleaved to form thrombin in the coagulation cascade
Role of fibrinogen
Fibrinogen can form bridges between platelets, by binding to their GpIIb/IIIa surface membrane proteins
Converted to fibrin and cross links with factor XIII to form clot
What do tissue factors do
Enables cells to initiate the blood coagulation cascades
It functions as the high-affinity receptor for coagulation factor VII
Potent initiator that is fully functional when expressed on cell surfaces
What is fibrinolysis
Process that prevents blood clots from growing and becoming problematic
How does fibrinolysis occur
Plasmin is produced in inactive form plasminogen
Plasminogen cannot cleave fibrin, but still has affinity for it, so incorporates into the clot
Tissue plasminogen activator and urokinase are the agents that convert plasminogen to active plasmin, thus allowing fibrinolysis
What are fibrin clots degraded by
Serine protease called plasmin
